Battery equalization circuit

Abstract

The application relates to a battery equalization circuit. The battery equalization circuit is connected with a plurality of cell modules, each cell module comprising a plurality of series-connected cells, and the battery equalization circuit comprises a cell group gating circuit and a transformer equalization circuit, the cell group gating circuit being connected between each cell module and the transformer equalization circuit, wherein the cell group gating circuit has a plurality of gating states, in each gating state, any cell module is connected with the transformer equalization circuit through the cell group gating circuit to form a charge-discharge loop, so that the cell module is charged and discharged through the transformer equalization circuit. The battery equalization circuit can directly charge and discharge the plurality of series-connected cells included in the cell module, the energy transfer is not limited between adjacent single cells, the energy transmission is more flexible, and the overall equalization efficiency of the battery pack is higher.

Description

Technical Field

[0001] This application relates to the field of battery balancing technology, and in particular to a battery balancing circuit. Background Technology

[0002] With the rapid development of the new energy industry, battery energy storage systems have been widely deployed. Limited by the rated voltage and capacity of individual battery cells, multiple cells are often connected in series to form a battery pack in practical applications to increase the overall voltage. However, inherent manufacturing differences and environmental variations between cells make it highly susceptible to overcharging or over-discharging of some cells during charging and discharging. This not only accelerates battery aging and weakens system stability but may also trigger safety risks such as thermal runaway. Therefore, voltage balancing has become an indispensable part of series-connected battery pack management systems.

[0003] In related technologies, battery balancing solutions are mostly based on bidirectional buck-boost converters, but their energy transfer is limited to adjacent individual cells, resulting in a single energy transmission path and low overall battery pack balancing efficiency. Summary of the Invention

[0004] Therefore, it is necessary to provide a battery balancing circuit that can improve battery balancing efficiency in response to the above-mentioned technical problems.

[0005] In a first aspect, this application provides a battery balancing circuit, which connects multiple cell modules. Each cell module includes multiple cells connected in series. The battery balancing circuit includes a cell group selection circuit and a transformer balancing circuit. The cell group selection circuit is connected between each cell module and the transformer balancing circuit.

[0006] The cell group selection circuit has multiple selection states. In each selection state, any cell module can be connected to the transformer equalization circuit through the cell group selection circuit to form a charging and discharging circuit, so that the cell module can be charged and discharged through the transformer equalization circuit.

[0007] In one embodiment, the cell group selection circuit includes a module selection switch group and a loop selection switch group; the module selection switch group includes N module selection switches, N≥2, and the N module selection switches are numbered sequentially; the loop selection switch group includes a first loop selection switch, a second loop selection switch, a third loop selection switch, and a fourth loop selection switch.

[0008] The first terminal of each module selection switch is connected to the positive or negative terminal of each cell module, respectively.

[0009] The second terminal of the odd-numbered module selection switch is connected to the first terminal of the first circuit selection switch and the first terminal of the third circuit selection switch.

[0010] The second terminal of the even-numbered module selection switch is connected to the first terminal of the second circuit selection switch and the first terminal of the fourth circuit selection switch.

[0011] The second terminals of the first circuit selection switch, the second circuit selection switch, the third circuit selection switch, and the fourth circuit selection switch are all connected to the transformer balancing circuit.

[0012] In one embodiment, the transformer equalization circuit includes a flyback transformer and a third switching transistor;

[0013] The first end of the secondary winding of the flyback transformer is connected to the first end of the third switching transistor;

[0014] The second terminal of the secondary winding of the flyback transformer is connected to the second terminal of the first circuit selector switch and the second terminal of the second circuit selector switch.

[0015] The second terminal of the third switch is connected to the second terminal of the third circuit selection switch and the second terminal of the fourth circuit selection switch.

[0016] In one embodiment, the cell group gating circuit has a module energy storage state;

[0017] In the module energy storage state, the two module selection switches connected to both ends of the target cell module, the circuit selection switch between one of the two module selection switches and the second end of the secondary winding of the flyback transformer, and the circuit selection switch between the other of the two module selection switches and the second end of the third switch are all in the conducting state. The third switch is in the conducting state, and the target cell module is connected to the secondary winding of the flyback transformer to form an energy storage circuit.

