Capacitive Touch Panel Detection Using Differential Row Scanning

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Solution Overview

Problem

Existing capacitive touch panel detection methods suffer from poor interference resistance and error determination due to varying interference at different times, leading to incorrect touch point coordinates.

Innovation Solution

A touch detection method that scans rows and columns simultaneously to obtain capacitance differential values, processes these values to determine absolute and relative capacitance equivalents, and uses a self-checking and averaging process to improve interference resistance and accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If single row or column scanning is used to reduce microprocessor load, then scanning efficiency is improved, but interference resistance deteriorates due to varying interference at different times

Engineering Contradiction:

Improvescanning efficiencyVSAvoidinterference resistance

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent divides the scanning process into multiple independent row scanning operations that can be performed simultaneously. Each row scanning operation is independent, allowing parallel execution without interfering with each other, thus maintaining high scanning efficiency while improving interference resistance through differential measurement.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces a differential measurement approach where the capacitance change is measured as a difference between two rows. This intermediary differential value eliminates common-mode interference affecting both rows simultaneously, thereby improving interference resistance while preserving scanning efficiency.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Difficulty of detecting and measuring

If capacitance conversion to frequency or voltage is performed to detect touch, then detection capability is improved, but measurement precision deteriorates due to incorrect touch point coordinates

Engineering Contradiction:

Improvedetection capabilityVSAvoidtouch point coordinate accuracy

Core Design Contradiction:

Difficulty of detecting and measuringVSMeasurement precision

Solution Approach 1:

The patent replaces the traditional single-row scanning mechanism with a parallel multi-row scanning system. This substitution allows simultaneous measurement of multiple rows, enabling more precise touch point determination through differential capacitance measurement while maintaining ease of detection.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the measurement parameter from single-row capacitance to differential capacitance between rows. This parameter change enables the system to distinguish touch points more accurately by measuring capacitance differences, thereby improving measurement precision while maintaining detection capability.

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If traditional single-row scanning is used, then circuit complexity is reduced, but reliability deteriorates due to error determination and coordinate drift

Engineering Contradiction:

Improvecircuit complexityVSAvoiddetection accuracy

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent merges multiple row scanning operations into a unified differential measurement system. By combining the measurement of multiple rows and processing their differential values, the system achieves higher reliability and accuracy without proportionally increasing circuit complexity, as the same basic scanning circuit is reused for multiple rows.

Inventive Principle:

Principle #5Merging (Combining)

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 method significantly enhances the interference resistance and accuracy of capacitive touch panel detection by eliminating common code interferences and providing reliable touch point coordinates.

Implementation Method 1

a capacitive matrix comprising a plurality of rows and columns of capacitors arranged in a grid pattern

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS8599168B2Touch detection method and circuit for capacitive touch panels

Publication Date: 2013.12.03 FOCALTECH SYST LTD

AI summary

A touch detection method for capacitive touch panels includes the steps of scanning the rows and columns of the capacitive matrix of a touch panel respectively; obtaining the capacitance differential value; processing the obtained capacitance differential value; and determining whether there is a touch on the touch panel in response to the processed capacitance differential value. The capacitance differential value is obtained by one of the steps of synchronously scanning two rows at the same time; synchronously scanning two columns at the same time; scanning one row to obtain the capacitance differential value between the row and a reference capacitance; and scanning one column to obtain the capacitance differential value between the column and a reference capacitance. The present invention creates conditions for the elimination of common code interferences and greatly improves the interference resistance of a capacitive touch panel.