Zero voltage output bias control circuit for sensors and method of calibrating zero voltage of sensors
By using a sensor zero-point voltage output bias control circuit, the sensor zero-point voltage is actively adjusted, which solves the problems of insufficient sensor signal acquisition accuracy and anti-interference capability, and achieves effective zeroing of temperature and time drift.
Patent Information
- Application Number
- CN202411382043.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-30
- Publication Date
- 2025-11-07
- Estimated Expiration
- 2044-09-30
AI Technical Summary
In existing technologies, the zero-point voltage output of sensors fluctuates, resulting in insufficient signal acquisition accuracy and anti-interference capability, and it cannot effectively cope with temperature drift and time drift.
A sensor zero-point voltage output bias control circuit is adopted. Through a differential amplifier circuit, a processor module, and a bias voltage adjustment module, the zero-point voltage of the sensor is actively adjusted to achieve accurate calibration.
It achieves precise calibration of the sensor's zero-point voltage, improves signal acquisition accuracy and anti-interference capability, and can effectively resist temperature and time drift.
Smart Images
Figure CN119270969B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of sensors, in particular to a zero voltage output bias control circuit of a sensor and a sensor zero voltage calibration method. BACKGROUND
[0002] Analog signal sensors are often used on electronic devices, such as air pressure sensors, temperature sensors, current sensors, voltage sensors, etc.
[0003] In a breath detection circuit, the analog sensor outputs a voltage signal, and the zero voltage (referring to the output voltage of the sensor under the condition of no external excitation (such as temperature, pressure, flow, etc.). This voltage value can be used as a calibration reference for subsequent measurement result compensation and correction) is often very small and fluctuates within a certain range, such as an air pressure sensor with a range of 1kPa, the zero point (standard atmospheric pressure) output is ±10mV. Signal acquisition units such as MCUs or DSPs and other integrated circuits with analog signal acquisition (ADC) functions can only acquire voltages within their operating voltage range. Inaccurate acquisition will occur near the lower and upper limits of the voltage range that the MCU can acquire. In order to improve the accuracy of acquisition, the output signal of the sensor will be amplified by a certain proportion before acquisition. The common method is to use a simple resistance divider to add a bias to the zero voltage of the sensor, such as adding 12mV, making the zero voltage of the sensor 2mV-22mV, which is all positive voltage. If the voltage acquisition range of the MCU is 0-3.3V and the acquisition resolution is 0.8mV, then after amplification by 150 times, the zero voltage of the sensor is 0.55V-3.3V. When inhaling, the sensor detects a decrease in air pressure of about 10Pa, and the zero voltage of the sensor decreases by 0.5mV and is amplified by 150 times, i.e. decreases by 75mV. The fluctuation of the zero voltage of the sensor will be amplified by 150 times and acquired by the MCU.
[0004] The above method can only fix the bias voltage. If the zero voltage is too high, the amplification factor will be limited, the signal acquisition accuracy cannot be improved, and the anti-interference ability cannot be improved. If the zero voltage is fixed at 1mV, it can be amplified by 3300 times, and the zero voltage of the sensor is 3.3V. Each time the sensor inhales, it decreases by 3300mV, and a larger change can achieve higher accuracy in inhalation detection.
[0005] All sensor zero output voltages will have temperature drift and time drift.
[0006] Temperature drift (temperature drift): the range of the zero voltage will change with the change of temperature, such as 0.001% / ℃.
[0007] Time drift: the range of zero voltage will change over time, there will be a certain drift such as 0.001% / month, or 0.001% / year every month.
[0008] The zero output of the sensor is a voltage range, such as -10mV~+10mV range or large or small, the signal acquisition system often can only collect positive voltage signal, in order to improve the collection accuracy, the output signal of the sensor also needs to be amplified by a certain proportion, the larger the amplification factor, the greater the feedback of the sensor output signal change, and therefore the higher the collection accuracy.
