Effect of junction temperature on heat dissipation of high power light emitting diodes

Abstract

The effect of junction temperature on heat dissipation of high power light emitting diodes (LEDs) is investigated. The theoretical aspect of junction temperature dependency of two major parameters—the forward voltage and the radiant flux—on heat dissipation is reviewed. Actual measurements of the heat dissipation over a wide range of junction temperatures are followed to quantify the effect of the parameters using commercially available LEDs. The results show that (1) the effect of the junction temperature dependency on heat dissipation is governed largely by the LED power efficiency and (2) each parameter contributes to the total heat dissipation in an opposite way so that the absolute changes of the heat dissipation are not significant over a wide range of junction temperature. An empirical model of heat dissipation is proposed for applications in practice.