Sensor fault detection circuit, fault detection method and electric vehicle

Abstract

The present application provides a sensor fault detection circuit, a fault detection method and an electric vehicle, which relate to the field of power electronics technology. The sensor fault detection circuit sensor includes a signal detection circuit and a controller. Among them, the signal detection circuit is used to detect the output voltage of the sensor and transmit the detection result to the controller. The controller is used to input a detection signal to the detection circuit of the sensor, and determine whether the sensor has a fault based on the detection signal and the detection result. The detection signal is an AC signal. The fault detection circuit of the sensor can be used to detect various types of sensors, and only one detection circuit is needed to achieve detection, without the need to set up two heterogeneous detection circuits, which can meet the requirements of functional safety and reduce costs.

Description

Technical Field

[0001] The present application relates to the field of power electronics technology, and in particular to a sensor fault detection circuit, a fault detection method, a power distribution unit and an electric vehicle. Background Art

[0002] With the increasing energy shortage and environmental pollution in modern society, new energy vehicles have received widespread attention from all walks of life. Among them, in new energy vehicles such as battery electric vehicles (BEV) and plug-in hybrid electric vehicles (PHEV), the power battery pack is connected to the vehicle's DC bus, which includes a positive DC bus and a negative DC bus. Sensors are generally used to detect the current of the DC line to identify short-circuit faults of the DC bus or overcurrent faults of the charging current.

[0003] For functional safety reasons, it is necessary to promptly detect sensor open circuit, short circuit, stuck, parameter drift and other faults to avoid failure to detect DC line faults due to sensor failure.

[0004] In order to meet the fault diagnosis coverage requirements of the functional safety ISO26262 standard for hardware random failures, the existing technology generally adopts a mechanism of comparing two sensor detection circuits to achieve high diagnostic coverage, which is explained in detail below.

[0005] See also Figure 1 , which is a schematic diagram of a fault detection circuit used in the prior art.

[0006] The positive port of the DC charging interface 10 is connected in series with the sensor 20a and the contactor 30a through the positive DC bus HV+, and then connected to the positive port of the power battery pack 50; the negative port of the DC charging interface 10 is connected in series with the sensor 20b and the contactor 30b through the negative DC bus HV-, and then connected to the negative port of the power battery pack 50. The sampling circuit 40a is used to transmit the sampling data of the sensor 20a to the microcontroller unit (MCU) 60, and the sampling circuit 40b is used to transmit the sampling data of the sensor 20b to the microcontroller unit 60. The microcontroller unit 60 compares and detects the two sampling counters to determine whether the sensor is faulty.

[0007] This solution requires the use of two detection circuits. According to the correlation failure requirements of the functional safety standard ISO26262, in order to ensure the independence of safety functions and safety mechanisms and avoid correlation failures, the two detection circuits need to be heterogeneous to ensure independence, that is, the hardware parameters of the two sensors and the two sampling circuits are different, which increases the cost. Summary of the invention

[0008] The present application provides a sensor fault detection circuit, a fault detection method, a power distribution unit and an electric vehicle, which can improve the functional safety of the sensor and reduce the hardware cost.

[0009] In the first aspect, the present application provides a sensor fault detection circuit for detecting faults in a sensor. In a typical application scenario, the sensor is a sensor, and the sensor is used to detect the current of the DC line of an electric vehicle, for example, detecting the current of the DC bus of an electric vehicle. The sensor fault detection circuit includes: a signal detection circuit and a controller. Among them, the controller first inputs a detection signal to the detection circuit of the sensor, and the signal detection circuit is used to detect the output voltage of the sensor and transmit the detection result to the controller; the controller then determines whether the sensor has a fault based on the detection signal and the detection result, and the detection signal is an AC signal.

[0010] After the controller sends a detection signal with known parameters to the detection circuit of the sensor, the detection signal is superimposed on the DC current of the DC circuit, and the detection result corresponding to the output voltage of the sensor is obtained by using the signal detection circuit. At this time, part of the detection result is the detection result corresponding to the DC current, and the other part is the detection result corresponding to the detection signal. Since the corresponding part of the detection signal in the detection signal is an AC signal, it can be separated by a filtering circuit. The controller compares the detection result with the detection signal to determine whether the sensor is faulty. The fault detection circuit of the sensor can detect multiple types of sensors, and only one detection circuit is needed to realize the detection. Compared with the traditional redundant sensor detection circuit solution, it has low cost and simple control, can meet the functional safety ISO26262 standard ASIL B and above requirements, and has high diagnostic coverage.

[0011] In combination with the first aspect, in a first possible implementation, the detection signal is a pulse width modulation signal having a preset frequency and a preset amplitude, and the controller obtains a response signal having a frequency of the preset frequency according to the detection result, and determines whether the sensor is faulty according to the amplitude of the response signal and the preset amplitude. Because the frequency of the response signal is the preset frequency, it is characterized that the response signal is the detection result of the sensor on the detection signal, and therefore the comparison result of the amplitude of the response signal and the preset amplitude can provide feedback on whether the current sensor is faulty.

[0012] In combination with the first aspect, in a second possible implementation, the fault detection circuit of the sensor further includes a drive circuit. An input end of the drive circuit is connected to a DC power supply, and the drive circuit increases the amplitude of the detection signal and transmits it to the detection circuit.

[0013] The detection signal output by the controller is generally an AC signal with a low voltage amplitude. When it is directly superimposed on the high-voltage DC in the detection circuit, the detection signal is easily submerged by the high-voltage DC, resulting in difficulty in separating the detection result to obtain a more accurate detection result corresponding to the detection signal. Therefore, it is necessary to set a drive circuit to amplify the detection signal, and the amplification factor of the drive circuit for the detection signal is a known parameter.

[0014] In combination with the first aspect, in a third possible implementation, the controller determines that the sensor is not faulty when the amplitude of the response signal is equal to a preset amplitude; determines that the sensor is open-circuited when the amplitude of the response signal is equal to the voltage of the DC power supply; determines that the sensor is short-circuited when the response signal is constant at zero; determines that the sensor has a stuck fault when the response signal is constant and greater than zero; and determines that the sensor has parameter drift when the response signal is a pulse width modulated signal and the amplitude is not equal to the preset amplitude.

[0015] The controller uses a comparator to compare the detection signal and the response signal. According to the safety standard ISO26262, the typical diagnostic coverage of the comparator is "high", that is, the diagnostic coverage can reach 99%, so it can meet the functional safety ASIL B and above indicators.

[0016] In combination with the first aspect, in a fourth possible implementation, the signal detection circuit includes a first differential amplifier and a first filtering circuit; the non-inverting input terminal of the first differential amplifier is connected to the positive output terminal of the sensor, the inverting input terminal of the first differential amplifier is connected to the negative output terminal of the sensor, and the output terminal of the first differential amplifier is connected to the first filtering circuit; the first differential amplifier is used to amplify the voltage across the sensor and transmit it to the first filtering circuit; the first filtering circuit obtains a detection result with a preset frequency from the amplified voltage, and sends the detection result to the controller.

[0017] The first filtering circuit uses a bandpass filter to obtain a detection result with a frequency that is a preset frequency, and the center frequency of the bandpass filter is the preset frequency.

[0018] In combination with the first aspect, in a fifth possible implementation, the detection signal includes at least two pulse width modulation signals, and the preset frequencies of the two pulse width modulation signals are different. The amplitudes of the at least two pulse width modulation signals may be the same or different, and the present application does not make specific limitations, but the amplitudes of all pulse width modulation signals are predetermined.

[0019] In combination with the first aspect, in a sixth possible implementation method, the controller obtains a response signal having the same frequency as at least two pulse width modulation signals based on the detection results, and determines that the sensor is faulty when the amplitudes of all response signals are different from the amplitudes of the pulse width modulation signals with the same frequency.

[0020] In combination with the first aspect, in a seventh possible implementation method, the detection signal is a three-way pulse width modulation signal, and the controller obtains a response signal whose frequency is the same as the three-way pulse width modulation signal according to the detection result; when the amplitude of at least two response signals is different from the amplitude of the pulse width modulation signal with the same frequency, the sensor is determined to be faulty.

[0021] In order to improve the degree of differentiation of multiple pulse width modulation signals and to facilitate the design of a bandpass filter, the preset frequencies of the multiple pulse width modulation signals may have a relatively obvious difference, for example, the preset frequencies of the three pulse width modulation signals are 9KHz, 42KHz, and 73KHz respectively.

