Design trade-offs to meet class a IEC 61000-3-2 regulations with passive circuits in low power applications

The last amendment to IEC 61000-3-2 regulations significantly modified the regulation. In fact, Class A limits are now much softer. As a consequence, many of the solutions presented in the last years are now more or less useless for low power applications. This is due to the fact that simpler solutions as a passive LC filter can meet the regulations if the power level is below 500 W. This paper presents a study of trade-off passive solutions to meet IEC 61000-3-2 regulations for power levels below 300 W, even for universal line voltage. As it is demonstrated in the paper, designing the filter in such a way that the series resistance is higher can reduce the size of the inductor although the efficiency is penalized. A trade-off between size and efficiency can be established and, in some cases, using just the resistor can reduce the input current harmonic content sufficiently to comply with the abovementioned regulation and with an acceptable efficiency penalty.