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 M s 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 P o and efficiency η were measured; 80% efficiency was obtained for a forward-type multilayered transformer.