Based On Direct Audio System Class-d Digital Power Amplifier

Audio Beam is a revolutionary way of projecting audio signal in a highly directional manner to the listener. With the nonlinear interaction of ultrasound in air, the system can generate a narrow beam of sound, which features a highly directional propagation in a specified region innovatively. The main target of this thesis is the design and realization of a digital power amplifier, which features high efficiency, low distortion and extremely low power consumption while driving the ultrasonic transducer of system with high power. The analysis and evaluation of amplification and directivity of system is performed according to the experimental results of Audio Beam system.Aimed at such a task, discussion and comparison as well as analysis among various types of power amplifier are carried out first. Then derived from the principle of Audio Beam technology, a solution that Class D digital power amplifier serves as the driver of ultrasonic transducer is proposed. The theory of directivity and nonlinear interaction of wave's propagation in air is investigated in detail, so that the idea that the establishment of sound field model serves as the guidance of signal processing and design of systematic configuration is proposed. Based on such a guideline, this thesis will perform a deeper research of analysis and design in the following aspects, presenting the analytic results and conclusion of designed system by the experiments of power amplification and directivity.1) According to the principle of Audio Beam technology, the systematic configuration and signal processing method is designed, and the analysis about the requirements of power amplifier is performed. Concerned with the features and applications of all the classes of power amplifier, a solution that Class D digital power amplifier is utilized as the realization of power amplification with high efficiency and low distortion in Audio Beam system is proposed.2) The proposed solution of amplification is converted into the design of circuit schematics, which is simulated by Multisim so that the feasibility of this solution is testified. Then a further discussion of realization of Audio Beam, which is detailed in the analysis of transducers loaded, the modulation of signals, the selection of key electronic components, and the design of function, circuits, and matching network. Ultimately, the design of practical circuits as well as the PCB (Printed Circuit Board) fabrication is fulfilled.3) The entire Audio Beam system is established by the designed Class D power amplifier and other parts. Finally, the experiments of power amplification and directivity are performed. According to the analysis of experimental results, it is concluded that the Class D power amplifier is capable of achievement of amplification with high efficiency and low distortion in Audio Beam system, which leads to successful realization of Audio Beam technology.