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Thread: Quick power supply question

  1. #1

    Default Quick power supply question

    High current (a relative term I guess) switchers or others - unloaded, tend to have a no load voltage close to their rating? As opposed to low current supplies generally having a significant higher no load voltage? I found my Cosel 24vdc switcher, highest praise to the heavens, and jury rigged it to test it's functionality, as I never have prior, purchased it new years ago. It's rated for 6.5 amps. It reads 24.3vdc. I'm not suggesting there's anything wrong, just was a bit surprised to see a voltage so "low", as in general wall warts tend to deliver significantly higher values, again unloaded.

  2. #2
    Join Date
    Jan 2014
    Freedom City
    Blog Entries



    24VDC supplies are usually within V when I check them, loaded, unloaded, in any case. (I've checked probably thousands.)

    Every wall wart that I've measured seems to do the same.

    I've got some old "Battery eliminators" that gave very high voltages unloaded. Quite a few that I've opened had a selenium rectifier and a resistor, no actual regulation.

  3. #3


    Some switchers are unstable with no load. Regulation relative to current load is related to the feedback gain and where it is taken from.

  4. #4
    Join Date
    Dec 2005
    Toronto ON Canada


    Switching supplies are generally regulated; low power wall warts are usually unregulated and will supply the rated voltage when pulled down with an appropriate load.


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