A method and system for high voltage power-off of electric vehicle in limp mode

Abstract

The present invention relates to the technical field of electric vehicles, and proposes a method and system for high-voltage power-off of an electric vehicle in limp mode. The power-off function, which is crucial to the safe operation of the electric vehicle, is controlled by a dedicated limp mode circuit, thereby avoiding the use of an expensive MCU and simplifying the difficulty of software design. The circuit has strong adaptability and can be used for limp mode shutdown control of other key relays or contactors. The analog circuit and delay control are used to leave enough time for the user to confirm the power-off operation, thereby avoiding the safety hazard of power loss caused by erroneous triggering of the power-off.

Description

Technical Field

[0001] The present disclosure relates to the technical field related to electric vehicles, and more specifically, to a method and system for high-voltage power-down of an electric vehicle in a limp home mode. Background Art

[0002] The statements in this section merely provide background information related to the present disclosure and do not necessarily constitute prior art.

[0003] In electric vehicles, the vehicle control unit (VCU) generally controls the on and off of the main positive relay and the main negative relay of the high-voltage circuit to realize the power on and off of the high-voltage electrical system. When the main controller chip (MCU) of the VCU operates normally, the high-voltage circuit relay is controlled according to the established logic, but when the MCU fails, the power-off function cannot be executed according to the normal control logic, which brings great hidden dangers to the safe operation of electric vehicles.

[0004] The industry generally adopts the method of designing redundant circuits to solve the problem of MCU failure, that is, using two MCUs. When one of the MCUs fails, the other MCU takes over the key control tasks. However, this method is not only costly, but also increases the difficulty of software design. For the specific problem that the key relay cannot be shut down due to MCU failure, there is a second solution, which is to use a watchdog monitoring chip to monitor the operating status of the MCU and design a special relay shutdown circuit. The existing automobile limp home control circuit uses a system basis chip SBC with a watchdog monitoring function to monitor the operation of the MCU. When the MCU cannot feed the dog, the SBC outputs a low-level valid "limp home enable signal" to enable the limp home control circuit, and controls the two limp output signals through two input signals.

[0005] The inventors found that the existing limp home control method for automobiles has the following deficiencies: First, the input signal of the limp home control circuit is a digital signal, which is easily interfered with under harsh working conditions and complex automobile electromagnetic environments. Second, the limp home control logic is too simple, and the limp home output is triggered when the digital input signal is valid, which can easily cause misoperation. In the case of MCU failure, if the high-voltage power-down operation is mistakenly triggered, it will directly cause the electric vehicle to lose power, posing a huge safety hazard. Summary of the invention

[0006] In order to solve the above problems, the present invention proposes a method and system for high-voltage power-off of an electric vehicle in limp mode. The power-off function, which is crucial to the safe operation of the electric vehicle, is controlled by a dedicated limp mode circuit, thereby avoiding the use of an expensive MCU and simplifying the difficulty of software design. The circuit has strong adaptability and can be used for limp mode shutdown control of other key relays or contactors. The analog circuit and delay control are used to leave enough time for the user to confirm the power-off operation, thereby avoiding the safety hazard of power loss caused by false triggering of the power-off.

[0007] In order to achieve the above objectives, the present disclosure adopts the following technical solutions:

[0008] One or more embodiments provide a method for powering off high voltage of an electric vehicle in limp mode, comprising the following steps:

[0009] Monitor the operating status of the vehicle controller's main control chip MCU and the status of the vehicle's start / stop switch;

[0010] When the MCU is operating normally, the on and off of the controlled components are controlled by the vehicle MCU and the normal mode high-voltage relay control circuit according to the state of the vehicle start-stop switch;

[0011] When the MCU fails, the MCU's control over the high-voltage circuit relay is disconnected through the limp mode pin of the SBC, and the high-voltage main positive relay is shut down by the limp mode high-voltage power-off confirmation circuit and the limp mode high-voltage relay control circuit, so that the controlled component is shut down after the set time of receiving the shutdown signal of the start-stop switch.

