A method and circuit for detecting a failure of a power switching device of a motor controller

Abstract

The application belongs to the technical field of motor fault detection, and is especially a motor controller power switch device fault detection method and circuit, wherein the method comprises the following modes: static detection, after MCU power-on initialization, firstly execute the normal fault detection program, and simultaneously wait for C1 charging, after C1 charging is completed, the power switch device detection program starts to run, firstly carries out static self-checking, three-phase output voltage circuit sampling circuit will respectively send three-phase voltage output values after voltage division by R5 and R6 into the ADC of MCU for sampling, at this time, the MCU judges the voltage values of each phase, the three-phase output voltage all satisfies "less than VBUS-1V and greater than 0.1V", and is preliminarily judged to be normal, then the next dynamic detection is carried out, if not satisfied, continue to judge "any phase voltage is greater than VBUS-1V", the application can detect the fault of the power inverter unit before each start-up operation, and can accurately identify whether the controller power unit belongs to upper bridge fault or lower bridge fault, and in addition, whether the motor is open-phase can also be detected.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of motor fault detection, and particularly relates to a motor controller power switch device fault detection method and circuit. BACKGROUND

[0002] As shown in Figure 1 and Figure 2 In the prior art, motor controllers, such as electric vehicle controllers, passenger vehicle controllers, and frequency converters, adopt a three-phase inverter bridge topology to complete DC to AC conversion for driving a motor. The three-phase inverter bridge usually uses MOS or IGBT as a power switch device. The power switch device is the core of the inverter unit, and its reliability and safety are crucial. To avoid damage to the power switch device, the controller is usually designed with an overcurrent or short-circuit protection circuit. The main protection method currently used by motor controllers is to detect the on-voltage drop of the controller power switch device, compare the signal with a reference voltage, and output an overcurrent signal when the current is greater than the reference value. The overcurrent signal is input to the power switch device drive circuit to disable the drive signal output, thereby achieving protection.

[0003] This protection method must design a relatively high protection threshold. The reason is that the existence of parasitic inductance will generate a sharp voltage spike when the power device switches, which will cause the protection circuit to be triggered incorrectly. In current engineering applications, the threshold is designed to be relatively high. However, setting a higher threshold may cause protection failure and damage to the power switch tube. In addition, most controllers in the prior art do not have power switch tube detection function. When the motor controller is damaged due to device failure, production assembly, manufacturing, or static electricity, the controller will run directly after power-on, causing secondary damage and more serious faults.

[0004] Based on the above situation, the present application provides a power device fault detection method and circuit for a motor controller. SUMMARY

[0005] To solve the above problems in the prior art, the present application provides a motor controller power switch device fault detection method and circuit, which can detect the fault of the power inverter unit before each start-up operation, accurately identify whether the controller power unit belongs to the upper bridge fault or the lower bridge fault, and detect whether the motor is missing a phase.

[0006] To achieve the above purpose, the present application provides the following technical solution: a motor controller power switch device fault detection method, which comprises the following modes:

[0007] Static detection, after the MCU power initialization, first execute the routine fault detection program, at the same time waiting for C1 charging, after C1 charging, power switch device detection program starts running, first static self-check, three-phase output voltage circuit sampling circuit will be three-phase voltage output value through R5, R6 voltage division and send to the ADC of MCU for sampling, at this time, MCU judges each phase voltage value, three-phase output voltage all meet "less than VBUS-1V and greater than 0.1V" preliminary judgment is normal, then proceed to the next step dynamic detection, do not meet continue to judge "any phase voltage greater than VBUS-1V", meet then think that the MOS tube upper bridge has a fault, MCU reports "MOS tube upper bridge fault", do not meet then think that the MOS tube lower bridge has a fault, report "MOS tube lower bridge fault";

[0008] Dynamic detection, in order to avoid misjudgment and carry out the open-phase detection, after static detection, dynamic detection needs to be executed again, first U-phase MOS lower bridge detection, during detection, MCU sends a 100uS pulse wave to U-phase lower bridge for driving U-phase lower bridge MOS, when U-phase lower bridge MOS is turned on, the bootstrap capacitor of upper bridge driving circuit is charged, during the process of sending the wave, U-phase voltage is detected and judged whether it is less than 0.1V, "no" program reports "MOS lower bridge fault", "yes" has no fault;

