Zero-point voltage output bias control circuit of sensor and zero-point voltage calibration method of sensor

Abstract

The invention discloses a zero-point voltage output bias control circuit of a sensor and a zero-point voltage calibration method of the sensor, and the circuit comprises the sensor which is used for outputting a differential voltage signal; the differential amplification circuit is used for amplifying the differential voltage signal; the processor comprises an ADC module, a DAC module and a controller module, the ADC module is used for converting the voltage signal into a digital signal which can be read by the controller module, and the DAC module is used for converting the digital signal output by the controller module into an analog signal; and the bias voltage adjusting module is used for adjusting the analog signal and the output voltage of the sensor so as to realize zero calibration of the sensor. The zero-point voltage output by the sensor can be actively controlled, accurate calibration is realized, and temperature drift and time drift of the sensor can be zeroed.

Description

Technical Field

[0001] The invention relates to the technical field of sensors, in particular to a zero-point voltage output bias control circuit of a sensor and a zero-point voltage calibration method of the sensor. Background Art

[0002] Analog signal sensors are often used in electronic devices, such as air pressure sensors, temperature sensors, current sensors, voltage sensors, etc.

[0003] In the breathing detection circuit, the analog sensor outputs a voltage signal, and the zero-point voltage (referring to the output voltage of the sensor without external excitation (such as temperature, pressure, flow, etc.). This voltage value can be used as a calibration reference for compensation and correction of subsequent measurement results) is often very small and fluctuates within a certain range. For example, for an air pressure sensor with a range of 1kPa, the zero-point (at standard atmospheric pressure) output is ±10mV. Signal acquisition units such as MCU or DSP and other integrated circuits with analog signal acquisition (ADC) functions can only collect voltages within their working voltage range. The lower and upper limits of the voltage range that the MCU can collect will be inaccurately collected. In order to improve the accuracy of the collection, the output signal of the sensor will be amplified by a certain proportion before collection. The common method is to use a simple resistor divider to add an offset to the zero-point voltage of the sensor, such as adding 12mV, so that the zero-point voltage of the sensor becomes 2mV~22mV, which are all positive voltages. If the voltage collection range of the MCU is 0~3.3V and the collection resolution is 0.8mV, then after amplification by 150 times, the zero-point voltage of the sensor is 0.55V~3.3V. When inhaling, the sensor detects that the air pressure drops by about 10Pa, and the zero-point voltage of the sensor will drop by 0.5mV and be amplified by 150 times, that is, it will drop by 75mV. The zero-point voltage fluctuation of the sensor will be amplified by 150 times and collected by the MCU.

[0004] The above method can only fix the bias voltage. If the zero-point voltage is too high, the amplification factor will be limited, the accuracy of signal acquisition cannot be improved, and the anti-interference ability cannot be improved. If the zero-point voltage is fixed at 1mV, it can be amplified 3300 times. The zero-point voltage of the sensor is 3.3V. Each time you inhale, it decreases by 3300mV. A larger change can achieve higher-precision inhalation detection.

[0005] All sensor zero output voltages will have temperature drift and time drift.

[0006] Temperature drift: The range of zero point voltage will change with the change of temperature, such as 0.001% / ℃.

[0007] Time drift: The range of zero voltage will change with time, and there will be a certain drift every month, such as 0.001% / month or 0.001% / year.

[0008] The zero-point output of the sensor is a voltage range, such as -10mV to +10mV, which may be large or small. The signal acquisition system can often only collect positive voltage signals. In order to improve the acquisition accuracy, the output signal of the sensor must be amplified by a certain proportion. The greater the amplification factor, the greater the signal change feedback of the sensor output, and therefore the higher the acquisition accuracy.

