Design and Performance Evaluation of an Air-Core Inductor for Point-of-Load (POL) Converter

This paper presents the design and evaluation of an air-core inductor for a point of load converter. The design steps for a circular spiral geometry inductor are outlined. Given the desired inductance and DC resistance of the inductor for a fixed footprint, the design steps result in geometrical properties such as the number of turns, width, etc. for the circular spiral inductor realization. Keeping the area of the geometry constant, square, and comb geometry inductors are also implemented. The three geometries (circular, square spiral, and comb geometry) are compared with respect to their inductance, DCR, AC Resistance, and flux distribution. A 12/1.8 V-5.5 A prototype is fabricated using GaN devices and circular spiral air-core inductor. The performance of the design for switching frequencies up to 5 MHz are reported. The efficiency of the converter as a function of the frequency of operation is experimentally obtained and reported.