In-Cell Touch Sensor Common Voltage Compensation
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Solution Overview
Problem
In-cell touch sensor technology for large-screen display devices suffers from non-uniform common voltage application due to RC delay variations, leading to picture quality deterioration and reduced touch sensitivity and recognition accuracy, as the common voltage varies across the screen, causing luminance issues and horizontal lines.
Innovation Solution
A touch sensing device with a feedback voltage transmitter and common voltage compensator, utilizing a feedback line, switching elements, and a feedback control line to compensate the common voltage to a reference level, ensuring uniform voltage application across the screen by connecting sensor lines to the feedback line and using a double feeding unit to reduce parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the common electrode is divided into sensor electrodes for touch sensing, then touch sensor functionality is achieved, but the common voltage becomes non-uniform across the screen causing picture quality deterioration
Solution Approach 1:
The common electrode is divided into multiple sensor electrodes (C1 to C4) that can function as both display common electrodes and touch sensing electrodes. This segmentation allows the system to achieve touch sensor functionality while maintaining the common voltage supply function, resolving the contradiction between versatility and voltage uniformity.
Solution Approach 2:
A feedback mechanism is implemented where the delay time of the common voltage applied to each sensor electrode is measured and used to generate compensation values. These compensation values are applied to adjust the common voltage timing for each electrode, ensuring uniform voltage application across the screen and improving picture quality.
2Adaptability or versatility
If sensor lines are made longer to reach distant sensor electrodes, then all electrodes can be connected, but RC delay increases causing non-uniform voltage application
Solution Approach 1:
Different compensation values are applied to different sensor electrodes based on their specific characteristics (line length, position). This local quality approach allows each electrode to receive appropriately timed voltage compensation, ensuring uniform voltage application across the entire screen despite varying line lengths.
Solution Approach 2:
The timing parameters of the common voltage applied to each sensor electrode are adjusted based on measured delay times. By changing the voltage application timing parameter for each electrode, the system compensates for RC delay variations caused by different line lengths, achieving uniform voltage application.
3Adaptability or versatility
If in-cell touch sensors are used in large-screen displays, then touch functionality is integrated, but parasitic capacitance increases reducing touch sensitivity and recognition accuracy
Solution Approach 1:
The touch sensing function is extracted and implemented using the divided common electrode segments as self-capacitance touch sensors. By utilizing the sensor electrodes' self-capacitance rather than relying on parasitic capacitance from pixel coupling, the system achieves touch functionality with improved sensitivity and recognition accuracy.
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
The solution effectively compensates for common voltage variations, improving picture quality and touch sensitivity by maintaining uniform voltage across the screen, reducing parasitic capacitance, and preventing luminance variations and horizontal lines.
Implementation Method 1
a feedback line D1, switching elements T1 connecting the sensor lines L1 to L4 to the feedback line D1
Implementation Method 2
switching elements T1 connecting the sensor lines L1 to L4 to the feedback line D1, a feedback control line D2
Implementation Method 3
a common voltage compensator Vcom comp which compensates the feedback voltage VFB to a reference voltage level
Implementation Method 4
The capacitance of the touch sensors may increase when a conductive object, such as a finger, touches the touch screen. Consequently, touch input can be detected by measuring changes in capacitance caused by a touch.
Implementation Method 5
the delay time of the common voltage Vcom applied to the sensor electrodes C1 to C4 may vary depending on the locations of the touch sensors, due to variations in length between the sensor lines L1 to L4, thus making picture quality nonuniform
Data Source
AI summary
A touch sensing device comprises a common electrode divided into a plurality of sensor electrodes, a plurality of sensor lines respectively connected to the plurality of sensor electrodes, a feedback voltage transmitter, and a common voltage compensator. The feedback voltage transmitter includes a feedback line, a plurality of switching elements configured to selectively connect the sensor lines to the feedback line, and a feedback control line configured to control selection of the switching elements. The common voltage compensator is configured to receive a feedback voltage supplied to the sensor lines through the feedback line while the sensor lines are connected to the feedback line through the plurality of switching elements, and compensate the feedback voltage to a reference voltage level.