Audio Playback Circuit Grounding to Suppress Power-On Pop Noise
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Solution Overview
Problem
Audio play devices such as sound boxes and headsets often generate an unpleasant 'squeaky' sound, known as a plosive or pop noise, during the power-on process due to rapid level changes in the output node of the audio amplifier circuit, which are coupled to the load through a coupling capacitor.
Innovation Solution
An audio play circuit with a plosive suppression circuit that includes a power supply module, a power amplifier, a coupling capacitor, and a plosive suppression circuit configured to disconnect the coupling capacitor from ground when the power supply voltage is below a certain threshold and connect it when the voltage reaches that threshold, using a controller, flip-flop, capacitor-resistor parallel module, and switching transistor to prevent level jumps and thus suppress plosives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the power supply is powered on, then the audio amplifier circuit can operate, but a plosive sound is generated due to rapid level change at the output node
Solution Approach 1:
The patent applies preliminary action by grounding the output node before power-on through a control circuit. The control circuit detects the power supply state and proactively connects the output node to ground through a switching element before the power amplifier becomes operational, preventing the rapid level change that causes plosive sounds. This preliminary grounding action eliminates the harmful effect before it can occur.
2Ease of operation
If a coupling capacitor is used to connect the audio amplifier output to the load, then audio signal transmission is achieved, but plosive sounds are coupled to the load during power-on
Solution Approach 1:
The patent introduces an intermediary control circuit between the power supply and the coupling capacitor. This control circuit includes voltage detection elements and switching components that act as mediators to prevent the harmful power-on transient from reaching the coupling capacitor and load. The intermediary circuit grounds the output node selectively, blocking the plosive signal path while allowing normal audio signal transmission through the coupling capacitor during operation.
3Speed
If the output node level changes rapidly from near 0 to specific level value, then the power amplifier becomes operational, but this rapid change generates plosive through the coupling capacitor
Solution Approach 1:
The patent applies preliminary anti-action by implementing a control circuit that detects the power supply voltage state and proactively grounds the output node before the power amplifier activates. The control circuit uses voltage comparison elements to monitor the power supply voltage and triggers a switching element to connect the output node to ground in advance. This preliminary anti-action counteracts the impending rapid level change that would otherwise generate plosive sounds through the coupling capacitor.
Data Source
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AI summary
The present application provides an audio play circuit and an audio play device. The audio play circuit includes a power supply module, a power amplifier, a coupling capacitor, a load, and a plosive suppression circuit. An output terminal of the power amplifier is connected to a first terminal of the coupling capacitor and an output terminal of the plosive suppression circuit, a second terminal of the coupling capacitor is connected to the load, and an output terminal of the power supply module is connected to a power supply terminal of the power amplifier and a power supply terminal of the plosive suppression circuit. The power supply module is configured to provide a direct current power supply voltage for the power amplifier and the plosive suppression circuit. When the direct current power supply voltage is less than a first voltage threshold, the plosive suppression circuit disconnects the first terminal of the coupling capacitor from a ground terminal, and when the direct current power supply voltage rises to the first voltage threshold, the plosive suppression circuit connects the first terminal of the coupling capacitor to the ground terminal. According to the embodiments of the present application, a plosive generated in a power-on process, of an audio play device powered by a single power supply can be suppressed.