An inertial measurement unit signal integration solving circuit

Abstract

The application discloses an inertial measurement unit signal integrated solving circuit, which is used for solving output signals of a fiber-optic gyroscope and a quartz accelerometer, and comprises an FPGA control circuit, a gyroscope solving circuit, an IF conversion circuit, a temperature acquisition circuit and a communication output circuit. The FPGA control circuit is connected with the gyroscope solving circuit, the IF conversion circuit, the temperature acquisition circuit and the communication output circuit respectively. The FPGA control circuit is connected with the gyroscope solving circuit and the IF conversion circuit respectively. The three-axis gyroscope signals and the quartz accelerometer signals are solved by the same FPGA control module in an integrated circuit board. The integrated circuit can realize SLD light source driving, three-axis fiber-optic gyroscope photoelectric signal solving, quartz accelerometer current signal solving, environment temperature acquisition and other functions. The integrated circuit has the advantages of high integration, low cost, small size, light weight and good application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of inertial measurement, more particularly, to an inertial measurement unit signal integrated solving circuit. BACKGROUND

[0002] At present, in the inertial navigation system, the fiber-optic gyroscope and the quartz accelerometer are widely used as core inertial sensitive devices, and therefore the corresponding signal solving circuit is also very important. In the past two decades, with the development of inertial technology, the research on inertial technology is more and more in-depth, and the system has higher and higher requirements on the precision, integration and cost of inertial devices, and the market demand for high-quality and low-cost inertial products is growing.

[0003] However, in the existing inertial measurement unit, most of the design methods are to design the three-axis fiber-optic gyroscope and the IF conversion module separately. This kind of separate design method is not conducive to miniaturization and integration design on the one hand, and will also bring additional devices and printed board manufacturing costs on the other hand. Therefore, it is of great engineering significance to carry out the integration research of the gyroscope solving circuit and the IF conversion circuit. SUMMARY

[0004] In view of at least one defect or improvement demand of the prior art, the present application provides an inertial measurement unit signal integrated solving circuit, which integrates the fiber-optic gyroscope and the IF conversion module, completes the three-axis gyroscope circuit signal solving, the quartz acceleration signal solving and the SLD light source driving, reduces the cost, reduces the volume and weight, and has good application prospect.

[0005] To achieve the above-mentioned purpose, an inertial measurement unit signal integrated solving circuit is provided for output signal solving of a fiber-optic gyroscope and a quartz accelerometer, characterized in that it comprises an FPGA control circuit, a gyroscope solving circuit and an IF conversion circuit, wherein,

[0006] The gyroscope solving circuit is used for receiving and solving the fiber-optic gyroscope signal, and comprises an amplification and filtering circuit, an AD acquisition circuit, a DA conversion circuit and a step wave driving circuit. The input end of the amplification and filtering circuit receives the fiber-optic gyroscope signal, the output end of the amplification and filtering circuit is connected with the input end of the AD acquisition circuit, the output end of the AD acquisition circuit is connected with one end of the FPGA control circuit, the DA conversion circuit is connected with the output end of the FPGA control circuit, and the output end of the DA conversion circuit is connected with the input end of the external step wave modulation circuit.

[0007] The IF conversion circuit is used for receiving the current signal of the quartz accelerometer and resolving, and comprises an integration circuit, a switching circuit and a positive and negative constant current source circuit, wherein the input end of the integration circuit is connected with the output end of the quartz accelerometer, the output end of the integration circuit is connected with the switching circuit, the signal control end of the switching circuit is connected with the IO port of the FPGA chip, the output end of the switching circuit is connected with the positive and negative constant current source circuit, and the other branch of the switching circuit is connected with the positive and negative constant current source circuit.

[0008] Further, the inertial measurement unit signal integrated resolving circuit of claim 1 further comprises a temperature acquisition circuit used for completing temperature data resolving of the circuit, wherein the temperature acquisition circuit comprises temperature sensors, the fiber optic gyroscope and the quartz accelerometer are both provided with the temperature sensors used for acquiring temperature data, and the output end of the temperature sensor is connected with the IO port of the FPGA chip of the FPGA control circuit.

