Display Device Touch Sensor Integrated Driving Circuit Voltage Ripple
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Solution Overview
Problem
Display devices, such as LCDs and OLEDs, face challenges in enhancing touch sensitivity and compensating for voltage ripples, which affect image definition and lead to issues like color mixture and horizontal block dimming.
Innovation Solution
A display device with a touch sensor incorporating an integrated driving circuit, common voltage ring line, and common voltage feedback line, which outputs different forms of common voltage for display and touch operations, and includes a compensation circuit to mitigate voltage ripples.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single common voltage line is used for both display and touch operations, then device complexity is reduced, but voltage ripples occur during touch driving that degrade display definition
Solution Approach 1:
The common voltage line is segmented into two separate lines: a first common voltage line for providing common voltage during display driving, and a second common voltage line for providing common voltage during touch sensing. This segmentation prevents voltage ripples from touch operations from affecting display quality while maintaining relatively simple device architecture.
2Reliability
If common voltage is continuously provided during touch driving, then touch sensitivity is maintained, but voltage ripples on the display panel increase and degrade image quality
Solution Approach 1:
The system alternates between display driving mode and touch sensing mode in periodic time-division multiplexing. During touch sensing periods, the first common voltage line is disconnected and the second common voltage line is activated. This periodic switching ensures touch sensitivity is maintained while preventing display-degrading voltage ripples from occurring during touch operations.
3Manufacturing precision
If the common voltage line is disconnected during touch driving, then voltage ripples are eliminated, but touch sensitivity in peripheral areas deteriorates
Solution Approach 1:
The common voltage provision is segmented into two independent pathways: the first common voltage line remains connected to the display panel during touch operations to maintain display stability, while the second common voltage line is activated specifically for touch sensing operations. This dual-line segmentation ensures both display definition and peripheral touch sensitivity are maintained simultaneously.
4Manufacturing precision
If separate common voltage lines are used for display and touch operations, then voltage ripple interference is eliminated, but device complexity and manufacturing cost increase
Solution Approach 1:
The common voltage lines are segmented at strategic locations within the display panel structure, allowing independent control during display and touch operations. This segmentation eliminates voltage ripple interference while keeping the overall device complexity manageable through integrated circuit design and compact line routing.
Solution Approach 2:
Different regions of the display panel are assigned different common voltage line connections: the first common voltage line serves the display area, while the second common voltage line serves the touch sensing area. This local quality differentiation allows separate voltage control for display and touch functions, eliminating interference while maintaining reasonable device complexity.
Data Source
AI summary
A display device is disclosed that has a touch sensor, which includes a display panel, an integrated driving circuit, a common voltage ring line, and a common voltage feedback line. The integrated driving circuit outputs a touch driving signal and a display common voltage for respectively driving a touchscreen and the display panel. The integrated driving circuit outputs the display common voltage through a common voltage ring pad in a period in which the display panel is driven and outputs a load-free common voltage having a form different from that of the display common voltage through the common voltage ring pad in a period in which the touchscreen is driven.