Optimal Damping of EMI Filter Input Impedance

Damping of EMI filter input impedance to avoid resonance with the source output impedance is presented. Optimization of the damping resistor to maximize the damping effects for a given damping capacitor or inductor while minimizing the power loss is proposed. Three different damping circuits are studied, and for each, an analytical model defining the optimal damping resistance is presented. Performances of these damping circuits are compared in terms of achievable damping effects and power dissipation, as well as size and volume of damping capacitors and inductors. A case study is also presented to illustrate the application of the proposed design.