Variable frequency interleaved parallel LLC resonant converter based on variable inductor

The LLC resonant converter has various advantages such as soft switching, high efficiency, and high power density. The LLC interleaved technology is applied to high power circumstances to reduce conduction losses and output ripple. However, there are differences between the parameters of multi-channel LLC converters, which leads to poor current sharing performance of the converter's parallel modules. In variable inductor, a constant current power source was used to control the saturation of the magnetic core in order to achieve the variation of the equivalent inductance. In this paper, variable inductor was applied to interleaved parallel LLC resonant converter. It realized online adjustment of the inductance, thus achieving interleaving and current sharing between the parallel modules. And a new DC gain expression of resonant network was derived to assist the 3D visualization analysis. What's more, the inductance of the variable inductor based on constant separation was deduced, which provides a theoretical guidance to the analysis and design of the variable inductor. A 480 W experimental prototype was designed to verify the effectiveness of this control strategy. © 2020, Harbin University of Science and Technology Publication. All right reserved.