DC-DC Converters and heat

Thread Starter

Jim_2.0

Joined May 14, 2006
51
Hi all

having an issue with an ARCH DC-DC converter I am using. it is an ST15-24F-15D model. ( 24v nominal in, +/-15V out, 15W ).

http://www.archcorp.com.tw/pdf/ST15.pdf

With the unit only drawing around 150mA on each line, we see excessive heat. 60 degrees C +.... This is intolerable in our design. Is it simply an issue with these type of converters and should we try a heat sink, or is something fundamentally wrong with what we are doing?
For the record we tried simply putting a high power 75 ohm resistor across each line, and 24V in, nothing else connected, and it still heated up... yet the manufacturers have informed us that it should not reach these sort of temperatures at this sort of load... ( It can supply +/- 500mA)

any ideas/wisdom?
 

mrmeval

Joined Jun 30, 2006
833
I don't see how that can be crisping at 140F and be right. I think there's a problem with either the device or your circuit is drawing way more than you think.

I'd suggest pulling the device and testing it with a known load that will draw the max your circuit requires. If it's still that hot contact the manufacturers tech rep and ask them what's going on with it. I don't see any information on thermal generation on that datasheet or I don't know where to look.
 

Thread Starter

Jim_2.0

Joined May 14, 2006
51
well putting a 75 ohm resistor across each power line as a simple test would have proved that it was my PCB creating the problem if the device did not heat up in this configuration.. but it did... i mean how can one go wrong with a 75ohm resistor... and 24V input. I get the same result from two different manufacturers, so its got me absolutely stumped...
 

bloguetronica

Joined Apr 27, 2007
1,372
There is also the question of the heatsink. Is it big enough? Did you used thermal conductive paste? Please, give me details about this.
 

nomurphy

Joined Aug 8, 2005
567
Then it's probably something obvious in the layout/connections to which you're not paying attention.

Maybe they're not 75 ohm resistors as you think, but 7.5 ohm resistors -- did you measure them? The spec says minimum load is 3%, try a 1K on the outputs.

ASSUME nothing, check it!
 
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