Converter for balancing voltage of battery pack

Abstract

The utility model discloses a converter for balancing voltage of a battery pack. Comprising an electric energy transfer unit, a first switch unit which is connected between the electric energy transfer unit and a first battery pack and works in a charging mode or an inversion mode, and a second switch unit which is connected between the electric energy transfer unit and a second battery pack and works in the charging mode or the inversion mode. Compared with the prior art, electric energy balance between the battery packs can be realized, electric energy in the first battery pack and the second battery pack can be used to the greatest extent, waste of the electric energy is reduced, over discharge of the battery packs is avoided, and the service life of the battery packs is prolonged.

Description

Technical Field

[0001] The utility model relates to a new energy vehicle, in particular to a converter for balancing the voltage of a battery pack. Background Art

[0002] To power new energy vehicles, they typically utilize high-voltage battery packs connected in series. However, in actual use, different batteries may experience varying levels of charge, leading to voltage imbalances between them. This voltage imbalance can affect the overall capacity of the series battery pack, shortening its lifespan and potentially causing safety incidents.

[0003] Therefore, how to design a battery pack voltage balancing converter that can achieve voltage balance between batteries is a technical problem that needs to be solved urgently in the industry. Utility Model Content

[0004] In view of the fact that the remaining power of different batteries is not equal in the prior art, the present invention proposes a converter for balancing the voltage of a battery pack.

[0005] The technical solution of this utility model is to propose a converter for balancing the voltage of a battery pack.

[0006] It includes an electric energy transfer unit, a first switch unit connected between the electric energy transfer unit and a first battery pack and working in a charging mode or an inversion mode, and a second switch unit connected between the electric energy transfer unit and a second battery pack and working in a charging mode or an inversion mode.

[0007] Furthermore, the first switch unit includes: a transformer T1, a first primary side conversion circuit connected between the transformer T1 and the power transfer unit, and a first secondary side conversion circuit connected between the transformer T1 and the first battery pack;

[0008] Wherein, the first primary-side conversion circuit and the first secondary-side conversion circuit both adopt full-bridge circuits.

[0009] Furthermore, the first primary-side conversion circuit and the first secondary-side conversion circuit include:

[0010] The first primary side conversion circuit comprises a first switch tube Q1 and a second switch tube Q2 constituting a first bridge arm, and a third switch tube Q3 and a fourth switch tube Q4 constituting a second bridge arm, wherein the first switch tube Q1 and the third switch tube Q3 are upper arm switches, and the second switch tube Q2 and the fourth switch tube Q4 are lower arm switches;

[0011] The midpoint of the first bridge arm is connected in series with a capacitor C1 and an inductor L1, and then connected to the primary winding of the transformer T1;

[0012] The first secondary side conversion circuit includes a fifth switch tube Q5 and a sixth switch tube Q6 forming a third bridge arm, and a seventh switch tube Q7 and an eighth switch tube Q8 forming a fourth bridge arm, wherein the fifth switch tube Q5 and the seventh switch tube Q7 are upper arm switches, and the sixth switch tube Q6 and the eighth switch tube Q8 are lower arm switches;

[0013] The midpoint of the third bridge arm is connected in series with a capacitor C2 and then connected to the secondary winding of the transformer T1.

[0014] Furthermore, the second switch unit includes: a transformer T2, a second primary side conversion circuit connected between the transformer T2 and the power transfer unit, and a second secondary side conversion circuit connected between the transformer T2 and the second battery pack;

[0015] Wherein, the second primary-side conversion circuit and the second secondary-side conversion circuit both adopt full-bridge circuits.

[0016] Furthermore, the second primary side conversion circuit and the second secondary side conversion circuit include:

[0017] The second primary side conversion circuit includes a ninth switching tube Q9 and a tenth switching tube Q10 constituting a fifth bridge arm, and an eleventh switching tube Q11 and a twelfth switching tube Q12 constituting a sixth bridge arm, wherein the ninth switching tube Q9 and the eleventh switching tube Q11 are upper arm switches, and the tenth switching tube Q10 and the twelfth switching tube Q12 are lower arm switches;

[0018] The midpoint of the fifth bridge arm is connected in series with a capacitor C3 and an inductor L2, and then connected to the primary winding of the transformer T2;

[0019] The second secondary side conversion circuit includes a thirteenth switching tube Q13 and a fourteenth switching tube Q14 constituting a seventh bridge arm, and a fifteenth switching tube Q15 and a sixteenth switching tube Q16 constituting an eighth bridge arm, wherein the thirteenth switching tube Q13 and the fifteenth switching tube Q15 are upper arm switches, and the fourteenth switching tube Q14 and the sixteenth switching tube Q16 are lower arm switches;

[0020] The midpoint of the seventh bridge arm is connected in series with a capacitor C4 and then connected to the secondary winding of the transformer T2.

