Diagnosis circuit based on analog comparator and diagnosis method thereof

Abstract

The invention relates to a diagnosis circuit based on an analog comparator, which comprises an MCU (Microprogrammed Control Unit), a DAC (Digital-to-Analog Converter) signal conversion unit, an analog comparator unit, an ultrasonic sensor peripheral unit, a signal driving circuit, a signal detection circuit and a power supply unit, the signal driving circuit drives the ultrasonic sensor peripheral unit to work, an analog signal output end generated by the ultrasonic sensor peripheral unit is connected with a signal input end of the signal detection circuit, and the MCU control unit is further connected with the analog comparator unit through the DAC signal conversion unit. A digital signal sent by the MCU control unit is converted into an analog signal through the DAC signal conversion unit, the analog signal is input into the analog comparator unit, and the analog comparator unit outputs a logic level back to the MCU control unit. In the aspect of transient voltage analysis, transient sampling is more convenient, the cost is low, the carrying load of a processor can be reduced, and the recognition efficiency of a sensor is improved.

Description

Technical Field

[0001] This invention relates to the field of automotive controller circuit design, specifically a diagnostic circuit and diagnostic method based on an analog comparator. Background Technology

[0002] In recent years, the government has intensified its control over diesel vehicle emissions, with stricter requirements for NOx emissions from diesel engines. Currently, SCR (Selective Catalytic Reduction) technology is considered one of the effective ways to reduce NOx emissions from heavy-duty diesel engines. In today's SCR systems, urea solution is typically used as a reducing agent, making a urea quality sensor an essential component of the diesel engine for real-time monitoring of the urea solution concentration in the tank. Ultrasonic urea quality sensors are the most widely used. These ultrasonic concentration sensors utilize the transducer principle; when a pulse signal is applied to the circuit, and its frequency equals the transducer's natural oscillation frequency, the piezoelectric crystal resonates, causing the resonant plate to vibrate and generate a high-frequency ultrasonic signal.

[0003] As a key component for diesel engine emissions, the urea quality sensor communicates with the vehicle's ECU (Electronic Control Unit) via a CAN network. Therefore, it must perform internal fault diagnosis and fault information message feedback in accordance with regulatory requirements and the J1939 protocol standard. Currently, the industry's open-circuit and short-circuit diagnosis of ultrasonic probe drive circuits is not perfect. Based on the high-frequency signal design principle of the ultrasonic transducer drive circuit and the transient repeatability of ultrasonic sensors, current and voltage sampling alone can only identify short-circuit faults to ground, and cannot effectively identify open-circuit faults in the drive signal or whether the connection is normal and stable. Summary of the Invention

[0004] To address the aforementioned problems, the purpose of this invention is to provide a diagnostic circuit and diagnostic method based on an analog comparator. To achieve the above objectives, the technical solution of the present invention is as follows: a diagnostic circuit based on an analog comparator, comprising an MCU control unit, a DAC signal conversion unit, an analog comparator unit, an ultrasonic sensor peripheral unit, a signal driving circuit, a signal detection circuit, and a power supply unit. The MCU control unit is electrically connected to the ultrasonic sensor peripheral unit through the signal driving circuit, enabling the signal driving circuit to drive the ultrasonic sensor peripheral unit to work. The analog signal output terminal generated by the ultrasonic sensor peripheral unit is connected to the signal input terminal of the signal detection circuit. The signal detection circuit transmits the waveform generated by the ultrasonic sensor peripheral unit to the analog comparator unit. The MCU control unit is also connected to the analog comparator unit through the DAC signal conversion unit, enabling the digital signal emitted by the MCU control unit to be converted into an analog signal by the DAC signal conversion unit and input to the analog comparator unit. The analog comparator unit outputs the logic level back to the MCU control unit. The MCU control unit is electrically connected to the power supply unit.

