CN-115184639-B - Triaxial MEMS accelerometer closed loop readout circuit

CN115184639BCN 115184639 BCN115184639 BCN 115184639BCN-115184639-B

Abstract

The invention discloses a triaxial MEMS accelerometer closed-loop reading circuit which comprises three uniaxial closed-loop reading circuits, wherein the three uniaxial closed-loop reading circuits are respectively connected with X, Y, Z shafts of the triaxial MEMS accelerometer, the output ends of the three uniaxial closed-loop reading circuits are connected with the data input end of an accelerometer signal digital quantization module, the output end of the accelerometer signal digital quantization module is connected with the input end of a digital processing module, and the output end of the digital processing module digitally outputs accelerometer signals. The three axial readout circuits can respectively realize signal simulation and digital output, each axial readout circuit can independently select closed-loop control or open-loop control, meanwhile, the memory and the control circuit are integrated inside, so that flexible configuration of parameters of the three axial readout circuits is realized, the processing error, the packaging error and the assembly error of the accelerometer are timely adjusted, the yield of the device is improved, and meanwhile, the signal simulation output and the digital output are compatible, so that the accelerometer is convenient for a user to use.

Inventors

SHAN YONGQI
ZHANG TAN
XIONG KUN

Assignees

四川微著科技有限公司

Dates

Publication Date: 20260508
Application Date: 20220512

Claims (6)

1. The three-axis MEMS accelerometer closed-loop reading circuit is characterized by comprising three single-axis closed-loop reading circuits, wherein the three single-axis closed-loop reading circuits are respectively connected with X, Y, Z axes of the three-axis MEMS accelerometer, the output ends of the three single-axis closed-loop reading circuits are connected with the data input end of an accelerometer signal digital quantization module, the output end of the accelerometer signal digital quantization module is connected with the input end of a digital processing module, and the output end of the digital processing module digitally outputs accelerometer signals; The single-axis closed loop reading circuit comprises a capacitor voltage conversion circuit, a low-pass filter, a proportional integral derivative controller, a mode control circuit, an accelerometer signal quantization module and a self-calibration module, wherein the capacitor voltage conversion circuit is connected with the triaxial MEMS accelerometer, the output end of the capacitor voltage conversion circuit is connected with the low-pass filter, the output end of the low-pass filter is connected with the proportional integral derivative controller, the output end of the proportional integral derivative controller is connected with the mode control circuit, the output end of the mode control circuit is connected with the accelerometer signal quantization module, and the output end of the capacitor voltage conversion circuit is also connected with the self-calibration module.
2. The triaxial MEMS accelerometer closed-loop readout circuit according to claim 1, wherein the uniaxial closed-loop readout circuit further comprises a feedback branch circuit, the feedback branch circuit is composed of a digital-to-analog converter, an analog adder and a high-voltage feedback circuit, two inputs of the analog adder are respectively connected with the output ends of the digital-to-analog converter and the proportional-integral-derivative controller, the output end of the analog adder is connected with a high-voltage feedback driving module, and the output of the high-voltage feedback driving module is used as a feedback output end to be connected with the accelerometer force balance input end.
3. The three-axis MEMS accelerometer closed-loop readout circuit of claim 1, wherein the capacitance-to-voltage conversion circuit comprises a differential operational amplifier and a demodulator connected with an output end of the differential operational amplifier, an amplification feedback capacitor is connected between an input end and an output end of the differential operational amplifier, and a zero offset compensation capacitor is connected in series between two input ends of the differential operational amplifier.
4. The closed-loop readout circuit of the triaxial MEMS accelerometer according to claim 1, further comprising a temperature sensor and a temperature signal analog-to-digital converter connected with the temperature sensor, wherein an output end of the temperature signal analog-to-digital converter is connected with the digital processing module.
5. The closed loop readout circuit of a tri-axis MEMS accelerometer of claim 1 or 4, wherein said communication interface of said digital processing module comprises one or more of I2C, SPI, RS485 digital communication interfaces.
6. The three-axis MEMS accelerometer closed-loop readout circuit of claim 1 or 4, wherein the digital processing module comprises a memory and a memory control module, wherein the memory is a one-time programmable memory or a multi-time erasable memory.

