Multi-Frequency Touch Sensing Circuit for Noise-Robust Displays
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Solution Overview
Problem
Display devices face challenges in accurately sensing touch inputs due to noise interference in capacitance-based touch panels, which affects the reliability and precision of touch detection.
Innovation Solution
The implementation of an input sensing device with analog front-end circuits that separate and recombine sensing signals of different frequencies, using charge amplification, filtering, and buffer components to generate digital sensing data, effectively removing noise and enhancing signal-to-noise ratio (SNR).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If capacitance-based touch panel sensing is used, then touch input detection is enabled, but noise interference reduces sensing accuracy
Solution Approach 1:
The sensing signal is segmented into multiple frequency components using Fast Fourier Transform (FFT). The sensing driver separates the capacitive sensing signal into first and second frequency components, allowing selective processing of different frequency ranges to isolate the touch signal from noise.
Solution Approach 2:
The invention extracts the useful sensing signal from the noisy composite signal by identifying and isolating specific frequency components. The touch sensing signal is extracted at a predetermined frequency while discarding noise components at other frequencies.
Solution Approach 3:
The sensing driver changes the frequency parameter of the driving signal to optimize signal-to-noise ratio. By operating at specific frequencies and using frequency-domain analysis, the system enhances the detectability of touch signals against background noise.
2Reliability
If multiple frequency components are separated and processed, then signal-to-noise ratio is improved, but device complexity increases
Solution Approach 1:
The analog front-end circuit is designed to perform multiple functions: capacitance-to-voltage conversion, differential amplification, and frequency-domain signal separation. This multi-functional approach consolidates what could be separate complex stages into a unified circuit architecture.
Solution Approach 2:
The invention replaces complex mechanical or hardware-based frequency filtering with software-based Fast Fourier Transform processing. The frequency separation is achieved through digital signal processing algorithms rather than multiple physical filter circuits.
Data Source
AI summary
An input sensing device includes first driving electrodes, second driving electrodes, and sensing electrodes, and a sensing driver that transmits a first driving signal to the first driving electrodes at a first frequency, transmits a second driving signal to the second driving electrodes at a second frequency, and determines a touch or approach of an external object based on sensing signals received from the sensing electrodes. The sensing driver includes analog front-end circuits that separate a sensing signal of the first frequency and a sensing signal of the second frequency that are received from the respective sensing electrodes, and generate digital sensing data based on a result of a recombination of the separated sensing signals.