AMOLED Sub-Pixel Circuit Layout for 400 dpi Resolution
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Solution Overview
Problem
Conventional AMOLED displays face limitations in achieving high resolutions (300-400 dpi or greater) due to space constraints from driving circuitry and alignment tolerances, leading to reduced pixel lifetime and insufficient space for all components.
Innovation Solution
The use of low-leakage current transistors, such as metal oxide transistors, along with an external sub-pixel compensation driver outside the active area, and the omission of storage capacitors, allows for high-resolution displays by reducing the size of sub-pixel circuitry and maintaining accurate drive currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional AMOLED display designs are used with standard driving circuitry, then the display can be manufactured with standard processes, but the resolution is limited to below 300 dpi due to space constraints from driving circuitry and alignment tolerances
Solution Approach 1:
The storage capacitor is extracted and removed from the sub-pixel circuit. The patent uses low-leakage current transistors to eliminate the need for storage capacitors, thereby freeing up sub-pixel area for higher resolution displays while maintaining accurate drive currents throughout the frame period.
Solution Approach 2:
The patent moves the compensation driver from within the sub-pixel area to an external location outside the active display area. This dimensional relocation allows the sub-pixel circuit to be minimized for high resolution while still providing necessary compensation functionality.
2Manufacturing precision
If the sub-pixel size is reduced to achieve higher resolution, then the resolution increases, but the pixel lifetime decreases due to reduced area for charge storage and increased stress
Solution Approach 1:
The low-leakage current transistors inherently maintain accurate drive currents without requiring additional charge storage components. This self-service capability eliminates the need for large storage capacitors, allowing smaller sub-pixel area while maintaining the electrical characteristics necessary for long pixel lifetime.
3Reliability
If storage capacitors are included in the sub-pixel circuit to maintain charge, then the drive current accuracy is maintained, but the sub-pixel area increases preventing high resolution
Solution Approach 1:
The storage capacitor is extracted and removed from the sub-pixel circuit. The patent uses low-leakage current transistors to eliminate the need for storage capacitors, thereby freeing up sub-pixel area for higher resolution displays while maintaining accurate drive currents throughout the frame period.
Solution Approach 2:
The patent changes the electrical parameters of the transistor by using metal oxide semiconductor materials with inherently lower leakage currents. This parameter change allows the transistor to hold charge accurately without requiring a storage capacitor, reducing sub-pixel area while maintaining drive current accuracy.
4Reliability
If more circuit components are included in each sub-pixel to ensure proper driving, then the display reliability improves, but the device complexity increases and space is consumed
Solution Approach 1:
The storage capacitor is extracted and removed from the sub-pixel circuit. The patent uses low-leakage current transistors to eliminate the need for storage capacitors, thereby freeing up sub-pixel area for higher resolution displays while maintaining accurate drive currents throughout the frame period.
Solution Approach 2:
The compensation functionality is segmented and moved to an external driver located outside the active display area. This separation allows the sub-pixel circuit to be simplified and minimized while still providing necessary compensation for display uniformity through the external driver.
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 enables AMOLED displays with resolutions of at least 300-400 dpi by ensuring accurate drive currents and display uniformity without increasing the sub-pixel size, thereby enhancing pixel lifetime and display quality.
Implementation Method 1
a switching transistor to hold a data voltage, the switching transistor having a leakage current of not more than about 10−15 A/μm; a driving transistor having a leakage current of not more than about 10−15 A/μm
Implementation Method 2
OLEDs make use of thin organic films that emit light when voltage is applied across the device
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
OLED displays having a resolution of 300 dpi, 400 dpi, or greater are provided. Devices as disclosed may use one or more transistors, such as metal oxide transistors, which have a leakage current of not more than about 10-15 A/µm. Displays having sub-pixels with a largest dimension on the order of 60 µm are also provided.