Parallel discharging device and method for electric vehicle

Abstract

The invention discloses a parallel discharging device and method for an electric vehicle. The parallel discharging device comprises a power battery module, a power distribution module, a positive temperature coefficient thermistor discharging loop module, a vehicle-mounted charging module, a micro-control processor discharging loop module and a driving motor module. The power battery module is connected with the power distribution module; the power distribution module is connected with the positive temperature coefficient thermistor discharge loop module, the vehicle-mounted charging module and the micro-control processor discharge loop module. And the micro-control processor discharging loop module is connected with the driving motor module. The method has the advantages that top-speed discharge is performed, a discharge path distribution strategy is performed in combination with an actual operation state, and the safety of a high-voltage system after power-off is improved; energy utilization is reasonable, energy waste is reduced, and the energy utilization rate of the whole vehicle is increased; redundancy is reliable, a dual discharge path is constructed, and an important redundancy safety guarantee is provided; intelligent cooperation is achieved, incoordination or conflicts between systems are avoided, and the discharging process is efficient and orderly.

Description

Technical Field

[0001] This invention belongs to the field of electric vehicle safety technology. Specifically, this invention relates to a parallel discharge device and method for electric vehicles, which integrates multiple on-board high-voltage loads to achieve faster and safer active discharge. Background Technology

[0002] The high-voltage system of an electric vehicle includes key components such as the motor controller, positive temperature coefficient (PTC) thermistor heater, and air conditioning compressor. These components all integrate large-capacity capacitor banks, whose main function is to stabilize the DC bus voltage and smooth current ripples. When an electric vehicle is powered on under high voltage, due to the energy storage characteristics of capacitors, high-voltage charge remains in the capacitor banks. If this charge cannot be quickly discharged through an effective means, the residual voltage may persist for several minutes or even longer. This residual high voltage poses a significant safety hazard, potentially causing electric shock accidents to maintenance or rescue personnel when touching high-voltage components, or triggering unexpected malfunctions of electrical components, thus leading to secondary safety risks.

[0003] For the active discharge requirements of high-voltage capacitors, existing technologies mainly provide two solutions.

[0004] The first approach involves adding a dedicated discharge resistor circuit to the high-voltage system. This circuit typically consists of a power resistor, a control switch, and its drive logic. When the system is powered down, the switch closes, allowing the capacitor's energy to be dissipated as heat through the resistor. This method offers a clear discharge path and controllable speed. However, its drawbacks are also significant: the added resistor, switch, and connecting components increase material costs; the power resistor and its heat dissipation design occupy valuable vehicle layout space; the additional electronic components and connection points reduce the overall system reliability; and the heat generated by the large energy discharge places additional demands on the vehicle's thermal management.

[0005] The second approach utilizes the drive motor itself as a discharge load. Specifically, this involves controlling the power switching devices in the motor controller to direct the energy from the bus capacitor to the motor's three-phase windings, where the energy is dissipated as heat. This method requires no additional hardware and is relatively low-cost. However, its effectiveness is highly dependent on the state of the drive motor and its controller. When the motor is stationary or in a specific fault mode, such as when the motor's resolver signal is abnormal, the power devices fail, or the controller's low-voltage power supply fails, the preset discharge circuit may not be established correctly, or the discharge current may be limited, resulting in a slow or even completely unenforceable discharge process. This introduces uncertainty into the reliability of the discharge function.

