Touch Driver IC Voltage Stabilization for In-Cell Displays
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Solution Overview
Problem
In touch display devices, the combination of touch panels and display panels leads to issues related to driving manner, resulting in reduced reliability and performance, particularly due to the time required to set up touch electrodes to a common voltage, which can cause defects like horizontal line defects during image display.
Innovation Solution
A touch display driving integrated circuit (IC) is developed, which includes a touch driver IC connected to touch electrodes through touch sensing lines, providing a sensing signal during touch periods and applying a common voltage to some touch electrodes while applying a different voltage to others, allowing for reduced settling time and normal image output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a common voltage is applied to all touch electrodes during the display period, then the touch electrodes stabilize at a uniform voltage level, but the settling time increases causing horizontal line defects in image display
Solution Approach 1:
The touch electrodes are divided into multiple groups, with each group connected to a separate touch sensing line. During the display period, different voltage levels are applied to different groups simultaneously, allowing parallel voltage stabilization across all electrodes without requiring sequential charging, thus reducing overall settling time while maintaining voltage stability.
Solution Approach 2:
During the touch scan period, the touch sensing lines are pre-charged to appropriate voltage levels before the display period begins. This preliminary charging action ensures that when the display period starts, the touch electrodes are already close to their target voltage levels, minimizing the additional settling time required during image display.
2Area of stationary object
If the touch panel and display panel are combined into an in-cell touch display device, then the area occupied by the device is reduced, but driving complexity increases causing reliability issues
Solution Approach 1:
The touch driver IC is designed to perform multiple functions: during the touch scan period, it operates as a touch sensing driver to detect touch input, and during the display period, it automatically switches to operating as a display driver to maintain proper voltage levels on touch electrodes for image display. This multi-functional design eliminates the need for separate dedicated drivers, reducing overall device complexity while maintaining the in-cell integrated structure.
Solution Approach 2:
The touch driver IC dynamically switches its operating mode between touch scan and display driving based on the current time period. This dynamic operation allows the same hardware circuit to adapt to different functional requirements, simplifying the overall device architecture while ensuring proper driving control for both touch sensing and display functions in the integrated in-cell structure.
3Loss of time
If different voltage levels are applied to different touch sensing lines during the display period, then the settling time is reduced and horizontal line defects are prevented, but the driving control complexity increases
Solution Approach 1:
The system operates in periodic cycles with distinct touch scan periods and display periods. During each display period, the touch driver IC automatically applies different voltage levels to different touch sensing line groups according to a predetermined pattern. This periodic operation with built-in voltage differentiation is controlled through timing signals, achieving fast settling times while managing control complexity through systematic periodic control rather than continuous complex management.
Data Source
AI summary
A touch display driving integrated circuit (IC) includes a touch driver IC and a source driver IC. The touch driver IC is to be connected to touch electrodes through touch sensing lines. The touch driver IC provides a sensing signal to first touch sensing lines among the touch sensing lines in a touch period, and applies a common voltage to the first touch sensing lines before the touch period is terminated. The source driver IC is to be connected to pixels through data lines.