[0022] By applying the majority voting circuit (referring to the safety standard ISO26262, the typical achievable diagnostic coverage of the majority voting circuit is high, that is, the diagnostic coverage can reach 99%), the potential fault diagnosis coverage can reach 90% or above, thereby achieving functional safety ASIL B level and above indicators.

[0023] In combination with the first aspect, in an eighth possible implementation, the fault detection circuit of the sensor further includes a drive circuit. An input end of the drive circuit is connected to a low-voltage power supply. The drive circuit is used to increase the amplitude of the detection signal and transmit it to the sensor.

[0024] In combination with the first aspect, in a ninth possible implementation, the signal detection circuit includes a second filtering circuit and a second differential amplifier. A non-inverting input terminal of the second differential amplifier is connected to a positive output terminal of the sensor, an inverting input terminal of the second differential amplifier is connected to a negative output terminal of the sensor, and an output terminal of the second differential amplifier is connected to the second filtering circuit.

[0025] The second differential amplifier is used to amplify the voltage across the sensor and transmit it to the second filtering circuit; the second filtering circuit is used to obtain a detection result having the same frequency as at least two pulse width modulation signals from the amplified voltage, and send the detection result to the controller.

[0026] In combination with the first aspect, in a tenth possible implementation manner, the sensor is any one of a current transformer, a Hall sensor, or a resistance shunt.

[0027] In combination with the first aspect, in an eleventh possible implementation manner, the controller is a controller of a battery management system (BMS) of the electric vehicle.

[0028] In combination with the first aspect, in a twelfth possible implementation, the controller is a controller of a power distribution unit (PDU) of the electric vehicle, and the power distribution unit is also called a high-voltage distribution box, or a high-voltage distribution box.

[0029] In combination with the first aspect, in a thirteenth possible implementation manner, the controller is a controller of a motor control unit (MCU) of the electric vehicle.

[0030] In a second aspect, the present application also provides a sensor fault detection method, the method comprising the following steps:

[0031] Inputting a detection signal into the detection circuit of the sensor, the detection signal being an AC signal;

[0032] Obtaining the detection result of the output terminal voltage of the sensor;

[0033] Determine whether the sensor is faulty based on the detection signal and the detection result.

[0034] In combination with the second aspect, in a first possible implementation manner, the detection signal is a pulse width modulation signal having a preset frequency and a preset amplitude, and determining whether the sensor has a fault according to the detection signal and the detection result specifically includes:

[0035] A response signal having a preset frequency is obtained according to the detection result, and whether the sensor is faulty is determined according to the amplitude of the response signal and the preset amplitude.

[0036] In conjunction with the second aspect, in a second possible implementation manner, the input end of the driving circuit is connected to a DC power supply, and determining whether the sensor is faulty according to the response signal specifically includes:

[0037] When the amplitude of the response signal is equal to the preset amplitude, it is determined that the sensor is not faulty;

[0038] When the amplitude of the response signal is equal to the voltage of the low-voltage power supply, determining that the sensor is open circuit;

[0039] When the response signal is constant at zero, it is determined that the sensor is short-circuited;

[0040] When the response signal is constant and greater than zero, it is determined that the sensor has a stuck fault;

[0041] When the response signal is a pulse width modulation signal and the amplitude is not equal to the preset amplitude, it is determined that the sensor has parameter drift.

[0042] In combination with the second aspect, in a third possible implementation manner, the detection signal includes at least two pulse width modulation signals, and the preset frequencies of the two pulse width modulation signals are different.

[0043] In combination with the second aspect, in a fourth possible implementation manner, determining whether the sensor is faulty according to the detection signal and the detection result specifically includes:

[0044] Response signals having the same frequency as at least two pulse width modulation signals are obtained according to the detection results. When the amplitudes of all response signals are different from the amplitudes of the pulse width modulation signals with the same frequency, it is determined that the sensor is faulty.

[0045] In combination with the second aspect, in a fifth possible implementation, the detection signal is a three-way pulse width modulation signal, and determining whether the sensor is faulty according to the detection signal and the detection result specifically includes:

[0046] Response signals having the same frequency as the three pulse width modulation signals are obtained according to the detection results. When the amplitudes of at least two response signals are different from the amplitudes of the pulse width modulation signals with the same frequency, it is determined that the sensor is faulty.

[0047] In a third aspect, the present application also provides a power distribution unit (PDU), which is also called a high-voltage distribution box. The input end of the power distribution unit is connected to the DC charging interface of the electric vehicle, and the output end of the power distribution unit is connected to the power battery pack of the electric vehicle. The power distribution unit includes the fault detection circuit of the sensor provided by the above implementation method, and also includes an on-board charger.

[0048] The input end of the on-board charger is connected to an AC power source, and the output end of the on-board charger is connected to a power battery pack. The on-board charger is used to charge the power battery pack using an AC power source. The controller is integrated with the controller of the power distribution unit.

[0049] In a fourth aspect, the present application also provides a motor control unit (MCU), the input end of the motor control unit is connected to the power battery pack of the electric vehicle, the output end of the motor control unit is connected to the motor of the electric vehicle, and the motor control unit includes the fault detection circuit of the sensor provided by the above implementation method, and also includes an inverter. The input end of the inverter is connected to the input end of the motor control unit, and the output end of the inverter is connected to the output end of the motor control unit. The inverter is used to convert the direct current provided by the power battery pack into alternating current and then provide it to the motor.

[0050] In a fifth aspect, the present application also provides an electric vehicle, which includes a fault detection circuit of a sensor provided in the above implementation, and also includes a DC bus, a power battery pack, and a sensor. The DC bus is connected to the power battery pack, and the DC bus is used to transmit direct current; the power battery pack is used to provide electrical energy for the electric vehicle; and the sensor is used to detect the current of the DC bus. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 A schematic diagram of a fault detection circuit used in the prior art;

[0052] Figure 2 An exemplary electric vehicle system structure diagram provided for an embodiment of the present application;

[0053] Figure 3 A schematic diagram of a fault detection circuit of a current sensor provided in an embodiment of the present application;

[0054] Figure 4 A schematic diagram of another fault detection circuit of a current sensor provided in an embodiment of the present application;

[0055] Figure 5 A schematic diagram of a controller provided in an embodiment of the present application;

[0056] Figure 6 A schematic diagram of a fault detection circuit of another current sensor provided in an embodiment of the present application;

[0057] Figure 7 A schematic diagram of a fault detection circuit of another current sensor provided in an embodiment of the present application;

[0058] Figure 8 A schematic diagram of another controller provided in an embodiment of the present application;

[0059] Fig. 9 A flow chart of a fault detection method for a current sensor provided in an embodiment of the present application;

[0060] Fig.10 A flowchart of another current sensor fault detection method provided in an embodiment of the present application;

[0061] Fig.11 A flowchart of another current sensor fault detection method provided in an embodiment of the present application;

[0062] Fig.12 A flowchart of another current sensor fault detection method provided in an embodiment of the present application;

[0063] Fig.13 A schematic diagram of a power distribution unit provided in an embodiment of the present application;

[0064] Fig.14 A schematic diagram of a motor control unit provided in an embodiment of the present application;

[0065] Fig.15 A schematic diagram of an electric vehicle provided in an embodiment of the present application. DETAILED DESCRIPTION

[0066] In order to enable those skilled in the art to better understand the technical solution provided by the embodiments of the present application, the application scenarios of the technical solution provided by the present application are first introduced below.

[0067] The battery electric vehicle (BEV) is powered by a power battery pack formed by rechargeable batteries (such as lead-acid batteries, nickel-cadmium batteries, nickel-metal hydride batteries or lithium-ion batteries, etc.), and the electric motor converts the electrical energy into mechanical energy to drive the electric vehicle.

[0068] Plug-in hybrid electric vehicles (PHEVs) include the engine, transmission, drive system, oil circuit and fuel tank of a traditional car, as well as the battery, charging port, motor and control circuit of an electric vehicle. They can achieve pure electric and zero-emission driving, and can also increase the vehicle's range through hybrid mode.

[0069] For the above types of new energy vehicles, current sensors are generally used to detect the charging current of the DC bus to identify short circuit faults or overcurrent faults of the charging current.

