OLED Pixel Circuit Simplification for Luminance Uniformity
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Solution Overview
Problem
In OLED displays, the non-uniform electrical characteristics of driving transistors lead to luminance differences between pixels, necessitating complex internal compensation methods to correct for these variations, which can be cumbersome and affect drive reliability.
Innovation Solution
A simplified pixel structure for OLED displays is implemented, utilizing a driving transistor, a scan transistor, a first emission control transistor, and an initialization control transistor, with a data voltage directly written to the source electrode of the driving transistor, reducing the number of transistors and stabilizing the initialization operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If internal compensation method with multiple transistors is used to correct luminance non-uniformity, then luminance uniformity is improved, but device complexity increases and aperture ratio decreases
Solution Approach 1:
The patent extracts and removes unnecessary transistors from the internal compensation circuit. Specifically, it eliminates the need for separate sampling transistor and storage transistor by using a simplified configuration where the driving transistor itself performs compensation functions, reducing the transistor count from 6-8 down to 5 while maintaining luminance uniformity correction capability
Solution Approach 2:
The patent makes the driving transistor perform multiple functions: it serves as both the driving transistor for controlling OLED luminance and as the compensation transistor for correcting threshold voltage variations. This multi-functionality reduces the need for separate compensation transistors and simplifies the overall pixel structure
2Manufacturing precision
If internal compensation method with multiple transistors is used to correct luminance non-uniformity, then luminance uniformity is improved, but aperture ratio decreases
Solution Approach 1:
By removing unnecessary transistors and circuit elements from the pixel structure, the patent increases the aperture ratio. The simplified configuration with fewer transistors occupies less area, allowing the light-emitting OLED region to expand and improve aperture ratio from typical values to above 60%
3Manufacturing precision
If complex internal compensation circuit is used, then luminance non-uniformity is reduced, but drive reliability decreases
Solution Approach 1:
The patent removes unnecessary transistors and circuit components that can fail, thereby improving drive reliability. By eliminating redundant elements in the compensation circuit, the system has fewer potential failure points while maintaining the essential luminance uniformity correction function
Solution Approach 2:
The patent implements preliminary compensation by pre-charging the storage capacitor to a voltage that accounts for threshold voltage variations before the driving phase. This preliminary action ensures that the driving transistor operates correctly from the start, improving reliability by preventing operation errors
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration simplifies the pixel structure, enhances drive reliability, and stabilizes luminance by eliminating the influence of threshold voltage variations, thereby improving the aperture ratio and reducing luminance non-uniformity.
Implementation Method 1
an organic light emitting diode to emit light by outputting the data voltage charged in the storage capacitor
Data Source
AI summary
A pixel for an organic light emitting diode (OLED) display and an OLED display are discussed. The pixel includes a driving transistor, a first transistor, a scan transistor, a first emission control transistor, and an initialization control transistor. The driving transistor includes a gate electrode connected to a first node, a drain electrode connected to a second node, and a source electrode connected to a third node. The first transistor is connected between the first node and the second node. The scan transistor is connected between the third node and a data line. The first emission control transistor is connected between the second node and an anode electrode of an organic light emitting diode. The initialization control transistor is connected between an input terminal of an initialization voltage and the anode electrode of the organic light emitting diode.