Difference between online and offline P/S?

Thread Starter

HawaiianKong

Joined Jan 25, 2012
2
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?
 

crutschow

Joined Mar 14, 2008
25,123
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.
 

Thread Starter

HawaiianKong

Joined Jan 25, 2012
2
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.
 

Aswinth

Joined Nov 1, 2016
27
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?
 
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