Speaker Coil Temperature Sensing With DC Bias Protection
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Solution Overview
Problem
Conventional temperature measurement methods for coils in sound signal converting devices require detecting both voltage and current, leading to complex circuits and potential excessive temperature rises due to high current usage, which can cause abnormal conditions and burnout.
Innovation Solution
A temperature measurement apparatus with a constant voltage source circuit and current value extracting circuit, or a constant current source circuit and voltage value extracting circuit, that allows for simple temperature measurement of the coil by applying a predetermined voltage or current, respectively, without affecting sound signals, and includes a protection mechanism to prevent excessive temperature rises.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a large amount of current is fed into the coil to vibrate the sound board, then the sound output is improved, but the temperature of the coil rises excessively causing abnormal conditions and burnout
Solution Approach 1:
The patent applies preliminary action by measuring the coil temperature before it reaches dangerous levels. The temperature measurement apparatus continuously monitors the coil temperature and the control unit preemptively adjusts the driving current or shuts down the coil before excessive temperature rise occurs, preventing burnout while maintaining optimal sound output power
Solution Approach 2:
The patent implements feedback control by using the temperature measurement apparatus to continuously monitor coil temperature and feeding this information back to the control unit. The control unit then adjusts the driving current based on the temperature feedback, creating a closed-loop system that maintains both high sound output and safe operating temperatures
2Measurement precision
If both voltage and current are detected to measure coil temperature, then temperature measurement accuracy is improved, but the circuit complexity increases
Solution Approach 1:
The patent applies the extraction principle by removing the voltage detection component from the temperature measurement system. Instead of detecting both voltage and current, the invention only detects the current passing through the coil and uses this single measurement to calculate temperature, thereby simplifying the circuit while maintaining measurement accuracy
Solution Approach 2:
The patent applies self-service by using the existing current detection circuit (already present for other purposes in the sound signal converting device) to provide the data needed for temperature measurement. The system leverages its own existing resources rather than adding separate detection circuits, reducing overall complexity
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
Enables accurate and efficient temperature measurement of the coil with a simple configuration, reducing power consumption and preventing abnormal conditions and burnout by interrupting or reducing coil energization when temperatures exceed a predetermined level.
Implementation Method 1
a constant voltage source circuit (21) connected to an input side of the coil (16) to apply a DC voltage having a predetermined voltage value to the coil (16); a current value extracting circuit (25, 26) connected to the coil (16) to extract a signal indicative of a value of direct current passing through the coil (16)
Implementation Method 2
obtaining a temperature of the coil (16) by use of the predetermined voltage value and the signal extracted by the current value extracting circuit (25, 26)
Data Source
AI summary
An audio signal output from a tone generator is fed into a coil provided in a transducer for vibrating a sound board, so that a sound signal is generated by the vibration of the sound board. A predetermined DC voltage supplied by a constant voltage source circuit is superimposed on the audio signal by an adding circuit, so that the superimposed signal is fed into the coil. A current passing through the coil is sensed by a current sensing resistor, so that only a DC voltage component of a voltage signal on the both ends of the resistor is extracted by a low-pass filter circuit to be supplied to a microcomputer via an A/D converting circuit. The microcomputer figures out a resistance value and a temperature of the coil by use of the DC voltage component and the certain DC voltage value.