An active equalization circuit

Abstract

The application relates to an active equalization circuit, belonging to the technical field of battery equalization in a battery management system. The system comprises a conversion unit, a control unit and a plurality of equalization modules. The equalization module comprises a unidirectional conduction device, a switching device, a transformer and a rectification filter circuit. The unidirectional conduction device, the primary winding of the transformer and the switching device are connected in series in any order, form a series structure and are connected to the output end of the conversion unit; the secondary winding of the transformer is connected with the input end of the rectification filter circuit; the output end of the rectification filter circuit is connected with the corresponding cell node; the unidirectional conduction device limits the current direction to avoid energy flow between the equalization modules; the control unit is connected with the switching device and is used for controlling the conduction state of the switching device. The active equalization circuit provided by the application has the advantages of simple structure, flexible control and high equalization efficiency.

Description

Technical Field

[0001] This invention relates to the field of battery balancing technology, and more particularly to an active balancing circuit. Background Technology

[0002] In current battery management systems (BMS), battery balancing technologies are divided into passive balancing and active balancing technologies. They are widely used for power transfer between multiple battery cells to improve the overall efficiency of the battery pack and extend its lifespan. Active balancing solutions are increasingly being adopted due to their advantages such as high efficiency and low energy consumption.

[0003] Active balancing methods mainly include bidirectional flyback, matrix switching, bidirectional buck-boost, and external power supply. Bidirectional flyback active balancing uses multiple flyback converters to transfer excess energy to other battery cells with below-average voltages. However, it suffers from the complexity, high cost, and large size of the flyback transformers. Matrix switching active balancing selectively connects battery cells using a controllable matrix switching network, allowing energy transfer between different cells within the battery pack. This matrix switching network often requires a large number of MOSFETs, leading to complex circuitry and high cost. Furthermore, this method typically only balances one battery cell at a time, resulting in limited balancing efficiency. Bidirectional buck-boost active balancing uses a bidirectional DC-DC converter to allow energy transfer between any two cells within the battery pack, achieving balancing. However, it suffers from significant energy loss, resulting in low balancing efficiency. External power supply active balancing primarily uses simple switching control logic to replenish the power to each battery cell. However, it relies on an external power supply, resulting in significant energy loss, slow balancing rate, and control lag.

[0004] Therefore, there is an urgent need for an active balancing technology that is simple in circuitry, low in cost, and highly efficient. Summary of the Invention

[0005] The present invention aims to provide a novel active equalization circuit that is simple in structure, easy to control, low in cost, and high in equalization efficiency, in order to overcome the problems of complex structure, high cost, large size, high control requirements, and low equalization efficiency in existing active equalization circuits.

[0006] This invention provides an active equalization circuit, comprising: The system comprises a conversion unit 20, a control unit 10, and several equalization modules 30. The input terminals (20a, 20b) of the conversion unit are connected to the battery pack 40 to receive DC power from the battery pack. The output terminals (20c, 20d) of the conversion unit are connected to one end of each equalization module 30 to convert the DC power into AC power for supplying the equalization modules. The other end of each equalization module is connected to a corresponding cell node 41 to perform equalization processing on the cell. The control unit 10 is connected to a switching device 33 in the equalization module. The control unit outputs a low-frequency signal to control the conduction state of the switching device, thereby enabling the replenishment operation of the target cell.

[0007] The equalization module includes a unidirectional conducting device 31, a transformer 32, a switching device 33, and a rectifier-filter circuit 34. The unidirectional conducting device 31, the primary winding of the transformer 32, and the switching device 33 are connected in series to form a series structure and are connected to the output terminals (20c, 20d) of the conversion unit 20, forming an energy transfer path. The relative order of the unidirectional conducting device 31, the primary winding of the transformer 32, and the switching device 33 can be arbitrarily changed to achieve the same electrical function. The secondary winding of the transformer 32 is connected to the input terminal of the rectifier-filter circuit 34, and the output terminal of the rectifier-filter circuit 34 is connected to the corresponding cell node 41.

