EMI reduction in Class-D amplifiers by actively reducing PWM ripple

Christiaan Egidius Lokin*, Ronan A.R. van der Zee, Daniel Schinkel, Bram Nauta

*Corresponding author for this work

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    Abstract

    Class-D amplifiers switch high voltages and currents at high frequencies and hence produce electromagnetic interference (EMI). This work presents a technique to reduce the high frequency ripple, which is still present after the output filter. A Class-A ripple reduction amplifier is put in parallel to the output of the Class-D amplifier, each having their own feedback loop with digital filters. High ripple reduction loop gain is achieved at the PWM frequency by using a resonator as digital loop filter. Dissipation in the Class-A amplifier is reduced by using a low common-mode signaling technique. Common-mode and differential-mode switching components at the PWM frequency are reduced by 27 dB and 18 dB respectively. Total system efficiency is 79% at 40 W output power.
    Original languageEnglish
    Pages (from-to)765-773
    Number of pages9
    JournalIEEE transactions on circuits and systems I: regular papers
    Volume67
    Issue number3
    Early online date26 Nov 2019
    DOIs
    Publication statusPublished - 1 Mar 2020

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    Keywords

    • Audio power amplifier
    • class-D amplifier
    • ripple reduction
    • delta-sigma analog to digital converter
    • electromatic interference (EMI)
    • BD modulation

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