Microphone Bias Switching to Prevent Plug-Removal Audio Artifacts
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Solution Overview
Problem
When a removable peripheral audio device is disconnected from a host device, the residual microphone bias can cause unwanted audio artifacts due to temporary contact between the plug and socket contacts, leading to undesirable sounds like pops or clicks.
Innovation Solution
A host device with a device connector and biasing path that includes a switch to disable the microphone biasing path upon detection of disconnection, using detection circuitry to isolate the microphone contact from the bias source, preventing unwanted bias from affecting the speakers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If microphone bias is continuously supplied to the device microphone contact, then the external microphone is properly biased and ready for use, but unwanted audio artifacts occur during plug removal due to residual bias
Solution Approach 1:
The detection circuitry detects the disconnection state and triggers the switch to disable the biasing path before other contacts make temporary contact during plug removal. This preliminary action of detecting disconnection and preemptively disabling bias prevents the harmful audio artifacts from occurring in the first place
Solution Approach 2:
The switch disables the biasing path in response to detected disconnection, applying a counter-action to remove the bias before it can cause harmful effects. This preliminary anti-action directly counteracts the potential harm of residual bias causing audio artifacts during the disconnection transient period
2Object-generated harmful factors
If a switch is added to disable the biasing path, then unwanted audio artifacts are prevented, but the device complexity increases
Solution Approach 1:
The switch, detection circuitry, and biasing path are integrated into a unified control system where the detection circuitry monitors the connection state and automatically controls the switch to enable or disable biasing. This merging of functions into a coordinated system achieves artifact prevention without proportionally increasing overall device complexity
Data Source
AI summary
A host device for use with a removable peripheral apparatus having a microphone, and to the biasing circuitry for said microphone. The host device may have a device connector for forming a mating connection with a respective peripheral connector. A source of bias is arranged to supply an electrical bias to a device microphone contact of the device connector via a biasing path. A capacitor is connected between a reference voltage node and a capacitor node of the biasing path. A first switch is located between the capacitor node and the device microphone contact. Detection circuitry detects disconnection of the peripheral connector and device connector; and control circuitry controls the switch to disable the biasing path.