Capacitive Touch Panel Opposite-Phase Driving for Low Ground Mass

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Solution Overview

Problem

Capacitive touch panels experience degraded touch performance under low ground mass (LGM) conditions due to unwanted charge induction from the same-phase coupling of touch sensing driving signals with the user's body, leading to reduced sensitivity.

Innovation Solution

A capacitive touch panel design that applies voltages of opposite phases to x-line and y-line channels, ensuring that the potential at the user's finger is zero, thereby maintaining charge sensitivity irrespective of the LGM state, and a method of driving the panel that adjusts voltage phases based on the ground state to prevent sensitivity deterioration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If same-phase voltages are applied to x-line and y-line channels for touch sensing, then the touch sensing mechanism operates normally under ideal ground conditions, but sensitivity deteriorates under low ground mass (LGM) conditions due to unwanted charge induction from the user's body

Engineering Contradiction:

Improvetouch sensing sensitivityVSAvoidtouch performance consistency

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent applies opposite-phase voltages to the x-line and y-line channels instead of same-phase voltages. Specifically, when a first voltage is applied to the x-line channel, a second voltage with opposite phase is applied to the y-line channel. This inversion of the conventional same-phase approach eliminates the unwanted charge induction effect that occurs under LGM conditions, thereby maintaining touch sensing sensitivity and performance consistency across different ground conditions.

Inventive Principle:

Principle #13The other way round (Inversion)

2Reliability

If opposite-phase voltages are applied to x-line and y-line channels to prevent sensitivity deterioration under LGM conditions, then touch performance remains consistent, but the device complexity increases due to additional control requirements

Engineering Contradiction:

Improvetouch performance consistencyVSAvoidvoltage control complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent integrates the opposite-phase voltage generation into the existing touch controller architecture. The touch controller is configured to generate and apply opposite-phase voltages to the x-line and y-line channels as part of its normal operation. This merging approach implements the opposite-phase solution without requiring separate dedicated hardware circuits, thereby maintaining touch performance consistency while minimizing increases in device complexity.

Inventive Principle:

Principle #5Merging (Combining)

3Measurement precision

If opposite-phase voltages are applied to maintain charge sensitivity under LGM conditions, then the amount of sensed charges remains stable, but energy consumption increases due to continuous voltage switching

Engineering Contradiction:

Improvecharge sensing accuracyVSAvoidenergy consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The patent employs periodic voltage application to the x-line and y-line channels, where opposite-phase voltages are applied in alternating sensing periods. During each sensing period, the touch controller applies voltages with opposite phases to detect touch input, then switches to a non-sensing state. This periodic operation maintains charge sensing accuracy under LGM conditions while reducing overall energy consumption compared to continuous voltage switching, as the system only actively switches voltages during necessary sensing intervals.

Inventive Principle:

Principle #19Periodic 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

The solution effectively reduces or prevents sensitivity deterioration in LGM conditions by maintaining the amount of sensed charges and ensuring consistent touch performance, even when the user and device have a poor earth ground state.

Implementation Method 1

a capacitive touch-screen panel employs a method using electrostatic capacitance of a human body

Methodology Applied

Scientific EffectElectrostatic capacitance: Capacitance

Implementation Method 2

variations of resistance and current, generated by capacitance of a human body, are measured, to recognize a touch

Methodology Applied

Scientific EffectElectrostatic induction: Electrostatic Induction

Data Source

PatentUS11782552B2Capacitive touch panel and method of driving capacitive touch panel

Publication Date: 2023.10.10 SAMSUNG ELECTRONICS CO LTD

AI summary

A capacitive touch panel includes a plurality of x-line channels extending in a first direction, a plurality of y-line channels extending in a second direction, different from the first direction, and processing circuitry configured to apply a first voltage to the x-line channels, apply a second voltage to the y-line channels, the first voltage and the second voltage having opposite phases to each other, and sense a contact on at least one of intersections of the plurality of x-line channels and the plurality of y-line channels.