[0009] All MCUs or other types of controllers have a voltage range and a resolution for collecting analog signals. For example, the voltage collection range of the STM32F103 series MCU is 0-3.3V, and the 12-bit ADC collection resolution is about 0.8mV, that is, the minimum voltage value that can be collected is 0.8mV. Data overflow beyond the range is invalid. If the zero-point output of the sensor is -10mV, the common method is to fix a positive bias voltage such as 12mV through a resistor divider circuit to make the zero point of the sensor 2mV, but there is a problem with the consistency of the sensor. Assuming that there is another sensor in the same batch with a zero-point output of 10mV, since the hardware design is a fixed voltage bias, a 12mV positive bias voltage is also added. At this time, the zero-point voltage of the sensor is 22mV, which reaches the upper limit of the MCU voltage collection after amplification 150 times, 3.3V, and the voltage change of the sensor output will be amplified 150 times. If the zero-point output of the sensor can be actively controlled to be 2mV, when the zero-point output is lower than 2mV, the bias voltage is added, and when the zero-point output is higher than 2mV, the voltage is controlled to be reduced. In this way, the signal can be amplified by 1650 times to reach the upper limit of 3.3V of MCU voltage acquisition. The voltage change of the sensor output will be amplified by 1650 times, which is 11 times higher than the former. If the zero point voltage of the sensor can be fixed at 0.2mV, it can be amplified by 16500 times, and the accuracy can be improved by another 10 times. In theory, as long as the resolution of the ADC module is high enough, the active bias voltage control method can infinitely improve the acquisition accuracy of small voltage signals.

[0010] Therefore, adaptive active bias voltage control can control the zero voltage of the sensor at a set fixed value every time the device is powered on, without worrying about temperature drift and time drift. Summary of the invention

[0011] The technical problem to be solved by the present invention is to provide a zero-point voltage output bias control circuit of a sensor and a zero-point voltage calibration method of the sensor in view of the shortcomings of the prior art, which can actively increase or decrease the zero-point voltage of the sensor and can zero-adjust the temperature drift and time drift of the sensor.

[0012] In order to solve the above technical problems, the technical solution adopted by the present invention is: a zero voltage output bias control circuit of a sensor, comprising:

[0013] A sensor for outputting a differential voltage signal;

[0014] A differential amplifier circuit, used for amplifying the differential voltage signal;

[0015] A processor, comprising an ADC module, a DAC module and a controller module, wherein the ADC module is used to convert a differential voltage signal into a digital signal readable by the controller module, and the DAC module is used to convert a digital signal output by the controller module into a voltage signal;

[0016] The bias voltage adjustment module is used to adjust the analog signal and the output voltage of the sensor to achieve zero point calibration of the sensor.

[0017] In one implementation, the sensor is connected to a first voltage follower and a second voltage follower; the output terminal of the first voltage follower is connected to the reverse input terminal of the differential amplifier circuit, and the second voltage follower is connected to the same input terminal of the differential amplifier circuit. The voltage follower improves the driving ability and anti-interference ability of the sensor output voltage.

[0018] In one implementation, the bias voltage regulation module includes a first circuit and a second circuit; the first circuit includes a fourth voltage follower, the same-direction input terminal of the fourth voltage follower is connected to the output of the DAC module, and the reverse input terminal and output terminal of the fourth voltage follower are connected to the anode of the first diode; the second circuit includes a fifth voltage follower, the same-direction input terminal of the fifth voltage follower is connected to the output of the DAC module, and the reverse input terminal and output terminal of the fifth voltage follower are connected to the cathode of the second diode; the cathode of the first diode and the anode of the second diode are connected between the output terminal of the second voltage follower and the same-direction input terminal of the differential amplifier circuit.

[0019] In one implementation, the differential amplifier circuit includes an operational amplifier, the inverting input terminal of the operational amplifier is connected to the output terminal of the operational amplifier through a first resistor; the inverting input terminal of the operational amplifier is connected to the ADC module through a second resistor, and the output terminal of the first voltage follower is connected between the second resistor and the ADC module.

[0020] In one implementation, the non-inverting input terminal of the operational amplifier is connected to the inverting input terminal and the output terminal of the third voltage follower through a third resistor, and the fourth resistor is connected between the non-inverting input terminal of the operational amplifier and ground; the third resistor and the output terminal of the third voltage follower are both connected to the ADC module; the cathode of the first diode and the anode of the second diode are connected between the output terminal of the second voltage follower and the non-inverting input terminal of the third voltage follower.

