POE is also known as a LAN-based power supply system (POL) or active Ethernet (Active Ethernet), and sometimes referred to as Ethernet power supply, which is the use of existing standard Ethernet transmission cable while transmitting data and The latest standard of electrical power specifications, and maintain compatibility with existing Ethernet systems and users. The IEEE 802.3af standard is a new standard based on the POE of the Ethernet power supply system. It adds the relevant standard for direct power supply via the network cable on the basis of IEEE 802.3. It is the extension of the existing Ethernet standard and the first international power distribution standard.
POE standard power supply system, the main power supply parameters:
1. Voltage between 44 and 57V, typically 48V.
2. Allow maximum current of 550mA, the maximum starting current of 500mA.
3. Typical operating current of 10 ~ 350mA, overload detection current of 350 ~ 500mA.
4. Under no-load conditions, the maximum current required is 5mA.
5. For the PD equipment to provide 3.84 ~ 12.95W five levels of power request, the maximum does not exceed 13W.
Development: PowerDsine, an Ethernet-powered chip maker, will convene an IEEE conference to formally submit a "high-power Ethernet power" standard that will support powering equipment such as laptops. PowerDsine will submit a white paper, it is recommended to 802.3af standard 48v input, 13w available power limit increased by 1 times. In addition to notebook computers, the new standard is also possible for the liquid crystal display and video voltage in 44 ~ 57V words such as power supply.
2009 IEEE out of a new 802.3AT, which provides the POE can provide higher power, more than 13W, can reach 30W!
PoE tests are now mostly analog:
1, the use of a simple PD (such as power design of the PD), probably U disk size, directly through the network cable to connect PSE, if the PD power light, it shows that the PSE can be normal power supply, this method is relatively simple, but the test is rough , The results are not accurate, and can not indicate whether the PSE follow the 802.3af / at standard.
2, the use of professional instrumentation. At present the industry really do PoE test professional instrument should only Sifos a, and previously IXIA have done, but as early as 06, 07 time has been stopped. This professional instrument test results are very accurate , In full compliance with the 802.3af / at standard, but need funds to buy.
802.3at new LLDP function can greatly save PSE resources. PD through LLDP can be applied to the PSE power adjustment at any time, so that PD in the standby state, you can greatly save the PSE output power.
At present, Sifos test instrument can already support LLDP function, is expected in the future PoE market, LLDP will be a great trend.