Thermal simulation of hybrid converters for distributed power supplies

This paper deals with Finite Element Modeling applied to the thermal analysis and design of power converter boards. We built a 3D model of PCB-mounted D2PAK power MOSFETs, and validated it through a comparison with measured temperatures on an ad-hoc designed and fabricated test board. The agreement between model and experiment is excellent. The model was then applied to the thermal analysis of a 400 V to 12 V DC/DC converter. The standard FR4 PCB implementation is shown to be thermally unacceptable, with a MOSFET temperature of 128deg C for 3.5 W of dissipated power. On the other hand, the same layout on a more innovative multilayer baseplate board with a 0.5 mm copper back layer and 70 micrometer thermally conductive dielectric behaves much better, with a MOSFET temperature of 94deg C for 12 W power dissipation.