In-Cell Touch Controller Waveforms for Low-Emission Touch Scanning
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Solution Overview
Problem
Existing touch-sensing technologies, such as multiphase self-capacitance and floating ground methods, face challenges in achieving high sensitivity and noise rejection, especially in in-cell touch controllers for automotive applications with strict emission requirements, due to high panel capacitance and sensitivity to external noise.
Innovation Solution
The implementation of a windowed sinusoidal waveform and custom transition waveform between display and sensing intervals, combined with a signal generator using a multi-level sigma-delta modulator and phase adjustments of sense channel signals, reduces emissions and improves signal-to-noise ratio (SNR) for capacitive sensing in in-cell touch displays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional touch-sensing methods (multiphase self-capacitance, floating ground) are used, then touch sensing functionality is achieved, but emissions are high and sensitivity to noise is increased
Solution Approach 1:
The patent implements separate display function intervals and touch scanning intervals, creating periodic action patterns. During display intervals, display signals are applied; during scanning intervals, touch sensing occurs with reduced emissions. This temporal separation reduces electromagnetic emissions while maintaining reliable touch detection through structured periodic measurement cycles.
Solution Approach 2:
The patent applies windowing functions (e.g., Hanning, Hamming, Blackman) to the touch scanning signal to modify its spectral characteristics. This parameter change in the signal domain reduces emissions by suppressing spectral leakage and side lobes, while the modified signal maintains sufficient energy for reliable touch sensing in the presence of noise.
2Measurement precision
If excitation energy is increased to improve signal-to-noise ratio, then touch sensing sensitivity is improved, but emissions increase
Solution Approach 1:
By concentrating touch scanning into specific intervals separated from display function intervals, the patent achieves high measurement precision during scanning periods when the system is optimized for sensing. The periodic structure allows sufficient excitation energy to be applied during scanning intervals without continuously increasing emissions, as display and sensing operations are time-multiplexed.
Solution Approach 2:
The patent modifies the excitation signal by applying windowing functions that shape the spectral content. This parameter change allows the signal to maintain adequate energy for high signal-to-noise ratio touch detection while reducing the spectral spread and peak emissions, achieving a balance between measurement precision and emission levels.
3Device complexity
If in-cell touch controller is used for automotive applications, then integration is improved, but emission requirements become stricter
Solution Approach 1:
The in-cell touch controller implements alternating display and scanning intervals, creating periodic operation that reduces emissions compared to continuous sensing. This temporal separation allows the integrated controller to meet strict automotive emission standards while maintaining full touch sensing functionality through structured periodic measurement cycles.
Solution Approach 2:
The patent applies windowing functions to modify the spectral characteristics of the touch scanning signal, reducing emissions by suppressing spectral leakage. This parameter change in the signal domain enables the integrated in-cell controller to comply with stringent automotive emission requirements while maintaining reliable touch detection performance.
Data Source
AI summary
Technology directed to low-emissions touch controller in in-cell touch display systems is described. One in-cell touch controller includes a signal generator circuit that is configured to generate a sense signal according to a sensing function, the sense signal including a windowed sinusoidal waveform. The controller generates a transition signal to transition the in-cell touch display between a display function and the sensing function. The controller drives the sense signal and the transition signal on common voltage (VCOM) layer of electrodes during a touch scanning interval. During a display function interval an integrated display driver is configured to drive a first signal on the VCOM layer of electrodes during a display function interval.