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Diodes in "series" is safe and ok?

arvinfx

Member
What is (is or are ? ) electrical characteristics of series diodes? like 2 diode with 100V reverse voltage and 1A forward current ?
 

Nigel Goodwin

Super Moderator
Most Helpful Member
As with paralleled diodes you should balance them - in this case with high value resistors in parallel with each diode - otherwise they won't share equally, and one diode (and then both) WILL fail. Spec wise, current same, voltage double.
 

danadak

Member
Here you can see two non matched diodes and the effects -

1) They have unbalanced power dissipation.
2) In reverse conduction one takes a lot more Vreverse than the other.
3) In forward conduction they have substantially different Vforward drop.

A way or partially equalizing the differences is to start a R in parallel with each
diode. But that leads to higher Ireverse going thru the load which may or may not
be a problem. So you trade off equalization with I reverse, but improve the balance
of Vreverse that the diodes experience.

1624109677965.png


Note in this example I did not use two of the same diode, so example might be more
extreme, but even using 2 of the same diodes, because of the log Vforward, one might
experience a lot more Pdissipation in one of the diodes, so that would have to be examined.

With 1K's strapped across each diode the Vreverse is much better balanced -

1624110160369.png


Regards, Dana.
 
Last edited:

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