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 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.

[1]  Andrea Baschirotto,et al.  A 40-nm CMOS, 1.1-V, 101-dB Dynamic-Range, 1.7-mW Continuous-Time $\Sigma\Delta$ ADC for a Digital Closed-Loop Class-D Amplifier , 2015, IEEE Transactions on Circuits and Systems I: Regular Papers.

[2]  Shigeki Inoue,et al.  A High-Efficiency Audio Power Amplifier , 1981 .

[3]  A.J.M. van Tuijl,et al.  A power efficient audio amplifier combining switching and linear techniques , 1998, Proceedings of the 24th European Solid-State Circuits Conference.

[4]  José Renes Pinheiro,et al.  DC-DC and DC-AC Series or Parallel Hybrid Converters , 2018, 2018 13th IEEE International Conference on Industry Applications (INDUSCON).

[5]  Geoffrey R. Walker.  A class B switch-mode assisted linear amplifier , 2003 .

[6]  MODULATION SCHEME FOR FILTERLESS SWITCHING AMPLIFIERS WITH REDUCED EMI BACKGROUND OF THE INVENTION , 2017 .

[7]  Bernd Deutschmann,et al.  Electromagnetic evaluation of Class-D switching schemes , 2015, 2015 11th Conference on Ph.D. Research in Microelectronics and Electronics (PRIME).

[8]  R. Schreier,et al.  Delta-sigma data converters : theory, design, and simulation , 1997 .

[9]  Feipeng Wang,et al.  An Improved Power-Added Efficiency 19-dBm Hybrid Envelope Elimination and Restoration Power Amplifier for 802.11g WLAN Applications , 2006, IEEE Transactions on Microwave Theory and Techniques.

[10]  Bo Zhang,et al.  An Advanced Spread Spectrum Architecture Using Pseudorandom Modulation to Improve EMI in Class D Amplifier , 2011, IEEE Transactions on Power Electronics.

[11]  Ronan van der Zee,et al.  High Efficiency Audio Power Amplifier , 1999 .

[12]  Jinkyu Jeong,et al.  High efficiency and high fidelity analogue/digital switching mixed mode amplifier , 1998 .

[13]  Mario Auer,et al.  Digitally assisted EMI-reduction techniques for Class-D amplifiers with digital control , 2017, 2017 11th International Workshop on the Electromagnetic Compatibility of Integrated Circuits (EMCCompo).

[14]  Mouton HduT,et al.  Digital Control of a PWM Switching Amplifier with Global Feedback , 2009 .

[15]  Paulo Santos,et al.  A Low-EMI 3-W Audio Class-D Amplifier Compatible With AM/FM Radio , 2013, IEEE Journal of Solid-State Circuits.

[16]  Lucien J. Breems,et al.  Audio at low and high power , 2008, ESSCIRC 2008 - 34th European Solid-State Circuits Conference.

[17]  Suki Kim,et al.  A design of a 10-W single-chip class D audio amplifier with very high efficiency using CMOS technology , 1999, IEEE Trans. Consumer Electron..

[18]  P.P. Siniscalchi,et al.  A 20 W/Channel Class-D Amplifier With Near-Zero Common-Mode Radiated Emissions , 2009, IEEE Journal of Solid-State Circuits.

[19]  Michael Clifford,et al.  A 2×20W 0.0013% THD+N Class-D audio amplifier with consistent performance up to maximum power level , 2018, 2018 IEEE International Solid - State Circuits Conference - (ISSCC).

[20]  Christos Christopoulos,et al.  Introduction to Electromagnetic Compatibility , 2007 .

[21]  Germano Nicollini,et al.  A 1 W 104 dB SNR Filter-Less Fully-Digital Open-Loop Class D Audio Amplifier With EMI Reduction , 2012, IEEE Journal of Solid-State Circuits.

[22]  Lucien Breems,et al.  A Multiphase Class-D Automotive Audio Amplifier With Integrated Low-Latency ADCs for Digitized Feedback After the Output Filter , 2017, IEEE Journal of Solid-State Circuits.