Short circuit protection circuit, short circuit protection method and electric vehicle

Abstract

A short-circuit protection circuit, a short-circuit protection method, and an electric vehicle are disclosed, relating to the field of electric vehicle technology. The short-circuit protection circuit includes a sensing resistor, a voltage comparator, and an MCU. The primary circuit of a push-pull switching circuit is grounded through the sensing resistor, and the push-pull switching circuit provides a driving voltage to the MCU's driving circuit. The first input terminal of the comparator is connected to a reference voltage, and the second input terminal of the comparator is connected to the first terminal of the sensing resistor, the second terminal of the sensing resistor being grounded. The comparator outputs a low level when the reference voltage is less than or equal to the voltage at the second input terminal; otherwise, it outputs a high level. When the MCU confirms that the comparator outputs a high level, it controls the push-pull switching circuit to operate; when it confirms that the comparator continuously outputs a low-level pulse signal, it controls the push-pull switching circuit to stop operating. Using this scheme, when a short-circuit fault occurs in a power switching device, all power switching devices can be simultaneously shut down, preventing the short-circuit fault from causing greater damage.

Description

Technical Field

[0001] This application relates to the field of electric vehicle technology, and in particular to a short-circuit protection circuit, a short-circuit protection method, and an electric vehicle. Background Technology

[0002] The power battery pack in new energy vehicles provides energy to various components of the vehicle, such as powering the vehicle's three-phase motor. Currently, new energy vehicles generally use a Motor Control Unit (MCU) to convert the DC power output from the power battery pack into three-phase AC power to drive the three-phase motor. Key components in the MCU are power switching devices, typically insulated-gate bipolar transistors (IGBTs) and silicon carbide metal-oxide-semiconductor (SiC MOSFETs).

[0003] For MCUs, the turn-on and turn-off control of their power switching devices is implemented by the driver chip inside the MCU. A short circuit in the power switching device will cause a DC short circuit, damaging the MCU and other circuit devices. Therefore, short circuit protection of the power switching device in the MCU is particularly important.

[0004] In existing technologies, to achieve short-circuit protection for power switching devices, a monitoring function is typically integrated into the MCU's driver chip to monitor the input switching commands and the actual switching state of the power switching devices. The diagnostic strategy involves the driver chip receiving a "turn off" command, then delaying for a certain period (typically a few microseconds) to determine if the power switching device is indeed off. If the turn-off condition is not met, a short-circuit fault is assumed, the fault is reported, and the controlled power switching device is simultaneously turned off. However, this approach requires the driver chip to possess corresponding monitoring capabilities, increasing the performance requirements. Furthermore, since the protection action only turns off a single power switching device, it can cause phase loss operation in the three-phase output, leading to operational instability and severe current fluctuations. Summary of the Invention

[0005] To address the aforementioned technical problems in the prior art, this application provides a short-circuit protection circuit, a short-circuit protection method, and an electric vehicle, which reduces the performance requirements of the driver chip and, when a short-circuit fault occurs in a power switching device, can simultaneously shut down all power switching devices to prevent the short-circuit fault from causing greater damage.

[0006] In one aspect, this application provides a short-circuit protection circuit, including: a sensing resistor, a comparator, and a motor controller MCU. The primary circuit of the push-pull switch circuit is grounded through the sensing resistor, and the push-pull switch circuit provides a drive voltage to the drive circuit of the MCU; the first input terminal of the comparator is connected to a reference voltage, the second input terminal of the comparator is connected to the first terminal of the sensing resistor, and the second terminal of the sensing resistor is grounded; the comparator outputs a high level when the reference voltage is greater than the voltage of the second input terminal, and outputs a low level when the reference voltage is less than or equal to the voltage of the second input terminal; the output terminal of the comparator is connected to the MCU; the MCU controls the push-pull switch circuit to operate when it confirms that the comparator outputs a high level, and controls the push-pull switch circuit to stop operating when it confirms that the comparator continuously outputs a low-level pulse signal, so as to de-energize the drive circuit.

[0007] In this scheme, when a gate short-circuit fault occurs in a power switching device, the short-circuited power switching device causes a short circuit in the MCU's drive circuit, increasing the ground current on the primary side of the push-pull switching circuit. This leads to an increase in the voltage division across the sensing resistor, causing the comparator's output level to no longer remain high. Furthermore, since the power switching devices in the push-pull switching circuit conduct alternately, the comparator's output is a low-level pulse signal. When the MCU confirms that the comparator is continuously outputting a low-level pulse signal, it controls the push-pull switching circuit to stop working. At this point, the drive circuit loses power and can no longer output drive signals to the MCU's power switching devices, enabling all power switching devices to turn off simultaneously and preventing further damage from the short-circuit fault. Moreover, this scheme has a simple circuit structure, is easy to implement, and reduces the performance requirements of the driver chip.

