An Active Load and Test Method for Evaluating the Efficiency of Audio Power Amplifiers
Automated testing of amplifier efficiency is made fast and flexible by using an active load that can simulate various conditions. The proposed method uses a controlled load that can range from 4 to 50 ohms with a phase between –60 and +60 degrees for frequencies from 20 Hz to 20 kHz. This active load has been used in an automated test procedure to capture efficiency maps of class-B and class-D amplifiers over a full range of operating conditions. While test results showed that the class-D amplifier outperformed the class-B amplifier, real-world efficiency was significantly lower than might be expected because of power supply efficiency, as well as the power consumption of driving stages and peripheral circuits.
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