High-Level Power Management of Audio Power Amplifiers for Portable Multimedia Applications

Abstract

Modern hand-held multimedia devices are equipped with high-power audio subsystems with built-in loudspeakers. These audio subsystems consume around 30% of the total system power, due to the poor efficiency of loudspeakers, even though high-efficiency class-D amplifiers are used. We introduce an elaborated system-level approach to the analysis of power consumption in amplifiers and consequent power saving for hand-held multimedia applications. Loudspeakers act like resistors below the resonant region and above the linear region, dissipating battery power without producing audible sound output. We exploit the poor frequency response of typical built-in miniature loudspeakers with inadequate enclosures, and limit the production of unnecessary frequencies that never become recognizable sound. We achieve up to 23% and 35% power reduction without appreciable fidelity degradation, with an SNR (signal to noise ratio) of 33% and 35%, for a class-AB and class-D amplifiers, respectively. All the data and experimental results in this paper are actual measurements using our in-house audio power analysis platform