[0008] In one possible implementation, the MCU includes a pulse capture timer. The pulse capture timer is used to detect the number of low-level pulse signals. When the number of low-level pulse signals reaches a first number, the MCU confirms that the comparator is continuously outputting low-level pulse signals.

[0009] In one possible implementation, the MCU is also used to control the push-pull switch circuit to resume operation after the push-pull switch circuit stops working for a first time period. If it is still confirmed that the comparator continues to output a low-level pulse signal, the MCU controls the push-pull switch circuit to stop working again; otherwise, it controls the push-pull switch circuit to continue working. When the number of times the push-pull switch circuit resumes working reaches a second number, the MCU stops controlling the push-pull switch circuit to resume working.

[0010] This implementation incorporates a recovery mechanism that enables recovery after the power switching device is turned off. If the gate-level short-circuit fault disappears, control of the power switching device can be restored normally, thus improving robustness.

[0011] In one possible implementation, the MCU is also used to report a short-circuit fault in the power switching device when the cumulative number of times the push-pull switching circuit resumes operation reaches a second number.

[0012] In one possible implementation, the MCU further includes a first set of pulse width modulation (PWM) signal output interfaces, a second set of PWM signal output interfaces, and an inverter circuit; the inverter circuit is used to convert DC power into AC power; the first set of PWM signal output interfaces is used to output drive signals for the push-pull switching circuit; the second set of PWM signal output interfaces is used to output drive signals for the inverter circuit; specifically, the MCU is used to control the first set of PWM signal output interfaces to stop outputting drive signals when the comparator continuously outputs a low-level pulse signal.

[0013] Secondly, this application also provides a short-circuit protection method applied to a short-circuit protection circuit. The short-circuit protection circuit includes a sensing resistor, a voltage comparator, and a motor controller MCU. The primary circuit of the push-pull switch circuit is grounded through the sensing resistor, and the push-pull switch circuit provides a driving voltage to the drive circuit of the MCU. The first input terminal of the comparator is connected to a reference voltage, and the second input terminal of the comparator is connected to the first terminal of the sensing resistor, the second terminal of the sensing resistor is grounded. The comparator outputs a high level when the reference voltage is greater than the voltage of the second input terminal, and outputs a low level when the reference voltage is less than or equal to the voltage of the second input terminal. The output terminal of the comparator is connected to the MCU. The method includes: controlling the push-pull switch circuit to work when it is confirmed that the comparator outputs a high level; and controlling the push-pull switch circuit to stop working when it is confirmed that the comparator continuously outputs a low-level pulse signal, so as to de-energize the drive circuit.

[0014] This method enables all power switching devices to turn off simultaneously, preventing further damage from short-circuit faults. Furthermore, the circuit structure for implementing this method is simple and easy to implement, reducing the performance requirements of the driver chip.

[0015] In one possible implementation, when it is confirmed that the comparator is continuously outputting a low-level pulse signal, the push-pull switching circuit is controlled to stop working. Specifically, this includes: detecting the number of low-level pulse signals, and when the number of low-level pulse signals reaches a first number, confirming that the comparator is continuously outputting a low-level pulse signal.

[0016] In one possible implementation, after the push-pull switch circuit stops working, the method further includes: after the push-pull switch circuit stops working for a first time period, controlling the push-pull switch circuit to resume working; if it is still confirmed that the comparator continuously outputs a low-level pulse signal, controlling the push-pull switch circuit to stop working again; otherwise, controlling the push-pull switch circuit to continue working; when the cumulative number of times the push-pull switch circuit resumes working reaches a second number, controlling the push-pull switch circuit to resume working is no longer required.

[0017] In one possible implementation, the method also includes:

[0018] When the cumulative number of times the push-pull switching circuit resumes operation reaches the second threshold, a short-circuit fault in the current power switching device is reported.

[0019] Thirdly, this application also provides an electric vehicle, which includes the short-circuit protection circuit provided by the first aspect and any implementation thereof, and further includes a push-pull switch circuit, a power battery pack and a motor; the MCU of the short-circuit protection circuit is also used to convert the DC power output by the power battery pack into AC power and supply it to the motor; the push-pull switch circuit is used to provide a drive voltage for the drive circuit of the MCU. Attached Figure Description

[0020] Figure 1 A schematic diagram of an electrical system for an electric vehicle provided in this application;

[0021] Figure 2 A schematic diagram of a motor controller provided in this application;

[0022] Figure 3 A schematic diagram of a short-circuit protection circuit provided in an embodiment of this application;

[0023] Figure 4 A schematic diagram of another short-circuit protection circuit provided in an embodiment of this application;

[0024] Figure 5 A waveform diagram of the output level of the comparator provided in the embodiments of this application;

[0025] Figure 6 A flowchart illustrating a short-circuit protection method provided in this application embodiment;

[0026] Figure 7 This is a schematic diagram of an electric vehicle provided in an embodiment of this application. Detailed Implementation

[0027] To enable those skilled in the art to better understand the present application, the application scenarios of the present application are described below.