[0009] All MCU or other types of controllers, the collected analog signal has a voltage range and a collection resolution, such as STM32F103 series MCU voltage collection range 0~3.3V, 12-bit ADC collection resolution about 0.8mV, that is, the minimum voltage value that can be collected is 0.8mV. If the data exceeds the range, it is invalid. If the sensor zero output is -10mV, the common method is to fix a positive bias voltage such as 12mV through a resistance voltage dividing circuit, so that the zero point of the sensor becomes 2mV, but the consistency problem of the sensor exists, assuming that another sensor in the same batch has a zero output of 10mV, since the hardware design is fixed voltage bias, the sensor also adds a 12mV positive bias voltage, at this time the zero voltage of the sensor is 22mV, after amplification by 150 times, the upper limit value of the MCU voltage collection is 3.3V, and the voltage change of the sensor output will be amplified by 150 times. If the zero output of the sensor can be actively controlled to 2mV, when the zero output is lower than 2mV, a bias voltage is added, and when the zero output is higher than 2mV, a voltage is controlled. In this way, the amplification factor can be increased by 1650 times to reach the upper limit value of the MCU voltage collection, and the voltage change of the sensor output will be amplified by 1650 times, which is 11 times higher than the former. If the zero voltage of the sensor can be fixed and controlled at 0.2mV, the amplification factor can be increased by 16500 times, and the accuracy can be increased by 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 collection accuracy of small voltage signals.
[0010] Therefore, the adaptive active bias voltage control can control the zero voltage of the sensor to a fixed value set at each power-on of the device, without worrying about temperature drift and time drift. SUMMARY
[0011] The technical problem to be solved by the present application is to provide a sensor zero voltage output bias control circuit and a sensor zero voltage calibration method, which actively raises or lowers the zero voltage of the sensor, and can zero the temperature drift and time drift of the sensor.
[0012] To solve the above technical problems, the technical scheme adopted by the present application is as follows: a zero voltage output bias control circuit of a sensor, comprising:
[0013] a sensor for outputting a differential voltage signal;
[0014] a differential amplification circuit for amplifying the differential voltage signal;
[0015] a processor comprising an ADC module, a DAC module and a controller module, the ADC module being used to convert the differential voltage signal into a digital signal readable by the controller module, and the DAC module being used to convert the digital signal output by the controller module into a voltage signal;
[0016] a bias voltage adjustment module for adjusting the analog signal and the output voltage of the sensor to realize zero point calibration of the sensor.
[0017] In an implementation manner, the sensor is connected with a first voltage follower and a second voltage follower; the output end of the first voltage follower is connected with the reverse input end of the differential amplification circuit, and the second voltage follower is connected with the same direction input end of the differential amplification circuit. The voltage follower improves the driving capability and anti-interference capability of the output voltage of the sensor.
[0018] In an implementation manner, the bias voltage adjustment module comprises a first circuit and a second circuit; the first circuit comprises a fourth voltage follower, the same direction input end of the fourth voltage follower being connected with the output of the DAC module, and the reverse input end and the output end of the fourth voltage follower being connected with the anode of a first diode; the second circuit comprises a fifth voltage follower, the same direction input end of the fifth voltage follower being connected with the output of the DAC module, and the reverse input end and the output end of the fifth voltage follower being connected with the cathode of a second diode; the cathode of the first diode and the anode of the second diode are connected between the output end of the second voltage follower and the same direction input end of the differential amplification circuit.
[0019] In an implementation manner, the differential amplification circuit comprises an operational amplifier, the reverse input end of the operational amplifier being connected with the output end of the operational amplifier through a first resistor; the reverse input end of the operational amplifier is connected with the ADC module through a second resistor, and the output end of the first voltage follower is connected between the second resistor and the ADC module.
[0020] In an implementation manner, 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 the ground; the third resistor and the output terminal of the third voltage follower are 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 adjusting module adjusts the analog signal and the output voltage of the sensor, and the specific implementation process of realizing the zero-point calibration of the sensor comprises the following steps:
[0022] When the differential amplifier input differential mode voltage is less than the target difference, the controller module controls the DAC module to output full-scale DAC1, and the second diode is cut off; the adjustment is started, the controller module controls the DAC module to output a first voltage DAC2, the first voltage is superimposed on Vc through the fourth voltage follower and the first diode, the controller module judges whether the differential amplifier input differential mode voltage at this time is less than the target difference, if yes, the controller module controls the DAC module to output a second voltage DAC2, the second voltage is superimposed on Vc through the fourth voltage follower and the first diode, and the process is repeated until the differential amplifier input differential mode voltage is equal to the target difference; wherein the forward conduction voltage drop of the diode D2 is Vf, the first voltage is greater than Vc+Vf before the adjustment starts, and the second voltage is greater than the first voltage;
[0023] When the differential amplifier input differential mode voltage 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 is started, the controller module controls the DAC module to output a first voltage value, the first voltage value passes through the fifth voltage follower, the second diode D2 is forward conduction, the Vc voltage value is reduced, the controller module judges whether the differential amplifier input differential mode voltage at this time is greater than the target difference, if yes, the controller module controls the DAC module to output a second voltage value, the second voltage value passes through the fifth voltage follower, the second diode D2 is forward conduction, and the Vc voltage value is reduced again, and the process is repeated until the differential amplifier input differential mode voltage is equal to the target difference; wherein the forward conduction voltage drop of the diode D2 is Vf, the first voltage value is less than Vc-Vf before the adjustment starts, and the second voltage value is less than the first voltage value;
[0024] Vc is the voltage of the connection point of the cathode of the first diode and 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 non-inverting input terminal of the differential amplification circuit.
