CLAIM: OF PRIORITY

This application claims the benefit of U.S. Provisional Patent Application Serial No. 62/137,350, titled ELECTROMAGNETIC INTERFERENCE (EMI) CONTROL FOR DEVICE CHARGERS, to William Dale Tischer, filed on March 24, 2015; U.S. Provisional Patent Application Serial No. 62/134,213, titled SYSTEMS AND METHODS FOR LIMITING LEAKAGE CURRENTS IN A CHARGING DEVICE, invented by William Dale Tischer, filed on March 17, 2015; and U.S. Provisional Patent Application Serial No. 62/132,573, titled REVERSE CHARGING PROTECTION FOR DEVICE CHARGER, to Wi Hi am Dale Tischer, filed on March 13, 2015, and the entire contents of each being incorporated herein by reference.

TECHNICAL FIELD

This disclosure generally relates to charging systems for portable electronic devices.

BACKGROUND

Portable electronic devices can be charged using a cable connected between the portable electronic device and a charging port provided by a charging enclosure, e.g., charging cart, wall -mounted charger, desktop charger, or other enclosures designed to securely charge or charge and manage, e.g., wirelessly or wired through LTSB or other connected protocols, the portable electronic device or devices. The charging enclosures can house multiple devices, but a singular device charger can also be included in the possible solutions to charging portable electronic devices.

To control electromagnetic emission and immunity, the cables used to attach to the portable electronic devices ca include a shield between the devices and the charger. The cable shield can include an aluminum foil surrounding 100%» of the power and/ or data conductors. The foil, however, can be physically weak. To impro ve the physical strength of the foil, manufacturers can cover it with a metal braid that does not cover 100% of the foil . The braid can be used to couple the cable shield to two connector housings (one on each end of the cable) in a mechanically secure manner that the foil does not provide on its own.

In addition, a drain wire may be included to aid in providing a low- impedance shield path for higher currents induced by strong magnetic fields. The shielded cable can attach to the electronic device through the connector, thereby providing a full 360-degree shielding solution for the device to reduce electromagnetic emissions and improve its immunity characteristics to electromagnetic interference, e.g., radiated emissions, electrical fast transients, electrostatic discharge (ESD), etc.

Portable electronic devices are typically charged using a cable connected between the portable electronic device and a charging port provided by a device charger designed to securely charge or charge and manage (wirelessly or through USB or other connected protocols) the portable electronic device or devices. The charging enclosure can house one or more devices.

The cables used to attach the charging port of the device charger to the portable electronic device typically use locking tabs, friction between the contacts of the cable and the device, or friction between a connector housing and a device connector shell to secure the cable to the device. In many cases, the device connector is polarized such that the cable can only be attached in such a way as to not reverse polarize the power connection going to the device for charging. If polarization were not provided, damage to the electronics, battery, or property could result depending on the batter}- technology and the amount of energy being provided by the charger and any fire-prevention method of the enclosure (flame retardant plastics, metal enclosure, etc.) But, because the connector of the cable used for charging is provided with polarizing features, the possibility of the user connecting the cable incorrectly to the portable electronic device is not normally possible.

This may not be the case for portable electronic device chargers that rely on a contact-only method for connecting the device charger to the portable electronic device. These devices can have contact pads on the sides or other faces of the portable electronic de vice that, when positioned in proximity to a spring pin attached to the device charger, can make contact using the pressure applied by spring force between the pin and the pad on the portable electronic device. Gravity applied to the portable electronic device or other forces can cause the spring pin to compress and apply the correct force to allow a low- resistance contact with the portable electronic device and charger. A benefit to the user is that the spring and contact method can allow quick insertion and removal of the portable electronic device from the charging cart, charging wall- mount unit, or charging desktop unit; there are no cables for the user to plug and unplug, which can be especially cumbersome in large charging carts where there can be numerous devices, e.g., 48 or more devices, to plug and unplug.

For each electronic device to be charged, the charging device ca include a power supply that converts the AC wall voltage, e.g., 120 or 230 VAC, to a lower DC voltage enabling the portable device to power and charge. These power supplies typically include common mode and differential mode filter capacitors connected across the Line and Neutral AC input connections and possibly additional capacitors from Line and Neutral to Earth ground. These capacitors connected across Line and Neutral are called "X" capacitors

(differential mode) and the capacitors connected from Line and Neutral to Earth ground are called "Y" capacitors (common mode).

The X and Y capacitors can be used to provide protection against electromagnetic interference (EMI) generated by portable electronic devices and power supplies. If not provided, the el ectromagnetic interference can exceed the limits for emissions determined and enforced by the Federal Communication Commission (FCC) in the U.S. and similar regulator ' agencies in other countri es. Because of this, almost all portable electronic device power supplies will have these X and Y capacitors.

Along with the need to filter electromagnetic interference, e.g., from the power cord of the portable electronic device power supplies, there is a need to minimize the l eakage current that can develop as a result of the X and Y capacitors. To improve electromagnetic capability (EMC) filtering, more capacitance can be added to the X and Y capacitors, but then higher leakage current can result. OVERVIEW

With typical power and data connections between portable electronic devices and charging/syncing systems, the cable system can include a shielded connection encapsulating the entire cable. The two end connectors can be shielded and the cable itself can be shielded and connected with a full 360- degree termination around the connectors. Portable electronic devices can include portable computing devices, laptops, tablets, cell phones, pages, radios, cameras, and other devices.

