Capacitive Touch Panel Noise Immunity via AC Drive Signal Timing

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Solution Overview

Problem

Electrostatic capacitance type touch panels are prone to malfunctions due to noise interference from sources like inverter fluorescent lamps and AC power sources, which can cause erroneous touch detection operations.

Innovation Solution

The implementation of an AC drive signal with multiple transition timing pairs, including a first and second transition timing pair with different intervals, is applied to the drive electrodes during touch detection periods to reduce noise interference by offsetting noise signals through electrostatic capacitance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If an electrostatic capacitance type touch panel is used, then the configuration is simplified and power consumption is reduced, but the panel becomes susceptible to noise interference from external sources

Engineering Contradiction:

ImproveconfigurationVSAvoidnoise interference

Core Design Contradiction:

Device complexityVSObject-affected harmful factors

Solution Approach 1:

The patent applies periodic AC drive signals with multiple transition timing pairs at different intervals to the drive electrodes. By using periodic signals with varying intervals (first transition interval and second transition interval), the system can distinguish touch signals from noise through pattern recognition, thereby reducing noise interference while maintaining the simplified electrostatic capacitance configuration

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent changes the temporal parameters of the drive signal by introducing multiple transition timing pairs with different intervals. This parameter variation allows the touch detection system to differentiate between periodic noise patterns and actual touch inputs, reducing susceptibility to external noise sources while keeping the device configuration simple

Inventive Principle:

Principle #35Parameter changes

2Reliability

If noise is applied to the touch panel, then the touch detection operation may operate erroneously, but using complex noise filtering methods increases device complexity

Engineering Contradiction:

Improvetouch detection accuracyVSAvoidnoise filtering mechanism

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The system uses periodic AC drive signals with multiple transition timing pairs to create a structured detection pattern. By analyzing the response to these periodic signals with varying intervals, the system can identify and filter noise without requiring complex additional filtering hardware or algorithms, thus maintaining reliability while avoiding increased device complexity

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent implements a feedback mechanism where the touch detection unit analyzes the response to AC drive signals with multiple transition timing pairs. This feedback allows the system to distinguish between noise and actual touch inputs by recognizing patterns, thereby improving touch detection accuracy without adding complex external filtering mechanisms

Inventive Principle:

Principle #23Feedback

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 configuration effectively reduces the likelihood of malfunction caused by noise, enhancing the immunity to disturbance noise and improving the accuracy of touch detection operations.

Implementation Method 1

touch detection electrodes each forming an electrostatic capacitance with corresponding one of the drive electrodes

Methodology Applied

Scientific EffectElectrostatic capacitance: Capacitance

Implementation Method 2

The AC drive signal involves multiple transition to generate one or more transition timing pairs... offsetting noise signals through electrostatic capacitance

Methodology Applied

Scientific EffectElectrostatic induction: Electrostatic Induction

Data Source

PatentUS9323374B2Display, touch detection unit, driving method, and electronic unit

Publication Date: 2016.04.26 MAGNOLIA WHITE CORP

AI summary

A display includes: display elements; drive electrodes; touch detection electrodes each forming an electrostatic capacitance with corresponding one of the drive electrodes; and a drive section applying an AC drive signal to the drive electrodes during each of a plurality of touch detection periods, the AC drive signal involving multiple transition to generate one or more transition timing pairs. The AC drive signal includes at least a first transition timing pair and a second transition timing pair over the plurality of touch detection periods. The first transition timing pair has a first transition interval, and the second transition timing pair has a second transition interval different from the first transition interval.