CN118549712A - Comb capacitance detection method of microsystem actuator - Google Patents

Abstract

The present application provides a method for detecting the comb capacitance of a microsystem actuator. The method applies a test voltage to a fixed comb tooth on one side of the microsystem actuator, and grounds two movable comb teeth in the side comb tooth assembly; uses another fixed comb tooth in the side comb tooth assembly as the comb tooth to be tested, and collects the detection signal of the comb tooth to be tested; uses a configured charge amplifier circuit to detect the collected detection signal to obtain a measured signal; and determines the comb capacitance detection result based on the measured signal. The method can realize a general method for detecting the comb capacitance of a microsystem actuator, and improves the detection efficiency.

Description

Comb capacitance detection method for micro-system actuators

Technical Field

The present application relates to the technical field of capacitance detection, and in particular to a method for detecting comb capacitance of a microsystem actuator.

Background Art

A microsystem, also known as a micro-electro-mechanical system (MEMS) or micromachine, is a miniature integrated system that uses integrated circuit manufacturing technology and micromachining technology to manufacture microstructures, microsensors, microactuators, control processing circuits and even interfaces, communications and power supplies on one or more chips.

In MEMS (micro-electromechanical systems) products, C-V (capacitance-voltage) conversion circuits are a common circuit structure used to convert physical quantities such as mechanical displacement or stress into electrical signals for measurement or processing. However, due to the diversity and complexity of MEMS products, the testing methods are often not unified, which brings challenges to testing. In this case, it is particularly important to find a common circuit structure test method for C-V conversion circuits.

Summary of the invention

The purpose of the embodiments of the present application is to provide a method for detecting the comb-teeth capacitance of a micro-system actuator, so as to implement a general method for detecting the comb-teeth capacitance of a micro-system actuator and improve the detection efficiency.

In a first aspect, a comb-tooth capacitance detection method of a microsystem actuator is provided, wherein each of the four sides of the microsystem actuator is provided with a comb-tooth assembly; each comb-tooth assembly includes two movable comb teeth and two fixed comb teeth, the two movable comb teeth are electrically connected and the two fixed comb teeth are electrically disconnected, and the method may include:

For one side of the microsystem actuator, a test voltage is applied to a fixed comb tooth, and two movable comb teeth in the comb tooth assembly on the side are grounded;

Another fixed comb tooth in the side comb tooth assembly is used as the comb tooth to be tested, and a detection signal of the comb tooth to be tested is collected;

The configured charge amplifier circuit is used to detect the collected detection signal to obtain the measured signal;

Based on the measured signal, a comb capacitance detection result is determined.

In a possible implementation, the charge amplifier circuit includes a carrier modulation circuit, a differential modulation circuit, a signal demodulation circuit and a filter amplifier circuit;

The configured charge amplifier is used to detect the collected carrier signal to obtain the measured signal, including:

The carrier modulation circuit modulates the detection signal on the carrier to obtain a carrier signal;

The differential modulation circuit converts the carrier signal into a voltage amplitude modulation signal;

The signal demodulation circuit demodulates the voltage amplitude modulation signal to obtain a demodulated signal;

The filtering and amplifying circuit processes the demodulated signal to obtain a measured signal.

In a possible implementation, the input end of the carrier modulation circuit inputs the collected detection signal, the first output end of the carrier modulation circuit is connected to the first input end of the differential modulation circuit, and the second output end of the carrier modulation circuit is connected to the second input end of the differential modulation circuit;

The first output end of the differential modulation circuit is connected to the first input end of the signal demodulation circuit, and the second output end of the differential modulation circuit is connected to the second input end of the signal demodulation circuit;

The first output end of the signal demodulation circuit is connected to the first input end of the filter amplifier circuit, the second output end of the signal demodulation circuit is connected to the second input end of the filter amplifier circuit, and the output end of the filter amplifier circuit outputs the measured signal.

In one possible implementation, the carrier modulation circuit includes a first variable capacitor and a second variable capacitor, the positive plate of the first variable capacitor and the positive plate of the second variable capacitor are connected, the connection point is the input end of the carrier modulation circuit, the negative plate of the first variable capacitor is the first output end of the carrier modulation circuit, and the negative plate of the second variable capacitor is the second output end of the carrier modulation circuit.