[0018] In one embodiment, the cell group gating circuit has a module energy release state;

[0019] In the module energy release state, the two module selection switches connected to both ends of the target cell module, the circuit selection switch between one of the two module selection switches and the second end of the third switch, and the circuit selection switch between the other of the two module selection switches and the second end of the secondary winding of the flyback transformer are all in the conducting state. The third switch is in the conducting state, and the target cell module and the secondary winding of the flyback transformer are connected to form an energy release circuit.

[0020] In one embodiment, the battery balancing circuit further includes a first impact protection circuit;

[0021] The first impulse protection circuit includes a first resistor, a first capacitor, and a first diode. The first resistor, the first capacitor, and the secondary winding of the flyback transformer are connected in parallel. The cathode of the first diode is connected to the first capacitor, and the anode of the first diode is connected to the secondary winding of the flyback transformer.

[0022] In one embodiment, the battery balancing circuit further includes an external DC power supply, a fourth switch, and a fifth switch;

[0023] An external DC power supply is connected to the primary winding of the flyback transformer. The fourth switch is located between the primary winding of the flyback transformer and the negative terminal of the external DC power supply, and the fifth switch is located between the primary winding of the flyback transformer and the positive terminal of the external DC power supply.

[0024] In one embodiment, the battery balancing circuit has an external power supply state and an external energy release state;

[0025] Under external power supply conditions, the fourth and fifth switching transistors are in the conducting state, and the external DC power supply is connected to the primary winding of the flyback transformer to form a power supply circuit.

[0026] Under external energy release conditions, the two module selection switches connected to both ends of the target cell module, the circuit selection switch between one of the two module selection switches and the second end of the secondary winding of the flyback transformer, and the circuit selection switch between the other of the two module selection switches and the second end of the third switch are all in the on state. The third switch is in the on state, and the target cell module and the secondary winding of the flyback transformer are connected to form an energy release circuit.

[0027] In one embodiment, the battery balancing circuit further includes a second impact protection circuit;

[0028] The second impulse protection circuit includes a second resistor, a second capacitor, and a second diode. The second resistor, the second capacitor, and the primary winding of the flyback transformer are connected in parallel. The cathode of the second diode is connected to the second capacitor, and the anode of the second diode is connected to the primary winding of the flyback transformer.

[0029] In one embodiment, the external DC power supply is 24V.

[0030] The aforementioned battery balancing circuit connects multiple cell modules, each cell module comprising multiple cells connected in series. The battery balancing circuit includes a cell group selection circuit and a transformer balancing circuit. The cell group selection circuit connects each cell module to the transformer balancing circuit. The cell group selection circuit has multiple selection states. In each selection state, any cell module is connected to the transformer balancing circuit through the cell group selection circuit to form a charge / discharge loop, allowing the transformer balancing circuit to charge and discharge the cell module. In this way, the battery balancing circuit can directly charge and discharge the multiple cells connected in series within a cell module. Energy transfer is not limited to adjacent individual cells, resulting in more flexible energy transmission and higher overall battery pack balancing efficiency. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the drawings used in the description of the embodiments of this application or related technologies will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the battery balancing circuit in one embodiment;

[0033] Figure 2 This is one of the structural schematic diagrams of the battery balancing unit inside the cell module in one embodiment;

[0034] Figure 3 This is a second schematic diagram of the structure of the battery equalization unit inside the cell module in one embodiment;

[0035] Figure 4 This is a schematic diagram of the battery balancing circuit in another embodiment;

[0036] Figure 5 This is a schematic diagram of the transformer equalization circuit in one embodiment;

[0037] Figure 6 This is a schematic diagram of the equalization current structure of the battery equalization circuit in one embodiment;

[0038] Figure 7 This is a schematic diagram of the equalization current structure of the battery equalization circuit in one embodiment;

[0039] Figure 8 This is a schematic diagram of the working waveforms of the battery equalization circuit in one embodiment;

[0040] Figure 9 This is a schematic diagram of the external DC power supply circuit in one embodiment;

[0041] Figure 10 This is a schematic diagram of the equalization current structure of the battery equalization circuit in another embodiment;

[0042] Figure 11 This is a schematic diagram of the equalization current structure of the battery equalization circuit in another embodiment;

[0043] Figure 12 This is a schematic diagram of the operating waveforms of the battery equalization circuit in another embodiment.

