Active balancing of energy among batteries

Abstract

Aspects of this technical solution can include obtaining a first voltage across a first battery coupled with a first node, the first voltage indicative of a first level of charge of the first battery, the first node having a first input voltage, obtaining a second voltage across a second battery coupled with a second node, the second voltage indicative of a second level of charge of the second battery, the second node having a first reference voltage, the first battery and the second battery coupled in series between the first node and the second node, coupling, via a power converter, a third node between the first battery and the second battery with a second input voltage, to change at least one of the first level of charge or the second level of charge, and coupling, via the power converter, the third node with a second reference voltage, to change at least one of the first level of charge or the second level of charge.

Description

ACTIVE BALANCING OF ENERGY AMONG BATTERIESTECHNICAL FIELD

[0001] The present implementations relate generally to electrical power systems, including but not limited to active balancing of energy among batteries.INTRODUCTION

[0002] Electrical energy is increasingly stored and transmitted by a wider range of devices. Concurrently, demands on efficiency in power delivery and conservation of power are increasing in view of increasing complexity of electrical power systems and demands for power availability and device longevity.SUMMARY

[0003] This technical solution is directed at least to methods, systems, and computer readable media for balancing charge of a plurality of batteries with a flexible architecture that can support a variety of battery arrangements. For example, an electrical or electronic device can be coupled with or integrated into a power storage device or system including a plurality of batteries arranged in series. The controller can rebalance charge between various batteries of the system, including among batteries coupled in series. This technical solution can balance charge across battery stacks coupled in parallel, including between batteries of different battery stacks that can be coupled in series according to a circuit architecture as discussed herein. This technical solution thus achieves at least a technical improvement to balance charge across a larger number of batteries distributed across both series and parallel arrangements, to improve storage life of each battery or battery stack, and to provide more consistent or even power delivery from a plurality of batteries. Thus, a technical solution for active balancing of energy among batteries is provided.

[0004] At least one aspect is directed to a method of balancing charge across a plurality of batteries. The method can include obtaining a first voltage across a first battery coupled with a first node, the first voltage indicative of a first level of charge of the first battery, the first node having a first input voltage. The method can include obtaining a second voltage across a second battery coupled with a second node, the second voltage indicative of a second level of charge of the second battery, the second node having a first reference voltage, the first battery and the isecond battery coupled in series between the first node and the second node. The method can include coupling, via a power converter, a third node between the first battery and the second battery with a second input voltage, to change at least one of the first level of charge or the second level of charge. The method can include coupling, via the power converter, the third node with a second reference voltage, to change at least one of the first level of charge or the second level of charge.

[0005] At least one aspect is directed to a system of balancing charge across a plurality of power sources. The system can include a first power source coupled with a first node having a first input voltage, the first power source having a first voltage indicative of a first level of charge of the first power source. The system can include a second power source coupled with a second node having a first reference voltage, the second power source having a second voltage indicative of a second level of charge of the second power source, the first power source and the second power source coupled in series between the first node and the second node. The system can include a power converter structured to change at least one of the first level of charge or the second level of charge, by coupling a third node between the first power source and the second power source with a second input voltage, and by the third node with a second reference voltage.

[0006] At least one aspect is directed to a non-transitory computer readable medium and can include one or more instructions stored thereon and executable by a processor. The processor can detect a first voltage across a first battery coupled with a first node, the first voltage indicative of a first level of charge of the first battery, the first node having a first input voltage. The processor can detect a second voltage across a second battery coupled with a second node, the second voltage indicative of a second level of charge of the second battery, the second node having a first reference voltage, the first battery and the second battery coupled in series between the first node and the second node. The processor can cause a power converter to couple a third node between the first battery and the second battery with a second input voltage, to change at least one of the first level of charge or the second level of charge. The processor can cause the power converter to couple the third node with a second reference voltage, to change at least one of the first level of charge or the second level of charge.BRIEF DESCRIPTION OF THE FIGURES

[0007] These and other aspects and features of the present implementations are depicted by way of example in the figures discussed herein. Present implementations can be directed to, but are not limited to, examples depicted in the figures discussed herein. Thus, this disclosure is not limited to any figure or portion thereof depicted or referenced herein, or any aspect described herein with respect to any figures depicted or referenced herein.

[0008] FIG. 1 depicts an example system according to this disclosure.

[0009] FIG. 2 depicts an example parallel system according to this disclosure.

[0010] FIG. 3 depicts an example switched system according to this disclosure.

[0011] FIG. 4 depicts an example multiple switched system according to this disclosure.

[0012] FIG. 5 depicts an example system in an example operating state according to this disclosure.

[0013] FIG. 6 depicts an example method of active balancing of energy among batteries according to this disclosure.DETAILED DESCRIPTION

[0014] Aspects of this technical solution are described herein with reference to the figures, which are illustrative examples of this technical solution. The figures and examples below are not meant to limit the scope of this technical solution to the present implementations or to a single implementation, and other implementations in accordance with present implementations are possible, for example, by way of interchange of some or all of the described or illustrated elements. Where certain elements of the present implementations can be partially or fully implemented using known components, only those portions of such known components that are necessary for an understanding of the present implementations are described, and detailed descriptions of other portions of such known components are omitted to not obscure the present implementations. Terms in the specification and claims are to be ascribed no uncommon or special meaning unless explicitly set forth herein. Further, this technical solution and the present implementations encompass present and future known equivalents to the known components referred to herein by way of description, illustration, or example.

[0015] Methods, systems, and computer readable media according to this disclosure can include various electrical components in communication with various control devices to balance power distribution across various power sources. For example, an electrical circuit can include a plurality of batteries arranged in a series configuration. For example, an electrical circuit can include a plurality of battery stacks each including a plurality of batteries arranged in a series configuration. The plurality of battery stacks can be arranged in series with each other, parallel with each other, or a combination thereof. Various batteries can be coupled with an electrical device to transmit charge, at one or more points between a series node that couples various stacks. The electronic controller can couple with various subsets of batteries of the system to balance charge between the batteries of the subset. For example, the electrical device can include an inverter or DC-DC converter that can operate to balance charge by reducing charge of a first battery or increase charge of a second battery in a battery stack or across different battery stacks. Thus, this technical solution can provide at least a technical improvement to balance charge among any two batteries that can be coupled in a series arrangement via the electronic controller.

