Integrated Power Supply

I’m starting out on my first serious project with a custom PCB (scary!!!). First thing I’d like to do is design an integrated power supply. Currently I’m using USB to power the system, but if I can plug the project straight into a 120 - 220V wall socket it would improve the packaging dramatically.

Are there any good examples anyone is aware of for something like this I can reference? Small is key. I’ve seen various power supply designs out there but I’m looking for something optimized for a low current application. On the breadboard with a photon the project draws around 130mA.

Typically for projects such as yours, you may see a barrel jack added to the board (or broken out) and transformer (wall wart) used. You can get these barrel jacks easily off of ebay really cheap!

So, commercially it makes sense. Most retail/commercial/industrial customers in North America and Europe insist on having some accredited lab approve your device (in the EU there are CE norms that mandate compliance by law). You don’t have to have your device qualified/certified by a lab (e.g. UL TÜV, Intertek, CSA) if you just source an adaptor with the appropriate certifications.

Plus, for your own safety, it makes sense… you’d be less likely to kill yourself or your loved-ones if you are only messing with 12volts! :wink:

But if you still want to go down that path, just look for a Buck Power Converter on the internet. I’m sure you can find a schematic of one out there you could alternatively build yourself. But, then you have to connect mains power to it… and you need strain relief, and you need to think about polarized plug, and you need to think…


Do you mean a device that hangs off the wall plug, with no wires? If I were building something like that I would use a board mount AC/DC converter module. For examples of that:

Funny thing, though. It’s cheaper to use an external AC/DC power supply with a barrel jack onto your board. Also, having the high voltage going directly into your device you’ll probably have to get additional safety certifications.

It does need to hang from the wall. This looks like a promising solution. Having a separate jack and power supply would look really lame. I’ve been wrestling with how to tackle this for a while, and if certification is needed, then I’ll probably just have to go down that path. Thanks for the help.

$10 a pop though…yikes! That’s a big hit. I guess that just how it goes with power supplies.

@icedMocha, be sure to carefully follow power isolation rules on your PCB. With live 220VAC coming into your board, you WILL need certification.


I know…going straight from AC is a problem, but for this project its kind of a given. This power converter is interesting. And they are retailing for $6.50 which is pretty good. Thank you. I have a lot to think about :wink:

Designing a switching AC/DC is not an easy first project, especially when it needs to be small, efficient and cheap. The easiest solution is to make the product USB pluggable and use a commercially available phone charger to power it. This way, you and the user will have a lot of options to choose from. These are available cheaply and in abundance, thanks to all the portable electronics.

If you are planning on commercializing the project, a lot of chinese OEM manufacturer will sell you these bare power supplies, albeit only in larger volumes.

Good luck!