Why is DC backup power used for power over Ethernet?
48V DC Power is used to supply equipment connected to the Ethernet. Rectifiers convert the commercial AC power to a DC voltage, typically 48 V. Batteries floating on the 48 V DC bus make this an uninterruptible DC supply with a typical reserve time of three to eight hours. The 48 VDC power is distributed to the network equipment, where it is converted to the low-voltage DC power used by the integrated digital circuits, typically by point-of-use power supplies. With only one AC-to-DC conversion stage and a solid connection from the battery to the load, the system has inherently high reliability and conversion efficiency. This system has been used for telecom systems for nearly one hundred years.