[0009] Then delay 100uS and continue to carry out U-phase MOS upper bridge detection, MCU continues to send a 100uS pulse wave to U-phase upper bridge for driving U-phase upper bridge MOS, during the process of sending the wave, U-phase voltage is detected whether it is greater than VBUS-1V, and V, W-phase voltage is detected whether it is greater than 1 / 2VBUS, if U-phase voltage is greater than VBUS-1V, U-phase upper bridge is normal, otherwise, report "MOS upper bridge fault", if V, W-phase voltage meets 1 / 2VBUS, it is normal, otherwise, report "open-phase fault";

[0010] After U-phase dynamic self-checking, the program delays 100uS to detect V, W-phase in the same logical order, when three-phase detection is completed without fault, the self-checking is passed.

[0011] The application also provides the following technical scheme: a motor controller power switch device fault detection circuit, comprising a microcontroller MCU, a power switch tube conduction voltage drop detection circuit, a biased gate driver, a phase voltage detection circuit and a three-phase inverter unit;

[0012] The MCU includes a PWM module, an ADC converter and a fault detection module, the PWM module is used for sending a PWM wave signal as a signal source for driving a power switch device, the ADC converter is used for detecting a phase output voltage when the PWM module sends a wave so as to judge whether the working state of the power switch device is normal, and the fault detection module is used for receiving a fault signal sent by an external power switch device conduction voltage drop detection circuit, and stops sending a wave immediately to protect when the external fault signal is received;

[0013] The gate drive circuit has a voltage bias function, and includes a bootstrap drive chip U1, a resistor R1, two capacitors C1 and C2, two diodes D1 and D2, and a bias resistor R4, wherein C1 is used as an energy storage capacitor to provide transient current for the drive chip, U1 is responsible for providing sufficient current for the power switch tube, R1, D1 and C2 are used as bootstrap elements to store energy for the opening of the upper bridge when the lower bridge of the power switch tube is opened, D2 is used as a clamping protection element to clamp the peak voltage generated when the power tube is turned off near GND, thereby protecting the drive chip, and R4 is used as a bias resistor to provide a certain bias voltage for the phase output voltage detection circuit, and the purpose is to judge whether the lower bridge of the power switch tube is faulty.

[0014] The phase output voltage sampling circuit is composed of R5 and R6, and is used for generating a pulse test signal to control the opening and closing of the upper and lower bridges when the MCU detection program is running, and the voltage at the time of opening and closing is collected to judge whether the working state of the upper and lower bridges is normal.

[0015] Compared with the prior art, the present application has the following advantages:

[0016] 1. The present application can detect the fault of the output power switch tube before the motor controller is powered on, and judge the fault type to belong to the upper bridge fault or the lower bridge fault, and can also detect whether the motor is missing phase.

[0017] 2. In the present application, through the improvement of the program algorithm of the MCU, the upper bridge fault and the lower bridge fault can be judged, and the specific fault phase can also be detected.

[0018] 3. In the present application, by increasing the bias of the gate drive circuit and cooperating with the fault detection program, the fault can be judged and the fault type can be detected before the motor controller is running, the fault can be quickly located, the maintenance and replacement are facilitated, and the secondary damage of the motor controller when the motor controller is running due to the failure to detect the damaged power switch tube in advance is avoided, the fault range is expanded, and the whole machine is seriously scrapped, thereby causing greater loss. BRIEF DESCRIPTION OF DRAWINGS

[0019] The accompanying drawings are used to provide a further understanding of the present application, and constitute a part of the specification, and are used to explain the present application together with embodiments of the present application, and do not constitute a limitation on the present application. In the drawings:

[0020] Figure 1 Structure diagram of over-current protection of motor controller in prior art;

[0021] Figure 2 Schematic diagram of gate drive circuit of three-phase inverter unit in prior art;

[0022] Figure 3 Structure diagram of over-current protection circuit of motor controller in the application;

[0023] Figure 4 Schematic diagram of gate drive circuit and phase voltage sampling circuit in the application;

[0024] Figure 5 Schematic diagram of three-phase inverter power unit in the application;

[0025] Figure 6 Flow chart of fault judgment program in the application;