[0021] Furthermore, in the first primary-side conversion circuit, the control timings of the first switch tube Q1 and the fourth switch tube Q4 are the same, the control timings of the second switch tube Q2 and the third switch tube Q3 are the same, and the control timings of the first switch tube Q1 and the second switch tube Q2 are complementary;

[0022] In the first secondary-side conversion circuit, the control timings of the fifth switch tube Q5 and the eighth switch tube Q8 are the same, the control timings of the sixth switch tube Q6 and the seventh switch tube Q7 are the same, and the control timings of the fifth switch tube Q5 and the sixth switch tube Q6 are complementary;

[0023] When the voltage of the first battery pack is higher than the voltage of the second battery pack, the first switch unit operates in the inverter mode: the switch tube of the first secondary conversion circuit leads the switch tube of the first primary conversion circuit by a phase shift angle.

[0024] Furthermore, in the second primary-side conversion circuit, the control timings of the ninth switch tube Q9 and the twelfth switch tube Q12 are the same, the control timings of the tenth switch tube Q10 and the eleventh switch tube Q11 are the same, and the control timings of the ninth switch tube Q9 and the tenth switch tube Q10 are complementary;

[0025] In the second secondary-side conversion circuit, the control timings of the thirteenth switch tube Q13 and the sixteenth switch tube Q16 are the same, the control timings of the fourteenth switch tube Q14 and the fifteenth switch tube Q15 are the same, and the control timings of the thirteenth switch tube Q13 and the fourteenth switch tube Q14 are complementary;

[0026] When the voltage of the first battery pack is higher than the voltage of the second battery pack, the second switch unit operates in a charging mode: the switch tube of the second secondary conversion circuit lags behind the switch tube of the second primary conversion circuit by a phase shift angle.

[0027] Furthermore, when the voltage of the first battery pack is lower than the voltage of the second battery pack, the first switch operates in a charging mode: the switch tube of the first secondary conversion circuit lags behind the switch tube of the first primary conversion circuit by a phase shift angle.

[0028] Furthermore, when the voltage of the first battery pack is lower than the voltage of the second battery pack, the second switch unit operates in the inverter mode: the switch tube of the second secondary conversion circuit leads the switch tube of the second primary conversion circuit by a phase shift angle.

[0029] Compared with the prior art, the present invention has at least the following beneficial effects:

[0030] The utility model can achieve electric energy balance between the battery packs, maximize the use of electric energy in the first battery pack and the second battery pack, reduce electric energy waste and avoid over-discharge of the battery packs, thereby extending the service life of the battery packs. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments or descriptions of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0032] Figure 1 This is a structural block diagram of a converter for balancing the battery pack voltage according to the present invention;

[0033] Figure 2 A specific circuit topology diagram of a converter for battery pack voltage balancing according to the present invention;

[0034] Figure 3 This is a control flow chart of the entire utility model;

[0035] Figure 4 This is a control timing diagram when the voltage of the second battery pack is higher than the voltage of the first battery pack. DETAILED DESCRIPTION

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

[0037] Thus, a feature indicated in this specification is intended to illustrate one of the features of one embodiment of the present invention, rather than implying that every embodiment of the present invention must have the described feature. In addition, it should be noted that this specification describes many features. Although certain features can be combined together to illustrate possible system designs, these features can also be used in other, not explicitly described, combinations. Thus, unless otherwise stated, the described combinations are not intended to be limiting.

[0038] The principle and structure of the present invention are described in detail below with reference to the accompanying drawings and embodiments.

[0039] To power new energy vehicles, they typically utilize high-voltage battery packs connected in series. However, in actual use, different batteries may experience varying levels of charge, leading to voltage imbalances between them. This voltage imbalance can affect the overall capacity of the series battery pack, shortening its lifespan and potentially causing safety incidents.

