my spec is :- 12 v input , 8v output 2A current, 5v output 1 A CurrentWhat is your spec? (vin, vout, pout)
If you give this then we can see for you.
If you give the spec i will send you an excel sheet shwing the calcs, and a representative sim in free ltspice.
The transformer you can do by emperical means.......pick a core, calc turns and see if your bmax etc is ok...if not, change it to next size up/down etc.
How to pick number of turns in transformer
A question about the actual numbers of turns to use is a very common one.
Turn it round, and tell yourself, you can have as many , or as few turns as you like as long as…
1…..The number of turns for a coil generally fits across the bobbin length (even if you do multiple layers) …you generally get better coupling if you use the full bobbin width.
2…you can get your turns ratio……for example, if you want a turns ratio of 3.5, then you cant pick a single turn primary because you cant have a 3.5 turn secondary.
3….You don’t saturate the core
4….you don’t suffer too high core losses
5…the turns fit on the bobbin space
6…you can terminate a coil to the former pin (eg a 3mm thick wire wont be easily solderable to a small former pin)
7…you dont have too many layers, as if you do , you may get proximity effect problems.
8…you dont get too much winding loss
9….you get leakage inductance reduced to your requirement
10….the turns fit on the bobbin…turns being litz or double coil etc
So make out a spreadsheet and carry it through….when you see you violate some condition, just change it till it converges to the right solution.
If you don’t know what number of turns to start with…pick any number out of your head and try and work it through…if its not viable your spreadsheet calculations will soon flag this up to you and you will be able to see if you need to reduce or increase it.
Thanks, and i presume you need isolation?my spec is :- 12 v input , 8v output 2A current, 5v output 1 A Current
Do you know the equation to work out how many turns gives inductance L?here is the flyback designed for you...jpeg schem and ltspice sim. LTspice is free
Just convert the .txt to .asc and you can run it.
Do you want me to send you link to the ferroxcube catalog so you can pick a core and start winding some turns?
Do you know the equation to work out how many turns gives inductance L?
And do you know about gapping in flyback txfmr?
1) In the first half of the cycle, current conducts in the primary side only. Flux field builds.explain fly back waveform.
This waveform is Vds. It's adviced to use the inductor current waveform to tell whether the converter is operating in CCM or DCM.