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Power Supply Scheme of POE Power Supply

Two power supply solutions for POE-The POE standard defines two methods for transmitting DC power to POE-compatible devices using Ethernet transmission cables:

One is called "Mid-Span", which uses idle pairs that are not used in the Ethernet cable to transmit DC power (that is, 1236 line sequence data and 4578 line sequence power), corresponding EndpointPSE support POE-enabled Ethernet switches, routers, hubs, or other network switching equipment.

Another method is the "End-Span", which is to transmit DC power simultaneously on the core wire used to transmit data, and its transmission uses a different frequency from the Ethernet data signal (that is, the 1236 line sequence simultaneously takes the data and electricity). MidspanPSE is a specialized power management device, usually placed with a switch. It has two RJ45 jacks corresponding to each port, one is connected to the switch with a short wire, and the other is connected to the remote device. It is foreseeable that End-Span will be promoted quickly. This is because Ethernet data and power transmission use common wire pairs, thus eliminating the need to set up special lines for independent power transmission. This is for only 8-core cables and matching standard RJ -45 socket is particularly significant.

PoE Switch

The working process of POE power supply

When PSE power supply equipment is arranged in a network, the POE power supply Ethernet working process is as follows.

1. Detection: In the beginning, the PSE device outputs a small voltage at the port until it detects that the connection of the cable terminal is a powered end device that supports the IEEE802.3af standard.

2. Classification of PD device: After detecting the PD of the power receiving device, 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 15μs), the PSE device starts to supply power to the PD device from a low voltage until it provides 48V DC power.

4. Power supply: Provide stable and reliable 48V DC power for PD devices to meet the power consumption of PD devices not exceeding 15.4W.

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

The above information is provided by industrial PoE manufacturer.