Bias-Derived Offset Compensation in Force Sensor Amplifier Circuits
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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 effectively.
Innovation Solution
A compensation circuit is introduced that includes voltage divider circuitry, current generator circuitry, and amplifier circuitry to adjust and cancel out offset voltages in the force sensor output signals. This circuitry generates a compensating current based on a control voltage derived from the bias voltage, which is injected into the amplifier to partially cancel the offset voltage, ensuring accurate detection of the desired sensor output.
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 the desired sensor output
Solution Approach 1:
A compensation circuit is introduced as an intermediary between the force sensor and the signal processing system. This circuit includes a voltage divider network that generates a compensation signal proportional to the bias voltage, which is then subtracted from the sensor output to eliminate offset voltage. The compensation circuit acts as a mediator that removes the harmful offset component while preserving the desired sensor signal.
Solution Approach 2:
The compensation circuit uses feedback from the bias voltage to generate a compensation signal. The voltage divider network samples the bias voltage and produces a proportional compensation voltage that is fed back to cancel the offset. This feedback mechanism ensures that the compensation adapts to variations in the bias voltage, maintaining measurement precision under different operating conditions.
2Measurement precision
If the wanted signal is very small compared to the offset voltage, then the force sensor can detect subtle inputs, but the offset voltage masks the desired output signal, making it difficult to process
Solution Approach 1:
The compensation circuit converts the harmful offset voltage into a beneficial compensation signal. By sampling the bias voltage through the voltage divider network and generating a proportional compensation voltage, the circuit transforms the offset problem into a solvable equation. The compensation voltage is subtracted from the sensor output, effectively removing the offset and revealing the subtle desired signal that was previously masked.
3Volume of moving object
If traditional mechanical switches are replaced with force sensors, then device size is reduced and space is saved, but the complexity of signal processing increases due to offset compensation requirements
Solution Approach 1:
The compensation circuit is merged with the force sensor into a single integrated unit. The voltage divider network, compensation voltage generation, and subtraction circuitry are combined with the sensor element, forming a unified force sensing assembly. This integration reduces the overall system complexity by eliminating separate compensation components and simplifies the signal processing architecture.
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.