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Transformer targets PoE products

Posted: 20 Mar 2006 ?? ?Print Version ?Bookmark and Share

Keywords:Pulse? power transformers? Power-over-Ethernet? Gina Roos?

Pulse, a Technitrol company, has introduced a series of high efficiency, off-the-shelf power transformers for the powered device (PD) side Power over Ethernet (PoE) products that meet the IEEE 802.3af standard.

Available in standard output voltages from 3.3V to 12V, the PoE series consists of twenty-two PD side PoE transformers for 3W, 7W and 13W output power levels. The 3.3-, 5- and 12V output voltage transformers are available at each of the three power levels. These transformers have been tested and approved for use with many of the most popular PoE ICs, according to the company.

The power sourcing unit delivers a loosely regulated 48V (33V 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, and 13W/Class 3.

The Pulse transformers are said to offer 50 percent lower leakage than other PoE power transformers, reducing the need for 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, and higher efficiency transformers directly increase the amount of power that can be delivered to the powered device, said the company.

The PoE series transformers are designed for continuous mode flyback topologies operating between 200kHz and 400kHz, which was chosen by all the major power IC vendors because it is the least expensive and produces 90 percent+ efficiency, said the company. The 1500 root mean square of voltage (Vrms) isolation between primary and secondary windings meets the isolation voltage specification for PoE applications as defined in the IEEE 802.3af standard. Each transformer has a primary side auxiliary winding to supply input power to the power IC, further reducing power loss.

Available in small packages, the footprint of the 13W/Class 3 output transformers is 40 percent smaller than competitive packages, according to the company. The footprints measure 13.2-by-10.7mm for the EP7 (8-pin SMT, 3W/Class 1), 15.2-by-12.7mm for the EP10 (10-pin SMT, 7 W/Class 2), and 17.8-by-12.7mm for the EP13 (10-pin SMT, 13W/Class 3) transformer.

A cross reference between many popular PoE power supply ICs and the PoE series transformers is located on the Pulse Website. Applications include 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.

Parts in this seriesPA1130NL-PA1138NL, PA1279NL-PA1284NL, PA1253NL, PA1260NL, PA1267NL, PA1269NL, PA1276NL, PA1277NL, PA1370NL, PA1528NL and PB2115NL are available on tape and reel packaging. All parts are RoHS-6 compliant.

Prices start at 69 cents per unit in quantities of 100,000. Individual part pricing may vary due to order configuration and shipping destination. Delivery is six to eight weeks.

- Gina Roos

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