Influence of a Cooling System on Power MOSFETs’ Thermal Parameters

Abstract

In the current paper, an analysis of the influence of cooling system selection on the thermal parameters of two thermally coupled power MOSFETs is presented. The required measurements of the thermal parameters were performed using the indirect electrical method at different values of power dissipated in the investigated transistors and various supply conditions for the active parts of their cooling systems. The results of the investigations are analysed and discussed. Functions modelling the observed dependences of thermal parameters of the investigated MOSFETs on the power that was dissipated in them as well as the supply conditions of the active parts of their cooling systems are proposed. A good agreement between the results of the measurements and the computations was obtained. It is shown that the use of active cooling systems makes it possible to reduce the value of the thermal resistance of the tested transistor up to 20 times. In each of the tested systems, the self- and transfer-thermal resistances decreased with an increase in the dissipated power and the rotational speed of the fan.