[0025] The application can actively control the zero-point voltage of the sensor output voltage, and realize accurate calibration.
[0026] In an implementation, the ADC module, the DAC module and the controller module are integrated.
[0027] In an implementation, the DAC module adopts a DAC chip or a DC / DC power supply chip.
[0028] As an inventive concept, the application further provides a method for calibrating a sensor zero point voltage by using the above-mentioned control circuit, which comprises the following steps:
[0029] The controller module judges whether the output differential mode voltage of the sensor is less than a target differential value, and if yes, controls the DAC module to output a full-scale DAC1, so that the output voltage of the bias voltage adjustment module is stabilized at a current value; at the beginning of adjustment, the controller module controls the DAC module to output a first voltage DAC2, which is superimposed on the output voltage of the bias voltage adjustment module, the controller module judges whether the input differential mode voltage of the differential amplifier is less than the target differential value, and if yes, controls the DAC module to output a second voltage DAC2, which is superimposed on the output voltage of the bias voltage adjustment module, the controller module judges whether the input differential mode voltage of the differential amplifier is less than the target differential value, and if yes, controls the DAC module to output a third voltage DAC3, and so on, until the input differential mode voltage of the differential amplifier is equal to the target differential value; 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 judges whether the output differential mode voltage of the sensor is greater than a target differential value, and if yes, controls the DAC module to output 0, so that the output voltage of the bias voltage adjustment module is stabilized at a current value; at the beginning of adjustment, the controller module controls the DAC module to output a first voltage value, which is passed through a fifth voltage follower to make a second diode D2 positively biased and conductive, and the output voltage of the bias voltage adjustment module is lowered, the controller module judges whether the input differential mode voltage of the differential amplifier is greater than the target differential value, and if yes, controls the DAC module to output a second voltage value, the controller module judges whether the input differential mode voltage of the differential amplifier is greater than the target differential value, and if yes, the controller module controls the DAC module to output a third voltage value, and so on, until the input differential mode voltage of the differential amplifier is equal to the target differential value; 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 input differential mode voltage of the differential amplifier is equal to the target differential value, the controller module saves the control value of the DAC module.
[0032] Compared with the prior art, the application has the beneficial effects that the application can actively control the zero voltage of the sensor output voltage, realize accurate calibration, and zero the temperature drift and time drift of the sensor. BRIEF DESCRIPTION OF DRAWINGS
[0033] Figure 1 The circuit structure block diagram of the embodiment of the application is shown in the figure.
[0034] Figure 2 The circuit principle diagram of the embodiment of the application is shown in the figure. DETAILED DESCRIPTION
[0035] In order to make the purpose, technical scheme and advantages of the embodiments of the application clearer, the technical scheme in the embodiments of the application will be clearly and completely explained in combination with the drawings in the embodiments of the application. Obviously, the described embodiments are part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.
