What is a POE power switch? How does the POE power switch work?

Published by Harmony June 23,2022



What is a POE power switch


A PoE power supply switch is a switch that provides power to the remote power receiving terminal through the network cable. It includes two functions: the network switch and the PoE power supply. It is a common power supply device in the PoE power supply system. The port supports output power up to 15.4W. IEEE802.3af standard, the port supports output power up to 30W, conforms to the IEEE802.3at standard, and supplies power to the standard POE terminal device through the power supply of the network cable, eliminating the need for additional power wiring.


The POE switch conforms to the IEEE802.3aT standard, and the port output power can reach 15-60W. Generally
speaking, the POE power supply switch is a switch that supports network cable power supply, which can not only
realize the data transmission function of the ordinary switch but also power the network terminal at the same time.


POE (Power Over Ethernet) refers to some IP-based terminals (such as IP phones, WLAN access points, APs,
networks) without any changes to the existing Ethernet Cat.5 cabling infrastructure. Cameras, etc., while transmitting
data signals, can also provide DC power supply technology for such devices. POE technology can ensure the normal
operation of existing networks while minimizing costs while ensuring the security of existing structured cabling.


POE is also known as POL (Power over LAN) or Active Ethernet, and is sometimes referred to as Power over
Ethernet. This is the simultaneous transmission of data using existing standard Ethernet transmission cables. The
latest standard specification for electrical power and maintains compatibility with existing Ethernet systems and users.


The IEEE 802.3af standard is a new standard based on the Power over Ethernet (PoE) system. It adds the standard for direct power supply through the network cable based on IEEE 802.3. It is an extension of the existing Ethernet standard and the first international standard for power distribution. standard.


How does the POE power switch work


When a POE power supply device is deployed in a network, the POE Ethernet power supply operation process is
as follows.


Detection: At the beginning, the POE device outputs a small voltage on the port until it detects that the cable terminal
is connected to a powered device that supports the IEEE802.3af standard.


PD end device classification: After detecting the power receiving device PD, the POE device may classify the PD
device and evaluate the power loss required by the PD device.


Start of power supply: During a configurable time (typically less than 15μs), the PSE device begins to supply power
from the low voltage to the PD device until 48V DC power is supplied.


Power supply: Provides stable and reliable 48V DC power for PD devices, which can meet the power consumption
of PD devices not exceeding 15.4W.


Power off: If the PD device is disconnected from the network, the PSE will stop powering the PD device quickly
(usually within 300 to 400 ms) and repeat the detection process to detect whether the cable terminal is connected
to the PD device.


A complete POE system includes two parts: power supply equipment (PSE, Power Sourcing Equipment) and
power supply equipment (PD, Power Device). The PSE device is a device that powers Ethernet client devices and
is the administrator of the entire POE Power over Ethernet process. The PD device is the PSE load that receives
power, that is, the client of the POE system.