Design of a flyback transformer using a stress-annealed iron-based nanocrystalline alloy

This paper presents some results from experiments carried out on a flyback converter whose transformer has been built with a new stress-annealed nanocrystalline (iron-based) material developed by our laboratory team. This original process has provided a low value of relative permeability (around 200) at a high induction level, thereby making it possible to store large amounts of energy. A flyback transformer without air-gap was thus tested in order to evaluate the performance of this material, with highly satisfactory results being obtained. Because of the material's low magnetic losses at a high induction level (up to 1 T) and high-frequency switching (up to 25 kHz), low transformer losses along with a low temperature rise were observed. A figure of merit is proposed in order to situate our material performances among others.