This may not be possible with no-cable or contact-only, e.g., spring pin contacts, charging techniques. With no-cable or contact-only connections, there is no back shell to make contact with the portable electronic device or the completion of the shield to control electromagnetic emission (EMC) and electromagnetic immunity (EMI). This disclosure describes techniques that can control EMC/ EMI in a no-cable or contact-only charger, e.g., charging cart, charging wall-mount, or charging desktop module.

The present inventor has also recognized, among other things, that a problem to be solved that can occur with no-cable (or cable-less) charging can include the possibility of inserting the portable electronic device into the device charger, such as a charging cart or a charging cabinet, e.g., a wall-mounted charger, desktop charger, or other enclosures (a plurality of lockers), such that the tablet or other portable electronic device is inserted in reverse position compared to the desired direction of the device. Various techniques of this disclosure can help provide a solution to this problem of reverse polarity can include, for example, providing a reverse charging protection for the charging ports within the charging device, e.g., charging cart, charging wall-mount, or charging desktop device.

Along with the need to prevent/reduce EMI, filter electromagnetic interference, and prevent reverse polarity, e.g., from the power cord of the portable electronic device power supplies, the present inventor has recognized a need to minimize leakage current in a charging system that can develop as a result of the X and Y capacitors. To improve electromagnetic capability (EMC) filtering, more capacitance can be added to the X and Y capacitors, but then higher leakage current can result. Charging stations can benefit by having a balance between maximizing filtering and minimizing leakage current. To further illustrate the ELECTROMAGNETIC INTERFERENCE CONTROL FOR DEVICE CHARGERS disclosed herein, a non-limiting list of examples is provided here:

In Example 1, a cable can comprise: a first conductor having a first end and a second end; a first contact connected to the first end of the first conductor; a second conductor having a first end and a second end; a second contact connected to the first end of the second conductor; a shield material disposed about the first conductor and the second conductor, the shield material having a first end and a second end, wherein the first end of the first conductor and the first end of the second conductor extend beyond the first end of the shield material; and a third conductor having a first end and a second end, wherein the first end is connected to the shield material and the second end is connected to at least one of the first conductor, the second conductor, the first contact, and the second contact.

In Example 2, the cable of Example 1 can optionally be configured such that the third conductor has a length extending from the first end to the second end, the length is between .5 and 20 mm.

In Example 3, the cable of any one or any combination of Examples 1-2 can optionally be configured such that the third conductor has a length extending from the first end to the second end, the length is between .5 and 3 mm.

In Example 4, the cable of any one or any combination of Exampl es 1 -3 can optionally be configured such that the third conductor has a length extending from the first end to the second end, the length is less than 1.5 mm.

In Example 5, the cable of any one or any combination of Examples 1-4 can optionally be configured such that the second end of the third conductor is connected to the first conductor and the first conductor has a negative polarity.

In Example 6, the cable of any one or any combination of Examples 1 -5 can optionally be configured to further comprise a connector coupled to the second end of the shield material.

In Example 7, the cable of Example 6 can optionally be configured such that the connector is configured to couple to an earth ground.

In Example 8, the cable of any one or any combination of Examples 1-7 can optionally be configured such that the shield material includes an inner shield of aluminum foil and an outer shield of braided metal. In Example 9, the cable of any one or any combination of Examples 1-8 can optionally be configured such that at least one of the first contact and the second contact is a spring loaded contact.

In Example 10, the cable of any one or any combination of Examples 1-9 can optionally be configured such that one of the first conductor and the second conductor is a conductor for one of power and data.

In Example 11, a charging system for portable electronic devices can comprise: an electrical power input configured to couple the charging system with a common power source; a plurality of docking stations, each docking station configured to receive at least one portable electronic device, wherein at least a portion of the plurality of docking stations are coupled to the common power source by a cable, the cable comprising: a first conductor having a first end and a second end; a first contact connected to the first end of the first conductor; a second conductor having a first end and a second end; a second contact connected to the first end of the second conductor; a shield material disposed about the first conductor and the second conductor, the shield material having a first end and a second end, wherein the first end of the first conductor and the first end of the second conductor extend beyond the first end of the shield material; and a third conductor having a first end and a second end, wherein the first end is connected to the shield material and the second end is connected to one of the first conductor, the second conductor, the first contact, and the second contact.

In Example 12, the charging system of Example I I can optionally be configured such that the third conductor has a length extending from the first end to the second end, the length is between .5 and 20 mm.

In Example 13, the charging system of any one or any combination of Examples 11-12 can optionally be configured such that the second end of the third conductor is connected to the first conductor and the fi rst conductor has a negative polarity.

In Example 14, the charging system of any one or any combination of

Examples 1 1-13 can optionally be configured to further comprise a connector coupled to the second end of the shield material.

In Example 15, the charging system of Example 14 can optionally be configured such that the connector is configured to couple to an earth ground. In Example 16, the charging system of any one or any combination of Examples 1 1 -15 can optionally be configured such that the shield material includes an inner shield of aluminum foil and an outer shield of braided metal.

In Example 17, the charging system of any one or any combination of Examples 11-16 can optionally be configured such that at least one of the first contact and the second contact is a spring loaded contact.

In Example 18, the charging system of any one or any combination of Examples 1 1-17 can optionally be configured such that the charging system is enclosed in a movable cart.

