From: krw@nowhere.com   
      
   On Mon, 14 Dec 2015 13:23:06 -0800, "nish"  wrote:   
      
   >I need to power about 20 devices that run off AC adapters that provide 5VDC   
   >or 12VDC to the device.   As I understand it, a lot of efficiency is lost   
   >stepping down from 208V/220VAC to 120VAC and then again in the conversion to   
   >12VDC.    What is the most energy efficient way to power these devices?   
      
   Why step down to 120V?  Most switching power supplies are happy from   
   ~90V to 250V.  Switching supplies will be the most efficient, as well.   
   >   
   >I am guessing that there is a rectifier that would take 208VAC input (thus   
   >avoiding the step down to 125VAC) and then efficiently (90% efficiency?)   
   >convert 208VAC to 12VDC or 5VDC, for multiple end devices.   
   >   
   >Alternately, I could identify individual AC to DC converters/adapters that   
   >do the conversion from 208VAC to 12VDC or 5VDC efficiently.   
   >   
   >What is the most energy efficient path to follow there?   
   >   
   Universal power supplies should be pretty much the same for small   
   currents.   
   >nish   
   >   
      
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