This book describes the operation and analysis of soft-commutated isolated DC-DC converters used in the design of high efficiency and high power density equipment. It explains the basic principles behind first- and second-order circuits with power switches to enable readers to understand the importance of these converters in high efficiency and high power density power supply design for residential, commercial, industrial and medical use as well as in aerospace equipment. With each chapter featuring a different power converter topology, the book covers the most important resonant converters, including series resonant converters; resonant LLC converters; soft commutation pulse width modulation converters; zero voltage switching; and zero current switching. Each topic is presented with full analysis, a showcase of the power stages of the converters, exercises and their solutions as well as simulation results, which mainly focus on the commutation analysis and output characteristic. This book is a valuable source of information for professionals working in power electronics, power conversion and design of high efficiency and high power density DC-DC converters and switch mode power supplies. The book also serves as a point of reference for engineers responsible for development projects and equipment in companies and research centers and a text for advanced students.