Signal short circuit diagnosis circuit

Abstract

The utility model relates to a signal short circuit diagnosis circuit used for diagnosing a CAN bus circuit. The CAN bus circuit comprises a CAN interface circuit and an MCU. The diagnosis circuit comprises a first voltage acquisition circuit which is connected with the CANH interface of the CAN interface circuit; the second voltage acquisition circuit is connected with a CANL interface of the CAN interface circuit; and the input end of the rail-to-rail operational amplifier circuit is connected with the first and second voltage acquisition circuits, and the output end is connected with the MCU. According to the utility model, the voltage acquisition circuit acquires the partial voltage values of the CANH and CANL signals, and the partial voltage values of the CANH and CANL signals can be transmitted to the MCU to the greatest extent by using the characteristic that the impedance of the input end and the impedance of the output end of the rail-to-rail operational amplifier circuit are equal, so that the voltage values of the CANH and the CANL are read in a high-precision manner, and the voltage states of the CANH and the CANL are finally judged. External disassembly and assembly and manual troubleshooting are not needed, and the effects that the fault analysis difficulty, the disassembly and assembly difficulty, the maintenance cost and the labor cost are greatly reduced are achieved.

Description

Technical Field

[0001] The utility model relates to the field of electronic circuits, and particularly to a diagnostic circuit for signal short circuit. Background Art

[0002] The CAN bus is the main application standard of the current automotive high-speed network system. When the CAN bus fails or data transmission is abnormal, various faults emerge in an endless stream. The CAN signal uses differential voltage transmission, and the two signal lines are called "CAN_H" and "CAN_L". Since the CAN network adopts multiple protocols, each control module port has a standard voltage under normal circumstances. When static, both CAN_H and CAN_L are 2.5V, which represents logic 1 at this time and is also called recessive; when dynamic, CAN_H is 3.5V and CAN_L is 1.5V, which represents logic 0 at this time and is also called dominant. Therefore, the voltage measurement method can determine whether the CAN signal line is short-circuited to the ground or the power supply, and whether there is a short circuit between the CAN signal differential lines. However, the existing conventional inspection method requires removing and installing the ECU controller from the placement location in the vehicle, and using a multimeter to read the voltage value. This test method has relatively cumbersome steps, is time-consuming and laborious, greatly increasing the maintenance cost and labor cost. Content of the Utility Model

[0003] The utility model provides a diagnostic circuit for signal short circuit to solve at least one of the above technical problems.

[0004] The technical solution of the utility model to solve the above technical problems is as follows: A diagnostic circuit for signal short circuit is used to diagnose whether a CAN bus short circuit occurs in a CAN bus circuit; wherein, the CAN bus circuit includes an ECU, and the ECU includes a CAN interface circuit, a CAN transceiver circuit, and an MCU; the CAN_L interface of the CAN transceiver circuit is electrically connected to the CAN_L interface of the CAN interface circuit, the CAN_H interface of the CAN transceiver circuit is electrically connected to the CAN_H interface of the CAN interface circuit, the RX interface of the CAN transceiver circuit is electrically connected to the TX interface of the MCU, and the TX interface of the CAN transceiver circuit is electrically connected to the RX interface of the MCU; the diagnostic circuit includes:

[0005] A first voltage acquisition circuit, electrically connected to the CAN_H interface of the CAN interface circuit;

[0006] A second voltage acquisition circuit, electrically connected to the CAN_L interface of the CAN interface circuit;

[0007] A rail-to-rail operational amplifier circuit, with its input terminals electrically connected to the first voltage acquisition circuit and the second voltage acquisition circuit respectively, and its output terminal electrically connected to the MCU.

[0008] Based on the above technical solutions, the present utility model can also be improved as follows.

