A DC-DC converter or another name known as buck regulator or switching regulator (because the input voltage can be either above or below the desired voltage output), provides stable regulated output voltage to supply electronic circuits.
LM2576 converter circuits perform same function as the commonly known voltage regulator LM7805 from National Semiconductor. The 7805 voltage regulator [...]

This DC-DC converter is designed to accept a range of input voltages that are present in a car’s electrical system, and provide a regulated 12v output. Nominally, the battery voltage is about 13.8v, but when the engine is being started, the voltage can often droop down to 6 or 7 volts for a short [...]

This 120V ac power source is built with a simple 120V : 24V center-tapped control transformer and four additional component. This circuit outputs a clean 200-V pk-pk square wave at 60 Hz and can supply up to 20W. The circuit is self-starting and free-running.
If Q1 is faster and has a higher gain than Q2 is [...]