A vehicle speed sensor acquisition and diagnosis circuit

Abstract

The technical scheme adopted by the present application is: a kind of vehicle speed sensor acquisition and diagnosis circuit, comprising: resistance R1, resistance R2, resistance R4, resistance R5, resistance R6, resistance R8, diode, MOS tube and battery;Signal input end is connected to ground through series-connected resistance R1 and resistance R2;The cathode of diode is connected between signal input end and resistance R1, and the anode of diode is electrically connected with the gate electrode of MOS tube through resistance R6;The anode of diode is connected with the drain electrode of MOS tube through resistance R4 and resistance R5;The gate electrode of MOS tube is connected to ground through resistance R8;The source electrode of MOS tube is directly connected to ground;The drain electrode of MOS tube is connected with the positive electrode of battery through resistance R5, and the negative electrode of battery is connected to ground;Sensor signal output end is connected between the drain electrode of MOS tube and resistance R5;Diagnosis signal output end is connected between resistance R1 and resistance R2.The present application can diagnose the fault type of vehicle speed sensor.

Description

Technical Field

[0001] This invention belongs to the field of automotive circuit technology, specifically relating to a vehicle speed sensor acquisition and diagnostic circuit. Background Technology

[0002] Existing vehicle speed sensor acquisition circuits typically acquire vehicle speed directly through the MCU after filtering and voltage division. These circuits lack diagnostic protection mechanisms and cannot detect situations such as short circuits to the power supply (12V and 24V), short circuits to ground, or open circuits. In practical applications, short circuits to the power supply, ground, or open circuits can cause the controller to acquire incorrect vehicle speed signals, leading to unintended consequences for the vehicle and violating automotive functional safety requirements. Furthermore, existing vehicle speed sensor acquisition circuits lack level conversion, making them susceptible to MCU damage. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the above-mentioned background technology and provide a vehicle speed sensor acquisition and diagnostic circuit that can diagnose the fault type of the vehicle speed sensor.

[0004] The technical solution adopted in this invention is: a vehicle speed sensor acquisition and diagnostic circuit, comprising: resistors R1, R2, R4, R5, R6, and R8, a diode, a MOSFET, and a battery; the signal input terminal is grounded via resistors R1 and R2 connected in series; the cathode of the diode is connected between the signal input terminal and resistor R1, and the anode of the diode is electrically connected to the gate of the MOSFET via resistor R6; the anode of the diode is connected to the drain of the MOSFET via resistors R4 and R5; the gate of the MOSFET is grounded via resistor R8; the source of the MOSFET is directly grounded; the drain of the MOSFET is connected to the positive terminal of the battery via resistor R5, and the negative terminal of the battery is grounded; the sensor signal output terminal is connected between the drain of the MOSFET and resistor R5; and the diagnostic signal output terminal is connected between resistors R1 and R2.

[0005] In the above technical solution, the signal input terminal is electrically connected to the signal output terminal of the vehicle speed sensor, and is used to receive the vehicle speed signal sent by the vehicle speed sensor.

[0006] In the above technical solution, the sensor signal output terminal is electrically connected to the vehicle speed signal input terminal of the microprocessor, and is used to send the vehicle speed signal after being acquired and processed by the vehicle speed sensor acquisition and diagnostic circuit to the microprocessor.

[0007] In the above technical solution, the diagnostic signal output terminal is electrically connected to the diagnostic signal input terminal of the microprocessor, and is used to send the diagnostic signal obtained after being collected by the vehicle speed sensor and processed by the diagnostic circuit to the microprocessor.

[0008] In the above technical solution, the microprocessor determines the fault mode of the vehicle speed sensor based on the received vehicle speed signal and diagnostic signal.

[0009] In the above technical solution, when the vehicle speed sensor is working normally, the vehicle speed signal read by the microprocessor is a square wave signal with an amplitude range of 0V to the battery voltage, and the output frequency is the same as the output pulse signal of the vehicle speed sensor, but the direction is opposite to that of the output pulse signal of the vehicle speed sensor.

[0010] In the above technical solution, when the vehicle speed signal voltage read by the microprocessor is stuck and equal to the battery voltage, and the diagnostic signal voltage is 0V, it is determined that the vehicle speed sensor is short-circuited to ground.

