OLED Pixel Circuit Data Line Merging for Aperture Ratio
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Solution Overview
Problem
The existing organic light emitting display devices face challenges in achieving uniform picture quality due to non-uniformity in the manufacturing process of thin film transistors, leading to deviations in current flowing through organic light emitting diodes, which reduces luminance and increases manufacturing costs due to the need for additional channels in the data driver.
Innovation Solution
The solution involves removing the reference power line and using the data line to sense the threshold voltage of the driving TFT, connecting it to either a digital-to-analog converter or an analog-to-digital converter based on a switch control signal, allowing for improved aperture ratio and reduced channel count in the data driver.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a reference power line is formed to sense the change of properties in the driving TFT of each pixel, then the picture quality uniformity is improved, but the aperture ratio of the pixel is reduced
Solution Approach 1:
The patent combines the sensing function and data transmission function into a single data line. The data line is used both to supply data voltage to the pixel during display mode and to sense the threshold voltage change of the driving TFT during sensing mode, eliminating the need for a separate reference power line and thereby preserving the aperture ratio while maintaining picture quality uniformity through TFT property compensation.
Solution Approach 2:
The data line is designed to perform multiple functions: it serves as both a data transmission line during normal display operation and as a sensing line for detecting TFT threshold voltage changes. This multi-functionality allows the removal of the dedicated reference power line, preventing aperture ratio reduction while still enabling picture quality uniformity through sensing and compensation of TFT property variations.
2Manufacturing precision
If a reference power line is formed to sense the change of properties in the driving TFT, then the current deviation between pixels is reduced, but the manufacturing cost is increased due to additional channels in the data driver
Solution Approach 1:
The patent merges the sensing function into the existing data driver infrastructure by using the data line for both data transmission and sensing. The data driver's existing channels are utilized to supply sensing voltages through the data lines and to receive sensing signals, eliminating the need for additional dedicated sensing channels and thereby reducing manufacturing cost while maintaining current uniformity across pixels.
Solution Approach 2:
The data driver is designed to perform dual functions: driving pixels during display mode and sensing TFT properties during sensing mode. By making the data driver channels multi-functional, the patent avoids increasing the channel count while still achieving current uniformity through sensing and compensation of TFT threshold voltage changes.
3Area of moving object
If the data line is used for sensing the threshold voltage, then the aperture ratio is improved by removing the reference power line, but the device complexity increases due to switch control requirements
Solution Approach 1:
The patent implements dynamic switching of the data line function between display mode and sensing mode through control signals. The switch connected to the data line is dynamically controlled to connect to different nodes (data input node during display mode, sensing output node during sensing mode) based on the operational phase, allowing the system to adapt its configuration and minimizing structural complexity while maintaining aperture ratio.
Data Source
AI summary
A display device is discussed, which includes: a light emitting diode to emit light; and a pixel circuit connected to the light emitting diode, the pixel circuit including; a data line; a driving power line; a sense signal line; a gate line; and a switch connected with the data line by a first terminal, a digital-to-analog converter by a second terminal, and an analog-to-digital converter by a third terminal, wherein the switch connects the data line to the digital-to-analog converter or the analog-to-digital converter on a basis of a switch control signal.