Michael Kleinigger writes:
If you’re like me, the first thing you do when wiring up a new circuit is to connect the power and ground rails (with the power source initially turned off… maybe). And you’ve probably got at least one power supply that’ll do the job. But what if you didn’t have the supply you needed? Perhaps all you’ve got is a 12V battery, and you’re in need of a 3.3V source. Well, if you’ve finished your chores, I hear Tosche Station will sell you some power converters. Failing that, you could always build your own. A simple buck converter will likely do the trick.
The buck converter takes a DC input voltage and reduces it by a controllable amount, much like a resistive voltage divider. But unlike your average voltage divider, the buck converter can efficiently supply a substantial output current. In fact, this circuit’s output current should be greater than its input current (on average). And no, that doesn’t violate any laws of physics; the converter’s output power will still be less than its average input power because its output voltage is lower than the voltage at its input. In mathematical terms, (PIN = VINIIN) > (POUT = VOUTIOUT), where IOUT = ILOAD above. Make sense?
Experimenting with Buck Converters - [Link]