OLED Display Voltage Follower Circuit for Brightness Uniformity
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Solution Overview
Problem
Organic light-emitting diode (OLED) displays face issues with non-uniform brightness due to variations in threshold voltages and electron mobilities of driving transistors, leading to current leakage when detecting and compensating threshold voltages, which requires additional modules and prolongs detection time.
Innovation Solution
An OLED display with a voltage follower connected to each sub-pixel, using operational amplifiers to maintain the voltage of the second node after the capacitor acquires the threshold voltage, preventing current leakage and allowing internal compensation without additional detection, storage, or cache modules.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If external compensation method is used to detect and sample electrical differences of driving transistors, then brightness uniformity is improved, but detection time is prolonged and additional detection module, storage module and cache module are required
Solution Approach 1:
The patent extracts the compensation function from the external detection system and integrates it into the pixel circuit itself. By using the existing capacitor and switching transistors within each pixel to store and compensate for threshold voltage differences, the need for separate external detection and storage modules is eliminated, thereby reducing detection time while maintaining brightness uniformity.
Solution Approach 2:
The pixel circuit performs self-compensation by using its own internal components (capacitor, switching transistors) to detect and compensate for threshold voltage differences. The capacitor stores the threshold voltage difference, and the circuit automatically adjusts the drive signal to compensate for these variations, eliminating the need for external service modules and reducing detection time.
2Illumination intensity
If additional detection module, storage module and cache module are added to implement external compensation, then brightness uniformity is improved, but device complexity is increased
Solution Approach 1:
The patent merges the compensation function with the existing pixel circuit structure. The capacitor that already exists in the pixel circuit is used to store threshold voltage differences, and the switching transistors are utilized for both driving and compensation purposes. This integration eliminates the need for separate detection and storage modules, reducing device complexity while maintaining brightness uniformity.
Solution Approach 2:
The switching transistors and capacitor in the pixel circuit serve multiple functions: they act as driving elements for the OLED and simultaneously function as detection and compensation components. This multi-functionality eliminates the need for dedicated detection and storage modules, thereby reducing device complexity while achieving brightness uniformity.
3Loss of time
If internal compensation method is used to compensate threshold voltage of driving transistor, then detection time is shortened, but current leakage of driving transistor occurs which impacts acquisition result
Solution Approach 1:
The patent performs preliminary action by quickly acquiring the threshold voltage difference using the capacitor before current leakage can significantly impact the measurement. The switching transistor is controlled to transfer the threshold voltage to the capacitor in a brief period, capturing the accurate value before leakage occurs, thus maintaining acquisition accuracy while shortening detection time.
Solution Approach 2:
The patent rushes through the detection process by using the switching transistor to quickly transfer the threshold voltage to the capacitor before current leakage can degrade the signal. This rapid acquisition method captures the threshold voltage difference accurately in a short time window, maintaining reliability while reducing detection time.
Data Source
AI summary
The present invention provides a method of driving a display panel and a driving device. The present invention determines sub-pixels shared by sub-pixel rendering technology through comparing differences of the color components, and the sub-pixels shared by the display image are not fixed. Since the sub-pixels with the smallest absolute value of the color component difference are selected for sharing, a contrast of an edge region of an image is improved, and distortion of an edge region of an image is reduced.