A Three Stage Architecture for a High Voltage Step-Down Wireless Charging System

In this paper, a step-down wireless architecture is proposed for low voltage and high current applications. In this scheme, the wireless stage employs a wireless DC-DC converter, which is cascaded with a buck converter to achieve necessary step-down ratio. Multiple compensation networks are analyzed and a network with load independent gain characteristic is identified, which enables the use of same topology for a wide voltage range from 24V to 48V. Further, a gain estimation for different stages to achieve minimum loss operation is also carried out. A 900W laboratory prototype is developed to verify the power transfer over an air gap of 100mm. At full load and fully aligned condition, system achieves an end to end (AC-DC) efficiency of nearly 87.5% at 24V and 91.2% at 48V.