In Example 19, the charging system of any one or any combination of

Examples 11-18 can optionally be configured such that the charging system is enclosed in a wall mounted cabinet.

In Example 20, the charging system of any one or any combination of Examples 11-19 can optionally be configured such that the first contact and the second contact are configured to couple to corresponding charging pads on the portable electronic device.

In Example 21 a device charger can comprise a plurality of docking stations configured to charge respective ones of a plurality of electronic devices, wherein individual docking stations include: a common power source shared by multiple docking stations; a cable-less connection configured to connect the power source to at least two contacts on one of the plurality of electronic devices: and a reverse current protection circuit configured to: detect that a reverse current is being supplied from the power source to the one of the plurality of electronic devices; and interrupt the reverse current.

In Example 22, the device charger of Example 21 can optionally be configured to further comprise a fault indicator circuit configured to generate a fault indicator signal when the reverse current protection circuit detects that a reverse current is being supplied from the power source to the one of the plurality of electronic devices.

In Example 23, the device charger of Example 22 can optionally be configured such that the fault indicator signal indicates that the one of the plurality of electronic devices is incorrectly positioned. In Example 24, the device charger of any one or any combination of Examples 22-23 can optionally be configured such that the fault indicator signal indicates that the one of the plurality of electronic devices is not being charged.

In Example 25, the device charger of any one or any combination of Examples 22-24 can optionally be configured such that the fault indicator signal includes an audible warning.

In Example 26, the device charger of any one or any combination of Examples 22-25 can optionally be configured such that the fault indicator signal includes a visual warning.

In Example 27, the device charger of any one or any combination of

Examples 22-26 can optionaily be configured such that the fault indicator signal is provided to a Wifi circuit.

In Example 28, the device charger of any one or any combination of Examples 22-27 can optionaily be configured such that the fault indicator signal is provided to a Blue Tooth Enabled (BTE) circuit.

In Example 29, the device charger of any one or any combination of Examples 21-28 can optionally be configured such that the reverse current protection circuit is a voltage limiting circuit.

In Example 30, the device charger of Example 29 can optionaily be configured such that the voltage limiting circuit is a crow-bar circuit.

In Example 31 , the device charger of any one or any combination of Examples 21-28 can optionaily be configured such that the reverse current protection circuit is a current limiting circuit.

In Example 32, the device charger of Example 31 can optionally be configured such that the current limiting circuit is a foldback circuit.

In Example 33, the device charger of any one or any combination of Examples 31-32 can optionally be configured such that the current limiting circuit includes a resettable fuse.

In Example 34, the device charger of Example 33 can optionally be configured such that the resettable fuse is a positive temperature coefficient fuse.

In Example 35, the device charger of any one or any combination of Examples 21-34 can optionally be configured such that the cable-less connection includes a first spring pin contact having a first polarity and a second spring pin contact having a second polarity. In Example 36, the device charger of any one or any combination of Examples 21 -35 can optionally be configured such that the cable-less connection includes a first spring pin contact having a first polarity, a second spring pin contact having a second polarity, and a third spring pin contact having the first polarity.

In Example 37, a docking station for charging a portable electronic device can comprise: a common power source shared by multiple docking stations; a cable-less connection configured to connect the power source to at least two contacts on the portable electronic device; and a reverse current protection circuit configured to: detect that a reverse current is being supplied from the power source to the portable electronic device; and interrupt the reverse current.

In Example 38, the docking station of Example 37 can optionally be configured to further comprise a fault indicator circuit configured to generate a fault indicator signal when the reverse current protection circuit detects that a reverse current is being supplied from the power source to the portable electronic device.

In Example 39, the docking station of Example 38 can optionally be configured such that the fault indicator signal includes at least one of an audible warning and a visual warning.

In Example 40, the docking station of any one or any combination of Examples 37-39 can optionally be configured such that the cable-less connection includes a first spring pin contact having a first polarity and a second spring pin contact having a second polarity.

In Example 41, an electrical load management system for charging batteries, the system comprising can comprise: an electrical power input configured to couple the load management system with a common power source; a plurality of electrical power outputs configured to couple the load management system with a plurality of electrical loads, each electrical load comprising a battery to be charged; a plurality of switches coupled between the power input and the power outputs; and a controller coupled to the plurality of switches, wherein, for groups of electrical loads that are not selected for charging, the controller is configured to open at least one switch connecting the unselected groups to a power supply line and a neutral conductor. In Example 42, the system of Example 41 can optionally be configured such that the battery is configured to power one of a tablet computer, a cell phone, and a laptop computer.

In Example 43, the system of any one or any combination of Examples 41-42 can optionally be configured such that each power output includes an X capacitor coupled between the power supply line and the neutral conductor; and a Y capacitor coupled between the power supply line and the neutral conductor to an earth ground.

In Example 44, the system of any one or any combination of Examples 41-43 can optionally be configured such that each of a plurality of switches is a ganged switch configured to connect or disconnect the power supply line and the neutral conductor between the power input and the power outputs.

In Example 45, the system of any one or any combination of Examples 41-44 can optionally be configured to further comprise a cart having a plurality of docking stations configured to receive one or more portable electronic devices each including the battery to be charged.

In Example 46, the system of any one or any combination of Examples 41-44 can optionally be configured to further comprise a wail mounted charging station having a plurality of docking stations configured to receive one or more portable electronic devices each including the battery to be charged.

