48V to 1V Active-Clamp Stacked Direct Forward Converter

Abstract

This thesis presents a 48 V-to-1 V stacked direct forward (SDF) dc-dc converter consisting of four 12 V-to-1 V direct forward (DF) modules connected in input-series outputparallel (ISOP) configuration. In each DF module, there is no secondary-side inductance, and a single-ended forward transformer is driven at a high duty cycle to reduce the switch root-mean-square currents. An active clamp is employed on the primary side to reset the transformer, limit the switch voltage stress, and facilitate zero voltage switching. The approach is verified by simulation results on a 12 V-to-1 V, 50 A, 200 kHz prototype module using GaN devices and a planar transformer, and having a peak efficiency of 93.9% and the full-load efficiency of 91.8%. In this thesis, experimental results are presented for a 12 V-to-1 V DF prototype. I would like to thank my thesis advisor, Dr. Dragan Maksimovic, for giving me the opportunity to do my master's thesis under his guidance. Thanks to his guidance and encouragement, I was able to gain a lot of valuable knowledge in the field of power electronics and keep myself motivated throughout the completion of my thesis. Additionally, I would like to thank Dr. Luca Corradini and Dr. Robert W. Erickson, who have helped me learn and better understand analysis, modeling, design and control techniques in power electronics. I would like to thank my peers who supported and encouraged me during the completion of my thesis. Finally, I would like to thank my parents for their support as well as inspiration throughout my graduate studies. v Contents Chapter