All electronic circuits require a clean and constant voltage DC power supply. In this chapter authors consider design concepts and approaches, with a few design examples of how fundamental design concepts and practices can be applied to develop the power conversion stages and the power management system. Traditional power distribution techniques in a system have relied on a centralized architecture where all the required power rails are derived from a single high-power switch mode power supply (SMPS). The distributed power architecture (DPA) approach is to distribute power at an intermediate "medium" voltage throughout the system and convert power locally. In the modern world of electronics, there are three different basic approaches available for the process of DC-to-DC conversion. These are the linear approach, the switching approach, and the charge pump approach. The chapter discusses the important aspects of designing a complete power supply using AC mains as the energy source.