In Example 47, a charging station for portable electronic devices can comprise: a load management system; an electrical power input configured to couple the load management system with a common power source; a plurality of electrical power outputs configured to couple the load management system with a plurality of electrical loads, each electrical load comprising a battery of the portable electronic device to be charged; a plurality of groups of electrical power outputs, each group containing at least of portion of the plurality of electrical power outputs;

a leakage current reduction system coupled to each group including: a power supply line; a neutral conductor; an X capacitor coupled between the power supply line and the neutral conductor at each electrical power output; a Y capacitor coupled between the power supply line and the neutral conductor to an earth ground at each electrical power output; at least one switch coupled between the power input and the power outputs; and a controller coupled to the switch; wherein, for groups of electrical loads that are not selected for charging, the controller is configured to open the at least one switch connecting the unselected groups to the power supply line and the neutral conductor.

In Example 48, the charging station of Example 47 can optionally be configured such that the portable electronic device is one of a tablet computer, a cell phone, and a laptop computer.

In Example 49, the charging station of any one or any combination of Examples 47-48 can optionally be configured such that at least one of the at least one switch is a ganged switch configured to connect or disconnect the power supply line and the neutral conductor between the power input and the power outputs.

In Example 50, the charging station of any one or any combination of Examples 47-49 can optionally be configured to further comprise a cart having a plurality of docking stations configured to receive one or more portable electronic devices each including the battery to be charged.

In Example 51, the charging station of any one or any combination of Examples 47-50 can optionally be configured to further comprise a wall mounted charging station having a plurality of docking stations configured to receive one or more portable electronic devices each including the battery to be charged.

In Example 52, the cable, the charging system, the device charger, the docking station, the system, or the charging station of any one or any combination of Examples 1 -5.1 can optionally be configured such that all elements, operations, or other options recited are available to use or select from.

In the drawings, which are not necessarily drawn to scale, like numerals may describe similar components in different views. Like numerals having different letter suffixes may represent different instances of similar components. The drawings illustrate generally, by way of example, but not by way of limitation, various embodiments discussed in the present document.

FIG. 1 depicts an example of a charging system that can include

Electromagnetic Compatibility and Electromagnetic Interference control, in accordance with at least one example of this disclosure. FIG. 2 is a block diagram of an example of a charging system that includes reverse current protection, in accordance with at least one example of this disclosure.

FIG. 3 is a schematic diagram of portions of an example of an existing charging circuit, showing various power supply capacitors,

FIG. 4 is a schematic diagram of portions of an example of a charging circuit, showing various power supply capacitors, in accordance with at least one example of this disclosure.

FIG. 5 depicts an example of a charging system that can include Electromagnetic Interference control and a reverse charging protection circuit, in accordance with at least one example of this disclosure.

FIG. 6 depicts an example of a charging system that can include Electromagnetic Interference control, a reverse charging protection circuit, and a leakage current limiting circuit in accordance with at least one example of this disclosure.

FIG. 7 is a flowchart of a method of charging portable devices in accordance with at least one example of this disclosure.

DETAILED DESCRIPTION

The above-described technique of providing a fully shielded interconnect cable may not be possible for portable electronic device chargers that use a contact-only technique for connecting the charger to the portable electronic device (no shielded connector). These devices can include contact pads on the sides or other faces of the portable electronic device that, when positioned in proximity to a spring pin attached to the charger, make contact using the pressure applied by the spring force between the charger pin and the pad on the portable electronic device. Gravity or mechanical forces applied to the portable electronic device can cause the spring pin to compress and apply the correct force, which can allow low-resistance contact with the portable electronic device charging contact pads and charger spring pins. The benefit to the user is that the spring pin and contact pad technique of charging can allow quick insertion and removal of the portable electronic device from the charging enclosure, e.g., charging cart, charging wall-mount unit, or charging desktop unit. There are no cables for the user to plug and unplug, which can be especially cumbersome and time consuming in large charging carts, for example, where there could he 48 or more devices to plug and unplug.

One problem that can occur with no-cable or contact-only charging techniques is the lack of control of radiated emissions from the portable electronic device and/or charger as well as ESD, transients, and electromagnetic interference from other nearby devices that coul d cause interruption of charging or, in the case of radiated emissions, electromagnetic interfere to other nearby devices, which can possibly exceed government limits of Electromagnetic Compatibility (EMC) and Electromagnetic Interference (EMI). With contact- only charging connections, there may not be a back shell or other means of terminating a cable shield to a shielding case or enclosure of the portable electronic device.

The present inventor has recognized a problem to solved can include limiting the EMI/ EMC in charging systems where the interface cable from the charger electronics to the charging pads on the portable electronic device can be long and in noisy RF environments or other electrically hostile environments consisting of ESD, EFT, etc. as well as RF interference from the charger and portable electronic device itself. The present inventor has recognized that a solution to this problem can include providing an electrical connection between one of the cable conductors, e.g. , negative conductor, and a shield of the cable.

FIG. 1 is a diagram of an example of a charging system 20A that ca include EMC/ EMI control, in accordance with this disclosure. The charging system 20 A of FIG. 1 can include a charger 24 (e.g., charging enclosure) configured to receive one or more portable electronic devices 26 and a connector 28 including a back header 30 and a cable 32 connected to a power source 34A and the charger 24. Example chargers 24 can include charging carts, charging cabinets, e.g., desktop units, wall-mounted units, lockers, charging frames or benches, e.g., airport benches, and the like, designed to securely charge or charge and manage portable electronic devices 26. The components in FIG. 1 are repeated as necessary for the number of portable electronic devices 26 that are supported.

