CROSS-REFERENCE TO RELATED APPLICATIONS

[0001 ] This patent application claims the benefit of priority from US Provisional Application 62/407, 171 filed on October 12, 2016 entitled "Multiple Source Charge Controller", the entire contents of which are included herein by reference.

FIELD OF THE INVENTION

[0002] The present application is related to the field of charge controllers used in battery charging and more specifically to a charge controller for regulating the supply and drainage of a battery storage device supplied by multiple power sources.

BACKGROUND OF THE INVENTION

[0003] Municipal lighting, such as street lighting, is an important part of our municipal infrastructure and is used in both urban and rural centers. However, the energy used to light our cities and streets can be a large part of the total energy consumed in a location. Rural lighting can present an additional challenge due to long distances from power sources. Rural lighting can also be inefficient as most of the time, there is no one around and lighting is only required when people are present. Power for lighting and other applications can be supplied from a variety of sources including batteries that must be recharged periodically. Alternate power sources include solar and wind power generators have been proposed to recharge batteries.

[0004] End uses for power include recharging electric vehicles, electric boat engines, and off- the-grid home battery storage systems.

[0005] Battery charging systems include a charge controller, charge regulator, or battery regulator which are electronic devices used to control the electric current added to, or extracted from, one or more batteries in order to maximize the life span of the batteries. This device will prevent the batteries from over charging and completely draining.

[0006] Some charge controllers have additional features, such as a low voltage disconnect (LVD), a separate circuit which powers down the load when the batteries become overly discharged to protect the batteries. [0007] More sophisticated charge controllers which extract the maximum capacity of a battery system are currently available in the market. These charge controllers use maximum power point tracking (MPPT) and pulse width modulation (PWM) technologies to optimize power extraction from a battery source. A MPPT controller, in addition to performing the function of a basic controller, also includes a voltage converter to convert the voltage of the source to match the batteries to be charged, with minimal loss of power. These controllers seek to keep the source voltage at their Maximum Power Point, while supplying the varying voltage requirements of the batteries being charged.

[0008] Charge controllers with battery monitoring capabilities are also now in use, mainly to monitor the temperature of the batteries in order to avoid overheating. Some charge controller systems also display data, transmit data to remote displays, and data logging to track electric flow over time.

[0009] When used with multiple charging sources, current charge controllers select between the multiple charging sources and only use one charging source to supply a battery at a time. The non-selected charging sources are not used to charge the battery.

[0010] Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.

SUMMARY OF THE INVENTION

[001 1 ] Embodiments according to a first major aspect of the invention include a rechargeable power system comprising a first power source generating a first variable voltage and a second power source generating a second variable voltage. A charge controller is coupled to the first power source and the second power source and a battery is coupled to the charge controller. The charge controller monitors the first variable voltage and the second variable voltage and selects one of the first variable voltage or the second variable voltage as a charging source for the battery. The charge controller couples the charging source to the battery and recharges the battery.

[0012] Further embodiments compromise a light source. The battery is coupled to the light source and powers the light source.

[0013] In other embodiments, the battery comprises a primary battery and a secondary battery. The charge controller determines that the charging source is sufficient to charge the primary battery and the charging source is also sufficient to simultaneously charge the secondary battery.

[0014] In some embodiments, the charge controller selects the charging source based on a prioritized list of the first power source and the second power source.

[0015] In other embodiments, the charge controller selects the charging source if it exceeds a low threshold.

[0016] In further embodiments, if the charging source is less than a high threshold, the charge controller couples the charging source to the battery through a boost regulator, the boost regulator increasing a voltage of the charging source to a level sufficient to charge the battery.

[0017] In other embodiments, a level of the first variable voltage is used as an indicator of an environmental condition and the environmental condition is used to enable the light source.

[0018] In some embodiments, the first power source is a piezo-electric converter.

[0019] In other embodiments, the first power source is a thermal generator and the thermal generator generates the first variable voltage from heat from the rechargeable power system.

[0020] In further embodiments, the charge controller also selects the other of the selected one of the first variable voltage or the second variable voltage, and combines the first variable voltage and the second variable voltage into the charging source.

