Highly accurate analysis method for LLC dc–dc converters with an improved transformer circuit model

An improved transformer circuit model is proposed for performing a more accurate analysis of LLC dc-dc converters. In the proposed model, the inductances and turns ratio are expressed by a coupling coefficient k. With the help of newly defined parameters for the transformer, voltage gain and switching frequency can be predicted with high accuracy and therefore it becomes possible to design a considerably practical design of the LLC dc-dc converter. The validity of the analysis method using the proposed transformer circuit model is verified by experimental results with a 500 W prototype.