[0070] The following uses the battery electric vehicle (BEV) scenario as an example for explanation.

[0071] See also Figure 2 , which is a structural diagram of an exemplary electric vehicle system provided in an embodiment of the present application.

[0072] The illustrated system includes a DC charging interface 10 , a power distribution unit (PDU) 201 , a power supply system 202 , an on-board charger (OBC) 203 , and a vehicle control unit (VCU) 204 .

[0073] The power supply system 202 is used to provide the electric vehicle with the required electrical energy.

[0074] The power supply system 202 includes a power battery pack 50 and a battery management system (BMS) 51 .

[0075] The battery management system 51 is a functional unit that monitors and manages the charge and discharge of the power battery pack 50 , and is used to ensure that the power supply system is in a safe and controllable state.

[0076] The illustrated system includes a high-voltage line loop and a controller area network (CAN) loop. The high-voltage line loop is a power loop with the power supply system 202 as the core. The controller area network loop is a communication loop with the vehicle control unit (VCU) 204 as the core.

[0077] When the electric vehicle is in a driving state, the power supply system 202 provides energy to the motor of the electric vehicle.

[0078] When the electric vehicle is in a charging state, an external charging pile replenishes energy for the power supply system 10 through the on-board charger 203 or the DC charging interface 10 .

[0079] Continue to see Figure 1 The power distribution unit 201 is also called a high-voltage distribution box, and includes current sensors 20 a and 20 b , a contactor 30 a , a sampling circuit 40 a and a micro control unit 60 .

[0080] Among them, the current sensor converts the current in the detection circuit into a voltage signal for output, and the detection circuit of the subsequent stage samples the voltage signal to obtain a voltage sampling value. The microcontroller unit includes an analog to digital converter (ADC), and the ADC obtains a digital voltage signal after analog-to-digital conversion of the voltage sampling value, and then uses the digital voltage signal to obtain the current value to realize the detection of the line current. The current sensor includes current transformers, Hall current sensors or resistor shunts, etc., which are introduced below.

[0081] The current transformer utilizes the principle of electromagnetic induction, including windings and closed magnetic cores. Its primary winding has fewer turns and is connected in series in the circuit of the current to be measured. Its secondary winding has more turns and is connected in series in the measuring instrument and the protection circuit. When the current transformer is working, its secondary circuit is always closed, so the impedance of the series coil of the measuring instrument and the protection circuit is very small, and the working state of the current transformer is close to short circuit.

[0082] The Hall current sensor utilizes the Hall effect. The specific principle is: when a current I is passed through the current input terminal of the Hall element and a magnetic field with a magnetic induction intensity of B is applied in the normal direction of the plane of the Hall element, an electric potential V will be generated in the direction perpendicular to the current and the magnetic field (i.e. between the Hall output terminals). This is called the Hall potential, and its magnitude is proportional to the product of the current I and the magnetic induction intensity B.

[0083] A resistor shunt is a precise resistor that can pass large currents. When current flows through the shunt, a small voltage appears across it. By measuring the voltage and converting the measurement result into current, the large current can be measured.

[0084] Figure 1 In order to meet the correlation failure requirements of the functional safety standard ISO26262, ensure the independence of safety functions and safety mechanisms, and avoid correlation failures, the solution shown needs to use two heterogeneous detection circuits, that is, the hardware parameters of the two current sensors and two sampling circuits are different, which increases the material management and procurement costs of the solution.

[0085] In order to solve the above problems, the present application provides a fault detection circuit, a fault detection method, a power distribution unit and an electric vehicle for a current sensor. The detection circuit sends a detection signal with known parameters to the detection circuit of the current sensor, and uses the signal detection circuit to obtain the detection result corresponding to the output voltage of the current sensor. At this time, part of the detection result is the detection result corresponding to the direct current, and the other part is the detection result corresponding to the detection signal. The controller compares the detection result with the detection signal to determine whether the current sensor is faulty. The fault detection circuit of the current sensor can detect multiple types of current sensors, and there is no need to set up two heterogeneous detection circuits. Only one detection circuit is needed to meet the requirements of the functional safety standard ISO26262, which reduces costs, and the diagnostic coverage of hardware random failures reaches 90% or more, reaching the functional safety ASIL B level and above indicators.

[0086] Among them, the Automotive Safety Integrity Level (ASIL) is a risk classification framework defined by ISO 26262 "Road Vehicle Functional Safety". ASIL is established after conducting a risk analysis of each hazard, considering the severity, exposure and controllability during vehicle operation.

[0087] ISO 26262 defines four different ASILs: ASIL A, ASIL B, ASIL C, and ASIL D. ASIL D is the highest safety integrity of the product, while ASIL A is the lowest safety integrity.

[0088] The terms "first", "second", etc. in the following description of this application are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features.

[0089] In the present application, unless otherwise clearly specified and limited, the term "connection" should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection or an indirect connection through an intermediate medium.

[0090] The amplitudes in the following description of this application all refer to the amplitudes of voltage.

[0091] In the following embodiments of the present application, the sensor is described as a current sensor as an example.

[0092] An embodiment of the present application provides a fault detection circuit of a current sensor, which is used to perform fault detection on a current sensor. The current sensor is used to detect the current of a DC bus of an electric vehicle, and is described in detail below with reference to the accompanying drawings.

[0093] In the embodiment of the present application, the current sensor 20a is taken as a Hall sensor as an example. When the current sensor 20a adopts other types of sensors, the working principle is similar, and the embodiment of the present application will not be repeated here.

[0094] See also Figure 3 , which is a schematic diagram of a fault detection circuit of a current sensor provided in an embodiment of the present application.

[0095] The DC bus of an electric vehicle includes a positive DC bus (indicated by HV+ in the figure) and a negative DC bus (indicated by HV- in the figure). The DC bus connects the DC charging interface and the power battery pack. The current sensor is used to detect the voltage on the DC bus to determine whether there is a charging overcurrent fault or a short circuit fault at this time.

[0096] The embodiment of the present application takes the current sensor detecting the current of the positive DC bus as an example. In other embodiments, the current sensor can also detect the current of the negative DC bus, or two current sensors can be set to detect the current of the positive DC bus and the negative DC bus respectively.

[0097] The contactors 30a and 30b are respectively arranged on the positive DC bus and the negative DC bus, and are used to disconnect when there is a charging overcurrent fault or a short circuit fault to protect the vehicle.

[0098] The fault detection circuit of the current sensor includes a controller 301 and a signal detection circuit 302 .

[0099] The controller 301 inputs a detection signal to the detection circuit of the current sensor, that is, injects the detection signal into the positive DC bus. The detection signal is a signal with known parameters, that is, the frequency and amplitude of the detection signal are predetermined.

[0100] In some embodiments, the frequency parameters and amplitude parameters of the detection signal are pre-configured and saved, and are called when fault detection is performed to generate the required detection signal.

[0101] At this time, the current sensor 20a detects the current of the detection line on which the detection signal is superimposed.

[0102] The signal detection circuit 302 is used to detect the voltage at the output end of the current sensor 20a and transmit the detection result to the controller 301. At this time, the detection result is a superposition of the following two parts: the detection result corresponding to the direct current and the detection result corresponding to the detection signal.

[0103] The controller 301 determines whether the current sensor 20 a is faulty according to the detection signal and the detection result.

[0104] In some embodiments, the controller 301 obtains the detection result corresponding to the detection signal from the detection result, and compares the amplitude of the detection result with the amplitude of the detection signal to determine whether the current sensor is faulty. It should be noted that in the actual circuit, in order to improve the driving effect, the detection signal of the input detection circuit will be amplified, and in order to improve the resolution of the detection signal obtained during signal detection, the voltage across the current sensor will be amplified, resulting in the amplitude of the detection result corresponding to the detection signal being amplified. At this time, the amplification factor is predetermined, and the amplitude of the detection result of the detection signal is divided by the amplification factor, and then compared with the amplitude of the detection signal.

[0105] The controller 301 may be an application specific integrated circuit (ASIC), a programmable logic device (PLD), a digital signal processor (DSP) or a combination thereof. The PLD may be a complex programmable logic device (CPLD), a field programmable gate array (FPGA), a generic array logic (GAL) or any combination thereof, which is not specifically limited in the embodiments of the present application.

