Differential Touch Sensing Circuit for Common-Mode Noise Rejection
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Solution Overview
Problem
Touch sensor panels face noise interference from electronic circuits and environmental sources, leading to false positives, false negatives, and reduced accuracy in touch recognition.
Innovation Solution
A differential amplifier is configured to receive and amplify touch signals, with noise isolated and introduced to both input ports, allowing the amplifier to eliminate or reduce noise, and a filter circuit is used to selectively amplify or filter frequencies, thereby improving signal accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a touch sensor panel uses integrated display circuits and sense channels to detect touch signals, then touch detection capability is improved, but noise interference from electronic circuits increases causing false positives and reduced accuracy
Solution Approach 1:
The patent segments the touch sensor panel into multiple independent sensing zones with separate sense channels, allowing noise to be isolated and rejected at the channel level. Each zone can be independently processed, so noise in one channel does not affect other channels, thereby maintaining overall detection accuracy despite the presence of electronic circuit noise.
Solution Approach 2:
The patent extracts and separates the noise signal from the touch signal by using dedicated noise cancellation circuits that independently process noise components. The noise is extracted from the sense channels and processed separately through differential amplification, allowing it to be removed before the final touch detection decision is made.
2Adaptability or versatility
If sense channels receive signals from multiple sources including other sense channels and display circuits, then signal processing capability is enhanced, but cross-channel noise coupling increases
Solution Approach 1:
The patent introduces differential amplifiers as intermediary components between sense channels and the processing logic. These amplifiers act as mediators that accept signals from multiple sources including other sense channels and display circuits, but through their differential configuration, they reject common-mode noise that couples across channels, thereby enabling versatile signal processing while blocking cross-channel noise interference.
Solution Approach 2:
The patent adds a differential signal dimension by processing touch signals through both inverting and non-inverting input ports of differential amplifiers. This dimensional transformation allows the system to process multiple signal sources simultaneously while using the differential configuration to reject noise that appears equally on both inputs, effectively separating useful signals from cross-channel noise coupling.
3Productivity
If noise is present on the touch signal, then false positive detection increases, but the system continues to operate without additional filtering components
Solution Approach 1:
The patent implements feedback mechanisms where the output of each sense channel is fed back to the differential amplifier configuration. This feedback allows the system to continuously monitor and adjust for noise conditions, using the differential amplification to compare expected versus actual signals and reject false positives that arise from noise, thereby maintaining reliable operation without sacrificing system continuity.
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 mitigates noise in touch signals, enhancing the accuracy of touch detection and recognition by isolating and eliminating noise, resulting in improved user experience and device performance.
Implementation Method 1
a differential amplifier is configured to receive and amplify the touch signal received from the touch electrodes
Implementation Method 2
the differential amplifier can be leveraged to mitigate noise in the touch signal... causing some or all of the noise signal to be eliminated by the differential amplifier
Implementation Method 3
a filter circuit is used to selectively amplify or filter frequencies
Data Source
AI summary
Techniques for mitigating noise in a touch signal are disclosed. To reduce or eliminate noise in a touch signal, the touch activity can be filtered out of a touch signal, thus isolating the noise. In some examples, the noise is then provided to the non-inverting input port of a differential amplifier while the unfiltered touch signal is provided to the inverting input port of the differential amplifier. The noise, which is now common on both inputs, is automatically eliminated or reduced by the differential amplifier.