An auxiliary power module and an auxiliary power supply method for a bidirectional DC charger

Abstract

The application relates to the field of chargers, and particularly discloses an auxiliary power module for a bidirectional direct-current charger, which comprises an input end, a first output end and a second output end, wherein the input end is connected with an external power supply, the first output end is connected with a DC / DC circuit to provide an insulation detection voltage for the bidirectional direct-current charger, and the second output end is connected with an anode of a diode D2; a cathode of the diode D2 is connected with the DC / DC circuit to provide auxiliary power supply when the DC / DC circuit works reversely. In the reverse off-grid mode, the auxiliary power module directly provides the insulation detection voltage required by the power stage DC / DC circuit for the electric vehicle, the no-load loss of the auxiliary power module is basically fixed after the auxiliary power module scheme is fixed, the power of the power module auxiliary power supply of the system control circuit and the DC / DC circuit is relatively fixed, the requirement for the external power supply power is significantly reduced, and therefore the auxiliary power module scheme provided by the application has more universal applicability.

Description

Technical Field

[0001] This invention relates to the field of DC chargers, and more specifically to an auxiliary power supply module for a bidirectional DC charger. Background Technology

[0002] With the rise of the pure electric vehicle market, the electric vehicle charger industry has also experienced rapid development. Meanwhile, bidirectional chargers can meet a wider range of application scenarios, such as: cooperating with the State Grid to achieve peak shaving and valley filling, providing power to household appliances during grid outages, and providing lighting for outdoor camping. The auxiliary power supply solution is a crucial aspect, needing to meet the auxiliary power requirements of the charger in forward charging mode, while also ensuring normal operation in reverse grid-connected and reverse off-grid modes.

[0003] Traditional auxiliary power supply solutions such as Figure 1 As shown, the bidirectional charger auxiliary power supply is mainly divided into three parts: power module auxiliary power supply, system power supply auxiliary power supply, and boost isolation power supply. The power module auxiliary power supply draws power from the bus voltage output terminal VBUS, and after passing through the auxiliary power supply circuit, it generates VCC1 to power the AC / DC and DC / DC primary circuits, and VCC2 to power the DC / DC secondary circuit. According to the power requirements of the power module control circuit, VCC1 and VCC2 will supply power to the power module control circuit individually or simultaneously. The system auxiliary power supply draws power from the AC side of the grid and mainly powers the system control circuit. The boost isolation power supply draws power from an external power source, and after passing through the boost isolation power supply, it outputs to the bus voltage. At the same time, the external power source can supply power to the system control circuit through diode D1.

[0004] In both forward charging mode and reverse grid-connected mode, the auxiliary power supply of the power module and the auxiliary power supply of the system can work normally because there is power on the grid side, and no external power supply is required to provide energy.

[0005] In reverse off-grid mode, the electric vehicle battery needs to discharge. However, before the electric vehicle closes the high-voltage DC contactor at the vehicle end, the charger needs to perform an insulation test according to the electric vehicle's given output voltage command. Only when the insulation test meets the requirements will the electric vehicle close the high-voltage DC contactor at the vehicle end and begin discharging. In reverse off-grid mode, the grid side is disconnected, so an external power supply must be provided to the system control circuit to ensure communication between the charger and the electric vehicle. At the same time, the external power supply also needs to be boosted to the bus voltage via a boost isolation power supply to power the auxiliary power supply of the power module. Only when the control current of the DC / DC circuit is present can the DC / DC circuit output the required output voltage VO of the electric vehicle under the control of the power module control circuit, and the system control circuit completes the insulation test.

[0006] When the insulation detection is completed, the high-voltage DC contactor inside the electric vehicle is closed, the power module control circuit controls the output of the high-voltage DC contactor K1 to be closed, the battery voltage of the electric vehicle is connected to the DC / DC output VO, the DC / DC circuit works reversely to provide energy for the bus by the battery of the electric vehicle, and then the AC / DC works reversely to complete the establishment of the voltage on the AC side, at this time, the power module control circuit can control the boost isolation power supply to be turned off, and the external power supply no longer needs to provide energy.

