OLED Pixel Circuit Topology for High-Resolution Current Control
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Solution Overview
Problem
The increase in definition of display apparatuses with light-emitting devices containing organic EL materials reduces the area of the light-emitting surface, leading to a decrease in the amount of current capable of flowing through the devices, necessitating fine control of current for luminance adjustment.
Innovation Solution
The display apparatus incorporates a pixel and circuit structure with specific connections of transistors and capacitors to control current flow, including n-channel switches and capacitors, allowing for precise current management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the definition of light-emitting devices is increased, then display resolution is improved, but the area of light-emitting surface decreases
Solution Approach 1:
The pixel circuit is divided into multiple functional blocks including first and second switching transistors, first and second capacitors, and a driving transistor, each performing specific functions in the current control process. This segmentation allows precise control of current flow to compensate for reduced light-emitting area while maintaining high resolution
2Measurement precision
If the area of light-emitting surface is reduced, then display definition increases, but the amount of current capable of flowing through the device decreases
Solution Approach 1:
The circuit changes multiple parameters including voltage levels (VDD1, VDD2, VSS1, VSS2), capacitance values (C1, C2), and transistor switching states to precisely control the current amount flowing through the light-emitting device, enabling fine current control despite reduced current capacity from smaller area
3Measurement precision
If fine control of current is implemented, then luminance adjustment precision is improved, but device complexity increases
Solution Approach 1:
The first capacitor C1 stores a first potential and the second capacitor C2 stores a second potential in advance during a first period, preparing the necessary voltage conditions before the light-emitting period. This preliminary action simplifies the control logic during operation while achieving fine current control precision
Data Source
AI summary
A display apparatus having high display quality is provided. The display apparatus includes a pixel and a circuit. The pixel includes a light-emitting device, a driving transistor, a first switch, a second switch, and a first capacitor. The circuit includes a third switch, a fourth switch, a fifth switch, and a second capacitor. A first terminal of the first switch is electrically connected to a first terminal of the first capacitor, one of a source and a drain of the driving transistor, and an anode of the light-emitting device. A gate of the driving transistor is electrically connected to a first terminal of the second switch and a second terminal of the first capacitor. A second terminal of the first switch is electrically connected to a first terminal of the third switch and a first terminal of the second capacitor. A second terminal of the second capacitor is electrically connected to a first terminal of the fourth switch and a first terminal of the fifth switch.