Design of an input filter to suppress conducted EMI of a single phase UPS inverter

A procedure to design an input filter for a single-phase UPS inverter to suppress conducted electromagnetic interference (EMI) is presented in this paper. The causes of the conducted common mode (CM) and differential mode (DM) EMI in a single-phase inverter are analyzed. Other methods to suppress EMI, such as the adoption of a snubber circuit and an input EMI filter, are discussed and the experiments were performed to verify their performance. Furthermore, effects due to the existence of parasitic components in the filter are illustrated. Finally, an EMI filter for a 400 W single-phase UPS inverter is designed to meet the VDE 0871 class A standard.