Single-Stage Duty-Controlled Half-Bridge Inverter for Compact Capacitive Power Transfer System

Capacitive wireless power transfer (CPT) is becoming a promising alternative to inductive power transfer (IPT) due to low costs and the simplicity of capacitive coupler. This paper presents a new architecture that makes CPT systems even simpler and easier to control. In the proposed scheme, a wide input voltage range is achieved by duty control while the output voltage is inherently load-independent, and this eliminates the need for an extra DC-DC converter. Our system also provides an extended zero-voltage-switching (ZVS) range to deal with both input and load variations. We carried out ZVS analysis for each MOSFET switch and based on this an optimal design was proposed. We implemented a prototype 160 W CPT system based on our design procedure, and its performance was then verified under a universal input voltage with load variations from 200-
$1000~\Omega $
. A DC-DC efficiency as high as 88.2% was achieved, showing the value of the proposed topology.