阅读说明：本技术 一种具有故障诊断的主动放电电路 (Active discharge circuit with fault diagnosis ) 是由 王军德 何民 聂文强 唐文秀 孔德尖 于 2021-08-03 设计创作，主要内容包括：本发明涉及一种具有故障诊断的主动放电电路,包括放电电路、故障检测电路和MCU,放电电路跨接在待放电的两极之间,MCU的信号输出端与放电电路的控制端连接,待放电的两极和放电电路的检测点分别与故障检测电路的信号输入端连接,MCU的信号输入端与故障检测电路的信号输出端连接；故障检测电路检测待放电的两极之间的直流电压值以及放电电路的状态；MCU根据待放电的两极之间的直流电压值以及放电电路的状态判断是否需要放电,然后输出控制信号；放电电路根据控制信号进行放电。本发明对薄膜电容的两极之间直流电压值以及放电电路的状态进行故障诊断,并控制放电电路对薄膜电容的两极进行放电,防止薄膜电容损害。(The invention relates to an active discharge circuit with fault diagnosis, which comprises a discharge circuit, a fault detection circuit and an MCU (microprogrammed control unit), wherein the discharge circuit is bridged between two electrodes to be discharged; the fault detection circuit detects a direct-current voltage value between two poles to be discharged and the state of the discharge circuit; the MCU judges whether discharging is needed or not according to the direct-current voltage value between the two electrodes to be discharged and the state of the discharging circuit, and then outputs a control signal; the discharge circuit discharges according to the control signal. The invention carries out fault diagnosis on the direct current voltage value between two poles of the film capacitor and the state of the discharge circuit, and controls the discharge circuit to discharge the two poles of the film capacitor, thereby preventing the film capacitor from being damaged.)

1. An active discharge circuit with fault diagnosis is characterized by comprising a discharge circuit, a fault detection circuit and an MCU (microprogrammed control unit), wherein the discharge circuit is bridged between two electrodes to be discharged;

the fault detection circuit is used for detecting a direct-current voltage value between two poles to be discharged and the state of the discharge circuit;

the MCU is used for judging whether discharging is needed or not according to the direct-current voltage value between the two electrodes to be discharged and judging whether a fault exists or not according to the state of the discharging circuit, and is also used for outputting a discharging control signal according to a judgment result;

the discharge circuit is used for discharging according to the control signal.

2. The active discharge circuit with fault diagnosis of claim 1, wherein the MCU is configured to determine whether discharge is required according to a dc voltage value between two electrodes to be discharged and determine whether there is a fault according to a state of the discharge circuit, and further configured to output a discharge control signal according to the determination result, comprising:

comparing the detected direct current voltage value with a preset voltage threshold value, and judging that the two electrodes to be discharged do not need to be discharged when the direct current voltage value is lower than the voltage threshold value; when the direct current voltage value is higher than or equal to the voltage threshold value, judging that the two electrodes to be discharged need to be discharged; if discharging is needed, the MCU judges whether the discharging circuit has a fault according to the state of the discharging circuit, if the discharging circuit has the fault, the MCU outputs an alarm signal, and if the discharging circuit has no fault, the MCU outputs a discharging control signal.

3. The active discharge circuit with fault diagnosis of claim 1, wherein the discharge circuit comprises a power resistor CR1, a power switch tube Q1 and a power switch tube Q2, two poles to be discharged comprise a high-voltage positive pole HV + and a high-voltage negative pole HV +, a current input end of the power switch tube Q1 is connected with the high-voltage positive pole HV + to be discharged after being connected with the power resistor CR1 in series, a current output end of the power switch tube Q1 is connected with a current input end of the power switch tube Q2, and a current output end of the power switch tube Q2 is connected with the high-voltage negative pole HV-; the control end of the power switch tube Q1 and the control end of the power switch tube Q2 are respectively connected with two signal output ends of the MCU.

