This buck converter design uses the LinkSwitch-TN IC to output DC directly from rectified mains outlet. It converts mains high voltage to smaller DC voltages suitable for electronics devices, and has the ability to output up to 360mA of current.
It’s based on the standard buck topology, except that the IC tolerates and works at very high voltages. It can convert DC voltages as high as 380V.
This circuit deals with live mains, make sure you know what you’re doing.
I was reading this paper (http://www.grix.it/UserFiles/Powermos/File/Alimentatore-senza-trasformatore/SOKAL_acfvsdsp.pdf) the other day in this case a power supply type this SM power supply “replaces”, Sometimes you need something simple and cheap.
There is also this application note from Microchip:
AN954, Transformerless Power Supplies: Resistive and Capacitive
http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1824&appnote=en021083
I’ve been chewing on this kind of psu for a while. Thinking about how to generate a 5V rail for my digital and relay sections in an audio design.
Most of the stuff I do is DIY… and I’ve come to the conclusion that it’s easier to let someone else do the hard work with these things…
From now on, I’m using the small ipod style 5V power supplies. They are a few dollars each on dealextreme and other websites. that gets thrown into a small 3v3 regulator on my msp430 boards.
I value my rare “DIY time” too highly to be caught up designing, soldering and debugging the power supply on a product where the main focus isn’t the power supply! :)