OVER-VOLTAGE PROTECTION CIRCUIT

Sajol Ghoshal Philip John Crawley

Tim Dhuyvetter John Camagna

Michael Altmann

BACKGROUND

Many networks such as local and wide area networks (LAN/WAN) structures are used to carry and distribute data communication signals between devices. Various network elements include hubs, switches, routers, and bridges, peripheral devices, such as, but not limited to, printers, data servers, desktop personal computers (PCs), portable PCs and personal data assistants (PDAs) equipped with network interface cards. Devices that connect to the network structure use power to enable operation. Power of the devices may be supplied by either an internal or an external power supply such as batteries or an AC power via a connection to an electrical outlet.

Some network solutions can distribute power over the network in combination with data communications. Power distribution over a network consolidates power and data communications over a single network connection to reduce installation costs, ensures power to network elements in the event of a traditional power failure, and enables reduction in the number of power cables, AC to DC adapters, and/or AC power supplies which may create fire and physical hazards. Additionally, power distributed over a network such as an Ethernet network may function as an uninterruptible power supply (UPS) to components or devices that normally would be powered using a dedicated UPS.

Additionally, network appliances, for example voice-over-lnternet-Protocol (VOIP) telephones and other devices, are increaseingly deployed and consume power. When compared to traditional counterparts, network appliances use an additional power feed. One drawback of VOIP telephony is that in the event of a power failure the ability to contact emergency services via an independently powered telephone is removed. The ability to distribute power to network appliances or circuits enable network appliances such as a VOIP telephone to

operate in a fashion similar to ordinary analog telephone networks currently in use.

Distribution of power over Ethernet (PoE) network connections is in part governed by the Institute of Electrical and Electronics Engineers (IEEE) Standard 802.3 and other relevant standards, standards that are incorporated herein by reference. However, power distribution schemes within a network environment typically employ cumbersome, real estate intensive, magnetic transformers. Additionally, power-over-Ethernet (PoE) specifications under the IEEE 802.3 standard are stringent and often limit allowable power. IEEE 802.3af-2003 sets standards for powering devices over an Ethernet network including setting of a maximum power requirement to a powered device (PD). The standard does not address powering of powered devices that require power in excess of the specification.

An IEEE 802.3af specification defines requirements for designing PoE equipment. The standard sets forth two types of devices including Power Sourcing Equipment (PSE) and Powered Devices (PD). According to the standard, the PSE supplies 48 volts with a current limit of 35OmA to the PD which may be one of a wide variety of devices such as Voice-over-lnternet-Protocol (VoIP) telephones, wireless access points, and many others. The standard limits the PSE to a continuous maximum power delivery of 15.2 watts, which after line losses amounts to a power delivery of 12.95 watts at the PD interface.

Different devices can require significantly different power levels. For example, a VoIP telephone can typically consume four to six watts while a dual- radio wireless access point can have a requirement of about 14-18 watts. In a conventional system, several power classification levels can be specified using handshakes between the PSE and the PD. The handshake operations typically begin when a PD product is connected to a PoE cable. The PSE reacts by sending a test voltage to determine whether the PD has a valid IEEE 802.3af signature. The detection signature results from a small current-limited voltage that is applied to the network cable. The voltage responds to the presence of a 25 Kω resistor in the PD.

Such probing by the PSE can create erroneous results for various reasons such as variations in cable length, presence of diode bridges at the PD interface, and other conditions or phenomena can potentially lead to errors in selection of supplied power, either failure to supply adequate power or, more typically, supplying of substantially more power than is necessary. For example, the output voltage for the PSE to drive the PD varies for different cable lengths. The diode bridge, which is required under the IEEE 802.3 standard to supply polarity protection in case a connector is attached backwards and to enable operation with a PSE that sources either -48V or +48V, also can result in a voltage drop that may be difficult to quantify using static techniques.

If the PD responds with to the PSE detection signal with a valid signature, a test is performed to determine the PD power consumption classification. During the classification test, the PD attempts to sink a known current according to the IEEE 802.3af classification table. If the PD does not supply a proper current sink, the PSE assumes a default type of Class 0 for the PD. The PSE supplies 48V to the PD only after results of the classification test are complete.

In the conventional operation, power allocation is a static process. The classification current identifies the amount of power to be supplied. A PD is designed to request a typically worst-case amount of power during the classification test, an amount that is typically estimated with a sufficient margin, often twenty to fifty percent, to prevent inoperability or failure due to lack of power due to coarse steps defined in the power classification table. Often the margin is extended to account for variability in actual power delivered by identical power supply models, a variability that may be significant even within the products of a particular manufacturer and within a particular model from the same manufacturer.

In the standard power management process, IEEE 802.3af handshake operations between the PSE and PD operate in the physical layer to set up a current, measure a current, then request a power supply level based on the measured current. The current can only be changed by terminating the link, then reinstating the link, and initializing using the handshake operation. Accordingly, the standard system is inherently static and cannot easily respond to dynamically changing demand without terminating the link.

Silicon-based electronic devices are susceptible to damage from spurious events that exert voltage/current stresses exceeding the normal operating limits of the devices.

Stress events can be surges on the power line originating from causes such as lightning strikes, but can also originate from human body discharge. If the stress event lasts sufficiently long or the spike in voltage is sufficiently severe, momentary current along a temporary path through the substrate can cause failure through overheating, which causes the silicon or metal to reach the melting point. Lighting and electro-static discharge (ESD) events can be very fast, with time constants as short as 6ns. The maximum voltage overstress during an event is typically determined by the reaction time of protection devices so that small parasitic changes can cause large variations in the magnitude of overstress.

In Power-over-Ethernet (PoE) applications a powered device (PD) physical interface (PHY) is particularly vulnerable. Although the PHY will unavoidably absorb part of the resulting surge, the function of the protection circuitry is to make the absorbed energy as small as possible by diverting most of the energy through the protection circuitry. Typical designs are intended to ensure that the energy dissipated in the PHY is lower than the energy of a strike as defined by International Electrotechnical Commission (IEC) standard 61000-4-2.

In some cases power is not available through the Ethernet line, so the PD is powered locally, for example through an AC adapter. Local powering of the PD presents substantial risk because the path to earth ground is more direct than when the device is powered through the Ethernet line, allowing a higher current and therefore a higher thermal energy level to dissipate.

To avoid damage, the protective circuitry must respond to a strike within a limited time frame, forming a relatively large current path through the protective circuits and dissipating a significant amount of thermal energy without being destroyed during the surge. High current has to be discharged through a low impedance path, thereby avoiding development of voltages that exceed component specifications. In addition, the protective circuitry must reset

sufficiently quickly to respond to subsequent strikes as soon as the strikes are likely to occur.

SUMMARY

According to an embodiment of a network device, a power converter comprises an input connection to a single power source, an output connection to a single coil, and a daisy-chain connection coupled to the output connection and configured to enable coupling of at least one additional daisy-chained power converter and at least one respective additional power source to the single coil. The power converter further comprises a power integrator coupled between the input connection and the output connection and adapted for summing power from the power sources into a single voltage on the single coil and a time multiplexer coupled to the power integrator configured to control power integration.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention relating to both structure and method of operation may best be understood by referring to the following description and accompanying drawings:

FIGURES 1A and 1 B are schematic block diagrams that respectively illustrate a high level example embodiments of client devices in which power is supplied separately to network attached client devices, and a switch that is a power supply equipment (PSE)-capable power-over

Ethernet (PoE) enabled LAN switch that supplies both data and power signals to the client devices;

FIGURE 2 is a functional block diagram illustrating a network interface including a network powered device (PD) interface and a network power supply equipment (PSE) interface, each implementing a non-magnetic transformer and choke circuitry;

FIGURES 3A and 3B are schematic block diagrams respectively illustrating examples of power controllers in isolated and non-isolated arrangements;

FIGURES 4A, 4B, 4C, and 4D are schematic block diagrams that depict embodiments of power converters that can integrate power from multiple sources into a single voltage;

FIGURE 5 is a schematic block and circuit diagram depicting an embodiment of a power converter formed to control power source switching based on measured current;

FIGURES 6A and 6B are schematic block and circuit diagrams illustrating embodiments of Power-over-Ethernet (PoE) systems that implement power conversion to integrate power from multiple sources into a single voltage; and

FIGURE 7A through 7D are flow charts illustrating embodiments of methods for power conversion in a network device;

FIGURE 8 is a schematic block diagram that depicts a dynamic power management system that can use one or more of multiple techniques for communicating over a network to manage power over Ethernet;

FIGURES 9A and 9B are schematic block and circuit diagrams that depict embodiments of a network device adapted for dynamic power management in a Power-over-Ethernet application in association with a Powered Device (PD);

FIGURES 1OA, 1OB, and 1 OC are schematic block and circuit diagrams illustrating embodiments of a network device adapted for dynamic power management in a Power-over-Ethernet application in association with a Power Sourcing Equipment (PSE);

FIGURES 11A and 11 B are schematic block diagrams that show embodiments of network systems adapted for dynamic power management in a Power-over-Ethernet application;

FIGURES 12A through 12F are flow charts that depict embodiments of power management methods that can be used in a Power-over-Ethernet application;

FIGURE 13 is a block diagram illustrating traditional classification levels for a Power over Ethernet application of the IEEE 802.3af standard; and

FIGURE 14 is a block diagram illustrating an enhanced classification scheme;

FIGURE 15A is a schematic block diagram that shows an embodiment of a network device comprising an integrated rectification and protection system;

FIGURE 15B is a schematic block diagram illustrating an embodiment of a network device with an integrated rectification and protection system adapted for usage with a T-Less Connect™ solid-state transformer;

FIGURES 16A and 16B are schematic flow charts depict embodiments of a method for rectification and surge protection in a Power-over-Ethernet application;

FIGURE 17 is a schematic block and circuit diagram illustrating a non- integrated rectification and protection circuit;

FIGURES 18A, 18B, and 18C are graphs showing over-voltage protection performance for a non-integrated protection circuit embodiment; and

FIGURES 19A, 19B, and 19C are graphs showing over-voltage protection performance for an integrated protection circuit embodiment comprising an integrated diode bridge and protection circuitry.

DETAILED DESCRIPTION

A time multiplexed scheduling technique can be used to drive multiple converter circuits to integrate power from multiple sources into a single voltage, summing power from the multiple sources into a single flyback transformer or buck inductor.

In some applications, the technique can be used in Power-over-Ethernet implementations to integrate power from two sources in the case of four-pair arrangements.

In some embodiments, adaptive power sharing for the individual converters based on power availability of the associated source. When the current limit of a source is exceeded, the power from other sources can automatically feed power to suit requirements of the receiving device.

Power sources can be any suitable arrangement, for example a two-pair and an auxiliary power source. The structure and technique may adaptively change current limits on each power source, enabling adaptive management of the amount of power that can be sourced from each power supply.

The structure and technique can be applied to enable both isolated and non-isolated power supply applications. The structure and technique can also enable a user to develop a single- chip controller, for example a pulse width modulator (PWM) controller. As additional power sources become available, multiple single-chip controllers can be daisy-chained to schedule control while connecting output lines in parallel to a single flyback transformer or buck inductor. Referring to FIGURES 3A and 3B, schematic block diagrams respectively illustrate examples of power controllers 300A, 300B in isolated and non-isolated arrangements. In either case, a pulse width modulator 312 is used to apply a power source 304 to a single coil 308. In FIGURE 3A, the isolated power controller 300A is transformer-based whereby the single coil 308 is the primary winding of a transformer 324 and includes an opto-isolator 326 coupled to isolate

a secondary winding of the transformer 324 from the power source 304. In FIGURE 3B, the non-isolated power controller 300B has the single coil 308 in the form of a down or buck inductor.

