An active balancing circuit, a battery balancing system and an active balancing method

Abstract

The application relates to the technical field of battery management, and discloses an active balancing circuit, a battery balancing system and an active balancing method. A single / dual-inductor Buck-Boost type double-channel energy exchange module is designed through a small inductor, and is matched with a switching matrix, so that active balancing of the voltages of each single battery in a battery pack can be realized. The volume and cost are greatly reduced, the balancing efficiency is significantly improved, the topology of the overall circuit is simple, the control is flexible, and the application is conducive to wide range of popularization and application.

Description

Technical Field

[0001] This invention relates to the field of battery management technology, and in particular to an active balancing circuit, a battery balancing system, and an active balancing method. Background Technology

[0002] With the development of energy storage technology, electric vehicles and battery energy storage systems are being applied more and more widely and deeply in various fields. Since battery packs in energy storage systems are mostly composed of multiple individual cells connected in series, the voltage of a single cell has a significant impact on the capacity of the entire system. If the voltage of a single cell becomes abnormal, whether too high or too low, it can potentially lead to a decline in the performance of the entire energy storage system and even safety issues. Therefore, to ensure the stable and efficient operation of energy storage systems, active balancing of the battery packs is particularly necessary and urgent.

[0003] In the design of battery management systems, existing active balancing schemes consist of two parts: a switching matrix and an energy exchange module. The energy exchange module can be designed in several ways:

[0004] (1) such as Figure 1 As shown, BUS1 and BUS2 are connected to a DC-DC converter and then to a bidirectional flyback converter for energy transfer with the total voltage. However, this method requires a large flyback transformer, which is also costly.

[0005] (2) such as Figure 2 As shown, the positive and negative terminals BUS1 and BUS2 of the high-voltage single-cell battery are connected to a DC-DC converter and an energy storage capacitor. After energy storage is completed, BUS1 and BUS2 are switched to the positive and negative terminals of the low-voltage single-cell battery to release the energy stored in the capacitor. However, this method requires a large energy storage capacitor and also has the problem of high cost.

[0006] (3) such as Figure 3 As shown, energy exchange is achieved through an external inductor and a Buck-Boost topology. There are two methods: First, the highest-voltage cell in a string and all subsequent cells in the string discharge simultaneously, charging the total voltage. Second, the total voltage of all cells in a string charges the lowest-voltage cell in the string and all subsequent cells in the string. The first and second methods are combined, with time-division multiplexing for energy balancing (discharging and charging) within a string. However, this method has low overall balancing efficiency and cannot achieve balancing of individual cells within a single string.

[0007] In conclusion, given the numerous problems and shortcomings of the existing active balancing schemes, it is necessary to conduct in-depth research and improvement on the existing technologies.

[0008] The above information is provided as background information only to aid in understanding the present invention, and does not constitute an assertion or admission that any of the above content can be used as prior art relative to the present invention. Summary of the Invention

[0009] This invention provides an active balancing circuit, a battery balancing system, and an active balancing method to solve the problems of large size, high cost, and low balancing efficiency in the prior art.

[0010] To achieve the above objectives, the present invention provides the following technical solution:

[0011] In a first aspect, the present invention provides an active balancing circuit connected to a battery pack, the circuit comprising a switching matrix and an energy exchange module; wherein...

[0012] The switching matrix is ​​connected between the battery pack and the energy exchange module, and is used to control each individual cell in the battery pack to switch into or out of the energy exchange module through channel A or channel B.

[0013] The energy exchange module is a single-inductor Buck-Boost type, including a controller U1, a first inductor L1, a first switching unit S1, a second switching unit S2, a third switching unit S3, and a fourth switching unit S4. The first switching unit S1 is connected between the total voltage VBAT output point of the battery pack and the first inductor L1, and is controlled by the controller U1. The second switching unit S2 is connected between GND and the first inductor L1, and is controlled by the controller U1. The third switching unit S3 is connected between channel A and the first inductor L1, and is controlled by the controller U1. The fourth switching unit S4 is connected between channel B and the first inductor L1, and is controlled by the controller U1.

[0014] Alternatively, the energy exchange module is a dual-inductor Buck-Boost type, including a controller U1, a first inductor L1, a second inductor L2, a first switching unit S1, a second switching unit S2, a third switching unit S3, a fourth switching unit S4, a fifth switching unit S5, and a sixth switching unit S6; the first switching unit S1 is connected between the total voltage VBAT output point of the battery pack and the first inductor L1, and is controlled by the controller U1; the second switching unit S2 is connected between GND and the second inductor L2, and is controlled by the controller U1; the third switching unit S3 is connected between channel A and the first inductor L1, and is controlled by the controller U1; the fourth switching unit S4 is connected between channel B and the second inductor L2, and is controlled by the controller U1; the fifth switching unit S5 is connected between the total voltage VBAT output point and the second inductor L2, and is controlled by the controller U1; the sixth switching unit S6 is connected between GND and the first inductor L1, and is controlled by the controller U1.

[0015] Furthermore, in the active equalization circuit, the first switching unit S1, the second switching unit S2, the third switching unit S3, the fourth switching unit S4, the fifth switching unit S5, and the sixth switching unit S6 are all MOS transistors.

[0016] Furthermore, in the active balancing circuit, when the energy exchange module is a single-inductor Buck-Boost type, the first switching unit S1 and the second switching unit S2 are both NMOS transistors, and the third switching unit S3 and the fourth switching unit S4 are both PMOS transistors;

[0017] When the energy exchange module is a dual-inductor Buck-Boost type, the first switching unit S1, the second switching unit S2, the fifth switching unit S5 and the sixth switching unit S6 are all NMOS transistors, and the third switching unit S3 and the fourth switching unit S4 are both PMOS transistors.

[0018] Furthermore, in the active balancing circuit, the battery pack comprises n individual cells connected in series; wherein n is greater than or equal to 2.

[0019] The switching matrix includes n+1 switching components and a switching control unit U2;

[0020] Each of the individual cells is connected to one end of a switching component at both ends, and only one end of the switching component is connected between any two adjacent individual cells.

[0021] The other end of the switching component with an odd ordinal number is connected in parallel and serves as channel A to the energy exchange module.

[0022] The other end of the switching component with an even ordinal number is connected in parallel to serve as channel B and is connected to the energy exchange module.

[0023] The switching control unit U2 is connected to each of the switching components and is used to control the on and off states of each switching component.

