丁類音频功率放大器的设计.doc

摘要 ABSTRACT Along with the social advance and the improvement of consumption, the quality of audio frequency equipments requested by people must advantage as well. At present, the request of audio frequency power amplifier which can protect environment and save energy leads to exploit highly efficient and digital audio frequency power amplifier which can connect other equipments. Class D audio frequency power amplifier meets above request completely. The work style of class D audio frequency power amplifier adopts the style of cut-over electric voltage. Simultaneously, to utilize the PWM signal control the time of leading time in sake of enlarging one signal. Its power supply adopts switch power source which can change AD into DC which produce high voltage and high frequency square wave by the accurate control of switch electric circuit. The output PWM signal adopts low filter to filter the high frequent signal and reserve modulating audio signal to drive the loudspeaker. The important technique problems in design process are high speed changing system , continual and stable line-respond and avoiding the interference of high frequent electromagnetic wave. In coming years, class D audio frequency power amplifier will take place of the traditional enlarger and become the main tendency in the audio frequency world. Keyword: Audio frequency power amplifier、Crossover、PWM、Output signal power、Power supply. 第一章 引 言 1.1 音频功率放大器的发展过程 在音频领域中，类、类、类音频功率放大器一直占据“统治地位，其发展经历了这样几个过程：所用器件从电子管、晶体管到集成电路过程；电路组成从单管到推挽过程；电路形式从变压器输出到OTL、OCL、BTL形式过程。其基本类型是模拟音频功率放大器，它们的最大缺点是工作效率太低，类音频功率放大器的最高工作效率为50%，类音频功率放大器的最高工作效率为78.5%，类音频功率放大器的工作效率介于二者之间。无论甲类、乙类、甲乙类音频功率放大器，当它们的输出功率小于额定输出功率时，效率就会更低，播放动态的语言、音乐时的平均工作效率只有30%左右。模拟音频功率放大器的效率低就意味着工作时有相当多的电能转化成热能，也就是说，这些类型的音频功率放大器必须有足够热器。因此，甲类、乙类、甲乙类音频功率放大器效率低、体积大。为此，人们曾经努力想设计出效率高的音频功率放大器，如G类音频功率放大器，但其最高效率仍然不大的散热器。例如，一台额定输出功率100W的甲类音频功率放大器需要有100W的散热器；一台额定输出功率1000W的乙类音频功率放大器需要有400W的散大于78.5%，且实际使用效率仍然很低。因此，模拟音频功率放大器效率低，所需散热器大、笨重，不符和当前节能环保的要求。 丁类音频功放不同于甲类、乙类和