In the illustrative implementation, the power controllers 300A, 300B are depicted as an integrated circuit 372 with components outside the integrated circuits 372 being external components.

The single integrated circuit 372 includes logic and timing elements which coordinate operations to drive the single coil 308 and internally to that IC the logic and the timing are set up for that single device. The illustrative power controllers 300A, 300B apply a single power source

304 to the coil 308 and are limited in the amount of power that can be applied to the coil 308. What may be desired is a power controller that supports a connected device with a higher power requirement. Multiple power sources, for example multiple pairs of RJ-45 or Ethernet cables, or auxiliary power sources can be coupled to combine power, creating an integrated power relationship that combines into a single output power. Accordingly, circuits and systems are sought that enable combination of multiple supplies to support the higher power requirement.

One application that can greatly benefit from a capability to support a higher power level is a Power-over-Ethernet (PoE) application.

Referring to FIGURES 4A, 4B, 4C, and 4D, four schematic block diagrams depict embodiments of power converters 400 that can integrate power from multiple sources into a single voltage. The power converter 400A(1), 400B(1), 400C(1), 400D(1) has an input connection 402 to a single power source 404(1), an output connection 406 to a single coil 408, and a daisy-chain connection 410 coupled to the output connection 406 and configured to enable coupling of one or more additional daisy-chained power converters 400A(2), 400B(2), 400C(2), 400D(2) and one or more respective additional power sources 404(2) to the single coil 408. The power converter 400A(1), 400B(1), 400C(1), 400D(1) further comprises a power integrator 412 coupled between the input connection 402 and the output connection 406 that is adapted for summing power from the power sources 404(1), 404(2) into a single voltage on the single coil 408. A time

multiplexer 414 is coupled to the power integrator 412 configured to control power integration.

The illustrative power converters 400A(1 ), 400B(1), 400C(1 ), 400D(1) can be implemented as single integrated circuit chips that can be used alone or can be used with two or more daisy-chained chips connected to combine multiple power sources.

Referring to FIGURE 4A, the power converter 400A is configured as an isolated four-pair power integration structure. The power converter 400A comprises a pulse width modulation circuit 412 that functions as the power integrator. The illustrative time multiplexer 414 comprises an oscillator 416 and a divide-by-N circuit 418 whereby N corresponds to the number of daisy-chained power converters 400A. The time multiplexer 414A further can comprise a detect clock 420 which detects a clock signal from a daisy-chained power converter 400A. A multiplexer 422 receives input signals from the divide-by-N circuit 418 and the detect clock 420 and drives the pulse width modulation circuit 412.

In the isolated arrangement, the single coil 408 in the power converter 400A is a primary winding of a single flyback transformer 424. Optical isolators 426 isolate a secondary winding of the single flyback transformer 424.

In the depicted example arrangement, power converters 400A can be two integrated circuits that are identical or approximately identical and combine two power sources including a first source shown as Vposi and return Vrtnl , and a second source shown as Vpos2 and return Vret2. The first and second power sources can be sets of paired cables, such as Registered Jack (RJ)-45 connectors or Ethernet connectors, which connect two the two separate integrated circuits. The two separate integrated circuits are configured to energize the primary winding 408 of the flyback transformer 424 in a time multiplexed fashion.

The separate integrated circuits corresponding to the power converters 400A(1) and 400A(2) can be connected to a common output connection 406 to the single primary winding 408. Timing signal lines are connected, or daisy- chained, for each of the integrated circuits and are input to the detect clock 420, which in turn supplies a timing signal to the multiplexer 422. The timing signal

from the other integrated circuit is applied to the detect clock 420 which generates a clock signal that is applied to the multiplexer 422. A divide-by-2 or more genehcally a divide-by-N 418 also generates a signal to the multiplexer 422 so that N power sources can be applied to the same primary winding 408. Accordingly, when a timing signal from another integrated circuit is asserted at the detect clock 420, then the other integrated circuit drives the primary 408, When the timing signal from the other integrated circuit is not asserted, the immediate integrated circuit drives the primary 408. For two power converter integrated circuits, each alternately drives the primary winding 408 in sequential time frames. For N power converter integrated circuits 400, each can drive the primary winding 408 for a portion of time in multiple time frames, for example in a round-robin fashion.

In various embodiments, the actual timing and framing can be arbitrary in a manner analogous to phasing. During one phase or time period the output signal to the coil 408 can be driven from one leg and then in another time period, another phase, another leg drives the output signal.

Time multiplexing facilitates power management by functioning as a control element for a feedback control system in which each power converter 400A(1) and 400A(2) has a feedback control loop. One power converter drives one feedback loop and the other power converter drives another feedback loop. Time multiplexing ensures that only one feedback loop is operational at any one time. For a system with N power converters, time multiplexing similarly ensures that only one of N feedback loops is operational at any time. The single power converter is operational in response to the respective associated feedback signal. For the isolated power integration structure 400A, the common mode of the pairs can be completely different voltages, accordingly two opto-isolators 426 are used to ensure isolation.

Referring to FIGURE 4B, the power converter 400B is configured as a non-isolated four-pair power integration structure. The power converter 400B comprises a pulse width modulation circuit 412 that functions as the power integrator. The illustrative time multiplexer 414B comprises an oscillator 416 and a divide-by-N circuit 418 whereby N corresponds to the number of daisy-chained

power converters 400B. The time multiplexer 414B further can comprise a detect clock 420 which detects a clock signal from a daisy-chained power converter 400B. A multiplexer 422 receives input signals from the divide-by-N circuit 418 and the detect clock 420 and drives the pulse width modulation circuit 412. In the non-isolated arrangement, the single coil 408 in the power converter

400A is a buck inductor 428.

For the non-isolated power converter 400B, a single feedback point can drive feedback loops for all power converters 400B(1), 400B(2), a suitable arrangement since the feedback loops are time multiplexed. Accordingly, the feedback is only active for one time period for one path and inactive for the other time period and the other path and vice versa.

Referring to FIGURE 4C, the power converter 400C is configured as an isolated four-pair power integration structure. The power converter 400C comprises a pulse width modulation circuit 412 that functions as the power integrator. The illustrative time multiplexer 414C comprises a delay-locked loop 430 coupled to drive the pulse width modulation circuit 412, an oscillator 416, a detect clock 420 which detects a clock signal from a daisy-chained power converter 400C. A multiplexer 422 receives input signals from the oscillator 416 and the detect clock 420 and drives the delay-locked loop 430. In the isolated arrangement, the single coil 408 in the power converter

400C is a primary winding of a single flyback transformer 424. Optical isolators 426 isolate a secondary winding of the single flyback transformer 424.

Referring to FIGURE 4D, the power converter 400D is configured as a non-isolated four-pair power integration structure. The power converter 400D comprises a pulse width modulation circuit 412 that functions as the power integrator. The illustrative time multiplexer 414D comprises a delay-locked loop 430 coupled to drive the pulse width modulation circuit 412, an oscillator 416, a detect clock 420 which detects a clock signal from a daisy-chained power converter 400D. A multiplexer 422 receives input signals from the oscillator 416 and the detect clock 420 and drives the delay-locked loop 430.

In the non-isolated arrangement, the single coil 408 in the power converter 400D is a buck inductor 428.

In some embodiments, the power converters 400 can be implemented in a Power-over-Ethernet (PoE) integrated circuit with power sources 404 configured as two wire pairs coupled to a Registered Jack (RJ)-45 connector. The power converters 400 can further comprise a magnetic transformer, a Powered Device (PD) controller, a diode bridge that couples the power source 404 to the PD controller, and a Powered Device (PD) coupled to the single coil and powered by the single voltage.

In other similar embodiments, the power converters 400 can be implemented in a Power-over-Ethernet (PoE) integrated circuit with power sources 404 configured as two wire pairs coupled to a Registered Jack (RJ)-45 connector. The power converters 400 can further comprise a non-magnetic transformer and diode bridge integrated into the PoE integrated circuit and coupled to the RJ-45 connectors, a Powered Device (PD) controller, a diode bridge that couples the power source to the PD controller, and a Powered Device (PD) coupled to the single coil and powered by the single voltage.

In some embodiments, the time multiplexer 414 can be configured to perform adaptive power sharing for the power integrator 400 based on power availability of the single power source and the additional power sources.

The power sources 404 can be two-wire pair sources, as shown, or auxiliary sources such as home or office supply lines.

In some embodiments, the power converter 400 can implement adaptive power management by using IEEE 802.3at standard classification or similar classification techniques. For example, a Powered Device (PD) can be coupled to the single coil 408, powered by the single voltage, and one or more of the power sources 404 can be a Power Sourcing Equipment (PSE). A controller or other suitable logic can be configured to communicate detection, classification, and operational information between the Power Sourcing Equipment (PSE) and the Powered Device (PD) for accommodating a power consumption classification of the PD and identifying characteristics of the power sources, for example the amount of power supplied and type of power source. The identified power characteristics can be used for adaptive sharing power through management of the time multiplexer 414.

In a typical Ethernet IEEE 802.3af standard implementation, detection and classification signals are communicated from the PD to the PSE including a power-consumption classification. The PSE returns operational information, enabling a PD response to the classification voltage. Communication of information that identifies characteristics of the various power sources enables management of the time multiplexer 414 to account for differences in supplies.

Typically upon request from the PSE, the PD sends power-consumption classification information to the PSE that identifies the current power consumption demand of the PD, accounting for dynamic changes in demand. For example, the PD can be a scanning video camera that has relatively low steady state power consumption when scanning motors are not operating but may have a large power demand at possibly brief and infrequent operating times when the scanning motors are active.

The controller or logic can communicate detection, classification, and operational information independently for each power source of the single power source and the additional power sources and for current power consumption demand of the Powered Device (PD) for identifying characteristics of the power sources.

In some implementations, the power converter 400 can operate in a single integrated circuit chip configuration whereby a single power source 404 supplies the output connection to the single coil 408. In other implementations, the same power converter 400 can be connected to operate in combination with multiple single integrated circuit chip power converters 400 in a daisy chain configuration as additional power sources 404 become available. In the daisy chain configuration, time multiplexers 414 for the multiple power converters 400 schedule power source control with the output connections 406 coupled in parallel to the single coil 408.

The power converters 400C, 400D depicted in FIGURES 4C and 4D are operationally similar to power converters 400A, 400B shown in FIGURES 4A and 4B but illustrate a different structure and technique for generating the timing signals by usage of a delay-locked loop to generate the time periods. The delay- locked loop structure may be more useful in structures that include a number N,

typically larger than 2, of integrated circuits that are staged one after another. The delay-locked loops are used to create the additional time periods. Like the divide-by-N implementation, the delay-locked loop circuit includes a clock detection but is driven differently. Each clock is driven from the output of the delay-locked loop and connected down a sequential chain.

Referring to FIGURE 5, a schematic block and circuit diagram depicts an embodiment of a power converter 500 formed to control power source switching based on measured current. The power converter 500, in addition to a power integrator 512 and time multiplexer 514, further comprises a current sensor 570 coupled to the power integrator 512. The time multiplexer 514 can be configured to detect a current sensed by the current sensor 570 that exceeds a predetermined maximum current. In response to a current that exceeds the maximum current, the time multiplexer 514 switches power sourcing from the power source 504(1 ) at the input connection 502 to one of the additional power sources 504(2).