[0009] Further, the CAN transceiver circuit includes:

[0010] A CAN transceiver U1, whose TXD pin is electrically connected to the RX interface of the MCU, whose RXD pin is electrically connected to the TX interface of the MCU, whose STB pin is electrically connected to the standby mode control interface of the MCU, whose VCC pin is connected to a 5V power supply, whose VIO pin is connected to a 3.3V power supply, and whose GND pin is grounded;

[0011] A capacitor C1, which is electrically connected between the ground and the VCC pin of the CAN transceiver U1;

[0012] A capacitor C2, which is electrically connected between the ground and the VIO pin of the CAN transceiver U1;

[0013] A capacitor C3, which is electrically connected between the ground and the VCC pin of the CAN transceiver U1;

[0014] A capacitor C4, which is electrically connected between the ground and the VIO pin of the CAN transceiver U1;

[0015] A capacitor C5, which is electrically connected between the ground and the RXD pin of the CAN transceiver U1;

[0016] A resistor R1, which is electrically connected between the ground and the STB pin of the CAN transceiver U1;

[0017] A common mode inductor LT1, one end of one coil of which is electrically connected to the CANL pin of the CAN transceiver U1, the other end of one coil of which is electrically connected to the CAN_L interface of the CAN interface circuit, one end of the other coil of which is electrically connected to the CANH pin of the CAN transceiver U1, and the other end of the other coil of which is electrically connected to the CAN_H interface of the CAN interface circuit;

[0018] A capacitor C6, one end of which is electrically connected to the other end of one coil of the common mode inductor LT1, and the other end of which is grounded;

[0019] A capacitor C7, one end of which is electrically connected to the other end of the other coil of the common mode inductor LT1, and the other end of which is grounded;

[0020] A resistor R2, one end of which is electrically connected to the other end of one coil of the common mode inductor LT1;

[0021] A resistor R3, one end of which is electrically connected to the other end of the other coil of the common mode inductor LT1;

[0022] A capacitor C8, one end of which is electrically connected to the other end of the resistor R2 and the other end of the resistor R3 respectively, and the other end of which is grounded;

[0023] An ESD protection diode, a pair of its pins are electrically connected to the other end of a coil of the common mode inductor LT1 and the other end of the other coil of the common mode inductor LT1 respectively, and the other pair of its pins are grounded.

[0024] Furthermore, the CAN transceiver circuit further includes:

[0025] A magnetic bead FB1, which is electrically connected between the 5V power supply and the VCC pin of the CAN transceiver U1;

[0026] A magnetic bead FB2, which is electrically connected between the 3.3V power supply and the VIO pin of the CAN transceiver U1;

[0027] A magnetic bead FB3, which is electrically connected between the other end of the other coil of the common mode inductor LT1 and the CAN_H interface of the CAN interface circuit;

[0028] A magnetic bead FB4, which is electrically connected between the other end of a coil of the common mode inductor LT1 and the CAN_L interface of the CAN interface circuit.

[0029] Furthermore, the model of the CAN transceiver U1 is TJA1044GT / 3.

[0030] Furthermore, the first voltage acquisition circuit includes:

[0031] A resistor R4, one end of which is electrically connected to the CAN_H interface of the CAN interface circuit;

[0032] A resistor R7, one end of which is electrically connected to the other end of the resistor R4, and the other end of which is grounded.

[0033] Furthermore, the second voltage acquisition circuit includes:

[0034] A resistor R5, one end of which is electrically connected to the CAN_L interface of the CAN interface circuit;

[0035] A resistor R9, one end of which is electrically connected to the other end of the resistor R5, and the other end of which is grounded.

[0036] Furthermore, the rail-to-rail operational amplifier circuit includes:

[0037] A resistor R6, one end of which is electrically connected between the resistor R4 and the resistor R7;

[0038] A capacitor C10, one end of which is electrically connected between the resistor R4 and the resistor R7, and the other end of which is grounded;

[0039] A resistor R8, one end of which is electrically connected between the resistor R5 and the resistor R9;

[0040] A capacitor C11, one end of which is electrically connected between the resistor R5 and the resistor R9, and the other end of which is grounded;

[0041] A rail-to-rail operational amplifier U2, the IN1+ pin of which is electrically connected to the other end of the resistor R6, the IN1- pin and the OUT1 pin of which are both electrically connected to the ADC_CANOH sampling interface of the MCU, the V- pin of which is grounded, the IN2+ pin of which is electrically connected to the other end of the resistor R8, the IN2- pin and the OUT2 pin of which are both electrically connected to the ADC_CANOL sampling interface of the MCU, and the V+ pin of which is connected to a 3.3V power supply;

[0042] A capacitor C9, one end of which is electrically connected to the V+ pin of the rail-to-rail operational amplifier U2, and the other end of which is grounded.

