The Structure and Its Leakage Inductance Model of Integrated LLC Transformer With Wide Range Value Variation

The integrated magnetics technology is famous in academic and industrial applications to achieve low profile and high power density of switch-mode power supply (SMPS). The integrated LLC transformer is widely used in LLC converter, where the transformer and resonant inductor are integrated into a magnetic component. However, the value Variation range of leakage inductance of conventional integrated transformer structures is limited due to the low profile and small volume in some planar applications. In this paper, a new integrated LLC transformer structure and its leakage inductance adjustment method are proposed. Based on the two-dimensional equivalent model of the structure, the distribution of the leakage magnetic field and the leakage inductance calculation model of the proposed transformer structure are established. The proposed structure can improve the value variation range of leakage inductance in some special applications and is easily achieved in the planner structure. Finally, the design guideline of the proposed integrated LLC transformer is obtained. Simulation results and prototype experiment results verify the correctness and flexibility of the theoretical analysis.