[0012] One or more embodiments provide a high voltage power-off system for an electric vehicle in limp mode, including a start-stop switch three-state detection circuit I, a limp mode high voltage power-off confirmation circuit II, a normal mode high voltage relay control circuit III, a limp mode high voltage relay control circuit IV, and an internal power supply enabling control circuit V;

[0013] The start-stop switch three-state detection circuit I is used to detect the working state of the start-stop switch;

[0014] When the MCU is operating normally, the vehicle's internal power supply enabling control circuit V enables the power supply of the normal mode high-voltage relay control circuit III, and disables the power supply of the limp mode high-voltage power-down confirmation circuit II. The MCU and the normal mode high-voltage relay control circuit III control the on and off of the high-voltage main positive relay.

[0015] When the MCU fails, the internal power supply enable control circuit V enables the power supply of the limp mode high voltage power-off confirmation circuit II and disables the power supply of the normal mode high voltage relay control circuit III. The limp mode high voltage power-off confirmation circuit II and the limp mode high voltage relay control circuit IV control the shutdown of the high voltage main positive relay, so that the high voltage main positive relay is turned off after the start-stop switch is pressed for the set time.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] In the present disclosure, by adopting a limp-mode high-voltage power-off confirmation circuit and a limp-mode high-voltage relay control circuit, the power-off function, which is crucial for the safe operation of electric vehicles, avoids the use of expensive MCUs and simplifies the difficulty of software design. The use of delay control allows sufficient time for the user to confirm the power-off operation, avoiding the safety hazard of power loss caused by false triggering of the power-off.

[0018] The advantages of the present disclosure and the advantages of additional aspects will be described in detail in the following specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings constituting a part of the present disclosure are used to provide a further understanding of the present disclosure. The exemplary embodiments of the present disclosure and the description thereof are used to explain the present disclosure but do not constitute a limitation of the present disclosure.

[0020] Figure 1 is a flow chart of the overall method of the embodiment of the present disclosure;

[0021] Figure 2 A three-state detection circuit diagram of a start-stop switch according to an embodiment of the present disclosure;

[0022] Figure 3 A circuit diagram of a limp home mode high voltage power-on confirmation circuit according to an embodiment of the present disclosure;

[0023] Figure 4 The first setting parameter of the embodiment of the present disclosure is Figure 3 The voltage at C2 terminal is U c The change curve of

[0024] Figure 5 The setting parameters of the embodiment of the present disclosure are as follows: Figure 3 Unit step response curve of the transfer function of the RC network

[0025] Figure 6 A high voltage circuit relay control circuit diagram of an embodiment of the present disclosure;

[0026] Figure 7 An internal power supply enables a control circuit according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0027] The present disclosure is further described below in conjunction with the accompanying drawings and embodiments.

[0028] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present disclosure. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present disclosure belongs.

[0029] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present disclosure. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof. It should be noted that, in the absence of conflict, the various embodiments in the present disclosure and the features in the embodiments can be combined with each other. The embodiments will be described in detail below in conjunction with the accompanying drawings.

[0030] Example 1

[0031] In the technical solutions disclosed in one or more embodiments, Figure 1 As shown, a method for high voltage power-off of an electric vehicle in limp mode comprises the following steps:

[0032] Step 1: Monitor the operating status of the main control chip MCU of the vehicle controller and the status of the vehicle start-stop switch;

[0033] Step 2: When the MCU is operating normally, the on / off of the controlled component is controlled by the vehicle MCU and the normal mode high-voltage relay control circuit according to the state of the vehicle start / stop switch;

[0034] Step 3. When the MCU fails, the MCU's control over the high-voltage circuit relay is disconnected through the limp mode pin of the SBC, and the high-voltage main positive relay is shut down by the limp mode high-voltage power-off confirmation circuit and the limp mode high-voltage relay control circuit, so that the controlled component is shut down after the set time of receiving the shutdown signal of the start-stop switch.

[0035] Among them, the controlled component can be a high-voltage main positive relay of the vehicle, a key relay or contactor on the vehicle, and the limp home mode shutdown control of other key relays or contactors on the vehicle can be implemented.

[0036] In this embodiment, by adopting the limp mode high voltage power-off confirmation circuit and the limp mode high voltage relay control circuit, the power-off function, which is crucial for the safe operation of the electric vehicle, avoids the use of expensive MCUs and simplifies the difficulty of software design. The use of delay control allows sufficient time for the user to confirm the power-off operation, avoiding the safety hazard of power loss caused by false triggering of the power-off.

