Active equalization circuit of series battery pack and electronic equipment

Abstract

The invention provides an active equalization circuit of a series battery pack. The active equalization circuit comprises a battery string, a matrix switch circuit, a transformer and a rectification inverter circuit, the matrix switch circuit is electrically connected with each single battery in the battery string and is configured to switch the on-off state of each switch of the matrix switch circuit according to the voltage state of the single battery, so that energy is bidirectionally transmitted between the single battery and the transformer; a primary winding of the transformer is electrically connected with the matrix switch circuit, and a secondary winding of the transformer is electrically connected with the rectification inverter circuit; and the rectification inverter circuit is electrically connected with the two ends of the battery string and is configured to switch the working state of the rectification inverter circuit according to the voltage state of the single battery, so that energy is bidirectionally transmitted between the whole battery string and the transformer. According to the embodiment of the invention, a polarity change-over switch between the primary winding of the transformer and the matrix switch and a high-frequency switch of a traditional converter are abandoned, the number of switching tubes on a current path is reduced, the hardware cost can be effectively reduced, and the energy loss can be reduced.

Description

Technical Field

[0001] The present application belongs to the field of power electronics, and in particular, relates to an active balancing circuit and electronic equipment for a series battery pack. Background Art

[0002] A battery pack is composed of many battery cells connected in series or in parallel and then in series. Due to various factors such as the inconsistency defects in the manufacturing process of the battery cells themselves, the different operating temperatures of batteries in different positions, battery aging, and changes in internal resistance, it is easy for the battery cells to be unbalanced, especially for batteries that have been used for a period of time or retired batteries. If they continue to be used, the "short board effect" will appear, that is, the discharge amount of the battery pack is determined by the battery cell with the smallest power, which not only affects the battery life of the entire battery pack, but also the battery cell with the smallest power may be over-discharged or over-charged, causing irreversible damage to the battery or even safety hazards. For this reason, it is necessary to balance the battery cells.

[0003] According to the different ways of handling mismatch energy, battery balancers can be divided into two categories: passive balancing (energy consumption balancing) and active balancing (non-energy consumption balancing). Among them, active balancing technology can effectively utilize the full power and capacity of the battery pack, with high overall efficiency and strong balancing ability, and is the main development direction of energy balancing technology in the future. Among them, the active balancing circuit based on matrix switches and isolated bidirectional DC / DC converters has the advantages of simple control, good balancing effect, and easy expansion. However, due to the large number of total switch tubes, there are problems of high hardware cost and large energy loss. Summary of the invention

[0004] The embodiments of the present application provide an active balancing circuit for a series battery pack and an electronic device, aiming to solve the problems of high hardware cost and large energy loss of related active balancing circuits.

[0005] In order to solve the above technical problems, the first aspect of the embodiment of the present application provides an active balancing circuit for a series battery pack, including a battery string, a matrix switch circuit, a transformer and a rectifier inverter circuit;

[0006] The matrix switch circuit is electrically connected to each single cell in the battery string and is configured to switch the switch state of each switch according to the voltage state of the single cell, so that energy is bidirectionally transmitted between the single cell and the transformer;

[0007] The primary winding of the transformer is electrically connected to the matrix switch circuit, and the secondary winding of the transformer is electrically connected to the rectifier inverter circuit;

[0008] The rectifier inverter circuit is electrically connected to both ends of the battery string and is configured to switch its own working state according to the voltage state of the single battery, so that energy can be bidirectionally transmitted between the entire battery string and the transformer.

[0009] In one embodiment, the matrix switch circuit includes a matrix switch and a matrix switch bus; the battery string is electrically connected to the matrix switch bus through the matrix switch, and the positive and negative ends of the matrix switch bus are electrically connected to the two ends of the primary winding of the transformer respectively.

[0010] In one embodiment, both ends of each single cell in the battery string are electrically connected to the matrix switch bus through a bidirectional switch in the matrix switch; wherein the number of bidirectional switches connected to the matrix switch bus is twice the number of single cells in the battery string.