[0106] The controller 301 also includes a memory for storing program instructions, preset frequencies and preset amplitudes of detection signals, and amplification factors of drive circuits and signal detection circuits, etc. The memory may be a non-volatile memory (NVM), such as a read-only memory (ROM), specifically an electrically erasable programmable read-only memory (EEROM) or an erasable programmable read-only memory (EPROM).

[0107] In the above description, the current sensor 20a is taken as a Hall sensor as an example. When the current sensor is a resistor shunt or a current transformer, the principle is similar, except that the resistor shunt or the current transformer needs to be connected in series to the detection circuit.

[0108] In summary, after the controller of the fault detection circuit provided in the embodiment of the present application sends a detection signal with known parameters to the detection circuit of the current sensor, the detection signal is superimposed on the DC power of the DC circuit, and the detection result corresponding to the output voltage of the current sensor is obtained by using the signal detection circuit. At this time, part of the detection result is the detection result corresponding to the DC current, and the other part is the detection result corresponding to the detection signal. Since the corresponding part of the detection signal in the detection result is an AC signal, it can be separated from the DC current by a filtering circuit. The controller compares the detection result with the detection signal to determine whether the current sensor is faulty. The fault detection circuit of the current sensor can detect various types of current sensors, and only one detection circuit is needed to realize the detection, without setting two heterogeneous detection circuits, thereby reducing the cost.

[0109] In some embodiments, the detection signal input by the controller 301 into the detection circuit is a pulse width modulation (PWM) signal having a preset frequency and a preset amplitude. The controller 301 obtains a response signal having a frequency of the preset frequency based on the detection result, and determines whether the current sensor is faulty based on the response signal.

[0110] The working principle of the fault detection circuit of the current sensor is explained below in conjunction with a specific implementation method thereof.

[0111] See also Figure 4 , which is a schematic diagram of another fault detection circuit of a current sensor provided in an embodiment of the present application.

[0112] The fault detection circuit of the illustrated current sensor further includes a drive circuit 310 .

[0113] The input end of the driving circuit 310 is connected to a DC power supply. The voltage of the DC power supply is not specifically limited in the embodiment of the present application, and can be, for example, 5 V. The voltage of the low-voltage DC power supply can be provided by a low-voltage battery of the electric vehicle.

[0114] The driving circuit 310 is arranged between the controller 301 and the detection circuit, and is used to increase the amplitude of the detection signal and transmit it to the detection circuit.

[0115] The detection signal output by the controller is generally an AC signal with a low voltage amplitude. When it is directly superimposed on the high-voltage direct current in the detection circuit, the detection signal is easily submerged by the high-voltage direct current, resulting in difficulty in separating the detection result to obtain a more accurate detection result corresponding to the detection signal. Therefore, it is necessary to set a drive circuit 310 to amplify the detection signal. The amplification factor α of the detection signal by the drive circuit 310 is a known parameter.

[0116] Figure 4 The driving circuit 310 shown specifically includes a controllable switch tube Q1 and a resistor R1, a first end of Q1 is connected to a DC power supply VCC, a second end of Q1 is connected to a detection circuit through R1, and a controller inputs a detection signal to a control end of Q1.

[0117] The controllable switch tube Q1 can be an insulated gate bipolar transistor (IGBT), a metal oxide semiconductor field effect transistor (MOSFET, hereinafter referred to as MOS tube), a silicon carbide metal oxide semiconductor (SiC MOSFET), etc., and the embodiment of the present application does not specifically limit this. In the following, Q1 is taken as a MOS tube and specifically an NMOS tube as an example. At this time, the first end of Q1 is the drain, the second end of Q1 is the source, and the control end of Q1 is the gate.

[0118] The amplified detection signal is superimposed on the high voltage direct current in the detection circuit, so that a voltage is generated at the output end of the current sensor 20 a . The signal detection circuit 302 detects the voltage at the output end of the current sensor 20 a .

[0119] The signal detection circuit 302 in the embodiment of the present application includes a first differential amplifier U1 and a first filter circuit.

[0120] The first filtering circuit shown in the figure is a band-pass filter (Band-pass Filter) 302b.

[0121] The non-inverting input terminal of the first differential amplifier U1 is connected to the positive output terminal of the current sensor, the inverting input terminal of the first differential amplifier U2 is connected to the second terminal of the current sensor, and the output terminal of the first differential amplifier is connected to the first filter circuit.

[0122] The first differential amplifier U1 amplifies the voltage across the current sensor and transmits the amplified voltage to the first filter circuit to improve the resolution of the voltage across the current sensor. The amplification factor β is a known parameter.

[0123] The first filtering circuit (ie, the bandpass filter 302b) obtains a detection result of a frequency being a preset frequency from the amplified voltage, and sends the detection result to the controller.

[0124] The specific implementation method and working principle of the bandpass filter 302b are relatively mature technologies and will not be described in detail in the embodiments of the present application.

[0125] The center frequency of the bandpass filter is the center frequency f0 of the passband of the bandpass filter, and is generally taken as f0=(f1+f2) / 2, where f1 and f2 are the side frequencies of the left and right sides of the bandpass filter that drop by 3dB. In order to obtain the detection result of the preset frequency, the center frequency f0 of the bandpass filter 302b is the preset frequency.

[0126] The signal detection circuit 302 shown in the figure further includes a low-pass filter 302 b. The low-pass filter 302 a is used to obtain a DC voltage signal from the amplified voltage and transmit it to the controller 301 .

[0127] After the controller 301 obtains the detection result that the frequency is the preset frequency, it uses the detection result to obtain a response signal whose frequency is the preset frequency, which is described in detail below.

[0128] See also Figure 5 , which is a schematic diagram of a controller provided in an embodiment of the present application.

[0129] The controller 301 includes an MCU 301 a , a detection signal generating circuit 301 b , an ADC 301 c , an ADC 301 d , and an ICU (Input Capture Unit) 301 e .

[0130] The MCU 301 a sends instructions to the detection signal generating circuit 301 b according to a preset program, so that the detection signal generating circuit 301 b configures a detection signal with a preset frequency and a preset amplitude.

[0131] ADC301c obtains the DC voltage signal transmitted by the low-pass filter 302a, performs analog-to-digital conversion on the DC voltage signal to obtain a digital voltage signal, and then sends it to MCU301a. MCU301a then uses the digital voltage signal to obtain a current value to detect the line current.

[0132] ADC301d obtains the detection result transmitted by the bandpass filter 302b, performs analog-to-digital conversion on the detection result and then transmits it to MCU301a. MCU301a pre-stores the amplification factor α of the drive circuit and the amplification factor β of the first differential amplifier, divides the amplitude of the detection result after analog-to-digital conversion by (αβ), and obtains a response signal with a preset frequency.

[0133] ICU301e is used to measure the pulse count, frequency and duty cycle of the detection result transmitted by the bandpass filter 302b.

[0134] After MCU301a obtains the response signal, it uses the amplitude of the response signal and the amplitude of the detection signal to determine whether the current sensor is faulty. In some embodiments, fault diagnosis can also be performed in combination with the measurement results of ICU301e, which is described in detail below.

[0135] When the amplitude of the response signal is equal to the preset amplitude, the MCU 301a determines that the current sensor has no fault.

[0136] When the amplitude of the response signal is equal to the voltage of the DC power supply, the MCU 301a determines that the current sensor is open.

[0137] When the response signal is constant at zero, the MCU 301 a determines that the current sensor is open.

[0138] When the response signal is constant and greater than zero (ie, the duty cycle measured by ICU301e is 100%), MCU301a determines that a stuck fault exists in the current sensor.

[0139] When the response signal is a pulse width modulation signal and the amplitude does not match the preset amplitude, the MCU301a determines that the current sensor has parameter drift, and at this time the measurement result of the current sensor is inaccurate.

[0140] See also Figure 6 , which is a schematic diagram of a fault detection circuit of another current sensor provided in an embodiment of the present application.

[0141] The fault detection circuit is shown in Figure 1. Figure 5 The difference lies in that the implementation method of the driving circuit is different. The driving circuit includes a resistor R1 and a PMOS tube Q2. The first end of R1 is connected to a DC power supply, the second end of R1 is connected to the drain of Q2 and a detection circuit, the controller 301 outputs a detection signal to the gate of Q2, and the source of Q2 is grounded.