4. The active discharge circuit with fault diagnosis of claim 3, wherein the fault detection circuit comprises sampling resistors R2 and R3, an isolation operational amplifier chip IC1, an operational amplifier IC 2-A, an input resistor R4, an input resistor R5 and a feedback resistor R6, the sampling resistors R2 and R3 are connected in series across the high voltage positive electrode HV + and the high voltage negative electrode HV-, the node of the sampling resistors R2 and R3 is connected with the signal input VIN of the isolation operational amplifier chip IC1 and is also connected with the node of the power switch Q1 and the power switch Q2, the high level output VOUTP of the isolation operational amplifier chip IC1 is connected in series with the input resistor R4 and then connected with the positive input terminal of the operational amplifier IC 2-A, the low level output VOUTN of the isolation operational amplifier chip IC1 is connected in series with the input resistor R5 and then connected with the negative input terminal of the operational amplifier IC 2-A, the reference voltage Vref is also input terminal of the operational amplifier IC 2-A, the signal output end of the operational amplifier IC 2-A is connected with the signal input end of the MCU, and the feedback resistor R6 is connected between the signal output end of the operational amplifier IC 2-A and the inverting input end of the operational amplifier IC 2-A in a bridge mode.

5. The active discharge circuit with fault diagnosis of claim 4, wherein the fault detection circuit further comprises an operational amplifier IC 2-B, a non-inverting input terminal of the operational amplifier IC 2-B is connected to the reference voltage Vref input, and an inverting input terminal of the operational amplifier IC 2-B is connected to a non-inverting input terminal of the operational amplifier IC 2-A in common with the signal output terminal of the operational amplifier IC 2-B.

6. The active discharge circuit with fault diagnosis of any one of claims 3 to 5, wherein the MCU comprises a main control chip IC3 and peripheral circuits thereof, the signal output end of the main control chip IC3 is provided with an amplifying circuit, and the signal output end of the main control chip IC3 is respectively connected with the control end of the power switch tube Q1 and the control end of the power switch tube Q2 through the amplifying circuit; the signal input end of the main control chip IC3 is provided with an ADC (analog to digital converter) conversion circuit, and the signal input end of the main control chip IC3 is connected with the signal output end of the fault detection circuit through the ADC conversion circuit.

Technical Field

The invention relates to the technical field of electric automobiles, in particular to an active discharge circuit with fault diagnosis.

Background

Most of the existing pure electric vehicles adopt a mode of adding a permanent magnet synchronous motor to a motor controller for power control, and in the process of switching the pure electric vehicles from a high-speed driving state to the whole speed reduction process of free sliding, a magnetic field of a permanent magnet rotor in the motor can cut a lead of a three-phase coil, so that counter electromotive voltage is generated, when the generated counter electromotive voltage is higher than the voltage of a film capacitor in the motor controller, the voltage of the film capacitor is increased, if the rotating speed is too high, the generated counter electromotive voltage is too large and exceeds the bearing range of the film capacitor, irreversible damage can be generated on the film capacitor; therefore, the active discharge of the voltage of the thin film capacitor is an effective method for preventing the thin film capacitor from being damaged, and the reliability of the active discharge function can be further ensured by adding the fault diagnosis function to the active discharge circuit.

Disclosure of Invention

The invention provides an active discharge circuit with fault diagnosis, which can judge whether discharge is needed or not by detecting a direct current voltage value between two poles of a thin film capacitor and the state of the discharge circuit, and controls the discharge circuit to discharge the two poles of the thin film capacitor when a discharge condition is reached so as to prevent the thin film capacitor from being damaged.

The technical scheme for solving the technical problems is as follows:

an active discharge circuit with fault diagnosis comprises a discharge circuit, a fault detection circuit and an MCU (microprogrammed control unit), wherein the discharge circuit is bridged between two electrodes to be discharged, a signal output end of the MCU is connected with a control end of the discharge circuit, the two electrodes to be discharged and a detection point of the discharge circuit are respectively connected with a signal input end of the fault detection circuit, and a signal input end of the MCU is connected with a signal output end of the fault detection circuit;

the fault detection circuit is used for detecting a direct-current voltage value between two poles to be discharged and the state of the discharge circuit;

the MCU is used for judging whether discharging is needed or not according to the direct-current voltage value between the two electrodes to be discharged and judging whether a fault exists or not according to the state of the discharging circuit, and is also used for outputting a discharging control signal according to a judgment result;

the discharge circuit is used for discharging according to the control signal.

Further, the MCU is configured to determine whether discharge is required according to a dc voltage value between two electrodes to be discharged and determine whether a fault exists according to a state of the discharge circuit, and further output a discharge control signal according to a determination result, including:

comparing the detected direct current voltage value with a preset voltage threshold value, and judging that the two electrodes to be discharged do not need to be discharged when the direct current voltage value is lower than the voltage threshold value; when the direct current voltage value is higher than or equal to the voltage threshold value, judging that the two electrodes to be discharged need to be discharged; if discharging is needed, the MCU judges whether the discharging circuit has a fault according to the state of the discharging circuit, if the discharging circuit has the fault, the MCU outputs an alarm signal, and if the discharging circuit has no fault, the MCU outputs a discharging control signal.