[0011] In one embodiment, each series node between the single cells in the battery string is electrically connected to the matrix switch bus through a bidirectional switch in the matrix switch; wherein the number of the bidirectional switches connected to the matrix switch bus is the number of single cells in the battery string plus one.

[0012] In one embodiment, the matrix switch bus voltage has a fixed polarity, and the rectifier inverter circuit includes a single secondary switch tube;

[0013] The matrix switch circuit is further configured to, when the secondary switch tube is turned off, turn on the bidirectional switches at both ends of the single battery to be balanced within a preset time, so that the single battery to be balanced charges and discharges the primary excitation inductance of the transformer;

[0014] The rectifier inverter circuit is also configured to turn on the secondary switch tube within a preset time when the bidirectional switches at both ends of the single battery to be balanced are turned off, so that the entire battery string charges and discharges the secondary excitation inductance of the transformer.

[0015] In one embodiment, the polarity of the matrix switch bus voltage is related to the position of the single battery to be balanced, and is expressed as positive polarity or negative polarity, and the rectifier inverter circuit adopts a bipolar full-bridge circuit or a bipolar half-bridge circuit; wherein the rectifier inverter circuit includes a first bidirectional switch group and a second bidirectional switch group;

[0016] The matrix switch circuit is further configured to, when the first bidirectional switch group and the second bidirectional switch group are turned off at the same time, turn on the bidirectional switches at both ends of the single battery to be balanced within a preset time, so that the single battery to be balanced charges and discharges the primary excitation inductance of the transformer;

[0017] The rectifier inverter circuit is also configured to, when the bidirectional switches at both ends of the single battery to be balanced are turned off, if the matrix switch bus exhibits positive polarity, turn on the first bidirectional switch group within a preset time, and if the matrix switch bus exhibits negative polarity, turn on the second bidirectional switch group within a preset time, so that the entire group of battery strings charges and discharges the secondary excitation inductance of the transformer.

[0018] In one embodiment, the bidirectional switch is composed of a common-source MOS pair or a common-drain MOS pair.

[0019] In one embodiment, the output port of the rectifier and inverter is connected to two ends of an external power source or an external battery pack to achieve energy balance with an external circuit.

[0020] In one embodiment, a filter circuit is further included, wherein a first end of the filter circuit is electrically connected to the battery string, and a second end of the filter circuit is electrically connected to the matrix switch circuit to shorten the ripple current loop.

[0021] A second aspect of the present application provides an electronic device, the electronic device comprising an active balancing circuit for a series battery pack as described in any one of the above.

[0022] The active balancing circuit of the series battery pack provided in the embodiment of the present application selects the single battery that needs to be energy balanced by changing the conduction and closing of the matrix switch, and then adjusts the working state of the rectifier inverter circuit through the energy flow direction, and finally realizes the bidirectional transmission of energy between the single battery in the series battery pack and the entire battery string to achieve the effect of energy balancing. The embodiment of the present application abandons the polarity switching switch between the primary winding of the transformer and the matrix switch and the high-frequency switch of the traditional converter, and directly connects the matrix switch to both ends of the transformer winding, reducing the number of switch tubes on the current path, which can effectively reduce hardware costs and reduce energy loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the related technologies or the embodiments of the present application, the drawings required for use in the description of the related technologies or the embodiments of the present application will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, not all embodiments. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 A schematic diagram of the structure of an active balancing circuit for a series battery pack provided in the first aspect of an embodiment of the present application;

[0025] Figure 2 A structural schematic diagram of a detailed active balancing circuit for a series battery pack provided in the first aspect of the embodiment of the present application;

[0026] Figure 3 A schematic diagram of a structure of an active balancing circuit for a series battery pack using a double matrix switch provided in the first aspect of an embodiment of the present application;

[0027] Figure 4 A schematic diagram of a structure of an active equalization circuit for a series battery pack using a single matrix switch provided in accordance with the first aspect of an embodiment of the present application;

