Modelling of a Parallel Hybrid Power Audio Amplifier

Parallel audio amplifier are hybrid amplifiers that couple a linear and a switching stage with a parallel connection. A proper control must be designed so that the voltage is controlled by the linear stage, while most of the current is driven by the switching stage. So doing the overall architecture achieves the typical efficiency of the switching stage and the distortion of the linear stage. In summary a nice trade-off between efficiency and distortion can be achieved, allowing to reduce heat dissipation keeping a pleasant sound reproduction. The above purposes can be achieved only with a proper control that must set accurately the balance between the two stages, and its implementation is very critical. The paper deals with the model of the hybrid audio amplifier architecture aiming at retriving the most critical items, and at defining simple relationships for the optimal design of the amplifier. A prototype hybrid amplifier was realized, that confirms the effectiveness of the proposed method.