[0043] Further, the model of the rail-to-rail operational amplifier U2 is TSV912AQDGKRQ1.

[0044] Further, the diagnostic circuit is integrated in the ECU.

[0045] Further, the CAN bus circuit further includes: a vehicle-mounted CAN controller; the CAN_L interface of the vehicle-mounted CAN controller is electrically connected to the CAN_L interface of the CAN interface circuit, and the CAN_H interface of the vehicle-mounted CAN controller is electrically connected to the CAN_H interface of the CAN interface circuit.

[0046] The beneficial effects of the present utility model are as follows: A diagnostic circuit for signal short circuit in the present utility model collects the divided voltage values of the CAN_H and CAN_L signals in the CAN bus circuit through the first voltage acquisition circuit and the second voltage acquisition circuit, and then transmits them to the rail-to-rail operational amplifier circuit. By utilizing the characteristic that the input and output impedances of the rail-to-rail operational amplifier circuit are equal, the divided voltage values of the CAN_H and CAN_L signals collected through the first voltage acquisition circuit and the second voltage acquisition circuit can be transmitted to the ADC sampling interface of the MCU to the greatest extent, so as to realize the high-precision acquisition of the voltage values of CAN_H and CAN_L. Finally, by obtaining the voltage values of CAN_H and CAN_L, the voltage states of CAN_H and CAN_L are judged: normal, short circuit to ground, short circuit to power supply, short circuit between signals; the present utility model can obtain the voltage values of CAN_H and CAN_L with high precision without external disassembly and manual troubleshooting, and can efficiently and quickly judge to find the fault location and cause, achieving the effects of greatly reducing the difficulty of fault analysis, disassembly, as well as the maintenance cost and labor cost. Description of the Drawings

[0047] Figure 1 This is the structural block diagram of a diagnostic circuit for signal short - circuit of the present utility model;

[0048] Figure 2 This is the circuit schematic diagram of the CAN transceiver circuit;

[0049] Figure 3 This is the circuit schematic diagram of a diagnostic circuit for signal short - circuit of the present utility model;

[0050] Figure 4 This is the circuit schematic diagram of the MCU. Specific embodiments

[0051] The principles and features of the present utility model will be described below in conjunction with the accompanying drawings. The examples given are only for explaining the present utility model and are not intended to limit the scope of the present utility model.

[0052] As Figure 1 shown, the CAN bus circuit of an automobile generally includes: a vehicle head unit CAN controller and an ECU, and the ECU includes a CAN interface circuit, a CAN transceiver circuit, and an MCU; the CAN_L interface of the CAN transceiver circuit is electrically connected to the CAN_L interface of the CAN interface circuit, the CAN_H interface of the CAN transceiver circuit is electrically connected to the CAN_H interface of the CAN interface circuit, the RX interface of the CAN transceiver circuit is electrically connected to the TX interface of the MCU, and the TX interface of the CAN transceiver circuit is electrically connected to the RX interface of the MCU; the CAN_L interface of the vehicle head unit CAN controller is electrically connected to the CAN_L interface of the CAN interface circuit, and the CAN_H interface of the vehicle head unit CAN controller is electrically connected to the CAN_H interface of the CAN interface circuit. The MCU is mainly responsible for the application layer data interaction with other nodes, transmitting the data to be sent to the CAN controller, or receiving the data from the CAN controller for processing, and then sending or receiving through the CAN transceiver to the CAN controller of the vehicle head unit.

