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  2016/12/28 下午 03:51:44        Administrator        General   0 Comments
What is PoE?
 
  • POE (Power Over Ethernet)
    • A technology that can transfer power and data to devices through the Ethernet using Cat 5. twisted pair cables.
    • Able to operate without the need to change the Ethernet cable architecture, saving time and money to configure the cables and relatively lowering the cost for the entire device system.
    • Equipped with remote power-on/power off capabilities, short-circuit protection, over/under-voltage protection and over-current protection.
  • PSE (Power Sourcing Equipment)
    • Responsible for injecting power into the Ethernet cable and implementing power plans and management.
  • PD (Power Device)
    • For example, IP phones, AP wireless network base stations, PDA or mobile phone chargers etc.
  • PSE End-Span:
    • Switches that include POE functions.
  • PSE Mid-Span:
    • Power supply trunk enhancer, which only provides power and not signals; the signal comes from your original inputand the PSE Mid-Span will output additional power.
IEEE 802.3af & IEEE 802.3at
Standard Poe Parameters and Comparison
  Available power Maximum power output Voltage range
(at PSE)
Voltage range
(at PD)
Maximum current Maximum cable resistance Supported wiring Supported mode
802.2af
(802.3at
Type 1)
12.95W 15.40W 44.0~57.0V 37.0~57.0V 350mA 20 ohm
(Cat 3)
Cat3
Cat5
Type A
(End-span)
Type B
(Mid-span)
802.3ar
Type 2
25.50W 34.20W 50.0~57.0V 42.5~57.0V 600mA
Per
mode
12.5 ohm
(Cat5)
Cat5 Type A & Type B
 
  • IEEE 802.3af:
    •  PSE provides voltages between 44~57V, approximately 350mA of direct current power; each port must at least be able to provide 15.4W of power and the wattage received by the PD terminal after passing 100 meters of cable must be at least 12.95W.
 
  • IEEE 802.3at:
    • PSE provides voltages between 50~57V, approximately 600mA of direct current power; each port must at least be able to provide 30W of power and the wattage received by the PD terminal after passing 100 meters of cable must be at least 25.5W.






1. Detection:
At first, the PSE equipment will output very small voltages at the terminal until it detects wherea power-receiving terminal device that supports the IEEE 802.3af standard is connected at the end-terminal of the cable.
 
2. Classification:
Once it detects the power-receiving terminal device (PD), the PSE equipment might categorize the PD device and assess the power loss needed by the PD device.
 
3. Start-Up:
Within the start-up period whenthe time can be configured (usually less than 15μs), the PSE equipment starts to supply power to the PD device starting with low voltages until it provides 48V of the direct current power.

4. Operation:
Providing stable and reliable 48V of direct current power to the PD device and satisfying the PD device with a power consumption of no more than 15.4W.
 
5. Disconnection:
If the PD device is disconnected from the network, the PSE will quickly (usually within 300~400ms) stop supplying power to the PD device and repeat the detection process to detect whether a PD device is connected at the end-terminal of the cable.


PoE Process(Cont.)
 
1. Detection:
At first, the PSE equipment will output very small voltages at the terminal until it detects that a power-receiving terminal device that supports the IEEE 802.3af standard is connected at the end-terminal of the cable.






2. Classification:
Once it detects the power-receiving terminal device (PD), the PSE equipment might categorize the PD device and assess the power loss needed by the PD device.




3. Start-Up:
Within the start-up period whenthe time can be configured (usually less than 15μs), the PSE equipment starts to supply power to the PD device starting with low voltages until it provides 48V of direct current power.




4. Operation:
Providing stable and reliable 48V of direct current power to the PD device and satisfying the PD device with a power consumption of no more than 15.4W.






5. Disconnection:
If the PD device is disconnected from the network, the PSE will quickly (usually within 300~400ms) stop supplying power to the PD device and repeat the detection process to detect whether a PD device is connected at the end-terminal of the cable.





















BIO-ST03-P2U1

 
  • 802.3af is divided into A Type and B Type, and the Ethernet transmission and power supply pins used are also different, resulting in the product device of the power-receiving terminal to also be different.
 
  • The following comparison table can be used to referto distinguishingfeatures between the pins:
    A Type: Power supply pins used are 1, 2, 3 and 6.
    B Type: Power supply pins used are 4, 5, 7 and 8.
 
The PSE terminal cannot supply power to all 8 pins simultaneously, but the PD terminal can be designed to receive power from all 8 pins.
  PSE (1,2,3,6 supply power) PSE (4,5,7,8 supplypower) PSE (all 8 pins supply power)
PD (1,2,3,6 receive power) V X X
PD (4,5,7,8 receive power) X V X
PD (all 8 pins receive power) V V V
 


 
  • The power supply pin is determined by the POE LAN Connector; some are only 1,2,3,6, some are only 4,5,7,8, but there are also methods thatallow all 8 pins to supply power. This is when a jumper or resistor needs to be used to select the power supply pin.




 
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