Closed-loop control circuit of silicon resonant pressure sensor and realization method thereof

Abstract

The invention provides a closed-loop control circuit of a silicon resonant pressure sensor and a realization method thereof. Capacitance variation signals are generated by vibration of a resonator (1) and then divided into two paths; one path of capacitance variation signals pass through a first digital module (4), a second digital module (5), a subtracter module (6), a reference digital signal (7) and a digital proportional controller (8) to form an amplified negative feedback error control quantity; the other path of capacitance variation signals pass through an alternating current extraction module (9) and a digital operation unit (10), and then offset processing and overflow detection are completed; a D / A converter (11) converts the processed digital quantity into an analog signal to drive the resonator to vibrate. A digital algorithm is adopted to replace an analog circuit, so that time consumed in analog rectification and filtering is shortened, and the dynamic performance of a system is improved; the precision of a sinusoidal signal effective value obtained through the digital algorithm is higher than that obtained through analog low-pass filtering, so that the stability of the amplitude of an sinusoidal signal in a closed loop is improved; the digital circuit lowers the power consumption of the whole system and improves the anti-interference capacity of the system.

Description

technical field [0001] The invention relates to a digital closed-loop control circuit of a silicon resonant pressure sensor and a realization method thereof, belonging to the field of pressure sensors. Background technique [0002] Silicon resonant pressure sensor is widely used because of its high precision, good stability, digital output and other advantages. The sensor is mainly composed of diaphragm, resonator and peripheral circuit. When the air pressure changes, the diaphragm will deform, which in turn changes the stiffness of the resonator, resulting in a change in the resonant frequency of the resonator. The current air pressure value can be obtained by measuring the resonant frequency. [0003] In order to achieve high-precision measurement and measurement of changing pressure, the silicon resonant pressure sensor must adopt a closed-loop drive; in order to improve the dynamic performance of the closed-loop control, the closed-loop circuit must adopt a digital drive...

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Problems solved by technology

[0006] It can be seen that the driving voltage of this closed-loop control scheme is AC, and when the oscillation starts, the output voltage of the preamplifier 3 is very small, although the control voltage of the variable gain amplifier 11 can be made very large, but because the variable gain amplifier 11 The input voltage is too small, resulting in a very small driving voltage, which results in a long closed-loop stabilization time

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