In-cell Multi-touch Panel Noise Reduction via Time Division Multiplexing
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Solution Overview
Problem
In-cell multi-touch panels face challenges with noise interference from source voltages and polarity inversion, leading to reduced system signal-to-noise ratio (SNR) and unstable touch coordinate determination, particularly as panel resolution increases, making it difficult to concurrently perform image displaying and touch sensing within the required time frame.
Innovation Solution
An in-cell multi-touch panel system with low noise and time division multiplexing, where the common grounding signal and touch driving signal share the same transparent electrical conductor layer, allowing different driving timings for display and touch control, and using frequency hopping to minimize noise interference, thereby improving the reliability of touch coordinate determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the common voltage layer and touch driving layer share the same transparent electrical conductor, then cost is reduced and device complexity is simplified, but noise interference increases and system SNR decreases
Solution Approach 1:
The patent divides the frame time into separate display cycle and touch cycle, segmenting the operation of the common voltage layer and touch driving layer in time. This allows the same transparent electrical conductor to be used for both functions without their signals interfering with each other, thus reducing noise while maintaining cost efficiency
Solution Approach 2:
The patent implements periodic switching between display operation and touch sensing operation within frame time. The common voltage layer operates during display cycles while the touch driving layer operates during touch cycles, creating a periodic pattern that eliminates continuous noise interference and improves system SNR
2Productivity
If display and touch control are performed concurrently, then productivity is improved, but noise interference from source voltages and polarity inversion increases
Solution Approach 1:
The patent segments frame time into display cycle and touch cycle, performing display and touch control in separate time periods rather than concurrently. This segmentation eliminates the noise interference that would occur during concurrent operation while still achieving high productivity through efficient time utilization
Solution Approach 2:
The patent ensures continuous operation by filling the entire frame time with useful actions - display operation during display cycles and touch sensing during touch cycles. This continuous utilization of time resources maintains high productivity while the sequential arrangement eliminates noise interference
3Manufacturing precision
If panel resolution is increased, then display quality is improved, but the time required for image displaying and touch sensing increases
Solution Approach 1:
The patent uses periodic action by dividing frame time into display cycle and touch cycle, allowing both high-resolution display and comprehensive touch sensing to be completed within the same frame period. This periodic structure ensures that increased resolution does not extend total operation time beyond the frame rate requirement
4Ease of manufacture
If the same transparent electrical conductor is used for both common grounding signal and touch driving signal, then ease of manufacture is improved, but reliability of touch coordinate determination decreases due to noise
Solution Approach 1:
The patent segments the operation into display cycle and touch cycle, allowing the same transparent electrical conductor to serve dual purposes without compromising reliability. During touch cycles, the conductor functions as touch driving layer while during display cycles it functions as common voltage layer, eliminating noise interference and ensuring accurate touch coordinate determination
Solution Approach 2:
The patent implements periodic switching between the two functions of the transparent electrical conductor. This periodic action ensures that noise from source voltages and polarity inversion does not continuously interfere with touch sensing, thereby maintaining high reliability while simplifying the manufacturing process
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 reduces noise interference, increases the linearity and reliability of touch point determination, and enhances the system SNR, enabling stable and accurate touch sensing while maintaining high display quality even at higher resolutions.
Implementation Method 1
a capacitive touch panel uses a capacitance change generated in an electrostatic combination of the arranged transparent electrodes and a human body to generate a current or voltage for detecting touching coordinates
Implementation Method 2
a capacitive touch panel uses a capacitance change generated in an electrostatic combination of the arranged transparent electrodes and a human body
Data Source
AI summary
An in-cell multi-touch panel system includes: an in-cell touch display panel, a touch display control system. In a first frame time interval, the touch display control system drives the in-cell touch display panel and samples the sensing voltage from the in-cell touch display panel to determine whether there is an approaching external object and noise interference. In a second frame time interval, the touch display control system finds out a frequency with minimum noise for use as a frequency of the touch driving signal when the noise interference exists. In a third frame time interval, the touch display control system is based on the frequency with minimum noise to correspondingly generate the touch driving signal so as to determine whether there is an approaching external object.