Organic Light Emitting Display Scan Signal Segmentation for Luminance Uniformity
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Solution Overview
Problem
In organic light emitting display devices, the luminance uniformity deteriorates due to the shifting threshold voltage of driving transistors, leading to suboptimal light generation and image quality, especially when representing grayscale images.
Innovation Solution
The implementation of a scan driving unit that supplies synchronized first and second scan signals, along with a data driving unit that provides bias power, ensures stable voltage application to transistors, using a wider second scan signal to maintain desired luminance and correct threshold voltage initialization, thereby enhancing luminance uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single scan signal is supplied to pixels, then the device structure is simple, but the threshold voltage of driving transistors shifts causing luminance non-uniformity
Solution Approach 1:
The scan signal is divided into two distinct parts: a first scan signal that supplies initialization power to set the driving transistor threshold voltage, and a second scan signal that supplies data signals for pixel operation. This segmentation allows each signal to perform its specific function optimally, preventing threshold voltage shifts and ensuring luminance uniformity while maintaining relatively simple device structure.
2Speed
If the scan signal width is narrow, then the response speed is fast, but the luminance representation is inaccurate during grayscale transitions
Solution Approach 1:
The first scan signal is applied before the second scan signal to pre-initialize the driving transistor threshold voltage. This preliminary action ensures that when the data signal is applied in the second scan period, the transistor is already in the correct operational state, enabling accurate luminance representation during grayscale transitions without requiring an excessively wide overall scan signal.
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 stabilizes the voltage application to transistors, ensuring uniform image representation across frames and improving the overall image quality by maintaining desired luminance levels.
Implementation Method 1
an organic light emitting diode generating light by recombination between electrons and holes
Data Source
AI summary
An organic light emitting display device includes a scan driving unit supplying a first scan signal and a second scan signal to each of a plurality of scan lines; a data driving unit supplying data signals to each of a plurality of data lines to be synchronized with the second scan signal; pixels positioned at intersections of the scan lines with the data lines, receiving bias power when the first scan signal is supplied, and receiving the data signals when the second scan signal is supplied.