Practical Thermal Modeling of Planar Magnetic Component devices

摘要

Electronic designers continuously strive to supply more power in a smaller volume and obviously with the highest reliability performances. Emerging Planar Magnetic Components use a combination of a low-profile high-frequency magnetic core and a Printed Circuit Board, which allow a large reduction in terms of weight and size. As a drawback, power densities are magnified and consequently thermal stress effects due to Joule heating and magnetic losses can be far more damaging. To assess a relevant three-dimensional numerical model of a realistic device, experimental characterizations were done. However, the numerical computation of such fine Detailed Thermal Model (DTM) appears to be time prohibitive. Thus the capability to replace expensive numerical computations by a much faster mathematical Reduced-Order Model (ROM) based on moment matching approach was demonstrated. The latter allows preserving a reliable approximation of the original numerical model and then creating a multipath Dynamic Compact Thermal Model (DCTM), using stochastic optimizations, which is compliant with a large set of boundary conditions and usable in many CFD tools. The present study details the confrontation of both surrogate models (ROM and DCTM) to the original numerical model. These various comparisons demonstrate that a high agreement, below 10% of discrepancy, can be reached for different cooling conditions. Finally, using shorter calculations based on RC-network approach, planar transformer designers can explore large operating conditions at earlier design stage.