The main advantage of Class-D audio amplifiers is high efficiency that is often stated to be more than 90% but, at idle or low power levels the efficiency is much lower. The waste energy is an environmental concern, a concern in mobile applications where long battery operation is required and a concern in other applications where multiple amplifier channels are generating heat problems. It is found that power losses at low power levels account for close to 78% of energy consumption based on typical consumer behavior investigations. This paper investigates the theoretical limits of ideal stepless power supply tracking and its influence on power losses, audio performance, and environmental impact for a 130 W class-D amplifier. Both modeled and experimental results verify that a large improvement of efficiency can be achieved with a new challenge for a self-oscillating controller to keep the audio quality in such a system. The energy consumption may be reduced by up to 72%. The investigation is extended to a commercialized class-D amplifier as well.
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