System Optimization: High-Frequency Buck Converter with 3D In-Package Air-Core Inductor

In this work, we present the analytical model of buck converter with 3D in-package air-core inductor (150 μm thick). To optimize the power efficiency at a targeted power density, models including 3D inductor and power switches are developed. Compared to 3D EM simulation, the proposed inductor model has a modeling error within 12% for the inductance calculation. With the proposed design methodology, an inductor with Q-factor up to 35 @ 300 MHz is achieved. From the system aspect, the loss breakdown in the integrated power converter is investigated. A 0.5-ratio buck converter can reach 88.5% efficiency @ 1–5W/mm2 based on the optimized inductor designs, with output voltage ranging from 0.7 V to 0.9 V and based on 28 nm CMOS.