[0021 ] Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Embodiments of the present invention will now be described, by way of example only, with reference to the attached Figures, wherein:

[0023] Figure 1 is a block diagram of a system using a multiple source charge controller circuit according to an embodiment of the invention;

[0024] Figure 2 provides a schematic diagram of the multiple source charge controller circuit illustrating an embodiment of the invention with four variable power sources;

[0025] Figures 3A and 3B illustrate a pulse width modulation (PWM) controller circuit;

[0026] Figure 4 depicts an exemplary battery charge controller circuit to protect the batteries from overcharging by regulating the supplied charging voltage; and

[0027] Figure 5 provides a conceptual flow diagram of the charge controller according to an embodiment with four variable power sources. DETAILED DESCRIPTION

[0028] Embodiments of the invention may be used in applications where multiple, variable source power supplies are used to provide electrical power to a device. One example is a battery powered streetlight that includes alternative or renewable energy sources such as solar panels, wind turbines, piezo-electric converters, thermal generator, and other sources, to power the streetlight and provide power to recharge the batteries. Figure 1 shows a system block diagram illustrating how the sub systems are inter-connected to the charge controller 10. In this example, the charge controller 10 is supplied by a plurality of alternate power sources 14, four sources in this example. The power sources 14 all provide a variable amount of power that varies due to changes in the external environment. Solar panels, or photovoltaic (PV) converters, supply more power when the sun is bright and none at night. Wind turbines supply a variable amount of power proportional to the wind velocity. Piezo-electric tiles or energy converters provide energy when subjected to variable mechanical stress or strain. A piezo-electric sensor array of these tiles, placed at the base of a streetlight would generate energy proportional to vibrations and movement experienced by the system, from internal or external vibrations, such as generated by passing traffic. Thermal generators or thermoelectric modules (TEG) generate energy proportional to the amount of heat they are exposed to and may also be used to harness the energy given off by electronic components and the streetlight lamp itself, thereby boosting the efficiency of the system. Energy produced by the sources is stored in one or more batteries 16 to provide power to light the lamps as the need arises. Battery charging may be done with the use of PWM technology, but may be done using other means as known in the art. Sensors 18 may be provided to improve the operation and energy efficiency of the system. For example, motion sensors can be used to determine when to turn the lights off or on. The charge controller 10 is electrically connected to the variable power sources, sensors and the batteries.

[0029] Batteries 16, power sources 12, and the power requirements of the system should be chosen to match and be used to set power, current, and voltage thresholds to be used by the system. For example, if lighting would be on for 12 hours per day and lighting sensors would be required for 12 hours per day, 2kWh of power per day may be required. This means that batteries would have to have a capacity of over 2k Wh per charge with additional capacity to account for delays in charging, charging inefficiencies, etc. Power sources would be provisioned with sufficient capacity to be able to recharge the batteries under worse case conditions. These requirements would be uses to select the number and type of solar cells, wind turbine, or other energy sources. Expected heat dissipation may be used to select the number and type of thermal generators. Expected vibrations can be used to select appropriate piezo-electric converters.

[0030] In an exemplary embodiment, four power sources 12 are coupled to the controller 10, connected in parallel to allow current to be supplied from any of the sources individually or in combination.

[0031 ] The variable power sources 12 are connected to a charge controller 10 which accepts inputs from sensors 18 and controls the system through outputs. The controller 10 is designed to monitor the power sources 12 and to control the system to provide a controlled output power of a determined voltage and current to efficiently recharge the batteries. Power source 12 voltages are checked according to a prioritized list. In this example, the list may be stored in the control logic of the charge controller, such as an ATmega IC manufactured by Atmel Corporation. The source voltages are monitored throughout the day. In an embodiment, the source voltages may be sampled every second, faster (e.g. hundreds of times per second), or slower. In an implementation, the power sources may comprise renewable energy sources that are connected to this charge controller. Preferably the load, such as a street light, may be selectively powered on. For instance, a streetlight may be powered on only when it is dark. The condition to determine that a load should be powered on may be evaluated from a voltage level of one or more of the sources. In an aspect, the source comprises a solar panel source, and the condition is met when the source voltage of the solar panel source falls below a threshold condition value. For instance, with a street lamp, when the sun sets the output from the solar panel source will drop. When the source voltages are observed in the source selection function, the charge controller may evaluate one or more of the source voltages to determine whether it is below the threshold condition value. In an aspect, the charge controller is programmed to check the voltage produced by the solar panel source, and then to supply power to the load when the voltage is below the threshold condition value (for example 6V). In an aspect, the load may comprise the streetlight. In an aspect, the load may comprise a secondary sensor and the charge controller only turns on the secondary sensor (such as a light sensor) when the voltage is below the threshold condition value. Operation of the main load, such as the street light, may then be regulated by the secondary sensor.

