In-Cell Touch Sensor Parasitic Capacitance Reduction

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Solution Overview

Problem

In display devices with in-cell touch sensors, parasitic capacitance between the common electrode and drive lines (source lines, gate lines) negatively impacts display performance, especially as panel size and resolution increase, leading to reduced detection sensitivity and responsiveness.

Innovation Solution

Implementing a code division multiplexing (CDM) drive method where drive signals are synchronized across multiple common electrodes, reducing the influence of parasitic capacitance by driving all electrodes simultaneously, except one, which is driven with an opposite polarity, and using this approach to improve touch detection accuracy and signal-to-noise ratio.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of stationary object

If a common electrode for display is used as an electrode for the touch sensor in an in-cell touch panel, then the device structure is simplified and integration is improved, but parasitic capacitance is generated between the common electrode and drive lines which worsens display function and reduces touch detection sensitivity

Engineering Contradiction:

Improveintegration of touch sensor and displayVSAvoidparasitic capacitance influence

Core Design Contradiction:

Area of stationary objectVSObject-affected harmful factors

Solution Approach 1:

The common electrode is divided into multiple segments (first common electrode and second common electrode) that can be independently controlled. This segmentation allows selective driving of electrode portions to minimize parasitic capacitance effects while maintaining touch detection functionality across the display area.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent employs periodic driving schemes where the common electrode is driven in alternating intervals with the touch detection operation. During touch detection periods, the common electrode driving is suspended or reduced, creating periodic windows where parasitic capacitance effects are minimized while still maintaining display functionality.

Inventive Principle:

Principle #19Periodic action

2Manufacturing precision

If display panels are made to have larger size and higher resolution, then display quality is improved, but the influence of parasitic capacitance grows which worsens display function

Engineering Contradiction:

Improvedisplay resolutionVSAvoidparasitic capacitance influence

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The common electrode is segmented into multiple independently controllable portions. This allows selective activation of specific electrode segments during touch detection, reducing the overall parasitic capacitance effect while maintaining high resolution touch detection capability across large display areas.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements dynamic control of the common electrode where the driving state (on/off or voltage level) is continuously adjusted based on the operational phase (display vs. touch detection). This dynamic adaptation allows the system to optimize performance for both high resolution display and touch detection while minimizing parasitic capacitance effects.

Inventive Principle:

Principle #15Dynamics

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 CDM drive method enhances touch detection sensitivity and reduces the impact of parasitic capacitance, leading to improved responsiveness and accuracy in detecting touch positions while minimizing power consumption and operational complexity.

Implementation Method 1

parasitic capacitance generated between the common electrode and drive lines (source lines, gate lines, etc.)

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

there is a possibility of a display being influenced by a parasitic capacitance generated between the common electrode and drive lines

Methodology Applied

Scientific EffectParasitic Capacitance: Parasitic Capacitance

Data Source

PatentUS10606385B2Display device including a sensor reducing influence of parasitic capacitance upon the sensor, and method of driving a display device

Publication Date: 2020.03.31 MAGNOLIA WHITE CORP

AI summary

A display device provided with a touch sensor, includes a plurality of common electrodes, a plurality of display elements arranged in a matrix, a plurality of gate lines electrically connected to the display elements and arranged in a row direction, and a plurality of source lines electrically connected to the display elements and arranged in a column direction. The plurality of common electrodes for display are also used for the touch sensor. An image display operation of the plurality of common electrodes for display and a driving operation of the plurality of common electrodes for the touch sensor are performed in a time sharing manner, and all of the gate lines and the source lines are caused to be in a floating state in the driving operation of the common electrodes for the touch sensor.