Experimental evaluation of a digital multi-level audio power amplifier

This paper presents the experimental evaluation of all-digital audio power amplifiers combining a multi-level inverter (9 levels) and the narrow pulse elimination technique (NPE). This technique removes the narrow pulses generated by conventional PWM modulators, reducing the distortion introduced by the non-ideal switching times of the power switches. With NPE the resolution of the generated PWM is no longer limited by the switching speed of the output switches, but only by the digital circuitry frequency. The use of the multi-level inverter with NPE frees the amplifier from any kind of feedback, allowing THD+N better than 0.25% at 80% of the maximum power output, and noise floor at -110 dB.