Capacitive Touch Display Common Electrode Driver Timing
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Solution Overview
Problem
Capacitance type touch sensors in display devices face accuracy and detection time issues due to parasitic capacitance between driving electrodes and wirings, which affects the waveform and transmission of drive signals.
Innovation Solution
A display device with a pixel array and common electrodes for capacitance type touch detection, where a common electrode driver supplies voltage for display and drive signals for touch detection, and switches connect source lines to common electrodes during touch detection periods, allowing for improved signal transmission and reduced parasitic capacitance effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a capacitance type touch sensor is used in a thin display device, then the device achieves compactness and simple structure, but parasitic capacitance increases causing deterioration in touch detection accuracy and increased detection time
Solution Approach 1:
The patent divides the touch detection process into separate time periods: display periods for normal operation and touch detection periods for capacitance measurement. This temporal segmentation allows the system to dedicate specific time slots to touch detection, isolating it from display operations and reducing interference from parasitic capacitance in the driving wirings.
Solution Approach 2:
The patent applies preliminary action by setting the gate lines to the same phase as the common electrodes before performing touch detection. This pre-synchronization ensures that the gate lines are in the correct state to minimize parasitic capacitance effects before the actual measurement begins, thereby improving detection accuracy.
2Length of moving object
If electrodes are placed closer to wirings to reduce device thickness, then the display device becomes thinner, but parasitic capacitance increases causing signal waveform deterioration and transmission delay
Solution Approach 1:
The patent implements periodic action by alternately switching between display periods and touch detection periods. During touch detection periods, the system specifically measures capacitance values after setting gate lines to minimize parasitic effects. This periodic measurement approach allows the system to maintain thin design while periodically compensating for parasitic capacitance interference, thereby reducing signal transmission delays and maintaining accuracy.
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 configuration enhances touch detection accuracy and reduces detection time by minimizing the impact of parasitic capacitance, enabling more precise and efficient touch sensing in display devices.
Implementation Method 1
A touch sensor employing a capacitance type system detects a touch using a fact that an electrode will change in its capacitance when an electric conductor approaches the electrode
Implementation Method 2
If parasitic capacitance is connected between a driving electrode and a wiring in a capacitance type touch sensor, a drive signal will deteriorate in waveform and is delayed in transmission
Data Source
AI summary
A display device is provided and includes common electrodes overlapping pixels; common driver configured to supply voltage during a display period and an AC drive signal for touch detection during touch detection period; source lines connected to columns of pixels; source driver configured to supply an image signal; gate lines connected to rows of the pixels; select transistors connected between source driver and source lines; and controller configured to supply DC control signal to gate terminals of select transistors during display period, supply an AC control signal to gate terminals of select transistors during touch detection period, wherein AC control signal is synchronous with AC drive signal.