[0142] When the gate input of Q2 is at a low level, it is turned on and the detection circuit is bypassed. When the gate input of Q2 is at a high level, it is turned off and the drive circuit inputs the detection signal with the amplitude amplified to the detection circuit.

[0143] remove Figure 4 and Figure 6 In addition to the implementation shown, the driving circuit 310 can also be implemented in other ways, such as using an operational amplifier for amplification, etc., which will not be described in detail in the embodiments of the present application.

[0144] The controller of the fault detection circuit provided in the embodiment of the present application can be independently set, for example, it can be independently set in the power distribution unit (i.e., the high-voltage matching power box) of the electric vehicle, or independently set in the battery management system of the electric vehicle, or independently set in the motor control unit of the electric vehicle.

[0145] The controller can also be implemented in a multiplexing manner, for example, the controller can reuse the controller of the power distribution unit (ie, the high-voltage matching box), or reuse the controller of the battery management system, or reuse the controller of the motor control unit.

[0146] The fault detection circuit can be used to detect current sensors such as current transformers, Hall current sensors or resistor shunts.

[0147] The controller 301 compares the detection signal and the response signal using a comparator. Referring to the safety standard ISO26262, the typical diagnostic coverage of the comparator is "high", that is, the diagnostic coverage can reach 99%.

[0148] In summary, the controller of the fault detection circuit sends a detection signal with a preset amplitude and a preset frequency to the detection circuit. The amplitude of the detection signal is amplified by the driving circuit and superimposed with the DC power of the DC line. The detection result corresponding to the output voltage of the current sensor is obtained by using the signal detection circuit. Since the corresponding part of the detection signal in the detection result is an AC signal, it can be separated from the detection result part of the DC current by a filtering circuit. The controller compares the filtered detection result with the detection signal to determine whether the current sensor is faulty. The fault detection circuit of the current sensor can detect multiple types of current sensors, and only one detection circuit is needed to realize the detection, without setting up two heterogeneous detection circuits, which reduces the cost. In addition, specific fault diagnosis can also be performed to determine the fault type of the current sensor, such as open circuit, short circuit, stuck or parameter drift, etc. The single-point diagnosis coverage can reach 90% or more, thereby achieving functional safety ASIL B and above indicators.

[0149] The following is a description of another implementation of the fault detection circuit, which is based on a majority voting circuit.

[0150] See also Figure 7 , which is a schematic diagram of a fault detection circuit of another current sensor provided in an embodiment of the present application.

[0151] The difference between the fault detection circuit of the current sensor and the above embodiments is that the detection signal sent by the controller 301 to the detection circuit is at least two pulse width modulation signals, and the preset frequencies of the two pulse width modulation signals are different.

[0152] At this time, the signal detection circuit 302 includes a second filter circuit and a second differential amplifier U2.

[0153] The second filtering circuit includes bandpass filters 302b1-302bn, wherein the value of n is the same as the number of paths of the pulse width modulation signal.

[0154] The non-inverting input terminal of the second differential amplifier U2 is connected to the positive output terminal of the current sensor 20a, the inverting input terminal of the second differential amplifier U2 is connected to the negative output terminal of the current sensor 20a, and the output terminal of the second differential amplifier U2 is connected to the second filter circuit.

[0155] The second differential amplifier U2 amplifies the voltage across the current sensor 20a and transmits the amplified voltage to the second filter circuit.

[0156] The second filtering circuit is used to obtain a detection result having the same frequency as at least two pulse width modulation signals from the amplified voltage, and send the detection result to the controller 301 .

[0157] The specific implementation method and working principle of the bandpass filters 302b1-302bn are relatively mature technologies and will not be described in detail in the embodiments of the present application.

[0158] In order to obtain a detection result with a preset frequency, the center frequency of each bandpass filter 302b1-302bn is respectively the same as the preset frequency of a pulse width modulation signal.

[0159] The signal detection circuit 302 shown in the figure further includes a low-pass filter 302 b . The low-pass filter 302 a is used to obtain a DC voltage signal from the amplified voltage and transmit the DC voltage signal to the controller 301 .

[0160] The controller 301 obtains a response signal having a preset frequency according to the detection result, which is described in detail below.

[0161] See also Figure 8 , which is a schematic diagram of another controller provided in an embodiment of the present application.

[0162] The controller 301 includes an MCU 301 a , a detection signal generating circuit 301 b , an ADC 301 c , ADCs 301 d 1 - 301 d n , and ICUs 301 e 1 - 301 en .

[0163] The MCU 301 a sends instructions to the detection signal generating circuit 301 b according to a preset program, so that the detection signal generating circuit 301 b configures a pulse width modulation signal with different preset frequencies.

[0164] ADC301c obtains the DC voltage signal transmitted by the low-pass filter 302a, performs analog-to-digital conversion on the DC voltage signal to obtain a digital voltage signal, and then sends it to MCU301a. MCU301a then uses the digital voltage signal to obtain a current value to detect the line current.

[0165] ADC301d1 obtains the detection result transmitted by the bandpass filter 302b, performs analog-to-digital conversion on the detection result and then transmits it to MCU301a. MCU301a pre-stores the amplification factor α of the driving circuit and the amplification factor β of the first differential amplifier, divides the amplitude of the detection result after analog-to-digital conversion by (αβ), and obtains the response signal of the pulse width modulation signal. The working principles of other ADCs are similar and will not be repeated here.

[0166] ICU301e1-301en are used to measure the pulse count, frequency and duty cycle of the detection results transmitted by the bandpass filters 302b1-302bn respectively.

[0167] After MCU301a obtains the multi-channel response signals, it uses the amplitudes of the multi-channel response signals and the amplitudes of the detection signals to determine whether the current sensor is faulty. It can also perform fault diagnosis in combination with the measurement results of ICU301e, which is described in detail below.

[0168] In some embodiments, the MCU 301a determines that the current sensor is faulty when the amplitudes of all response signals are different from the amplitudes of the pulse width modulation signals of the same frequency.

[0169] In some embodiments, MCU301a determines that the current sensor is not faulty when the amplitude of each response signal is equal to the preset amplitude of the pulse width modulation signal of the same frequency; determines that the current sensor is open-circuited when the amplitude of at least two response signals is equal to the voltage of the DC power supply; determines that the current sensor is open-circuited when at least two response signals are constant at zero; determines that the current sensor has a stuck fault when at least two response signals are constant and greater than zero; determines that the current sensor has parameter drift when at least two response signals are pulse width modulation signals and the amplitude does not match the preset amplitude, and the measurement result of the current sensor is inaccurate.

[0170] The amplitude of each detection signal may be the same or different, and this embodiment of the present application does not limit this.

[0171] The embodiment of the present application does not specifically limit the number of pulse width modulation signals included in the detection signal. In practical applications, in order to achieve redundant fault judgment, reduce the probability of misjudgment, and reasonably control the number of bandpass filters in the second filtering circuit, in a preferred embodiment, the detection signal can be a three-way pulse width modulation signal. The controller obtains response signals with the same frequency as the three-way pulse width modulation signals according to the detection results. When the amplitudes of at least two response signals are different from the amplitudes of the pulse width modulation signals with the same frequency, it is determined that the current sensor is faulty.

[0172] The embodiment of the present application does not specifically limit the preset frequencies of the multiple pulse width modulation signals. In practical applications, in order to improve the degree of distinction between the multiple pulse width modulation signals and to facilitate the design of the bandpass filter, there can be a relatively obvious difference between the preset frequencies of the multiple pulse width modulation signals. For example, the preset frequencies of the three pulse width modulation signals are 9KHz, 42KHz, and 73KHz, respectively.

[0173] The driving circuit of the fault detection circuit provided in this embodiment can also adopt Figure 6 The implementation method shown will not be repeated here.

[0174] The controller of the fault detection circuit can be independently set, for example, it can be independently set in the power distribution unit (i.e., high-voltage matching box) of the electric vehicle, or independently set in the battery management system of the electric vehicle, or independently set in the motor control unit of the electric vehicle.

[0175] The controller can also be implemented in a multiplexing manner, for example, the controller can reuse the controller of the power distribution unit (ie, the high-voltage matching box), or reuse the controller of the battery management system, or reuse the controller of the motor control unit.

[0176] The fault detection circuit can be used to detect current sensors such as current transformers, Hall current sensors or resistor shunts.