[0021] The bias voltage adjustment module adjusts the analog signal and the output voltage of the sensor to achieve zero point calibration of the sensor. The specific implementation process includes:

[0022] When the differential amplifier input differential mode voltage is less than the target difference, the DAC module is controlled to output the full-scale DAC1, and the second diode is cut off; the adjustment starts, the DAC module is controlled to output the first voltage DAC2, and the first voltage is superimposed on Vc after passing through the fourth voltage follower and the first diode. The controller module determines whether the differential amplifier input differential mode voltage at this time is less than the target difference. If so, the DAC module is controlled to output the second voltage DAC2, and the second voltage is superimposed on Vc after passing through the fourth voltage follower and the first diode, and so on, until the differential amplifier input differential mode voltage is equal to the target difference; wherein, the forward biased conduction voltage drop of the diode D2 is Vf, the first voltage is greater than Vc+Vf before the start of the adjustment, and the second voltage is greater than the first voltage;

[0023] When the differential-mode voltage input to the differential amplifier is greater than the target difference, the controller module controls the DAC module to output 0, and the first diode is cut off; the adjustment starts, the controller module controls the DAC module to output a first voltage value, the first voltage value passes through the fifth voltage follower, so that the second diode D2 is forward-biased and turned on, and the Vc voltage value decreases, and the controller module determines whether the differential-mode voltage input to the differential amplifier at this time is greater than the target difference. If so, the DAC module is controlled to output a second voltage value, and the second voltage value passes through the fifth voltage follower, so that the second diode D2 is forward-biased and turned on, and the Vc voltage value decreases again, and so on, until the differential-mode voltage input to the differential amplifier is equal to the target difference; wherein the forward-biased conduction voltage drop of the diode D2 is Vf, the first voltage value is less than Vc-Vf before the start of the adjustment, and the second voltage value is less than the first voltage value;

[0024] Vc is the voltage at the connection point between the cathode of the first diode, the anode of the second diode and the signal line, and the signal line refers to the signal line between the output terminal of the second voltage follower and the same-direction input terminal of the differential amplifier circuit.

[0025] The present invention can actively control the zero-point voltage of the sensor output voltage to achieve accurate calibration.

[0026] In one implementation, the ADC module, DAC module, and controller module are integrated into one.

[0027] In one implementation, the DAC module uses a DAC chip or a DC / DC power supply chip.

[0028] As an inventive concept, the present invention also provides a method for implementing sensor zero voltage calibration using the above control circuit, the method comprising:

[0029] The controller module determines whether the zero-point output differential mode voltage of the sensor is less than the target difference. If so, the DAC module is controlled to output the full-scale DAC1, so that the output voltage of the bias voltage adjustment module is stabilized at the current value; when the adjustment starts, the controller module controls the DAC module to output the first voltage DAC2, and the first voltage is superimposed on the output voltage of the bias voltage adjustment module. The controller module determines whether the differential amplifier input differential mode voltage is less than the target difference. If so, the DAC module is controlled to output the second voltage DAC2, and the second voltage is superimposed on the output voltage of the bias voltage adjustment module. The controller module determines whether the differential amplifier input differential mode voltage is less than the target difference. If so, the DAC module is controlled to output the third voltage DAC3, and so on, until the differential amplifier input differential mode voltage is equal to the target difference; wherein, the first voltage is greater than the output voltage of the bias voltage adjustment module before the adjustment starts, the second voltage is greater than the first voltage, and the third voltage is greater than the second voltage;

[0030] The controller module determines whether the output differential mode voltage of the sensor is greater than the target difference. If so, the DAC module is controlled to output 0, so that the output voltage of the bias voltage adjustment module is stabilized at the current value; when the adjustment starts, the DAC module is controlled to output a first voltage value. The first voltage value passes through the fifth voltage follower, so that the second diode D2 is forward biased and turned on, and the output voltage of the bias voltage adjustment module is reduced. The controller module determines whether the differential mode voltage input to the differential amplifier is greater than the target difference. If so, the DAC module is controlled to output a second voltage value. The controller module determines whether the differential mode voltage input to the differential amplifier is greater than the target difference. If so, the controller module controls the DAC module to output a third voltage value, and so on, until the differential mode voltage input to the differential amplifier is equal to the target difference; wherein the first voltage value is less than the output voltage of the bias voltage adjustment module before the adjustment starts, the second voltage value is less than the first voltage value, and the third voltage value is less than the second voltage value.

