Voice Coil Temperature Control via Heat Transfer Model
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Solution Overview
Problem
Audio output apparatuses face overheating issues due to rapid temperature changes in voice coils, leading to potential damage and errors in temperature control, which can result in delayed gain adjustments and risk of overheating.
Innovation Solution
An audio output apparatus and method that uses a heat transfer model algorithm to calculate voice coil temperature and adjust output levels by determining gain values based on threshold intervals, ensuring the voice coil operates within safe temperature ranges and maintaining sound quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the audio output apparatus operates at high output level for a long period, then the output level is maintained, but the voice coil temperature increases to melting point causing damage
Solution Approach 1:
The system performs preliminary temperature estimation using a heating model algorithm before the voice coil actually reaches dangerous temperatures. By continuously monitoring power supply levels and estimating temperature trends in advance, the control system can proactively adjust gain values to prevent overheating, rather than waiting for temperature sensors to detect actual high temperatures.
Solution Approach 2:
The system implements a feedback control mechanism where the estimated voice coil temperature is continuously fed back to adjust the gain value. When the estimated temperature approaches the melting point of the coating layer, the system automatically reduces the gain to decrease power input, creating a closed-loop control that maintains temperature within safe operating limits while preserving maximum possible output level.
2Temperature
If the voice coil temperature is rapidly decreased when audio signal is not input, then cooling occurs, but the permanent magnet temperature lags causing error in temperature estimation
Solution Approach 1:
The system dynamically changes the thermal parameters in the heating model algorithm based on the operational state. When the audio signal is not input and the voice coil is cooling rapidly, the system adjusts the thermal capacity parameters to account for the different cooling rates of the voice coil versus the permanent magnet. This allows accurate temperature estimation even during rapid transient conditions where the two components are at different temperatures.
Solution Approach 2:
The temperature estimation system is made dynamic by continuously updating the thermal model parameters based on real-time operating conditions. During rapid cooling phases, the system adapts the thermal time constants to reflect the asymmetric cooling behavior between the voice coil and permanent magnet, allowing the estimation algorithm to track actual temperatures accurately despite the lag between components.
3Productivity
If power is re-supplied to the voice coil in a state where it has higher temperature than room temperature, then operation resumes, but the error in temperature estimation delays control timing causing risk of overheating
Solution Approach 1:
When power is re-supplied to the voice coil, the system immediately initiates preliminary temperature estimation using the heating model algorithm with initial conditions based on the previous operating state. This preliminary estimation occurs before any significant temperature change takes place, allowing the control system to establish appropriate gain values proactively and prevent overheating from the moment operation resumes, rather than waiting for temperature to actually rise.
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
Effectively controls voice coil temperature, preventing overheating and maintaining sound quality by adjusting output levels based on calculated temperature values, thereby reducing the risk of damage and ensuring stable operation.
Implementation Method 1
Electric current is introduced to a voice coil wound around a vibrating plate that transmits vibration to the atmosphere, and a temperature of the voice coil is increases with the introduction of electric current
Implementation Method 2
The heat capacity of the permanent magnet provided to generate vibration in response to electric current flowing on voice coil is about 200 times greater than that of the voice coil
Data Source
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AI summary
An audio output apparatus and a method are provided, which includes calculating (S920) a temperature value of a voice coil of the audio output apparatus using a heat transfer model algorithm, in response to power being supplied to the voice coil; adjusting (S930) an output level of an audio signal by determining a gain value to adjust the output level of the audio signal according to the calculated voice coil temperature value, and outputting (S940) the audio signal with the adjusted output level.