Low profile high frequency power supplies using thick film planar transformers

A programme of work investigating transformers for use in high switching speed power supply units is described. The transformers are of a planar structure, allowing a low profile. The use of thick film on ceramic technology allows efficient heat transfer from the transformer, combined with low resistivity conductor tracks. An advanced form of planar transformer, intended for operation at 2 MHz, has been researched, and is shown to allow a particularly compact structure. Finite element modelling techniques with a three dimensional (3D) model are used to predict transformer performance and hence allow optimisation of the design. Resulting from this work a test transformer has been designed and fabricated. This transformer achieves efficiencies of 93%, in excellent agreement with the theoretical predictions