hey Guys! i'm a new member. And what drove me to be one is that i'm making my own cell phone charger with a rating of 5V and 350mA . And i'm sort of in need of help of you guys. If you'll so kind (someone) , please help me in making one like that of a Nokia phone charger and i badly need the schematic diagram. And another thing is i'm an electronics eng'g student so apparently, i have to be through this and understand my field. It's not that i don't understand, it's just that i'm having a hard time tracing the pcb layout of the nokia charger i opened and ,well cannibalized, and dissected. I want to be pretty 200% sure what i'm doing is on the right track, or else i wound end up burning our house down.

Another thing is that i'm perplexed about the transformer inside my nokia charger. it's utterly small and "it has four terminals" on one side and two on the other side. obviously the 2-terminal-side has a definite voltage output and can be easily understood but how about the other side? to-which-is-which connection is this connection for the the other etc...

So PLEASE GUYS . ANYONE. help me out. specially those are really good in this stuff. please please please. this could get my grade passed or "failed". I'll REALLY APPRECIATE IT if you'll help me. IT WOULD mean SALVATION.




- divergent_inquirer

 

A typical commercial phone charger uses a switched-mode supply.

The transformer will be driven at high frequency using a transistor switch from high voltage DC (the AC input rectified and smoothed).

The other windings will be for output and feedback.

This is not a DIY project, it's using 'live' mains and rather dangerous.

For the low power involved, you would be far better off using a conventional mains transformer and rectifier down to say 8 or 9V, then do the voltage regulation from there where it's fully isolated from the AC suply.

You could use either a 7805 type linear regulator or something like a 'simple switcher' IC for higher efficiencies and less heat production.

Using a low voltage switched regulator, you could design it for 12V input so it could work with either a 12V wall wart supply or from a vehicle 12V system.

 

Have you tried contacting Nokia ?