Image Credit – Baumer Ltd.
Power over Ethernet (PoE) controllers are used to control the delivery of DC power and data from power source equipment (PSE) to powered devices (PD). They perform PD detection and classification, -48 V power distribution, and fault protection on multiple channels.
PoE controllers implement the DC disconnect techniques specified in the IEEE 802.3af, the power distribution standard from the Institute of Electrical and Electronics Engineers (IEEE) for PoE devices that provide up to 15.4 W of power per port. Products that comply with IEEE 802.3at provide more than 15.4 W of power pert port, and are referred to as PoE+ devices.
Advantages of PoE controllers include their power management capabilities and their ability to deliver both power and data along the same cable. Some PoE controllers can manage power autonomously, without the intervention of a host controller that connects the host system (i.e., computer) to other network and storage devices.
How PoE Controllers Work
PoE controllers have two main parts: PoE switches and PoE adapters. PoE switches are powered from an integral DC terminal block and can send both power and data through an Ethernet cable. PoE adapters consist of a base unit and a terminal unit. The base unit plugs into the power outlet, and the terminal unit is connected through the Ethernet cable.
In PoE systems, the DC-DC converter that supplies power to the PD uses an Ethernet cable with center-tapped transformers on both the sending and receiving ends. In manual mode, the ports on a PoE controller wait for instructions from the host system. In semi-automatic mode, the ports detect and classify the PDs that are attached. The status of these attempts is reported to the host, and a host command turns power on to the port.
Ports and Performance
When selecting PoE controllers, industrial buyers need to specify the number of ports, input voltage and input power, and output voltage and output power. Smaller PoE controllers typically have 8 or 16 ports. Larger devices have 24, 48 or even 96 ports. Data rate and operating temperature are also performance parameters to consider.
Form Factors and Features
Power over Ethernet controllers are available in two form factors: integrated circuit (IC) and standalone module. Product features include indicators, short circuit protection, temperature monitoring and support for a serial interface such as I2C.
Power over Ethernet (PoE) controllers are used to power access points, midspan PSE, RFID devices, routers, switches, VoIP devices, video equipment and cameras.