In a possible implementation, the capacitance value of the first variable capacitor is the sum of the configured static capacitance value and the target capacitance change; the capacitance value of the second variable capacitor is the difference between the configured static capacitance value and the target capacitance change.

In a possible implementation, the differential modulation circuit includes a first operational amplifier, a second operational amplifier, a first feedback capacitor, a second feedback capacitor, a first DC bias resistor, and a second DC bias resistor; wherein:

The negative plate of the first feedback capacitor, one end of the first DC bias resistor and the negative input terminal of the first operational amplifier intersect, and the intersection is the first input terminal of the differential modulation circuit; the positive plate of the first feedback capacitor, the other end of the first DC bias resistor and the output terminal of the first operational amplifier intersect, and the intersection is the first output terminal of the differential modulation circuit;

The negative plate of the second feedback capacitor, one end of the second DC bias resistor and the negative input terminal of the second operational amplifier intersect, and the intersection is the second input terminal of the differential modulation circuit; the positive plate of the second feedback capacitor, the other end of the second DC bias resistor and the output terminal of the second operational amplifier intersect, and the intersection is the second output terminal of the differential modulation circuit;

The positive input terminal of the first operational amplifier and the positive input terminal of the second operational amplifier are respectively connected to a configured reference voltage.

In a possible implementation, the signal demodulation circuit is a TS5A23159 signal demodulation chip, the NO1 pin and the NC2 pin of the TS5A23159 signal demodulation chip are the first input end of the signal demodulation circuit, and the NO2 pin and the NC1 pin of the TS5A23159 signal demodulation chip are the second input end of the signal demodulation circuit;

The first output end of the signal demodulation circuit is the COM1 pin of the TS5A23159 signal demodulation chip, and the second output end of the signal demodulation circuit is the COM2 pin of the TS5A23159 signal demodulation chip;

The IN1 pin and IN2 pin of the TS5A23159 signal demodulation chip input the same clock signal CLK, and the clock signal has the same frequency as the detection signal.

In one possible implementation, the method further includes:

When CLK is at a high level, the COM1 pin in the TS5A23159 signal demodulation chip is connected to the NO1 pin, the COM02 pin is connected to the NO2 pin, the first output end of the signal demodulation circuit outputs the signal of the first input end, and the corresponding second output end outputs the signal of the second input end;

When CLK is at a low level, the COM1 pin in the TS5A23159 signal demodulation chip is connected to the NC1 pin, the COM02 pin is connected to the NC2 pin, the first output end of the signal demodulation circuit outputs the signal of the second input end, and the corresponding second output end outputs the signal of the first input end.

In a possible implementation, the filtering and amplifying circuit includes a first resistor, a second resistor, a third resistor, a fourth resistor, a first capacitor, a second capacitor, and a third operational amplifier;

One end of the first resistor is the first input end of the filter amplifier circuit, and one end of the second resistor is the second input end of the filter amplifier circuit;

The other end of the first resistor intersects with one end of the third resistor, the negative plate of the first capacitor and the negative input terminal of the third operational amplifier respectively;

The other end of the third resistor, the positive plate of the first capacitor and the output end of the third operational amplifier intersect, and the intersection is the output end of the filter amplifier circuit;

The other end of the second resistor intersects the positive plate of the second capacitor, one end of the fourth resistor and the positive input end of the third operational amplifier respectively;

The negative plate of the second capacitor and the other end of the fourth resistor are respectively connected to a reference voltage.

In a possible implementation, the peak-to-peak value of the test voltage is 30V.