[0006] In recent years, with the rapid and continuous increase in the proportion of new energy vehicles in the global automotive market, high-voltage electrical safety in vehicles has become a key area for industry regulation and standard setting. Relevant vehicle safety regulations have set clear requirements for the performance of high-voltage systems under emergency conditions. For example, after a collision, the high-voltage system must discharge the bus voltage to below the human safety voltage threshold within an extremely short time, typically less than one second, to completely eliminate secondary disasters caused by high voltage. Current technologies, which rely solely on the drive motor windings for energy consumption, have a single discharge circuit and lack design redundancy. When a specific fault occurs in the electric drive system itself, the entire discharge logic may fail, and the high-voltage charge cannot be discharged in time, leaving the system still exposed to high-voltage hazards. This highlights the shortcomings of current solutions in terms of robustness and safety. Summary of the Invention

[0007] The present invention aims to overcome the shortcomings of the prior art and provide a parallel discharge device and method for electric vehicles, which integrates multiple on-board high-voltage loads to achieve faster and safer redundancy active discharge.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a parallel discharge device and method for electric vehicles, comprising a power battery module 1, a power distribution module PDU, a positive temperature coefficient thermistor discharge circuit module PTC, an on-board charging module 2, a microcontroller discharge circuit module MCU, and a drive motor module MOTOR; the power battery module 1 is connected to the power distribution module PDU; the power distribution module PDU is connected to the positive temperature coefficient thermistor discharge circuit module PTC, the on-board charging module 2, and the microcontroller discharge circuit module MCU respectively; the microcontroller discharge circuit module MCU is connected to the drive motor module MOTOR.

[0009] The power battery module 1 transmits the processed power to the power distribution module PDU; the power distribution module PDU distributes power according to the system to the positive temperature coefficient thermistor discharge circuit module PTC, the on-board charging module 2 and the microcontroller discharge circuit module MCU; the microcontroller discharge circuit module MCU transmits drive commands to the drive motor module MOTOR.

[0010] The power battery module 1 includes a power battery pack unit, a negative electrode contactor unit, an electric heating wire unit, a film heating contactor unit, a battery management unit (BMS), a pre-charge contactor unit, a pre-charge pack unit, a positive electrode contactor unit, and a fast-charge positive electrode contactor unit.

[0011] The on-board charging module 2 includes an on-board charger unit (OBC) and a DC-DC converter unit (DCDC).

[0012] The microcontroller discharge circuit module (MCU) and the positive temperature coefficient thermistor discharge circuit module (PTC) are connected in parallel across the high-voltage capacitor. The MCU includes an internally integrated insulated-gate bipolar transistor (IGBT) circuit and a motor winding. The PTC includes a positive temperature coefficient thermistor heater and a control circuit. The PTC can recover and reuse the generated heat energy.

[0013] The discharge triggering conditions of the parallel discharge device in electric vehicles are obtained in real time by the vehicle controller (VCU) by acquiring the high-voltage system status signal.

[0014] When both the microcontroller discharge circuit module (MCU) and the positive temperature coefficient thermistor discharge circuit module (PTC) are normal, the main circuit discharges; when the MCU is abnormal, the PTC discharge circuit module discharges; when the PTC discharge circuit module is abnormal, the MCU discharges.

[0015] The vehicle control unit (VCU) continuously monitors the voltage of the high-voltage capacitor. When the voltage drops to a safe threshold, the discharge process ends.

[0016] A parallel discharge device and method for electric vehicles, the method comprising the following steps:

[0017] S1: When an electric vehicle finishes charging, is powered off normally, or is powered off due to a fault, input a discharge command to start the discharge operation.

[0018] S2: When the main positive and main negative relays of the battery management unit (BMS) in power battery module 1 reach the preset state; when the microcontroller discharge circuit module (MCU) and the positive temperature coefficient thermistor discharge circuit module (PTC) have no discharge prohibition faults; and when the temperature values ​​of the microcontroller discharge circuit module (MCU), the positive temperature coefficient thermistor discharge circuit module (PTC), and the drive motor module (MOTOR) are below the preset threshold, discharge begins.

[0019] S3: When both the microcontroller discharge circuit module (MCU) and the positive temperature coefficient thermistor discharge circuit module (PTC) are normal, the main circuit is discharged; when the PTC is abnormal, the microcontroller discharge circuit module (MCU) is discharged; when the microcontroller discharge circuit module (MCU) is abnormal, the PTC is discharged.

[0020] S4: The microcontroller discharge circuit module (MCU) determines the critical signal threshold. When the critical signal threshold is normal, it enters S5; when it is abnormal, it enters S2.