[0177] In summary, the fault detection circuit can be used to detect various types of current sensors, and only one detection circuit is needed to achieve detection, without setting up two heterogeneous detection circuits, which reduces costs, and for the potential fault diagnosis coverage requirements of the functional safety standard ISO26262, by applying the majority voting circuit (referring to the safety standard ISO26262, the typical diagnostic coverage that can be achieved by the majority voting circuit is high, that is, the diagnostic coverage can reach 99%), the potential fault diagnosis coverage can reach 90% and above, thereby achieving functional safety ASIL B level and above indicators. In addition, specific fault diagnosis can also be performed to determine the fault type of the current sensor and provide guidance for fault maintenance.

[0178] Based on the fault detection circuit of the current sensor provided in the above embodiments, the embodiment of the present application further provides a fault detection method of the current sensor, which is described in detail below with reference to the accompanying drawings.

[0179] See also Fig. 9 , which is a flow chart of a fault detection method for a current sensor provided in an embodiment of the present application.

[0180] The illustrated method includes the following steps:

[0181] S901: Input a detection signal to the detection circuit of the current sensor, where the detection signal is an AC signal.

[0182] In some embodiments, the frequency parameters and amplitude parameters of the detection signal are pre-configured and saved, and are called when fault detection is performed to generate the required detection signal.

[0183] At this time, the current sensor 20a detects the current of the detection line on which the detection signal is superimposed.

[0184] S902: Obtain the detection result of the output terminal voltage of the current sensor.

[0185] At this time, the detection result is a superposition of the following two parts: the detection result corresponding to the direct current and the detection result corresponding to the detection signal.

[0186] S903: Determine whether the current sensor is faulty according to the detection signal and the detection result.

[0187] A partial detection result corresponding to the detection signal is obtained from the detection result, and the amplitude of the partial detection result is compared with the amplitude of the detection signal to determine whether the current sensor is faulty.

[0188] In the actual circuit, in order to improve the driving effect, the detection signal of the input detection circuit will be amplified, and in order to improve the resolution of the signal detection, the voltage at both ends of the current sensor will be amplified, resulting in the amplitude of the detection result corresponding to the detection signal being amplified. Therefore, the amplification factor can be determined in advance, and the amplitude of the detection result of the detection signal is divided by the amplification factor and then compared with the amplitude of the detection signal.

[0189] In summary, the detection method provided in this embodiment can detect various types of current sensors. Since the method does not need to compare the data of multiple sampling channels, only one detection circuit is needed to realize the detection, and there is no need to set up two heterogeneous detection circuits, which reduces the cost compared with the prior art solutions.

[0190] The following is an explanation in conjunction with a specific implementation method.

[0191] See also Fig.10 , which is a flow chart of another current sensor fault detection method provided in an embodiment of the present application.

[0192] This method can be applied to Figure 4 or Figure 6 The fault detection circuit shown in the figure comprises the following steps:

[0193] S1001: Sending a detection signal to a driving circuit, where the detection signal is a pulse width modulation signal with a preset frequency and a preset amplitude.

[0194] S1002: The driving circuit amplifies the amplitude of the detection signal and then transmits it to the detection circuit.

[0195] S1003: Obtain the detection result of the output terminal voltage of the current sensor.

[0196] S1004: Obtain a response signal having a preset frequency according to the detection result.

[0197] The amplification factors of the driving circuit and the signal detection circuit are predetermined, and the amplitude of the detection result of the detection signal is divided by the amplification factor to obtain the amplitude of the response signal.

[0198] S1005: Determine whether the response signal is constant at zero, if not, proceed to S1007; if yes, proceed to S1006.

[0199] S1006: Determine that the current sensor is short-circuited, and proceed to S1014.

[0200] S1007: Determine whether the amplitude of the response signal is equal to the voltage of the low-voltage power supply. If not, proceed to S1008; if so, proceed to S1009.

[0201] S1008: Determine whether the response signal is constant, if not, proceed to S1010; if so, proceed to S1011.

[0202] S1009: Determine that the current sensor is open circuit, and proceed to S1014.

[0203] S1010: Determine whether the amplitude of the response signal is equal to the preset amplitude, if not, proceed to S1012; if yes, proceed to S1013.

[0204] S1011: Determine that the current sensor has a stuck fault, and proceed to S1014.

[0205] S1012: Determine that the current sensor has no faults, and proceed to S1014.

[0206] S1013: Determine that the current sensor has parameter drift, and proceed to S1014.

[0207] S1014: Fault detection ends.

[0208] In practical applications, taking into account the influence of noise in the detection process and the measurement error, an error threshold can be set in advance when comparing the amplitudes. When the absolute value of the difference between the amplitude of the response signal and the preset amplitude is less than the error threshold, it is determined that the amplitude of the response signal is equal to the preset amplitude.

[0209] The order of the above steps is only for the convenience of explanation and does not constitute a limitation on the present application. Those skilled in the art may appropriately adjust and replace the order of the above steps in specific applications. For example, they may first determine whether the current sensor has an open circuit fault.

[0210] Another detection method is described below, which can be applied to Figure 7 The fault detection circuit shown.

[0211] See also Fig.11 , which is a flow chart of another current sensor fault detection method provided in an embodiment of the present application.

[0212] S1101: Sending a detection signal to a driving circuit, where the detection signal is a plurality of pulse width modulation signals with different preset frequencies.

[0213] The embodiment of the present application does not specifically limit the preset frequencies of the pulse width modulation signals. In practical applications, in order to improve the degree of distinction between the pulse width modulation signals and to facilitate the design of the bandpass filter, there can be a relatively obvious difference between the preset frequencies of the pulse width modulation signals. For example, the preset frequencies of the three pulse width modulation signals are 9KHz, 42KHz, and 73KHz, respectively.

[0214] S1102: The driving circuit amplifies the amplitude of the detection signal and then transmits it to the detection circuit.

[0215] S1103: Obtain the detection result of the output terminal voltage of the current sensor.

[0216] S1104: Acquire, according to the detection result, a response signal having the same frequency as at least two pulse width modulation signals.

[0217] The amplification factors of the driving circuit and the signal detection circuit are predetermined, and the amplitude of the detection result of the detection signal is divided by the amplification factor to obtain the amplitude of the response signal.

[0218] S1105: When the amplitudes of all response signals are different from the amplitudes of the pulse width modulation signals of the same frequency, it is determined that the current sensor is faulty.

[0219] Another detection method is described below, which can be applied to Figure 7 The fault detection circuit shown.

[0220] See also Fig.12 , which is a flow chart of another current sensor fault detection method provided in an embodiment of the present application.

[0221] S1201: Sending a detection signal to the driving circuit, where the detection signal is three pulse width modulation signals with different preset frequencies.

[0222] S1202: The driving circuit amplifies the amplitude of the detection signal and then transmits it to the detection circuit.

[0223] S1203: Obtain the detection result of the output terminal voltage of the current sensor.

[0224] S1204: Acquire response signals having the same frequencies as the above three pulse width modulation signals according to the detection results.

[0225] The amplification factors of the driving circuit and the signal detection circuit are predetermined, and the amplitude of the detection result of the detection signal is divided by the amplification factor to obtain the amplitude of the response signal.

[0226] S1205: When the amplitudes of at least two response signals are different from the amplitudes of the pulse width modulation signal with the same frequency, it is determined that the current sensor is faulty.

[0227] In some embodiments, the above method can also refer to Fig.10 The steps in the embodiment are used to perform specific fault diagnosis, for example, when at least two response signals are constantly zero, it is determined that a short circuit fault exists in the current sensor.

[0228] In summary, using the detection method provided in the embodiment of the present application, only one detection circuit is needed to realize the detection, and there is no need to set up two heterogeneous detection circuits, which reduces the cost. In addition, specific fault diagnosis can also be performed to determine the fault type of the current sensor, such as open circuit, short circuit, stuck or parameter drift. The potential fault diagnosis coverage of this method can reach 90% or more, thereby achieving functional safety ASIL B level and above indicators.

[0229] Based on the fault detection circuit of the current sensor provided in the above embodiment, the embodiment of the present application further provides a power distribution unit, namely, a high-voltage distribution box of an electric vehicle, which is described in detail below with reference to the accompanying drawings.

