A Wide Operating Range Converter Using a Variable-Inverter-Rectifier-Transformer with Improved Step-Down Capability

This paper proposes the design of a dc-dc converter for portable charger applications that uses a Variable-Inverter-Rectifier-Transformer (VIRT) with improved step-down capability. The proposed design leverages an improved rectifier structure to achieve high efficiency (up to 96.2 %) across a wide range of input (120 - 380 V) and output voltages (5 - 20 V) at an output power of up to 50 W. The new rectifier configuration incorporates a bypass switch which allows for a full utilization of the effective transformer core area across all modes of operation, improving the core loss of the transformer. Moreover, a hybrid Litz-PCB construction of the VIRT transformer further reduces copper loss by mitigating skin and proximity effects, and enables integration of the LLC converter magnetics into a single component. A hardware prototype of the converter achieves a box power density of 23.2 W/in³, and maintains high efficiency and low worst-case power loss across the wide input and output voltage ranges.