Contents I. Introduction
Planar magnetic components [1] offer unique advantages compared to conventional wire wound components in power electronics applications. Lower profile, good thermal characteristics, small leakage inductance and repeatability of component characteristics are often named in this respect. However, there are also advantages of conventional wire wound components like e.g. allowing for a larger fraction of the winding area to be filled with copper. Therefore, at present it has to be decided individually for each application which is the best technology for and design of the magnetic components. For this purpose a large number of alternatives has to be assessed. Making prototypes of planar magnetic components is cumbersome since making their windings involves a considerable effort like e.g. printed circuit board manufacturing. Therefore, efficient and sufficiently accurate analytical models are valuable tools for the design of planar magnetic components. Analytical models have already been published for the losses in the cores of magnetic components [2], losses in planar windings [3] and temperature rise of planar transformers [4]. The winding capacitance model described in [5] relies on assumptions that hold only for wire wound components. This paper describes an analytical model of winding capacitances valid for planar transformers. The new model is compared qualitatively with that valid for wire wound components. It is validated against measured capacitances of some prototypes. Furthermore this paper describes an analytical model of dielectric losses in the windings of planar transformers. It is discussed how this can be used to optimize the thickness of the insulation layers between the copper layers of the planar winding.
