Organic EL Display Mobility Correction Circuit
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Solution Overview
Problem
In organic EL displays, variations in threshold voltage and mobility of drive transistors lead to non-uniform luminance across the screen, affecting the display's uniformity and image quality.
Innovation Solution
A display device with a mobility correction function is implemented, where a switching transistor is used to adjust the correction period based on the signal potential, allowing negative feedback of drive current to the pixel capacitor to cancel out mobility variations, ensuring consistent luminance across pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a simple matrix system is used for organic EL display, then the configuration is simple, but the display size becomes large and high-definition display is difficult to realize
Solution Approach 1:
The display is divided into multiple pixels arranged in a matrix, with each pixel containing independent drive transistors and capacitors. This segmentation allows for compact pixel design that enables high-definition displays while maintaining manageable configuration complexity through modular architecture.
Solution Approach 2:
The patent transitions from simple row-column scanning to a multi-dimensional active matrix control system using both first and second scanning lines intersecting with signal lines, creating a three-dimensional control space that enables precise pixel addressing in high-definition displays.
2Manufacturing precision
If active matrix system with TFTs is used to control current in each pixel, then high-definition display is achieved, but variations in threshold voltage and mobility cause non-uniform luminance
Solution Approach 1:
The patent implements feedback mechanisms where the pixel capacitor stores voltage information and the drive transistor uses this stored information to regulate current flow to the light emitting element, compensating for transistor parameter variations and ensuring uniform luminance across the display.
Solution Approach 2:
The patent adjusts the timing parameters of the scanning signals, specifically controlling the duration and timing of the correction period relative to the light emitting period, to optimize the compensation effect for transistor variations and maintain luminance uniformity.
3Reliability
If correction period is extended to compensate for mobility variations, then luminance uniformity improves, but the timing margin for other operations reduces
Solution Approach 1:
The patent makes the correction period duration dynamic by adjusting it based on the signal potential level. For high signal potentials, a shorter correction period is used, while for low signal potentials, a longer correction period is applied, optimizing both luminance uniformity and timing efficiency.
Solution Approach 2:
The patent changes the timing parameters of the correction period based on the operating conditions, specifically adapting the correction duration to the signal potential level to achieve optimal compensation while maintaining sufficient timing margins for other pixel operations.
Data Source
AI summary
A display device is disclosed. The display device includes: a pixel array unit and a driving unit which drives the pixel array unit. The pixel array unit includes rows of first scanning lines and second scanning lines, columns of signals, pixels in a matrix state arranged at portions where the scanning lines and the signal lines cross each other and power supply lines and ground lines supplying power to respective pixels. The driving unit includes a first scanner performing line-sequential scanning to pixels by each row by supplying a first control signal to each first scanning line sequentially, a second scanner supplying a second control signal to each second scanning line sequentially so as to correspond to the line-sequential scanning and a signal selector supplying a video signal to rows of signal lines so as to correspond to the line-sequential scanning.