In-Cell Touch Display Driving Voltage Control for Block Dim
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Solution Overview
Problem
Existing display devices with integrated in-cell type touch screens suffer from image-quality defects like block dim due to luminance differences between common electrodes used as driving and sensing electrodes, and suboptimal touch performance resulting from insufficient amplitude of the driving pulse.
Innovation Solution
Applying a common voltage as the minimum voltage to the driving electrode during touch sensing periods and using a reference voltage for touch sensing during non-sensing periods, thereby minimizing voltage differences and maximizing the amplitude of the driving pulse.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a driving pulse with maximum voltage VTX_HIGH and minimum voltage VTX_LOW is applied to the driving electrode during touch driving period, then touch sensing capability is enabled, but a voltage difference occurs between driving electrode and sensing electrode causing block dim in image quality
Solution Approach 1:
The patent applies periodic action by dividing the operation into display driving period and touch driving period. During display driving period, common voltage is applied to both electrodes for uniform luminance. During touch driving period, driving pulse is applied to driving electrode for touch sensing. This periodic switching resolves the contradiction by separating the conflicting requirements of luminance uniformity and touch sensing capability in time domain.
Solution Approach 2:
The patent changes voltage parameters dynamically: during display driving period, both electrodes receive common voltage Vcom; during touch driving period, driving electrode receives driving pulse with VTX_HIGH and VTX_LOW while sensing electrode receives reference voltage VRX_REF. This parameter change enables the system to achieve both uniform luminance during display and sufficient voltage difference for touch sensing.
2Object-affected harmful factors
If the minimum voltage VTX_LOW of the driving pulse is higher than the common voltage, then the voltage difference between driving electrode and sensing electrode is reduced, but the amplitude of the driving pulse becomes insufficient degrading touch performance
Solution Approach 1:
The patent optimizes the voltage parameters of the driving pulse by setting VTX_LOW equal to Vcom (common voltage) rather than making it higher. This parameter setting maximizes the amplitude of the driving pulse (VTX_HIGH - VTX_LOW), ensuring sufficient voltage difference for accurate touch sensing while maintaining compatibility with the common electrode structure.
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 prevents block dim and enhances touch sensing performance by maintaining a consistent voltage and increasing the amplitude of the driving pulse, improving the overall image quality and touch sensitivity.
Implementation Method 1
a mutual capacitance to be generated between the touch driving area and the touch sensing area
Data Source
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AI summary
Disclosed is a display device. The display device includes a panel, a display driver IC, and a touch IC. The panel includes a plurality of driving electrodes and a plurality of sensing electrodes. The display driver IC outputs a common voltage to the driving electrode and the sensing electrode in a display driving interval, outputs a reference voltage to the driving electrode during a touch non-sensing period in a touch driving interval, and outputs a driving pulse to the driving electrode to receive a sensing signal from the sensing electrode during a touch sensing period in the touch driving interval. The touch IC transfers a control signal and a selection signal for selecting the touch sensing period and the touch non-sensing period to the display driver, and senses whether there is a touch with the sensing signal and the reference voltage.