[0028] See Figure 1 The figure is a schematic diagram of an electric vehicle electrical system provided in this application.

[0029] The electrical system of the electric vehicle shown in the diagram mainly includes a motor controller 10, a motor 90, a power battery pack 30, a high-voltage distribution box 40, a DC / DC converter circuit 50, a low-voltage battery 60, a DC charging circuit 70, and an on-board charger 80.

[0030] The power battery pack 30 provides high-voltage direct current (VDC) to the electric vehicle. A portion of this VDC is converted to alternating current (AC) via the high-voltage distribution box 40 and the motor controller 10, supplying the motor 90 to drive the electric vehicle. Another portion of the VDC is converted to low-voltage direct current via the high-voltage distribution box 40 and the DC / DC converter circuit 50, supplying the low-voltage battery 60 and / or the low-voltage system of the electric vehicle. The high-voltage distribution box 40 can also be referred to as a power distribution unit (PDU).

[0031] When an electric vehicle is charging, in some embodiments, the electric vehicle charges the power battery pack 30 through a DC charging circuit 70. At this time, the DC charging circuit 70 is connected to a DC charging pile. This charging method is also called "DC fast charging". DC fast charging has a larger charging power.

[0032] In other embodiments, the electric vehicle is charged via an on-board charger (OBC) 80, which is connected to an AC charging station or the AC power grid. Some on-board chargers 80 can also simultaneously charge the low-voltage battery 60.

[0033] See Figure 2 The figure is a schematic diagram of a motor controller provided in this application.

[0034] The illustrated motor controller 10 includes a driver chip 11 and an inverter circuit 12.

[0035] In this application and the following description, the inverter circuit 12 is described as a three-phase two-level inverter circuit, which outputs three-phase AC power to the three-phase motor 90 of the electric vehicle. The driver chip 11 can also be called a driver circuit.

[0036] In the diagram, power switching devices Q0-Q5 are IGBTs. When a gate-level short circuit occurs in the power switching devices, a short circuit occurs between the gate and emitter of the IGBT. The driver chip typically supplies a 15V pulse-width modulation (PWM) signal to the power switching devices. When a short circuit occurs between the gate and emitter of the IGBT, the 15V power supply to the driver chip is also short-circuited, causing the power supply circuit to generate a large current and potentially damage it.

[0037] To address the aforementioned technical issues, this application provides a short-circuit protection circuit, a short-circuit protection method, and an electric vehicle. This solution adds a detection resistor and a voltage comparator to the primary-side ground terminal of the push-pull switching circuit in the MCU's driver chip. When a short circuit occurs in a power switching device, the output level of the voltage comparator flips, triggering the MCU to detect the short-circuit fault. At this time, the MCU can shut down the power output of the push-pull circuit, thereby promptly shutting down all power switching devices and protecting all power switching devices at the system level, preventing further damage caused by the short-circuit fault.

[0038] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be described below with reference to the accompanying drawings.

[0039] The terms "first" and "second" used in this application description are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated.

[0040] In this application, unless otherwise expressly specified and limited, the term "connection" shall be interpreted broadly. For example, "connection" may be a fixed connection, a detachable connection, or an integral part; it may be a direct connection or an indirect connection through an intermediate medium.

[0041] See Figure 3 The figure is a schematic diagram of a short-circuit protection circuit provided in an embodiment of this application.

[0042] This short-circuit protection circuit is used to protect the power switching devices and the power supply circuit of the MCU drive circuit in electric vehicles. The MCU drive circuit is powered by a push-pull switching circuit 20. The short-circuit protection circuit includes: a detection resistor R1, a comparator U1, and an MCU10.

[0043] The push-pull switching circuit 20 includes a primary circuit 21 and a secondary circuit 22.

[0044] The primary-side circuit 21 includes controllable switching devices. The MCU 10 controls the push-pull switching circuit 20 by outputting pulse-width modulation (PWM) signals to the controllable switching devices included in the primary-side circuit 21, so that the push-pull switching circuit 20 uses the input voltage to generate the positive and negative drive voltages required by the drive circuit of the MCU 10. Figure 2 As shown in the voltage requirements, the push-pull switch circuit 20 can use an input voltage of 12V. The positive drive voltage output by the secondary circuit 22 of the push-pull switch circuit 20 is 15V, which is output to the VCC port of the driver chip 11, and the negative drive voltage is -8V, which is output to the VEE port of the driver chip 11.

[0045] The short-circuit protection circuit includes a detection resistor R1, a comparator U1, and an MCU10.

[0046] In this embodiment, the primary circuit 21 of the push-pull switching circuit 20 is grounded through a sensing resistor R1. The push-pull switching circuit provides a driving voltage to the driving circuit of the MCU 10, and the driving voltage is output by the secondary circuit 22. That is, the solution of this application adds a sensing resistor R1 in series between the primary circuit 21 and ground. The first end of the sensing resistor R1 is connected to the second input terminal of the comparator U1, the second end of the sensing resistor R1 is grounded, and the first input terminal of the comparator U1 is connected to the reference voltage Vref.