[0016] FIG. 1 depicts an example system according to this disclosure. As illustrated by way of example in FIG. 1, a system 100 can include at least a first node 102, a second node 104, a power converter 110, a first power source 120, a second power source 122, a third node 130, and a controller 140. The controller 140 can include one or more logical or electronic devices including but not limited to integrated circuits, logic gates, flip flops, gate arrays, programmable gate arrays, and the like. The controller 140 can include a processor 142 and a memory 144. Battery packs in high-voltage environments can be coupled with the controller 140 or can each include distinct instances of the controller 140, which can monitor parameters of the pack including a state of charge (SOC). The controller 140 may report one or more of the parameters over a communications port. The controller 140 may monitor the SOC of individual cells as well as net SOC of the battery pack.

[0017] The first node 102 can include a portion of the system 100 coupled with an electrical element at an input voltage having a first level for an electronic circuit. For example, the electrical element can correspond to a voltage source providing or generating the input voltage having the first level (e.g., a DC voltage source). For example, the electrical element can correspond to an electrical device at the input voltage having the first level. For example, the first voltage is a high voltage. The second node 104 can include a portion of the system 100coupled with an electrical element at a reference voltage having a second level for an electronic circuit different than the first level. For example, the electrical element can correspond to a voltage source providing or generating the reference voltage having the first level (e.g., a ground wire). For example, the electrical element can correspond to an electrical device at the reference voltage having the first level. For example, the second voltage is a reference or ground voltage.

[0018] The power converter 110 can include a device configured to modulate or vary one or more electrical properties of electricity transmitted therethrough or thereby. For example, the power converter 110 is a DC-DC converter configured to modulate DC voltage between voltages bounded by one or more of the input voltage and the reference voltage. The power converter 110 can operate to selectively couple the one or more of the first power source 120 and the second power source 122 with one or more of the first node 102 and the second node 104. For example, the power converter 110 can include a circuit to altematingly couple either the first power source 120 or the second power source 122 with one of the first node 102 or the second node 104 and the power converter 110. Thus, the power converter 110 can transmit energy between the first power source 120 and the second power source 122. For example, the power converter 110 is an inverter. For example, the first node 102 is an input voltage node structured to provide input voltage different from reference voltage or ground voltage. For example, the second node 104 is a reference voltage node structured to provide reference voltage or ground voltage. For example, the third node 130 is a power source node structured to electrically couple the first power source 120 and the second power source 122 in series.

[0019] The power converter 110 can operate bi-directionally, to both provide power to one or more power sources, including the first power source 120 and the second power sources 122, and to draw power from one or more power sources, including the first power source 120 and the second power sources 122. The power converter 110 can correspond to any of a buck converter, a boost converter, and a buck-boost converter. For example, the power converter 110 can operate in one or more of a buck mode, a boost mode and a buck-boost mode, according to or in response to a voltage at the first node 102. For example, the power converter 110 can be coupled with a number of power sources according to a voltage capacity or current capacity of one or more of the power converter 110 and the power sources coupled with the power converter 110. For example, the power converter 110 can control flow of power according to the capabilities of the storage devices and demand on the main DC system bus as discussedherein. In some embodiments, the power converter can be coupled with power sources of a same type or batteries of a same type.

[0020] In some embodiments, multiple instances of the system 100 can be coupled in parallel to increase power capacity. Using multiple DC-DC converters achieves a technical improvement to create a power system that can power and draw power from differing types of power sources simultaneously or concurrently. This, in turn, allows the system 100 (e.g., via the controller 140) to best select power density and energy density to achieve a higher system efficiency. Power density and energy density can vary based on type of power source (e.g., battery vs. fuel cell) and type of battery as discussed herein.

[0021] The first power source 120 can be coupled in series with the second power source 122. The first power source 120 can be coupled with or between the first node 102 and the third node 130. The second power source 122 can be coupled in series with the first power source 120. The second power source 122 can be coupled with or between the third node 130 and the second node 104. The first power source 120 and the second power source 122 can each include one or more electrical, electronic, electromechanical, electrochemical, or like devices or systems for at least one of receiving, storing and distributing input power. For example, the first power source 120 and the second power source 122 together form a stack of batteries. For example, each of the first power source 120 and the second power source 122 can include lithium-ion or like energy storage. For example, one or more of the first power source 120 and the second power source 122 is integrated with, integrable with, or separable from the system 100. The third node 130 can be coupled with one or more of the power converter 110, the first power source 120, and the second power source 122. For example, the power converter 110 can alternatingly couple with the first power source 120 and the second power source 122 to induce a current that charges one of the first power source 120 and the second power source 122 that has a lower charge level among the two. For example, the first power source 120 and second power source 122 can be rechargeable batteries, and can be battery packs each including many individual cells connected in series to achieve a particular voltage. Cell voltage can vary based on technology and chemistry, and can generally be measured in singles of volts (e.g., - 10 V to 10 V). Hundreds of cells can be connected in series in a battery pack to achieve high voltage (400-800V or more) for various high-voltage environments. For example, high-voltage environments can include battery electric vehicles (BEVs), hybrid electric vehicles (HEVs),plug-in hybrid electric vehicles (PHEVs), or stationary grid scale storage systems or portable energy storage systems.

[0022] For example, the first power source 120 and second power source 122 can include cell balancing within the battery pack, via an integrated instance of the controller 140. For high- power systems (e.g., traction drives for mining vehicles or rail engines) in high-voltage environments, packs of multiple batteries (e.g., multiple instances of the first power source 120 or the second power source 122) may be connected in series to achieve the higher voltage desired for multi -mega-Watt applications. In some embodiments, battery packs are connected in series or may have parallel strings of series connected packs. Here, the states of charge among the packs will inevitably drift apart during normal charging and discharging cycles.

[0023] The processor 142 can execute one or more instructions associated with the system 100. The processor 142 can include an electronic processor, an integrated circuit, or the like including one or more of digital logic, analog logic, digital sensors, analog sensors, communication buses, volatile memory, nonvolatile memory, and the like. The processor 142 can include, but is not limited to, at least one microcontroller unit (MCU), microprocessor unit (MPU), central processing unit (CPU), embedded controller (EC), or the like. The processor 142 can include a processor memory operable to store or storing one or more instructions for operating components of the processor 142 and operating components operably coupled to the processor 142. The one or more instructions can include at least one of firmware, software, hardware, operating systems, embedded operating systems, and the like.