[0005] Furthermore, the MCU control unit consists of a CPU, memory, input / output interfaces, and matching peripheral circuits. It is responsible for the logic control and monitoring of the entire circuit, specifically including driving the ultrasonic sensor, identifying the output logic level of the analog comparator unit, and inputting the DAC signal conversion unit.

[0006] Furthermore, the DAC signal conversion unit consists of a DAC converter, an amplifier, and an output filter, which are used to convert digital signals into analog signals. After being integrated by the amplifier and the output filter, the output is a recognizable threshold voltage analog signal.

[0007] Furthermore, the analog comparator unit consists of three parts: signal input, signal processing, and logic output. Its function is to provide a digitally programmable threshold and output high and low levels based on the ultrasonic judgment result.

[0008] Furthermore, the ultrasonic sensor peripheral unit consists of two parts: the transducer body and the signal wires. It is a passive device in the ultrasonic sensor diagnostic circuit, performing the transmission and reception of ultrasonic waves.

[0009] Furthermore, the signal driving circuit is controlled by the MCU control unit to configure specific transmission pulses and frequencies, gain and signal thresholds, and integrate them into an excitation voltage that can drive the ultrasonic sensor peripheral unit to transmit ultrasonic waves, thereby enabling the ultrasonic sensor peripheral unit to work continuously.

[0010] Furthermore, the signal detection circuit collects the transmitted waveforms from the ultrasonic sensor peripheral unit and integrates them through filtering to form a sampled waveform that can be recognized by the analog comparator unit.

[0011] Furthermore, the power supply unit plays a role in stabilizing voltage and supplying power to various components within the entire system.

[0012] The present invention also provides a diagnostic method based on an analog comparator diagnostic circuit, including the aforementioned analog comparator-based diagnostic circuit, comprising the following steps: Step 1: Power-on initialization, system preparation phase; Step 2, signal sampling and processing stage: The ultrasonic sensor driving circuit releases the driving excitation signal, the ultrasonic sensor transducer sends high-frequency oscillation waves, and confirms whether an echo signal is received. If an echo signal is received, the circuit is normally connected. Step 3, during the comparator's operation phase, continuous trigger sampling is performed based on the ultrasonic drive pin waveform sampling results. The MCU software triggers reference voltages V1 and V2, and performs circuit diagnosis based on whether the sampled waveform of the signal pin triggers the rising edge of V1 (high voltage) and the rising edge of V2 (low voltage). If the sampling process triggers one rising edge of V1 for each excitation waveform, a secondary judgment is entered to determine whether the sampling waveform triggers the rising edge of V2 (low voltage). If the sampled waveform triggers both one rising edge of V1 and one rising edge of V2 (low voltage), it is determined to be an open circuit. If the sampled waveform triggers both one rising edge of V1 and more than one rising edge of V2 (low voltage), it is determined to be a normal signal. If the sampled waveform cannot trigger the rising edge of V1 (high voltage), but can trigger one rising edge and one falling edge of V2 (low voltage), it is determined to be a short circuit to ground. Step four, the result output stage, outputs the result signal based on the judgment result in step three.

[0013] Step 5, System Feedback Phase: The urea quality sensor MCU sends the judgment result to the external communication circuit in the form of a CAN message, providing feedback on the current circuit diagnosis result.

[0014] With the above settings, compared with the prior art, the present invention provides a reliable method for waveform recognition of ultrasonic sensors by combining a DAC with transient detail sampling and a comparator. In terms of transient voltage analysis, compared with the traditional processor + high-speed ADC mode, the combination of DAC and comparator is more convenient for highly repeatable transient sampling, and has a lower cost. It can also reduce the workload of the processor and improve the recognition efficiency of the sensor. Attached Figure Description

[0015] The present invention will now be further described with reference to the accompanying drawings.