[0053] A diagnostic circuit for signal short - circuit of the present utility model is used to diagnose whether a CAN bus short - circuit occurs in the above - mentioned CAN bus circuit; as Figure 1 shown, the diagnostic circuit is integrated in the ECU, and it includes:

[0054] A first voltage acquisition circuit, electrically connected to the CAN_H interface of the CAN interface circuit, for acquiring the divided voltage value of the CAN_H signal transmitted on the CAN_H interface of the CAN interface circuit;

[0055] The second voltage acquisition circuit is electrically connected to the CAN_L interface of the CAN interface circuit and is used to acquire the divided voltage value of the CAN_L signal transmitted on the CAN_L interface of the CAN interface circuit;

[0056] The rail-to-rail operational amplifier circuit has its input terminals electrically connected to the first voltage acquisition circuit and the second voltage acquisition circuit respectively, and its output terminal is electrically connected to the MCU. It is used to perform arithmetic amplification processing on the divided voltage value of the CAN_H signal and the divided voltage value of the CAN_L signal, and transmit them to the ADC sampling interface of the MCU to the greatest extent.

[0057] Thus, the MCU can accurately read the voltage values of CAN_H and CAN_L through the ADC sampling interface. According to the voltage values of CAN_H and CAN_L read by the MCU, it can be manually judged whether the above CAN bus circuit has a CAN bus short circuit.

[0058] In addition, the MCU can also judge the voltage states of CAN_H and CAN_L according to the read voltage values of CAN_H and CAN_L: normal, short circuit to ground, short circuit to power supply, short circuit between signals; and send the message frame with abnormal read status to the vehicle-mounted CAN controller through the CAN transceiver circuit and the CAN interface circuit, and easily determine what kind of abnormal state it is by reading the message frame, and then repair the fault state.

[0059] It should be noted here that: the MCU judging the voltage states of CAN_H and CAN_L according to the read voltage values of CAN_H and CAN_L and generating a message frame corresponding to the state does not involve the improvement of the computer program, which is the basic function of the MCU.

[0060] In this specific embodiment, as Figure 2 shown:

[0061] The CAN transceiver circuit includes:

[0062] The CAN transceiver U1 with the model number TJA1044GT / 3, its TXD pin is electrically connected to the RX interface of the MCU, its RXD pin is electrically connected to the TX interface of the MCU, its STB pin is electrically connected to the standby mode control interface of the MCU, its VCC pin is connected to the 5V power supply, its VIO pin is connected to the 3.3V power supply, and its GND pin is grounded;

[0063] The capacitor C1 is electrically connected between the ground and the VCC pin of the CAN transceiver U1;

[0064] The capacitor C2 is electrically connected between the ground and the VIO pin of the CAN transceiver U1;

[0065] A capacitor C3, electrically connected between the ground and the VCC pin of the CAN transceiver U1;

[0066] A capacitor C4, electrically connected between the ground and the VIO pin of the CAN transceiver U1;

[0067] A capacitor C5, electrically connected between the ground and the RXD pin of the CAN transceiver U1;

[0068] A resistor R1, electrically connected between the ground and the STB pin of the CAN transceiver U1;

[0069] A common-mode inductor LT1, one end of one coil thereof is electrically connected to the CANL pin of the CAN transceiver U1, the other end of one coil thereof is electrically connected to the CAN_L interface of the CAN interface circuit, one end of the other coil thereof is electrically connected to the CANH pin of the CAN transceiver U1, and the other end of the other coil thereof is electrically connected to the CAN_H interface of the CAN interface circuit;

[0070] A capacitor C6, one end thereof is electrically connected to the other end of one coil of the common-mode inductor LT1, and the other end thereof is grounded;

[0071] A capacitor C7, one end thereof is electrically connected to the other end of the other coil of the common-mode inductor LT1, and the other end thereof is grounded;

[0072] A resistor R2, one end thereof is electrically connected to the other end of one coil of the common-mode inductor LT1;

[0073] A resistor R3, one end thereof is electrically connected to the other end of the other coil of the common-mode inductor LT1;

[0074] A capacitor C8, one end thereof is electrically connected to the other end of the resistor R2 and the other end of the resistor R3 respectively, and the other end thereof is grounded;