Description

Triaxial MEMS accelerometer closed loop readout circuit Technical Field The invention relates to the technical field of micro-electro-mechanical control, in particular to a closed-loop reading circuit of a triaxial MEMS accelerometer. Background The MEMS accelerometer works according to Newton mechanics principle, the micro mass block senses inertial acceleration, and causes stress deformation of the cantilever beam to cause corresponding capacitance change, and the circuit detects the capacitance change to indirectly obtain acceleration data. The internal structure of the MEMS accelerometer (shown in figure 1) is particularly fine, and a mass block, comb teeth, a beam, gas and the like are arranged in the MEMS accelerometer, wherein the mass block is generally required to be in the order of 10-7g, the comb teeth clearance is generally required to be below 8um, the gas pressure is generally required to control the low-pressure state in the order of 10-3Pa, and even the normal pressure is ensured, so that the gas pressure cannot be changed too much in the use process. However, the MEMS can introduce process deviation, different axial direction deviation and batch deviation during processing, and the process errors can cause the parameters to deviate from the design requirement values, and even different batches and different axial directions can have inconsistency and the like, so that the closed-loop control parameters, zero deviation, scale factors and the like of the MEMS accelerometer device are inconsistent. In addition, packaging errors and mounting errors can also have a significant impact on device uniformity. Therefore, accelerometer readout circuitry needs to take measures to improve device uniformity and yield. Disclosure of Invention The invention aims to provide a closed-loop readout circuit of a triaxial MEMS accelerometer. In order to achieve the above purpose, the invention is implemented according to the following technical scheme: The invention comprises three single-axis closed-loop reading circuits, wherein the three single-axis closed-loop reading circuits are respectively connected with X, Y, Z axes of the triaxial MEMS accelerometer, the output ends of the three single-axis closed-loop reading circuits are connected with the data input end of the accelerometer signal digital quantization module, the output end of the accelerometer signal digital quantization module is connected with the input end of the digital processing module, and the output end of the digital processing module digitally outputs accelerometer signals. The single-axis closed loop reading circuit is composed of a capacitor voltage conversion circuit, a low-pass filter, a proportional integral derivative controller, a mode control circuit, an accelerometer signal quantization module and a self-calibration module, wherein the capacitor voltage conversion circuit is connected with the triaxial MEMS accelerometer, the output end of the capacitor voltage conversion circuit is connected with the low-pass filter, the output end of the low-pass filter is connected with the proportional integral derivative controller, the output end of the proportional integral derivative controller is connected with the mode control circuit, the output end of the mode control circuit is connected with the accelerometer signal quantization module, and the output end of the capacitor voltage conversion circuit is also connected with the self-calibration module. As an improvement, the single-shaft closed-loop readout circuit further comprises a feedback branch circuit, the feedback branch circuit is composed of a digital-to-analog converter, an analog adder and a high-voltage feedback circuit, two inputs of the analog adder are respectively connected with the output ends of the digital-to-analog converter and the proportional-integral-derivative controller, the output end of the analog adder is connected with a high-voltage feedback driving module, and the output of the high-voltage feedback driving module is used as a feedback output end to be connected with an accelerometer force balance input end. Specifically, the capacitance-to-voltage conversion circuit comprises a differential operational amplifier and a demodulator connected with the output end of the differential operational amplifier, wherein an amplifying feedback capacitor is connected between the input end and the output end of the differential operational amplifier, and a zero offset compensation capacitor is connected in series between the two input ends of the differential operational amplifier. Preferably, the device also comprises a temperature sensor and a temperature signal analog-to-digital converter connected with the temperature sensor, wherein the output end of the temperature signal analog-to-digital converter is connected with the digital processing module. Preferably, the communication interface of the digital processing module comprises one or more of a plurality of d