[0047] The voltage input to the second input terminal of comparator U1 is the voltage divider of R1. Given that the resistance value of R1 is a known parameter, this voltage divider is used to characterize the magnitude of the current to ground in the primary circuit.

[0048] The comparator U1 is a voltage comparator that outputs a corresponding level signal based on the voltage values ​​at the first and second input terminals. Specifically, comparator U1 outputs a high level when the reference voltage Vref is greater than the voltage at the second input terminal, and outputs a low level when the reference voltage Vref is less than or equal to the voltage at the second input terminal.

[0049] The output of comparator U1 is connected to MCU10.

[0050] In this embodiment, the value of Vref can be the voltage division U0 of the detection resistor R1 when a gate-level short circuit occurs in the power switching device. Alternatively, the value of Vref can be slightly smaller than the voltage division U0 of the detection resistor R1 when a gate-level short circuit occurs in the power switching device, for example, Vref can be set to 0.9 times U0. The specific value of U0 can be determined by pre-calibrating through testing.

[0051] When comparator U1 outputs a high level, it indicates that Vref is greater than the voltage division of the sensing resistor R1, meaning that no power switching device is experiencing a gate-level short circuit, and the ground current of the primary circuit 21 is normal. MCU10 is used to control the push-pull switching circuit 20 to work when it is confirmed that comparator U1 outputs a high level.

[0052] When comparator U1 outputs a low-level pulse signal, it indicates that a gate-level short circuit has occurred in the power switching device, causing an abnormal increase in the ground current of the primary circuit 21. The comparator U1 outputs a low-level pulse signal rather than a continuous low-level signal because the primary circuit 21 of the push-pull switching circuit 20 also includes power switching devices. When the MCU10 controls the power switching devices to alternately turn on or off, it causes the ground line of the primary circuit 21 to alternately conduct, resulting in the comparator U1 outputting a low-level pulse signal. When the MCU10 confirms that the comparator U1 is continuously outputting a low-level pulse signal, it controls the push-pull switching circuit 20 to stop working. At this time, the MCU10's drive circuit is de-energized, and the drive circuit can no longer drive the power switching devices in the inverter circuit, thus causing all power switching devices to turn off simultaneously.

[0053] In summary, using the solution provided in this application, when a gate-level short circuit occurs in a power switching device, the MCU can control the push-pull switching circuit to stop working. At this time, the drive circuit loses power and can no longer output drive signals to the MCU's power switching devices, enabling all power switching devices to turn off simultaneously, avoiding single-phase operation in the three-phase output and preventing greater damage caused by short-circuit faults. Furthermore, this solution has a simple circuit structure, is easy to implement, and reduces the performance requirements of the drive chip.

[0054] The following explanation uses a specific circuit as an example.

[0055] See Figure 4 This figure is a schematic diagram of another short-circuit protection circuit provided in an embodiment of this application.

[0056] The MCU10 in the figure includes a first set of PWM signal output interfaces, which are used to output drive signals for the push-pull switching circuit 20. Figure 4 The first set of PWM signal output interfaces includes ATOM4.2 and ATOM4.3.

[0057] Furthermore, MCU10 also includes a second set of PWM signal output interfaces ( Figure 4 (Not shown in the diagram), the second set of PWM signal output interfaces is used to output the drive signals for the inverter circuit. The second set of PWM signal output interfaces can be found in [reference needed]. Figure 2 As shown, used for output Figure 2 PWM0-PWM5 in the example.

[0058] The primary and secondary circuits of the push-pull switching circuit 20 achieve energy transfer through a transformer. The primary circuit includes power switching devices S1 and S2. S1 and S2 can be insulated gate bipolar transistors (IGBTs), metal-oxide-semiconductor field-effect transistors (MOSFETs), silicon carbide-metal-oxide-semiconductor field-effect transistors (SiC MOSFETs), etc. In this embodiment, S1 and S2 are specifically NMOS transistors for illustration. S1 and S2 are turned on when their gates are connected to a high level.

[0059] When the push-pull switching circuit 20 is working, the MCU10 sends PWM signals to S1 and S2, and controls S1 and S2 to conduct alternately, so that the push-pull switching circuit 20 outputs the driving voltage required by the driving circuit.

[0060] In the prior art, the sources of S1 and S2 are directly grounded. In the solution of this application embodiment, the sources of S1 and S2 are connected to the first terminal of the sampling resistor R1, and the second terminal of the sampling resistor R1 is grounded.

[0061] The first terminal of comparator U1 is connected to the reference voltage Vref, and the second terminal of comparator U1 is connected to the first terminal of the sampling resistor R1. The output terminal of comparator U1 is connected to MCU10 to output a level signal to MCU10. Figure 4 The output of comparator U1 is connected to the TIM5_7 port of MCU10.

