Design of very low profile magnetic components using flex foils

Several magnetic components (transformers and inductors) have been designed with very low profile (4 mm height) cores. To achieve such a low height, full custom cores have been used, together with an advanced technology (flex foils) for the windings. This freedom in the selection of dimensions and materials makes the design procedure completely different to the traditional schemes with commercial cores. The process used to obtain an optimum design is described in this paper. It is based on the use of models based on finite element analysis (FEA) tools, and spreadsheets. This procedure has been applied to the design of a transformer and an inductor, with a size of 10/spl times/10/spl times/4 mm/sup 3/ for each, to be used in an onboard power converter in telecommunication systems. Experimental results of a 5 W, low output voltage (3.3 V/spl times/1.5 A) prototype with these magnetic components are included in the paper.