Loudspeaker Flux-Based Current Control for Nonlinear Distortion
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Solution Overview
Problem
Moving coil acoustic transducers experience significant distortion as they increase acoustic output, leading to undesirable size, weight, cost, and inefficiency, particularly in automotive applications, where higher output and lower distortion are needed for active noise cancellation and other audio applications.
Innovation Solution
An active sensor-less, low machine instructions per second (MIPS) algorithm and model for correcting non-linear behavior in loudspeakers using moving coil transducers, which predicts the voice coil position and generates corrected current signals to compensate for distortion caused by diaphragm suspension and voice coil motor, compatible with automotive hardware.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If moving coil acoustic transducers increase acoustic output, then power and sound output are improved, but distortion increases and device complexity increases
Solution Approach 1:
The system uses feedback control by measuring the actual voice coil position (through current measurement and model-based position estimation) and comparing it with the desired position, then adjusting the drive signal to compensate for non-linearities. The controller generates corrected drive signals that account for the non-linear relationship between current and position, effectively reducing distortion while maintaining high acoustic output.
Solution Approach 2:
The system changes the operating parameters dynamically by adjusting the drive current based on the predicted voice coil position and non-linear characteristics. The model predicts position as a function of current, and the controller modifies the current parameter in real-time to compensate for non-linear behavior, allowing high power output with reduced distortion.
2Power
If moving coil acoustic transducers increase acoustic output, then power is improved, but device size and weight increase
Solution Approach 1:
The system achieves higher acoustic output from a smaller, lighter transducer by dynamically changing the drive parameters. The model-based control optimizes the current waveform to compensate for non-linearities, allowing a compact transducer design to deliver high power output without requiring larger magnetic structures or heavier components.
3Power
If moving coil acoustic transducers increase acoustic output, then power is improved, but manufacturing cost increases
Solution Approach 1:
The system achieves high power output through software-based parameter optimization rather than hardware upgrades. By implementing model-based control that adjusts drive currents to compensate for non-linearities, the system delivers high acoustic output from standard, cost-effective transducer components, avoiding the need for expensive precision-manufactured hardware.
4Power
If moving coil acoustic transducers increase acoustic output, then power is improved, but efficiency decreases
Solution Approach 1:
The system improves efficiency through feedback control that optimizes the drive signal based on actual transducer behavior. By measuring current and using the model to predict position, the controller adjusts the drive signal to operate the transducer in its most efficient range, reducing energy losses from non-linear effects and improving the conversion efficiency from electrical to acoustic power.
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 improved control over transducer displacement and excursion, enabling higher output while reducing size, weight, and cost, and enhances performance in applications like active noise cancellation and echo cancellation by minimizing non-linear distortion.
Implementation Method 1
determine a flux density value for the loudspeaker... The flux density value corresponds to a product of magnetic flux of an air gap for the voice coil in the loudspeaker and a length of a voice coil wire in the loudspeaker
Data Source
AI summary
In at least another embodiment, an audio amplifier system including the memory and the audio amplifier is provided. The audio amplifier includes the memory and is programmed to receive an audio input signal and to generate a target current signal based on the audio input signal and a velocity of a diaphragm of a loudspeaker. The audio amplifier is further programmed to generate a corrected current signal based at least on the target current signal and on a predicted position of a voice coil of the loudspeaker and determine the predicted position of the voice coil of the loudspeaker based on a flux density value. The flux density value corresponds to a product of magnetic flux of an air gap for the voice coil in the loudspeaker and a length of a voice coil wire in the loudspeaker.