[0026] Figure 7 Schematic diagram of PWM wave generation timing in the application. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments of the application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application. EMBODIMENT

[0028] Please refer to Figures 1-7 The application provides the following technical solution: a motor controller power switch device fault detection method, which comprises the following modes:

[0029] Static detection: after the MCU is powered on and initialized, the routine fault detection program is first executed, and C1 is charged at the same time. After C1 is charged, the power switch device detection program starts to run. First, static self-checking is performed. The three-phase output voltage circuit sampling circuit sends the three-phase voltage output values through R5 and R6 voltage division to the ADC of the MCU for sampling. At this time, the MCU judges the phase voltage values. If the three-phase output voltages all meet the condition of "less than VBUS-1V and greater than 0.1V", it is preliminarily judged to be normal, and then the next step of dynamic detection is performed. If the condition is not met, it is continuously judged that "any phase voltage is greater than VBUS-1V". If the condition is met, it is considered that the MOS tube upper bridge has a fault, and the MCU reports "MOS tube upper bridge fault". If the condition is not met, it is considered that the MOS tube lower bridge has a fault, and the MCU reports "MOS tube lower bridge fault". The specific fault judgment program flow chart is shown in Figure 6 ;

[0030] Dynamic detection, in order to avoid misjudgment and phase loss detection, dynamic detection needs to be performed again after the static detection is passed. First, the U-phase MOS lower bridge detection is performed. During the detection, the MCU sends a 100uS pulse wave to the U-phase lower bridge ( Figure 7 :T0)is used to drive the U-phase lower bridge MOS tube. When the U-phase lower bridge MOS is turned on, it also charges the bootstrap capacitor of the upper bridge drive circuit. During the wave transmission process, the U-phase voltage is detected and judged whether it is less than 0.1V. If "no", the program reports "MOS lower bridge fault". If "yes", there is no fault; then delay 100uS ( Figure 7 :T1) and then continue to detect the U-phase MOS upper bridge. The MCU continues to send a 100uS pulse wave to the U-phase upper bridge ( Figure 7 :T2), used to drive the U-phase upper bridge MOS tube, detect whether the U-phase voltage is greater than VBUS-1V during the wave transmission process, and detect whether the V and W phase voltages are greater than 1 / 2VBUS. If the U-phase voltage is greater than VBUS-1V, the U-phase upper bridge is normal, otherwise it will report "MOS upper bridge fault". If the V and W phase voltages meet 1 / 2VBUS, they are normal. If not, it will report "phase loss fault"; after the U-phase dynamic self-test passes, the program delay is 100uS ( Figure 7 :T3)Detect V and W phases in the same logical order. When all three phases are detected and there is no fault, the self-test is passed. The specific PWM wave timing is shown in the following table. Figure 7 .

[0031] See Figures 1-7 The present invention also provides the following technical solutions: A motor controller power switch device fault detection circuit, including a microcontroller (hereinafter referred to as MCU), a power switch tube conduction voltage drop detection circuit, a gate driver with bias, a phase voltage detection circuit and a three-phase inverter unit. The specific block diagram is shown in Figure 3 ;

[0032] The microcontroller includes a PWM module, an ADC converter, and a fault detection module. The PWM module is used to generate PWM wave signals as a signal source to drive the power switching device. The ADC converter is used to detect the phase output voltage when the PWM module generates the wave to determine whether the working status of the power switching device is normal. The fault detection module is used to receive fault signals sent by the on-state voltage drop detection circuit of the external power switching device. If an external fault signal is received, the module will immediately stop the wave generation for protection.

[0033] The power switch tube conduction voltage drop detection circuit is the same as the circuit used in the prior art;

[0034] The gate drive circuit with voltage bias function comprises a bootstrap drive chip U1, a resistor R1, two capacitors C1 and C2, two diodes D1 and D2, and a bias resistor R4. C1 is used as an energy storage capacitor to provide transient current for the drive chip, U1 is responsible for providing sufficient current for the power switch tube, R1, D1 and C2 are used as bootstrap elements to store energy for the upper bridge when the lower bridge of the power switch tube is turned on, D2 is used as a clamping protection to clamp the peak voltage generated when the power tube is turned off near GND, thereby protecting the drive chip, and R4 is used as a bias resistor to provide a certain bias voltage for the phase output voltage detection circuit, so as to determine whether the lower bridge of the power switch tube is faulty.