[0230] See also Fig.13 , which is a schematic diagram of a power distribution unit provided in an embodiment of the present application.

[0231] The input end of the power distribution unit 1300 is connected to the DC charging interface of the electric vehicle (represented by HV+ and HV- in the figure), and the output end is connected to the power battery pack 50 of the electric vehicle. The power distribution unit 1300 includes the fault detection circuit of the current sensor provided in the above embodiment, and also includes an on-board charger (On-Board Charger, OBC) 1301.

[0232] The input end of the on-board charger 1301 is connected to an AC power source, and the output end of the on-board charger 1301 is connected to a power battery pack. The on-board charger 1301 is used to convert AC power into DC power to charge the power battery pack 50.

[0233] The fault detection circuit of the current sensor includes a controller 301 and a signal detection circuit 302. The specific implementation and working principle of the fault detection circuit can be found in the relevant descriptions in the above embodiments, and the embodiments of the present application will not be repeated here.

[0234] The current sensor 20a, contactors 30a and 30b may be disposed inside the power distribution unit 1300, or outside the power distribution unit 1300, which is not specifically limited in the embodiment of the present application.

[0235] In some embodiments, the controller 301 may be integrated with the controller of the onboard charger 1301 .

[0236] The current sensor 20a may specifically be a current transformer, a Hall current sensor, or a resistance shunt, etc., which is not specifically limited in the embodiment of the present application.

[0237] Using the power distribution unit provided by the embodiment of the present application, the controller of its fault detection circuit sends a detection signal with a preset amplitude and a preset frequency to the detection circuit. The amplitude of the detection signal is amplified by the driving circuit and superimposed with the DC power of the DC circuit. The signal detection circuit is used to obtain the detection result corresponding to the output voltage of the current sensor. Since the corresponding part of the detection signal in the detection result is an AC signal, it can be separated from the detection result part of the DC current by a filtering circuit. The controller compares the filtered detection result with the detection signal to determine whether the current sensor is faulty. The power distribution unit can detect multiple types of current sensors, and only one detection circuit is needed to realize the detection, without setting two heterogeneous detection circuits, which reduces the cost. In addition, specific fault diagnosis can also be performed to determine the fault type of the current sensor, such as open circuit, short circuit, stuck or parameter drift, thereby improving the safety of the power distribution unit.

[0238] In addition, in some embodiments, the controller implements the comparison of the detection signal and the response signal based on the function of the comparator, and the typical diagnostic coverage of the comparator is "high", that is, the diagnostic coverage can reach 99%. In other embodiments, the comparison of the detection signal and the response signal is implemented by applying a majority voting circuit, and the typical diagnostic coverage that can be achieved by the majority voting circuit is "high", that is, the diagnostic coverage can reach 99%. Therefore, the single-point diagnostic coverage of this solution can reach 90% and above, thereby achieving functional safety ASIL B level and above indicators.

[0239] Based on the fault detection circuit of the current sensor provided in the above embodiment, the embodiment of the present application further provides a motor control unit (Motor Control Unit, MCU), which is described in detail below with reference to the accompanying drawings.

[0240] See also Fig.14 , which is a schematic diagram of a motor control unit provided in an embodiment of the present application.

[0241] The input end of the motor control unit 1400 is connected to the power battery pack 50 of the electric vehicle, and the output end of the motor control unit 1400 is connected to the motor 70 of the electric vehicle.

[0242] The motor control unit 1400 includes the fault detection circuit of the current sensor provided in the above embodiments, and also includes an inverter 1401 .

[0243] The input end of the inverter 1401 is connected to the input end of the motor control unit, that is, connected to the power battery pack 50 ; the output end of the inverter 1401 is connected to the output end of the motor control unit.

[0244] The inverter 1401 does not work when the power battery pack 50 is being charged, but works when the electric vehicle is in a driving state, converting the direct current provided by the power battery pack 50 into alternating current and then providing it to the motor 70 .

[0245] The fault detection circuit of the current sensor includes a controller 301 and a signal detection circuit 302. The specific implementation and working principle of the fault detection circuit can be found in the relevant descriptions in the above embodiments, and the embodiments of the present application will not be repeated here.

[0246] The current sensor 20a and the contactors 30a and 30b may be disposed inside the motor control unit 1400 or outside the motor control unit 1400, which is not specifically limited in the embodiment of the present application.

[0247] In some embodiments, the controller 301 may be integrated with a controller of the motor control unit 1400 .

[0248] The current sensor 20a may specifically be a current transformer, a Hall current sensor, or a resistance shunt, etc., which is not specifically limited in the embodiment of the present application.

[0249] Using the motor control unit provided by the embodiment of the present application, the controller of its fault detection circuit sends a detection signal with a preset amplitude and a preset frequency to the detection circuit. The amplitude of the detection signal is amplified by the driving circuit and superimposed with the DC power of the DC circuit. The detection result corresponding to the output voltage of the current sensor is obtained by using the signal detection circuit. Since the corresponding part of the detection signal in the detection result is an AC signal, it can be separated from the detection result part of the DC current by a filtering circuit. The controller compares the filtered detection result with the detection signal to determine whether the current sensor is faulty. The motor control unit can detect multiple types of current sensors, and only one detection circuit is needed to realize the detection, without setting two heterogeneous detection circuits, which reduces the cost. In addition, specific fault diagnosis can also be performed to determine the fault type of the current sensor, such as open circuit, short circuit, stuck or parameter drift, thereby improving the safety of the motor control unit.

[0250] In addition, in some embodiments, the controller implements the comparison of the detection signal and the response signal based on the function of the comparator, and the typical diagnostic coverage of the comparator is "high", that is, the diagnostic coverage can reach 99%. In other embodiments, the comparison of the detection signal and the response signal is implemented by applying a majority voting circuit, and the typical diagnostic coverage that can be achieved by the majority voting circuit is "high", that is, the diagnostic coverage can reach 99%. Therefore, the single-point diagnostic coverage of this solution can reach 90% and above, thereby achieving functional safety ASIL B level and above indicators.

[0251] Based on the fault detection circuit of the current sensor provided in the above embodiment, the embodiment of the present application further provides an electric vehicle, which is described in detail below with reference to the accompanying drawings.

[0252] See also Fig.15 , which is a schematic diagram of a tram vehicle provided in an embodiment of the present application.

[0253] The electric vehicle 1500 includes the current sensor fault detection circuit 1501 provided in the above embodiment, and also includes a DC bus, a power battery pack 50 and a current sensor 20a.

[0254] The fault detection circuit 1501 of the current sensor includes a controller and a signal detection circuit. The specific implementation method and working principle of the fault detection circuit can be found in the relevant descriptions in the above embodiments, and the embodiments of the present application will not be repeated here.

[0255] The power battery pack 50 is used to provide electric energy for the electric vehicle.

[0256] The DC bus is connected to the power battery pack 50 , and the DC bus is used to transmit direct current.

[0257] The DC bus includes a positive DC bus and a negative DC bus, and the current sensor 20a is used to detect the current of the positive DC bus or the negative DC bus. In some embodiments, two current sensors can be provided to detect the current of the positive DC bus and the negative DC bus respectively.

[0258] The current sensor 20a may specifically be a current transformer, a Hall current sensor, or a resistance shunt, etc., which is not specifically limited in the embodiment of the present application.

[0259] The electric vehicle includes a fault detection circuit of a current sensor. The controller of the fault detection circuit sends a detection signal with a preset amplitude and a preset frequency to the detection circuit. The amplitude of the detection signal is amplified by the driving circuit and superimposed with the DC power of the DC circuit. The signal detection circuit is used to obtain the detection result corresponding to the output voltage of the current sensor. Since the corresponding part of the detection signal in the detection result is an AC signal, it can be separated from the detection result part of the DC current by a filtering circuit. The controller compares the filtered detection result with the detection signal to determine whether the current sensor is faulty. The motor control unit can detect multiple types of current sensors, and only one detection circuit is needed to realize the detection, without setting two heterogeneous detection circuits, which reduces the cost. In addition, specific fault diagnosis can be performed to determine the fault type of the current sensor, such as open circuit, short circuit, stuck or parameter drift, thereby improving the safety of the electric vehicle.

