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Synthetic design of the transformer in flyback switching AC-DC converters

This paper presents the synthetic design of the transformer in flyback switching AC-DC converters. Firstly, the maximal power transferred by a standard size magnetic core such as EE-20 or EE-25 is theoretically determined. To obtain accurate analysis, a method based on the nonlinear finite element analysis (FEA) of electromagnetic field is employed. Secondly, from the view of reducing the maximal magnetic flux density in the transformer with the same power, it is proved that the discontinuous conducting mode has more advantages than the continuous conducting mode. Several rules for designing the transformer are presented. As an example, the transformer of an existing converter is re-designed by using the proposed approach. With a nonlinear 2-D FEA field-circuit coupled switching detailed model built in Matlab/Simulink surrounding, the performance of the new converter is obtained.