In-Cell Touch Display Load Reduction Circuit

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Solution Overview

Problem

In-cell touch type display devices suffer from reduced touch sensitivity and performance due to capacitive loads caused by overlapping sensing and signal lines, leading to RC delays and distorted touch driving signals.

Innovation Solution

The implementation of a load reduction circuit that outputs touch driving signals to the gate line during the touch sensing period, minimizing capacitive loads by applying the same waveform signals to both ends of the coupling capacitor, thereby reducing signal current inflow and RC delays.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Length of moving object

If sensing line overlaps signal line to achieve thin profile, then device thickness is reduced, but capacitive load increases causing RC delay

Engineering Contradiction:

Improvedevice thicknessVSAvoidRC delay

Core Design Contradiction:

Length of moving objectVSLoss of time

Solution Approach 1:

The patent applies the principle of converting harm into benefit by using the overlapping sensing line and signal line configuration (which originally causes capacitive load) as the basis for the solution. During the touch sensing period, the same touch driving signal is applied to both the sensing line and the signal line, transforming the harmful capacitive coupling into a beneficial arrangement where no voltage difference exists across the capacitance, thereby eliminating the harmful effect while maintaining the thin profile design

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Adaptability or versatility

If sensing line overlaps signal line, then in-cell touch configuration is achieved, but capacitive load produces signal current inflow

Engineering Contradiction:

Improvein-cell touch configurationVSAvoidsignal current inflow

Core Design Contradiction:

Adaptability or versatilityVSObject-generated harmful factors

Solution Approach 1:

The patent converts the harmful signal current inflow caused by capacitive coupling into a beneficial situation by applying the same touch driving signal to both the sensing line and signal line during the touch sensing period. This eliminates the voltage difference across the capacitive coupling, thereby preventing signal current inflow while maintaining the in-cell touch configuration

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent employs periodic action by selectively controlling the signal line during different periods: during the touch sensing period, the signal line receives the touch driving signal to eliminate capacitive load effects, while during the display period, normal display signals are applied. This time-division multiplexing approach resolves the capacitive coupling issue without compromising the in-cell touch functionality

Inventive Principle:

Principle #19Periodic action

3Measurement precision

If touch driving signal is applied to sensing line, then touch sensing is enabled, but pulse waveform is distorted due to RC delay

Engineering Contradiction:

Improvetouch sensing capabilityVSAvoidsignal waveform distortion

Core Design Contradiction:

Measurement precisionVSLoss of information

Solution Approach 1:

The patent converts the harmful RC delay effect into a beneficial situation by applying the same touch driving signal to both the sensing line and signal line. This eliminates the voltage difference across the capacitive coupling, preventing signal current inflow and waveform distortion, thereby preserving the pulse waveform integrity while enabling touch sensing capability

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 solution significantly reduces capacitive loads by 75% or more, enhancing touch performance by minimizing RC delays and signal distortions, resulting in improved touch sensitivity and accuracy.

Implementation Method 1

a coupling capacitance is produced and a capacitive load is produced... a capacitive load Lc exists between the sensing line SL and the signal line SGL

Methodology Applied

Scientific EffectCapacitive load: Capacitance

Implementation Method 2

since the sensing line overlaps a signal line such as a gate line or data line, a coupling capacitance is produced

Methodology Applied

Scientific EffectCoupling capacitance: Capacitance

Data Source

PatentUS10180757B2In-cell touch type display device to reduce capacitive load and driving IC thereof

Publication Date: 2019.01.15 LG DISPLAY CO LTD

AI summary

An in-cell touch type display device includes a touch electrode that is in a touch panel and arranged at each touch block; a sensing line that is connected to the touch electrode, and transfers a touch driving signal from a source driving circuit during a touch sensing period; a gate-in panel (GIP) circuit that is in an array substrate, and outputs a gate signal to a gate line crossing and overlapping the sensing line, during a display period; and a load reduction circuit that outputs the touch driving signal to the gate line during the touch sensing period.