Journal article
Carrier Distortion in Hysteretic Self-Oscillating Class-D Audio Power: Amplifiers: Analysis and Optimization
An important distortion mechanism in hysteretic self-oscillating (SO) class-D (switch mode) power amplifiers-–carrier distortion-–is analyzed and an optimization method is proposed. This mechanism is an issue in any power amplifier application where a high degree of proportionality between input and output is required, such as in audio power amplifiers or xDSL drivers.
From an average-mode point of view, carrier distortion is shown to be caused by nonlinear variation of the hysteretic comparator input average voltage with the output average voltage. This easily causes total harmonic distortion figures in excess of 0.1–0.2%, inadequate for high-quality audio applications.
Carrier distortion is shown to be minimized when the feedback system is designed to provide a triangular carrier (sliding) signal at the input of a hysteretic comparator. The proposed optimization method is experimentally proven in an audio power amplifier leading to THD figures that are comparable to the state of the art.
Experimental hardware is a hysteretic SO bandpass current-mode-controlled single-ended audio power amplifier capable of 45 W into 8 Omega or 80 W into 4 Omega from a pm34 V supply with less than 0.03% THD from 100 Hz to 6.7 kHz. Carrier distortion is shown to account for this limitation in THD performance.
Language: | English |
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Publisher: | IEEE |
Year: | 2009 |
Pages: | 714-729 |
ISSN: | 19410107 and 08858993 |
Types: | Journal article |
DOI: | 10.1109/TPEL.2008.2007956 |
ORCIDs: | Andersen, Michael A. E. |
Audio Driver circuits Feedback High power amplifiers Hysteresis Optimization methods Power amplifiers Signal design Switches THD Total harmonic distortion Voltage audio-frequency amplifiers carrier distortion class-D comparators (circuits) feedback feedback system frequency 100 Hz to 6.7 kHz harmonic distortion high-quality audio hysteretic hysteretic SO bandpass current-mode-controlled single-ended audio power amplifier hysteretic comparator input average voltage hysteretic self-oscillating class-D audio power amplifiers power 45 W power 80 W power amplifier power amplifiers resistance 4 ohm resistance 8 ohm sliding total harmonic distortion triangular carrier signal xDSL drivers