In some embodiments, the time multiplexer 514 can be configured to adaptively change the predetermined maximum current whereby power sourced by the single power source 504(1) and the additional power sources 504(2) is adaptively managed. The various power converter arrangements can be used for any suitable power application. One example of a highly suitable application for usage of the power converters and the illustrative power conversion technique is a Power- over-Ethernet application. The combined power sources can be any suitable power source from various types of lines that are capable of supplying power including twisted pairs and Ethernet cables, as well as other power supply lines. In various applications, all power sources may be supplied on the same type of lines, or power sources may be connected from different types of lines.

The power sources can be supplied from communication lines, or may be a battery, a wall power source, or others. Referring to FIGURES 6A and 6B, schematic block and circuit diagrams illustrate embodiments of a Power-over-Ethernet (PoE) system 650A, 650B that implement power conversion to integrate power from multiple sources into a

single voltage. The Power-over-Ethernet (PoE) system 650A, 650B comprises one or more modular power converters 600(1), 600(2) configured for coupling between respective power sources 604(1), 604(2) and a single coil 608 of a Powered Device (PD) 652 in a daisy-chain arrangement whereby output connections 606 of the modular power converters 600(1 ), 600(2) are coupled in parallel to the single coil 608. The modular power converters 600(1), 600(2) can each comprise a power integrator 612 and a time multiplexed scheduler 614 that drives multiple power integrators 612 for multiple modular power converters 600 to integrate power from corresponding multiple sources 604 into a single voltage on the single coil 608.

As shown in FIGURE 6A, the modular power converters 600A(1), 600A(2) can be implemented as a Power-over-Ethernet (PoE) integrated circuit. The power sources 604(1), 604(2) can be configured as two wire pairs coupled to a Registered Jack (RJ)-45 connector. The modular power converters 600A(1 ), 600A(2) can further comprise a magnetic transformer 654 coupled to the RJ-45 connector, a Powered Device (PD) controller 656 coupled to the power source 604(1), and a diode bridge 658 that couples the power source 604(1 ) to the PD controller 656.

In some embodiments, the time multiplexed scheduler 614 can be configured to perform adaptive power sharing for the power integrator 612 based on power availability of the power sources 604(1), 604(2).

In various applications and arrangements, the power sources 604(1), 604(2) can be two-wire pair sources, auxiliary sources, or the like.

As shown in FIGURE 6B, the modular power converters 600B(1), 600B(2) can be implemented as a Power-over-Ethernet (PoE) integrated circuit. The power sources 604(1), 604(2) can be configured as two wire pairs coupled to Registered Jack (RJ)-45 connectors. The modular power converters 600B(1 ), 600B(2) can further comprise a non-magnetic transformer and diode bridge 660 integrated into the PoE integrated circuit and coupled to the RJ-45 connectors, a Powered Device (PD) controller 656 coupled to the power source 604(1) and coupled to the non-magnetic transformer and diode bridge 660. The modular

power converters 600B(1), 600B(2) couple the power source 604(1 ) to the PD controller 656.

The non-magnetic transformer and diode bridge 660 can be a T-Less Connect™ solid-state transformer that separates Ethernet signals from power signals and/or that operates by floating ground potential of the Ethernet PHY relative to earth ground.

Various embodiments of Power-over-Ethernet (PoE) systems can be formed in various configurations. For example, the single coil 608 can be a primary winding of a single flyback transformer or a buck inductor. In various implementations, the power integrator 612 can be a Pulse Width Modulator (PWM), a forward bridge, a half bridge, a Pulse Frequency Modulator (PFM), a Pulse Amplitude Modulator (PAM), or any other suitable conversion device or technique. The time multiplexed scheduler 614 can be implemented based on any suitable control element such as a divide-by-N circuit, a Delay-Locked Loop (DLL), or similar devices.

The power converter 600 can further by constructed to adaptively control the power integrator 612 according to the IEEE 802.3at standard or similar classification techniques. The Powered Device (PD) 652 can communication with power sources 604 that may include a Power Sourcing Equipment (PSE). The PD controller 656 may include a processor, controller, or other logic, or another logic in the power converter 600 can be used to communicate detection, classification, and operational information between the Power Sourcing Equipment (PSE) and the Powered Device (PD) 652, enabling identification of characteristics of the associated power source so that the time multiplexed scheduler 614 can adaptively share power.

In various PoE system embodiments, the modular power converters can further comprise a current sensor coupled to the power integrator in combination with a the time multiplexed scheduler configured to detect a current sensed by the current sensor that exceeds a predetermined maximum current. In response to a current exceeding the maximum current, the time multiplexed scheduler can switch sourcing of the power sources.

In further embodiments, the time multiplexed scheduler can be configured to adaptively change the predetermined maximum current so that power sourced by the power sources is adaptively managed.

In the illustrative embodiments, each modular power converter 600B(1 ) and 600B(2) has two-pair input connections. Each two-pair connection passes through a diode bridge 660. As a result, a particular power is delivered through each power converter integrated circuit and a load shares the power supplied between the two converters. Power is summed from each of the two groups of pairs. The modular power converters not only route the power but also sum the power. For purposes of example only, ten watts may be supplied by one power source and ten by the second power source so that a total of twenty watts can be generated at the coil. Note that any suitable wattage may be summed for any suitable number of daisy-chained converters. Note also that the power sourced by the individual sources can be different. Referring to FIGURE 7A with reference to FIGURES 6A and 6B, a flow chart illustrates an embodiment of a method 700 for power conversion in a network device. Power is integrated 702 from multiple sources into a single voltage with power integration driven 706 according to time multiplexed scheduling 704. The integrated power is applied 708 onto a single winding of a flyback transformer or buck inductor.

Referring to FIGURE 7B also with reference to FIGURES 6A and 6B, a flow chart illustrates an embodiment of a method 710 in which power is converted 712 for usage in an application of a Power-over-Ethernet (PoE) configuration. Power is integrated 714 from at least two sources selected from two-wire pair sources and auxiliary sources.

Referring to FIGURE 7C, a flow chart depicts an embodiment of a method 720 that adaptively controls power. The method further comprises determining 722 power available among the multiple sources and adaptively sharing 724 power based on availability from the different sources. Some embodiments may use additional measured parameters to adaptively control power sourcing. For example, FIGURE 7D illustrates an embodiment of a power control method 730 that can be implemented in

combination with the structures shown in FIGURE 5. The method 730 may further comprise measuring 732 current associated with the power sources and determining 734 when the measured current exceeds a predetermined current limit. Power sourcing can be adaptively switched 736 when the current limit is exceeded. In some embodiments, current limits for the power sources can be adaptively changed 738, enabling adaptive management 740 of the power sourced among the power sources.

Dynamic power management controllers are respectively configured for usage in a Power Sourcing Equipment (PSE) and a Powered Device (PD) coupled by a network cable in a configuration that transfers power and communication signals from the PSE to the PD. The dynamic power management controllers are configured to communicate power management information over the network cable at a Transmission Control Protocol / Internet Protocol (TCP/IP) layer and/or a Media Access Control (MAC) layer. Dynamic power management enables allocation of power from one or more Power Sourcing Equipment (PSE) and one or more Powered Devices (PDs) according to instantaneous demand. An individual PD may have a wide range of power demand according to conditions and application. Some devices draw a relatively constant level of power. A majority of devices can have a wide range of power consumption that vary over time. Dynamic power management enables supplied power levels to change depending on operations a device is performing.

For example, a hand-held consumer camera that is not panning or tilting draws on the order of six watts of power. However, when the camera is tilted the motors are activated and draw a substantial amount of power such as up to 20 watts. Some operators may only pan a few times in a day or week. Accordingly, a dynamic power management technique can be applied, for example, in a system with a 200 watt power supply that is designed to allocate, on average, 20 watts over ten ports, and that 99% of the time draws no more than a total of 100 watts. The dynamic power management application can dynamically adjust power using a statistical power management approach, for example, by supplying ten watts per port and responding to requests by the PDs for more power, when appropriate.

The dynamic power management system enables a PD to essentially immediately request a power level based on instantaneous demand. For a system with a maximum total demand that is less than the total supply, the system responds to PDs requesting a higher power while allocating a smaller power level to PDs that do not request a higher power. The probability is that peak requirements will not be synchronized except in a worst case scenario.

Various combinations of dynamic power management techniques can operate at one or more of multiple levels or layers. For example, dynamic power management can be supported by one or more of three methods. Ethernet packets can be used at the Transmission Control Protocol / Internet Protocol

(TCP/IP) levels to request selected power, for example an increased power, from a Power Sourcing Equipment (PSE). In other embodiments and applications, a method can support a dynamic power management method using Type of Service (TOS) bits in a Transmission Control Protocol / Internet Protocol (TCP/IP) header to assign priority according to traffic, for example a higher priority assigned to high priority traffic, for statistical power management. Some embodiments and/or applications can optionally support a method of indicating information in an 8b/10b encoder to transmit requests to a PSE.

For higher power applications, the PSE and PD can negotiate at the Institute of Electrical and Electronics Engineers (IEEE) Standard 802.3af level, for example indicating that the PD is enabled for high power such as with maximum power enabled, for static power management.

The illustrative techniques can be used for dynamic and statistical power management for performance individually or in combination to improve power supply utilization.

Referring to FIGURE 8, a schematic block diagram illustrates a dynamic power management system 800 that can use one or more of multiple techniques for communicating over a network to manage power over Ethernet. The network includes communication between Power Sourcing Equipment (PSE) 810 and a Powered Device (PD) 808 over a network cable 806. A single method or a combination of multiple methods can be used to transmit power management information over an Ethernet system.

At the physical layer 812, shown as layer 1 , power management information is communicated through a current-based classification scheme, for example according to IEEE 802.3af standard and/or an enhanced classification scheme which implement static power management that can be combined with dynamic power management.

At the Media Access Control (MAC) layer 814, shown as layer 2, power management information is communicated using 8b/10b reserved codes for communicating demand-based power requirements. The 8b/10b line codes, as conventionally used in communications, maps 8-bit symbols into 10-bit symbols to attain DC balance and bounded disparity, and further enable sufficient state transitions in the serial data stream to facilitate clock recovery from embedded data. The 8b/10b line codes facilitate high data rates by reducing intersymbol interference. Eight bits of data are transmitted as a 10-bit entity called a symbol or character. The lower five data bits are encoded into a 6-bit group and the higher three bits encoded into a four-bit group. The code groups are concatenated to form a 10-bit symbol for transmission. According to published standard, the symbols can be data symbols or special symbols, which can be control characters indicating end-of-frame, link idle, skip, and other similar link- level conditions. In the illustrative power management system, the 8b/1 Ob special symbols can be enhanced or extended in comparison to standard usage to define power management information that can be transferred between PSE and PD. The 8b/10b special symbols can be defined to perform power management including symbols to increase power and to reduce power. In an example 8b/10b operation, Ethernet communicates at a rate 100 megabits but actually transmits 125 megabits due to the addition of two extra bits that facilitate error correcting and can be used to create spare codes in the additional bits. In an illustrative dynamic power management operation, the spare codes can be used to request increases or reductions in power. In other embodiments or applications, the spare codes may be used to define requested power levels.

The layer 2 operation can be operative when the link is connected and an application is functioning in the Internet Protocol (IP) level or layer 2. Packets are sent back and forth between the PSE and PD, including requests by the PD for higher power, requests to reduce power to nominal levels, requests appropriate for conditions, possibly in combination with other information to facilitate power management.

At the Transmission Control Protocol / Internet Protocol (TCP/IP) layer 816, illustrated as layer 3, an Ethernet packet can be sent from the PD 808 to the PSE 810 to indicate various information and/or conditions such as power demand or requirements, current power requirements, device (PD) identification and other information relating to the PD 808, and other information. In some embodiments, Type of Service (TOS) bits can be used to specify priority for supplying power among devices.