[0016] Figure 1 This is a circuit structure block diagram of the present invention; Figure 2 This is a schematic diagram of the DAC and comparator logic of the present invention; Figure 3 This is a schematic diagram illustrating the working principle of the ultrasonic sensor of the present invention; Figure 4 This is a flowchart of the diagnostic method of the present invention; Figure 5 This is a schematic diagram of an example of an open-circuit waveform of the present invention; Figure 6 This is a schematic diagram of a normal signal waveform example of the present invention; Figure 7 This is a schematic diagram of a signal short-circuit waveform to ground according to the present invention. Detailed Implementation Example 1

[0017] like Figure 1 As shown, a diagnostic circuit based on an analog comparator includes an MCU control unit, a DAC signal conversion unit, an analog comparator unit, an ultrasonic sensor peripheral unit, a signal driving circuit, a signal detection circuit, and a power supply unit. The MCU control unit is electrically connected to the ultrasonic sensor peripheral unit through the signal driving circuit, enabling the signal driving circuit to drive the ultrasonic sensor peripheral unit to work. The analog signal output terminal generated by the ultrasonic sensor peripheral unit is connected to the signal input terminal of the signal detection circuit. The signal detection circuit transmits the waveform generated by the ultrasonic sensor peripheral unit to the analog comparator unit. The MCU control unit is also connected to the analog comparator unit through the DAC signal conversion unit, enabling the digital signal emitted by the MCU control unit to be converted into an analog signal by the DAC signal conversion unit and input to the analog comparator unit. The analog comparator unit outputs the logic level back to the MCU control unit. The MCU control unit is electrically connected to the power supply unit.

[0018] like Figure 1 As shown, specifically, the MCU control unit consists of a CPU, memory, input / output interfaces, and matching peripheral circuits. It is responsible for the logic control and monitoring of the entire circuit, including driving the ultrasonic sensor, identifying the logic level output of the comparator unit, and inputting the DAC signal conversion unit.

[0019] The DAC signal conversion unit consists of a DAC converter, an amplifier, and an output filter. It converts digital signals into analog signals, which are then integrated by the amplifier and output filter to output a recognizable threshold voltage analog signal. The comparator unit consists of signal input, signal processing, and logic output. Its function is to provide a digitally programmable threshold and output high and low levels based on the ultrasonic wave judgment result. The ultrasonic sensor peripheral unit consists of a transducer body and signal wires. It is the passive device of the circuit and performs ultrasonic wave transmission and reception. The signal driving circuit is controlled by the MCU control unit. It is configured for specific transmission pulses and frequencies, gain, and signal thresholds, and integrated to form an excitation voltage that can drive the ultrasonic sensor peripheral unit to transmit ultrasonic waves, enabling the ultrasonic sensor peripheral unit to work continuously. The signal detection circuit collects the transmitted waveforms of the ultrasonic sensor peripheral unit and filters and integrates them to form a sampled waveform that can be recognized by the comparator unit. The power supply unit plays a role in voltage stabilization and power supply to various components in the whole system.

[0020] like Figure 2 As shown, the external independent reference voltage of the comparator is triggered by the MCU software as a digital signal, which is converted into an analog signal by the DAC as a threshold voltage, and is used to compare with the waveform sampling result of the ultrasonic drive pin. The waveform sampling result signal of the ultrasonic drive pin is applied to the non-inverting input of the comparator, and the DAC provides the threshold voltage at the inverting input. Whenever the signal is greater than its threshold, the comparator will generate a logic high level output and feed it back to the MCU.

[0021] like Figure 3 As shown, this invention uses an MCU combined with a TDC1000 ultrasonic sensing analog front-end (AFE) chip to excite and acquire ultrasonic signals, supporting multiple sensor frequencies (31.25kHz to 4MHz). Example 2

