ST AN4006 Application Note: Designing a High-Efficiency (60 W on 4 Pairs) PoE Converter Using the PM8803 and an External Current Booster
Summary
Design robust, high-power Power over Ethernet (PoE) solutions with this comprehensive application note. We introduce a complete reference design for building an ultra-efficient 60W PoE converter based on the PM8803 controller and integrated current booster module. This guide is essential for electrical engineers developing advanced power systems that exceed standard IEEE specifications by utilizing a high-power, four-pair delivery method. The manual provides full schematics, bill of materials, detailed efficiency measurements, and operational waveforms to ensure optimal design performance validation.
Page 1 Text Content
AN4006
Application note
Designing a high-efficiency (60 W on 4 pairs) Po E converter
using the PM8803 and an external current booster
Introduction Power over Ethernet (Po E) applications are covered by the IEEE 802.3 working group with specifications released in 2003 (IEEE 802.3af) and in 2009 (IEEE 802.3at). Power at the input of the powered device (PD) increased from 12.95 W (of the .af standard) to 25.5 W (made available by the .at standard). In both cases the power delivery was based on the “2-pair” system, where 4 wires of the Ethernet cable are used (Tx, Rx pairs or spare pairs). Applications requiring more power are constantly emerging and some solutions are already on the market even though there is no standard fully supporting these applications yet. Some of the alternatives are based on a 4-pair delivery system that allows doubling the power delivered along the Ethernet cable with respect to a 2-pair system. This document focuses on a reference design for a high-efficiency, high-power PD (up to 60 W input) power converter based on an active-clamp forward topology with self-driven synchronous rectification using the PM8803 as the main controller. The total power is delivered on the 4 pairs of a single Ethernet cable by a high-power injector. The PM8803 is a highly integrated device embedding an IEEE 802.3at compliant powered device (PD) interfaced with a PWM controller and support for auxiliary sources. To manage the higher input current (up to 1.4 A) of high-power applications, a simple current booster is introduced in parallel to the PM8803 internal hot-swap MOSFET. The proposed converter prototype is built from the PM8803 demonstration board, but several component changes have been introduced in order to manage the higher current on the input/output section of the converter. Schematics of the Po E converter are given in Section 2 while the bill of material is detailed in Section 3. In Section 4 efficiency measurements together with main waveforms of the Po E interface and power converter are shown.
February 2012 Doc ID 022454 Rev 1 1/19
www.st.com
Page Summary Contents For ST AN4006 Application Note: Designing a High-Efficiency (60 W on 4 Pairs) PoE Converter Using the PM8803 and an External Current Booster
Manual Details
| Brand | Current |
|---|---|
| Pages | 19 |
| File Size | 3.11 MB |
| Published | May 31, 2026 |
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Frequently Asked Questions
What PoE standards does this converter support?
It covers IEEE 802.3af and IEEE 802.3at specifications, supporting power delivery via both 2-pair and 4-pair systems.
How is the unit capable of delivering high power levels?
The design focuses on a 4-pair delivery system, allowing the total power to be delivered by a high-power injector which can double the power compared to a 2-pair system.
What component handles managing higher input current?
To manage the higher input current (up to 1.4 A), a simple current booster is introduced in parallel to the PM8803 internal hot-swap MOSFET.