Type of Service (TOS) bits are a set of four-bit flags in the Internet Protocol (IP) header. When any one of the TOS bit flags is set, a datagram is handled by a router in a manner different from handling of datagrams with no TOS bits set. Each of the four TOS bits has a different purpose and only one TOS bit may be set at any time. TOS bits are termed "type of service" by virtue of usage to enable an application that transmits data to inform the network of the type of network service to be delivered. According to conventional specifications, available classes of network service include minimum delay, maximum throughput, maximum reliability, and minimum cost.

In some conditions and/or applications, the latency for a datagram to travel from a source host to a destination host may be important. A network provider that can use multiple network connections with variable latency between the network connections may ensure that faster network connections are used when the minimum delay class of network service is selected.

In other conditions and/or applications, latency may be immaterial but the volume of data that is transmitted during a time interval may be important. A network provider may choose to route datagrams specified as maximum throughput to higher bandwidth network routes whereby higher latency of the routes can be tolerated.

Maximum reliability service can be selected for conditions and/or applications in which certainty that data arrive at the destination without retransmission is desired. Some network connections are more reliable than others. When maximum reliability service is desired, the network provider may ensure that more reliable networks are used for transmission.

Minimum cost service may be invoked when the cost of transmission is sought. Bandwidth leasing rates may be variable among multiple network connections. When minimum cost service is selected, a network provider may route a datagram over lost cost routes. In the illustrative power management system, TOS bit usage can be enhanced or extended in comparison to standard usage to define power management information that can be transferred between PSE and PD that specifies priority for supplying power among multiple devices.

Accordingly, the traditional usage of Type of Service (TOS) bits in the TCP/IP header is to specify priority of bandwidth allocation. A packet with TOS bits specifying higher priority is allocated bandwidth over a packet with lower priority. If insufficient bandwidth exists to handle all requests, lower priority packets may be discarded and transmission blocked while higher priority packets are successfully transmitted. The illustrative technique extends the operation of TOS bits to define power priority on the basis that, if information has higher priority and packets cannot afford to be lost, then similarly power to the PD cannot afford to be lost.

In various embodiments, the TCP/IP layer 816 operations of the dynamic power management system can include power control commands or information in a TCP/IP packet. At the top of the TCP/IP stack, a packet is decoded and the IP address and port address are placed on the header of the TCP/IP packet which can be sent from a PD to a PSE to request the PSE to increase power or reduce power. The packets can also encode further information such as statistical information, average power drawn, fault information and other types of information. Codes can be defined for encoding the power management information. Some bits can be assigned indicating demand for power, requests to reduce power, a specific amount of power can be requested, or the like.

The power management application 818 operates at layer 4.

Referring to FIGURES 9A and 9B, schematic block and circuit diagrams depict embodiments of network devices 900 adapted for dynamic power management in a Power-over-Ethernet application in association with a Powered Device (PD) 908. The illustrative network device 900 comprises a dynamic power management (DPM) controller 902 adapted for coupling to a network connector 904 that connects to a network cable 906 in a configuration that transfers power and communication signals to a Powered Device (PD) 908. The dynamic power management controller 902 can transmit power management information over the network cable 906 at a Transmission Control Protocol / Internet Protocol (TCP/IP) layer and/or a Media Access Control (MAC) layer.

The powered end station for the PD shown in FIGURE 9A has a magnetic transformer coupling. The powered end station for the PD shown in FIGURE 9B includes a T-Less Connect™ solid-state transformer. In some embodiments or applications, the dynamic power management controller 902 can be configured to encode an Ethernet packet at the Transmission Control Protocol / Internet Protocol (TCP/IP) layer that requests a supply power level from a Power Sourcing Equipment (PSE) device 910.

Some embodiments and/or applications may comprise the dynamic power management controller 902 that can be configured to encode Type of Service

(TOS) bits in a Transmission Control Protocol / Internet Protocol (TCP/IP) header of the TCP/IP layer to assign priority for traffic for statistical power management. For example, the dynamic power management controller 902 can be configured to encode an Ethernet packet at the Transmission Control Protocol / Internet Protocol (TCP/IP) layer for sending to a Power Sourcing Equipment (PSE) device 910 a request identifying at least one information item. The type of information items may include, for example, current Powered Device (PD) operating power, anticipated PD operating power, PD device identification, PD device operating information, PD device priority assignment, and other similar types of information. Conventionally, Type of Service (TOS) bits are defined as a set of four-bit flags in the Internet Protocol (IP) header. In conventional operation, if any one of the bit flags is set, routers handle a datagram differently than datagrams that

have no TOS bits set. The four bits each have a different purpose and only a single one of the TOS bits is conventionally allowed to be set at any time, disallowing combinations of set bits. Bit flags are called Type of Service bits by virtue of enabling an application that transmits data to inform a network of the type of network service needed by the application. Conventional classes of network service availability are minimum delay, maximum throughput, maximum reliability, minimum cost.

In contrast, the illustrative network device 900 extends functionality of the Type of Service (TOS) bits beyond standard or conventional operations to enable assignment of priority for traffic for statistical power management.

The dynamic power management controller 902 can also or alternatively be configured to encode 8b/10b reserved codes at the Media Access Control (MAC) layer. The 8b/10b reserved codes can request a demand-based power from a Power Sourcing Equipment (PSE) device 910. The dynamic power management controller 902 can further be configured to incorporate static power management by sending detection and classification information in a plurality of phases and a plurality of cycles at a physical layer from the Powered Device (PD) 908 to a Power Sourcing Equipment (PSE) 910.

Referring to FIGURES 1OA, 1OB, and 1OC, schematic block and circuit diagrams illustrate embodiments of network devices 1000 adapted for dynamic power management in a Power-over-Ethernet application in association with a Power Sourcing Equipment (PSE) 1010. The network device 1000 comprises a dynamic power management controller 1002 adapted for coupling to a network connector 1004 that connects to a network cable 1006 in a configuration that sends power from a Power Sourcing Equipment (PSE) 1010 and communicates signals between the PSE 1010 and a Powered Device (PD) 1008. The dynamic power management controller 1002 is configured to communicate power management information over the network cable 1006 at a Transmission Control Protocol / Internet Protocol (TCP/IP) layer and/or a Media Access Control (MAC) layer.

In some implementations, the dynamic power management controller 1002 can be configured to decode an Ethernet packet at the Transmission Control

Protocol / Internet Protocol (TCP/IP) layer received at the Power Sourcing Equipment (PSE) 1010 and to transmit power from the PSE 1010 to the requesting Powered Device (PD) 1008 at a supply power level according to the decoded packet. FIGURES 1OA and 10B show power sourcing switches for Power-over-

Ethernet devices using traditional power sourcing alternatives via a magnetic transformer coupling wherein power is transmitted over existing data-signal wire pairs and power is supplied through spare wires of a typical CAT-5 cable, respectively. The switch for a Power Souring Equipment (PSE) shown in FIGURE 10C includes non-magnetic power supply circuitry, such as a T-Less Connect™ solid-state transformer.

Various embodiments or applications of the dynamic power management controller 1002 can also or alternatively be configured to decode Type of Service (TOS) bits in a Transmission Control Protocol / Internet Protocol (TCP/IP) header of the TCP/IP layer and enforce priority for traffic to one or more requesting Powered Devices (PDs) 1008 using statistical power management.

Also at the TCP/IP layer, the dynamic power management controller 1002 can be configured to decode an Ethernet packet at the Transmission Control Protocol / Internet Protocol (TCP/IP) layer received at the Power Sourcing Equipment (PSE) 1010 and to transmit power from the PSE 1010 to the requesting Powered Device (PD) 1008 at a supply power level according to one or more information items in the decoded packet. Various information items can be one or more of current Powered Device (PD) operating power, anticipated PD operating power, PD device identification, PD device operating information, PD device priority assignment, or other similar parameters.

The dynamic power management controller 1002 in various embodiments and/or implementations can manage power at the Media Access Control (MAC) layer either in place of or in addition to management at the TCP/IP layer. At the MAC layer, the dynamic power management controller 1002 can be configured to decode 8b/10b reserved codes at the Media Access Control (MAC) layer received at the Power Sourcing Equipment (PSE) 1010 and to transmit demand-

based power from the PSE 1010 to the requesting Powered Device (PD) 1008 at a supply power level according to the decoded reserved codes.

In further embodiments or applications, the dynamic power management controller 1002 can further be configured to combine static and dynamic power management by receiving classification information in multiple phases and multiple cycles at a physical layer at the Power Sourcing Equipment (PSE) detection 1010 that is transmitted from the Powered Device (PD) 1010. The PSE 1010 can respond by sending operational information from the PSE 1010 to the PD 1008 at the physical layer. Referring to FIGURES 11A and 11 B, schematic block diagrams show embodiments of network systems 1100 adapted for dynamic power management in a Power-over-Ethernet application. The network system 1100 comprises dynamic power management controllers 1 102 _P S _E and 1102 _PD respectively configured for usage in a Power Sourcing Equipment (PSE) 1110 and a Powered Device (PD) 1108 coupled by a network cable 1106 in a configuration that transfers power and communication signals from the PSE 1110 to the PD 1108. The dynamic power management controllers 1 102 _P S _E and 1 102 _PD is configured to communicate power management information over the network cable 1106 at a Transmission Control Protocol / Internet Protocol (TCP/IP) layer and/or a Media Access Control (MAC) layer.

FIGURES 11A and 11 B show network systems using traditional power sourcing alternatives via a magnetic transformer coupling wherein power is transmitted over existing data-signal wire pairs and power is supplied through spare wires of a typical CAT-5 cable, respectively. In other embodiments, the magnetic transformers can be replaced with non-magnetic power supply circuitry, such as a T-Less Connect™ solid-state transformer.

At the Transmission Control Protocol / Internet Protocol (TCP/IP) layer, a dynamic power management controller 1102 _PD at the Powered Device (PD) 1108 can be configured to encode and send an Ethernet packet at the TCP/IP layer that requests a supply power level from a Power Sourcing Equipment (PSE) device 1110. The dynamic power management controller 1102 _PSE at the PSE 1110 can be configured to receive and decode the Ethernet packet and to

transmit power from the PSE 1110 to the requesting PD 1108 at a supply power level as directed by the decoded packet.

In some embodiments, the network system 1100 can operate in the Transmission Control Protocol / Internet Protocol (TCP/IP) layer whereby a dynamic power management controller 1102 _PD at the Powered Device (PD) 1108 can be configured to encode and send Type of Service (TOS) bits in a TCP/IP header of the TCP/IP layer to assign priority for traffic for statistical power management. The dynamic power management controller 1 102 _PSE at the Power Sourcing Equipment (PSE) 1110 can be configured to receive and decode the Type of Service (TOS) bits and enforce priority for traffic to one or more requesting Powered Devices (PD) 1108 using statistical power management.

In various embodiments of the network system 1100, a dynamic power management controller 1102 _PD at the Powered Device (PD) 1108 can be configured to encode an Ethernet packet at the Transmission Control Protocol / Internet Protocol (TCP/IP) layer and send the Ethernet packet to a Power Sourcing Equipment (PSE) device 1110 a request identifying one or more information items such as current PD operating power, anticipated PD operating power, PD device identification, PD device operating information, PD device priority assignment, and others. A dynamic power management controller 1102 _PSE at the PSE 1110 can decode the Ethernet packet and transmit power from the PSE 1110 to the requesting PD 1108 at a supply power level that is determined on the basis of the information item or items in the decoded Ethernet packet.

