Dynamic Pilot Tone Throttling for Voice Coil Thermal Monitoring
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Solution Overview
Problem
Current consumer electronic devices with internal speakers face challenges in monitoring voice coil temperature effectively, leading to potential magnet overheating and demagnetization, which can cause structural damage.
Innovation Solution
A system and method that injects a dynamic pilot tone into the audio path to measure voltage and current signals, allowing for resistance estimation and temperature monitoring of the voice coil, with the pilot tone level adjusted based on temperature or power estimates to maintain safe output levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a static pilot tone is injected into the audio path for thermal monitoring, then the temperature measurement capability is provided, but the measurement precision deteriorates due to varying audio signal levels affecting the pilot tone signal-to-noise ratio
Solution Approach 1:
The patent applies dynamics by transitioning from a static pilot tone to a dynamic pilot tone whose level is adjusted in real-time based on the audio signal level. The system continuously monitors the audio signal level and modifies the pilot tone amplitude accordingly, ensuring optimal signal-to-noise ratio across varying operating conditions. This dynamic adaptation resolves the contradiction by making the pilot tone responsive to changing signal conditions rather than fixed.
Solution Approach 2:
The system implements feedback by using the detected audio signal level to control the pilot tone level. The audio signal level information is fed back to the pilot tone generator, which adjusts the pilot tone amplitude based on this feedback. This closed-loop control ensures that the pilot tone maintains adequate signal-to-noise ratio regardless of the audio signal level, thereby improving temperature measurement precision.
2Measurement precision
If the pilot tone level is increased to improve temperature monitoring accuracy, then the measurement precision improves, but the power consumption increases and may cause additional heating of the voice coil
Solution Approach 1:
The system uses dynamics by adjusting the pilot tone level adaptively rather than maintaining a fixed high level. The pilot tone generator modifies the pilot tone amplitude in real-time based on the audio signal level and temperature conditions. When audio signal level is high or temperature is low, the pilot tone level is reduced, minimizing power consumption and additional heating. When audio signal level is low or temperature monitoring accuracy is critical, the pilot tone level is increased appropriately.
Solution Approach 2:
The patent applies parameter changes by varying the pilot tone level parameter dynamically based on operating conditions. The system changes the pilot tone amplitude parameter in response to audio signal level and temperature measurements, optimizing the balance between measurement accuracy and power consumption. This parameter adaptation allows the system to use minimal pilot tone power when conditions permit and increase power only when necessary for accurate monitoring.
3Reliability
If continuous temperature monitoring is performed using a constant pilot tone, then the reliability of thermal protection is improved, but the device complexity increases due to continuous signal processing requirements
Solution Approach 1:
The system applies periodic action by updating the pilot tone level at discrete intervals based on audio signal level measurements rather than continuously adjusting it. The pilot tone generator periodically reassesses the audio signal level and modifies the pilot tone amplitude accordingly. This periodic update approach maintains reliable temperature monitoring while reducing the continuous signal processing burden compared to fully continuous adjustment.
4Device complexity
If the pilot tone is injected at a fixed level, then the device complexity is minimized, but the measurement precision deteriorates under varying audio signal conditions
Solution Approach 1:
The system applies self-service by having the pilot tone generator automatically adjust its own output level based on the audio signal level it detects. The pilot tone generation circuit monitors the audio signal and self-regulates the pilot tone amplitude without requiring external control. This self-adjusting mechanism improves measurement precision across varying conditions while adding minimal complexity compared to fixed-level operation.
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 enables precise temperature monitoring of the voice coil, preventing overheating and ensuring the integrity of the speaker by dynamically adjusting the pilot tone levels in response to temperature thresholds, thus extending the lifespan of the magnet and maintaining audio quality.
Implementation Method 1
current is applied to the speaker driver which causes the voice coil to generate heat
Implementation Method 2
process the measured voltage and current signals of the speaker to determine the resistance estimate of the voice coil
Implementation Method 3
resistance estimate of the voice coil, which is then converted to the temperature of the voice coil
Data Source
AI summary
Method of throttling a pilot tone for thermal monitoring of an electro-mechanical actuator starts by computing a power estimate based on a driving signal. A first temperature estimate is then computed based on the power estimate. The pilot tone may be generated by adjusting a level of the pilot tone based on at least one of the power estimate or the first temperature estimate. The pilot tone is injected into the driving signal to generate a driving output signal that is outputted by an electro-mechanical actuator. Other embodiments are also described.