The comb-tooth capacitance detection method for a microsystem actuator provided in the embodiment of the present application is directed to one side of the microsystem actuator, a test voltage is applied to a fixed comb tooth, and two movable comb teeth in the side comb tooth assembly are grounded; another fixed comb tooth in the side comb tooth assembly is used as the comb tooth to be tested, and a detection signal of the comb tooth to be tested is collected; a configured charge amplifier circuit is used to detect the collected detection signal to obtain a measured signal; based on the measured signal, the comb-tooth capacitance detection result is determined. This method can realize a general comb-tooth capacitance detection method for a microsystem actuator, and improves the detection efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

FIG1 is a schematic diagram of a comb tooth structure of a comb tooth assembly in a micro-system actuator provided in an embodiment of the present application;

FIG2 is a schematic flow chart of a comb capacitance detection method for a microsystem actuator provided in an embodiment of the present application;

FIG3 is a schematic diagram of a circuit structure of a charge amplifier circuit provided in an embodiment of the present application;

FIG4 is a schematic diagram of a circuit structure of a carrier modulation circuit provided in an embodiment of the present application;

FIG5 is a schematic diagram of a circuit structure of a differential modulation circuit provided in an embodiment of the present application;

FIG6 is a schematic diagram of a TS5A23159 signal demodulation chip provided in an embodiment of the present application;

FIG7 is a schematic diagram of a circuit structure of a filter amplifier circuit provided in an embodiment of the present application;

FIG8 is a schematic structural diagram of a comb capacitance detection device for a microsystem actuator provided in an embodiment of the present application.

DETAILED DESCRIPTION

The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments of the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present application. Unless otherwise defined, the technical terms or scientific terms used in this application should be the common meanings understood by people with general skills in the field to which the present invention belongs. The "first", "second" and similar words used in this application do not indicate any order, quantity or importance, but are only used to distinguish different components. "Including" or "including" and other similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connected", "coupled" or "connected" and other similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

The micro-system actuator has a comb-tooth structure capacitor structure: a comb-tooth assembly is arranged on each of the four sides of the micro-system actuator; each comb-tooth assembly includes two movable comb teeth and two fixed comb teeth, the two movable comb teeth are electrically connected, and the two fixed comb teeth are electrically disconnected. The comb-tooth structure of each comb-tooth assembly can be shown in FIG1. In combination with FIG1, it can be seen that comb teeth 2 and comb teeth 4 are fixed comb teeth, and comb teeth 1 and comb teeth 3 are movable comb teeth. The structure composed of comb teeth 1 and comb teeth 2 in the comb-tooth assembly is completely symmetrical with the structure composed of comb teeth 3 and comb teeth 4, and the movable comb teeth (comb teeth 1) corresponding to comb teeth 2 and the movable comb teeth (comb teeth 3) corresponding to comb teeth 4 are electrically connected, that is, electrically connected, and comb teeth 2 and comb teeth 4 are electrically disconnected.

All movable comb teeth in the comb tooth assemblies on the four sides of the microsystem actuator are electrically connected, and all fixed comb teeth in the comb tooth assemblies on the four sides are powered but not conductive, that is, they are independent of each other.

The preferred embodiments of the present application are described below in conjunction with the drawings in the specification. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present application, and are not used to limit the present application. In addition, the embodiments and features in the embodiments of the present application may be combined with each other if there is no conflict.

FIG2 is a flow chart of a comb capacitance detection method for a micro-system actuator provided in an embodiment of the present application. As shown in FIG2 , the method may include:

Step S210: For one side of the microsystem actuator, a test voltage is applied to a fixed comb tooth, and two movable comb teeth in the side comb tooth assembly are grounded.

For one side of the microsystem actuator, in conjunction with Figure 1, a test voltage with a peak value of 30V is applied to the fixed comb teeth 2. After the two movable comb teeth 1 and 3 are grounded, the two movable comb teeth 1 and 3 will move (move left and right in the x direction), and a changing capacitance value will be generated relative to the comb teeth 2 and 4.

Step S220: another fixed comb tooth in the side comb tooth assembly is used as the comb tooth to be tested, and a detection signal of the comb tooth to be tested is collected.

Since the comb teeth 4 will generate a variable capacitance value, if the comb teeth 4 are used as the comb teeth to be tested, a detection signal corresponding to the variable capacitance value can be collected.

Step S230: Use the configured charge amplifier circuit to detect the collected detection signal to obtain a measured signal.

Step S240: Determine the comb capacitance detection result based on the measured signal.

