OLED Pixel Circuit Layout for Low-Leak PWM Uniformity
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Solution Overview
Problem
Existing display devices using organic light-emitting diodes (OLEDs) face challenges in achieving high yield and uniformity of display quality, particularly when employing pulse width modulation (PWM) drive to avoid irregularities in low-gradation screens.
Innovation Solution
The display device incorporates a pixel circuit with a first transistor having a smaller leak current compared to other transistors, and utilizes a partition structure to divide subpixels, enabling efficient light emission through pulse width modulation while minimizing screen irregularities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional transistors are used in pixel circuits for OLED display devices, then the device complexity is reduced and manufacturing is easier, but the leak current increases causing screen irregularities and poor display quality uniformity
Solution Approach 1:
The patent applies local quality by using oxide transistors specifically for the first transistor connected to the data signal line in pixel circuits, while other transistors may use different structures. This localized application of oxide semiconductor technology addresses the leak current issue at the critical location where data signals are input, improving display quality uniformity without requiring all transistors to be oxide-based, thus balancing performance and manufacturing complexity.
2Reliability
If pulse width modulation drive is used to avoid irregularities in low-gradation screens, then the display quality is improved, but the yield and uniformity of display quality become difficult to control
Solution Approach 1:
The patent employs parameter changes by utilizing the unique electrical characteristics of oxide transistors, particularly their extremely low leak current property, to enable precise control of current supply to OLEDs during PWM drive. This allows for accurate luminance adjustment and maintains display quality uniformity across differentgradation levels, thereby improving both display quality and yield simultaneously.
3Manufacturing precision
If the first transistor connected to the data signal line has larger leak current, then the manufacturing is simpler and more robust, but the current control precision deteriorates causing screen irregularities
Solution Approach 1:
The patent applies local quality by using oxide transistors specifically for the first transistor connected to the data signal line in pixel circuits, while other transistors may use different structures. This localized application of oxide semiconductor technology addresses the leak current issue at the critical location where data signals are input, improving display quality uniformity without requiring all transistors to be oxide-based, thus balancing performance and manufacturing complexity.
Data Source
AI summary
A display device can include a base, a plurality of pixels arranged in a display area on the base, and a data signal line supplying a data signal to each of the plurality of pixels. Each of the plurality of pixels can include a pixel circuit including a plurality of transistors and a light emitting element driven by the pixel circuit. The pixel circuit can drive the light emitting element to emit light in time division. The first transistor can be connected to the data signal line, among the plurality of transistors including the pixel circuit, can be an oxide transistor.