[0009] Further, the inertial measurement unit signal integrated resolving circuit further comprises a communication output circuit connected with the FPGA control circuit and used for external communication of the inertial measurement unit signal integrated resolving circuit.

[0010] Further, the fiber optic gyroscope further comprises a light source driving circuit, an SLD light source and a photoelectric detector used for completing light source current driving and light source temperature control, the light source driving circuit is connected with the SLD light source, one end of the photoelectric detector is connected with the SLD light source, and the other end of the photoelectric detector is connected with the gyroscope resolving circuit.

[0011] The light source driving circuit comprises a temperature control circuit and a constant current source driving circuit, wherein the temperature control circuit comprises a temperature controller, and the constant current source driving circuit comprises a voltage reference and a bypass circuit.

[0012] The temperature control end of the temperature controller and the output end of the voltage reference are connected with the SLD light source, and the light source tail fiber of the SLD light source is connected with the fiber optic gyroscope optical path.

[0013] Further, the AD sampling circuit comprises an AD converter, wherein the power supply pin of the AD converter is connected with a 3.3V power supply, the digital output pins D0-D13 of the AD converter are connected with the normal IO port of the FPGA chip of the FPGA control circuit, and the clock pin CLK of the AD converter is connected with the global clock pin of the FPGA chip.

[0014] Further, the DA conversion circuit selects a DA converter to complete the conversion from digital quantity to analog quantity, wherein the positive and negative power supply pins of the DA converter are connected with a +5V power supply circuit respectively, the digital quantity calculated by the FPGA chip of the FPGA control circuit is input to the digital input pin DB0-DB15 of the DA converter through the normal IO port input pin of the FPGA chip, and the clock pin CLK of the DA converter is connected with the global clock pin of the FPGA chip.

[0015] Further, the FPGA control circuit comprises an FPGA chip and an external Flash configuration circuit, the external Flash configuration circuit comprises a Flash chip, and the FPGA chip is connected with the gyro calculation circuit and the IF conversion circuit respectively, wherein the SI pin of the Flash chip is connected with the MOSI pin of the FPGA chip 501, the DIN pin of the Flash chip is connected with the DIN pin of the FPGA chip 501, the CS pin of the Flash chip is connected with the CSO_B pin of the FPGA chip 501, and the SCLK pin of the Flash chip is connected with the CCLK pin of the FPGA chip 501.

[0016] Further, the integration circuit comprises an operational amplifier, a sampling resistor and a filter capacitor, the sampling resistor is connected with the negative input end of the operational amplifier, the positive input end of the operational amplifier is grounded, and the negative input end and the output end of the operational amplifier are connected with the filter capacitor, and one end of the filter capacitor is grounded.

[0017] Overall, compared with the prior art, the above technical scheme conceived by the present application can achieve the following beneficial effects:

[0018] The inertial measurement unit signal integration calculation circuit provided by the present application integrates the FPGA control circuit, the gyro calculation circuit and the IF conversion circuit in the circuit board, and the same FPGA control circuit is used to complete the calculation of the three-axis fiber-optic gyroscope data and the quartz accelerometer data. The present application provides the connection relationship between the gyro calculation circuit, the IF conversion circuit and the FPGA master control chip, the circuit design is simple, the number of devices, the printed board space are significantly saved, the production cost is reduced, the wiring between the printed boards is saved, the circuit is practical and convenient, the manual soldering between multiple circuits is avoided, and the circuit is convenient to disassemble and debug. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0020] Figure 1 A structure block diagram of an inertial measurement unit signal integrated solving circuit provided by the embodiment of the application is provided;

[0021] Figure 2 An AD sampling circuit schematic diagram of a gyro solving part of the inertial measurement unit signal integrated solving circuit provided by the embodiment of the application is provided;

[0022] Figure 3 An DA conversion circuit schematic diagram of the gyro solving part of the inertial measurement unit signal integrated solving circuit provided by the embodiment of the application is provided;

[0023] Figure 4 An IF integration circuit schematic diagram of the gyro solving part of the inertial measurement unit signal integrated solving circuit provided by the embodiment of the application is provided;

[0024] Figure 5 An FPGA control circuit schematic diagram of the gyro solving part of the inertial measurement unit signal integrated solving circuit provided by the embodiment of the application is provided. DETAILED DESCRIPTION

[0025] In order to make the object, technical solutions and advantages of the application clearer, the application is further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the application and do not limit the application. In addition, the technical features involved in each embodiment of the application described below can be combined with each other as long as they do not conflict with each other.

