Self-Powered Audio Compressor Circuit With Dynamic Impedance Control
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Solution Overview
Problem
Existing audio compressor circuits fail to effectively limit audio volume at low input levels and require a separate power supply, making them unsuitable for non-powered portable devices.
Innovation Solution
A passive audio compressor circuit with a voltage-controlled resistance and AC voltage control unit that adjusts impedance dynamically, allowing for flexible maximum output level adjustment without a specific energy source, suitable for use in non-powered portable devices like headsets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separate power supply is used in the compressor circuit, then the circuit can provide stable compression performance, but the device complexity increases and portability is reduced
Solution Approach 1:
The compressor circuit extracts and utilizes the power it needs directly from the audio signal passing through it, making the circuit self-powered. The signal itself serves as the energy source, eliminating the need for external power supplies while maintaining compression functionality.
Solution Approach 2:
The audio signal serves dual purposes: it carries the audio information to be compressed and simultaneously provides the power energy required for compression. This multi-functionality resolves the contradiction by making the signal both the work object and the energy source.
2Reliability
If the compressor circuit is designed to work at high input levels, then compression performance is improved, but the circuit fails to effectively limit volume at low input levels
Solution Approach 1:
The circuit employs dynamic impedance adjustment that adapts to the instantaneous signal level. The impedance changes continuously based on the signal amplitude, enabling effective compression across a wide range of input levels from very low to high levels.
Solution Approach 2:
The compressor circuit changes its electrical impedance parameter dynamically in response to signal level variations. This parameter change enables the circuit to maintain effective compression performance across different input levels without requiring external power or complex control circuits.
3Use of energy by moving object
If a passive compressor circuit is used without power supply, then portability and energy efficiency are improved, but the ability to maintain proper functioning at low input levels is reduced
Solution Approach 1:
The passive compressor circuit harvests the energy required for compression directly from the passing audio signal itself. This self-service approach enables the circuit to function at low input levels without external power while maintaining compression effectiveness through dynamic impedance adjustment.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides a flexible and energy-efficient means to limit audio volume, ensuring compliance with noise exposure regulations by maintaining low distortion and adjustable output levels, even at low input levels, without the need for a separate power supply.
Implementation Method 1
an AC to DC voltage converter for generating a DC control voltage signal based on the input signal
Implementation Method 2
a voltage controlled resistance for providing the output voltage having a voltage swing controlled by the DC control voltage signal
Data Source
Figure 1~2b
Figure 2c~2e
Figure 3
AI summary
The application relates to a compressor circuit for a listening device, the compressor circuit comprising a pair of input terminals and a pair of output terminals, the compressor circuit being adapted for receiving an electric input signal representing an audio signal with an input voltage swing Vipp at the input terminals and for providing a possibly compressed version of the input signal as an output signal with an output voltage swing Vopp at the output terminals. The application further relates to a listening device and to the use of the compressor circuit. The object of the present application is to provide a compressor circuit with a proper functioning also at relatively low input levels. The problem is solved in that an AC to DC voltage converter for generating a DC-control voltage based on the electric input signal or an AC signal derived therefrom, and a voltage controlled resistance for providing an output voltage swing Vopp controlled by the DC-control voltage, wherein the compressor circuit is energized by the electric input signal. An advantage thereof is that a compressor circuit facilitating a flexible adjustment of the maximum output level is provided. The invention may e.g. be used in portable and non-powered listening devices, e.g. headsets or active ear protection devices.