[0024] Furthermore, in the active equalization circuit, each of the switching components includes a seventh switching unit and an eighth switching unit connected in series;

[0025] Both the seventh and eighth switching units are MOS transistors, and the conduction direction of the seventh switching unit is opposite to that of the eighth switching unit.

[0026] In a second aspect, the present invention provides a battery balancing system, including a battery pack and an active balancing circuit as described in the first aspect above.

[0027] Thirdly, the present invention provides an active balancing method applied to the battery balancing system provided in the second aspect above, the method comprising:

[0028] S101. When the energy exchange module is a single-inductor Buck-Boost type and the voltage of the single cell in the x-th string is high, determine whether x is odd or even; if it is odd, execute S102-S103; if it is even, execute S104-S105.

[0029] S102. Set the A channel of the switching matrix to x, disconnect the fourth switching unit S4, and turn on the first switching unit S1, the second switching unit S2, and the third switching unit S3 to form a Boost circuit with the first inductor L1. The voltage of the individual cells in the xth string and below is boosted to be equal to the total voltage VBAT through the Boost circuit. Then, the boosted individual cells in the xth string and below discharge the total voltage VBAT until the voltage of the individual cells in the xth string is balanced.

[0030] S103. Set the B channel of the switching matrix to x-1, disconnect the second switching unit S2 and the third switching unit S3, and turn on the first switching unit S1 and the fourth switching unit S4 to form a Buck step-down circuit with the body diode of the first inductor L1 and the second switching unit S2. The total voltage VBAT is discharged through the Buck step-down circuit to discharge the individual cells in the x-1th string and below until the voltage of the individual cells in the x-1th string and below is balanced.

[0031] S104. Set the B channel of the switching matrix to x, disconnect the third switching unit S3, and turn on the first switching unit S1, the second switching unit S2, and the fourth switching unit S4 to form a Boost circuit with the first inductor L1. The voltage of the individual cells in the xth string and below is boosted to be equal to the total voltage VBAT through the Boost circuit. Then, the boosted individual cells in the xth string and below discharge the total voltage VBAT until the voltage of the individual cells in the xth string is balanced.

[0032] S105. Set the A channel of the switching matrix to x-1, disconnect the second switching unit S2 and the fourth switching unit S4, and turn on the first switching unit S1 and the third switching unit S3 to form a Buck step-down circuit with the body diode of the first inductor L1 and the second switching unit S2. The total voltage VBAT is used to discharge the individual cells in the (x-1)th string and below through the Buck step-down circuit until the voltage of the individual cells in the (x-1)th string and below is balanced.

[0033] Fourthly, the present invention provides an active balancing method applied to the battery balancing system provided in the second aspect above, the method comprising:

[0034] S201. When the energy exchange module is a single-inductor Buck-Boost type and the voltage of the single cell in the x-th string is low, determine whether x is odd or even; if it is odd, execute S202-S203; if it is even, execute S204-S205.

[0035] S202. Set the A channel of the switching matrix to x, disconnect the second switching unit S2 and the fourth switching unit S4, and turn on the first switching unit S1 and the third switching unit S3 to form a Buck step-down circuit with the body diode of the first inductor L1 and the second switching unit S2. The total voltage VBAT is discharged through the Buck step-down circuit to discharge the individual cells of the xth string and below until the voltage of the individual cells of the xth string is balanced.

[0036] S203. Set the B channel of the switching matrix to x-1, disconnect the third switching unit S3, and turn on the first switching unit S1, the second switching unit S2, and the fourth switching unit S4 to form a Boost circuit with the first inductor L1. The voltage of the individual cells in the x-1th string and below is boosted to be equal to the total voltage VBAT through the Boost circuit. Then, the boosted individual cells in the x-1th string and below discharge the total voltage VBAT until the voltage of the individual cells in the x-1th string and below is balanced.

[0037] S204. Set the B channel of the switching matrix to x, disconnect the second switching unit S2 and the third switching unit S3, and turn on the first switching unit S1 and the fourth switching unit S4 to form a Buck step-down circuit with the body diode of the first inductor L1 and the second switching unit S2. The total voltage VBAT is used to discharge the individual cells of the xth string and below through the Buck step-down circuit until the voltage of the individual cells of the xth string is balanced.

[0038] S205. Set the A channel of the switching matrix to x-1, disconnect the fourth switching unit S4, and turn on the first switching unit S1, the second switching unit S2, and the third switching unit S3 to form a Boost circuit with the first inductor L1. The voltage of the individual cells in the (x-1)th string and below is boosted to be equal to the total voltage VBAT through the Boost circuit. Then, the boosted individual cells in the (x-1)th string and below discharge the total voltage VBAT until the voltage of the individual cells in the (x-1)th string and below is balanced.

[0039] Fifthly, the present invention provides an active balancing method applied to the battery balancing system provided in the second aspect above, the method comprising:

[0040] S301. When the energy exchange module is a dual-inductor Buck-Boost type and the voltage of the single cell in the x-th string is high, determine whether x is odd or even; if it is odd, execute S302; if it is even, execute S303.

[0041] S302. Set channel A of the switching matrix to x and channel B to x-1. Turn on the third switching unit S3 and the fourth switching unit S4. The PWM control of the sixth switching unit S6 forms a Boost circuit with the first inductor L1. The voltage of the individual cells in the xth string and below is boosted to be equal to the total voltage VBAT through the Boost circuit. Then, the boosted individual cells in the xth string and below discharge the total voltage VBAT through the body diode of the first switching unit S1. At the same time, the second switching unit S2 is turned off. The PWM control of the fifth switching unit S5 and the body diode of the second switching unit S2 form a Buck circuit with the second inductor L2 to discharge the individual cells in the (x-1th)th string and below. The PWM control of the fifth switching unit S5 controls the current value of channel A and channel B of the switching matrix to be the same but opposite in direction, thus completing the discharge of the individual cells in the xth string.

[0042] S303. Set channel B of the switching matrix to x and channel A to x-1. Turn on the third switching unit S3 and the fourth switching unit S4. The second switching unit S2 forms a boost circuit with the second inductor L2 through PWM control. The boost circuit boosts the voltage of the individual cells in the xth string and below to be equal to the total voltage VBAT. Then, the boosted individual cells in the xth string and below discharge the total voltage VBAT through the body diode of the fifth switching unit S5. At the same time, the sixth switching unit S6 is turned off. The first switching unit S1 forms a buck circuit with the body diode of the sixth switching unit S6 and the first inductor L1 to discharge the individual cells in the (x-1th)th string and below. The PWM control of the first switching unit S1 controls the current values ​​of channel A and channel B of the switching matrix to be the same but opposite in direction, thus completing the discharge of the individual cells in the xth string.