[0040] To address the above-mentioned problems, the present invention proposes a battery pack voltage balancing converter, which includes a power transfer unit, a first switch unit connected between the power transfer unit and a first battery pack and operating in a charging mode or an inverter mode, and a second switch unit connected between the power transfer unit and a second battery pack and operating in a charging mode or an inverter mode.

[0041] The first switch unit and the second switch unit can both operate in a charging mode or an inverter mode, and when the first switch unit and the second switch unit operate in the charging mode, the power transfer unit outputs power to the first battery pack and the second battery pack;

[0042] When the first switch unit and the second switch unit operate in the inverter mode, the first battery pack and the second battery pack output electric energy to the electric energy transfer unit.

[0043] like Figure 1 As shown, HV1 is a first battery pack, HV2 is a second battery pack, and the two battery packs are connected in series to form a series battery pack. In this embodiment, the first switch unit and the second switch unit can operate independently;

[0044] When the first switch unit operates in inverter mode and the second switch unit operates in charging mode, the first battery pack outputs power to the power transfer unit via the first switch unit, and the power transfer unit outputs power to the second battery pack via the second switch unit. This allows the first battery pack to supply power to the second battery pack. This can be used when the voltage (or charge) of the first battery pack is higher than the voltage (or charge) of the second battery pack. By supplying power to the second battery pack via the first battery pack, voltage balance between the first and second battery packs can be ensured.

[0045] When the first switch unit is operating in charging mode and the second switch unit is operating in inverter mode, the second battery pack will output power to the power transfer unit through the second switch unit, and the power transfer unit will output power to the first battery pack through the first switch unit. In this case, the second battery pack can supply power to the first battery pack. This situation can be used when the voltage (or power) of the second battery pack is higher than that of the first battery pack. After the second battery pack supplies power to the first battery pack, it can ensure voltage balance between the first and second battery packs.

[0046] Therefore, through the above design, the present invention can achieve energy balance between the battery packs, maximize the use of the energy in the first battery pack and the second battery pack, reduce energy waste and avoid over-discharge of the battery packs, thereby extending the service life of the battery packs.

[0047] Furthermore, the first switch unit in the present invention includes: a transformer T1, a first primary side conversion circuit connected between the transformer T1 and the power transfer unit, and a first secondary side conversion circuit connected between the transformer T1 and the first battery pack;

[0048] Wherein, the first primary-side conversion circuit and the first secondary-side conversion circuit both adopt full-bridge circuits.

[0049] See Figure 2 The first primary side conversion circuit includes a first switching tube Q1 and a second switching tube Q2 constituting a first bridge arm, and a third switching tube Q3 and a fourth switching tube Q4 constituting a second bridge arm, wherein the first switching tube Q1 and the third switching tube Q3 are upper arm switches, and the second switching tube Q2 and the fourth switching tube Q4 are lower arm switches;

[0050] The midpoint of the first bridge arm is connected in series with capacitor C1 and inductor L1, and then connected to the primary winding of transformer T1;

[0051] The first secondary-side conversion circuit includes a fifth switching tube Q5 and a sixth switching tube Q6 forming a third bridge arm, and a seventh switching tube Q7 and an eighth switching tube Q8 forming a fourth bridge arm, wherein the fifth switching tube Q5 and the seventh switching tube Q7 are upper-arm switches, and the sixth switching tube Q6 and the eighth switching tube Q8 are lower-arm switches.

[0052] The midpoint of the third bridge arm is connected in series with a capacitor C2 and then connected to the secondary winding of the transformer T1.

[0053] Here, the first primary conversion circuit and the first secondary conversion circuit can both rectify or invert the current in the circuit by controlling the on / off state of their switching tubes, thereby enabling the first battery pack to normally output electric energy to the electric energy transfer unit, and enabling the electric energy transfer unit to normally output electric energy to the first battery pack.

[0054] Furthermore, the second switch unit in the present invention includes: a transformer T2, a second primary side conversion circuit connected between the transformer T2 and the power transfer unit, and a second secondary side conversion circuit connected between the transformer T2 and the second battery pack;

[0055] Wherein, the second primary side conversion circuit and the second secondary side conversion circuit both adopt full-bridge circuits.