[0028] Figure 5 A circuit structure diagram of a series battery pack active balancing circuit using double matrix switches provided in a refinement of the first aspect of the embodiment of the present application;

[0029] Figure 6 A structural schematic diagram of a detailed active balancing circuit for a series battery pack using a single matrix switch provided in the first aspect of the embodiment of the present application;

[0030] Figure 7 A schematic structural diagram of another refined active balancing circuit for a series battery pack using a single matrix switch provided in the first aspect of the embodiment of the present application;

[0031] Figure 8 A circuit structure diagram of another refined active balancing circuit for a series battery pack using a single matrix switch provided in the first aspect of the embodiment of the present application;

[0032] Fig. 9 A schematic diagram of the structure of a bidirectional switch provided in the first aspect of the embodiment of the present application;

[0033] Fig.10 A circuit structure diagram of another refinement of an active equalization circuit for a series battery pack using a single matrix switch provided in the first aspect of the embodiment of the present application;

[0034] Fig.11 A schematic structural diagram of another detailed active balancing circuit for a series battery pack provided in the first aspect of the embodiment of the present application;

[0035] Fig.12 A schematic diagram of the structure of an electronic device provided in accordance with the second aspect of an embodiment of the present application. DETAILED DESCRIPTION

[0036] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0037] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0038] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0039] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, "plurality" means one or more, unless otherwise clearly and specifically defined.

[0040] Figure 1 A schematic diagram of the structure of an active equalization circuit for a series battery pack provided in the first aspect of an embodiment of the present application is shown. For ease of explanation, only the parts related to the present embodiment are shown, which are described in detail as follows:

[0041] In this embodiment, the active balancing circuit of the series battery group includes a battery string 101, a matrix switch circuit 102, a transformer 103 and a rectifier inverter circuit 104;

[0042] The matrix switch circuit 102 is electrically connected to each single cell in the battery string 101 and is configured to switch the switch state of each switch according to the voltage state of the single cell, so that energy can be bidirectionally transmitted between the single cell and the transformer 103;

[0043] The primary winding of the transformer 103 is electrically connected to the matrix switch circuit 102 , and the secondary winding of the transformer 103 is electrically connected to the rectifier inverter circuit 104 ;

[0044] The rectifier inverter circuit 104 is electrically connected to both ends of the battery string and is configured to switch its own working state according to the voltage state of the single battery, so that energy can be bidirectionally transmitted between the entire battery string 101 and the transformer 103 .

[0045] Specifically, the battery string is composed of a plurality of single cells connected in series, and connected to the two ends of the primary winding of the transformer through a matrix switch. When the energy of a single cell in the battery string is greater than that of other cells, it is necessary to balance the energy of this single cell. At this time, the matrix switch will switch the switch state corresponding to the single cell that needs to be balanced, so that the single cell is connected to the primary winding of the transformer, and then the transformer transmits the energy of the primary winding to the secondary winding. Since the secondary winding is connected to the AC side of the rectifier inverter circuit, the rectifier inverter circuit realizes the rectification function at this time, and rectifies the energy on the AC side and transmits it back to the two ends of the entire battery string from the DC side of the rectifier inverter circuit, finally realizing the energy balance from the single cell to the entire battery string. It can be understood that, in the same way, when the energy of a single cell is smaller than that of other cells, the energy of the entire battery string is reversely transmitted to the DC side of the rectifier inverter circuit. At this time, the rectifier inverter circuit realizes the inverter function to convert DC to AC, and then finally transmits the energy to the single cell to be balanced through the selection of the transformer and the matrix switch.

