I've been playing and experimenting with inductors and SMPS for a while and I found that if you don't have a load, the output voltage can go extremely high and that will fry FETs and ICs, I lost several FETs before I figured that on out, I was looking for about 40 volts out and used 60 volt FETs figuring that was plenty, finally tried a 400 volt FET and I was getting an output of 190 volt and that was killing my 60 volt components. I've been using a 555 chip to make 40 watt, 40 volt circuits driven by 12 - 14 volts DC.
Kinarfi