[0008] The unidirectional conducting device 31 can be any of the following: a diode, a Schottky diode, a synchronous rectifier MOSFET, or an active conducting device composed of MOSFETs, whose gate receives a control signal to achieve the unidirectional conducting function. This device has unidirectional conducting characteristics, preventing reverse current flow and limiting the current direction to from the conversion unit 20 to the equalization module 30, thus preventing energy crosstalk between the equalization modules (30-1, 30-2, ..., 30-n). It should be understood that the unidirectional conducting device is not limited to the specific device types listed above; other devices or circuit structures with unidirectional conducting characteristics can also be used, and the specific implementation method is not limited.

[0009] The switching device 33 can be any one of an NMOS transistor, PMOS transistor, bipolar transistor, or insulated-gate bipolar transistor. Its conduction state is controlled by the control unit 10 to achieve energy transfer control of the target battery cell. It should be understood that the switching device is not limited to the types listed above, and other devices or circuit structures capable of achieving switching control functions can also be used, and the specific implementation method is not limited.

[0010] The rectifier-filter circuit 34 includes a diode 341 and a capacitor 342. The anode of the diode 341 is connected to one end of the secondary winding of the transformer 32, and the cathode of the diode 341 is connected to one end of the capacitor 342, forming a first connection terminal connected to the battery cell. The other end of the capacitor 342 is connected to the other end of the secondary winding of the transformer 32, forming a second connection terminal connected to the battery cell. The diode 341 converts the alternating current output from the secondary winding of the transformer 32 into direct current, and the capacitor 342 filters the direct current and outputs it to the connection terminal of the target battery cell 41. Furthermore, the rectifier-filter circuit can also be implemented using synchronous rectifier devices, LC filter structures, or integrated power management modules. It should be understood that the structure of the rectifier-filter circuit is not limited to the above embodiments, and other circuit forms capable of achieving rectification and filtering functions can also be used.

[0011] The conversion unit 20 includes an inverter, which can be any one of a full-bridge inverter, half-bridge inverter, push-pull inverter, multi-level inverter, forward inverter, flyback inverter, two-transistor forward inverter, or LLC resonant inverter. The input terminals (20a, 20b) of the flyback inverter are connected to the battery pack 40 to receive DC power from the battery pack 40. The output terminals (20c, 20d) of the flyback inverter are connected to one end of each of the plurality of equalization modules 30 to convert DC power into AC power to supply the equalization modules 30. It should be understood that the inverter is not limited to the above topology; other inverter structures with energy conversion functions can also be used, as long as they have the function of converting DC power into AC power. The specific implementation method is not limited.

[0012] Compared with existing active balancing schemes, the advantages of this invention are as follows: 1. High equalization efficiency, capable of equalizing multiple channels simultaneously; 2. The switching control strategy of the equalization module is simple, providing easy low-frequency switching control without the need for a high-frequency PWM signal; 3. The isolation method between each battery cell is simple; isolation can be achieved through a forward transformer. 4. The circuit structure is simpler. Each equalization module only needs to be equipped with one switching device, and there is no need to configure flyback transformers in each equalization module, which significantly reduces the number of devices and the space occupied, and at the same time significantly reduces the overall manufacturing cost.

[0013] 5. High reliability: By simplifying the circuit structure and reducing single points of failure, the long-term operational stability of the entire machine is improved. 6. Flexible and scalable structure with multiple structural variations, allowing for design for different battery packs and convenient modular deployment; 7. It has higher energy transfer efficiency, generates less heat, and has a significant energy-saving effect. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying 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.