[0024] The system 100 can be coupled with at least one of a system power source or a system electrical load via the first node 102 and the power converter 110. For example, the system 100 can be coupled in parallel with the system power source between the first node 102 and at least one of the second node 104 or a reference voltage or ground voltage distinct from a voltage at the second node 104. The system power source can correspond to any source of electrical energy. For example, the system power source can correspond to or include at least one of a regenerative braking system of a vehicle, one or more fuel cells, one or more diesel generators, one or more gasoline generators, one or more natural gas generators, one or more solar panels, one or more wind turbines, or one or more electrical connections with a power utility, but is not limited thereto. The system electrical load can correspond to any device that can consume electrical energy. For example, the system electrical load can correspond to or include at least one of a traction motor, one or more electric heaters, one or more electrical controllers, one ormore electronic controllers, one or more pumps (e.g., water, air, inert gas, natural gas), or one or more electrical connections with a power utility, but is not limited thereto. For example, the system 100 can be coupled in parallel as discussed herein with any number of system power sources or any number of system electrical loads, or any combination thereof. For example, the system 100 can be coupled with at least one of a system power source or a system electrical load with a DC power bus corresponding to, coupled with, or integrated with the first node 102. For example, the power bus can operate at a voltage greater than or less than a nominal voltage of one or more of the power sources as discussed herein.

[0025] In some embodiments, a non-transitory computer readable medium can include one or more instructions stored thereon and executable by a processor to detect a first voltage across a first battery coupled with a first node, the first voltage indicative of a first level of charge of the first battery, the first node having a first input voltage, detect a second voltage across a second battery coupled with a second node, the second voltage indicative of a second level of charge of the second battery, the second node having a first reference voltage, the first battery and the second battery coupled in series between the first node and the second node, cause a power converter to couple a third node between the first battery and the second battery with a second input voltage, to change at least one of the first level of charge or the second level of charge, and cause the power converter to couple the third node with a second reference voltage, to change at least one of the first level of charge or the second level of charge. For example, the memory 144 is the non-transitory computer readable medium. The memory 144 can store data associated with the controller 140. The memory 144 can include one or more hardware memory devices to store binary data, digital data, or the like. The memory 144 can include one or more electrical components, electronic components, programmable electronic components, reprogrammable electronic components, integrated circuits, semiconductor devices, flip flops, arithmetic units, or the like. The memory 144 can include at least one of a non-volatile memory device, a solid-state memory device, a flash memory device, or a NAND memory device. The memory 144 can include one or more addressable memory regions disposed on one or more physical memory arrays. A physical memory array can include a NAND gate array disposed on, for example, at least one of a particular semiconductor device, integrated circuit device, and printed circuit board device.

[0026] FIG. 2 depicts an example parallel system according to this disclosure. As illustrated by way of example in FIG. 2, a parallel system 200 can include at least a power converter 210,a second upper battery 220, a second lower battery 222, a third upper battery 230, a third lower battery 232, a second battery node 240, and a third battery node 242. The first power source 120 and the second power source 122 are respectively illustrated by way of example as the first battery 120 and the second battery 122, but are not limited thereto.

[0027] The power converter 210 can correspond at least partially in one or more of structure and operation to the power converter 110. The power converter 210 can include a plurality of inputs that can each be selectable to couple with one or more of the third node 130, the second battery node 240, and the third battery node 242. For example, the power converter 210 can select or be caused to select by a controller device, the third node 130 and the second battery node 240, to transfer charge between the first battery 120 and the second lower battery 222. For example, the power converter 210 can select or be caused to select by a controller device, the third node 130 and the second battery node 240, to transfer charge between the lower battery 120 and the second upper battery 220. The power converter 210 can induct current in a given battery coupled with a given battery node, according to a switching operation or duty cycle of the power converter 210 with respect to each node with which the power converter 210 is coupled or can be coupled. Excessive SOC imbalance can lead to reduced storage capacity, shortened battery life, and cell damage. Thus, this technical solution provides a technical improvement to balance SOC among battery packs connected in series strings and among packs across multiple strings. To accomplish this, the technical solutions can include, the power converter 210 having inputs selectively connected to one or more batteries having the highest SOC (e.g., as reported by the controller 140), and outputs selectively connected to batteries with the lowest SOC. The power converter 210 may be bi-directional, where the inputs and outputs can reverse roles, or can be uni-directional.

[0028] In some embodiments, the system can include a plurality of power sources including the first power source and excluding the second power source, where the plurality of power sources is coupled in parallel with the first node. For example, a plurality of power sources including the first power source and excluding the second power source includes the first battery 120, the second upper battery 220, and the third upper battery 230, and excludes the second battery 122. The second upper battery 220 can correspond at least partially in one or more of structure and operation to the first battery 120. The second upper battery 220 can be coupled in series with at least one of the second battery 122, second lower battery 222, or the third lower battery 232. For example, the power converter 210 can couple the second upperbattery 220 with one of the second battery 122, the second lower battery 222, or the third lower battery 232 respectively via the third node 130, the second battery node 240, or the third battery node 242. The second upper battery 220 can be coupled with or between the first node 102 and at least one of the third node 130, the second battery node 240, or the third battery node 242. Thus, the power converter 210 can achieve a technical improvement to couple the second upper battery 220 in series with at least one of the second battery 122, second lower battery 222, or the third lower battery 232.

[0029] In some embodiments, the system can include a second plurality of power sources including the second power source and excluding the first power source, where the second plurality of power sources is coupled in parallel with the second node. For example, a second plurality of power sources including the second power source and excluding the first power source includes the second battery 122, the second lower battery 222, and the third lower battery 232, and excludes the first battery 120. The second lower battery 222 can correspond at least partially in one or more of structure and operation to the second battery 122. The second lower battery 222 can be coupled in series with at least one of the first battery 120, the second upper battery 220, or the third upper battery 230. For example, the power converter 210 can couple the second lower battery 222 with one of the first battery 120, the second upper battery 220, or the third upper battery 230 respectively via the third node 130, the second battery node 240, or the third battery node 242. The second lower battery 222 can be coupled with or between at least one of the third node 130, the second battery node 240, or the third battery node 242, and the second node 104. Thus, the power converter 210 can achieve a technical improvement to couple the second lower battery 222 in series with at least one of the first battery 120, the second upper battery 220, or the third upper battery 230.