[0022] like Figure 4 As shown, a diagnostic method based on an analog comparator diagnostic circuit includes the aforementioned analog comparator diagnostic circuit and comprises the following steps: Step 1: Power-on initialization, system preparation phase; Step 2, signal sampling and processing stage: The ultrasonic sensor driving circuit releases the driving excitation signal, the ultrasonic sensor transducer sends high-frequency oscillation waves, and confirms whether an echo signal is received. If an echo signal is received, the circuit is normally connected. Step 3, during the comparator's operation phase, continuous trigger sampling is performed based on the ultrasonic drive pin waveform sampling results. The MCU software triggers reference voltages V1 and V2, and performs circuit diagnosis based on whether the sampled waveform of the signal pin triggers the rising edge of V1 (high voltage) and the rising edge of V2 (low voltage). If the sampling process triggers one rising edge of V1 for each excitation waveform, a secondary judgment is entered to determine whether the sampling waveform triggers the rising edge of V2 (low voltage). If the sampled waveform triggers both one rising edge of V1 and one rising edge of V2 (low voltage), it is determined to be an open circuit. If the sampled waveform triggers both one rising edge of V1 and more than one rising edge of V2 (low voltage), it is determined to be a normal signal. If the sampled waveform cannot trigger the rising edge of V1 (high voltage), but can trigger one rising edge and one falling edge of V2 (low voltage), it is determined to be a short circuit to ground. Step four, the result output stage, outputs the result signal based on the judgment result in step three.

[0023] Step 5, System Feedback Phase: The urea quality sensor MCU sends the judgment result to the external communication circuit in the form of a CAN message, providing feedback on the current circuit diagnosis result.

[0024] like Figure 5 The waveform shown is the open-circuit waveform of the signal. In each excitation cycle, the peak value of the signal pin sampling waveform is greater than V1 and greater than V2. Therefore, the sampling waveform can trigger both the V1 high voltage rising edge and the V2 low voltage rising edge once. like Figure 6 The signal waveform shown is normal. Within each excitation cycle, the peak value of the sampled waveform of the signal pin is greater than V1 only once and greater than V2 multiple times. Therefore, the sampled waveform can trigger the V1 high voltage rising edge once and the V2 low voltage rising edge more than once. like Figure 7 The waveform shown is a short circuit to ground. In each excitation cycle, the peak value of the signal pin sampling waveform is greater than V2, and there is one rising edge and one falling edge. Therefore, the sampling waveform cannot trigger the rising edge of V1 high voltage, but it can trigger the rising edge of V2 low voltage once and the falling edge of V2 low voltage once. The system uses a direct polling control method to make multiple judgments to prevent false signal output. The MCU chip in this invention integrates a hardware DAC module and a comparator module. The method can be implemented either by combining the MCU's internal analog comparator with a software strategy or by using a simulator peripheral IC.

[0025] The diagnostic circuit of this invention compares the ultrasonic sensor excitation waveform with the diagnostic waveform using a comparator combined with the principle of a DAC. Through amplitude calibration, it can accurately identify the normal connection state, open circuit state, and short circuit state of the ultrasonic probe excitation signal circuit.

[0026] The diagnostic circuit and method of the present invention, in terms of transient voltage analysis, compared with the traditional processor + high-speed ADC mode, the combination of DAC and comparator is more convenient for highly repeatable transient sampling, and has a lower cost. It can also reduce the workload of the processor and improve the recognition efficiency of the sensor.

[0027] The above description is merely an illustrative embodiment of the present invention and is not intended to limit the scope of the invention. Any equivalent changes and modifications made by those skilled in the art without departing from the concept and principles of the present invention should fall within the scope of protection of the present invention.

Claims

1. A diagnostic circuit based on an analog comparator, characterized in that: The system includes an MCU control unit, a DAC signal conversion unit, an analog comparator unit, an ultrasonic sensor peripheral unit, a signal driving circuit, a signal detection circuit, and a power supply unit. The MCU control unit is electrically connected to the ultrasonic sensor peripheral unit through the signal driving circuit, enabling the signal driving circuit to drive the ultrasonic sensor peripheral unit to work. The analog signal output terminal generated by the ultrasonic sensor peripheral unit is connected to the signal input terminal of the signal detection circuit. The signal detection circuit sends the waveform generated by the ultrasonic sensor peripheral unit to the analog comparator unit. The MCU control unit is also connected to the analog comparator unit through the DAC signal conversion unit, enabling the digital signal sent by the MCU control unit to be converted into an analog signal by the DAC signal conversion unit and input to the analog comparator unit. The analog comparator unit outputs the logic level back to the MCU control unit. The MCU control unit is electrically connected to the power supply unit.