[0035] The phase output voltage sampling circuit is composed of R5 and R6, which is used to generate a pulse test signal to control the upper and lower bridges when the MCU detection program is running, and to determine whether the working state of the upper and lower bridges is normal by collecting the voltage when the switch is turned on.

[0036] The three-phase inverter power unit is a core device for DC-AC conversion, and power MOS or IGBT power switch device is usually selected according to different application fields. In the present application, power MOS is used as the switching device (it should be pointed out that using IGBT or other similar devices with switching function as the power switch does not exceed the protection scope of the present application), and the specific principle diagram of the power unit is shown in Figure 5 .

[0037] In the present embodiment, only one phase overcurrent protection current, gate drive and phase voltage sampling circuit are listed, and the other phase circuits are the same in three-phase application.

[0038] In the present embodiment, the mechanism of the detection program and the hardware detection circuit designed in the present application for judging faults is as follows: in most cases, MOS damage will appear as short circuit, and the voltage between the drain and the source of the MOS after short circuit is 0V. Therefore, when the upper bridge of the MOS is damaged, the phase output voltage is approximately equal to the bus voltage (VBUS), and when the lower bridge of the MOS is damaged, the phase output voltage is approximately equal to 0V. However, in normal case, the phase output voltage is also 0V because of the existence of the phase output pull-down resistor. Therefore, if the circuit is not specially processed, it will not be able to distinguish between the damage of the lower bridge of the MOS and the normal case. In order to solve this problem, the present application designs a bias voltage of about 0.5V on the gate drive circuit, so that the phase output voltage is about 0.5V in normal case, avoiding the confusion between the damage of the lower bridge of the MOS and the normal case. Based on the above principle, it is provided in the present embodiment that the upper bridge fault threshold is greater than VBUS-1V, the lower bridge fault threshold is less than 0.1V, and the open-phase fault threshold is less than 1 / 2VCC.

[0039] In addition, Figure 4For the gate drive circuit, sampling circuit schematic diagram in the application, the circuit working principle is as follows: after the system is powered on, the power supply VCC passes through R1 and D1 to the upper end of C1 and R4, reaches the upper end of R5 after passing through C1 and R4, and finally returns to the negative pole through R5 and R6, wherein the upper end of R5 is connected with VS of the gate drive chip and S of the upper bridge power switch tube as phase output, R5 and R6 constitute a voltage divider as a phase voltage detection circuit, and the initial voltage of C1 is 0V when the upper bridge power switch tube is powered on. Because C1 is connected with R5 and R6 in series, VCC charges it, the voltage across C1 begins to gradually increase, and after a period of time, the voltage of C1 tends to be stable, and the voltage is about equal to VCC. When the charging is completed, the voltage at the upper end of R5 is a bias voltage (in this embodiment, VCC is 12V, the resistance value of R4 is 1M, and the resistance values of R5 and R6 are 39k and 1k respectively), and the phase output voltage is about 0.5V. Therefore, the phase output voltage should be about 0.5V when there is no fault.

[0040] In the embodiment, the motor controller power device fault detection method and circuit provided by the application can detect the fault of the output power switch tube before the motor controller is powered on and work, and judge whether the fault type belongs to upper bridge fault or lower bridge fault. In addition, the detection method and circuit provided by the application can also detect whether the motor is missing phase. In the application, through the improvement of the program algorithm of the MCU, not only the upper bridge fault and the lower bridge fault can be judged, but also the specific fault belonging to which phase can be detected. Through the bias mode of the gate drive circuit cooperating with the fault detection program, the fault can be judged and the fault type can be detected before the motor controller runs, so that the fault can be quickly located, the maintenance and replacement are facilitated, and the secondary damage of the motor controller when the motor controller runs after the power switch tube is damaged, the expansion of the fault range and the scrapping of the whole machine in serious cases are avoided, so that greater loss is caused.

[0041] Other alternatives of the application use any other power switch device with switching characteristics, such as MOS, IGBT, triode, etc. as the three-phase power unit; use other types of gate drive circuits (including gate drive circuits composed of separate components); replace the bias resistor in the gate drive circuit with other circuits or components with bias function (including constant current source circuit, etc.); use the ideas and logic of the fault judgment program in the application or similar programs.

