Sigma-delta closed-loop control circuit in multi-stage noise shaping (MASH) structure for micro-machined accelerometer

Abstract

The invention discloses a sigma-delta closed-loop control circuit in an MASH structure for a micro-machined accelerometer and belongs to the field of measurement and processing of acceleration signals. The circuit is composed of a charge amplifier 5, a high-pass filter 6, a diode 7, a low-pass filter 8, a fully differential amplifier9, a phase compensation circuit 10, a comparator 12, a D trigger I 13, an integrator 14, a D trigger II 15 and an analog switch 16. The circuit has the advantages that compared with a single-ring structure, the MASH structure has the advantages that a system can be absolutely stable, and the stability is not changed with increase of cascading orders; meanwhile, by the aid of the MASH structure, the idle noise can be restrained effectively, and the influence of the idle noise on the system can be reduced; besides, by the aid of the MASH structure, the amplitude range of input signals can be expanded, so that the amplitude of the input signals can reach the maximum conversion value.

Description

technical field [0001] The invention relates to a MASH structure sigma-delta (ΣΔΜ) closed-loop control circuit for a micromechanical accelerometer, belonging to the field of acceleration signal measurement and processing. Background technique [0002] Micromachined accelerometers have the characteristics of small size, light weight, low power consumption, low cost, good reliability, and great value in military and civilian applications, so they have become the focus of research institutions and companies in various countries. Among them, the capacitive micromachined accelerometer has the advantages of high sensitivity and little influence of temperature, so it has gradually become the mainstream of micromachined accelerometer design. The working principle of the capacitive micromachined accelerometer is: when there is an acceleration signal, the central mass of the micromachined accelerometer will be displaced in the direction of the acceleration signal, resulting in a chang...

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Problems solved by technology

[0005] For a closed-loop system, the second-order system is absolutely stable, and it becomes conditionally stable if it exceeds the second order, and the higher the order, the lower the stability

In the single-loop structure ΣΔΜ digital closed-loop control system, the micromachined accelerometer itself can be equivalent to a second-order link, so after adding a high-order modulator, the system order is greater than 2, resulting in a decrease in system stability

At the same time, the ability of the single-loop structure to suppress idle noise is not high, and the amplitude of the input signal is also limited, thereby reducing the performance of the single-loop structure ΣΔΜ digital closed-loop control circuit of the micromechanical accelerometer

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