A MOSFET short-circuit fault detection system and method for a three-phase bridge inverter circuit

Abstract

The present invention discloses a MOSFET short-circuit fault detection system and method for a three-phase bridge inverter circuit, wherein the detection system comprises an input power supply, a pre-driver IC, an MCU module, an inverter, a phase relay, a motor, a pull-up resistor and a voltage divider circuit; the inverter is used to convert the input power supply into a frequency-variable alternating current for the power supply machine to drive the motor to rotate; the phase relay is connected in series to the three-phase input end of the motor, and the phase relay is used to cut off the output voltage and current of the inverter when the inverter fails. The present invention provides a MOSFET short-circuit fault detection system and method for a three-phase bridge inverter circuit, so that the system can detect the fault of the inverter MOSFET when powering on and initializing, and can also detect the corresponding fault of the phase relay MOSFET, and can accurately locate the single faulty MOSFET, so as to avoid the fault flowing into the driving link of the car, and ensure the personal safety of the driver and passengers.

Description

Technical Field

[0001] The invention relates to a MOSFET short-circuit fault detection system and method for a three-phase bridge inverter circuit. Background Art

[0002] At present, most of the brushless DC motor control solutions use a three-phase bridge inverter to output variable frequency AC to control the motor rotation. As the main component of the inverter, MOSFET works in a high-speed switching state, which can generally reach more than 20KHz. The extremely high voltage overshoot at the moment of opening and closing and the high heat generated by high-speed switching make MOSFET very easy to damage. In addition, the reverse electromotive force generated by the high-speed rotation of the motor can easily cause the MOSFET to break down. After the MOSFET breaks down, the vehicle DC power supply will be directly loaded to the motor coil, causing the motor coil current to be too large, resulting in huge heat generation in a short period of time or even combustion, which can easily cause major traffic accidents.

[0003] Most of the existing technical solutions for MOSFET fault detection use series current detection resistors to detect the three-phase current of the motor. When a phase current is detected to be too large or too small, the output of the inverter is cut off by the phase relay to prevent further motor jamming or coil burnout. However, this detection method is only applicable to the operation of the motor. As important safety components of the car, the electric power steering and electric power brake system will cause the power to fail suddenly when the inverter is turned off during driving, making it difficult for the driver to control the vehicle, especially at high speeds. Traffic accidents are very likely to occur.

[0004] like Figure 1 In the prior art shown, the whole system consists of six parts: power input, pre-driver IC, inverter, phase relay, motor, and phase current monitoring. The inverter is composed of six MOSFETs to form a bridge circuit, and the phase relay is composed of three MOSFETs connected in series to the three-phase input of the motor. Terminal voltage monitoring collects the motor terminal voltage through ADC and provides it to the single-chip microcomputer. The inverter is mainly used to drive the DC brushless motor to rotate, and the input DC 12V voltage is converted into variable frequency AC power for the power supply machine through MOSFET high-speed switching. The pre-driver IC controls the six MOSFETs of the inverter to switch according to a certain timing logic strategy by receiving the PWM instruction of the MCU. The phase relay is mainly used to cut off its output voltage and current when the inverter fails, ensuring that the motor does not malfunction and the motor coil is not burned. Phase current monitoring detects the current of the three phases U, V, and W of the inverter through the current sampling resistor, and inputs it to the MCU for monitoring and judging whether the inverter and the motor are working normally.

[0005] In the usual solution, when the system is powered on and initialized, the pre-driver IC does not work, and all MOSFETs in the inverter are in the OFF state. After the system is initialized, the pre-driver IC starts to work according to the MCU PWM instruction to control the MOSFET to switch on and off. Therefore, when the system is powered on and initialized, if a single MOSFET in the upper or lower bridge of the inverter is in a short-circuit fault state, or any phase relay MOSFET is in a short-circuit fault state, the fault cannot be detected by the current sampling resistor.