In some embodiments, the configured charge amplifier circuit may include a carrier modulation circuit GYRO (or mass block), a differential modulation circuit (C-V conversion module), a signal demodulation circuit and a filter amplifier circuit. The differential modulation circuit may be a switch capacitor chip or a charge amplifier chip.

For step S230, specifically:

The carrier modulation circuit modulates the detection signal on the carrier to obtain a carrier signal;

The differential modulation circuit converts the carrier signal into a voltage amplitude modulated signal;

The signal demodulation circuit demodulates the voltage amplitude modulation signal to obtain a demodulated signal;

The filter amplifier circuit processes the demodulated signal to obtain the measured signal.

Further, as shown in FIG3 , the connection mode of the charge amplifier circuit is:

The input terminal of the carrier modulation circuit GYRO inputs the collected detection signal V _rade ,

The first output terminal of the carrier modulation circuit is connected to the first input terminal of the differential modulation circuit, and the second output terminal of the carrier modulation circuit GYRO is connected to the second input terminal of the differential modulation circuit;

The first output terminal _V1 of the differential modulation circuit is connected to the first input terminal of the signal demodulation circuit, and the second output terminal _V2 of the differential modulation circuit is connected to the second input terminal of the signal demodulation circuit;

The first output terminal V _de1 of the signal demodulation circuit is connected to the first input terminal of the filter amplifier circuit, the second output terminal V _de2 of the signal demodulation circuit is connected to the second input terminal of the filter amplifier circuit, and the output terminal of the filter amplifier circuit outputs the measured signal V _out .

(1) As shown in FIG. 4 , the carrier modulation circuit may include a first variable capacitor and a second variable capacitor, wherein the capacitance value of the first variable capacitor is the sum of the configured static capacitance value C ₀ and the target capacitance change ΔC; and the capacitance value of the second variable capacitor is the difference between the configured static capacitance value C ₀ and the target capacitance change ΔC.

The positive plate of the first variable capacitor is connected to the positive plate of the second variable capacitor, and the connection point is the input end of the carrier modulation circuit. The negative plate of the first variable capacitor is the first output end of the carrier modulation circuit, and the negative plate of the second variable capacitor is the second output end of the carrier modulation circuit.

(2) As shown in FIG5 , the differential modulation circuit may include a first operational amplifier U1A, a second operational amplifier U1B, a first feedback capacitor C _f1 , a second feedback capacitor C _f2 , a first DC bias resistor R _f1 , and a second DC bias resistor R _f2 ; wherein:

The negative plate of the first feedback capacitor C _f1 , one end of the first DC bias resistor R _f1 and the negative input terminal of the first operational amplifier U1A intersect, and the intersection is the first input terminal of the differential modulation circuit;

The positive plate of the first feedback capacitor C _f1 , the other end of the first DC bias resistor R _f1 and the output end of the first operational amplifier U1A intersect, and the intersection is the first output end of the differential modulation circuit;

The negative plate of the second feedback capacitor C _f2 , one end of the second DC bias resistor R _f2 and the negative input terminal of the second operational amplifier U1B intersect, and the intersection is the second input terminal of the differential modulation circuit;

The positive plate of the second feedback capacitor C _f2 , the other end of the second DC bias resistor R _f2 and the output end of the second operational amplifier U1B intersect, and the intersection is the second output end of the differential modulation circuit;

The positive input terminal of the first operational amplifier U1A and the positive input terminal of the second operational amplifier U1B are respectively connected to the configured reference voltage V _ref1 .

The first operational amplifier and the second operational amplifier may both be AD8652; R _f1 and R _f2 are 100 MΩ; C _f1 and C _f2 are 3 pF, and the static capacitor C ₀ is 3 pF.

(3) As shown in FIG6 , the signal demodulation circuit is a TS5A23159 signal demodulation chip. The analog switch-based signal demodulation circuit is designed using the TS5A23159, which is a dual-channel single-pole double-throw analog switch modem launched by TI. The on-resistance of the two channels is as low as 1Ω and is well matched, with excellent THD (Total Harmonic Distortion) performance.

