PoE

規格

IEEE

  • 802.3af
  • 802.3at
  • 802.3bt

Keywords

  • PSE: Power sourcing equipment
  • PD: Powered device

IEEE 802.3at-2009 (as known as oE+, PoEP (?))

  • cat 5e or more required.
  • class0(Type-1): Min PSE Power 15.4W, Max PD Power 12.95W (0.44–12.95 W at the PD; default classification)
  • class1(Type-1): Min PSE Power 4W, Max PD Power 3.84W (0.44–3.84 W at the PD)
  • class2(Type-1): Min PSE Power 7W, Max PD Power 6.49W (3.84–6.49 W at the PD)
  • class3(Type-1): Min PSE Power 15.4W, Max PD Power 12.95W
  • class4(Type-2): Min PSE Power 30.0W, Max PD Power 25.5W (12.95 W to 25.50 W at the PD).
  • back compatible with IEEE802.3af-2003
  • Type1: Low power, Type2: High power
    • Cabling: CAT5E required
    • Voltage: PSE voltage from 44V to 57V (50V to 57V for Type-2 PSEs)
    • Current level: 600mA assuming cable temperature is 50C or lower
    • Polarity: End-Spans can use MDI or MDI-X (Positive or Negative Polarity)
    • Pulse transformer inductance: – End-Span PSE (Switch) & PDs: 120µH (allows usage of IEEE802.3af magnetics) – Mid-Span: 350µH, Midspan Alternative-A 10/100 installations require regulation
    • Power Feeding: 2-pairs and 4-pairs possible – Focus on 2-pairs Medium Power: PSE 30W output, PD 25.5W input – 4-pairs High Power should be based on 2x2-pairs: PSE 60W output, PD 51W input
  • Type1ではPDのL1 negotiation(Classification) だけで可能(ほかはOptional)だが，Type2ではPDのL1, L2 negotiation, およびPSEのL1 negotiationが必須．

IEEE 802.3af

  • Cat 3 or more required.
  • IEEE 802.3af-2003的には
    • up to 15.4 W of DC power(minimum 44 VDC and 350 mA) to each device.Only 12.95 W is assured to be available at thepowered device (PD) as some power isdissipated in the cable.
  • 距離上限は100m. cat5eと一緒．
  • Approved: up to 12.95W (350mA) at 48V DC

– Approved in 2003 for PDs up to 12.95W (350mA) at 48V DC – PoE requires handshake before applying power – Power Sourcing Equipment (PSE) transmits power over 2 pairs (4 of 8 wires) on Cat5/5e/6 cable – Connect/disconnect protocol for applying/disconnecting power

  • Detect device that needs power
  • Determines power needed
  • When to turn on power
  • Detect device disconnect (AC and DC disconnect)
  • When to remove power – Physical layer mechanism for PSE’s to characterize power demands of individual PD’s and thus manage power delivered per port.

IEEE 802.3btも存在．これはより大電力．(ref: http://www.ieee802.org/802_tutorials/2017-07/PracticalPoEtutorial-7-10-17.pdf)

  • Type 3
    • Covers Classes 1-6
    • Classes 1-4 as before (i.e. IEEE 802.3-2015)
    • Class 5: 45W PSE, 40W PD
    • Class 6: 60W PSE, 51W PD
    • Minimum port voltage = 50V
  • Type 4
    • Covers Classes 7 and 8
    • Class 7: 75W PSE, 62W PD
    • Class 8: 90W PSE, 71.3W PD
    • Minimum port voltage = 52V

references

  • ref: https://www.ieee.li/pdf/viewgraphs/introduction_to_poe_802.3af_802.3at.pdf
  • ref: https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst6500/ios/12-2SX/configuration/guide/book/power_over_ethernet.pdf