Pixel Circuit Voltage Control for OLED Compensation
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Solution Overview
Problem
OLED display devices face issues of display inhomogeneity and slow compensation speed due to inaccurate and unfixed voltage at the anode of OLEDs, caused by direct connection of pixel drive circuits to the voltage terminal and parallel connection of sensing transistors, leading to inaccurate grayscale and reduced compensation speed.
Innovation Solution
A pixel circuit unit with a voltage control circuit that disconnects during data voltage writing stages, allowing the supply voltage receiving terminal of the light-emitting drive circuit to not receive the first supply voltage, and series connection of sensing transistors to reduce capacitance on the sensing signal line, improving voltage accuracy and compensation speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If pixel drive circuits are directly connected to the voltage terminal, then the circuit structure is simple, but the voltage at the anode of OLED becomes inaccurate and unfixed
Solution Approach 1:
The patent introduces a voltage control circuit as an intermediary component between the voltage terminal and the light-emitting drive circuit. This voltage control circuit includes a control transistor that mediates the voltage transmission, ensuring the supply voltage receiving terminal receives a fixed and accurate voltage during data writing stage, thereby resolving the voltage accuracy issue while maintaining reasonable circuit complexity.
Solution Approach 2:
The patent segments the voltage supply path by separating the voltage control function from the data writing function. The voltage control circuit operates independently to regulate voltage, while the data writing circuit handles signal input. This segmentation allows precise voltage control without interfering with the data writing process.
2Device complexity
If sensing transistors are connected in parallel, then the connection is simple, but the capacitance on the sensing signal line increases reducing compensation speed
Solution Approach 1:
The patent inverts the conventional parallel connection approach by connecting sensing transistors in series. This inversion reduces the total capacitance on the sensing signal line from the sum of all individual transistor capacitances to just the capacitance of one transistor equivalent, thereby significantly increasing the compensation speed while maintaining a simple connection structure.
3Duration of action of stationary object
If voltage control circuit is connected during data writing, then voltage is continuously supplied, but voltage accuracy decreases and compensation becomes slow
Solution Approach 1:
The patent implements periodic action by controlling the voltage control circuit to operate in distinct stages: during the data writing stage, the voltage control circuit is disconnected to allow accurate voltage measurement and compensation; during the display stage, the voltage control circuit is connected to supply stable voltage to the light-emitting drive circuit. This periodic switching ensures both voltage accuracy during compensation and continuous voltage supply during display.
Data Source
AI summary
A pixel circuit unit, a driving method thereof, a display panel and a display device are disclosed. The pixel circuit unit includes a plurality of pixel drive circuits and a voltage control circuit including a first terminal and a second terminal; the first terminal is connected with a first voltage terminal to receive a first supply voltage provided by the first voltage terminal; each pixel drive circuit includes a light-emitting drive circuit including a supply voltage receiving terminal and a control terminal; the supply voltage receiving terminal is electrically connected with the second terminal, so as to allow the supply voltage receiving terminal to be capable of receiving the first supply voltage; and the voltage control circuit is configured to be disconnected in a data voltage writing stage, so that the supply voltage receiving terminal does not receive the first supply voltage in the data voltage writing stage.