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Spread spectrum techniques for Class-D audio amplifiers to reduce EMI

Spread-Spectrum-Methoden für Klasse-D-Verstärker zur Reduktion von EMI

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Abstract

For battery powered portable devices it is required to have circuits that combine high efficiency with a small footprint. In the case of Class-D amplifiers the high efficiency can be achieved by applying pulse-width modulation (PWM) to generate the desired output signal. Classical PWM requires an output filter to suppress the idle current. In order to avoid this filter a different modulation scheme is used, which however introduces a larger amount of electromagnetic emissions. Therefore spread-spectrum techniques are applied to distribute the emissions over a wider frequency range. In this article methods are discussed that allow the use of spread-spectrum modulation without introducing audible artifacts due to the modulation.

Zusammenfassung

Für batterieversorgte mobile Geräte werden Komponenten benötigt, die einerseits eine kleine Baugröße andererseits auch einen geringen Stromverbrauch aufweisen. Im Fall von Klasse-D-Verstärkern wird die hohe Effizienz dadurch erreicht, dass man Pulsweitenmodulation (PWM) verwendet, um das gewünschte Ausgangssignal zu erhalten. Klassische PWM benötigt ein Filter am Ausgang, um Ruheströme in der Last zu vermeiden. Zur Vermeidung dieses Filters setzt man andere Modulationsverfahren ein, welche ein größeres Maß an elektromagnetischen Emissionen erzeugen. Aus diesem Grund verwendet man Spread-Spectrum-Modulation, damit diese Emissionen über einen größeren Frequenzbereich verteilt werden. In diesem Beitrag werden Spread-Spectrum-Methoden vorgestellt, die auch für Audio-Anwendungen geeignet sind.

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Authors and Affiliations

  1. Institute of Electronics, Graz University of Technology, Inffeldgasse 12, 8010, Graz, Austria

    Mario Auer & Timuçin Karaca

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  1. Mario Auer
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  2. Timuçin Karaca
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Correspondence to Mario Auer.

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Auer, M., Karaca, T. Spread spectrum techniques for Class-D audio amplifiers to reduce EMI. Elektrotech. Inftech. 133, 43–47 (2016). https://doi.org/10.1007/s00502-015-0384-4

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  • DOI: https://doi.org/10.1007/s00502-015-0384-4

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