[0031] When the differential amplifier input differential mode voltage is equal to the target difference value, the controller module saves the control value of the DAC module.

[0032] Compared with the prior art, the present invention has the following beneficial effects: the present invention can actively control the zero-point voltage of the sensor output voltage, realize accurate calibration, and zero-adjust the temperature drift and time drift of the sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a circuit structure block diagram of an embodiment of the present invention;

[0034] Figure 2 The schematic diagram of the circuit of the embodiment of the present invention is shown in FIG. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] Example 1

[0037] This embodiment provides a zero voltage output bias control circuit of a sensor, such as Figure 1As shown, it includes a sensor 10, a voltage follower 20, a voltage follower 30, a DAC (digital-to-analog converter, which is an electronic device or circuit for converting a digital signal into a corresponding analog signal. A DAC is usually composed of a digital signal input terminal, an analog output terminal, and a control circuit. The MCU has a DAC module inside. For example, the DAC module inside the MCU has a 12-bit resolution. When the setting value is 4095, the MCU will generate a 3.3V voltage output) module 40, a bias voltage adjustment module 50, a voltage follower 60, a differential amplifier circuit 70, and an ADC (analog-to-digital converter, which converts the voltage from the external loop into a differential amplifier circuit) connected in sequence. The analog signal of the environment (such as temperature, pressure, light intensity, etc. from the sensor) is converted into digital form so that the microprocessor or other digital circuit can process and analyze the data. When converting analog signals into digital signals, computers can only process binary numbers 0 and 1. When collecting analog voltage signals, the input analog signal is first converted into a corresponding digital signal through the internal ADC function module. For example, the power supply of the MCU is 3.3V, and the internal ADC module has a resolution of 12 bits. That is, when the input voltage signal is 3.3V, the maximum value after being converted into a digital signal is 2 to the 12th power 4096) module 80, controller 90 (MCU). The sensor 10 is used to output a differential voltage signal, the voltage follower 20 and the voltage follower 30 are used as buffer stages to increase the driving force and anti-interference ability of the sensor output voltage, the ADC module 80 converts the analog voltage signal into a digital signal readable by the controller 90 (MCU), the DAC module 40 converts the digital signal output by the controller 90 (MCU) into an analog signal, the bias voltage adjustment module controls and adjusts the output voltage of the DAC module 40 and the output voltage of the voltage follower 20, the voltage follower 60 buffers the output signal of the bias voltage adjustment module 50 and then outputs it, and the differential amplifier circuit 70 amplifies the signals of the voltage follower 30 and the voltage follower 60.

[0038] The bias voltage control module 50 includes a first circuit and a second circuit. The first circuit includes a fourth voltage follower U5 and a first diode D1; the second circuit includes a fifth voltage follower U6 and a second diode D2. The first circuit is connected to the controller module 90 (MCU) through a DAC module, and the second circuit is connected to the controller module 90 (MCU) through a DAC module. The sensor 10 is connected to the first voltage follower U1 and the second voltage follower U3 at the rear stage, and the third voltage follower U4 is connected between the first circuit, the second circuit and the differential amplifier circuit U2.

[0039] The differential amplifier circuit includes a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, and an operational amplifier U2, wherein R1 = R4, and R2 = R3.

[0040] Figure 2In the system, the power supply voltage is the same. In the initial state, U1, U3, and U4 are all followers, so the original voltages output by the sensors are Vn=Vd, Vp=Vc=Ve, and are all less than Vcc (system power supply). In order to read the original values ​​of Ve and Vd, the controller module controls the DAC module to make the DAC1 output full scale, so that Vb is greater than Vc, and the diode D2 is cut off. At this time, the Vc voltage will not decrease; the MCU controls the DAC2 to output 0, so that Va is less than Vc, and the diode D1 is cut off. At this time, Vc will not increase.