[0011] When the vehicle speed signal voltage read by the microprocessor is stuck at 0V, and the diagnostic signal voltage is AxR2 / (R1+R2)V, it is determined that the vehicle speed sensor is short-circuited to the microprocessor power supply, where A is the voltage value of the microprocessor power supply.

[0012] When the vehicle speed signal voltage read by the microprocessor is stuck at 0V and the diagnostic signal voltage is BxR2 / (R1+R2)V, it is determined that the vehicle speed sensor is short-circuited to its power supply, where B is the voltage value of the power supply of the vehicle speed sensor.

[0013] When the vehicle speed signal read by the microprocessor is stuck at 0V and the diagnostic signal voltage is CxR2 / (R1+R2)V, it is determined that the vehicle speed sensor is open-circuited, where C is the battery voltage value.

[0014] The above technical solution also includes a resistor R3 and a capacitor C2; the diagnostic signal output terminal is connected between resistors R1 and R2 via resistor R3; the diagnostic signal output terminal is grounded via capacitor C2.

[0015] The above technical solution also includes a resistor R7 and a capacitor C1; the sensor signal output terminal is connected between the resistor R5 and the drain of the MOS transistor via the resistor R7; the sensor signal output terminal is grounded via the capacitor C1.

[0016] In the above technical solution, a capacitor C3 is connected in parallel across the resistor R8.

[0017] The beneficial effects of this invention are as follows: This invention proposes a novel diagnostic protection mechanism that can effectively diagnose situations where the vehicle body sensor is short-circuited to its own power supply, short-circuited to the microprocessor power supply, short-circuited to ground, or open-circuited. This effectively prevents the controller from acquiring incorrect vehicle speed signals, thus avoiding unintended consequences for the vehicle and violating automotive functional safety requirements. Simultaneously, this invention performs level conversion on the output signal of the vehicle speed sensor, reducing the signal voltage amplitude output to the microprocessor and effectively protecting the microprocessor. This invention can process high-frequency input signals with high accuracy and strong anti-interference capabilities. The diagnostic trigger threshold of this invention can be adjusted according to different sensors, thus effectively adapting to different vehicle speed sensors. Attached Figure Description

[0018] Figure 1 This is a circuit diagram of the present invention;

[0019] Figure 2 This is a schematic diagram illustrating an application scenario of the present invention. Detailed Implementation

[0020] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments to facilitate a clear understanding of the present invention, but these descriptions do not constitute a limitation on the present invention.

[0021] like Figure 1 As shown, this invention provides a vehicle speed sensor acquisition and diagnostic circuit, including: resistors R1, R2, R4, R5, R6, and R8, a diode, a MOSFET, and a battery; the signal input terminal is grounded via resistors R1 and R2 connected in series; the cathode of the diode is connected between the signal input terminal and resistor R1, and the anode of the diode is electrically connected to the gate of the MOSFET via resistor R6; the anode of the diode is connected to the drain of the MOSFET via resistors R4 and R5; the gate of the MOSFET is grounded via resistor R8; the source of the MOSFET is directly grounded; the drain of the MOSFET is connected to the positive terminal of the battery via resistor R5, and the negative terminal of the battery is grounded; the sensor signal output terminal is connected between the drain of the MOSFET and resistor R5; the diagnostic signal output terminal is connected between resistors R1 and R2.

[0022] Specifically, the signal input terminal is electrically connected to the signal output terminal of the vehicle speed sensor and is used to receive the vehicle speed signal sent by the vehicle speed sensor.

[0023] Specifically, the sensor signal output terminal is electrically connected to the vehicle speed signal input terminal of the microprocessor, and is used to send the vehicle speed signal after being acquired and processed by the vehicle speed sensor acquisition and diagnostic circuit to the microprocessor.

[0024] Specifically, the diagnostic signal output terminal is electrically connected to the diagnostic signal input terminal of the microprocessor, and is used to send the diagnostic signal obtained after being collected by the vehicle speed sensor and processed by the diagnostic circuit to the microprocessor.

