The Impact of Rectifier Filter Capacitance on Buck Converter Output Voltage in Wireless Power Receiver System With Input Current Source

Wireless power transfer (WPT) technology offers a more convenient and safer alternative to traditional contact-based power supply methods. In many WPT systems, a two-stage receiver configuration, comprising a rectifier and a dc–dc converter, is commonly used. This article examines how the rectifier filter capacitance affects the output voltage of the buck converter in wireless power receiver system with input current source. Prior research often assumed a large capacitance, leading to a conclusion that the output voltage was unaffected by capacitance changes. However, this is not the case when the capacitance is intentionally reduced, causing the buck converter to switch from continuous voltage mode to discontinuous voltage mode, thereby linking the output voltage to the capacitance. Similar findings can be also observed in other dc–dc converters, such as the Boost converter. This article calculates the critical capacitance and output voltage for the buck converter in both continuous voltage mode and discontinuous voltage mode and develops small-signal models, providing design guidelines for rectifier filter capacitance. The theoretical findings are validated through simulation and experiments.