Optimum Design of High Frequency Transformer Based on Winding Spacing

When designing a series resonant converter, a resonant inductor is usually connected on series in the circuit which leads to an increase in the weight of the device. If the leakage inductance of the transformer is used as a resonant inductor, the weight will be reduced, but the high-frequency leakage flux will bring higher losses. In order to solve this problem, this paper deduces the analytical expression of leakage inductance with respect to winding spacing by magnetic field partitioning method, and constructs a mathematical model about the weight of series resonant inductor. The minimum weight is set as the optimization target, the transformer efficiency as constraints. The Fmincon function in matlab is used to obtain the optimal value of the winding spacing. A three-winding transformer prototype with rated working frequency of 15 kHz and rated power of 25 kW was designed and wounded through this method. The experimental results of the transformer were consistent with the theoretical calculations. The optimization method in this paper can provide reference for the design of high frequency transformers for series resonant converters.