A comparative study of carrier-frequency modulation techniques forconducted EMI suppression in PWM converters
Tse, K.K.; Henry Shu-Hung Chung; Ron Hui, S.Y.; So, H.C.
Industrial Electronics, IEEE Transactions on
Volume 49, Issue 3, Jun 2002 Page(s):618 - 627
Digital Object Identifier 10.1109/TIE.2002.1005389
Summary:A rigorous mathematical analysis and a comparative study of
carrier-frequency modulation (CFM) techniques for the conducted
electromagnetic interference (EMI) suppression in pulsewidth-modulated
converters is presented. CFM techniques dither the switching period with
a small amplitude variation around the nominal value, so that the
harmonic power is redistributed over the spectrum of concern. Two types
of dithering signals, including the periodic and random signals, are
investigated in this paper. The operational characteristics as well as
the input and output power spectra of the converters with the two
modulating signals are compared. In particular, their characteristics in
the low- and high-frequency harmonic power redistribution will be
depicted. It is shown that random CFM (RCFM) gives a more effective way
to disperse the harmonics around the switching frequency than the
periodic CFM (PCFM) with the same frequency deviation. However, RCFM
introduces higher low-frequency harmonics than the PCFM at the converter
output. Furthermore, effects of the resolution filter bandwidth in the
electromagnetic compatibility analyzer on conducted EMI measurement is
discussed. The validity of the analyses is confirmed experimentally by
using a dc/dc buck converter operating in continuous conduction mode
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