High inductance thin-film transformer for high switching frequency

This paper presents the design, fabrication, and characterization of on silicon integrated thin-film transformers for power applications at switching frequencies between 1 MHz and 10 MHz. Two designs of microtransformers are developed where the footprint of both designs is the same but each design has different winding style. Primary and secondary windings are interleaved in the first design and separated in the second design. Both designs show an inductance of 400 nH and 800 nH, respectively. The microtransformer devices are used and tested in a dc-dc converter that runs at a 4MHz switching frequency. The dc-dc converter with the microdevice achieves a flat efficiency curve with 72% peak efficiency.