Hello.
Guts of 1A USB charger from AC have a minuscule transformer. Where to source such ? Part number ? The adapter accepts "100 to 240VAC" How can such tiny thing work on a quarter kilovolt ?
Re-purposing / canibalizing an adapter just like this, found it is for real, has about a cubic centimetre transformer. Is there any trick to achieve its performance/isolation ?

 

The yellow tape provides the insulation. Most of them would be made to order, but there are a few types available off the shelf to work with the more popular flyback controller ICS.
https://www.we-online.com/components/products/datasheet/750315829.pdf

 

Hello.
Guts of 1A USB charger from AC have a minuscule transformer. Where to source such ? Part number ? The adapter accepts "100 to 240VAC" How can such tiny thing work on a quarter kilovolt ?
Re-purposing / canibalizing an adapter just like this, found it is for real, has about a cubic centimetre transformer. Is there any trick to achieve its performance/isolation ?
View attachment 320416

The "100 to 240VAC" AC is rectified to DC. The small transformer is a high frequency switching supply type as per the link provided by @Ian0

 

The reason it can be so small is that it is operating at 100kHz or so.

 

Thanks. Not made for nor works on mains frequency ! OK, understood !

 

The reason it can be so small is that it is operating at 100kHz or so.

The beauty of using a much higher frequency is that the transformers can be much smaller for a given power level. That is why the surplus avionics goodies all use 400 cycle or even 800 cycle transformers.