Common-Mode Choke for Common-Mode and Differential-Mode Noise Suppression in Low-Power AC-to-DC Power Converters in Sensor Power Modules

Abstract

This paper proposes a common-mode (CM) choke with an asymmetrical CM winding and differential-mode (DM)noise suppression for low-power AC-to-DC power converters in sensor power modules. For a conventional CM choke with symmetricalwinding, the CM and DM noises are also attenuated by the magnetizing inductance (LM) and very small leakage inductance(Lk) owing to the higher coupling factor, respectively, of the CM choke. However, because the number of turns is limited accordingto the shape and size of the CM choke, determining the proper Lk to eliminate the DM noise thoroughly is difficult. Therefore, a bulkyCM choke is required for a larger Lk. Typically, another DM choke is used for DM noise attenuation. Thus, the cost and size of theelectromagnetic interference (EMI) filters for use with a conventional CM choke can increase. To solve these problems, we proposea CM choke with an asymmetrical winding. In contrast to the conventional CM choke with a symmetrical winding, the Lm of theCM choke with an asymmetrical winding can suppress both CM and DM noises. Therefore, the proposed CM choke can effectivelyattenuate CM and DM noises with fewer and smaller turns. This method can be applied to all types of AC-to-DC power convertersof sensor power modules that use two- or three-stage systems. To confirm the validity and superiority of the proposed CM choke,this paper compares the total, DM, and CM noise characteristics between conventional and proposed CM chokes. Finally, a practicalapproach to designing EMI filters and the design procedures are also addressed.