How to Choose PoE Power Injector?


With the maturity of power supply technology in PoE Ethernet, more and more network products are providing support for PoE power injector standards. There are also various forms of PoE power injector in the market. Next, we will analyze how to select the PoE power injector that meets our requirements, and what should be paid attention to when selecting the PoE power injector.

1. According to the actual needs of the site, the corresponding port number of PoE power injector is selected, including single port, double port, four ports, eight ports, 12 ports, 16 ports and 24 ports, which can meet the needs of the site for PoE power injector. When using multi-port PoE power injector, it is appropriate to have one or two ports redundant for actual use in case of future capacity increase or emergency reserve.

2. The determination of power is the most important point in selecting PoE power injector. When selecting the matching PSE, the POE power injector with output power greater than the rated power of the PD of the receiving equipment should be selected. When choosing multi-port PoE power injector, the total rated power of all the equipments should be less than the actual total output power of the PoE power injector, leaving enough redundancy to make the PoE system work in a more stable state.

3. The confirmation of network transmission rate The data transmission of PoE power injector is divided into 10/100M self-adaptive and 10/100/1000M self-adaptive. When the transmission rate required by the network is Gigabit transmission, it is necessary to select a Gigabit POE power supply.

4. The IEEE802.3af/at standard allows PSE to have three forms of power supply sequence:
1). Lines 4 and 5 are positive, while lines 7 and 8 are negative.
2). The 1 and 2 lines are negative, while the 3 and 6 lines are positive.
3). Lines 1 and 2 are positive, while lines 3 and 6 are negative.

At present, most of the receiving equipments support any of the above three lines to supply power, but some only support one of them to supply power. Before choosing PoE power injector, the power supply sequence of the power supply equipment should be confirmed by the product specification of the power supply equipment or technical support from the manufacturer.

5. The IEEE802.3af standard clearly defines the output voltage of PSE as DC44V-DC57V. Considering the loss of the power line, the input voltage of PD is between DC36V and DC57V, and the typical value is DC48V. Nowadays, many receiving devices support both power adapter and PoE. Although many power adapters of receiving equipment use DC power supply less than 48V, such as DC12V, DC5V, etc.

As long as it is confirmed that the PoE power injector of the receiving equipment meets the IEEE802.3af standard, the PoE power injector can be supplied directly.

6. The selection of lightning-proof PoE power injector is constantly increasing due to the different installation locations of the receiving equipments, lightning surge, static electricity and other shocks in the external environment. In order to better protect the power supply system between switch and PSE in the network, lightning-proof PoE power injector is needed.