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

Abstract

A dual spiral sandwiched thin film inductor with a dimension of 5 mm 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 H and 4 up to 5 MHz, respectively. Using the FeBN film inductor, a hybrid dc/dc converter (15 mm 12 mm 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.Index Terms-DC/DC converter, magnetic core, permeability, thin film inductor.

An efficient way to expand the operating frequency of the thin film inductor

“…Under this condition, the thin film inductors appear. Numerous studies on development of thin film magnetic material [1][2][3], design and fabrication process of the devices have been performed [4][5][6], but up to now it only had been used in the Micro-DC/DC converter, whose converter operation is just 3 MHz, and quality factor 1-2 [7,8]. It has not been applied at higher frequency, because its properties are limited by the resonance frequency and Q factor.…”