[asterisk-users] Quiet 24 port POE gig switch

[Bernd Felsche]

"Wilton Helm" <whelm at compuserve.com> wrote:

>>A modern switched mode PSU ought to be more than 90% efficient,

>In theory, yes, in practice, not likely.  It is harder to get high
>efficiency from an isolated supply than a non-isolated one.  I get ads
>from IC manufacturers all the time about there 90 to 95% efficient
>solutions, but these are boost or buck regulators--non-isolated.  State
>of the art in commercial practice for isolated supplies is around 80 to
>85%, and typical commercial practice is more like 70 to 80%.  

The per-port regulators would be non-isolated. Probably feeding off
an internal 48V bus.

>Now you
>have more like 60 watts of heat radiating from this power supply.  Go
>stick a 60 watt light bulb (incandescent) in a small metal box and see
>how easy it is to keep cool.

Well, the bulb has a peak permissible operation temperature of about
160 degrees C ... so likely no extra cooling required. :-)
-- 
/"\ Bernd Felsche - Innovative Reckoning, Perth, Western Australia
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