At the Media Access Control (MAC) layer, a dynamic power management controller 1102 _PD at the Powered Device (PD) 1108 can encode and send 8b/10b reserved codes at the Media Access Control (MAC) layer that request a demand- based power from a Power Sourcing Equipment (PSE) device 1110. A dynamic power management controller 1102 _PSE at the PSE 1110 can receive and decode the 8b/10b reserved codes and transmit demand-based power from the PSE 1110 to the requesting PD 1108 at a supply power level as specified by the decoded reserved codes.

At the physical layer, some embodiments of a dynamic power management controller 1102 _PD at the Powered Device (PD) 1108 can also send detection and classification information in multiple phases and cycles at the physical layer to the Power Sourcing Equipment (PSE) 1110. A dynamic power management controller 1102 _PSE at the PSE 1110 can further configured to receive the detection and classification information and send operational information from the PSE 1110 to the PD 1108 at the physical layer.

Referring to FIGURE 13, a block diagram illustrates traditional classification levels for a Power over Ethernet application of the IEEE 802.3af standard. The IEEE 802.3af standard defines classification for interactions between a Power Sourcing Equipment (PSE) and a Powered Device (PD). The PD supplies current/time in three phases for communicating detection via a 25Kω resistor and classification via a current from 2-14 milliamps. Classification, for example power demand classification, specifies the power demand for the PD, which may vary according to time and/or conditions. Detection indicates presence of the PD. The PSE senses current/time in three phases for sensing detection and classification of the PD and returns operational signals to the PD.

The IEEE 802.3af standard classes 0 through 4 are shown along with the PD response to Classification voltage in a range from 15.5 to 20.5 volts. The power sourcing equipment (PSE) raises the voltage to about 15.5 to 20.5V and the PD receives the signal in the range and sends out a current depending on the desired classification. The PSE identifies the classification range, responds with verification if appropriate and enters the selected operational mode in the IEEE 802.3af process for setting classification levels. The dynamic power management controllers 1102 _PD and 1102 _PSE can implement an enhanced classification scheme whereby classification can be extended to multiple cycles. For example, as shown in the block diagram of FIGURE 14 the levels defined using traditional IEEE 802.3af classification can be repeated a selected number N times to enable encoding of more information. Each classification cycle specifies four levels, supporting 4 ^N different classifications. The handshake scheme of IEEE 02.3af classification remains the same whereby the PD learns the PSE type and the PSE learns the PD type. The

multiple cycle operation and coding scheme avoids misidentification and enables a large number and expansion of classes.

In some embodiments, for example the illustrative embodiment, the Powered Device (PD) 1108 and the Power Sourcing Equipment (PSE) 1110 can be configured for Power-over-Ethernet (PoE) operation.

Referring to FIGURE 12A, a flow chart depicts an embodiment of a power management method 1200 that can be used in a Power-over-Ethernet application. The power management method 1200 comprises transmitting 1202 power from a Power Sourcing Equipment (PSE) to a Powered Device (PD) via a network cable. Signals are communicated 1204 bidirectionally between the PSE and the PD via the network cable. Power management information is also bidirectionally communicated 1206 over the network cable at a Transmission Control Protocol / Internet Protocol (TCP/IP) layer and/or a Media Access Control (MAC) layer. Referring to FIGURE 12B, a flow chart illustrates a particular embodiment of a power management method 1210 for application in the Transmission Control Protocol / Internet Protocol (TCP/IP) layer. At the Powered Device (PD) an Ethernet packet is encoded 1212 at the TCP/IP layer that requests a supply power level from a Power Sourcing Equipment (PSE) device. The Ethernet packet is sent 1214 from the PD to the PSE and the PSE receives 1216 the Ethernet packet. The PSE decodes 1218 the Ethernet packet and transmits 1219 power from the PSE to the requesting PD at a supply power level according to the decoded packet.

FIGURE 12C is a flow chart showing another embodiment of a power management method 1220 that also communicates via the TCP/IP layer. In the illustrative power management method 1220, the Powered Device (PD) encodes 1222 Type of Service (TOS) bits in a Transmission Control Protocol / Internet Protocol (TCP/IP) header of the TCP/IP layer to assign 1224 traffic priority for statistical power management. The PD sends 1225 the TCP/IP header with encoded TOS bits to the PSE. The PSE receives 1226 the TCP/IP header with the encoded TOS bits at the PSE and decodes 1227 the TOS bits. The PSE

enforces 1228 priority for traffic to one or more requesting PDs using statistical power management.

Referring to FIGURE 12D, a flow chart illustrates a further embodiment of a power management method 1230 that also communicates via the TCP/IP layer. In the illustrative power management method 1230, a Powered Device (PD) encodes 1232 an Ethernet packet at the Transmission Control Protocol / Internet Protocol (TCP/IP) layer and sends 1234 a request identifying one or more information items in the Ethernet packet to a Power Sourcing Equipment (PSE) device. The information items may include one or more of current PD operating power, anticipated PD operating power, PD device identification, PD device operating information, PD device priority assignment, or the like. The PSE receives 1235 and decodes 1236 the Ethernet packet, then transmits 1238 power from the PSE to the requesting PD at a supply power level as directed by the information item or items contained in the decoded Ethernet packet. Referring to FIGURE 12E, a flow chart illustrates a particular embodiment of a power management method 1240 for application in the Media Access Control (MAC) layer. A Powered Device (PD) encodes 1242 8b/10b reserved codes at the Media Access Control (MAC) layer that request 1243 a demand- based power from a Power Sourcing Equipment (PSE) device, then sends 1244 the 8b/10b reserved codes from the PD to the PSE. A PSE receives 1245 and decodes 1246 the 8b/10b reserved codes, then transmits 1248 demand-based power from the PSE to the requesting PD at a supply power level as directed according to the decoded reserved codes.

In some embodiments, in addition to the dynamic power management in the MAC layer and/or the TCP/IP layer the power management method can further be operative in the physical layer which implements static power management. FIGURE 12F is a schematic flow chart showing a power management method 1250 that further operates in the physical layer. The power management method 1250 further comprises sending 1252 detection and classification information in multiple phases and multiple cycles at a physical layer from the Powered Device (PD) to the Power Sourcing Equipment (PSE). The detection and classification information is received 1254 at the PSE. The

PSE sends 1256 operational information from the PSE to the PD at the physical layer.

The illustrative dynamic power management technique enables a wide variety of power allocation beyond the four levels of classification supported in standard IEEE 802.3 usage, and enables dynamic management without requiring a link to be terminated and restarted.

Dynamic power management also enables increases in demand of powered devices. Current standards support power at a defined level, for example 13 watts per port, while future standards may enable much higher power, such as 30 to 60 watts per port or likely higher power levels in the more extended future. For illustrative purposes, a system may include PDs that usually use 4 watts of power but occasionally use 13 watts. A static system would set power requirements to cover the maximum power level so that a ten port system with each port having a maximum power level of 13 watts would use a power supply sufficient for 130 watts.

Static power management may be tolerable for a maximum power of 13 watts per port. However, the new standard with 30 to 60 watts per port and 24 to 48 ports requires a very large power supply.

Dynamic power management enables higher demand devices in combinations with a large number of ports while using a power supply of reasonable size. Dynamic power management enables usage of a smaller power supply since, for average conditions, the maximum requirement need not be sourced. In conditions that demand of the PDs exceeds the size of the power source, the dynamic power management controller can insert a delay to extend the power demand spike over a selected time interval.

An illustrative design technique may supply sufficient power to support all ports at the average plus additional supply capacity to enable a sufficient number of ports to operate at full power. Communication between PSE and PD can be used to select a suitable power level for each port. The dynamic power management system can prioritize allocation of power among ports in the event of a conflict and communicate information between PSEs and PDs to implement the allocation. For example in one priority scheme,

the PSE is may manage 48 volts and all PDs send a request to increase power. With the Ethernet protocol an acknowledge (ACK) signal may be sent that indicates an inability to immediately increase power due to the current priority of allocation. In one scheme, the user PDs may define which devices have priority. Another scheme defines a TCP/IP frame with a Type of Service (TOS) bit which defines priority over network bandwidth to drop packets in congestive conditions. A packet with the lowest priority is dropped first. The same TOS priority scheme can be used so that if a power request exceeds the power supply then the lowest priority packet is dropped first. Accordingly, traffic can be maximized since if packets are dropped in a communication between PSE and PD, supply of power to the PD is likely superfluous.

An integrated circuit configured for coupling to lines between a network connector and an Ethernet physical layer (PHY) comprises a diode bridge and protection circuitry integrated onto a common integrated circuit whereby parasitics in an energy discharge path and stress on the PHY and the diode bridge are reduced.

One aspect of performance in a Power-over-Ethernet (PoE) system is immunity to over-voltage and surge events. The events can be caused by inductive coupling of external lightning events or simply by static electricity buildup on Ethernet cabling. The discharge of energy into sub-micron semiconductor devices can easily become destructive. Typically, expensive and ruggedized external components such as sidactors can be added to shield silicon-based devices from the stresses of external surge events. The external components typically have high capacitance and tend to degrade overall system performance in high speed communication links.

Integrating the diodes and protection circuitry enables a much faster response to a surge event, and hence permits the use of smaller, cheaper, lower voltage components.

Referring to FIGURE 15A, a schematic circuit and block diagram illustrates an embodiment of a network device 1500 comprising an integrated rectification and protection system 1502. The network device 1500 comprises a protection circuit 1504 configured for coupling to lines 1506 between a network

connector 1508 and an Ethernet physical layer (PHY) 1510. The protection circuit 1504 comprises a diode bridge 1512 and protection circuitry 1514 integrated onto a common integrated circuit 1516. The word "common" is defined herein as referring to commonality of integration of the diode bridge 1512 and the protection circuitry 1514 on a single integrated circuit chip 1516, and specifically is not used to indicate typical or conventional usage or functionality of the integrated circuit or for any other definition.

The protection circuit 1504 can be configured for coupling lines 1506 between the network connector 1508 and the Ethernet PHY 1510 that carry signal and power in a Power-over-Ethernet arrangement.

In the illustrative configuration, the protection circuit diode bridge 1512 is coupled to center taps 1518 of an Ethernet transformer 1520 coupled to the lines 1506 between the network connector 1508 and the Ethernet PHY 1510.

In the illustrative embodiment, the protection circuit 1504 can comprise the integrated diode bridge 1512 coupled between a supply line 1522 and a reference line 1524. The integrated protection circuitry 1514 is also coupled between the supply line 1522 and the reference line 1524. A power switch 1526 is coupled to the supply line 1522 and controlled by the protection circuitry 1514.

In the illustrative embodiment, the power switch 1526 is depicted as a p- channel power switch Metal Oxide Semiconductor Field-Effect Transistor

(MOSFET) that is coupled to the supply line 1522 and controlled by the protection circuitry 1514.

In some embodiments, for example as shown in FIGURE 15A, a Powered Device (PD) controller 1528 can be integrated into the protection circuit 1504 and coupled between the supply line 1522 and the reference line 1524.

In some embodiments, the network device 1500 can operate on power on the communication line, which is typical in a Power-over-Ethernet (PoE) arrangement. Accordingly, the network device 1500 can further comprise a power transformer 1530 coupled between the supply line 1522 and the reference line 1524. One or more capacitors 1532 can also be coupled between the supply line 1522 and the reference line 1524. A switch 1534 can be coupled to the reference line 1524. For the network device 1500 powered by the line, the

protection circuit 1504 further comprises the integrated diode bridge 1512 and the integrated protection circuitry 1514 coupled between a supply line 1522 and a reference line 1524. A power switch 1526 is coupled to the supply line 1522 and controlled by the protection circuitry 1514. A pulse width modulator 1536 integrated into the protection circuit 1504, coupled between the supply line 1522 and the reference line 1524, and configured to control the switch 1534.

