Development of PoE and application of magnetic components​

2022.8.24 Articles GOTREND Technology Co.,Ltd

Development of PoE and application of magnetic components​

Are there any types and specifications of PoE ?  What is the principle of power supply?


1.What is PoE ?

Power over Ethernet (PoE) is also known as PoE power. The most basic definition is also a characteristic, an application that uses a network cable to deliver power to a device.

Traditionally, devices require a network connection and a power connection, but with PoE, only the network connection is required, powered by the network connector. This technology enables the device to be powered without the need for an additional power outlet.

PoE uses Cat5e and Cat6 Ethernet cables, capable of transmitting 10 / 100 / 1000 Mbps data and 15 / 30 / 60 / 90W power over distances up to 100m, provides power to a remote powered device (PD). Additionally, it complies with the IEEE 802.3af and 802.3at standards established by the Institute of Electrical and Electronics Engineers.

Over time, the standard has evolved and can now deliver up to 90W, making it useful for a wide variety of applications, including network routers and repeaters, VoIP phones, IP security cameras, wireless and Bluetooth access points, laptop and tablet charging systems, LED lighting and controllers, and a variety of building automation devices.

Since the ratification of IEEE 802.3af in 2003, PDs with higher power demands have been added, so PoE technology has continued to evolve. Can provide up to 60W to 95W of power, each protocol has a different name, such as: UPoE, LTPoE, PoH, PoE++, 4PPoE ; However, the common ones are still identified by these three code names PoE, PoE+, and PoE++


IEEE802.3 Protocol History :

POE IEEE802.3 Protocol History


PoE Type 1, Type 2, Type 3 :

PoE Type 1,2,3



Power wattage and specification details :

Power wattage and specification details

Type 3, Type 4  VS.  PSE & PD 
Type 3, Type 4 vs PSE & PD


2. Characteristics of PoE application technology :

PoE can use CAT-5 to transmit power from the cable, and it has two roles of data and power line at the same time. If the remote system adopts PoE, it will make the system architecture simpler and greatly reduce the number of cables, which is not only easy to maintain and use, but also reduces costs.

PoE itself has both stability and security, and also has a remote monitoring function, which does not require an adapter.

2-1 Reduce costs :

The PoE specification allows the Ethernet network itself to transmit power, eliminating the need for sockets. Naturally, it saves the electrician the expense and trouble of installing the socket, and it only needs to install and support one cable instead of two.

2-2 Reduce the risk of power supply :

PoE can centralize the power supply of each network device in one place, or use an uninterruptible power supply system (UPS) to support network devices scattered in various places, even if regional power outage will not make the system inoperable.

2-3 Easy to install and manage :

PoE is no longer limited by power supply, EX: IP camera, in some specific places such as intersections, can be directly erected without power supply to solve the problem of power supply.

2-4 Security :

PoE only supplies power to the devices that need power supply, and does not need to add power to the power supply devices, thus eliminating the risk of leakage on the line.

2-5 More Enhanced Applications :

With the establishment of the IEEE 802.3af standard and continuous technical enhancements, a large number of other applications will emerge rapidly, including Bluetooth access points, lighting systems, network printers, IP Telephones, Web cameras, wireless network APs, access control card readers and monitoring systems, …etc.


3. Three categories of PoE

(1) Traditional LAN transformer

( GTX : Traditional LAN transformer )

A LAN transformer must be used as electrical isolation between the PHY chip and the cable. In PoE and PoE+ lines, since current needs to be injected, the LAN transformer is bound to become the most ideal device for current injection. At the same time, due to the current passing through the transformer, the LAN transformer must consider the coil heating and core saturation issues, and must meet the IEEE802.3af (PoE) and IEEE802.3at (PoE+) standards.


(2) New Inductor Type Discrete Lan transformer

Inductive separation network transformer :

It can effectively solve the shortcomings of Traditional Lan transformers such as cumbersome production process, large labor dependence, and long lead time. Can be used in Lan-Com products to replace traditional ethernet transformers. The main advantage is that the inductors produced by fully automatic winding can be directly SMT mount to the PCB board, which can improve production efficiency and module yield rate.

Netcom customers have accelerated the introduction of new discrete network transformers to replace traditional network transformers, which can be applied to 10G, 2.5/5G, 10/100/1G Mbps network signal isolation and filtering, and provide PoE, PoE+, PoE++ power supply functions.


New Inductor Type Discrete Lan transformer


(3) GTX Series - Power transformer

(GTX Power transformer):

The power transformer used in the DC-DC conversion module is actually a typical Flyback or Forward transformer, which achieves the function of voltage conversion and energy distribution. 
▶ Check out the GOTREND POE Transformer.


• Type 1: PoE Transformer

The input voltage range of the PoE transformer is generally 36~57Vdc, and the maximum output power It is 12.95W, which conforms to the IEEE802.3af standard

• Type 2: PoE+ Transformer

The input voltage range of the PoE+ transformer is expanded to 42.5~57Vdc, and the maximum output power can reach 30W, which conforms to the IEEE802.3at standard.

• Type 3: PoE+ + Transformer

The input voltage range of the PoE++ transformer is expanded to 42.5~57Vdc, and the maximum output power can reach 100W, which conforms to the IEEE802.3bt standard.


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