The usual form for active filters is the active RC filter, which is also called an electronic filter. The prime forms of passive filtering are capacitor filters, inductance filters, and complex filters (including inverted L-type, LC filter, LCπ-type filter and RCπ-type filter, etc.). Trial and error will most likely be the best means of zeroing in on the best filter design. In this case, time will need to be spent engineering the circuit layout to mitigate the interference, then add filters and snubbers as needed. Common-mode current (noise or signals that flow in the same relative direction in a pair of lines or all of the lines) and differential-mode current (noise or signals that are either present in one of the lines or flow in opposite directions in a pair of lines) could both lead to interference that may require filtering. To begin, identify the main EMI offenders, and find any coupling paths.ĭesigners may need to block common- or differential-mode noise, depending on the device and its operation. Designing an EMI Filter for Power Suppliesįilter circuit architectures, which are typically used in power supplies, can fall into passive and/or active filtering categories. For example, you may need to meet Comité International Spécial des Perturbations Radioélectriques (CISPR) (or Federal Communications Commission, FCC) EMI specifications, and other such guides in a variety of countries. When deciding on a suitable EMI filter design, designers must find out which regional EMI regulations need to be met to pass the necessary performance levels for qualification. Radiated: This type of interference propagates via the air from radiators (e.g., electric motors) and RF transmissions like cell phones and other radio products.ĮMI will most likely disrupt other electrical/electronic devices such as loudspeakers, motor controls, communication systems, and more, especially in industrial environments.Conducted: This can enter wires and cables that carry power and/or signals.

However, in many cases, a more extensive EMI filter design might be necessary to remove, or at least mitigate EMI so as to not impede achieving the desired performance goals.

Emi Filter Design Software