A battery equalization circuit based on complementary half-bridge, and its control system and method.

Abstract

This invention discloses a battery equalization circuit based on complementary half-bridges, its control system, and its method, belonging to the field of electrochemical energy storage. Voltage equalization between two individual cells within a battery unit is achieved through a switched inductor circuit, while voltage equalization among all battery units is achieved through a (quasi-resonant) switched capacitor circuit. Each complementary half-bridge circuit in the switching array consists of a P-channel MOSFET and an N-channel MOSFET connected in series. Each complementary half-bridge circuit is driven by an isolated optocoupler, a push-pull circuit, or an integrated driver chip. The driver circuit is powered by the corresponding battery unit, thus eliminating the need for an auxiliary power supply. All complementary half-bridge circuits are controlled by two square wave signals with the same frequency, duty cycle, and phase. This invention reduces the number of switching transistors required for the equalization circuit and simplifies the driver design of the switching array, which is of great significance for reducing the cost and size of the battery equalization circuit, as well as the design and implementation difficulty.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical energy storage, and relates to a battery balancing circuit based on complementary half-bridge and its control system and method. Background Technology

[0002] As the global energy structure undergoes a profound transformation towards low-carbon and electrification, lithium-ion batteries, with their advantages of high energy density, long cycle life, and low self-discharge rate, have become the core energy carrier in fields such as new energy vehicles, grid energy storage, portable electronic devices, and aerospace. Typically, a large number of lithium-ion battery cells are connected in series to form battery strings to meet the voltage and power requirements of different applications. However, due to differences in manufacturing processes, changes in ambient temperature, and aging effects during use, energy mismatch can occur between different battery cells. If a battery string operates in an energy mismatch state for an extended period, it will reduce the performance of the battery string and may even induce major safety accidents. Voltage balancing circuits, as an important component of the battery management system, ensure that the voltage of the battery cells in the battery string is consistent, which is crucial for ensuring the safe and efficient operation of the battery string.

[0003] Battery balancing technology can be broadly categorized into passive balancing and active balancing. Passive balancing achieves voltage equalization between individual battery cells by dissipating excess energy through resistors. While passive balancing circuits are simple in structure and low in cost, energy loss and thermal management issues during the balancing process make them unsuitable for high-energy-density battery strings used for extended periods. Active balancing circuits, on the other hand, utilize energy storage components such as transformers, inductors, and capacitors to redistribute energy among unbalanced battery cells to achieve voltage equalization. Active balancing circuits effectively improve balancing speed and efficiency, resulting in higher-performance voltage equalization.

[0004] However, existing active equalization circuits require a large number of switching transistors, and the design of the driving circuit is very complex, which increases the cost and implementation difficulty of the entire equalization circuit. Therefore, it is urgent to optimize the topology and driving architecture of existing active equalization circuits to minimize the number of switching transistors and the design complexity of the driving circuit while ensuring the performance of the equalization system, thereby reducing the cost of the equalization system and making it easier to design and implement. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a battery equalization circuit based on a complementary half-bridge, as well as its control system and method. This circuit and its control system and method can achieve voltage equalization of battery strings, and the number of switching transistors used and the design complexity of the driving circuit are relatively low.

[0006] To achieve the above objectives, this invention discloses a battery balancing circuit based on complementary half-bridges, comprising a battery string, a switch array, and an energy storage element; the battery string is composed of several battery cells connected in series, and each battery cell includes two battery cells connected in series; the switch array is composed of several complementary half-bridge circuits connected in series, each complementary half-bridge circuit including an upper bridge arm P-channel MOSFET device S1 and a lower bridge arm N-channel MOSFET device S2, wherein the drain (D) of the upper bridge arm P-channel MOSFET device S1 is connected to the drain (D) of the lower bridge arm N-channel MOSFET device S2, and the S-channel MOSFET device S2 in the previous complementary half-bridge circuit is connected to the drain (S) of the lower bridge arm N-channel MOSFET device S2. The source (S) of the upper arm P-channel MOSFET device S1 in the next complementary half-bridge circuit is connected to the source (S) of the battery cell. Each battery cell corresponds to one complementary half-bridge circuit and one energy storage element. In the complementary half-bridge circuit, the drain (D) of the upper arm P-channel MOSFET device S1 is connected to the midpoint of the corresponding battery cell via an inductor L. The source (S) of the upper arm P-channel MOSFET device S1 is connected to the positive terminal of the corresponding battery cell. The source (S) of the lower arm N-channel MOSFET device S2 is connected to the negative terminal of the corresponding battery cell. One end of the energy storage element is connected to the drain (D) of the upper arm P-channel MOSFET device S1, and the other ends of all energy storage elements are connected in a star configuration.

