Development of nanocrystalline Mn-Zn ferrites for forward type DC-DC converter for switching mode power supplies

Abstract

Nanocrystalline Mn-Zn ferrites have been successfully synthesised using the microwave-hydrothermal method for high frequency applications. The nanopowders were characterised using X-ray diffraction (XRD) and transmission electron microscopy (TEM). They were annealed using the microwave sintering method at 900°C for 20 min. The frequency dependence of the dielectric constant ε′ and and the initial permeability μ i were measured in the range 10 Hz to 1.3 GHz. The saturation magnetisation Ms and coercive force H c were obtained using a vibration sample magnetometer (VSM) in the field of 20 kOe. The total power loss was measured in the range of 100 kHz to 1 MHz with a flux density of 50 mT on the annealed samples. Conductor-embedded ferrite transformers were fabricated and the output power Po and efficiency η were measured; 80% efficiency was obtained for a forward-type multilayered transformer. © 2010 W. S. Maney & Son Ltd.