[0037] The above steps can be implemented by designing a circuit. In step 1, the operation of the MCU is monitored by an SBC with a watchdog monitoring function, and the start-stop switch is used as the input control signal of the high-voltage power-off function in the limp-mode. This embodiment provides a high-voltage power-off system for electric vehicles in limp-mode, such as Figure 2-Figure 7 As shown, the designed circuit may include: a start-stop switch three-state detection circuit I, a limp mode high voltage power-off confirmation circuit II, a normal mode high voltage relay control circuit III, a limp mode high voltage relay control circuit IV, and an internal power supply enable control circuit V.

[0038] In step 2, when the MCU operates normally, the vehicle internal power supply enabling control circuit V enables the power supply of the normal mode high-voltage relay control circuit III, and disables the power supply of the limp mode high-voltage power-down confirmation circuit II, and the MCU and the normal mode high-voltage relay control circuit III control the on and off of the high-voltage main positive relay;

[0039] In step 3, when the MCU fails, the internal power supply enable control circuit V enables the power supply of the limp mode high voltage power-off confirmation circuit II and disables the power supply of the normal mode high voltage relay control circuit III. The limp mode high voltage power-off confirmation circuit II and the limp mode high voltage relay control circuit IV control the shutdown of the high voltage main positive relay, so that the high voltage main positive relay is turned off after the start-stop switch is pressed for the set time.

[0040] The set time may be about 4 seconds.

[0041] In some embodiments, the start-stop switch three-state detection circuit I includes a start-stop switch circuit and a voltage-dividing current-limiting circuit, as shown in the circuit diagram. Figure 2 shown.

[0042] The start-stop switch circuit and the vehicle's physical switch button are integrated in the start-stop switch module and connected to the VCU through the SSBin interface. The signal line connecting the VCU to the start-stop switch is SSBin. The vehicle's physical switch button is specifically the start-stop switch of the vehicle, which controls the start-stop switch that powers on the vehicle.

[0043] Optionally, the start-stop switch circuit includes two resistors R4 and R5 connected in series, one end of which is grounded and the other end is connected to the VCU after being connected in series, and the other end is grounded, and the start-stop switch is connected in parallel at both ends of one of the resistors.

[0044] The voltage division and current limiting circuit can be set in the VCU. After the output signal of the SSBin interface is voltage divided and current limited, it is connected to the ADC pin of the MCU through ADin, and the three states of the start-stop switch are determined by the MCU.

[0045] Optionally, the voltage-divider current-limiting circuit includes a first resistor R1 and a second resistor R2 connected in series, and also includes a first capacitor C1 and a third resistor R3. The connection point of the first resistor R1 and the second resistor R2 is connected to the VCU through an SSBin interface. The first capacitor C1 and the third resistor R3 are connected in series and connected to both ends of the second resistor R2. The connection point of the first capacitor C1 and the third resistor R3 is grounded, and the connection point of the third resistor R3 and the second resistor R2 is the output terminal ADin of the voltage-divider current-limiting circuit.

[0046] When the start-stop switch is in the input disconnect, pressed, and popped-up states, the nominal voltage value of SSBin is recorded as V open 、V press 、V release By reasonably selecting the values ​​of resistors R1, R2, R3, R4, and R5, V open 、V press 、V release The following relations are satisfied:

[0047] V press (1±0.2) <V release (1±0.2) <V open ·(1±0.2)(1)

[0048] The R1, R2, R3, R4, and R5 are ordinary resistors with an accuracy of ±5%, and the resistance values ​​are recorded as R1, R2, R3, R4, and R5 respectively. The nominal voltage value is the voltage value of SSBin when R1, R2, R3, R4, and R5 take the nominal resistance value.

[0049] The ADin voltage value is recorded as V ssb_mcu , SSBin voltage value is recorded as V ssb , the two satisfy the following relationship:

[0050]

[0051] The MCU determines the three states of the start-stop switch based on the analog-to-digital conversion result of ADin and the magnitude relationship between the start-stop switch input disconnection, pressing, and pop-up states. The switch signal is transmitted to the VCU through the wiring harness. If this wire is broken, it means the input is disconnected.

[0052] In some embodiments, the limp home mode high voltage power-off confirmation circuit II includes a start-stop switch press confirmation circuit and a high voltage power-off countdown circuit connected in sequence, and the circuit form is as follows: Figure 3 shown.

