Get the scoop on how to power share between isolated PoE channels

PD power redundancy is another type of applications that requires two power channels. Typical applications include the support of finance hot lines or security utilities. Two PoE channels serve as redundancy to each other, and power sharing is a desirable feature to share the load between the two PoE channels and to reduce the overall conduction losses on the cable wires when both supplies are present.

If the two channels are from separate PSEs, isolation between the two channels will prohibit power sharing on the primary side of the DC-DC converter stage, and it is necessary to adopt a power sharing scheme on the secondary side of the isolation transformers. This article presents two schemes of power sharing on the secondary side between two isolated PoE channels. One is by series connection of the output ports of two modules, the other by paralleling the module outputs. Experimental results obtained with National's LM5071 and LM5072 Evaluation boards are presented.