Audio Output Attenuation Circuit for Pop-Free Source Switching
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Solution Overview
Problem
Conventional audio systems face issues with unwanted pops in audio signals, which can damage speakers and harm listeners, and existing technologies fail to effectively manage abrupt DC voltage offset transitions, leading to potential damage and discomfort.
Innovation Solution
An audio output circuit with a port attenuation circuit that performs ramp-to-mute and ramp-from-mute operations using voltage steps to convert abrupt DC voltage offset transitions into more gradual transitions, meeting a pop disturbance threshold of −65 dBV, and includes a port attenuation control circuit and an attenuation switch network to achieve this.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If abrupt DC voltage offset transitions are allowed in audio signals, then audio source switching is simple and fast, but speaker damage and listener injury may occur due to unwanted pops
Solution Approach 1:
The patent applies preliminary action by performing ramp-to-mute operation before switching audio sources. The attenuation circuit gradually reduces the output signal to a mute state before connecting a new audio source, preventing abrupt voltage transitions that cause pops. This preparatory attenuation action ensures speaker protection while enabling safe source switching.
Solution Approach 2:
The patent segments the audio signal path into multiple controllable attenuation stages. By dividing the signal transmission into sequential ramp-to-mute and ramp-from-mute operations, the circuit can control voltage transitions in discrete steps, preventing harmful pops while maintaining reliable speaker protection.
2Object-affected harmful factors
If ramp-to-mute and ramp-from-mute operations are performed to reduce DC voltage offset transitions, then pop disturbances are inhibited, but the audio signal transmission time is increased
Solution Approach 1:
The patent applies partial action by implementing attenuation only during the brief transition period between audio source switching, rather than continuously attenuating the signal. The ramp-to-mute and ramp-from-mute operations are activated only when needed for source switching, minimizing the time penalty while effectively inhibiting pop disturbances during critical transition moments.
3Device complexity
If conventional audio output circuits are used without attenuation, then the circuit is simple, but abrupt DC voltage offset transitions can damage speakers and injure listeners
Solution Approach 1:
The patent introduces an intermediary attenuation circuit between the audio source and the output amplifier. This intermediary component gradually transitions the DC voltage offset during source switching, mediating the harmful abrupt transitions while protecting the speaker and listener. The attenuation circuit acts as a buffer that smooths voltage changes without significantly complicating the overall system.
Data Source
AI summary
An audio output circuit includes a port attenuation circuit, which is configured to convert an abrupt dc voltage offset transition between a pair of audio signals received in sequence at an input thereof into a more gradual transition. This conversion is achieved by performing, in sequence, a ramp-to-mute operation on a first of the pair of audio signals and a ramp-from-mute operation on a second of the pair of audio signals. The ramp-to-mute operation includes ramping an output of the audio output circuit from a dc voltage offset associated with the first of the pair of audio signals to a reference dc voltage offset. The ramp-from-mute operation includes ramping the output of the audio output circuit from the reference dc voltage offset to a dc voltage offset associated with the second of the pair of audio signals. These ramping operations may be performed using voltage steps having uniform step size.