AMOLED Pixel Compensation Circuit for Display Uniformity
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Solution Overview
Problem
Active Matrix Organic Light Emitting Diode (AMOLED) displays experience non-uniformity and instability due to threshold voltage drift and varying supply voltage across transmission lines, leading to inconsistent image display across different areas of the panel.
Innovation Solution
An organic light emitting diode pixel compensation circuit is designed with specific transistors and capacitors to read the difference between supply voltage and threshold voltage, storing this difference in capacitors to generate drive current independently of these voltages, ensuring consistent light emission across the panel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the number of transmission lines is increased to power larger AMOLED displays, then the display size can be increased, but voltage attenuation across transmission lines becomes more serious leading to display non-uniformity
Solution Approach 1:
The patent implements local compensation at each pixel level by measuring the actual voltage at the pixel and adjusting the drive signal accordingly. This local quality approach ensures that each pixel receives the appropriate compensation for its specific voltage conditions, thereby maintaining display uniformity across the entire large-sized display panel.
Solution Approach 2:
The patent employs feedback mechanisms where the actual voltage at each pixel is measured and used to adjust the drive signal. This feedback loop compensates for voltage attenuation in transmission lines, ensuring that display uniformity is maintained even as display size increases and more transmission lines are required.
2Manufacturing precision
If TFT process stability is improved to reduce threshold voltage drift, then manufacturing precision can be enhanced, but the inherent variability in thin film transistors still causes non-uniformity
Solution Approach 1:
The patent implements self-service compensation where each pixel circuit autonomously measures its own threshold voltage and adjusts its drive signal accordingly. This self-service approach allows each pixel to compensate for its specific TFT characteristics without requiring external intervention, thereby achieving display uniformity despite inherent TFT variability.
Solution Approach 2:
The patent uses feedback mechanisms to measure the actual threshold voltage of each TFT and adjust the drive signal to compensate for threshold voltage drift. This feedback-based compensation ensures that display uniformity is achieved even when manufacturing precision varies across different TFTs.
3Device complexity
If a conventional pixel circuit is used without compensation, then device complexity is low, but threshold voltage drift and supply voltage variations cause non-uniform display
Solution Approach 1:
The patent segments the pixel circuit into multiple functional modules including threshold voltage compensation modules and supply voltage compensation modules. This segmentation allows each module to independently handle specific compensation tasks, achieving display uniformity while keeping the overall circuit design modular and manageable.
Solution Approach 2:
The patent designs universal compensation circuits that can handle both threshold voltage drift and supply voltage variations using the same basic circuit architecture. This multi-functionality approach allows a single compensation circuit to address multiple sources of non-uniformity, reducing overall device complexity while maintaining display uniformity.
Data Source
AI summary
An organic light emitting diode pixel compensation circuit is disclosed. The compensation circuit compensates threshold voltage of a TFT and supply voltage in a pixel circuit to address non-uniform in a display. In the circuit, a first transistor transmits a data signal to a first capacitor based on a scan signal; a second transistor transmits a reference signal to the first capacitor based on a first light emission signal; a third transistor connects a gate of a drive transistor with a drain of the drive transistor based on the scan signal to read the difference between supply voltage and threshold voltage of the drive transistor and to transmit the difference to the first capacitor and a second capacitor; and the drive transistor generates the drive current based on the supply voltage and the voltage on the first capacitor to drive an organic light emitting diode emit light.