Not really groundbreaking but I think the most helpful thing is that the DC-DC converter is a switchmode one which can be quite handy if you want to put it into some kind of battery powered project where you don’t want to piss away the power by bleeding off the voltage with a linear regulator.

Another tip – there are literally hundreds of chargers like these in dollar stores around the country. They have non-USB connectors on them, but you can get a whole switching DC-DC supply for a buck, and adjust it with one or two resistors. Watch out for the color coding on the wires though, the wire colors are often reversed with red being negative and black being positive.

Be careful of the dollar store chargers. some a linear discrete designs. I usually use ones from the phone carriers and get them at yard sales or thrift stores. About 90% of them use the Onsemi part or a second source. Some will even have a tag hanging on the cord saying “intelligent charger 33063″ Most will be set for 5V to supply the actual charging circuit in the phone for the Li-ion battery. Some will have un-used component locations for actual charge control circuitry.

Simple but effective.

The empty “C” and the jumper “L” on the ones that produce lots of noise (both radiated and on the supply) are probably the equivalent of C3 and L1, respectively, on the schematic given: they are part of the output filter. If you end up with one of these and need to decrease your output noise, add a (large-ish) electrolytic at C. If you can, an inductor at L would be ideal – if not, a wire-wound or spiral-cut small-value resistor can be substituted. Either way, the key on the output is filtration. Especially as that is part of your regulation feedback.

If you are more interrested in the chip Dave made a blogpost of it: http://www.eevblog.com/2010/09/10/eevblog-110-lets-design-a-dc-to-dc-switchmode-converter/