[0043] Sixthly, the present invention provides an active balancing method applied to the battery balancing system provided in the second aspect above, the method comprising:

[0044] S401. When the energy exchange module is a dual-inductor Buck-Boost type and the voltage of the single cell in the x-th string is low, determine whether x is odd or even; if it is odd, execute S402; if it is even, execute S403.

[0045] S402. Set channel A of the switching matrix to x and channel B to x-1. Turn on the third switching unit S3 and the fourth switching unit S4. Through the PWM control of the first switching unit S1, a Buck step-down circuit is formed with the first inductor L1. The total voltage VBAT is discharged to the individual cells in the xth string and below through the Buck step-down circuit. At the same time, the sixth switching unit S6 is turned off. Through the PWM control of the second switching unit S2 and the fifth switching unit S5, a Boost step-up circuit is formed to form the individual cells in the x-1th string and below to discharge the total voltage VBAT. Through the PWM control of the first switching unit S1, the current values ​​of channel A and channel B are controlled to be the same in value and opposite in direction, thus completing the charging of the individual cells in the xth string.

[0046] S403. Set channel B of the switching matrix to x and channel A to x-1. Turn on the third switching unit S3 and the fourth switching unit S4. Through the PWM control of the fifth switching unit S5, a Buck step-down circuit is formed with the second inductor L2. The total voltage VBAT is discharged to the individual cells in the xth string and below through the Buck step-down circuit. At the same time, the second switching unit S2 is turned off. Through the PWM control of the first switching unit S1 and the sixth switching unit S6, a Boost step-up circuit is formed to form the individual cells in the x-1th string and below, discharging the total voltage VBAT. Through the PWM control of the fifth switching unit S5, the current values ​​of channel A and channel B are controlled to be the same in value and opposite in direction, thus completing the charging of the individual cells in the xth string.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] This invention provides an active balancing circuit, a battery balancing system, and an active balancing method. By designing a small inductor single / dual inductor Buck-Boost dual-channel energy exchange module, and in conjunction with a switching matrix, it can achieve active balancing of the voltage of each individual cell in the battery pack. This not only significantly reduces the size and cost, but also significantly improves the balancing efficiency. At the same time, the overall circuit topology is simple and the control is flexible, which is conducive to its widespread application.

[0049] The present invention has other features and advantages, which will be apparent from or will be set forth in detail in the accompanying drawings and the following detailed description, which together serve to explain the particular principles of the invention. Attached Figure Description

[0050] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0051] Figure 1 This is one of the circuit structure diagrams of energy exchange modules in the prior art;

[0052] Figure 2 This is the second schematic diagram of the circuit structure of an energy exchange module in the prior art;

[0053] Figure 3 This is the third schematic diagram of the circuit structure of an energy exchange module in the prior art;

[0054] Figure 4 This is one of the circuit structure diagrams of the energy exchange module in the active balancing circuit provided in Embodiment 1 of the present invention;

[0055] Figure 5 This is the second schematic diagram of the circuit structure of the energy exchange module in the active balancing circuit provided in Embodiment 1 of the present invention;

[0056] Figure 6 This is a schematic diagram of the circuit structure of the switching matrix in the active equalization circuit provided in Embodiment 1 of the present invention;

[0057] Figure 7 This is one of the flowcharts of an active balancing method provided in Embodiment 3 of the present invention;

[0058] Figure 8 This is one of the flowcharts of an active balancing method provided in Embodiment 3 of the present invention;

[0059] Figure 9 This is the third flowchart of an active balancing method provided in Embodiment 3 of the present invention;

[0060] Figure 10 This is the fourth flowchart of an active balancing method provided in Embodiment 3 of the present invention. Detailed Implementation

[0061] 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 embodiments of the present invention, and not all embodiments. 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.

[0062] Example 1

[0063] Please refer to Figure 4-5 Embodiment 1 of the present invention provides an active balancing circuit connected to a battery pack, the circuit including a switching matrix and an energy exchange module;

[0064] The switching matrix, positioned between the battery pack and the energy exchange module, plays a crucial role in signal and energy transmission control. Specifically, it controls individual cells within the battery pack, enabling them to enter or leave the energy exchange module via channel A or channel B. This design allows individual cells within the battery pack to flexibly participate in the energy exchange process according to actual needs, thus providing a solid foundation for balanced battery pack management.

[0065] There are two different structural types of energy exchange modules. The first structural type is the single-inductor Buck-Boost type, such as... Figure 4 As shown. This type of energy exchange module includes a controller U1, a first inductor L1, a first switching unit S1, a second switching unit S2, a third switching unit S3, and a fourth switching unit S4. In terms of circuit connections, the first switching unit S1 is connected between the battery pack's total voltage VBAT output point and the first inductor L1, and its operation is controlled by the controller U1; the second switching unit S2 is connected between GND (ground terminal) and the first inductor L1, and is also controlled by the controller U1; the third switching unit S3 is connected between channel A and the first inductor L1, and its on / off state and operation are also determined by the controller U1; the fourth switching unit S4 is connected between channel B and the first inductor L1, and is also under the control of the controller U1. Through the coordinated operation of these switching units, under the intelligent regulation of the controller U1, efficient energy conversion and transmission can be achieved, thereby achieving the goal of battery pack balancing.

[0066] The second structural type is the dual-inductor Buck-Boost type, such as... Figure 5 As shown. This type of energy exchange module consists of a controller U1, a first inductor L1, a second inductor L2, a first switching unit S1, a second switching unit S2, a third switching unit S3, a fourth switching unit S4, a fifth switching unit S5, and a sixth switching unit S6. In terms of circuit connections, the first switching unit S1 is connected between the battery pack's total voltage VBAT output point and the first inductor L1, and is controlled by the controller U1; the second switching unit S2 is connected between GND and the second inductor L2, and its operating state is regulated by the controller U1; the third switching unit S3 is connected between channel A and the first inductor L1, and its operation is directed by the controller U1; the fourth switching unit S4 is connected between channel B and the second inductor L2, and also operates under the control of the controller U1; the fifth switching unit S5 is connected between the total voltage VBAT output point and the second inductor L2, and its operation is determined by the controller U1; the sixth switching unit S6 is connected between GND and the first inductor L1, and is also under the control of the controller U1. This dual-inductor structural design further enhances the flexibility and adaptability of the energy exchange module, enabling efficient balancing of the battery pack under more complex operating conditions.