In some embodiments, the network device 1500 can operate on power from a wall socket either as a sole power source or in combination with power obtained from the lines. For the network device 1500 powered from the wall socket, the protection circuit 1504 further comprises a wall jack power source 1538 and an Alternating Current (AC) charger 1540 coupled to the wall jack power source 1538 and coupled between the supply line 1522 and the reference line 1524. One or more capacitors 1542 can also be coupled between the supply line 1522 and the reference line 1524. A switch 1534 can be coupled to the reference line 1524. For the network device 1500 powered by the wall socket, the protection circuit 1504 further comprises the integrated diode bridge 1512 and the integrated protection circuitry 1514 coupled between a supply line 1522 and a reference line 1524. A power switch 1526 is coupled to the supply line 1522 and controlled by the protection circuitry 1514. Referring to FIGURE 15B, a schematic circuit and block diagram shows an embodiment of a network device 1550 with an integrated rectification and protection system 1552 adapted for usage with a T-Less Connect™ solid-state transformer 1554. The network device 1550 comprises a protection circuit diode bridge 1512 coupled to a T-Less Connect™ solid-state transformer 1554 coupled to the lines 1506 between the network connector 1508 and the Ethernet PHY 1510. The T-Less Connect™ solid-state transformer 1554 functions as a nonmagnetic transformer and choke circuit that separates Ethernet signals from power signals, for example by floating ground potential of the Ethernet PHY relative to earth ground. Referring again to FIGURE 15A, in accordance with another embodiment of a network device 1500, an integrated circuit 1516 configured for coupling to lines 1506 between a network connector 1508 and an Ethernet physical layer (PHY) 1510 comprising a diode bridge 1512 and protection circuitry 1514

integrated onto a common integrated circuit 1516 whereby parasitics in an energy discharge path and stress on the PHY 1510 and the diode bridge 1512 are reduced.

The network device 1500 can further comprise one or more capacitors 1542 coupled between the supply line 1522 and the reference line 1524. The integrated circuit 1516 comprises the integrated diode bridge 1512 coupled between the supply line 1522 and the reference line 1524, a p-channel power switch Metal Oxide Semiconductor Field-Effect Transistor (MOSFET) 1526 coupled to the supply line 1522, and the integrated protection circuitry 1514 coupled between the supply line 1522 and the reference line 1524. The integrated protection circuitry 1514 has a rail clamp control line 1544 coupled to the p-channel power switch MOSFET 1526 that turns on the p-channel power switch MOSFET 1526 hard in a surge condition whereby charge is redirected to a capacitor of the one or more capacitors 1542. The protection integrated circuit 1516 further includes a driver 1546 with an output terminal coupled to the rail clamp control line 1544 that drives the gate of the power switch 1526. A voltage surge that passes through the diode stack builds a voltage, the driver 1546 controls the power switch 1526 so that the protection circuitry 1514 takes the extra energy and drives the diode bridge 1512 harder to reduce the resistance for a short period of time on the power switch 1526. For an illustrative example, the power switch may be a 60V or 80V device whereby the voltage between the drain and source is 60V or 80V. The power switch 1526 turns on with a voltage of 3-5 volts applied to the gate. In response to an over-voltage surge, the driver 1546 can drive the power switch 1526 with a voltage applied to the gate of 8-10 volts, turning the power switch 1526 on very hard and reducing the on-resistance of the power switch 1526, thereby pushing the current through the capacitor 1542. In the illustrative embodiment, the power switch 1526 is positioned on the positive or source side of the power lines, contrary to more usual positioning of power switches on the ground or negative path. Placement of the power switch 1526 on the positive or source path presents a relative size cost since p-channel devices tend to be about 60% slower than n-channel devices. Therefore, in the illustrative embodiment the

power switch 1526 can be relatively large, for example on the order of twice as large as switches used for similar purposes.

Positioning of the power switch 1526 in the positive pathway enables the network device 1500 to be grounded at a common earth ground, which can improve performance since an over-voltage surge strikes to ground. Referring to FIGURE 15A, the modeled strike path includes a 330ω resistor that is the strike resistance and a 15OpF capacitor connected to earth ground. The protection integrated circuit 1516 couples to the taps of Ethernet transformer 1520, connected to the RJ45 connector 1508 where the strike passes. In some embodiments, the network device 1500 can comprise one or more capacitors 1542 coupled between the supply line 1522 and the reference line 1524. The integrated circuit 1516 comprises the integrated diode bridge 1512 and the integrated protection circuitry 1514 coupled between the supply line 1522 and the reference line 1524. A p-channel power switch MOSFET 1526 coupled to the supply line. The integrated circuit 1516 is configured whereby a high frequency strike short-circuits a capacitor of the capacitor or capacitors 1542 and passes to ground.

A current resulting from a surge condition passes through a diode in the integrated diode bridge 1512, causing the diode to ring. The current passes out to the tip and through to the power switch 1526 to the capacitor 1542, for example an 8OnF or 100 nF capacitor. High frequency oscillations applied to the capacitor 1542 short-circuit the integrated circuit 1504 and drive the high voltage to ground. Accordingly, a high frequency strike is canceled through the capacitor 1542 not though any electromagnetic or MOS-based devices, which would be too slow to turn on to address the surge. In comparison to an active device, the capacitor 1542 is always active with functionality simply dependent on frequency of applied signals. For example, at DC, the capacitor 1542 forms a completely open circuit. At highest frequencies, the capacitor 1542 is short-circuited.

In some embodiments, the network device 1500 can operate on power either from an Ethernet line or a wall socket. Accordingly, the network device 1500 can comprise both a power transformer 1530 and a wall jack power source 1538 coupled between the supply line 1522 and the reference line 1524. An AC

charger 1540 can be coupled to the wall jack power source 1538 and coupled between the supply line 1522 and the reference line 1524. One or more capacitors 1542 can also be coupled between the supply line 1522 and the reference line 1524. A switch 1534 can be coupled to the reference line 1524. For the network device 1500 powered by either the Ethernet line or the wall socket, the integrated circuit 1516 further comprises the integrated diode bridge 1512 and the integrated protection circuitry 1514 coupled between a supply line 1522 and a reference line 1524. A power switch 1526 is integrated into the integrated circuit 1516 and coupled to the supply line 1522. The power switch 1526 is controlled by the protection circuitry 1514. A pulse width modulator 1536 can be integrated into the integrated circuit 1516 and coupled between the supply line 1522 and the reference line 1524. The pulse width modulator 1536 configured to control the switch 1534.

Thus, the network device 1500, as a Power-over-Ethernet (PoE) device, can operate on power received from the communication lines or from a wall socket. If power is received from the lines, then the entire network device 1500 is floating so when hit with a hard ESD discharge or lightning strike the housing holding the device 1500 jumps in voltage but has no connection to ground other than a very high impedance path from insulation of the housing to ground. In contrast, when the network device 1500 is connected to a wall jack 1538, a reference voltage powers the device 1500 from a typical AC charger, such as can be used to power a laptop computer. The AC charger has an internal transformer that transforms 1 10 volts down to 12, 24, or 48 volts and rectifies the voltage. The AC charger also connects a capacitor, for example a 3nF capacitor, between the output terminal of the charger to ground.

For the network device 1500 inside the housing with the AC charger connected to the housing, upon occurrence of a lightning strike a surge passes through a capacitor, for example 30OpF, and a resistor, such as 330ω, and the capacitor is connected to earth ground. The moment the power switch 1526 is turned on to discharge the capacitor, the switch 1526 drives the surge through an earth ground capacitor, depicted as 3nF, which is technically a hard short circuit since the capacitor is very large at 3nF. Thus, the power switch 1526 enables formation of a hard short-circuit to ground without any intervening devices.

When the external AC power adapter is coupled to the device 1500, power can also be obtained from another source, such as the communication line. Therefore, a diode 1548 is coupled in series with the positive path so that the supply cannot be reversed. Positioning of the n-channel MOSFET power switch 1526 and the diode 1548 on the positive pathway is contrary to more common switch arrangements which place a switch and diode on the ground pathway. In the event of a lightning strike, the discharge passes through the p-channel power switch 1526 and the capacitor 1542, then through the ground pathway, through the large 3nF capacitor 1542 and to ground. Referring again to FIGURE 15A, an embodiment of a network device 1500 comprises an over-voltage protection integrated circuit 1516 that is configured for usage in a Power-over-Ethernet (PoE) application coupling to lines 1506 between a network connector 1508 and an Ethernet physical layer (PHY) 1510. The over- voltage protection integrated circuit 1516 comprises a diode bridge 1512 and an integrated protection circuitry 1514, both integrated into the over-voltage protection integrated circuit 1516 and coupled between the supply line 1522 and the reference line 1524. A power switch 1526 is integrated into the over-voltage protection integrated circuit 1516 coupled to the supply line 1522 and is controlled by the protection circuitry 1514. In some embodiments, the power switch 1526 can be a p-channel power switch MOSFET.

In some embodiments, the over-voltage protection integrated circuit 1516 can further comprise a Powered Device (PD) controller 1528 integrated into the over-voltage protection circuit 1516 and coupled between the supply line 1522 and the reference line 1524. In the illustrative embodiment, the diode bridge 1512 coupled to center taps 1518 of an Ethernet transformer 1520 coupled to the lines between the network connector 1508 and the Ethernet PHY 1510.

In some embodiments, for example as depicted in FIGURE 15B, the diode bridge 1512 can be coupled to a T-Less Connect™ solid-state transformer coupled to the lines 1506 between the network connector 1508 and the Ethernet PHY 1554.

Referring to FIGURES 16A and 16B, several schematic flow charts depict embodiments of a method 1600 for rectification and surge protection in a Power- over-Ethernet application. As shown in FIGURE 16A, the method 1600 for over- voltage protection in a network device comprises integrating 1602 a diode bridge and protection circuitry into a single or common integrated circuit. A supply line and a reference line are formed 1604 in the integrated circuit. The diode bridge and the protection circuitry are coupled 1606 between the supply line and the reference line. A power switch is integrated 1608 into the common integrated circuit and coupled 1610 to the supply line. The power switch is controlled 1612 via the protection circuitry.

Referring to FIGURE 16B, a method 1620 may further comprise actions of coupling 1622 the single or common integrated circuit to lines between a network connector and an Ethernet PHY whereby parasitics are reduced 1624 in an energy discharge path, reducing 1626 stresses on the Ethernet PHY and the diode bridge.

In a typical embodiment, the method can be used to protect against over- voltage in a Power-over-Ethernet (PoE) configuration.

Referring to FIGURE 17, a schematic block and circuit diagram illustrates a non-integrated rectification and protection circuit 1700. The typical circuit 1700 has a discrete breakdown device 1714 outside a PD control circuit 1728 to clamp the surge voltage and form a large current path for the surge to ground. The discrete breakdown device 1714 can be a typical standalone protection circuit. The surge path is around the PD Controller 1728, having the disadvantage that key protective components are dependant on board parasitic and layouts which can vary, making consistent performance difficult. In contrast, the network devices 1500 and 1550 have the diode bridge 1512 and protection circuitry 1514 integrated along with the PD controller 1528 and power switch 1526, all of which play a critical role in determining how the high current due to a surge event is discharged. Lighting strike and large voltage surges are generally modeled as a capacitor charged to a high voltage and then discharged through a resistor. The values of the capacitor (C) and resistor (R) determine the type of energy burst

that will occur on the device under test (DUT). If the RC time is small, the currents are generally high and last for a short time frame. If the If the RC time is larger, the currents are generally lower, but last for a longer time frame.