[0041] Example 2

[0042] This embodiment provides a method for implementing sensor zero-point voltage calibration using the control circuit of Embodiment 1.

[0043] Since the voltages of the front and rear stages of the voltage follower are equal, the common-mode voltage (in differential signal processing circuits such as differential amplifiers, common-mode voltage refers to the voltage component applied to two input signals at the same time. Corresponding to the embodiment of the present invention, Vn and Vp are common-mode voltages) output by the sensor is equal to the Vd voltage. Vp is equal to the voltage at point Vc, and also equal to the voltage at point Ve, Vn = Vd, Vp = Vc = Ve. After the ADC module converts the voltage signals of Vd and Ve into digital signals, it transmits them to the controller module for processing to determine the size of their difference, that is, the differential-mode voltage (referring to the potential difference between the signal lines, corresponding to the embodiment of the present invention, Vp-Vn is the differential-mode voltage) (Ve)-(Vd) = (Vp)-(Vn). The output common-mode voltages Vn and Vp of the sensor have large amplitudes, generally 1 / 2 of the system power supply voltage, and are both less than the MCU power supply voltage. Set the target difference (differential-mode voltage) to be controlled to be fixed to Vm.

[0044] 1. When Vp-Vn, i.e. (Ve)-(Vd), is less than Vm, a bias voltage needs to be added to the Vc point. The controller module will control the DAC module to output the full-scale DAC1. After the voltage follower U6, the voltage is Vb, Vb>Vc, so that the diode D2 is cut off, and the voltage of Vc will not decrease; at the beginning of the first adjustment, assuming that the voltage drop Vf of the forward biased conduction of the diode D2 is fixed to 0.7V, the controller controls the DAC module to output DAC2 to the first voltage value greater than Vc+0.7V, and after the voltage follower U5, the voltage is Va, Va>Vc+0.7V, D1 is turned on, and at this time Vc has increased the bias voltage, and after the follower U4, the voltage is Ve. The ADC module converts the voltage value of Ve to the controller module, and the controller module determines whether (Ve)-(Vd) is still less than Vm at this time. If it is still less than Vm, the second adjustment starts, and the controller module controls the DAC module to output DAC2 to a second voltage value greater than the first voltage value. After the voltage follower U5, the voltage is Va, Va>Vc+0.7V, D1 is turned on, and at this time Vc has increased the bias voltage. After the follower U4, the voltage is Ve. The ADC module converts the voltage value of Ve to the controller module, and the controller module determines whether (Ve)-(Vd) is still less than Vm at this time. After multiple cycles of adjustment, (Ve)-(Vd)=Vm. The adjustment of Vp plus bias voltage is completed.

[0045] 2. When Vp - Vn, that is, (Ve) - (Vd), is greater than Vm, it is necessary to reduce the voltage of Vc. The controller module will control the DAC module to output DAC2 as 0. After passing through the voltage follower U5, the voltage is also 0. Since Va < Vc, the diode D1 is cut off, so that the voltage of Vc will not increase. At the beginning of the first adjustment, assuming that the forward voltage drop Vf of the forward-biased conduction of the diode D2 is fixed at 0.7V, the controller controls the DAC module to output DAC1 as the first voltage value less than Vc - 0.7V. After passing through the voltage follower U6, the voltage is Vb. When the diode D2 is forward-biased and conducting, Vc = Vb + 0.7V = Ve. The ADC module converts the voltage value of Ve to the controller module, and the controller module determines whether (Ve) - (Vd) is still greater than Vm. Since Vb is less than Vc - 0.7V at this time, D2 conducts, which will pull down the voltage of Vc. After passing through the follower U4, the voltage is Ve. The ADC module converts the voltage value of Ve to the controller module, and the controller module determines whether (Ve) - (Vd) is still greater than Vm at this time. If it is still greater than Vm, the second adjustment starts. The controller module controls the DAC module to output DAC1 as the second voltage value less than the first voltage value. After passing through the voltage follower U6, the voltage is Vb. After Vb decreases again, Vc = Vb + 0.7V = Ve, so that Ve also decreases again. The ADC module converts the voltage value of Ve to the controller module, and the controller module determines whether (Ve) - (Vd) is still greater than Vm. After multiple adjustments in a loop, finally (Ve) - (Vd) = Vm, completing the adjustment of reducing the voltage of Vp.