[0260] It should be understood that in the present application, "at least one (item)" means one or more, and "plurality" means two or more. "And / or" is used to describe the association relationship of associated objects, indicating that three relationships may exist. For example, "A and / or B" can mean: only A exists, only B exists, and A and B exist at the same time, where A and B can be singular or plural. The character " / " generally indicates that the objects associated before and after are in an "or" relationship. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, at least one of a, b or c can mean: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, c can be single or multiple.

[0261] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In addition, some or all of the units and modules can be selected according to actual needs to achieve the purpose of the embodiment scheme. Ordinary technicians in this field can understand and implement it without paying creative work.

[0262] The above is only a specific implementation of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A fault detection circuit, characterized in that: The fault detection circuit comprises: a signal detection circuit and a controller; wherein, The signal detection circuit is used to detect the output terminal voltage of the sensor and transmit the detection result to the controller, wherein the voltage detection result corresponding to the output terminal voltage of the sensor includes a first detection result corresponding to the direct current on the detection line and a second detection result corresponding to the detection signal, and the detection result is the second detection result separated from the voltage detection result by the signal detection circuit; The controller is used to input a detection signal to the detection circuit of the sensor, obtain a response signal with a preset frequency according to the detection result, and determine whether the sensor is faulty according to the amplitude of the response signal and the preset amplitude, wherein the detection signal is a pulse width modulated signal with the preset frequency and the preset amplitude.

2. The fault detection circuit according to claim 1, characterized in that: The sensor fault detection circuit also includes a drive circuit; The input end of the driving circuit is connected to a DC power supply; The driving circuit is used to increase the amplitude of the detection signal and then transmit it to the detection circuit.

3. The fault detection circuit according to claim 2, characterized in that: The controller is used to determine that the sensor is not faulty when the amplitude of the response signal is equal to the preset amplitude; and to determine that the sensor is open circuit when the amplitude of the response signal is equal to the voltage of the DC power supply; When the response signal is constant at zero, it is determined that the sensor is short-circuited; When the response signal is constant and greater than zero, it is determined that the sensor has a stuck fault; when the response signal is a pulse width modulated signal and the amplitude is not equal to the preset amplitude, it is determined that the sensor has a parameter drift.

4. The fault detection circuit according to any one of claims 1 to 3, characterized in that: The signal detection circuit includes a first differential amplifier and a first filter circuit; The non-inverting input terminal of the first differential amplifier is connected to the positive output terminal of the sensor, the inverting input terminal of the first differential amplifier is connected to the negative output terminal of the sensor, and the output terminal of the first differential amplifier is connected to the first filtering circuit; The first differential amplifier is used to amplify the voltage output by the sensor and transmit the amplified voltage to the first filtering circuit; The first filtering circuit is used to obtain a detection result whose frequency is the preset frequency from the amplified voltage, and send the detection result to the controller.

5. The fault detection circuit according to claim 1, characterized in that: The detection signal includes at least two pulse width modulation signals, and the two pulse width modulation signals correspond to different preset frequencies.

6. The fault detection circuit according to claim 5, characterized in that: The controller obtains response signals having the same frequency as the at least two pulse width modulation signals according to the detection results, and determines that the sensor is faulty when the amplitudes of all the response signals are different from the amplitudes of the pulse width modulation signals with the same frequency.

7. The fault detection circuit according to claim 5, characterized in that: The detection signal is a three-way pulse width modulation signal. The controller obtains a response signal having the same frequency as the three-way pulse width modulation signal according to the detection result. When the amplitude of at least two of the response signals is different from the amplitude of the pulse width modulation signal with the same frequency, the sensor is determined to be faulty.

8. The fault detection circuit according to any one of claims 5 to 7, characterized in that: The fault detection circuit of the sensor also includes a drive circuit; The input end of the driving circuit is connected to a low voltage power supply; The driving circuit is used to increase the amplitude of the detection signal and then transmit it to the sensor.

9. The fault detection circuit according to any one of claims 5 to 7, characterized in that: The signal detection circuit includes a second filter circuit and a second differential amplifier; The non-inverting input terminal of the second differential amplifier is connected to the positive output terminal of the sensor, the inverting input terminal of the second differential amplifier is connected to the negative output terminal of the sensor, and the output terminal of the second differential amplifier is connected to the second filtering circuit; The second differential amplifier is used to amplify the voltage across the sensor and transmit the amplified voltage to the second filtering circuit; The second filtering circuit is used to obtain a detection result having the same frequency as the at least two pulse width modulation signals from the amplified voltage, and send the detection result to the controller.

10. A sensor fault detection method, characterized in that: The fault detection method of the sensor comprises: Inputting a detection signal into the detection circuit of the sensor, wherein the detection signal is a pulse width modulation signal having a preset frequency and a preset amplitude; Acquire a detection result of the output terminal voltage of the sensor, wherein the voltage detection result corresponding to the output terminal voltage of the sensor includes a first detection result corresponding to the direct current on the detection line and a second detection result corresponding to the detection signal, and the detection result is the second detection result separated from the voltage detection result; A response signal having a frequency equal to the preset frequency is acquired according to the detection result, and whether the sensor is faulty is determined according to the amplitude of the response signal and the preset amplitude.

11. The fault detection method according to claim 10, characterized in that: The amplitude of the detection signal is increased by a driving circuit and then transmitted to the sensor, the input end of the driving circuit is connected to a DC power supply, and the determination of whether the sensor is faulty according to the amplitude of the response signal and the preset amplitude specifically includes: When the amplitude of the response signal is equal to the preset amplitude, it is determined that the sensor has no fault; When the amplitude of the response signal is equal to the voltage of the DC power supply, determining that the sensor is open circuit; When the response signal is constant at zero, it is determined that the sensor is short-circuited; When the response signal is constant and greater than zero, it is determined that the sensor has a stuck fault; When the response signal is a pulse width modulation signal and the amplitude is not equal to the preset amplitude, it is determined that parameter drift exists in the sensor.

12. The fault detection method according to claim 10, characterized in that: The detection signal includes at least two pulse width modulation signals, and the two pulse width modulation signals correspond to different preset frequencies.

13. The fault detection method according to claim 12, characterized in that: The step of acquiring a response signal having a frequency equal to the preset frequency according to the detection result, and determining whether the sensor has a fault according to the amplitude of the response signal and the preset amplitude, specifically includes: Response signals having the same frequency as the at least two pulse width modulation signals are acquired according to the detection results, and when the amplitudes of all the response signals are different from the amplitudes of the pulse width modulation signals with the same frequency, it is determined that the sensor is faulty.

14. The fault detection method according to claim 12, characterized in that: The detection signal is a three-way pulse width modulation signal, and the step of acquiring a response signal having a frequency of the preset frequency according to the detection result, and determining whether the sensor has a fault according to the amplitude of the response signal and the preset amplitude, specifically includes: Response signals having the same frequency as the three pulse width modulation signals are acquired according to the detection results, and when the amplitudes of at least two of the response signals are different from the amplitudes of the pulse width modulation signals with the same frequency, it is determined that the sensor is faulty.

15. A power distribution unit, characterized in that: The input end of the power distribution unit is used to connect to the DC charging interface of the electric vehicle, and the output end of the power distribution unit is used to connect to the power battery pack of the electric vehicle. The power distribution unit includes the sensor fault detection circuit according to any one of claims 1 to 9, and also includes an on-board charger; The input end of the on-board charger is used to connect to an AC power source, and the output end of the on-board charger is used to connect to the power battery pack; The on-board charger is used to charge the power battery pack using the AC power supply; The controller is integrated with a controller of the power distribution unit.

16. A motor control unit, characterized in that: The input end of the motor control unit is connected to the power battery pack of the electric vehicle, the output end of the motor control unit is connected to the motor of the electric vehicle, and the motor control unit includes the sensor fault detection circuit according to any one of claims 1 to 9, and also includes an inverter; The input end of the inverter is connected to the input end of the motor control unit, and the output end of the inverter is connected to the output end of the motor control unit; The inverter is used to convert the direct current provided by the power battery pack into alternating current and then provide it to the motor.

17. An electric vehicle, characterized in that: The sensor fault detection circuit according to any one of claims 1 to 9 further comprises a DC bus, a power battery pack and a sensor; The DC bus is connected to the power battery pack; The DC bus is used to transmit direct current; The power battery pack is used to provide electrical energy for the electric vehicle; The sensor is a sensor used to detect the current of the DC bus.

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