Online Input Impedance Extraction of SMPS with Different Impedance of Two Power Lines to Ground

It is important to acquire the impedance of switched-mode power supply (SMPS) under its operating condition for designing electromagnetic interference (EMI) filter. The online impedance extraction technique has become a research hot topic. However, the result of current online measurement technique is inaccurate due to ignorance of the different impedance of two power lines to ground of SMPS. To cope with this, an online impedance extraction technique is proposed in this paper. Considering the practical characteristics of impedance of two power lines to ground, the extraction principle and method is developed based on the established measurement models. Finally, the measurement platform with SMPS and measurement device under operating condition is built. Experimental results validate that the proposed technique can extract the differential mode (DM) and the impedance of two power lines to ground.