Loudspeaker Current Feedback Circuit for Distortion and Excursion Control
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Solution Overview
Problem
Conventional loudspeaker systems face challenges in producing high-quality sound with minimal distortion and excessive diaphragm displacement, often requiring expensive materials and enclosures, which can lead to damage, especially in micro-speakers.
Innovation Solution
A system comprising a speaker, an amplifier, a current sensor, and a compensator circuit that applies a transfer function matching the speaker's resistance and inductance to provide feedback and adjust the audio signal, reducing diaphragm displacement and tonal distortion while enhancing sound quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional loudspeaker systems use high-quality materials and properly designed enclosures to produce pleasant sounds, then sound quality is improved, but device cost and complexity increase
Solution Approach 1:
The patent applies pre-distortion to the audio signal, which changes the signal parameters (frequency components, amplitude) in advance to compensate for anticipated distortion. This allows conventional speakers to produce high-quality sound without requiring expensive enclosures or materials, as the distortion compensation is achieved through signal processing rather than physical design improvements
Solution Approach 2:
The patent replaces mechanical solutions (high-quality enclosures, specialized materials) with an electrical/electronic solution (pre-distortion signal processing). Instead of improving the physical speaker system to reduce distortion, the invention uses digital signal processing to pre-compensate for distortion, substituting mechanical complexity with electronic control
2Productivity
If loudspeakers operate at high power to increase sound volume, then productivity is improved, but diaphragm displacement increases causing damage
Solution Approach 1:
The patent applies pre-distortion to the audio signal before it reaches the speaker. This preliminary action modifies the signal characteristics in advance, allowing the speaker to operate at higher power levels for increased volume while the pre-applied distortion compensation prevents excessive diaphragm displacement and potential damage
3Manufacturing precision
If equalizers are used to tune sound waves for pleasant sounds, then sound quality is improved, but device complexity increases
Solution Approach 1:
The patent combines the distortion compensation function with the audio signal processing chain. Instead of adding separate equalizer components to tune sound quality, the pre-distortion is integrated into the existing audio processing path, achieving both distortion compensation and sound quality improvement through a unified signal processing approach
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 high-quality sound production with reduced diaphragm displacement, minimal distortion, and increased sound volume, allowing for the use of less expensive speakers and enclosures, while maintaining sound quality across the useful frequency range.
Implementation Method 1
The current sensor senses current passing through the speaker and provides a current sensor signal indicative thereof
Implementation Method 2
The audio signals are applied to the voice coil, which results in the diaphragm moving the cone back and forth at high speeds to create sound waves
Implementation Method 3
The compensator circuit applies a transfer function to the current sensor signal to provide a compensation signal as feedback into the analog audio input signal, the transfer function matching at least one of resistance and inductance of the speaker
Data Source
AI summary
A system for driving an audio speaker that has an impedance, the system comprising: a scaler having an analog input and a scaler output that is an attenuated analog input; an amplifier having an amplifier input coupled to the scaler output and an amplifier output; a current sensor having a sensor input coupled to the speaker and a sensor output, the current sensor configured to generate a sensor signal at the sensor output responsive to a current from the audio speaker; and a compensator circuit having a circuit input coupled to the sensor output and a circuit output coupled to the amplifier input, the compensator circuit configured to supply a compensation signal to the amplifier input by applying a transfer function to the sensor signal.