[0036] Embodiment 1
[0037] The embodiment provides a zero voltage output bias control circuit of a sensor, as shown in the figure. Figure 1As shown, it includes sensors 10, voltage follower 20, voltage follower 30, DAC (digital analog converter, an electronic device or circuit that converts digital signals into corresponding analog signals. DAC is usually composed of digital signal input, analog output, control circuit. MCU has a DAC module inside, for example, the MCU internal DAC module is 12-bit resolution, when the setting value is 4095, the MCU will generate a 3.3V voltage output) module 40, bias voltage adjustment module 50, voltage follower 60, differential amplifier circuit 70, ADC (analog-to-digital converter, which converts analog signals from the external environment (such as temperature, pressure, light intensity, etc. from the sensor) into digital form so that microprocessors or other digital circuits can process and analyze these data. Analog signals are converted to digital signals, computers can only process binary numbers 0 and 1, when collecting analog voltage signals, they are first converted into corresponding digital signals by the internal ADC function module, for example, the power supply of the MCU is 3.3V, and the internal ADC module is 12-bit resolution. That is, when the input voltage signal is 3.3V, the maximum value of the digital signal after conversion is 2 to the power of 12, 4096) module 80, controller 90 (MCU). Among them, the sensor 10 is used to output the differential voltage signal, the voltage follower 20 and the voltage follower 30 are used as the buffer stage to increase the driving force and anti-interference force 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 outputs the output signal of the bias voltage adjustment module 50 after buffering, 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, and 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 the DAC module, and the second circuit is connected to the controller module 90 (MCU) through the DAC module. The sensor 10 is connected to a first voltage follower U1 and a second voltage follower U3 in the rear stage, and the first circuit, the second circuit and the differential amplifier circuit U2 are connected to a third voltage follower U4.
[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 initial state, U1, U3, U4 are followers, so the original voltage Vn = Vd, Vp = Vc = Ve output by the sensor is 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 DAC1 output full scale, so that Vb is greater than Vc, diode D2 is cut off, and Vc voltage will not decrease; the MCU controls DAC2 to output 0, so that Va is less than Vc, diode D1 is cut off, and Vc will not increase.
[0041] Embodiment 2
[0042] The embodiment provides a method for calibrating zero point voltage of a sensor by using the control circuit in embodiment 1.
[0043] Because the front and rear stage voltages of the voltage follower are equal, the common mode voltage (in a differential signal processing circuit such as a differential amplifier, the common mode voltage refers to a voltage component applied to two input signals at the same time. In the embodiment of the application, Vn and Vp are the common mode voltage) output by the sensor is equal to the Vd voltage. Vp is equal to the Vc point voltage and also equal to the Ve point voltage, Vn = Vd, Vp = Vc = Ve. After the ADC module converts the voltage signals of Vd and Ve into digital signals, the digital signals are transmitted to the controller module for processing, and the difference between Vd and Ve, i.e., the differential mode voltage (referring to the potential difference between a signal line and another signal line, in the embodiment of the application, Vp-Vn is the differential mode voltage) (Ve)-(Vd) = (Vp)-(Vn) is determined. The output common mode voltage Vn and Vp of the sensor have a large amplitude, generally 1 / 2 of the system power supply voltage, and are less than the MCU power supply voltage. The target difference (differential mode voltage) to be controlled is set to be fixed as Vm.
[0044] 1、When Vp-Vn, that is (Ve)-(Vd) is less than Vm, bias voltage needs to be added to Vc. The controller module will control the DAC module to output full-scale DAC1, and the voltage after the voltage follower U6 is Vb, Vb>Vc, making diode D2 cut off, and the voltage of Vc will not decrease; the first adjustment begins, and suppose the voltage drop Vf of diode D2 when it is positively biased and turned on is fixed at 0.7V, the controller controls the DAC module to output DAC2 as the first voltage value greater than Vc+0.7V, and the voltage after the voltage follower U5 is Va, Va>Vc+0.7V, D1 is turned on, at this time Vc has already increased bias voltage, and the voltage after the follower U4 is Ve, the ADC module converts the voltage value of Ve to the controller module, and the controller module judges whether (Ve)-(Vd) is still less than Vm at this time. If it is still less than Vm, the second adjustment begins, the controller module controls the DAC module to output DAC2 as the second voltage value greater than the first voltage value, and the voltage after the voltage follower U5 is Va, Va>Vc+0.7V, D1 is turned on, at this time Vc has already increased bias voltage, and the voltage after the follower U4 is Ve, the ADC module converts the voltage value of Ve to the controller module, and the controller module judges whether (Ve)-(Vd) is still less than Vm at this time. After multiple cycles of adjustment, (Ve)-(Vd)=Vm is finally achieved. The adjustment of adding bias voltage to Vp is completed.
