Several design techniques are compared for producing a power factor correction (PFC) boost inductor operating in discontinuous conduction mode. In this application, fringing fields associated with high frequency current pulses cause problems of winding loss in the vicinity of an air gap, in particular with planar core shapes. For this reason, a planar inductor in which a lumped gap is replaced by a distributed air gap material is described and investigated. The consequences of lumped versus distributed air gap for the losses of the boost inductor are investigated. A significant reduction in ac winding loss of the planar structure with the composite core is demonstrated. However, the trade-off between reduced winding loss and increased core loss for this technique has to be considered along with the selection of proper winding technology. Four boost inductor design realizations are built and compared. Presented winding loss models are verified with measurements on prototypes operating in an 80 W PFC converter.