OLED Pixel Drive Circuit Voltage Uniformity
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Solution Overview
Problem
In OLED display panels, there is a voltage drop in initialization, driving, and common voltages along the direction away from the source driver, leading to brightness differences between the edges of the display panel and affecting color uniformity, especially with through holes which exacerbate color spots (mura) in low grayscale states.
Innovation Solution
A pixel driving circuit is designed with a driving transistor, storage capacitor, data writing unit, threshold compensation unit, light emitting control units, and reset units, where the light emitting element's terminal loads a second power supply voltage, improving voltage uniformity and reducing brightness variations across the display panel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an initialization lead is provided to initialize pixel electrodes with initialization voltage, then the pixel electrodes can be properly initialized, but voltage drop occurs along the direction away from the source driver, causing brightness differences and color uniformity issues
Solution Approach 1:
The patent applies local quality by providing separate initialization leads (first initialization lead and second initialization lead) that extend in different directions (first direction and second direction) to different regions of the display panel. This ensures that each region receives initialization voltage from the nearest lead, minimizing voltage drop and maintaining uniform brightness and color across the entire panel.
2Ease of manufacture
If through holes are provided in the display panel, then the display structure can be optimized, but color spots (mura) are exacerbated in low grayscale states
Solution Approach 1:
The patent applies equipotentiality by ensuring that pixel electrodes in different regions (including regions with through holes) are initialized to the same potential through the use of multiple initialization leads. This compensates for the disruptive effect of through holes on voltage distribution, maintaining uniform color and eliminating mura effects in low grayscale states.
Data Source
AI summary
A pixel driving circuit includes: a driving transistor connected to a first node, a second node and a third node; a first light-emitting control unit connected to the second node; a second light-emitting control unit connected to the third node and a fourth node; a first reset unit connected to the fourth node, and configured to load a second power supply voltage to the fourth node in response to a scan signal. One end of the light-emitting element is connected to the fourth node, and the other end of the light-emitting element is used for loading the second power supply voltage.