Time Domain Modelling of a Wireless Power Transfer System using a Buck-Boost Converter for Voltage Regulation

This paper presents a time domain analysis of a Wireless Power Transfer (WPT) system having one transmitter and one receiver in which constant output voltage is maintained by a buck-boost converter placed after the rectifier on the receiver side. The practical modes of operation of the resonant tank are identified, and exact solutions have been derived for the circuit parameters like gain, currents, and voltages in the tank. This helps in preventing overdesign of components from approximate solutions provided by frequency domain modelling. The system is operated in the strongly coupled region below resonant frequency to achieve zero voltage switching (ZVS), by choosing the appropriate duty ratio of the buck-boost converter, which has not been done in existing literature. Experimental results on a $5\mathrm{W}, 5\mathrm{V}$ prototype are used to verify the analysis.