Off-the-shelf transformers for PoE applications said to be highly efficient
19 April 2006
Passive Components
Pulse is offering a series of high efficiency, small footprint, off- the-shelf power transformers for powered device side Power over Ethernet (PoE) products.
They meet IEEE standard 802.3af and have been tested and approved for use with many of the most popular PoE ICs and are available in standard output voltages from 3,3 V to 12 V.
Purchasing standard PoE transformers off-the-shelf significantly reduces both lead time and cost, says Pulse, making them readily available and economical for small volume PoE applications that do not warrant custom designed transformers. Applications for this series include Voice over Internet Protocol (VoIP) phones, security cameras, web cameras, wireless routers, gaming machines, retail point of information systems, building access control systems, and battery chargers for mobile phones and PDAs.
The PoE series consists of 22 powered device side PoE transformers for 3 W, 7 W and 13 W output power levels. Pulse claims that these transformers have 50% lower leakage than other PoE power transformers, reducing the need for inefficient snubber circuits and increasing overall power supply efficiency. Power supply efficiency is crucial for PoE applications because limited input power is available over the Ethernet cable.
The power sourcing unit (PSU) delivers a loosely regulated 48 V (33-75 V) input to the powered device over the Ethernet cable. The powered device converts the 48 V input to a regulated output voltage at the required power level. The PoE standard allows the PD to request one of three levels or classes of power: 3 W/Class 1, 7 W/Class 2, and 13 W/Class 3. Pulse has designed 3,3 V, 5,0 V, and 12,0 V output voltage transformers at each of the three power levels.
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