Tms320c67-based Design of a Digital Audio Power Amplifier Introducing Novel Feedback Strategy

The fundamental problem of pulse-width modulation (PWM) based open-loop digital Class-D audio power amplifiers is the inherent nonlinearity of the PWM process, which necessitates the application of a precompensating linearization algorithm. Severe technical difficulties arising from the stringent speed requirements of both electronic circuitry, and digital signal processing devices make the implementation of highfidelity digital power amplifiers even more challenging, despite today's advanced technology. A versatile simulation model of a digital power amplifier was developed, and the performance of three existing linearization techniques was evaluated. A digital signal processor based laboratory prototype of a digital power amplifier was designed and built, incorporating two of the simulated linearization methods. The laboratory prototype proves the effectiveness of the linearization methods for low-power PWM-signals. The laboratory prototype was also used to identify further problems associated with the open-loop digital Class-D amplifier concept, such as the influence of a non-ideal switching stage. Finally, an alternative pseudo-feedback strategy was suggested, which employs a linear adaptive filter.