PV module integrated LLC resonant converter with an extended input voltage range

This paper explores the integration of two control methods, variable frequency control and fixed frequency phase shifting control for the effective operation of LLC resonant converter over an extended voltage range that can exceed 2:1. The variable frequency method is used to regulate the output voltage while the input voltage is low to use the higher gain curve whereas the phase shifting method is used when the input voltage is higher. This dual mode control is designed in such a way that the primary switches will achieve zero voltage switching (ZVS) and secondary rectifiers will achieve zero current switching (ZCS) over the entire voltage range. Moreover, the conversion efficiency is also increased at light load condition with this proposed control. A soft transition has been achieved at transition point from one control method to other control method. To confirm the validity of this paper, an experimental prototype of 300W has been built and 98.1% peak efficiency has been achieved at nominal voltage at 50% load.