[0025] Specifically, the microprocessor determines the fault mode of the vehicle speed sensor based on the received vehicle speed signal and diagnostic signal.

[0026] Specifically, when the vehicle speed sensor is working normally, the vehicle speed signal read by the microprocessor is a square wave signal with an amplitude range of 0V to the battery voltage, and the output frequency is the same as the output pulse signal of the vehicle speed sensor, but the direction is opposite to that of the output pulse signal of the vehicle speed sensor.

[0027] Specifically, if the vehicle speed signal voltage read by the microprocessor is stuck and equal to the battery voltage, and the diagnostic signal voltage is 0V, then it is determined that the vehicle speed sensor is short-circuited to ground.

[0028] When the vehicle speed signal voltage read by the microprocessor is stuck at 0V, and the diagnostic signal voltage is AxR2 / (R1+R2)V, it is determined that the vehicle speed sensor is short-circuited to the microprocessor power supply, where A is the voltage value of the microprocessor power supply.

[0029] When the vehicle speed signal voltage read by the microprocessor is stuck at 0V and the diagnostic signal voltage is BxR2 / (R1+R2)V, it is determined that the vehicle speed sensor is short-circuited to its power supply, where B is the voltage value of the power supply of the vehicle speed sensor.

[0030] When the vehicle speed signal read by the microprocessor is stuck at 0V and the diagnostic signal voltage is CxR2 / (R1+R2)V, it is determined that the vehicle speed sensor is open-circuited, where C is the battery voltage value.

[0031] Specifically, it also includes resistor R3 and capacitor C2; the diagnostic signal output terminal is connected between resistor R1 and resistor R2 via resistor R3; the diagnostic signal output terminal is grounded via capacitor C2.

[0032] Specifically, it also includes a resistor R7 and a capacitor C1; the sensor signal output terminal is connected between the resistor R5 and the drain of the MOS transistor via the resistor R7; the sensor signal output terminal is grounded via the capacitor C1.

[0033] Specifically, a capacitor C3 is connected in parallel across the resistor R8.

[0034] like Figure 2 As shown in the specific embodiment provided by the present invention, the vehicle speed sensor is powered by a 12V power supply, and the output signal of the vehicle speed sensor is sent to the microprocessor via the vehicle speed sensor acquisition and diagnostic circuit. In this specific embodiment, the battery voltage is 5V, and the power supply voltage of the microprocessor is 24V.

[0035] like Figure 1 As shown, VF1 represents the vehicle speed signal output from the sensor signal output terminal of the vehicle speed sensor acquisition and diagnostic circuit, VF2 represents the diagnostic signal output from the diagnostic signal output terminal, and VF3 represents the pulse signal received from the vehicle speed sensor output from the signal input terminal.

[0036] The pulse signal output by the vehicle speed sensor (amplitude 0-12V, output frequency changes with vehicle speed 100Hz-4KHz) is connected to the circuit through VF3.

[0037] When the pulse signal output by the vehicle speed sensor is 0V, the cathode of diode D1 is pulled low to 0V, diode D1 is turned on, the gate voltage of MOSFET T2 is 0V, MOSFET T2 is in the off state (gate turn-on voltage is less than 0.8V), at this time the drain voltage of MOSFET T2 is 5V, the output voltage of VF1 is 5V, and the microprocessor MCU reads a high level that is opposite to the actual waveform direction.

[0038] When the pulse signal output by the vehicle speed sensor is 12V, the cathode of diode D1 is pulled up to 12V, and the diode does not conduct. At this time, the gate voltage of MOSFET T2 is 5xR8 / (R4+R6+R8)V, reaching the turn-on voltage. The drain voltage of MOSFET T2 is pulled down to 0V, and the voltage of VF1 is approximately 0V. The microprocessor MCU reads a low level, which is opposite to the actual waveform. Resistors R4, R6, and R8 form the gate bias voltage circuit, ensuring that the MOSFET can be fully turned on and off when the input signal changes. Resistor R5 limits the output current after the MOSFET is turned on, preventing excessive current from burning out the MOSFET. Resistor R7 and capacitor C1 form an RC filter to filter out high-frequency noise in the pulse signal, with a filter cutoff frequency of 1 / (2πR7C1)Hz. The function of capacitor C3 is to fully pull down the input level.

