LED boost converter destroying FET

[MarkC]

I have an LED boost converter that keeps destroying the FET.

If I fire it up without the FET I get the expected 55v on the Drain and a crazy 95% duty cycle drive on the Gate.  I have changed the driver IC (OB3350CP) but this made no difference.  Any ideas what else can cause the driver IC to do this.  The inductor is going to saturate like this and the resulting failure of the FET is understandable.

[fzabkar]

There is a current sense resistor which should protect the MOSFET. Perhaps the inductor has shorted turns?

https://www.electronica-max.com/pdf/OB3350CP-226708.pdf

Perhaps you could disconnect the LED string and then inject a small variable voltage into the FB pin of the OB3350CP. You could then see whether the duty cycle changes.

[rob77]

you get max duty cycle when the controller thinks it's needed   either the current sense resistor is too small or the voltage feedback is calculated wrong. post your schematic with actual used component values.