[0053] Optionally, the start-stop switch press confirmation circuit includes a first series resistor voltage divider circuit, a comparator U1 and a transistor Q1, the output end of the first series resistor R6, R7 voltage divider circuit is connected to the negative input end of the comparator U1, and the positive input end of the comparator U1 is connected to the SSBin interface of the VCU; the output end of the comparator U1 is connected to the base of the transistor Q1, and the state of the start-stop switch is determined by whether the transistor Q1 is turned on or off.

[0054] The input of the start-stop switch pressing confirmation circuit is SSBin. SSBin is connected to the positive input of the analog comparator U1, and the voltage obtained by dividing the Vcc through resistors R6 and R7 is connected to the negative input of U1. By reasonably selecting the resistance values ​​of R6 and R7, after the start-stop switch is pressed, the voltage at the positive input is lower than the voltage at the negative input, U1 outputs a low level, the transistor Q1 is turned on, and the collector is a high level. When the start-stop switch is in the input disconnection or pop-up state, the voltage at the positive input of U1 is higher than the voltage at the negative input, U1 outputs a high level, and Q1 is turned off.

[0055] In this embodiment, a start-stop switch circuit and a start-stop switch press confirmation circuit are provided, which can improve the accuracy of start-stop switch state detection, improve the accuracy of vehicle limp home power-off control, reduce system misoperation, and improve vehicle driving safety.

[0056] Optionally, the high voltage power-down countdown circuit can use a timer circuit or a circuit such as Figure 3 The circuit structure shown includes a resistor-capacitor network, a comparator U2, and a second series resistor voltage divider circuit. The input end of the resistor-capacitor network is connected to the output end of the start-stop switch press confirmation circuit, that is, the emitter of the triode Q1. The second series resistor voltage divider circuit and the resistor-capacitor network are respectively connected to the input end of the comparator U2. The output end of the comparator U2 is connected to the limp mode high-voltage relay control circuit IV.

[0057] The second series resistor voltage divider circuit includes two resistors R12 and R13 connected in series.

[0058] The RC network includes resistor R9, resistor R10, resistor R11 and capacitor C2. One end of resistor R9 is connected to resistor R10 and resistor R11 respectively, and the other end of R10 is grounded. Resistor R11 is connected to capacitor C2, and the other end of capacitor C2 is grounded. The voltage across capacitor C2 is the output voltage.

[0059] The input of the high-voltage power-down countdown circuit is the collector of the transistor Q1, which is connected to the positive input of the comparator U2 through the resistor-capacitor network, and the voltage obtained by dividing the Vlimp through the resistors R12 and R13 is connected to the negative input of U2. By reasonably selecting the resistance values ​​of R9, R10, R11, R12, and R13 and the capacitance value of capacitor C2, when the time interval set by pressing the start-stop switch is higher than the voltage of the negative input, such as about 4 seconds, U2 outputs a high level and is connected to the limp mode high-voltage relay control circuit through LimpCtrl. Figure 4 The following figure shows R9 = 47kΩ, R 10 =56kΩ, R 11 =130kΩ, R 12 =47kΩ, R 13 =47kΩ、C2=10uF、V limp =12v when C2 terminal voltage U c The change curve.

[0060] The input of the RC network is the collector voltage of Q1, and the output is the voltage U at the end of capacitor C2. c , its transfer function is:

[0061]

[0062] Among them, R9, R 10 , R 11 are the resistance values ​​of resistor R9, resistor R10, and resistor R11 respectively, and C2 is the capacitance value of C2. Figure 5 R9 = 47kΩ, R 10 =56kΩ, R 11 Unit step response curve of the RC network transfer function when C2 = 130kΩ and C2 = 10uF.

[0063] In this embodiment, Vcc is the power supply of the low voltage system of the electric vehicle, Vlimp is the power supply of the high voltage power-on confirmation circuit in limp mode, and the enabling and disabling of Vlimp is controlled by the internal power supply enabling control circuit V.

[0064] In some embodiments, the high-voltage circuit relay control circuit includes two parts: a normal mode high-voltage relay control circuit III and a limp mode high-voltage relay control circuit IV. Figure 6 shown.

[0065] Optionally, the normal mode high voltage relay control circuit III includes a normal mode on control circuit and a normal mode off control circuit.

