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The design of an analogue class-D audio amplifier using Z-domain methodsKemp, Pieter Stephanus 03 1900 (has links)
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. Read more
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Novel Three-Level Modulation Technique for A Class-D Audio AmplifierLin, Yu-Hsiu 07 September 2005 (has links)
This thesis presents a novel three-level modulation technique for a Class-D audio amplifier, attempting to improve the poor performance of the conventional two-level modulation scheme at low input levels. The main drawback of the conventional two-level PWM (pulse-width modulation) and SDM (sigma-delta modulation) Class-D amplifier is that, with a zero input or small input, the excessively fast switching action at the output causes unwanted switching loss and switching noise, resulting in unnecessary energy waste and SNDR degradation. The presented three-level modulation circuit mainly consists of a linear feedback compensator, two comparators, and a switching logic circuit. The simulation and experimental results shows that the proposed three-level modulation s cheme outperforms the two-level sigma-delta modulation scheme in both efficiency and performance.
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Sliding-Mode Quantized Control of a Class-D Audio Power AmplifierTsai, Yung-Huei 29 August 2008 (has links)
This thesis focuses on the design and implementation of a three-level Class D audio amplifier by applying recently developed sliding-mode quantized control. The designed controller, which consists of the analog filters and logic circuit, switches an H-bridge Class-D amplifier with a lowpass LC filter and operates it in the sliding mode, in order to achieve desired stability and high fidelity in the audio band. The experimental result shows that the lowest THD+N (total harmonic distortion plus noise) can be as low as 0.02% at 1 kHz. The performance is better than most of the available commercial products.
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A detailed analysis of the imperfections of pulsewidth modulated waveforms on the output stage of a class D audio amplifierKoeslag, Francois 03 1900 (has links)
Thesis (PhD (Electrical and Electronic Engineering))--University of Stellenbosch, 2009. / Although the Class D topology offers several advantages, its use in audio amplification
has previously been limited by the lack of competitiveness in fidelity compared to its linear
counterparts. During the past decade, technological advances in semiconductor technology
have awakened new interest since competitive levels of distortion could now be achieved. The
output stage of such an amplifier is the primary limiting factor in its performance. In this
dissertation, four non-ideal effects existing in this stage are identified and mathematically
analysed. The analytical analysis makes use of a well-established mathematical model, based
on the double Fourier series method, to model the imperfections introduced into a naturally
sampled pulsewidth modulated waveform. The analysis is complemented by simulation using
a strategy based on Newton’s numerical method. The theory is verified by a comparison
between the analytical-, simulated- and experimental results.
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Výkonový audio zesilovač využívající AC/DC měnič / Power audio amplifier with AC/DC converterMelša, Vojtěch January 2012 (has links)
The aim of this work was to design and construct a simple audio amplifier, which would be based of involvement and components used in switching power sources on the maximum degree (for example from usual ATX sources for computer). The main motivation for development is the existence of many old sources that do not use and big interest of users for the construction of home audio amplifiers for small and medium power. Amplifiers based on switching power sources with greater efficiency and less weight than comparable classic amplifiers (working in classes A, B or AB). Their disadvantage is the complicated design and introduction of distortion and spurious signals to the amplified signal. This work will be described a design of simple amplifier, which will minimize these negative effects. For shortcomings and wrong parameters this proposed involvement will be eventually described and implemented design of amplifier in class D.
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