The analysis and application of the near-field characteristics in the EMI filter

The electromagnetic interference (EMI) filter plays an important role in the EMI noise suppression. As the development of the switch mode power supply (SMPS), the power density of the SMPS improves every year. As a result the distance between components becomes smaller and smaller. The near-field magnetic coupling between components becomes larger and larger. However there are fewer studies about the near-field coupling between components in the EMI filter. Yet no methods have been proposed to use the parasitic parameters to improve the low frequency performance of the EMI filter. A new method which contains a capacitor series in an inductor was proposed to improve the performance of the EMI filter near the series resonance frequency. Also the series inductor integration method by using the near-field magnetic coupling method was proposed. The series inductor can be adjusted by controlling the near-field magnetic coupling of the EMI filter. The consistency of the tendency between the experiment results and simulation results verify the proposed method to be correct and feasible. It provides a new idea for the minimization of the EMI filter.