In-cell Touch Display Gate Potential Leakage Control
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Solution Overview
Problem
In-cell touch display devices face a striped pattern issue due to leakage along transistors in the shift register, causing the gate potential and gate pulse to be lower than the preset level during touch sensing periods, which affects the display quality.
Innovation Solution
A control circuit is used to define separate gate line driving periods and touch sensing periods within a frame, where the backlight module is turned off during touch sensing periods, minimizing leakage current and maintaining the gate potential level of the driving transistor in the shift register.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If touch sensing period is inserted in each frame period, then touch sensing function is improved, but gate potential level drops due to leakage current
Solution Approach 1:
The frame period is segmented into distinct gate line driving periods and touch sensing periods. During gate line driving periods, the backlight is turned on for normal display operation. During touch sensing periods, the backlight is turned off to minimize leakage current while touch sensing continues. This temporal segmentation allows both display function and touch sensing function to coexist without mutual interference.
Solution Approach 2:
The system employs periodic switching between gate line driving periods and touch sensing periods within each frame period. This periodic action allows the gate potential to be refreshed during gate line driving periods when the backlight is on, and enables touch sensing during touch sensing periods when the backlight is off, creating a rhythmic operation pattern that maintains both display quality and touch sensitivity.
2Reliability
If backlight module is turned off during touch sensing period, then leakage current is reduced, but display continuity is interrupted
Solution Approach 1:
The display frame is segmented into multiple scanlines that are driven sequentially during gate line driving periods. When the backlight is turned off for touch sensing, only the current scanline or a small portion of the display is temporarily affected. The remaining scanlines continue to be driven and maintained during subsequent gate line driving periods, ensuring overall display continuity is preserved despite periodic backlight interruptions.
Solution Approach 2:
The backlight is turned off only during specific touch sensing periods rather than continuously, and only for the duration necessary to perform touch sensing. This partial action approach minimizes the impact on display continuity while achieving the goal of reducing leakage current. The gate line driving circuit continues to operate during these periods to maintain display content, compensating for the backlight interruption.
Data Source
AI summary
An in-cell touch display device includes an in-cell touch panel, a backlight module driving circuit, a backlight module, a gate driving circuit, a touch processing circuit and a control circuit. The in-cell touch panel includes a plurality of gate lines and a plurality of touch sensing units. The control circuit is used for defining a plurality of gate line driving periods separated from each other in the time and at least one touch sensing period in a frame period. The touch sensing period is between two adjacent gate line driving periods. During the gate line driving periods, the control circuit controls the gate driving circuit to drive the gate lines sequentially and outputs a signal to the backlight module driving circuit to turn on the backlight module. During each touch sensing period, the control circuit controls the touch processing circuit to output a driving signal to the touch sensing units and outputs a signal to the backlight module driving circuit to turn off the backlight module.