Jim Lux wrote: > At 08:41 AM 8/11/2006, Geoff Jacobs wrote: <snip> > > Sure you would.. Actually, these days, you might use an IGBT, depending > on the switch rate..
Well, it was just a guess based on the bare pcb of PicoPSU supplies. > Switching PSUs all rely on rectifying the AC supply to generate a DC bus > voltage, that is then converted to the DC voltage you want. There's a > half dozen or so circuit topologies, but they all basically rely on > turning the DC on and off quickly and then doing something useful with > it. The two basic strategies are: You turn it into high frequency AC, > then run that through a transformer, and rectify and filter it to low > voltage DC. THis saves the iron and copper cost of a high power > transfomer (since the core mass is inversely proportional to > frequency... 20kHz or 100kHz saves a bunch over 60Hz) Okay, just like modern inverter-based TIG supplies. :) But aren't they already doing this at the prime rectifier to step up to 300-ish V DC? > The other strategy is to take the HV DC, and pulsewidth modulate it, > then filter it, to make a lower voltage (the classic "buck" converter). > That is, take 100VDC, turn it on and off with a 5% duty cycle, low pass > filter, and get 5V. I see, and switching speed is dictated by factors like desired ripple in the output voltage for a given load while still avoiding the use of those coke-bottle caps in the LC filter (preserving such supplies for USAF rail-gun experiments). Anyway, where do you see these people trying to derive their power savings and/or reliability improvement by pushing DC to the racks? p.s. Forgive any dupes -- I don't know if I got to them in time. -- Geoffrey D. Jacobs Go to the Chinese Restaurant, Order the Special _______________________________________________ Beowulf mailing list, Beowulf@beowulf.org To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
