Capacitive Sensor Readout Circuit With Offset-Canceling Feedback
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Solution Overview
Problem
Capacitive differential sensor readout circuits face significant noise and power consumption challenges due to offsets in capacitance-to-voltage converters, which affect the overall performance of MEMS gyroscope sensors.
Innovation Solution
A readout circuit with a feedback circuit including a sampling unit and a filter unit is introduced to generate and feed back an averaged differential signal, reducing or neutralizing DC voltage offsets in the capacitance-to-voltage converter, and a common-mode voltage signal is superposed to maintain optimal operating conditions, thereby reducing noise and improving efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a capacitance-to-voltage converter is used in the readout circuit, then the sensor can convert capacitive output signals to voltage signals, but DC voltage offsets are introduced that increase noise and reduce measurement precision
Solution Approach 1:
The patent implements a feedback circuit that samples the output signal from the capacitance-to-voltage converter, processes it through a filter unit to extract the DC offset component, and feeds it back to cancel the offset. This closed-loop feedback mechanism continuously compensates for the DC voltage offset, reducing noise and improving measurement precision without sacrificing the converter's signal transformation capability
Solution Approach 2:
The feedback circuit includes a sampling unit and filter unit that extract the DC offset component from the converter's output signal. By separating and removing the harmful DC offset component while preserving the useful AC signal component, the circuit eliminates the noise source without affecting the main signal transformation function
2Measurement precision
If the readout circuit includes additional feedback components (sampling unit and filter unit), then DC voltage offsets are reduced, but the device complexity increases
Solution Approach 1:
The feedback circuit is integrated with the capacitance-to-voltage converter in a unified readout circuit architecture. The sampling unit, filter unit, and feedback path are merged into the existing converter structure, sharing common components and signal paths where possible, thereby reducing the overall complexity increase while achieving offset compensation
Data Source
AI summary
A readout circuit for a capacitive differential sensor including periodic output signals. The readout circuit includes: one capacitance-to-voltage converter for output signals of the sensor; and one feedback circuit including a sampling unit and a filter unit, the sampling unit being configured to sample a differential signal of two oppositely-phased output signals of the capacitance-to-voltage converter and to generate a sampled differential signal, the filter unit being configured to average the sampled differential signals and to generate an averaged differential signal, and the feedback circuit being configured to feed the averaged differential signal as feedback into the capacitance-to-voltage converter. A sensor system including a readout circuit is also described.