PCB integrated inductors for low power DC/DC converter

Abstract—This paper discusses the use of printed circuit board (PCB) integrated inductors for low power dc/dc buck converters. Coreless, magnetic plates and closed core structures are compared in terms of achievable inductance, power handling and efficiency in a footprint of 10 10mm2. The magnetic layers consist of electro-plated NiFe, so that the process is fully compatible with standard PCB process. Analytic and finite element method (FEM) methods are applied to predict inductor performance for typical current waveforms encountered in a buck converter. Conventional mag-netic design procedures are applied to define optimum winding and core structures for typical inductor specifications. A 4.7 H PCB integrated inductor with dc current handling of up to 500 mA is presented. This inductor is employed in a 1.5 W buck converter using a commercial control integrated circuit (IC). The footprint of the entire converter measures 10 10mm2 and is built on top of the integrated inductor to demonstrate the concept of integrated passives in power electronic circuits to achieve ultra flat and com-pact converter solutions. Index Terms—Electroplating, embedded PCB magnetics, inte-grated magnetics, low power conversion, magnetic design study, ultra flat inductors. I