[0021] S5: The microcontroller discharge circuit module (MCU) enters active discharge mode, controlling the IGBT circuit of the insulated gate bipolar transistor to turn on.

[0022] S6: Calculate the discharge power boundary based on temperature, and calibrate the direct-axis current and quadrature-axis current using the actual drive motor module MOTOR.

[0023] S7: The microcontroller discharge circuit module (MCU) identifies the setting signal, exits active discharge, enters S8 if the setting signal is identified, and enters S4 if the setting signal is not identified.

[0024] S8: The microcontroller discharge circuit module (MCU) switches to the off mode, and the insulated gate bipolar transistor (IGBT) turns off.

[0025] S9: The positive temperature coefficient thermistor discharge circuit module PTC judges the critical signal threshold. When the critical signal threshold is normal, it enters S10; when it is abnormal, it enters S2.

[0026] S10: The positive temperature coefficient thermistor discharge circuit module PTC enters active discharge mode, controlling the IGBT circuit of the insulated gate bipolar transistor to turn on.

[0027] S11: Calculate the discharge power boundary based on temperature and give the discharge current;

[0028] S12: The positive temperature coefficient thermistor discharge circuit module PTC identifies the setting signal, exits active discharge, enters S13 if the setting signal is identified, and enters S9 if the setting signal is not identified.

[0029] S13: The PTC working mode of the positive temperature coefficient thermistor discharge circuit module jumps to off, and the IGBT of the insulated gate bipolar transistor circuit turns off.

[0030] S14: Discharge Termination Judgment: When the operating mode of the microcontroller discharge circuit module MCU switches to off, the operating mode of the positive temperature coefficient thermistor discharge circuit module PTC switches to off, and the voltage drops to the safety threshold, the discharge ends.

[0031] The technical effects of this invention are as follows: Rapid discharge: By using a microcontroller (MCU) discharge circuit module and a positive temperature coefficient (PTC) discharge circuit module in parallel discharge, and combining this with a discharge path allocation strategy based on actual operating conditions, the power advantages of both are fully utilized. Compared to a single discharge circuit, the discharge time can be shortened by 30%-50%, significantly improving the safety of the high-voltage system after power-off; Rational energy utilization: The heat generated during the discharge process of the PTC discharge circuit module can be recovered and reused according to actual needs, reducing energy waste and improving the overall vehicle energy utilization rate; Redundancy and reliability: A dual discharge path is constructed, utilizing the original vehicle microcontroller discharge circuit module... The MCU electrical circuit module and the PTC positive temperature coefficient thermistor discharge circuit module hardware ensure robustness and provide crucial redundancy for safety, even if one path fails due to a fault. Resource optimization: It deeply explores and coordinates the two inherent high-voltage loads of the vehicle, eliminating the need for or reducing the specifications of dedicated discharge resistors, maximizing the functionality of existing hardware resources, and further saving costs and space. Intelligent coordination: Unified scheduling through the vehicle controller (VCU) ensures the synchronous start and termination of the two discharge paths, avoiding incoordination or conflict between systems, making the discharge process efficient and orderly. Attached Figure Description

[0032] This manual includes the following figures, which illustrate the following:

[0033] Figure 1 This is a block diagram of the logical structure of the present invention;

[0034] Figure 2 This is a flowchart of the method of the present invention;

[0035] The diagram is labeled as follows: 1. Power battery module; 2. On-board charging module. Detailed Implementation

[0036] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings, in order to help those skilled in the art to have a more complete, accurate and in-depth understanding of the inventive concept and technical solution of the present invention, and to facilitate its implementation.