[0030] The third upper battery 230 can correspond at least partially in one or more of structure and operation to the first battery 120. The third upper battery 230 can be coupled in series with at least one of the second battery 122, second lower battery 222, or the third lower battery 232. For example, the power converter 210 can couple the third upper battery 230 with one of the second battery 122, the second lower battery 222, or the third lower battery 232 respectively via the third node 130, the second battery node 240, or the third battery node 242. The third upper battery 230 can be coupled with or between the first node 102 and at least one of the third node 130, the second battery node 240, or the third battery node 242. Thus, the power converter 210 can achieve a technical improvement to couple the third upper battery 230 inseries with at least one of the second battery 122, second lower battery 222, or the third lower battery 232.

[0031] The third lower battery 232 can correspond at least partially in one or more of structure and operation to the second battery 122. The third lower battery 232 can be coupled in series with at least one of the first battery 120, the second upper battery 220, or the third upper battery 230. For example, the power converter 210 can couple the third lower battery 232 with one of the first battery 120, the second upper battery 220, or the third upper battery 230 respectively via the third node 130, the second battery node 240, or the third battery node 242. The third lower battery 232 can be coupled with or between at least one of the third node 130, the second battery node 240, or the third battery node 242, and the second node 104. Thus, the power converter 210 can achieve a technical improvement to couple the third lower battery 232 in series with at least one of the first battery 120, the second upper battery 220, or the third upper battery 230.

[0032] The second battery node 240 can correspond at least partially in one or more of structure and operation to the third node 130. The second battery node 240 can be coupled with one or more of the power converter 210, the second upper battery 220, and the second lower battery 222. For example, the power converter 110 can altematingly couple the second upper battery 220 with the batteries 122, 222 or 232, to induce a current that charges one of the second upper battery 220. For example, the power converter 110 can altematingly couple the second lower battery 222 with the batteries 120, 220 or 230, to induce a current that charges one of the second upper battery 220 and the second lower battery 222, if the second upper battery 220 has a lower charge than a coupled second battery 122, 222, or 232. The third battery node 242 can correspond at least partially in one or more of structure and operation to the third node 130. The third battery node 242 can be coupled with one or more of the power converter 210, the third upper battery 230, and the third lower battery 232. For example, the power converter 110 can altematingly couple the third upper battery 230 with the batteries 122, 222 or 232, to induce a current that charges one of the third upper battery 230 or the third lower battery 232, if the third upper battery 230 has a lower charge than a coupled second battery 122, 222, or 232.

[0033] For example, a plurality of batteries can include the first battery and exclude the second battery, where the plurality of batteries is coupled in parallel with the first node. For example, the system can include a plurality of switches, where each switch of the plurality of switches is coupled with a respective battery of the plurality of batteries. For example, the system caninclude a second plurality of batteries with the second battery and exclude the first battery, where the second plurality of batteries is coupled in parallel with the second node. For example, the system can include a plurality of second switches, where each switch of the plurality of second switches is coupled with a respective battery of the second plurality of batteries.

[0034] FIG. 2 is illustrated by way of example including the first battery 120, the second upper battery 220, the third upper battery 230, the second battery 120, the second lower battery 222, and the third lower battery 232, but is not limited thereto. For example, any battery illustrated herein by way of example, including one or more of the first battery 120, the second upper battery 220, the third upper battery 230, the second battery 120, the second lower battery 222, and the third lower battery 232 can correspond to any power source as discussed herein. For example, one or more of the first battery 120, the second upper battery 220, the third upper battery 230, the second battery 120, the second lower battery 222, and the third lower battery 232, can correspond at least to any type of battery as discussed herein, or any type of capacitor (e.g., an ultracapacitor) as discussed herein.

[0035] FIG. 3 depicts an example switched system according to this disclosure. As illustrated by way of example in FIG. 3, a system 300 can include at least a second input voltage node 302, a second reference voltage node 304, a DC-DC converter 310, a first upper switch 320, a second upper switch 322, a third upper switch 324, a first lower switch 330, a second lower switch 332, a third lower switch 334, a first battery connection 340, a second battery connection 342, a third battery connection 344, a first switch connection 350, a second switch connection 352, and a third switch connection 354. The first power source 120 and the second power source 122 are respectively illustrated by way of example as the first battery 120 and the second battery 122, but are not limited thereto.

[0036] The second input voltage node 302 can include a portion of the system 100 coupled with the electrical element at a second input voltage having a third level for an electronic circuit different than the first level and the second level. For example, the electrical element can correspond to the DC-DC converter providing the second input voltage based on the input voltage having the first level (e.g., a DC voltage source). For example, the electrical element can correspond to the DC-DC converter 310. The DC-DC converter 310 can provide the second input voltage via an electrical device at the input voltage having the first level. For example, the third voltage is a high voltage less than the first voltage at the first node 102. The second reference voltage node 304 can include a portion of the system 100 coupled with an electricalelement at a second reference voltage having a fourth level for an electronic circuit different than the first level, the second level and the third level. For example, the electrical element can correspond to a voltage source providing or generating the second reference voltage having the fourth level (e.g., a neutral voltage). For example, the electrical element can correspond to an electrical device at the reference voltage having the fourth level. For example, the fourth voltage is a second reference voltage.

[0037] The DC-DC converter 310 can correspond at least partially in one or more of structure and operation to the power converter 110 or 210. For example, the DC-DC converter 310 can include a plurality of inputs that can each be selectable to be coupled with one or more of the first battery connection 340, the second battery connection 342, and the third battery connection 344. For example, the power converter 210 can select or be caused to select by a controller device, the third node 130 and the second battery node 240, to transfer charge between the first battery 120 and the second lower battery 222. For example, the DC-DC converter 310 can select or be caused to select by a controller device, the third node 130 and the second battery node 240, to transfer charge between the lower battery 120 and the second upper battery 220. The DC-DC converter 310 can induce current in a given battery coupled with a given battery node, according to a switching operation or duty cycle of the power converter with respect to each node with which the DC-DC converter 310 is coupled or can be coupled. For example, the DC-DC converter 310 can switch between applying one or more of the first, second, third, or fourth voltages to one or more of the third node 130, the second battery node 240, and the third battery node 242. This, the DC-DC converter 310 can provide a technical improvement to charge multiple batteries arranged across battery stacks at a higher efficiency based on applying an input voltage or a reference voltage among a plurality of available voltages.