[0006] Therefore, how to detect the inverter's MOSFET fault when the vehicle is started to avoid power loss during driving is an urgent problem to be solved. Summary of the invention

[0007] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a MOSFET short-circuit fault detection system and method for a three-phase bridge inverter circuit, so that the system can detect the fault of the inverter MOSFET during power-on and initialization, and can also detect the corresponding fault of the phase relay MOSFET, and can accurately locate a single faulty MOSFET to avoid the fault flowing into the vehicle driving link, thereby ensuring the personal safety of the driver and passengers.

[0008] In order to solve the above technical problems, the technical solution of the present invention is:

[0009] On one hand, the present invention provides a MOSFET short-circuit fault detection system for a three-phase bridge inverter circuit, which includes an input power supply, a pre-driver IC, an MCU module, an inverter, a phase relay, a motor, a pull-up resistor and a voltage divider circuit;

[0010] The inverter is used to convert the input power into variable frequency alternating current for the power supply machine to drive the motor to rotate;

[0011] The phase relay is connected in series to the three-phase input terminal of the motor, and the phase relay is used to cut off the output voltage and current of the inverter when a fault occurs in the inverter;

[0012] The MCU module monitors the motor terminal voltage through a voltage divider circuit;

[0013] The pre-driver IC controls the inverter to perform switching operation according to a sequential logic strategy by receiving a PWM instruction from the MCU;

[0014] A single phase of the motor is connected to an input power supply via a pull-up resistor.

[0015] Furthermore, the inverter is a bridge circuit composed of six MOSFETs.

[0016] Furthermore, the phase relay includes three MOSFETs respectively connected in series to the three-phase input terminals of the motor.

[0017] Another aspect of the present invention provides a detection method of a MOSFET short-circuit fault detection system of a three-phase bridge inverter circuit, comprising:

[0018] Step S1, when the three-phase bridge inverter is powered on and the MOSFET is not faulty, the normal state voltage of the motor terminal is monitored by the MCU module;

[0019] Step S2: After the three-phase bridge inverter is powered on, the MCU module monitors the voltage of the motor terminal in real time, and compares the real-time monitoring voltage monitored by the MCU module with the normal state voltage;

[0020] Step S3: If the real-time monitoring voltage detected by the MCU module is different from the normal state voltage, it is determined that a short circuit fault occurs in the MOSFET of the three-phase bridge inverter circuit.

[0021] Furthermore, the short-circuit fault of the MOSFET of the three-phase bridge inverter circuit in step S3 includes a short-circuit fault of the inverter upper bridge MOSFET and phase relay and a short-circuit fault of the inverter lower bridge MOSFET.

[0022] Furthermore, the method for detecting a phase relay short circuit fault specifically comprises the following steps:

[0023] When the MOSFET is not faulty after power-on, the inverter MOSFETs are in the OFF state, the phase relays are in the OFF state, the pre-driver IC is in the off state, and the motor terminal voltage monitored by the MCU module is equal to the ground. At this time, the real-time monitoring voltage of the motor terminal monitored by the MCU module is the normal voltage of the system power-on. The normal voltage X1 of the system power-on is:

[0024]

[0025] Among them, ΔADC is the ADC reading error, Vmcu is the MCU power supply voltage, m is the number of ADC sampling bits, R1 is the upper voltage divider resistor, R2 is the lower voltage divider resistor, and R3 is the pull-up resistor;

[0026] When the U-phase relay is short-circuited, the current flows through the pull-up resistor and the voltage divider circuit to the ground. At this time, the real-time monitoring voltage of the motor terminal detected by the MCU module is the phase relay short-circuit fault alarm value. The phase relay short-circuit fault alarm value Y1 is:

[0027]

[0028] Wherein, ΔADC is the ADC reading error, Vmcu is the MCU power supply voltage, m is the number of ADC sampling bits, R1 is the upper voltage divider resistor, R2 is the lower voltage divider resistor, R3 is the pull-up resistor, Vin is the input power supply voltage, and ΔVmcu is the MCU power supply voltage error;

[0029] When the V-phase relay or the W-phase relay is short-circuited, the current passes through the pull-up resistor to the motor coil and then to the ground through the voltage divider circuit. At this time, the real-time monitoring voltage of the motor terminal detected by the MCU module is equal to the short-circuit fault alarm value Y1 of the phase relay.

