Research on a High-Efficiency Half-Turn Matrix Planar Transformer Structure for LLC Resonant Converter

In a high-frequency power converter above MHz, the loss caused by the AC resistance of the transformer winding becomes the bottleneck restricting the efficiency of the converter. A new half-turn matrix planar transformer structure is proposed for the half-bridge LLC resonant converter which is commonly used in high-frequency power converter to solve this problem. Compared with traditional planar transformers, the minimum turns ratio of the winding is shifted from "n: 1" to "0.5n: 0.5", and the AC loss of the primary and secondary windings is reduced to half of the original. Moreover, the proposed transformer also uses the principle of magnetic flux cancellation to reduce the core loss and it is more convenient for the termination of the secondary windings and the synchronous rectifiers, reducing the termination loss and via loss. Different half-turn matrix transformer structures are studied in this paper and the optimized design methods are proposed. Based on ANSYS Maxwell simulation, the transformer loss is reduced compared with the traditional one under 1 MHz frequency and 1kW power condition and the flux balance is achieved.