Position of current sensing current transformer in Buck Converter?

[treez]

Hello,
Do you agree that the siting of the current transformer in each of the buck converters of this interleaved buck converter is wrong?
-i.e. even though the primary of the current sense transformer is only 1uH, (which means the leakage seen in the primary will only be about 10nH ), this is still going to put a serious overvoltage spike on the drain of the switching FET)?

 

[FvM]

10 nH would be in the range of transistor package and other circuit inductances. In your design there's an additional transformer flyback voltage due to the asymmetrical shunt.

 

[treez]

I agree there's a flyback voltage, though the secondary to primary turns ratio is 100:1, so surely the voltage stress that this puts on the fet will be negligible?

 

[FvM]

The 10k shunt translates to 1 ohm primary, so you get 1V/per A during switch-off.