Switching-based topologies for high-efficiency audio amplifiers

The paper describes the PCB-realization of two high-efficiency amplifiers for consumer audio applications. A 35 Wrms output power delivered to an 8 11 speaker is referred as case study. The first architecture implements a switching amplifier with 3-state Pulse Width Modulation (PWM) while the second solution is an hybrid topology: a linear amplifier is assisted by a switching (buck) converter to increase efficiency for output power higher than 2 Wrms. Compared to conventional linear and class D amplifiers the proposed schemes allow for good performances in terms of harmonic distortion and power efficiency with different trade-offs: the hybrid topology achieves a 0.11 % distortion for a 77 % power efficiency while the 3-state PWM switching amplifier features a 91 % efficiency and a 0.23 % distortion.