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Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
Well, it's not as bad as you think, because two diode chips that are inside the same package hopefully came from the same wafer. That's not guaranteed, though. And they're bonded to the same heat spreader, which should keep their temperatures as close as possible.
Most low-voltage dual Schottky diodes say "OK for parallel operation" on the datasheet. But if a dual diode didn't specifically say that on its datasheet, I wouldn't parallel it.
Registered Member #2628
Joined: Fri Jan 15 2010, 12:23AM
Location:
Posts: 627
They are probably from the same wafer, but as Steve stated, I dont think that thermal runaway will be too much of an issue, its the same device, not 2 different diodes on seperate heatsinks. another thing bieng, since the rectifiers will only see 40A (inrush isnt really a worry, there is softstart). I figured one diode will be able to hand the current just fine, as ive stated earlier, the other diode was connected in hopes of just bieng able to handle 120A, but there is no intention on using them to thier full ratings.
Either way, if you have anything else to add, feel free to for the sake of this topic, but now I am no longer using this bridge, Ive found a pair of nice rectifier bricks (rated 100A each), and Ill use them instead of these devices. I will save these diodes for something else, (I used 2 of them as freewheeling diodes for an sot-227 IGBT bridge that lacked inbuilt diodes with no issues, this is a different story though, since there are 2 devices (4 diodes) for 4 IGBTs).
@Electra "but it would be a pity not to be able to fully utilize that transformer, for what it’s rated for, whatever that is btw."
-The transformer is rated to 4.8KVA, but at these powers, it runs cool, can probably be pushed a bit higher, but I will not, best to leave that thing within its ratings, I dont want to risk its death, and 4.8KVA is more then enough for my use.
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
I have never had problems with paralelling diodes of the same type. The voltage drop is not constant, might be something like 0.6V with small currents (the current sharing might not work for small currents) but over a volt at max current, at which point the drop on the diodes' internal resistances should "force" similar currents through them.
Registered Member #193
Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022
Just a thought. Use one of them- it should do the job. If some glitch fries it then you can use the other. OK, maybe if you have both in parallel then it won't fry, but only using one should keep one in reserve anyway.
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Any harm in paralleling these diodes?
