OLED Display Compensation for Degradation and Channel Length Modulation
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Solution Overview
Problem
Organic light emitting display devices face degradation issues over time, leading to decreased image brightness, and existing methods fail to accurately compensate for channel length modulation of driving transistors, which affects current uniformity.
Innovation Solution
An organic light emitting display device with a data accumulating unit, storage units for current and voltage change information, and a timing controller that generates altered data to compensate for OLED degradation by considering channel length modulation of driving transistors, ensuring consistent current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If OLED is operated over time, then light emission function is achieved, but OLED degradation occurs leading to decreased image brightness
Solution Approach 1:
The patent applies preliminary action by storing compensation data in advance that corresponds to different levels of OLED degradation. The system pre-calculates and stores compensation values for various stress accumulation levels, allowing it to quickly retrieve and apply appropriate compensation without real-time calculation delays. This enables the system to proactively compensate for degradation before it significantly impacts image brightness.
Solution Approach 2:
The patent implements feedback by using accumulation stress information that reflects the actual degradation state of the OLED. The system continuously monitors stress accumulation in pixels and uses this feedback to dynamically select and apply appropriate compensation data, creating a closed-loop system that adapts to the actual degradation level and maintains consistent image brightness over time.
2Ease of operation
If driving transistor is driven in saturation region, then current control is simplified, but current varies due to channel length modulation
Solution Approach 1:
The patent applies parameter changes by storing compensation data that corresponds to different voltage conditions (Vds levels) in the saturation region. Instead of changing the operating region, the system maintains saturation region operation for simplicity but introduces compensation parameters that account for channel length modulation effects at different voltage levels, thereby achieving current uniformity while preserving ease of operation.
3Device complexity
If simple degradation compensation is applied, then implementation is easier, but channel length modulation is not compensated leading to inaccurate compensation
Solution Approach 1:
The patent applies segmentation by dividing the compensation data into distinct segments or groups, where each segment corresponds to specific combinations of stress accumulation levels and voltage conditions. This segmented approach allows the system to handle complex channel length modulation compensation through organized, manageable data structures, making the implementation more systematic and less complex while maintaining high compensation accuracy.
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
The solution effectively compensates for OLED degradation, maintaining desired luminance by adjusting data signals based on accumulated stress and voltage changes, thereby accurately reproducing images.
Implementation Method 1
an organic light emitting display device displays an image using an OLED generating light according to hole-electron recombination
Data Source
AI summary
An organic light emitting display device includes: pixels including driving transistors positioned in regions divided by scan lines and data lines; a data accumulating unit arranged to accumulate first data; a first storage unit storing current and voltage change information corresponding to a degradation of an organic light emitting diode (OLED); a second storage unit storing a compensation value corresponding at least partially to channel length modulation of the driving transistors; and a timing controller programmed to carry out an altering of first data corresponding to an ith pixel so as to generate second data to be supplied to the ith pixel, the altering carried out according to: accumulation stress information for the ith pixel, the accumulation stress information corresponding to the accumulated first data and being stored in the data accumulating unit, the current and voltage change information, and a compensation value corresponding to the ith pixel.