[0066] The normal mode conduction control circuit includes transistor Q2, transistor Q3, diode D4 and transistor Q4. The base of transistor Q2 is connected to Mcu_on of MCU, that is, the conduction signal output terminal. The collector of transistor Q2 is connected to the base of transistor Q3. The collector of transistor Q3 is connected to Vnor power supply. In limp mode, Vnor power supply is disabled. The emitter of transistor Q3 is connected to the base of transistor Q4 through resistor R16. The collector of transistor Q4 is connected to the power supply Vcc. The emitter of transistor Q3 is connected to diode D4 through resistor R15. The cathode of diode D4 is the control output terminal Relay_ctrl.

[0067] The input signal of the normal mode conduction control circuit is Mcu_on from the MCU, and the output signal is Relay_ctrl, which controls the conduction of the high-voltage main positive relay.

[0068] When the MCU is operating normally, Vnor supplies power normally, and Mcu_on's control over the conduction of Relay_ctrl is valid. When Mcu_on is high, transistors Q2 and Q3 are turned on, Q3 collector outputs high level, unidirectional diode D4 is turned on, Relay_ctrl signal outputs high level, and the high-voltage main positive relay is turned on. When entering limp mode, Vnor power supply is disabled, Q3 is turned off, D4 is turned off, and Mcu_on's control over the conduction of Relay_ctrl is invalid.

[0069] Optional, such as Figure 6 As shown, the normal mode shutdown control circuit includes transistors Q5 and Q6 connected in sequence, and a unidirectional diode D3. The collector of the transistor Q6 is connected to the Vnor power supply. In the limp mode, the Vnor power supply is disabled, and the cathode of the unidirectional diode D3 is connected to the shutdown interlock circuit.

[0070] Specifically, the shutdown and conduction interlock circuit includes a transistor Q7, the collector of the transistor Q7 is connected to the control output terminal Relay_ctrl through a resistor R6, the collector of the transistor Q7 is connected to the power supply Vcc through a resistor R19, the collector of the transistor Q7 is connected to the base of the transistor Q7 through a diode D1, a resistor R18, a resistor R20, and a resistor R21 connected in series, the base and emitter of the transistor Q7 are directly connected through a capacitor C4, and the connection point of the resistor R20 and the resistor R21 is connected to the output end of the normal mode shutdown control circuit.

[0071] The input signal of the normal mode shutdown control circuit is Mcu_off from the MCU, and the output signal is Relay_ctrl.

[0072] In normal mode, the high-voltage main positive relay is controlled to be turned off. When the MCU is operating normally, Vnor is powered normally. When Mcu_off is high, transistors Q5 and Q6 are turned on, the collector of Q6 outputs a high level, the unidirectional diode D3 is turned on, the transistor Q7 is turned on, the collector outputs a low level, and the Relay_ctrl signal outputs a low level, turning off the high-voltage main positive relay.

[0073] When entering the limp home mode, the Vnor power supply is disabled, the transistor Q6 is turned off, the unidirectional diode D3 is turned off, and the shutdown control of Relay_ctrl by Mcu_off becomes invalid.

[0074] The limp mode high voltage relay control circuit IV is the limp mode shutdown control circuit. Figure 6 As shown, the input signal is LimpCtrl from the limp mode high voltage power-down confirmation circuit, and the output signal is Relay_ctrl. The limp mode high voltage relay control circuit IV includes a diode D2 connected to the turn-off interlock circuit of the normal mode high voltage relay control circuit III.

[0075] In limp mode, when LimpCtrl is at a high level, the unidirectional diode D2 is turned on, the transistor Q7 is turned on, the collector Q7 outputs a low level, the Relay_ctrl signal outputs a low level, and the high-voltage circuit relay is turned off.

[0076] In the limp mode of Q7, when LimpCtrl is at a low level, the unidirectional diodes D1 and D2 are cut off, the base of Q7 is kept at the on-state voltage through capacitor C4, Q7 continues to remain on, the Relay_ctrl signal outputs a low level, and the high-voltage circuit relay continues to remain off.

[0077] Optionally, when Relay_ctrl outputs a high level, the relay is turned on, and when Relay_ctrl outputs a low level, the relay is turned off.

[0078] Among them, Vnor is the power supply of the normal mode conduction control circuit and the normal mode shutdown control circuit, and the enabling and disabling of Vnor is controlled by the internal power supply enabling control circuit V.