The charger 24 of FIG. 1 can be configured to charge the one or more portable electronic devices 26 using no-cable or contact-only charging techniques. In an example, the charger 24 can include a charging port such as a docking station 36. The docking station 36 can include a slot, a cradle, a tray, an enclosure, or any feature that can aid in organizing or retaining one or more portable electronic devices 26 while charging. The docking station 36 can be configured to receive and retain the portable electronic device 26 while charging.

As seen in FIG. 1, the portable electronic device 26 can include one or more charging pads, such as a first charging pad 38A and a second charging pad 38B, (e.g., a positive charging pad and a negative charging pad). In other example configurations, the portable electronic device 26 can include three charging pads. The cable 32 of FIG. 1 can connect to the charging pads 38A, 38B of the portable electronic device 26 using pins, e.g., spring pins or other contacts, when the device 26 is inserted into the charger 24 such as into the docking station 36.

The docking station 36 can include a first contact 42A and a second contact 42B. The first and second contacts 42 A, 42B can be pins, pads, bushings, or any known type of electrical contact and in an example, can be spring loaded. In some cases the charger 24 can include other connections besides power, such as data connections for uploading, downloading, or syncing data. In an example, the first and second contacts 42A, 42B are not spring loaded. In an example, the portable electronic device 26 can be electrically connected in the docking station 36 using gravity, friction, and/or magnetism to provide good electrical contact between the portable electronic device 26 and the charger 24.

The cable 32 can be of any length suitable for the physical and electrical needs of the charger 24. At the source side of current, the cabl e 32 can include a connector 28 with a back shell 30, e.g., a USB connector, a pin header, or other type of electrical connector, such that the back shell 30 can be connected through the charger 24 to earth ground 48. The cable 32 can include a jacket 50 that can be a non-conductive material that can provide mechanical protection of the cable 32, In an example, the jacket 50 can be a plastic, a rubber, a polymer, a textile, or composites of the aforementioned materials. The cable 32 can also include a shield 52. In an example, the shield 52 ca be located underneath the jacket 50. In an example, the shield 52 can be coupled, interwoven, or formed as part of the jacket 50. The shield 52 can control EMC/ EMI as the cable 32 conducts electricity to charge a portable electronic device 26. In an example, the shield 52 can include an inner shield 54 that can be an aluminum foil shield. In an example, the shield 52 can include an outer shield 56 that can be a braided shield, such as a metal braid shield. Under the shield 52, the cable 32 can include one or more conductors such as a first conductor 58A and a second conductor 58B that can provide electric power from power source 34A of the charger 24. The first and second conductors 58A, 58B can be opposite polarities. In an example, the first conductor 58A can be a negative conductor and the second conductor 58B can be a positive conductor.

The outer shield 56 of the cable 32 can be terminated at the current source side to the back shell 30 of the connector 28 in a 360-degree

mechanically secure connection. The outer shield 56 can cover the first and second conductors 58A, 58B inside the cable 32 in a percentage that can var - according to the tightness of the braid of the outer shield 56. In some examples, the outer shield coverage percentage can be at least 90%. In some examples, the coverage percentage can be at least 95%).

The inner shield 54 can be located inside of the outer shield 56, and can be in an example an aluminum foil or other suitable shielding material that can provide 100% cable shielding coverage. The conductors 58A, 58B can be twisted or straight within the cable 32. Data conductors can also be included in the cable 32, e.g., USB D+ and D- signals. On the current sink side, where the cable 32 makes contact with the portable electronic device 26, the negative polarity and positive polarity charging voltage conductors of the cable 32 can be terminated with the first contact 42A and the second contact 42B. The first and second contacts 42A, 42B can secured to the cable 32 end with solder or any other suitable securing means. The charger 24 can include a docking station 36 having a molded receiver or case that can surround portions of the cabling, conductors, contacts and any printed circuit board assembly, and the like.

In accordance with various techniques of this disclosure, the shield 52 can be terminated electrically and mechanically secured to the first contact 42A or the second contact 42B by a shield connector 62. Although the first contact 42A can be a negative polarity, and the second contact 42B ca be a positive polarity, the polarities of the first contact 42A and the second contact 42B can be reversed. In an example, one of the first conductor 58A or the second conductor 58B of the cable 32 can be electrically connected to the outer shield 56 by a shield connector 62, which can then be electrically connected to one of the first or second conductor 58A, 58B. In another example, the shield connector 62 can electrically connect the shield 52 to one of the first or second contacts 42A, 42B. The electrical connection can be made by soldering, crimping, welding, or any other known method of electrical connection.

To minimize inductance at radio frequencies (RF), a length 61 of the shield connector 62 can be physically very short. For portable electronic devices charged using a cable connected between the portable electronic device and a charging port, any RF noise that is coming from the portable electronic device or the charger (due to ringing or other noise associated with DC-DC conversion) can typically be controlled by two fully shielded connectors. However, with no- cable or contact-only charging techniques, such as described in this disclosure, because neither the first and second contacts 42A, 42B of the charger 24 nor the first and second pads 38A, 38B of the portable electronic device 26 are shielded, it can be beneficial to terminate the shield 52 on the docking station 36 side such that the RF wavelength does not escape and turn the unshielded conductors into an antenna.