[0032] An implementation of a variable power source system is represented in Figure 2 illustrating a circuit schematic diagram of a case where the two or more charging sources comprises four charging sources. In this implementation, the charge controller is operative to receive and select between the four variable power sources. The schematic drawing is representative of four variable sources that can be separately connected to the controller in parallel. This circuitry consists a power supply 38, integrated circuit voltage regulator IC 40 (such as a LM317 IC), NPN power transistors 32 (such as a TIP 3055), resistors 34 and variable resistors 36. The supply voltage from the power supply 38 is converted to DC through the use of transformers 30. The amperage is increased with the use of the power transistor, while the variable resistors 36 regulates the output voltage 28. The four voltage outputs represent the four variable sources.

[0033] The charge controller has three main functions; source selection, voltage boosting, and battery charging.

[0034] Source Selection

[0035] In an implementation, the controller comprises a microcontroller, (for example, an ATmega 2560 IC which is a low-power CMOS 8- bit microcontroller based on the AVR enhanced RISC architecture). Switches, such as solid state relays (SSR) coupled to the charge controller carry on the switching functions as per the instructions given by the microcontroller. Each source is connected to the controller through two SSRs. These relays are solid state electronic switching devices which switch power to the load circuitry, and a coupling mechanism to enable the control signal to activate this switch without mechanical parts. When the IC issues a control signal the source will be connected to the charge controlling circuitry through the relay.

[0036] Source selection is done according to a sequence that may be a predetermined or prioritized list. In one embodiment, the voltage sources are checked starting with solar, then wind, piezo-electric converters and then thermal generators. The controller IC will measure each voltage source to determine if it is greater than a low threshold, for example 8V, below which the source may not be used, even with the use of a boosting regulator. The controller IC will also measure each voltage source to determine if it is greater than a high threshold, for example 27V, above which it can be used without boosting. The high threshold may be chosen based on the charging requirements of the batteries in the system. The controller may intelligently measure each voltage source and omit sources that may not presently be used such as a solar source at night, or a thermal generator when the temperature is too low. If the voltage is between the low threshold and the high threshold it will be boosted to meet or exceed the high threshold. If the voltage is greater than the high threshold, then the controller will assert a control signal to one of the relays to connect the circuit to the charge controller. Otherwise the source will be connected to the inverting unit through the other relay. This procedure is performed for all four sources.

[0037] Voltage Boosting

[0038] When the source voltage checked by the controller is between the low and the high thresholds, then they are connected to the charge controller through the inverter unit which is a boost voltage regulator to produce a high voltage output from a lower voltage input. This inverter unit may be designed incorporating a pulse width modulator (PWM) control circuit (such as a SG3525 manufactured by ON Semiconductor) converter which will convert low DC voltage input into a high voltage output with the use of PWM controlling. The batteries used in the system are typically 24V batteries so the high threshold is set corresponding to the battery charging voltage of 27V. Thus, the voltages produced by the sources will be stepped up to 27V by this inverter unit. For batteries that use a lower or higher voltage, the high threshold would be set at an appropriate level to enable charging.

[0039] Accordingly, an embodiment of the invention may exploit a DC to DC inverter circuit where the push-pull inverter circuit is operative to step up source voltages that are above a low threshold voltage value, but below a pre-determined high threshold charging voltage value. The voltages are stepped up by sending them through the push-pull inverter circuit. The stepped up voltages may then be combined and supplied to a charging circuit to charge the batteries. Such a DC to DC inverter circuit may, for example, be incorporated into a load such as a battery-powered street light. In embodiments that use a 24V battery, the push-pull inverter circuit may be operative to step up the supplied source voltages to a charging voltage of 27V.

