Thin film micro-transformers for future power conversion

This paper presents an investigation into the use of micro-fabricated transformers for future power conversion in the 5-10 MHz frequency range. The structure of the micro-transformers is described and an analytical model is used to optimize the transformer for maximum efficiency. The optimized devices are based on improved fabrication processes which give 80 μm thick copper conductors and a two layer laminated magnetic core. The optimization suggests that an efficiency of 82% at an output power of 3.5 W can be achieved. Initial small signal results are presented for micro-transformers fabricated using the improved processes. The estimated efficiency of the fabricated microtransformer based on these results is 78%.