Active equalization circuit

Abstract

The invention relates to an active equalization circuit, and belongs 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 one-way conduction device, a switching device, a transformer and a rectification filter circuit. The one-way conduction device, the primary winding of the transformer and the switching device are connected in series according to any sequence to form a series structure and are connected to the output end of the conversion unit; a secondary winding of the transformer is connected with the input end of the rectification filter circuit; the output end of the rectifying and filtering circuit is connected with the corresponding battery cell node; the one-way conduction device limits the current direction so as to avoid energy streaming between the equalization modules; and the control unit is connected with the switching device and is used for controlling the conducting state of the switching device. The active equalization circuit provided by the invention is simple in structure and flexible to control, can simultaneously equalize a plurality of channels, and is high in equalization efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery equalization, and in particular to an active equalization circuit. BACKGROUND

[0002] In current battery management systems (BMS), battery equalization technology is divided into passive equalization technology and active equalization technology, which are widely used for power transfer between multiple batteries to improve the overall use efficiency and prolong the life of the battery pack. Active equalization solutions are increasingly adopted due to their high efficiency, low energy consumption, and other advantages.

[0003] The active equalization methods mainly include bidirectional flyback, matrix switch, bidirectional buck-boost, and external power supply. The bidirectional flyback active equalization method mainly transfers the excess energy of multiple flyback converters to other battery units below the average voltage. However, it has the problems of complex flyback transformer, high cost, and large size. The matrix switch active equalization method selectively connects battery units through a controllable matrix switch network, allowing energy transfer between different batteries in the battery pack. However, the matrix switch network often requires a large number of MOSFET tubes to build, resulting in complex circuit, high cost. In addition, this method can only balance one battery unit at any time, with limited balancing efficiency. The bidirectional buck-boost active equalization method uses bidirectional DC-DC converters to allow energy transfer between any two batteries in the battery pack, achieving balancing, but it has high energy loss, resulting in low balancing efficiency. The external power supply active equalization method mainly controls the power supply of each battery unit through simple switching logic, but it relies on external power supply units, has large energy loss, and has the problems of slow balancing rate and control lag.

[0004] Therefore, in view of the current active equalization technology, there is an urgent need for an active equalization technology with simple circuit, low cost, and high balancing efficiency. SUMMARY

[0005] The present application aims to provide a new active equalization circuit with simple structure, easy control, low cost, and high balancing efficiency, to overcome the problems of complex structure, high cost, large size, high control requirements, and low balancing efficiency in existing active equalization circuits.

[0006] The present application provides an active equalization circuit, comprising: The conversion unit 20, the control unit 10, the several equalization modules 30, the input end (20a, 20b) of the conversion unit is connected with the battery pack 40 to receive the direct current from the battery pack, the output end (20c, 20d) of the conversion unit is connected with one end of the several equalization modules 30, converts the direct current into alternating current to supply the equalization modules, the other end of each equalization module is connected with the corresponding cell node 41 to carry out the equalization treatment on the cell. The control unit 10 is connected with the switching device 33 in the equalization module, the control unit outputs the low-frequency signal to control the conduction state of the switching device to realize the power compensation operation on the target cell.

[0007] The equalization module includes the unidirectional conduction device 31, the transformer 32, the switching device 33 and the rectifier filter circuit 34, the unidirectional conduction 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 end (20c, 20d) of the conversion unit 20 to form an energy transfer path. The series structure connection mode can arbitrarily change the relative order of the unidirectional conduction device 31, the primary winding of the transformer 32 and the switching device 33 as long as the same electrical function is realized. The secondary winding of the transformer 32 is connected with the input end of the rectifier filter circuit 34, and the output end of the rectifier filter circuit 34 is connected with the corresponding cell node 41.

[0008] The unidirectional conduction device 31 can be a diode, a Schottky diode, a synchronous rectification MOSFET or an active conduction device composed of a MOSFET, and its gate receives a control signal to realize any one of the unidirectional conduction functions. The device has a unidirectional conduction characteristic, prevents the reverse flow of current, limits the current direction to be from the conversion unit 20 to the equalization module 30, and avoids the energy flow between the equalization modules (30-1, 30-2, …, 30-n). It should be understood that the unidirectional conduction device is not limited to the specific device types listed above, but can also use other devices or circuit structures with unidirectional conduction characteristics, and the specific implementation mode is not limited.