[0007] The above scheme is a common solution in the existing bidirectional charger, and from the above working process, it can be seen that the scheme is mainly limited by the no-load loss of the reverse off-grid mode DC / DC circuit. If the external power supply is a car lighter, the maximum current capacity of the car lighter is usually 10A, that is, the rated maximum power is 120W. The total demand power of the power module control circuit and the power module auxiliary power supply is different from 15W to 35W, and the influence of the actual power conversion efficiency (85%) and the need to reserve a certain margin (according to 80% derating) to prevent damage when the lighter is used are considered. Therefore, the maximum no-load loss of the DC / DC circuit should not exceed 50W. However, the no-load loss of the DC / DC circuit will vary greatly for different application conditions. For example, the AC side is a single-phase system or a three-phase system, the bus voltage is higher in the three-phase system, and the no-load loss is larger. The DC / DC circuit has different topological structures, such as CLLC, DAB or phase-shifted full-bridge and other topologies. Due to the differences in topological structure and control method, the no-load loss varies greatly. For example, the no-load loss of the DAB topology is difficult to reduce to below 100W. The DC / DC circuit uses single-output or multi-parallel output, the larger the power of the charger, the more parallel circuits are needed, and the more parallel circuits, the no-load will increase exponentially. These reasons will all lead to the existing scheme not having universal applicability, and if the power of the lighter is too high, it may also cause the lighter internal fuse to burn out, which has certain safety hazards. Similarly, if the external power supply uses an external battery, due to the fixed no-load loss of the DC / DC circuit under different application conditions, the same problem will also exist, such as the need to equip different capacity batteries under different application conditions.

[0008] In summary, the auxiliary power supply scheme of the existing bidirectional charger in off-grid mode has great differences in the no-load loss of the DC / DC circuit and does not have universal applicability, and there are certain safety hazards. SUMMARY

[0009] The present application provides a new auxiliary power supply module for a bidirectional DC charger to solve the problem of the existing bidirectional charger in off-grid mode.

[0010] The technical scheme adopted by the present application is as follows:

[0011] An auxiliary power supply module for a bidirectional DC charger includes:

[0012] The input terminal is connected to an external power supply;

[0013] The first output terminal is connected to the output terminal of the DC / DC circuit and provides an insulation detection voltage for the bidirectional DC charger.

[0014] The second output terminal is connected to the anode of diode D2, and the cathode of diode D2 is connected to the auxiliary power supply VCC2 of the DC / DC circuit to provide auxiliary power supply when the DC / DC circuit operates in reverse.

[0015] Furthermore, the auxiliary power supply module is configured as a boost isolated power supply, which includes two flyback circuits. The two flyback circuits are configured as a first flyback circuit and a second flyback circuit. The output terminal of the first flyback circuit is configured as a first output terminal, and the output terminal of the second flyback circuit is configured as a second output terminal.

[0016] Furthermore, one end of the primary coil of the first flyback circuit is connected to the positive terminal of an external power supply, the other end of the primary coil of the first flyback circuit is connected to the drain of the switching transistor Q2, the source of the switching transistor Q2 is grounded, the gate of the switching transistor Q2 is connected to the output terminal of the first PWM controller, and the secondary coil of the first flyback circuit outputs the voltage value required for insulation detection through a rectifier circuit.

[0017] Furthermore, one end of the primary coil of the second flyback circuit is connected to the positive terminal of an external power supply, the other end of the primary coil of the second flyback circuit is connected to the drain of the switching transistor Q3, the source of the switching transistor Q3 is grounded, the gate of the switching transistor Q3 is connected to the output terminal of the second PWM controller, and the secondary coil of the second flyback circuit outputs the auxiliary power supply VCC2 required for the reverse operation of the DC / DC circuit through diode D2.

[0018] Furthermore, the power supply circuit of the system control board is connected to the cathode of diode D1, and the anode of diode D1 is connected to the external power supply.

[0019] Furthermore, the boost isolation power supply also includes a boost circuit, and the two flyback circuits are connected to the external power supply via the boost circuit.

