Touch Drive Signal Harmonic Control for In-Cell Display Noise
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Solution Overview
Problem
In-cell touch displays emit noise due to harmonic components of the touch drive signal, affecting receivers, and sinusoidal touch drive signals reduce touch detection sensitivity.
Innovation Solution
A display system with a touch drive signal that includes odd-order harmonics different from a designated frequency, reducing radiation of electromagnetic waves and improving touch detection sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a sinusoidal touch drive signal is used, then electromagnetic wave radiation is reduced, but touch detection sensitivity deteriorates
Solution Approach 1:
The patent changes the frequency parameters of the touch drive signal by incorporating specific harmonic frequencies (odd-order harmonics) while excluding certain frequencies (designated frequency and its harmonics). This parameter modification allows the signal to maintain low electromagnetic radiation characteristics of sinusoidal waves while improving touch detection sensitivity through the addition of harmonic content.
Solution Approach 2:
The touch drive signal is constructed as a composite waveform combining a fundamental frequency with specific odd-order harmonics. This composite signal structure integrates the benefits of sinusoidal waves (low radiation) with the enhanced detection capabilities of multi-frequency signals, creating a hybrid signal that outperforms simple sinusoidal waves.
2Measurement precision
If a touch drive signal with harmonics is used, then touch detection sensitivity is improved, but electromagnetic wave radiation increases
Solution Approach 1:
The patent extracts and removes specific frequency components (the designated frequency and its harmonics) from the touch drive signal spectrum. By selectively eliminating these problematic frequencies while retaining the fundamental frequency and certain odd-order harmonics, the signal maintains high touch detection sensitivity without the harmful electromagnetic radiation associated with complete harmonic content.
3Device complexity
If common electrodes are used for both image display and touch detection, then device complexity is reduced, but signal interference increases
Solution Approach 1:
The patent implements a multi-functionality approach where the same common electrodes serve dual purposes: image display and touch detection. The specially designed touch drive signal with selective harmonics enables these electrodes to perform both functions simultaneously without significant signal interference, eliminating the need for separate electrode structures.
Data Source
AI summary
In a display system, a display device includes a plurality of common electrodes commonly used for image display and touch detection. A second drive circuit supplies a touch drive signal to each of the plurality of common electrodes. A touch detection circuit detects a touch by an object on the display device based on a detection signal received from each of the plurality of common electrodes. The touch drive signal includes a harmonic having a frequency different from a designated frequency and does not include a harmonic having the designated frequency.