Why is the no load current so high on my DC DC converter?

Discussion in 'General Electronics Chat' started by eddie500, May 1, 2016.

  1. eddie500

    Thread Starter Member

    Nov 5, 2011
    21
    2
    I bought this 12 volt 25 amp DC DC converter, which has a input current range of 36 - 75 volts. I plan to use this for a project.

    When using 73 volts input, I noticed the DC DC converter was getting super hot.

    I thought I had a possible short, but I hooked up my fluke and checked the amps. With "no load" it was pulling 90 mA at the 73v input.

    That is a whopping 6 watts of power with no load on the DC DC converter.

    I thought there was something wrong until I checked the specifications and found that it is rated to draw between 80 mA and 140 mA with a typical 110 mA draw.

    I was very suprised about this high draw and no load.

    Is this normal for DC DC converters? Should I have bought something else?

    Here is the data sheet below of what I bought with full specs.
    http://www.mouser.com/ds/2/632/DS_Q48SC12025-372467.pdf
     
  2. ElectronicMotor

    Member

    May 1, 2016
    53
    6
    Just off the cuff, as a technician, I don't think the inverter is faulty, since it is brand new. It is 91% efficient at 300 W, leaving 10% power lost. 10% of 300 W is 30W lost. 6 W isn't too bad in standby mode. I think your inverter is fine, but don't quote me on that.
     
    DickCappels likes this.
  3. KJ6EAD

    Senior Member

    Apr 30, 2011
    1,425
    363
    The short answer: because you're supplying it with a high (least efficient) input voltage and you've done no thermal management.
     
  4. Sensacell

    Well-Known Member

    Jun 19, 2012
    1,124
    266
    The design of DC-DC converters always requires some compromise- it's impossible to design one that is super-efficient across all possible loads and input voltages, so they optimize it for a reasonable load scenario.

    When it's unloaded, the efficiency is terrible, load it up and that 90 mA becomes insignificant.
     
  5. DickCappels

    Moderator

    Aug 21, 2008
    2,646
    631
    I am quoting you on that because I agree with your analysis :)
     
Loading...