OLED Compensation Circuit Sense Transistor Ratio Matching
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Solution Overview
Problem
Active-matrix organic light emitting diode (AMOLED) display panels face an afterimage phenomenon due to differences in threshold voltage drift, causing unequal light-emitting currents and brightness across sub-pixels, which existing compensation technologies fail to adequately address.
Innovation Solution
A compensation circuit with sense transistors in one-to-one correspondence with sub-pixels, where the channel width-to-length ratios of sense transistors are designed to match and vary within a specific range relative to the driving transistors, ensuring identical gate-source voltages across sub-pixels by connecting sense transistors in series with driving transistors and providing a reference voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional compensation technologies are used, then some compensation effect is achieved, but the afterimage phenomenon cannot be adequately addressed due to unequal light-emitting currents and brightness across sub-pixels
Solution Approach 1:
The patent divides the pixel into multiple sub-pixels (red, green, blue) and provides separate sense transistors for each sub-pixel, allowing independent compensation for each sub-pixel's threshold voltage drift. This segmentation enables precise control of light-emitting currents for each sub-pixel, addressing the afterimage phenomenon caused by unequal brightness.
Solution Approach 2:
The patent applies different channel width-to-length ratios to sense transistors corresponding to different sub-pixels based on their specific compensation needs. Each sense transistor is designed with local quality characteristics matched to its corresponding driving transistor, enabling customized compensation for each sub-pixel's threshold voltage drift while maintaining overall brightness uniformity.
2Manufacturing precision
If sense transistors are designed with different channel width-to-length ratios to match driving transistors, then identical gate-source voltages are achieved across sub-pixels, but the device complexity increases
Solution Approach 1:
The patent uses sense transistors that serve multiple functions: they act as compensation elements to match gate-source voltages across sub-pixels, and simultaneously function as part of the pixel circuit structure. By making the sense transistors multi-functional, the patent achieves precise voltage consistency without proportionally increasing device complexity.
Solution Approach 2:
The patent adjusts the channel width-to-length ratios of sense transistors as a key parameter to achieve identical gate-source voltages. By carefully selecting and varying this geometric parameter across different sub-pixels, the patent achieves precise voltage matching while keeping the overall transistor configuration manageable and manufacturable.
Data Source
AI summary
A compensation circuit and a manufacturing method thereof, a pixel circuit, a compensation device and a display device are disclosed. The OLED compensation circuit includes at least two sense transistors, the at least two sense transistors are in one-to-one correspondence with at least two sub-pixels in a pixel, and a first electrode of each of the sense transistors is electrically connected to a driving transistor of corresponding one of the sub-pixels; a magnitude relationship between channel width-to-length ratios of driving transistors of any two sub-pixels of the at least two sub-pixels is identical with a magnitude relationship between channel width-to-length ratios of two sense transistors corresponding to the two sub-pixels.