A system and a method to measure the junction temperature of leds

Abstract

In this study, a new method of measuring LED junction temperature is given. The linear relative radiant power/temperature variation has been utilized in this method. This method can be applied at pulsed high currents of LED. The measurement system used here consists of a pulse oscillator, an appropriate LED driving circuit and a photodetector circuit. A photodetector voltage, which is proportional to the radiant power of LED, has been measured by using an oscilloscope, and junction temperature have been determined by making easy calculations on it. A constant, which is obtained from linear relative radiant power/junction temperature characteristics, has been used in this calculation.