On 2018-Sep-21, at 4:03 PM, Noel Chiappa via cctalk wrote: There are a thousand configurations for power supplies possible depending on what needs to be accomplished: circuit isolation (e.g. mains from load), EI conversion up or down, degree of regulation, economy tradeoffs, etc. An example that perhaps fits what you're thinking of is the old motor-generator setups which convert 60Hz to 400Hz, the 400Hz then being used as input to a variety of supplies. It's useful to keep in mind that regulation and EI conversion are different objectives but they can be achieved either separately or in concert. What we commonly refer to as a "linear power supply" does EI conversion (and circuit isolation) in one stage (the transformer), followed by an independent regulator stage. Your common modern generic switching supply integrates EI conversion, regulation and circuit isolation into one feedback loop across one transformer (switching at high frequency). A buck converter is inherently a switching converter, the buck operation requires the switching to function. There is a corresponding boost converter with a different circuit topology around the inductor, for . . boosting voltage. There are also boost-buck converters. Dropping 5V to 3.3V or 1.xV for ICs is often accomplished with little on-board buck converters which you may not have realised were there, to avoid the losses and heat of a linear regulator.

On Sep 21, 2018, at 6:03 PM, Noel Chiappa via cctalk <cctalk at classiccmp.org> wrote: Noel, here?s one way to think about buck converters. The coil (inductor) serves as a way of giving the flow of electrons ?inertia?. It?s not really inertia, it?s energy built up in the magnetic field of the inductor, but it acts like inertia. You want the electrons to have (say) 3.3 V of energy per electron - that translates into an equivalent ?speed? of the electrons. So if the power supply can put out a train of electrons moving at that speed (plus or minus a little), the load will be happy. But, the available (battery, or whatever) energy source drops electrons out at (say) 5V. The buck converter lets the 5V shove the ?train? of electrons forward for a while, until it?s a little above the 3.3V ?speed? at the load, then stops the 5V shove and lets the train run on ?inertia? (stored energy in the inductor) for a while - the voltage will be dropping at the load, but only slowly. When it drops low enough, the converter opens the switch to the 5V and starts speeding up the train again. The bigger the inductor, the more ?inertia? the current flow has, and the longer the train takes to speed up and slow down, and the slower the switching rate can be for a give above and below voltage tolerance at the load. The inductor serves both to slow the rate at which the train speeds up (fighting against the 5V source and storing energy into its field) and to slow the rate at which the train slows down (powering the load out of the stored energy). This is a slightly dangerous analogy in some ways - electrons do *not* have any useful inertia in circuits, for example. I think Brent or any of the regulars can probably point out other conceptual problems, as well. But, hopefully it?ll help in thinking about what a buck supply is trying to do. - Mark