September 2nd, 2009

ronin

Transformerless 120V power supplies for low current applications.


http://ww1.microchip.com/downloads/en/AppNotes/00954A.pdf

Not the most efficient things in the world, and they can't supply more than about 15 mA of current without problems starting. But pretty impressive what you can build with just a resistor, capacitor and zener diode, eh?

And with one transistor rigged to turn on or off based on the current state of the zener, you can make the circuit even better.