[0037] Figure 1The present invention provides a logical structure block diagram of a parallel discharge device and method for an electric vehicle, comprising a power battery module 1, a power distribution module PDU, a positive temperature coefficient thermistor discharge circuit module PTC, an on-board charging module 2, a microcontroller discharge circuit module MCU, and a drive motor module MOTOR. The power battery module 1 is connected to the power distribution module PDU. The power distribution module PDU is connected to the positive temperature coefficient thermistor discharge circuit module PTC, the on-board charging module 2, and the microcontroller discharge circuit module MCU, respectively. The microcontroller discharge circuit module MCU is connected to the drive motor module MOTOR.

[0038] The power battery module 1 transmits the processed power to the power distribution module PDU; the power distribution module PDU distributes power according to the system to the positive temperature coefficient thermistor discharge circuit module PTC, the on-board charging module 2 and the microcontroller discharge circuit module MCU; the microcontroller discharge circuit module MCU transmits drive commands to the drive motor module MOTOR.

[0039] The power battery module 1 includes a power battery pack unit, a negative electrode contactor unit, an electric heating wire unit, a film heating contactor unit, a battery management unit (BMS), a pre-charge contactor unit, a pre-charge pack unit, a positive electrode contactor unit, and a fast-charge positive electrode contactor unit. An insulation detection device is connected between the power battery pack unit and the battery management unit (BMS).

[0040] The on-board charging module 2 includes an on-board charger unit (OBC) and a DC-DC converter unit (DCDC). The OBC is responsible for converting external AC power into DC power to charge the power battery. The DC-DC converter unit (DCDC) is responsible for converting the high-voltage DC power from the power battery into the 12V / 24V DC power required by the vehicle's low-voltage equipment. The former only operates during charging, while the latter operates continuously throughout the vehicle's entire lifecycle, together forming the core of energy conversion and distribution in electric vehicles.

[0041] The microcontroller discharge circuit module (MCU) and the positive temperature coefficient thermistor discharge circuit module (PTC) are connected in parallel across the high-voltage capacitor. The MCU includes an internally integrated insulated-gate bipolar transistor (IGBT) circuit and a motor winding. The PTC includes a positive temperature coefficient thermistor heater and a control circuit. The PTC can recover and reuse the generated heat energy.

[0042] The discharge triggering conditions of the parallel discharge device in electric vehicles are obtained in real time by the vehicle controller (VCU) by acquiring the high-voltage system status signal.

[0043] The Vehicle Control Unit (VCU) is the central decision-making core of an electric vehicle. It receives signals from all sensors, including those related to the accelerator pedal, brakes, and battery status. After calculation, it issues precise commands to all subsystems, such as the motor, battery, and thermal management system, coordinating vehicle functions such as drive, braking, and energy recovery. It is the highest control unit for achieving safe, efficient, and intelligent vehicle operation.

[0044] When both the microcontroller discharge circuit module (MCU) and the positive temperature coefficient thermistor discharge circuit module (PTC) are normal, the main circuit discharges; when the MCU is abnormal, the PTC discharge circuit module discharges; when the PTC discharge circuit module is abnormal, the MCU discharges.

[0045] The vehicle control unit (VCU) continuously monitors the voltage of the high-voltage capacitor. When the voltage drops to a safe threshold, the discharge process ends.

[0046] Figure 2 This is a flowchart of the method of the present invention. A parallel discharge device and method for an electric vehicle are described, the method comprising the following steps:

[0047] S1: When an electric vehicle finishes charging, is powered off normally, or is powered off due to a fault, input a discharge command to start the discharge operation.

[0048] S2: When the main positive and main negative relays of the battery management unit (BMS) in power battery module 1 reach the preset state; when the microcontroller discharge circuit module (MCU) and the positive temperature coefficient thermistor discharge circuit module (PTC) have no discharge prohibition faults; and when the temperature values ​​of the microcontroller discharge circuit module (MCU), the positive temperature coefficient thermistor discharge circuit module (PTC), and the drive motor module (MOTOR) are below the preset threshold, discharge begins.

[0049] S3: When both the microcontroller discharge circuit module (MCU) and the positive temperature coefficient thermistor discharge circuit module (PTC) are normal, the main circuit is discharged; when the PTC is abnormal, the microcontroller discharge circuit module (MCU) is discharged; when the microcontroller discharge circuit module (MCU) is abnormal, the PTC is discharged.

