Multichannel Audio Amplifier Limiting Using Shared Power Reserve Feedback
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Solution Overview
Problem
In audio systems with multiple amplifier channels, existing solutions fail to efficiently manage power supply energy reserves, leading to potential switch-off and audible distortion, as they either over-limit power or do not account for the collective power demand of all channels.
Innovation Solution
A device and method that dynamically adjust gain and clipping levels for each amplifier channel based on the energy reserve of the power supply, using an attenuation function and a clipping function, where gain decreases below a threshold and increases above it, and clipping levels are determined as a monotonic function of the energy reserve, to prevent power supply switch-off while minimizing distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dynamic range compressor or limiter is used to limit the RMS level of the audio signal, then the power supply switch-off is prevented, but the full output power capability of the system is not exploited and audible distortion occurs
Solution Approach 1:
The patent implements dynamic gain adjustment and clipping level determination based on the real-time energy reserve of the power supply. The gain decreases when energy reserve is below threshold and increases up to maximum value when above threshold, allowing the system to adaptively exploit available power while preventing switch-off.
Solution Approach 2:
The system continuously monitors the energy reserve of the power supply and uses this feedback to dynamically adjust the gain and clipping levels. This closed-loop control enables the limiter to respond to actual power availability, preventing both switch-off and excessive distortion.
2Reliability
If independent limiters are used on each audio channel, then individual channel protection is provided, but the multichannel advantage of shared power supply is not obtained
Solution Approach 1:
The patent merges the power management function across all amplifier channels by using a single energy reserve indicator to control gain and clipping levels for all channels simultaneously. This unified approach allows the system to treat the shared power supply as a single resource, optimizing total system power utilization while maintaining individual channel protection.
3Power
If the power supply is rated for maximum instantaneous power, then sufficient power headroom is provided, but the cost and size of the power supply increases
Solution Approach 1:
The system performs preliminary assessment of the power supply's energy reserve and proactively adjusts gain and clipping levels before power overload occurs. This preventive approach allows the use of smaller, less expensive power supplies while maintaining the ability to handle peak power demands through dynamic control.
Data Source
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AI summary
A method for use in an audio system including a plurality of amplifier channels of corresponding audio channels. Each of the amplifier channels receives a respective input audio signal and is powered by a same power supply. The method comprises: obtaining (810) a value of an indicator, wherein the indicator is representative of an energy reserve of the power supply; for each of the amplifier channels, determining (830) a gain to be applied by an attenuation function to the respective input audio signal and a clipping level to be applied by a clipping function to the output of the attenuation function; wherein the gain decreases when the value of the indicator is below a threshold and the gain increases up to a maximum value when the value of the indicator is above the threshold, wherein the threshold is representative of a nominal energy level at which the power supply is in nominal operation; wherein the clipping level is determined as a monotonic function of the value the indicator.