OLED Pixel Circuit Leakage Current Reduction via Dual Power Initialization
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Solution Overview
Problem
Existing organic light emitting display devices face challenges in maintaining high brightness while minimizing black brightness and leakage current, which can deteriorate picture quality.
Innovation Solution
The proposed solution involves a pixel circuit with a driving transistor and additional transistors that control current flow from a first power source to a second power source via an organic light emitting diode (OLED), utilizing separate initializing power sources to manage gate electrode initialization and anode electrode initialization, thereby reducing leakage current and improving black display ability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If OLEDs emit light at low current, then power consumption is reduced, but black brightness increases
Solution Approach 1:
The patent applies preliminary action by initializing the gate electrode voltage to a specific level (ELVSS or higher) before the OLED emission phase begins. This pre-initialization ensures that when low current is supplied during emission, the transistor operates in an optimized state that minimizes leakage current and prevents black brightness, allowing the OLED to display true black at low power consumption levels.
2Illumination intensity
If the voltage of the second power source is reduced to implement high brightness, then the voltage of the initializing power source is reduced, but leakage current increases
Solution Approach 1:
The patent segments the power management into two independent power sources: a first power source (ELVDD) for high-voltage operation during emission to drive high brightness, and a second power source (ELVSS) for low-voltage initialization to minimize leakage current. By separating these functions and allowing independent voltage optimization, the system achieves high brightness during emission while maintaining low leakage current during non-emission phases, resolving the trade-off between brightness and leakage.
3Device complexity
If a single power source is used for initialization, then device complexity is reduced, but picture quality deteriorates due to increased leakage current
Solution Approach 1:
The patent divides the initialization function into two separate transistors: a first transistor connected to the first power source (ELVDD) for high-voltage initialization, and a second transistor connected to the second power source (ELVSS) for low-voltage initialization. This segmentation allows each transistor to operate in its optimal voltage range, minimizing leakage current while maintaining simple circuit implementation. The dual-transistor approach achieves superior picture quality without significantly increasing device complexity.
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 configuration enhances the display's ability to maintain high brightness while reducing black brightness and leakage current, thereby improving overall picture quality.
Implementation Method 1
An organic light emitting display generates images based on light from organic light emitting diodes (OLEDs)
Data Source
AI summary
A pixel includes an organic light emitting diode (OLED), a pixel circuit, and first and second transistors. The OLD includes a cathode electrode connected to a second power source. The pixel circuit includes a driving transistor having a gate electrode initialized by a third power source. The driving transistor controls the amount of current flowing from a first power source to the second power source via the OLED. The first transistor is connected between a fourth power source and the second power source and an anode electrode of the OLED. The first transistor is turned on based on a scan signal is supplied to a scan line. The second transistor is connected between a data line and the pixel circuit. The second transistor is turned on when the scan signal is supplied to the ith scan line.