Temperature dependent thermal resistance in power LED assemblies and a way to cope with it

Different high-end white power LEDs from different LED vendors were studied. The aim of the study was to find the optimal choice of LEDs and thermal management solutions for a street-lighting application. The primary concern was the (real) junction-to-heatsink thermal resistance of the LED or LED assembly and the real junction temperature and the actual light output of the individual LEDs under test. Since in many cases the junction-to-heatsink thermal resistance showed temperature dependence, like-with-like comparison in terms of light output characteristics was done as function of the real junction temperature instead of the reference temperature.