Coreless Inductor Design for MHz-Frequency GaN Converters

This paper presents a systematic design methodology for PCB-embedded coreless inductors targeting MHz-frequency GaN power converters. The methodology integrates closed-form analytical models with full-wave electromagnetic simulations, incorporating correction factors for proximity effects, fringing fields, and frequency-dependent losses to achieve inductance prediction accuracy within 5%. Experimental validation using a square spiral inductor in a 1-MHz, 10-W GaN HEMT synchronous buck converter demonstrates superior linearity with inductance variation below 5% at 6-A load current, compared to 45% degradation in equivalent ferrite-core designs. Comprehensive electromagnetic compatibility assessment confirms 35-dB margin below CISPR32 Class B conducted emission limits without additional shielding. Thermal characterization validates continuous 6-A operation with junction temperatures remaining 20° C below ferrite alternatives, on the other hand the coreless design exhibiting 3 times larger PCB footprint. The air-core topology eliminates core losses and magnetic saturation, reducing second harmonic distortion by 8 dB while maintaining quality factor Q = 23 at 1 MHz. This validated design framework establishes practical guidelines for integrating high-performance coreless magnetics in next-generation high-frequency power conversion systems where linear behavior, thermal performance, and power density are critical design constraints.