OLED Subpixel Circuit Segmentation for Lifetime Variation
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Solution Overview
Problem
The variation in life times of red, green, and blue organic light emitting diodes in active matrix type organic light emitting display devices leads to luminance reduction and white balance issues, complicating the circuit arrangement and reducing the aperture ratio as pixel size decreases.
Innovation Solution
Implementing a time division control drive method for organic light emitting diodes with relatively longer life times and a general drive method for those with shorter life times, where R and G diodes share a pixel circuit and B diodes are driven continuously, using emission control signals to manage their emission times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a general drive method is used for all organic light emitting diodes, then the circuit arrangement is simple, but the life time variation between red, green, and blue diodes causes luminance reduction and white balance issues
Solution Approach 1:
The pixel circuit is segmented into multiple sub-pixel circuits, with each sub-pixel circuit dedicated to driving a specific organic light emitting diode (red, green, or blue). This segmentation allows each sub-pixel circuit to be independently optimized for its specific diode's characteristics, particularly its lifetime and luminance decay properties, thereby resolving the white balance issues caused by lifetime variation while maintaining manageable circuit complexity through modular design
Solution Approach 2:
Different drive methods are applied to different sub-pixel circuits based on their specific requirements. The red sub-pixel circuit uses a first drive method optimized for its lifetime characteristics, while the green and blue sub-pixel circuits use a second drive method optimized for their respective characteristics. This local quality approach allows each sub-pixel to be driven with the most appropriate method for its specific lifetime and luminance decay properties, improving overall luminance stability
2Productivity
If pixel size is reduced to increase display resolution, then the display density increases, but the aperture ratio decreases and circuit arrangement becomes more complex
Solution Approach 1:
The green and blue sub-pixel circuits are merged to share a common emission control line, reducing the total number of control lines required in the pixel circuit. This merging strategy reduces circuit complexity and allows for more efficient space utilization within the pixel, enabling higher display resolution while maintaining an acceptable aperture ratio by minimizing the area occupied by circuitry
3Productivity
If pixel size is reduced to increase display resolution, then the display density increases, but the circuit arrangement complexity increases
Solution Approach 1:
The emission control lines are designed with multi-functionality, where a single emission control line serves multiple sub-pixel circuits (specifically, the common emission control line controls both green and blue sub-pixels). This universal approach reduces the total number of control lines required, thereby reducing circuit arrangement complexity while still enabling high display resolution through efficient space utilization
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 the difference in life times of the organic light emitting diodes, maintaining luminance and aperture ratio, thereby solving white balance variations and image sticking issues without reducing the display's performance.
Implementation Method 1
Light is emitted from the R, G, or B organic emission layer by a voltage applied to the anode electrode and the cathode electrode in the organic light emitting diode
Data Source
AI summary
An organic light emitting diode (OLED) display device and a method for driving the OLED display device are provided. A gate drive circuit provides scan signals in sub-frames to scan lines. A data drive circuit provides a data signal to data lines. An emission control signal generation circuit provides first and second emission control signals to control the OLEDs. A display region includes pixels arranged in a matrix and connected to the scan lines, data lines, emission control lines, and power lines. The pixels include a first and a second unit pixel portion. The first unit pixel portion performs a time division control drive by driving a plurality of organic light emitting diodes by one shared pixel circuit. In the second unit portion one organic light emitting diode is driven by an independent pixel circuit.