[0046] The active balancing circuit of the series battery pack provided in the embodiment of the present application selects the single battery that needs to be energy balanced by changing the conduction and closing of the matrix switch, and then adjusts the working state of the rectifier inverter circuit through the energy flow direction, and finally realizes the bidirectional transmission of energy between the single battery in the series battery pack and the entire battery string to achieve the effect of energy balancing. The embodiment of the present application abandons the polarity switching switch between the primary winding of the transformer and the matrix switch and the high-frequency switch of the traditional converter, and directly connects the matrix switch to both ends of the transformer winding, reducing the number of switch tubes on the current path, which can effectively reduce hardware costs and reduce energy loss.

[0047] exist Figure 1 Based on the active balancing circuit of the series battery pack provided, this embodiment also provides a detailed structural schematic diagram of the active balancing circuit of the series battery pack, for details, please refer to Figure 2 In some embodiments, the matrix switch circuit includes a matrix switch and a matrix switch bus; the battery string is electrically connected to the matrix switch bus through the matrix switch, and the positive and negative ends of the matrix switch bus are electrically connected to the two ends of the primary winding of the transformer respectively.

[0048] Specifically, the series battery string is connected to the matrix switch bus through a matrix switch, the positive and negative ends of the matrix switch bus are respectively connected to the two ends of the primary winding of the transformer, the secondary side of the transformer is connected to the AC side of the rectifier inverter circuit with bidirectional energy flow, and finally the DC end of the rectifier inverter circuit is connected back to the two ends of the battery pack. The matrix switch is directly connected to the two ends of the transformer winding through the matrix switch bus, without the need to use a polarity switching circuit and a high-frequency isolation converter switch, so that the number of switch tubes on the current path is reduced, reducing the hardware cost. Furthermore, the current on the low-voltage side of the transformer is large, and the current path is shortened by canceling the polarity switching switch and the high-frequency switch of the traditional converter, so that the energy loss is reduced. It can be understood that the matrix switch can adopt a double switch form or a single switch form. When a double switch is adopted, the matrix switch bus voltage is unipolar and is not affected by the number and position of the connected single battery cells. When a single switch is adopted, the bus voltage polarity is related to the position of the connected battery cell. The specific situation will be described in detail in the subsequent steps.

[0049] like Figure 3 The figure shows a schematic diagram of the structure of a series battery pack active balancing circuit using a double matrix switch provided by the first aspect of the embodiment of the present application. In some embodiments, both ends of each single cell in the battery string are electrically connected to the matrix switch bus through a bidirectional switch in the matrix switch; wherein the number of bidirectional switches connected to the matrix switch bus is twice the number of single cells in the battery string.

[0050] Specifically, when double switches are used, both ends of each single battery are connected to the matrix switch bus through a bidirectional switch. The number of bidirectional switches on the matrix switch bus in a single battery string is twice the number of battery cells. The bus voltage is unipolar, showing positive or negative polarity, and is not affected by the position of the connected battery cell. Therefore, there is no need to use a polarity switching circuit, which shortens the current path and reduces the path loss of energy.

[0051] like Figure 4 Shown is a structural schematic diagram of an active balancing circuit for a series battery group using a single matrix switch provided in the first aspect of an embodiment of the present application. In one embodiment, the series nodes between each single cell in the battery string are electrically connected to the matrix switch bus through a bidirectional switch in the matrix switch; wherein the number of bidirectional switches connected to the matrix switch bus is the number of single cells in the battery string plus one.

[0052] Specifically, when a single switch is used, each series node of a single battery is connected to the matrix switch bus in sequence through a bidirectional switch. The number of bidirectional switches on the matrix switch bus in a single battery string is the number of battery cells plus one, and the bus voltage polarity is related to the position of the connected battery cell. Figure 4 As shown, when the matrix switch SL5 and matrix switch S L4 When the matrix switch S is connected to balance the battery cells, the bus voltage of the matrix switch is positive at the top and negative at the bottom. L4 and matrix switch S L3 When connected to balance the battery cells, the matrix switch bus voltage appears negative at the top and positive at the bottom.