[0079] In some embodiments, the internal power supply enable control circuit V controls the enabling and disabling of Vnor and Vlimp, such as Figure 7 shown.

[0080] The internal power supply enable control circuit V is implemented by a transistor on-off control circuit, including transistors Q8, Q9, Q10 and Q11 connected in sequence, the base of the transistor Q8 is connected to the limp mode pin Limp of the SBC, the collector of the transistor Q8 is connected to the power supply Vcc, the collector of the transistor Q8 is connected to the power supply output Vnor terminal through a resistor, the emitter of the transistor Q8 is connected to the base of the transistor Q9 through a resistor R22, and the collector of the transistor Q9 is connected to the power supply output Vnor terminal; the emitter of the transistor Q8 is connected to the base of the transistor Q10, the collector of the transistor Q10 is connected to the base of the transistor Q11, the collector of the transistor Q11 is connected to the power supply Vcc, the emitter of the transistor Q10 is connected to the emitter of the transistor Q11 through a capacitor C2, and the emitter of the transistor Q11 is the power supply output Vlimp terminal.

[0081] When the MCU is in normal operation, the limp mode pin Limp of the SBC outputs a high level, Q8, Q9, Q10, and Q11 are turned off, Vnor power supply is enabled, and Vlimp power supply is disabled; when in limp mode, Limp outputs a low level, Q8, Q9, Q10, and Q11 are turned on, Vlimp power supply is enabled, and Vnor power supply is disabled.

[0082] The above description is only a preferred embodiment of the present disclosure and is not intended to limit the present disclosure. For those skilled in the art, the present disclosure may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present disclosure shall be included in the protection scope of the present disclosure.

[0083] Although the above describes the specific implementation methods of the present disclosure in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present disclosure. Technical personnel in the relevant field should understand that on the basis of the technical solution of the present disclosure, various modifications or variations that can be made by those skilled in the art without creative work are still within the scope of protection of the present disclosure.

Claims

1. A high voltage power-down system for an electric vehicle in limp mode, characterized in that: It includes a start-stop switch three-state detection circuit I, a limp mode high-voltage power-down confirmation circuit II, a normal mode high-voltage relay control circuit III, a limp mode high-voltage relay control circuit IV and an internal power supply enabling control circuit V; The start-stop switch three-state detection circuit I is used to detect the working state of the start-stop switch; When the MCU is operating normally, the vehicle's internal power supply enabling control circuit V enables the power supply of the normal mode high-voltage relay control circuit III, and disables the power supply of the limp mode high-voltage power-down confirmation circuit II. The MCU and the normal mode high-voltage relay control circuit III control the on and off of the high-voltage main positive relay. When the MCU fails, the internal power supply enabling control circuit V enables the power supply of the limp mode high voltage power-off confirmation circuit II and disables the power supply of the normal mode high voltage relay control circuit III. The limp mode high voltage power-off confirmation circuit II and the limp mode high voltage relay control circuit IV control the shutdown of the high voltage main positive relay, so that the high voltage main positive relay is shut down after the start-stop switch is pressed for the set time. The start-stop switch three-state detection circuit I includes a start-stop switch circuit and a voltage-dividing and current-limiting circuit; The start-stop switch circuit includes two resistors connected in series, one end of the series circuit is grounded, and the other end is connected to the SSBin interface of the VCU, and the start-stop switch is connected in parallel to both ends of one of the resistors; The voltage division and current limiting circuit is set in the VCU, and the output signal of the SSBin interface is subjected to voltage division and current limiting; The limp mode high voltage power-off confirmation circuit II includes a start-stop switch pressing confirmation circuit and a high voltage power-off countdown circuit connected in sequence; The start-stop switch pressing confirmation circuit includes a first series resistor voltage divider circuit, a comparator U1 and a transistor Q1, wherein the output end of the first series resistor voltage divider circuit is connected to the negative input end of the comparator U1, and the positive input end of the comparator U1 is connected to the SSBin interface of the VCU; the output end of the comparator U1 is connected to the base of the transistor Q1, and the state of the start-stop switch is judged by whether the transistor Q1 is turned on or off; The normal mode high voltage relay control circuit III includes a normal mode on control circuit and a normal mode off control circuit; A normal mode conduction control circuit includes a transistor Q2, a transistor Q3, a diode D4 and a transistor Q4, wherein the base of the transistor Q2 is connected to the conduction signal output terminal Mcu_on of the MCU, the collector of the transistor Q2 is connected to the base of the transistor Q3, the collector of the transistor Q3 is connected to the Vnor power supply, and in the limp mode, the Vnor power supply is disabled, the emitter of the transistor Q3 is connected to the base of the transistor Q4 through a resistor R16, and the collector of the transistor Q4 is connected to the power supply Vcc; the emitter of the transistor Q3 is connected to the diode D4 through a resistor R15, and the cathode of the diode D4 is the control output terminal; The normal mode shutdown control circuit includes a transistor Q5 and a transistor Q6 connected in sequence, and a unidirectional diode D3. The collector of the transistor Q6 is connected to the Vnor power supply. In the limp mode, the Vnor power supply is disabled, and the cathode of the unidirectional diode D3 is connected to the shutdown interlock circuit. The turn-off interlock circuit includes a transistor Q7, the collector of the transistor Q7 is connected to the control output terminal through a resistor R6, the collector of the transistor Q7 is connected to the power supply Vcc through a resistor R19, the collector of the transistor Q7 is connected to the base of the transistor Q7 through a diode D1, a resistor R18, a resistor R20, and a resistor R21 connected in series, the base and the emitter of the transistor Q7 are directly connected through a capacitor C4, and the connection point of the resistor R20 and the resistor R21 is connected to the output terminal of the normal mode turn-off control circuit; The limp mode high voltage relay control circuit IV includes a diode D2 connected to the off-on interlock circuit of the normal mode high voltage relay control circuit III.

