What Is Power Over Ethernet (PoE) Technology ?

PoE (Power over Ethernet) refers to a technology that transmits electric power and data simultaneously over twisted-pair Ethernet cable to IP terminal devices (such as IP phones, APs, IP cameras, etc.) PoE technology enables the security of existing structured cabling while ensuring the normal operation of the network, which greatly minimizes costs.

Why PoE Switch?

With the rise of the Internet of Things (IoT) and smart cities, there are more and more mobile terminals such as wireless APs, cameras, and IP phones. The deployment location of this type of terminal is very flexible, and the mode of power supply by wires is difficult, resulting in high wiring costs.

In addition,in many large-scale local area network applications, administrators need to manage multiple terminal devices at the same time. These devices require unified power supply and management. Due to the limitation of power supply location, it brings great inconvenience to power supply management. Based on this, the requirement to provide power support through Ethernet itself is becoming increasingly urgent. Power over Ethernet just solves the above needs.

PSE is essentially a power management chip. The AC power supply of the switch converts 220V AC power into low-voltage DC output for the internal devices of the switch, and the PSE chip is one of its workloads; the PSE chip outputs low-voltage DC power to the PD, and the PD is its only workload.

The total PoE power supply, single port power supply, number of power supply ports and other parameters are determined by the PSE chip.

PoE Protocol Introduction – PoE+/PoE ++

IEEE standards committee to solve the problem of adaptability between different manufacturers of power supply and powered devices, will have released three PoE standards: IEEE 802.3af standard, IEEE 802.3at standard, IEEE 802.3bt standard. So what is the difference between these three standards?

In June 2003, the IEEE 802.3 working group developed the IEEE 802.3af standard, as an extension of the Ethernet standard, the power supply, transmission and reception of network power are carefully specified. For example, the IEEE 802.3af standard specifies that PSE devices need to provide up to 15.4W of DC power on each port.

Due to some power dissipation in the cable, only 12.95 W is available for powered devices. In October 2009, the IEEE 802.3at standard was born to correspond to the needs of high-power terminals. The IEEE 802.3at standard is compatible with the 802.3af standard and provides up to 25.5 W of power to meet the new requirements.

In September 2018, to further enhance PoE power supply as well as optimize the standard, the IEEE Standards Committee’s released the IEEE 802.3bt standard. The IEEE 802.3bt standard further enhances the power supply capability with Type 3 providing up to 51 W of power supply and Type 4 providing up to 71.3 W of power supply. Support for 2.5GBASE-T, 5GBASE-T and 10GBASE-T is also included, expanding the use of applications such as high-performance wireless access points and surveillance cameras.

The power supply technology corresponding to the IEEE 802.3af standard is generally referred to as PoE power supply, the power supply technology corresponding to the IEEE 802.3at standard is referred to as PoE+ power supply, and the power supply technology corresponding to the IEEE 802.3bt standard is referred to as PoE++ power supply, also known as 4PPoE. The parameters corresponding to the three power supply technologies are shown in the figure below.

What devices Asterfusion has that can support PoE power

Smart Power Supply Unit supports setting PoE power supply time periods, automatically powering down PD devices during idle time and powering up PD devices during non-idle time, providing a more flexible PoE power supply solution; it supports intelligent power supply management. When the power demand of all PD devices exceeds that which can be provided by the PSE chipset, the system will prioritize the power supply demand of critical services according to the priority of interface power supply.

Unregulated PD devices will generate high inrush current when powered on instantly. The device supports overload detection, real-time monitoring of PD device workload, and termination of power supply to PD devices when abnormal conditions such as short circuit or current and voltage exceed the threshold value occur.

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