DC-DC Converters and heat

Discussion in 'General Electronics Chat' started by Jim_2.0, Sep 27, 2007.

  1. Jim_2.0

    Thread Starter Well-Known Member

    May 14, 2006
    51
    0
    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?
     
  2. mrmeval

    Distinguished Member

    Jun 30, 2006
    833
    2
    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.
     
  3. nomurphy

    AAC Fanatic!

    Aug 8, 2005
    567
    12
    No, it shouldn't get nearly so hot -- provided you're not doing something incorrect (misconnections, wrong input voltage).

    If you're getting the same results on multiple units from this supplier, then they leave a lot to be desired.

    Have you looked at Cherokee or Power One?
    http://www.cherokeepwr.com
    http://www.power-one.com
     
  4. Jim_2.0

    Thread Starter Well-Known Member

    May 14, 2006
    51
    0
    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...
     
  5. cumesoftware

    Senior Member

    Apr 27, 2007
    1,330
    10
    There is also the question of the heatsink. Is it big enough? Did you used thermal conductive paste? Please, give me details about this.
     
  6. nomurphy

    AAC Fanatic!

    Aug 8, 2005
    567
    12
    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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