[0040] Switching power regulation obtained through the push-pull converter is advantageous due to high power conversion efficiency and increased design flexibility. The converter consists of two transistors where as they each turn on in alternate cycles (the two transistors are never on at the same time). Transformer secondary current flows at the same time as primary current (when either of the switches is on). Voltage regulation is performed by Pulse Width Modulation (PWM) where the feedback loop adjusts the output voltage by changing the on time of the transistors.

[0041 ] PWM Battery Charging

[0042] There are two popular methods that can be used for battery charging. One is the maximum power point tracking (MPPT) and the other is pulse width modulation (PWM). Using the MPPT method, the controller will adjust its input voltage to obtain the maximum power from the solar, wind, or other sources and then transform this power to supply for varying loads of the batteries. The PWM method uses switching power devices to regulate the charging adjusting the current from the sources according to the batteries conditions. In an exemplary embodiment, the charge controller employs PWM technology to take advantage of its higher efficiency in low power applications and economical to use. When a battery voltage reaches the desired set point, the PWM algorithm slowly reduces the charging current to avoid heating and gassing of the batteries, yet the charging continues to return the maximum amount of energy to the batteries in the shortest time. The result is a higher charging efficiency, rapid recharging, and a healthy battery at full capacity.

[0043] Figure 4 illustrates an exemplary battery charge controller circuit may be used to protect the batteries from overcharging by regulating the supplied charging voltage. Figures 3A and 3B depict an exemplary PWM controller circuit that may be used to regulate the supplied charging voltage wherein the duty cycle of the controller circuit is increased / decreased based upon whether the non-inverting input voltage is greater than / lower than the inverting input voltage. This determination being made as depicted within the PWM controller front-end as depicted in Figure 3A which drives the output stage depicted in Figure 3B. For instance, in the example of the battery powered streetlight, the battery charge controller circuit may maintain the supplied charging voltage at 27V.

[0044] Charge controller operates as the batteries charging unit which, in an exemplary design, includes adjustable switching regulators (such as LM2596 step-down switching regulators), MOSFETs and other electronic components. The inverter output and the direct supply from the sources are connected together and supplied to this smart charging unit. Output voltage of the unit is set to a high threshold, for example 27V, by adjusting the potentiometer connected to the LM2596. The LM2596 is a step-down DC-DC converter with wide input voltage ranges up to 40V and capable of delivering up to 3A DC load current. As this current is not sufficient to charge the batteries, MOSFETs are installed to acquire the current produced by the sources. Six MOSFETs are installed to distribute the current among them in order to reduce heat produced by them while operation. A feedback is given to the LM2596 from the output voltage to maintain the output voltage at 27V. As in the inverting unit, this also use PWM technique to regulate the voltage.

[0045] FEATURES

[0046] Embodiments of the invention comprise a multiple source pulse width modulation (PWM) charge controller operative to control a variable power source system having a plurality of variable power sources, a battery pack and sensors. The controller may include a relay circuit with integrated circuits to evaluate and select from the plurality of variable power sources, and a DC to DC push-pull converter circuit to step-up the received generated voltages to a charging voltage, and an inverter circuit design for pulse width modulation to obtain the best regulated output from the sources to charge the batteries.

[0047] The controller may include the features to provide higher performance. One such feature is the automatic switching between sources according to the output voltage of the sources under different operating conditions. Another feature includes night time detection to turn on the lamps through monitoring solar power sources. A further feature includes the charging of a secondary battery or supplying power to a secondary source when there is excessive output voltage generated by the sources. Current may also be combined from the source outputs combined in parallel to obtain a higher current to charge the batteries. Furthermore, the DC to DC push-pull converter circuit is used to increase source voltages that are not sufficient to charge the batteries.

[0048] Embodiments include source switching technology for multiple sources with variable voltage output conditions, source output voltage checking and parallel source addition to improve the charging current and step-up voltage. The source-switching controller may include source selection of one or more of a plurality of input variable voltage sources, voltage step-up of the selected one or more sources to a charging voltage, and combination of the stepped-up voltages.

[0049] In an embodiment, a multiple source charge controller is provided such as depicted in Figure 5 with a conceptual flow diagram. The multiple source charge controller is operative to receive a plurality of source inputs which are connected in parallel and managed to supply a controlled voltage output to charge a set of one or more batteries. In an aspect, the controller is operative to perform at least one of source selection, voltage boosting and battery charging using PWM or other methods.

