buck converter

A switching circuit that steps voltage down efficiently, like a gearbox trading high voltage for high current. A switch chops the input into pulses; an inductor acts as a flywheel storing energy during the on-time and coasting it to the load during the off-time, while a capacitor smooths the result. The output settles at V_in × D, so 12 V at 42% duty cycle gives a clean 5 V — at 90%+ efficiency, unlike a wasteful linear regulator.

Bucks are everywhere a chip needs a lower rail than the battery or adapter provides: the 1.0 V core of a CPU, the 3.3 V of a microcontroller, the USB-PD output of a laptop charger. The inductor and capacitor are sized by the switching frequency and how much ripple you tolerate; faster switching shrinks them but heats the switches more.