A restricted source of power supply is analyzed in this text - namely the switching mode power supplies (SMPS), which utilize the Pulse Width Modulation (PWM) technique to operate. Even though restricted, such a class of power supply is vital to circuits, as most modern electronic equipment is dependent on this form of technology to feed electronic boards. Its main advantages are greater efficiency, and its minimum physical size and weight. Interdisciplinary knowledge such as circuit theory, semiconductor devices theory and technology, magnetics theory and technology, linear and non-linear control theory, is involved in the design of an SMPS. This volume aims to provide designers with an in-depth overview of current interdisciplinary methods involved in the design of switching mode power supplies, providing the reader with a tool whereby the learning time can be reduced and information about switching mode power supplies design processes can be easily accessed. The text adopts a systemic approach, subdividing the information into functional blocks whose properties and relationships are evaluated and compared with each other. A comprehensive list of references to the literature is given to enable the reader to follow up in more detail.