Magnetics modeling for improving cross -regulation in multiple -output flyback converters

Operation and characteristics of a multiple-output flyback converter strongly depend on the transformer leakage inductances. Steady-state output voltages and cross-regulation properties of the converter are determined by how well the transformer windings are coupled. In the past, analytical results taking into account the effects of the leakage inductances have not been available except for the simplest cases limited to two secondary windings, or based on other simplifying assumptions about the transformer model.;In this thesis, qualitative and quantitative design-oriented analytical results are presented based on magnetic models that can be easily correlated to the winding geometry. The complex operation of a multiple-output flyback converter is effectively explained using the full-order extended cantilever model. This is a general circuit model that has the correct number of independent parameters, and the model parameters can be directly measured. Furthermore, an N-port magnetics model description, which is closely related to the extended cantilever model, is used to analyze the steady-state cross-regulation performance. The selected magnetics models, which are valid for arbitrarily complex magnetics configurations, allow qualitative and quantitative explanation of the observed behavior of the multiple-output flyback, as well as a general steady-state solution in terms of the leakage inductance parameters. The analytical model is used as the basis for engineering the flyback transformer. The interleaved-winding design approach and magnetics design guidelines are presented to achieve improved cross-regulation performance.