Design of the planar transformer in llc resonant converters for micro-grid applications

LLC resonant converters may be applied as an intermediate converter in low power level micro-grid systems. The field of planar magnetics is continuously pushing its utilization in resonant converters as higher power densities and lower profiles are achieved. The design process for the planar transformer is significant due to the gap being placed on the magnetic core for the proper magnetizing inductance requirement. The optimum design methodology for the conventional transformer has been extended to the planar transformer. Design considerations and equations are presented. The planar transformer for a 240 W, 105 kHz LLC resonant converter was fabricated. The experiments were carried out and the results verify the design methodology and the implementation method.