By limiting the length 61 of the shield connector 62, the appropriate attenuation can be maintained both for emission and susceptibility to RF. By way of specific example, the spectrum of interest for far field RF noise typically ends at about 1 gigahertz (GHz). The wavelength at l~GHz is about 300 millimeters (mm). To attenuate about 20-dB of EMI, the length 61 of the shield connector 62 can be limited to about l/20 ^th of the wavelength at the frequency spectrum of interest, e.g., l/20 ^lh of 300 mm or about 15-mm. To attenuate about 40-dB of EMI, the length 61 of the shield connector 62 should be about 1.5-mm or less. By terminating the shield connector 62 to the first conductor 58A or the first contact 42 A (each of which could have negative polarity), for example, the "ground" of the portable electronic device 26 can be coupled to the shield 52 of the cable 32 via the portable electronic device negative polarity pad on the device and ultimately to Earth ground 48 through the charger 24.

In FIG. 1, the first end of the inner shield 54, the outer shield 56, the first conductor 58A and the second conductor 58B, can be considered the end near the portable electronic device 26. The length of the first and second contacts 42A, 42B and any unshielded conductors can be minimized according to the constraints of the charging port or docking station configurations. In an example, the first end of the shield 52 can be as close to the first and second contacts as possible.

Various techniques of this disclosure described above can solve the problem of RF emission and RF interference (EMC/ EMI) of portable electronic devices with chargers that include a no-cable or contact-only, e.g., spring pin contact, configuration. Without the RF reduction techniques of this disclosure, users can potentially cause interference with or experience interference from nearby electronics and/or other devices such as cell phones or other transmitters which would cause interruption in charging or data transmission between the portable electronic device and the charging/ syncing device. Other interference can arise from electrostatic discharge (ESD), electrical fast transients (EFT), and other electrically hostile events that when introduced to systems that are not shielded or implement the present invention, can cause interruption or even damage to the portable electronic devices.

In addition, this disclosure describes various techniques for providing a reverse current protection circuit for one or more charging ports or docking stations within a charging system for portable electronic devices. The charging system can be configured as a charging cart or a charging cabinet, e.g., a wali- mounted charger, desktop charger, or other enclosures (including one or more lockers or other storage units), that utilize no-cable charging techniques. The reverse protection circuit can include, for example, a crow-bar circuit, current limit circuits, e.g.. Positive Temperature Coefficient (PTC) or other resettable fuses, fold-back current limiting circuits, and the like.

FIG. 2 is a block diagram of an example of a charging system 20B that can include reverse current protection, in accordance with this disclosure. The charging system 20B can include a power source 34B that utilizes a cable-less charging assembly such as spring pin contacts 64, and a reverse current protection circuit 68. The spring pin contacts 64 can flex as needed and make contact with the contacts on a portable electronic device as the device is inserted into a charging port in the charging system 20B. In another example, the contact connection can be aided by gravity, friction, or other means in conjunction with or in replacement of spring force. The charging system 20B can be configured to charge one or more portable electronic devices in respective charging ports of docking stations (not depicted). In some examples, the charging system 20B can include 48 docking stations, where each docking stations is configured to receive a portable electronic device. The components depicted in FIG. 2 can be duplicated, as necessary, for the number of docking stations in the charging system 20B. Other examples configurations can include more than 48 charging docks, or less than 48 charging docks.

In some examples, the charging system 20B can have a cable-less charging assembly that can include spring pin contacts 64 that provide charging power to an electronic device, e.g., tablet computer, laptop computer, and other portable electronic devices. In an example, the spring pin contacts 64, can be any known type of electrical contact, such as a pad, a bushing, and may or may not include a spring element. As shown in FIG. 2, the three spring pin contacts 64 can be arranged such that the first contact 66A has a first polarity (e.g., negative), the second contact 66B has a second polarity (e.g., positive), and the third contact 66C has the first polarity (e.g., negative). In another example, the charging system 20B can include two spring pin contacts and be arranged such that the first contact has a first polarity (e.g., negative) and the second contact has a second polarity (e.g., positive).

In these or other combinations or arrangements, it can be physically possible for a user to position a portable electronic device into the charging system 20B in a reverse direction such that the contacts of the charger are not in correct alignment with the polarity of the portable electronic device contacts. In some cases, even positioning the portable electronic device in a partially inserted position within the charging system 2B can result in opposite polarity contact and application of a reverse polarity charge to the portable electronic device being charged. Applying a reverse polarity charge ca damage the portable electronic device and/or the charging system 20B.

As mentioned above, the present inventor has recognized, among other things, that a solution to the problem with no-cable charging of inserting the portable electronic device into the device charger, e.g., charging cart, charging wall-mount, or charging desktop unit, such that the tablet or other portable electronic device is inserted in reverse position can include, for example. pro viding a re v erse current protection circuit 68 for one or more of the docking stations within the charging system 20B, e.g., charging cart, charging wall- mount, or charging desktop device. The reverse current protection circuit 68 can include, for example, a crow-bar circuit, a current limiting device such as PTC or other resettable fuse device, a fold-back current limiting device, and the like. Upon detecting a reverse current, the reverse current protection circuit 68 can interrupt charging to the docking station that contains the incorrectly positioned device.

