Display Device Circuit Compensation for Organic EL Luminance Degradation
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Solution Overview
Problem
Organic EL displays experience luminance reduction and screen burn-in due to uneven current luminous efficiency degradation across pixels, leading to reduced device life and display quality.
Innovation Solution
A display device circuit that compensates for current luminous efficiency reduction by adjusting the drive voltage of the light emitting element, using a multiplier circuit to maintain constant light emission intensity by setting the gate-source voltage proportional to the display data signal and the turn-on voltage of the organic EL element, thereby mitigating the effects of luminous efficiency deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If uniform current is supplied to all pixels, then uniform display characteristics are obtained initially, but luminance unevenness and screen burn-in occur as the organic EL element deteriorates at different rates across pixels
Solution Approach 1:
The patent implements a feedback mechanism where the drive voltage applied to each pixel is adjusted based on the measured or characterized turn-on voltage of its organic EL element. By continuously adapting the drive voltage to compensate for individual element variations and deterioration, the system maintains uniform luminance output across all pixels throughout the device lifetime, thereby resolving the contradiction between initial uniformity and long-term durability
Solution Approach 2:
The patent changes the drive voltage parameter dynamically to compensate for variations in turn-on voltage among different organic EL elements. By adjusting this electrical parameter based on each element's characteristics, the system achieves uniform current luminous efficiency across pixels even as they deteriorate at different rates, thus extending device life while maintaining display quality
2Illumination intensity
If the turn-on voltage of the organic EL element increases due to deterioration, then the current luminous efficiency decreases, but simply increasing drive current to compensate causes excessive power consumption and accelerates deterioration
Solution Approach 1:
The patent precisely adjusts the drive voltage parameter to match the turn-on voltage of each organic EL element, optimizing the operating point to maintain efficient current-to-luminance conversion. This prevents excessive power consumption while compensating for efficiency degradation, as the drive voltage is increased only to the extent necessary to overcome turn-on voltage shifts rather than blindly increasing current
Solution Approach 2:
The system uses feedback from turn-on voltage measurements to dynamically adjust the drive voltage, ensuring that power consumption remains optimized even as the organic EL element deteriorates. This feedback loop prevents both under-driving (which would reduce luminance) and over-driving (which would waste power and accelerate degradation), thereby resolving the contradiction between maintaining light output and managing power usage
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 solution effectively maintains consistent light emission intensity across pixels, reducing luminance unevenness and extending the life of the organic EL display by compensating for the degradation in current luminous efficiency, thus addressing the issue of screen burn-in and display quality.
Implementation Method 1
In a display device including a self light emitting element such as an organic EL element, light emission may be controlled pixel by pixel... In a case where an organic EL element is used as the light emitting element, light emission intensity is proportional to a current flowing through the element
Data Source
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AI summary
To compensate for a change of light emission intensity caused by deterioration of a light emitting element, provided is a display device including a drive element (Tl) which controls a drive current to be supplied to a light emitting element (EL) in accordance with a data signal representing a target luminance of the light emitting element (EL). The light emitting element (EL) emits light in accordance with a current flowing through the light emitting element (EL). The data signal is corrected in accordance with a voltage applied at both terminals of the light emitting element (EL) so that the drive current to be supplied to the light emitting element (EL) increases with an increase in an amount of a voltage drop of the light emitting element (EL).