Current sharing is an important issue in both isolated and non-isolated DC-DC converters. In the paper, average current sharing is modelled and analyzed for both interleaved multi-phase buck converters and isolated DC-DC converters with current doubler rectifiers. Important design rules and guidelines are provided based on the modelling and analyses. A passive current sharing method is presented to achieve balanced current sharing between two inductors in a current doubler rectifier. Experimental results are presented to verify the modelling of the proposed topology