[0050] S4: The microcontroller discharge circuit module (MCU) determines the critical signal threshold. When the critical signal threshold is normal, it enters S5; when it is abnormal, it enters S2.

[0051] S5: The microcontroller discharge circuit module (MCU) enters active discharge mode, controlling the IGBT circuit of the insulated gate bipolar transistor to turn on.

[0052] S6: Calculate the discharge power boundary based on temperature, and calibrate the direct-axis current and quadrature-axis current using the actual drive motor module MOTOR.

[0053] S7: The microcontroller discharge circuit module (MCU) identifies the setting signal, exits active discharge, enters S8 if the setting signal is identified, and enters S4 if the setting signal is not identified.

[0054] S8: The microcontroller discharge circuit module (MCU) switches to the off mode, and the insulated gate bipolar transistor (IGBT) turns off.

[0055] S9: The positive temperature coefficient thermistor discharge circuit module PTC judges the critical signal threshold. When the critical signal threshold is normal, it enters S10; when it is abnormal, it enters S2.

[0056] S10: The positive temperature coefficient thermistor discharge circuit module PTC enters active discharge mode, controlling the IGBT circuit of the insulated gate bipolar transistor to turn on.

[0057] S11: Calculate the discharge power boundary based on temperature and give the discharge current;

[0058] S12: The positive temperature coefficient thermistor discharge circuit module PTC identifies the setting signal, exits active discharge, enters S13 if the setting signal is identified, and enters S9 if the setting signal is not identified.

[0059] S13: The PTC working mode of the positive temperature coefficient thermistor discharge circuit module jumps to off, and the IGBT of the insulated gate bipolar transistor circuit turns off.

[0060] S14: Discharge Termination Judgment: When the operating mode of the microcontroller discharge circuit module MCU switches to off, the operating mode of the positive temperature coefficient thermistor discharge circuit module PTC switches to off, and the voltage drops to the safety threshold, the discharge ends.

[0061] In step S2, the main positive and main negative relays of the battery management unit (BMS) in the power battery module 1 reach a preset state, which is 0x0:Open.

[0062] In step S3, both the microcontroller discharge circuit module (MCU) and the positive temperature coefficient thermistor discharge circuit module (PTC) are functioning normally. 20ms after the vehicle controller (VCU) sends the MCU_Discharge signal, the VCU then sends the PTC_Discharge signal to discharge the main circuit. When the MCU malfunctions, the VCU sends the PTC_Discharge signal, and the PTC discharge circuit module performs the discharge. Similarly, when the PTC malfunctions, the VCU sends the MCU_Discharge signal, and the MCU discharge circuit module performs the discharge.

[0063] In step S4, the microcontroller discharge circuit module (MCU) determines the critical signal thresholds. These critical signal thresholds are: MCU_InverterTemp≤70℃, MCU_MotorTemp≤130℃, MCU_MotorSpd≤150rpm, and MCU_FaultLevel: None (FaultLevel_5).

[0064] In step S6, the actual drive motor module MOTOR calibrates the direct axis current iq=0 and the quadrature axis current id=XX.

[0065] In step S7, the microcontroller discharge circuit module (MCU) identifies the setting signal, which is MCU_DC_Link_Volt≤60V, 100μs.

[0066] In step S9, the positive temperature coefficient thermistor discharge circuit module PTC determines the critical signal threshold, which is PTC_IGBTTemp≤70℃ and PTC_FaultLevel: no FaultLevel_3.

[0067] In step S11, the given discharge current is:

[0068] I=I_base+Kp·e(t)+Ki·∫e(τ)dτ+Kd·de(t) / dt.

[0069] In step S12, the positive temperature coefficient thermistor discharge circuit module PTC identifies the setting signal, which is PTC_HighVolt≤60V, 100μs.

