Optimal Common Mode Target Impedance for Conducted Emission Noise Suppression in Motor Driver Circuits

Although the traditional inverter/SMPS circuit for home appliances or automobiles has a long history, unexpected common mode noise problems when implemented increase development time and cost. In this paper, we proposed a concept of a common mode target impedance based EMC design methodology to optimally suppress conducted emission(CE) noise and reduce the cost and time consumption. The proposed target impedance can be extracted by measurement of common mode impedance and CE spectrum. By designing common mode impedance based on the proposed target impedance, EMC debugging process can be minimized and unnecessary overdesign can be prevented. A motor driver circuit of a washing machine is designed using the target impedance. It is verified that the CE spectrum can be satisfied the standard with 7.5 dB margin.