Novel, thick-film, planar transformers for high-frequency applications

Shippen, Anthony James (1996) Novel, thick-film, planar transformers for high-frequency applications. (MPhil thesis), Kingston University, .


The design of very compact switched mode power supplies (SMPS) requires compact, high reliability transformers for operation at high frequencies (1-10MHz) which possess excellent electrical isolation between primary and secondary windings. For conventional wirewound transformers, operation at high frequencies can present problems due to parasitic reactances, variable performance and complex manufacturing procedures. Thick-film techniques can seem to offer a possible solution to these problems. A programme of work was carried out at Kingston University in cooperation with ERA Technology Ltd. and Custom Interconnect Ltd. aimed at developing transformers for this application. A variety of thick-film planar transformer structures were fabricated and their use within high speed switching supplies was investigated. The effect of winding and ferrite core geometries on the power efficiency of the planar transformer was investigated and the results are presented. It was concluded that transformer power efficiency could be significantly improved by increasing the thickness of the winding conductors. A programme of work to investigate methods for achieving this is described. A prototype thick-film hybrid SMPS for lighting applications, incorporating a planar transformer, was designed and fabricated. The SMPS was operated successfully to power a 12V quartz-halogen lamp from the 240V AC mains supply.

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