Touch Screen Controller Noise Synchronization

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Solution Overview

Problem

Existing touch screen devices face interference from display-generated noise, which affects capacitance measurements and leads to errors in touch detection and location, with current noise suppression methods being costly, complex, or increasing device thickness.

Innovation Solution

A method and apparatus that employ a noise detector and state machine to synchronize signal generation and measurement, combined with noise filtering techniques such as median filtering and noise blanking, to reduce the influence of display noise on touch screens.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If transparent shielding electrode is located between display and touch screen, then display noise shielding is improved, but device thickness increases

Engineering Contradiction:

Improvedisplay noise shieldingVSAvoiddevice thickness

Core Design Contradiction:

Object-affected harmful factorsVSLength of stationary object

Solution Approach 1:

The patent extracts the noise shielding function from a separate physical shielding layer and integrates it into the existing touch screen controller circuitry. The controller now performs digital signal processing to remove display noise from capacitance measurements, eliminating the need for additional physical shielding layers that would increase device thickness.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces the mechanical/physical approach of noise shielding (using transparent shielding electrodes and increased spacing) with an electronic/digital approach. The touch screen controller uses digital signal processing algorithms to identify and remove display-generated noise from the capacitance signals, achieving noise reduction without additional physical layers.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Object-affected harmful factors

If PLL synchronization system is used, then noise suppression is improved, but circuit complexity and processor overhead increase

Engineering Contradiction:

Improvenoise suppressionVSAvoidcircuit complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent uses simple, low-cost digital processing techniques implemented in existing touch screen controller firmware rather than expensive PLL synchronization hardware. The solution leverages standard digital signal processing algorithms that can be executed on existing microcontrollers without requiring specialized high-speed processors or complex synchronization circuitry.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent replaces the hardware-based PLL synchronization system with software-based digital signal processing. Instead of using dedicated synchronization hardware and complex circuitry, the controller uses firmware algorithms to analyze capacitance signals and remove display noise, reducing both circuit complexity and processor requirements.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If Tx signal strength is increased, then touch detection sensitivity is improved, but battery consumption increases

Engineering Contradiction:

Improvetouch detection sensitivityVSAvoidbattery consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The patent implements digital signal processing with noise removal algorithms that allow the system to maintain high touch detection sensitivity without increasing Tx signal strength. By actively removing display noise from the capacitance measurements, the system can use lower Tx signal levels while still achieving accurate touch detection, thereby reducing power consumption.

Inventive Principle:

Principle #23Feedback

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 reduces display noise interference, improving the signal-to-noise ratio and enhancing the accuracy of touch detection while maintaining a slim and lightweight device design.

Implementation Method 1

a noise detector for producing an output in response to an edge of recognized noise

Methodology Applied

Scientific EffectNoise detection:

Implementation Method 2

a state machine responsive to the output for synchronizing the generation and measurement of the signals used to measure the capacitances

Methodology Applied

Scientific EffectSynchronization:

Implementation Method 3

the inter-electrode capacitance between the Rx and Tx electrodes changes. The Rx and Tx electrodes are periodically scanned by means of a touch screen controller

Methodology Applied

Scientific EffectCapacitance measurement: Capacitance

Data Source

PatentUS9229577B2Method and apparatus for reducing coupled noise influence in touch screen controllers

Publication Date: 2016.01.05 PARADE TECHNOLOGIES LTD

AI summary

Apparatuses and methods to reduce the influence of a noise signal on touch screen controllers are described. One apparatus includes a detector to determine a presence of a noise signal from a display coupled to a capacitive touch screen. The apparatus also includes a synchronization circuit to synchronize signals produced by a touch screen controller with the noise signal to reduce the influence of the noise signal on capacitance measurements by the touch screen controller.