[0046] By the above steps, the zero voltage of the sensor output voltage can be actively controlled to achieve precise calibration.

[0047] When the controller module determines that Ve - Vd = Vm, it saves the control value of the control DAC module and stops calibration. The differential amplifier circuit amplifies the difference Vm of Ve - Vd and then transmits it to the controller through the ADC module. The controller reads the converted data, completing a high-precision sensor signal reading.

[0048] (Vp - Vn), that is, the value of the zero voltage, is smaller. The amplification factor of the differential amplifier circuit can be designed to be larger. When there is a small change in the sensor signal, it will be amplified by a larger multiple. After the ADC module converts it, the threshold value judged by the controller module can be larger, and the judgment error is smaller, with high precision.

[0049] All semiconductor devices have temperature drift and time drift. The same is true for sensors. The zero output voltage is different in different temperature regions. The sensor will also produce zero voltage drift after working for a long time. Through the above method, the active control of the zero voltage can be realized, and the temperature drift and time drift of the sensor can be zeroed.

[0050] Although the preferred embodiments of the present application have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0051] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A zero voltage output bias control circuit of a sensor, characterized in that: include: A sensor for outputting a differential voltage signal; A differential amplifier circuit, used for amplifying the differential voltage signal; A processor, comprising an ADC module, a DAC module and a controller module, wherein the ADC module is used to convert a voltage signal into a digital signal readable by the controller module, and the DAC module is used to convert a digital signal output by the controller module into a voltage signal; The bias voltage adjustment module is used to adjust the analog signal and the output voltage of the sensor to achieve zero point calibration of the sensor.

2. The zero voltage output bias control circuit of the sensor according to claim 1, characterized in that: The ADC module, DAC module and controller module are integrated into one.

3. The zero voltage output bias control circuit of the sensor according to claim 1, characterized in that: The DAC module adopts a DAC chip or a DC / DC chip.

4. The zero voltage output bias control circuit of the sensor according to claim 1, characterized in that: The sensor is connected to a first voltage follower and a second voltage follower; the output terminal of the first voltage follower is connected to a reverse input terminal of the differential amplifier circuit, and the second voltage follower is connected to a non-inverting input terminal of the differential amplifier circuit.

5. The zero-point voltage output bias control circuit of the sensor according to claim 4, characterized in that: The bias voltage regulation module includes a first circuit and a second circuit; the first circuit includes a fourth voltage follower, the same-direction input terminal of the fourth voltage follower is connected to the output of the DAC module, and the reverse input terminal and output terminal of the fourth voltage follower are connected to the anode of the first diode; the second circuit includes a fifth voltage follower, the same-direction input terminal of the fifth voltage follower is connected to the output of the DAC module, and the reverse input terminal and output terminal of the fifth voltage follower are connected to the cathode of the second diode; the cathode of the first diode and the anode of the second diode D2 are connected between the output terminal of the second voltage follower and the same-direction input terminal of the differential amplifier circuit.

6. The zero voltage output bias control circuit of the sensor according to claim 4 or 5, characterized in that: The differential amplifier circuit includes an operational amplifier, the inverting input terminal of the operational amplifier is connected to the output terminal of the operational amplifier through a first resistor; the inverting input terminal of the operational amplifier is connected to the ADC module through a second resistor, and the output terminal of the first voltage follower is connected between the second resistor and the ADC module.

7. The zero-point voltage output bias control circuit of the sensor according to claim 6, characterized in that: The non-inverting input terminal of the operational amplifier U2 is connected to the inverting input terminal and the output terminal of the third voltage follower through the third resistor, and the third resistor and the output terminal of the third voltage follower are both connected to the ADC module; the cathode of the first diode and the anode of the second diode are connected between the output terminal of the second voltage follower and the non-inverting input terminal of the third voltage follower.

