Structure Design of a Four-Pillar Magnetically Integrated Fractional-Turn Planar Transformer and its Loss Analysis

In the field of high-frequency transformers, winding losses and core losses constrain the improvement of the power density of planar transformers. Reducing losses on the AC resistor and losses on the core is the key to improving the energy transfer efficiency of planar transformers. Aiming at the half-bridge LLC resonant converter, this paper proposes a novel structure of a four-pillar magnetically integrated fractional-turn planar transformer. In terms of the core structure, according to the principle of magnetic integration, integrate four discrete magnetic cores into a single core, effectively reducing the core volume, so reduces core losses. In the winding, the secondary winding for half-turn structure, compared with the traditional planar transformer, the primary winding and the secondary winding turns ratio from n:1 to 0.5n:0.5, the primary winding and secondary winding loss reduced to the original 1 of 2. The secondary side windings are combined with the windings of the same current direction by suitable arrangement. By increasing the current path, effectively reduces the problem of uneven distribution of current density in the winding and reduces the AC losses on the winding. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.