[0026] In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device including a series of steps or units is not limited to the listed steps or units, but can optionally include steps or units not listed or can optionally include other steps or units inherent to the process, method, product or device.

[0027] The embodiment provides an inertial measurement unit signal integrated solving circuit for solving output signals of three-axis fiber-optic gyroscopes and quartz accelerometers, which comprises an FPGA control circuit 50, a gyro solving circuit 30 and an IF conversion circuit 40, and the gyro solving circuit 30 and the IF conversion circuit 40 are both connected to the FPGA control circuit 50.

[0028] Generally, three-axis fiber-optic gyroscopes and IF conversion modules are designed separately and each has an independent FPGA control unit. In order to improve the integration degree, the FPGA control circuit 50 in the embodiment is connected to the gyro solving circuit 30 and the IF conversion circuit 40 respectively, and three-axis gyro signal and quartz accelerometer signal are solved by the same FPGA control module in the integrated circuit board.

[0029] In a preferred embodiment, Figure 1 The structure block diagram of the integrated signal calculation circuit of the inertial measurement unit of the embodiment of the application is shown in the figure, wherein the fiber-optic gyroscope is a three-axis fiber-optic gyroscope, which comprises a light source driving circuit 20, an SLD light source and a photoelectric detector, one end of the photoelectric detector is connected with the SLD light source, the other end is connected with a gyroscope calculation circuit 30 for completing the light source current driving and the light source temperature control, a constant current source circuit is designed to constantly drive the SLD light source, which comprises a voltage reference and a bypass circuit; at the same time, a constant temperature control circuit is designed to ensure that the light source works at a constant temperature, wherein the constant current source driving circuit 202 adopts a high-precision operational amplifier to complete the driving current generation, the operational amplifier is selected to be a high-precision and low-noise operational amplifier, and the temperature control circuit 201 comprises a temperature controller, the temperature controller is selected to be a high-performance temperature controller, and those skilled in the art can make adaptive adjustment according to the needs, which is not limited in the present scheme. Specifically, the driving current end of the constant current source driving circuit 202 and the temperature control end of the temperature control circuit 201 are connected with the SLD light source, the tail fiber of the SLD light source is connected into the three-axis fiber-optic gyroscope light path, and the output end of the SLD light source is connected into the photoelectric detector.

[0030] The output end of the photoelectric detector is connected with the input end of the gyroscope calculation circuit 30, and one end of the gyroscope calculation circuit 30 is connected with the FPGA control circuit 50; the output end of the quartz accelerometer is connected with the input end of the IF conversion circuit 40, and the output end of the IF conversion circuit 40 is connected with the FPGA control circuit 50.

[0031] Further, the gyroscope calculation circuit 30 comprises an amplification and filtering circuit 301, an AD acquisition circuit 302, a DA conversion circuit 303 and a step wave driving circuit 304, the input end of the amplification and filtering circuit 301 is connected with the output end of the photoelectric detector, and receives the three-axis fiber-optic gyroscope signal. After the three-axis fiber-optic gyroscope signal is filtered and amplified, it enters the AD acquisition circuit 302 to complete the conversion from an analog quantity to a digital quantity, and the AD converter with a model such as A1D1 is selected in the embodiment, preferably, Figure 2 The AD sampling circuit diagram of the gyroscope calculation part of the integrated signal calculation circuit of the inertial measurement unit of the embodiment of the application is shown in the figure, the power supply pin of the AD converter is connected with a 3.3V power supply, the analog quantity input pin of the AD converter is connected with the analog differential input pins VIN+ and VIN-, the power supply pin AVDD and the reference ground ADNG are connected with filtering capacitors A1C24-A1C33, the digital quantity output pins D0-D13 of the AD converter are connected with the normal IO port of the FPGA chip 501, and the clock pin CLK of the AD converter is connected with the global clock pin of the FPGA chip 501.

