Due to the progress in electronic components and equipment development achieved in the last decades, electrical energy conversion is today a rapidly expanding field of power and electrical engineering. Different kinds of power supplies are used everywhere in normal daily routines at home, office, medicine, industry, and energy transmission machines and processes. The problems this book addresses are the basics of electrical energy conversion with power electronic converters. The goal is to describe, explain and compare different modes of low, middle and high power electronic system performance and arrangement in terms of their possibility to effectively convert electrical energy. The work is mainly intended to serve as a textbook for college and university-level bachelor, master, and doctoral students as well as for experienced engineers and researchers. To this aim, the classical circuits, systems, and mathematical models are examined here carefully. Primarily, the up-to-date electronic equipment used in many applications is discussed. For better appreciation, every part of the book is completed with clear conclusions and wealth of control questions.