Active loudspeaker

Abstract

In an active loudspeaker, a bridge rectifier generates an unregulated DC voltage from the AC mains power supply voltage. A self-oscillating pulse modulator generates a pulse-modulated switch signal that is controlling a power switch stage which is switching the unregulated DC voltage. The power-switched signal is low-pass filtered and driving a high-impedance speaker element. The amplifier is compensating fluctuations and noise in the unregulated DC voltage by feeding a reference signal back to the pulse modulator which is derived by voltage-dividing the power-switched signal. The audio volume is regulated by adjusting the voltage divider ratio of the feedback signal. The loudspeaker provides galvanic voltage isolation of the speaker inputs through an audio input stage to comply with safety regulations. This invention eliminates the regulated switched-mode power supply in active loudspeaker applications and thereby reduces cost and weight.

Dependencies are inferred from the claim text.