[0015] Figure 1 This is a system schematic diagram of the active equalization circuit in this invention; Figure 2 for Figure 1 Enlarged view of a portion of the image; Wherein: 10 - Control unit, 20 - Conversion unit, 30 - Equalization module, 31 - Unidirectional conduction device, 32 - Transformer, 33 - Switching device, 34 - Rectifier and filter circuit, 341 - Diode, 342 - Capacitor, 40 - Battery pack, 41 - Battery cell. Detailed Implementation

[0016] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0017] like Figure 1 As shown, an embodiment of the present invention provides an active balancing circuit, comprising: a conversion unit 20, a control unit 10, and a plurality of balancing modules 30. The input terminals (20a, 20b) of the conversion unit are connected to a battery pack 40 to receive DC power from the battery pack. The output terminals (20c, 20d) of the conversion unit are connected to one end of each of the plurality of balancing modules 30 to convert the DC power into AC power to supply the balancing modules. The other end of each balancing module is connected to a corresponding cell node 41 to perform balancing processing on the cell. The control unit 10 is connected to a switching device 33 in the balancing module. The control unit outputs a low-frequency signal to control the conduction state of the switching device, thereby realizing the charging operation of the target cell.

[0018] Specifically, in this embodiment, the equalization module 30 includes a unidirectional conducting device 31, a transformer 32, a switching device 33, and a rectifier filter circuit 34. The unidirectional conducting device 31, the primary winding of the transformer 32, and the switching device 33 are connected in series to form a series structure and are connected to the output terminals (20c, 20d) of the conversion unit 20, forming an energy transfer path. The secondary winding of the transformer 32 is connected to the input terminal of the rectifier filter circuit 34, and the output terminal of the rectifier filter circuit 34 is connected to the corresponding cell node 41.

[0019] In other feasible embodiments, the relative order of the unidirectional conducting device 31, the primary winding of the transformer 32, and the switching device 33 can be arbitrarily changed to achieve the same electrical function.

[0020] Specifically, in this embodiment, the unidirectional conducting device 31 is a diode, with its anode connected to the conversion unit 20 and its cathode connected to the equalization module 30. The function of the diode 31 is to limit the current direction and prevent energy crossflow between the equalization modules 30.

[0021] In other feasible embodiments, the unidirectional conducting device 31 can be a Schottky diode, a synchronous rectifier MOSFET, or an active conducting device composed of MOSFETs, whose gate receives a control signal to achieve the unidirectional conducting function. It should be understood that the unidirectional conducting device is not limited to the specific device types listed above, and other devices or circuit structures with unidirectional conducting characteristics can also be used.

[0022] Specifically, in this embodiment, the switching device 33 is an NMOS transistor. Its conduction state is controlled by the control unit 10 to achieve energy transfer control of the target battery cell.

[0023] In other feasible embodiments, the switching device 33 can be one of a PMOS transistor, a bipolar transistor, or an insulated-gate bipolar transistor. It should be understood that the switching device is not limited to the types listed above, and other devices or circuit structures capable of implementing switching control functions can also be used.

[0024] Specifically, in this embodiment, the rectifier-filter circuit 34 includes a diode 341 and a capacitor 342. The anode of the diode 341 is connected to one end of the secondary winding of the transformer 32, and the cathode of the diode 341 is connected to one end of the capacitor 342 to form a first connection terminal connected to the battery cell. The other end of the capacitor 342 is connected to the other end of the secondary winding of the transformer 32 to form a second connection terminal connected to the battery cell. The diode 341 converts the alternating current output from the secondary winding of the transformer 32 into direct current, and the capacitor 342 filters the direct current and outputs it to the connection terminal of the target battery cell 41.

[0025] In other feasible embodiments, the rectifier-filter circuit 34 is a synchronous rectifier device, an LC filter structure, or an integrated power management module. It should be understood that the structure of the rectifier-filter circuit is not limited to the above embodiments, and other circuit forms capable of achieving rectification and filtering functions can also be used.

