Comparison of two alternative junction temperature setting methods aimed for thermal and optical testing of high power LEDs

Characterization of LEDs and other semiconductor devices demands at least accurate monitoring of the junction temperature (Tj), also its control in more complex cases. In practical LED lighting appliances “hot lumens” are meaningful, as most lamps are used in steady state with power applied. Analysis in cold state provides only indirect information about the intended operation. On the other hand, direct T
_j
measurement is not trivial - the most viable way is to measure the forward voltage (V
_F
) which is a function of junction temperature. In this paper we compare two ways of V
_F
-based T
_j
regulation of LEDs capable for electrical-optical-thermal characterization in a single session in terms of accuracy and time consumption.