[0038] In some embodiments, the computer readable medium includes one or more instructions executable by the processor to cause, via a switch, electrical isolation of the third node from the second reference voltage during the coupling the third node with the second input voltage, and cause, via a switch, electrical isolation of the third node from the second input voltage during the coupling the third node with the second reference voltage. For example, the system 300 can include the controller 150 to cause coupling and isolation via one or more of the switches 320, 322, 324, 330, 332, and 334. For example, the controller 140 can open and close one or more of the switches 320, 322, 324, 330, 332, and 334 by one or more instructions or signals of the processor 142.

[0039] In some embodiments, in the system, the first power source corresponds to a first battery having a first type, and the second power sources corresponds to a second battery having a second type. Electrical storage devices (e.g., power sources) can have varying characteristics, including power density and energy density. In general, a device with higher power density can have lower energy density, and vice versa. Power density can affect responsiveness of an electrical system. For example, transient capability, an aspect of power density, can affect responsiveness when delivering energy. For example, higher transient capability can be correlated with lower heat generation (e.g., via heat loss) when absorbing energy. Energy density can affect system availability or uptime. For example, overall storage capacity, an aspect of energy density, can correspond to amount or frequency of time spent offline by a system to recharge. Thus, it is advantageous to incorporate or support incorporation of power sources of multiple types in a power system.

[0040] For example, a first battery can have a first type corresponding to a lithium ion phosphate (LFP) battery. For example, a second battery can have a second type corresponding to a lithium-titanium-oxide (LTO) battery or an ultracapacitor. For example, a battery having the LFP structure can have high energy density and thus be advantageous for bulk electricity storage. The LFP battery can also be efficiently scaled for electricity storage on a cost basis. For example, a battery having the LTO structure can have high power density and thus be advantageous for transient capabilities. For example, an ultracapacitor can have high power density, and thus be advantageous for environments requiring the most responsiveness for transients. The ultracapacitor can also be scaled for electricity storage.

[0041] In some embodiments, the system can include a first switch disposed between the power converter and the third node, where the first switch is structured to isolate the third node from the second input voltage during the coupling the third node with the second reference voltage. For example, the first upper switch 320 is disposed between the DC-DC converter 310 and the battery connections 340, 342 and 344. The first upper switch 320 can couple and decouple the second input voltage node 302 and the first battery connection 340. For example, the first switch is an upper switch among the switches 320, 322 and 324. For example, the third node is one of the battery connections 340, 342 or 344. In some embodiments, the system can include a plurality of switches, each switch of the plurality of switches coupled with a respective power source of the plurality of power sources. For example, the plurality of switches includes one or more of the switches 320, 322. and 324.

[0042] In some embodiments, the first switch is structured to isolate the third node from the second input voltage during the coupling the third node with the second reference voltage. For example, the first upper switch 320 couples the first battery 120 with the DC-DC converter 310 via the second input voltage node 302, and isolates the first battery 120 from the DC-DC converter 310 and the second input voltage node 302. The second upper switch 322 can couple and decouple the second input voltage node 302 and the second battery connection 342. For example, the second upper switch 322 couples the second upper battery 220 with the DC-DC converter 310 via the second input voltage node 302, and isolates the second upper battery 220 from the DC-DC converter 310 and the second input voltage node 302. The third upper switch 324 can couple and decouple the second input voltage node 302 and the third battery connection 344. For example, the third upper switch 324 couples the third upper battery 230 with the DC- DC converter 310 via the second input voltage node 302, and isolates the third upper battery 230 from the DC-DC converter 310 and the second input voltage node 302. For example, the first upper switch 320, the second upper switch 322, and the third upper switch 324 can each include a transistor or capacitor, but are not limited thereto. The DC-DC converter 310 or a controller device as discussed herein can selectively and individually actuate the first upper switch 320, the second upper switch 322, and the third upper switch 324 to couple or isolate portions of the system 300 as discussed herein.

[0043] In some embodiments, the system can include a second switch disposed between the power converter and the third node. For example, the first lower switch 330 is disposed between the DC-DC converter 310 and the battery connections 340, 342 and 344. The first lower switch 330 can couple and decouple the second node 104 and the first battery connection 340. For example, the second switch is a lower switch among the switches 330, 332 and 334. In some embodiments, the system can include a plurality of second switches, each switch of the plurality of second switches coupled with a respective power source of the second plurality of power sources. For example, the plurality of second switches includes one or more of the switches 330, 332. and 334.

[0044] In some embodiments, the second switch is structured to isolate the third node from the second reference voltage during the coupling of the third node with the second input voltage. For example, the first lower switch 330 couples the second battery 122 with the DC-DC converter 310 via the second node 104, and isolates the second battery 122 from the DC-DC converter 310 and the second node 104. The second lower switch 332 can couple and decouplethe second node 104 and the second battery connection 342. For example, the second lower switch 332 couples the second lower battery 222 with the DC-DC converter 310 via the second node 104, and isolates the second lower battery 222 from the DC-DC converter 310 and the second node 104. The third lower switch 334 can couple and decouple the second node 104 and the third battery connection 344. For example, the third lower switch 334 couples the third lower battery 232 with the DC-DC converter 310 via the second node 104, and isolates the third lower battery 232 from the DC-DC converter 310 and the second node 104. For example, the first lower switch 330, the second lower switch 332, and the third lower switch 334 can each include a transistor or capacitor, but are not limited thereto. The DC-DC converter 310 or a controller device as discussed herein can selectively and individually actuate the first lower switch 330, the second lower switch 332, and the third lower switch 334 to couple or isolate portions of the system 300 as discussed herein.

[0045] The first battery connection 340 can correspond at least partially in one or more of structure and operation to the third node 130, and can be coupled with the first upper switch 320 and the first lower switch 330 via the first switch connection 350. The second battery connection 342 can correspond at least partially in one or more of structure and operation to the second battery node 240, and can be coupled with the second upper switch 322 and the second lower switch 332 via the second switch connection 352. The third battery connection 344 can correspond at least partially in one or more of structure and operation to the third battery node 242, and can be coupled with the third upper switch 324 and the third lower switch 334 via the third switch connection 354.

