PoE power supply process

December 2, 2019

First, let's look at the power supply principle and process of PoE.


PoE power supply process

When PSE power supply devices are deployed in a network, the power supply process of PoE Ethernet is shown in the following figure.


PoE power supply process

1. Testing


At first, the PSE device outputs a very small voltage at the port until it detects that the cable terminal is connected to a receiving terminal that supports the IEEE 802.3af standard.


2. Classification of PD-End Equipment


When the receiving device PD is detected, the PSE device may classify the PD device and evaluate the power loss required by the PD device.


3. Start Power Supply


During the start-up period of a configurable time (generally less than 15 microseconds), PSE devices begin to supply power from low voltage to PD devices until 48V DC power supply is provided.


4, power supply


It provides stable and reliable 48V DC power for PD equipment, and meets the power consumption of PD equipment which does not exceed 15.4W.


5, power failure


If the PD device is disconnected from the network, the PSE will quickly stop supplying power to the PD device (usually within 300-400 ms) and repeat the detection process to check whether the terminal of the cable is connected to the PD device.