On August 12, 2013 at 2:28 AM Tom Metro <[email protected]> wrote: > Here's a video that describes the 3 major architectures for > uninterruptable power supplies, then tears apart an APC rack mount UPS > to match up the real components to the theoretical block digram: > > http://www.youtube.com/watch?v=Fj7e3WGUKO8&feature=em-subs_digest > > I went into it figuring I already knew how a UPS worked, but still > learned some things. (AVR UPSs really just use an auto transformer and a > couple of relays to implement voltage boosting/reduction? That's > surprisingly granular.)
The mind-bending moment occurs towards the end, when he tries to find the circuit which charges the backup battery. It seemingly is not there. Imagine an H-bridge driving the primary of a transformer that is producing AC out when the UPS has no line input. Cool. Imagine the same H-bridge when line input is available. It is sort of backward. Enough that the protective diodes of the MOSFETs are conducting. What do you have then? A bridge rectifier supplying current back to the battery, which coincidentally has some hefty capacitors to filter the voltage and help charge the battery. Ingenious. Well it is a little more complicated, but that is the basic nifty insight :-) peabo _______________________________________________ Hardwarehacking mailing list [email protected] http://lists.blu.org/mailman/listinfo/hardwarehacking
