Measurements of thermal resistance of power LEDs

Abstract

Purpose – The purpose of this paper is to present a new method of measuring thermal resistance of power light-emitting diodes (LEDs). Properties of power LEDs strongly depend on their internal temperature. The value of this temperature depends on the cooling conditions characterized by thermal resistance. Design/methodology/approach – The new method of measuring the value of this parameter belongs to the group of electric methods. In this method, the problem of estimating the value of electrical power converted into light is solved. By comparing the values of the case temperature obtained for the LED operating in the forward mode and the reverse-breakdown mode, the thermal power is estimated. On the basis of the measured value of the thermally sensitive parameter (the LED forward voltage) and the estimated value of the thermal power, thermal resistance is calculated. Findings – The elaborated method was used to measure thermal resistance of the selected types of power LEDs operating at different cooling conditions. The correctness of the elaborated measurement method was proved by comparing the results of measurements obtained with the use of the new method and the infrared method. Research limitations/implications – On the basis of the obtained results of measurements and the catalog data of the tested diodes, the dependence of the measurement error of thermal resistance of the LED on its luminous efficiency is discussed. Originality/value – The new measurement method is easy to use and more accurate than the classical method of thermal resistance measurement of the diode.