Martin,

a couple efficiency numbers:
- straight transformers (AC to AC) ~ 98% (~2% loss)
- modern DC to DC converters from 90 to 98%, depending on the current.

it is more efficient to turn 120/240V AC into DC and then use a high frequency 
switching circuit to generate 5V DC than using a 'real' transformer at 50/60 Hz 
and regulate it.

Leslie

-------------------------------------------- 
On Thu, 7/17/14, Martin DeYoung via CnC-List <[email protected]> wrote:

 Subject: Re: Stus-List USB ports and users
 To: "D Harben" <[email protected]>, "[email protected]" 
<[email protected]>
 Date: Thursday, July 17, 2014, 11:28 AM
 
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