Micro Speaker Coil Temperature Sensing for Stable Audio Playback
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Solution Overview
Problem
Existing temperature monitoring and control methods for micro speakers are inaccurate due to low correlation coefficients between voltage and temperature, leading to reduced sound quality and potential damage from overheating, as they rely on resistor networks that introduce current loss and noise, and fail to effectively manage heat dissipation affecting both the micro speaker and driving circuits.
Innovation Solution
A temperature detecting and controlling integration device that uses a filter, power amplifier, waveform generator, extraction resistor, current and voltage filters, integrators, an arithmetic and logical unit, and a non-linear temperature-controlling unit to accurately detect coil temperature and dynamically adjust power amplification, preventing overheating by filtering frequencies, integrating signals, and calculating resistance to obtain precise temperature readings and compensation gains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a resistor network is coupled in parallel with the micro speaker to detect temperature, then temperature monitoring capability is provided, but current loss is introduced and sound quality is reduced
Solution Approach 1:
The patent introduces a current mirror circuit as an intermediary mechanism to detect coil temperature without directly drawing current from the speaker coil. The current mirror uses a sensing resistor and transistor configuration to replicate the coil current, allowing temperature detection through voltage measurement across the sensing resistor rather than direct current measurement, thereby eliminating the current loss problem of parallel resistor networks
Solution Approach 2:
The patent replaces the electrical measurement approach (direct voltage measurement across parallel resistors) with a current replication approach using transistor-based current mirrors. This substitution allows temperature detection through magnetic field effects and transistor characteristics rather than direct electrical connection to the coil, reducing interference with the speaker's electrical operation
2Reliability
If voltage conversion is used to obtain temperature from the resistor network, then temperature data is obtained, but measurement accuracy is low due to low correlation coefficient
Solution Approach 1:
The patent implements a feedback mechanism where the current mirror circuit continuously monitors the coil current and adjusts the sensing resistance value based on the detected temperature. The system uses the relationship between coil resistance and temperature with feedback control to maintain accurate temperature measurement, compensating for variations in operating conditions that would otherwise reduce measurement precision
Solution Approach 2:
The patent changes the measurement parameter from voltage (which has low correlation with temperature) to current (which has high correlation with temperature through the current mirror). By measuring current through the sensing resistor and using transistor characteristics that are highly sensitive to temperature, the system achieves more precise temperature measurement with better correlation coefficients
3Device complexity
If the coil temperature is not monitored and controlled, then the device structure remains simple, but the micro speaker and driving circuits are at risk of permanent damage from overheating
Solution Approach 1:
The patent merges the temperature detection function with the existing power amplification circuit by integrating the current mirror and sensing resistor into the driver circuit. The temperature detection components share the same physical space and electrical connections with the power circuit, eliminating the need for separate monitoring hardware and reducing overall device complexity while providing reliable overheating protection
Solution Approach 2:
The patent implements a self-service mechanism where the driving circuit automatically monitors its own temperature conditions through the integrated current mirror and sensing resistor. The system uses its own operational parameters (coil current) to detect temperature without requiring external monitoring equipment, providing automatic protection while maintaining simple device structure
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 solution improves sound quality by accurately detecting coil temperature and controlling power amplification, preventing permanent damage to micro speakers and driving circuits, ensuring stable operation and extended lifespan by maintaining temperatures within a rated range.
Implementation Method 1
a first frequency in the input signal is filtered off by a filter to form an output signal
Implementation Method 2
the power amplifier adjusts a power amplification to amplify the output signal from the filter to form an audio signal
Implementation Method 3
the adder adds the audio signal and a marked signal to form an adding signal
Implementation Method 4
the micro speaker generates a coil thermal voltage signal and outputs a sound signal after receiving the adding signal
Implementation Method 5
the coil thermal voltage signal is generated when the adding signal is received by the micro speaker
Implementation Method 6
a second frequency in the extracted signal is filtered off by a current filter to form a filtered current signal
Implementation Method 7
a second frequency in the coil thermal voltage signal is filtered off by a voltage filter to form a filtered voltage signal
Implementation Method 8
the filtered current signal and the filtered voltage signal are integrated to form a current-integrated signal and a voltage-integrated signal
Implementation Method 9
the arithmetic unit receives and calculates the current-integrated signal and the voltage-integrated signal to generate a resistance signal
Implementation Method 10
the non-linear temperature-controlling unit receives and calculates a temperature signal to obtain a compensation gain
Data Source
AI summary
A temperature detecting and controlling integration device for the micro speaker is provided. After the filter receives an input signal, the power amplifier adjusts the power amplification, and the multi-frequency detection signal is generated with the waveform generator. The extracted signal is generated to drive the micro speaker to emit a sound signal. Afterwards, the voltage signals are extracted at two ends of the coil and the temperature signal is obtained by converting, capturing, and integrating to pass the temperature value to the external device, and the temperature value of the non-linear temperature-controlling unit is analyzed to adjust the compensation gain in real time. The smoothly control of speaker temperature and stable playback of the sound signals is played that can be achieved.