[0042] In addition, the contents not described in detail in the embodiment are in the category of prior art and common knowledge.

[0043] Finally, it should be noted that the above only describes the preferred embodiments of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art will appreciate that the technical solutions described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalent ones. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for detecting a fault in a power switch device of a motor controller, characterized in that: The method includes the following steps: Static detection: After the MCU is powered on and initialized, it first executes the conventional fault detection program while waiting for C1 to charge. After C1 is charged, the power switch device detection program starts running. First, a static self-test is performed. The three-phase output voltage circuit sampling circuit will respectively divide the three-phase voltage output values ​​through R5 and R6 and send them to the MCU's ADC for sampling. At this time, the MCU judges the voltage value of each phase. If the three-phase output voltage meets the requirement of "less than VBUS-1V and greater than 0.1V", it is preliminarily judged to be normal and the next step of dynamic detection is carried out. If it does not meet the requirement, the next step is to judge whether "any phase voltage is greater than VBUS-1V". If it meets the requirement, the MCU will determine that the MOS tube upper bridge is faulty and report "MOS tube upper bridge fault". If it does not meet the requirement, the MOS tube lower bridge is faulty and report "MOS tube lower bridge fault". Dynamic detection: To avoid misjudgment and phase loss detection, dynamic detection must be performed again after the static detection passes. First, the U-phase MOS lower bridge is detected. During the detection, the MCU sends a 100uS pulse wave to the U-phase lower bridge to drive the U-phase lower bridge MOS tube. When the U-phase lower bridge MOS is turned on, the bootstrap capacitor of the upper bridge drive circuit is charged. During the pulse generation process, the U-phase voltage is detected and determined to be less than 0.1V. If "No", the program reports "MOS lower bridge fault"; if "Yes", there is no fault; Then, after a delay of 100uS, the U-phase MOS upper bridge detection continues. The MCU continues to send a 100uS pulse wave to the U-phase upper bridge to drive the U-phase upper bridge MOS tube. During the wave transmission process, it detects whether the U-phase voltage is greater than VBUS-1V, and at the same time detects whether the V and W phase voltages are greater than 1 / 2VBUS. If the U-phase voltage is greater than VBUS-1V, the U-phase upper bridge is normal. Otherwise, it will report "MOS upper bridge fault". If the V and W phase voltages meet 1 / 2VBUS, it is normal. If not, it will report "phase loss fault". After the U phase dynamic self-test passes, the program delays 100uS and then tests the V and W phases in the same logical order. When all three phases are tested and there are no faults, the self-test passes.

2. A motor controller power switch device fault detection circuit, characterized in that: It includes a microcontroller MCU, a power switch tube conduction voltage drop detection circuit, a gate driver with bias, a phase voltage detection circuit and a three-phase inverter unit; The MCU includes a PWM module, an ADC converter, and a fault detection module. The PWM module is used to generate PWM wave signals as the signal source for driving the power switching device. The ADC converter detects the phase output voltage when the PWM module generates the wave to determine whether the working status of the power switching device is normal. The fault detection module is used to receive fault signals sent by the on-state voltage drop detection circuit of the external power switching device. Upon receiving the external fault signal, it immediately stops the wave generation for protection. The gate drive circuit has a voltage bias function and includes a bootstrap driver chip U1, a resistor R1, two capacitors C1 and C2, two diodes D1 and D2, and a bias resistor R4. C1 acts as a storage capacitor to provide transient current for the driver chip, and U1 is responsible for providing current to the power switch tube. R1, D1, and C2 act as bootstrap elements to store energy for the upper bridge when the lower bridge of the power switch tube is turned on. D2 acts as a clamping protection to clamp the peak voltage generated when the power tube is turned off to near GND, thereby protecting the driver chip. R4 acts as a bias resistor to provide a certain bias voltage for the phase output voltage detection circuit to determine whether the lower bridge of the power switch tube is faulty. The phase output voltage sampling circuit is composed of R5 and R6. Its function is to generate a pulse test signal to control the upper and lower bridge switches when the MCU detection program is running. By collecting the voltage during switching, it can determine whether the upper and lower bridges are working normally.

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