[0045] 2、When Vp-Vn, that is, (Ve)-(Vd) is greater than Vm, the voltage of Vc needs to be reduced. The controller module will control the DAC module to output DAC2 as 0, and the voltage after the voltage follower U5 is also 0, VaVc, so that the diode D1 is cut off, so that the voltage of Vc will not rise; the first adjustment starts, assuming that the voltage drop Vf of the diode D2 when it is positively biased and conducts is fixed at 0.7V, the controller controls the DAC module to output DAC1 as the first voltage value less than Vc-0.7V, and the voltage after the voltage follower U6 is Vb, when the diode D2 is positively biased and conducts, Vc=Vb+0.7V=Ve. The ADC module converts the voltage value of Ve to the controller module, and the controller module judges whether (Ve)-(Vd) is still greater than Vm. Since Vb is less than Vc-0.7V at this time, D2 is conducting, which will lower the voltage of Vc, and the voltage after the follower U4 is Ve. The ADC module converts the voltage value of Ve to the controller module, and the controller module judges whether (Ve)-(Vd) is still greater than Vm. 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, and the voltage after the voltage follower U6 is Vb. After Vb is reduced again, Vc=Vb+0.7V=Ve, so that Ve is also reduced again, the ADC module converts the voltage value of Ve to the controller module, and the controller module judges whether (Ve)-(Vd) is still greater than Vm. After several cycles of adjustment, (Ve)-(Vd)=Vm is finally achieved, and the adjustment of the reduction of Vp voltage is completed.
[0046] Through the above steps, the zero voltage of the sensor output voltage can be actively controlled, and accurate calibration can be achieved.
[0047] When the controller module judges that Ve-Vd=Vm, the control value of the DAC module is saved, and the calibration is stopped. After the difference Vm of Ve-Vd is amplified by the differential amplification circuit, it is transmitted to the controller through the ADC module, and the controller reads the converted data, completing one high-precision sensor signal reading.
[0048] The smaller the value of (Vp-Vn), that is, the zero voltage, the larger the amplification multiple of the differential amplification circuit can be designed. When the sensor signal has a slight change, it will be amplified by a larger multiple, and after conversion by the ADC module, the threshold value of the controller module can be larger, the error of the judgment is smaller, and the precision is high.
[0049] All semiconductor devices have temperature drift and time drift, and sensors also have temperature drift and time drift. The zero output voltage is different in different temperature regions, and the zero voltage will drift after the sensor has been working for a long time. Through the above method, the zero voltage can be actively controlled, and the temperature drift and time drift of the sensor can be adjusted to zero.
[0050] While the preferred embodiments of the application have been described, additional variations and modifications can be made to these embodiments by those skilled in the art once they have the benefit of the present disclosure without departing from the spirit and scope of the application. Accordingly, it is intended that such additions and modifications be included within the scope of the application. It is the following claims, including any amendments thereto, which define the scope of the application.
[0051] Obviously, numerous modifications and variations of the present application are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims and their equivalents, the application can be practiced otherwise than as specifically described.
Claims
1. A zero voltage output bias control circuit for a sensor, characterized by, The application relates to a sensor signal processing circuit, which comprises the following parts: a sensor for outputting a differential voltage signal; a differential amplification circuit 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 for converting a voltage signal into a digital signal readable by the controller module, and the DAC module is used for converting a digital signal output by the controller module into a voltage signal; a bias voltage adjusting module for adjusting the voltage signal and the output voltage of the sensor to realize zero-point calibration of the sensor; the sensor is connected with a first voltage follower and a second voltage follower; the output end of the first voltage follower is connected with the reverse input end of the differential amplification circuit, and the second voltage follower is connected with the same direction input end of the differential amplification circuit; the bias voltage adjusting module comprises a first circuit and a second circuit; the first circuit comprises a fourth voltage follower, the same direction input end of the fourth voltage follower is connected with the output of the DAC module, the reverse input end and the output of the fourth voltage follower are connected with the anode of a first diode; the second circuit comprises a fifth voltage follower, the same direction input end of the fifth voltage follower is connected with the output of the DAC module, the reverse input end and the output of the fifth voltage follower are connected with the cathode of a second diode; the cathode of the first diode and the anode of the second diode are connected between the output end of the second voltage follower and the same direction input end of the differential amplification circuit. The ADC module, the DAC module and the controller module are integrated. The DAC module adopts a DAC chip or a DC / DC chip. The differential amplification circuit comprises an operational amplifier, the reverse input end of the operational amplifier is connected with the output end of the operational amplifier through a first resistor; the reverse input end of the operational amplifier is connected with the ADC module through a second resistor, and the output end of the first voltage follower is connected between the second resistor and the ADC module. The same direction input end of the operational