Touch Sensor Differential Electrode Structure for Display Noise Rejection
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Solution Overview
Problem
Touch sensors in display devices face reduced sensitivity due to noise interference from the display panel, particularly from parasitic capacitance and common mode noise, which affects the accuracy and reliability of touch input detection.
Innovation Solution
The implementation of a touch sensor design that includes a substrate with first, second, and third electrodes, along with a sensing circuit featuring signal receivers and a gain regulator, where the third electrodes are electrically connected to the signal receivers and share a common wiring line, effectively canceling common mode noise and improving signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a touch sensor is integrated with a display panel, then the overall device structure is simplified and manufacturing efficiency is improved, but noise interference from the display panel reduces touch detection sensitivity
Solution Approach 1:
The touch sensor electrodes are segmented into multiple groups (first, second, and third electrodes) with different functions. The first and second electrodes form sensing capacitors for touch detection, while the third electrodes are specifically dedicated to noise detection and cancellation, separating the sensing function from the noise cancellation function to improve measurement precision while maintaining integration benefits
Solution Approach 2:
The third electrodes act as intermediary elements that detect common mode noise from the display panel and provide reference signals to the differential amplifier. This intermediary structure enables the system to cancel noise without requiring physical separation of the touch sensor from the display panel, thus maintaining manufacturing efficiency while improving touch detection sensitivity
2Measurement precision
If third electrodes are added for noise cancellation, then signal-to-noise ratio is improved and touch detection accuracy is enhanced, but device complexity increases
Solution Approach 1:
The third electrodes are merged with the existing electrode structure by using the same conductive material and formation process as the first and second electrodes. The differential amplifier circuit merges the sensing signals from multiple electrodes and automatically cancels common mode noise through its inherent differential operation, reducing the need for additional complex noise cancellation circuitry
Solution Approach 2:
The third electrodes serve multiple functions: they detect common mode noise, provide reference signals for differential amplification, and can be used for both capacitive and resistive touch sensing. This multi-functionality reduces device complexity by eliminating the need for separate noise detection and touch sensing systems
3Measurement precision
If differential amplification with reference terminals is used, then common mode noise is canceled and sensitivity is improved, but manufacturing precision requirements increase
Solution Approach 1:
The third electrodes are positioned to maintain equipotential relationships with the first and second electrodes during normal operation. By designing the electrode layouts and spacing to create symmetric capacitive coupling, the system achieves common mode noise cancellation through equipotential balancing, reducing sensitivity to manufacturing alignment variations
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 design enhances the sensitivity and accuracy of touch input detection by reducing noise interference, thereby improving the overall performance of the touch sensor and display device.
Implementation Method 1
noise interference from the display panel, particularly from parasitic capacitance and common mode noise
Implementation Method 2
the third electrodes are electrically connected to the signal receivers and share a common wiring line, effectively canceling common mode noise and improving signal-to-noise ratio
Data Source
AI summary
A touch sensor including a substrate including an active area and a non-active area, a plurality of first electrodes extending in first direction on the active area, a plurality of second electrodes extending in a second direction crossing the first direction on the active area, a plurality of third electrodes including electrode portions disposed in the first electrodes, respectively, being separated from the first electrodes, and extending in the first direction on the active area, and a sensing circuit including a plurality of signal receivers receiving sensing signals from the first electrodes, respectively, in which each of the signal receivers includes first and second input terminals connected to a pair of first and third electrodes corresponding to each other, respectively, and outputs a signal corresponding to a voltage difference between the first and second input terminals.