[0044] Explanation of reference numerals in the attached figures:

[0045] 10. Battery balancing circuit; 20. Battery balancing unit;

[0046] 11. Cell group selection circuit; 12. Transformer balancing circuit;

[0047] 111, Module selection switch group; 112, Circuit selection switch group;

[0048] 21. Switch selection circuit; 22. Inductor balancing circuit;

[0049] L1, inductor; S 11 The first switching transistor; S 12 The second switching transistor;

[0050] T, flyback transformer; Q1, third switching transistor;

[0051] 13. First impact protection circuit; 14. Second impact protection circuit;

[0052] R1, the first resistor; C1, the first capacitor; D1, the first diode;

[0053] R2, the second resistor; C2, the second capacitor; D2, the second diode;

[0054] V, external DC power supply; Q2, fourth switching transistor; Q3, fifth switching transistor. Detailed Implementation

[0055] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0056] It should be noted that the terms "first," "second," etc., used in this application can be used to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish the first element from the second element. The terms "comprising" and "having," and any variations thereof, used in this application, are intended to cover non-exclusive inclusion. The term "multiple" used in this application refers to two or more. The term "and / or" used in this application refers to one of the embodiments, or any combination of multiple embodiments.

[0057] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0058] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0059] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0060] In the description of this specification, references to terms such as "some embodiments," "other embodiments," and "ideal embodiments" indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative descriptions of the above terms do not necessarily refer to the same embodiments or examples.

[0061] In the embodiments of this application, such as Figure 1 As shown, a battery balancing circuit 10 is provided. The battery balancing circuit 10 connects multiple cell modules. Each cell module includes multiple cells connected in series. The battery balancing circuit 10 includes a cell group selection circuit 11 and a transformer balancing circuit 12. The cell group selection circuit 11 is connected between each cell module and the transformer balancing circuit 12.

[0062] The battery balancing circuit 10 connects to multiple cell modules and is used to balance the energy of the multiple cell modules. Each cell module includes multiple cells connected in series, and the multiple cell modules constitute a battery pack.

[0063] The cell group selection circuit 11 can be composed of multiple switches. The switches can be devices that can control the on and off of the circuit, such as relays, metal-oxide-semiconductor field-effect transistors or insulated-gate bipolar transistors. The transformer equalization circuit 12 can be a bidirectional flyback circuit. The transformer equalization circuit 12 can include energy storage elements. Energy is transferred by storing and releasing energy through the energy storage elements, realizing bidirectional energy flow.

[0064] The cell group selection circuit 11 has multiple selection states. In each selection state, any cell module can be connected to the transformer equalization circuit 12 through the cell group selection circuit 11 to form a charging and discharging circuit, so that the cell module can be charged and discharged through the transformer equalization circuit 12.

[0065] The cell group selection circuit 11 is connected between each cell module and the transformer equalization circuit 12. Multiple selection states can be formed by the on and off of each switch in the cell group selection circuit 11. In each selection state, any cell module is connected to the transformer equalization circuit 12 through the cell group selection circuit 11 to form a charging and discharging circuit.

[0066] If the cell module is connected to the transformer balancing circuit 12 through the cell group selection circuit 11 to form a charging circuit, the cell module is charged through the transformer balancing circuit 12, transferring the energy from the energy storage element in the transformer balancing circuit 12 to the cell module. If the cell module is connected to the transformer balancing circuit 12 through the cell group selection circuit 11 to form a discharging circuit, the cell module discharges to the transformer balancing circuit 12, transferring the energy from the cell module to the transformer balancing circuit 12. In this way, by using different selection states, each cell module can be connected to the transformer balancing circuit 12 to form a charging and discharging circuit, eliminating the need for an independent transformer balancing circuit 12 for each cell module, thus simplifying the size and cost of the battery balancing circuit 10.

[0067] For example, when the average voltage of the first cell module is detected to be lower than that of other cell modules, the cell module selection circuit 11 selects the first cell module to form a charging loop with the transformer balancing circuit 12, so as to charge the first cell module through the transformer balancing circuit 12. Optionally, the energy stored in the transformer balancing circuit 12 can be obtained by charging other cell modules or by charging with an external DC power supply.

