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PWM Amplifier Control Loops with Minimum Aliasing Distortion

PWM class-D audio power amplifiers contain typically a control loop filter network and a comparator producing the PWM signal. The comparator performs a sampling operation whenever it changes state. A previous paper by the author analyzed this sampling behavior from a small signal point of view. The present paper attempts to formulate a large-signal model that accounts for the non-linear effects of the sampling due to aliasing of high frequency carrier components. The model is validated using simulations and a class of loop filters is presented that obtains minimum aliasing distortion thanks to the use of quadrature sampling. Finally, measurement data are presented for real applications using the principles described.

Authors: Neesgaard, Claus; Risbo, Lars
Affiliations: Texas Instruments Denmark A/S; Texas Instruments Inc(See document for exact affiliation information.)
AES Convention:120 (May 2006) Paper Number:6693 Import into BibTeX
Session Subject:Signal Processing; High Resolution Audio

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