Comparison of Secondary Topology of the LLC Converter for Photovoltaic Application

LLC converter is a popular topology for renewable energy area. Microconverter is such an application for modular photovoltaic system solution. The converter is designed with large voltage conversion ratio for the individual PV panel to dc bus connection and requires full galvanic isolation for safety. In this paper, LLC converters with active full-bridge and active voltage-doubler secondary topology are studied in comparison. Operating analysis is presented for system understanding and functionality comparison. Then performance is analyzed and supported with hardware testing verification. Overall, it validates the advantages of LLC topology in such application. In addition, it is revealed that though there are similarities in operation, the differences in the secondary topology effect the parasitic parameters in the circuitry, which have significant influences in performance for such high-efficiency circuits. The result proves that active voltage-doubler secondary LLC studied has advantages in transformer design and performance.