Thesis (MScEng)--Stellenbosch University, 2012 / ENGLISH ABSTRACT: The class-D audio power amplifier has found widespread use in both the consumer and
professional audio industry for one reason: efficiency. A higher efficiency leads to a smaller
and cheaper design, and in the case of mobile devices, a longer battery life.
Unfortunately, the basic class-D amplifier has some serious drawbacks. These include
high distortion levels, a load dependent frequency response and the potential to radiate
EMI. Except for EMI, the aforementioned issues can be mitigated by the proper
implementation of global negative feedback. Negative feedback also has the potential to
indirectly reduce EMI, since the timing requirements of the output devices can be relaxed.
This thesis discusses the design of a clocked analogue controlled pulse-width modulated
class-D audio amplifier with global negative feedback. The analogue control loop
is converted to the z-domain by modelling the PWM comparator as a sampling operation.
A method is implemented that improves clip recovery and ensures stability during
over-modulation. Loop gain is shaped to provide a high gain across the audio band, and
ripple compensation is implemented to minimize the negative effect of ripple feedback.
Experimental results are presented. / AFRIKAANSE OPSOMMING: Die klas-D klankversterker geniet wydverspreide gebruik in beide die verbruiker en professionele
oudio industrie vir een rede: benuttingsgraad. ’n Hoër benuttingsgraad lei
tot ’n kleiner en goedkoper ontwerp, en in die geval van draagbare toestelle, tot langer
batterylewe.
Ongelukkig het die basiese klas-D klankversterker ernstige tekortkominge, naamlik hoë
distorsievlakke, ’n lasafhanklike frekwensierespons en die vermoë om EMI te genereer.
Behalwe vir EMI kan hierdie kwessies deur die korrekte toepassing van globale negatiewe
terugvoer aangespreek word. Negatiewe terugvoer het ook die potensiaal om EMI indirek
te verminder, aangesien die tydvereistes van die skakel stadium verlaag kan word.
Hierdie tesis bespreek die ontwerp van ’n geklokte analoog-beheerde pulswydte-modulerende
klas-D klankversterker met globale negatiewe terugvoer. Die analoogbeheerlus
word omgeskakel na die z-vlak deur die PWM vlakvergelyker as ’n monster operasie te
modelleer. ’n Metode word geïmplementeer wat die stabiliteit van die lus verseker tydens
oormodulasie. Die lusaanwins word gevorm om ’n hoë aanwins in die oudioband te
verseker en riffelkompensasie word geïmplementeer om die negatiewe effek van terugvoerriffel
teen te werk. Eksperimentele resultate word voorgelê.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/20084 |
| Date | 03 1900 |
| Creators | Kemp, Pieter Stephanus |
| Contributors | Mouton, H. du T., Putzeys, B., Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_Za |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 126 p. : ill. |
| Rights | Stellenbosch University |
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