In-Cell Touch Data Driving Circuit Parasitic Capacitance
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Solution Overview
Problem
In-cell touch sensors embedded in display panels experience increased parasitic capacitance due to coupling with pixels, leading to deteriorated touch sensitivity and recognition accuracy, and existing solutions that reduce parasitic capacitance by adding switch elements increase the size and cost of data drive ICs.
Innovation Solution
A timing controller generates sync signals to alternate touch sensor driving periods and display driving periods, using a data driving circuit with switches to couple output buffers to signal lines during specific phases and a charge share period, and supplies AC signals to data lines during touch sensor driving periods to minimize parasitic capacitance without increasing IC chip size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If AC voltage is supplied to data lines during touch sensor driving period, then parasitic capacitance of touch sensor is reduced, but device complexity increases due to additional switch elements
Solution Approach 1:
The data driving circuit is designed to perform dual functions: driving display pixels during display periods and driving touch sensors during touch periods. The same output buffers and switch elements are reused for both purposes, eliminating the need for separate dedicated touch sensor driving circuits and reducing overall IC complexity despite the added functionality
Solution Approach 2:
The circuit dynamically switches between two operational modes (display driving and touch sensing) using time-division multiplexing. Switch elements selectively connect output buffers to either pixel electrodes or touch sensor electrodes based on the current period type, allowing the system to adapt its configuration in real-time without requiring permanent dedicated pathways for each function
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 and recognition accuracy while maintaining a compact IC size by reducing parasitic capacitance through efficient timing control and signal phase management.
Implementation Method 1
Parasitic capacitance connected to the in-cell touch sensors is increased due to coupling between the in-cell touch sensors and the pixels
Data Source
AI summary
A touch display device includes a timing controller to generate a sync signal for controlling timing of a touch sensor driving period and a display driving period, where the display driving period comprises a first phase to drive odd signal lines according to a first polarity and to drive even signal lines according to a second polarity, a second phase to drive the odd signal lines according to the second polarity and to drive the even signal lines according to the first polarity, and a charge share period between the first phase and the second phase. A set of charge sharing switches couple the odd and even signal lines together during the charge share period and couple the odd and even signal lines together during the touch sensor driving period.