OLED Control Circuit Corrects Luminance Drift via Voltage Feedback
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Solution Overview
Problem
The time degradation of organic electroluminance light-emitting diodes (OLEDs) in optoelectronic devices leads to variations in luminance or intensity for the same current value, affecting image reproduction by causing each OLED to emit light differently, which existing technologies have not effectively addressed.
Innovation Solution
The implementation of a control circuit with transistors and a voltmeter to measure and correct gray scale voltages based on reference values, accounting for time degradation by applying reset and reference voltages to accurately adjust the driving current for each OLED, ensuring consistent luminance across pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If OLEDs are used to generate images with current-controlled luminance, then full color image display is achieved, but time degradation causes luminance variations and inconsistent intensity for the same current value
Solution Approach 1:
The patent applies preliminary action by measuring the voltage across each OLED at the beginning to determine its individual characteristics before degradation occurs. These initial measurements are stored and used as reference values for subsequent correction calculations, allowing the system to compensate for aging effects in real-time without requiring continuous recalibration.
Solution Approach 2:
The patent implements feedback by continuously monitoring the voltage across each OLED and comparing it against the stored reference value. The control circuit calculates correction values based on the voltage deviation and applies these corrections to the gray scale data, creating a closed-loop system that automatically compensates for luminance drift caused by time degradation.
2Reliability
If correction circuits are added to compensate for time degradation, then luminance consistency is improved, but device complexity increases
Solution Approach 1:
The patent achieves multi-functionality by having the control circuit perform multiple tasks: it drives the OLED pixels, measures their voltage characteristics, stores reference values, calculates correction factors, and applies gray scale data all through a single integrated controller. This eliminates the need for separate dedicated correction hardware and reduces overall system complexity.
Solution Approach 2:
The system implements self-service by using the OLED's own voltage characteristics as the basis for correction. Each OLED's inherent electrical properties are measured and used to generate its own correction profile, eliminating the need for external calibration equipment or complex sensor systems.
3Measurement precision
If voltage measurements are taken to correct gray scale data, then luminance accuracy is improved, but measurement and control complexity increases
Solution Approach 1:
The patent uses voltage as an intermediary parameter to indirectly measure OLED degradation. Instead of directly measuring luminance output which would require complex optical sensors, the system measures the electrical voltage across each OLED, which correlates with degradation state. This voltage intermediary simplifies the measurement system while providing sufficient information for correction.
Data Source
AI summary
An optoelectronic device includes a first transistor, a second transistor, and a control circuit. The first transistor is electrically connected between a power supply and a light-emitting element, has a gate to receive a gray scale voltage, and supplies the light-emitting element with a driving current corresponding to the gray scale voltage. The second transistor has a gate electrically connected to an electrode of the light-emitting element and a source or drain electrically connected to a circuit including a voltmeter. The control circuit reads a measurement value of the voltmeter when the gate of the first transistor receives the gray scale voltage, and corrects a next gray scale voltage applied to the gate of the first transistor based on the measurement value.