A High-performance 65 W Universal ac-dc Converter Using a Variable-Inverter-Rectifier-Transformer with Improved Step-down Capability

This paper presents the design and implementation of an ac-dc converter for portable charger applications that uses a new variant of the recently-proposed Variable-Inverter-Rectifier-Transformer (VIRT) technique. This new version of the VIRT technique provides improved efficiency and step-down capability through inclusion of a bypass switch. The proposed design adopts both the Variable Frequency Multiplier (VFX) and the VIRT with bypass technique to maintain high performance across a wide range of input (85 - 265 V
ac
) and output voltages (5 - 20 V
dc
) at an output power of up to 65 W. The VIRT with bypass technique enables full utilization of the transformer core area across all modes of operation and significantly reduces transformer loss. The hardware prototype achieves a displacement power density of 44.6 W/in
³
and peak efficiency of 95.1% at the rated power of 65 W.