Further, the discharge circuit comprises a power resistor CR1, a power switch tube Q1 and a power switch tube Q2, two poles to be discharged comprise a high-voltage positive pole HV + and a high-voltage negative pole HV +, a current input end of the power switch tube Q1 is connected with the high-voltage positive pole HV + to be discharged after being connected with the power resistor CR1 in series, a current output end of the power switch tube Q1 is connected with a current input end of the power switch tube Q2, and a current output end of the power switch tube Q2 is connected with the high-voltage negative pole HV-tobe discharged; the control end of the power switch tube Q1 and the control end of the power switch tube Q2 are respectively connected with two signal output ends of the MCU.

Further, the fault detection circuit comprises sampling resistors R2 and R3, an isolation operational amplifier chip IC1, an operational amplifier IC 2-A, an input resistor R4, an input resistor R5 and a feedback resistor R6, wherein the sampling resistors R2 and R3 are connected in series and bridged between a high-voltage positive electrode HV + and a high-voltage negative electrode HV-, a node of the sampling resistors R2 and R3 is connected with a VIN (signal input end) of the isolation operational amplifier chip IC1 and a node of a power switch tube Q1 and a power switch tube Q2, a VOUTP (high-level output end) of the isolation operational amplifier chip IC1 is connected with a positive input end of the operational amplifier IC 2-A after being connected with the input resistor R4 in series, a VOUTN (low-level output end) of the isolation operational amplifier chip IC1 is connected with an input resistor R5 in series and then connected with a negative input end of the operational amplifier IC 2-A, a reference voltage is further input to the positive input end of the operational amplifier IC 2-A, a signal output end of the operational amplifier IC 2-A is connected with a signal input end of the MCU Vref-A, the feedback resistor R6 is coupled across the signal output of the operational amplifier IC 2-A and the inverting input of the operational amplifier IC 2-A.

Further, the fault detection circuit further comprises an operational amplifier IC 2-B, wherein the non-inverting input terminal of the operational amplifier IC 2-B is connected with the reference voltage Vref input, and the inverting input terminal of the operational amplifier IC 2-B and the signal output terminal of the operational amplifier IC 2-B are connected with the non-inverting input terminal of the operational amplifier IC 2-A in common.

Further, the MCU includes a main control chip IC3 and peripheral circuits thereof, the signal output terminal of the main control chip IC3 is provided with an amplifying circuit, and the signal output terminal of the main control chip IC3 is connected to the control terminal of the power switch tube Q1 and the control terminal of the power switch tube Q2 through the amplifying circuit; the signal input end of the main control chip IC3 is provided with an ADC (analog to digital converter) conversion circuit, and the signal input end of the main control chip IC3 is connected with the signal output end of the fault detection circuit through the ADC conversion circuit.

The invention has the beneficial effects that: the invention can effectively protect high-voltage devices such as a film capacitor and the like in the motor controller, avoid overvoltage damage risk caused by overhigh counter potential voltage, and can also carry out fault diagnosis on the power device of the discharge circuit. When the voltage of high-voltage devices such as a film capacitor and the like is overhigh due to vehicle faults, the circuit can safely and reliably carry out active discharge on the voltage of the film capacitor, and prevent the damage of a larger area of a vehicle caused by the overvoltage and the explosion of the film capacitor. The invention improves the running safety of the vehicle, thereby having better practical application prospect.

Drawings

FIG. 1 is a block diagram of the system components of the present invention;

FIG. 2 is a circuit diagram of the present invention.

Detailed Description

The principles and features of this invention are described below in conjunction with the following drawings, which are set forth by way of illustration only and are not intended to limit the scope of the invention.

As shown in fig. 1 to 2, the present embodiment provides an active discharge circuit with fault diagnosis, which is disposed on a thin film capacitor inside a motor controller and is mainly used for performing discharge protection on the thin film capacitor. The device comprises a discharge circuit, a fault detection circuit and an MCU (microprogrammed control Unit), wherein the discharge circuit is bridged between two electrodes to be discharged (namely two polar plates of a thin-film capacitor), the signal output end of the MCU is connected with the control end of the discharge circuit, the two electrodes to be discharged and the detection point of the discharge circuit are respectively connected with the signal input end of the fault detection circuit, and the signal input end of the MCU is connected with the signal output end of the fault detection circuit;

the fault detection circuit is used for detecting a direct-current voltage value between two poles to be discharged and the state of the discharge circuit;

the MCU is used for judging whether discharging is needed or not according to the direct-current voltage value between the two electrodes to be discharged and judging whether a fault exists or not according to the state of the discharging circuit, and is also used for outputting a discharging control signal according to a judgment result;

the discharge circuit is used for conducting discharge according to the control signal so as to reduce the voltage between two electrodes to be discharged.

