OLED Display Brightness Uniformity via Gate Voltage Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Organic light emitting display apparatuses face issues with uneven brightness due to voltage drops in power lines, leading to non-uniform display brightness across pixels located at varying distances from the global power line.
Innovation Solution
The solution involves a method of driving the organic light emitting display apparatus by adjusting the gate voltage of driving transistors based on the distance of pixels from the global power line, using a data signal that includes an emphasis signal with varying voltage levels and application times determined by the pixel's location, and employing a mesh structure of power lines to compensate for voltage drops, ensuring consistent brightness across the display.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If power lines are used to supply power voltage to pixels, then power voltage is delivered to driving transistors, but voltage drops occur in the power lines causing uneven brightness
Solution Approach 1:
The patent applies local quality by adjusting the gate voltage of driving transistors according to their specific locations on the display panel. Pixels farther from the global power line receive higher gate voltages to compensate for voltage drops, while pixels closer to the power line receive lower gate voltages. This location-dependent parameter adjustment ensures uniform brightness across the display area despite the inherent voltage drops in the power distribution network.
2Illumination intensity
If the gate voltage is increased for pixels farther from the global power line, then brightness uniformity is improved, but the complexity of the driving system increases
Solution Approach 1:
The patent implements preliminary action by pre-calculating and storing the relationship between pixel locations and required gate voltage compensation values in a lookup table or memory structure. During operation, the data driver simply retrieves the appropriate compensation value based on the pixel's location without performing real-time complex calculations. This approach achieves the necessary voltage compensation while keeping the driving system relatively simple and efficient.
3Power
If a mesh structure of power lines is employed, then voltage drops are compensated, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent applies segmentation by dividing the power distribution into a hierarchical structure with a global power line and multiple local power lines branching off to different pixel rows or columns. This segmented approach allows the system to manage voltage drops more effectively than a single long power line, while avoiding the excessive complexity of a fully meshed structure. Each segment can be independently optimized and manufactured.
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 approach ensures improved uniformity in display brightness by adjusting the gate voltage and transistor sizes according to the pixel's location, effectively mitigating the effects of voltage drops and resulting in consistent light emission across the display panel.
Implementation Method 1
An organic light emitting display apparatus displays images by using an organic light emitting diode (OLED) that emits light by using recombination of electrons and holes
Data Source
AI summary
An organic light emitting display apparatus includes: a plurality of pixels, each of the pixels including a light emitting device and a driving transistor configured to supply a driving current to the light emitting device based on a scan signal and a data signal; and a plurality of power lines configured to transfer a power voltage supplied from a global power line to the driving transistor of each of the pixels, wherein a level of a gate voltage of the driving transistor when the light emitting device emits light is determined by a distance between a corresponding one of the pixels and the global power line.