2. The diagnostic circuit based on an analog comparator as described in claim 1, characterized in that: The MCU control unit consists of a CPU, memory, input / output interfaces, and matching peripheral circuits. It is responsible for the logic control and monitoring of the entire circuit, specifically including driving the ultrasonic sensor, identifying the output logic level of the analog comparator unit, and inputting the DAC signal conversion unit.

3. The diagnostic circuit based on an analog comparator as described in claim 1, characterized in that: The DAC signal conversion unit consists of a DAC converter, an amplifier, and an output filter. It is used to convert digital signals into analog signals, and then the output is a recognizable threshold voltage analog signal after being integrated by the amplifier and the output filter.

4. A diagnostic circuit based on an analog comparator as described in claim 1, characterized in that: The analog comparator unit consists of three parts: signal input, signal processing, and logic output. Its function is to provide a digitally programmable threshold and output high and low levels based on the ultrasonic judgment result.

5. A diagnostic circuit based on an analog comparator as described in claim 1, characterized in that: The ultrasonic sensor peripheral unit consists of two parts: the transducer body and the signal wires. It is a passive device in the ultrasonic sensor diagnostic circuit, which performs the transmission and reception of ultrasonic waves.

6. A diagnostic circuit based on an analog comparator as described in claim 1, characterized in that: The signal driving circuit is controlled by the MCU control unit. It is configured for specific transmission pulses and frequencies, gain and signal thresholds, and integrated into an excitation voltage that can drive the ultrasonic sensor peripheral unit to emit ultrasonic waves, so as to make the ultrasonic sensor peripheral unit work continuously.

7. A diagnostic circuit based on an analog comparator as described in claim 1, characterized in that: The signal detection circuit collects the transmitted waveforms from the ultrasonic sensor peripheral unit and integrates them through filtering to form a sampled waveform that can be recognized by the analog comparator unit.

8. A diagnostic circuit based on an analog comparator as described in claim 1, characterized in that: The power supply unit plays a role in stabilizing voltage and supplying power to various components in the entire system.

9. A diagnostic method based on an analog comparator diagnostic circuit, comprising a diagnostic circuit based on an analog comparator as described in any one of claims 1-8, characterized in that, Includes the following steps: Step 1: Power-on initialization, system preparation phase; Step 2, signal sampling and processing stage: The ultrasonic sensor driving circuit releases the driving excitation signal, the ultrasonic sensor transducer sends high-frequency oscillation waves, and confirms whether an echo signal is received. If an echo signal is received, the circuit is normally connected. Step 3, during the comparator's operation phase, continuous trigger sampling is performed based on the ultrasonic drive pin waveform sampling results. The MCU software triggers reference voltages V1 and V2, and performs circuit diagnosis based on whether the sampled waveform of the signal pin triggers the rising edge of V1 (high voltage) and the rising edge of V2 (low voltage). If the sampling process triggers one rising edge of V1 for each excitation waveform, a secondary judgment is entered to determine whether the sampling waveform triggers the rising edge of V2 (low voltage). If the sampled waveform triggers both one rising edge of V1 and one rising edge of V2 (low voltage), it is determined to be an open circuit. If the sampled waveform triggers both one rising edge of V1 and more than one rising edge of V2 (low voltage), it is determined to be a normal signal. If the sampled waveform cannot trigger the rising edge of V1 (high voltage), but can trigger one rising edge and one falling edge of V2 (low voltage), it is determined to be a short circuit to ground. Step four, the result output stage, outputs the result signal based on the judgment result in step three; Step 5, System Feedback Phase: The urea quality sensor MCU sends the judgment result to the external communication circuit in the form of a CAN message, providing feedback on the current circuit diagnosis result.

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