Hi,

I've got a high Power multi-phase DC-DC boost converter I've designed and I want to make EXTRA sure in case of of MOSFET failure, (which shouldn't happen thanks to other design choices) that if one of the boost MOSFETs fail that that MOSFET doesn't catch on fire.

Picture several MOSFETs switching several inductors at 250 kHz with extremely low resistance to ground. Since this device is going to be living in a car I'm afraid/paranoid of moisture or the unforeseen event (maybe even just random poor MOSFET quality), causing a MOSFET to runaway despite other protections as a result of the parallel nature of the converter boosting.

I could use thermistors to monitor temperature, but I figure, the surest way to save the fire hazard is to FUSE each switching MOSFET boost leg at twice the legs peak current (say each of the 4 legs provides 2.5 A RMS for an output of 10 A, then I would use 4 fuses at 5A for each leg.

Any issue fusing switching MOSFETs directly at 250 kHz high power? Not sure what contact resistance a fuse holder will add either.

 

Fuse holders and fuses have a very low resistance thus you don't have to worry about it.