Pixel Circuit for OLED Luminance Consistency
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Solution Overview
Problem
Existing organic light emitting display devices face challenges in maintaining consistent current supply to organic light emitting diodes, leading to deviations in luminance across pixels.
Innovation Solution
A pixel configuration is introduced, featuring a light emitting diode, capacitors, and transistors connected in a specific manner to allow for operation at various driving frequencies, ensuring stable current supply and luminance consistency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional pixel circuit is used, then the device structure is simple, but the current supply to organic light emitting diodes deviates and luminance consistency deteriorates
Solution Approach 1:
The pixel circuit is divided into multiple functional blocks: a driving transistor for current control, a compensation transistor for threshold voltage compensation, and multiple capacitors (first capacitor for gate voltage storage, second capacitor for additional compensation) for parameter stabilization. This segmentation allows each component to address specific reliability issues independently, improving current supply stability while maintaining manageable complexity through modular design.
2Productivity
If the pixel operates at high driving frequency, then the productivity is improved, but the current supply deviation increases and luminance consistency worsens
Solution Approach 1:
The compensation transistor and capacitors perform preliminary compensation of threshold voltage variations and voltage drops before the light emission phase. The first capacitor stores the compensated gate voltage, and the second capacitor provides additional compensation, ensuring that the driving transistor receives pre-corrected control signals even at high driving frequencies, thereby maintaining luminance consistency.
Solution Approach 2:
The compensation transistor creates a feedback mechanism that senses and compensates for voltage drops and threshold voltage variations in the driving transistor. This feedback loop adjusts the gate voltage dynamically, ensuring stable current supply to the organic light emitting diode regardless of driving frequency changes, thus maintaining luminance consistency at high productivity.
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 proposed pixel configuration enables stable and consistent light emission across pixels, effectively addressing deviations in current supply and luminance, thereby enhancing display quality.
Implementation Method 1
An organic light emitting display device displays an image by using an organic light emitting diode that generates light by the recombination of electrons and holes
Data Source
AI summary
A pixel including: a light emitting diode; a first capacitor connected between first and second nodes; a second capacitor connected between the second node and a third node; a first transistor including a first electrode connected to the second node, a second electrode connected to an anode of the light emitting diode, and a gate electrode connected to the first node; a second transistor including a first electrode connected to the third node, a second electrode connected to a reference voltage line, and a gate electrode connected to a first scan line; a third transistor including a first electrode electrically connected to the first node, a second electrode connected to the reference voltage line, and a gate electrode connected to a second scan line; and a fourth transistor including a first electrode connected to a data line, a second electrode connected to the third node, and a gate electrode connected to a third scan line.