Dual-Transformer Inductor-Less LLC Resonant Converter Topology

Abstract

This paper proposes a novel resonant inductor less LLC converter with series connected transformers suitable for high input-output voltage ratio applications. The converter consists of two series connected transformers. The leakage inductances are utilized as LLC circuit components, forming the resonant series inductance while the other is the magnetizing element of each transformer, the external capacitance is added to complete the LLC circuit structure. One of the transformers is used to inject voltage into the LLC network to enlarge the voltage gain, while the other operates as a regular LLC converter transformer. The proposed topology presents multiple advantages: 1) high voltage gain is achieved with reduced switching frequency range, 2) higher efficiency at higher voltage gains. The simulation results proved that the converter achieved high efficiency over a wide range of voltage gain using the adopted strategy.