[0075] An ESD protection diode, a pair of pins thereof are electrically connected to the other end of one coil of the common-mode inductor LT1 and the other end of the other coil of the common-mode inductor LT1 respectively, and the other pair of pins thereof are grounded;

[0076] A bead FB1, electrically connected between the 5V power supply and the VCC pin of the CAN transceiver U1;

[0077] A bead FB2, electrically connected between the 3.3V power supply and the VIO pin of the CAN transceiver U1;

[0078] A bead FB3, electrically connected between the other end of the other coil of the common-mode inductor LT1 and the CAN_H interface of the CAN interface circuit;

[0079] The magnetic bead FB4 is electrically connected between the other end of a coil of the common-mode inductor LT1 and the CAN_L interface of the CAN interface circuit.

[0080] In addition, the CAN transceiver circuit further includes a connector J1 for providing a power supply interface and a CAV signal interface.

[0081] Figure 2 Among them, the markings, categories, and function descriptions of each device are shown in Table 1 below.

[0082] Table 1

[0083]

[0084] Figure 2 Among them, the function descriptions of each signal are shown in Table 2 below.

[0085] Table 2

[0086] Signal Functional Description KL30_VCC12_IN Positive Power GND Negative Power KL15_IG Power Control Signal CAN0H High Level of CAN Bus CAN0L Low Level of CAN Bus CANH0 High Level of CAN Bus after Common Mode Inductor CANL0 Low Level of CAN Bus after Common Mode Inductor VDD_5V 5V Power Supply for CAN Transceiver VDD_CAN&MCU Power Supply for CAN Transceiver IO Port and MCU_3.3V MCU_CAN0_TX Transmission Data Input MCU_CAN0_RX Received Data Output MCU_CAN0_STB Control Standby Mode

[0087] In this specific embodiment, as Figure 3 shown:

[0088] The first voltage acquisition circuit includes:

[0089] A resistor R4, one end of which is electrically connected to the CAN_H interface of the CAN interface circuit;

[0090] A resistor R7, one end of which is electrically connected to the other end of the resistor R4, and the other end of which is grounded.

[0091] The second voltage acquisition circuit includes:

[0092] A resistor R5, one end of which is electrically connected to the CAN_L interface of the CAN interface circuit;

[0093] A resistor R9, one end of which is electrically connected to the other end of the resistor R5, and the other end of which is grounded.

[0094] The rail-to-rail operational amplifier circuit includes:

[0095] A resistor R6, one end of which is electrically connected between the resistor R4 and the resistor R7;

[0096] A capacitor C10, one end of which is electrically connected between the resistor R4 and the resistor R7, and the other end of which is grounded;

[0097] A resistor R8, one end of which is electrically connected between the resistor R5 and the resistor R9;

[0098] A capacitor C11, one end of which is electrically connected between the resistor R5 and the resistor R9, and the other end of which is grounded;

[0099] The rail-to-rail operational amplifier U2 with the model number TSV912AQDGKRQ1, its IN1+ pin is electrically connected to the other end of the resistor R6, its IN1- pin and OUT1 pin are both electrically connected to the ADC_CANOH sampling interface of the MCU, its V- pin is grounded, its IN2+ pin is electrically connected to the other end of the resistor R8, its IN2- pin and OUT2 pin are both electrically connected to the ADC_CANOL sampling interface of the MCU, and its V+ pin is connected to a 3.3V power supply;

[0100] A capacitor C9, one end of which is electrically connected to the V+ pin of the rail-to-rail operational amplifier U2, and the other end is grounded.

[0101] Figure 3 Among them, the markings, categories and function descriptions of each device are shown in Table 3 below.

[0102] Table 3

[0103]

[0104]

[0105] Figure 3 Among them, the function descriptions of each signal are shown in Table 4 below.