[0067] In one specific embodiment provided in this example, the types of key components constituting the energy exchange module, namely each switching unit, are clearly defined. Specifically, the first switching unit S1, the second switching unit S2, the third switching unit S3, the fourth switching unit S4, the fifth switching unit S5, and the sixth switching unit S6 are all selected from MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors). MOSFETs, with their unique electrical characteristics such as high input impedance, low on-resistance, and fast switching speed, can effectively meet the requirements of the switching units in the circuit to achieve fast and precise on / off control, thereby ensuring the stable operation of the energy exchange module.

[0068] To further illustrate the specific selection of switching units in different types of energy exchange modules, the following examples are provided:

[0069] When the energy exchange module adopts a single-inductor Buck-Boost structure, specific considerations are needed for the selection of the switching unit type. Specifically, the first switching unit S1 and the second switching unit S2 both use NMOS transistors (N-type metal-oxide-semiconductor field-effect transistors). When an NMOS transistor is turned on, a low-impedance path is formed between its source and drain, allowing current to flow from the drain to the source, resulting in low on-resistance and effectively reducing energy loss. Simultaneously, its fast switching speed allows for rapid response to control signals, enabling rapid circuit switching. The third switching unit S3 and the fourth switching unit S4 both use PMOS transistors (P-type metal-oxide-semiconductor field-effect transistors). The conductivity characteristics of a PMOS transistor are opposite to those of an NMOS transistor; when turned on, current flows from the source to the drain. Using PMOS transistors as the third and fourth switching units forms a complementary switching combination with the NMOS transistors, enabling efficient bidirectional energy transfer between the battery pack and the inductor under the control of the controller, thus fulfilling the core function of the single-inductor Buck-Boost energy exchange module.

[0070] When the energy exchange module adopts a dual-inductor Buck-Boost structure, the selection of switching unit types differs. In this case, the first switching unit S1, the second switching unit S2, the fifth switching unit S5, and the sixth switching unit S6 all use NMOS transistors. These NMOS transistors perform different connection and control tasks in the circuit, achieving flexible connections between the battery pack's total voltage, ground terminal, and inductors through rapid and accurate switching, providing a channel for bidirectional energy flow. The third switching unit S3 and the fourth switching unit S4 still use PMOS transistors. The PMOS transistors and NMOS transistors work together, under the unified command of the controller, to control the energy transmission paths between channels A and B and the inductors, ensuring that the dual-inductor Buck-Boost energy exchange module can efficiently and stably achieve balanced voltage regulation of each individual battery cell within the battery pack.

[0071] By rationally selecting and matching the switching units in different types of energy exchange modules as described above, the active balancing circuit in this embodiment of the invention can fully leverage the performance advantages of MOSFETs, achieve efficient operation of the energy exchange module, thereby ensuring the active balancing of the voltage of each individual cell in the battery pack and improving the performance and reliability of the entire battery management system.

[0072] Please refer to Figure 6 In one embodiment of this invention, a detailed design description is provided for the battery pack and the associated switching matrix.

[0073] Specifically, the battery pack is carefully assembled from n individual battery cells (BAT) connected in series. Here, n is explicitly specified to be a positive integer greater than or equal to 2 to ensure the battery pack has sufficient capacity and voltage output capability to meet the needs of diverse application scenarios. Figure 6 In the illustration, for easy identification and description, these n individual cells are sequentially labeled BAT(1) to BAT(n). This ordered numbering method not only helps to locate each individual cell during circuit design and analysis, but also facilitates subsequent operations such as state monitoring, fault diagnosis, and equalization control of the battery pack.

[0074] The switching matrix, as a key component for realizing flexible connection and control between the battery pack and the energy exchange module, consists of n+1 switching components and a switching control unit U2.

[0075] Each individual cell BAT is connected to one end of a switching component at each end. Furthermore, only one end of a switching component connects to each pair of adjacent individual cell BATs. This connection method ensures that each individual cell within the battery pack can interact with the switching matrix independently and in an orderly manner, while effectively simplifying the circuit topology and reducing circuit complexity and cost.

[0076] In the switching matrix, channels are divided according to the arrangement ordinal numbers of the switching components. Specifically, the other ends of the switching components with odd-numbered arrangement ordinal numbers are connected in parallel to form channel A, which is connected to the energy exchange module; while the other ends of the switching components with even-numbered arrangement ordinal numbers are connected in parallel to form channel B, which is also connected to the energy exchange module. By dividing the parallel channels according to odd and even ordinal numbers, each individual cell in the battery pack can flexibly switch into or out of the energy exchange module through channels A and B, providing path selection for subsequent energy balancing regulation.

[0077] The switching control unit U2 plays a core control role in the entire switching matrix. It is connected to each switching component and controls the on / off state of each component by outputting control signals. This centralized control method allows the switching matrix to quickly and accurately adjust the connection between each individual battery cell and the energy exchange module according to the actual operating state and balancing requirements of the battery pack, thereby ensuring efficient and stable voltage balancing of each individual battery cell within the battery pack.

[0078] For example, to further optimize the performance and reliability of the switching components, each switching component adopts a structure consisting of a seventh switching unit S7 and an eighth switching unit S8 connected in series. Figure 6 In the diagram, the n+1 seventh switching units S7 are numbered sequentially as S7(0) to S7(n), and the n+1 eighth switching units S8 are numbered sequentially as S8(0) to S8(n).

[0079] In one embodiment of this invention, both the seventh switching unit S7 and the eighth switching unit S8 are MOSFETs. Furthermore, it is specifically stipulated that the conduction direction of the seventh switching unit S7 is opposite to that of the eighth switching unit S8. The specific function of these designs is to ensure the normal operation of the switching matrix.

[0080] In summary, this embodiment provides a solid technical foundation for the active equalization and regulation of the voltage of each individual cell in the battery pack through the design and optimization of the battery pack and switching matrix, which helps to improve the battery pack's lifespan, safety, and overall performance.

[0081] Although this invention uses terms such as switching matrix and energy exchange module frequently, the possibility of using other terms is not excluded. These terms are used merely for the convenience of describing and explaining the essence of this invention; interpreting them as any additional limitation would contradict the spirit of this invention.

