Touch Driver Frequency Asymmetry for Display Image Quality
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Solution Overview
Problem
Display devices with integrated touch sensing units experience image quality distortions when both the display and touch sensing units are driven simultaneously, particularly during low-speed driving modes, due to interference in harmonic components.
Innovation Solution
The implementation of a display device with a touch driver that operates at a different frequency and timing than the display driver, specifically by adjusting the touch waiting periods and driving frequencies in various modes to minimize interference and maintain touch sensitivity while reducing image quality distortions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the display driver operates at a low frequency (low-speed driving mode), then power consumption is reduced, but image quality distortions occur due to interference with touch sensing operations
Solution Approach 1:
The touch driver operates in a low-speed driving mode with periodic touch sensing operations at a first frequency that is different from the display driving frequency. By periodically activating the touch sensing unit only during specific time periods when the display is not updating, the patent eliminates continuous interference between touch and display operations, thereby reducing image quality distortions while maintaining acceptable power consumption levels.
2Measurement precision
If the touch sensor is driven continuously at high frequency, then touch detection sensitivity is maintained, but image quality distortions increase due to simultaneous display operation
Solution Approach 1:
The touch driver performs touch sensing operations periodically rather than continuously. The touch sensing unit is activated only during specific time periods within each frame, allowing touch detection to occur at sufficient intervals to maintain sensitivity while avoiding continuous interference with display operations that causes image quality distortions.
Solution Approach 2:
The touch driver is configured to perform touch sensing operations during specific time periods before display updates occur. By anticipating and completing touch sensing tasks during designated time windows, the system ensures touch detection sensitivity is maintained while preventing interference with subsequent display operations.
3Device complexity
If the display driver and touch driver operate at the same frequency, then synchronization is simplified, but harmonic interference causes image quality distortions
Solution Approach 1:
The patent deliberately creates an asymmetric frequency relationship between the touch driver and display driver, where the touch driver operates at a first frequency that is explicitly different from the display driving frequency. This frequency asymmetry breaks the harmonic relationship that would otherwise cause interference patterns, eliminating image quality distortions while the synchronization mechanism remains manageable through dedicated control logic.
Data Source
AI summary
A display device includes a touch sensor, a touch driver, and display driver. The touch driver drives the touch sensor at a first frequency, provides touch driving signals to touch electrodes during a touch sensing period of a touch frame period, and stops providing the touch driving signals during a touch waiting period of the touch frame period. The display drivers drives a display panel at a second frequency lower than the first frequency in a first mode, provides scan signals to pixels during a display period of a display frame period, and stops providing the scan signals during a display waiting period of the display frame period. When the display driver switches from the first mode to a second mode, the display driver drives the display at a third frequency lower than the second frequency, and the touch driver increases the touch waiting period of the touch frame period.