To reduce the volume of the power converter without reducing conversion efficiency, the volume of magnetic components can be reduced by increasing the switching frequency. However, this is accompanied by a notable increase in the depletion of switching and magnetic components. 
This project proposed a technique with which effective core volume can be increased to reduce core loss. The high-frequency core loss was analyzed from the perspective of core volume to identify an effective method for increasing the effective cross-sectional area and magnetic circuit length of core. This technique was applied to a quarter-turn transformer to optimize core loss that cannot be effectively reduced because of the fraction-turn transformer structure.
This project used an LLC resonant converter with a switching frequency of 1.5 MHz, an input voltage of 380 V, an output voltage of 12 V, and an output power of 1 kW. The goal of the design was a maximum efficiency of 96% and a power density of 41 W/cm3.

This project based on the quarter-turn transformer winding that provides a mathematical analysis to understand the influence of the effective cross-sectional area and magnetic circuit length of the core on loss, to identify the optimal value for volume growth, and to explain how the additional effective volume of core can reduce loss. 

This project details the use of the simulation software, Maxwell, with the existing specifications to analyze the influence of the additional magnetic circuit in the fractional turn transformer on core loss and copper loss and to identify the equivalent effective cross-sectional area of core.

LLC converters are frequently used as isolated converters in server power supplies. To increase power density in a limit volume, we need to focus on high efficiency and high power density when designing converters.

This project also explored the use of a two-stage method to increase the effective volume of core and thus reduce core loss subject to high-frequency switching. A mathematical model was used to describe the effects of additional effective volume of core on core loss reduction. In addition, a finite element analysis 3D simulation was used to verify the degree to which additional effective volume reduced core loss.