POE (Power over Ethernet) switch is a switch that can power network devices. Its technical standards and specifications are crucial to ensure the stability and reliability of the system. The following is a detailed description of the technical standards and specifications of POE switches:
1. Main technical standards
IEEE 802.3af standard
Release time: 2003
Parameter regulations: This standard defines the maximum power supply power of POE switches as 15.4W (typical value is 12.95W), the maximum voltage is 48V (AC voltage is between 44~57V), the maximum current is 350mA, and the maximum transmission distance is 100 meters.
Application scenario: Suitable for low-power network devices such as IP phones, IP cameras, wireless access points, etc.
IEEE 802.3at (PoE+) standard
Release time: 2009 (some say 2019, but 2009 is more authoritative and widely accepted)
Parameter regulations: Provides higher power transmission capability, with a maximum transmission power of 30W. The power receiving device PD can be as large as 25.50W.
Application scenarios: It can provide sufficient power for more devices, such as IP phones, Wi-Fi access points, IP cameras, high-performance laptops, high-speed balls, desktop virtualization all-in-one machines, cash register (POS) terminal devices, etc.
Other features: Supports two-way communication, allowing PD to send information to PSE to adjust power requirements.
IEEE 802.3bt (PoE++) standard
Release time: 2018
Parameter regulations: Further expand the power transmission capability of POE, and the transmission power of each port can reach 60W~90W, and even reach the power limit of 100W.
Application scenarios: It can provide reliable power supply for more high-power devices, such as medical equipment, industrial equipment (such as industrial cameras, sensors, controllers, etc.), high-power LED lighting, etc.
Technical features: It can power the 8 copper cores of a network cable at the same time, requiring PSE and PD to support higher voltage and power transmission, requiring more advanced hardware design and more complex negotiation process.
2. Technical specifications
Power supply process specifications
Detection: The PSE device outputs a very small voltage at the port to detect whether the connection at the cable terminal is a powered device (PD) that supports the corresponding POE standard.
PD device classification: After detecting the powered device PD, the POE device classifies the PD device and evaluates its required power loss.
Start power supply: During the startup period (generally less than 15μs), the PSE device starts to supply power to the PD device from a low voltage until a stable and reliable DC power supply is provided.
Power supply monitoring: Real-time monitoring of the power consumption of the PD device to ensure that it does not exceed the specified power limit.
Power failure: If the PD device is disconnected from the network, the PSE device will quickly (generally within 300~400ms) stop supplying power to it and repeat the detection process.
Device compatibility specification
The POE standard has backward compatibility. For example, PoE++ switches can also be used for devices that support IEEE 802.3af or IEEE 802.3at standards.
POE switches should be able to automatically detect and identify powered devices that meet the corresponding standards to avoid damaging devices that do not support POE.
Safety and protection specifications
POE switches should have a high-security anti-power surge design to prevent power fluctuations from damaging the device.
When a short circuit or other power failure occurs, the POE switch should start the short circuit protection function, cut off the power supply to prevent equipment damage, and avoid network failures caused by line failures or installation errors.
3. Management and maintenance specifications
POE switches should support port power supply priority settings to ensure continuous power supply to key network nodes.
Managed POE switches should adopt cluster technology to support stacking and centralized management of multiple devices to save address resources and improve management efficiency.
In summary, the technical standards and specifications of POE switches cover power supply, voltage, current, transmission distance, power supply process, equipment compatibility, safety and protection, management and maintenance, etc. These standards and specifications ensure the stability and reliability of the POE power supply system and provide strong guarantees for the power supply of various network devices.