forward converter duty cycle question

Looking at the forward converter topology illustrated here:

I think it's to keep the transformer from saturating.

John

I know. The magnetic field needs time to collapse. I'm asking does the mag field collapse faster with fewer turns on N1'.

Yes. However, note that the transistor's drain voltage would then be Vin+(N1*Vin/N1'). The series diode on the secondary would also see higher voltage (Vin*N2/N1').

John

Ouch.

That means when N1=N1', drain voltage is 2Vin. I didn't know that.

You must have missed it. 5th paragraph below the schematic it says...

"Due to this the transistor drain-source voltage steps up to Vds > 2Vin when the transistor is turned off."

Sorry.

John