OLED Pixel Initialization Voltage Control for Color Dragging
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Solution Overview
Problem
Organic light emitting display devices experience a color dragging phenomenon where certain organic light emitting diodes emit light later than others due to varying charging times under low-luminance conditions, primarily because of differing emission efficiencies and the need for small driving currents.
Innovation Solution
The display device controls initialization voltages based on luminance conditions, using lookup tables to determine specific initialization voltages for each pixel, adjusting power voltages to optimize charging times and prevent color dragging by ensuring uniform emission across different luminance levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a small driving current is supplied to organic light emitting diodes with high emission efficiency, then power consumption is reduced, but charging time increases causing color dragging phenomenon
Solution Approach 1:
The patent applies preliminary action by setting different initialization voltages for organic light emitting diodes based on their emission efficiency before the actual display operation. High emission efficiency OLEDs are given higher initialization voltages to pre-charge their capacitors, ensuring they reach operational voltage quickly even when driven with small currents for power savings. This preliminary voltage adjustment prevents the color dragging phenomenon while maintaining low power consumption during normal operation.
2Loss of energy
If different driving currents are supplied to organic light emitting diodes of different colors, then emission efficiency is optimized, but synchronization of light emission is compromised
Solution Approach 1:
The patent implements local quality by assigning different initialization voltage levels to individual OLEDs based on their specific emission efficiency characteristics. Each color sub-pixel (red, green, blue) receives a customized initialization voltage from the timing controller, allowing each to reach its operational state simultaneously despite having different current requirements. This localized voltage adjustment ensures both energy efficiency and emission synchronization.
3Device complexity
If a fixed initialization voltage is applied to all organic light emitting diodes, then device complexity is reduced, but color dragging phenomenon occurs under varying luminance conditions
Solution Approach 1:
The patent applies dynamics by making the initialization voltage adaptive rather than fixed. The timing controller dynamically selects and applies appropriate initialization voltages to each OLED based on real-time luminance conditions and the specific characteristics of each diode. This dynamic voltage adjustment ensures reliable emission synchronization across different operating conditions without requiring overly complex hardware modifications.
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
The solution effectively reduces or eliminates the color dragging phenomenon by optimizing charging times and ensuring synchronized emission across all pixels, regardless of luminance levels, thereby improving display quality and reducing power consumption.
Implementation Method 1
organic light emitting display devices display images using an organic light emitting diode that generates light by recombination of electrons and holes
Data Source
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AI summary
A display device includes: a first pixel including a first organic light emitting diode; an initialization voltage generator for generating a first initialization voltage to be supplied to an anode of the first organic light emitting diode; and a timing controller including a first lookup table in which a plurality of first initialization voltage values corresponding to a plurality of maximum luminances are recorded, the timing controller being configured to determine a value of the first initialization voltage, based on reception information on a target maximum luminance and the first lookup table.