Audio Power Limiter Circuit That Preserves Burst Waveforms
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Solution Overview
Problem
Power limiting circuits using feedback compressors struggle to handle burst power waveforms effectively, as they tend to attenuate signals prematurely due to varying load impedance with frequency, leading to failure in passing unattenuated burst waveforms even when the average power is within limits.
Innovation Solution
The solution involves a feedback compressor circuit that combines an audio signal with an auxiliary attenuation signal and a compressed attenuation signal from a feedback compressor circuit, using a low-pass filter to determine the attenuation amount, allowing for dynamic adjustment of the threshold and filter state to preserve burst power waveforms by smoothing power measurements and delaying attenuation application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a feedback compressor applies attenuation as soon as output exceeds threshold, then power limits are enforced, but burst power waveforms are prematurely attenuated even when average power is within limits
Solution Approach 1:
The system performs preliminary action by integrating power measurements over time before triggering attenuation. The feedback compressor accumulates energy information and only applies compression when the integrated energy exceeds the threshold, allowing brief burst signals to pass through without attenuation while still enforcing average power limits.
Solution Approach 2:
The system dynamically adjusts the compression behavior based on the temporal characteristics of the input signal. By using an energy-based threshold comparison rather than instantaneous power measurement, the system adapts its response to differentiate between sustained high-power signals (which should be compressed) and brief burst signals (which should pass through).
2Measurement precision
If load impedance variation with frequency is considered, then accurate power measurement is achieved, but computational complexity and latency increase
Solution Approach 1:
The system uses feedback by measuring both voltage and current at the output and computing instantaneous power as their product. This feedback approach directly measures the actual power delivered to the load without requiring explicit knowledge of the load impedance characteristics, thereby achieving accurate power measurement while avoiding complex impedance modeling calculations.
Data Source
AI summary
Example embodiments provide a process that includes one or more of receiving an audio signal at a feedback compressor circuit, receiving an auxiliary attenuation signal from an auxiliary attenuation source, determining a threshold power level based on a value of the auxiliary attenuation signal, determining an output power level of the audio signal exceeds the threshold power level, combining the audio signal with the auxiliary attenuation signal from the auxiliary attenuation source and a compressed attenuation signal from the feedback compressor circuit to create a combination signal, and generating an audio output signal of the feedback compressor circuit based on the combination signal.