[0039] When the vehicle speed sensor is working normally, the microprocessor reads the vehicle speed signal VF1 and generates a square wave signal with an amplitude of 0-5V and a frequency of 100Hz-4KHz, which is opposite in direction to the actual input pulse signal VF3. Resistors R1 and R2 divide the voltage to collect the input signal to determine whether it is short-circuited to ground, short-circuited to the power supply, or open-circuited.

[0040] When the vehicle speed sensor is short-circuited to ground, the pulse signal output by the vehicle speed sensor is stuck at 0V. Therefore, the vehicle speed signal VF1 read by the microprocessor MCU is stuck at 5V, and the voltage of the diagnostic signal VF2 is 0V.

[0041] When the vehicle speed sensor is short-circuited to the 24V power supply (i.e., the power supply of the microprocessor), the microprocessor MCU reads the vehicle speed signal VF1 and it is stuck at 0V, and the diagnostic signal VF2 voltage is 24xR2 / (R1+R2)V.

[0042] When the vehicle speed sensor is short-circuited to the 12V power supply (i.e., the power supply of the vehicle speed sensor itself), the microprocessor reads the vehicle speed signal VF1 and it is stuck at 0V, and the diagnostic signal VF2 voltage is 12xR2 / (R1+R2)V.

[0043] When the vehicle speed sensor is open-circuited, the microprocessor (MCU) reads the vehicle speed signal VF1 and it freezes at 0V. The 5V battery voltage passes through diode D1 and is then divided by resistors R1 and R2, resulting in a diagnostic voltage VF2 of 5 x R2 / (R1 + R2) V. Resistor R3 and capacitor C2 form an RC low-pass filter circuit with a filter cutoff frequency of 1 / (2πR3C2) Hz. Resistor R3 also limits current, protecting the MCU pins from damage due to overcurrent.

[0044] Therefore, the specific fault diagnosis logic for a microprocessor is as follows:

[0045] When the microprocessor reads a vehicle speed signal voltage VF1 of 5V for 2 seconds and the diagnostic signal voltage VF2 is 0V, the fault mode of the vehicle speed sensor is determined to be a short circuit to ground.

[0046] When the vehicle speed signal voltage VF1 read by the microprocessor is 0V and lasts for 2s, and the diagnostic signal voltage VF2 is 24xR2 / (R1+R2)V, it is determined that the vehicle speed sensor is short-circuited to the microprocessor's 24V power supply, that is, the power supply terminal of the vehicle speed sensor and the power supply terminal of the microprocessor are stuck together.

[0047] When the microprocessor reads the vehicle speed signal VF1 as 0V for 2 seconds, and the diagnostic signal VF2 voltage is 12xR2 / (R1+R2)V, it is determined that the vehicle speed sensor is short-circuited to its own 12V power supply.

[0048] When the microprocessor reads the vehicle speed signal VF1 as 0V for 2 seconds, and the diagnostic signal VF2 voltage is 5xR2 / (R1+R2)V.

[0049] The details are shown in the table below:

[0050]

[0051]

[0052] This invention proposes a novel diagnostic protection mechanism that can effectively diagnose situations where vehicle body sensors are short-circuited to their own power supply, short-circuited to the microprocessor power supply, short-circuited to ground, or open-circuited. This effectively prevents the controller from acquiring erroneous vehicle speed signals, thus avoiding unintended consequences for the vehicle and violating automotive functional safety requirements. Simultaneously, this invention performs level conversion on the output signal of the vehicle speed sensor, reducing the signal voltage amplitude output to the microprocessor and effectively protecting the microprocessor. This invention can handle high-frequency input signals with high accuracy and strong anti-interference capabilities. The diagnostic trigger threshold of this invention can be adjusted according to different sensors, thus effectively adapting to various vehicle speed sensors.

[0053] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0054] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0055] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0056] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit its scope of protection. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that after reading the present invention, they can still make various changes, modifications or equivalent substitutions to the specific implementation of the invention, but these changes, modifications or equivalent substitutions are all within the scope of protection of the pending claims of the invention.

