A megahertz switching dc/dc converter using FeBN thin film inductor

A dual spiral sandwiched thin film inductor with a dimension of 5 mm x 5 mm was fabricated by a LIGA-like micromachined process. FeBN magnetic films were used as a core material. The inductance and quality factor value of the inductor were measured approximately 1 muH and 4 up to 5 MHz, respectively. Using the FeBN film inductor, a hybrid dc/dc converter (15 mm x 12 mm x 1.5 mm) was designed and fabricated. The circuit topology of the converter was a zero voltage switching clamp voltage (ZVS-CV) buck converter. An input of 3.6 V was bucked to 2.7 V at a switching frequency of 1.8 MHz. The maximum power was 1.5 W. The measured efficiency of the buck converter reached a maximum value of 80% and kept stable up to 300 mA of load currents at 1.8 MHz.