Mn-Zn ferrite line EMI suppressor for power switching noise in the impulse/high current bias regime

Abstract

Ferrite cores 50 mm long were formed from large ferrite tubes obtained using fine Mn-Zn ferrite powder (M-30-IHIS) extruded and sintered at 1280 degrees C for 2 h. Core impedance was measured in the HF range (0.1-100 MHz), varying the number of coil turns and DC bias. Characteristic parameters such as maximum of impedance Z(m), frequency of maximum impedance F-m, and suppressing range f around F-m were determined for each configuration. The analyzed ferrite cores were tested as round cable suppressors in the impulse regime. Impulses were generated by MOSFET transistor switching of high currents (1-10 A). The number of turns, impulse current, and DC bias current were varied in the range from 0 to 10 A. Magnetic interference configurations were formed on the ferrite core using opposite wound coils and tested in the impulse regime. Suppressor responses to different impulses were mutually compared and analyzed. Finally, two ferrite cores were EM coupled by a short circuited coil to form a novel line EMI suppressor aimed for suppression of power switching noise. Several configurations were formed with coupled cores acting on a magnetically interfering principle with opposite coils. The realized configurations were analyzed in view of application for EMI suppression in an uninterruptible power supply and AC/DC and DC/DC converters.