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High Power Density EMI Filter Design with Consideration of Parasitics

Fig. 1. Attenuation requirement for low and high frequencies.
A compact EMI filter has become one of the critical requirements for a high-power-density converter design, especially in transportation applications. This paper proposes a design procedure for a more compact EMI filter with consideration of both low-frequency and high-frequency attenuation requirements. For the sake of simplicity, EMI filter transfer gain is utilized to conduct the analysis. With the proposed method, the best stage number and components value can be systematically derived for a given fixed operating point. From the design results, the multiple-stage EMI filter has a minimum volume even when the low-frequency and high-frequency attenuation requirements are high.

Fig. 2. Design procedure.
Fig. 3. Minimum volume design.
Fig. 4. Single stage or multiple stage selection.