Thermal modeling of planar transformer for switching power converters

This paper presents thermal simulations for reliability-oriented design of planar transformers for medium-power, high-frequency DC–DC converters. The modeling approach is based on accurate 3D finite-element thermal simulation of the transformer structure; inputs to the finite-element thermal model are the magnetic and electrical power losses extracted by experimental characterization of a planar transformer test-bench we designed and assembled. The simulation results are compared with those of infra-red thermal measurements. The simulations allowed to evaluate the effect of frequency and output current on the temperature distribution inside the transformer, thus setting limits for reliable operation, and to analyze alternative designs aimed at improving thermal management and, consequently the transformer reliability.