Pixel Circuit Bright Spot Defect Control via Transistor Segmentation
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Solution Overview
Problem
Display devices face issues with bright spot defects due to excessive driving current supplied to light-emitting elements, which are not effectively minimized by existing technologies.
Innovation Solution
Incorporating a specific configuration of transistors, including a driving transistor, emission control transistors, and a compensation transistor with different types and semiconductor layers, such as polycrystalline silicon and oxide semiconductor layers, to control the driving current and initialize voltages, thereby preventing excessive current supply to the light-emitting element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional transistor configuration is used to drive the light-emitting element, then the device structure is simple, but excessive driving current causes bright spot defects and potential damage to the display panel
Solution Approach 1:
The patent divides the driving function into multiple specialized transistors: a driving transistor for current control, emission control transistors for timing control, and initialization transistors for voltage reset. This segmentation allows each transistor to perform its specific function optimally, preventing bright spot defects while maintaining manageable complexity through clear functional division.
Solution Approach 2:
The patent introduces emission control transistors as intermediaries between the driving transistor and the light-emitting element. These intermediary transistors control the timing of current supply to the light-emitting element, preventing excessive current accumulation that causes bright spot defects, while the driving transistor maintains its simple current control function.
2Reliability
If emission control transistors are added to control driving current timing, then bright spot defects are minimized, but the transistor count and circuit complexity increase
Solution Approach 1:
The emission control transistors serve multiple functions: they control the timing of current supply to the light-emitting element, prevent excessive current accumulation, and work in coordination with the driving transistor to maintain overall pixel control. This multi-functionality justifies their addition by providing multiple benefits from a single component type.
Solution Approach 2:
The initialization transistors perform preliminary actions by resetting the voltage levels of the driving transistor gate and light-emitting element electrode before each new frame or sub-frame. This preliminary voltage reset prevents residual charge from causing bright spot defects in subsequent frames, ensuring consistent display quality.
3Manufacturing precision
If multiple initialization transistors are used to reset voltages, then voltage control precision is improved, but the device complexity increases
Solution Approach 1:
The patent applies local quality by providing separate initialization transistors for different parts of the pixel circuit: one initialization transistor for the driving transistor gate and another for the light-emitting element electrode. Each initialization transistor provides precise voltage control tailored to the specific requirements of its target component, improving overall voltage control precision.
Data Source
AI summary
A pixel includes: a driving transistor including a gate electrode coupled to a first node, a first electrode coupled to a second node, and a second electrode coupled to a third node; a first initialization transistor coupled between the first node and a first initialization voltage line, and including a gate electrode coupled to a scan line, where the first initialization voltage line is configured to supply a first initialization voltage; a first emission control transistor coupled between a fourth node and a fifth node and including a gate electrode coupled to the first node; a second emission control transistor coupled between the third node and the fifth node and including a gate electrode coupled to an emission control line; and a light-emitting element coupled between the fourth node and a driving low voltage line. The driving transistor and the first emission control transistor are different types of transistors.