[0007] Furthermore, the energy storage element is a resonant cavity or a capacitor.

[0008] Furthermore, the resonant cavity includes a resonant capacitor C connected in series. r and resonant inductance L r .

[0009] This invention discloses a control system based on a complementary half-bridge battery balancing circuit, including a driving circuit. The output terminal of the driving circuit is connected to the gate (G) of the upper bridge arm P-channel MOSFET device S1 and the gate (G) of the lower bridge arm N-channel MOSFET device S2 in each complementary half-bridge circuit.

[0010] Furthermore, the driving circuit consists of several dual-input dual-output isolated optocouplers, wherein one isolated optocoupler corresponds to one battery cell, the power supply on the output side of the isolated optocoupler is connected to the positive terminal of the corresponding battery cell, the reference ground on the output side of the isolated optocoupler is connected to the negative terminal of the corresponding battery cell, and the two output signals of the isolated optocoupler are respectively connected to the gate of the upper arm P-channel MOSFET device S1 and the lower arm N-channel MOSFET device S2 in the complementary half-bridge circuit.

[0011] Furthermore, the driving circuit consists of several single-input single-output isolated optocouplers, wherein two isolated optocouplers correspond to one battery cell, the power supply of the output side of the two isolated optocouplers is connected to the positive terminal of the corresponding battery cell, the reference ground of the output side of the two isolated optocouplers is connected to the negative terminal of the corresponding battery cell, the output signal of the top isolated optocoupler is connected to the gate of the upper bridge arm P-channel MOSFET device S1 in the complementary half-bridge circuit, and the output signal of the bottom isolated optocoupler is connected to the gate of the lower bridge arm N-channel MOSFET device S2 in the complementary half-bridge circuit.

[0012] Furthermore, the driving circuit includes several push-pull circuits or integrated driving chips, wherein the output power supply of the push-pull circuit or integrated driving chip is connected to the positive terminal of the corresponding battery cell, the output ground of the push-pull circuit or integrated driving chip is connected to the negative terminal of the corresponding battery cell, and the output signal of the push-pull circuit or integrated driving chip is respectively connected to the gate of the upper arm P-channel MOSFET device S1 and the lower arm N-channel MOSFET device S2 in the complementary half-bridge circuit.

[0013] This invention discloses a control method for a battery equalization circuit based on a complementary half-bridge. The control system for the battery equalization circuit based on the complementary half-bridge includes: all complementary half-bridge circuits in the switch array are controlled by two square wave signals with the same frequency, duty cycle, and phase; the upper arm P-channel MOSFET device S1 and the lower arm N-channel MOSFET device S2 in the complementary half-bridge circuit are always complementary in conduction; when the drive signal of the upper arm P-channel MOSFET device S1 in the complementary half-bridge circuit is low, the upper arm P-channel MOSFET device S1 is turned on; when the drive signal of the lower arm N-channel MOSFET device S2 in the complementary half-bridge circuit is high, the lower arm N-channel MOSFET device S2 is turned on.

[0014] Furthermore, specifically including: When the MOSFET device corresponding to the high-voltage battery cell in the battery cell is turned on, the high-voltage battery cell charges the inductor L; when the MOSFET device corresponding to the low-voltage battery cell in the battery cell is turned on, the inductor L discharges the low-voltage battery cell; through the continuous switching between the two working states, the voltage balance between the two battery cells in the battery cell is finally achieved. When the MOSFET device corresponding to the high-voltage battery cell in the battery string is turned on, the high-voltage battery cell charges the energy storage element; when the MOSFET device corresponding to the low-voltage battery cell in the battery string is turned on, the energy storage element discharges the low-voltage battery cell; through the continuous switching between the two operating states, voltage balance among all battery cells in the battery string is finally achieved.

[0015] The present invention has the following beneficial effects: This invention discloses a battery equalization circuit based on complementary half-bridges, its control system, and its method. Each complementary half-bridge circuit in the switching array consists of a P-channel MOSFET and an N-channel MOSFET connected in series. This invention achieves voltage equalization between two individual battery cells within a battery unit through a switched inductor circuit, and achieves voltage equalization among all battery cells through a (quasi-resonant) switched capacitor circuit. This invention reduces the number of switching transistors required by the switching array by half, and all driving circuits are directly powered by the corresponding battery cells, thereby reducing the cost and size of the equalization circuit, as well as the design and implementation difficulty. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a circuit diagram of the present invention; Figure 2 The driving circuit diagram for the isolated optocoupler; Figure 3 This is a schematic diagram of the drive signals for the switch array; Figure 4 A circuit diagram for voltage balancing within a battery cell; Figure 5 This is a circuit diagram for voltage balancing between battery cells. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] In the description of this invention, it should be understood that the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0020] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0021] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes such combinations. For example, A and / or B can represent three cases: A alone, A and B simultaneously, and B alone. Additionally, the character " / " in this invention generally indicates that the preceding and following objects have an "or" relationship.

