Difference between online and offline P/S?

Discussion in 'General Electronics Chat' started by HawaiianKong, Jan 25, 2012.

  1. HawaiianKong

    Thread Starter New Member

    Jan 25, 2012
    I was asked today what the difference was between an online power supply and offline power supply (as in switching, not UPS), and I couldn't come up with a good answer. Anybody have some input?
  2. crutschow


    Mar 14, 2008
    An online switching supply operates directly from the AC mains without an AC mains power transformer. They are relatively light weight because of the absence of the mains transformer. Some of the new, small wall-warts operate that way.

    An offline supply operates from a DC voltage coming from some other source such as a battery or a mains transformer-rectifier.
    anhnha and HawaiianKong like this.
  3. HawaiianKong

    Thread Starter New Member

    Jan 25, 2012
    Thanks! I had a vague notion that online meant drawn from line AC, but wasn't sure, and I think I exhausted Google while looking for a concise answer. I'm glad that it's as black-and-white as it sounds.
  4. Aswinth

    New Member

    Nov 1, 2016
    Hi, had to bring this topic back to life since I have few questions related to it and this was the only relevant place I could find.

    I was also confused on online and offline converters till I read crutschow's answer. But then I proceeded with that concept and came across this IC LNK304
    Datasheet: https://www.power.com/sites/default/files/product-docs/lnk302_304-306.pdf

    The data sheet mentions the IC as a offline switcher IC, but its application circuit shows AC voltage directly being inputted to the IC without main transformer. So does that not mean it is working as online converter? What am I missing here?