[0062] See also Figure 5 The figure shows the waveform of the output level of the comparator provided in the embodiment of this application.

[0063] The output level of comparator U1 is represented by Gate_OC_uc.

[0064] In this embodiment, the value of Vref can be the voltage division U0 of the detection resistor R1 when a gate-level short circuit occurs in the power switching device. Alternatively, the value of Vref can be slightly smaller than the voltage division U0 of the detection resistor R1 when a gate-level short circuit occurs in the power switching device, for example, Vref can be set to 0.9 times U0. The specific value of U0 can be determined by pre-calibrating through testing.

[0065] When no power switching device experiences a gate-level short circuit, the ground current of the primary circuit 21 is normal. During the process of MCU10 controlling S1 and S2 to conduct alternately, when S1 is on and S2 is off, the first terminal of R1 outputs voltage to U1. When S1 is off and S2 is on, the first terminal of R1 outputs voltage to U1. However, regardless of the above situation, the voltage output from the first terminal of R1 to U1 is less than or equal to Vref. Therefore, the output of U1 is always high.

[0066] When the MCU10 confirms that the comparator U1 outputs a high level, it controls the push-pull switch circuit 20 to work, that is, to output drive signals to S1 and S2 normally. At this time, the push-pull switch circuit 20 can generate the drive voltage required by the drive circuit normally.

[0067] When a gate-level short circuit occurs in a power switching device, the ground current of the primary circuit 21 increases abnormally. During the process of MCU10 controlling S1 and S2 to conduct alternately, when S1 is on and S2 is off, the voltage output from the first terminal of R1 to U1 is greater than Vref; when S1 is off and S2 is on, the voltage output from the first terminal of R1 to U1 is greater than Vref. However, during the switching process where S1 and S2 are simultaneously off, no current flows through R1, and the voltage output from the first terminal of R1 to U1 is less than Vref. Therefore, the output level of U1 is a low-level pulse signal.

[0068] When MCU10 confirms that comparator U1 continuously outputs a low-level pulse signal, it controls the push-pull switching circuit 20 to stop working. In one possible implementation, MCU10 includes a pulse capture timer. The pulse capture timer captures the moments of level changes on external pins and converts these moments into timer count values, thereby achieving high-precision time measurement. Specifically, the pulse capture timer can perform edge capture, such as capturing rising edges. When a rising edge is detected, it can be considered that a low-level pulse has occurred. The pulse capture timer can also trigger MCU interrupts to cause the MCU to execute corresponding control actions.

[0069] The solution in this embodiment utilizes a pulse capture timer to detect the number of low-level pulse signals. When the number of low-level pulse signals reaches a first quantity, the MCU10 can be triggered to confirm that the comparator U1 continuously outputs low-level pulse signals. If the first quantity is not reached, it indicates that the power switching devices of the inverter circuit do not have a continuous gate-level short-circuit fault.

[0070] This application does not limit the first quantity in its embodiments. In practice, various applications exist. If the first quantity is set too small, misjudgments due to chance cannot be avoided. If the first quantity is set too large, it may lead to excessive delay in disconnecting the power switching device, reducing safety. Therefore, the solution in this application embodiment, through testing, sets the first quantity to 10. It is understood that the above values ​​for the first quantity are merely suggestions and do not constitute a limitation on the technical solution of this application.

[0071] MCU10 controls the push-pull switching circuit 20 to stop working, that is, it controls the first group of PWM signal output interfaces to stop outputting drive signals, so that S1 and S2 remain in the off state, and the push-pull switching circuit 20 no longer outputs voltage. At this time, the drive circuit of MCU10 is de-energized, and the drive circuit can no longer drive the various power switching devices in the inverter circuit. Therefore, all power switching devices are turned off simultaneously, avoiding the three-phase output from operating with a single phase, avoiding greater damage caused by short circuit faults, preventing the primary coil current of the push-pull switching circuit 20 from increasing, preventing the transformer from burning out, and protecting the 12V power supply.

[0072] Furthermore, the solution in this application embodiment can also implement a recovery mechanism after the fault disappears, which can attempt to recover after the power switching device is turned off. If the gate-level short circuit fault disappears, the control of the power switching device can be restored normally, thus improving robustness. This will be explained in detail below.

[0073] After MCU10 stops outputting drive signals to S1 and S2, it resumes operation of the push-pull switching circuit 20 after a first period of inactivity. At this time, S1 and S2 alternately conduct again. If the gate-level short-circuit fault of the power switching device disappears, the output level of U1 will remain high, allowing MCU10 to maintain normal drive to S1 and S2, thus restoring normal operation of MCU10.

[0074] When the MCU10 controls the push-pull switching circuit 20 to resume operation, if the gate-level short-circuit fault of the power switching device still exists, U1 will continue to output a low-level pulse signal, and the MCU10 will control the push-pull switching circuit to stop working again.

