Investigation of Power Converter's Near Field EMI Containment Using Passive Filters

With the advent of the wide-bandgap devices, it has become possible to switch at a faster rate (on and off) along with higher switching frequencies. This results in attaining higher power density, smaller filter size, and lighter weight for the power converter. But the bottleneck of taking advantage of these ultra-fast devices is spurious behavior during operation due to cross talk and electromagnetic interference inheriting from higher dv/dt and di/dt. To meet the standard and to ensure robust operation, EMI filter is in place for a time being; mostly to meet conducted emission requirements. To deal with radiation, shielding is a common practice. This work aims to understand how much the EMI filter helps with radiated EMI reduction. A converter with a traditional passive EMI filter is considered to evaluate the effect of the filter on the near magnetic field adjacent to the converter. The observed phenomenon has been analyzed and explained to understand to what extent the conducted EMI filter helps with mitigating radiated emission.