PowerDsine IEEE802.3 User Manual
IEEE802.3at Task Force
Technical and market considerations
regarding PoEp output voltage range
Vancouver BC, November 2005
Arkadiy Peker
Daniel Feldman
Yair Darshan
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Part A
Technical Considerations regarding
PoEp output voltage range
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Objectives
To discuss optimum voltage range for PoEp
To show advantages of having PoEp minimum voltage of 51V
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PowerDsine Presentation October 2005 Page 3
HP POE voltage range
Maximum voltage: 57V (safety consideration)
What is most optimum value for minimum voltage?
PoEp group objective; maximum power within practical limit (Power
Dissipation, Safety consideration)
Power dissipation is function of the current
Increasing minimum voltage reduces current level for the same load
power or
Increasing Power delivery to the load for a given current value.
Hence same infrastructure delivers more power to PDs for given
PSE PS size and cost
Bottom line: more applications may supported
– Larger POEp market
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PowerDsine Presentation October 2005 Page 4
PoEp minimum voltage
Lets assume current is 0.35A and calculate power delivered to the load by four
pairs
51V44V
3.06W 3.06WPower dissipation
on 4 pair
32.64W27.74WMaximum power
delivered to the PD
It means, that at 51V, for the same power dissipation on the cable, power
delivered to the load will be 4.9W more then at 44V.
The advantage of higher voltage is further increased for higher currents than
0.35A
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PowerDsine Presentation October 2005 Page 5
PoEp minimum voltage
Let us look on this issue under another angle assume minimum load need
to be delivered to PD by four pair is 40W
Power dissipation on a cables for 51V PSE will be 2.45W less then for 44V
Advantages of higher voltage is increase with increasing power level
51V44V
40W40WPd power
0.44A0.54ACurrent per pair
on a cables (4P)
for ~500W PSE PS
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4.85W7.3WPower dissipation
44.88W47.52WPSE power
0.890.84System efficiency
PowerDsine Presentation October 2005 Page 6
PoEp minimum voltage
51V required smaller PSE power supply then at 44V, for the same
load.
The technical advantage is clear for using higher voltage minimum
voltage level for POEp PSE.
Let consider different options in PoEp Power architectures :
- AC input and battery back up
- AC UPS input
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PowerDsine Presentation October 2005 Page 7
PoEp Power Architecture-AC Input
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PowerDsine Presentation October 2005 Page 8
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