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+DC_out_rtn, what does this mean..

Discussion in 'Power Electronics' started by spikey1973, Apr 13, 2018.

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  1. spikey1973

    spikey1973

    32
    1
    Jul 16, 2014
    Hey Guys (and galls)

    I got my hand on a muRata MVAC400 Series PSU

    https://power.murata.com/data/acdcsupplies/mvac400.pdf

    now i want to go and connect it and found that the main output (J2) has 6 pins +DC_out and 6 pins +DC_out_rtn as 12 pin molex connector output.

    unfortunately i am unfamiliar with this +DC_out_rtn terminalogy, i assume rtn means return? and therefor use +DC_out as Positive and +DC_out_return as Negative and use this as 24VDC out, or does this mean something else, and should i take other things in consideration here (before) i can use it as 24VDC. and if is isn't exactly the same then what is the difference?

    i ask before i try to measure as last time i measured something i didn't fiully understood i blow up a PSU.

    kind regards

    Matt
     
  2. BobK

    BobK

    7,682
    1,688
    Jan 5, 2010
    It means return as in the current comes out through the positive pins and returns through the return. It is the negative side of the power supply, often labelled as ground.

    Bob
     
    spikey1973 likes this.
  3. Minder

    Minder

    3,182
    691
    Apr 24, 2015
    That supply appears to have the Remote Sense terminals.
    In this case a pair of conductors is taken to the remote load to detect any volt drop, and then correct the output accordingly,
    If not used it is customary to connect the respective +sense and -sense to the main +ve & -ve terminals.
    M.
     
    spikey1973 likes this.
  4. hevans1944

    hevans1944 Hop - AC8NS

    4,647
    2,169
    Jun 21, 2012
    Maybe this graphic from your linked datasheet will help:

    upload_2018-4-13_14-32-7.png
     
    spikey1973 likes this.
  5. spikey1973

    spikey1973

    32
    1
    Jul 16, 2014
    It does indeed, just out of curiosity. What would be the downside if I didn't connect the sense to the respective leads ?

    Additionally I have a power switch before this CPU and the load itself is switched too. Leaving the option for a switch at the pwr_on to +5v_aux_rtn unwanted. So I was planning on making that a permanent connection (short)

    Kind regards

    Matt

     
    Last edited: Apr 13, 2018
  6. duke37

    duke37

    5,364
    772
    Jan 9, 2011
    Often the sense terminals are connected to the respective output terminals via high value resistors so that the sense circuit works and the output terminals is controlled.. If the sense terminals are connected to the load, then that is where the voltage is controlled so any voltage drop in the cable is compensated for.
     
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  7. Minder

    Minder

    3,182
    691
    Apr 24, 2015
    All of the P.S. I have used that use remote sense lines connect the sense to the +ve and COM out terminals if remote sense is not used..
    Which would make sense when you think about it.
    It would be no different that connecting to the remote load.
    The spec sheet does not appear to mention it, but you could try without, if a problem occurs, connect them.
    M.
     
    spikey1973 likes this.
  8. spikey1973

    spikey1973

    32
    1
    Jul 16, 2014
    Thank you all very much, been very helpfull. but i seem to have bumped into another issue i would like to understand properly.

    Under the heading: STATUS AND CONTROL SIGNALS

    ps_on:

    This pin must be pulled low (sink current >2mA) to +5V_AUX_RTN to turn on the main and Fan (V2) output. The +5V_AUX output is independent of the PS_ON signal, and comes up automatically when the input AC or input DC voltage is applied within their specified operating ranges.

    pwr_oke:

    Open collector logic goes high 50-200ms after the main output is within regulation; it goes low at least 6msecs before loss of regulation. Internal 10K pull up to +5V_Aux is provided. Applications using the PWR_OK signal should maintain a minimum load of 5W on the main or fan output.


    I think i understand the ps_on function, it gives you the option to add an on switch, by pulling the pin to low +5V_aux_rtn "starting the output on main output and fan.

    i use this psu to power a mainboard (not a normal pc though), there is a switch adding power to the psu, and ofcourse the mainboard also has it's switch on function internally once the power is supplied by the psu. so a 3rd switch in function is unnecesairy and frankly unwanted. do i interprit it correctly that the pwr_oke function supplies power without the necessity for a switch as long 5W load is pulled?

    and ifso, what would be the difference between using pwr_oke and adding a short (instead of a switch) over ps_on and +5v_aux_rtn. and if i want to use pwr_oke.. how should i connect this? the mainboard will definately pull more the 5 w.

    help on this issue will again be very much appreciated.
     
  9. BobK

    BobK

    7,682
    1,688
    Jan 5, 2010
    If you want to power to come on whenever the power supply is powered, short it to the return (ground.)

    The pwr_ok is an output that indicates the supply is regulating properly. You don't have to do anything with it. It only works correctly if you are drawing at least 5W of power.

    Bob
     
    spikey1973 likes this.
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