What is the poe supply voltage?

What is POE power supply

POE (POwer Over Ethernet) refers to some IP-based terminals (such as IP phones, WLAN access points APs, network cameras) without any changes to the existing Ethernet Cat.5 cabling infrastructure. While transmitting data signals, it can also provide DC power for such devices. POE is also known as POL (Power Over LAN) or Active Ethernet (AcTIve Ethernet), sometimes referred to as Power over Ethernet. This is the simultaneous transfer of data using existing standard Ethernet transmission cables. The latest standard specification for electrical power and maintains compatibility with existing Ethernet systems and users.

What is the poe supply voltage?

Characteristics

POE technology can ensure the normal operation of existing networks while minimizing costs while ensuring the security of existing structured cabling. The IEEE 802.3af standard is a new standard based on the Power over Ethernet (PoE) system. It adds the standard for direct power supply through the network cable based on IEEE 802.3. It is an extension of the existing Ethernet standard and the first international standard for power distribution. standard.

Related standards

There is no standard for early POE applications, and idle power is used.

1. IEEE 802.3af IEEE 802.3af (15.4W) has become the first POE power supply standard, which specifies the Ethernet power supply standard and is the mainstream implementation standard for POE applications.

The IEEE began to develop the standard in 1999. The first vendors to participate were 3COm, Intel, POwerDsine, Nortel, Mitel and NaTIOnal SemicOnductOr. However, the shortcomings of this standard have always restricted the expansion of the market. Until June 2003, the IEEE approved the 802.3af standard, which specifies power detection and control issues in remote systems and provides access to IP phones, security systems, and wireless LANs over Ethernet cables to routers, switches, and hubs. The way in which devices such as points are powered is specified. The development of IEEE 802.3af includes the efforts of many corporate experts, which also allows the standard to be tested in all aspects.

A typical Power over Ethernet system. Keep the Ethernet switch device in the wiring closet and power the twisted pair cable of the LAN with a power supply hub (Midspan HUB). At the end of the twisted pair, the power source is used to drive phones, wireless access points, cameras, and other devices. To avoid power outages, a UPS can be used.

2. IEEE 802.3at

IEEE802.3at (25.5W) was born in response to the needs of high-power terminals. On the basis of 802.3af compatibility, it provides greater power supply requirements to meet new demands.

In order to comply with the IEEE 802.3af specification, the POE power consumption on the powered device (PD) is limited to 12.95W, which is sufficient for traditional IP phones and webcams, but with dual-band access, video telephony, With the advent of high-power applications such as PTZ video surveillance systems, the 13W power supply clearly does not meet the demand, which limits the range of applications for Ethernet cable power. To overcome the POE's power budget constraints and push it to new applications, the IEEE has set up a new task force to explore ways to increase the power limits of the international power standard. The IEEE802.3 Working Group created the POEPlus research team in November 2004 to evaluate the technical and economic feasibility of IEEE802.3at implementation. The plan to establish an IEEE 802.3at investigation committee was approved in July 2005. The new standard, called POwer-Over-Ethernet Plus (POEP) IEEE 802.3at, defines a device with a power requirement higher than 12.95W as Class 4 (this level is described in IEEE 802.3af, but is reserved for future use). Extend the power level to 25W or higher.

What is the poe supply voltage?

Why is the voltage supplied by the POE specified as 48 volts?

Although POE power supply is more convenient and there are more people to use, it is estimated that many people are like me. It is very confused about why its power supply voltage is 48V. If you ask others, others will directly answer that it is the POE standard in the industry. It is stipulated, why is it prescribed as 48V? Focus on the development of POE switch equipment Fengrunda technology to explain briefly.

In fact, when the POE power supply standard was identified in the early days, there was a debate about how much the power supply voltage was set. After continuous discussion and research, the voltage is set at 48V, it is also possible to float up and down, that is, the power supply voltage is between 44-57V. Then why not 40V or 60V?

Anyone who knows the power supply of POE knows that it is realized by the network cable, that is, the power signal and the data signal are transmitted to the power receiving device at the other end in the network cable. If the voltage at the power supply terminal is insufficient, or the voltage is 40V, the data signal will be caused. The transmission distance has dropped drastically, perhaps only 30 meters and 40 meters. Since the POE power supply is definitely for convenience, it is desirable to transmit a longer distance, so the power supply voltage cannot be too low.

In this case, it would be good to set a higher 60V. It is estimated that some people think so. Indeed, the higher the voltage, the farther the power transmission will be. But don't forget the network cable, how much it can withstand. When the network cable is powered, there will be current. The higher the current, the stronger the strength of the cable. If it exceeds 2A, problems or dangers will occur. Just like the wires used in our homes, if the wires themselves are very thin, but connected to a very powerful appliance, then the possibility of burning the wires is stored. Returning to the POE power supply, the voltage is naturally not so large, taking 48V is a compromise.

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