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Reverse Polarity Protection

Reverse Polarity Protection

Reverse Polarity Protection

Can you comment on the downside of the attached circuit comparing to other methods of reverse polarity protection? I do not want to use bridge or diode for power dissipation reasons ( parallel reverse bias diode will blow the fuse so that is also not an option). This circuit will see occasional +/-250V,70us pulse during its operation. The nominal input voltage is 16V-36V. My major concern is if the MOSFET will survive when input is hit by -250V. The filter module shown with part number at output side is from Vicor.

RE: Reverse Polarity Protection

Why are you putting transient protection on a module that actually is a trasient protection module?

I don't have time right now to confirm, but I think that there might even be reverse polarity protection in the Vicor products as well. Many of the mil standards quoted include all sorts of tests. I have distant recollection everything was built in. The purpose of the Vicor product line is to eliminate virtually all of the discrete components. Dirty military vehicle power on one side, clean system power on the other.

Have you made contact with their application engineers? If you haven't, then you should. Such contacts can eliminate nearly 100% of design risk. Typically no charge, very friendly.

RE: Reverse Polarity Protection

The FIAM does not include polarity reversal, as shown in in Figure 5 of the datasheet: http://www.vicorpower.com/documents/datasheets/ds_...

Why don't you just get a transistor that can handle the voltage? Or use something else to clip the spikes?

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RE: Reverse Polarity Protection

Transient protection is Vicor's recommendation. The bridge is what they are recommending for reverse polarity protection. But the voltage loss/power loss in the bridge is not desirable. The MOSFET needed for this job needs to handle only 100V and this fit the budget from all the specs needed. Not sure about the -100V that will hit it after the TVS with FIAM9 in series.

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