Touch Panel Noise Reduction via Common Voltage Ripple Reversal

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Solution Overview

Problem

Touch panels coupled with liquid crystal panels experience noise interference due to common voltage ripples, leading to a lower signal-to-noise ratio in sensing signals.

Innovation Solution

A reverse circuit is used to receive and reverse common voltage ripples from the liquid crystal panel, outputting these reversed ripples to the touch sensor to cancel out noise interference, thereby improving the signal-to-noise ratio of sensing signals.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the touch sensor is coupled to the liquid crystal panel, then the touch panel can perform integrated sensing and display functions, but common voltage ripples from the liquid crystal panel couple into the touch sensor and degrade the signal-to-noise ratio

Engineering Contradiction:

Improveintegrated sensing and display functionsVSAvoidsignal-to-noise ratio of sensing signal

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent introduces a common voltage ripple filter as an intermediary component between the liquid crystal panel and touch sensor. This filter receives the common voltage from the liquid crystal panel, filters out ripple components through its capacitive network, and provides a cleaned common voltage to the touch sensor, thereby preventing noise coupling while maintaining integrated functionality

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent extracts the harmful common voltage ripples from the combined system by using the filter to separate the ripple components from the useful common voltage signal. The filter selectively removes the high-frequency ripple noise while preserving the DC common voltage level needed for touch sensor operation

Inventive Principle:

Principle #2Taking out (Extraction)

2Reliability

If common voltage ripples are present in the liquid crystal panel, then the liquid crystal display can operate, but the ripples couple into the touch sensor and cause noise interference in sensing signals

Engineering Contradiction:

Improveliquid crystal display operationVSAvoidnoise interference in sensing signal

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent converts the harmful common voltage ripples into a benefit by using them to charge the filter capacitors during ripple peaks, then using the stored charge in capacitors to compensate during valley periods. This transforms the noisy ripple signal into a smoothed common voltage that benefits both the liquid crystal display operation and touch sensor performance

Inventive Principle:

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

Solution Approach 2:

The filter capacitors are预先 configured in the circuit to cushion against incoming voltage ripples before they can couple into the touch sensor. The capacitors act as energy reservoirs that absorb voltage spikes and provide steady voltage during dips, preventing noise interference in advance

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Data Source

PatentUS8508503B2Touch panel and method of reducing noise coupled by a common voltage of a touch panel

Publication Date: 2013.08.13 AU OPTRONICS CORP

AI summary

A touch panel includes a touch sensor, a liquid crystal panel, and a reverse circuit. The reverse circuit receives common voltage ripples of the liquid crystal panel, and outputs reversed common voltage ripples after reversing the common voltage ripples. After the touch sensor receives the reversed common voltage ripples, the touch sensor outputs a sensing signal according to the reversed common voltage ripples.