TFT Channel Width Variation for RC Delay Compensation
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Solution Overview
Problem
Liquid crystal display devices face image quality deterioration due to charging rate deviations and kickback voltage deviations caused by resistance-capacitance delay in data lines, particularly for pixels farther from the voltage source.
Innovation Solution
The solution involves varying the channel width and parasite capacitance of thin film transistors along data lines by adjusting the size of semiconductor layers and overlapping areas between electrodes, and using storage capacitance to compensate for signal delays and voltage deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If data lines are extended to reach distant pixels, then coverage area increases, but charging rate deviation increases
Solution Approach 1:
The patent applies local quality by varying the channel width of thin film transistors based on their position along the data line. TFTs closer to the data driving circuit have smaller channel widths, while TFTs farther away have larger channel widths. This localized adjustment compensates for the increased RC delay in distant pixels, ensuring uniform charging rates across the entire display panel despite the extended data line coverage.
2Speed
If channel width is increased to compensate for RC delay, then charging rate improves, but kickback voltage deviation increases
Solution Approach 1:
The patent employs parameter changes by systematically adjusting the channel width parameter of TFTs based on their distance from the data driving circuit. This controlled variation in channel width compensates for RC delay effects and maintains uniform charging rates. Additionally, the patent introduces compensation capacitances to further adjust voltage levels, ensuring that kickback voltage deviations are minimized while maintaining improved charging rates across the display panel.
3Stability of the object's composition
If parasite capacitance is increased to reduce kickback voltage, then voltage stability improves, but charging speed decreases
Solution Approach 1:
The patent applies local quality by positioning compensation capacitances specifically at pixels farther from the data driving circuit, where kickback voltage deviations are more pronounced. This localized addition of capacitance provides voltage stability where needed without unnecessarily slowing down the charging speed of pixels closer to the data driving circuit, thus optimizing the balance between voltage stability and charging speed across the entire panel.
4Manufacturing precision
If TFT size is varied to compensate for distance, then charging uniformity improves, but device complexity increases
Solution Approach 1:
The patent employs parameter changes by systematically varying the channel width parameter of TFTs based on their position along the data line. This controlled variation in a single critical parameter (channel width) provides a straightforward method to achieve charging uniformity across the display panel, avoiding the need for complex multi-parameter adjustments or sophisticated control circuits.
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 reduces charging rate and kickback voltage deviations, thereby improving image quality by ensuring consistent signal delivery and voltage distribution across the display panel.
Implementation Method 1
pixels which are far away from the one end of the data line may be charged with less than a target voltage due to a resistance-capacitance delay (RC delay) of the data line
Implementation Method 2
Each of the plurality of thin film transistors has a gate electrode, a source electrode, a drain electrode and a parasite capacitance generated between the gate electrode and the drain electrode
Implementation Method 3
the storage capacitance for each pixel may be varied to avoid image quality deterioration
Data Source
AI summary
Deterioration of image quality in a display device due to kickback voltages may be reduced or prevented by varying parasite capacitance, the size of the semiconductor layer, and/or storage capacitance in each of thin film transistors for the pixels in the display. Various embodiments of display devices capable of reducing or preventing kickback voltages are disclosed.