In addition, in some example implementations, the charging system 20B can optionally include a fault indicator circuit 70. In some examples, when the reverse current protection circuit 68 detects a reverse current, the reverse current protection circuit 68 can provide a signal to the fault indicator circuit 70. In response to receiving the signal, the fault indicator circuit 70 can generate a fault indicator signal that can alert a user that an electronic device was incorrectly positioned within the charging system 20B and, as a result, charging can be suspended, e.g., for that particular charging port. For example, the fault indicator circuit 70 can generate and provide a fault indicator signal to one or more of a iFi circuit 72, a visual alarm circuit 74, an audible alarm circuit 76, or a Blue Tooth Enabled (BTE) circuit 78. In an example, the WiFi circuit 72 can provide a message via text or the like. In an example, the visual alarm circuit 74, can include a light or LED to provide a visual warning. In an example, the audible alarm circuit 76 can include a horn or buzzer to provide an audible warning. In an example, the Blue Tooth Enabled (BTE) circuit 78 can provide a message via text or the like after receiving the fault indicator signal.

In addition, a charging system for portable electronic devices can include circuitry that can minimize leakage currents. A problem that can exist with charging devices, e.g. , charging carts, charging cabinets (desktop units, wall- mounted units, l ockers, or any other type of frame, including benches), and the like, is that the leakage currents can increase as more and more devices begin charging. This can be problematic for some Information Technology (IT) power systems where the neutral is not at Earth ground but instead at an impedance higher than Earth. These power supplies typically include common mode and differential mode filter capacitors connected across the Line and Neutral AC input connections and possibly additional capacitors from Line and Neutral to Earth ground. These capacitors connected across Line and Neutral are called "X" capacitors (differential mode) and the capacitors connected from Line and Neutral to Earth ground are called 'Ύ" capacitors (common mode). The X and Y capacitors can be used to provide protection against electromagnetic interference (EMI) generated by portable electronic devices and power supplies.

By way of a non-limiting specific example, notebooks typically have leakage current values of about 85 microamps (uA) per device power supply and the National Electrical Code (NEC) limit for IT equipment such as charging carts can be about 3.5 milliamp (mA). In an example, if 40 notebook power supplies are placed in a charging cart, the total leakage current could be about 40 x 85uA or about 3.4 mA, which is below the limit of 3.5 mA. In reality, however, the total leakage current can be significantly higher due to the paralleling and serializing of the X and Y capacitors during switching of power within the cart and with an IT power system in normal conditions (and possibly worse in single-fault conditions).

A reason for this higher leakage current may be because some cart manufacturers generally turn on and off different groups of devices to keep the charging current under the current limits, e.g., 10 or 12-amp, to which households, schools, and businesses are limited in 230 or 120- volt countries. When the switching takes place, the Line is opened and closed to different groups of power supplies. When this occurs, the X and Y capacitors are still providing a path to Earth in series and parallel combinations through Neutral in the unpowered power supplies.

The leakage current can approach two or more times the leakage current when partial power is being applied to the cart versus when all devices are switched on. This has surprised many safely test laboratories that thought that the worst-case condition would occur when all devices are on. In realit ', the leakage current ca be higher when partial groups are on due to controller timers switching certain groups off in order to limit the mains current below the National Electrical Code limit.

The present inventor has recognized that the problem of keeping the Earth leakage current (also known as the touch current or Protective Earth { ^" PL ^" ) leakage current) to a minimum while maximizing the number of portable electronic devices within a charging device in order to meet the increasing demands of consumers while internal power is routed to different groups of portable electronic power supplies can include the solution of opening and closing both the Line and the Neutral legs of mains power being distributed to the different groups within the charging device. If only Line or Neutral are opened to remove power to the group of power supplies, a current path between Line or Neutral and Earth ground can still occur between the many power supplies in the cart due to the paralleling and serializing of the X and Y capacitors within each portable electronic device power supply.

FIG. 3 is a schematic diagram of portions of an example of an existing charging circuit 80 of a charging device, showing various power supply capacitors. FIG. 3 depicts X capacitors 82 and first and second Y capacitors 84A, 84B and the associated leakage current 96 (shown as arrows) of the charging device with multiple portable device power supplies installed and when switching between groups of multiple portable device power supplies. The charging circuit 80 can include several groups of multiple power supplies, such as group 1 94A, group 2 94B, group 3 94C, and group N 94D . The power supplies are labeled as power supply number 1 86A, power supply number N-l 86B and power supply number N 86C to indicate that any number of power s upplies might be included in any particular group of the charging circuit 80.

As seen in FIG. 3, switches 92A-D are included only on the line conductor 88 and not on the neutral conductor 90 for each particular group 94A- D. Switch 1 92A is closed and Switch 2 92B through Switch N 92D are open. Even though Switch 2 through Switch N 92B-D are open, leakage current 96 still flows through the neutral conductor 90 and the X and Y capacitors 82, 84A, 84B to Earth ground 98. In the existing circuit of FIG. 3, despite switching current on and off to various power supplies used for charging, the X and Y filter capacitors 82, 84A, 84B are not being switched out of the circuit.