In an illustrative example such as the case of contact discharge, a 150pf capacitor can be charged to 8000V relative to earth ground and is connected to one of the RJ45 pins via a 330 ohm resistor. Peak discharge currents can be as large as 25A. In a positive strike on RJ 1 , Diode 2 (D2) will forward bias and discharge into the clamping circuit through the return path into earth ground. Any parasitic resistance due to the bond wire, skin effect, or board traces significantly increase the voltage spike across the terminals of the protection circuitry. The parasitic resistances Rp1-4 on the contact and board trace, board trace inductances Lp1 -2 and the packaged diode bond inductances are modeled in FIGURE 17. A wave front time constant of the surge event is typically 6ns, so that small changes in device reaction time can cause large changes in voltage events.

Referring again to FIGURE 17, the protection circuitry 1714 and PD controller 1728 are typically implemented in ruggedized high voltage circuitry and are less susceptible to over-voltage than the Ethernet PHY 1710, which is typically implemented in sensitive, sub-micron process. Hence, the protection circuitry 1714 is constructed to absorb most of the charge while developing a small voltage across the PHY terminals and ensuring that the bridge diodes are not subjected to large voltage excursions that exceed specified ratings. Since Power-over-Ethernet operates from a typical 48V supply, voltage excursions are added to the 48V supply, making challenging to remain below the diode reverse bias voltage rating.

As shown in the voltage waveforms depicted in FIGURE 18C, after the switch is closed discharging the 8kV charge into the circuit, a severe ringing in the voltage results across the external bridge diodes than can reach voltages in excess of 120V. Parasitic resistance and inductances largely contribute to the ringing. If board parasitics are higher, a likely possibility since the selected model shown is somewhat optimistic, voltages on the external diodes can rise even higher than 120V. With 25A surging through the board at high frequencies, for

example in a 1 nanosecond wave front, and the combined influence of skin effects, an additional 1 ω resistance can add 25V to the diode voltage.

Referring to FIGURE 18A, a graph depicts Voltage Stress waveforms resulting for over-voltage on the discrete circuit shown in FIGURE 17. The PHY voltage is approximately 1 1 .5V with some ringing. The internal supplies VDD48 rise up from 48V nominal value to about 54V, voltage at which most external sidactors/surge suppressors are not turned on since the turn-on voltage is approximately 70V. Accordingly, the sidactors/surge suppressors do not supply any protection. A sidactor becomes operational to protect a circuit at a particular voltage, for example 60 to 72 volts but is susceptible to high frequency strikes in a very fast event lasting about a nanosecond. For example, contact discharge strike of 15000 volts can be so fast that sidactor protection fails, whereby the sidactor does not turn on fast enough and the voltage can shoot high above the specified level, resulting in passage of up to hundreds of volts before sidactor activation. In contrast, a sidactor is effective for protecting against a surge or lightning strike which is much slower and lasts longer than a contact discharge, for example lasting 20 to 40 nanoseconds, due to higher energy, for example imposing a surge in the range of thousands of volts. In response to a surge such as a lightning strike, the sidactors turn on and clamp the voltage to a set maximum such as 72 volts, drawing and dissipating energy from the current path.

Referring to FIGURE 18B, a graph depicts Current Stress waveforms in an over-voltage condition on the discrete circuit shown in FIGURE 17. In the current waveforms in FIGURE 18B, the contact discharge current of approximately 25A is the strike current surging through the 330ω resistor once the switch is closed. About 12 Amps flows though the external 8OnF capacitor wherein the total capacitance is 10OnF, with a capacitor C2, for example 2OnF, internal to the PD controller. Approximately 2 Amps flow into the PHY clamp circuit and the power switch M1 which is presumed to be enabled takes 5 Amps. FIGURE 18C, a graph shows Voltage Stress waveforms in an over-voltage condition on the discrete circuit depicted in FIGURE 17 including positive and negative strikes. Waveforms indicate positive and negative strikes that place a

large stress on the external bridge diodes. Negative strikes are shunted to the ground return path through the diode path D5.

Referring again to FIGURES 15A and 15B in combination with graphs in FIGURES 19A, 19B, and 19C, over-voltage protection performance is shown for the integrated diode bridge 1512 and protection circuitry 1514 system for comparison to the non-integrated system depicted in FIGURE 17 and associated graphs in FIGURES 18A through 18C. As shown in FIGURES 19A, 19B, and 19C, integrating the diode bridge 1512 and protection circuitry 1514 significantly reduces parasitics in the energy discharge path and reduces stress applied to the PHY 1510 and the diode bride 1512. The integrated combination enables a lower impedance path for the surge current, thus reducing the voltage build-up with high currents. A 62V rail clamp can also be used turn on the P-Channel Power Switch MOSFET 1526 hard thus adding an alternate path for the charge to go through the 4.7uF capacitor, a path that is more useful in lighting strikes, where the time constants are longer.

The integrated circuit 1516 is configured to constrain the maximum possible voltage that can be imposed across the diodes, enabling usage of reasonably-sized diodes while avoiding damage or destruction under conditions of a large voltage surge. Integration of the diode bridge 1512 and the protection circuitry 1514 substantially eliminates circuit board and bonding package parasitics of the diodes and other components in a non-integrated implementation that is susceptible to very fast transients and contact discharge into a voltage pulse that can cause high frequency ringing at voltages as large as 120 or 150 volts or more, or even 180 to 200 volts for implementations with too close spacing of components.

Integration of the diode bridge 1512 and the protection circuitry 1514 also can substantially eliminate parasitic oscillations that result from dynamic current changes on circuit traces in a non-integrated implementation and the voltage which rapidly can arise on the traces. The voltage resulting from resistance on the traces can add substantially to the voltage on the line, for example increasing voltage by up to half or more of the line signal, not including ringing or overshoots that can occur due to the inductive nature of the circuit.

FIGURE 19A is a graph illustrating Voltage Stress waveforms in an over- voltage condition during operation of the protection circuit 1504 including the integrated diode bridge 1512 and protection circuitry 1514. The integrated design reduces the over-voltage strike stress across input terminals to the diodes by as much as 50%, to about 55V.

FIGURE 19B is a graph illustrating Current Stress waveforms in an over- voltage condition during operation of the protection circuit 1504 including the integrated diode bridge 1512 and protection circuitry 1514. As shown in the current waveforms in FIGURE 19B, about 13 Amps of the strike current flows though the external capacitor C1 , for example an 8OnF capacitor. In the illustrative configuration, the total capacitance is 100nf with 2OnF internal to the PD controller 1528. Approximately 2 Amps flow into the PHY clamp circuit and the power switch M1 takes 5.5 Amps, improving reliability of the PHY 1510 under ESD and surge stress events. FIGURE 19C is a graph illustrating Voltage Stress waveforms in an over- voltage condition for positive and negative strikes during operation of the protection circuit 1504 including the integrated diode bridge 1512 and protection circuitry 1514.

In summary, comparing the waveforms in FIGURES 19A through 19C for the integrated protection circuit 1504 to waveforms in FIGURES 18A through 18C for a non-integrated system, integrating the diode bridge 1512 and protection circuitry 1514 significantly increases the reaction time of protection devices and increases PHY immunity to over-voltage stress events. Integrating the components also substantially reduces board-to-board variation and increases overall manufacturability.

As shown in the examples depicted by the graphs, the integrated diode configuration has lower peak diode voltages, for example 57V as compared to 120V. The integrated diode arrangement has lower peak electrostatic discharge (ESD) clamp voltages, shown as 10V in comparison to 1 1 .5V. The integrated diode system has lower ESD clamp currents of 1.8A compared to 2.6A. The integrated diode configuration more effectively uses the switch to control excursions, an Iswitch of 5.22A in comparison to 4.03A.

The protection circuit 1504 with integration of the diode bridge 1512 and the protection circuitry 1514 is configured whereby high frequency ringing is reduced or eliminated.

Diodes in the diode bridge 1712 in the non-integrated implementation propagate high frequency ringing as the non-integrated diodes set up a current through the diodes that tends to be capacitive in behavior. A very high frequency pulse passing through the diode tends to have an inductive behavior, creating even more ringing on the diode. Thus in addition to external parasitic oscillations, inductance also aggravates the ringing. The diodes become inductive and, when inductive, create an even higher ringing. The integrated protection circuit 1504 avoids the high frequency ringing of non-integrated diodes which are highly sensitive to surges.

Performance shown in the illustrative examples is expected to be improved even further by implementation of switch gate controls from the Rail clamp.

The illustrative network device 1500, the diode bridge 1512 and protection circuitry 1514 are integrated into the protection circuit 1504 at least partly in recognition that for high frequency events, the sidactor used in non-integrated designs does not turn on with sufficient quickness to address various types of over-voltage. The integrated protection circuit 1504 is formed to pass current through the circuit as quickly as possible. One aspect of integrated circuit operation is that a high frequency oscillation resulting from an over-voltage condition is canceled by passing through a capacitor. Another aspect of integrated circuit operation is usage of a power switch 1526 on the positive or supply side of the integrated circuit 1516 that is a relatively large active device.

The IEEE 802.3 Ethernet Standard, which is incorporated herein by reference, addresses loop powering of remote Ethernet devices (802.3af). Power over Ethernet (PoE) standard and other similar standards support standardization of power delivery over Ethernet network cables to power remote client devices through the network connection. The side of link that supplies power is called Powered Supply Equipment (PSE). The side of link that receives power is the Powered device (PD). Other implementations may supply power to network

attached devices over alternative networks such as, for example, Home Phoneline Networking alliance (HomePNA) local area networks and other similar networks. HomePNA uses existing telephone wires to share a single network connection within a home or building. In other examples, devices may support communication of network data signals over power lines.

In various configurations described herein, a magnetic transformer of conventional systems may be eliminated while transformer functionality is maintained. Techniques enabling replacement of the transformer may be implemented in the form of integrated circuits (ICs) or discrete components. FIGURE 1A is a schematic block diagram that illustrates a high level example embodiment of devices in which power is supplied separately to network attached client devices 112 through 116 that may benefit from receiving power and data via the network connection. The devices are serviced by a local area network (LAN) switch 110 for data. Individual client devices 112 through 116 have separate power connections 118 to electrical outlets 120. FIGURE 1 B is a schematic block diagram that depicts a high level example embodiment of devices wherein a switch 110 is a power supply equipment (PSE)-capable power- over Ethernet (PoE) enabled LAN switch that supplies both data and power signals to client devices 112 through 116. Network attached devices may include a Voice Over Internet Protocol (VOIP) telephone 112, access points, routers, gateways 114 and/or security cameras 116, as well as other known network appliances. Network supplied power enables client devices 112 through 116 to eliminate power connections 118 to electrical outlets 120 as shown in FIGURE 1A. Eliminating the second connection enables the network attached device to have greater reliability when attached to the network with reduced cost and facilitated deployment.

Although the description herein may focus and describe a system and method for coupling high bandwidth data signals and power distribution between the integrated circuit and cable that uses transformer-less ICs with particular detail to the IEEE 802.3af Ethernet standard, the concepts may be applied in non-Ethernet applications and non-IEEE 802.3af applications. Also, the concepts may be applied in subsequent standards that supersede or complement the IEEE 802.3af standard.

