Touch Sensing Circuit Using Load-Free Signals for EMI Immunity

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Solution Overview

Problem

Touch display devices experience degraded accuracy due to electromagnetic noise from surrounding electronic devices, which existing technologies fail to adequately address without adding capacitor elements.

Innovation Solution

A touch display device and touch sensing circuit that employs load-free driving signals with phase and amplitude differences to reduce parasitic capacitance, forming a low-pass filter that increases the cutoff frequency and improves noise immunity without using additional capacitor elements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If electromagnetic noise shielding measures are implemented, then noise resistance is improved, but device complexity increases

Engineering Contradiction:

Improvenoise resistanceVSAvoidcircuit complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent combines the noise filtering function with the existing driver circuits by having them output both touch driving signals and load-free driving signals simultaneously. The driver circuits serve dual purposes: driving the display panels and providing noise immunity through load-free signals, thereby eliminating the need for separate filtering circuits and reducing overall device complexity.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The driver circuits are designed to perform multiple functions: they drive the display panels during display periods and generate load-free driving signals during touch periods. This multi-functionality allows the same hardware to provide both display operation and electromagnetic noise shielding, improving reliability without adding dedicated noise resistance components.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Measurement precision

If capacitor elements are added to filter electromagnetic noise, then touch accuracy is improved, but device complexity and cost increase

Engineering Contradiction:

Improvetouch accuracyVSAvoidcomponent quantity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The system uses its own driver circuits to generate load-free driving signals that serve as the filtering mechanism. Instead of requiring external capacitor elements to filter noise, the driver circuits themselves produce compensating signals that cancel electromagnetic interference, achieving touch accuracy improvement through self-service rather than additional components.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The load-free driving signals act as an intermediary mechanism between the driver circuits and the touch electrodes. These signals mediate the interaction by providing a filtering effect through phase and amplitude differences, eliminating the need for physical capacitor elements while maintaining touch accuracy.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If load-free driving signals with phase and amplitude differences are applied, then electromagnetic noise immunity is improved, but energy consumption increases

Engineering Contradiction:

Improveelectromagnetic noise immunityVSAvoidenergy consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The driver circuits continuously output both touch driving signals and load-free driving signals during touch periods without interruption. This continuous operation ensures constant electromagnetic noise immunity while optimizing energy usage by maintaining steady-state signal generation rather than requiring additional energy-intensive switching or modulation operations.

Inventive Principle:

Principle #20Continuity of useful action

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

Enhances touch accuracy by effectively removing electromagnetic noise and improving immunity to electromagnetic interference, while maintaining operational efficiency without the need for additional capacitor elements.

Implementation Method 1

a touch sensing circuit configured to output a pulse type touch driving signal to at least one of the plurality of touch electrodes

Methodology Applied

Scientific EffectCapacitance sensing: Capacitance

Implementation Method 2

the touch electrode, a peripheral pattern adjacent to the touch electrode, and a sensing line electrically connecting the touch electrode and the touch sensing circuit may constitute a low pass filter

Methodology Applied

Scientific EffectLow-pass filtering: Filter (electronic)

Data Source

PatentUS11614830B2Touch display device and touch sensing circuit

Publication Date: 2023.03.28 LG DISPLAY CO LTD

AI summary

Embodiments of the present disclosure relate to a touch display device and a touch sensing circuit that apply a load-free driving signal having a phase difference or amplitude difference from the touch driving signal to a touch display panel. According to embodiments of the present disclosure, electromagnetic noise immunity may be improved and touch accuracy may be increased. The touch sensing circuit comprises: a touch driving circuit configured to output a pulse type touch driving signal to at least one of a plurality of touch electrodes disposed on a touch display panel; and a load-free driving signal output circuit configured to output at least one load-free driving signal having a frequency equal to a frequency of the touch driving signal and having a phase difference or amplitude difference from the touch driving signal.