Pixel Circuit Voltage Switching to Prevent OLED Deterioration
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Solution Overview
Problem
Existing high-resolution display devices face pixel deterioration due to high current density during light emission, which is not effectively addressed in current technologies.
Innovation Solution
A pixel structure with specific transistor configurations and voltage levels is implemented, including a first transistor connected to a first node, a second transistor between a data line and a third node, a third transistor connected to a power line, and a fourth transistor connected to an initialization voltage, with a light emitting element between a second power line, utilizing different voltage levels during emission and deterioration prevention periods to manage current flow and prevent pixel degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If high current density is supplied to the light emitting element during emission, then luminance and brightness are improved, but pixel deterioration accelerates
Solution Approach 1:
The patent implements periodic voltage level switching between emission mode (first voltage level) and deterioration prevention mode (second voltage level higher than first voltage level). During emission periods, the light emitting element operates at first voltage level for luminance, then switches to second voltage level during deterioration prevention periods to reverse charge accumulation and mitigate degradation, creating a cyclic operation pattern that balances performance and longevity
Solution Approach 2:
The patent dynamically changes the voltage level parameter supplied to the light emitting element based on operational phase. The voltage level transitions from first voltage level during emission to second voltage level (higher than first voltage level) during deterioration prevention, modifying the electrical parameter to achieve both luminance output and durability protection at different time points
2Reliability
If voltage level is increased to prevent pixel deterioration, then pixel longevity is improved, but power consumption increases
Solution Approach 1:
The high second voltage level is applied periodically only during deterioration prevention periods rather than continuously, allowing the system to achieve pixel protection benefits while limiting energy consumption to specific time windows. The emission periods operate at lower first voltage level, creating an energy-efficient cyclic pattern
Solution Approach 2:
The deterioration prevention period with elevated second voltage level is scheduled in advance after emission periods to proactively reverse charge accumulation before it causes damage. This preliminary protective action prevents deterioration rather than reacting to it, extending pixel life while managing energy usage predictably
Data Source
AI summary
A pixel includes: a first transistor including first and second electrodes connected to first and second nodes, respectively, and a gate electrode connected to a third node; a second transistor connected between a data line and the third node, and including a gate electrode; a third transistor connected between a first power line and the first node, and including a gate electrode connected to an emission control line; a fourth transistor including a first electrode connected to the second node, a second electrode connected to a third power line, and a gate electrode; and a light emitting element connected between the second node and a second power line. During an emission period, the second power voltage has a first voltage level. During a deterioration prevention period after the emission period, the second power voltage has a second voltage level. The second voltage level is higher than the first voltage level.