2. A high voltage power-down system for an electric vehicle in limp home mode as claimed in claim 1, characterized in that: The voltage-divider current-limiting circuit includes a first resistor R1 and a second resistor R2 connected in series, and also includes a first capacitor C1 and a third resistor R3. The connection point of the first resistor R1 and the second resistor R2 is connected to the VCU through an SSBin interface. The first capacitor C1 and the third resistor R3 are connected in series and connected to both ends of the second resistor R2. The connection point of the first capacitor C1 and the third resistor R3 is grounded, and the connection point of the third resistor R3 and the second resistor R2 is the output end of the voltage-divider current-limiting circuit.

3. A high voltage power-down system for an electric vehicle in limp home mode as claimed in claim 1, characterized in that: The detected start-stop switch states include input disconnection, pressed and pop-up states.

4. A high voltage power-down system for an electric vehicle in limp home mode as claimed in claim 1, characterized in that: The high voltage power-down countdown circuit uses a timer circuit; The high-voltage power-down countdown circuit includes a resistor-capacitor network, a comparator U2, and a second series resistor voltage divider circuit. The input end of the resistor-capacitor network is connected to the output end of the start-stop switch press confirmation circuit. The second series resistor voltage divider circuit and the resistor-capacitor network are respectively connected to the input end of the comparator U2. The output end of the comparator U2 is connected to the limp mode high-voltage relay control circuit IV.

5. The high voltage power-down system for electric vehicles in limp home mode as claimed in claim 1, characterized in that: The internal power supply enable control circuit V realizes the enable control of the power supply output through the transistor on-off control circuit.

6. A method for high-voltage power-off of an electric vehicle in limp mode based on a high-voltage power-off system of an electric vehicle in limp mode according to any one of claims 1 to 5, characterized in that: The steps include: Monitor the operating status of the vehicle controller's main control chip MCU and the status of the vehicle's start / stop switch; When the MCU is operating normally, the on and off of the controlled components are controlled by the vehicle MCU and the normal mode high-voltage relay control circuit according to the state of the vehicle start-stop switch; When the MCU fails, the MCU's control over the high-voltage circuit relay is disconnected through the limp mode pin of the SBC, and the high-voltage main positive relay is shut down by the limp mode high-voltage power-off confirmation circuit and the limp mode high-voltage relay control circuit, so that the controlled component is shut down after the set time of receiving the shutdown signal of the start-stop switch.

7. A method for powering off high voltage of an electric vehicle in limp home mode as claimed in claim 6, characterized in that: The controlled components are the vehicle's high-voltage main positive relay, related relays or contactors on the vehicle.

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