Low-Power Modulation in an Amplifier

Abstract

A switching audio amplifier may include a modulation enhancement feature, in which the pulse-width modulated (PWM) signals driving the output stage are reduced or increased by identical step sizes to create an auxiliary PWM scheme representative of an idle (low-power) state of the input signal. The PWM signals, provided to a full-bridge power stage circuit for example, may be thereby reduced to another state to reduce power dissipation in a switch-mode power supply. By incrementally adjusting the PWM duty-cycle identically in all PWM signals to a value less than (or up to) 50%, the amount of current dissipated in the output load may be effectively controlled. The PWM pulses may be adjusted up or down, while checking for saturation corresponding to both minimum and maximum pulse-widths. A dampener circuit may be used to set the time between incremental adjustments, to further reduce audible pops and clicks.

Description

PRIORITY CLAIM[0001]This application claims benefit of priority of U.S. provisional application Ser. No. 61 / 543,998 titled “Circuits and Methods Used in Audio Signal Processing”, filed Oct. 6, 2011, which is hereby incorporated by reference in its entirety as though fully and completely set forth herein.FIELD OF THE INVENTION[0002]The present invention relates generally to signal processing, and more particularly performing low-power modulation in an amplifier.DESCRIPTION OF THE RELATED ART[0003]Signal processing represents a combined application of electrical / computer engineering and mathematical principles, primarily directed to the analysis of and operation on either discrete or continuous time signals. Signals of interest can include sound, images, time-varying measurement values and sensor data, for example biological data such as electrocardiograms, control system signals, telecommunication transmission signals such as radio signals, and many others. Signals are typically anal...

AI Technical Summary

Benefits of technology

[0008]Various embodiments of an audio amplifier include circuitry to perform modulation enhancement. Specifically, a low-power modulation scheme may be implemented in an amplifier as a deterministic pulse-width modulation scheme by which the gate drive signals are eliminated at or near zero-crossing boundaries, to reduce power loss that may occur during switching and/or conduction, without introducing a transient in a power stage circuit of the audio amplifier. In some embodiments, the amplifier may be either a class-BD or a class-AD amplifier capable of accepting a bipolar input, where zero value inputs, referred to as mute or digital silence in audio systems, would normally be output through a pulse-width modulation (PWM) scheme in which the duty-cycle of the PWM signal is 50%, and both positive and negative PWM signals are equal

Problems solved by technology

This permits signal processing using digital circuits such as microprocessors and computers, and while analog to digital conversion can be prone to loss, most modern audio systems use the digital approach because digital signal processing techniques are overall more powerful and efficient than

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