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bridge rectifier ratings

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David Hess:

--- Quote from: calexanian on June 08, 2019, 08:16:28 pm ---Just doing a casual search turned up a whole new crop of reasonably priced Schottkey rectifiers in that current range. There most have been a new process developed recently because some of them are just a few dollars in single piece quantity while others are well in excess of ten dollars and they have similar specs. Leads me to believe the new parts have better fab processes.
--- End quote ---

Inexpensive power schottky diodes have been around for a while in modern power packages.  I think what changed is demand in off-line switching power supplies.

floobydust:
I think 40-55V parts would not be reliable, and we don't have a PIV number.
A problem is a 24VDC vehicle electrical system transients are to ~450V. So a blocking diode would need to have a PIV rating higher than most Schottky's. Could try TVS and clamp to say 100V, but the trains have a bunch of inductive loads as well as lighting and transients- could be high energy. I think it's 300Ah battery.

OP breaks open the piggy bank and uses a real 150A stud-mount diode Vishay VS-45L $27. Cold 25°C Vf=1.0V at 100A, so 100W of heat. On a Wakefield 486K $75, or something smaller with a fan. $100 for a solution and 3/4 of the dollars are for the heatsink.

Schottky, maybe two MBR80100 80A 100V. Cold 25°C Vf=0.75V at 50A, so 75W of heat for a pair assuming good current sharing.

A MOSFET ideal diode needs to be much less than 10mohm and say 100V rated. Most are D2PAK with fake specs and no real way to heatsink them, despite claims of a few milliohm RDS on. I would probably look at using MOSFET array if they could be protected against transients.

T3sl4co1l:
FWIW, automotive fast transients aren't very severe, they can mostly be handled by a small TVS.  A big diode like this, won't have a problem (and will probably be rated for much more avalanche than required).

That leaves load dump, which is a good reason to have a bit of extra voltage rating.  A 100V schottky probably wouldn't be bad.

Personally, I would use a 200V PN diode, some module thing rated for the current, it'll cost up to maybe $50.  Bolt it to a big chunk of metal (preferably aluminum) and it's done.

Tim

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