Product category:
Transformers and Inductors
News Release from: Focus EDL | Subject: Pulse EP7, EP10 and EP13
Edited by the Electronicstalk Editorial
Team on 20 March 2006
Transformers are made for PoE designs
A series of high-efficiency small-footprint off-the-shelf power transformers target powered device side power over Ethernet products that meet IEEE802.3af.
Focus EDL has a series of high-efficiency small-footprint off-the-shelf power transformers for powered device (PD) side power over Ethernet (PoE) products that meet IEEE standard 802.3af Produced by Pulse, the parts are approved for use with many of the most popular PoE ICs and are available in standard output voltages from 3.3 to 12V
This article was originally published on Electronicstalk on 28 Feb 2005 at 8.00am (UK)
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The PoE series consists of 22 powered device side PoE transformers for 3, 7 and 13W output power levels.
The Pulse transformers have 50% lower leakage than other PoE power transformers, reducing the need for inefficient snubber circuits and increasing overall power supply efficiency.
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Power supply efficiency is crucial for PoE applications because limited input power is available over the Ethernet cable.
Higher efficiency transformers directly increase the amount of power that can be delivered to the powered device.
The power sourcing unit (PSU) delivers a loosely regulated 48V (33 to 75V) input to the powered device over the Ethernet cable.
The powered device converts the 48V 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: 3W/Class 1, 7W/Class 2, 13W/Class 3.
Pulse has designed 3.3V, 5.0V, and 12.0V output voltage transformers at each of the three power levels.
Three sizes of power transformers and three output voltage levels for each power class allow designers to select the smallest and most efficient package for the class of PoE device they are designing and to use standard, off-the-shelf components.
The transformers are designed for continuous mode flyback topologies operating between 200 and 400kHz.
This topology has been chosen by all the major power IC vendors because it is the least expensive and produces better than 90% efficiency.
The 1500V RMS isolation between primary and secondary windings meets the isolation voltage specification for PoE applications as defined in the IEEE802.af standard.
Each transformer has a primary side auxiliary winding to supply input power to the power IC, further reducing power loss.
These PoE series transformers maximise the usage of available height and minimise PCB footprint.
The footprint of the 13W/Class 3 output transformers is 40% smaller than competitive packages.
Industry standard footprints provide the opportunity to develop a second source, if required.
The footprints are 13.2 x 10.7mm for the EP7 (8-pin SMT, 3W/Class 1), 15.2 x 12.7mm for the EP10 (10-pin SMT, 7W/Class 2), and 17.8 x 12.7mm for the EP13 (10-pin SMT, 13W/Class 3) transformer.
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