FIG. 4 is a schematic diagram of portions of an example of a charging circuit 100, showing various power supply capacitors, in accordance with at least one example this disclosure. As in FIG. 3, the charging circuit 100 can include X capacitor 82, Y capacitors 84A and 84B, power supply number 1 86 A, power supply number N-l 86B, power supply number N 86C, group I 94A, group 2 94B, group 3 94C, and group N 94D. In FIG. 4, rather than only opening a switch on the line conductor 88, a controller in the charging device (not depicted) can open both the line conductor 88 and the neutral conductor 90 using one or more switches 102A-H. The pairs of switches 102A-B, 102 C-D, etc. can be ganged together or operate separately. Thus, for groups of devices that are not being charged, such as Group 2 94B through Group N 94D in FIG. 4, there is no leakage current 96 through their associated power supplies to Earth ground 98. Rather, the only leakage current 96 is associated with an energized bank, or group 1 94A. When multiple groups of devices are being charged, the leakage current can be much less than the existing circuit 80 of FIG. 3.

FIG. 5 depicts an example of a charging system 104 that can include EMC/ EMI control and a reverse charging protection circuit, in accordance with at least one example of this disclosure. The charging system 104 can include a charge port or docking station 106 that can be configured to retain and charge a portable electronic device as described above. In connection with the docking station 106, the charging system can include EMC/ EMI control 108 similar to the shielded cable as described above. In addition, the charging system 104 can include a reverse charging protection circuit I 10 similar to the reverse charging protection described above.

FIG. 6 depicts an example of a charging system 105 that can include EMC/ EMI control, a reverse charging protection circuit, and a leakage current limiting circuit in accordance with at least one example of this disclosure. The charging system 10.5 can include the docking station 106, the EMC/' EMI control 108, and the reverse charging protection circuit 110 as described in FIG. 5. In addition, the charging system 105 can be coupled to a leakage current limiting system 1 12 as described above in FIG. 4. In an example a charging system can include any combination of two of the three subsystems, the EMC/ EMI control 108, the reverse charging protection circuit 110, and the leakage current limiting system 112.

FIG. 7 is a flowchart of a method of charging portable devices in accordance with at least one example of this disclosure. The method 114 can include the steps of: a) shielding a cable coupling a power source to a docking station, the cable having a negative conductor and a positive conductor 116; b) the shielding including an outer shield and an inner shield 1 18; c) connecting at least one of the outer shield or the inner shield to one of the negative conductor or the positive conductor 120. In addition, the method 114 can include the steps of: d) protecting the portable device with a reverse current protection circuit, the reverse current protection circuit coupled between the power source and the docking station 122; and e) providing a fault indicator signal if the portabl e device is loaded into the docking station with reverse polarity 124.

Additional Notes

Each of these non-limiting examples can stand on its own, or can be combined in various permutations or combinations with one or more of the other examples.

The above detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the invention can be practiced. These embodiments are also referred to herein as "examples." Such examples can include elements in addition to those shown or described.

However, the present inventors also contemplate examples in which only those elements shown or described are provided. Moreover, the present inventors also contemplate exampl es using any combination or permutation of those elements shown or described (or one or more aspects thereof), either with respect to a particular example (or one or more aspects thereof), or with respect to other examples (or one or more aspects thereof) shown or described herein.

In the event of inconsistent usages between this document and any documents so incorporated by reference, the usage in this document controls. in this document, the terms "a" or "an" are used, as is common in patent documents, to include one or more tha one, independent of any other instances or usages of "at least one" or "one or more." In this document, the term "or" is used to refer to a nonexclusive or, such that "A or B" includes "A but not B," "B but not A," and "A and B," unless otherwise indicated. In this document, the terms "including" and "in which" are used as the plain-English equivalents of the respective terms "comprising" and "wherein." Also, in the following claims, the terms "including" and "comprising" are open-ended, that is, a system, device, article, composition, formulation, or process that includes elements in addition to those listed after such a term in a claim are still deemed to fall within the scope of that claim. Moreover, in the following claims, the terms "first," "second," and "third," etc. are used merely as labels, and are not intended to impose numerical requirements on their objects.

Method examples described herein can be machine or computer- implemented at least in part. Some examples can include a computer-readable medium or machine-readable medium encoded with instructions operable to configure an electronic device to perform methods as described in the above examples. An implementation of such methods can include code, such as microcode, assembly language code, a higher-level language code, or the like. Such code can include computer readable instructions for performing various methods. The code may form portions of computer program products. Further, in an example, the code can be tangibly stored on one or more volatile, non- transitory, or non-volatile tangible computer-readable media, such as during execution or at other times. Examples of these tangible computer-readable media can include, but are not limited to, hard disks, removable magnetic disks, removable optical disks (e.g., compact disks and digital video disks), magnetic cassettes, memor ' cards or sticks, random access memories (RAMs), read only memories (ROMs), and the like.

The above description is intended to be illustrative, and not restrictive. For example, the above-described examples (or one or more aspects thereof) may be used in combination with each other. Other embodiments can be used, such as by one of ordinary skill in the art upon reviewing the above description. The Abstract is provided to comply with 37 C.F.R. §1.72(b), to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Also, in the above Detailed Description, various features may be grouped together to streamline the disclosure. Tins should not be interpreted as intending that an unclaimed disclosed feature is essential to any claim. Rather, inventive subject matter may lie in less than all features of a particular disclosed embodiment. Thus, the following claims are hereby incorporated into the Detailed Description as examples or embodiments, with each claim standing on its own as a separate embodiment, and it is contemplated that such embodiments can be combined with each other in various combinations or permutations. The scope of the invention should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.