Capacitance Sensing Noise Cancellation via Differential Integration

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Solution Overview

Problem

Capacitive-type touch screens face challenges in accurately sensing touch inputs due to electrical noise from sources like wireless communications modules and display apparatuses, which hinder the detection of capacitance changes.

Innovation Solution

A capacitance sensing apparatus and method that integrates a driving circuit unit, sensing circuit unit with first and second integrating circuits, and an operating unit to calculate a voltage difference between output voltages from these circuits, effectively removing noise interference by controlling the variable capacitor in the first integrating circuit to set its output to zero when noise is present and inverting and integrating the second change in capacitance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If capacitance sensing is performed in the presence of electrical noise from wireless communications modules and display apparatuses, then the sensing operation can proceed, but the measurement precision deteriorates due to inaccurate capacitance change detection

Engineering Contradiction:

Improvecapacitance change detection accuracyVSAvoidelectrical noise interference

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent applies noise cancellation technology to convert the harmful electrical noise into a beneficial filtering process. By detecting the noise signal through the second integrating circuit and subtracting it from the original signal in the differential amplifier, the harmful noise is transformed into a removable component, thereby improving capacitance measurement accuracy in noisy environments

Inventive Principle:

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

Solution Approach 2:

The patent introduces an intermediary noise cancellation system consisting of the second integrating circuit and differential amplifier. This intermediary structure mediates between the noisy capacitance sensing signal and the final measurement result, filtering out noise components while preserving the actual capacitance change information related to touch inputs

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If noise cancellation processing is implemented using integrating circuits and differential amplification, then the measurement precision improves by removing noise influence, but the device complexity increases

Engineering Contradiction:

Improvetouch input detection accuracyVSAvoidsensing circuit structure

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent merges the noise cancellation function with the existing capacitance sensing circuitry by integrating the second integrating circuit and differential amplifier into the signal processing path. This combining approach allows noise filtering to be achieved without requiring completely separate processing systems, thereby limiting the increase in device complexity while still improving measurement precision

Inventive Principle:

Principle #5Merging (Combining)

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 significantly reduces the influence of noise on capacitance measurements, allowing for accurate determination of touch inputs by generating a voltage difference that isolates and removes noise signals, thereby enhancing the reliability of touch input detection in capacitive-type touch screens.

Implementation Method 1

a first integrating circuit detecting a first change in capacitance generated in a plurality of second electrodes by the driving signal

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

a second integrating circuit connected to another first electrode adjacent to the first electrode to which the driving signal is applied, and the operating unit determines the touch input based on the first and second changes in capacitance

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS8976149B2Capacitance sensing apparatus and method, and touch screen apparatus

Publication Date: 2015.03.10 SAMSUNG ELECTRONICS CO LTD

AI summary

There is provided a capacitance sensing apparatus including: a driving circuit unit sequentially applying a driving signal to each of a plurality of first electrodes; a sensing circuit unit including a first integrating circuit detecting a first change in capacitance generated in a plurality of second electrodes by the driving signal and a second integrating circuit connected to another first electrode adjacent to the first electrode to which the driving signal is applied; and an operating unit connected to the sensing circuit unit to determine a touch input, wherein the second integrating circuit detects a second change in capacitance generated due to noise in the another first electrode, and the operating unit determines the touch input based on the first and second changes in capacitance.