Analysis of Winding Coverage in Planar Transformers with Fractional Turns for High Frequency LLC Resonant Converters

This paper proposes the analysis of a high frequency LLC resonant converter for the winding coverage of a high-frequency fractional-turn planar transformer. In order to analyze the transformer coupling caused by winding coverage, the influence of the secondary side's leakage inductance magnitude on the zero-voltage switching of the primary-side circuit is discussed. The equivalent method of the transformer T model is used to analyze the interval of the LLC resonant converter. This paper focuses on the winding coverage of the fractional-turns transformer and discusses AC resistance and leakage flux. The magnetic component simulation software Maxwell is used to draw the fractional-turn winding and the core model, divide the winding into four areas, and observe the magnetic field intensity distribution of each area vertically. Then, an LLC resonant converter with an input voltage of 380 V, an output voltage of 12 V, an output power of 800 W, an operating frequency of 960 kHz, maximum efficiency of 95.01%, and a power density of 29.89 W/cm3 is realized.