[0053] exist Figure 3 Based on the battery pack active balancing circuit provided, this embodiment also provides a detailed circuit structure diagram of the series battery pack active balancing circuit using double matrix switches. For details, please refer to Figure 5 , in some embodiments, the matrix switch bus voltage is of fixed polarity, and the rectifier inverter circuit includes a single secondary switch tube;

[0054] The matrix switch circuit is also configured to turn on the bidirectional switches at both ends of the single battery to be balanced within a preset time when the secondary switch tube is turned off, so that the single battery to be balanced charges and discharges the primary excitation inductance of the transformer;

[0055] The rectifier inverter circuit is also configured to turn on the secondary switch tube within a preset time when the bidirectional switches at both ends of the single battery to be balanced are turned off, so that the entire battery string charges and discharges the secondary excitation inductance of the transformer.

[0056] Furthermore, when the matrix switch part adopts a double switch form, since the bus voltage polarity is fixed, a single switch tube can be directly used on the secondary side. When the matrix switch is turned on, the selected single cell charges the excitation inductance of the primary side of the transformer. After charging is completed, the matrix switch is turned off and the secondary side switch tube is turned on. Energy is released from the secondary side of the transformer to the entire battery string, realizing the transfer of energy from the single cell to the entire group, and vice versa.

[0057] exist Figure 4 Based on the battery pack active balancing circuit provided, this embodiment also provides a detailed circuit structure diagram of the series battery pack active balancing circuit using a single matrix switch. For details, please refer to Figure 6 and Figure 7 In some embodiments, the polarity of the matrix switch bus voltage is related to the position of the single battery to be balanced, and is expressed as positive polarity or negative polarity. The rectifier inverter circuit adopts a bipolar full-bridge circuit or a bipolar half-bridge circuit; wherein the rectifier inverter circuit includes a first bidirectional switch group and a second bidirectional switch group;

[0058] The matrix switch circuit is further configured to turn on the bidirectional switches at both ends of the single battery to be balanced within a preset time when the first bidirectional switch group and the second bidirectional switch group are turned off at the same time, so that the single battery to be balanced charges and discharges the primary excitation inductance of the transformer;

[0059] The rectifier inverter circuit is also configured to, when the bidirectional switches at both ends of the single battery to be balanced are turned off, if the matrix switch bus exhibits positive polarity, turn on the first bidirectional switch group within a preset time, and if the matrix switch bus exhibits negative polarity, turn on the second bidirectional switch group within a preset time, so that the entire battery string charges and discharges the secondary excitation inductance of the transformer.

[0060] Furthermore, when the matrix switch part adopts a single switch form, since the bus voltage polarity can be positive or negative, a bipolar full-bridge or bipolar half-bridge circuit is adopted on the secondary side. L5 and S L4 Connect to balance the battery cells, turn on the matrix switch to charge the transformer excitation inductance, turn on the corresponding bidirectional switch on the secondary side after closing, and release the energy to the entire battery pack through the secondary side of the transformer, realizing the transfer of energy from the single cell to the entire group; when the bus voltage is negative at the top and positive at the bottom, for example, S L4 and S L3 Connect to balance the battery cells, turn on the matrix switch to reversely charge the transformer excitation inductance, and then turn on the other pair of bidirectional switches corresponding to the secondary side. Energy is released to the entire battery pack through the secondary side of the transformer, realizing the transfer of energy from the single cell to the entire group. The same applies to the transfer of energy from the entire group to the single cell.

[0061] In some optional embodiments, the rectifier inverter circuit adopts a full-bridge circuit or a half-bridge circuit.

[0062] It is understandable that, since the voltage difference of the single cells in the battery string is very small, and the current on the low-voltage side of the transformer is large and there are many devices, the voltage coupled to both ends of the high-voltage side of the transformer is not enough to turn on the body diode of the high-voltage side MOS tube. Therefore, the high-voltage side can directly adopt the traditional bridge circuit (including full-bridge and half-bridge), as shown in the following figure. Figure 8 shown.

