Organic Light Emitting Display Device Capacitor Charging Circuit
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Solution Overview
Problem
Existing organic light emitting display devices face difficulties in accurately charging storage capacitors to the desired voltage level due to charge-sharing between parasitic and storage capacitors, leading to deteriorated display quality, especially when attempting to display black or gray gradations.
Innovation Solution
The implementation of a second power supply unrelated to the first power supply for organic light emitting diodes, which allows for precise charging of storage capacitors using a third power supply with a lower voltage level, thereby compensating for voltage loss and enabling the display of images with desired luminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a storage capacitor is charged through a data line with parasitic capacitor, then the storage capacitor receives voltage corresponding to the data signal, but charge-sharing between parasitic capacitor and storage capacitor causes inaccurate charging
Solution Approach 1:
The patent segments the charging process into two independent stages: first charging the storage capacitor through the data line, then charging it again through a dedicated capacitor charging line. This segmentation eliminates the charge-sharing effect by separating the data signal transmission path from the capacitor charging path, allowing accurate voltage storage without interference from parasitic capacitors.
Solution Approach 2:
The patent introduces a capacitor charging line as an intermediary component specifically for charging the storage capacitor. This intermediary path is separate from the data line, allowing the storage capacitor to be charged without going through the parasitic capacitor in the data line, thus eliminating the charge-sharing problem while maintaining accurate voltage levels.
2Ease of manufacture
If conventional charging method is used, then the storage capacitor charges through data line, but display quality deteriorates when displaying black or gray gradations
Solution Approach 1:
The patent segments the charging process into two independent stages: first charging the storage capacitor through the data line, then charging it again through a dedicated capacitor charging line. This segmentation eliminates the charge-sharing effect by separating the data signal transmission path from the capacitor charging path, allowing accurate voltage storage without interference from parasitic capacitors.
Solution Approach 2:
The patent applies preliminary action by first charging the storage capacitor with the data signal voltage, then performing a second charging operation through the capacitor charging line to compensate for any voltage loss. This preliminary charging followed by correction ensures accurate voltage levels are achieved, enabling proper display of black and gray gradations.
3Measurement precision
If a second power supply is introduced for independent capacitor charging, then accurate voltage charging is achieved, but device complexity increases
Solution Approach 1:
The patent makes the capacitor charging line multi-functional by using it for both initializing the storage capacitor voltage and for charging the storage capacitor to the desired voltage level. This universal use of the capacitor charging line reduces the need for separate dedicated charging circuits, thereby achieving accurate voltage charging without proportionally increasing device complexity.
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 solution effectively charges storage capacitors independently of the first power supply, ensuring accurate voltage levels and improving display quality by reducing charge-sharing issues, allowing for the display of images with desired luminance and reducing manufacturing costs by eliminating the need for complex polysilicon crystallization processes.
Implementation Method 1
The storage capacitor charges a voltage corresponding to a data signal supplied to a data line and supplies the voltage to a driving transistor
Implementation Method 2
Organic light emitting display devices display an image, using organic light emitting diodes that produce light by recombining electrons and holes
Data Source
AI summary
An organic light emitting display device includes: a scan driver; a data driver; a display unit including pixels located at crossing regions of scan lines and data lines; first power lines coupled between a first power supply and the pixels; at least one second power line located outside the display unit and coupled to a second power supply having a voltage different from a voltage of the first power supply; at least one third power line coupled to a third power supply having a voltage different from the voltage of the first power supply; and fourth power lines coupled to the pixels, wherein the pixels are charged with voltages corresponding to the data signals and the third power supply and are configured to control the amount of current flowing from the first power supply in response to the voltages charges in the pixels.