Level Shifter Voltage Stability for Touch Sensing
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Solution Overview
Problem
The existing display devices with touch sensors experience increased noise in touch sensor signals due to parasitic capacitance, leading to waveform distortion of load-free driving signals, which degrades touch sensor performance, and removing the stabilizing capacitor can cause malfunctions.
Innovation Solution
A display device design that includes a power supply unit generating specific voltages, a control signal generating unit defining display and touch sensing periods, and a level shifter that converts these signals into output clocks to match the waveform of gate pulses and load-free driving signals, allowing for a load-free driving signal with the same phase as the touch sensor driving signal to be applied to gate lines without removing the stabilizing capacitor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a stabilizing capacitor is connected to the VGL line of the level shifter, then the VGL voltage is stabilized, but the waveform of the load-free driving signal is distorted due to the capacitor
Solution Approach 1:
The patent divides the operation into two distinct periods: display period and touch sensing period. During the display period, the stabilizing capacitor remains connected to stabilize VGL. During the touch sensing period, the capacitor is disconnected (or a different circuit configuration is used) to prevent waveform distortion of the load-free driving signal. This temporal segmentation allows both voltage stability and signal accuracy to be maintained in their respective operational contexts.
Solution Approach 2:
The patent employs dynamic switching of the stabilizing capacitor connection state based on the operational period. The capacitor is dynamically connected during the display period and dynamically disconnected during the touch sensing period. This dynamic adjustment allows the system to adapt its electrical characteristics to match the requirements of each operational phase, resolving the contradiction between stability and waveform accuracy.
2Manufacturing precision
If the stabilizing capacitor is removed from the VGL line, then the waveform distortion is eliminated, but noise of the gate low voltage increases causing the level shifter to malfunction
Solution Approach 1:
The patent segments the operational requirements into two phases: during the display period, the stabilizing capacitor is connected to ensure low noise and reliable level shifter operation. During the touch sensing period, the capacitor is disconnected to eliminate waveform distortion. This segmentation allows the system to meet both reliability and waveform accuracy requirements at different times.
Solution Approach 2:
The patent implements periodic switching of the stabilizing capacitor based on the periodic nature of display and touch sensing operations. The capacitor is periodically connected during display periods and periodically disconnected during touch sensing periods. This periodic action pattern matches the operational rhythm of the display device, allowing the system to maintain both reliability and signal integrity through rhythmic adjustment of the electrical configuration.
3Object-affected harmful factors
If a load-free driving signal is applied to gate lines during touch sensing period, then parasitic capacitance between touch sensors and pixel lines is reduced, but waveform distortion occurs due to the stabilizing capacitor
Solution Approach 1:
The patent segments the gate line driving into two modes: during the display period, normal gate pulses are applied for pixel scanning. During the touch sensing period, a load-free driving signal is applied to minimize parasitic capacitance effects on touch sensor signals. The stabilizing capacitor is simultaneously disconnected during this period to prevent waveform distortion of the load-free signal, allowing both benefits to be achieved in the touch sensing context.
Solution Approach 2:
The patent dynamically changes the gate line driving signal characteristics based on the operational period. During touch sensing, the gate driver transitions to providing a load-free driving signal with appropriate waveform characteristics that minimize parasitic coupling. The dynamic disconnection of the stabilizing capacitor during this period ensures the load-free signal maintains its intended waveform, enabling effective parasitic capacitance reduction without signal distortion.
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 prevents waveform distortion of load-free driving signals, reducing noise and improving touch sensing sensitivity by minimizing parasitic capacitance between touch sensors and pixel array lines.
Implementation Method 1
a level shifter receiving the synchronization signal, the input clock, the first voltage, the second voltage, and the third voltage and generating an output clock swinging between the first voltage and the second voltage during the display period
Implementation Method 2
a waveform of the load-free driving signal may be distorted due to a stabilizing capacitor connected to the VGL line connected to the level shifter
Implementation Method 3
noise of the touch sensor signal may be increased due to capacitor coupling that occurs through parasitic capacitance between the touch sensors and lines of the pixel array
Data Source
AI summary
Provided is a display device including a level shifter generating an output clock swinging between a first voltage and a third voltage during a display period and swinging between a second voltage and the third voltage during a touch sensing period. Waveform distortion of a no-load alternating current (AC) signal may be prevented without eliminating a stabilizing capacitor of the level shifter, and thus, sensing sensitivity may be increased by reducing noise of a touch sensor signal.