Switching it up

Yesterday I was poking the hornet's nest. Today we're back to power supplies. The change is as rapid as the weather changes in Colorado. Many requested I explain switching supplies. And so we shall. Let us begin by remembering what a conventional power supply consists of: a transformer (to isolate and set the voltage you need), a diode bridge (to direct the AC into separate + and - paths), and a capacitor to store and release energy between the plus and minus transitions. The end goal of the power supply: convert the wall AC into usable DC (like that of a battery). And what, you might ask, is in one of these new fangled switching power supplies you read about? The same three main elements. Indeed, a SMPS (Switch Mode Power Supply) has exactly the same elements and purpose as that of a conventional supply. Yet if you were to look at the two supplies in a side-by-side comparison they would look quite unlike each other. The conventional power supply is what we are used to: big heavy transformer, a handful of parts that include large capacitors, all mounted on the floor of our stereo's chassis or on a circuit board. In a nutshell, a conventional power supply is BIG. For example, if you look inside one of our products that use a conventional supply, well over half the internal real estate is devoted to the power supply. Take a look at the insides of our NuWave DAC. A close look at the insides reveals only the smallest amount of circuit board near the rear of the unit has DAC electronics. Everything else is power supply. When we look instead at a SMPS we would see something very much smaller. Perhaps a tenth the size of what's in the picture of the DAC. The output DC voltage of both would be identical, the elements that make up the two supplies are the same, yet one is considerably bigger than the other. How can this be? The first hint is this: while both supply types have the same elements, the SMPS has an additional element in front of the power transformer. This new element in the design is where all the magic happens and makes the miniaturization of the supply possible.