Methods for estimating junction temperature of AC LEDs

Light-emitting diodes operating on alternating current (AC) are gaining popularity in lighting applications. The junction temperature of an LED significantly influences performance. Although there are many proven methods for estimating the junction temperature of direct current (DC) LEDs, only a few methods have been proposed for AC LEDs. Two different methods were investigated and analyzed for their accuracy in estimating AC LED junction temperature: a low reference current pulse used to measure the voltage across the junction, and an active cooling system to recover the first half cycle current (rms). Method details are provided. The results suggest that the voltage drop method for AC LEDs is a viable method to estimate junction temperature.