POE (Power Over Ethernet) refers to some IP-based terminals (such as IP telephones, wireless LAN access points APs, network cameras) without any changes to the existing Ethernet Cat.5 cabling infrastructure. Etc.) While transmitting data signals, it is also possible to provide DC powered technology for such devices. POE is also referred to as Power over LAN (PoP) or Active Ethernet, sometimes also referred to as Power over Ethernet. This is the use of existing standard Ethernet transmission cables for the simultaneous transmission of data and The latest standard specification of electrical power, and maintain compatibility with existing Ethernet systems and users.
Features
POE technology can ensure the normal operation of existing networks while ensuring the safety of existing structured cabling, and minimize costs. The IEEE802.3af standard is a new standard for POE based on Power over Ethernet (POE). It adds the relevant standard for direct power supply via the network cable based on IEEE 802.3. It is an extension of the existing Ethernet standard and is also the first one about power distribution. International standards.
Related standards
There is no standard for early application of PoE, and idle power supply is used.
1, IEEE802.3af
IEEE802.3af (15.4W) became the first PoE power supply standard, which stipulated the Power over Ethernet standard. It is now the mainstream implementation standard for PoE applications.
The IEEE began to develop this standard in 1999. The earliest vendors involved were 3Com, Intel, Power Dsine, Nortel, Mitel, and National Semiconductor. However, the shortcomings of the standard have always restricted the expansion of the market. Until June of 2003, the IEEE approved the 802.3af standard, which clearly stipulates power detection and control in remote systems, and provides routers, switches, and hubs with Ethernet cables to IP phones, security systems, and wireless LAN access points. The method of power supply for such equipment is stipulated. The development of IEEE802.3af includes the efforts of many company experts, which also makes the standard can be tested in various aspects.
A typical Power over Ethernet system. Keep the Ethernet switch device in the wiring closet, and use a power supply hub (Midspan HUB) to provide power to the LAN's twisted pair cable. At the end of the twisted pair, this power is used to drive phones, wireless access points, cameras, and other devices. To avoid power outages, use a UPS.
2, IEEE802.3at
IEEE802.3at (25.5W) was born in response to the needs of high-power terminals. Based on 802.3af compatibility, it provides greater power supply requirements and meets new demands.
In order to comply with the IEEE802.3af specification, PoE power consumption on powered devices (PDs) 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 13 W power supply clearly cannot meet the demand, which limits the application range of the Ethernet cable power supply. To overcome PoE's limitations on power budgets and push them to new applications, the IEEE established a new task force to explore ways to increase the power limits of the international power standard. In order to evaluate the possibility of IEEE802.3at implementation technically and economically, the IEEE802.3 Working Group created the PoE Plus research team in November 2004. Later, in July 2005, the plan to establish the IEEE802.3at investigation committee was approved. The new standard is called Power-over-Ethernet Plus (PoEP) IEEE802.3at, which defines a device with a power requirement higher than 12.95W as Class4 (this level is described in IEEE802.3af but reserved for future use). The power level extends to 25W or higher.
System Components
The system structure of POE:
A complete POE system includes two parts: PSE (Power Sourcing Equipment) and PD (Powered Device). The PSE device is a device that provides power for Ethernet client devices and is also the administrator of the entire PoE Power over Ethernet process. The PD device is a PSE load that receives power, that is, client devices of a POE system, such as IP phones, network security cameras, APs, and PDAs or mobile phone chargers, and many other Ethernet devices (in fact, any power Devices that do not exceed 13W can get corresponding power from the RJ 45 socket). Based on the IEEE 802.3af standard, the two establish information links regarding the connection status, device type, and power consumption level of the power-receiving device PD, and use this to provide power to the PD through the Ethernet through the PSE.
When the supply arrangement when the working process <br> <br> POE feeding terminal device in a network, POE PoE working process is shown below.
1. Detection: At the beginning, the POE device outputs a very small voltage at the port until it detects that the connection of the cable terminal is a power-receiving device that supports the IEEE 802.3af standard.
2. PD-side device classification: After detecting the PD of the power-receiving end device, the POE device may classify the PD device and evaluate the power loss required by the PD device.
3. Start of power supply: During a startup period of a configurable time (generally less than 15μs), the PSE device starts to supply power from the low voltage to the PD device until a 48V DC power supply is provided.
4. Power supply: Provides a stable and reliable 48V DC power for the PD equipment, to meet the PD equipment does not exceed 15.4W power consumption.
5. Power-off: If the PD device is disconnected from the network, the PSE will stop powering the PD device quickly (usually within 300 to 400 ms) and repeat the detection process to check whether the cable's terminal is connected to the PD device.
The principle of supply <br> <br> standard UTP cable has four twisted pairs, but use only two pairs of them in 10MBASE-T and 100MBASE-T in. IEEE802.3af allows two uses. When the idle pin power is applied, pins 4 and 5 are positive, and pins 7 and 8 are negative.
When the data pin is used for power supply, the DC power supply is added to the midpoint of the transmission transformer, which does not affect the data transmission. In this way the pairs 1, 2 and the pairs 3, 6 can be of any polarity.
The standard does not allow the application of both cases. The power supply device PSE can only provide one usage, but the power application device PD must be able to adapt to both situations at the same time. The standard specifies that the power supply is usually 48V, 13W. It is easier for the PD device to provide 48V to low voltage conversion, but at the same time there should be an insulation safety voltage of 1500V.
The latest development
Power-supply chip maker Power Dsine will hold an IEEE conference to formally submit the “High-Power Power over Ethernet†standard, which will support the power supply for laptops and other devices. Power Dsine will submit a white paper recommending that the 802.3af standard's 48v input, 13w of the available power limit be doubled. In addition to laptops, the new standard may also power LCD monitors and video phones.
