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Hi Easy Peasy, thanks so much for your feedback.

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Above is Vds on secondary mosfets with no snubbers.

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Above is Vds on secondary mosfet with RC snubbers added (4 X 1nf + 33R 5W), that's about best I could get it with lots of trial and error.

Yes switching frequency is 100Khz

This is at low loads 1A @ 48V out.

This is without the syncronous fets being driven (body diodes doing the rectification) below the DCM threshold setting of the UCC28951.  So I don't have Vgs waveforms because the gates are always low.

PCB is four layer.  Not sure how to post the layout in a readable form (done in AD10).

Sorry, yes, probably an abomination, I'm a newby at this.