amplifier U2 is connected with the reverse input end and the output end of a third voltage follower through a third resistor, and the third resistor and the output end of the third voltage follower are connected with the ADC module; the cathode of the first diode and the anode of the second diode are connected between the output end of the second voltage follower and the same direction input end of the third voltage follower. The specific implementation process of the bias voltage adjusting module for adjusting the voltage signal and the output voltage of the sensor to realize zero-point calibration of the sensor comprises the following steps: 2. The sensor's zero voltage output bias control circuit according to claim 1, characterized in that, 3. The sensor's zero voltage output bias control circuit according to claim 1, wherein, 4. The sensor's zero voltage output bias control circuit according to claim 1, wherein, 5. The sensor's zero voltage output bias control circuit according to claim 4, characterized in that, 6. The sensor's zero voltage output bias control circuit according to claim 5, wherein, When the differential amplifier input differential mode voltage is less than the target difference, the controller module controls the DAC module to output full scale, and the second diode is cut off; the adjustment is started, the controller module controls the DAC module to output a first voltage, the first voltage is superimposed on Vc through the fourth voltage follower and the first diode, the controller module judges whether the differential amplifier input differential mode voltage at this time is less than the target difference, if yes, the controller module controls the DAC module to output a second voltage, the second voltage is superimposed on Vc 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 first voltage is greater than the sum of Vc before the adjustment starts and the positive bias conduction voltage drop Vf of the second diode D2, and the second voltage is greater than the first voltage; When the differential amplifier input differential mode voltage 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 is started, the controller module controls the DAC module to output a first voltage value, the first voltage value passes through the fifth voltage follower to make the second diode conduct in positive bias, and the Vc voltage value is reduced, the controller module judges whether the differential amplifier input differential mode voltage at this time is greater than the target difference, if yes, the controller module controls the DAC module to output a second voltage value, the second voltage value passes through the fifth voltage follower to make the second diode conduct in positive bias, and the Vc voltage value is reduced again, and so on until the differential amplifier input differential mode voltage is equal to the target difference; wherein the first voltage value is less than the difference between Vc before the adjustment starts and the positive bias 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 of the connection point of the cathode of the first diode and the anode of the second diode and the signal line, and the signal line refers to the signal line between the output end of the second voltage follower and the same direction input end of the differential amplification circuit.
7. A method for calibrating the zero voltage of a sensor using the control circuit according to any one of claims 1 to 5, characterized in that, The method comprises: The controller module judges whether the output differential mode voltage of the sensor zero point is less than the target difference, if yes, the controller module controls the DAC module to output full scale, so that the output voltage of the bias voltage adjustment module is stabilized at the current value; when the adjustment is started, the controller module controls the DAC module to output a first voltage, the first voltage is superimposed on the output voltage of the bias voltage adjustment module, the controller module judges whether the differential amplifier input differential mode voltage is less than the target difference, if yes, the controller module controls the DAC module to output a second voltage, the second voltage is superimposed on the output voltage of the bias voltage adjustment module, the controller module judges whether the differential amplifier input differential mode voltage is less than the target difference, if yes, the controller module controls the DAC module to output a third voltage, 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; The controller module judges whether the output differential mode voltage of the sensor is greater than the target differential value, if yes, the DAC module is controlled to output 0, so that the output voltage of the bias voltage adjusting module is stabilized at the current value; when starting to adjust, the controller module controls the DAC module to output a first voltage value, the first voltage value passes through the fifth voltage follower, the second diode is positively biased and turned on, the output voltage of the bias voltage adjusting module is reduced, the controller module judges whether the input differential mode voltage of the differential amplifier is greater than the target differential value, if yes, the DAC module is controlled to output a second voltage value, the controller module judges whether the input differential mode voltage of the differential amplifier is greater than the target differential value, if yes, the DAC module is controlled to output a third voltage value, and so on, until the input differential mode voltage of the differential amplifier is equal to the target differential value; wherein the first voltage value is less than the output voltage of the bias voltage adjusting 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.
8. The method of claim 7, wherein, When the input differential mode voltage of the differential amplifier is equal to the target differential value, the controller module saves the control value of the DAC module.
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