When a POE powered switch is used in a network, its working process is as follows:
Detection: At first, the POE powered switch outputs a very small voltage at the port until it detects the IEEE802.3af - standard power device connected to the cable terminal.
PD classification: When the power device is detected, the POE powered switch
may classify the PD and assess the power loss required for the PD.
Start power supply: During a time-configurable(usually less than 15 μs) start-up period, the POE powered switch starts power supply from low voltage to the PD until it provides a 48V DC power supply.
Power supply: It provides stable and reliable 48V DC power for the PD to meet the power consumption of the PD that is less than or equal to 15.4W.
Power off: If the PD is disconnected from the network, the POE powered switch will quickly (generally within 300 to 400ms) stop power supply for the PD, and repeat the detection process to detect whether the cable terminal is connected to the PD.
A complete POE system consists of a PSE (Power Sourcing Equipment) and a PD (Power Device), and a POE powered switch is one kind of the PSE. The PSE is a device that supplies power to the Ethernet client device and is also the manager of the whole POE Ethernet power supply process. The PD is the PSE load that receives the power supply, that is, the client of the POE system.