3T2C Pixel Circuit for OLED Uniformity
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Solution Overview
Problem
Non-uniform displaying on OLED panels due to varying high system voltage and threshold voltage differences across pixel circuits in traditional AMOLED displays, leading to inconsistent luminance across the panel.
Innovation Solution
A pixel circuit with a 3T2C architecture, comprising three transistors and two capacitors, where the luminance is controlled solely by the data signal and independent of the threshold voltage of the transistors and system voltage, ensuring consistent light emission across the panel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a traditional 2T1C pixel circuit architecture is used, then the device complexity is reduced, but the display uniformity deteriorates due to voltage-dropping effects and threshold voltage variations
Solution Approach 1:
The pixel circuit is segmented into multiple functional blocks: a first transistor for data signal input, a second transistor for reference signal input, a third transistor for current mirroring, and two capacitors for voltage storage. This segmentation allows independent control and compensation of voltage variations, improving display uniformity while maintaining reasonable complexity
Solution Approach 2:
A reference signal line is introduced as an intermediary element to provide a stable reference voltage that compensates for voltage-dropping effects in the high system voltage line. The second transistor and second capacitor work together as intermediary components to establish this reference, enabling uniform display across the panel
2Device complexity
If the high system voltage OVDD is connected to each pixel circuit, then the power supply is simplified, but the luminance consistency deteriorates due to voltage-dropping effects in the wiring
Solution Approach 1:
The circuit design creates equipotential conditions by using the second transistor and second capacitor to establish a reference voltage that compensates for voltage drops. The third transistor is configured to mirror currents based on this reference, ensuring that luminance remains consistent despite variations in the high system voltage OVDD across different pixel locations
3Ease of manufacture
If the TFT threshold voltage varies across pixel circuits, then the manufacturing process is simplified, but the current uniformity through OLEDs deteriorates
Solution Approach 1:
The circuit implements feedback through the third transistor configured in a current mirror arrangement. The third transistor receives control signals from the first transistor (data signal) and uses the reference signal path to compensate for threshold voltage variations. This feedback mechanism ensures that current uniformity through OLEDs is maintained despite TFT threshold voltage differences across the panel
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 3T2C architecture effectively addresses non-uniform displaying by isolating luminance control from transistor threshold voltage and system voltage variations, resulting in improved uniformity and performance of OLED displays.
Implementation Method 1
organic light emitting diodes (OLEDs), also named as organic electroluminescence (OEL)
Implementation Method 2
a first capacitor, a second capacitor and a lighting device
Data Source
AI summary
A pixel circuit relating to an organic light emitting diode (OLED) and a display using the same and a driving method thereof are provided. The pixel circuit submitted by the present invention adopts a 3T2C architecture (i.e. three TFTs plus two capacitors), and which circuit topology being driven by the corresponding scan signals and data signal may make the luminance shown by the pixel circuit only relate to the data signal and do not relate to the threshold voltage of a transistor used to drive a lighting element (i.e. OLED), a system high voltage received by the pixel circuit, and a potential between an anode and a cathode of the lighting element, such that the problem of non-uniform displaying on the OLED display panel may be improved or resolved effectively.