MEMS Sensor Offset Cancellation With Dual-Mode Feedback Control
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Solution Overview
Problem
Micro-electromechanical system (MEMS) sensors introduce offsets that are not effectively removed by existing technologies, especially during startup and normal operation, affecting the accuracy of sensor readings.
Innovation Solution
A device and method utilizing an offset cancellation module with a digital-to-analog converter and a negative feedback system to dynamically adjust the gain and remove the offset introduced by MEMS sensors and associated analog reading circuitry, employing multiple operational modes to optimize offset removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a low-pass filter is used to remove offset, then the offset removal is achieved, but the response speed during startup operation is slow
Solution Approach 1:
The patent implements a dual-mode offset cancellation system that dynamically switches between startup mode and normal operation mode. During startup, the system operates in startup mode with offset cancellation enabled to quickly remove offset. Once startup is complete, it transitions to normal operation mode where the offset cancellation is disabled to preserve fast response. This dynamic switching resolves the contradiction by providing fast offset removal when needed while maintaining fast response speed during normal operation.
2Measurement precision
If offset cancellation is applied during normal operation, then offset removal accuracy is improved, but the system complexity increases
Solution Approach 1:
The patent segments the offset cancellation function into distinct operational modes (startup mode and normal operation mode) that are selectively activated. The system includes a startup detector that monitors operation state and controls the activation of offset cancellation. This segmentation allows the complex offset cancellation functionality to be applied only when necessary (during startup), thereby improving offset removal accuracy without permanently increasing system complexity during normal operation.
Solution Approach 2:
The system dynamically adjusts its complexity by enabling or disabling the offset cancellation path based on operational state. The startup detector and mode controller dynamically switch the system between having offset cancellation active (startup mode) and inactive (normal operation mode). This dynamic approach allows the system to maintain high measurement precision during startup while keeping the system simple and responsive during normal operation.
3Measurement precision
If gain is adjusted to counteract offset, then offset removal is achieved, but the stability of the reading circuitry may be affected
Solution Approach 1:
The patent applies preliminary anti-action by implementing offset cancellation during the startup phase before normal operation begins. The system proactively removes offset during startup when the system is still initializing, preventing offset from affecting normal operation. By addressing the offset issue preliminarily during startup, the system avoids the need for continuous gain adjustment during normal operation, thereby maintaining circuit stability while achieving accurate offset removal.
Solution Approach 2:
The system performs preliminary offset cancellation action during startup operation before transitioning to normal operation. The startup detector identifies when the system is in startup state and activates offset cancellation accordingly. This preliminary action ensures that offset is removed before normal measurement begins, achieving high measurement precision without requiring continuous intervention that could destabilize the circuit during normal operation.
Data Source
AI summary
The present disclosure is directed to a system that includes a sensor and a signal conditioner coupled to the sensor. The signal conditioner includes signal processing circuitry coupled to the sensor and offset cancellation circuitry. The offset cancellation circuitry includes a sign detector configured to output a high signal or a low signal based on a sign of an output signal from the signal processing circuitry, an integrator coupled to the sign detector, and a divider coupled to the integrator and to an input of the signal processing circuitry.