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Old 17th September 2006, 03:48 PM   #1
Danko is offline Danko  Hungary
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Default oops!!

I was testing my 50V -> 5-15V synchronous buck regulator, when the 0.01R current sense resistor, series with the 50V DC bus exploded, and the PCB was burning in flames
The output current was about 60A. I think the mosfets cross-conducted, and they become a "short-circuit", and the 0.01R burned.
The MOSFETs were FDP3632, paralelled 2 on the upper side, and the lower side.

btw, the 1.5mm^2 wire in a bucket of water was a good dummy load :-)

Here was the resistor....

http://sziget.mine.nu/~danko/aramkor...t/dscn0466.jpg

Wear eye-protecting glasses, when you experiment with high power stuffs!!!!
Your safeti is the most important!
(I was wearing also)
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Old 19th September 2006, 06:58 AM   #2
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Umm... what resistor??? all I see is masive pile of charcole...

Tell me about eye protection, had a chunk of mosfet almost hit my eye (about an inch away) now I always wear saftey glasses when first or testing time come
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Old 19th September 2006, 10:53 AM   #3
Eva is offline Eva  Spain
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I can only see a pile of junk in that picture, how about showing the actual prototype?
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Old 19th September 2006, 04:02 PM   #4
poobah is offline poobah  United States
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You have cross-conduction... or, you ran out of inductor (saturation).

The joys of SMPS desing!

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Old 19th September 2006, 04:52 PM   #5
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Quote:
Originally posted by poobah

The joys of SMPS desing!

Hi poobah,

It seems to me that you dont need to wear glasses to protect your eyes from the small wonders of smps designing!
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Old 19th September 2006, 05:04 PM   #6
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Default Re: oops!!

Quote:
Originally posted by Danko
I was testing my 50V -> 5-15V synchronous buck regulator, when the 0.01R current sense resistor, series with the 50V DC bus exploded, and the PCB was burning in flames
The output current was about 60A. I think the mosfets cross-conducted, and they become a "short-circuit", and the 0.01R burned.
The MOSFETs were FDP3632, paralelled 2 on the upper side, and the lower side.

btw, the 1.5mm^2 wire in a bucket of water was a good dummy load :-)

Here was the resistor....

http://sziget.mine.nu/~danko/aramkor...t/dscn0466.jpg

Wear eye-protecting glasses, when you experiment with high power stuffs!!!!
Your safeti is the most important!
(I was wearing also)
Hi,

Cool pic

You might suffer from uneven power loss in the fets as you have two in parallel......

I always use one big fet rather than two..... much better solution IMHO.

\Jens
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Old 19th September 2006, 05:41 PM   #7
poobah is offline poobah  United States
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...ahem... DESIGN...

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Old 19th September 2006, 07:45 PM   #8
Nordic is offline Nordic  South Africa
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Actaly Poobah looked normal until the day wanted to see close-up what made a nest of tantalums smoke....
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Old 19th September 2006, 08:22 PM   #9
poobah is offline poobah  United States
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I have blown up up tantalums... how did you know?

Ever seen a wookiee on fire?

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Old 20th September 2006, 08:45 PM   #10
subwo1 is offline subwo1  United States
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I found that using only one gate resistor per paralleled MOSFET set ended a problem with them failing.
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