Force Sensor Compensation Circuit for Offset and Noise Cancellation

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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 and complicate signal processing.

Innovation Solution

A compensation circuit is introduced, comprising voltage divider circuitry, current generator circuitry, and amplifier circuitry, which adjusts to match the component mismatch ratio of the force sensor. This circuit generates a compensating current to cancel out offset voltages and noise in the force sensor's output signal.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If force sensors are used as user input devices, then mechanical wear and susceptibility to damage are reduced, but offset voltages and noise in the output signal increase, masking the desired sensor output

Engineering Contradiction:

Improveresistance to damage and mechanical wearVSAvoidsignal accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent converts the harmful offset voltage and noise signals into a beneficial compensation mechanism. By detecting the offset voltage present when no force is applied, the system generates a compensating signal that is subtracted from subsequent measurements, thereby eliminating the harmful effect of offset and noise while preserving the useful force detection capability

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent introduces an intermediary compensation circuit between the force sensor and the measurement system. This intermediary component processes the sensor output by generating and applying a compensating signal that counteracts the offset voltage and noise, allowing the useful force signal to be extracted accurately without being masked by the harmful components

Inventive Principle:

Principle #24Intermediary (Mediator)

2Volume of moving object

If force sensors are used instead of mechanical switches, then device size is reduced, but signal processing complexity increases due to offset compensation requirements

Engineering Contradiction:

Improvedevice sizeVSAvoidsignal processing complexity

Core Design Contradiction:

Volume of moving objectVSDevice complexity

Solution Approach 1:

The patent implements a self-service compensation mechanism where the force sensor system automatically performs offset compensation without requiring external calibration or complex processing. The system uses its own output signals to generate the compensating voltage, thereby eliminating the need for additional complex circuitry or software processing while maintaining accurate force measurement

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS20250047293A1Force sensing systems

Publication Date: 2025.02.06 CIRRUS LOGIC INT SEMICON LTD

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.