[0056] See Figure 2 The second primary-side conversion circuit includes a ninth switching tube Q9 and a tenth switching tube Q10 constituting a fifth bridge arm, and an eleventh switching tube Q11 and a twelfth switching tube Q12 constituting a sixth bridge arm, wherein the ninth switching tube Q9 and the eleventh switching tube Q11 are upper-arm switches, and the tenth switching tube Q10 and the twelfth switching tube Q12 are lower-arm switches.

[0057] The midpoint of the fifth bridge arm is connected in series with capacitor C3 and inductor L2, and then connected to the primary winding of transformer T2;

[0058] The second secondary-side conversion circuit includes a thirteenth switching tube Q13 and a fourteenth switching tube Q14 forming a seventh bridge arm, and a fifteenth switching tube Q15 and a sixteenth switching tube Q16 forming an eighth bridge arm, wherein the thirteenth switching tube Q13 and the fifteenth switching tube Q15 are upper-arm switches, and the fourteenth switching tube Q14 and the sixteenth switching tube Q16 are lower-arm switches.

[0059] The midpoint of the seventh bridge arm is connected in series with a capacitor C4 and then connected to the secondary winding of the transformer T2.

[0060] Here, the second primary conversion circuit and the second secondary conversion circuit can rectify or invert the current in the circuit by controlling the on-off state of their switching tubes, thereby enabling the second battery pack to normally output electric energy to the electric energy transfer unit, and enabling the electric energy transfer unit to normally output electric energy to the second battery pack.

[0061] See Figure 2 The power transfer unit uses capacitor C0, which can serve as both an energy storage unit, storing the power output by the first or second battery pack, and a power supply unit, outputting power to the first or second battery pack. It can also serve as a transfer unit, enabling power transfer between the first and second battery packs.

[0062] See Figure 2 The present invention further includes a first voltage transformation unit connected to the transformer T1, the first voltage transformation unit comprising a seventeenth switching tube Q17, an eighteenth switching tube Q18, a nineteenth switching tube Q19, a twentieth switching tube Q20, an inductor L3, and a capacitor C5;

[0063] Here, the seventeenth switch tube Q17 and the eighteenth switch tube Q18 form a synchronous rectification circuit, the nineteenth switch tube Q19 and the twentieth switch tube Q20 form a power switching circuit, and the inductor L3 and the capacitor C5 form a filter circuit. Through the configuration of the first voltage transformation unit, a regulated output voltage can be output for use by the load.

[0064] Furthermore, the present invention further includes a second voltage transformation unit connected to the transformer T2, the second voltage transformation unit comprising a twenty-second switch tube Q22, a twenty-third switch tube Q23, a twenty-fourth switch tube Q24, a twenty-fifth switch tube Q25, an inductor L4, and a capacitor C6;

[0065] Here, the twenty-second switch tube Q22 and the twenty-third switch tube Q23 form a synchronous rectification circuit, the twenty-fourth switch tube Q24 and the twenty-fifth switch tube Q25 form a power switching circuit, and the inductor L4 and the capacitor C6 form a filter circuit. Through the setting of the second transformer unit, an regulated output voltage can be output for use by the load.

[0066] See Figure 3 The overall control process of the utility model includes the following steps:

[0067] Step 1: Detect HV1 (HV1 is the voltage of the first battery pack) and HV2 (here HV2 is the voltage of the second battery pack) to obtain the voltage difference between HV1 and HV2;

[0068] Step 2: Determine whether the voltages of HV1 and HV2 are balanced based on the preset voltage difference and the voltage difference;

[0069] If the voltage difference is less than or equal to the preset voltage difference, the voltages of HV1 and HV2 are determined to be balanced, and the process jumps to step 1.

[0070] If the voltage difference is greater than the preset voltage difference, it is determined that the voltages of HV1 and HV2 are unbalanced, and then;

[0071] Step 3: Compare the voltage of the first battery pack with the voltage of the second battery pack; control the first switch unit and the second switch unit to operate in corresponding modes according to the comparison result of the voltage of the first battery pack with the voltage of the second battery pack, so that the voltage of the first battery pack and the voltage of the second battery pack are less than or equal to the preset voltage difference, balance the voltage between the first battery pack and the second battery pack, and execute step 1 after step 3 is completed.