[0026] Specifically, in this embodiment, the conversion unit 20 includes a flyback inverter. The input terminals (20a, 20b) of the flyback inverter 20 are connected to the battery pack 40 to receive DC power from the battery pack 40. The output terminals (20c, 20d) of the flyback inverter are connected to one end of the plurality of equalization modules 30 to convert DC power into AC power to supply the equalization modules 30.

[0027] In other feasible embodiments, the conversion unit 20 can be any one of a full-bridge inverter, a half-bridge inverter, a push-pull inverter, a multilevel inverter, a forward inverter, a two-transistor forward inverter, or an LLC resonant inverter. It should be understood that the inverter is not limited to the above topologies and can also employ other inverter structures with energy conversion functions, as long as they have the ability to convert direct current to alternating current.

[0028] According to the appendix Figure 2 The working principle of the equalization module 30 will be described in detail below. For ease of explanation, only the working process of equalization modules 30-1 and 30-2 will be used as examples. The working principles of other equalization modules (30-1, 30-2, ..., 30-n) are similar and will not be described again. In the appendix Figure 2 In this configuration, the AC signal enters through the output ports (20c, 20d) of the conversion unit 20 and serves as the input to the equalization modules 30-1 and 30-2. The following four scenarios then arise: 1. When neither cell 41-1 nor cell 41-2 needs to be charged and balanced, both switching devices 33-1 and 33-2 are in the off state.

[0029] 2. When battery cells 41-1 and 41-2 need to be charged and balanced at the same time, switching devices 33-1 and 33-2 are turned on simultaneously. Energy is transferred to the secondary winding through transformers 32-1 and 32-2. After passing through the rectifier and filter circuit 34, battery cells 41-1 and 41-2 are charged simultaneously.

[0030] 3. When cell 41-1 needs to be charged and balanced, while cell 41-2 does not, switch 33-1 is turned on and switch 33-2 is turned off. Energy is transferred to the secondary winding through transformer 32-1 and then converted into DC power by the subsequent rectifier and filter circuit 34 to charge cell 41-1. It is worth noting that although switch 33-2 is in the off state, due to the possible presence of a body diode structure inside, current may flow from the primary winding of transformer 32-1 through switch 33-1, switch 33-2, and transformer 32-2, forming a new loop. To avoid unexpected backflow, a unidirectional conduction device 31-2 is specifically provided to block this abnormal loop, thereby ensuring that energy is only transferred to the target cell 41-1 and preventing interference to other balancing modules.

[0031] 4. When cell 41-2 needs to be charged and balanced, while cell 41-1 does not, switch 33-2 is turned on and switch 33-1 is turned off. Energy is transferred to the secondary winding through transformer 32-2 and then converted into DC power by the subsequent rectifier and filter circuit 34 to charge cell 41-2. It is worth noting that although switch 33-1 is in the off state, due to the possible presence of a body diode structure inside, current may flow from the primary winding of transformer 32-2 sequentially through switch 33-2, switch 33-1, and transformer 32-1 to form a new loop. To avoid unexpected backflow, a unidirectional conduction device 31-1 is specifically provided to block this abnormal loop, thereby ensuring that energy is only transferred to the target cell 41-2 and preventing interference to other balancing modules.

[0032] To prevent unexpected current backflow between any equalization modules, the invention includes unidirectional conduction devices (such as 31-1, 31-2, ..., 31-n in the figure) in each equalization module to block any abnormal loops that may form, thereby ensuring that energy transfer only occurs between the target cells and preventing other equalization modules from being interfered with or falsely triggered.

