Touch IC Time-Division Driving for Display Crosstalk Compensation
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Solution Overview
Problem
Current display devices with integrated touch screens face limitations in achieving a touch report rate equal to or higher than the display frame rate, which restricts the performance and accuracy of touch input detection, particularly when significant changes in display patterns occur, such as from black to white patterns, leading to display-to-touch crosstalk (DTX) issues.
Innovation Solution
The solution involves a display device with a panel that operates in time-division mode, dividing each frame into first and second display durations and corresponding touch durations, where a touch IC applies touch scan signals and a display driver IC transfers display information between these durations to compensate for touch sensitivity, effectively increasing the touch report rate by applying touch scan signals twice within one frame.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the display device uses a general driving scheme with one touch driving period per frame, then the device complexity is reduced, but the touch report rate cannot reach or exceed the display frame rate
Solution Approach 1:
The frame period is segmented into multiple touch driving periods (first touch driving period and second touch driving period) instead of using a single touch driving period. This segmentation allows the touch report rate to exceed the display frame rate by performing touch sensing operations multiple times within one frame period, thereby resolving the contradiction between increasing productivity and maintaining manageable device complexity.
2Productivity
If the display device increases the touch report rate above 60 Hz, then the touch screen performance is improved, but the general driving scheme cannot secure the necessary touch report rate
Solution Approach 1:
The driving scheme is made dynamic by adaptively adjusting the timing and number of touch driving periods based on display patterns. When display patterns change (which can cause DTX), the system performs touch driving multiple times per frame to maintain accurate touch detection. This dynamic approach ensures high touch report rates (improving reliability of touch performance) while only increasing complexity when necessary.
3Productivity
If the display device performs touch driving multiple times per frame, then the touch report rate increases above display frame rate, but the device complexity increases
Solution Approach 1:
Display information from the current frame is transferred to the touch IC in advance during the display driving period, before the touch driving period begins. This preliminary action allows the touch IC to have the necessary display information ready for compensation calculations, enabling multiple touch driving periods per frame without proportionally increasing overall system complexity, as the data preparation is done beforehand.
4Measurement precision
If the display device uses DTX compensation based on lookup table, then the display-to-touch crosstalk is compensated, but the touch report rate cannot equal or exceed the display frame rate
Solution Approach 1:
The system implements a feedback mechanism where touch raw data is compensated using display information that is transferred in advance. The compensation process uses the transferred display information to calculate correction values that are applied to touch raw data, creating a closed-loop system that continuously refines touch detection accuracy. This feedback approach enables both high measurement precision and high productivity by allowing multiple compensation cycles per frame.
Data Source
AI summary
The display device with integrated touch screen includes a panel configured to time-division operate during first and second display durations and first and second touch durations at every frame, a touch IC configured to apply a touch scan signal to a plurality of electrodes to allow the panel to perform touch driving during the first and second touch durations, and a display driver IC configured to, when the first touch duration of an n+1st frame is started, transfer display information about the second display duration of an nth frame and display information about the first display duration of the n+1st frame to the touch IC, and when the second touch duration of the n+1st frame is started, transfer display information about the first display duration of the n+1st frame and display information about the second display duration of the n+1st frame to the touch IC.