[0075] The solution in this application does not specifically limit the first time period. In practical applications, the first time period should be a relatively short period, such as 50ms. This ensures that if the gate-level short-circuit fault can be eliminated in time, the push-pull switching circuit will not stop working for too long, meaning the MCU's inverter circuit will not stop working for too long, and the vehicle will not lose power for too long, thus ensuring that it is imperceptible to the user. For example, taking a first time period of 50ms as an example, after the MCU first controls the push-pull switching circuit to stop working, it controls the push-pull switching circuit to resume working after a 50ms interval. At this time, a continuous high level is detected from the comparator output, indicating that the gate-level short-circuit fault has disappeared. Therefore, the total time the MCU's inverter circuit stops working is 50ms, which is short and imperceptible to the driver, improving the driving experience while ensuring safety.

[0076] In the scheme of this application embodiment, the upper limit of the number of times the MCU10 controls the push-pull switch circuit 20 to resume operation is a second number. If the number of times the push-pull switch circuit 20 resumes operation is less than the second number, it is considered that the gate-level short-circuit fault of the power switching device has disappeared, and a short-circuit fault is not reported. If the cumulative number of times the push-pull switch circuit 20 resumes operation reaches the second number, the MCU10 reports that a short-circuit fault has occurred in the power switching device.

[0077] The fact that the push-pull switching circuit has resumed operation for the second consecutive number of times indicates that the gate-level short-circuit fault in the power switching device of the inverter circuit cannot be eliminated.

[0078] In one possible implementation, the MCU10 can report a short-circuit fault in a power switching device to the Vehicle Control Unit (VCU) so that the VCU can promptly alert the user.

[0079] This application does not specifically limit the second quantity. In practical applications, if the second quantity is set too small, the fault may be reported before the short-circuit fault disappears. If the first quantity is set too large, it may lead to a delayed notification to the user, reducing security. Therefore, the solution in this application embodiment, through testing, sets the second quantity to 3. It is understood that the above values ​​for the second quantity are only suggestions and do not constitute a limitation on the technical solution of this application.

[0080] MCU10 can be an Application Specific Integrated Circuit (ASIC), a Programmable Logic Device (PLD), a Digital Signal Processor (DSP), or a combination thereof. The aforementioned PLD can be a Complex Programmable Logic Device (CPLD), a Field-Programmable Gate Array (FPGA), a Generic Array Logic (GAL), or any combination thereof; this application does not impose specific limitations on the embodiments thereof.

[0081] In summary, the solution provided by this application eliminates the need for the MCU's driver chip to have its own monitoring function, allowing for a wider range of driver chip selections. When a gate-level short-circuit fault occurs in the power switching devices, all power switching devices can be simultaneously turned off, preventing further damage from the short-circuit fault. Furthermore, due to the involvement of the main control MCU, this solution also features a fault recovery mechanism. After turning off all power switching devices, it attempts to recover; if the gate-level short-circuit fault disappears, the system can return to normal, demonstrating high system robustness.

[0082] Based on the short-circuit protection circuit provided in the above embodiments, this application also provides a short-circuit protection method. This method is applied to an MCU. When it is confirmed that the comparator outputs a high level, the push-pull switch circuit is controlled to work; when it is confirmed that the comparator continuously outputs a low-level pulse signal, the push-pull switch circuit is controlled to stop working so as to de-energize the drive circuit. The following is a detailed description in conjunction with the accompanying drawings.

[0083] See Figure 6 The figure is a flowchart of a short-circuit protection method provided in an embodiment of this application.

[0084] The method includes the following steps:

[0085] S11: Obtain the level signal output by comparator U1.

[0086] The MCU is connected to the output of comparator U1. The first input of comparator U1 is connected to a reference voltage, and the second input is connected to the voltage divider of the sensing resistor R1. Comparator U1 outputs a high level when the reference voltage is greater than the voltage at the second input; and outputs a low level when the reference voltage is less than or equal to the voltage at the second input.

[0087] S12: Determine whether the output of comparator U1 is high.

[0088] If yes, it indicates that there is no gate-level short-circuit fault in any of the power switching devices of the inverter circuit at this time, and S13 is executed; otherwise, S14 is executed.

[0089] S13: Normal drive push-pull switch circuit operation.

[0090] Since there are no gate-level short-circuit faults in the power switching devices of the inverter circuit, the MCU drives the push-pull switching circuit to work, and the push-pull switching circuit can output driving voltage for the MCU's driving circuit.

[0091] S14: Determine whether the number of low-level pulses has reached the first quantity.

[0092] The MCU includes a pulse capture timer. The pulse capture timer captures the moments when the level changes on external pins and converts these moments into timer count values, thereby achieving high-precision time measurement. Specifically, the pulse capture timer can capture edges, such as rising edges. When a rising edge is detected, it can be considered that a low-level pulse has occurred.