The NO1 pin and the NC2 pin of the TS5A23159 signal demodulation chip are the first input end of the signal demodulation circuit, and the NO2 pin and the NC1 pin of the TS5A23159 signal demodulation chip are the second input end of the signal demodulation circuit;

The first output end of the signal demodulation circuit is the COM1 pin of the TS5A23159 signal demodulation chip, and the second output end of the signal demodulation circuit is the COM2 pin of the TS5A23159 signal demodulation chip;

The IN1 pin and IN2 pin of the TS5A23159 signal demodulation chip input the same clock signal CLK, and the clock signal has the same frequency as the detection signal.

In the specific work, V1 and V2 are demodulated once through analog switch phase-sensitive detection, and the control clock CLK is in the same frequency as Vrate. When CLK is high, the COM1 pin in the TS5A23159 signal demodulation chip is connected to the NO1 pin, the CMO2 pin is connected to the NO2 pin, and the first output end of the signal demodulation circuit outputs the V _de1 signal corresponding to the first input end, and the corresponding second output end outputs the V _de2 signal corresponding to the second input end; when CLK is low, the COM1 pin in the TS5A23159 signal demodulation chip is connected to the NC1 pin, the CMO2 pin is connected to the NC2 pin, and the first output end of the signal demodulation circuit outputs the V _de1 signal corresponding to the second input end, and the corresponding second output end outputs the V _de2 signal corresponding to the first input end. Among them, CLK and V _rate are in the same frequency and phase, CLK is a 0V-5V square wave with a frequency of 1MHz.

(4) For filter amplifier circuit:

The demodulation circuit output signals V _de1 and V _de2 contain high-frequency carrier and low-frequency capacitance signal. It is necessary to suppress the high-frequency signal and amplify the capacitance signal through a filtering and amplifying circuit. The operational amplifier can be AD8652, and _Va is the configured standard voltage value.

According to Kirchhoff's current equation and the operational amplifier's "virtual short" and "virtual break" principles, the circuit equation is listed:

The above formula can be simplified as:

It should be noted that _R3 in the formula is R3, _R4 is R4, _R5 is R5, _C5 is C5, and _C6 is C6.

From the analysis, it can be obtained that R3 and R5 are used to determine the circuit amplification factor, and C5 and R5 form a first-order low-pass filter network to suppress the high-frequency components in the circuit, and the cut-off frequency f _H =1/(2πR5C5).

Further, as shown in FIG7 , the filter amplifier circuit may include a first resistor R3 , a second resistor R4 , a third resistor R5 , a fourth resistor R6 , a first capacitor C5 , a second capacitor C6 and a third operational amplifier U3A;

One end of the first resistor R3 is the first input end of the filter amplifier circuit, and one end of the second resistor R4 is the second input end of the filter amplifier circuit;

The other end of the first resistor R3 intersects with one end of the third resistor R5, the negative plate of the first capacitor C5 and the negative input terminal of the third operational amplifier U3A respectively;

The other end of the third resistor R5, the positive plate of the first capacitor C5 and the output end of the third operational amplifier U3A intersect, and the intersection is the output end of the filter amplifier circuit;

The other end of the second resistor R4 intersects the positive plate of the second capacitor C6, one end of the fourth resistor R6 and the positive input end of the third operational amplifier U3A respectively;

The negative plate of the second capacitor C6 and the other end of the fourth resistor R6 are respectively connected to the reference voltage V _ref .

Among them, the parameters are: R3, R4 are 10kΩ, R5, R6 are 100kΩ, C5, C6 are 6pF, Vref is 2.5V, and the third operational amplifier can be AD8652.

The comb-tooth capacitance detection method for a microsystem actuator provided in the embodiment of the present application is directed to one side of the microsystem actuator, a test voltage is applied to a fixed comb tooth, and two movable comb teeth in the side comb tooth assembly are grounded; another fixed comb tooth in the side comb tooth assembly is used as the comb tooth to be tested, and a detection signal of the comb tooth to be tested is collected; a configured charge amplifier circuit is used to detect the collected detection signal to obtain a measured signal; based on the measured signal, the comb-tooth capacitance detection result is determined. This method can realize a general comb-tooth capacitance detection method for a microsystem actuator, and improves the detection efficiency.

