Liquid Crystal Display Touch Signal Ripple Synchronization
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Solution Overview
Problem
In liquid crystal display devices with thin panels, the proximity of touch sensing electrodes to common electrodes leads to parasitic capacitance, causing interference between touch driving signals and display voltages, which affects touch sensing and screen display performance.
Innovation Solution
The implementation of a touch controller that generates a touch driving signal with specific ripple components synchronized with display voltages, adjusting polarity to minimize distortion and ensure that touch signals do not impact screen display, by forming third ripple components from first and second ripple components and synchronizing with data voltage periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the distance between sensing electrode and common electrode is shortened to reduce display panel thickness, then the display panel becomes thinner, but parasitic capacitance increases causing interference between touch driving signals and display voltages
Solution Approach 1:
The patent applies periodic action by synchronizing the touch driving signal with the display voltage in a periodic manner. The touch driving signal is supplied only during specific periods when display voltage is not applied, creating temporal separation between the two signals. This periodic operation allows the sensing electrode to be close to the common electrode for thin display panels while preventing parasitic capacitance interference through time-based signal isolation.
Solution Approach 2:
The patent implements preliminary action by pre-establishing the synchronization relationship between touch driving signals and display voltages before actual operation. The system determines the timing and polarity of touch driving signals based on predetermined synchronization with display voltage cycles, ensuring that harmful capacitive coupling is avoided from the outset through planned signal timing.
2Measurement precision
If voltage of sensing electrode is increased to improve touch sensing performance, then touch sensing capability improves, but voltage interference on common electrode increases affecting screen display
Solution Approach 1:
The patent uses periodic action to supply touch driving signals at specific time intervals synchronized with display voltage cycles. By timing the high-voltage touch sensing signals to occur only when display electrodes are not active, the system achieves improved touch sensing precision while preventing voltage interference on the common electrode through temporal separation of signal application.
Solution Approach 2:
The patent employs feedback mechanisms where the touch controller monitors and adjusts touch driving signal timing and polarity based on the display voltage state. This feedback control ensures that high-voltage touch sensing operations are synchronized with display voltage cycles, allowing precise touch detection while automatically preventing harmful voltage interference on the common electrode through adaptive signal timing.
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 solution effectively isolates touch driving signals from display voltages, reducing distortion and ensuring accurate touch sensing without affecting screen display performance, even on thin panels.
Implementation Method 1
a common electrode forming first capacitance with the plurality of pixel electrodes; a plurality of sensing electrodes forming second capacitance with the common electrode
Implementation Method 2
a liquid crystal layer interposed between the two display panels, and a predetermined voltage is applied to the plurality of pixel electrodes and the common electrode to realign liquid crystal molecules of the liquid crystal layer to thereby adjust an amount of transmitted light
Implementation Method 3
as a distance between a sensing electrode in a touch screen panel and a common electrode in a display panel is shortened, parasitic capacitance which is undesirable is formed between the two electrodes and affects voltages of the respective electrodes
Data Source
AI summary
Provided is a liquid crystal display device including: a plurality of pixel electrodes to which a display voltage is supplied; a common electrode forming first capacitance with the plurality of pixel electrodes, and having a common voltage supplied thereto; a plurality of sensing electrodes forming second capacitance with the common electrode, and having a touch driving signal supplied thereto; and a touch controller supplying the touch driving signal, wherein a voltage of the common electrode includes a first ripple component that is generated due to variation in the display voltage and a second ripple component that is generated due to variation in the touch driving signal, and the touch controller supplies the touch driving signal such that a polarity of the second ripple component is determined based on a polarity of the first ripple component.