EMI Reduction in Class-D Amplifiers by Actively Reducing PWM Ripple

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 t...

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Bibliographic Details
Published in:IEEE transactions on circuits and systems. I, Regular papers Regular papers, 2020-03, Vol.67 (3), p.765-773
Main Authors: Lokin, Christiaan E., van der Zee, Ronan A. R., Schinkel, Daniel, Nauta, Bram
Format: Article
Language:English
Subjects:
Amplifiers
Audio power amplifier
BD modulation
Bridge circuits
class-D amplifier
delta-sigma analog to digital converter
Digital filters
Electromagnetic interference
electromagnetic interference (EMI)
Feedback loop
Feedback loops
Frequency modulation
High frequencies
Pulse width modulation
Reduction
ripple reduction
Ripples
Switches
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Summary: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.
ISSN:1549-8328
1558-0806
DOI:10.1109/TCSI.2019.2952543