High-Density Low-Profile Coupled Inductor Design for Integrated Point-of-Load Converters

Low-profile integrated point-of-load (POL) converter is today's industry trend for portable electronic applications. Magnetics is the major challenge and bottleneck for achieving a low-profile high-power-density integrated POL. So, how to design a low-profile magnetic becomes one of the key technologies for integrated POL. Inverse coupling is one of the possible methods used to reduce inductor size due to the dc flux cancelling effect. Several integrated low-profile coupled inductor structures with different flux patterns (vertical flux and lateral flux) are proposed and studied in this paper based on low-temperature co-fired ceramics (LTCC) technology. Two LTCC coupled inductor prototypes are designed and fabricated to verify the theoretical analysis. A 1.5-MHz, 5-1.2 V, 40-A 3-D integrated buck converter with LTCC coupled inductor substrate is also fabricated. The peak efficiency of this integrated converter is as high as 89%. The power density of this integrated converter is as high as 680 W/in3, which is almost six times higher than today's industry products with the same current level.