Research And Design Of Digital Pulse Width Modulator In Class D Audio Power Amplifier

Taking the project "Theoretical Research on Key Techniques and Integrated Design of High Performance Stereo Class D Audio Power Amplifier" as background, a digital pulse width modulation solution in Class D audio power amplifier is presented based on the study of the principle of the Class D audio power amplifier and digital audio processing technology. The solution converts digital audio signal to pulse-width-modulated signal in digital environment without DAC and reduces the cost and difficulty for the realization of Class D audio power amplifier with digital signal input.Firstly, the working principle and characteristics of various audio power amplifiers are introduced in the paper. Then, the key techniques of the solution are analyzed thoroughly. On the basis of system structure discussion, the digital pulse width modulator is designed on the RTL in Verilog HDL. To improve performance, the modulator, working at98.304MHz clock domain, up-samples the input signal and shapes noise by integrating sample rate convertor and sigma-delta modulator. And three-level modulation mode, using triangle wave as a carrier, is conformed for the modulator. Furthermore, the synthesis, timing analysis and layout are done with2.5V0.25μm CMOS standard cell library.The simulation and verification are completed with the EDA tools such as ModelSim, Matlab etc. According to the simulation results, the function and performance of the digital pulse width modulator have met all the requirements.