[0106] Table 4

[0107] Signal Functional Description CAN0H High Level of CAN Bus CAN0L Low Level of CAN Bus P_CAN0H Collected High Level Voltage of CAN Bus after Voltage Dividing Resistor P_CAN0L Collected Low Level Voltage of CAN Bus after Voltage Dividing Resistor ADC_CAN0H Collected High Level Voltage of CAN Bus after Rail-to-Rail Operational Amplifier ADC_CAN0L Collected Low Level Voltage of CAN Bus after Rail-to-Rail Operational Amplifier

[0108] In this specific embodiment, the circuit principle of the MCU is as Figure 4 shown.

[0109] Figure 4 Among them, the markings, categories and function descriptions of each device are shown in Table 5 below.

[0110] Table 5

[0111]

[0112]

[0113] Figure 4 Among them, the function descriptions of each signal are shown in Table 6 below.

[0114] Table 6

[0115] Signal Functional Description MCU_RESET# MCU Reset Signal MCU_SWD_DIO SWD Data Signal MCU_SWD_CLK SWD Clock Signal MCU_LPUART0_TX Serial Port Debugging Transmission Signal MCU_LPUART0_RX Serial Port Debugging Reception Signal ADC_CAN0H Collected High Level Voltage of CAN Bus after Rail-to-Rail Operational Amplifier ADC_CAN0L Collected Low Level Voltage of CAN Bus after Rail-to-Rail Operational Amplifier MCU_CAN0_TX Transmission Data Input MCU_CAN0_RX Received Data Output MCU_CAN0_STB Control Standby Mode

[0116] In a diagnostic circuit for signal short circuit of the present utility model, the principle of judging the voltage states of CAN_H and CAN_L according to the voltage values of CAN_H and CAN_L read by the MCU is as follows:

[0117] The common causes of CAN faults and short circuits include short circuits between CAN_H and CAN_L, short circuits between CAN_H and CAN_L and the power supply, etc.

[0118] 1) Short circuit between CAN_H and CAN_L:

[0119] When there is a short circuit between CAN_H and CAN_L, the CAN network will shut down and communication will no longer be possible. By detecting that the signal voltages of CAN_H and CAN_L are both 2.5V, through the acquisition of voltage by the diagnostic circuit, the ADC of the MCU samples and reads the signal voltage values of CAN_H and CAN_L to judge the short circuit state and provide the corresponding fault code to the in-vehicle CAN controller.

[0120] 2) Short circuit between CAN_H and the power supply (positive pole):

[0121] When there is a short circuit between CAN_H and the power supply (positive pole), according to the fault tolerance characteristics of the CAN bus, the entire CAN network may become incommunicable. Taking the short circuit to the 12V power supply as an example, the CAN_H voltage is set to 12V and the CAN_L voltage is set to approximately 12V. Through the acquisition of voltage by the diagnostic circuit, the ADC of the MCU samples and reads the signal voltage values of CAN_H and CAN_L to judge the short circuit state and provide the corresponding fault code to the in-vehicle CAN controller.

[0122] 3) Short circuit between CAN_H and GND (negative pole):

[0123] When there is a short circuit between CAN_H and GND (negative pole), according to the fault tolerance characteristics of the CAN bus, the entire CAN network may become incommunicable. The CAN_H voltage is set to 1V and the CAN_L voltage is set to 0V. Through the acquisition of voltage by the diagnostic circuit, the ADC of the MCU samples and reads the signal voltage values of CAN_H and CAN_L to judge the short circuit state and provide the corresponding fault code to the in-vehicle CAN controller.

[0124] 4) Short circuit between CAN_L and the power supply (positive pole):

[0125] When there is a short circuit between CAN_L and the power supply (positive pole), according to the fault tolerance characteristics of the CAN bus, the entire CAN network may become incommunicable. The CAN_H and CAN_L voltages are set to 12V. Through the acquisition of voltage by the diagnostic circuit, the ADC of the MCU samples and reads the signal voltage values of CAN_H and CAN_L to judge the short circuit state and provide the corresponding fault code to the in-vehicle CAN controller.

