65W PoE DC-DC converter

Posted on Feb 6, 2014

A solution to one aspect of Power over Ethernet (PoE) is presented here utilizing the ON Semiconductor NCP1031 series of monolithic, high-voltage switching regulators with internal MOSFET. The application note provides details for constructing an inexpensive, high efficiency, 5. 0 V DC power supply with a power output of 5. 0 to 6. 5 W, (output power

65W PoE DC-DC converter
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is conversion mode dependent ” see DC/DC converter operation description below). The associated input circuitry for responding to PoE detection and classification protocol is also included. ON Semiconductor can provide a demonstration printed-circuit-board (PCB) with this circuitry upon request. As a result of IEEE Standard 802. 3AF, it is now possible to inject DC power through Ethernet data transmission lines to power Ethernet communication devices as long as the end power requirement is less than 13 W. The parametric details of DC power transmission and the associated terminology is outlined in this IEEE document. POE consists of two power entities: Power Sourcing Equipment (PSE) and Powered Devices (PDs). The PSEs typically provide 48 Vdc nominal to the LAN cables while the PDs are small DC/DC converters at the load end of the cables which transform the 48 V to logic levels such as 5. 0 Vdc or 3. 3 Vdc or both, to power the communications equipment. The PDs should be able to operate with a maximum average input power of 12. 95 W and tolerate an input voltage range of 36 to 57 Vdc. In addition, a certain "protocol" is required in which the PD is detected (Signature Mode) and then classified (Classification Mode) according to its maximum power level. Note that from the 4th and 5th columns on the table, that the current drawn from the PSE falls between the Iclass minimum and maximum values for a given power...

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