[0072] Specifically, the comparison result is that one of the first battery pack and the second battery pack is a high-voltage battery pack, and the other is a low-voltage battery pack; wherein the voltage of the high-voltage battery pack is higher than the voltage of the low-voltage battery pack.

[0073] The switch unit connected to the high-voltage battery pack is controlled to operate in an inverter mode, and the high-voltage battery pack transmits electric energy to the electric energy transfer unit; the switch unit connected to the low-voltage battery pack is controlled to operate in a charging mode, and the electric energy transfer unit transmits electric energy to the low-voltage battery pack until the voltage difference between the voltage of the first battery panel and the voltage of the second battery pack is less than or equal to the preset voltage difference.

[0074] For example, when the voltage of HV2 is higher than that of HV1, the control method is to control the second switch unit to operate in the inverter mode, and HV2 transmits power to the power transfer unit until the voltage difference between HV1 and HV2 is less than or equal to the preset voltage difference, thus achieving battery voltage balance.

[0075] The first switch unit is controlled to operate in the charging mode, and the power transfer unit transmits power to HV1 until the voltage difference between HV1 and HV2 is less than or equal to the preset voltage difference, thereby achieving battery voltage balance.

[0076] Furthermore, in order to ensure the execution of the above control method in the present invention, it is necessary to switch the first switch unit and the second switch unit to operate in the charging mode or the inverter mode, wherein the control logic of the first switch unit is:

[0077] In the first primary side conversion circuit, the control timings of the first switch tube Q1 and the fourth switch tube Q4 are the same, the control timings of the second switch tube Q2 and the third switch tube Q3 are the same, and the control timings of the first switch tube Q1 and the second switch tube Q2 are complementary;

[0078] In the first secondary side conversion circuit, the control timings of the fifth switch Q5 and the eighth switch Q8 are the same, the control timings of the sixth switch Q6 and the seventh switch Q7 are the same, and the control timings of the fifth switch Q5 and the sixth switch Q6 are complementary.

[0079] When the voltage difference between the first battery pack and the second battery pack reaches a preset voltage difference, and when the voltage of the first battery pack is higher than the voltage of the second battery pack, the first switching unit operates in the inverter mode: the switching tube of the first secondary conversion circuit leads the switching tube of the first primary conversion circuit by a phase shift angle;

[0080] When the voltage of the first battery pack is lower than the voltage of the second battery pack, the first switch unit operates in the inverter mode: the switch tube of the first secondary conversion circuit lags behind the switch tube of the first primary conversion circuit by a phase shift angle.

[0081] The control logic for the second switch unit is as follows:

[0082] In the second primary side conversion circuit, the control timings of the ninth switch tube Q9 and the twelfth switch tube Q12 are the same, the control timings of the tenth switch tube Q10 and the eleventh switch tube Q11 are the same, and the control timings of the ninth switch tube Q9 and the tenth switch tube Q10 are complementary;

[0083] In the second secondary side conversion circuit, the control timings of the thirteenth switch Q13 and the sixteenth switch Q16 are the same, the control timings of the fourteenth switch Q14 and the fifteenth switch Q15 are the same, and the control timings of the thirteenth switch Q13 and the fourteenth switch Q14 are complementary.

[0084] When the voltage difference between the first battery pack and the second battery pack reaches a preset voltage difference, and when the voltage of the first battery pack is higher than the voltage of the second battery pack, the second switch unit operates in a charging mode: the switch tube of the second secondary-side conversion circuit lags behind the switch tube of the second primary-side conversion circuit by a phase shift angle;

[0085] When the voltage of the first battery pack is lower than the voltage of the second battery pack, the second switch unit operates in the inverter mode: the switch tube of the second secondary conversion circuit leads the switch tube of the second primary conversion circuit by a phase shift angle.

[0086] It should be pointed out that the above configuration is only an example of the present invention in one application scenario. Based on the above configuration, the present invention can achieve balancing of the series battery pack regardless of the charging mode, driving mode, and inverter mode.

[0087] The utility model satisfies the power increase requirement without adding additional circuits, and the two HV-LV (HV1-LV1 and HV2-LV2) can be used as mutual backup, which improves the integration and reliability and also improves the user experience.