[0068] Optionally, to further improve battery balancing efficiency, a battery balancing unit 20 can be further provided inside each cell module. The battery balancing unit 20 is used to perform energy balancing between the cells within each cell module, such as... Figure 2 As shown, B1 to B5 are multiple series-connected cells in the cell module. The battery balancing unit 20 may include a switch selection circuit 21 and an inductor balancing circuit 22. The switch selection circuit 21 includes multiple cell selection switches connected in parallel. The inductor balancing circuit 22 includes an inductor L1 and a first switching transistor S. 11 Second switch S 12 Each cell selection switch has its first terminal connected to the connection node of two adjacent cells in the cell module, as well as the positive and negative terminals of the cell module. The second terminal of each cell selection switch is connected to the first terminal of inductor L1. The second terminal of inductor L1 is connected to the first switching transistor S...11 The first terminal and the second switching transistor S 12 The first terminal is connected to the first switching transistor S. 11 The second terminal is connected to the positive terminal of the battery pack, and the second switching transistor S 12 The second terminal is connected to the negative terminal of the cell assembly. The switch selection circuit 21 is connected between each cell in the cell assembly and the inductor balancing circuit 22. The switch selection circuit 21 forms an energy storage circuit by selecting the connection between the first cell in the cell assembly and the inductor balancing circuit 22, and forms an energy release circuit by selecting the connection between the second cell and the inductor balancing circuit 22, so as to transfer the energy of the first cell to the second cell.

[0069] Optionally, the battery balancing unit 20 described above can also be as follows: Figure 3 As shown, the battery balancing unit 20 is composed of multiple switching transistors and inductors L2 and L3 to achieve energy balance among the cells in the battery cell module. The battery balancing unit 20 can also be other circuit structures, as long as it can achieve energy balance among the cells; this application does not impose any restrictions on this.

[0070] The aforementioned battery balancing circuit 10 connects multiple cell modules, each cell module comprising multiple cells connected in series. The battery balancing circuit 10 includes a cell group selection circuit 11 and a transformer balancing circuit 12. The cell group selection circuit 11 connects each cell module to the transformer balancing circuit 12. The cell group selection circuit 11 has multiple selection states. In each selection state, any cell module is connected to the transformer balancing circuit 12 through the cell group selection circuit 11 to form a charging / discharging loop, allowing the cell module to be charged and discharged through the transformer balancing circuit 12. Thus, the battery balancing circuit 10 can directly charge and discharge the multiple cells connected in series within a cell module. Energy transfer is not limited to adjacent individual cells, resulting in more flexible energy transmission and higher overall battery pack balancing efficiency.

[0071] In the embodiments of this application, such as Figure 4As shown, the cell group selection circuit 11 includes a module selection switch group 111 and a loop selection switch group 112. The module selection switch group 111 includes N module selection switches, where N ≥ 2, and the N module selection switches are numbered sequentially. The loop selection switch group 112 includes a first loop selection switch, a second loop selection switch, a third loop selection switch, and a fourth loop selection switch. The first terminal of each module selection switch is connected to the positive or negative terminal of each cell module. The second terminal of the odd-numbered module selection switches is connected to the first terminal of the first loop selection switch and the first terminal of the third loop selection switch. The second terminal of the even-numbered module selection switches is connected to the first terminal of the second loop selection switch and the first terminal of the fourth loop selection switch. The second terminals of the first loop selection switch, the second loop selection switch, the third loop selection switch, and the fourth loop selection switch are all connected to the transformer equalization circuit 12.

[0072] In particular, the number of module selection switches in module selection switch group 111 is the number of cell modules plus one, so that... Figure 4 Taking a four-cell module as an example, there are five module selection switches, with odd-numbered module selection switches being K. T1 K T3 K T5 The even-numbered module selection switch is K. T2 K T4 .

[0073] Optionally, the module selection switch can be a relay, and the circuit selection switch can be a device capable of controlling the on / off state of the circuit, such as a metal-oxide-semiconductor field-effect transistor (MOSFET) or an insulated-gate bipolar transistor (IGBT). Because relays have very low conduction losses, using relays for the module selection switch achieves extremely high energy transfer efficiency during energy transmission, eliminating the need for complex heat dissipation designs. Furthermore, relays are less expensive, reducing the overall cost of the cell equalization unit. The circuit selection switch, on the other hand, requires frequent switching operations. The core advantages of MOSFETs or IGBTs lie in their lack of mechanical contacts and extremely high switching speed, resulting in fast response times, making them suitable for applications requiring frequent operation.

[0074] In the above embodiments, under the joint control of the switches in the module selection switch group 111 and the loop selection switch group 112, the connection between different battery cell modules and the transformer equalization circuit 12 is realized, thereby achieving energy transmission between different battery cell modules. Simultaneously, by selecting a relay as the module selection switch and a metal-oxide-semiconductor field-effect transistor or an insulated-gate bipolar transistor as the loop selection switch, the cost of the battery cell equalization unit is further reduced while ensuring response speed and transmission efficiency.

