A High Performance Class D Audio Power Amplifier Based On Sigma-delta Modulation

Audio power amplifier is widely used in home theater Systems, powered speaker systems and so on. Besides high fidelity, high power and high efficiency become more and more important for audio power amplifier. So it is of greatly practical importance to design an audio power amplifier with high fidelity and high efficiency.The paper is based on the project"Theoretical Research on Key Techniques and Integrated Design of High Performance Class D Audio Power Amplifier", after a detailed research on all kinds of common audio power amplifiers and their efficiency and distortion, an audio power amplifier XD2902 with high fidelity and high efficiency is designed. For the main theory and technology involved in this design are still in the research phase, there are many opportunities for further development and application.Firstly, systematic expatiation is made to the audio power amplifier in the system view, and several kinds of audio power amplifiers together with their characteristics are introduced, then the operating principle and common modulation methods of class D audio power amplifier are described in detail, finally the system scheme studied in this paper is proposed. The system scheme consists of integrator, comparator, output stage and feedback. The continuous-time sigma-delta modulation (CT-SDM) technique with noise-shaping effect is utilized in this design. A self-oscillating modulator which occupies smaller chip area is obtained based on CT-SDM.On the basis of this new system scheme, key circuits are creatively designed in this paper. Low noise and wide bandwidth OTA can satisfy the requirement of low THD. Programmable bidirectional over-current protection circuit ensures the safety of the chip. Protection control circuit can realize the function of self-reset.The whole circuit is designed based on the 0.6μm BCD process. The simulation and verification are completed by the EDA tools such as Cadence etc. According to the simulation results, the function and performance of the whole circuit have met all the requirements.