PowerDsine IEEE802.3 - Manual (Page 9)

PowerDsine Presentation October 2005 Page 9
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PoEp Power Architecture-AC Input
„ One of the arguments for not using 51V power supply is that back up
battery operates up to ~ 43 - 44V.
„ However most batteries used in telecommunication have one of the
terminal grounded (mostly positive)
„ This would prevent direct use of this batteries in POE and would
require to have isolated converter between batteries and PSE
regardless of output voltage considerations
„ Therefore increasing output voltage to ~51V would not add any
system cost
„ But boost converter would be useful even in case of isolated
batteries (DC UPS), which really is not very popular power
architecture.