[0020] In order to solve the problem that the auxiliary power supply scheme of bidirectional chargers in off-grid mode is not universally applicable due to the large difference in no-load loss of DC / DC circuits, the present invention provides a new auxiliary power supply module for bidirectional DC chargers.

[0021] An auxiliary power supply module for a bidirectional DC charger includes:

[0022] The first auxiliary power supply has its input terminal connected to an external power source and its output terminal connected to the output terminal of a DC / DC circuit to provide an insulation detection voltage for the bidirectional DC charger.

[0023] The second auxiliary power supply has its input terminal connected to the electric vehicle battery and its output terminal connected to the DC / DC circuit auxiliary power supply VCC2 or the bus voltage output terminal VBUS, providing auxiliary power supply when the DC / DC circuit operates in reverse.

[0024] In order to solve the problem that the auxiliary power supply schemes for bidirectional chargers in off-grid mode are not universally applicable due to the large difference in no-load losses of DC / DC circuits, this invention provides a new auxiliary power supply method for bidirectional DC chargers.

[0025] An auxiliary power supply method for a bidirectional DC charger includes:

[0026] Obtain the voltage value required for insulation testing of electric vehicles;

[0027] Drive the auxiliary power supply module to output insulation detection voltage;

[0028] Close the high-voltage DC contactor K1;

[0029] The auxiliary power module outputs a reverse working voltage to the DC / DC circuit, or the electric vehicle battery provides a reverse working voltage to the DC / DC circuit.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] 1. This invention can connect an external power supply to a boost isolation power supply and output the insulation detection voltage required by the electric vehicle according to the output voltage command issued by the system control circuit. Compared with the existing solution, it reduces the no-load loss generated by the power stage DC-DC converter. Since the power supply power of the board control circuit and the power supply module control circuit are small and fixed, the requirements for external power supply can be significantly reduced, and the universality of the auxiliary power supply solution can be enhanced.

[0032] 2. In this invention, the input terminal of the first auxiliary power supply is connected to an external power source, and the output terminal of the first auxiliary power supply is connected to the output terminal of the DC / DC circuit to provide insulation monitoring voltage for the bidirectional DC charger. The input terminal of the second auxiliary power supply is connected to the electric vehicle battery, and the output terminal of the second auxiliary power supply is connected to the auxiliary power supply VCC2 of the DC / DC circuit or the bus voltage output terminal VBUS to provide auxiliary power supply when the DC / DC circuit is working in reverse. That is, the reverse working voltage of this invention is provided by the electric vehicle battery, which can reduce the dependence on external power source. Attached Figure Description

[0033] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the 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.

[0034] Figure 1 : A schematic diagram of the principle of a boost isolation power supply for an existing bidirectional DC charger;

[0035] Figure 2 The schematic diagram of the auxiliary power supply module for a bidirectional DC charger provided in this embodiment of the invention;

[0036] Figure 3 The circuit diagram of the boost isolation power supply provided in this embodiment of the invention. Detailed Implementation

[0037] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0038] Example 1:

[0039] Figure 2 The diagram illustrates a schematic block diagram of an auxiliary power supply module for a bidirectional DC charger according to an embodiment of the present invention. The auxiliary power supply module for the bidirectional DC charger includes an input terminal, a first output terminal, and a second output terminal. The input terminal is connected to an external power source. The first output terminal is connected to the output terminal of a DC / DC circuit to provide an insulation detection voltage for the bidirectional DC charger. The second output terminal is connected to the anode of a diode D2. The cathode of the diode D2 is connected to the auxiliary power supply VCC2 of the DC / DC circuit to provide auxiliary power for the reverse operation of the DC / DC circuit.

[0040] It should be noted that in the reverse off-grid mode of this embodiment, the insulation detection voltage required by the electric vehicle is not required to be output by the power stage DC / DC circuit. Instead, it is directly provided by the auxiliary power module. After the auxiliary power module scheme is fixed, its no-load loss is also basically fixed. The auxiliary power supply power of the power module of the system control circuit and the DC / DC circuit is relatively fixed, and the requirements for external power supply power are significantly reduced. Therefore, the auxiliary power module scheme provided in this embodiment has more universal applicability, and the applicable scheme systems are more diverse. It is no longer affected by the system architecture, power level and DC / DC circuit topology.

