Class-D Audio Amplifier Residual Signal Noise Elimination
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Solution Overview
Problem
Class-D audio amplifiers often produce additional noise due to residual signals caused by feedback circuits, even when the audio input signal is turned off.
Innovation Solution
A noise elimination device is introduced, comprising a residual signal detector and a multiplexer. The multiplexer outputs zero data into the pulse width modulator when the residual signal detector detects a residual input signal, thereby eliminating noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a feedback circuit is used in the sigma-delta modulator, then the audio signal conversion accuracy is improved, but residual signals are generated causing output noise
Solution Approach 1:
The patent introduces a noise elimination device as an intermediary component between the sigma-delta modulator and pulse width modulator. This device includes a residual signal detector that monitors for residual signals and a multiplexer that replaces residual signals with zero data, thereby eliminating the harmful effect of residual signals on output noise while preserving the feedback circuit's audio signal conversion accuracy
Solution Approach 2:
The noise elimination device implements a feedback mechanism by continuously detecting residual signals in the modulator output and dynamically adjusting the signal input to the pulse width modulator. When residual signals are detected, the system feeds back zero data through the multiplexer to cancel out the harmful residual components, maintaining clean output without compromising the original feedback circuit's functionality
2Loss of energy
If the audio input signal is turned off, then power consumption is reduced, but residual signals still produce noise in the output
Solution Approach 1:
The noise elimination device performs preliminary action by detecting residual signals before they propagate to the output stage. Even when the audio input is turned off, the residual signal detector identifies lingering signals and the multiplexer proactively replaces them with zero data, preventing noise generation without requiring additional power consumption from the main audio processing path
Data Source
AI summary
A noise elimination device for a Class-D audio amplifier includes a residual signal detector and a multiplexer, wherein the multiplexer is electrically connected with a sigma-delta modulator (SDM) and a pulse width modulator (PWM) of the Class-D audio amplifier and the residual signal detector. The residual signal detector is configured to detect whether an input signal of the Class-D audio amplifier is residual. The multiplexer is configured to output zero data into the pulse width modulator when the residual signal detector detects that the input signal of the Class-D audio amplifier is residual.