Current-Source Loudspeaker Control for Nonlinear Distortion
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Solution Overview
Problem
Conventional loudspeakers, particularly those designed for portability and compactness, suffer from increased audio distortion due to nonlinear behavior, which impairs sound quality and speech intelligibility, necessitating an anti-distortion system to enhance sound reproduction.
Innovation Solution
A nonlinear control system for loudspeakers using a current source amplifier is implemented, which corrects audio distortion by pre-distorting the current to the speaker driver, thereby controlling the motion of moving components and preventing excessive displacement and overheating, while simplifying digital signal processing requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If voltage source amplifier is used, then the system can drive loudspeakers, but nonlinear distortion increases at high output levels
Solution Approach 1:
The patent transforms the amplifier from a voltage source to a current source, changing the fundamental electrical parameter being controlled. This parameter change allows the amplifier to maintain low distortion while delivering high power to the loudspeaker, as the current source topology inherently provides better control over the speaker coil current regardless of impedance variations.
2Device complexity
If conventional amplifier topology is used, then the circuit is simple, but feedback signal contains unwanted information degrading performance
Solution Approach 1:
The patent extracts and removes the problematic feedback path from the conventional amplifier topology. By eliminating the feedback signal that contains unwanted information from the amplifier output, the system avoids the performance degradation that would result from feeding distorted signals back to the input stage.
Solution Approach 2:
The patent introduces a current sensing mechanism as an intermediary element that directly measures the current through the loudspeaker coil without relying on voltage feedback. This intermediary measurement provides accurate current information for control purposes without the distortions present in conventional voltage feedback paths.
3Device complexity
If amplifier output is connected directly to loudspeaker, then the connection is simple, but impedance variations cause current changes and distortion
Solution Approach 1:
The patent changes the control parameter from voltage to current. By controlling the amplifier to output a constant current that is independent of loudspeaker impedance variations, the system maintains accurate current control through the speaker coil even when impedance changes occur during the audio signal cycle.
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 system improves sound quality, enhances bass output, and provides protection to the loudspeaker by reducing nonlinear audio distortion, achieving improved audio reproduction with reduced computational demands and lower costs.
Implementation Method 1
a transformer coupled to a secondary winding to provide a feedback signal proportional to the current through the loudspeaker coil
Data Source
Figure 1~2
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AI summary
One embodiment provides a system for nonlinear control of a loudspeaker. The system comprises a current source amplifier connected to the loudspeaker, and a controller connected to the current source amplifier. The controller is configured to determine a target displacement of a diaphragm of the speaker driver based on a source signal for reproduction via the loudspeaker, determine a control current based on the target displacement of the diaphragm and a first physical model of the loudspeaker, and transmit a control current signal specifying the control current to the current source amplifier. The current source amplifier outputs the control current to drive the speaker driver based on the control current signal. An actual displacement of the diaphragm during the reproduction of the source signal is controlled based on the control current, via the control current signal.