Thorseth, Anders

Copenhagen University Research Information System

Characterization, Modeling, and Optimization of Light-Emitting Diode System

Denne afhandling udforsker karakterisering, modellering og optimering af lysemitterende dioder (LED) til generel belysning. En automatiseret forsgsopstilling er blevet udviklet til spektro-radiometrisk karakterisering af LED komponenter, for forskellige indstillinger af strm og driftstemperatur. Den automatiserede forsgsopstilling har været brugt til at karakterisere kommercielle LED komponenter. Det er vist, at kvante eektivitet kan tilnærmes ved en simpel parabolsk funktion. De undersgte modeller af spektralfordelinger fra lysdioder enkelt og dobbelt Gauss-funktioner som er strengt empiriske, og en semi empirisk model baseret på kvasi Fermi niveauer og andre basale faststof principper. De frie parametre in modellerne er ttet til de målte spektralfordelinger. Resultatet viser en hj korrelation mellem den målte LED spektralfordelinger og modellerne. Når man sammenligner kromaticiteten af de målte spektralfordelinger med de modellerede spektralfordelinger viser afvigelsen sig at være strre end den nedre grænse for menneskets opfattelse af farver. En metode er udviklet til at optimere erfarvede klynge LED systemer med hensyn til lyskvalitet, ved hjælp af flermålet optimering. Resultaterne er simulerede spektralfordelinger med egenskaber lig traditionelle lyskilder, og med høj lyskvalitet. Som en del af dette projekt er disse teknikker blevet anvendt i praktiske belysningsprojekter. De beskrevne eksempler er belysning af historiske genstande og belysning af planter for at øge fotosyntesen.This thesis explores, characterization, modeling, and optimization of light-emitting diodes (LED) for general illumination. An automated setup has been developed for spectral radiometric characterization of LED components with precise control of the settings of forward current and operating temperature. The automated setup has been used to characterize commercial LED components with respect to multiple settings. It is shown that the droop in quantum efficiency can be approximated by a simple parabolic function. The investigated models of the spectral power distributions (SPD) from LEDs are the strictly empirical single and double Gaussian functions, and a semi empirical model using quasi Fermi levels and other basic solid state principles. The models are fitted to measured SPDs, using the free parameters. The result show a high correlation between the measured LED SPD and the tted models. When comparing the chromaticity of the measured SPD with tted models, the deviation is found to be larger than the lower limit of human color perception. A method has been developed to optimize multicolored cluster LED systems with respect to light quality, using multi objective optimization. The results are simulated SPDs similar to traditional light sources, and with high light quality. As part of this work the techniques have been applied in practical illumination applications. The presented examples are historical artifacts and illumination of plants to increase photosynthesis

Online Research Database In Technology

Characterization, Modeling, and Optimization of Light-Emitting Diode Systems

http://orbit.dtu.dk/ws/files/6469076/Thorseth2011.pdf

Characterization, Modeling, and Optimization of Light-Emitting Diode Systems

Abstract

Similar works

Full text

Available Versions

Copenhagen University Research Information System

Online Research Database In Technology