Multi-Transducer Thermal Control Using Individual Coil Estimation
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Solution Overview
Problem
Conventional methods fail to accurately determine the individual coil temperatures of multiple transducers driven by a single amplifier, leading to inadequate thermal protection and potential damage due to overheating.
Innovation Solution
A system and method that includes a temperature estimator and thermal control subsystem to monitor physical quantities of multiple transducers, estimate individual coil temperatures, and adjust the output signal to prevent overheating by applying attenuation or power limiting based on these estimates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single amplifier drives multiple transducers in parallel, then the device complexity is reduced and power efficiency is improved, but the measurement precision of individual transducer temperatures is lost
Solution Approach 1:
The patent segments the measurement process by injecting distinct pilot tones at different frequencies to each transducer through the shared amplifier. The processing system then separates and analyzes the response signals at these specific frequencies to calculate individual coil resistances and temperatures for each transducer, enabling precise individual measurement despite the shared amplification path.
Solution Approach 2:
The patent introduces pilot tones as intermediary signals that carry identification information through the shared amplifier system. These pilot tones act as mediators that allow the processing system to distinguish between different transducers and their thermal states, enabling individual temperature monitoring without requiring separate amplifiers.
2Ease of operation
If conventional voltage and current monitoring is used, then the ease of operation is maintained, but the reliability of thermal protection is insufficient for multiple transducers
Solution Approach 1:
The patent implements feedback by continuously monitoring the transducer responses to injected pilot tones and using this information to calculate real-time coil temperatures. The system uses this temperature feedback to dynamically adjust the drive signals and apply thermal protection to individual transducers, ensuring reliable operation while maintaining ease of use through automated control.
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 prevents thermal damage to multiple transducers by accurately estimating and controlling their temperatures, ensuring safe operation and extending the lifespan of the devices.
Implementation Method 1
A processing system may then monitor voltage and current signal feedback from the transducer (e.g., via analog-to-digital converters), and from such monitored voltage and current feedback, calculate resistance of a coil of the transducer. The calculated resistance Re may then be mapped directly to coil temperature through the following linear relationship: T=Tamb+α(Remeasured−Recal)
Implementation Method 2
a single amplifier driving a dual audio transducer comprising a woofer (for playback of audio at lower audible frequencies) and a tweeter (for playback of audio at higher audio frequencies) in parallel
Implementation Method 3
One common failure mode for over-driven transducers (e.g., speakers/haptics) is thermal damage. As an example, for speakers, if the voice coil exceeds a maximum temperature, the glues that hold the voice coil together and connect it to the diaphragm can melt and cause irreparable damage.
Data Source
AI summary
An audio system may include a plurality of transducers, a temperature estimator, and a thermal control subsystem. The temperature estimator may be configured to monitor physical quantities associated with a plurality of transducers and based on the physical quantities, determine an estimated temperature associated with a first transducer of the plurality of transducers. The thermal control subsystem may be configured to generate an output signal based on an input signal, the output signal for driving the plurality of transducers and control the output signal based on the estimated temperature.