[0082] This invention provides an active balancing circuit that utilizes a small inductor to design a single-inductor or dual-inductor Buck-Boost dual-channel energy exchange module, cleverly combined with a switching matrix, to effectively achieve active voltage balancing of individual cells within a battery pack. Compared to traditional balancing circuits, this circuit offers several significant advantages. First, in terms of size and cost, the use of small inductors and a simplified circuit design significantly reduces the overall circuit size and manufacturing costs, which is crucial for lowering the overall cost of the battery management system and enhancing the product's market competitiveness. Second, regarding balancing efficiency, the optimized topology enables more efficient energy exchange and balancing operations, allowing the voltage of each individual cell within the battery pack to reach equilibrium faster and more accurately, thereby effectively extending the battery pack's lifespan and improving its overall performance. Furthermore, the circuit's overall topology is simple and clear, and its flexible control methods facilitate its widespread adoption and use in a broad range of battery management applications.

[0083] Example 2

[0084] Embodiment 2 of the present invention provides a battery balancing system, including a battery pack and an active balancing circuit as provided in Embodiment 1 above.

[0085] As the foundation for energy storage and supply in the entire battery balancing system, the stability and consistency of the battery pack's performance play a crucial role in the overall system's operation. It typically consists of multiple individual cells connected in series, designed to provide voltage and current outputs that meet the needs of different application scenarios. The active balancing circuit is the key technological highlight of this battery balancing system. Based on the innovative circuit design concept and structure described in Example 1, it achieves active voltage balancing of each individual cell within the battery pack.

[0086] Through the coordinated operation of the aforementioned functional modules, this battery balancing system not only effectively solves the voltage imbalance problem caused by differences in the performance of individual cells during battery pack use, extending the battery pack's lifespan and improving its overall performance and reliability, but also offers numerous other significant benefits. From an economic perspective, the system reduces replacement costs due to premature battery pack failure, lowering the overall operation and maintenance costs of the energy system. From an environmental perspective, it helps improve the utilization rate of battery resources, reduces pollution from discarded batteries, and achieves green and sustainable development goals. From a technical perspective, the system's active balancing and adjustment capabilities enhance the stability and adaptability of the battery pack under various operating conditions, providing strong technical support for the development of the new energy field.

[0087] In summary, the battery balancing system provided in Embodiment 2 of the present invention, with its unique system structure, powerful functional execution capabilities, and significant beneficial effects, demonstrates broad application prospects and important practical value in the field of battery management technology.

[0088] Example 3

[0089] Please refer to Figure 7-10 This is a flowchart illustrating an active balancing method provided in Embodiment 1 of the present invention. This method is applied to the active balancing system provided in Embodiment 2 above, aiming to achieve active balancing adjustment of the voltage of each individual cell in the battery pack, thereby improving the overall performance and service life of the battery pack.

[0090] In the first implementation, such as Figure 7 As shown, when the energy exchange module is a single-inductor Buck-Boost type and the voltage of the individual battery in the x-th string is high, the method specifically includes the following steps:

[0091] S101. When the energy exchange module is a single-inductor Buck-Boost type and the voltage of the single cell in the x-th string is high, determine whether x is odd or even. If it is odd, execute S102-S103; if it is even, execute S104-S105.

[0092] It should be noted that this judgment is the basis for the diversion of power in subsequent operation steps, because the control strategies of x-string batteries with different parity are different when equalizing.

[0093] S102. Set the A channel of the switching matrix to x, disconnect the fourth switching unit S4, and turn on the first switching unit S1, the second switching unit S2, and the third switching unit S3 to form a Boost circuit with the first inductor L1. The voltage of the individual cells in the xth string and below is boosted to be equal to the total voltage VBAT through the Boost circuit. Then, the boosted individual cells in the xth string and below discharge the total voltage VBAT until the voltage of the individual cells in the xth string is balanced.

[0094] It should be noted that the function of the boost circuit is to increase the input voltage. Here, this circuit boosts the voltage of the individual cells in the xth string and below to be equal to the total voltage VBAT. After the boost is complete, the boosted individual cells in the xth string and below discharge the total voltage VBAT. During the discharge process, energy is transferred from the higher-voltage cells to the overall voltage system. As the discharge progresses, the voltage of the individual cells in the xth string gradually decreases until an equilibrium state is reached.

[0095] S103. Set the B channel of the switching matrix to x-1, disconnect the second switching unit S2 and the third switching unit S3, and turn on the first switching unit S1 and the fourth switching unit S4 to form a Buck step-down circuit with the body diode of the first inductor L1 and the second switching unit S2. The total voltage VBAT is used to discharge the individual cells in the x-1th string and below through the Buck step-down circuit until the voltage of the individual cells in the x-1th string and below is balanced.

[0096] It should be noted that the function of the Buck step-down circuit is to reduce the input high voltage. At this time, the total voltage VBAT is discharged to the individual cells in the (x-1)th and subsequent strings through this step-down circuit. Through this reverse energy transfer, the voltage of the cells in the (x-1)th and subsequent strings is further adjusted so that they also reach a balanced state.

[0097] S104. Set the B channel of the switching matrix to x, disconnect the third switching unit S3, and turn on the first switching unit S1, the second switching unit S2, and the fourth switching unit S4 to form a Boost circuit with the first inductor L1. The voltage of the individual cells in the xth string and below is boosted to be equal to the total voltage VBAT through the Boost circuit. Then, the boosted individual cells in the xth string and below discharge the total voltage VBAT until the voltage of the individual cells in the xth string is balanced.

[0098] It should be noted that the same circuit is used to boost the voltage of individual cells in the xth string and below to be equal to the total voltage VBAT. Then, the boosted cells discharge the total voltage VBAT until the voltage of the individual cells in the xth string is balanced.

[0099] S105. Set the A channel of the switching matrix to x-1, disconnect the second switching unit S2 and the fourth switching unit S4, and turn on the first switching unit S1 and the third switching unit S3 to form a Buck step-down circuit with the body diode of the first inductor L1 and the second switching unit S2. The total voltage VBAT is used to discharge the individual cells in the (x-1)th string and below through the Buck step-down circuit until the voltage of the individual cells in the (x-1)th string and below is balanced.

[0100] It should be noted that the total voltage VBAT is also used to discharge the individual cells in the (x-1)th and lower strings through this step-down circuit, ultimately achieving voltage balance among these cells.

[0101] In the second implementation, such as Figure 8As shown, when the energy exchange module is a single-inductor Buck-Boost type and the voltage of the individual battery cell in the x-th string is low, the method specifically includes the following steps. Explanations of terms or descriptions that are the same as or corresponding to those in the above embodiments will not be repeated here:

[0102] S201. When the energy exchange module is a single-inductor Buck-Boost type and the voltage of the single cell in the x-th string is low, determine whether x is odd or even. If it is odd, execute S202-S203; if it is even, execute S204-S205.