[0046] FIG. 3 is illustrated by way of example including the first battery 120, the second upper battery 220, the third upper battery 230, the second battery 120, the second lower battery 222, and the third lower battery 232, but is not limited thereto. For example, any battery illustrated herein by way of example, including one or more of the first battery 120, the second upper battery 220, the third upper battery 230, the second battery 120, the second lower battery 222, and the third lower battery 232 can correspond to any power source as discussed herein. For example, one or more of the first battery 120, the second upper battery 220, the third upper battery 230, the second battery 120, the second lower battery 222, and the third lower battery 232, can correspond at least to any type of battery as discussed herein, or any type of capacitor (e.g., an ultracapacitor) as discussed herein.

[0047] FIG. 4 depicts an example multiple switched system according to this disclosure. As illustrated by way of example in FIG. 4, a multiple switched system 400 can include at least an input voltage connection 402, a first input switch 410, a second input switch 412, a third input switch 414, a first upper battery connection 420, a second upper battery connection 422, and a third upper battery connection 424. The input voltage connection 402 can include a portion of the system 100 coupled with an electrical element at the input voltage having the first level. For example, the input voltage connection 402 can couple with the first node 102 to receive the first voltage of a high voltage. The first power source 120 and the second power source 122 are respectively illustrated by way of example as the first battery 120 and the second battery 122, but are not limited thereto.

[0048] The first input switch 410 can couple and decouple the input voltage connection 402 and the first upper battery connection 420. For example, the first input switch 410 couples the first battery 120 with the DC-DC converter 310 via the input voltage connection 402, and isolates the first battery 120 from the DC-DC converter 310 and the input voltage connection 402. The second input switch 412 can couple and decouple the input voltage connection 402 and the second upper battery connection 422. For example, the second input switch 412 couples the second upper battery 220 with the DC-DC converter 310 via the input voltage connection 402, and isolates the second upper battery 220 from the DC-DC converter 310 and the input voltage connection 402. The third input switch 414 can couple and decouple the input voltage connection 402 and the third upper battery connection 424. For example, the third input switch 414 couples the third upper battery 230 with the DC-DC converter 310 via the input voltage connection 402, and isolates the third upper battery 230 from the DC-DC converter 310 and the input voltage connection 402. For example, the first input switch 410, the second input switch 412, and the third input switch 414 can correspond at least partially in one or more of structure and operation to the first upper switch 320, the second upper switch 322, and the third upper switch 324. The DC-DC converter 310 or a controller device as discussed herein can selectively and individually actuate the first input switch 410, the second input switch 412, and the third input switch 414 to couple or isolate portions of the system 300 as discussed herein.

[0049] FIG. 4 is illustrated by way of example including the first battery 120, the second upper battery 220, the third upper battery 230, the second battery 120, the second lower battery 222, and the third lower battery 232, but is not limited thereto. For example, any battery illustrated herein by way of example, including one or more of the first battery 120, the second upperbattery 220, the third upper battery 230, the second battery 120, the second lower battery 222, and the third lower battery 232 can correspond to any power source as discussed herein. For example, one or more of the first battery 120, the second upper battery 220, the third upper battery 230, the second battery 120, the second lower battery 222, and the third lower battery 232, can correspond at least to any type of battery as discussed herein, or any type of capacitor (e.g., an ultracapacitor) as discussed herein.

[0050] FIG. 5 depicts an example system in an example operating state according to this disclosure. As illustrated by way of example in FIG. 5, a system in an example operating state 500 can include at least a switching DC-DC converter 510, a closed first upper switch 520, a closed first lower switch 522, an open second upper switch 530, an open second lower switch 532, an open third upper switch 540, and an open third lower switch 542. For example, the operating state 500 is a state of the system 300 in which the first battery 120 transfers charge to the second battery 122. The configurations to transfer charge according to disclosure are not limited to the example illustrated in FIG. 5. The systems 200, 300 and 400 can transmit charge between any upper battery and any lower battery, to bring the level of charge at these batteries together. The switching DC-DC converter 510 can correspond at least partially in one or more of structure and operation to the DC-DC converter 310, and can include a transformer to induce current in the system 300 in the operating state 500.

[0051] The closed first upper switch 520 can couple the first battery 120 and the second battery 122 with the DC-DC converter 510 at the second input voltage node 302. Thus, the closed first upper switch 520 causes the DC-DC converter 510 to operate with a current induced at a first transformer coil of the DC-DC converter 510, where the current is induced according to the voltage at the second input voltage node 302. The closed first lower switch 522 can couple the first battery 120 and the second battery 122 with the DC-DC converter 510 at the second node 104. Thus, the closed first lower switch 522 causes the DC-DC converter 510 to operate with a current induced at a second transformer coil of the DC-DC converter 510, where the current is induced according to the voltage at the second node 104.

[0052] The open second upper switch 530 can isolate the second upper battery 220 and the second lower battery 222 from the DC-DC converter 510 at the second input voltage node 302. The open second lower switch 532 can isolate the second upper battery 220 and the second lower battery 222 from the DC-DC converter 510 at the second node 104. The open third upper switch 540 can isolate the third upper battery 230 and the third lower battery 232 from the DC-DC converter 510 at the second input voltage node 302. The open third lower switch 542 can isolate the third upper battery 230 and the third lower battery 232 from the DC-DC converter 510 at the second node 104. However, each of the above-noted switches can be opened and closed to transmit charge between any upper battery and any lower battery as discussed herein.

[0053] In some embodiments, a method of balancing charge across a plurality of batteries includes obtaining a first voltage across a first battery coupled with a first node, the first voltage indicative of a first level of charge of the first battery, the first node having a first input voltage, obtaining a second voltage across a second battery coupled with a second node, the second voltage indicative of a second level of charge of the second battery, the second node having a first reference voltage, the first battery and the second battery coupled in series between the first node and the second node, coupling, via a power converter, a third node between the first battery and the second battery with a second input voltage, to change at least one of the first level of charge or the second level of charge, and coupling, via the power converter, the third node with a second reference voltage, to change at least one of the first level of charge or the second level of charge.

[0054] FIG. 5 is illustrated by way of example including the first battery 120, the second upper battery 220, the third upper battery 230, the second battery 120, the second lower battery 222, and the third lower battery 232, but is not limited thereto. For example, any battery illustrated herein by way of example, including one or more of the first battery 120, the second upper battery 220, the third upper battery 230, the second battery 120, the second lower battery 222, and the third lower battery 232 can correspond to any power source as discussed herein. For example, one or more of the first battery 120, the second upper battery 220, the third upper battery 230, the second battery 120, the second lower battery 222, and the third lower battery 232, can correspond at least to any type of battery as discussed herein, or any type of capacitor (e.g., an ultracapacitor) as discussed herein. The first power source 120 and the second power source 122 are respectively illustrated by way of example as the first battery 120 and the second battery 122, but are not limited thereto.