Various embodiments of the depicted system may support solid state, and thus non-magnetic, transformer circuits operable to couple high bandwidth data signals and power signals with new mixed-signal IC technology, enabling elimination of cumbersome, real-estate intensive magnetic-based transformers. Typical conventional communication systems use transformers to perform common mode signal blocking, 1500 volt isolation, and AC coupling of a differential signature as well as residual lightning or electromagnetic shock protection. The functions are replaced by a solid state or other similar circuits in accordance with embodiments of circuits and systems described herein whereby the circuit may couple directly to the line and provide high differential impedance and low common mode impedance. High differential impedance enables separation of the physical layer (PHY) signal from the power signal. Low common mode impedance enables elimination of a choke, allowing power to be tapped from the line. The local ground plane may float to eliminate a requirement for 1500 volt isolation. Additionally, through a combination of circuit techniques and lightning protection circuitry, voltage spike or lightning protection can be supplied to the network attached device, eliminating another function performed by transformers in traditional systems or arrangements. The disclosed technology may be applied anywhere transformers are used and is not limited to Ethernet applications.

Specific embodiments of the circuits and systems disclosed herein may be applied to various powered network attached devices or Ethernet network appliances. Such appliances include, but are not limited to VoIP telephones, routers, printers, and other similar devices. Referring to FIGURE 2, a functional block diagram depicts an embodiment of a network device 200 including a T-Less Connect™ solid-state transformer. The illustrative network device comprises a power potential rectifier 202 adapted to conductively couple a network connector 232 to an integrated circuit 270, 272 that rectifies and passes a power signal and data signal received from the network connector 232. The power potential rectifier 202 regulates a received power and/or data signal to ensure proper signal polarity is applied to the integrated circuit 270, 272.

The network device 200 is shown with the power sourcing switch 270 sourcing power through lines 1 and 2 of the network connector 232 in combination with lines 3 and 6.

In some embodiments, the power potential rectifier 202 is configured to couple directly to lines of the network connector 232 and regulate the power signal whereby the power potential rectifier 202 passes the data signal with substantially no degradation.

In some configuration embodiments, the network connector 232 receives multiple twisted pair conductors 204, for example twisted 22-26 gauge wire. Any one of a subset of the twisted pair conductors 204 can forward bias to deliver current and the power potential rectifier 202 can forward bias a return current path via a remaining conductor of the subset.

FIGURE 2 illustrates the network interface 200 including a network powered device (PD) interface and a network power supply equipment (PSE) interface, each implementing a non-magnetic transformer and choke circuitry. A powered end station 272 is a network interface that includes a network connector 232, non-magnetic transformer and choke power feed circuitry 262, a network physical layer 236, and a power converter 238. Functionality of a magnetic transformer is replaced by circuitry 262. In the context of an Ethernet network interface, network connector 232 may be a RJ45 connector that is operable to receive multiple twisted wire pairs. Protection and conditioning circuitry may be located between network connector 232 and non-magnetic transformer and choke power feed circuitry 262 to attain surge protection in the form of voltage spike protection, lighting protection, external shock protection or other similar active functions. Conditioning circuitry may be a diode bridge or other rectifying component or device. A bridge or rectifier may couple to individual conductive lines 1-8 contained within the RJ45 connector. The circuits may be discrete components or an integrated circuit within non-magnetic transformer and choke power feed circuitry 262. In an Ethernet application, the IEEE 802.3af standard (PoE standard) enables delivery of power over Ethernet cables to remotely power devices. The portion of the connection that receives the power may be referred to as the

powered device (PD). The side of the link that supplies power is called the power sourcing equipment (PSE).

In the powered end station 272, conductors 1 through 8 of the network connector 232 couple to non-magnetic transformer and choke power feed circuitry 262. Non-magnetic transformer and choke power feed circuitry 262 may use the power feed circuit and separate the data signal portion from the power signal portion. The data signal portion may then be passed to the network physical layer (PHY) 236 while the power signal passes to power converter 238.

If the powered end station 272 is used to couple the network attached device or PD to an Ethernet network, network physical layer 236 may be operable to implement the 10 Mbps, 100 Mbps, and/or 1 Gbps physical layer functions as well as other Ethernet data protocols that may arise. The Ethernet PHY 236 may additionally couple to an Ethernet media access controller (MAC). The Ethernet PHY 236 and Ethernet MAC when coupled are operable to implement the hardware layers of an Ethernet protocol stack. The architecture may also be applied to other networks. If a power signal is not received but a traditional, non-power Ethernet signal is received the nonmagnetic power feed circuitry 262 still passes the data signal to the network PHY.

The power signal separated from the network signal within non-magnetic transformer and choke power feed circuit 262 by the power feed circuit is supplied to power converter 238. Typically the power signal received does not exceed 57 volts SELV (Safety Extra Low Voltage). Typical voltage in an Ethernet application is 48-volt power. Power converter 238 may then further transform the power as a DC to DC converter to provide 1.8 to 3.3 volts, or other voltages specified by many Ethernet network attached devices.

Power-sourcing switch 270 includes a network connector 232, Ethernet or network physical layer 254, PSE controller 256, non-magnetic transformer and choke power supply circuitry 266, and possibly a multiple-port switch. Transformer functionality is supplied by non-magnetic transformer and choke power supply circuitry 266. Power-sourcing switch 270 may be used to supply power to network attached devices. Powered end station 272 and power sourcing switch 270 may be applied to an Ethernet application or other network-

based applications such as, but not limited to, a vehicle-based network such as those found in an automobile, aircraft, mass transit system, or other like vehicle. Examples of specific vehicle-based networks may include a local interconnect network (LIN), a controller area network (CAN), or a flex ray network. All may be applied specifically to automotive networks for the distribution of power and data within the automobile to various monitoring circuits or for the distribution and powering of entertainment devices, such as entertainment systems, video and audio entertainment systems often found in today's vehicles. Other networks may include a high speed data network, low speed data network, time-triggered communication on CAN (TTCAN) network, a J1939-compliant network,

ISO1 1898-compliant network, an ISO1 1519-2-compliant network, as well as other similar networks. Other embodiments may supply power to network attached devices over alternative networks such as but not limited to a HomePNA local area network and other similar networks. HomePNA uses existing telephone wires to share a single network connection within a home or building.

Alternatively, embodiments may be applied where network data signals are provided over power lines.

Non-magnetic transformer and choke power feed circuitry 262 and 266 enable elimination of magnetic transformers with integrated system solutions that enable an increase in system density by replacing magnetic transformers with solid state power feed circuitry in the form of an integrated circuit or discreet component.

In some embodiments, non-magnetic transformer and choke power feed circuitry 262, network physical layer 236, power distribution management circuitry 254, and power converter 238 may be integrated into a single integrated circuit rather than discrete components at the printed circuit board level. Optional protection and power conditioning circuitry may be used to interface the integrated circuit to the network connector 232.

The Ethernet PHY may support the 10/100/1000 Mbps data rate and other future data networks such as a 10000 Mbps Ethernet network. Non-magnetic transformer and choke power feed circuitry 262 supplies line power minus the insertion loss directly to power converter 238, converting power first to a 12V supply then subsequently to lower supply levels. The circuit may be implemented

in any appropriate process, for example a 0.18 or 0.13 micron process or any suitable size process.

Non-magnetic transformer and choke power feed circuitry 262 may implement functions including IEEE 802.3. af signaling and load compliance, local unregulated supply generation with surge current protection, and signal transfer between the line and integrated Ethernet PHY. Since devices are directly connected to the line, the circuit may be implemented to withstand a secondary lightning surge.

For the power over Ethernet (PoE) to be IEEE 802.3af standard compliant, the PoE may be configured to accept power with various power feeding schemes and handle power polarity reversal. A rectifier, such as a diode bridge, a switching network, or other circuit, may be implemented to ensure power signals having an appropriate polarity are delivered to nodes of the power feed circuit. Any one of the conductors 1 , 4, 7 or 3 of the network RJ45 connection can forward bias to deliver current and any one of the return diodes connected can forward bias to form a return current path via one of the remaining conductors. Conductors 2, 5, 8 and 4 are connected similarly.

Non-magnetic transformer and choke power feed circuitry 262 applied to PSE may take the form of a single or multiple port switch to supply power to single or multiple devices attached to the network. Power sourcing switch 270 may be operable to receive power and data signals and combine to communicate power signals which are then distributed via an attached network. If power sourcing switch 270 is a gateway or router, a high-speed uplink couples to a network such as an Ethernet network or other network. The data signal is relayed via network PHY 254 and supplied to non-magnetic transformer and choke power feed circuitry 266. PSE switch 270 may be attached to an AC power supply or other internal or external power supply to supply a power signal to be distributed to network-attached devices that couple to power sourcing switch 270. Power controller 256 within or coupled to non-magnetic transformer and choke power feed circuitry 266 may determine, in accordance with IEEE standard 802.3af, whether a network-attached device in the case of an Ethernet network-attached device is a device operable to receive power from power supply equipment. When determined that an IEEE 802.3af compliant powered device

(PD) is attached to the network, power controller 256 may supply power from power supply to non-magnetic transformer and choke power feed circuitry 266, which is sent to the downstream network-attached device through network connectors, which in the case of the Ethernet network may be an RJ45 receptacle and cable.

IEEE 802.3af Standard is to fully comply with existing non-line powered Ethernet network systems. Accordingly, PSE detects via a well-defined procedure whether the far end is PoE compliant and classify sufficient power prior to applying power to the system. Maximum allowed voltage is 57 volts for compliance with SELV (Safety Extra Low Voltage) limits.

For backward compatibility with non-powered systems, applied DC voltage begins at a very low voltage and only begins to deliver power after confirmation that a PoE device is present. In the classification phase, the PSE applies a voltage between 14.5V and 20.5V, measures the current and determines the power class of the device. In one embodiment the current signature is applied for voltages above 12.5V and below 23 Volts. Current signature range is 0-44mA.

The normal powering mode is switched on when the PSE voltage crosses 42 Volts where power MOSFETs are enabled and the large bypass capacitor begins to charge. A maintain power signature is applied in the PoE signature block - a minimum of 10mA and a maximum of 23.5kohms may be applied for the PSE to continue to feed power. The maximum current allowed is limited by the power class of the device (class 0-3 are defined). For class 0, 12.95W is the maximum power dissipation allowed and 400ma is the maximum peak current. Once activated, the PoE will shut down if the applied voltage falls below 30V and disconnect the power MOSFETs from the line.

Power feed devices in normal power mode provide a differential open circuit at the Ethernet signal frequencies and a differential short at lower frequencies. The common mode circuit presents the capacitive and power management load at frequencies determined by the gate control circuit.

Terms "substantially", "essentially", or "approximately", that may be used herein, relate to an industry-accepted tolerance to the corresponding term. Such

an industry-accepted tolerance ranges from less than one percent to twenty percent and corresponds to, but is not limited to, component values, integrated circuit process variations, temperature variations, rise and fall times, and/or thermal noise. The term "coupled", as may be used herein, includes direct coupling and indirect coupling via another component, element, circuit, or module where, for indirect coupling, the intervening component, element, circuit, or module does not modify the information of a signal but may adjust its current level, voltage level, and/or power level. Inferred coupling, for example where one element is coupled to another element by inference, includes direct and indirect coupling between two elements in the same manner as "coupled".

While the present disclosure describes various embodiments, these embodiments are to be understood as illustrative and do not limit the claim scope. Many variations, modifications, additions and improvements of the described embodiments are possible. For example, those having ordinary skill in the art will readily implement the steps necessary to provide the structures and methods disclosed herein, and will understand that the process parameters, materials, and dimensions are given by way of example only. The parameters, materials, and dimensions can be varied to achieve the desired structure as well as modifications, which are within the scope of the claims. Variations and modifications of the embodiments disclosed herein may also be made while remaining within the scope of the following claims. For example, various aspects or portions of a network interface are described including several optional implementations for particular portions. Any suitable combination or permutation of the disclosed designs may be implemented.