Audio Clipping Prevention Under Amplifier Supply Voltage Droop
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Solution Overview
Problem
Personal audio devices face issues with audio signal clipping due to decreased amplifier supply voltage, as existing methods to limit battery power consumption can lead to voltage regulation loss under heavy loading conditions, impacting the ability to properly reproduce audio signals.
Innovation Solution
An integrated circuit with a processing unit that predicts voltage supply levels and attenuates the audio input signal to prevent clipping by monitoring the amplitude of the audio output signal and the available supply voltage, using an audio clipping prevention subsystem to maintain voltage headroom and adjust attenuation based on the rate of change of the supply voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the boost converter limits its consumption from the battery to protect the battery, then battery power consumption is reduced, but the boosted supply voltage loses regulation under heavy loading conditions, causing audio signal clipping
Solution Approach 1:
The system performs preliminary actions by detecting the rate of change of the boosted supply voltage and predicting potential clipping conditions before they occur. The audio signal is attenuated in advance when voltage droop is detected, preventing clipping from occurring in the first place rather than correcting it after the fact.
Solution Approach 2:
The system implements feedback by continuously monitoring the boosted supply voltage and its rate of change, then using this information to dynamically adjust the attenuation of the audio signal. This closed-loop control ensures that the audio output remains clipped-free while allowing the boost converter to operate at optimal power levels.
2Reliability
If the boost converter increases power delivery to maintain voltage regulation, then audio signal quality is maintained, but battery power consumption increases and brownout events may occur
Solution Approach 1:
The system applies partial attenuation to the audio signal only when and where needed to prevent clipping, rather than uniformly reducing all audio output. This allows the boost converter to deliver sufficient power for high-quality audio reproduction without excessive power consumption, applying correction only to the extent necessary to prevent clipping.
Solution Approach 2:
The system dynamically adjusts the audio signal attenuation based on real-time monitoring of the boosted supply voltage and its rate of change. The attenuation level is continuously adapted to match the actual power delivery conditions, allowing maximum audio quality when power is sufficient and preventing clipping when power is limited.
3Power
If the amplifier operates at maximum power output, then audio output amplitude is maximized, but the supply voltage decreases due to battery protection limiting, causing clipping
Solution Approach 1:
The system takes preliminary action by detecting voltage droop conditions and attenuating the audio signal before clipping occurs. The processor monitors the rate of change of the boosted supply voltage and preemptively reduces the audio signal amplitude when voltage depression is detected, preventing distortion of the audio waveform.
Solution Approach 2:
The system uses feedback from voltage monitoring to dynamically control the audio signal level. When the boost converter limits current delivery and voltage droop is detected, the feedback loop automatically reduces the audio signal amplitude to match the available power, ensuring clean undistorted output at the maximum achievable level.
Data Source
Figure 1A~1B
Figure 2
Figure 3~4
AI summary
A method may include receiving information indicative of an amplitude of an audio output signal, receiving information indicative of a predicted voltage of a power supply of a signal path having an audio input for receiving an audio input signal and an audio output for generating the audio output signal based on the audio input signal, predicting from the information indicative of the amplitude of the audio output signal and the information indicative of the predicted voltage of the power supply whether the audio output signal will exceed an available supply voltage generated by the power supply, and responsive to determining the audio output signal will exceed the available supply voltage generated by the power supply, attenuating the audio input signal or a derivative thereof to reduce the amplitude of the audio output signal such that the audio output signal does not exceed the available supply voltage of the power supply.