[0055] FIG. 6 depicts an example method of active balancing of energy among batteries according to this disclosure. At least one of the systems 100-500, or a controller device that can be coupled therewith, can perform method 600. This disclosure is not limited to the method 600 discussed herein by way of example.

[0056] In some embodiments, a method of balancing charge across a plurality of batteries includes obtaining a first voltage across a first battery coupled with a first node, the first voltage indicative of a first level of charge of the first battery, the first node having a first input voltage. At 610, the method 600 can obtain a first voltage across a first battery coupled with a first node, the first voltage indicative of a first level of charge of the first battery, the first node having a first input voltage. For example, the first battery is the first battery 120, and the first level of charge is 70%, as illustrated in FIG. 5.

[0057] In some embodiments, a method of balancing charge across a plurality of batteries includes obtaining a second voltage across a second battery coupled with a second node, the second voltage indicative of a second level of charge of the second battery, the second node having a first reference voltage, the first battery and the second battery coupled in series between the first node and the second node. At 620, the method 600 can obtain a second voltage across a second battery coupled with a second node, the second voltage indicative of a second level of charge of the second battery, the second node having a first reference voltage, the first battery and the second battery coupled in series between the first node and the second node. For example, the second battery is the second battery 122, and the first level of charge is 67%, as illustrated in FIG. 5. For example, the first reference voltage is the voltage level at the reference node 104.

[0058] In some embodiments, a method of balancing charge across a plurality of batteries includes coupling, via a power converter, a third node between the first battery and the second battery with a second input voltage, to change at least one of the first level of charge or the second level of charge. At 630, the method 600 can couple, via a power converter, a third node between the first battery and the second battery with a second input voltage, to change at least one of the first level of charge or the second level of charge. For example, the first level of charge reduces from 70% toward 67%. For example, the second level of charge increases toward 70% from 67%.

[0059] In some embodiments, a method of balancing charge across a plurality of batteries includes coupling, via the power converter, the third node with a second reference voltage, to change at least one of the first level of charge or the second level of charge. At 640, the method 600 can couple, via the power converter, the third node with a second reference voltage, to change at least one of the first level of charge or the second level of charge. For example, the second reference voltage is the voltage at the second reference node 304.

[0060] In some embodiments, the method 600 includes charging the second battery 122 from the first battery 120 responsive to the second level of charge being lower than the first level of charge. For example, the power converter 110 selectively couples with the first battery 120 and the second battery 122 according to a first duty cycle of the power converter 110, to discharge the first battery 120 and to charge the second battery 122.

[0061] In some embodiments, the method 600 includes charging the first battery 120 from the second battery 122, wherein the first level of charge is lower than the second level of charge. For example, the power converter 110 selectively couples with the first battery 120 and the second battery 122 according to a duty cycle of the power converter 110, to discharge the second battery 122 and to charge the first battery 120.

[0062] In some embodiments, the method 600 includes coupling a plurality of batteries including the first battery 120 in parallel with the first node, to exclude the second battery 122 from the plurality of batteries. For example, the system 300 is structured to couple a plurality of batteries including the first battery 120 in parallel, and to exclude the second battery 122 from the parallel configuration of the plurality of batteries by coupling the second battery 122 in series with the plurality of batteries including the first battery 120

[0063] In some embodiments, the method 600 includes detecting that the first level of charge is lower than respective charges of each of the plurality of batteries. For example, the controller 140 detects the first level of charge corresponding to the first battery 120 via the first node 102 and the third node 130, according to electrical voltage or current at the power converter 110. For example, the controller 140 detects the second level of charge corresponding to the second battery 122 via the second node 104 and the third node 130, according to electrical voltage or current at the power converter 110.

[0064] In some embodiments, in the method 600, a plurality of batteries including the second battery 122 is coupled in parallel with the second node 104, and the plurality of batteries excludes the first battery 120. For example, the system 300 is structured to couple a plurality of batteries including the second battery 122 in parallel, and to exclude the first battery 120 from the parallel configuration of the plurality of batteries by coupling the first battery 120 in series with the plurality of batteries including the second battery 122.

[0065] In some embodiments, the method 600 includes identifying that the second level of charge is lower than respective charges of each of the plurality of batteries. For example, thecontroller 140 identifies that the second level of charge is lower than respective charges of each of the plurality of batteries according to a current flow induced through coupled batteries, where current is induced to flow from a battery or batteries with higher charge to a different battery or batteries with lower charge.

[0066] In some embodiments, the method 600 includes isolating, via a switch, the third node 130 from the second input voltage during the coupling the third node 130 with the second reference voltage. For example, at least one of the switches 330, 332 or 334 can selectively isolate the third node 130 from the second input voltage during the coupling the third node 130 with the second reference voltage. At least one of the switches 330, 332 or 334 can be controlled according to a duty cycle of the power converter 110 as discussed herein, but are not limited to controlled according to the duty cycle or cycles discussed herein by way of example.

[0067] In some embodiments, the method 600 includes isolating, via a switch, the third node 130 from the second reference voltage during the coupling the third node 130 with the second input voltage. For example, at least one of the switches 330, 332 or 334 can selectively isolate the third node 130 from the second reference voltage during the coupling the third node 130 with the second input voltage. At least one of the switches 330, 332 or 334 can be controlled according to a duty cycle of the power converter 110 as discussed herein, but are not limited to controlled according to the duty cycle or cycles discussed herein by way of example.

[0068] FIG. 6 is illustrated by way of example with reference to the first battery 120, the second upper battery 220, the third upper battery 230, the second battery 120, the second lower battery 222, and the third lower battery 232, but is not limited thereto. For example, any battery referenced in method 600 herein by way of example, including one or more of the first battery 120, the second upper battery 220, the third upper battery 230, the second battery 120, the second lower battery 222, and the third lower battery 232 can correspond to any power source as discussed herein. For example, one or more of the first battery 120, the second upper battery 220, the third upper battery 230, the second battery 120, the second lower battery 222, and the third lower battery 232, can correspond at least to any type of battery as discussed herein, or any type of capacitor (e.g., an ultracapacitor) as discussed herein.

