ABSTRACT
With all applications, a filter design must start with a set of requirements, and the performance requirements of the filter are critical to design success. Ultimately, the electromagnetic interference filter must pass electromagnetic compatibility qualification, and the differential-mode loss requirement is the first design challenge. To be able to achieve this, it is necessary to make a close approximation of the dB loss by analysis. This design goal is often difficult to reach, especially for the high-current filters, where the required loss is heavy at low frequency. If the cutoff frequency allows the filter to attenuate the lower harmonics, higher capacitor currents result, which heat the capacitors because of the equivalent series resistance. The disadvantage is that the common mode grows to very large sizes as the cutoff frequency is lowered, but there is no lower-frequency limit for bandpass or other reasons.