[0041] Furthermore, there is a wider and more flexible selection of auxiliary power supply control chips, and if a frequency hopping operating mode is adopted, the no-load loss of the control chip is lower.

[0042] Furthermore, such as Figure 3 As shown, in this embodiment, the auxiliary power module is configured as a boost isolated power supply. The boost isolated power supply includes two flyback circuits, which are configured as a first flyback circuit and a second flyback circuit. The output terminal of the first flyback circuit is configured as a first output terminal, and the output terminal of the second flyback circuit is configured as a second output terminal.

[0043] Furthermore, one end of the primary coil of the first flyback circuit is connected to the positive terminal of an external power supply, the other end of the primary coil of the first flyback circuit is connected to the drain of the switching transistor Q2, the source of the switching transistor Q2 is grounded, the gate of the switching transistor Q2 is connected to the output terminal of the first PWM controller, and the secondary coil of the first flyback circuit outputs the voltage value required for insulation detection through a rectifier circuit.

[0044] Furthermore, one end of the primary coil of the second flyback circuit is connected to the positive terminal of an external power supply, the other end of the primary coil of the second flyback circuit is connected to the drain of the switching transistor Q3, the source of the switching transistor Q3 is grounded, the gate of the switching transistor Q3 is connected to the output terminal of the second PWM controller, and the secondary coil of the second flyback circuit outputs the auxiliary power supply VCC2 required for the reverse operation of the DC / DC circuit through diode D2.

[0045] Furthermore, the power supply circuit of the system control board is connected to the cathode of diode D1, and the anode of diode D1 is connected to the external power supply.

[0046] Furthermore, the boost isolation power supply also includes a boost circuit, and the two flyback circuits are connected to the external power supply via the boost circuit.

[0047] Furthermore, the boost isolation power supply includes a first flyback circuit, with the first output terminal connected to the first flyback circuit and the second output terminal connected to the electric vehicle battery.

[0048] Specifically, the external power supply voltage used in this embodiment is 12V.

[0049] Specifically, in this embodiment, the first PWM controller, the second PWM controller, and the third PWM controller can be implemented by the controller in the power module control circuit, or by the controller in the system control circuit, or by a commonly used auxiliary power supply analog control chip, without much restriction.

[0050] Specifically, such as Figure 3As shown in the figure, PWM controller 1 is configured as the first PWM controller, PWM controller 2 is configured as the second PWM controller, and PWM controller 3 is configured as the third PWM controller.

[0051] The working principle of this embodiment:

[0052] In both forward charging and reverse grid-connected modes, the auxiliary power supply for the power module can draw power from the bus voltage output terminal VBUS, and after isolation, provide the necessary auxiliary power to the power module. The auxiliary power supply for the system control circuit is provided by the system power supply auxiliary power supply, which draws power from the AC grid and after isolation, provides the necessary auxiliary power to the system control circuit. In both of these operating modes, the external power supply does not need to provide energy, and the boost isolation power supply is controlled by the system control circuit to be in a non-operating state.

[0053] In reverse off-grid mode, because the AC grid voltage is disconnected, the electric vehicle battery is also disconnected before the bidirectional DC charger completes the insulation test. Therefore, before the bidirectional DC charger can obtain energy from the electric vehicle battery, it must be powered by an external power source.

[0054] An external power supply is directly connected to the system control circuit through diode D1 to provide energy, ensuring that the bidirectional DC charger can communicate with the electric vehicle and obtain the output voltage value required by the electric vehicle for insulation testing of the bidirectional DC charger, as well as other relevant information about the vehicle end or the electric vehicle battery.

