High density low profile coupled inductor design for integrated Point-of-Load converter

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 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 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 in this paper based on low temperature co-fired ceramics (LTCC) technology. This paper also reveals that the lateral flux coupled inductor structure can have higher inductance density than vertical flux structure. Two LTCC coupled inductor prototypes are designed and fabricated to verify the theoretical analysis. A 1.5MHz, 5V to 1.2V, 3D integrated buck converter with LTCC coupled inductor substrate is also fabricated. The power density of this integrated converter is as high as 700W/in³.