EMI (electromagnetic interference) suppression filters for AC power lines eliminate electromagnetic noise entering equipment from commercial power lines or noise generated from electronic equipment.
Common mode chokes, line bypass capacitors, and across-the-line capacitors are generally used as AC line EMI suppression filters.
Common mode chokes are the most important in suppressing common mode noise. The choice of common mode choke therefore has a great impact on the overall filter performance. Murata provides two types of common mode chokes: standard and high-frequency types. The hybrid choke coil is a high-performance EMI suppression device that can suppress both common mode noise and differential mode noise at the same time. It is effective in AC power supplies with active devices for regulating higher harmonic current, which tends to emit relatively high levels of differential mode noise.