Organic EL Display Pixel Circuit Mobility Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Organic electroluminescence (EL) display devices face challenges in achieving uniform luminance due to dispersions in threshold voltages and mobilities of driving transistors, which affect image quality and scalability.
Innovation Solution
A display device and method that incorporate a pixel array with driving and sampling transistors, a sustaining capacitor, and a two-stage write system for correcting threshold and mobility voltages, using a signal selector and write scanner to apply reference, intermediate, and video signal voltages in a time division manner to enhance mobility correction and power efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a simple matrix system is used for driving the organic EL display device, then the configuration is simple, but it is difficult to realize a large-scaled and high-definition display device
Solution Approach 1:
The pixel circuit is divided into multiple functional components: driving transistor for current control, sampling transistor for signal input, and sustaining capacitor for voltage maintenance. This segmentation enables complex functionality within each pixel while maintaining overall system scalability for large-scale high-definition displays
Solution Approach 2:
The patent implements dynamic voltage control through multiple signal lines (first signal line for threshold correction, second signal line for mobility correction, third signal line for video signal) that can be independently adjusted. This dynamic control allows the display device to adapt to variations in transistor characteristics while maintaining uniform luminance across the display
2Device complexity
If conventional single-stage write system is used, then the circuit operation is simple, but the mobility correction ability is insufficient leading to luminance unevenness
Solution Approach 1:
The write system is segmented into two distinct stages: first stage writes threshold correction voltage through the sampling transistor to correct threshold voltage dispersion, and second stage writes mobility correction voltage to correct mobility dispersion. This segmentation enables precise correction of different transistor parameter variations, achieving uniform luminance across the display
Solution Approach 2:
The threshold correction is performed as a preliminary action before the mobility correction and video signal writing. By first establishing the correct threshold voltage baseline, the subsequent mobility correction and image signal writing can proceed with improved accuracy, ensuring optimal luminance uniformity
3Ease of operation
If the sampling transistor conducts continuously for both threshold correction and video signal input, then the operation is simple, but the mobility correction ability is reduced
Solution Approach 1:
The sampling transistor operates in periodic cycles: conducting during the first signal line phase for threshold correction, remaining non-conducting during the second signal line phase for mobility correction, and conducting again during the third signal line phase for video signal input. This periodic operation enables precise mobility correction while maintaining systematic control
Solution Approach 2:
The non-conduction state of the sampling transistor serves as an intermediary condition that isolates the mobility correction process. By preventing signal leakage through the sampling transistor during mobility correction, the system achieves precise mobility correction without interference from other signal lines
Data Source
AI summary
Disclosed herein is a display device, including: a pixel array in which pixel circuits each having a light emitting element, a driving transistor for applying a current corresponding to a gate-to-source voltage to the light emitting element connected to a source side by applying a drive voltage across a drain and a source, a sampling transistor for inputting a signal line voltage to a gate of the driving transistor by being caused to conduct, and a sustaining capacitor connected between the gate and the source of the driving transistor for sustaining a video signal voltage inputted thereto are disposed in a matrix; a signal selector; a drive control scanner; and a write scanner.