[0088] See Figure 4 , the control process of the utility model is:

[0089] At time t0, the voltage of HV2 is greater than the voltage of HV1, and the voltage difference between HV1 and HV2 is D greater than the preset voltage difference. At this time, it is determined that HV1 and HV2 are unbalanced.

[0090] During the process from t0 to t1, Figure 4 The timing control method shown controls the direction of power flow by controlling the switching tube of the second secondary conversion circuit to advance the switching tube of the second primary conversion circuit by a phase shift angle θ, so that the second switching unit operates in the inverter mode. During this process, electric energy flows out of HV2, then flows through the second secondary conversion circuit, the second primary conversion circuit, and finally flows to the energy transfer unit.

[0091] The switching tube of the first secondary conversion circuit is controlled to lag the switching tube of the first primary conversion circuit by a phase shift angle φ, so that the first switching unit operates in charging mode. During this process, electric energy flows into HV1, causing the electric energy to flow out of the energy transfer unit, and then flows through the first primary conversion circuit, the first secondary conversion circuit, and finally to HV1. In other words, the higher voltage HV2 is used to transmit electric energy to the lower voltage HV1.

[0092] Until time t1, the voltage difference between HV1 and HV2 is less than or equal to the preset voltage difference, thus achieving voltage balance between HV1 and HV2.

[0093] In addition, when the voltage difference D between HV1 and HV2 is greater than the preset voltage difference, and the voltage of HV1 is greater than the voltage of HV2, the switch tube of the first secondary-side conversion circuit is controlled to advance the switch tube of the first primary-side conversion circuit by a phase shift angle θ, so that the first switch unit operates in the inverter mode and power flows out of HV1; and the switch tube of the second secondary-side conversion circuit is controlled to lag the switch tube of the second primary-side conversion circuit by a phase shift angle φ, so that the second switch unit operates in the charging mode and power flows into HV2.

[0094] The preset voltage difference has a value range of greater than or equal to 0 and less than or equal to 10.

[0095] When the voltage between the first battery pack and the second battery pack is less than the preset voltage difference, it can be determined that the voltages between the first battery pack and the second battery pack are balanced.

[0096] For another example, when the voltage of HV1 is higher than that of HV2, the control method is as follows: control the first switch unit to operate in the inverter mode, and HV1 transmits electric energy to the electric energy transfer unit; control the second switch unit to operate in the charging mode, and the electric energy transfer unit transmits electric energy to HV2 until the voltage difference between HV1 and HV2 is ≤ the preset voltage difference, thereby achieving battery voltage balance.

[0097] In a preferred embodiment of the present invention, the preset voltage difference is set to 10V.

[0098] Compared with the prior art, the present invention has at least the following beneficial effects:

[0099] The utility model can achieve electric energy balance between the battery packs, maximize the use of electric energy in the first battery pack and the second battery pack, reduce electric energy waste and avoid over-discharge of the battery packs, thereby extending the service life of the battery packs.

[0100] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A battery pack voltage balancing converter, characterized in that: The invention comprises an electric energy transfer unit, a first switch unit connected between the electric energy transfer unit and the first battery pack and operating in a charging mode or an inverter mode, and a second switch unit connected between the electric energy transfer unit and the second battery pack and operating in a charging mode or an inverter mode; The first switch unit includes: a transformer T1, a first primary side conversion circuit connected between the transformer T1 and the power transfer unit, and a first secondary side conversion circuit connected between the transformer T1 and the first battery pack; Wherein, the first primary side conversion circuit and the first secondary side conversion circuit both adopt full-bridge circuits; The first primary side conversion circuit and the first secondary side conversion circuit include: The first primary side conversion circuit comprises a first switch tube Q1 and a second switch tube Q2 constituting a first bridge arm, and a third switch tube Q3 and a fourth switch tube Q4 constituting a second bridge arm, wherein the first switch tube Q1 and the third switch tube Q3 are upper arm switches, and the second switch tube Q2 and the fourth switch tube Q4 are lower arm switches; The midpoint of the first bridge arm is connected in series with a capacitor C1 and an inductor L1, and then connected to the primary winding of the transformer T1; The first secondary side conversion circuit includes a fifth switch tube Q5 and a sixth switch tube Q6 forming a third bridge arm, and a seventh switch tube Q7 and an eighth switch tube Q8 forming a fourth bridge arm, wherein the fifth switch tube Q5 and the seventh switch tube Q7 are upper arm switches, and the sixth switch tube Q6 and the eighth switch tube Q8 are lower arm switches; The midpoint of the third bridge arm is connected in series with a capacitor C2 and then connected to the secondary winding of the transformer T1; The second switch unit includes: a transformer T2, a second primary side conversion circuit connected between the transformer T2 and the power transfer unit, and a second secondary side conversion circuit connected between the transformer T2 and the second battery pack; Wherein, the second primary-side conversion circuit and the second secondary-side conversion circuit both adopt full-bridge circuits.

