Because of their high efficiency, low volume, and reduced weight, switched Class D audio amplifiers exist in a wide range of applications. However, there are difficult technical issues. This research presents a multiloop feedback topology for the PWM Class D high-quality audio amplifiers that includes: (a) the output filter inside the feedback loop, (b) the means for directly regulating the load voltage, and (c) compensation of the nonlinearities of the output filter. This approach guarantees a flat frequency response regardless of the load and provides a low THD even when smaller, less linear, and less expensive output filter components are used. The theory of the multiloop configuration is analyzed. The proposed topology was built into an integrated power amplifier, which demonstrates the effectiveness of this approach.
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