No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

Switched mode, Class-D power amplification allows for high efficiency power amplification of an audio signal. This thesis investigates its application to high power car audio systems where there is a demand for efficient high power amplification. Examination of the present car audio power amplifiers, which comprise a switched mode power supply combined with a linear output stage, has shown that there is significant scope for improvement in efficiency and power density. A novel power stage in which the attributes of a switched-mode power supply and full bridge output stage is presented. It is demonstrated that elimination of the intermedjate DC supply results in an amplifier which has a significantly lower part count, size and cost compared to conventional designs. Two different modulation schemes are explored (PWM and PDM) with a view to finding the most suitable for the new power stage. The theoretical performances of the modulators are verified by practical measurements. The design of high order DeltaSigma modulators is difficult as they show unstable behaviour and an alternative design methodology has been presented to ease this task. The mechanisms which introduce distortion in a practical amplifier are discussed, and for the case of a PWM driven output stage, a new model is presented to predict the effect of dead time on harmonic distortion. This form of distortion is shown to be the dominant cause of open loop non-linearity. The use of feedback is also investigated and yields a factor of 20 improvement in amplifier total harmonic distortion . The design throughout has been supported with practical results and these have illustrated the importance for careful circuit layout in high frequency switching systems.

Thesis (Ed.D.)--Boston University / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / This study was designed to investigate student understanding of fundamental concepts in the engineering course, signals and systems. The aim of this study was threefold: (1) to identify faulty reasonings students invoke in their study of signals and systems; (2) to identify the reasoning resources that explain the origin of student faulty reasonings; and (3) to identify consistencies in students' invocation of reasoning resources across different signals and systems topics. Fifty-one undergraduate students majoring in aerospace engineering at the Massachusetts Institute of Technology participated in this study. Seven oral problems were designed to test student understanding of central topics in the study of continuous-time linear, time-invariant systems. Participants were divided into seven cohorts and each cohort was interviewed on a different problem. Interview transcriptions were analyzed based from a complex systems perspectiv to identify the knowledge elements of reasoning resources that characterize student reasoning in signals and systems. [TRUNCATED] / 2031-01-02