Touch Sensing Device Double Feeding Voltage Uniformity
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Solution Overview
Problem
Conventional in-cell touch sensor technology on large-screen display devices experiences non-uniform common voltage distribution due to varying sensor line lengths, leading to picture quality degradation, reduced touch sensitivity, and recognition accuracy.
Innovation Solution
A touch sensing device with a double feeding mechanism that connects sensor lines at both ends during the display driving period to ensure uniform common voltage distribution and isolates them during the touch sensor driving period, applying an AC signal with the same phase as the touch driving signal to minimize parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the common electrode is divided into sections for touch sensors, then touch sensor functionality is enabled, but common voltage becomes non-uniform on large screens leading to picture quality degradation
Solution Approach 1:
The sensor lines are divided into multiple segments with independent control. Each segment can be independently connected or disconnected from the common voltage source, allowing differential voltage application to different regions of the display to compensate for RC delay variations across the screen.
Solution Approach 2:
Different voltage levels are applied to different regions of the display based on their specific RC delay characteristics. The controller adjusts the common voltage level for each sensor line segment according to its position and electrical characteristics, achieving local optimization of voltage uniformity.
2Area of stationary object
If sensor lines are made longer to cover large screen areas, then touch coverage is improved, but RC delay increases causing non-uniform voltage distribution
Solution Approach 1:
Long sensor lines are divided into multiple shorter segments that can be independently controlled. This segmentation reduces the RC delay within each segment while maintaining overall coverage, allowing each segment to be optimized for its specific length and position.
Solution Approach 2:
The system pre-calculates and stores RC delay compensation values for different sensor line segments based on their positions and lengths. During operation, the controller automatically applies the appropriate compensation voltage to each segment without real-time calculation, ensuring uniform voltage distribution across the entire large screen.
3Length of stationary object
If in-cell touch sensors are used to maintain display thickness, then display profile is maintained, but parasitic capacitance increases reducing touch sensitivity
Solution Approach 1:
The system uses periodic AC signaling for touch sensing rather than DC levels. By using AC signals at specific frequencies and measuring capacitive coupling effects, the system can detect touch events despite the presence of parasitic capacitance from the in-cell sensor structure, maintaining both thin profile and touch sensitivity.
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 ensures uniform common voltage across the display device, enhancing picture quality, touch sensitivity, and recognition accuracy on large-screen displays by reducing parasitic capacitance and RC delay variations.
Implementation Method 1
a first feeding unit that supplies a common voltage to a first end of the sensor lines during a display driving period of the touch sensing device and supplies a touch driving signal to the first end of the sensor lines during a touch sensor driving period
Implementation Method 2
The touch sensors are connected to pixels through parasitic capacitance
Implementation Method 3
The differences in length between the sensors lines L1 to L4 cause variations in the delay time of the common voltage Vcom applied to the sensor C1 to C4 with the touch sensor positions, resulting in non-uniform picture quality. Due to the RC delay, the delay time of the sensor driving signal Tdrv also varies depending on the touch sensor positions.
Implementation Method 4
The sensing circuit senses a touch input by measuring a change in capacitance
Data Source
AI summary
A touch sensing device and a driving method thereof are provided. The driving method comprises short-circuiting touch sensors by connecting sensor lines to supply a common voltage to the sensor lines through one end and the other end of the sensor lines during a display driving period.