[0075] In one embodiment of this application, such as Figure 5 As shown, the transformer equalization circuit 12 includes a flyback transformer T and a third switch Q1; the first end of the secondary winding of the flyback transformer T is connected to the first end of the third switch Q1; the second end of the secondary winding of the flyback transformer T is connected to the second end of the first circuit selection switch and the second end of the second circuit selection switch; the second end of the third switch Q1 is connected to the second end of the third circuit selection switch and the second end of the fourth circuit selection switch.

[0076] The third switch Q1 can be a relay, a metal-oxide-semiconductor field-effect transistor, or an insulated-gate bipolar transistor, or other device capable of controlling the switching on and off of the circuit. The flyback transformer T is the energy storage element in the transformer equalization circuit 12, and can be a flyback transformer, a bidirectional flyback transformer T, or a multi-winding flyback transformer T.

[0077] In one embodiment, please refer to... Figure 5 The battery balancing circuit 10 also includes a first impact protection circuit 13; the first impact protection circuit 13 includes a first resistor R1, a first capacitor C1 and a first diode D1, the first resistor R1, the first capacitor C1 and the secondary winding of the flyback transformer T are connected in parallel, the cathode of the first diode D1 is connected to the first capacitor C1, and the anode of the first diode D1 is connected to the secondary winding of the flyback transformer T.

[0078] In the battery balancing circuit 10, the first surge protection circuit 13 is used to absorb the voltage spikes generated by the leakage inductance of the flyback transformer T, protecting the switching transistors from breakdown. The first diode D1 can be a fast recovery diode or a Schottky diode, because the duration of the voltage spike is extremely short (nanosecond level). Therefore, the first diode D1 needs to have an extremely high switching speed to work effectively. The parameters of the first resistor R1 and the first capacitor C1 need to be precisely matched according to the circuit conditions. Too large a capacitor or too small a resistor will lead to excessive losses and reduced efficiency; too small a capacitor or too large a resistor may not be able to effectively absorb the voltage spikes, resulting in damage to the switching transistors.

[0079] In the embodiments of this application, such as Figure 6 As shown, the cell group selection circuit 11 has a module energy storage state. In the module energy storage state, the two module selection switches connected to the two ends of the target cell module, the circuit selection switch between one of the two module selection switches and the second end of the secondary winding of the flyback transformer T, and the circuit selection switch between the other of the two module selection switches and the second end of the third switch Q1 are all in the conducting state. The third switch Q1 is in the conducting state, and the target cell module is connected to the secondary winding of the flyback transformer T to form an energy storage circuit.

[0080] like Figure 6As shown, the cell group selection circuit 11 is used to enter the module energy storage state upon receiving the module energy storage control signal. The target cell module can be the cell module with the highest average voltage among multiple cell modules. In the module energy storage state, the target cell module is connected to the secondary winding of the flyback transformer T to form an energy storage loop. The module energy storage control signal can be a control signal issued by the battery management system or the main control chip. The module energy storage control signal can be a PWM drive pulse, which controls the on / off state of the cell group selection circuit 11 and the third switch Q1 at different times to form a loop between the second cell module and the transformer equalization circuit 32.

[0081] For example, please continue to refer to Figure 6 Taking the target battery cell module as battery cell module 1 as an example, at t a0 -t a1 At any given time, after receiving the module energy storage control signal, the cell group selection circuit 11 turns on the two module selection switches K connected to both ends of the cell module 1. T1 K T2 The first circuit selection switch S is turned on. T1 Fourth circuit selection switch S T4 With other switches off, transformer balancing circuit 32 turns on the third switch Q1, enabling cell module 1 and module selection switch K to switch on. T1 First circuit selection switch S T1 flyback transformer T secondary winding W 12 Third switch Q1, fourth circuit selection switch S T4 With module selector switch K T2 A circuit is formed, which is used as the secondary winding W of the flyback transformer T through cell module 1. 12 During charging, the direction of the circuit current is as follows: Figure 6 As shown in the image.

