Force Sensor Offset Compensation Circuit for Small-Signal Detection
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Solution Overview
Problem
Force sensors used as user input devices in electronic devices face challenges due to offset voltages and noise in their output signals, which can mask the desired sensor output, especially when the wanted signal is very small compared to the offset voltage, making it difficult to detect and process accurately.
Innovation Solution
A compensation circuit is introduced that includes voltage divider circuitry, current generator circuitry, and amplifier circuitry to generate a compensating current that cancels out the offset voltage, using adjustable resistances to match the component mismatch ratios of the force sensor, thereby producing a compensated differential output signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If force sensors are used as user input devices, then mechanical wear and susceptibility to damage are reduced, but offset voltage and noise in the output signal increase, making it difficult to detect small signals
Solution Approach 1:
The patent converts the harmful offset voltage into a useful calibration reference. By measuring the offset voltage when no force is applied and using it to adjust the sensor's zero-point, the previously harmful offset becomes a beneficial calibration mechanism that improves measurement precision while maintaining the sensor's mechanical reliability
Solution Approach 2:
The patent applies parameter changes by adjusting the electrical parameters (voltage offsets, gain factors) of the sensor system through digital calibration. The calibration process modifies the output signal parameters to compensate for the inherent offset voltage, enabling accurate detection of small force signals while preserving the sensor's mechanical advantages
2Measurement precision
If the component mismatch ratio of the voltage divider circuitry is made adjustable to correspond to the force sensor, then compensation accuracy is improved, but device complexity increases
Solution Approach 1:
The patent implements dynamics by making the voltage divider circuitry adjustable rather than fixed. The ability to change the component mismatch ratio dynamically allows the circuit to adapt to different sensor configurations and calibration requirements, improving compensation accuracy while the adjustability is implemented through practical circuit design choices that balance complexity and performance
Data Source
AI summary
The present disclosure relates to a compensation circuit for compensating for an offset voltage that is present in an output signal output by a force sensor. The compensation circuit comprises: voltage divider circuitry, the voltage divider circuitry configured to receive a bias voltage that is also supplied to the force sensor and to output a control voltage derived from the bias voltage, wherein a component mismatch ratio of the voltage divider circuitry is adjustable to correspond to a component mismatch ratio of the force sensor; current generator circuitry configured to receive the control voltage and to generate a compensating current based on the received control voltage; and amplifier circuitry configured to receive the differential signal output by the force sensor and the compensating current and to output a compensated differential output signal in which the offset voltage is at least partially cancelled.