Design of a PCM PWM Totally Digital Audio Power Amplifier
Designs of Digital Amplifiers based upon Pulse-Width Modulation (PWM) principles have used single or dual-slope Analog-to-Digital (A/D) conversion technique, which suffers from several drawbacks; and is not really compatible with the current Digital Audio formats, such as Compact Disks (CD). The idea of a total Digital Amplifier has been explored, but recent findings can be misleading in suggesting the Digital Amplifier be severely compromised due to hardware limitations. This paper presents spectral analyses of the PWM principles which lead to a very high performance design of a total Digital Amplifier fully compatible to the Digital CD format. A simple yet innovative Pulse-Code Modulation (PCM)- to- PWM processor is designed which overcomes the limitations of current semiconductor technology and preserves the quality of the high-resolution PCM samples. In turn, the open-loop performance of the Digital Amplifier is essentially identical to the PCM quality, making open-loop operations possible. To combat output device speed limitations (slow turn-on, turn-off switching time) a novel error correction is included to eliminate low-level distortion. A computer-aided design of several Digital and Analog Filters is also presented.
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