[0126] 5) Short circuit between CAN_L and GND (negative pole);

[0127] When there is a short circuit between CAN_L and GND (negative pole), according to the fault tolerance characteristics of the CAN bus, the entire CAN network may fail to communicate. The voltages of CAN_H and CAN_L are both set to 0V. Through the acquisition of voltage by the diagnostic circuit, the ADC of the MCU samples and reads the signal voltage values of CAN_H and CAN_L to judge the short circuit state and provide corresponding fault codes to the in-vehicle CAN controller.

[0128] The corresponding states of the above five short circuit situations are shown in Table 7 below (taking 12V as an example).

[0129] Table 7

[0130] CAN Bus Short Circuit Status CAN_H Output Voltage CAN_L Output Voltage Short Circuit between CAN_H and CAN_H 2.5V 2.5V Short Circuit of CAN_H to Power Supply (Positive Pole) 12V About 12V Short Circuit of CAN_H to GND (Negative Pole) 1V 0V Short Circuit of CAN_L to Power Supply (Positive Pole) About 12V 12V Short Circuit of CAN_L to GND (Negative Pole) 0V 0V

[0131] In summary, the diagnostic circuit for signal short circuit of the present utility model does not require external disassembly and manual troubleshooting. Through the diagnostic message of the CAN bus, it can accurately locate and intelligently analyze the cause of the CAN bus short circuit, achieve efficient and rapid judgment to find the fault location and cause, so as to repair the vehicle and completely eliminate the fault. The present utility model can significantly reduce the difficulty of fault analysis, disassembly, as well as the maintenance cost and labor cost.

[0132] The above are only the preferred embodiments of the present utility model, and are not intended to limit the present utility model. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present utility model shall be included in the protection scope of the present utility model.

Claims

1. A signal short circuit diagnosis circuit, characterized in that: Used to diagnose whether a CAN bus short circuit occurs in a CAN bus circuit; wherein the CAN bus circuit includes an ECU, and the ECU includes a CAN interface circuit, a CAN transceiver circuit and an MCU; the CAN_L interface of the CAN transceiver circuit is electrically connected to the CAN_L interface of the CAN interface circuit, the CAN_H interface of the CAN transceiver circuit is electrically connected to the CAN_H interface of the CAN interface circuit, the RX interface of the CAN transceiver circuit is electrically connected to the TX interface of the MCU, and the TX interface of the CAN transceiver circuit is electrically connected to the RX interface of the MCU; the diagnostic circuit includes: A first voltage acquisition circuit, electrically connected to the CAN_H interface of the CAN interface circuit; A second voltage acquisition circuit is electrically connected to the CAN_L interface of the CAN interface circuit; A rail-to-rail operational amplifier circuit, wherein the input end is electrically connected to the first voltage acquisition circuit and the second voltage acquisition circuit respectively, and the output end is electrically connected to the MCU.

2. The signal short circuit diagnosis circuit according to claim 1, characterized in that: The CAN transceiver circuit comprises: CAN transceiver U1, whose TXD pin is electrically connected to the RX interface of the MCU, whose RXD pin is electrically connected to the TX interface of the MCU, whose STB pin is electrically connected to the standby mode control interface of the MCU, whose VCC pin is connected to a 5V power supply, whose VIO pin is connected to a 3.3V power supply, and whose GND pin is grounded; A capacitor C1 electrically connected between ground and a VCC pin of the CAN transceiver U1; A capacitor C2 electrically connected between ground and a VIO pin of the CAN transceiver U1; A capacitor C3 electrically connected between ground and a VCC pin of the CAN transceiver U1; A capacitor C4 electrically connected between ground and a VIO pin of the CAN transceiver U1; A capacitor C5 electrically connected between ground and the RXD pin of the CAN transceiver U1; A resistor R1, electrically connected between ground and the STB pin of the CAN transceiver U1; A common mode inductor LT1, one end of one coil of which is electrically connected to the CANL pin of the CAN transceiver U1, the other end of one coil of which is electrically connected to the CAN_L interface of the CAN interface circuit, one end of another coil of which is electrically connected to the CANH pin of the CAN transceiver U1, and the other end of another coil of which is electrically connected to the CAN_H interface of the CAN interface circuit; A capacitor C6, one end of which is electrically connected to the other end of a coil of the common mode inductor LT1, and the other end of which is grounded; A capacitor C7, one end of which is electrically connected to the other end of the other coil of the common mode inductor LT1, and the other end of which is grounded; A resistor R2, one end of which is electrically connected to the other end of a coil of the common mode inductor LT1; a resistor R3, one end of which is electrically connected to the other end of the other coil of the common mode inductor LT1; A capacitor C8, one end of which is electrically connected to the other end of the resistor R2 and the other end of the resistor R3, and the other end of which is grounded; The ESD protection diode has a pair of pins electrically connected to the other end of one coil of the common mode inductor LT1 and the other end of the other coil of the common mode inductor LT1, and the other pair of pins is grounded.

