具備USB介面之雙聲道全數位式音頻放大器設計

Abstract

本論文以數位Sigma-Delta Modulator為基礎設計D類音頻放大器。D類音頻放大器，相對於A類或AB類放大器，有效率高、功率級設計較易的優勢。D類放大器常以Pulse-Width Modulator產生切換式控制訊號，但有諧波失真的問題。相對的，Sigma-Delta Modulator架構較Pulse-Width Modulator複雜，沒有固定的諧波干擾。其回授量化誤差，經過迴圈轉移函數，改變量化誤差能量分佈，得到更高的訊號雜訊比。設計高階Sigma-Delta Modulator有穩定性的問題。本論文將設計與實現穩定數位Sigma-Delta Modulator、USB介面與切換式功率放大器，完成一全數位式音頻放大器。

The objective of this thesis is to design a Class D audio amplifier based on digital Sigma-Delta Modulation. Comparing to the traditional Class A or Class AB amplifiers, audio amplifiers based on Class D topology are more efficient in terms of energy conversion and have low cost. Class D amplifiers commonly rely on Pulse-Width Modulation to generate the output switching waveforms which often result in problems such as harmonic distortions. On the other hand, using Sigma-Delta Modulation, it is possible to design the loop filter so that the harmonic distortion is reduced. However, stability problem occurs in designing a high order Sigma-Delta Modulator. This thesis will analyze and implement a stable digital Sigma-Delta Modulator, USB interfaces, and a switching power stage to complete a full digital audio amplifier.