Microphone Bias Circuit Switching to Prevent Speaker Pop Noise
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Solution Overview
Problem
Existing microphone biasing circuitry in electronic devices often results in unwanted bias being applied to speaker contacts when a peripheral device is removed, causing undesirable audio artifacts such as pops or clicks due to the lingering voltage on socket contacts.
Innovation Solution
A host device with a device connector and biasing path that includes a switch to disable the biasing path within 100 μs of disconnection detection, using detection circuitry to isolate the microphone contact from the bias source and connect it to a reference voltage, thereby preventing unwanted bias from affecting the speakers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If microphone biasing circuitry is continuously active to ensure proper microphone operation, then the microphone is ready for immediate use, but unwanted bias voltage remains on socket contacts during disconnection causing audio artifacts
Solution Approach 1:
The detection circuitry detects the disconnection state in advance before the plug is fully removed, and the control circuitry proactively disables the biasing path and discharges the capacitor beforehand, preventing the unwanted bias from affecting the speaker contacts during the disconnection process
Solution Approach 2:
A switch is introduced as an intermediary component in the biasing path, controlled by the control circuitry based on detection circuitry output, to isolate the capacitor and biasing circuitry from the socket contacts when disconnection is detected, thereby preventing the harmful voltage transfer
2Object-affected harmful factors
If the biasing path is disabled quickly upon disconnection detection, then audio artifacts are prevented, but the microphone may not be ready for immediate reconnection
Solution Approach 1:
The biasing path is disabled and the capacitor is discharged in advance upon detection of disconnection, preventing audio artifacts. Upon reconnection, the system quickly restores biasing, minimizing the readiness time loss
Solution Approach 2:
The biasing path is periodically enabled and disabled based on the connection state detected by the detection circuitry, allowing the system to quickly transition between states without maintaining continuous bias, thus reducing overall power consumption and readiness time
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.