OLED Pixel Circuit Driving Method for Luminance Uniformity
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Solution Overview
Problem
Organic light emitting display (OLED) devices experience luminance uniformity issues due to differences in emission waiting times and threshold voltages across pixels, leading to voltage drops and degraded display quality.
Innovation Solution
The OLED device incorporates a pixel unit with specific transistors and capacitors, along with a driving unit that divides the frame into distinct periods for initialization, threshold voltage compensation, data writing, and emission, ensuring all pixels emit light simultaneously and uniformly, thereby minimizing luminance uniformity defects and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sequential emission driving is used to simplify the driving method, then device complexity is reduced, but luminance uniformity deteriorates due to different emission waiting times for pixels on different scan lines
Solution Approach 1:
The patent applies preliminary action by initializing the anode electrode voltage of all pixels before the emission period through a dedicated initialization period. This pre-initialization ensures that regardless of when data is written during the scanning process, all pixels start with the same anode voltage level before emission, thereby eliminating luminance uniformity issues caused by different emission waiting times while maintaining sequential driving simplicity
Solution Approach 2:
The patent segments the frame period into distinct sub-periods: non-emission period, first initialization period, threshold voltage compensation period, data writing period, second initialization period, and emission period. This temporal segmentation allows different operations (initialization, compensation, data writing) to occur in specific time windows, ensuring proper pixel state preparation before simultaneous emission while maintaining the simplicity of sequential scan line driving
2Stability of the object's composition
If higher voltages are applied to compensate for voltage drops during long emission waiting times, then luminance uniformity is improved, but power consumption increases
Solution Approach 1:
The patent uses preliminary action by performing voltage initialization of the anode electrode before the emission period in a dedicated first initialization period. This pre-initialization eliminates the need to apply higher compensation voltages during emission waiting times, as all pixels start with the correct voltage level beforehand, thereby maintaining luminance uniformity while minimizing power consumption
Solution Approach 2:
The patent implements periodic action by structuring the frame into repeating periods with specific functions: initialization periods reset voltages, data writing periods update pixel data, and emission periods display images. This periodic structure ensures that voltage levels are regularly reset and maintained at optimal levels without requiring continuous high voltage application, thus achieving luminance uniformity with reduced power consumption
3Manufacturing precision
If threshold voltage compensation is implemented to improve luminance uniformity, then manufacturing precision is improved, but device complexity increases due to additional transistors and capacitors
Solution Approach 1:
The patent applies universality by designing the pixel circuit with multi-functional components: the first and second capacitors serve both as storage elements for pixel data and as compensation mechanisms for threshold voltage variations. The switching transistors control multiple operations including data writing, threshold voltage compensation, and anode electrode initialization. This multi-functionality achieves precise luminance uniformity through threshold voltage compensation while minimizing the increase in device complexity by avoiding dedicated separate components for each function
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 that all pixels emit light at the same time, compensates for threshold voltage variations, and reduces power consumption by eliminating the need for higher voltages due to voltage drops, resulting in improved luminance uniformity and reduced energy usage.
Implementation Method 1
an organic light emitting diode (EL), and a third capacitor (C3). The driving transistor (TD) is configured to control a driving current flowing through the organic light emitting diode
Data Source
AI summary
An organic light emitting display device includes a pixel unit and a driving unit. The pixel unit includes at least one pixel and the driving unit is configured to drive the pixel unit. The at least one pixel includes a first switching transistor, a second switching transistor, a third switching transistor, a fourth switching transistor, a first capacitor, a second capacitor, an organic light emitting diode, a third capacitor, and a driving transistor.