Metal Oxide Transistor Pixel Circuit for Low Leakage OLED Displays
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Solution Overview
Problem
Existing organic light emitting display apparatuses face challenges in minimizing bezel area and enhancing resolution due to leakage currents at low frequencies, which deteriorate the organic light emitting device and limit the number of scan lines and transistors that can be reduced.
Innovation Solution
The use of a metal oxide transistor in the pixel driving circuit, which reduces leakage current and allows for a higher compensation rate for driving current in all gray levels, enabling a smaller bezel area and higher resolution even when driven at low frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the number of scan lines and transistors is minimized to reduce bezel area and enhance resolution, then the display panel achieves higher resolution and smaller bezel, but leakage current increases at low frequencies causing organic light emitting device deterioration
Solution Approach 1:
The patent changes the material parameter of the transistor from conventional semiconductor to metal oxide semiconductor, which fundamentally alters the electrical characteristics to achieve low leakage current. This parameter change enables the transistor to maintain high reliability even with minimized scan lines and transistors, resolving the contradiction between resolution enhancement and device deterioration prevention
Solution Approach 2:
The patent employs metal oxide semiconductor material (such as IGZO - indium gallium zinc oxide) which combines the advantages of both semiconductor and insulator properties. This composite material approach creates a transistor that can operate with extremely low leakage current, enabling both high resolution through transistor minimization and high reliability through leakage current suppression
2Area of stationary object
If conventional transistors are used to minimize the number of scan lines and transistors, then the bezel area is reduced, but leakage current occurs at low frequencies reducing display performance
Solution Approach 1:
The patent changes the material composition parameter of the transistor to metal oxide semiconductor, which inherently provides insulator-like characteristics at the off-state. This parameter change reduces leakage current to negligible levels, enabling aggressive minimization of scan lines and transistors for smaller bezel area without suffering from energy loss due to leakage
3Manufacturing precision
If the number of transistors is reduced to enhance resolution, then the display achieves higher resolution, but compensation capability for driving current decreases
Solution Approach 1:
The patent changes the transistor material to metal oxide semiconductor, which provides stable electrical characteristics and low variability. This parameter change ensures that even with fewer transistors, each transistor maintains consistent performance, thereby preserving the compensation capability for driving current across all gray levels while achieving higher resolution
Data Source
AI summary
A display apparatus includes a plurality of pixels each including an organic light emitting device and a pixel driving circuit. The pixel driving circuit includes a driving transistor controlling a driving current flowing in the organic light emitting device and a first, second, third, fourth, and fifth switching transistor, the third switching transistor selectively connecting a second node which is a drain electrode of the driving transistor to a third node which is a gate electrode of the driving transistor. The third switching transistor differs from a type of each of the driving transistor and the first, second, fourth, and fifth switching transistors. Accordingly, even when the organic light emitting display apparatus is driven at a low frequency, a bezel area is reduced, and a high resolution of a display panel is realized.