3. The signal short circuit diagnosis circuit according to claim 2, characterized in that: The CAN transceiver circuit also includes: A magnetic bead FB1, which is electrically connected between a 5V power supply and a VCC pin of the CAN transceiver U1; A magnetic bead FB2, which is electrically connected between a 3.3V power supply and a VIO pin of the CAN transceiver U1; A magnetic bead FB3, which is electrically connected between the other end of the other coil of the common mode inductor LT1 and the CAN_H interface of the CAN interface circuit; The magnetic bead FB4 is electrically connected between the other end of a coil of the common mode inductor LT1 and the CAN_L interface of the CAN interface circuit.

4. The signal short circuit diagnosis circuit according to claim 2, characterized in that: The model of the CAN transceiver U1 is TJA1044GT / 3.

5. The signal short circuit diagnosis circuit according to claim 1, characterized in that: The first voltage acquisition circuit comprises: A resistor R4, one end of which is electrically connected to the CAN_H interface of the CAN interface circuit; The resistor R7 has one end electrically connected to the other end of the resistor R4 and the other end grounded.

6. The signal short circuit diagnosis circuit according to claim 5, characterized in that: The second voltage acquisition circuit comprises: A resistor R5, one end of which is electrically connected to the CAN_L interface of the CAN interface circuit; The resistor R9 has one end electrically connected to the other end of the resistor R5 and the other end grounded.

7. The signal short circuit diagnosis circuit according to claim 6, characterized in that: The rail-to-rail operational amplifier circuit comprises: a resistor R6, one end of which is electrically connected between the resistor R4 and the resistor R7; A capacitor C10, one end of which is electrically connected between the resistor R4 and the resistor R7, and the other end of which is grounded; a resistor R8, one end of which is electrically connected between the resistor R5 and the resistor R9; A capacitor C11, one end of which is electrically connected between the resistor R5 and the resistor R9, and the other end of which is grounded; A rail-to-rail operational amplifier U2, whose IN1+ pin is electrically connected to the other end of the resistor R6, whose IN1- pin and OUT1 pin are both electrically connected to the ADC_CANOH sampling interface of the MCU, whose V- pin is grounded, whose IN2+ pin is electrically connected to the other end of the resistor R8, whose IN2- pin and OUT2 pin are both electrically connected to the ADC_CANOL sampling interface of the MCU, and whose V+ pin is connected to a 3.3V power supply; The capacitor C9 has one end electrically connected to the V+ pin of the rail-to-rail operational amplifier U2 and the other end grounded.

8. The signal short circuit diagnosis circuit according to claim 7, characterized in that: The model of the rail-to-rail operational amplifier U2 is TSV912AQDGKRQ1.

9. The signal short circuit diagnosis circuit according to claim 7, characterized in that: The diagnostic circuit is integrated in the ECU.

10. The signal short circuit diagnosis circuit according to claim 1, characterized in that: The CAN bus circuit also includes: a vehicle CAN controller; a CAN_L interface of the vehicle CAN controller is electrically connected to the CAN_L interface of the CAN interface circuit, and a CAN_H interface of the vehicle CAN controller is electrically connected to the CAN_H interface of the CAN interface circuit.

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