Touch Display Panel Parasitic Capacitance Reduction
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Solution Overview
Problem
Parasitic capacitance between touch electrodes and display electrodes in touch display devices degrades touch sensing performance and delays signal transmission, particularly affecting pen-touch sensing accuracy and recognition rates.
Innovation Solution
A touch display device and method that apply specific touch-driving signals to touch electrodes during different periods, including a first touch-driving period for finger sensing, a second touch-driving period for pen-touch sensing where a signal corresponding to the touch-driving signal is applied to the display electrode, and a third touch-driving period for receiving downlink signals, thereby reducing or eliminating parasitic capacitance and enhancing signal transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If touch electrodes and display electrodes are arranged on the same panel to provide both touch recognition and display functions, then the device can recognize finger touches and pen touches, but parasitic capacitance is produced between the electrodes which degrades touch sensing performance
Solution Approach 1:
The touch sensing period is divided into multiple sub-periods (first, second, third, fourth sub-periods) with different driving strategies. During the first and third sub-periods, constant voltage is applied to the display electrode to minimize parasitic capacitance interference. During the second sub-period, the display electrode is disconnected or set to floating state to further reduce interference. This temporal segmentation allows the system to maintain both touch sensing capability and display function while mitigating parasitic capacitance effects.
Solution Approach 2:
The touch driving circuit periodically switches the display electrode between constant voltage state, disconnected state, and floating state across different sub-periods within each touch sensing period. This periodic action creates optimal conditions for touch signal detection at specific moments while maintaining overall system functionality. The periodic switching enables the system to overcome the parasitic capacitance issue by creating alternating windows of low-interference states.
2Use of energy by moving object
If display electrodes are driven with various voltages and signals for display operation, then the display function is maintained, but parasitic capacitance interferes with touch electrode signals and delays signal transmission
Solution Approach 1:
Before performing touch signal detection, the touch driving circuit preemptively sets the display electrode to constant voltage or floating state to prevent parasitic capacitance formation. This preliminary anti-action occurs during the first and third sub-periods where the display electrode is deliberately held at stable potential before actual touch sensing begins in the second sub-period, thereby preventing rather than correcting signal delays.
Solution Approach 2:
The system performs preliminary setup of electrode states during the first sub-period by applying constant voltage to the display electrode and preparing the touch electrode for sensing. This preliminary action ensures that when actual touch detection occurs in the second sub-period, the parasitic capacitance has already been minimized or eliminated, allowing for faster and more accurate signal transmission without delay.
3Device complexity
If the same touch-driving signal is applied to both touch electrodes and display electrodes during the same period, then circuit simplification is achieved, but parasitic capacitance cannot be reduced and pen-touch sensing accuracy deteriorates
Solution Approach 1:
The touch driving circuit dynamically adjusts the display electrode state across different sub-periods rather than maintaining a static configuration. During the first sub-period, the display electrode receives constant voltage; during the second sub-period, it is disconnected or set to floating state; during the third sub-period, constant voltage is reapplied. This dynamic state changes enable the system to achieve both circuit simplicity and high pen-touch sensing accuracy by adapting the electrode configuration to the specific sensing requirements of each sub-period.
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 effectively reduces parasitic capacitance, prevents signal delays, and improves the recognition rate of pen-touch signals, enhancing the overall performance of pen-touch sensing in touch display devices.
Implementation Method 1
the parasitic capacitance produced between the display electrodes and the touch electrodes can degrade touch sensing performance
Data Source
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AI summary
Discussed are a touch display panel, a touch display device, and a driving method thereof, wherein a constant voltage is applied to a cathode electrode during a period for sensing a finger touch or a pen touch, thereby performing touch sensing while performing display driving. In addition, a signal having the same phase and potential as the signal applied to the touch electrode is applied to the cathode electrode during a period for transmitting an uplink signal to the pen, thereby eliminating parasitic capacitance between the touch electrode and the cathode electrode, preventing transmission delay of the uplink signal, improving the recognition rate of the uplink signal, and enhancing the performance of pen-touch sensing.