[0030] Furthermore, the inverter upper bridge MOSFET short circuit fault detection method specifically comprises the following steps:

[0031] When the inverter upper bridge MOSFET is short-circuited, the current passes through the short-circuited MOSFET and the voltage divider circuit to the ground. At this time, the real-time monitoring voltage of the motor terminal detected by the MCU module is the inverter upper bridge MOSFET short-circuit fault alarm value. The inverter upper bridge MOSFET short-circuit fault alarm value Y2 is:

[0032]

[0033] Y2>Y1;

[0034] Among them, ΔADC is the ADC reading error, Vmcu is the MCU power supply voltage, m is the ADC sampling bit number, R1 is the upper voltage divider resistor, R2 is the lower voltage divider resistor, Vin is the input power supply voltage, and ΔVmcu is the MCU power supply voltage error.

[0035] Furthermore, the detection conditions of the inverter upper bridge MOSFET short-circuit fault and the phase relay short-circuit fault are the same, and the real-time monitoring voltage value of the motor terminal monitored by the MCU module is assumed to be V0;

[0036] When V0<X1, the system is judged to be normal;

[0037] When X1≤V0<Y1, the system determines that a phase relay short circuit fault occurs;

[0038] When Y1≤V0≤Y2, the system determines that a short circuit fault has occurred in the inverter upper bridge MOSFET.

[0039] Further, the method for detecting the short-circuit fault of the inverter lower bridge MOSFET in step S3 specifically comprises the following steps:

[0040] When the system is initialized after power-on and the MOSFET is not faulty, the inverter MOSFETs are in the OFF state, the phase relays are in the OFF state, the pre-driver IC is in the ON state, but no drive command is issued. At this time, the real-time monitoring voltage of the motor terminal detected by the MCU module is the normal voltage for system initialization. The normal voltage for system initialization X2 is:

[0041]

[0042] Where Ir is the pre-driver IC leakage current, ΔADC is the ADC reading error, Vmcu is the MCU power supply voltage, m is the ADC sampling bit number, R1 is the upper voltage divider resistor, R2 is the lower voltage divider resistor, Vin is the input power supply voltage, ΔVmcu is the MCU power supply voltage error,

[0043] When the inverter lower bridge MOSFET short-circuit fault occurs, the leakage current of the pre-driver IC flows into the ground through the short-circuited MOSFET. At this time, the real-time monitoring voltage of the motor terminal detected by the MCU module is the inverter lower bridge MOSFET short-circuit fault alarm value. The inverter lower bridge MOSFET short-circuit fault alarm value Y3 is:

[0044]

[0045] Among them, ΔADC is the ADC reading error, Vmcu is the MCU power supply voltage, n is the number of AD conversion bits, R1 is the upper voltage divider resistor, and R2 is the lower voltage divider resistor.

[0046] Further, when the pre-driver IC is turned on, the inverter lower bridge MOSFET short-circuit fault detection is performed, and the real-time monitoring voltage value of the motor terminal monitored by the MCU module is assumed to be V0;

[0047] When Y3≤V0<X2, the system determines that a short circuit fault occurs in the inverter lower bridge MOSFET.

[0048] By adopting the above technical solution, the present invention provides a detection method for the following two fault conditions of the brushless DC motor control inverter:

[0049] 1. The inverter upper bridge MOSFET and phase relay are short-circuited.

[0050] 2. The inverter lower bridge MOSFET is short-circuited.