Corresponding to the above method, the embodiment of the present application further provides a comb capacitance detection device for a microsystem actuator, as shown in FIG8 , the device comprising:

The acquisition unit 810 is used for applying a test voltage to a fixed comb tooth on one side of the microsystem actuator and grounding two movable comb teeth in the side comb tooth assembly, using another fixed comb tooth in the side comb tooth assembly as the comb tooth to be tested, and acquiring a detection signal of the comb tooth to be tested;

The detection unit 820 is used to detect the collected detection signal using a configured charge amplifier circuit to obtain a measured signal;

The determination unit 830 is used to determine the comb capacitance detection result based on the measured signal.

The functions of each functional unit of the comb-tooth capacitance detection device of the microsystem actuator provided in the above-mentioned embodiments of the present application can be realized through the above-mentioned method steps. Therefore, the specific working process and beneficial effects of each unit in the comb-tooth capacitance detection device of the microsystem actuator provided in the embodiments of the present application will not be repeated here.

Those skilled in the art will appreciate that the embodiments in the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt a complete hardware embodiment, a complete software embodiment, or a form of an embodiment combining software and hardware. Moreover, the present application may adopt a form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes.

In the embodiment of the present application, the flowchart and/or block diagram of the method, device (system) and computer program product according to the embodiment of the present application are described with reference to. It should be understood that each process and/or box in the flowchart and/or block diagram, and the combination of the process and/or box in the flowchart and/or block diagram can be realized by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device produce a device for realizing the function specified in one process or multiple processes in the flowchart and/or one box or multiple boxes in the block diagram.

These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory produce a manufactured product including an instruction device that implements the functions specified in one or more processes in the flowchart and/or one or more boxes in the block diagram.

These computer program instructions may also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, whereby the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one or more processes in the flowchart and/or one or more boxes in the block diagram.

Although the preferred embodiments of the present application have been described, those skilled in the art may make additional 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 embodiments of the present application.

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

Claims (10)