In this embodiment, the MCU is configured to determine whether discharge is required according to a dc voltage value between two electrodes to be discharged and determine whether a fault exists according to a state of the discharge circuit, and is further configured to output a discharge control signal according to a determination result, including:

comparing the detected direct current voltage value with a preset voltage threshold value, and judging that the two electrodes to be discharged do not need to be discharged when the direct current voltage value is lower than the voltage threshold value; when the direct current voltage value is higher than or equal to the voltage threshold value, judging that the two electrodes to be discharged need to be discharged; if discharging is needed, the MCU judges whether the discharging circuit has a fault according to the state of the discharging circuit, if the discharging circuit has the fault, the MCU outputs an alarm signal, and if the discharging circuit has no fault, the MCU outputs a discharging control signal.

In this embodiment, the discharge circuit includes a power resistor CR1, a power switch transistor Q1, and a power switch transistor Q2, and the power switch transistor Q1 and the power switch transistor Q2 both use power MOS transistors. The two poles to be discharged comprise a high-voltage positive pole HV + and a high-voltage negative pole HV +, the current input end of the power switch tube Q1 is connected with the high-voltage positive pole HV + to be discharged after being connected with the power resistor CR1 in series, the current output end of the power switch tube Q1 is connected with the current input end of the power switch tube Q2, and the current output end of the power switch tube Q2 is connected with the high-voltage negative pole HV-tobe discharged; the control end of the power switch tube Q1 and the control end of the power switch tube Q2 are respectively connected with two signal output ends of the MCU. In the discharge circuit, a node between the power switch Q1 and the power switch Q2 is connected to a failure detection circuit as a detection point of the discharge circuit.

In this embodiment, the fault detection circuit includes sampling resistors R2 and R3, an isolation operational amplifier chip IC1, an operational amplifier IC 2-a, an input resistor R4, an input resistor R5 and a feedback resistor R6, the sampling resistors R2 and R3 are connected in series and bridged between a high voltage positive electrode HV + and a high voltage negative electrode HV-, a node of the sampling resistors R2 and R3 is connected to a VIN signal input terminal of the isolation operational amplifier chip IC1 and also connected to a node of a power switch Q1 and a Q2, a high level output terminal VOUTP of the isolation operational amplifier chip IC1 is connected in series to the input resistor R4 and then connected to a non-inverting input terminal of the operational amplifier IC 2-a, a low level output terminal VOUTN of the isolation operational amplifier chip IC1 is connected in series to the input resistor R5 and then connected to an inverting input terminal of the operational amplifier IC 2-a, a non-inverting input terminal of the operational amplifier IC 2-a further inputs a reference voltage, a signal output terminal of the operational amplifier IC 2-a, the feedback resistor R6 is coupled across the signal output of the operational amplifier IC 2-A and the inverting input of the operational amplifier IC 2-A.

In this embodiment, the fault detection circuit further comprises an operational amplifier IC 2-B, wherein the non-inverting input terminal of the operational amplifier IC 2-B is connected to the reference voltage Vref input, and the inverting input terminal of the operational amplifier IC 2-B and the signal output terminal of the operational amplifier IC 2-B are commonly connected to the non-inverting input terminal of the operational amplifier IC 2-A.

In this embodiment, the MCU includes a main control chip IC3 and peripheral circuits thereof, the signal output terminal of the main control chip IC3 is provided with an amplifying circuit, and the signal output terminal of the main control chip IC3 is connected to the control terminal of the power switch tube Q1 and the control terminal of the power switch tube Q2 through the amplifying circuit, respectively; the signal input end of the main control chip IC3 is provided with an ADC (analog to digital converter) conversion circuit, and the signal input end of the main control chip IC3 is connected with the signal output end of the fault detection circuit through the ADC conversion circuit.