[0032] The triaxial fiber-optic gyroscope signal is converted by AD and enters the FPGA control circuit 50 to solve the triaxial fiber-optic gyroscope signal, the solved triaxial fiber-optic gyroscope signal is connected to the DA conversion circuit 303, the generated analog signal is generated by the ladder wave driving circuit 304 to generate the ladder wave, and the modulation of the triaxial fiber-optic gyroscope signal is completed.

[0033] Preferably, Figure 3 The DA conversion circuit schematic diagram of the gyroscope solving part of the inertial measurement unit signal integrated solving circuit embodiment of the application is shown in the figure, the DA converter is selected to complete the conversion from digital quantity to analog quantity, the positive and negative power supply pins of the DA converter are connected to the +5V power supply circuit respectively, the supply pins VDD and VSS are connected to the reference ground ADNG through the filter capacitors A1C53-A1C58, the digital quantity solved by the FPGA chip 501 is input to the DA digital input pin DB0-DB15 through the general IO port input pin of the FPGA control circuit 50, the clock pin CLK of the DA converter is connected to the global clock pin of the FPGA chip 501, and the analog quantity output IOUTA and IOUTB pin is connected to the amplification driving circuit.

[0034] Preferably, the IF conversion circuit 40 comprises an integration circuit 401, a switching circuit 402 and a positive and negative constant current source circuit 403, the input end of the integration circuit 401 is connected to the output end of the quartz accelerometer, a part of the quartz accelerometer current is connected to the operational amplifier input end of the integration circuit 401 to complete the conversion from current to voltage after the integration capacitor, and the other part is connected to the input end of the switching circuit 402, the signal control end of the switching circuit 402 is connected to the IO port of the main control chip FPGA, and the current flow direction is controlled by the IO port.

[0035] Further, the integration circuit 401 comprises an operational amplifier, a sampling resistor and a filter capacitor, the sampling resistor is connected to the negative input end of the operational amplifier, the positive input end of the operational amplifier is grounded, the negative input end and the output end of the operational amplifier are connected to the input end of the filter capacitor, one end of the filter capacitor is connected to the ground, Figure 4 The IF integration circuit schematic diagram of the gyroscope solving part of the inertial measurement unit signal integrated solving circuit embodiment of the application is shown in the figure, the quartz accelerometer current enters the negative input end (the 2 pin of U1) of the high-precision and low-noise operational amplifier after the sampling resistor A1R42, the positive input end (the 3 pin of U1) of the operational amplifier is grounded, the filter capacitor A1C73 is connected between the 2 pin and the 3 pin of the operational amplifier U1, the high-stability integration capacitor A1C70 is connected between the 2 pin and the 6 pin of the operational amplifier U1, the current integration is completed, the output after the integration is connected to the FPGA general IO port after the filter capacitor A1C90, and the filter capacitors A1C71, A1C72, A1C74 and A1C75 are connected between the 7 pin and the 4 pin of the operational amplifier U1 positive and negative power supply ends and the reference ground AGND respectively.

[0036] Preferably, the FPGA control circuit 50 comprises an FPGA chip 501 and an external Flash configuration circuit 502, the external Flash configuration circuit 502 comprises a Flash chip, and the FPGA chip 501 is connected with the gyro calculation circuit 30 and the IF conversion circuit respectively. Figure 5 The schematic diagram of the gyro calculation part FPGA control circuit of the inertial measurement unit signal integrated calculation circuit is shown in the figure, the power supply pin of the Flash chip for storing programs is connected with a 3.3V power supply, the JTAG port TCK, TDI, TMS and TDO of the FPGA chip 501 are left for the printed board soldering pad, the SI pin of the Flash chip is connected with the MOSI pin of the FPGA chip 501, the DIN pin of the Flash chip is connected with the DIN pin of the FPGA chip 501, the CS pin of the Flash chip is connected with the CSO_B pin of the FPGA chip 501, and the SCLK pin of the Flash chip is connected with the CCLK pin of the FPGA chip 501.