[0051] The phase voltage of the motor's three-phase input terminals U, V, and W is input to the MCU through a voltage divider circuit for voltage monitoring to determine whether the inverter and motor are operating normally. By adding a pull-up resistor to the single-phase motor to connect the power supply, the monitoring voltage is different from the monitoring voltage in the normal state when a fault occurs, thereby detecting the fault. The difference between the monitoring voltage in the normal state and the fault state caused by the leakage current when the pre-driver IC is turned on can be used to detect the occurrence of a fault. The inverter's MOSFET fault is detected when the vehicle is started, thereby avoiding the loss of power assistance during driving and ensuring the personal safety of the driver and passengers. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 A schematic diagram of a motor controller system of the prior art of the present invention;

[0053] Figure 2 It is a principle block diagram of a MOSFET short-circuit fault detection system of a three-phase bridge inverter circuit of the present invention;

[0054] Figure 3 It is an equivalent circuit of the normal state of the system of the present invention after power-on;

[0055] Figure 4 It is an equivalent circuit of the U-phase relay of the present invention when it fails to short-circuit;

[0056] Figure 5 It is an equivalent circuit of the V and W phase relays of the present invention when they are short-circuited;

[0057] Figure 6 The equivalent circuit of the inverter upper bridge MOSFET of the present invention when it is short-circuited;

[0058] Figure 7 An equivalent circuit of a normal state when the system of the present invention is initialized;

[0059] Figure 8 This is an equivalent circuit of the inverter lower bridge MOSFET when it fails in a short circuit. DETAILED DESCRIPTION

[0060] In order to make the contents of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments in conjunction with the accompanying drawings.

[0061] Embodiment 1

[0062] like Figure 2 As shown, this embodiment provides a MOSFET short-circuit fault detection system for a three-phase bridge inverter circuit, which includes an input power supply, a pre-driver IC, an MCU module, an inverter, a phase relay, a motor, a pull-up resistor and a voltage divider circuit.

[0063] Specifically, the inverter is used to convert the DC 12V voltage of the input power supply into variable-frequency AC power for the power supply machine through MOSFET high-speed switching, driving the motor to rotate. The inverter is a bridge circuit composed of six MOSFETs.

[0064] The phase relay includes three MOSFETs connected in series to the three-phase input terminals of the motor, and the three MOSFETs are connected in series to the U, V, and W input terminals of the three-phase motor. The phase relay is connected in series to the three-phase input terminals of the motor. The phase relay is used to cut off the output voltage and current of the inverter when a fault occurs in the inverter, to ensure that the motor does not malfunction and the motor coil is not burned.

[0065] The MCU module monitors the motor terminal voltage through a voltage divider circuit, and AD sampling is performed by the ADC inside the MCU module. The voltage divider circuit is composed of an upper voltage divider resistor R1 and a lower voltage divider resistor R2 connected in series.

[0066] The pre-driver IC receives the PWM command from the MCU and controls the six MOSFETs of the inverter to switch according to a certain timing logic strategy.

[0067] A single phase of the motor is connected to the input power supply through a pull-up resistor. When a short-circuit fault occurs in the MOSFET in the phase relay, the power current flows through the motor coil through the pull-up resistor and then flows through the short-circuited MOSFET, generating a voltage on the voltage divider circuit, thereby detecting the short-circuit state.

[0068] like Figure 2 As shown, in this embodiment, a pull-up resistor R3 is added to the single-phase input end of the motor to connect the power supply, and the motor terminal voltage is sampled and collected by the MCU module ADC. When a phase relay short-circuit fault occurs, the power current flows through the motor coil through the pull-up resistor, and then flows through the short-circuited phase relay MOSFET; when the inverter upper bridge MOSFET is short-circuited, the current passes through the short-circuited inverter upper bridge MOSFET through the voltage divider circuit to the ground, and a voltage is generated on the voltage divider circuit, so that the short-circuit state can be detected.

[0069] In addition, when the pre-driver IC is powered but not outputting, its output pin will generate a small leakage current. Based on this characteristic, the present invention will power the pre-driver IC when the system is powered on and initialized, but the MCU will not send a PWM instruction to make it work. The voltage generated by the leakage current on the sampling resistor is used to determine whether the inverter lower bridge MOSFET is short-circuited.