In this embodiment, the isolation operational amplifier IC1, the operational amplifier IC 2-a, the operational amplifier IC 2-B, and the main control chip IC3 are all powered by an additional power supply node in the vehicle control system, for example, as shown in fig. 2, the high voltage side of the isolation operational amplifier IC1 is powered by a power supply formed between the node V _ ADC of the system and the high voltage negative electrode HV-of the film capacitor, and the low voltage side is powered by a power supply formed between the node VCC5A of the system and GND; in this embodiment, the operational amplifier IC 2-a and the operational amplifier IC 2-B actually use an operational amplifier chip IC2 having two identical functional blocks, which is powered by a power supply formed between the system nodes VCC5A and GND, as shown in fig. 2.

The working principle is as follows:

under the normal working state of the vehicle, the main control chip IC3 of the MCU controls the power switch tubes Q1 and Q2 to be in the off state, and the power resistor CR1 is in the non-working state at the moment. At this time, the bus direct-current voltage (the voltage between the high-voltage positive electrode HV + and the high-voltage negative electrode HV-corresponding to the thin-film capacitor) can be input to the VIN pin of the isolation operational amplifier chip IC1 through the divided voltages of the sampling resistors R2 and R3, the sampling voltage after the isolation conversion is output to the positive phase input end and the negative phase input end of the operational amplifier IC 2-A through the VOUTP and VOUTN pins, and the output end of the operational amplifier IC 2-A forms negative feedback through the resistor R6 to form an inverse proportion operational circuit. The sampled voltage after the isolation conversion is properly adjusted by the inverting proportional operational circuit of the operational amplifier IC 2-A, wherein the resistances of the feedback resistor R6, the input resistor R5, and the input resistor R4 determine the amplification factor of the operational amplifier IC 2-A. The output end of the operational amplifier IC 2-a outputs the adjusted sampling voltage to an ADC analog-to-digital conversion pin (i.e., an input pin of the ADC conversion circuit) of the signal input end of the MCU main control chip IC3, and the magnitude of the bus dc voltage is obtained through the internal calculation of the MCU main control chip IC3, so that whether the discharge between the two poles of the thin film capacitor is required can be determined.

Before the vehicle executes the active discharge state, the fault diagnosis of the power device is executed, and the steps are as follows: firstly, the MCU master control chip IC3 controls a power MOS tube Q1 to be switched on and a power MOS tube Q2 to be switched off, at the moment, a power resistor CR1 and a sampling resistor R2 are connected in parallel and then are connected in series with R3, at the moment, the bus direct-current voltage (the voltage between a high-voltage anode HV + and a high-voltage cathode HV-corresponding to a thin-film capacitor) is input to a VIN pin of an isolation operational amplifier chip IC1 through the divided voltages of CR1// R2 and R3, and finally, calculation verification is carried out inside the MCU master control chip IC3, so that whether the power resistor CR1 and the power MOS tube Q1 meet the discharge requirement at the moment is judged; and secondly, the main control chip IC3 of the MCU controls the power MOS tube Q1 to be disconnected from the Q2 to be conducted, at the moment, the R3 is in a short-circuited state, the voltage input to the VIN pin of the isolation operational amplifier chip IC1 is zero, and finally, the power MOS tube Q2 is judged whether to meet the discharge requirement or not through calculation verification in the MCU main control chip IC 3. The active discharge function can be performed only when the fault diagnosis passes.

Under the condition that the vehicle executes an active discharge state under the control of the MCU, the MCU main control chip IC3 controls the power MOS tubes Q1 and Q2 to be in a conducting state, the power resistor CR1 is in a working state at the moment, and the active discharge current is equal to the ratio of bus direct-current voltage (voltage between a high-voltage positive electrode HV + and a high-voltage negative electrode HV-corresponding to a thin-film capacitor) to the resistance value of the power resistor CR1 (in the parameter setting of the electric element, as the resistance values of the sampling resistors R2 and R3 are about thousands of times larger than the resistance value of the power resistor CR1, the discharge current of loops of the sampling resistors R2 and R3 can be ignored). When the voltage between the two electrode plates of the film capacitor is reduced to a safe range, the MCU controls the discharge circuit to stop discharging.

The invention can effectively protect high-voltage devices such as a film capacitor and the like in the motor controller, avoid overvoltage damage risk caused by overhigh counter potential voltage, and can also carry out fault diagnosis on the power device of the discharge circuit. When the voltage of high-voltage devices such as a film capacitor and the like is overhigh due to vehicle faults, the circuit can safely and reliably carry out active discharge on the voltage of the film capacitor, and prevent the damage of a larger area of a vehicle caused by the overvoltage and the explosion of the film capacitor. The invention improves the running safety of the vehicle, thereby having better practical application prospect.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.