Leakage Inductance Calculation of Inductor Integrated Planar Transformer

The design and fabrication of magnetic components is one of the most important issues in realizing high-density switching power converters. An integrated magnetics (IM) technique has been used to reduce the size and cost of the magnetic components. In this technique, a leakage inductance can be used as a series inductor connected to the transformer for applications using resonant techniques, such as LLC resonant converter and other zero-voltage switching converters. The calculation of the leakage inductance is required to accurately control the value of the inductance in designing an IM device. This paper describes the calculation of the leakage inductance for the inductor integrated planar transformer used for the high-density LLC resonant converter. The leakage fluxes through the leakage layer is first considered to calculate the biggest part of the leakage inductance. The windings and insulators are also considered to improve calculation accuracy under the uneven number of windings for the PCB layer. Leakage inductance is calculated using magnetic energy equation and equivalent magnetic circuit. Experimental results are provided to verify the effectiveness of the proposed calculation method.