OLED Pixel Circuit Reference Voltage Charging
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Solution Overview
Problem
Existing organic light emitting display devices face challenges in maintaining desired voltage levels in storage capacitors due to voltage drops and ripples in the power supply, affecting image quality.
Innovation Solution
The solution involves an organic light emitting display device with a data driver, scan driver, and a display panel comprising pixels with specific transistors and capacitors, where a reference voltage is used to charge storage capacitors independently of the power supply voltage, and emission control transistors manage power supply to compensate for voltage drops and ripples.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a storage capacitor is charged using the first power supply voltage, then the pixel can display images by supplying current to the organic light emitting diode, but voltage drops and ripples in the first power supply cause inconsistent voltage charging in storage capacitors across different pixels, degrading image quality
Solution Approach 1:
A reference voltage line is introduced as an intermediary element to provide a stable reference potential for charging storage capacitors. This reference voltage acts as a mediator between the power supply and the pixel circuit, isolating the capacitor charging process from voltage drops and ripples in the first power supply, thereby ensuring consistent voltage charging across all pixels regardless of power supply fluctuations
Solution Approach 2:
The patent changes the reference potential parameter by introducing a dedicated reference voltage line with low impedance to ground. This parameter change ensures that the storage capacitor charges to a consistent voltage level relative to this stable reference rather than relative to the fluctuating first power supply voltage, eliminating image quality degradation caused by power supply variations
2Ease of operation
If the first power supply voltage is used to charge storage capacitors, then pixel operation is enabled, but voltage drops across the display device make it difficult to charge desired voltage in storage capacitors of different pixels
Solution Approach 1:
The patent segments the power supply function by separating the first power supply (for driving current) from the reference voltage supply (for capacitor charging reference). This segmentation allows the storage capacitor to be charged independently using the stable reference voltage, eliminating the coupling between power supply voltage drops and capacitor charging precision, thereby achieving consistent voltage charging across all pixels
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 approach allows for consistent voltage charging in storage capacitors, maintaining image quality by compensating for power supply voltage drops and ripples, ensuring stable image display across different pixels.
Implementation Method 1
the organic light emitting display displays images by using organic light emitting diodes which generate light through the recombination of electrons and holes
Implementation Method 2
a capacitor to store voltage corresponding to the data signal and the second power according to operations of the first and second switching devices
Data Source
Figure 1
Figure 2~3
AI summary
A pixel circuit coupled to a data line, a scan line, an emission control line, a power supply, a reference power source, and a light emitting element, includes: a data switch coupled between the data line and a first node, and having a control electrode coupled to the scan line; a reference switch coupled between the reference power source and a second node, and having a control electrode coupled to the scan line; a capacitor coupled between the first node and the second node; a driving transistor coupled between the power supply and the light emitting element, and having a gate electrode coupled to the second node; and an emission control switch coupled between the power supply and the first node, and having a control electrode coupled to the emission control line.