[0070] Embodiment 2

[0071] This embodiment provides a detection method of a MOSFET short-circuit fault detection system of a three-phase bridge inverter circuit, which includes:

[0072] Step S1, when the three-phase bridge inverter is powered on and the MOSFET is not faulty, the normal state voltage of the motor terminal is monitored by the MCU module;

[0073] Step S2: After the three-phase bridge inverter is powered on, the MCU module monitors the voltage of the motor terminal in real time, and compares the real-time monitoring voltage monitored by the MCU module with the normal state voltage;

[0074] Step S3: If the real-time monitoring voltage detected by the MCU module is different from the normal state voltage, it is determined that a short circuit fault occurs in the MOSFET of the three-phase bridge inverter circuit.

[0075] In step S3 of this embodiment, the short-circuit fault of the MOSFET of the three-phase bridge inverter circuit includes a short-circuit fault of the inverter upper bridge MOSFET and phase relay and a short-circuit fault of the inverter lower bridge MOSFET.

[0076] Specifically, the method for detecting a phase relay short circuit fault comprises the following steps:

[0077] Figure 3 This is the equivalent circuit when the MOSFET is not faulty after power-on. When the MOSFET is not faulty after power-on, the inverter MOSFETs are in the OFF state, the phase relays are in the OFF state, the pre-driver IC is in the off state, and the motor terminal voltage monitored by the MCU module is equal to the ground. Considering the ADC reading error and the error caused by the LSB conversion, the real-time monitoring voltage of the motor terminal monitored by the MCU module is the normal voltage of the system power-on. The normal voltage X1 of the system power-on is:

[0078]

[0079] Among them, ΔADC is the ADC reading error, Vmcu is the MCU power supply voltage, m is the number of ADC sampling bits, R1 is the upper voltage divider resistor, R2 is the lower voltage divider resistor, and R3 is the pull-up resistor;

[0080] Figure 4 This is the equivalent circuit when the U-phase relay is short-circuited. When the U-phase relay is short-circuited, the current flows through the pull-up resistor and the voltage divider circuit to the ground. At this time, the real-time monitoring voltage of the motor terminal detected by the MCU module is the phase relay short-circuit fault alarm value. The phase relay short-circuit fault alarm value Y1 is:

[0081]

[0082] Wherein, ΔADC is the ADC reading error, Vmcu is the MCU power supply voltage, m is the number of ADC sampling bits, R1 is the upper voltage divider resistor, R2 is the lower voltage divider resistor, R3 is the pull-up resistor, Vin is the input power supply voltage, and ΔVmcu is the MCU power supply voltage error;

[0083] Figure 5 This is the equivalent circuit when the V-phase or W-phase relay is short-circuited. When the V-phase relay or the W-phase relay is short-circuited, the current flows through the pull-up resistor to the motor coil and then to the ground through the voltage divider circuit. Compared with the pull-up resistor, the internal resistance of the motor coil can be ignored. At this time, the real-time monitoring voltage of the motor terminal detected by the MCU module is equal to the phase relay short-circuit fault alarm value Y1.

[0084] Specifically, the method for detecting the short-circuit fault of the inverter upper bridge MOSFET comprises the following steps:

[0085] Figure 6 This is the equivalent circuit when the inverter upper bridge MOSFET is short-circuited. When the inverter upper bridge MOSFET is short-circuited, the current passes through the short-circuited MOSFET and the voltage divider circuit to the ground. At this time, the real-time monitoring voltage of the motor terminal monitored by the MCU module is the inverter upper bridge MOSFET short-circuit fault alarm value. The inverter upper bridge MOSFET short-circuit fault alarm value Y2 is:

[0086]

[0087] Y2>Y1;

[0088] Compared with the real-time monitoring voltage Y1 monitored when the phase relay is short-circuited, the real-time monitoring voltage Y2 when the upper bridge MOSFET is short-circuited is much higher;

[0089] Among them, ΔADC is the ADC reading error, Vmcu is the MCU power supply voltage, m is the ADC sampling bit number, R1 is the upper voltage divider resistor, R2 is the lower voltage divider resistor, Vin is the input power supply voltage, and ΔVmcu is the MCU power supply voltage error.

