Yes, but sometimes the fuse and main switching device break at the same time, oops! Way back when I worked on power converters the fast fuses (the big silver in sand type) cost about as much as the SCRs, and it was still a race which would break first.
Grant.
-- http://bugs.id.au/
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Don't forget that the load dump pulse is distributed to all devices in the system, so although the the obvious design approach would be to use a low value TVS (to clamp as soon a possible), you may then be the device taking the majority of the dump energy (close to the battery, low impedance path). Chosing a larger voltage rating TVS, you may never actually see a large current in your device and the lifetime of your unit could be improved
Regards
Klaus
True, you can't set the TVS at 15-20% above rated voltage unless it is behind a series resistor. With many of my designs the client would prefer that it keeps working through spikes even though the standard allows an interruption, so I try to oblige. Then any sort of overvoltage protection can be at about twice the rated voltage. Unfortunately that restricts my pick of PWM chips to very few :-(
If for some reason there must be clamping as soon as possible the usual TVS devices are too small, then you almost have to resort to a TL431 approach with a big fat FET in there, with tons of SOA reserves.
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
Sometimes I work on aerospace stuff and there nearly everything is behind a breaker. It's no problem, if the breaker comes then something is busted in the connected device already. The devices themselves must be designed so they can stomach the spike without tripping the breaker, otherwise they'd fail certification.
In a car, if someone would plug in a 700W inverter, load it to the hilt and there was a 20A breaker it would simply trip. Nothing in the inverter should die.
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
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