[0093] If so, it is determined that there is a gate-level short-circuit fault in the power switching device of the inverter circuit, and S15 is executed. Otherwise, it indicates that the low-level pulse detected at this time is accidental, or that the gate-level short-circuit fault terminal of the power switching device of the inverter circuit appears briefly and then disappears quickly, and S13 is executed.

[0094] S15: Controls the push-pull switch circuit to stop working.

[0095] The MCU controls the push-pull switching circuit to stop working, that is, it controls the first group of PWM signal output interfaces to stop outputting drive signals, so that the power switching devices in the push-pull switching circuit remain in the off state, and the push-pull switching circuit no longer outputs voltage. At this time, the MCU's drive circuit is de-energized, and the drive circuit can no longer drive the various power switching devices in the inverter circuit, thus causing all power switching devices to turn off simultaneously.

[0096] S16: Determine whether the number of times the push-pull switch circuit has resumed operation has reached the second number.

[0097] If yes, execute S18; otherwise, execute S17.

[0098] S17: Controls the push-pull switch circuit to resume operation after the first period of inactivity.

[0099] After the push-pull switching circuit stops operating for the first time period, the MCU controls the push-pull switching circuit to resume operation. If the gate-level short-circuit fault of the power switching device disappears, the output level of U1 will remain high, and the MCU can maintain normal drive of the power switching device in the push-pull switching circuit, thus restoring normal operation of the MCU. If the gate-level short-circuit fault of the power switching device still exists, U1 will continue to output a low-level pulse signal, and the MCU will again control the push-pull switching circuit to stop operating.

[0100] S18: Report a gate-level short circuit fault.

[0101] At this point, the push-pull switching circuit has resumed operation for the second consecutive time, indicating that the gate-level short-circuit fault in the power switching device of the inverter circuit cannot be eliminated. The MCU can report the existence of a short-circuit fault in the power switching device to the VCU so that the VCU can promptly notify the user.

[0102] It is understood that the order and limitations of the above steps are for illustrative purposes only and do not constitute a limitation on the technical solution of this application. In practical applications, the above steps can be modified.

[0103] In summary, using the method provided in this application, when a gate-level short-circuit fault occurs in the power switching devices, all power switching devices can be turned off simultaneously, preventing the short-circuit fault from causing greater damage. Furthermore, this method also has a fault disappearance recovery mechanism, which can attempt recovery after turning off all power switching devices. If the gate-level short-circuit fault disappears, the system can return to normal, demonstrating high system robustness.

[0104] Based on the short-circuit protection circuit and short-circuit protection method provided in the above embodiments, this application also provides an electric vehicle, which will be described in detail below with reference to the accompanying drawings.

[0105] See Figure 7 The figure is a schematic diagram of an electric vehicle provided in an embodiment of this application.

[0106] The electric vehicle 1000 includes: a short-circuit protection circuit, a push-pull switch circuit 20, a power battery pack 30, and a motor 90.

[0107] The short-circuit protection circuit includes a detection resistor R1, a comparator U1, and an MCU10.

[0108] For details on the working principles of the detection resistor R1, comparator U1, and MCU10, please refer to the descriptions in the above embodiments. These details will not be repeated here.

[0109] The MCU10 of the short-circuit protection circuit is also used to convert the DC power output from the power battery pack 30 into AC power and supply it to the motor 90.

[0110] The push-pull switch circuit 20 is used to provide drive voltage for the drive circuit of MCU10.

[0111] In the electric vehicle provided in this application embodiment, when a gate short-circuit fault occurs in a power switching device, the short-circuited power switching device causes a short circuit in the power supply of the MCU's drive circuit. This increases the ground current on the primary side of the push-pull switching circuit, leading to an increase in the voltage division of the sensing resistor. At this time, the comparator's output level no longer remains high. Furthermore, since the power switching devices in the push-pull switching circuit conduct alternately, the comparator's output is a low-level pulse signal. When the MCU confirms that the comparator is continuously outputting a low-level pulse signal, it controls the push-pull switching circuit to stop working. At this time, the drive circuit loses power and can no longer output drive signals to the MCU's power switching devices, enabling all power switching devices to turn off simultaneously, avoiding greater damage caused by the short-circuit fault. Moreover, this solution has a simple circuit structure, is easy to implement, and reduces the performance requirements of the driver chip.

[0112] In addition, due to the involvement of the main control MCU, the solution also has a fault disappearance recovery mechanism, which can attempt to recover after all power switching devices are turned off. If the gate-level short circuit fault disappears, the system can return to normal, and the system has high robustness.

[0113] It should be understood that in this application, "at least one (item)" means one or more, and "more than" means two or more. "And / or" is used to describe the relationship between related objects, indicating that three relationships can exist. For example, "A and / or B" can represent three cases: only A exists, only B exists, and both A and B exist simultaneously, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one (item) of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one (item) of a, b, or c can represent: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, and c can be single or multiple.

