This book provides a comprehensive yet deep and wide description of DC-DC switching power supply circuits, to which much attention is being paid as a key technology in green IT, especially in automotive and consumer electronics industry. It covers buck converters, isolated converters, PFC converters, their modeling and analysis, several control methods, passive components, and their several recent applications (on-chip power supplies, DC-DC and AC-DC converter applications, single-inductor multi-output DC-DC converters, energy harvest applications, wireless power delivery, charge pump circuits, and power amplifiers). The authors are from academia and industry, so the contents are well balanced. All of the contributors have been engaged in the research and development of their respective areas. Some authors are pioneers and inventors, such as in hysteretic PWM and random switching controls. Thus, the book includes original content and lucid explanations of the various essential topics it covers.