[Boatanchors] Wall Warts and Switcher Power Supplies

[Robert Nickels]

On 11/27/2012 6:59 AM, David C. Hallam wrote:
> Do switcher PS continue to draw current whether or not they are in use 
> as do wall warts? 

As Brian said, they consume much less standby power when the device is 
not being actively used, which is one of the two big reasons behind this 
change.   Some studies estimate that US households were wasting $3.5B 
annually, or a continuous consumption of 70-125 watts by the 20-25 
transformer-type wall-warts plugged in at the average house.  The 
standby power consumption goal for new generation power supplies was set 
at 1% by 2010 and 1/2% by 2013 ("One Watt Initiative").

The other reason is overall efficiency.  Linear power supplies average 
40-50% efficient in turning AC into DC, the rest is turned into "waste 
heat" (which, in northern climes this time of year, isn't really 
wasted).    Switched-mode power supplies average 80-90% efficiency 
according to Energy Star, and many toward the high end of that range.    
So, the more a device is actively used, the greater the potential energy 
savings.

Energy Star research shows the average breakout of usage is 73% Active, 
24% Standby, and 3% Sleep.    So if you apply the appropriate 
improvement in efficiency it comes up as a Big Deal. But since all those 
SMPS contain low frequency power oscillators loosely coupled to an 
antenna (AC power wiring), for radio types - not so much.   The $7 five 
volt switcher I got to power my Raspberry Pi will give a pretty good 
simulation of a solar flare on the lower bands!

73, Bob W9RAN