Capacitive Touch Screen Panel Using Level Shift for Noise Reduction

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Solution Overview

Problem

Conventional capacitive touch screen panels face challenges in detecting touch signals due to external noise, parasitic capacitance, and common electrode interference, especially when integrated into display devices like LCDs, leading to detection errors and increased manufacturing costs.

Innovation Solution

A capacitive touch detecting device and method that utilize a sensor pad and a driving pad spaced apart by an insulator, detecting voltage variations to identify a level shift caused by touch capacitance, thereby minimizing noise and parasitic capacitance influences and enabling reliable touch signal detection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a conventional capacitive touch screen panel detects micro-current changes, then touch detection capability is achieved, but the detection device becomes expensive and multiple touches cannot be recognized

Engineering Contradiction:

Improvetouch detection capabilityVSAvoiddetection device cost and capability

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The touch screen is divided into multiple independent sensor patterns (first sensor pattern, second sensor pattern, etc.) arranged in different regions. Each sensor pattern can independently detect touch events, enabling multi-touch recognition. The segmentation of detection zones allows simultaneous detection of multiple touch points without requiring expensive specialized detection devices.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A driving pattern is introduced as an intermediary element that applies AC voltage to the sensor patterns. This driving pattern acts as a mediator that enables the sensor patterns to detect touch capacitance changes without requiring complex detection circuitry. The driving pattern converts the detection task into measuring voltage variations caused by touch capacitance, simplifying the detection device.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If the touch screen panel is integrated into a display device with a common electrode, then built-in touch screen functionality is achieved, but noise and parasitic capacitance cause detection errors

Engineering Contradiction:

Improvebuilt-in integration capabilityVSAvoiddetection accuracy

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The sensor patterns are electrically isolated from the common electrode by introducing a driving pattern as an intermediate layer. This extraction separates the touch detection function from the display's common electrode, removing the source of noise and parasitic capacitance interference. The sensor patterns now interact only with the driving pattern, eliminating detection errors caused by the common electrode.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent uses simple AC voltage signals applied through the driving pattern as a temporary, easily replaceable method to activate sensor patterns during detection cycles. This approach replaces complex, expensive shielding and isolation structures with simple, inexpensive AC signaling that can be quickly switched on and off to perform detection without permanent structural modifications.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Measurement precision

If linear sensor patterns are used to detect touch signals, then multiple touch points can be recognized, but external noise and parasitic capacitance interfere with signal detection

Engineering Contradiction:

Improvemultiple touch point recognitionVSAvoidnoise and parasitic capacitance interference

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The sensor patterns are dynamically activated and deactivated through the driving pattern using AC voltage signals. By selectively enabling only the necessary sensor patterns at specific times, the system reduces exposure to noise and parasitic capacitance while maintaining the ability to detect multiple touch points. This dynamic activation strategy minimizes interference during detection operations.

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 allows for accurate detection of touch signals with reduced noise interference, facilitating the integration of touch screens into display devices and improving touch resolution for multiple inputs and gestures.

Implementation Method 1

a sensor pad (10) that forms a first capacitance between a touch input instrument and the sensor pad (10), and forms a second capacitance between a common electrode (220) of a display device (200) and the sensor pad (10)

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS8982095B2Capacitive touch detecting device and method and capacitive touch screen panel using level shift, and display device using the capacitive touch screen panel

Publication Date: 2015.03.17 G2TOUCH CO LTD

AI summary

Provided are a capacitive touch detecting device, a capacitive touch detecting method, and a touch screen panel, using a level shift, and a display device having a built-in touch screen panel, which minimizes an influence due to noise or a parasitic capacitance, and detects a touch input by positively using a signal induced by a common electrode of a liquid crystal display (LCD).