[0070] In step S14, when the working mode of the microcontroller discharge circuit module MCU switches to OFF, the working mode of the positive temperature coefficient thermistor discharge circuit module PTC switches to OFF, and the voltage drop safety threshold MCU_DC_Link_Volt ≤ 60V, the discharge ends after 100μs.

[0071] The role and effect of the embodiments

[0072] Rapid Discharge: The discharge circuit utilizes a parallel connection between the microcontroller (MCU) and the positive temperature coefficient (PTC) thermistor discharge circuit module. A discharge path allocation strategy is implemented based on actual operating conditions to fully leverage the power advantages of both modules. Compared to a single discharge circuit, discharge time can be reduced by 30%-50%, significantly improving the safety of the high-voltage system after power-off. Optimal Energy Utilization: The heat generated during the discharge process of the PTC thermistor discharge circuit module can be recovered and reused according to actual needs, reducing energy waste and improving the overall vehicle energy efficiency. Redundancy and Reliability: A dual discharge path is constructed, utilizing the original vehicle microcontroller discharge circuit module... The MCU and PTC (Positive Temperature Coefficient) thermistor discharge circuit module hardware ensure robustness and provide crucial redundancy for safety, even if one path fails due to a fault. Resource optimization: It deeply explores and coordinates the two inherent high-voltage loads of the vehicle, eliminating the need for or reducing the specifications of dedicated discharge resistors, maximizing the functionality of existing hardware resources, and further saving costs and space. Intelligent coordination: Unified scheduling through the vehicle controller (VCU) ensures the synchronous start and termination of the two discharge paths, avoiding incoordination or conflict between systems, making the discharge process efficient and orderly.

[0073] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the inventive concept and technical solution; or the direct application of the inventive concept and technical solution to other situations without modification, are all within the protection scope of the present invention.

Claims

1. A parallel discharge device and method for electric vehicles, characterized in that: It includes a power battery module (1), a power distribution module (PDU), a positive temperature coefficient thermistor discharge circuit module (PTC), an on-board charging module (2), a microcontroller discharge circuit module (MCU), and a drive motor module (MOTOR); the power battery module (1) is connected to the power distribution module (PDU); the power distribution module (PDU) is connected to the positive temperature coefficient thermistor discharge circuit module (PTC), the on-board charging module (2), and the microcontroller discharge circuit module (MCU) respectively; the microcontroller discharge circuit module (MCU) is connected to the drive motor module (MOTOR).

2. The parallel discharge device and method for electric vehicles as described in claim 1, characterized in that: The power battery module (1) transmits the processed power to the power distribution module (PDU); the power distribution module (PDU) distributes the power to the positive temperature coefficient thermistor discharge circuit module (PTC), the on-board charging module (2) and the microcontroller discharge circuit module (MCU) according to the system; the microcontroller discharge circuit module (MCU) transmits the drive command to the drive motor module (MOTOR).

3. The parallel discharge device and method for electric vehicles as described in claim 1, characterized in that: The power battery module (1) includes a power battery pack unit, a negative electrode contactor unit, an electric heating wire unit, a membrane heating contactor unit, a battery management unit (BMS), a precharge contactor unit, a precharge pack unit, a positive electrode contactor unit, and a fast-charging positive electrode contactor unit.

4. The parallel discharge device and method for electric vehicles as described in claim 1, characterized in that: The on-board charging module (2) includes an on-board charger unit (OBC) and a DC-DC converter unit (DCDC).

5. The parallel discharge device and method for electric vehicles as described in claim 1, characterized in that: The microcontroller discharge circuit module (MCU) and the positive temperature coefficient thermistor discharge circuit module (PTC) are connected in parallel across the high-voltage capacitor. The microcontroller discharge circuit module (MCU) includes an internally integrated insulated gate bipolar transistor (IGBT) circuit and a motor winding. The positive temperature coefficient thermistor discharge circuit module (PTC) includes a positive temperature coefficient thermistor heater and a control circuit. The positive temperature coefficient thermistor discharge circuit module (PTC) can recover and utilize the generated heat energy.

