基于PWM的D类音频功率放大器的设计

Design of class-D audio-frequency power amplifier based on PWM

系统旨在设计一种D类功率放大器,以高频三角波作为载波,对音频信号进行采样,生成PWM(Pulse Width Modulation)调制信号。采用高速开关管组成的互补对称式H桥电路对信号的功率进行放大,再将放大后的信号送入4阶Butterworth低通滤波器进行滤波,得到理想的音频信号。系统主要针对音频信号进行处理,对输入频率20 Hz^20k Hz,振幅30~250 m V的音频信号可以实现很好的功率放大效果,最大不失真输出功率大于1 W,最高效率可达到83%。还能对输入信号进行可调放大,实现信号输出功率可调。

The system is intended to design a class-D power amplifier which uses a sort of high frequency triangle wave to process the input signal into the PWM （ pulse with modulation） signal. To gain ideal output signals, the system amplifies the power of signal through the high-speed switch tube composed of complementary symmetry H-bridge circuit and filters the am- plifying signal by 4-th order Butterworth low pass filter. The system can amplify the input signal and adjust output power. The main aim for this system is to process the audio signal and a satisficed result is gained when the frequency of input signal is between 20 Hz ~ 20 kHz and the amplitude of that is between 30 mV - 250 mV. Using these technologies, the maximum effi- ciency of 83% can be achieved and the maximum non-distortion output power exceed 1 W. According to the test results, the function and performance of the whole circuit can meet all the requirements.