Design of a planar inductor for DC-DC converter on flexible foil applications

This paper presents the design of a planar inductor for a DC-DC converter for flexible foil applications. The design challenges related to the flexible foil structure and the DC-DC converter requirements are analysed. The main design challenges are due to the constraints on the inductor physical size, the proximity of a conductive plane to the inductor and very high operating frequency of the DC-DC converter. The methodology of the inductor design is based primarily on EM simulations of the inductor structure and on the evaluation of the simulation results in the context of the resulting lumped-element electrical model. The simulations are verified by measurements of the inductors processed on the FR4 substrate which presently emulates the flexible foil substrate.