Junction temperature estimation for LED lamp with forward voltage method

Abstract

For estimating the junction temperature (Tj) of LED lamp, the Tj of LED module powering by rated current (135mA DC) and working in the thermal environment of LED lamp is measured with traditional forward voltage method in experiment 1. To calculate the Tj of LED lamp in actual working conditions (220V AC), a correction factor is introduced into the original model to process the deviation of output currents of LED driver electronics, as demonstrated in experiment 2. Compared with the surface temperature of LED obtained by infrared imaging method, the result in experiment 2 can effectively reflect the change in Tj of LED lamp under different ambient temperatures, which differs the surface temperature by 3~4°C. While due to a significant effect on the thermal environment of LED lamp introduced by LED driver electronics, the result in experiment 1 is approximately 9~10°C lower than that in experiment 2.