[0009] The switching device 33 can be any one of an NMOS transistor, a PMOS transistor, a bipolar transistor or an insulated gate bipolar transistor. Its conduction state is controlled by the control unit 10 to realize the energy transfer control of the target cell. It should be understood that the switching device is not limited to the types listed above, but can also use other devices or circuit structures capable of realizing the switching control function, and the specific implementation mode is not limited.

[0010] The rectification filter circuit 34 includes a diode 341 and a capacitor 342, an anode of the diode 341 is connected with one end of the secondary winding of the transformer 32, a cathode of the diode 341 is connected with one end of the capacitor 342 and forms a first connection end connected with the battery cell, the other end of the capacitor 342 is connected with the other end of the secondary winding of the transformer 32 and forms a second connection end connected with the battery cell. The diode 341 converts the alternating current output by the secondary winding of the transformer 32 into direct current, the capacitor 342 filters the direct current and outputs to the connection end of the target battery cell 41. In addition, the rectification filter circuit can also be realized by using a synchronous rectification device, an LC filter structure or an integrated power management module. It should be understood that the structure of the rectification filter circuit is not limited to the above embodiment, and other circuit forms capable of realizing the functions of rectification and filtering can also be used.

[0011] The conversion unit 20 includes an inverter, which can be any one of a full-bridge inverter, a half-bridge inverter, a push-pull inverter, a multi-level inverter, a forward inverter, a flyback inverter, a double-tube forward inverter and an LLC resonant inverter. The input end (20a, 20b) of the flyback inverter is connected with the battery pack 40 to receive direct current from the battery pack 40, and the output end (20c, 20d) of the flyback inverter is connected with one end of the plurality of equalization modules 30 to convert the direct current into alternating current for the equalization modules 30. It should be understood that the inverter is not limited to the above topology, and other inverter structures with energy conversion function can also be used, as long as they have the function of converting direct current into alternating current, and the specific implementation mode is not limited.

[0012] Compared with the existing active equalization scheme, the present application has the following advantages: 1. High equalization efficiency, multiple channels can be equalized at the same time; 2. The switching control strategy of the equalization module is simple, which is a simple low-frequency switching control without high-frequency PWM signal; 3. The isolation between each battery unit is simple, which can be realized by a forward transformer; 4. The circuit structure is more simple, only one switching device is needed for each equalization module, and no flyback transformer is needed in each equalization module, thereby significantly reducing the number of devices and the occupied space, and significantly reducing the overall manufacturing cost.

[0013] 5. High reliability, by simplifying the circuit structure, reducing single point failure, improving the long-term operation stability of the whole machine; 6. Flexible structure, expandable, multiple structure variant schemes, can be designed for different battery packs, convenient for 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 the embodiment, the equalization module 30 includes a unidirectional conducting device 31, a transformer 32, a switching device 33, and a rectification filter circuit 34. The unidirectional conducting device 31, a primary winding of the transformer 32, and the switching device 33 are connected in series, forming a series structure and connected to the output end (20c, 20d) of the conversion unit 20, forming an energy transfer path. A secondary winding of the transformer 32 is connected to the input end of the rectification filter circuit 34, and the output end of the rectification filter circuit 34 is connected to the corresponding cell node 41.

[0019] In other possible embodiments, the series structure connection mode can arbitrarily change the relative order of the unidirectional conducting device 31, the primary winding of the transformer 32, and the switching device 33, as long as the same electrical function is achieved.

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

[0021] In other possible embodiments, the unidirectional conducting device 31 can be a Schottky diode, a synchronous rectification MOSFET, or an active conducting device composed of a MOSFET, the gate of which receives a control signal to achieve one of the unidirectional conducting functions. It should be understood that the unidirectional conducting device is not limited to the specific device types listed above, but can also use other devices or circuit structures with unidirectional conducting characteristics.

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

[0023] In other possible 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, but can also use other devices or circuit structures that can achieve switching control functions.

