Capacitive Touch Panel Noise Cancellation via Segmented Scanning

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Solution Overview

Problem

Capacitive touch panels face challenges in accurately detecting touch positions due to increased noise susceptibility, particularly in thin designs where noise removal methods like reference electrodes or common noise calculation are ineffective, leading to reduced accuracy and operational region constraints.

Innovation Solution

A capacitive touch panel design that divides detection periods into sub-periods, allowing for sequential drive voltage input to scanning electrodes and simultaneous capacitance detection across groups of detecting electrodes, with a control circuit calculating noise and signal changes to determine accurate touch positions without the need for additional shielding electrodes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the distance between detecting electrodes and display is reduced to improve design property and reduce thickness, then the touch panel becomes more susceptible to noise from the display

Engineering Contradiction:

ImprovethicknessVSAvoidnoise

Core Design Contradiction:

Volume of moving objectVSObject-affected harmful factors

Solution Approach 1:

The detection period is divided into multiple sub-detection periods, and detecting electrodes are divided into multiple groups. This segmentation allows sequential scanning of different electrode groups, enabling noise cancellation through differential measurement between adjacent groups while maintaining thin design.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements periodic scanning by sequentially applying drive voltages to different scanning electrodes in different sub-detection periods. This periodic action enables time-multiplexed measurement that distinguishes touch signals from continuous noise through temporal differentiation.

Inventive Principle:

Principle #19Periodic action

2Object-affected harmful factors

If a reference electrode is provided to remove noise, then the actual touch panel operation region is reduced

Engineering Contradiction:

ImprovenoiseVSAvoidoperation region

Core Design Contradiction:

Object-affected harmful factorsVSArea of stationary object

Solution Approach 1:

The detecting electrodes serve dual functions: they detect touch signals and simultaneously serve as reference electrodes for noise cancellation. By dividing detecting electrodes into multiple groups that are sequentially scanned, the system uses adjacent electrode groups as mutual references without requiring dedicated reference electrode areas.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The system uses its own detecting electrodes to generate reference signals for noise cancellation. Adjacent detecting electrode groups are scanned alternately, and their differential measurements provide self-referenced noise cancellation without external reference components.

Inventive Principle:

Principle #25Self-service

3Device complexity

If common noise calculation method is used without reference electrode, then touch information accuracy deteriorates when signals are simultaneously input to multiple detecting electrodes

Engineering Contradiction:

ImprovestructureVSAvoidtouch information accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

Detecting electrodes are divided into multiple groups that are sequentially activated in different sub-detection periods. This segmentation ensures that only one group is actively scanning at any given time, preventing simultaneous signal inputs that would cancel each other out while still enabling common noise calculation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system dynamically switches between different detecting electrode groups in a time-multiplexed manner. By controlling which group is active at each sub-detection period, the system maintains measurement accuracy while enabling noise cancellation through temporal separation of signals.

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

This approach effectively removes noise and enhances detection accuracy, even in thin designs integrated with displays, allowing for precise touch position detection while reducing noise interference.

Implementation Method 1

detect a capacitance near an intersection between an array of a plurality of detecting electrodes and a plurality of scanning electrodes

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS9678598B2Touch panel

Publication Date: 2017.06.13 MAGNOLIA WHITE CORP

AI summary

A capacitive touch panel includes a scanning circuit portion for inputting a drive voltage to each scanning electrode sequentially in 1st to n-th sub detection periods, a capacitance detection circuit portion for detecting a capacitance detection signal of the each detecting electrode in the 1st to n-th groups, and a control circuit portion for calculating a capacitance detection signal change amount from the capacitance detection signals of a plurality of the detecting electrodes detected by the capacitance detection circuit portion, and calculating coordinates of a touch position based on the capacitance detection signal change amounts. The control circuit portion determines, in consecutive sub detection periods, the capacitance detection signal change amount of the each detecting electrode in two groups from which the capacitance detection signals are detected in the consecutive sub detection periods, based on the capacitance detection signals consecutively detected from at least one same detecting electrode.