[0069] Having now described some illustrative implementations, the foregoing is illustrative and not limiting, having been presented by way of example. In particular, although many of the examples presented herein involve specific combinations of method acts or systemelements, those acts and those elements may be combined in other was to accomplish the same objectives. Acts, elements and features discussed in connection with one implementation are not intended to be excluded from a similar role in other implementations.

[0070] The phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” “having,” “containing,” “involving,” “characterized by,” “characterized in that,” and variations thereof herein, is meant to encompass the items listed thereafter, equivalents thereof, and additional items, as well as alternate implementations consisting of the items listed thereafter exclusively. In one implementation, the systems and methods described herein consist of one, each combination of more than one, or all of the described elements, acts, or components.

[0071] References to “or” may be construed as inclusive so that any terms described using “or” may indicate any of a single, more than one, and all of the described terms. References to at least one of a conjunctive list of terms may be construed as an inclusive OR to indicate any of a single, more than one, and all of the described terms. For example, a reference to “at least one of ‘A’ and ‘B’ can include only ‘A’, only ‘B’, as well as both ‘A’ and ‘B’. Such references used in conjunction with “comprising” or other open terminology can include additional items. References to “is” or “are” may be construed as nonlimiting to the implementation or action referenced in connection with that term. The terms “is” or “are” or any tense or derivative thereof, are interchangeable and synonymous with “can be” as used herein, unless stated otherwise herein.

[0072] Directional indicators depicted herein are example directions to facilitate understanding of the examples discussed herein, and are not limited to the directional indicators depicted herein. Any directional indicator depicted herein can be modified to the reverse direction, or can be modified to include both the depicted direction and a direction reverse to the depicted direction, unless stated otherwise herein. While operations are depicted in the drawings in a particular order, such operations are not required to be performed in the particular order shown or in sequential order, and all illustrated operations are not required to be performed. Actions described herein can be performed in a different order. Where technical features in the drawings, detailed description or any claim are followed by reference signs, the reference signs have been included to increase the intelligibility of the drawings, detailed description, and claims. Accordingly, neither the reference signs nor their absence have any limiting effect on the scope of any clam elements.

[0073] Scope of the systems and methods described herein is thus indicated by the appended claims, rather than the foregoing description. The scope of the claims includes equivalents to the meaning and scope of the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A method of balancing charge across a plurality of batteries, the method comprising: obtaining a first voltage across a first battery coupled with a first node, the first voltage indicative of a first level of charge of the first battery, the first node having a first input voltage; obtaining a second voltage across a second battery coupled with a second node, the second voltage indicative of a second level of charge of the second battery, the second node having a first reference voltage, the first battery and the second battery coupled in series between the first node and the second node; coupling, via a power converter, a third node between the first battery and the second battery with a second input voltage, to change at least one of the first level of charge or the second level of charge; and coupling, via the power converter, the third node with a second reference voltage, to change at least one of the first level of charge or the second level of charge.

2. The method of claim 1, further comprising: charging the second battery from the first battery responsive to the second level of charge being lower than the first level of charge.

3. The method of claim 1, further comprising: charging the first battery from the second battery, wherein the first level of charge is lower than the second level of charge.

4. The method of claim 1, further comprising: coupling a plurality of batteries including the first battery in parallel with the first node, to exclude the second battery from the plurality of batteries.

5. The method of claim 4, further comprising: detecting that the first level of charge is lower than respective charges of each of the plurality of batteries.

6. The method of claim 1, wherein a plurality of batteries including the second battery is coupled in parallel with the second node, and the plurality of batteries excludes the first battery.

7. The method of claim 6, further comprising: identifying that the second level of charge is lower than respective charges of each of the plurality of batteries.

8. The method of claim 1, further comprising: isolating, via a switch, the third node from the second input voltage during the coupling the third node with the second reference voltage.

9. The method of claim 1, further comprising: isolating, via a switch, the third node from the second reference voltage during the coupling the third node with the second input voltage.

10. A system of balancing charge across a plurality of power sources, the system comprising: a first power source coupled with a first node having a first input voltage, the first power source having a first voltage indicative of a first level of charge of the first power source; a second power source coupled with a second node having a first reference voltage, the second power source having a second voltage indicative of a second level of charge of the second power source, the first power source and the second power source coupled in series between the first node and the second node; a power converter structured to change at least one of the first level of charge or the second level of charge, by coupling a third node between the first power source and the second power source with a second input voltage, and by the third node with a second reference voltage.

11. The system of claim 10, wherein the first power source corresponds to a first battery having a first type, and the second power sources corresponds to a second battery having a second type.

12. The system of claim 11, further comprising: a first switch disposed between the power converter and the third node, wherein the first switch is structured to isolate the third node from the second input voltage during the coupling the third node with the second reference voltage.

13. The system of claim 11, further comprising: a second switch disposed between the power converter and the third node.

14. The system of claim 13, wherein the second switch is structured to isolate the third node from the second reference voltage during the coupling the third node with the second input voltage.

15. The system of claim 10, further comprising: a plurality of power sources including the first power source and excluding the second power source, wherein the plurality of power sources is coupled in parallel with the first node.

16. The system of claim 15, further comprising: a plurality of switches, each switch of the plurality of switches coupled with a respective power source of the plurality of power sources.

17. The system of claim 15, further comprising: a second plurality of power sources including the second power source and excluding the first power source, wherein the second plurality of power sources is coupled in parallel with the second node.

18. The system of claim 17, further comprising: a plurality of second switches, each switch of the plurality of second switches coupled with a respective power source of the second plurality of power sources.

19. A non-transitory computer readable medium including one or more instructions stored thereon and executable by a processor to: detect a first voltage across a first battery coupled with a first node, the first voltage indicative of a first level of charge of the first battery, the first node having a first input voltage; detect a second voltage across a second battery coupled with a second node, the second voltage indicative of a second level of charge of the second battery, the second node having a first reference voltage, the first battery and the second battery coupled in series between the first node and the second node; cause a power converter to couple a third node between the first battery and the second battery with a second input voltage, to change at least one of the first level of charge or the second level of charge; and cause the power converter to couple the third node with a second reference voltage, to change at least one of the first level of charge or the second level of charge.

20. The computer readable medium of claim 18, the computer readable medium further including one or more instructions executable by the processor to: cause, via a switch, electrical isolation of the third node from the second reference voltage during the coupling the third node with the second input voltage; and cause, via a switch, electrical isolation of the third node from the second input voltage during the coupling the third node with the second reference voltage.

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