8. The zero-point voltage output bias control circuit of the sensor according to claim 7, characterized in that: The bias voltage adjustment module adjusts the analog signal and the output voltage of the sensor to achieve zero point calibration of the sensor. The specific implementation process includes: When the differential-mode voltage input to the differential amplifier is less than the target difference, the DAC module is controlled to output the full scale, and the second diode is cut off; the adjustment starts, the controller module controls the DAC module to output the first voltage, and the first voltage is superimposed on Vc after passing through the fourth voltage follower and the first diode. The controller module determines whether the differential-mode voltage input to the differential amplifier at this time is less than the target difference. If so, the DAC module is controlled to output the second voltage, and the second voltage is superimposed on Vc after passing through the fourth voltage follower and the first diode, and so on, until the differential-mode voltage input to the differential amplifier is equal to the target difference; wherein the first voltage is greater than the sum of Vc before the start of the adjustment and the forward biased conduction voltage drop Vf of the second diode D2, and the second voltage is greater than the first voltage; When the differential-mode voltage input to the differential amplifier is greater than the target difference, the DAC module is controlled to output 0, and the first diode is cut off; the adjustment starts, the controller module controls the DAC module to output a first voltage value, the first voltage value passes through the fifth voltage follower, so that the second diode is forward-biased and turned on, and the Vc voltage value decreases, and the controller module determines whether the differential-mode voltage input to the differential amplifier at this time is greater than the target difference. If so, the DAC module is controlled to output a second voltage value, the second voltage value passes through the fifth voltage follower, so that the second diode is forward-biased and turned on, and the Vc voltage value decreases again, and so on, until the differential-mode voltage input to the differential amplifier is equal to the target difference; wherein the first voltage value is less than the difference between Vc before the start of the adjustment and the forward-biased conduction voltage drop Vf of the second diode D2, and the second voltage value is less than the first voltage value; Vc is the voltage at the connection point between the cathode of the first diode / the anode of the second diode and the signal line, and the signal line refers to the signal line between the output terminal of the second voltage follower and the same-direction input terminal of the differential amplifier circuit.

9. A method for implementing sensor zero voltage calibration using the control circuit according to any one of claims 1 to 7, characterized in that: The method includes: The controller module determines whether the output differential mode voltage of the sensor zero point is less than the target difference. If so, the DAC module is controlled to output the full scale so that the output voltage of the bias voltage adjustment module is stabilized at the current value; when the adjustment starts, the controller module controls the DAC module to output a first voltage, which is superimposed on the output voltage of the bias voltage adjustment module. The controller module determines whether the differential mode voltage input to the differential amplifier is less than the target difference. If so, the DAC module is controlled to output a second voltage, which is superimposed on the output voltage of the bias voltage adjustment module. The controller module determines whether the differential mode voltage input to the differential amplifier is less than the target difference. If so, the DAC module is controlled to output a third voltage, and so on, until the differential mode voltage input to the differential amplifier is equal to the target difference; wherein the first voltage is greater than the output voltage of the bias voltage adjustment module before the adjustment starts, the second voltage is greater than the first voltage, and the third voltage is greater than the second voltage; The controller module determines whether the output differential mode voltage of the sensor is greater than the target difference. If so, the DAC module is controlled to output 0, so that the output voltage of the bias voltage adjustment module is stabilized at the current value; when the adjustment starts, the controller module controls the DAC module to output a first voltage value, and the first voltage value passes through the fifth voltage follower to make the second diode forward-biased and turned on, and the output voltage of the bias voltage adjustment module is reduced. The controller module determines whether the differential mode voltage input to the differential amplifier is greater than the target difference. If so, the DAC module is controlled to output a second voltage value. The controller module determines whether the differential mode voltage input to the differential amplifier is greater than the target difference. If so, the DAC module is controlled to output a third voltage value, and so on, until the differential mode voltage input to the differential amplifier is equal to the target difference; wherein, the first voltage value is less than the output voltage of the bias voltage adjustment module before the adjustment starts, the second voltage value is less than the first voltage value, and the third voltage value is less than the second voltage value.

10. The method according to claim 9, characterized in that When the differential amplifier input differential mode voltage is equal to the target difference value, the controller module saves the control value of the DAC module.

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