5-order continuous low-pass resonance feedforward type sigma-delta modulator closed-loop control circuit of micromechanical accelerometer

Abstract

The invention discloses a 5-order continuous low-pass resonance feedforward type sigma-delta modulator closed-loop control circuit of a micromechanical accelerometer, and belongs to the field of acceleration signal measurement processing of the micromechanical accelerometer. A circuit is composed of a charge amplifier 5, a high-pass filter 6, a diode 7, a low-pass filter 8, a full differential amplifier 9, a phase compensation circuit 10, an integrating circuit I11, an integrating circuit II 12, an integrating circuit III 13, a repeater 14, a summator 15, a comparator 16, a D-trigger 17 and an analog switch 18. The 5-order continuous low-pass resonance feedforward type sigma-delta modulator closed-loop control circuit of the micromechanical accelerometer has the advantages that local negative feedback is added to an integration link, so that a second integrator and a third integrator are equivalent to a 2-order resonance link equivalent, the resonance frequency fR of the equivalent 2-order resonance link is equal to a theoretical bandwidth frequency ft, the noise in the system theoretical bandwidth range [0 Hz, ft Hz] is effectively lowered, and the signal-to-noise ratio is improved.

Description

technical field [0001] The invention relates to a 5th-order continuous low-pass resonance feedforward sigma-delta modulator closed-loop control circuit for a micro-mechanical accelerometer, belonging to the field of measurement and processing of acceleration signals of the micro-mechanical accelerometer. Background technique [0002] Micromachined accelerometer is an important microelectromechanical system (MEMS) inertial sensor, and it is also one of the earliest MEMS devices to start research. It has been widely used in military and civilian fields. The working principle of the micromachined accelerometer is: when the external acceleration signal is loaded on the micromachined accelerometer, the central mass of the accelerometer will be displaced in the acceleration direction, resulting in a change in the detection capacitance. By detecting the change, the acceleration can be calculated the size of. In order to realize a high-precision micro-machined accelerometer, it is ...

AI Technical Summary

Problems solved by technology

In order to realize a high-precision micro-machined accelerometer, it is necessary to compensate the error. The closed-loop control method is often used. At present, the analog closed-loop control method is more commonly used, but the analog closed-loop control system has some disadvantages: a large acceleration signal is easy to As a result, the central mass of the micromechanical accelerometer is adsorbed to the electrodes, and the system parameters are easily affected by external factors, and it is difficult to achieve precise control, etc.

[0004]The open-loop forward path of the system is composed of a micromachined accelerometer and three first-order integrators in series. When the frequency of the accelerometer signal is greater than the resonance of the accelerometer itself When the signal passes through the micromachined accelerometer, the gain decreases with a slope of 40dB / dec, and when passing through each integrator, the gain decreases with a slope of 20dB / dec, so the system open-loop gain decreases with a slope of 100dB / dec, causing the system The noise level of the final output signal increases with a slope of 100dB / dec, and the noise shaping capability of the system decreases, thus limiting the effective bandwidth of the system

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