Loudspeaker Coil Resistance Sensing for Ambient Temperature Estimation
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Solution Overview
Problem
Existing ambient temperature sensing methods for electronic devices are often complex, inaccurate, and unreliable, particularly in portable devices where dedicated temperature sensors are costly and have long response times due to their design.
Innovation Solution
A circuit and method utilizing a loudspeaker's thermal model to determine ambient temperature by calculating the overall temperature of the loudspeaker or amplifier and subtracting the temperature change caused by power dissipation, allowing for ambient temperature estimation without a dedicated temperature sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a dedicated temperature sensor is used for ambient temperature sensing, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The loudspeaker is made to serve dual functions: audio output and ambient temperature sensing. By measuring the DC resistance of the loudspeaker coil, which varies with temperature, the same component performs both acoustic and thermal sensing roles, eliminating the need for a dedicated temperature sensor and reducing device complexity
Solution Approach 2:
The loudspeaker's own electrical properties (DC resistance) are utilized for temperature measurement. The system uses the loudspeaker's inherent characteristic that its coil resistance changes with temperature, allowing the component to sense its own temperature state without requiring external sensing infrastructure
2Measurement precision
If a dedicated temperature sensor is used for ambient temperature sensing, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The loudspeaker serves dual purposes as both audio output device and temperature sensor, eliminating the need to manufacture and assemble separate temperature sensing components, thereby reducing manufacturing cost
Solution Approach 2:
The solution uses the existing loudspeaker component that is already present in the device for its primary audio function, rather than adding expensive dedicated temperature sensing components. The loudspeaker's electrical properties are leveraged for free temperature measurement
3Measurement precision
If a dedicated temperature sensor is used for ambient temperature sensing, then measurement accuracy is improved, but response time increases
Solution Approach 1:
The loudspeaker measures its own temperature through its coil resistance in real-time during normal operation. Since the loudspeaker is already present and operational in the device, it can immediately provide temperature data without the thermal mass and response time delays associated with dedicated temperature sensors
4Device complexity
If the loudspeaker's overall temperature is measured to determine ambient temperature, then simplicity is improved, but measurement accuracy deteriorates due to power dissipation effects
Solution Approach 1:
The temperature measurement is divided into two components: the overall temperature of the loudspeaker and the temperature change due to power dissipation. By separately determining these two components and subtracting the power dissipation effect, the ambient temperature can be accurately derived from the loudspeaker's temperature
Solution Approach 2:
The system uses feedback from the loudspeaker's electrical characteristics (DC resistance measurements) to continuously monitor and adjust the temperature calculation. By measuring the coil resistance at different states and using the known relationship between resistance and temperature, the system can compensate for power dissipation effects and accurately determine ambient temperature
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 simplifies and enhances the accuracy of ambient temperature sensing in electronic devices, particularly in portable electronics, by leveraging the loudspeaker's thermal dynamics to provide a reliable and efficient method for ambient temperature measurement.
Implementation Method 1
the DC resistance of a loudspeaker coil and circuitry arranged to determine the overall temperature of the loudspeaker based on the DC resistance of the loudspeaker coil
Implementation Method 2
determine a change in temperature of the loudspeaker or the amplifier resulting from power dissipated in the loudspeaker or the amplifier
Data Source
Figure 1
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AI summary
A circuit and method for determining an ambient temperature for an electronic device having a loudspeaker are described. An amplifier drives the loudspeaker and first circuitry is configure to determine an overall temperature of the loudspeaker or the amplifier. Second circuitry is configured to determine a change in temperature of the loudspeaker or the amplifier resulting from power dissipated in the loudspeaker or the amplifier. Third circuitry is configured to subtract a signal representative of the change in temperature from a signal representative of the overall temperature and output a signal representative of the ambient temperature for the electronic device.