Comparative analysis of methods for obtaining equivalent capacitance in single-layer EMI filter inductors

The parasitic capacitance significantly impacts the high-frequency characteristics of EMI filter inductors used in power electronic applications. Accurate evaluation of this parasitic capacitance is crucial for optimizing inductor performance, which in turn enhances the effectiveness of EMI filters. Numerous modeling approaches have been proposed to achieve this goal. This paper compares and analyzes two commonly used methods for obtaining equivalent capacitance: the distributed-parameter based method and the energy-conservation based method. The numerical approach decouples several capacitances in the distributed-parameter method, enabling a detailed comparison with the formulas used in the energy-conservation method. Additionally, the relationship between these methods and the core geometry is thoroughly explored. By comparing the capacitance values obtained from both methods with experimental data, the paper delineates the applicable scope of each method.