Selective Capacitor Sizing for OLED Sub-Pixel Charging
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Solution Overview
Problem
In organic light-emitting display devices, the delayed charging of parasitic capacitance due to low driving current results in delayed light emission, leading to inaccurate color representation and deteriorated image quality.
Innovation Solution
The design includes sub-pixels with capacitors of varying capacitance, where the capacitance of the first capacitor in sub-pixels that take longer to charge is increased, allowing for a larger charging current and reducing the time to charge the parasitic capacitance, thereby preventing color representation issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the driving current is reduced to achieve low luminance emission, then the light-emitting element can operate at lower brightness levels, but the charging time of parasitic capacitance increases causing delayed light emission
Solution Approach 1:
The patent applies local quality by providing different capacitor sizes to different sub-pixels based on their specific charging characteristics. Sub-pixels with longer charging times receive larger capacitors to compensate, while those with shorter charging times use smaller capacitors. This localized differentiation optimizes the balance between luminance and charging time for each sub-pixel individually.
Solution Approach 2:
The patent changes the capacitor size parameter to address the charging time issue. By varying the capacitor capacitance values across different sub-pixels, the system adjusts the charging characteristics to match the driving current levels, ensuring timely light emission across all sub-pixels while maintaining desired luminance output.
2Loss of time
If the capacitor size is increased to reduce charging time, then the parasitic capacitance charges faster, but the device complexity increases due to varying capacitor configurations
Solution Approach 1:
The patent implements local quality by configuring different capacitor sizes specifically for different sub-pixels based on their individual charging characteristics. This targeted approach only increases complexity where necessary, rather than uniformly increasing all capacitor sizes, thus optimizing the balance between charging speed and device complexity.
Solution Approach 2:
The patent segments the display into sub-pixels with differentiated capacitor configurations. By dividing the display area into multiple sub-pixels and assigning appropriate capacitor sizes to each segment based on their charging characteristics, the system manages complexity through structured differentiation rather than uniform treatment.
3Device complexity
If uniform capacitor sizes are used across all sub-pixels, then the device structure is simplified, but sub-pixels with low driving current experience delayed light emission and color representation errors
Solution Approach 1:
The patent applies local quality by providing differentiated capacitor sizes to different sub-pixels based on their specific charging characteristics and driving current levels. This ensures that each sub-pixel receives the appropriate capacitor configuration to maintain timely light emission and accurate color representation, preventing the reliability issues associated with uniform capacitor designs.
Solution Approach 2:
The patent changes the capacitor size parameter across different sub-pixels to optimize their performance. By adjusting the capacitance values according to the driving current characteristics of each sub-pixel, the system ensures reliable and timely light emission, preventing color representation errors while maintaining manageable device complexity.
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 ensures timely charging of parasitic capacitance across sub-pixels, preventing color representation failures and maintaining image quality by synchronizing the light emission of different sub-pixels.
Implementation Method 1
a first capacitor disposed between a first sub supply voltage line from which a first supply voltage is applied and the second electrode of the driving transistor
Implementation Method 2
an organic light-emitting display device includes a light-emitting element so that each of the pixels of the display panel can emit light by themselves
Data Source
AI summary
A light-emitting display device includes first and second sub pixels each of which includes a driving transistor including first and second electrodes and a gate electrode, and being configured to control an electric current flowing from the first electrode to the second electrode according to a data voltage applied to a gate electrode, a light-emitting element connected to the second electrode, and a first capacitor disposed between a first sub supply voltage line to which a first supply voltage is applied and the second electrode. The first sub supply voltage line is disposed to overlap the second electrode. A capacitance of a first capacitor of the first sub pixel versus a capacitance of a first capacitor of the second sub pixel is selectively determined to correspond to an amount of the overlap between the first sub supply voltage line and the second electrode.