[0033] In the description of this application, it should be noted that the terms "upper" and "lower," etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the module or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or a link; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two elements. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0034] It should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0035] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. An active equalization circuit, characterized in that, include: The system comprises a conversion unit (20), a control unit (10), and several equalization modules (30); the input terminals (20a, 20b) of the conversion unit are connected to the battery pack (40) to receive DC power from the battery pack; the output terminals (20c, 20d) of the conversion unit are connected in parallel to one end of each of the several equalization modules (30) to convert the DC power into AC power and independently distribute it to the parallel branch formed by each equalization module; the other end of each equalization module is connected to the corresponding cell node (41) to perform equalization processing on the cell; the control unit (10) is connected to the switching device (33) in the equalization module to control its conduction state and realize the power replenishment operation of the target cell; the equalization module (30) includes a unidirectional conduction device (31), a transformer (32), a switching device (33), and a rectifier filter circuit (34), wherein the unidirectional conduction device and the primary winding of the transformer are connected in parallel to the battery pack (40) to receive DC power from the battery pack (40); the output terminals (20c, 20d) of the conversion unit are connected in parallel to one end of ... The three components, including the group and the switching device, are connected in series to form a series structure. The series structure of several equalization modules (30) is connected to the output terminal (20c, 20d) of the conversion unit as independent parallel branches, forming multiple independent energy transfer paths. The unidirectional conducting device (31) has unidirectional conducting characteristics and is used to block abnormal loops caused by the body diode structure of the switching device in the parallel branch, so as to limit the current direction and avoid energy crossflow between the equalization modules (30). The secondary winding of the transformer is connected to the input terminal of the rectifier and filter circuit, and the output terminal of the rectifier and filter circuit is connected to the corresponding cell node (41). The conversion unit (20) includes an inverter. The input terminal of the inverter is connected to the battery pack to receive DC power from the battery pack. The output terminal of the inverter is connected to one end of the several equalization modules to convert DC power into AC power to supply the equalization modules.

2. The active equalization circuit according to claim 1, characterized in that, The relative order of the unidirectional conducting device (31), the primary winding of the transformer (32), and the switching device (33) can be arbitrarily changed in the series connection method, as long as the same electrical function is achieved.

3. The active equalization circuit according to claim 1, characterized in that, The unidirectional conducting device (31) is a diode.

4. The active equalization circuit according to claim 1, characterized in that, The unidirectional conduction device (31) is a Schottky diode, a synchronous rectifier MOSFET, or an active conduction device composed of MOSFETs, whose gate receives a control signal to achieve the unidirectional conduction function.

5. The active equalization circuit according to claim 1, characterized in that, The switching device (33) is a controllable conducting device, and its conducting state is controlled by the control unit (10) to realize the energy transfer control of the target cell.

6. The active equalization circuit according to claim 5, characterized in that, The switching device (33) is an NMOS transistor.

7. The active equalization circuit according to claim 5, characterized in that, The switching device (33) is a PMOS transistor, a bipolar transistor, or an insulated gate bipolar transistor.

8. The active equalization circuit according to claim 1, characterized in that, The transformer (32) is a transformer with electrical isolation capability. Its secondary winding is connected to a rectifier and filter circuit to transfer energy to the target cell.

9. The active equalization circuit according to claim 1, characterized in that, The rectifier and filter circuit (34) includes a rectifier and a filter. The rectifier converts the AC power output from the secondary winding of the transformer into DC power. The filter filters the DC power and outputs it to the target cell connection terminal.

10. The active equalization circuit according to claim 9, characterized in that, The rectifier filter circuit (34) includes a diode (341) and a capacitor (342). The anode of the diode (341) is connected to one end of the secondary winding of the transformer (32). The cathode of the diode (341) is connected to one end of the capacitor (342) to form a first connection terminal connected to the battery cell. The other end of the capacitor (342) is connected to the other end of the secondary winding of the transformer (32) to form a second connection terminal connected to the battery cell.

11. The active equalization circuit according to claim 1, characterized in that, The conversion unit (20) is a flyback inverter.

12. The active equalization circuit according to claim 1, characterized in that, The conversion unit (20) is any one of a full-bridge inverter, a half-bridge inverter, a multi-level inverter, a push-pull inverter, a forward inverter, a two-tube forward inverter, or an LLC resonant inverter.

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