Matching off the shelf transformer to PI Expert design
Posted by: Mack
on
Hello,
I have used PI Experto to create a design. I contacted Wurth Elektronik for the transformer as designed. They recommended an off the shelf transformer P/N 7508110127.
I would like to know how to verify this in my design before I go to layout of the PCB.
Thanks,
Steve
Comments
Hi Wesley, From Wurth Elektronik the turns are Primary 85 secondary 6. If I understand you correctly, this will work very well for my design. Thanks, Steve
Hi.
Yes, it should work.
Cheers,
Wesley
Hi Steve.
With that datasheet you won't be able to make a flux density analysis with 100% guarantee, but everything else should work rather well, since you have the turns ratio between primary and secondary (14.16:1).
First you can place the correct Vo on pixls.
you can then select the VOR so that you have the correct turns ratio: VOR = (Vo+Vdiode) * Np / Ns. You can now change your Po / efficiency so that you get the correct value for Lp.
You also know the saturation current, so you want your ILIMITMAX to be below that value (with some tolerance).
In terms of the number of turns in the transformer you could try an make an educated guess here: since the primary to secondary turns ration is 14.16:1 and we know that the number of turns need to be integer numbers (most of the time), we can assume 6 turns of secondary (which will give us 84.96 turns on the primary). The auxiliary winding will also get a nice round number of 19 turns which gives some weight to the theory of 6 turns on the secondary. I can't guarantee these numbers to be right (you'd have to ask the manufacturer), but there's a good chance that they are.