| Different from Class A, Class B and Class AB working in the linear region, Class D audio power amplifiers work in switching mode, with a theoretically 100% efficiency, and thus features high efficiency and small size. In recent years, as the development of portable device market, Class D amplifiers have gotten more attentions. Based on thorough analysis on the system, this thesis put forward a design of a fully-digital Class D audio power amplifier and implemented it.The first section of this thesis is the introduction. The second one discussed the design of the interpolation filter in the Class D system, and proposes a FIR filter design method to reduce the hardware overhead. The third section theoretically analyzed several modulation schemes and compared their pros and cons, and interpreted the guidance when designing the noise shaper. In the fourth section, several mainstream nonlinear compensation algorithms were deeply analyzed and an optimized compensation method based on 2X interpolation linearization was proposed, which is capable of reducing THD while consumes a relatively low hardware overhead. The fifth section focused on the principle and implementation of PWM modulation signal generation. Finally, simulation results, tape-out information and conclusion were given in the sixth and the seventh part. The Class D system realized in this thesis achieves a dynamic range of over 93dB, capable of handling input signal with 16-bit resolution. With the support of the proposed 2X interpolation nonlinear compensation method, the system also achieves a THD lower than -80dB, meeting the requirements in hi-fi applications.The whole system has been implemented in the standard SMIC 0.18μm 1P6M LOGIC Salicide process and has been taped out. |
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