OLED Pixel Circuit Brightness Uniformity via Pre-Charged Capacitors
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Solution Overview
Problem
Organic light-emitting display apparatuses face non-uniform brightness due to voltage drops in power lines, affecting image generation and display quality.
Innovation Solution
The apparatus includes a pixel structure with transistors and capacitors that apply different power levels during a frame, using reset, threshold, and emission control signals to manage data voltages and compensate for threshold voltages, ensuring uniform brightness by charging capacitors based on specific voltage combinations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If power lines are used to supply voltage to pixels, then the display can be driven, but voltage drops occur causing non-uniform brightness
Solution Approach 1:
The patent applies preliminary action by pre-charging capacitors during a first frame period with voltages that will be needed for the second frame period. This advance preparation allows the pixel circuit to maintain stable operation and uniform brightness during the second frame without being affected by voltage drops in the power lines, as the required charges are already stored in the capacitors.
Solution Approach 2:
The patent introduces capacitors as intermediary elements between the power lines and the OLED. These capacitors store electrical charge and act as buffers, decoupling the pixels from direct voltage fluctuations in the power lines. By charging these intermediary capacitors in advance during the first frame, the system ensures stable voltage supply during the second frame, thereby maintaining brightness uniformity.
2Illumination intensity
If different power levels are applied during frames, then brightness uniformity is improved, but device complexity increases
Solution Approach 1:
The patent employs periodic action by dividing the display operation into alternating first and second frame periods. During the first frame, capacitors are charged with specific voltages; during the second frame, these pre-charged capacitors are utilized to maintain uniform brightness. This periodic switching between charging and utilization phases allows the system to achieve brightness uniformity through a relatively simple control mechanism that repeats in regular intervals.
3Use of energy by moving object
If capacitors are charged based on voltage combinations, then power consumption is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the charging voltages of the capacitors based on the specific display frame and operational requirements. During the first frame, capacitors are charged to predetermined voltages that are optimized for the second frame operation. This parameter adjustment allows the system to reduce overall power consumption by only charging capacitors to the necessary levels rather than maintaining maximum charge continuously, while the manufacturing precision is managed through standardized capacitor specifications.
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 solution enhances brightness uniformity by irrelevantly applying reset, reference, or set voltages to the organic light-emitting diode, reducing power consumption and achieving simultaneous emission across all pixels.
Implementation Method 1
Each pixel includes an organic light-emitting diode that generates light based on a recombination of electrons and holes in an organic emission layer
Implementation Method 2
a first capacitor connected between the first node and the third node. The first capacitor may be charged based on a reset voltage from the data line, the first data voltage, and a threshold voltage of the third transistor
Data Source
AI summary
An organic light-emitting display apparatus includes a pixel and a power supply. The pixel is connected to a scan line, a data line, and a power line and includes an organic light-emitting diode to emit light based on a first data voltage. The power supply applies different levels of power to the pixel during one frame. The pixel holds a second data voltage to be used during a next frame when the organic light-emitting diode emits light based on the first data voltage during the one frame.