Touch Screen Controller Noise Suppression via Sync Signal Decoupling
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Solution Overview
Problem
As touch sensitive displays in handheld electronic devices become thinner, they experience increased noise coupling from the display layer to the sensing layer, degrading the accuracy of touch sensing due to parasitic capacitances.
Innovation Solution
A touch screen controller asynchronously measures capacitance between sense and drive lines, disconnecting the sense line during the rising edge of the horizontal sync signal to reduce noise coupling, using a digital block to generate control signals that selectively decouple the sense line and control the driver to minimize noise interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the touch sensitive display is made thinner, then the device thickness is reduced, but noise coupling from the display layer to the sensing layer increases
Solution Approach 1:
The patent extracts and removes the harmful noise component from the system by selectively disconnecting the sense line from the controller during periods when display noise is present. The switch isolates the sensing circuitry from the noisy display layer, effectively taking out the harmful electrical noise from the signal path while maintaining the thin display structure.
Solution Approach 2:
The patent applies preliminary action by proactively disconnecting the sense line before noise from the display layer can couple into the sensing circuit. The controller identifies when noise is likely to occur (during display refresh cycles) and preemptively isolates the sense line, preventing noise contamination before it degrades measurement accuracy.
2Measurement precision
If the sense line remains connected continuously, then measurement continuity is maintained, but noise from the display layer degrades measurement accuracy
Solution Approach 1:
The patent implements periodic action by rhythmically connecting and disconnecting the sense line in synchronization with the display refresh cycle. The switch is closed during measurement periods for accurate sensing, then opened during display refresh periods when noise is generated, creating a periodic connect-disconnect pattern that balances measurement needs with noise avoidance.
Solution Approach 2:
The patent applies dynamics by making the connection state of the sense line variable rather than static. The switch dynamically transitions between connected and disconnected states based on the operational phase - connected during touch measurement for continuity, disconnected during display refresh to prevent noise coupling, adapting the connection status to real-time system needs.
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 significantly reduces noise from the display layer, enhancing the accuracy and robustness of touch data generation while minimizing baseband shift and receiver saturation risks.
Implementation Method 1
a single drive line is driven with a wave, such as a square wave or sine wave. The capacitance between the sense lines and the driven drive line is sensed at the point where they intersect. Presence of a human finger or a conductive object alters the expected capacitance at the intersection point
Implementation Method 2
disconnect from the sense line for a given period of time following a rising edge of the horizontal sync signal so as to reduce capacitive coupling of display noise from the horizontal sync signal to the sensing layer
Data Source
AI summary
An electronic device includes a touch screen controller. The touch screen controller is configured to asynchronously measure a capacitance between a sense line and a drive line of a sensing layer with respect to a horizontal sync signal of a display layer. In addition, the touch screen controller is also configured to disconnect from the sense line for a given period of time following a rising edge of the horizontal sync signal so as to reduce capacitive coupling of display noise from the horizontal sync signal to the sensing layer.