Touch Panel Noise Cancellation via Common Electrode Reference
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Solution Overview
Problem
Hybrid in-cell touch panels used in organic EL display devices face issues with false touch sensing due to noise interference from electrodes within the organic EL element, affecting the accuracy of touch sensing.
Innovation Solution
A touch panel structure incorporating a pixel, a touch sensor, and an integrator circuit, where the touch sensor includes two electrodes and an operational amplifier with one input terminal connected to the sensing electrode and the other to the common electrode, allowing for noise cancellation and improved signal-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a hybrid in-cell touch panel or full in-cell touch panel is used in an organic EL display device, then the display device can be made thinner and more inexpensive, but false touch sensing occurs due to noise interference from electrodes in the organic EL element
Solution Approach 1:
The patent connects the common electrode of the organic EL element to the second input terminal of the operational amplifier, converting the harmful noise signal from the common electrode into a useful reference signal. The operational amplifier subtracts this reference noise signal from the sensing electrode signal, transforming the harmful interference into a beneficial noise cancellation mechanism that improves touch sensing accuracy
Solution Approach 2:
The operational amplifier serves as an intermediary device between the sensing electrode and the touch sensing controller. It processes the sensing signal by subtracting the common electrode noise signal, acting as a mediator that filters out interference while preserving the actual touch information before transmitting it to the controller
2Measurement precision
If the second input terminal of the operational amplifier is connected to the common electrode, then noise cancellation is achieved, but the circuit complexity increases
Solution Approach 1:
The common electrode serves dual functions: it acts as the cathode for the organic EL element's light emission and simultaneously serves as a noise reference signal source for the touch sensing circuit. This multi-functionality eliminates the need for separate noise reference electrodes, reducing overall device complexity while maintaining noise cancellation capability
Solution Approach 2:
The patent merges the organic EL common electrode with the noise reference function by connecting it to the second input terminal of the operational amplifier. This consolidation combines the display function and touch sensing noise reference function into a single electrode structure, simplifying the overall device architecture
Data Source
AI summary
A touch panel or the like having a novel structure in which an influence of noise of an electrode included in an organic EL element on an electrode for touch sensing can be suppressed is provided.A voltage of the electrode for touch sensing and a voltage for reference are input to input terminals of an operational amplifier, and in an integrator circuit in which a change in capacitance due to touch sensing is sensed, the input terminal to which the voltage for reference is supplied is connected to a common electrode included in the organic EL element. Such a structure does not amplify but can cancel noise of the electrode for touch sensing, on which noise of the common electrode is superimposed.