| Summary: | 碩士 === 國立臺灣科技大學 === 電子工程系 === 107 === This paper proposes an isolated DC-DC converter for cloud servers. With a switching frequency in the range of MHz, an LLC resonant converter is selected that can achieve zero voltage switching over the full load range. It replaces the traditional switch components with wide bandgap devices, like GaN, to reduce the turn-off loss of the power components. This paper proposes a new half-turn transformer structure, which uses magnetic flux cancellation to reduce the core loss. The secondary winding is a half-turn to achieve a fractional winding that maintains a winding ratio of 16:1. Solving the problem of increasing the volume of the fractional-circle transformer in previous research, the new half-turn transformer can simultaneously achieve the goal of reducing core loss and volume while increasing power density. Parametric form is used to calculate the core loss and copper loss to achieve an optimized design in the limited circuit layout area. The magnetic simulation software Maxwell of ANSYS is used to verify the circuit behavior with a planner transformer, which conforms to the previous design theory. Finally, the implemented 800-W LLC resonant converter with the proposed design switches at 1 MHz, has an input voltage of 380 V and an output voltage of 12 V, achieves a maximum efficiency of 95.21%, and has a power density of 55 W/cm3.
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