Force Sensor Noise Reduction via Wheatstone Bridge Segmentation
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Solution Overview
Problem
Force detection signals in force sensors for display panels are often affected by noise from peripheral circuits, leading to reduced accuracy in force detection.
Innovation Solution
A force sensor design incorporating a Wheatstone bridge configuration with transistors and resistors, where the equivalent resistance of specific transistors is matched to minimize noise interference, and a time-division switching method is employed to enhance signal accuracy by calculating force detection values from differences in output voltages during distinct detection periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a force sensor is integrated into a display panel to enable force touch detection, then force detection capability is improved, but noise from peripheral circuits couples with the detection signal and reduces measurement precision
Solution Approach 1:
The force sensor circuit is segmented into four distinct transistor components (first, second, third, and fourth transistors) arranged in a bridge configuration. This segmentation allows differential measurement where the output signal represents the difference between opposing transistor pairs, effectively canceling out common-mode noise from peripheral circuits while preserving the force detection capability.
2Difficulty of detecting and measuring
If transistors are used in the force sensor circuit to detect force magnitude, then force detection sensitivity is improved, but noise coupling with peripheral circuits increases and affects signal accuracy
Solution Approach 1:
The circuit implements a differential feedback mechanism where the output signal is derived from the voltage difference between two transistor pairs. This feedback arrangement automatically compensates for noise introduced by peripheral circuits, as the noise appears equally on both sides of the differential measurement and is thereby rejected, maintaining high signal accuracy despite increased sensitivity.
3Measurement precision
If a Wheatstone bridge configuration with multiple transistors is used, then noise rejection is improved, but device complexity increases
Solution Approach 1:
The force sensor circuit merges multiple transistor components into a unified bridge configuration where the first and second transistors form one branch and the third and fourth transistors form another branch. This merging approach achieves noise rejection through differential measurement while consolidating the circuit structure, reducing the need for separate noise filtering components and thereby managing overall device complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively reduces noise influence and improves the accuracy of force detection signals by leveraging the differential resistance changes in transistors under external forces, thereby enhancing the precision of force measurement in display panels.
Implementation Method 1
leveraging the differential resistance changes in transistors under external forces
Data Source
AI summary
The present disclosure provides a force sensor, a display panel, and a force detection method. The force sensor includes a first input terminal, a second input terminal, a first output terminal, and a second output terminal. A first resistor is connected between the first input terminal and the first output terminal. A first transistor and a second transistor are connected in parallel between the first output terminal and the second input terminal. A third transistor and a fourth transistor are connected in parallel between the second input terminal and the second output terminal. A further first resistor is connected between the second output terminal and the first input terminal. An equivalent resistance of the first transistor is equal to that of the fourth transistor, and an equivalent resistance of the second transistor is equal to that of the third transistor.