[0055] After the system control circuit obtains external power and works normally, it can first use the control signal to make the PWM controller 3 output a signal to the boost circuit, so that it starts to work. The boost circuit starts to work according to the output voltage V1 that has been set in the hardware circuit, and completes the establishment of the output voltage V1. The output voltage V1 setting value can be designed according to actual needs, such as 48V, 60V, etc.

[0056] Furthermore, the system control circuit uses a control signal to cause the PWM controller 1 to output a signal to the first flyback circuit, enabling it to start working. Its output voltage is the voltage value Vo required by the electric vehicle. Different electric vehicles require different insulation detection voltages due to different battery voltages. The output voltage command can be set by the system control circuit. After the Vo voltage is established, the system control circuit starts to perform insulation detection. If the insulation detection is passed, the system control circuit uses a control signal to cause the PWM controller 1 to stop outputting signals, turn off the Vo output, and inform the electric vehicle that the insulation detection has been completed, requiring the electric vehicle to close the high-voltage DC contactor K1 at the vehicle end.

[0057] Furthermore, the system control circuit uses a control signal to cause the PWM controller 2 to output a signal to the second flyback circuit, enabling it to start working. Its output voltage is the auxiliary power supply voltage required for the DC / DC circuit to work in reverse. After passing through the bypass diode D2, it is connected to VCC2 to prepare the conditions for the DC / DC circuit to work in reverse.

[0058] The system control circuit communicates with the power module control circuit, requiring the closure of the high-voltage DC contactor K1 at the output terminal. At this time, the electric vehicle battery voltage is connected to the DC / DC circuit output terminal Vo, and the DC / DC circuit starts to work in reverse, completing the establishment of the bus voltage output terminal VBUS. When VBUS outputs according to the target voltage, the power module auxiliary power supply starts to work. At this time, the auxiliary power supply of both the AC / DC circuit and the DC / DC circuit of the power module is provided by it. Then, the AC / DC circuit starts to work in reverse, completing the establishment of the AC side voltage. When the AC side voltage is established, the system control auxiliary power supply starts to work and begins to provide energy to the system control circuit. At this time, the system control circuit can use control signals to stop the output signals of PWM controller 2 and PWM controller 3, and the external power supply no longer needs to provide energy to the bidirectional charger.

[0059] Example 2:

[0060] This embodiment provides an auxiliary power supply module for a bidirectional DC charger, including a first auxiliary power supply and a second auxiliary power supply. The input terminal of the first auxiliary power supply is connected to an external power source, and the output terminal of the first auxiliary power supply is connected to the output terminal of a DC / DC circuit to provide an insulation detection voltage for the bidirectional DC charger. The input terminal of the second auxiliary power supply is connected to an electric vehicle battery, and the output terminal of the second auxiliary power supply is connected to the auxiliary power supply VCC2 of the DC / DC circuit or the bus voltage output terminal VBUS to provide auxiliary power supply when the DC / DC circuit operates in reverse.

[0061] The working principle of this embodiment:

[0062] The working principle of this embodiment is basically the same as that of embodiment one. The difference is that this embodiment connects to the electric vehicle battery through the second auxiliary power input terminal. When the insulation test is passed, the electric vehicle closes the high voltage DC contactor K1 at the vehicle end, thereby energizing the second auxiliary power supply.

[0063] When the output of the second auxiliary power supply is connected to the bus voltage output terminal VBUS of the DC / DC circuit, the second auxiliary power supply is powered on and the bus voltage output terminal VBUS is established. When VBUS outputs the target voltage, the auxiliary power supply of the power module starts working, and the auxiliary power supply VCC2 of the DC / DC circuit is powered on. At this time, the auxiliary power supply of both the AC / DC circuit and the DC / DC circuit of the power module is provided by it. Then the AC / DC circuit starts to work in reverse and completes the establishment of the AC side voltage. When the AC side voltage is established, the system control auxiliary power supply starts working and begins to provide energy to the system control circuit, thereby realizing bidirectional power supply.