[0058] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

Claims

1. A vehicle speed sensor acquisition and diagnostic circuit, characterized in that, include: Resistors R1, R2, R4, R5, R6, R8, diodes, MOSFETs, and batteries; The signal input terminal is grounded via resistors R1 and R2 connected in series; the cathode of the diode is connected between the signal input terminal and resistor R1, and the anode of the diode is electrically connected to the gate of the MOSFET via resistor R6; the anode of the diode is connected to the drain of the MOSFET via resistors R4 and R5; the gate of the MOSFET is grounded via resistor R8; the source of the MOSFET is directly grounded; the drain of the MOSFET is connected to the positive terminal of the battery via resistor R5, and the negative terminal of the battery is grounded; the sensor signal output terminal is connected between the drain of the MOSFET and resistor R5; the diagnostic signal output terminal is connected between resistors R1 and R2.

2. The vehicle speed sensor acquisition and diagnostic circuit according to claim 1, characterized in that: The signal input terminal is electrically connected to the signal output terminal of the vehicle speed sensor and is used to receive the vehicle speed signal sent by the vehicle speed sensor.

3. The vehicle speed sensor acquisition and diagnostic circuit according to claim 2, characterized in that: The sensor signal output terminal is electrically connected to the vehicle speed signal input terminal of the microprocessor, and is used to send the vehicle speed signal after being acquired and processed by the vehicle speed sensor acquisition and diagnostic circuit to the microprocessor.

4. The vehicle speed sensor acquisition and diagnostic circuit according to claim 3, characterized in that: The diagnostic signal output terminal is electrically connected to the diagnostic signal input terminal of the microprocessor, and is used to send the diagnostic signal obtained after being collected by the vehicle speed sensor and processed by the diagnostic circuit to the microprocessor.

5. The vehicle speed sensor acquisition and diagnostic circuit according to claim 4, characterized in that: The microprocessor determines the fault mode of the vehicle speed sensor based on the received vehicle speed signal and diagnostic signal.

6. The vehicle speed sensor acquisition and diagnostic circuit according to claim 5, characterized in that: When the vehicle speed sensor is working normally, the microprocessor reads a square wave signal with an amplitude range of 0V to the battery voltage and an output frequency that is the same as the frequency of the output pulse signal of the vehicle speed sensor. This square wave signal is in the opposite direction to the output pulse signal of the vehicle speed sensor.

7. The vehicle speed sensor acquisition and diagnostic circuit according to claim 5, characterized in that: If the vehicle speed signal voltage read by the microprocessor is stuck and equal to the battery voltage, and the diagnostic signal voltage is 0V, then it is determined that the vehicle speed sensor is short-circuited to ground. When the vehicle speed signal voltage read by the microprocessor is stuck at 0V, and the diagnostic signal voltage is AxR2 / (R1+R2)V, it is determined that the vehicle speed sensor is short-circuited to the microprocessor power supply, where A is the voltage value of the microprocessor power supply. When the vehicle speed signal voltage read by the microprocessor is stuck at 0V and the diagnostic signal voltage is BxR2 / (R1+R2)V, it is determined that the vehicle speed sensor is short-circuited to its power supply, where B is the voltage value of the power supply of the vehicle speed sensor. When the vehicle speed signal read by the microprocessor is stuck at 0V and the diagnostic signal voltage is CxR2 / (R1+R2)V, it is determined that the vehicle speed sensor is open-circuited, where C is the battery voltage value.

8. The vehicle speed sensor acquisition and diagnostic circuit according to claim 1, characterized in that: It also includes resistor R3 and capacitor C2; the diagnostic signal output terminal is connected between resistor R1 and resistor R2 via resistor R3; the diagnostic signal output terminal is grounded via capacitor C2.

9. The vehicle speed sensor acquisition and diagnostic circuit according to claim 1, characterized in that: It also includes a resistor R7 and a capacitor C1; the sensor signal output terminal is connected between the resistor R5 and the drain of the MOS transistor via the resistor R7; the sensor signal output terminal is grounded via the capacitor C1.

10. The vehicle speed sensor acquisition and diagnostic circuit according to claim 1, characterized in that: A capacitor C3 is connected in parallel across the resistor R8.

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