In the beginning of the article, the fundamentals of Switching Power Conversion will be explained and a brief description of the various stages that compose a PSU will be made. In addition, we will make a quick reference to some switching regulator topologies used currently. A few pages dedicated to PSU protections are following and next we take a look at ATX, EPS and 80 PLUS specifications. Finally, in Appendix A we make a quick reference to the most significant electronic components currently used not only in PSU manufacturing but also in every modern electronics device. So you will learn the basic concepts of inductors, capacitors, resistors, transistors and diodes, in order to get familiar with them and understand better some concepts discussed in this article.