Self-Powered Audio Compressor Circuit for Low-Level Volume Limiting
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Solution Overview
Problem
Existing audio compressor circuits fail to effectively limit audio volume at low input levels and do not function properly without a separate power supply, making them unsuitable for non-powered portable devices.
Innovation Solution
A compressor circuit that uses an AC to DC voltage converter and a voltage-controlled resistance, energized by the input signal, to provide a flexible adjustment of the maximum output level, with features like a drop resistance and AC voltage control unit, allowing it to function as a passive unit suitable for non-powered portable devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a separate power supply is used in the compressor circuit, then the circuit can provide sufficient power for active compression, but the device complexity and power consumption increase, making it unsuitable for non-powered portable devices
Solution Approach 1:
The compressor circuit is energized by the input signal itself rather than requiring a separate power supply. The AC to DC voltage converter extracts energy from the input audio signal to generate the DC control voltage, making the circuit self-powered and suitable for passive portable devices
Solution Approach 2:
The input signal serves dual purposes: it is both the audio signal to be compressed and the power source for the compression circuit. This eliminates the need for separate power supply components and reduces overall device complexity
2Device complexity
If existing compressor circuits are used without proper power supply, then device simplicity is maintained, but the circuit fails to effectively limit audio volume at low input levels
Solution Approach 1:
The circuit uses an AC to DC voltage converter to transform the input signal parameters, generating a DC control voltage that properly activates the voltage-controlled resistance. This parameter transformation ensures reliable compression functionality across all input levels without requiring external power
3Device complexity
If the compressor circuit is made passive to eliminate power supply, then portability is improved, but the ability to provide flexible adjustment of maximum output level is reduced
Solution Approach 1:
The AC to DC voltage converter creates a feedback mechanism where the input signal level directly controls the DC control voltage, which in turn adjusts the voltage-controlled resistance. This automatic feedback loop provides flexible output level adjustment adapted to the input signal characteristics without requiring external power or manual controls
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 enables a compressor circuit that is energetically passive, yet functionally active, providing a flexible adjustment of the maximum output level and reducing distortion, suitable for use in non-powered portable devices like headsets, while ensuring compliance with noise exposure regulations.
Implementation Method 1
an AC to DC voltage converter for generating a DC-control voltage based on the electric input signal or an AC signal derived therefrom
Data Source
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 compressor circuit comprising. 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.