培訓影片系列
乙太網路供電 (PoE) 訓練系列
本訓練系列提供了介紹性主題,並且亦針對具有 PoE 設計進階知識的人員提供更深入的技術訓練。
什麼是乙太網路供電?
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Hello, everyone, and welcome to PoE101. This training video series consists of four short videos used to build our Power over Ethernet knowledge step by step. After watching this series, you will gain an understanding of the value that PoE offers, PoE power basics, the PSE PD handshake including detection and classification, startup, and more.
In this first video, I will explain what is PoE, what is the value of PoE, and which end equipments use PoE. I will then close by showing how you can familiarize yourself with TI's PoE portfolio on TI.com.
PoE is a mature and growing technology used to conveniently deliver power through Ethernet cables to a load. There are two main controllers, which enable PoE technology. One is the PSE or Power Sourcing Equipment controller, which is used to provide power to the load. Common PSE end equipment include Ethernet switches, routers, et cetera.
The other is the PD or Powered Device controller, which is used to receive power at the load. Common PD end equipment include IP phones, IP cameras, et cetera.
The picture at the bottom is a high-level block diagram of a PoE system. On the left side, you can see a PSE controller, which is responsible for providing the right amount of DC power to the PD after negotiation. A microcontroller on the PSE side is optional in case you would like to implement [? port ?] power management.
On the right side, you can see a PD controller, which is responsible for receiving power from the PSE. A DC/DC converter is used on the PD side in order to drop the 48 volts [? rail ?] down to 24 volts, 12 volt, 5 volt, or whatever voltage [? rail ?] needed to power your load.
Now let's see the value of PoE. One advantage of PoE is the convenience of installation and use. Since power and data can be sent up to 100 meter over an over Ethernet cable, this allows PoE devices to be installed in remote places.
A second advantage is that PoE is the standards based technology, which allows for a safe and robust method of powering PoE-enabled devices. In addition, PoE ICs have long lifetimes and part obsoleting is uncommon.
A third advantage is that PoE has adjustable power levels, which enable PoE to be used in various end equipment. Up to 90 watts can be sent and 71 watts received after 100 meter of Ethernet cable per IEEE 802.3bt standard. A fourth advantage of using PoE is for power redundancy. That is PoE can be used with another supply like an AC/DC adapter or battery pack in order to reduce the risk of losing power at the load.
A fifth advantage is that IEEE 802.3 compliant devices ensure that data-only loads are never powered, for example, like notebook. So compliant PoE devices can plug into any RJ-45 ports without concern for damaging equipment. Last but not least, PoE products certified by the Ethernet Alliance can obtain the interoperability logo, which enables customers to be confident that their end equipment will interoperate with other certified products. For more detail regarding the EA logo, please click the links below to read our blog and watch our training video.
There are many traditional applications which use PoE, such as Ethernet switches, IP phones, IP cameras, et cetera. In addition to traditional applications, more and more emergent end equipment are adopted PoE, such as PoE lighting, digital signage, industrial control systems, building automation applications, and more.
For informational regarding TI solutions and TI designs, check out our TI.com/PoE landing page. Here you can learn more about the new IEEE 802.3bt standard, search for PD and PSE controllers, as well as find reference designs, training videos, and more. To continue learning more about PoE, check out my next video in this series where I dive into PoE power basics. Thanks for watching.