Numerical Computation and Design Verification of Integrated Magnetics Used in Linear Level Control Converters

Abstract

In this paper a novel structure of a 1.08 kW planar Linear Level Control (LLC) transformer with magnetic integration is evaluated by using the Finite Element Method (FEM) based numerical modeling techniques. The developed planar LLC transformer has a number of advantages and it is suitable for use in the LLC resonant converter. The most significant advantage of the LLC transformer is that it adjusts the resonant inductance more effectively by changing the air-gap between the magnetic insertion and the transformer core. Compared to the conventional integrated transformers, the developed LLC transformer cannot only adjust the resonant inductance easily, but also achieves a 30% reduction in volume. To evaluate the performance of the LLC transformer, two prototype transformers (one is the proposed structure and the other is the conventional Top Up structure) have been fabricated and tested. FEM numerical modeling techniques are employed to solve the 3-Dimensional (3-D) quasi-static magnetic field problems and investigate the power losses, eddy current and magnetic flux distributions in high frequency. The numerical simulation results are consistent with the measurements. Furthermore, a sectorization technique of windings is also introduced to relieve the redundant computation process of the 3D analysis.