[0090] In summary, the detection conditions of the inverter upper bridge MOSFET short-circuit fault and the phase relay short-circuit fault are the same. Assume that the real-time monitoring voltage value of the motor terminal monitored by the MCU module is V0;

[0091] When V0<X1, the system is judged to be normal;

[0092] When X1≤V0<Y1, the system determines that a phase relay short circuit fault occurs;

[0093] When Y1≤V0≤Y2, the system determines that a short circuit fault has occurred in the inverter upper bridge MOSFET.

[0094] Specifically, the method for detecting the short-circuit fault of the inverter lower bridge MOSFET in step S3 specifically includes the following steps:

[0095] Figure 7This is the equivalent circuit of the inverter and motor in the normal state when the system is initialized. When the system is initialized after power-on and the MOSFET is not faulty, the MOSFETs of the inverter are OFF, the phase relays are OFF, and the pre-driver IC is in the ON state, but no drive command is issued. At this time, the real-time monitoring voltage of the motor terminal detected by the MCU module is the normal voltage for system initialization. The normal voltage for system initialization X2 is:

[0096]

[0097] Where Ir is the pre-driver IC leakage current, ΔADC is the ADC reading error, Vmcu is the MCU power supply voltage, m is the ADC sampling bit number, R1 is the upper voltage divider resistor, R2 is the lower voltage divider resistor, Vin is the input power supply voltage, ΔVmcu is the MCU power supply voltage error,

[0098] Figure 8 This is the equivalent circuit when the inverter lower bridge short-circuit fault occurs. When the inverter lower bridge MOSFET short-circuit fault occurs, the leakage current of the pre-driver IC flows into the ground through the short-circuited MOSFET. At this time, the real-time monitoring voltage of the motor terminal detected by the MCU module is the inverter lower bridge MOSFET short-circuit fault alarm value. The inverter lower bridge MOSFET short-circuit fault alarm value Y3 is:

[0099]

[0100] Among them, ΔADC is the ADC reading error, Vmcu is the MCU power supply voltage, n is the number of AD conversion bits, R1 is the upper voltage divider resistor, and R2 is the lower voltage divider resistor.

[0101] In summary, the inverter lower bridge MOSFET short-circuit fault detection is performed when the pre-driver IC is turned on, and the real-time monitoring voltage value of the motor terminal monitored by the MCU module is set to V0;

[0102] When Y3≤V0<X2, the system determines that a short circuit fault occurs in the inverter lower bridge MOSFET.