[0024] Specifically, in the embodiment, the rectification and filtering 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 and forms a first connection end connected to the battery cell, and the other end of the capacitor 342 is connected to the other end of the secondary winding of the transformer 32 and forms a second connection end connected to the battery cell. The diode 341 converts the alternating current output by the secondary winding of the transformer 32 into direct current, and the capacitor 342 filters the direct current and outputs it to the connection end of the target battery cell 41.

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

[0026] Specifically, in the embodiment, the conversion unit 20 includes a flyback inverter. The input ends (20a, 20b) of the flyback inverter 20 are connected to the battery pack 40 to receive direct current from the battery pack 40, and the output ends (20c, 20d) of the flyback inverter are connected to one end of the plurality of balancing modules 30 to convert the direct current into alternating current for the balancing modules 30.

[0027] In other possible embodiments, the conversion unit 20 is any one of a full-bridge inverter, a half-bridge inverter, a push-pull inverter, a multi-level inverter, a forward inverter, a double-tube forward inverter, and an LLC resonant inverter. It should be understood that the inverter is not limited to the above topologies, and other inverter structures with energy conversion functions can also be used as long as they have the function of converting direct current into alternating current.

[0028] According to the attached Figure 2 The working principle of the balancing module 30 is described in detail. For the sake of convenience, only the working process of the balancing modules 30-1 and 30-2 is described, and the working principles of the other balancing modules (30-1, 30-2, …, 30-n) are similar and will not be described again: In the attached Figure 2 The alternating current signal enters through the output ports (20c, 20d) of the conversion unit 20 and serves as the input part of the balancing modules 30-1 and 30-2. Next, there are four cases: 1. When neither battery cell 41-1 nor battery cell 41-2 needs to be charged and balanced, the switching device 33-1 and the switching device 33-2 are both in the off state.

[0029] 2. When both battery cells 41-1 and 41-2 need to be equalized, switch devices 33-1 and 33-2 are opened simultaneously, energy is transmitted to the secondary winding through transformers 32-1 and 32-2, and after the subsequent rectifier filter circuit 34, it is converted into direct current to charge battery cells 41-1 and 41-2 simultaneously.

[0030] 3. When battery cell 41-1 needs to be equalized, and battery cell 41-2 does not need to be equalized, switch device 33-1 is opened, and switch device 33-2 is closed, energy is transmitted to the secondary winding through transformer 32-1, and after the subsequent rectifier filter circuit 34, it is converted into direct current to charge battery cell 41-1. It is worth noting that although switch device 33-2 is in a closed state, due to the possible existence of a body diode structure inside it, current may form a new loop from the primary winding of transformer 32-1 through switch device 33-1, switch device 33-2, and transformer 32-2. To avoid the occurrence of unintended backflow, the invention deliberately sets up unidirectional conduction device 31-2 to block this abnormal loop, thereby ensuring that energy is only transmitted to target battery cell 41-1, avoiding interference with other equalization modules.

[0031] 4. When battery cell 41-2 needs to be equalized, and battery cell 41-1 does not need to be equalized, switch device 33-2 is opened, and switch device 33-1 is closed, energy is transmitted to the secondary winding through transformer 32-2, and after the subsequent rectifier filter circuit 34, it is converted into direct current to charge battery cell 41-2. It is worth noting that although switch device 33-1 is in a closed state, due to the possible existence of a body diode structure inside it, current may form a new loop from the primary winding of transformer 32-2 through switch device 33-2, switch device 33-1, and transformer 32-1. To avoid the occurrence of unintended backflow, the invention deliberately sets up unidirectional conduction device 31-1 to block this abnormal loop, thereby ensuring that energy is only transmitted to target battery cell 41-2, avoiding interference with other equalization modules.

[0032] To prevent unintended current backflow between any equalization modules, the invention sets up unidirectional conduction devices (such as 31-1, 31-2, …, 31-n in the figure) in each equalization module to block the abnormal loop that may be formed, thereby ensuring that energy transmission only occurs between target battery cells, avoiding interference or false triggering of other equalization modules.