[0103] S202. Set the A channel of the switching matrix to x, disconnect the second switching unit S2 and the fourth switching unit S4, and turn on the first switching unit S1 and the third switching unit S3 to form a Buck step-down circuit with the body diode of the first inductor L1 and the second switching unit S2. The total voltage VBAT is used to discharge the individual cells of the xth string and below through the Buck step-down circuit until the voltage of the individual cells in the xth string is balanced.

[0104] It should be noted that by discharging through the total voltage VBAT, the voltage of the lower-voltage battery in the x-th string is increased until it reaches equilibrium.

[0105] S203. Set the B channel of the switching matrix to x-1, disconnect the third switching unit S3, and turn on the first switching unit S1, the second switching unit S2, and the fourth switching unit S4 to form a Boost circuit with the first inductor L1. The voltage of the individual cells in the x-1th string and below is boosted to be equal to the total voltage VBAT through the Boost circuit. Then, the boosted individual cells in the x-1th string and below discharge the total voltage VBAT until the voltage of the individual cells in the x-1th string and below is balanced.

[0106] It should be noted that this process, on the one hand, further adjusts the voltage of the cells in the (x-1)th and subsequent strings, and on the other hand, maintains the voltage balance of the entire battery system through energy transfer.

[0107] S204. Set the B channel of the switching matrix to x, disconnect the second switching unit S2 and the third switching unit S3, and turn on the first switching unit S1 and the fourth switching unit S4 to form a Buck step-down circuit with the body diode of the first inductor L1 and the second switching unit S2. The total voltage VBAT is used to discharge the individual cells of the xth string and below through the Buck step-down circuit until the voltage of the individual cells in the xth string is balanced.

[0108] It should be noted that the total voltage VBAT discharges the individual cells in the xth and subsequent strings through this step-down circuit, raising their voltage to an equalized state.

[0109] S205. Set the A channel of the switching matrix to x-1, disconnect the fourth switching unit S4, and turn on the first switching unit S1, the second switching unit S2, and the third switching unit S3 to form a Boost circuit with the first inductor L1. The voltage of the individual cells in the (x-1)th string and below is boosted to be equal to the total voltage VBAT through the Boost circuit. Then, the boosted individual cells in the (x-1)th string and below discharge the total voltage VBAT until the voltage of the individual cells in the (x-1)th string and below is balanced.

[0110] It should be noted that the boost circuit boosts the voltage of individual cells in the (x-1)th and subsequent strings to be equal to the total voltage VBAT. Then, the boosted cells discharge the total voltage VBAT, ultimately achieving voltage balance among all related cells.

[0111] In the third implementation, such as Figure 9 As shown, when the energy exchange module is a dual-inductor Buck-Boost type and the voltage of the individual battery in the x-th string is high, the method specifically includes the following steps. Explanations of terms or descriptions that are the same as or corresponding to those in the above embodiments will not be repeated here:

[0112] S301. When the energy exchange module is a dual-inductor Buck-Boost type and the voltage of the single cell in the x-th string is high, determine whether x is odd or even; if it is odd, execute S302; if it is even, execute S303.

[0113] S302. Set channel A of the switching matrix to x and channel B to x-1. Turn on the third switching unit S3 and the fourth switching unit S4. The PWM control of the sixth switching unit S6 forms a Boost circuit with the first inductor L1. The Boost circuit boosts the voltage of the individual cells in the xth string and below to be equal to the total voltage VBAT. Then, the boosted individual cells in the xth string and below discharge the total voltage VBAT through the body diode of the first switching unit S1. At the same time, the second switching unit S2 is turned off. The PWM control of the fifth switching unit S5 and the body diode of the second switching unit S2 form a Buck circuit with the second inductor L2 to discharge the individual cells in the (x-1th)th string and below. The PWM control of the fifth switching unit S5 controls the current values ​​of channel A and channel B of the switching matrix to be the same but opposite in direction, thus completing the discharge of the individual cells in the xth string.

[0114] It should be noted that PWM control can precisely adjust the on and off times of the switching elements, thereby controlling the output voltage and current of the circuit. The body diode provides a current path when the switching transistor is off, serving both protection and freewheeling functions.

[0115] This current control method can ensure the balance and stability of energy transfer, and finally complete the discharge of the individual cells in the x-th string, reducing their voltage to an equal state.

[0116] S303. Set channel B of the switching matrix to x and channel A to x-1. Turn on the third switching unit S3 and the fourth switching unit S4. The second switching unit S2 forms a boost circuit with the second inductor L2 through PWM control. The boost circuit boosts the voltage of the individual cells in the xth string and below to be equal to the total voltage VBAT. Then, the boosted individual cells in the xth string and below discharge the total voltage VBAT through the body diode of the fifth switching unit S5. At the same time, the sixth switching unit S6 is turned off. The first switching unit S1 forms a buck circuit with the body diode of the sixth switching unit S6 and the first inductor L1 to discharge the individual cells in the (x-1th)th string and below. The PWM control of the first switching unit S1 controls the current values ​​of channel A and channel B of the switching matrix to be the same but opposite in direction, thus completing the discharge of the individual cells in the xth string.

[0117] In the fourth embodiment, such as Figure 10 As shown, when the energy exchange module is a dual-inductor Buck-Boost type and the voltage of the individual battery in the xth string is low, the method specifically includes the following steps. Explanations of terms or descriptions that are the same as or corresponding to those in the above embodiments will not be repeated here:

[0118] S401. When the energy exchange module is a dual-inductor Buck-Boost type and the voltage of the single battery cell in the x-th string is low, determine whether x is odd or even; if it is odd, execute S402; if it is even, execute S403.

[0119] S402. Set channel A of the switching matrix to x and channel B to x-1. Turn on the third switching unit S3 and the fourth switching unit S4. Through the PWM control of the first switching unit S1, a Buck step-down circuit is formed with the first inductor L1. The total voltage VBAT is discharged to the individual cells in the xth string and below through the Buck step-down circuit. At the same time, the sixth switching unit S6 is turned off. Through the PWM control of the second switching unit S2 and the fifth switching unit S5, a Boost step-up circuit is formed to form the individual cells in the x-1th string and below, discharging the total voltage VBAT. Through the PWM control of the first switching unit S1, the current values ​​of channel A and channel B are controlled to be the same in value and opposite in direction, thus completing the charging of the individual cells in the xth string.

