Limits and Opportunities for Distributed Inductors in High-Current, High-Frequency Applications

Issues relating to the design of distributed (parallel) inductors for high-current, high-frequency applications, such as voltage regulator modules (VRM's) are investigated through component design and analysis based on standard planar ferrite cores. Distributed solutions are shown to provide a smaller footprint and volume over equivalent lumped inductors through improved utilization of winding and core materials. The potential for size reduction provided by increased operating frequency is shown to be limited by the loss characteristics of available core materials and the size of conductors needed to handle large currents. The opportunity for improving light-load efficiency of VRM's through switching out of parallel inductors is introduced, and the potential level of improvement in loss provided under light-load conditions is illustrated.