oops!!

Danko · 17th September 2006, 03:48 PM

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)

ifrythings · 19th September 2006, 06:58 AM

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

Eva · 19th September 2006, 10:53 AM

I can only see a pile of junk in that picture, how about showing the actual prototype?

poobah · 19th September 2006, 04:02 PM

You have cross-conduction... or, you ran out of inductor (saturation).

The joys of SMPS desing!

Workhorse · 19th September 2006, 04:52 PM

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!

JensRasmussen · 19th September 2006, 05:04 PM

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

poobah · 19th September 2006, 05:41 PM

...ahem... DESIGN...

Nordic · 19th September 2006, 07:45 PM

Actaly Poobah looked normal until the day wanted to see close-up what made a nest of tantalums smoke....

poobah · 19th September 2006, 08:22 PM

I have blown up up tantalums... how did you know?

Ever seen a wookiee on fire?

subwo1 · 20th September 2006, 08:45 PM

I found that using only one gate resistor per paralleled MOSFET set ended a problem with them failing.

17th September 2006, 03:48 PM	#1
Danko diyAudio Member Join Date: Apr 2004 Location: Hungary	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) __________________ Best regards, Danko

19th September 2006, 10:53 AM	#3
Eva diyAudio Member Join Date: Oct 2003 Location: Near the sea	I can only see a pile of junk in that picture, how about showing the actual prototype? __________________ I use to feel like the small child in The Emperor's New Clothes tale

20th September 2006, 08:45 PM	#10
subwo1 diyAudio Member Join Date: Jan 2002 Location: North American Continent	I found that using only one gate resistor per paralleled MOSFET set ended a problem with them failing. __________________ USMPS http://groups.yahoo.com/group/switchmode/

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19th September 2006, 06:58 AM	#2
ifrythings diyAudio Member Join Date: Oct 2005	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

19th September 2006, 04:02 PM	#4
poobah diyAudio Member Join Date: Nov 2005	You have cross-conduction... or, you ran out of inductor (saturation). The joys of SMPS desing!

19th September 2006, 05:41 PM	#7
poobah diyAudio Member Join Date: Nov 2005	...ahem... DESIGN...

19th September 2006, 07:45 PM	#8
Nordic diyAudio Member Join Date: Sep 2005	Actaly Poobah looked normal until the day wanted to see close-up what made a nest of tantalums smoke....

19th September 2006, 08:22 PM	#9
poobah diyAudio Member Join Date: Nov 2005	I have blown up up tantalums... how did you know? Ever seen a wookiee on fire?

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