Capacitive Touch Sensing Noise Removal via Switched Discharge
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Solution Overview
Problem
Capacitive-type touch screens face inaccuracies in detecting touch input due to noise interference from sources like wireless communication modules, which affect the measurement of capacitance changes.
Innovation Solution
A capacitive sensing apparatus and method that includes a first integration circuit unit, a comparison circuit unit, and a noise removal unit with switches to discharge charges from a capacitor when the output signal exceeds a reference level, minimizing noise impact and ensuring accurate capacitance measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If capacitive-type touch screens are used to enable multi-touch and intuitive input, then ease of operation and input accuracy are improved, but measurement precision deteriorates due to noise interference from wireless communication modules
Solution Approach 1:
A noise removal unit is introduced as an intermediary component between the sensing electrode and the measurement circuit. This unit includes a switch that opens when noise is detected, preventing noise from reaching the measurement circuit while allowing valid capacitance signals to pass through, thus resolving the contradiction between ease of operation and measurement precision
Solution Approach 2:
The system incorporates a feedback mechanism where the output signal from the first integration circuit unit is fed back to the noise removal unit. When the signal exceeds a reference level (indicating noise), the feedback controls the switch to open and remove the noise, thereby maintaining measurement precision while preserving the ease of operation of the touch screen
2Measurement precision
If noise removal switches are added to discharge capacitor charges when noise is detected, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The noise removal unit is merged with the existing integration circuit unit by sharing the same capacitor and using the existing signal path. The switch is integrated into the circuit such that it can open or close based on the signal level, combining noise removal functionality with the existing measurement circuit rather than adding a completely separate system, thus improving measurement precision while minimizing the increase in device complexity
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 removes noise-induced errors, allowing for precise detection of touch inputs by stabilizing the output voltage and enhancing the accuracy of capacitance sensing in capacitive touch screens.
Implementation Method 1
a first integration circuit unit including a first capacitor charged by a change in capacitance occurring in a sensing electrode
Implementation Method 2
a comparison circuit unit comparing a level of an output signal of the first integration circuit unit with a predetermined reference level
Implementation Method 3
a noise removal unit including a plurality of switches operating according to an output of the comparison circuit unit, wherein the comparison circuit unit controls an operation of each of the plurality of switches to discharge charges charged in the first capacitor when the level of the output signal of the first integration circuit unit is higher than the reference level
Data Source
AI summary
There are provided an apparatus for sensing capacitance, a method for sensing capacitance, and a touch screen apparatus. The apparatus for sensing capacitance includes; a first integration circuit unit including a first capacitor charged by a change in capacitance occurring in a sensing electrode; a comparison circuit unit comparing a level of an output signal of the first integration circuit unit with a predetermined reference level; and a noise removal unit including a plurality of switches operating according to an output of the comparison circuit unit, wherein the comparison circuit unit controls an operation of each of the plurality of switches to discharge charges charged in the first capacitor when the level of the output signal of the first integration circuit unit is higher than the reference level.