POE cable power supply scheme and advantages
What is POE - POE (Power Over Ethernet) refers to the existing Ethernet Cat.5 布线基础架构不作任何改动的情况下，在为一poe供电些基于IP的终端（如IP电话机、无线局域网接入点AP、网络摄像机等）传输数据信号的同时，还能为此类设备提供直流供电的技术。 POE也被称为基于局域网的供电系统(POL, Power over LAN )或有源以太网( Active Ethernet)，有时也被简称为以太网供电，这是利用现存标准以太网传输电缆的同时传送数据和电功率的最新标准规范，并保持了与现存以太网系统和用户的兼容性。 POE的两种供电方案——————POE标准为使用以太网的传输电缆输送直流电到POE兼容的设备定义了两种方法：一种称作“中间跨接法”( Mid -Span ),使用以太网电缆中没有被使用的空闲线对来传输直流电,相应的Endpoint PSE支持POE功能的以太网交换机、路由器、集线器或其他网络交换设备。另一种方法是“末端跨接法”(End-Span),是在传输数据所用的芯线上同时传输直流电,其输电采用与以太网数据信号不同的频率。Midspan PSE是一个专门的电源管理设备,通常和交换机放在一起。它对应每个端口有两个RJ45插孔,一个用短线连接至交换机,另一个连接远端设备。可以预见,End-Span会迅速得到推广,这是由于以太网数据与输电采用公用线对,因而省去了需要设置独立输电的专用线,这对于仅有8芯的电缆和相配套的标准RJ-45插座意义特别重大。 POE供电的工作过程 当在一个网络中布置 PSE供电端设备时,POE以太网供电工作过程如下所示。 1. 检测：一开始,PSE设备在端口输出很小的电压,直到其检测到线缆终端的连接为一个支持IEEE 802.3af标准的受电端设备。 2. PD端设备分类：当检测到受电端设备PD之后,PSE设备可能会为PD设备进行分类,并且评估此PD设备所需的功率损耗。 3. 开始供电：在一个可配置时间(一般小于15μs)的启动期内,PSE设备开始从低电压向PD设备供电,直至提供48V的直流电源。 4. 供电：为PD设备提供稳定可靠48V的直流电,满足PD设备不越过 15.4W的功率消耗。 5. 断电：若PD设备从网络上断开时,PSE就会快速地(一般在300～400ms之内)停止为PD设备供电,并重复检测过程以检测线缆的终端是否连接PD设备。 Cabling infrastructure does not make any changes to the case, in a Poe power supply terminal based on some IP (such as IP telephone, wireless LAN access point AP network camera, etc.) for the transmission of data signals at the same time, can also provide DC power supply technology for this kind of equipment. POE is also known as the power supply system based on LAN (POL, Power over LAN (Active Ethernet) or active Ethernet), is sometimes referred to as Ethernet, this is the use of existing standard Ethernet transmission cable and the new standard of data transmission and electric power standard, and keep up with existing Ethernet systems and users compatibility. Two kinds of power supply scheme of POE - POE standard for transmission cable using Ethernet transmission DC to POE compatible devices defined in two ways: one is called "mid span" (Mid -Span), has not been used in Ethernet cable to transmit the idle line DC, corresponding Endpoint PSE supports POE function of Ethernet switches, routers, hubs or other network switching equipment. Another method is the "end of the cross method" (End-Span), is used in the transmission of the data used in the core line while the transmission of DC power, its transmission and Ethernet data signals with different frequencies. Midspan PSE is a dedicated power management device, usually placed with the switch. It has two RJ45 ports for each port, one is connected to the switch in the short term, and the other is connected to the remote device. Can foreknow, End-Span will spread rapidly, this is because the Ethernet data transmission and the common line of, thus eliminating the need for independent transmission line is provided, the standard RJ-45 for only 8 core cable socket significance and related major. The working process of the POE power supply when the PSE power supply end device is arranged in a network, the working process of the POE Ethernet power supply is as follows. 1 detection: at the beginning, the PSE device outputs a small voltage at the port until it detects the connection of the cable terminal to a 802.3af terminal for supporting the IEEE standard. 2 PD end device classification: when the PD of the PD is detected, the PSE device may classify the PD device and evaluate the power loss required for this device. 3 power supply: in a configurable time (typically less than 15 s) during the start-up period, the PSE device begins to supply power from the low voltage to the PD device until the 48V DC power supply is supplied. 4 power supply: PD equipment to provide a stable and reliable 48V DC, to meet the PD equipment does not exceed the power consumption of 15.4W. 5 power off: if the PD device is disconnected from the network, PSE will quickly (usually within 300 ~ 400ms) to stop power supply for the PD device, and repeat the detection process to detect whether the cable terminal is connected to the PD device.
