Enhanced measurement techniques for power LED characterisation

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Supervisor:
Dr. Ender Ferenc
Department of Electron Devices

This thesis provides a short insight into the thermal dependence of semiconductor diodes and the combined optical and thermal characterization of LEDs. Nowadays, importance of high-performance light-emitting diodes is rapidly growing in different areas of lighting technology. The reasons behind this growing expansion in popularity are better efficiency, color rendering index, energy consumption and life expectancy compared to the conventional light sources.

In addition to the increasing luminous flux from a single case and the steady increase in efficiency and luminous efficacy, the power increases in a higher rate. Consequently the dissipation density increases too, which is the main issue to prioritize the consideration of the thermal domain.

In my thesis I briefly present the temperature dependence of the diodes, in particular, the ’junction to case’ thermal resistance. I give an overview about the measurement procedure and the related standards required to determine the thermal resistance. I give a short description of the related JEDEC standards for combined thermal and radiometric/photometric measurements of LEDs. I also give an overview about the determination of the operating temperature of the pn-junction. I present the importance and the determination method of the diffusion capacity and the setup of the related measurements.

I briefly discuss the possibilities of designing white LEDs by covering the available literature, especially the white LEDs produced by the phosphor method. I present the operation, the spatial arrangement and the conversion efficiency of the phosphors. Furthermore, I give a short description of a possible way of phosphor development. I also present our combined opto-thermal measurement technique for phosphors.

Finally, I describe the test setups of our measurements and I evaluate the acquired results.

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