A Direct Junction Temperature Measurement Technique For Power Leds

A study on power light-emitting diode (LED) junction temperature sensing based on the measurements of its forward voltage is presented. The linear dependence on temperature of the voltage drop across a power LED in the wide temperature range from T = 35 up to 175 degrees C, for different bias currents, is investigated. The experimental measurements, repeated on three devices with the same parts number, exhibit a good degree of linearity. Moreover, the proposed sensors have excellent performances at the bias current of 1.4 mA with good repeatability and maintaining a stable output over more cycles of measurements.