Novel Modulation Strategies for Class-D Amplifier

Recent advances in semiconductor technology have renewed interest in class-D audio amplifiers, especially for portable devices and consumer electronics. In addition to higher efficiency, class-D amplifiers are smaller, lighter, streamlined, cool and quiet with extended battery life compared to the conventional linear amplifiers. A typical class-D amplifier increases the efficiency of amplifiers in consumer and professional applications from the industry norm of approximately 50 percent to 90 percents or better. In this paper, two zero voltage switching (ZVS) modulation strategies are proposed to achieve the goals of high fidelity and high efficiency. Field programmable gate array (FPGA) implementations of the proposed modulation strategies are also provided in this paper. In order to verify the correctness of the proposed methods, a FPGA-based class-D audio amplifier prototype is developed and realized. Experimental results are then presented to validate the proposed modulation strategies. According to the experimental results, the proposed test system is able to deliver more than 15 W into a 4 Omega load with an efficiency of 80% and total harmonic distortion (THD) less than 2 %.

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