Touch Screen Controller Display Noise Table Subtraction
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Solution Overview
Problem
The increasing proximity between display and touch panels in touch screens leads to enhanced capacitance and resulting display noise in touch sensing signals, which deteriorates touch sensing performance due to higher frame refresh rates and thinner display panels.
Innovation Solution
A touch screen driving circuit and controller system that utilizes a display noise table (DNT) to extract feature values from image data and driving states, allowing for the subtraction of display noise from touch sensing values to generate noise-reduced touch values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the display panel is made thinner to reduce overall device thickness, then the device form factor is improved, but the capacitance between display and touch panels increases causing display noise in touch sensing signals
Solution Approach 1:
The patent extracts and separates the display noise component from the touch sensing signal through dedicated noise measurement circuits and signal processing. The display noise is measured independently during non-touch periods and then subtracted from the touch sensing signal to obtain a clean touch signal, effectively removing the harmful noise effect.
Solution Approach 2:
The patent performs preliminary measurement of display noise during non-touch periods before actual touch sensing occurs. By measuring and storing the display noise characteristics in advance, the system prepares the noise compensation data needed for subsequent touch sensing operations, enabling effective noise removal when touch events occur.
2Speed
If the frame refresh rate of the touch panel is increased to improve responsiveness, then the touch response speed is improved, but the display noise in the touch sensing signal increases
Solution Approach 1:
The patent implements periodic measurement of display noise at specific intervals during non-touch periods, synchronized with the display and touch panel refresh cycles. This periodic noise measurement approach captures the time-varying display noise characteristics at different frame rates, enabling accurate noise compensation even when the refresh rate changes to improve responsiveness.
3Length of stationary object
If the distance between display panel and touch panel is reduced to improve device thinness, then the overall device thickness is improved, but the capacitance coupling increases causing noise in touch sensing
Solution Approach 1:
The patent introduces an intermediary signal processing mechanism that measures the display noise generated by the display panel's operation and uses this measured noise as a reference to compensate the touch sensing signal. The intermediary noise measurement circuit acts as a mediator between the display panel and touch panel, capturing the coupling effect and enabling its removal from the touch signal.
4Device complexity
If display noise is not removed from touch sensing signal, then the system complexity is low, but the touch sensing performance deteriorates due to noise interference
Solution Approach 1:
The patent segments the signal processing into distinct functional blocks: a display noise measurement circuit that independently measures noise during non-touch periods, a storage unit that holds the measured noise data, and a touch signal processing circuit that subtracts the stored noise from the touch sensing signal. This segmentation allows for manageable complexity while achieving effective noise removal and improved touch sensing performance.
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 reduces display noise in touch sensing signals, thereby enhancing touch sensing performance and maintaining signal quality despite increased frame refresh rates and thinner display panels.
Implementation Method 1
the capacitance between electrodes of the two panels may increase, and accordingly, noise caused by signals driven for display operation in a touch sensing signal
Data Source
AI summary
A touch screen controller, a touch screen driving circuit and a touch screen system are provided. The touch screen driving circuit configured to drive a touch screen includes an analog driving circuit configured to provide driving signals to a display panel and a touch panel of the touch screen, and generate a touch sensing value based on a touch sensing signal from the touch panel; a display noise table (DNT) comprising display noise information indicating display noise that varies according to a driving state of the touch screen and image data; a feature extractor configured to extract a plurality of feature values from the driving state and the image data; and a touch processor configured to read a display noise value mapped to the plurality of feature values from the DNT, subtract the display noise value from the touch sensing value and generate a touch value.