laptop charger ferrite core transformer

[Airian_007]

Can anyone tell me if i can use a laptop charger ferrite core transformer in reverse to get 310v from 12 volts

 

[Flyback]

its possible, but if you want the same current ration, remember that now your input curret is higher as its from 12v, so you will be dissipating a lot more in the perfidious leakage inducatnce...........this will need heavy snubbing.

 

[Airian_007]

ok thanks for your reply.
actually its hard to find a suitable core around me. what if i rewind the same core for 12v to 310v i just want to experiment...will it work then?

 

[ChrisP58]

Possibly, but not likely. At least not without making some severe compromises in the design of your pwm controller.

Transformers (or more accurately, coupled inductors) used in high frequency flyback power supplies are vastly different than line frequency transformers. In particular, the input to output voltage ratio is not locked to any particular turns ratio.

 

[Flyback]

laptop = 100w+?
Thus not likely a flyback.
I think they are usually half bridges?
or 2TFC's
And vin = 400V not 310...unless it USA mains , as PFC output is ~310v there.

 

[ChrisP58]

QUOTE=Flyback;1131536]laptop = 100w+?
Thus not likely a flyback.
I think they are usually half bridges?
or 2TFC's
And vin = 400V not 310...unless it USA mains , as PFC output is ~310v there.[/QUOTE]

All of the laptop adapters that I have worked on have been flybacks. But I will admit, that three pieces are hardly a representative sample. As for a saying that supply greater than 100 watts cannot be a flyback. Well, I have a 120 watt (15V @ 8A) supply on my bench right now that is a flyback. I also have a netbook (which I still consider to be a laptop) that runs on a 40 Watt adapter (19V @ 2.1A)

And why would a PFC output be 310v in USA? All of the PFC supplies I've seen here have been ~385 to match the world wide standard. Even if an engineer were to design a PFC supply for use only in the USA, and wanted a low DC rail voltage, he would likely use something around 190 volts. (120v x 1.414 plus a bit)

Now, back to the Op's question.
You should start with defining the output power you need, and the input voltage you have.
- Then choose a topology, and design a circuit to fill that need.
- Then see what the requirements of the transformer are, and see if you can match it to the characteristics of the transformer you have from your adapter.

 

[Flyback]

And why would a PFC output be 310v in USA? All of the PFC supplies I've seen here have been ~385 to match the world wide standard. Even if an engineer were to design a PFC supply for use only in the USA, and wanted a low DC rail voltage, he would likely use something around 190 volts. (120v x 1.414 plus a bit)

my mistake, good point.

15V @ 8A and flyback...from presumably 90-265VAC input.
It would be very interesting to see the size of the RCD snubber used...particularly the power resistor size in the snubber (drain voltage clamp)

In a flyback, you have energy in that blessed leakage inductor and it gets dissipated...even quasi resonant flybacks end up dissipating all the energy in the leakage.

The problem is that the current in the leakage keeps flowing when the fet turns off (for a little bit), and as such you end up with some of the power current going into the snubber aswell, (because the secondary diode doesnt break over immediately).
So you could end up with a chunky set of snubber resistors in a 100W+ Flyback.

Not to mention fet switching losses since V drain = Vin + referred vsec.

Theres been a lot of threads on 100W+ flybacks......but ive never seen anyone proove the flyback f for 200W+.

Guitar amplifiers are the ones that want high power flybacks...because they have high power ,, but only intermittently...so they like flybacks.