Design of a Class-D Audio Amplifier

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Dr. Sütő Zoltán
Department of Automation and Applied Informatics

Class D is an emerging type of audio amplifiers. Nowadays, the most popular types are class A and B, and their combinations. While the last two types work in linear operation, class D amplifiers follow a completely different approach: they utilize switching semiconductor elements.

This concept is familiar in the field of modern motor drives, and it is very popular because of their relatively easy implementation, versatility, and last but not least their outstanding efficiency. The latest developments in semiconductor technology result in faster switching speeds and lower losses, which make the switching-mode devices competitive in their respective applications.

This thesis focuses on the basic requirements of the implementation of a simple class D amplifier. First the main operating principles are presented, along with some possible alternatives that the designer may choose from. The chosen system layout concept and the component selection are explained in details.

After thorough component selection, the steps of circuit schematic creation are shown. Based on the acquired schematics and practical guidelines, a printed circuit board is designed in order to carry the selected components, and the finished product covers the hardware requirements.

The constructed amplifier is controlled by a microcontroller, and the programming of said device, which is approached in a graphical manner, is explained. This includes studying the communication between the onboard devices, and utilizing he digital filtering capability of the selected audio processor. For this latter part, the filter design process is also presented.

Finally, further development possibilities are shown along with their anticipated effect on the performance and quality of the class D amplifier, and it is explained why a well-designed power supply is crucial for them.


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