[0082] In one embodiment, the cell group selection circuit 11 has a module energy release state. In the module energy release state, the two module selection switches connected to both ends of the target cell module, the loop selection switch between one of the two module selection switches and the second end of the third switch tube Q1, and the loop selection switch between the other of the two module selection switches and the second end of the secondary winding of the flyback transformer T are all in the on state. The third switch tube Q1 is in the on state, and the target cell module is connected to the secondary winding of the flyback transformer T to form an energy release circuit.

[0083] In the module energy release state, the two module selection switches connected to both ends of the target cell module, the circuit selection switch between one of the two module selection switches and the second end of the third switch Q1, and the circuit selection switch between the other of the two module selection switches and the second end of the secondary winding of the flyback transformer T are all in the conducting state. The third switch Q1 is in the conducting state, and the target cell module and the secondary winding of the flyback transformer T are connected to form an energy release circuit.

[0084] The cell group selection circuit 11 is also used to control the target cell module to form an energy release circuit with the secondary winding of the flyback transformer T when a module energy release control signal is received, thereby charging the target cell module through the secondary winding of the flyback transformer T. In one energy conversion process, the target cell module in the energy storage state and the target cell module in the energy release state are different modules. That is, one cell module is connected to the secondary winding of the flyback transformer T to form an energy storage circuit, and then another cell module is connected to the secondary winding of the flyback transformer T to form an energy release circuit, thus performing energy conversion between the two cell modules.

[0085] The module energy release control signal can be a control signal issued by the battery management system or the main control chip. The module energy release control signal can be a PWM drive pulse. By controlling the on and off of the cell group selection circuit 31 and the third switch Q1 at different times, a loop is formed between the first cell module and the transformer equalization circuit 32.

[0086] For example, such as Figure 7 As shown, at t a1 -t a2 Taking cell module 2 as an example, when the target cell module receives the module release control signal, the cell module selection circuit 31 is in the module release state and turns on the two module selection switches K connected to the two ends of cell module 2. T2 K T3 , conduction module selector switch K T2 The fourth circuit selection switch S between the second terminal of the third switch Q1 and the third switch Q1 T4 , conduction module selector switch K T3 The second circuit selection switch S between the second terminal of the secondary winding of the flyback transformer T and the second terminal of the flyback transformer T. T2 With other switches off, transformer balancing circuit 32 turns on the third switch Q1, enabling cell module 2 and module selection switch K to be activated. T2 Second circuit selection switch S T2 flyback transformer T secondary winding W 12 Third switch Q1, fourth circuit selection switch S T4 With module selector switch K T3 An energy release circuit is formed, which is then transmitted through the secondary winding W of the flyback transformer T.12 To charge cell module 2, the direction of the circuit current is as follows: Figure 7 As shown in the figure. The operating waveform of the battery equalization circuit 40 during operation can be as follows: Figure 8 As shown. Where, u Q1 This is the drive signal for the third switch Q1, i W12 For the current flowing through the secondary winding W of the flyback transformer T 12 The current, u KT1 u KT2 u KT3 To control the module selection switch K T1 K T2 K T3 The drive signal, u ST1 u ST2 u ST3 u ST4 Select switch S for the circuit T1 S T2 S T3 S T4 The driving signal.

[0087] In the above embodiments, the energy transfer between different cell modules is realized through the battery balancing circuit 10, which transfers the energy of the cell module with high average voltage to the cell module with low average voltage, thereby achieving voltage balancing of the entire battery pack.

[0088] In one embodiment, such as Figure 9 As shown, the battery balancing circuit 10 also includes an external DC power supply V, a fourth switch Q2, and a fifth switch Q3; the external DC power supply V is connected to the primary winding of the flyback transformer T, the fourth switch Q2 is located between the primary winding of the flyback transformer T and the negative terminal of the external DC power supply V, and the fifth switch Q3 is located between the primary winding of the flyback transformer T and the positive terminal of the external DC power supply V.

[0089] The external DC power supply V is 24V. Powered by the external DC power supply V, the flyback transformer T can be charged so that energy can be transferred to the battery cell module with low average voltage through the flyback transformer T.

[0090] For example, please continue to refer to Figure 9 The battery balancing circuit 10 also includes a second impact protection circuit 14; the second impact protection circuit 14 includes a second resistor R2, a second capacitor C2 and a second diode D2, the second resistor R2, the second capacitor C2 and the primary winding of the flyback transformer T are connected in parallel, the cathode of the second diode D2 is connected to the second capacitor C2, and the anode of the second diode D2 is connected to the primary winding of the flyback transformer T.

