Study of the resonance phenomenon in switching mode power supply (SMPS)

Multi resonance is highly possible to appear inside conductive and radiated frequency range. This paper presents simplified equivalent circuit model used to study the resonance phenomenon in switching mode power supply (SMPS). Indeed, the electromagnetic interference (EMI) caused by a resonance is a critical factor, and is a source of the high conducted EMI that physically affects the tested AC/DC converter used for telecom applications (to comply with the standard EN300 386 conducted emission requirements). The proposed equivalent circuit model contains essential couplings, parasitic elements, and sources occurred in the common mode current path. This series resonance circuit is primarily composed of input cables; equivalent voltage source and the intentional parameters of the converter are examined theoretically. Experimental results are presented to confirm the cause.