having trouble finding a suitable transformer for SMPS

Thread Starter


Joined Feb 22, 2021
I am trying to essentially copy one of those cheap wall outlet to usb charger(yes I am being careful)
I have taken apart of few of them to see what they are using and they all have some relatively TINY foot prints(<16mm x 16mm) for how much current(around 1A) they are able to pass through.

Am I missing something about SMPS? do SMPS allow more current to pass through than the transformer is rated for? or are these manufacturers of these power bricks just throttling these transformers ?

Also if you have any suggestions for small transformers that are good for going from mains(110VAC) to 5VDC but also has an auxiliary winding to run the TOP257GN-TL chip I am using, that would also be helpful


Joined Feb 24, 2006
They may be pushing the limitations, but I doubt doubt that they are exceeding them. You may have to get a design kit from one of the manufacturers (Wurth(?)) and make your own. That is the only real way to be sure.

Design Kits - Würth | Mouser

There are lots of simulation models in LTspice for the premade transformers.