Capacitive Force Detection Differential Interference Cancellation

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Solution Overview

Problem

Existing force detection technologies in capacitive touch screens face interference from the display device and load grounding capacitor, leading to reduced sensitivity and increased thickness when attempting to enhance force detection capabilities.

Innovation Solution

A force detection apparatus utilizing a first and second detection capacitor configured for differential processing to cancel interference signals, with the force detection electrode and reference detection electrode arranged within a surface to minimize thickness and suppress temperature drift, allowing for enhanced sensitivity without additional thickness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a shielding layer is arranged between the display device and the force detection electrode to address interference, then the interference from the display device is reduced, but the cost increases and the entire thickness of the display screen increases

Engineering Contradiction:

Improveinterference from display deviceVSAvoidthickness of display screen

Core Design Contradiction:

Object-affected harmful factorsVSLength of stationary object

Solution Approach 1:

The patent extracts and eliminates the shielding layer from the structure, instead using a differential detection method where a first detection capacitor and second detection capacitor are arranged to inherently cancel out interference signals from the display device through differential processing, achieving interference rejection without adding thickness

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces the physical shielding layer (mechanical structure) with an electrical differential detection method, using signal processing to cancel interference rather than physically blocking it, thereby reducing structural complexity and thickness

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If the force detection electrode is arranged closer to the middle frame to improve force detection sensitivity, then the sensitivity of force detection is improved, but the interference from the load grounding capacitor increases

Engineering Contradiction:

Improvesensitivity of force detectionVSAvoidinterference from load grounding capacitor

Core Design Contradiction:

Measurement precisionVSObject-generated harmful factors

Solution Approach 1:

The patent converts the harmful interference signal from the load grounding capacitor into a useful differential signal by arranging the first and second detection capacitors symmetrically, where the interference appears equally in both capacitors and can be canceled through differential processing, turning a disadvantage into a solution

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent uses symmetric arrangement of detection capacitors relative to the middle frame, creating a balanced structure where interference from the load grounding capacitor affects both capacitors equally, enabling differential cancellation of the interference while maintaining high sensitivity to asymmetric force inputs

Inventive Principle:

Principle #4Asymmetry

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 cancels interference signals and suppresses temperature drift, thereby enhancing the sensitivity of force detection without increasing the product thickness, providing improved user experience and accuracy in force detection.

Implementation Method 1

a first detection capacitor and a second detection capacitor configured to perform differential processing for a capacitance of the first detection capacitor

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

configured to perform differential processing for a capacitance of the first detection capacitor to cancel an interference signal

Methodology Applied

Scientific EffectElectrostatic Induction: Electrostatic Induction

Data Source

PatentEP3457258B1Pressure detection apparatus and method, touch control device and electronic terminal

Publication Date: 2021.07.28 SHENZHEN GOODIX TECH CO LTD

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AI summary

Embodiments of the present invention provide a force detection apparatus and method, a touch device and an electronic terminal. The apparatus includes: a first detection capacitor, and a second detection capacitor configured to perform differential processing for a capacitance of the first detection capacitor to cancel an interference signal; wherein the first detection capacitor includes a force detection electrode, and the second detection capacitor includes a reference detection electrode, the force detection electrode and the reference detection electrode being arranged within a surface, such that the first detection capacitor and the second detection capacitor are simultaneously coupled to the interference signal causing interference to force detection, and differential processing is performed for capacitances of the first detection capacitor and the second detection capacitor. In this way, the interference signal, for example, an interference signal caused by a display device, is canceled, and sensitivity of force detection is enhanced. In addition, since temperature changes of the force detection apparatus are also reflected by the first detection capacitor and the second detection capacitor, and differential processing is performed for the capacitances of the first detection capacitor and the second detection capacitor, the impacts are offset, such that temperature drift is inhibited.