Amplifier Mode Switching Using Audio Masking to Suppress Pops
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Solution Overview
Problem
Audio amplifiers in portable devices face challenges in mode-switching between current source and voltage source modes, leading to undesirable sound artifacts like clicks or pops, which affect battery life and user experience due to inefficiencies and noise floor issues.
Innovation Solution
An audio controller with a mode state engine that generates control signals for mode transitions between current source and voltage source modes, using a masking sound to minimize the audibility of artifacts by identifying suitable masking sounds based on crest factors and average audio levels, and controlling output resistance changes in steps to reduce discontinuities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If mode switching between current source and voltage source modes is implemented to optimize power usage, then battery life is improved, but sound artifacts like clicks or pops are generated
Solution Approach 1:
The system performs preliminary detection of audio signal characteristics (crest factor, zero-crossing points) before mode switching occurs. By identifying optimal switching moments in advance based on signal analysis, the system prepares to switch modes at the most favorable时机, minimizing artifact generation while maximizing power savings during extended operation periods
Solution Approach 2:
The invention converts the potentially harmful effect of mode-switching artifacts into a beneficial outcome by using the audio signal itself as a masking resource. High-energy portions of the audio signal are deliberately utilized to mask the switching artifacts, transforming what would be audible distortions into imperceptible events, thereby enabling more aggressive mode switching for better battery life
2Loss of energy
If mode switching is performed to reduce power consumption, then energy efficiency is improved, but the noise floor increases
Solution Approach 1:
The system analyzes audio signal characteristics before mode switching to identify optimal switching opportunities. By detecting zero-crossing points and evaluating crest factors in advance, the system determines when switching between current source and voltage source modes will have minimal impact on noise floor, enabling energy-efficient operation while maintaining audio quality
Solution Approach 2:
The invention dynamically changes operating parameters (output impedance, current limit) during mode transitions based on real-time audio signal analysis. By adjusting these parameters according to signal characteristics, the system minimizes noise floor elevation during switching while maximizing power consumption reduction, achieving better energy efficiency without significant noise penalty
3Speed
If output resistance changes are made abruptly during mode transition, then switching speed is improved, but discontinuities in audio signal are generated
Solution Approach 1:
The system performs preliminary detection of audio signal zero-crossing points and characteristics before initiating mode transitions. By identifying optimal switching moments in advance where the signal is naturally at or near zero, the system prepares to change output resistance with minimal disruption, achieving fast switching while maintaining signal continuity and avoiding audible discontinuities
Data Source
AI summary
Circuits, devices and methods related to mode-switching of amplifiers. In some embodiments, an audio controller can include a mode state engine configured to receive an enable signal and generate a control signal for controlling a mode transition of an amplifier between a current source mode and a voltage source mode, with the mode transition of the amplifier resulting in an artifact sound. The audio controller can further include an enable component configured to provide the enable signal to the mode state engine based on a masking sound in an audio signal, such that the artifact sound is substantially masked by the masking sound during the mode transition of the amplifier.