Alternating Polarity Lighting Device for Organic EL Thermal Management
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Solution Overview
Problem
Organic EL devices used in front lights for liquid crystal panels face challenges with short luminance life and deterioration due to high current requirements for maintaining luminance, especially when the light is continuously on, leading to overheating and reduced display quality.
Innovation Solution
A lighting device structure that alternates the polarity of electrical power supply to light emitting elements connected in forward and reverse directions, allowing one set to emit light while the other cools, extending the life by switching when luminance decreases to a threshold, and using a detector to maintain balanced light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If organic EL device is used as light source with reflective film, then light shielding is achieved, but luminance life becomes short due to high current requirements and overheating
Solution Approach 1:
The light emitting elements are divided into multiple groups (first light emitting element group and second light emitting element group) that can be independently controlled. By segmenting the organic EL device into multiple operable units, the system can activate only the necessary groups to reduce overall current consumption and heat generation, thereby extending luminance life while maintaining required illumination intensity.
Solution Approach 2:
The patent implements periodic operation by alternately activating different light emitting element groups. Instead of continuous operation at high current, the system uses periodic pulsed operation where groups are activated in sequence, allowing thermal management and reducing cumulative stress on the organic EL materials, thus extending operational life.
2Illumination intensity
If high current is applied to obtain expected luminance, then illumination intensity is improved, but temperature increases causing deterioration of light emitting elements
Solution Approach 1:
By dividing the light emitting elements into multiple independently controllable groups, the patent enables selective activation of only the groups necessary to achieve the required luminance. This segmentation reduces the total current flowing through any single group, thereby reducing heat generation and temperature increase while maintaining the needed illumination intensity.
Solution Approach 2:
The control circuit acts as an intermediary between the power supply and the light emitting elements, managing current distribution intelligently. It allocates current to different groups based on display requirements, using pulse width modulation and selective activation to achieve desired luminance with minimized current consumption and heat generation.
3Illumination intensity
If light emitting elements are continuously activated, then illumination is maintained, but deterioration of elements occurs due to sustained high temperature
Solution Approach 1:
The patent implements periodic operation by alternately activating different light emitting element groups. Instead of continuous operation, the system uses pulsed operation where groups are activated in sequence with rest periods, allowing thermal management and reducing cumulative stress on the organic EL materials, thus extending operational life while maintaining required illumination.
Solution Approach 2:
The system strategically deactivates certain light emitting element groups during operation, allowing them to cool down and recover. By rotating between different groups and not continuously activating all elements, the patent enables thermal recovery periods that reduce deterioration and extend the overall reliability and lifespan of the display device.
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
This approach extends the life of the lighting device by reducing overheating and maintaining luminance, ensuring longer operational periods and improved display quality by alternating light emission between elements.
Implementation Method 1
a plurality of light emitting elements 31 which emit light by a forward direction current
Data Source
AI summary
A lighting device at least has: a plurality of light emitting elements that emit light by a forward direction current; a direct-current power supply; a first wiring and a second wiring for supplying electrical power to the plurality of light emitting elements from the direct-current power supply; and a switch for switching the polarity of the electrical power to be supplied to the first wiring and the second wiring; in which the plurality of light emitting elements include forward direction connection in which the forward direction current flows when the electrical power having a positive polarity is applied to the first wiring and reverse direction connection in which the forward direction current flows when the electrical power having a positive polarity is applied to the second wiring and being connected between the first wiring and the second wiring.