Hi all..!
I recently opened a mobile charger and found the circuit inside it unfathomable.!
The circuit diagrams are attached along with this post. I would like to know the purpose of the components used in them; to help my project (making a mobile charger).
I think,
(i)Q1 is the fast switching transistor for PWM
(ii)D2 acts as a regulator diode with very low leakage current
(iii)D4 is a fast switching diode, acting as a free-wheeling diode
(iv)C5 acts as the shunt capacitor filter
(v)D1 rectifies the current, Q1 regulates it with the help of D2 but then if it becomes a regulated DC, how can the transformer couple it to the next section?

Are there any mistakes in the conclusions I have drawn? Please help!

 

This is a banned topic on AAC (Line Powered supplies).

What you have is a switching supply that makes a high frequency from the line, which goes through the small transformer for isolation.

 

Banning actually depends on the OP's experience.

We cannot lock a 30 years experienced tech's project or professors thread, right ?

 

Banning actually depends on the OP's experience.

We cannot lock a 30 years experienced tech's project or professors thread, right ?

Agreed, hence the abbreviated answer, waiting for a mod's call on it.

 

thanks! why is this topic banned? 'n is this banned online only? can i do it?

 

thanks! why is this topic banned? 'n is this banned online only? can i do it?

It's only the terms of service of this forum. That circuit will work using the cores above.

The rule is no automotive modifications, due to safety reasons, mostly. We don't want our members to be killed because of something we helped them change on lighting or engine.

I hope that makes sense. There's a list of sites that do discuss automotive projects tacked in the forum.

Though as I stated, the cores I listed will substitute in the circuit you asked about. The rules have been changed since that thread 2 years ago.

 

k. thanks..
but i think that educating someone about the dangers in a field is better than just shutting one's eyes to that field completely. i believe that it's the absence of proper backup that makes people do things on their own, blinded of the obstacles in their path...
sorry if i sound offensive, i didn't mean to be..
n please don't worry, i m not going to get myself killed!!

 

My suggestion is to read the ToS, it is pretty clear on the subject. I strongly suggest everyone read it once.

The only reason I haven't closed this one yet is I haven't figured out where the load is. It is one the hot side then this thread should indeed be closed. It will be if needed.

We regularly get people who have absolutely no electronic experience trying to save a few buck and endangering everyone around them.

 

well.. the load is to be placed across the capacitor C5.
btw, u yourself seem to believe that "Good enough is enemy of the best"; why then don't u feel like helping someone understand the problems in experimenting?? my prime objective is not to save a few bucks, but to know why each n everyone of those components are placed where they are.. just for the sake of knowing.. i hope u get it..

 

My problem is with people hurting themselves, and worse, encouraging other people to hurt themselves. We have users of all age and skill levels here, this isn't just about you. As for learning, you have been told by several people, you can not make a power supply safe without the isolation a transformer offers.

After all this fuss your circuit is not a transformerless power supply. In other words, it passes muster as far as I am concerned. At this point that was my only interest in this thread. I may be corrected by other moderators, we do have this thread under discussion, but there is no way for the line power to connect to the load (which is presumably outside the case).

It is common to see really high power power supplies, such as the type used to charge fork lift batteries, have circuitry on the hot side of the transformer using TRIACs.

Computer Power Supply Units also use something similar. They convert the AC line power to DC, then convert it into high frequency so a really small light weight transformer can handle the high power without the weight penalty a 50/60 Hz transformer has. Lower frequencies require more iron in their core along with more wiring than high frequency transformers do.