Conducted CM Resonance Damping Method Considering Complex Permeability of Core

A high-frequency common-mode (CM) resonance peak appears in the MHz range of the noise spectrum due to the impedance interaction between parasitic capacitances and inductances in power converters. Conventional suppression methods, such as increasing the filter inductance or adding a parallel RL damping branch, inevitably increase inductance and size, thereby increasing the suppression cost and reducing the power density of converters. The imaginary part of the magnetic core's complex permeability results in an equivalent resistance. This resistance exhibits a frequency-dependent characteristic, being relatively high at high frequencies while remaining low at low frequencies. Based on this characteristic, this letter proposes a simple and compact CM resonance damping method. First, the damping mechanism of the proposed method is analyzed. Then, the negative impact of the core's equivalent inductance on resonance suppression is evaluated, and the corresponding design method is further developed. Experiments on a 40-kW dc-dc converter verify the effectiveness of the proposed method and its advantages in reducing volume and weight.