Voice Coil Temperature Estimation via Pre-emphasis Filtering
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Solution Overview
Problem
Existing systems for monitoring the temperature of a voice coil in speakers face errors in estimating resistance due to limited quantization levels caused by bandwidth constraints in communication interfaces, leading to potential overheating issues.
Innovation Solution
A system that includes pre-emphasis and de-emphasis filters to enhance the dynamic range of current and voltage sense signals, allowing for more accurate quantization and transmission of pilot tone signals, which are then used to estimate the voice coil's resistance and temperature, thereby protecting the speaker from overheating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the sensed data is compressed to 8-bits due to bandwidth constraints, then the data transmission is feasible within bandwidth limits, but the quantization levels are reduced causing error in temperature estimation
Solution Approach 1:
The patent applies pre-emphasis filtering to the sensed data before quantization and transmission. This preliminary action boosts the pilot tone signal components in the frequency domain, ensuring that even after 8-bit compression, sufficient quantization levels remain to accurately represent the pilot tone and calculate temperature. The pre-emphasis is performed before the bandwidth constraint acts on the data.
Solution Approach 2:
The patent changes the frequency domain parameters of the sensed data by applying gain adjustments to specific frequency bands. The pre-emphasis filter modifies the spectral distribution of the quantized data, emphasizing frequencies corresponding to the pilot tone (e.g., 1-30 Hz) while de-emphasizing other frequencies. This parameter transformation allows accurate temperature estimation despite 8-bit compression.
2Measurement precision
If more quantization levels are allocated to represent the pilot tone signal, then the temperature estimation accuracy is improved, but the bandwidth requirement increases
Solution Approach 1:
The patent transforms the data parameters by applying pre-emphasis filtering that reshapes the frequency spectrum. This allows the system to maintain high measurement precision for the pilot tone signal while keeping the overall data volume suitable for 8-bit transmission. The frequency domain transformation concentrates the essential temperature information into specific spectral regions that can be efficiently represented with limited quantization levels.
Solution Approach 2:
The pre-emphasis filter acts as an intermediary processing step between sensing and transmission. It modifies the sensed data to prioritize the pilot tone components, allowing the system to achieve high measurement precision without requiring proportional increases in transmission bandwidth. The filter mediates between the need for accuracy and the constraint of limited data transmission capacity.
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
The system achieves high-resolution temperature estimation and accurate voice coil resistance measurement, reducing errors and effectively preventing overheating by increasing the number of quantization levels available for the pilot tone signal, ensuring precise control of the speaker's operating temperature.
Implementation Method 1
a first pre-emphasis filter which has an input coupled to receive the digitized current sense signal. The first pre-emphasis filter applies a gain to the signal components at the second frequency band and provides a pre-emphasized current sense signal
Implementation Method 2
a second pre-emphasis filter which has an input coupled to receive the digitized voltage sense signal. The second pre-emphasis filter applies a gain to the signal components at the second frequency band and provides a pre-emphasized voltage sense signal
Implementation Method 3
the temperature of a voice coil is estimated by determining the resistance of the voice coil at very low frequencies (e.g., 1-30 Hz). The resistance of the voice coil corresponds to its temperature
Data Source
AI summary
A system for determining the temperature of a voice coil of a speaker includes a first pre-emphasis filter which has an input coupled to receive a digitized current sense signal. The first pre-emphasis filter applies a gain to signal components at a selected frequency band and provides a pre-emphasized current sense signal. The system includes a second pre-emphasis filter which has an input coupled to receive a digitized voltage sense signal. The second pre-emphasis filter applies a gain to the signal components at the selected frequency band and provides a pre-emphasized voltage sense signal. The system includes a first quantizer module configured to map the pre-emphasized signal to a quantized current sense signal, and includes a second quantizer module configured to map the pre-emphasized voltage sense signal to a quantized voltage sense signal.