Touch Sensing Circuit Common-Mode Noise Compensation
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Solution Overview
Problem
Touch sensing circuits in electronic devices suffer from sensitivity reduction due to common-mode noise interference, which is caused by voltage disturbances from display noise, leading to inaccurate touch detection.
Innovation Solution
A touch sensing circuit comprising analog front-end circuits, a noise processing circuit, and a compensation circuit that generates and compensates for average noise to suppress common-mode noise, improving sensitivity and accuracy of touch detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the touch sensing circuit uses the common electrode substrate and coupling capacitors for touch sensing, then the touch sensing function is achieved, but the common voltage is prone to interference and jitter due to impedance and voltage drop, reducing sensing accuracy
Solution Approach 1:
The patent segments the sensing signal processing into multiple channels (first sensing signal from first sensing line, second sensing signal from second sensing line) and processes them separately through dedicated first and second analog front-end circuits, then combines the results. This segmentation allows independent noise filtering for each channel, improving overall sensing precision while maintaining reliability.
Solution Approach 2:
The patent introduces an intermediary processing stage that receives both sensing signals, filters common-mode noise, and generates a compensated sensing signal. This intermediary circuit acts as a mediator between the noisy raw signals and the final touch detection, removing common voltage interference before the sensing decision is made.
2Ease of operation
If the touch sensing circuit processes sensing signals directly from the sensing lines, then the touch detection function is maintained, but the display noise transmitted via coupling capacitors interferes with the sensing signals, reducing sensitivity
Solution Approach 1:
The patent extracts and removes the common-mode noise component from the sensing signals through dedicated filtering circuits. The first and second analog front-end circuits separately process their respective signals, extracting the useful touch information while eliminating the common voltage interference that would otherwise reduce sensing sensitivity.
Solution Approach 2:
The patent implements a feedback mechanism where the processed sensing signals are combined and used to generate compensation signals that are fed back to improve the accuracy of touch detection. The system continuously monitors and adjusts based on the combined sensing information, enhancing sensitivity while maintaining operational ease.
3Adaptability or versatility
If the common voltage is provided through the buffer and impedance to the common electrode substrate, then the display panel operation is enabled, but the voltage disturbance from electronic components is transmitted to the sensing lines, causing common-mode noise
Solution Approach 1:
The patent converts the harmful common-mode noise into a beneficial filtering opportunity. By deliberately designing the system to recognize and extract the common-mode component from multiple sensing channels, the noise that would normally degrade performance is instead used to improve accuracy through differential processing and common-mode rejection techniques.
Data Source
AI summary
The present application provides a touch sensing circuit, which comprises a plurality of analog front-end circuits, a noise processing circuit, and a compensation circuit. The analog front-end circuits generate a plurality of output signals according to a plurality of sensing signals. The noise processing circuit is coupled to the analog front-end circuits and generates an average noise according to the output signals. The compensation circuit is coupled to the noise processing circuit and compensates the output signals according to the average noise. By applying the touch sensing circuit of the present application, the influence of common-mode noise may be suppressed and the sensitivity of sensing touches may be improved.