[0063] like Fig. 9 The figure is a schematic diagram of the structure of a bidirectional switch provided in the first aspect of the embodiment of the present application. In some embodiments, the bidirectional switch is composed of a common-source MOS pair of transistors or a common-drain MOS pair of transistors.

[0064] Furthermore, in order to reduce switching losses, when the matrix switch side charges and discharges the transformer excitation inductance, it is not necessary for all switch tubes to operate simultaneously. In the same pair of bidirectional switches, one can be constantly turned on while the other operates at high frequency. In addition, since the body diode of a MOS tube in the high-frequency bidirectional switch is in the same direction as the operating voltage drop, it can also be in a constantly turned on state during operation to further reduce switching losses. Figure 7 For example, S L4 and S L5 When the battery is discharged, S L4 Constant conduction, SL5 When working at high frequency, due to S L5b The body diode and battery voltage drop are in the same direction, so S L5b Can be constantly turned on, only by controlling S L5a Control is implemented to reduce switching losses; when charging the battery cells, S L5a Can be constantly turned on, only by controlling S L5b Similarly, S L5 Constant conduction, S L4 The same is true for high frequency operation and the same applies to the charge and discharge control of other battery cells.

[0065] exist Figure 7 Based on the provided active balancing circuit for battery packs, this embodiment also provides another refined circuit structure diagram of the active balancing circuit for series battery packs using a single matrix switch, as shown in FIG. Fig.10 As shown, in one embodiment, the output port of the rectifier inverter circuit is connected to both ends of an external power source or an external battery pack to achieve energy balance with the external circuit.

[0066] like Fig.11 What is shown is a structural schematic diagram of another refined active balancing circuit for a series battery pack provided in this embodiment. In some embodiments, it also includes a filter circuit, wherein a first end of the filter circuit is electrically connected to the battery string, and a second end of the filter circuit is electrically connected to the matrix switch circuit to shorten the ripple current loop.

[0067] In summary, the active balancing circuit of the series battery pack provided in the embodiment of the present application selects the single battery that needs to be energy balanced by changing the on and off of the matrix switch, and then adjusts the working state of the rectifier inverter circuit by the energy flow direction, and finally realizes the bidirectional transmission of energy between the single battery in the series battery pack and the entire battery string to achieve the effect of energy balancing. The embodiment of the present application abandons the polarity switching switch between the primary winding of the transformer and the matrix switch and the high-frequency switch of the traditional converter, and directly connects the matrix switch to both ends of the transformer winding, reducing the number of switch tubes on the current path, which can effectively reduce hardware costs and reduce energy losses.

[0068] Fig.12 A schematic diagram of an electronic device provided in the second aspect of an embodiment of the present application is shown. As shown in the figure, the second aspect of an embodiment of the present application provides an electronic device A, and the electronic device includes a battery pack active balancing circuit 10 as described in any one of the above items.

[0069] The technicians in the relevant field can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional units and modules is used as an example for illustration. In practical applications, the above-mentioned function allocation can be completed by different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiment can be integrated in a processing unit, or each unit can exist physically separately, or two or more units can be integrated in one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units. In addition, the specific names of the functional units and modules are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of this application. The specific working process of the units and modules in the above-mentioned system can refer to the corresponding process in the aforementioned method embodiment, which will not be repeated here.

[0070] References to "one embodiment" or "some embodiments" etc. described in the specification of this application mean that one or more embodiments of the present application include specific features, structures or characteristics described in conjunction with the embodiment. Therefore, the statements "in one embodiment", "in some embodiments", etc. that appear in different places in this specification do not necessarily refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "including", "comprising", "having" and their variations all mean "including but not limited to", unless otherwise specifically emphasized in other ways.

