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4.15.2 System Configuration
In a power over Ethernet system, operating power is applied from a power source (PSU-power supply unit) over the LAN
infrastructure to powered devices (PDs), which are connected to ports. Under some conditions, the total output power required
by PDs can exceed the maximum available power provided by the PSU. The system with a PSU is capable of supplying less
power than the total potential power consumption of all the PoE ports in the system. In order to maintain the function of the
majority of the ports, power management is implemented.
The PSU input power consumption is monitored by measuring voltage and current .The input power consumption is equal to the
system's aggregated power consumption .The power management concept allows all ports to be active and activates additional
ports, as long as the aggregated power of the system is lower than the power level at which additional PDs cannot be
connected .When this value is exceeded, ports will be deactivated, according to user-defined priorities. The power budget is
managed according to the following user-definable parameters: maximum available power, ports priority and maximum
allowable power per port.
Reserved Power
There are five modes for configuring how the ports/PDs may reserve power and when to shut down ports.
Classification mode
In this mode each port automatic determines how much power to reserve according to the class the connected PD belongs
to, and reserves the power accordingly. Four different port classes exist and one for 4, 7, 15.4 and 30.8 watts.
Class
Usage
0
Default
1
Optional
2
Optional
3
Optional
4
Optional
1.
2.
Allocation mode
In this mode, the user allocates the amount of power that each port may reserve. The allocated/reserved power for each
port/PD is specified in the Maximum Power fields. The ports are shut down when total reserved power exceeds the amount
of power that the power supply can deliver.
In this mode, the port power is not turned on if the PD requests more available power.
Range of maximum power used by the PD
0.44 to 12.95 watts
0.44 to 3.84 watts
3.84 to 6.49 watts
6.49 to 12.95 watts (or to 15.4 watts)
12.95 to 25.50 watts (or to 30.8 watts)
Table 4-15-1: Standard PoE Parameters and Comparison
In this mode the Maximum Power fields have no effect.
The PoE chip of PD69004 designed to that Class level 0 will be assigned to 15.4 watts in
AF mode and 30.8 watts in AT mode under classification power limit mode. It is
hardware limited.
User's Manual of WGS Managed Series
Classification unimplement
334
Class Description
Very low power
Low power
Mid power
High power
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