Touch Display Device Driving Sequence for Sensing Accuracy
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Solution Overview
Problem
Capacitive touch display devices face challenges in maintaining touch sensing accuracy and sensitivity due to interference from pixel voltages during display periods and limited touch sensing frequency during blank periods, which affects the design of the driving sequence between the display and touch panels.
Innovation Solution
A method and device that periodically reduce the output period of pixel voltages to establish a touch sensing period, allowing the touch sensing circuit to perform multiple touch sensing actions in a time-sharing manner with the display driving circuit, thereby avoiding data disturbance and enhancing touch sensitivity without compromising accuracy or display quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If touch sensing is performed during the display period when data is written to the display panel, then touch sensing frequency is improved, but touch sensing accuracy deteriorates due to disturbance from pixel voltages
Solution Approach 1:
The display period is segmented into multiple sub-periods, with specific periods designated for touch sensing operations. The source output signal is divided into enable periods and non-enable periods, allowing touch sensing to occur during non-enable periods when pixel voltages are stable, thus avoiding interference while maintaining high sensing frequency
Solution Approach 2:
Touch sensing is performed periodically during specific non-enable periods of the source output signal. The system alternates between display updating periods and touch sensing periods in a regular pattern, ensuring both display quality and touch sensitivity are maintained without mutual interference
2Measurement precision
If touch sensing is performed only during blank periods when no data is written to the display screen, then touch sensing accuracy is improved, but touch sensing frequency is limited to refresh frequency
Solution Approach 1:
The blank period is segmented into multiple touch sensing opportunities. Instead of performing one touch sensing operation per frame, the system divides the blank period into multiple sub-periods where touch sensing can be performed sequentially, increasing the touch sensing frequency beyond the display refresh frequency
Solution Approach 2:
Touch sensing operations are scheduled in advance during the non-enable periods of the source output signal. The system proactively allocates specific time slots for touch sensing before the enable period begins, ensuring that touch data is collected at high frequency without interfering with the subsequent display data writing process
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 enhances touch sensitivity by preventing data disturbance from pixel voltages and increases touch sensing data refresh rate beyond the frame per second limit, while maintaining smooth image display and accurate touch detection.
Implementation Method 1
The capacitive touch display device detects the position of the touch point by detecting a capacitance variation of a touch panel
Data Source
AI summary
A touch display device and a method for driving the same are provided. The touch display device includes a display panel and a touch panel. In the method, the touch display device provides a source output signal and outputs a plurality of pixel voltages during an enable period of the source output signal to drive the display panel. The touch display device periodically reduces the enable period of the source output signal according to a horizontal synchronization signal corresponding to a turned-on sequence of each row of pixels, so as to establish a touch sensing period. Based thereon, the touch sensing circuit scans the touch panel during the touch sensing period that does not overlap with the enable period of the source output signal, so as to obtain sensing signals for accurately indicating electrical variations of the touch panel.