[0091] In the battery balancing circuit 10, the second surge protection circuit 14 and the first surge protection circuit 13 have the same function: to absorb the voltage spikes generated by the leakage inductance of the flyback transformer T and protect the switching transistors from breakdown. The selections of the second resistor R2, the second capacitor C2, and the second diode D2 are the same as those of the first resistor R1, the first capacitor C1, and the first diode D1.

[0092] In the above embodiments, an external DC power supply V is provided. The external DC power supply V can charge and replenish the battery cell modules with low average voltage, thereby achieving voltage balance between different battery cell modules. At the same time, the voltage of other battery cell modules is not affected during the balancing process. The external DC power supply V directly charges the battery cell modules with low average voltage, eliminating the need for two processes of charging and discharging between modules, resulting in higher energy transfer efficiency.

[0093] In one embodiment, the battery balancing circuit 10 has an external power supply state and an external energy release state; in the external power supply state, the fourth switch Q2 and the fifth switch Q3 are in the conducting state, and the external DC power supply V is connected to the primary winding of the flyback transformer T to form a power supply circuit.

[0094] like Figure 10 As shown, the battery balancing circuit 10 is used to be in an external power supply state when it receives an external power supply control signal, and turns on the fourth switch Q2 and the fifth switch Q3 so that the external DC power supply V and the primary winding of the flyback transformer T form a power supply circuit, and the primary winding of the flyback transformer T is charged by the external DC power supply V.

[0095] The external power supply control signal can be a control signal issued by the battery management system or the main control chip, and the external power supply control signal can be a PWM drive pulse.

[0096] For example, such as Figure 10 As shown, at time t0-t1, after receiving the external power supply control signal, the transformer equalization circuit 12 turns on the fourth switch Q2 and the fifth switch Q3, so that the external DC power supply V, the fourth switch Q2, the fifth switch Q3 and the primary winding W of the flyback transformer T are connected. 11 A power supply circuit is formed, with the external DC power supply V acting as the primary winding W of the flyback transformer T. 11 During charging, the direction of the circuit current is as follows: Figure 10 As shown in the image.

[0097] Under external energy release conditions, the two module selection switches connected to both ends of the target cell module, the circuit selection switch between one of the two module selection switches and the second end of the secondary winding of the flyback transformer T, and the circuit selection switch between the other of the two module selection switches and the second end of the third switch Q1 are all in the on state. The third switch Q1 is in the on state, and the target cell module and the secondary winding of the flyback transformer T are connected to form an energy release circuit.

[0098] The battery balancing circuit 10 is used to enter an external energy release state upon receiving an external energy release control signal. This external energy release control signal can be a control signal issued by the battery management system or the main control chip, and can be a PWM drive pulse. The target cell module is a voltage module with a low average voltage.

[0099] For example, such as Figure 11 As shown, taking cell module 1 as an example, at time t1-t2, the battery balancing circuit 40 receives the external energy release control signal and is in the external energy release state, thus turning on the control module selection switch K connected to both ends of cell module 1. T1 and module selector switch K T2 , conduction module selector switch K T1 The first circuit selection switch S between the secondary winding of the flyback transformer T and the second terminal of the flyback transformer T T1 , conduction module selector switch K T2 The fourth circuit selection switch S between the second terminal of the third switch Q1 and the third switch Q1 T4 With other switches off, transformer balancing circuit 32 turns on the third switch Q1, enabling cell module 1 and module selection switch K to switch on. T1 First circuit selection switch S T1 flyback transformer T secondary winding W 12 Third switch Q1, fourth circuit selection switch S T4 With module selector switch K T2 An energy release circuit is formed, which is then transmitted through the secondary winding W of the flyback transformer T. 12 To charge cell module 1, the direction of the circuit current is as follows: Figure 11 As shown in the figure. The operating waveform of the battery equalization circuit 40 during operation can be as follows: Figure 12 As shown.

[0100] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this application.

[0101] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A battery balancing circuit, characterized in that, The battery balancing circuit connects multiple cell modules, each cell module includes multiple cells connected in series, and the battery balancing circuit includes a cell group selection circuit and a transformer balancing circuit. The cell group selection circuit is connected between each cell module and the transformer balancing circuit. The cell group selection circuit has multiple selection states. In each selection state, any cell module is connected to the transformer equalization circuit through the cell group selection circuit to form a charging and discharging circuit, so that the cell module can be charged and discharged through the transformer equalization circuit.

