Switch Mode Multilevel (Class D) Power Amplifiers

Student: Tiam Boon Chiew

Supervisor: Dr. Geoff Walker

Category: Electrical Engineering Thesis Project

An amplifier plays an important role in an audio system. It simply amplifies the input audio signal to an increased power level to drive a speaker, reconstructing the original signal. In recent markets, the Class AB amplifier seems to be dominating the audio equipment. However, when it comes to the power efficiency class D amplifiers have a better output efficiency compared to these classical amplifiers (such as class A, B, and AB). This is based on the fact that a Class D amplifier utilizes the switching operation whereby transistors are either fully on or fully off. Hence ideally, it can achieve the amplification with zero power dissipation. As a result a smaller heat sink is required and the amplifier size can be greatly reduced.

The focus on this thesis is to design a high efficiency, compact size Switchmode Multilevel (Class D) Power Amplifier. As an amplifier, this design will consist of 3 stages an input stage, gain stage and output stage. Additional control loops are included in the PWM stage and the overall circuit design to compensate the non-linearities characteristic of the amplifier.

The result of the design are discussed and follow through to realization, where upon the effectiveness of each of the implementation is evaluated. These evaluations lead to the conclusion that the design is able to achieve higher efficiency with low THD <1%.

Poster Presentation (PDF)

Thesis Document (PDF)