Higher Q from Pot Core Inductors

Abstract

To obtain the maximum Q (quality factor) from a given inductor structure, the designer must employ his whole bag of design tools. When that inductor operates at several megahertz or more, the bag must often be turned inside out. This paper provides design techniques necessary to maximize inductor Q, with particular emphasis on higher frequency applications. Loss analysis (l/Q) calculations for magnetic core loss and winding losses are discussed. Such practical information as capacitive loss constants and actual measured wire diameters needed for loss calculations are included. How to use the calculations to determine the optimum wire type and size is shown. Optimization examples included are based on actual inductors using IEC 14/8 mm pot cores. The design of a particular ferrite pot core inductor operating in the 15-40-MHz range is outlined. Here the relationship between achieving a given inductance and maximizing Q is explored. Also discussed are special considerations of winding lead placement and hardware effects.