1. A method for detecting the comb capacitance of a microsystem actuator, characterized in that each of the four sides of the microsystem actuator is provided with a comb assembly; each comb assembly includes two movable comb teeth and two fixed comb teeth, the two movable comb teeth are electrically connected and the two fixed comb teeth are electrically disconnected, and the method comprises: For one side of the microsystem actuator, a test voltage is applied to a fixed comb tooth, and two movable comb teeth in the comb tooth assembly on the side are grounded; Another fixed comb tooth in the side comb tooth assembly is used as the comb tooth to be tested, and a detection signal of the comb tooth to be tested is collected; The configured charge amplifier circuit is used to detect the collected detection signal to obtain the measured signal; Based on the measured signal, a comb capacitance detection result is determined. 2. The method according to claim 1, characterized in that the charge amplifier circuit comprises a carrier modulation circuit, a differential modulation circuit, a signal demodulation circuit and a filter amplifier circuit; The configured charge amplifier is used to detect the collected carrier signal to obtain the measured signal, including: The carrier modulation circuit modulates the detection signal on the carrier to obtain a carrier signal; The differential modulation circuit converts the carrier signal into a voltage amplitude modulation signal; The signal demodulation circuit demodulates the voltage amplitude modulation signal to obtain a demodulated signal; The filtering and amplifying circuit processes the demodulated signal to obtain a measured signal. 3. The method according to claim 2, characterized in that the input end of the carrier modulation circuit inputs the collected detection signal, the first output end of the carrier modulation circuit is connected to the first input end of the differential modulation circuit, and the second output end of the carrier modulation circuit is connected to the second input end of the differential modulation circuit; The first output end of the differential modulation circuit is connected to the first input end of the signal demodulation circuit, and the second output end of the differential modulation circuit is connected to the second input end of the signal demodulation circuit; The first output end of the signal demodulation circuit is connected to the first input end of the filter amplifier circuit, the second output end of the signal demodulation circuit is connected to the second input end of the filter amplifier circuit, and the output end of the filter amplifier circuit outputs the measured signal. 4. The method as claimed in claim 3 is characterized in that the carrier modulation circuit includes a first variable capacitor and a second variable capacitor, the positive plate of the first variable capacitor is connected to the positive plate of the second variable capacitor, the connection point is the input end of the carrier modulation circuit, the negative plate of the first variable capacitor is the first output end of the carrier modulation circuit, and the negative plate of the second variable capacitor is the second output end of the carrier modulation circuit. 5. The method as claimed in claim 4 is characterized in that the capacitance value of the first variable capacitor is the sum of the configured static capacitance value and the target capacitance change; the capacitance value of the second variable capacitor is the difference between the configured static capacitance value and the target capacitance change. 6. The method according to claim 3, wherein the differential modulation circuit comprises a first operational amplifier, a second operational amplifier, a first feedback capacitor, a second feedback capacitor, a first DC bias resistor, and a second DC bias resistor; wherein: The negative plate of the first feedback capacitor, one end of the first DC bias resistor and the negative input terminal of the first operational amplifier intersect, and the intersection is the first input terminal of the differential modulation circuit; the positive plate of the first feedback capacitor, the other end of the first DC bias resistor and the output terminal of the first operational amplifier intersect, and the intersection is the first output terminal of the differential modulation circuit; The negative plate of the second feedback capacitor, one end of the second DC bias resistor and the negative input terminal of the second operational amplifier intersect, and the intersection is the second input terminal of the differential modulation circuit; the positive plate of the second feedback capacitor, the other end of the second DC bias resistor and the output terminal of the second operational amplifier intersect, and the intersection is the second output terminal of the differential modulation circuit; The positive input terminal of the first operational amplifier and the positive input terminal of the second operational amplifier are respectively connected to a configured reference voltage. 7. The method according to claim 3, characterized in that the signal demodulation circuit is a TS5A23159 signal demodulation chip, the NO1 pin and the NC2 pin of the TS5A23159 signal demodulation chip are the first input end of the signal demodulation circuit, and the NO2 pin and the NC1 pin of the TS5A23159 signal demodulation chip are the second input end of the signal demodulation circuit; The first output end of the signal demodulation circuit is the COM1 pin of the TS5A23159 signal demodulation chip, and the second output end of the signal demodulation circuit is the COM2 pin of the TS5A23159 signal demodulation chip; The IN1 pin and IN2 pin of the TS5A23159 signal demodulation chip input the same clock signal CLK, and the clock signal has the same frequency as the detection signal. 8. The method according to claim 7, characterized in that the method further comprises: When CLK is at a high level, the COM1 pin in the TS5A23159 signal demodulation chip is connected to the NO1 pin, the COM02 pin is connected to the NO2 pin, the first output end of the signal demodulation circuit outputs the signal of the first input end, and the corresponding second output end outputs the signal of the second input end; When CLK is at a low level, the COM1 pin in the TS5A23159 signal demodulation chip is connected to the NC1 pin, the COM02 pin is connected to the NC2 pin, the first output end of the signal demodulation circuit outputs the signal of the second input end, and the corresponding second output end outputs the signal of the first input end. 9. The method according to claim 3, characterized in that the filtering and amplifying circuit comprises a first resistor, a second resistor, a third resistor, a fourth resistor, a first capacitor, a second capacitor and a third operational amplifier; One end of the first resistor is the first input end of the filter amplifier circuit, and one end of the second resistor is the second input end of the filter amplifier circuit; The other end of the first resistor intersects with one end of the third resistor, the negative plate of the first capacitor and the negative input terminal of the third operational amplifier respectively; The other end of the third resistor, the positive plate of the first capacitor and the output end of the third operational amplifier intersect, and the intersection is the output end of the filter amplifier circuit; The other end of the second resistor intersects the positive plate of the second capacitor, one end of the fourth resistor and the positive input end of the third operational amplifier respectively; The negative plate of the second capacitor and the other end of the fourth resistor are respectively connected to a reference voltage. 10. The method according to claim 1, wherein the peak-to-peak value of the test voltage is 30V.