[0050] Source selection may be performed by evaluating the plurality of source inputs based on a prioritized list. The controller being operative to check the voltage of each source input based on its position in the prioritized list. If the checked voltage is greater than a minimum voltage as defined by a low threshold (for example 8V) then the checked voltage will be evaluated to determine whether it is above a charging voltage (for example 27 V). If the checked voltage is above the charging voltage, then the source input is connected to charge the one or more batteries. If the checked voltage is below the charging voltage (though above the minimum voltage), then the checked voltage is stepped-up to the charging voltage, and then connected to charge the one or more batteries. The controller may then evaluate another source input based on the order in the prioritized list. [0051 ] The checked voltages may be stepped up using a step-up converter, such as a push- pull converter. When the source voltage checked by the controller is in between 8V- 27V, then they are connected to the charge controller through the inverting unit. This inverting unit may be designed incorporating a PWM control circuits (such as the SG3525). The batteries, installed in the system are typically 24V batteries so the charging voltage is kept at 27V. Thus, the voltages produced by the sources will be stepped up to 27V by this inverting unit.

[0052] Battery charging may be performed using either maximum power point tracking (MPPT) or pulse width modulation (PWM). In the MPPT method, the controller will adjust its input voltage to harvest the maximum power from the solar or wind sources and then utilize excess power to supply current to charge batteries. In the PWM method, the controller uses power switching devices to regulate the charging by limiting the current supplied from the sources according to the batteries conditions. In an implementation the charge controller employs PWM technology to take advantage of its higher efficiency in low power applications and economical use. When a battery voltage reaches the regulation set point, the PWM algorithm slowly reduces the charging current to avoid heating and gassing of the batteries, yet the charging continues to return the maximum amount of energy to the batteries in the shortest time. The result is a higher charging efficiency, rapid recharging, and a healthy battery at full capacity.

[0053] The ensuing description provides representative embodiment(s) only, and is not intended to limit the scope, applicability or configuration of the disclosure. Rather, the ensuing description of the embodiment(s) will provide those skilled in the art with an enabling description for implementing an embodiment or embodiments of the invention. It being understood that various changes can be made in the function and arrangement of elements without departing from the spirit and scope as set forth in the appended claims. Accordingly, an embodiment is an example or implementation of the inventions and not the sole implementation. Various appearances of "one embodiment," "an embodiment" or "some embodiments" do not necessarily all refer to the same embodiments. Although various features of the invention may be described in the context of a single embodiment, the features may also be provided separately or in any suitable combination. Conversely, although the invention may be described herein in the context of separate embodiments for clarity, the invention can also be implemented in a single embodiment or any combination of embodiments.

[0054] Reference in the specification to "one embodiment", "an embodiment", "some embodiments" or "other embodiments" means that a particular feature, structure, or characteristic described in connection with the embodiments is included in at least one embodiment, but not necessarily all embodiments, of the inventions. The phraseology and terminology employed herein is not to be construed as limiting but is for descriptive purpose only. It is to be understood that where the claims or specification refer to "a" or "an" element, such reference is not to be construed as there being only one of that element. It is to be understood that where the specification states that a component feature, structure, or characteristic "may", "might", "can" or "could" be included, that particular component, feature, structure, or characteristic is not required to be included.

[0055] Reference to terms such as "left", "right", "top", "bottom", "front" and "back" are intended for use in respect to the orientation of the particular feature, structure, or element within the figures depicting embodiments of the invention. It would be evident that such directional terminology with respect to the actual use of a device has no specific meaning as the device can be employed in a multiplicity of orientations by the user or users.

[0056] Reference to terms "including", "comprising", "consisting" and grammatical variants thereof do not preclude the addition of one or more components, features, steps, integers or groups thereof and that the terms are not to be construed as specifying components, features, steps or integers. Likewise, the phrase "consisting essentially of, and grammatical variants thereof, when used herein is not to be construed as excluding additional components, steps, features integers or groups thereof but rather that the additional features, integers, steps, components or groups thereof do not materially alter the basic and novel characteristics of the claimed composition, device or method. If the specification or claims refer to "an additional" element, that does not preclude there being more than one of the additional element.