[0037] In a preferred embodiment, the inertial measurement unit signal integrated calculation circuit further comprises a temperature acquisition circuit 60, the temperature sensor is connected with the fiber optic gyro ring and the quartz acceleration respectively, the output digital quantity is acquired and calculated by the FPGA control circuit 50, the temperature data calculation of the circuit is completed, the temperature acquisition circuit comprises a temperature sensor and a temperature sensor power supply, and the output end of the temperature sensor is connected with the IO port of the FPGA chip 501 of the FPGA control circuit 50.

[0038] In a preferred embodiment, the inertial measurement unit signal integrated calculation circuit further comprises a communication output circuit 70, which is used for completing the external communication function of the whole inertial measurement unit signal integrated calculation circuit, including a serial transceiver and a peripheral configuration resistance-capacitance circuit. Specifically, the serial transceiver can be selected, for example, a high-speed communication level conversion chip is selected to complete the external RS422 communication.

[0039] The integrated calculation circuit can efficiently complete the calculation of the three-axis fiber optic gyro data, the quartz acceleration and the data by one main control chip, can successfully calculate the gyro signal, the accelerometer signal and drive the SLD light source. The circuit design is simple, which significantly saves the number of devices, the printed board space, reduces the production cost, and saves the wiring between the printed boards. In addition, the integrated calculation circuit is practical and convenient, avoids manual soldering between multiple circuits, is convenient to disassemble and assemble, and is easy to debug. In addition, the high-precision fiber optic gyro calculation circuit and the high-precision charge balance scheme are adopted to cooperatively complete the calculation of the fiber optic gyro, the acceleration and the data.

[0040] It should be noted that, for the aforementioned method embodiments, the sequences of the described actions can be changed, and the actions described in different embodiments can be performed in the same way or in combination. It should also be noted that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to the application.

[0041] In the above embodiments, the description of each embodiment focuses on different aspects, and the parts not described in detail in a certain embodiment can be referred to the relevant description of other embodiments.

[0042] In the several embodiments provided by the present application, it should be understood that the disclosed device can be implemented in other ways. For example, the device embodiments described above are only schematic. The division of the units is only a logical function division. There can be another division during actual implementation. For example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the displayed or discussed mutual couplings or direct couplings or communication connections between different units, can be indirect couplings or communication connections through some interfaces, devices or units, and can be electrical or other forms.

[0043] The units described as separate components can or can not be physically separate, and the components displayed as units can or can not be physical units, i.e. they can be located in one place, or can be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the embodiment.

[0044] The above is only exemplary embodiments of the present disclosure, which cannot limit the scope of the present disclosure. Any equivalent changes and modifications made according to the teachings of the present disclosure are still within the scope of the present disclosure. Those skilled in the art will easily think of other embodiments of the present disclosure after considering the specification and practicing the disclosure herein. The present application is intended to cover any variations, uses or adaptive changes of the present disclosure, which follow the general principles of the present disclosure and include common knowledge or conventional technical means in the art not described in the present disclosure. The specification and examples are only considered as exemplary, and the scope and spirit of the present disclosure are defined by the claims.

[0045] The technical features of the above embodiments can be combined in any way. To make the description simple, not all possible combinations of the technical features in the above embodiments are described, however, as long as the combination of the technical features does not exist contradictory, it should be considered as the scope of the present disclosure.

[0046] Those skilled in the art can easily understand that the above description is only the preferred embodiment of the present application, and is not intended to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An inertial measurement unit signal integration and solution circuit for solving the output signals of fiber optic gyroscopes and quartz accelerometers, characterized in that: include: FPGA control circuit (50), gyro solution circuit (30) and IF conversion circuit (40); wherein, The gyro solution circuit (30) is used to receive and solve the fiber optic gyro signal, and comprises an amplifying and filtering circuit (301), an AD acquisition circuit (302), a DA conversion circuit (303), and a step wave driving circuit (304), wherein the input end of the amplifying and filtering circuit (301) receives the fiber optic gyro signal, the output end of the amplifying and filtering circuit (301) is connected to the input end of the AD acquisition circuit (302), the output end of the AD acquisition circuit (302) is connected to one end of the FPGA control circuit (50), the DA conversion circuit (303) is connected to the output end of the FPGA control circuit (50), and the output end of the DA conversion circuit (303) is connected to the input end of an external step wave modulation circuit (304); The IF conversion circuit (40) is used to receive the current signal of the quartz accelerometer and perform a calculation, and comprises an integration circuit (401), a switching circuit (402) and a positive and negative constant current source circuit (403), wherein the input end of the integration circuit (401) is connected to the output end of the quartz accelerometer, the output end of the integration circuit (401) is connected to the switching circuit (402), the signal control end of the switching circuit (402) is connected to the IO port of the FPGA chip (501), the output end of the switching circuit (402) is connected to the positive and negative constant current source circuit (403), and the other branch of the switching circuit (402) is connected to the positive and negative constant current source circuit (403); A temperature acquisition circuit (60) is used to complete the temperature data calculation of the circuit. The temperature acquisition circuit (60) includes a temperature sensor. The fiber optic gyroscope and the quartz accelerometer are both provided with a temperature sensor for collecting temperature data. The output end of the temperature sensor is connected to the IO port of the FPGA chip (501) of the FPGA control circuit (50).

