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Interesting failure of buck converter

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Fraser:
Excellent news  :-+ So you think thermal runaway is the issue ?

Fraser

mikeselectricstuff:

--- Quote from: Fraser on May 28, 2019, 04:14:10 pm ---Excellent news  :-+ So you think thermal runaway is the issue ?

Fraser

--- End quote ---
Not runaway - I'm pretty sure that it was the heat from the converter that was pushing the diode over the edge. 

Jay_Diddy_B:
Hi Mike,

I had a look at the datasheet:



That is not a lot of margin when operating from 48V supply.

I also think it is telling that the do not present a data when operating at 48V on the datasheet. They show scope shots operating into a short with 43V input and lots of data at 12, 24 and 32V.

They also show 50V input capacitors. I would want to see 20 or 30% margin.

I know that they do say 'Operating input voltage from 5.5 V to 48 V'

You might want to take a page out photonicinduction's playbook and turn one up till it pops. :D


Regards,

Jay_Diddy_B

mikeselectricstuff:
Unfortunately there aren't many small 48V converters like this at sensible prices - I'd seen that chip used in another big installation with several hundred nodes, so was fairly happy using it. Something I was concerned about, and did test for, was whether overvoltage transients caused by connecting & disconnecting the supply caused issues, but it seems fine.
 

thinkfat:
I think I'm going to try this on one of my LMR14030 based buck converters. I'm guessing it'd show a similar failure if I drive the input voltage high enough. That's going to be interesting to watch.

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