Thermal modeling of the cooling of a power MOSFET by heat pipes

In this work, a model is developed in order to simulate the cooling of a power MOSFET by heat pipe systems. The MOSFET is modeled by a RC thermal circuit approach on the basis on its thermal characteristics delivered by the manufacturer. The heat pipe is also modeled by a RC thermal circuit. The thermal resistances and capacitances of the heat pipe model are determined by both experiments and theoretical calculations. The model aims to determine the junction temperature of the MOSFET as well as the heat pipe temperatures in response to a periodic heat input power as a function of different parameters such as the duty ratio, D, and the duration of the variant time heat input, Tp. The results indicate that for, a given duration Tp, the duty ratio affects the junction temperature which oscillates between minimum and maximum values. Moreover, the maximum and minimum junction temperatures increase with the duty ratio. For a given duty ratio, the junction temperature is also affected by the duration of the heat input power. The maximum junction temperature increases with Tp, however, the minimum junction temperature decreases as the heat input power duration increases. In all cases, the junction temperature values remain lower than the maximum ones allowed for the safety operation of the MOSFET.