[0064] When the output of the second auxiliary power supply is connected to the DC / DC circuit auxiliary power supply VCC2, the second auxiliary power supply is powered on, and thus the DC / DC circuit auxiliary power supply VCC2 is powered on. At this time, the power module auxiliary power supply works, and then the DC / DC circuit bus voltage output terminal VBUS is powered on. Then the AC / DC circuit starts to work in reverse, and completes the establishment of AC side voltage. After the AC side voltage is established, the system control auxiliary power supply starts to work and begins to provide energy to the system control circuit, thus realizing bidirectional power supply.

[0065] The present invention also provides an auxiliary power supply method for a bidirectional DC charger, which utilizes the aforementioned auxiliary power supply module. Specifically, the method includes:

[0066] Obtain the voltage value required for insulation testing of electric vehicles;

[0067] Drive the auxiliary power supply module to output insulation detection voltage;

[0068] Close the high-voltage DC contactor K1;

[0069] The auxiliary power module outputs a reverse working voltage to the DC / DC circuit, or the electric vehicle battery provides a reverse working voltage to the DC / DC circuit.

[0070] In summary, the auxiliary power supply solution of the present invention has wider applicability, can be applied to a wider variety of systems, and is no longer affected by system architecture, power level, and DC / DC circuit topology.

[0071] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process, and the scope of the preferred embodiments of the invention includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as will be understood by those skilled in the art to which embodiments of the invention pertain.

[0072] Those skilled in the art will understand that all or part of the steps of the methods described in the above embodiments can be implemented by a program instructing related hardware, and the program can be stored in a computer-readable storage medium. When executed, the program includes one or a combination of the steps of the method embodiments.

[0073] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0074] The above embodiments are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. An auxiliary power supply module for a bidirectional DC charger, characterized in that, include: The input terminal is connected to an external power supply; The first output terminal is connected to the output terminal of the DC / DC circuit and provides an insulation detection voltage for the bidirectional DC charger. The second output terminal is connected to the anode of diode D2, and the cathode of diode D2 is connected to the auxiliary power supply VCC2 of the DC / DC circuit to provide auxiliary power supply when the DC / DC circuit is working in reverse. The auxiliary power module is configured as a boost isolated power supply, which includes two flyback circuits. The two flyback circuits are configured as a first flyback circuit and a second flyback circuit. The output terminal of the first flyback circuit is configured as a first output terminal, and the output terminal of the second flyback circuit is configured as a second output terminal. One end of the primary coil of the first flyback circuit is connected to the positive terminal of an external power supply, and the other end of the primary coil of the first flyback circuit is connected to the drain of the switching transistor Q2. The source of the switching transistor Q2 is grounded, and the gate of the switching transistor Q2 is connected to the output terminal of the first PWM controller. The secondary coil of the first flyback circuit outputs the voltage value required for insulation detection through a rectifier circuit. One end of the primary coil of the second flyback circuit is connected to the positive terminal of the external power supply, and the other end of the primary coil of the second flyback circuit is connected to the drain of the switching transistor Q3. The source of the switching transistor Q3 is grounded, and the gate of the switching transistor Q3 is connected to the output terminal of the second PWM controller. The secondary coil of the second flyback circuit outputs the auxiliary power supply VCC2 required for the reverse operation of the DC / DC circuit through the diode D2.

2. The auxiliary power supply module for a bidirectional DC charger according to claim 1, characterized in that, The system control circuit is connected to the cathode of diode D1, and the anode of diode D1 is connected to the external power supply.

3. The auxiliary power supply module for a bidirectional DC charger according to claim 1, characterized in that, The boost isolation power supply also includes a boost circuit, and the two flyback circuits are connected to the external power supply via the boost circuit.

4. A method for providing auxiliary power supply to a bidirectional DC charger based on the auxiliary power module described in any one of claims 1-3, characterized in that, include: Obtain the voltage value required for insulation testing of electric vehicles; Drive the auxiliary power supply module to output insulation detection voltage; Close the high-voltage DC contactor K1, which is located between the DC / DC circuit and the electric vehicle battery; The auxiliary power module outputs a reverse working voltage to the DC / DC circuit, or the electric vehicle battery provides a reverse working voltage to the DC / DC circuit.

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