[0022] It should be understood that although terms such as first, second, third, etc., may be used in the embodiments of the present invention to describe the preset range, these preset ranges should not be limited to these terms. These terms are only used to distinguish the preset ranges from one another. For example, without departing from the scope of the embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0023] Depending on the context, the word "if" as used here can be interpreted as "when," "when," "in response to determination," or "in response to detection." Similarly, depending on the context, the phrase "if determination" or "if detection (of the stated condition or event)" can be interpreted as "when determination," "in response to determination," "when detection (of the stated condition or event)," or "in response to detection (of the stated condition or event)."

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0025] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0026] Example 1 refer to Figure 1 The battery balancing circuit based on complementary half-bridges of this invention includes a battery string, a switch array, and an energy storage element. The battery string is composed of several battery cells connected in series, and each battery cell includes two battery cells connected in series. The switch array is composed of several complementary half-bridge circuits connected in series. Each complementary half-bridge circuit includes an upper bridge arm P-channel MOSFET device S1 and a lower bridge arm N-channel MOSFET device S2. The drain (D) terminal of the upper bridge arm P-channel MOSFET device S1 is connected to the drain (D) terminal of the lower bridge arm N-channel MOSFET device S2. In the previous complementary half-bridge circuit, the source (S) terminal of the lower bridge arm N-channel MOSFET device S2 is connected to the source (S) terminal of the next complementary half-bridge circuit. In a complementary half-bridge circuit, the source (S) terminals of the upper arm P-channel MOSFET device S1 are connected together. Each battery cell corresponds to one complementary half-bridge circuit and one energy storage element. In the complementary half-bridge circuit, the drain (D) terminal of the upper arm P-channel MOSFET device S1 is connected to the midpoint of the corresponding battery cell via an inductor L. The source (S) terminal of the upper arm P-channel MOSFET device S1 is connected to the positive terminal of the corresponding battery cell. The source (S) terminal of the lower arm N-channel MOSFET device S2 is connected to the negative terminal of the corresponding battery cell. One end of the energy storage element is connected to the drain (D) terminal of the upper arm P-channel MOSFET device S1, and the other ends of all energy storage elements are connected together.

[0027] In this embodiment, the energy storage element is a resonant cavity or a capacitor; wherein, the resonant cavity includes a resonant capacitor Cr and a resonant inductor Lr connected in series.

[0028] It should be noted that the on-resistance of the upper arm P-channel MOSFET S1 and the lower arm N-channel MOSFET S2 in each complementary half-bridge circuit should be as consistent as possible, and the withstand voltage of the switching transistors should be greater than the maximum voltage of the individual battery cells. V Bmax Capacitor L r The withstand voltage should be greater than ( n -1) V Bmax .

[0029] Example 2 This embodiment discloses a control system based on a complementary half-bridge battery equalization circuit, including a drive circuit, wherein the drive circuit is an isolated optocoupler, a push-pull circuit, or an integrated drive chip.

[0030] refer to Figure 2 The driving circuit consists of several dual-input dual-output isolated optocouplers, where one isolated optocoupler corresponds to one battery cell. The power supply on the output side of the isolated optocoupler is connected to the positive terminal of the corresponding battery cell, and the reference ground on the output side of the isolated optocoupler is connected to the negative terminal of the corresponding battery cell. The two output signals of the isolated optocoupler are respectively connected to the gate of the upper arm P-channel MOSFET device S1 and the lower arm N-channel MOSFET device S2 in the complementary half-bridge circuit.

[0031] refer to Figure 2 The driving circuit consists of several single-input single-output isolated optocouplers, wherein two isolated optocouplers correspond to one battery cell, the power supply of the output side of the two isolated optocouplers is connected to the positive terminal of the corresponding battery cell, the reference ground of the output side of the two isolated optocouplers is connected to the negative terminal of the corresponding battery cell, the output signal of the top isolated optocoupler is connected to the gate of the upper bridge arm P-channel MOSFET device S1 in the complementary half-bridge circuit, and the output signal of the bottom isolated optocoupler is connected to the gate of the lower bridge arm N-channel MOSFET device S2 in the complementary half-bridge circuit.

