Touch Sensor Panel Differential Drive for Noise-Resistant Sensing
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Solution Overview
Problem
Existing touch sensor panels suffer from high noise levels, which degrade the signal-to-noise ratio (SNR) and affect the accuracy and reliability of touch detection.
Innovation Solution
Implementing differential driving and sensing techniques, where touch nodes are driven with complementary drive signals and sensed differentially, alternating high and low electrostatic fringe fields to reduce noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If capacitive touch sensor panels use fringing electrical fields to detect touch, then touch detection capability is enabled, but noise levels increase and signal-to-noise ratio deteriorates
Solution Approach 1:
The touch sensor panel segments the electrode array into multiple independent groups that can be driven with different signals. This segmentation allows differential driving techniques to be applied, where adjacent groups use complementary signals to cancel noise while maintaining touch detection capability.
Solution Approach 2:
The patent changes the electrical parameters of the drive signals by using complementary signaling (inverted phases) on adjacent electrode groups. This parameter change enables noise cancellation through differential sensing, improving the signal-to-noise ratio while maintaining touch detection accuracy.
2Device complexity
If touch sensor panels integrate sensing circuitry into display pixel stack-up, then device integration is improved, but noise from display systems increases
Solution Approach 1:
The patent extracts the touch sensing function from the display system by using differential driving and sensing techniques that isolate touch signals from display noise. The complementary signaling approach separates touch detection from display operation, reducing noise coupling between the two functions.
Solution Approach 2:
The patent introduces asymmetry in the driving scheme by applying complementary signals to adjacent electrode groups rather than uniform signaling. This asymmetric approach creates differential modes that are insensitive to symmetric noise sources from the display system, reducing noise interference.
3Object-affected harmful factors
If differential driving with complementary signals is applied to adjacent electrode groups, then noise is reduced and signal-to-noise ratio improves, but device complexity increases
Solution Approach 1:
The patent merges the drive signal generation for multiple electrode groups into a coordinated system where complementary signals are generated from a common source. This merging approach, while introducing differential signaling, uses shared circuitry and synchronized operation to limit the increase in overall 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
Enhances the signal-to-noise ratio (SNR) in touch sensor panels, improving touch detection accuracy and reducing noise interference from display systems.
Implementation Method 1
The electrostatic fringe field coupling of the driven touch nodes can substantially alternate high and low with successive receiver electrodes in a repeating pattern
Data Source
AI summary
Touch sensor panels (or touch screens) can improve signal-to-noise ratio (SNR) using touch electrode patterns for differential drive and/or differential sense techniques. In some examples, a touch sensor panel can include a two-dimensional array of touch nodes formed from a plurality of touch electrodes. Each column (or row) of touch nodes can be driven with a plurality of drive signals. For example, a first column (or row) of touch nodes can be driven by a first drive signal applied to one or more first touch nodes in the first column (or row) and a second drive signal applied to a one or more second touch nodes of the first column (or row). In some examples, the first drive signal and the second drive signal can be complimentary drive signals. In some examples, each row (or column) of touch electrodes can be sensed by differential sense circuitry.