How do EMI filters work?

Conducted EMI signals are in the frequency range up to 30MHz and are carried mainly in the AC or DC power line from the source to the affected systems. The solution is to fit an input EMI filter.

An EMI filter used on the power line is basically a low pass filter that:

  • Prevents the entry of high frequency interference carried by the AC power line into the protected equipment.
  • Prevents the exit of interference energy generated within the protected equipment into the AC power line.

Fig. A-An EMI filter has to suppress incoming and outgoing interference. Before an effective EMI filter can be selected or designed, system and equipment designers alike should understand the nature of conducted EMI.