2. The battery balancing circuit according to claim 1, characterized in that, The cell group selection circuit includes a module selection switch group and a loop selection switch group; the module selection switch group includes N module selection switches, N≥2, and the N module selection switches are numbered sequentially; the loop selection switch group includes a first loop selection switch, a second loop selection switch, a third loop selection switch, and a fourth loop selection switch. The first terminal of each module selection switch is connected to the positive or negative terminal of each cell module, respectively. The second terminal of the odd-numbered module selection switch is connected to the first terminal of the first circuit selection switch and the first terminal of the third circuit selection switch. The second terminal of the even-numbered module selection switch is connected to the first terminal of the second circuit selection switch and the first terminal of the fourth circuit selection switch. The second terminals of the first circuit selection switch, the second circuit selection switch, the third circuit selection switch, and the fourth circuit selection switch are all connected to the transformer balancing circuit.

3. The battery balancing circuit according to claim 2, characterized in that, The transformer equalization circuit includes a flyback transformer and a third switching transistor; The first end of the secondary winding of the flyback transformer is connected to the first end of the third switching transistor; The second end of the secondary winding of the flyback transformer is connected to the second end of the first circuit selection switch and the second end of the second circuit selection switch. The second terminal of the third switch is connected to the second terminal of the third circuit selection switch and the second terminal of the fourth circuit selection switch.

4. The battery balancing circuit according to claim 3, characterized in that, The cell group selection circuit has a module energy storage state; In the module energy storage state, the two module selection switches connected to both ends of the target cell module, the circuit selection switch between one of the two module selection switches and the second end of the secondary winding of the flyback transformer, and the circuit selection switch between the other of the two module selection switches and the second end of the third switch are all in the on state. The third switch is in the on state, and the target cell module and the secondary winding of the flyback transformer are connected to form an energy storage circuit.

5. The battery balancing circuit according to claim 3, characterized in that, The cell group selection circuit has a module energy release state; In the module's energy release state, the two module selection switches connected to both ends of the target cell module, the circuit selection switch between one of the two module selection switches and the second end of the third switch, and the circuit selection switch between the other of the two module selection switches and the second end of the secondary winding of the flyback transformer are all in the on state. The third switch is in the on state, and the target cell module and the secondary winding of the flyback transformer are connected to form an energy release circuit.

6. The battery balancing circuit according to claim 3, characterized in that, The battery equalization circuit also includes a first impact protection circuit. The first impulse protection circuit includes a first resistor, a first capacitor, and a first diode. The first resistor, the first capacitor, and the secondary winding of the flyback transformer are connected in parallel. The cathode of the first diode is connected to the first capacitor, and the anode of the first diode is connected to the secondary winding of the flyback transformer.

7. The battery balancing circuit according to claim 3, characterized in that, The battery balancing circuit also includes an external DC power supply, a fourth switching transistor, and a fifth switching transistor; The external DC power supply is connected to the primary winding of the flyback transformer. The fourth switch is located between the primary winding of the flyback transformer and the negative terminal of the external DC power supply. The fifth switch is located between the primary winding of the flyback transformer and the positive terminal of the external DC power supply.

8. The battery balancing circuit according to claim 7, characterized in that, The battery balancing circuit has an external power supply state and an external energy release state; Under the external power supply state, the fourth and fifth switching transistors are in the on state, and the external DC power supply is connected to the primary winding of the flyback transformer to form a power supply circuit; Under the external energy release state, the two module selection switches connected to both ends of the target cell module, the circuit selection switch between one of the two module selection switches and the second end of the secondary winding of the flyback transformer, and the circuit selection switch between the other of the two module selection switches and the second end of the third switch are all in the on state. The third switch is in the on state, and the target cell module and the secondary winding of the flyback transformer are connected to form an energy release circuit.

9. The battery balancing circuit according to claim 7, characterized in that, The battery equalization circuit also includes a second impact protection circuit. The second impulse protection circuit includes a second resistor, a second capacitor, and a second diode. The second resistor, the second capacitor, and the primary winding of the flyback transformer are connected in parallel. The cathode of the second diode is connected to the second capacitor, and the anode of the second diode is connected to the primary winding of the flyback transformer.

10. The battery balancing circuit according to any one of claims 7 to 9, characterized in that, The external DC power supply is 24V.

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