On Sun, Feb 5, 2012 at 8:33 AM, Sean Breheny wrote: > Hi all, > > I keep encountering the term "off-line" in switching power supply > literature. It seems to refer to power supplies which are intended to > operate from non-isolated, rectified and filtered AC mains line > voltage. Do I have this definition correct? I've never actually seen > the term defined and so far Google has not turned up a definition > which is relevant to the topic at hand. > > Does anyone know the origin of this term? What is the opposite of this > term? DC-DC converter? "on-line"? (seems like it should be on-line but > I'm not even sure what this would mean) > > Is it short for "off-the-line" meaning that it is powered by the AC > mains line? What term is used when the AC input IS isolated and > stepped-down first by a 60 (or 50) Hz transformer? I have seen such > designs, mainly for older equipment which is designed for use at high > mains voltages like 480V 3-phase. > > Thanks for any wisdom you can impart! http://www.smpstech.com/tutorial/t01int.htm The PSMA Handbook ( http://www.smpstech.com/books/bookp.htm#PSMA0001 ) defines off line power supply as: Off Line Power Supply -- 1) A power supply in which the ac line voltage is rectified and filtered without using a line frequency isolation transformer. 2) A power supply switched into service upon line loss to provide power to the load without significant interruption. Also called Off Line Switchers (OLS). --=20 Xiaofan --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .