OLED Reference Voltage Lines for Brightness Uniformity
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Solution Overview
Problem
Existing OLED display devices face challenges in achieving optimized brightness due to threshold voltage deviations among driving transistors, which affect the uniformity and quality of image display.
Innovation Solution
The implementation of reference voltage lines for each sub-pixel type, such as red, green, blue, and white, allows for the application of independent reference voltages based on sensed threshold voltages, ensuring optimal brightness by compensating for variations in threshold voltages among driving transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single reference voltage is used for all sub-pixels, then the device complexity is reduced, but the brightness uniformity and display quality deteriorate due to threshold voltage deviations among driving transistors
Solution Approach 1:
The reference voltage lines are segmented into multiple independent lines, with each line dedicated to a specific sub-pixel type (red, green, blue, or white). This segmentation allows each sub-pixel type to receive a customized reference voltage that compensates for its specific threshold voltage characteristics, thereby improving brightness uniformity without significantly increasing overall device complexity.
Solution Approach 2:
Different reference voltages are applied to different sub-pixel types based on their local characteristics. The sensing unit measures threshold voltages for each sub-pixel type, and the reference voltage generation unit generates type-specific reference voltages. This local quality approach ensures that each sub-pixel type operates at optimal brightness while maintaining manageable device complexity.
2Manufacturing precision
If reference voltages are adjusted for each sub-pixel type, then the brightness optimization is improved, but the device complexity increases due to multiple reference voltage lines and sensing circuits
Solution Approach 1:
The sensing unit and reference voltage generation unit serve multiple sub-pixel types simultaneously. The sensing unit can sense threshold voltages for different sub-pixel types, and the reference voltage generation unit can generate appropriate reference voltages for each type. This multi-functionality approach allows brightness optimization for all sub-pixel types while avoiding the need for completely separate sensing and generation circuits for each type, thus limiting the increase in device complexity.
3Manufacturing precision
If threshold voltage compensation is implemented, then the display quality is improved, but the operation time increases due to additional sensing and adjustment steps
Solution Approach 1:
The sensing unit performs threshold voltage sensing and the reference voltage generation unit generates compensated reference voltages during the initialization phase or non-display periods. By performing these compensation actions in advance, the actual display operation can proceed without significant time loss, as the appropriate reference voltages are already prepared for each sub-pixel type.
Solution Approach 2:
The threshold voltage sensing and reference voltage generation are performed periodically, such as during each frame's initialization period or during blanking intervals. This periodic action allows the display to maintain high quality through continuous compensation while minimizing the time impact on the actual display operation, as compensation occurs during natural idle periods in the display cycle.
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 enables the realization of high-quality images with optimized brightness by accurately adjusting the reference voltages for each sub-pixel, addressing the issue of threshold voltage deviations and enhancing the overall display performance.
Implementation Method 1
a plurality of first sub-pixels having first light emitting elements emitting first color light... second light emitting elements emitting second color light... third light emitting elements emitting third color light... fourth light emitting elements emitting fourth color light
Data Source
AI summary
An OLED display device that includes multiple reference voltage lines. One reference voltage line provides a reference voltage to red, green and blue sub-pixels. Another reference voltage line provides a different reference voltage to white sub-pixels. The reference voltages can be controlled independently of each other to control brightness of the display device.