Feedback Compressor Circuit for Undistorted Audio Burst Power Limiting
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Solution Overview
Problem
Power limiting circuits struggle to handle burst power waveforms effectively, as existing feedback compressors 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
A feedback compressor circuit configuration that combines an auxiliary attenuation signal with a compressed attenuation signal from a feedback compressor circuit, using a low-pass filter to delay attenuation and preserve burst power waveforms by determining the threshold power level dynamically, allowing the amplifier to output a 1200 W burst without distorting the signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a feedback compressor attenuates the signal when power exceeds threshold, then power limiting is achieved, but burst waveforms are distorted even when average power is within limits
Solution Approach 1:
The system dynamically adjusts the compression threshold based on the time-averaged power level. When a burst waveform exceeds the threshold momentarily, the compressor applies attenuation. The dynamic element introduces a time-averaging mechanism that distinguishes between temporary peaks and sustained power levels, allowing burst waveforms to pass through unattenuated when their average power remains within limits while still limiting sustained excessive power.
Solution Approach 2:
The system performs preliminary averaging of the power signal before applying compression thresholds. By pre-processing the power measurement through time-averaging, the system prepares a smoothed reference level that anticipates the burst nature of the waveform. This preliminary action allows the compressor to make informed attenuation decisions based on historical power levels rather than instantaneous peaks alone.
2Measurement precision
If load impedance varies with frequency, then power dissipation varies with frequency, but modeling load becomes computationally expensive and introduces latency
Solution Approach 1:
The system uses the feedback compressor's existing power measurement infrastructure to serve dual purposes: both audio compression control and true power measurement. By leveraging the voltage and current measurements already taken for compression, the system calculates actual power delivery without requiring separate load modeling computations. This self-service approach eliminates the need for complex impedance modeling while maintaining measurement accuracy.
Solution Approach 2:
The system implements a feedback loop that continuously monitors actual power delivery and uses this information to control compression. Rather than predicting power based on load models, the feedback mechanism directly measures voltage and current at the output, computes actual power, and uses this real information to drive compression decisions. This feedback approach eliminates computational latency associated with predictive modeling.
3Speed
If attenuation is applied as soon as output exceeds threshold, then power control is responsive, but burst waveforms fail to pass unattenuated even when average power is below threshold
Solution Approach 1:
The system dynamically adapts the compression threshold based on time-averaged power levels. Rather than using a fixed threshold, the threshold evolves with the signal's statistical properties. This dynamic adaptation allows the system to respond quickly to genuine power excursions while tolerating temporary bursts that remain within acceptable average power limits. The dynamic nature creates a responsive yet permissive system that distinguishes between problematic and acceptable signal variations.
Solution Approach 2:
The system employs periodic sampling and averaging of the power signal to establish compression control. By continuously sampling power levels and computing running averages over defined time windows, the system creates a periodic assessment rhythm that naturally filters out short-term bursts. This periodic action allows burst waveforms to complete their cycles before triggering attenuation, ensuring that only sustained power excursions result in compression.
Data Source
AI summary
Example embodiments provide a process that includes one or more of receiving an audio signal at a feedback compressor circuit, determining how much to attenuate the audio signal when a power level of the audio signal exceeds a threshold power level, combining the audio signal with an auxiliary attenuation signal from an 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.