[0032] When the driving circuit is a push-pull circuit or an integrated driving chip, the power supply on the output side of the push-pull circuit or integrated driving chip is connected to the positive terminal of the corresponding battery cell, and the reference ground on the output side of the push-pull circuit or integrated driving chip is connected to the negative terminal of the corresponding battery cell. The two output signals of the push-pull circuit or integrated driving chip are respectively connected to the gate of the upper arm P-channel MOSFET device S1 and the lower arm N-channel MOSFET device S2 in the complementary half-bridge circuit.

[0033] Example 3 This embodiment discloses a control method for a battery equalization circuit based on complementary half-bridges, including: controlling all complementary half-bridge circuits in the switch array using two square wave signals with the same frequency, duty cycle and phase.

[0034] refer to Figure 3In the complementary half-bridge circuit, the upper arm P-channel MOSFET S1 and the lower arm N-channel MOSFET S2 are always complementary in conduction. The dead time of the upper arm P-channel MOSFET S1 and the lower arm N-channel MOSFET S2 is achieved by setting the delay of the rising and falling edges of the two square wave signals. When the drive signal of the upper arm P-channel MOSFET S1 in the complementary half-bridge circuit is low, the upper arm P-channel MOSFET S1 is turned on. When the drive signal of the lower arm N-channel MOSFET S2 in the complementary half-bridge circuit is high, the lower arm N-channel MOSFET S2 is turned on.

[0035] refer to Figure 4 High-voltage battery cells in battery units B k,1 When the corresponding MOSFET device is turned on, the high-voltage battery cell B k,1 Give inductor L k Charging; low-voltage battery cells in the battery unit B k,2 When the corresponding MOSFET device is turned on, the inductor L k For low-voltage battery cells B k,2 Discharge; through continuous switching between two operating states, the two individual battery cells within the battery unit are ultimately discharged. B k,1 and B k,2 Voltage balance between them.

[0036] refer to Figure 5 High-voltage battery cells in battery string B i When the corresponding MOSFET device is turned on, the high-voltage battery cell B i Charging energy storage components; low-voltage battery units in the battery string B j When the corresponding MOSFET device is turned on, the energy storage element supplies energy to the low-voltage battery cell. B j Discharge; by continuously switching between two operating states, the two battery cells within the battery string are ultimately discharged. B i and B j Voltage balance between them.

[0037] This invention has the following characteristics: In this invention, each complementary half-bridge circuit in the switching array consists of a P-channel MOSFET and an N-channel MOSFET connected in series. Voltage equalization between two individual battery cells is achieved through a switched inductor circuit, and voltage equalization among all battery cells is achieved through a (quasi-resonant) switched capacitor circuit. Compared to existing (quasi-resonant) switched capacitor equalization circuits, this invention reduces the number of switching transistors required in the switching array by half, resulting in lower cost and smaller size.

[0038] All half-bridge circuits in this invention are driven by isolated optocouplers, push-pull circuits, or integrated driver chips, and the driving circuits are directly powered by the corresponding battery cells, thus eliminating the need for an auxiliary power supply. Compared to existing active balancing circuits based on pulse transformers and isolated gate drivers, this invention has lower cost and size, and is easier to design and implement.

[0039] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and disclosure of the invention. This application is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the following claims.

[0040] It should be understood that the present invention is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

[0041] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the present invention. Any simple modifications, alterations, or equivalent structural changes made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A complementary half-bridge based battery equalization circuit, characterized in that, The system includes a battery string, a switch array, and energy storage elements. The battery string is composed of several battery cells connected in series, and each battery cell includes two battery cells connected in series. The switch array is composed of several complementary half-bridge circuits connected in series. Each complementary half-bridge circuit includes an upper bridge arm P-channel MOSFET device S1 and a lower bridge arm N-channel MOSFET device S2. The drain (D) terminal of the upper bridge arm P-channel MOSFET device S1 is connected to the drain (D) terminal of the lower bridge arm N-channel MOSFET device S2. The source (S) terminal of the lower bridge arm N-channel MOSFET device S2 in the preceding complementary half-bridge circuit is connected to the source (S) terminal of the upper bridge arm N-channel MOSFET device S2 in the following complementary half-bridge circuit. The source (S) of the P-channel MOSFET device S1 is connected; one battery cell corresponds to one complementary half-bridge circuit and one energy storage element. In the complementary half-bridge circuit, the drain (D) of the upper bridge arm P-channel MOSFET device S1 is connected to the midpoint of the corresponding battery cell via inductor L, the source (S) of the upper bridge arm P-channel MOSFET device S1 is connected to the positive terminal of the corresponding battery cell, and the source (S) of the lower bridge arm N-channel MOSFET device S2 is connected to the negative terminal of the corresponding battery cell. One end of the energy storage element is connected to the drain (D) of the upper bridge arm P-channel MOSFET device S1, and the other ends of all energy storage elements are connected in a star configuration.

