High-efficiency DC-DC converter chip size module with integrated soft ferrite

This letter describes a power supply module with an ultrathin, high-efficiency switching dc-dc converter system in order to meet increasing demand for smaller, thinner and lighter devices in portable electronic equipment. Usually, the inductor is the largest passive components in a converter system. We formed inductors on ferrite wafers as a substrate to mount an IC chip using thin film technology. This realized a significantly small and thin module. The external size of the module is 3.5 mm /spl times/ 3.5 mm /spl times/ 1.0 mm. Its maximum output power is 1 W, and its efficiency is up to 93.4%. A high power density of 81.6 W/cc was realized.