Improved winding design for planar inductors

This paper examines design issues in low-profile inductors carrying high AC ripple current as well as large direct current for use in a 60 W power factor correcting power converter. Specifically, the effect of air gaps in the core structure on multilayer flex circuit (MFC) planar winding losses is examined. Some design guidelines for the construction of planar MFC windings that meet the desired goals of high power density and high efficiency are explored. The use of a flux "keep-away" region for the conductors of a planar winding design is modeled numerically. Experimental measurements of two MFC winding prototypes confirm the results of the numerical modeling.