2. The complementary half-bridge based battery equalization circuit of claim 1, wherein, The energy storage element is a resonant cavity or a capacitor.

3. The complementary half-bridge based battery equalization circuit of claim 2, wherein, The resonant cavity comprises a resonant capacitance C connected in series r and a resonant inductance L r .

4. A control system for the complementary half-bridge based battery equalization circuit of any of claims 1-3, characterized in that, It includes a driving circuit, the output of which is connected to the gate (G) of the upper bridge arm P-channel MOSFET device S1 and the gate (G) of the lower bridge arm N-channel MOSFET device S2 in each complementary half-bridge circuit.

5. The control system based on the complementary half-bridge battery equalization circuit according to claim 4, characterized in that, The driving circuit consists of several dual-input dual-output isolated optocouplers, wherein one isolated optocoupler corresponds to one battery cell, the power supply on the output side of the isolated optocoupler is connected to the positive terminal of the corresponding battery cell, the reference ground on the output side of the isolated optocoupler is connected to the negative terminal of the corresponding battery cell, and the two output signals of the isolated optocoupler are respectively connected to the gate of the upper arm P-channel MOSFET device S1 and the lower arm N-channel MOSFET device S2 in the complementary half-bridge circuit.

6. The control system based on the complementary half-bridge battery equalization circuit according to claim 4, characterized in that, The driving circuit consists of several single-input single-output isolated optocouplers, wherein two isolated optocouplers correspond to one battery cell, the power supply of the output side of the two isolated optocouplers is connected to the positive terminal of the corresponding battery cell, the reference ground of the output side of the two isolated optocouplers is connected to the negative terminal of the corresponding battery cell, the output signal of the top isolated optocoupler is connected to the gate of the upper arm P-channel MOSFET device S1 in the complementary half-bridge circuit, and the output signal of the bottom isolated optocoupler is connected to the gate of the lower arm N-channel MOSFET device S2 in the complementary half-bridge circuit.

7. The control system based on the complementary half-bridge battery equalization circuit according to claim 4, characterized in that, The driving circuit includes several push-pull circuits or integrated driving chips. The output power supply of the push-pull circuit or integrated driving chip is connected to the positive terminal of the corresponding battery cell, and the output reference ground of the push-pull circuit or integrated driving chip is connected to the negative terminal of the corresponding battery cell. The output signals of the push-pull circuit or integrated driving chip are respectively connected to the gate of the upper arm P-channel MOSFET device S1 and the lower arm N-channel MOSFET device S2 in the complementary half-bridge circuit.

8. A control method for a battery equalization circuit based on a complementary half-bridge, characterized in that, The control system based on the battery equalization circuit based on the complementary half-bridge as described in claim 4 includes: all complementary half-bridge circuits in the switch array are controlled by two square wave signals with the same frequency, duty cycle and phase; the upper arm P-channel MOSFET device S1 and the lower arm N-channel MOSFET device S2 in the complementary half-bridge circuit are always complementaryly turned on; when the drive signal of the upper arm P-channel MOSFET device S1 in the complementary half-bridge circuit is low, the upper arm P-channel MOSFET device S1 is turned on; when the drive signal of the lower arm N-channel MOSFET device S2 in the complementary half-bridge circuit is high, the lower arm N-channel MOSFET device S2 is turned on.

9. The control method for a battery equalization circuit based on a complementary half-bridge according to claim 8, characterized in that, Specifically, it includes: When the MOSFET device corresponding to the high-voltage battery cell in the battery unit is turned on, the high-voltage battery cell charges the inductor L. When the MOSFET device corresponding to the low-voltage battery cell in the battery cell is turned on, the inductor L discharges the low-voltage battery cell; through the continuous switching between the two working states, the voltage balance between the two battery cells in the battery cell is finally achieved. When the MOSFET device corresponding to the high-voltage battery cell in the battery string is turned on, the high-voltage battery cell charges the energy storage element; when the MOSFET device corresponding to the low-voltage battery cell in the battery string is turned on, the energy storage element discharges the low-voltage battery cell; through the continuous switching between the two operating states, voltage balance among all battery cells in the battery string is finally achieved.

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