Touch Sensor Power Supply Voltage Switching for Parasitic Capacitance

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Solution Overview

Problem

Display devices with integrated touch sensors face increased power consumption and reduced accuracy due to parasitic capacitance between the touch sensing unit and the display panel, which affects the performance of touch sensing operations.

Innovation Solution

A power supply system that uses pulse width modulation (PWM) to adjust voltage levels, applying DC voltage during display time and AC voltage during touch sensing time, with the touch sensing unit operating based on mutual- and self-capacitance sensing methods to minimize parasitic capacitance and optimize power usage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a touchscreen panel is disposed on the display device, then touch sensing functionality is provided, but parasitic capacitance between the touch panel and display device increases

Engineering Contradiction:

Improvetouch sensing functionalityVSAvoidparasitic capacitance

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies dynamic voltage switching where the touch sensing unit alternates between operating at a first voltage level during display operation and a second voltage level during touch sensing operation. This dynamic voltage adjustment reduces parasitic capacitance effects while maintaining touch sensing functionality, resolving the contradiction between providing touch functionality and minimizing parasitic capacitance interference.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the voltage parameter of the touch sensing unit based on operational mode. During display operation, the touch sensing unit operates at a first voltage level, and during touch sensing operation, it switches to a second voltage level. This parameter change reduces parasitic capacitance between the touch panel and display device, thereby minimizing harmful electrical interference while preserving touch sensing capability.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the touch sensing unit operates continuously, then touch detection is always available, but power consumption increases

Engineering Contradiction:

Improvetouch detection availabilityVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent implements periodic operation of the touch sensing unit by alternating between display operation mode and touch sensing operation mode. The control circuit switches the touch sensing unit between a first voltage level during display operation and a second voltage level during touch sensing operation. This periodic action ensures touch detection is available when needed while reducing power consumption during display operation, resolving the contradiction between continuous availability and power efficiency.

Inventive Principle:

Principle #19Periodic action

3Measurement precision

If AC voltage is applied to reduce parasitic capacitance, then touch sensing accuracy improves, but voltage level management complexity increases

Engineering Contradiction:

Improvetouch sensing accuracyVSAvoidvoltage level management

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent introduces a control circuit as an intermediary between the power supply and the touch sensing unit. This control circuit manages the switching between different voltage levels based on operational mode (display operation or touch sensing operation). The control circuit simplifies voltage level management by automatically selecting appropriate voltage levels, thereby improving touch sensing accuracy while minimizing the complexity burden on the overall system.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 reduces power consumption and enhances the accuracy of touch sensing operations by managing voltage levels and types to minimize parasitic capacitance, ensuring efficient and precise touch detection without distorting the displayed image.

Implementation Method 1

a pulse width modulation (PWM) controller controlling the converter to adjust a voltage level of the first voltage

Methodology Applied

Scientific EffectPulse width modulation (PWM):

Implementation Method 2

a pulse width modulation (PWM) controller controlling the converter to adjust a voltage level of the first voltage. The ground voltage is applied to the converter as a direct current (DC) voltage during a first time and as a pulse wave having a predetermined amplitude during a second time

Methodology Applied

Scientific EffectPulse width modulation (PWM):

Implementation Method 3

the touch sensing unit operating based on mutual- and self-capacitance sensing methods to minimize parasitic capacitance

Methodology Applied

Scientific EffectCapacitance sensing: Capacitance

Data Source

PatentUS10712853B2Display device including touch sensors and method of driving the same

Publication Date: 2020.07.14 LG DISPLAY CO LTD

AI summary

A power supply and a method of driving the same. A converter receives an input voltage from a battery and outputs a first voltage through an output terminal, such that a ground voltage of the output terminal changes. A pulse width modulation (PWM) controller controls the converter to adjust the voltage level of the first voltage. The ground voltage is applied to the converter as a direct current (DC) voltage during a first time and as a pulse wave having a predetermined amplitude during a second time. The PWM controller controls the first voltage to have different voltage levels during the first time and the second time.