6. The parallel discharge device and method for electric vehicles as described in claim 1, characterized in that: The discharge triggering condition of the electric vehicle parallel discharge device is obtained by real-time acquisition of the high-voltage system status signal through the vehicle controller (VCU).

7. The parallel discharge device and method for electric vehicles as described in claim 5, characterized in that: When both the microcontroller discharge circuit module (MCU) and the positive temperature coefficient thermistor discharge circuit module (PTC) are normal, the main circuit discharges; when the microcontroller discharge circuit module (MCU) is abnormal, the positive temperature coefficient thermistor discharge circuit module (PTC) discharges; when the positive temperature coefficient thermistor discharge circuit module (PTC) is abnormal, the microcontroller discharge circuit module (MCU) discharges.

8. The parallel discharge device and method for electric vehicles as described in claim 6, characterized in that: The vehicle control unit (VCU) continuously monitors the voltage of the high-voltage capacitor, and stops discharging when the voltage drops to a safe threshold.

9. A parallel discharge device and method for an electric vehicle as described in any one of claims 1-8, characterized in that: The method includes the following steps: S1: When an electric vehicle finishes charging, is powered off normally, or is powered off due to a fault, input a discharge command to start the discharge operation. S2: When the main positive and main negative relays of the battery management unit (BMS) in the power battery module (1) reach the preset state; the microcontroller discharge circuit module (MCU) and the positive temperature coefficient thermistor discharge circuit module (PTC) have no discharge prohibition fault; the temperature values ​​of the microcontroller discharge circuit module (MCU), the positive temperature coefficient thermistor discharge circuit module (PTC), and the drive motor module (MOTOR) are below the preset threshold, discharge begins; S3: When both the microcontroller discharge circuit module (MCU) and the positive temperature coefficient thermistor discharge circuit module (PTC) are normal, the main circuit is discharged; when the positive temperature coefficient thermistor discharge circuit module (PTC) is abnormal, the microcontroller discharge circuit module (MCU) is discharged; when the microcontroller discharge circuit module (MCU) is abnormal, the positive temperature coefficient thermistor discharge circuit module (PTC) is discharged. S4: The microcontroller discharge circuit module (MCU) judges the critical signal threshold. When the critical signal threshold is normal, it enters S5; when it is abnormal, it enters S2. S5: The microcontroller discharge circuit module (MCU) enters the active discharge mode and controls the insulated gate bipolar transistor (IGBT) circuit to turn on; S6: Calculate the discharge power boundary based on temperature, and calibrate the direct-axis current and quadrature-axis current using the actual drive motor module (MOTOR); S7: The microcontroller discharge circuit module (MCU) identifies the setting signal, exits active discharge, enters S8 if the setting signal is identified, and enters S4 if the setting signal is not identified. S8: The operating mode of the microcontroller discharge circuit module (MCU) switches to off, and the insulated gate bipolar transistor (IGBT) circuit is turned off; S9: Positive temperature coefficient thermistor discharge circuit module (PTC) judges the critical signal threshold. When the critical signal threshold is normal, it enters S10; when it is abnormal, it enters S2. S10: The positive temperature coefficient thermistor discharge circuit module (PTC) enters the active discharge mode, controlling the insulated gate bipolar transistor circuit (IGBT) to turn on; S11: Calculate the discharge power boundary based on temperature and give the discharge current; S12: The positive temperature coefficient thermistor discharge circuit module (PTC) identifies the setting signal and exits active discharge. If the setting signal is identified, it enters S13; if it is not identified, it enters S9. S13: The positive temperature coefficient thermistor discharge circuit module (PTC) switches to the off mode, and the insulated gate bipolar transistor (IGBT) circuit turns off; S14: Discharge Termination Judgment: When the operating mode of the microcontroller discharge circuit module (MCU) switches to off, the operating mode of the positive temperature coefficient thermistor discharge circuit module (PTC) switches to off, and the voltage drops to the safety threshold, the discharge ends.

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