[0114] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on its differences from other embodiments. The device embodiments described above are merely illustrative, and the units and modules described as separate components may or may not be physically separate. Furthermore, some or all of the units and modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0115] The above description is only a specific embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A short-circuit protection circuit, characterized in that, include: Detection resistors, comparators, and motor controller MCUs; The primary circuit of the push-pull switch circuit is grounded through the detection resistor, and the push-pull switch circuit provides the driving voltage for the driving circuit of the MCU. The first input terminal of the comparator is connected to the reference voltage, the second input terminal of the comparator is connected to the first terminal of the sensing resistor, and the second terminal of the sensing resistor is grounded. The comparator is configured to output a high level when the reference voltage is greater than the voltage at the second input terminal, and output a low level when the reference voltage is less than or equal to the voltage at the second input terminal. The output of the comparator is connected to the MCU; The MCU is used to control the push-pull switch circuit to work when it is confirmed that the comparator outputs a high level, and to control the push-pull switch circuit to stop working when it is confirmed that the comparator continuously outputs a low level pulse signal, so as to de-energize the drive circuit.

2. The short-circuit protection circuit according to claim 1, characterized in that, The MCU includes a pulse capture timer; The pulse capture timer is used to detect the number of low-level pulse signals. When the number of low-level pulse signals reaches a first number, the MCU confirms that the comparator continuously outputs low-level pulse signals.

3. The short-circuit protection circuit according to claim 2, characterized in that, The MCU is also used to control the push-pull switch circuit to resume operation after the push-pull switch circuit stops working for a first time period. If it is still confirmed that the comparator continues to output a low-level pulse signal, the MCU controls the push-pull switch circuit to stop working again; otherwise, it controls the push-pull switch circuit to continue working. When the number of times the push-pull switch circuit resumes working reaches a second number, the MCU stops controlling the push-pull switch circuit to resume working.

4. The short-circuit protection circuit according to claim 3, characterized in that, The MCU is also used to report a short circuit fault in the power switching device when the cumulative number of times the push-pull switching circuit resumes operation reaches the second number.

5. The short-circuit protection circuit according to claim 1, characterized in that, The MCU also includes a first set of pulse width modulation (PWM) signal output interfaces, a second set of PWM signal output interfaces, and an inverter circuit; The inverter circuit is used to convert direct current into alternating current. The first set of PWM signal output interfaces is used to output the drive signal of the push-pull switching circuit; The second set of PWM signal output interfaces is used to output the drive signal of the inverter circuit; Specifically, the MCU is used to control the first group of PWM signal output interfaces to stop outputting drive signals when it is confirmed that the comparator is continuously outputting a low-level pulse signal.

6. A short-circuit protection method, characterized in that, This invention is applied to a short-circuit protection circuit, which includes a sensing resistor, a voltage comparator, and a motor controller (MCU). The primary circuit of a push-pull switching circuit is grounded through the sensing resistor, and the push-pull switching circuit provides a driving voltage to the driving circuit of the MCU. The first input terminal of the comparator is connected to a reference voltage, and the second input terminal of the comparator is connected to the first terminal of the sensing resistor, the second terminal of which is grounded. The comparator outputs a high level when the reference voltage is greater than the voltage at the second input terminal. When the reference voltage is less than or equal to the voltage at the second input terminal, the output is low, and the output terminal of the comparator is connected to the MCU; the method includes: When the comparator outputs a high level, the push-pull switch circuit is controlled to operate. When it is confirmed that the comparator continuously outputs a low-level pulse signal, the push-pull switch circuit is controlled to stop working, so as to de-energize the drive circuit.

7. The short-circuit protection method according to claim 6, characterized in that, When it is confirmed that the comparator continuously outputs a low-level pulse signal, controlling the push-pull switching circuit to stop working specifically includes: The number of low-level pulse signals is detected, and when the number of low-level pulse signals reaches a first number, it is confirmed that the comparator continuously outputs low-level pulse signals.

8. The short-circuit protection method according to claim 7, characterized in that, After the push-pull switch circuit is stopped from operating, the method further includes: After the push-pull switch circuit stops working for a first period of time, the push-pull switch circuit resumes working. If it is still confirmed that the comparator continues to output a low-level pulse signal, the push-pull switch circuit stops working again; otherwise, the push-pull switch circuit continues to work. When the cumulative number of times the push-pull switch circuit resumes operation reaches a second number, the push-pull switch circuit will no longer be controlled to resume operation.

9. The short-circuit protection method according to claim 8, characterized in that, The method further includes: When the cumulative number of times the push-pull switch circuit resumes operation reaches the second number, a short-circuit fault in the power switching device is reported.

10. An electric vehicle, characterized in that, The electric vehicle includes the short-circuit protection circuit according to any one of claims 1-5, and further includes a push-pull switch circuit, a power battery pack and a motor; The MCU of the short-circuit protection circuit is also used to convert the DC power output from the power battery pack into AC power and supply it to the motor; The push-pull switching circuit is used to provide drive voltage for the drive circuit of the MCU.

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