2. The battery pack voltage balancing converter according to claim 1, characterized in that: The second primary side conversion circuit and the second secondary side conversion circuit include: The second primary side conversion circuit includes a ninth switching tube Q9 and a tenth switching tube Q10 constituting a fifth bridge arm, and an eleventh switching tube Q11 and a twelfth switching tube Q12 constituting a sixth bridge arm, wherein the ninth switching tube Q9 and the eleventh switching tube Q11 are upper arm switches, and the tenth switching tube Q10 and the twelfth switching tube Q12 are lower arm switches; The midpoint of the fifth bridge arm is connected in series with a capacitor C3 and an inductor L2, and then connected to the primary winding of the transformer T2; The second secondary side conversion circuit includes a thirteenth switching tube Q13 and a fourteenth switching tube Q14 constituting a seventh bridge arm, and a fifteenth switching tube Q15 and a sixteenth switching tube Q16 constituting an eighth bridge arm, wherein the thirteenth switching tube Q13 and the fifteenth switching tube Q15 are upper arm switches, and the fourteenth switching tube Q14 and the sixteenth switching tube Q16 are lower arm switches; The midpoint of the seventh bridge arm is connected in series with a capacitor C4 and then connected to the secondary winding of the transformer T2.

3. The battery pack voltage balancing converter according to claim 2, characterized in that: In the first primary-side conversion circuit, the control timings of the first switch tube Q1 and the fourth switch tube Q4 are the same, the control timings of the second switch tube Q2 and the third switch tube Q3 are the same, and the control timings of the first switch tube Q1 and the second switch tube Q2 are complementary; In the first secondary-side conversion circuit, the control timings of the fifth switch tube Q5 and the eighth switch tube Q8 are the same, the control timings of the sixth switch tube Q6 and the seventh switch tube Q7 are the same, and the control timings of the fifth switch tube Q5 and the sixth switch tube Q6 are complementary; When the voltage of the first battery pack is higher than the voltage of the second battery pack, the first switch unit operates in the inverter mode: the switch tube of the first secondary conversion circuit leads the switch tube of the first primary conversion circuit by a phase shift angle.

4. The battery pack voltage balancing converter according to claim 3, characterized in that: In the second primary-side conversion circuit, the control timings of the ninth switch tube Q9 and the twelfth switch tube Q12 are the same, the control timings of the tenth switch tube Q10 and the eleventh switch tube Q11 are the same, and the control timings of the ninth switch tube Q9 and the tenth switch tube Q10 are complementary; In the second secondary-side conversion circuit, the control timings of the thirteenth switch tube Q13 and the sixteenth switch tube Q16 are the same, the control timings of the fourteenth switch tube Q14 and the fifteenth switch tube Q15 are the same, and the control timings of the thirteenth switch tube Q13 and the fourteenth switch tube Q14 are complementary; When the voltage of the first battery pack is higher than the voltage of the second battery pack, the second switch unit operates in a charging mode: the switch tube of the second secondary conversion circuit lags behind the switch tube of the second primary conversion circuit by a phase shift angle.

5. The battery pack voltage balancing converter according to claim 4, wherein: When the voltage of the first battery pack is lower than the voltage of the second battery pack, the first switch unit operates in a charging mode: the switch tube of the first secondary conversion circuit lags behind the switch tube of the first primary conversion circuit by a phase shift angle.

6. The battery pack voltage balancing converter according to claim 5, wherein: When the voltage of the first battery pack is lower than the voltage of the second battery pack, the second switch unit operates in the inverter mode: the switch tube of the second secondary conversion circuit leads the switch tube of the second primary conversion circuit by a phase shift angle.

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