[0103] The specific embodiments described above further illustrate the technical problems, technical solutions and beneficial effects solved by the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A MOSFET short-circuit fault detection method for a three-phase bridge inverter circuit, characterized in that: It includes: Step S1, when the three-phase bridge inverter is powered on and the MOSFET is not faulty, the normal state voltage of the motor terminal is monitored by the MCU module; Step S2: After the three-phase bridge inverter is powered on, the MCU module monitors the voltage of the motor terminal in real time, and compares the real-time monitoring voltage monitored by the MCU module with the normal state voltage; Step S3: If the real-time monitoring voltage detected by the MCU module is different from the normal state voltage, it is determined that a short circuit fault occurs in the MOSFET of the three-phase bridge inverter circuit; The short-circuit fault of the MOSFET of the three-phase bridge inverter circuit in step S3 includes a short-circuit fault of the upper bridge MOSFET and the phase relay of the inverter and a short-circuit fault of the lower bridge MOSFET of the inverter; The method for detecting a phase relay short-circuit fault specifically comprises the following steps: When the MOSFET is not faulty after power-on, the inverter MOSFETs are in the OFF state, the phase relays are in the OFF state, the pre-driver IC is in the off state, and the motor terminal voltage monitored by the MCU module is equal to the ground. At this time, the real-time monitoring voltage of the motor terminal monitored by the MCU module is the normal voltage of the system power-on. The normal voltage X1 of the system power-on is: Among them, ΔADC is the ADC reading error, Vmcu is the MCU power supply voltage, m is the number of ADC sampling bits, R1 is the upper voltage divider resistor, R2 is the lower voltage divider resistor, and R3 is the pull-up resistor; When the U-phase relay is short-circuited, the current flows through the pull-up resistor and the voltage divider circuit to the ground. At this time, the real-time monitoring voltage of the motor terminal detected by the MCU module is the phase relay short-circuit fault alarm value. The phase relay short-circuit fault alarm value Y1 is: Wherein, ΔADC is the ADC reading error, Vmcu is the MCU power supply voltage, m is the number of ADC sampling bits, R1 is the upper voltage divider resistor, R2 is the lower voltage divider resistor, R3 is the pull-up resistor, Vin is the input power supply voltage, and ΔVmcu is the MCU power supply voltage error; When the V-phase relay or the W-phase relay is short-circuited, the current passes through the pull-up resistor to the motor coil and then to the ground through the voltage divider circuit. At this time, the real-time monitoring voltage of the motor terminal detected by the MCU module is equal to the short-circuit fault alarm value Y1 of the phase relay; The method for detecting a short-circuit fault of an inverter upper bridge MOSFET specifically comprises the following steps: When the inverter upper bridge MOSFET is short-circuited, the current passes through the short-circuited MOSFET and the voltage divider circuit to the ground. At this time, the real-time monitoring voltage of the motor terminal detected by the MCU module is the inverter upper bridge MOSFET short-circuit fault alarm value. The inverter upper bridge MOSFET short-circuit fault alarm value Y2 is: Y2>Y1; Wherein, ΔADC is the ADC reading error, Vmcu is the MCU power supply voltage, m is the number of ADC sampling bits, R1 is the upper voltage divider resistor, R2 is the lower voltage divider resistor, Vin is the input power supply voltage, and ΔVmcu is the MCU power supply voltage error; The detection conditions of the inverter upper bridge MOSFET short-circuit fault and the phase relay short-circuit fault are the same, and the real-time monitoring voltage value of the motor terminal monitored by the MCU module is assumed to be V0; When V0<X1, the system is judged to be normal; When X1≤V0<Y1, the system determines that a phase relay short circuit fault occurs; When Y1≤V0≤Y2, the system determines that a short circuit fault has occurred in the inverter upper bridge MOSFET; The method for detecting the short-circuit fault of the inverter lower bridge MOSFET in step S3 specifically comprises the following steps: When the system is initialized after power-on and the MOSFET is not faulty, the inverter MOSFETs are in the OFF state, the phase relays are in the OFF state, the pre-driver IC is in the ON state, but no drive command is issued. At this time, the real-time monitoring voltage of the motor terminal detected by the MCU module is the normal voltage for system initialization. The normal voltage for system initialization X2 is: Where Ir is the pre-driver IC leakage current, ΔADC is the ADC reading error, Vmcu is the MCU power supply voltage, m is the ADC sampling bit number, R1 is the upper voltage divider resistor, R2 is the lower voltage divider resistor, Vin is the input power supply voltage, ΔVmcu is the MCU power supply voltage error, When the inverter lower bridge MOSFET short-circuit fault occurs, the leakage current of the pre-driver IC flows into the ground through the short-circuited MOSFET. At this time, the real-time monitoring voltage of the motor terminal detected by the MCU module is the inverter lower bridge MOSFET short-circuit fault alarm value. The inverter lower bridge MOSFET short-circuit fault alarm value Y3 is: Among them, ΔADC is the ADC reading error, Vmcu is the MCU power supply voltage, n is the number of AD conversion bits, R1 is the upper voltage divider resistor, and R2 is the lower voltage divider resistor; When the pre-driver IC is turned on, the inverter lower bridge MOSFET short-circuit fault detection is performed, and the real-time monitoring voltage value of the motor terminal monitored by the MCU module is set to V0; When Y3≤V0<X2, the system determines that a short circuit fault occurs in the inverter lower bridge MOSFET.

Images