Design of LLC converter using method figure of merit for perspective semiconductors and magnetic components

Abstract

Nowadays the demands for efficiency and high density of electronic device are really high. Therefore, great emphasis is put on the properties of electronic components such as diodes, transistors, transformers and more. Hence the scientific discipline Figure of Merit (FoM), which is dealing with this issue, was created. The paper deals with implementation method figure of merit to the proposed converter to achieve an increase of qualitative parameters of the converter. This method can be used as optimization tool of quality indicators for power supply systems. The main advantage of using FoM assessment technique for certain system's components is the elimination of simulation and physical experiments for efficiency evaluation. Using the method FoM there have been analyzed several older and perspective diodes, transistors and magnetics components. These components have been tested by simulations and measurements. Based on the results of the measurements of converter at various operational conditions, it has been found out that the assumptions for FoM transistors do not match with the measured values. It was therefore necessary to modify the calculations for FoM parameter of transistors for applications which use the inertial body diode. The relevance of FoM parameter was finally evaluated in the way of efficiency investigation (one of qualitative indicators), while different materials of transformers were also verified. In the final part of the paper there is describes a realized simulation analysis using a perspective semiconductor component to the synchronous rectifier the investigated converter. It was found that synchronous rectifier achieves a reduction in power losses of more than 15 watts in the proposed LLC converter compared to Si diode rectifier and 10 watts with SiC diodes. Price of a synchronous rectifier is comparable to the price of a rectifier using SiC diode. Of course, the rectifier circuit using a synchronous rectifier is much more demanding for the initial implementation.