Detecting circuit of capacitance type MEMS (micro-electromechanical system) sensor

Abstract

The invention relates to a detecting circuit of a capacitance type MEMS (micro-electromechanical system) sensor. The detecting circuit comprises a resonance unit which is formed after a first capacitor to be detected is connected with a second capacitor to be detected; the resonance unit is connected with a differential frequency circuit through a frequency detecting unit; an output end of the frequency detecting unit is respectively connected with a first movable pole plate of the first capacitor to be detected and a second movable pole plate of the second capacitor to be detected; the first capacitor to be detected and the second capacitor to be detected are correspondingly connected with each other to form the resonance unit; resonance frequency can be generated in the resonance unit; the resonance unit can compensate energy damped due to resonance; and the frequency detecting unit drives the differential frequency circuit to output corresponding frequency signals according to the resonance frequency outputted by the resonance unit. An active circuit is used for compensating energy loss of an energy storage device, an electrostatic feedback mechanism is utilized to form a closed-loop system to stably output frequency, anti-interference ability is increased, and the detecting circuit is simple and compact in structure and high in measurement accuracy and anti-interference ability, facilitates monolithic integration, overcomes energy loss and is stable and reliable.

Description

technical field [0001] The invention relates to a detection circuit, in particular to a detection circuit of a capacitive MEMS sensor, and belongs to the technical field of capacitive MEMS sensor detection. Background technique [0002] Capacitive MEMS sensors are widely used in industrial, civil, aerospace, defense and other fields. Due to the size of the capacitive MEMS sensor, the output signal of this type of sensor is extremely weak. The output signal of a typical capacitive MEMS sensor is in the order of fF. Such a small size to be measured determines the importance of the weak capacitive detection circuit, and its performance is very important for MEMS. System performance plays an important role. [0003] In order to improve the output linearity of MEMS sensors and suppress common mode noise, most of the sensitive capacitors in capacitive MEMS sensors are in the form of differential capacitors. The existing micro-differential capacitance detection methods mainly inc...

AI Technical Summary

Problems solved by technology

Although the output signal is frequency information with strong anti-interference, the capacitor charging and discharging process directly related to frequency is very sensitive to voltage, and the conversion process of charging and discharging is controlled by transistors, and there will be charge injection and charge feedthrough effects at the moment of state switching. Seriously affect the detection accuracy

[0004] In addition, Fang Jiancheng, Song Xing, Sheng Wei et al.'s "A Detection Circuit for Micro-Differential Capacitors" (Patent No. ZL200810112292.2) proposes a frequency-selective network composed of the capacitor to be tested and a fixed inductance and combined with a phase-locked loop The method of tracking the circuit to form a resonant unit to detect capacitance, the composition of the frequency selection network is too ideal, does not consider the characteristics of electronic component loss and energy weakening in the actual situation, which restricts the accuracy of this test method to a certain extent; System, sensitive to external interference, not conducive to stable signal output

[0005] None of the above methods is suitable for the field of high-precision MEMS capacitance detection. In order to meet the needs of high-precision detection, it is necessary to design a MEMS capacitance detection method with high measurement accuracy, strong anti-interference ability, overcoming energy loss, and simple structure that is conducive to monolithic integration.

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