Recently, the IEEE has released a new 802.3AT, which specifies that POE can provide higher power, exceeding 13W, and can reach 30W!
Features
POE technology can ensure the normal operation of existing networks while ensuring the safety of existing structured cabling, and minimize costs. The IEEE802.3af standard is a new standard for POE based on Power over Ethernet (POE). It adds the relevant standard for direct power supply via the network cable based on IEEE 802.3. It is an extension of the existing Ethernet standard and is also the first one about power distribution. International standards.
Related standards
There is no standard for early application of PoE, and idle power supply is used.
1, IEEE802.3af
IEEE802.3af (15.4W) became the first PoE power supply standard, which stipulated the Power over Ethernet standard. It is now the mainstream implementation standard for PoE applications.
The IEEE began to develop this standard in 1999. The earliest vendors involved were 3Com, Intel, Power Dsine, Nortel, Mitel, and National Semiconductor. However, the shortcomings of the standard have always restricted the expansion of the market. Until June of 2003, the IEEE approved the 802.3af standard, which clearly stipulates power detection and control in remote systems, and provides routers, switches, and hubs with Ethernet cables to IP phones, security systems, and wireless LAN access points. The method of power supply for such equipment is stipulated. The development of IEEE802.3af includes the efforts of many company experts, which also makes the standard can be tested in various aspects.
A typical Power over Ethernet system. Keep the Ethernet switch device in the wiring closet, and use a power supply hub (Midspan HUB) to provide power to the LAN's twisted pair cable. At the end of the twisted pair, this power is used to drive phones, wireless access points, cameras, and other devices. To avoid power outages, use a UPS.
2, IEEE802.3at
IEEE802.3at (25.5W) was born in response to the needs of high-power terminals. Based on 802.3af compatibility, it provides greater power supply requirements and meets new demands.
In order to comply with the IEEE802.3af specification, PoE power consumption on powered devices (PDs) 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 13 W power supply clearly cannot meet the demand, which limits the application range of the Ethernet cable power supply. To overcome PoE's limitations on power budgets and push them to new applications, the IEEE established a new task force to explore ways to increase the power limits of the international power standard. In order to evaluate the possibility of IEEE802.3at implementation technically and economically, the IEEE802.3 Working Group created the PoE Plus research team in November 2004. Later, in July 2005, the plan to establish the IEEE802.3at investigation committee was approved. The new standard is called Power-over-Ethernet Plus (PoEP) IEEE802.3at, which defines a device with a power requirement higher than 12.95W as Class4 (this level is described in IEEE802.3af but reserved for future use). The power level extends to 25W or higher.
System Components
The system structure of POE:
A complete POE system includes two parts: PSE (Power Sourcing Equipment) and PD (Powered Device). The PSE device is a device that provides power for Ethernet client devices and is also the administrator of the entire PoE Power over Ethernet process. The PD device is a PSE load that receives power, that is, client devices of a POE system, such as IP phones, network security cameras, APs, and PDAs or mobile phone chargers, and many other Ethernet devices (in fact, any power Devices that do not exceed 13W can get corresponding power from the RJ 45 socket). Based on the IEEE 802.3af standard, the two establish information links regarding the connection status, device type, and power consumption level of the power-receiving device PD, and use this to provide power to the PD through the Ethernet through the PSE.
When the supply arrangement when the working process <br> <br> POE feeding terminal device in a network, POE PoE working process is shown below.
1. Detection: At the beginning, the POE device outputs a very small voltage at the port until it detects that the connection of the cable terminal is a power-receiving device that supports the IEEE 802.3af standard.
2. PD-side device classification: After detecting the PD of the power-receiving end device, the POE device may classify the PD device and evaluate the power loss required by the PD device.
3. Start of power supply: During a startup period of a configurable time (generally less than 15μs), the PSE device starts to supply power from the low voltage to the PD device until a 48V DC power supply is provided.
4. Power supply: Provides a stable and reliable 48V DC power for the PD equipment, to meet the PD equipment does not exceed 15.4W power consumption.
5. Power-off: If the PD device is disconnected from the network, the PSE will stop powering the PD device quickly (usually within 300 to 400 ms) and repeat the detection process to check whether the cable's terminal is connected to the PD device.
The principle of supply <br> <br> standard UTP cable has four twisted pairs, but use only two pairs of them in 10MBASE-T and 100MBASE-T in. IEEE802.3af allows two uses. When the idle pin power is applied, pins 4 and 5 are positive, and pins 7 and 8 are negative.
When the data pin is used for power supply, the DC power supply is added to the midpoint of the transmission transformer, which does not affect the data transmission. In this way the pairs 1, 2 and the pairs 3, 6 can be of any polarity.
The standard does not allow the application of both cases. The power supply device PSE can only provide one usage, but the power application device PD must be able to adapt to both situations at the same time. The standard specifies that the power supply is usually 48V, 13W. It is easier for the PD device to provide 48V to low voltage conversion, but at the same time there should be an insulation safety voltage of 1500V.
The latest development
Power-supply chip maker Power Dsine will hold an IEEE conference to formally submit the “High-Power Power over Ethernet†standard, which will support the power supply for laptops and other devices. Power Dsine will submit a white paper recommending that the 802.3af standard's 48v input, 13w of the available power limit be doubled. In addition to laptops, the new standard may also power LCD monitors and video phones.
Recently, the IEEE has released a new 802.3AT, which specifies that POE can provide higher power, exceeding 13W, and can reach 30W!
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