Capacitive Touch Sensing Circuit Noise Removal via Differential Signal Processing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Capacitive touchscreens face challenges in accurately sensing capacitance changes due to electrical noise from sources like wireless communications modules and display apparatuses, which existing noise removal methods are ineffective against noise frequencies equivalent to or multiples of the operation frequency.
Innovation Solution
A touch sensing device and touchscreen device design where node capacitors formed in adjacent sensing electrodes are charged with voltages of opposite polarities to detect capacitance changes and calculate the difference between these changes, using an integrating circuit unit and subtracting unit to generate and process analog signals, effectively removing noise by calculating the difference in levels between these signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If two operational amplifiers are connected to each electrode with opposite phase signals to remove noise, then noise removal capability is improved, but device volume and area are increased
Solution Approach 1:
The patent combines the functions of two separate operational amplifiers into a single operational amplifier by using a differential capacitor connection method. The first and second capacitors are connected to opposite phases of the same electrode, and their outputs are combined through a differential amplifier configuration, reducing the number of operational amplifiers from two to one while maintaining noise removal capability
Solution Approach 2:
The single operational amplifier in the patent performs multiple functions that previously required two separate amplifiers. It simultaneously processes signals from both the first and second capacitors, performs differential amplification, and maintains noise rejection, thereby achieving multi-functionality with a single component
2Measurement precision
If two operational amplifiers are connected to each electrode to sense capacitance changes, then measurement precision is improved, but device complexity is increased
Solution Approach 1:
The patent merges the signal processing functions of two operational amplifiers into a single operational amplifier by using differential capacitor connections. The first capacitor connects to the inverting terminal and the second capacitor connects to the non-inverting terminal, with both processed through one operational amplifier, simplifying the circuit while maintaining measurement precision
Solution Approach 2:
The patent introduces differential capacitors as intermediary elements that bridge the electrode to the operational amplifier. These capacitors serve as mediators that enable single operational amplifier processing while maintaining the signal differential structure needed for accurate capacitance measurement
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 removes noise interference, allowing for accurate detection of touch inputs and gestures by converting the output into a digital signal that determines the number of touch inputs and their coordinates, enhancing the reliability of capacitive touchscreens.
Implementation Method 1
an integrating circuit unit generating a first analog signal by integrating a change in capacitance generated in a first sensing electrode among the plurality of sensing electrodes and generating a second analog signal from a change in capacitance generated in a second sensing electrode adjacent to the first sensing electrode
Implementation Method 2
a subtracting unit calculating a difference in levels between the first and second analog signals
Data Source
AI summary
There are provided a touch sensing device and a touchscreen device, the touch sensing device including a plurality of driving electrodes extended in a first axial direction, a plurality of sensing electrodes extended in a second axial direction intersecting with the first axial direction, an integrating circuit unit generating a first analog signal by integrating a change in capacitance generated in a first sensing electrode among the plurality of sensing electrodes and generating a second analog signal from a change in capacitance generated in a second sensing electrode adjacent to the first sensing electrode, and a subtracting unit calculating a difference in levels between the first and second analog signals.