@MASTERSTHESIS\{IMM2004-03285,
    author       = "C. B. Rasmussen",
    title        = "Hydrid Digital-Analog Feedback Audio Amplifiers",
    year         = "2004",
    school       = "Informatics and Mathematical Modelling, Technical University of Denmark, {DTU}",
    address      = "Richard Petersens Plads, Building 321, {DK-}2800 Kgs. Lyngby",
    type         = "",
    note         = "Supervised by Assoc. Prof. Jan Larsen",
    url          = "http://www2.compute.dtu.dk/pubdb/pubs/3285-full.html",
    abstract     = "This thesis is concerned with the topic of digital control of the power stage of a Class D amplifier with digital input. The thesis contains an examination of the error sources in the analog power stage, where the main contributors to distortion are identified.

The analog control system for digital class D amplifiers, {PEDEC,} is explained, and it's influence on the amplifiers performance is shown. The two digital modulation forms dAIM and {WPWM} are described. The quantization noise caused by вз modulation is  examined as both modulators contain elements of the [ ] modulator.

A Simulink model is implemented in {MATLAB,} to allow for simulation of modulator and power stage. This model is verified against existing real amplifiers, and serves as a simulation platform for development of control systems. The demands on digital control systems is determined in terms of allowable delay and required bandwidth.

Two forms of feedback are discussed and implemented in Simulink, using the previous designed amplifier model. The first model is with a simple feedback of timing information, while the second is with feedback of amplitude information as well. The second is designed by discretizing the analog control system {PEDEC}.

In Danish:

Denne rapport omhandler emnet digital regulering af effekttrinnet i en klasse D forst{\ae}rker med digitalt input. Rapporten indeholder en gennemgang af fejl-kilderne i det analoge effekttrin, og de st{\o}rste bidragydere til forvr{\ae}nging bliver identificerede.

Det analoge reguleringssystem, {PEDEC,} til digitale klasse D forst{\ae}rker er forklaret, og der er redegjort for dets inflydelse p{\aa} forst{\ae}rkerens performance. De to digitale modulationsmetoder dAIM og {WPWM} bliver beskrevet. Da begge modulatorer indeholder elementer af [ ] modulatoren er kvantiserings- st{\o}jen for{\aa}rsaget af denne modulering blevet unders{\o}gt.

En Simulink model er blevet implementeret i {MATLAB} for at kunne simulere b{\aa}de modulator og effekttrin. Denne model er blevet sammenlignet med virkelige forst{\ae}rkere og tjener som evalueringsgrundlag for test af reguleringssystemer. Kravene til et digitalt reguleringssystem bliver bestemt udfra den kr{\ae}vede b{\aa}ndbredde, og den tilladelige forsinkelse.

To forskellige feedback metoder bliver diskuteret, og bliver ved hj{\ae}lp af den designede forst{\ae}rkermodel implementeret i Simulink. Den f{\o}rste model anvender et simpelt feedback af timinginformation. Den anden model anvender et feedback af amplitudeinformation. Reguleringssystemet i det andet system er skabt ved at diskretisere det analoge system {PEDEC}."
}