Transformers are made for power over Ethernet

High-efficiency small-footprint off-the-shelf power transformers are designed for powered device side power over Ethernet products.

Pulse has launched a series of high-efficiency small-footprint off-the-shelf power transformers for powered device side power over Ethernet (PoE) products.

They meet IEEE802.3af 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 to 12V.

Purchasing standard PoE transformers off-the-shelf significantly reduces both lead time and cost, 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 with 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.

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 (33-75V) 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, and 13W/Class 3.

Pulse has designed 3.3, 5.0 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 Pulse PoE series 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 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 Pulse 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.

"The IEEE802.3af specification standardises the requirements for delivering power to electronic devices over Cat5 Ethernet cables making standard, off-the-shelf PoE transformers possible".

"Each transformer has been tested and approved by a power supply IC company offering a PoE solution".

"This simplifies the design and layout of a power supply using these transformers", said Geoff Wildman, Pulse Power Division Product Line Manager.

A crossreference between many of the popular PoE power supply ICs and the PoE series transformers is available on the Pulse website.

All parts are RoHS-6 compliant.

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