OLED Pixel Compensation Circuit for Luminance Uniformity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Organic light emitting displays face issues with non-uniform luminance due to increased impedance from driving transistors and variations in threshold voltages across pixel units, leading to inconsistent light emission and increased current consumption.
Innovation Solution
The implementation of a power supply unit with multiple voltage terminals, including a sustain power terminal, and a pixel unit configuration with specific transistor connections and a storage capacitor to compensate for voltage drops and threshold voltage deviations, ensuring uniform luminance across the display.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of driving transistors in pixel units is increased, then the current control capability is improved, but the impedance increases causing current consumption to increase
Solution Approach 1:
The pixel unit is divided into multiple functional blocks with dedicated transistors: switching transistor for data signal control, storage capacitor for voltage storage, driving transistor for current control, and compensation transistors for threshold voltage correction. This segmentation allows each component to perform its specific function efficiently, improving overall current control capability while optimizing power consumption through specialized circuit paths.
2Use of energy by moving object
If driving voltages are reduced according to internal resistance of voltage lines, then power consumption is reduced, but luminance uniformity deteriorates
Solution Approach 1:
The compensation circuit uses feedback mechanisms where the storage capacitor stores the threshold voltage of the driving transistor, and compensation transistors adjust the gate voltage based on detected threshold variations. This feedback loop compensates for voltage drops caused by line resistance, ensuring uniform luminance across the display while maintaining optimized power consumption levels.
Solution Approach 2:
The storage capacitor pre-charges to the threshold voltage before the driving transistor operates, and compensation transistors pre-adjust the gate voltage to account for expected voltage drops. This preliminary action ensures that the driving transistor receives the correct gate voltage despite internal resistance effects, maintaining luminance uniformity without excessive power consumption.
3Device complexity
If the same data voltage is applied to all pixels, then the circuit complexity is reduced, but luminance uniformity deteriorates due to threshold voltage deviation
Solution Approach 1:
Each pixel unit is equipped with local compensation circuitry including storage capacitors and compensation transistors that are specifically configured to handle threshold voltage variations in that particular pixel. This local quality approach allows each pixel to self-correct its threshold voltage deviation independently, achieving uniform luminance across the entire display while keeping the overall circuit design relatively simple and modular.
Data Source
AI summary
An organic light emitting display and associated method includes: initializing a first node of a storage capacitor, connected between the first node and a second node, with a first driving voltage that is provided from a first power terminal; applying a sustain voltage to the first node and placing a driving transistor in a diode connection state, wherein the driving transistor comprises a gate electrode connected to the second node, an electrode connected to the first power terminal, and another electrode connected to an organic light emitting diode through a third node; applying a data signal, provided from the data line through a switching transistor comprising a gate electrode connected to a scan line, an electrode connected to the data line, and another electrode connected to a first node, to the first node; and generating a compensation voltage by applying the first driving voltage to the first node.