2. The inertial measurement unit signal integration and solution circuit according to claim 1, wherein: It also includes a communication output circuit (70), which is connected to the FPGA control circuit (50) and is used for the inertial measurement unit signal integration and solution circuit to communicate externally.

3. The inertial measurement unit signal integration and solution circuit according to claim 1, wherein: The fiber optic gyroscope further includes a light source driving circuit (20), an SLD light source, and a photodetector for completing light source current driving and light source temperature control, wherein the light source driving circuit (20) is connected to the SLD light source, and one end of the photodetector is connected to the SLD light source, and the other end is connected to the gyroscope solution circuit (30); The light source driving circuit (20) comprises a temperature control circuit (201) and a constant current source driving circuit (202); wherein the temperature control circuit (201) comprises a temperature controller, and the constant current source driving circuit (202) comprises a voltage reference and a bypass circuit; The temperature control end of the temperature controller and the output end of the voltage reference are connected to the SLD light source, and the light source pigtail of the SLD light source is connected to the optical path of the fiber optic gyroscope.

4. The inertial measurement unit signal integration and solution circuit according to claim 1, wherein: The AD acquisition circuit (302) includes an AD converter, wherein a power supply pin of the AD converter is connected to a 3.3V power supply, digital output pins D0 to D13 of the AD converter are connected to common IO ports of the FPGA chip (501) of the FPGA control circuit (50), and a clock pin CLK of the AD converter is connected to a global clock pin of the FPGA chip (501).

5. The inertial measurement unit signal integration and solution circuit according to claim 1, wherein: The DA conversion circuit (303) uses a DA converter to complete the conversion of the digital signal to the analog signal, wherein the positive and negative power supply pins of the DA converter are respectively connected to the ±5V power supply circuit, the digital quantity calculated by the FPGA chip (501) of the FPGA control circuit (50) is connected to the digital input pins DB0 to DB15 of the DA converter via the common IO port input pins of the FPGA chip (501), and the clock pin CLK of the DA converter is connected to the global clock pin of the FPGA chip (501).

6. The inertial measurement unit signal integration and solution circuit according to claim 1, wherein: The FPGA control circuit (50) includes an FPGA chip (501) and an external Flash configuration circuit (502). The external Flash configuration circuit (502) includes a Flash chip. The FPGA chip (501) is connected to the gyro solution circuit (30) and the IF conversion circuit (40), respectively. The SI pin of the Flash chip is connected to the MOSI pin of the FPGA chip (501); the DIN pin of the Flash chip is connected to the DIN pin of the FPGA chip (501); the CS pin of the Flash chip is connected to the CSO_B pin of the FPGA chip (501); and the SCLK pin of the Flash chip is connected to the CCLK pin of the FPGA chip (501).

7. The inertial measurement unit signal integration and solution circuit according to claim 1, wherein: The integration circuit (401) comprises an operational amplifier, a sampling resistor and a filter capacitor, wherein the sampling resistor is connected to the negative input terminal of the operational amplifier, the positive input terminal of the operational amplifier is grounded, the negative input terminal and the output terminal of the operational amplifier are connected to the input terminal of the filter capacitor, and one end of the filter capacitor is grounded.

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