[0120] S403. Set channel B of the switching matrix to x and channel A to x-1. Turn on the third switching unit S3 and the fourth switching unit S4. Through the PWM control of the fifth switching unit S5, a Buck step-down circuit is formed with the second inductor L2. The total voltage VBAT is discharged to the individual cells in the xth string and below through the Buck step-down circuit. At the same time, the second switching unit S2 is turned off. Through the PWM control of the first switching unit S1 and the sixth switching unit S6, a Boost step-up circuit is formed to form the individual cells in the x-1th string and below, discharging the total voltage VBAT. Through the PWM control of the fifth switching unit S5, the current values ​​of channel A and channel B are controlled to be the same in value and opposite in direction, thus completing the charging of the individual cells in the xth string.

[0121] It should be noted that, in Figure 9-10 In this system, the Boost and Buck circuits can be controlled simultaneously based on the actual situation of the entire series of individual cells. The only thing to note is that the Boost and Buck circuits are separated by odd and even values.

[0122] In summary, through the detailed balancing process described above for different energy exchange module types and individual battery voltage states, the active balancing method provided in Embodiment 3 of this invention can accurately and efficiently achieve balanced adjustment of the voltage of each individual battery in the battery pack, effectively improving the performance and reliability of the battery pack, and providing strong technical support for the development of battery management technology.

[0123] Finally, it should be noted that although the above embodiments have been described in the description and drawings of this invention, this should not limit the scope of patent protection of this invention. Any technical solutions that are based on the essential concept of this invention, utilize the content described in the description and drawings of this invention to make equivalent structural or procedural substitutions or modifications, as well as the direct or indirect application of the technical solutions of the above embodiments to other related technical fields, are all included within the scope of patent protection of this invention.

Claims

1. An active balancing circuit, connected to a battery pack, characterized in that, The circuit includes a switching matrix and an energy exchange module; wherein... The switching matrix is ​​connected between the battery pack and the energy exchange module, and is used to control each individual cell in the battery pack to switch into or out of the energy exchange module through channel A or channel B. The energy exchange module is a single-inductor Buck-Boost type, including a controller U1, a first inductor L1, a first switching unit S1, a second switching unit S2, a third switching unit S3, and a fourth switching unit S4. The first switching unit S1 is connected between the total voltage VBAT output point of the battery pack and the first terminal of the first inductor L1, and is controlled by the controller U1. The second switching unit S2 is connected between GND and the first terminal of the first inductor L1, and is controlled by the controller U1. The third switching unit S3 is connected between channel A and the second terminal of the first inductor L1, and is controlled by the controller U1. The fourth switching unit S4 is connected between channel B and the second terminal of the first inductor L1, and is controlled by the controller U1. Alternatively, the energy exchange module is a dual-inductor Buck-Boost type, including a controller U1, a first inductor L1, a second inductor L2, a first switching unit S1, a second switching unit S2, a third switching unit S3, a fourth switching unit S4, a fifth switching unit S5, and a sixth switching unit S6; the first switching unit S1 is connected between the total voltage VBAT output point of the battery pack and the first terminal of the first inductor L1, and is controlled by the controller U1; the second switching unit S2 is connected between GND and the first terminal of the second inductor L2, and is controlled by... The controller U1; the third switching unit S3 is connected between channel A and the second terminal of the first inductor L1, and is controlled by the controller U1; the fourth switching unit S4 is connected between channel B and the second terminal of the second inductor L2, and is controlled by the controller U1; the fifth switching unit S5 is connected between the total voltage VBAT output point and the first terminal of the second inductor L2, and is controlled by the controller U1; the sixth switching unit S6 is connected between GND and the first terminal of the first inductor L1, and is controlled by the controller U1; The battery pack comprises n individual cells connected in series; wherein n is greater than or equal to 2. The switching matrix includes n+1 switching components and a switching control unit U2; Each of the individual cells is connected to one end of a switching component at both ends, and only one end of the switching component is connected between any two adjacent individual cells. The other end of the switching component with an odd ordinal number is connected in parallel and serves as channel A to the energy exchange module. The other end of the switching component with an even ordinal number is connected in parallel to serve as channel B and is connected to the energy exchange module. The switching control unit U2 is connected to each of the switching components and is used to control the on and off states of each switching component.

2. The active equalization circuit according to claim 1, characterized in that, The first switching unit S1, the second switching unit S2, the third switching unit S3, the fourth switching unit S4, the fifth switching unit S5, and the sixth switching unit S6 are all MOSFETs.

3. The active equalization circuit according to claim 2, characterized in that, When the energy exchange module is a single-inductor Buck-Boost type, the first switching unit S1 and the second switching unit S2 are both NMOS transistors, and the third switching unit S3 and the fourth switching unit S4 are both PMOS transistors. When the energy exchange module is a dual-inductor Buck-Boost type, the first switching unit S1, the second switching unit S2, the fifth switching unit S5 and the sixth switching unit S6 are all NMOS transistors, and the third switching unit S3 and the fourth switching unit S4 are both PMOS transistors.

4. The active equalization circuit according to claim 1, characterized in that, Each of the switching components includes a seventh switching unit and an eighth switching unit connected in series; Both the seventh and eighth switching units are MOS transistors, and the conduction direction of the seventh switching unit is opposite to that of the eighth switching unit.

5. A battery balancing system, characterized in that, It includes a battery pack and an active balancing circuit as described in any one of claims 1-4.

6. An active balancing method, applied to the battery balancing system as described in claim 5, characterized in that, The method includes: S101. When the energy exchange module is a single-inductor Buck-Boost type and the voltage of the single cell in the x-th string is high, determine whether x is odd or even; if it is odd, execute S102-S103; if it is even, execute S104-S105. S102. Set the A channel of the switching matrix to x, disconnect the fourth switching unit S4, and turn on the first switching unit S1, the second switching unit S2, and the third switching unit S3 to form a Boost circuit with the first inductor L1. The voltage of the individual cells in the xth string and below is boosted to be equal to the total voltage VBAT through the Boost circuit. Then, the boosted individual cells in the xth string and below discharge the total voltage VBAT until the voltage of the individual cells in the xth string is balanced. S103. Set the B channel of the switching matrix to x-1, disconnect the second switching unit S2 and the third switching unit S3, and turn on the first switching unit S1 and the fourth switching unit S4 to form a Buck step-down circuit with the body diode of the first inductor L1 and the second switching unit S2. The total voltage VBAT is discharged through the Buck step-down circuit to discharge the individual cells in the x-1th string and below until the voltage of the individual cells in the x-1th string and below is balanced. S104. Set the B channel of the switching matrix to x, disconnect the third switching unit S3, and turn on the first switching unit S1, the second switching unit S2, and the fourth switching unit S4 to form a Boost circuit with the first inductor L1. The voltage of the individual cells in the xth string and below is boosted to be equal to the total voltage VBAT through the Boost circuit. Then, the boosted individual cells in the xth string and below discharge the total voltage VBAT until the voltage of the individual cells in the xth string is balanced. S105. Set the A channel of the switching matrix to x-1, disconnect the second switching unit S2 and the fourth switching unit S4, and turn on the first switching unit S1 and the third switching unit S3 to form a Buck step-down circuit with the body diode of the first inductor L1 and the second switching unit S2. The total voltage VBAT is used to discharge the individual cells in the (x-1)th string and below through the Buck step-down circuit until the voltage of the individual cells in the (x-1)th string and below is balanced.

