OLED Pixel Circuit Wiring Simplification via Data Line Initialization
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Solution Overview
Problem
In organic light emitting displays, threshold voltage variations in driving transistors lead to non-uniform displaying due to manufacturing process inconsistencies, causing leakage currents and complex wiring line structures.
Innovation Solution
The proposed organic light emitting display simplifies the wiring line structure by using a scan driver and data driver to supply scan signals and data signals, respectively, with an initialization voltage shared across pixels, eliminating the need for an additional initialization line and reducing leakage current through a six-transistor pixel circuit that includes a storage capacitor and specific transistor configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If an initialization line is added to initialize driving transistors, then threshold voltage uniformity is improved, but device complexity and wiring line structure become more complex
Solution Approach 1:
The data line is designed to serve dual functions: transmitting data signals during the display period and providing initialization voltage during the initialization period. This eliminates the need for a separate initialization line, resolving the contradiction between achieving threshold voltage uniformity and maintaining simple wiring structure.
Solution Approach 2:
The system alternates between different operational periods: during the initialization period, the data line supplies initialization voltage to initialize driving transistors; during the display period, the same data line supplies data signals. This periodic switching allows one line to perform multiple functions without interference.
2Reliability
If a separate initialization line is used, then transistor initialization is improved, but leakage current increases due to additional wiring paths
Solution Approach 1:
By making the data line multi-functional to also serve as an initialization voltage line, the patent eliminates additional wiring paths that would create leakage current paths. The same physical infrastructure is used for both initialization and data transmission, removing the source of harmful leakage current.
3Object-generated harmful factors
If six-transistor pixel circuit is used, then leakage current is minimized, but device complexity increases compared to simpler circuits
Solution Approach 1:
The six-transistor circuit performs preliminary initialization of the driving transistor before data signal input. By pre-initializing the transistor threshold voltage through the initialization voltage supplied via the data line, the circuit prepares the transistor in an optimal state, which helps minimize leakage current during subsequent operation.
Solution Approach 2:
The storage capacitor in the six-transistor circuit stores the initialization voltage and provides feedback to maintain stable threshold voltage. This feedback mechanism ensures the driving transistor operates consistently, minimizing leakage current while the transistor configuration itself is optimized to balance complexity and performance.
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 solution minimizes leakage current and reduces voltage changes in the driving transistor, resulting in improved image uniformity and reduced manufacturing costs by eliminating the need for an initialization line, while maintaining desired brightness and simplifying the pixel structure.
Implementation Method 1
the organic light emitting display displays images using organic light emitting diodes that emit light through the recombination of electrons and holes
Data Source
AI summary
An organic light emitting display includes a scan driver configured to supply scan signals to scan lines and to supply emission control signals to emission control lines, a data driver configured to supply data signals and an initialization voltage to data lines, and pixels positioned at crossing regions of the scan lines and the data lines, each of the pixels comprising an organic light emitting diode (OLED) and a first transistor for controlling an amount of current supplied from a first power source and having a second electrode coupled to the first power source and a first electrode coupled to the OLED, wherein a gate electrode of the first transistor of a first pixel from among the pixels positioned on an ith (“i” is a positive integer) horizontal line is coupled to a corresponding one of the data lines via a second pixel from among the pixels positioned on an (i−1)th horizontal line in a period where the initialization voltage is supplied to the data lines.