OLED Initialization Voltage Sources for Color Dragging
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Solution Overview
Problem
Organic light emitting displays face a color dragging phenomenon where green organic light emitting diodes emit light later than other colors due to longer charging times under low-luminance conditions, causing color inaccuracies in gray scale representation.
Innovation Solution
The display device employs a configuration with different initialization voltage sources for each pixel circuit, including a first and second initialization voltage source, and optionally a third, to optimize the charging and emission timing of red, green, and blue organic light emitting diodes, ensuring synchronized light emission across colors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the driving current magnitude for green organic light emitting diodes is reduced to achieve high emission luminance efficiency, then power consumption is reduced, but the charging time of capacitors increases causing color dragging phenomenon
Solution Approach 1:
The patent applies preliminary action by providing a first initialization voltage to the pixel circuit before the emission period begins. This pre-charges the capacitor associated with the green organic light emitting diode, so that when the emission period starts, the capacitor is already partially charged, reducing the time needed to reach the required voltage level for light emission. This resolves the contradiction by preparing the system in advance to compensate for the slow charging that would occur during normal operation at low current.
Solution Approach 2:
The patent changes the voltage parameter by providing different initialization voltages for different pixel circuits. Specifically, green pixel circuits receive a higher first initialization voltage compared to other colors, which accelerates the charging process of their capacitors. This parameter change allows the system to maintain low driving current for power efficiency while achieving sufficient charging speed to prevent color dragging.
2Manufacturing precision
If different initialization voltage sources are provided for each pixel circuit to synchronize light emission timing, then color dragging phenomenon is reduced, but device complexity increases
Solution Approach 1:
The patent applies local quality by providing different initialization voltage characteristics to different pixel circuits based on their specific needs. Green pixel circuits receive a higher first initialization voltage with greater magnitude, while other color pixel circuits receive a second initialization voltage with lower magnitude. This localized differentiation ensures that each color channel is optimized for its specific charging requirements, achieving synchronized emission timing and accurate color representation without uniformly increasing complexity across the entire display device.
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 reduces the color dragging phenomenon by ensuring that all organic light emitting diodes emit light simultaneously, improving color accuracy and reducing perceived color shifts during gray scale representation.
Implementation Method 1
Organic light emitting displays generate images using pixels that emit light from organic light emitting diodes
Implementation Method 2
The organic light emitting diodes may emit red, blue, and green light based on the different band gaps of organic materials in the organic light emitting diodes
Implementation Method 3
it may take a long time to charge the capacitors of the green organic light emitting diodes under low-luminance conditions
Data Source
AI summary
A display device includes first and second initialization voltage sources and first and second pixel circuits. The first initialization voltage source provides a first initialization voltage. The second initialization voltage source provides a second initialization voltage less than the first initialization voltage. The first pixel circuit includes a first organic light emitting diode. The second pixel circuit includes a second organic light emitting diode with an organic material having a band gap different from a band gap of an organic material in the first organic light emitting diode. The first pixel circuit is coupled to the first initialization voltage source and the second initialization voltage source. The second pixel circuit is coupled to a single initialization voltage source.