Samsung Charger USB Theory of operation

[Mohamed.saleh]

I teared down Samsung Charger USB, and traced the circuitry trying to study it's theory of operation. but I couldn't. It's of course 220V AC to 5V DC. Can anyone help me understanding it?

 

[betwixt]

That schematic can't be right but basically it's a transistor oscillator running from the rectified incoming AC. The high frequency allows a small ferrite transformer to be used instead of a larger iron cored type. The secondary of the transformer produces the low voltage output to the phone.

Brian.

 

[Mohamed.saleh]

am pretty much sure that I traced every node in the circuit and it's correct

 

[FvM]

It can't be right because Q1 and Q2 never become forward biased. Most connections may be right though.

But even a complete schematic won't tell much without all component values and transformer parameters. What are you trying to achieve?