Introduction

Imagine we are at some busy "metro" terminus one evening at peak hour. Almost instantly, thousands of commuters swarm the station trying to make their way home. Of course there is no train big enough to carry all of them simultaneously. So, what do we do? Simple! We split this sea of humanity into several trainloads and move them out in rapid succession. Many of these outbound passengers will later transfer to alternative forms of transport. So for example, trainloads may turn into bus-loads or taxi-loads, and so on. But eventually, all these "packets" will merge once again, and a throng will be seen, exiting at the destination.

Switching power conversion is remarkably similar to a mass transit system. The difference is that instead of people, it is energy that gets transferred from one level to another. So we draw energy continuously from an "input source," chop this incoming stream into packets by means of a 'switch' (a transistor), and then transfer it with the help of components (inductors and capacitors), that are able to accommodate these energy packets and exchange them among themselves as required. Finally, we make all these packets merge again, and thereby get a smooth and steady flow of energy into the output.

So, in either of the cases above (energy or people), from the viewpoint of an observer, a stream will be seen entering, and a similar one exiting. But at an intermediate stage, the transference...