[0033] In the description of the present application, it should be noted that the orientation or positional relationship indicated by the terms "upper" and "lower" and the like is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the modules or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. Unless otherwise expressly specified and limited, the terms "mounting", "connection" and "connection" should be interpreted broadly, for example, it can be a fixed connection, or a detachable connection, or an integral connection; it can be a mechanical connection, or a connection; it can be directly connected, or indirectly connected through an intermediate medium, or the internal communication of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0034] It should be noted that in the present application, relational terms such as "first" and "second" and the like are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the terms "include", "contain" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or device. Without more limitations, the element defined by the statement "including a" does not exclude the presence of other identical elements in the process, method, article or device including the element.

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

Claims

1. An active equalization circuit, characterized by, The application relates to a battery equalization system, which comprises a conversion unit (20), a control unit (10) and a plurality of equalization modules (30), the input end (20a, 20b) of the conversion unit is connected with a battery pack (40) to receive direct current from the battery pack, the output end (20c, 20d) of the conversion unit is connected with one end of the plurality of equalization modules (30) to convert the direct current into alternating current for supplying the equalization modules, the other end of each equalization module is connected with a corresponding battery cell node (41) to perform equalization treatment on the battery cell, the control unit (10) is connected with a switching device (33) in the equalization module to control the on-off state of the switching device and realize power compensation operation on a target battery cell. The equalization module comprises a one-way conduction device (31), a transformer (32), a switching device (33) and a rectifier filter circuit (34), the one-way conduction device, the primary winding of the transformer and the switching device are connected in series to form a series structure and are connected to the output end (20c, 20d) of the conversion unit to form an energy transfer path, the secondary winding of the transformer is connected with the input end of the rectifier filter circuit, and the output end of the rectifier filter circuit is connected with the corresponding battery cell node (41).

2. The active equalization circuit of claim 1, wherein, The series structure connection mode can arbitrarily change the relative order of the one-way conduction device (31), the primary winding of the transformer (32) and the switching device (33) as long as the same electrical function is realized.

3. The active equalization circuit of claim 2, wherein, The one-way conduction device (31) has a one-way conduction characteristic and prevents reverse current flow, thereby limiting the current direction from the conversion unit to the equalization module and avoiding energy flow between the equalization modules.

4. The active equalization circuit of claim 2, wherein, The one-way conduction device (31) is a diode.

5. The active equalization circuit of claim 4, wherein, The one-way conduction device (31) is a Schottky diode, a synchronous rectification MOSFET or an active conduction device formed by a MOSFET, and the gate thereof receives a control signal to realize the one-way conduction function.

6. The active equalization circuit of claim 4, wherein, The switching device (33) is a controllable conduction device, and the on-off state thereof is controlled by the control unit (10) to realize energy transfer control on the target battery cell.

7. The active equalization circuit of claim 2, wherein, The switching device (33) is an NMOS transistor.

8. The active equalization circuit of claim 7, wherein, The switching device (33) is a PMOS transistor, a bipolar transistor or an insulated gate bipolar transistor.

9. The active equalization circuit of claim 7, wherein, The transformer (32) is a transformer with electrical isolation capability, and the secondary winding thereof is connected with a rectifier filter circuit to transfer energy to a target battery cell.

10. The active equalization circuit of claim 2, wherein, The rectifier filter circuit (34) comprises a rectifier device and a filter device, the rectifier device converts alternating current output by the secondary winding of the transformer into direct current, and the filter device performs filtering treatment on the direct current and outputs the direct current to a target battery cell connection end.

11. The active equalization circuit of claim 2, wherein, ​ 12. The active equalization circuit of claim 11, wherein, The rectification filter circuit (34) comprises a diode (341) and a capacitor (342), an anode of the diode (341) is connected with one end of a secondary winding of the transformer (32), a cathode of the diode (341) is connected with one end of the capacitor (342) and forms a first connection end connected with the battery cell, the other end of the capacitor (342) is connected with the other end of the secondary winding of the transformer (32) and forms a second connection end connected with the battery cell.

13. The active equalization circuit of claim 1, wherein, The conversion unit (20) comprises an inverter, an input end of the inverter is connected with the battery pack to receive direct current from the battery pack, and an output end of the inverter is connected with one end of the plurality of balancing modules to convert the direct current into alternating current to supply the balancing modules.

14. The active equalization circuit of claim 13, wherein, The conversion unit (20) is a flyback inverter.

15. The active equalization circuit of claim 13, wherein, 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 double-tube forward inverter or an LLC resonant inverter.

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