Touch Display Noise Reduction via Auxiliary Drive Signals
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Solution Overview
Problem
Conventional display devices using self-cap driving methods for touch panels face performance degradation due to noise interference from the display panel, which affects touch sensing accuracy.
Innovation Solution
The implementation of auxiliary drive signals synchronized with touch drive signals on gate and data lines during the touch sensing period, along with auxiliary lines formed at opposite sides of the gate-off voltage supply line, to mimic and enhance the touch drive signal, thereby reducing noise interference and preventing signal delay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the touch electrode is used as a common electrode in the image display period, then the device complexity is reduced, but noise is generated in the display panel which degrades touch panel performance
Solution Approach 1:
The image display period is divided into multiple sub-periods with different common electrode voltage levels. During the touch sensing period, the common electrode voltage is set to a first voltage level, while during other periods it uses a second voltage level. This temporal segmentation allows the system to maintain dual functionality of the common electrode while minimizing noise interference with touch sensing.
2Reliability
If the touch drive signal is applied to the touch electrode, then touch sensing is enabled, but the square voltage waveform is influenced by noise from the display panel
Solution Approach 1:
The common electrode voltage parameter is dynamically changed based on the operating period. During touch sensing, the voltage is set to a first level that minimizes noise, while during image display it uses a second level optimized for display performance. This parameter adjustment resolves the conflict between touch sensing reliability and noise reduction.
3Object-affected harmful factors
If auxiliary drive signals are supplied to gate lines and data lines, then noise interference is reduced, but the device complexity increases
Solution Approach 1:
Auxiliary drive signals are supplied to gate lines and data lines before and during the touch sensing period to preemptively counteract noise interference. By preparing these compensating signals in advance and synchronizing them with the touch drive signal, the system reduces noise without requiring complex real-time processing, thus balancing noise reduction with device complexity.
Data Source
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AI summary
A touch display device comprises a controller (22) to generate a touch sync signal for controlling timing of a touch sensing period and a display period. A touch panel has a plurality of touch electrodes in a display area (AA) of the touch display device. The touch panel generates touch sensing signals indicating whether or not a touch occurs during the touch sensing period. A gate driver (20) supplies gate pulses to gate lines (GL) of the touch panel during the display period and supplies a gate line auxiliary drive signal (ATS1) from a first transfer line (VGLL) onto the gate lines during the touch sensing period that mimics a touch drive signal (TS). One or more auxiliary lines (AL) supply a supplemental auxiliary drive signal (ATS3) during the touch sensing period that mimics the touch drive signal.