Loudspeaker Voice Coil Temperature Limiting via Input Signal Measurement
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Solution Overview
Problem
Speakers, particularly those in mobile devices, are prone to damage due to overheating caused by excessive power applied to their voice coils, with existing solutions either causing amplifier clipping or failing to account for individual tolerance and ambient temperature.
Innovation Solution
A system and method that directly measures the amplifier output signal to determine and control the temperature of the voice coil by using a sensing circuit, filters, a resistance estimator module, and a temperature estimator module to adjust the audio gain and prevent overheating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the voltage swing of the amplifier is limited to prevent voice coil overheating, then the speaker is protected from damage, but amplifier clipping occurs which degrades sound quality
Solution Approach 1:
The system continuously monitors the actual voice coil temperature through resistance measurement and feeds this information back to the audio processor. The audio processor then adjusts the audio signal in real-time based on the measured temperature, allowing the amplifier to operate at higher voltage swings without causing clipping, while still preventing voice coil overheating through adaptive control rather than static limiting
Solution Approach 2:
The system changes the operating parameters dynamically by adjusting the audio signal based on real-time voice coil resistance measurements. Instead of using a fixed voltage swing limit that causes clipping, the system adapts the audio parameters according to the actual temperature conditions, allowing maximum loudness operation while preventing overheating through continuous parameter adjustment rather than static limitation
2Reliability
If a speaker model is used to track speaker condition and estimate temperature, then temperature limiting can be applied, but the process is time-consuming and fails to account for individual speaker tolerance and ambient temperature
Solution Approach 1:
The system performs self-characterization by directly measuring the actual voice coil resistance and temperature during operation, rather than relying on pre-established models. The audio processor uses the measured resistance values to directly calculate temperature and determine power handling capabilities in real-time, eliminating the need for time-consuming model establishment while accurately accounting for individual speaker variations and ambient conditions through direct measurement
Solution Approach 2:
The system replaces the complex software-based speaker modeling approach with a direct physical measurement approach using resistance measurement circuits. Instead of using computational models to estimate temperature and power handling, the system directly measures the electrical resistance of the voice coil, which provides an immediate and accurate indicator of temperature and speaker condition, thereby eliminating model establishment time and improving accuracy
3Reliability
If existing temperature limiting solutions are used, then speaker protection is attempted, but they do not account for individual speaker tolerance and ambient temperature variations
Solution Approach 1:
The system implements continuous feedback by measuring the actual voice coil resistance during operation and using this information to adapt the audio signal processing in real-time. This feedback mechanism allows the system to account for individual speaker tolerance variations and ambient temperature conditions, as the measured resistance values directly reflect the actual speaker state under specific environmental conditions, enabling customized protection for each speaker unit
Solution Approach 2:
The system replaces generic model-based temperature estimation with direct electrical resistance measurement of the voice coil. This direct measurement approach inherently accounts for individual speaker tolerance variations and ambient temperature effects, as the resistance measurement reflects the actual physical state of the specific speaker unit being tested, thereby providing adaptive protection tailored to each speaker's actual characteristics and operating conditions
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
This approach effectively protects the speaker by ensuring the voice coil operates within safe temperature and resistance thresholds, preventing damage while maintaining sound quality and compatibility with various ambient conditions.
Implementation Method 1
a resistance estimator module that estimates a resistance of the voice coil based upon the measured voltage and current
Implementation Method 2
a temperature estimator module that calculates a temperature of the voice coil based upon the estimated resistance and power dissipation of the voice coil
Data Source
AI summary
Aspects of the disclosure pertain to a system and method for providing temperature limiting for a voice coil of a speaker. The system and method provide the aforementioned temperature limiting based upon monitoring (e.g., measurement) of an amplifier output signal provided to the speaker. Providing the aforementioned temperature limiting promotes improved protection for the speaker.