Platform for monitoring the temperature of power LED junction by using the embedded protection diode

Abstract

The junction operating temperature of a power LED can be estimated by measuring with a thermocouple the temperature of the closest accessible metal part of the LED package, which is in most of the cases one of the electrical terminals, and making a calculation by taking into consideration the thermal resistances of the materials included in the LED structure. In the situations where the electrical terminals are not accessible, being placed right under the LED package, the thermocouple could be placed on the mounting PCB used heatsink, as close as possible to the thermal pad of the LED, but this may introduce errors, making the temperature estimation not accurate. The junction operating temperature can also be estimated by measuring the forward voltage of the LED, knowing the temperature coefficient of the forward voltage. In this paper the authors proposed an innovative method for measuring the operating temperature of power LEDs, using as temperature sensor the protection reverse diode embedded in the LED package.