Research on High Power Charging Power Supply Based on LLC and LCL-T Resonant Converter

Abstract

Electric vehicle charging uses constant current followed by a constant voltage charging method, the MOSFETs operate over a large range of frequencies, which will cause trouble to the design of magnetic components, and the magnetizing current is circulated in the resonant tank, which will lead to more core loss. In this paper, a new resonant converter based on inductive multiplexing of LLC and LCL-T is studied to reduce the switching frequency range by using the inherent output characteristics of the converter. During the constant voltage charging phase, the LLC resonant tank operates as a constant voltage source to provide a stable charging voltage. In the LLC resonant tank, the resonant inductor is equated to the secondary side, and this resonant inductor is reused to develop the LCL-T resonant tank for the constant current charging stage, which is equivalent to a constant current source to provide a stable charging current. The resonant converter in this paper has lower losses and higher efficiency compared to other LLC resonant converters. A prototype with 3.3 kW is created to test the theoretical analysis.