基于Fusion器件的数字音频处理系统及PWM变换电路的实现

基于Fusion器件的数字音频处理系统及PWM变换电路的实现

指导教师：孙冬 参赛队员：吕效军 张晋宇 王培胜 郑州轻工业学院电气信息工程学院

第二届“Actel杯”中国大学生FPGA设计竞赛摘 要 在多媒体技术蓬勃发展的今天，人们对于音频放大器的要求越来越高，包括缩小产品尺寸、减小热量散发、支持音频多通道和高保真等等都已成为评估音频放大器的一些基本要素，如何使音频放大器能够同时达到以上的要求成为设计的关键，在这种情况下D类音频放大器开始受到了人们的重视。 本课题来源于ZLG杯FPGA大学生电子科技竞赛：基于Fusion器件的数字音频处理系统及PWM变换电路的实现。其研发在于应用Fusion器件的开发板，设计一种D类功率放大器，并采用Verilog语言设计PWM变换电路。本课题属于基础理论、算法和产品的研究。目标是彻底弄清楚∑△调制应用于D类放大器的原理。 在对国外D类数字音频放大器相关的研究情况进行了广泛细致的调研的基础上，对D类音频处理算法进行了认真的研究。研制了数据接口、数字滤波器、∑△调制器、数字脉宽调制器等模块并将其构成了一个完整的音频处理系统。 论文对D类放大器的原理结构，数字音频算法进行了详尽的阐述，并介绍了电路内部各个模块的功能。∑△调制器是本课题设计的重点，也是其中的难点，本文从调制器的原理分析入手，详细的介绍了单环多阶调制器的设计与实现，并采用matlab软件对一阶、二阶和三阶调制器进行了仿真，为实践研究提供了有力的理论依据，给出了Verilog源程序。同时，提出了本设计方案中存在的问题，为了解决H桥式电路开关频率的限制，给出一种新的MASH调制器结构，为今后的研究指明了方向。

关键字：Fusion FPGA，delta-sigma，D类放大器 Abstract Nowadays,with the rapid development of mutimedia technology,more and more requirements are being put forward to the audio amplifiers,including reducing the sizes and caloric emission of products,supporting multi-channel audio and Hi-Fi.The items above have become some elements of evaluating audio amplifiers.How to make audio amplifiers to conform to all the items above,has become the key of design.Under the circumstances,people has started to place importance on class-D audio amplifiers. The subject, Digital audio processing system based on Fusion FPGA devices and design of PWM transform circuits,is from ZLG cup of Electronic Science and Technology University Students FPGA race. This subject is to apply R & D Fusion device development board and design a Class D power amplifier, and design PWM Converter by using Verilog language,and completely apply delta-sigma modulation to class-D amplifier. After research on some information from abroad about class-D digital audio amplifier,more research are done on class-D audio processing algorithm.In the project,the modules have developed which include data interface,digital filter,sigma-delta modulator,digital pulse width modulator and so on,and then put them together to make a complete audio processing system. The essay not only includes the principle and architecture of class-D amplifier,the digital audio algorithm,but also introduces the function of each module in the circuit.The design of Σ △ modulator is the focus of this issue,and also one of the difficulties.This article startly analyzes the principle of the modulator, and detailed introduces the design and implementation of single-loop multi-stage modulator, then simulate first order、second order and third-order modulator， and offers a strong theoretical basis for the practice research later, and shows the Verilog source code. At the same time, the problem of the design is introduced, in order to solve the H-bridge circuit switching frequency limitations, and give a new structure of the MASH modulator for the future research.

Key word:Fusion FPGA，Sigma-Delta Modulation,D-class Amplifier 目 录 1绪 论 ................................................................. 1 1.1课题研究背景及来源 .................................................. 1 1.2 国内外研究现状 ..................................................... 3 1.3本文研究主要内容 .................................................... 3

2数字音频处理系统方案设计 .............................................. 4 2.1 Fusion器件 ......................................................... 4 2.2方案设计 ............................................................ 4 2.2.1技术方案比较 .................................................. 5 2.2.2应用技术分析 .................................................. 5 2.3功能特点 ............................................................ 5 2.4主要技术指标 ........................................................ 5

3系统硬件设计 .......................................................... 6 3.1系统硬件整体设计 .................................................... 6 3.2 前级音频处理电路 ................................................... 7 3.3 FPGA处理电路 ....................................................... 7 3.4 H桥驱动及保护电路 .................................................. 7 3.5单片机人机接口电路 .................................................. 8

4 ∑△调制器的原理、分析与设计 ........................................ 10 4.1过采样技术 ......................................................... 10 4.2 ∑△调制器的噪声整形 ............................................. 11 4.3 二阶与高阶∑△调制器 .............................................. 14 4.4∑△调制器的种类 ................................................... 15 4.5单环一比特量化调制器分析 ........................................... 16 4.5.1单环拓扑 ..................................................... 16 4.5.2一阶调制器仿真 ............................................... 16 4.5.3 二阶调制器仿真 ............................................... 17 4.5.4 三阶调制器仿真 ............................................... 18