I'm trying to determine what harmonic emission limits our 200W power supplies need to comply with.
IEC1000-4-3 has a flow chart that selects the limits based on the application. Since our products are used in ITE and ISM applications, I skip through the flowchart sections dealing with three-phase equipment, portable tools, and lighting equipment. The next decision point in the flowchart asks whether the input current has 'the special waveshape' and is less than 600W. If yes, we apply Class D limits (no motors in our applications); if no, use Class A limits. It appears that simple circuit redesigns (as compared to active PFC preregulators) could reshape the current waveform outside 'the special waveshape', and allow me to use Class A limits. Instead of a Class D 3rd harmonic limit of 680mA on my 200W supply (200Watt * 3.4mA/Watt), I would now have a Class A 3rd harmonic limit of 2.3A. I realize that even harmonics are included with the Class A limits. Do we really have that much latitude with our product design?