7. An active balancing method, applied to the battery balancing system as described in claim 5, characterized in that, The method includes: S201. When the energy exchange module is a single-inductor Buck-Boost type and the voltage of the single cell in the x-th string is low, determine whether x is odd or even; if it is odd, execute S202-S203; if it is even, execute S204-S205. S202. Set the A channel of the switching matrix to x, disconnect the second switching unit S2 and the fourth switching unit S4, and turn on the first switching unit S1 and the third switching unit S3 to form a Buck step-down circuit with the body diode of the first inductor L1 and the second switching unit S2. The total voltage VBAT is discharged through the Buck step-down circuit to discharge the individual cells of the xth string and below until the voltage of the individual cells of the xth string is balanced. S203. Set the B channel of the switching matrix to x-1, disconnect the third switching unit S3, and turn on the first switching unit S1, the second switching unit S2, and the fourth switching unit S4 to form a Boost circuit with the first inductor L1. The voltage of the individual cells in the x-1th string and below is boosted to be equal to the total voltage VBAT through the Boost circuit. Then, the boosted individual cells in the x-1th string and below discharge the total voltage VBAT until the voltage of the individual cells in the x-1th string and below is balanced. S204. Set the B channel of the switching matrix to x, disconnect the second switching unit S2 and the third switching unit S3, and turn on the first switching unit S1 and the fourth switching unit S4 to form a Buck step-down circuit with the body diode of the first inductor L1 and the second switching unit S2. The total voltage VBAT is used to discharge the individual cells of the xth string and below through the Buck step-down circuit until the voltage of the individual cells of the xth string is balanced. S205. Set the A channel of the switching matrix to x-1, disconnect the fourth switching unit S4, and turn on the first switching unit S1, the second switching unit S2, and the third switching unit S3 to form a Boost circuit with the first inductor L1. The voltage of the individual cells in the (x-1)th string and below is boosted to be equal to the total voltage VBAT through the Boost circuit. Then, the boosted individual cells in the (x-1)th string and below discharge the total voltage VBAT until the voltage of the individual cells in the (x-1)th string and below is balanced.

8. An active balancing method, applied to the battery balancing system as described in claim 5, characterized in that, The method includes: S301. When the energy exchange module is a dual-inductor Buck-Boost type and the voltage of the single cell in the x-th string is high, determine whether x is odd or even; if it is odd, execute S302; if it is even, execute S303. S302. Set channel A of the switching matrix to x and channel B to x-1. Turn on the third switching unit S3 and the fourth switching unit S4. The PWM control of the sixth switching unit S6 forms a Boost circuit with the first inductor L1. The voltage of the individual cells in the xth string and below is boosted to be equal to the total voltage VBAT through the Boost circuit. Then, the boosted individual cells in the xth string and below discharge the total voltage VBAT through the body diode of the first switching unit S1. At the same time, the second switching unit S2 is turned off. The PWM control of the fifth switching unit S5 and the body diode of the second switching unit S2 form a Buck circuit with the second inductor L2 to discharge the individual cells in the (x-1th)th string and below. The PWM control of the fifth switching unit S5 controls the current value of channel A and channel B of the switching matrix to be the same but opposite in direction, thus completing the discharge of the individual cells in the xth string. S303. Set channel B of the switching matrix to x and channel A to x-1. Turn on the third switching unit S3 and the fourth switching unit S4. The second switching unit S2 forms a boost circuit with the second inductor L2 through PWM control. The boost circuit boosts the voltage of the individual cells in the xth string and below to be equal to the total voltage VBAT. Then, the boosted individual cells in the xth string and below discharge the total voltage VBAT through the body diode of the fifth switching unit S5. At the same time, the sixth switching unit S6 is turned off. The first switching unit S1 forms a buck circuit with the body diode of the sixth switching unit S6 and the first inductor L1 to discharge the individual cells in the (x-1th)th string and below. The PWM control of the first switching unit S1 controls the current values ​​of channel A and channel B of the switching matrix to be the same but opposite in direction, thus completing the discharge of the individual cells in the xth string.

9. An active balancing method, applied to the battery balancing system as described in claim 5, characterized in that, The method includes: S401. When the energy exchange module is a dual-inductor Buck-Boost type and the voltage of the single cell in the x-th string is low, determine whether x is odd or even; if it is odd, execute S402; if it is even, execute S403. S402. Set channel A of the switching matrix to x and channel B to x-1. Turn on the third switching unit S3 and the fourth switching unit S4. Through the PWM control of the first switching unit S1, a Buck step-down circuit is formed with the first inductor L1. The total voltage VBAT is discharged to the individual cells in the xth string and below through the Buck step-down circuit. At the same time, the sixth switching unit S6 is turned off. Through the PWM control of the second switching unit S2 and the fifth switching unit S5, a Boost step-up circuit is formed to form the individual cells in the x-1th string and below to discharge the total voltage VBAT. Through the PWM control of the first switching unit S1, the current values ​​of channel A and channel B are controlled to be the same in value and opposite in direction, thus completing the charging of the individual cells in the xth string. S403. Set channel B of the switching matrix to x and channel A to x-1. Turn on the third switching unit S3 and the fourth switching unit S4. Through the PWM control of the fifth switching unit S5, a Buck step-down circuit is formed with the second inductor L2. The total voltage VBAT is discharged to the individual cells in the xth string and below through the Buck step-down circuit. At the same time, the second switching unit S2 is turned off. Through the PWM control of the first switching unit S1 and the sixth switching unit S6, a Boost step-up circuit is formed to form the individual cells in the x-1th string and below, discharging the total voltage VBAT. Through the PWM control of the fifth switching unit S5, the current values ​​of channel A and channel B are controlled to be the same in value and opposite in direction, thus completing the charging of the individual cells in the xth string.

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