[0071] The embodiments described above are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. An active balancing circuit for a series battery pack, characterized in that: It includes a battery string, a matrix switch circuit, a transformer and a rectifier inverter circuit; The matrix switch circuit is electrically connected to each single cell in the battery string and is configured to switch the switch state of each switch according to the voltage state of the single cell, so that energy is bidirectionally transmitted between the single cell and the transformer; The primary winding of the transformer is electrically connected to the matrix switch circuit, and the secondary winding of the transformer is electrically connected to the rectifier inverter circuit; The rectifier inverter circuit is electrically connected to both ends of the battery string and is configured to switch its own working state according to the voltage state of the single battery, so that energy can be bidirectionally transmitted between the entire battery string and the transformer.

2. The active balancing circuit for series connected battery packs as claimed in claim 1, characterized in that: The matrix switch circuit includes a matrix switch and a matrix switch bus; the battery string is electrically connected to the matrix switch bus through the matrix switch, and the positive and negative ends of the matrix switch bus are electrically connected to the two ends of the primary winding of the transformer respectively.

3. The active balancing circuit for a series battery pack as claimed in claim 2, characterized in that: Both ends of each single battery in the battery string are electrically connected to the matrix switch bus through a bidirectional switch in the matrix switch; wherein the number of the bidirectional switches connected to the matrix switch bus is twice the number of single batteries in the battery string.

4. The active balancing circuit for series connected battery packs as claimed in claim 2, characterized in that: The series node between each single battery in the battery string is electrically connected to the matrix switch bus through a bidirectional switch in the matrix switch; wherein the number of the bidirectional switches connected to the matrix switch bus is the number of single batteries in the battery string plus one.

5. The active balancing circuit for series connected battery packs as claimed in claim 3, characterized in that: The matrix switch bus voltage is of fixed polarity, and the rectifier inverter circuit includes a single secondary switch tube; The matrix switch circuit is further configured to, when the secondary switch tube is turned off, turn on the bidirectional switches at both ends of the single battery to be balanced within a preset time, so that the single battery to be balanced charges and discharges the primary excitation inductance of the transformer; The rectifier inverter circuit is also configured to turn on the secondary switch tube within a preset time when the bidirectional switches at both ends of the single battery to be balanced are turned off, so that the entire battery string charges and discharges the secondary excitation inductance of the transformer.

6. The active balancing circuit for series connected battery packs as claimed in claim 4, characterized in that: The polarity of the matrix switch bus voltage is related to the position of the single battery to be balanced, and is expressed as positive polarity or negative polarity. The rectifier inverter circuit adopts a bipolar full-bridge circuit or a bipolar half-bridge circuit; wherein the rectifier inverter circuit includes a first bidirectional switch group and a second bidirectional switch group; The matrix switch circuit is further configured to, when the first bidirectional switch group and the second bidirectional switch group are turned off at the same time, turn on the bidirectional switches at both ends of the single battery to be balanced within a preset time, so that the single battery to be balanced charges and discharges the primary excitation inductance of the transformer; The rectifier inverter circuit is also configured to, when the bidirectional switches at both ends of the single battery to be balanced are turned off, if the matrix switch bus exhibits positive polarity, turn on the first bidirectional switch group within a preset time, and if the matrix switch bus exhibits negative polarity, turn on the second bidirectional switch group within a preset time, so that the entire group of battery strings charges and discharges the secondary excitation inductance of the transformer.

7. The active balancing circuit for a series battery pack according to any one of claims 3 to 6, characterized in that: The bidirectional switch is composed of a common-source MOS pair of transistors or a common-drain MOS pair of transistors.

8. The active balancing circuit for a series battery pack according to any one of claims 3 to 6, characterized in that: The output port of the rectifier inverter circuit is connected to an external power source or two ends of an external battery pack to achieve energy balance with the external circuit.

9. The active balancing circuit for series connected battery packs as claimed in claim 1, characterized in that: It also includes a filter circuit, a first end of the filter circuit is electrically connected to the battery string, and a second end of the filter circuit is electrically connected to the matrix switch circuit to shorten the ripple current loop.

10. An electronic device, characterized in that: The electronic device comprises the active balancing circuit of the series-connected battery pack as claimed in any one of claims 1 to 9.

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