Speaker Electrostatic Capacity Detection Using Stepped Center Pole
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing audio speakers face challenges in accurately detecting electrostatic capacity between electrodes due to noise interference from electromagnetic waves, static electricity, and mechanical vibrations, which affects sound quality, especially in low tone regions.
Innovation Solution
A speaker design featuring nonmetallic voice coil bobbins with first and second electrodes on the inner peripheral face, separated by a predetermined space, and a stepped portion on the center pole, where the first facing area increases and the second facing area decreases, allowing for accurate detection of electrostatic capacity through signal subtraction, with nonmagnetic electric conductor films laminated through an insulator film to reduce noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electrostatic capacity detection is performed using conventional electrodes, then the MFB circuit can detect diaphragm operation state, but the detection accuracy deteriorates due to noise from electromagnetic waves, static electricity, and mechanical vibrations
Solution Approach 1:
The patent divides the single electrode into two separate electrodes (first electrode and second electrode) positioned at different locations on the voice coil bobbin. This segmentation allows the system to detect electrostatic capacity changes at multiple positions, enabling noise cancellation by comparing the signals from both electrodes and eliminating common-mode noise interference.
Solution Approach 2:
The patent introduces a subtracter circuit as an intermediary component that processes the signals from the first and second electrodes. The subtracter calculates the difference between the two electrode signals, effectively eliminating common noise components (electromagnetic waves, static electricity, mechanical vibrations) while preserving the useful electrostatic capacity information related to diaphragm motion.
2Reliability
If the electrostatic capacity between electrodes is made larger to improve detection, then the signal strength increases, but the device complexity increases due to additional electrodes and signal processing
Solution Approach 1:
The patent implements a feedback mechanism where the subtracter circuit continuously processes the signals from both electrodes and feeds back the noise-canceled electrostatic capacity information to the MFB circuit. This feedback loop enables real-time compensation for noise interference without requiring additional complex hardware components.
Solution Approach 2:
The patent changes the detection parameter from measuring absolute electrostatic capacity at a single point to measuring the difference in electrostatic capacity between two points. This parameter transformation allows the system to maintain high signal reliability while using only two simple electrodes and a subtracter circuit, avoiding the need for complex multi-electrode arrays.
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 design effectively cancels disturbance noise and enhances the detection of true electrostatic capacity, improving sound quality by reducing distortion, particularly in low tone regions, and increasing the reliability of the output signal.
Implementation Method 1
detecting an electrostatic capacity that is formed between the electrodes and the center pole
Implementation Method 2
nonmagnetic electric conductor films which are laminated through an insulator film for reducing noise
Implementation Method 3
a diaphragm is commonly structured to be vibrated by an excitation effect between a voice coil bobbin, an iron core which is inserted into the voice coil bobbin and referred to as a center pole, and a magnet which generates a magnetic flux passing through the voice coil bobbin and the center pole
Data Source
AI summary
A speaker may include a center pole, a voice coil bobbin having a nonmetallic pipe body, and a first and a second electrodes which are provided on an inner peripheral face of the pipe body for detecting an electrostatic capacity. The first and the second electrodes are disposed so as to be separated from each other with a predetermined space along an axial direction of the center pole. Further, a stepped portion may be formed in the side circumferential face of the center pole such that, when the voice coil bobbin is operated, a first facing area of the first electrode to the side circumferential face defined by the stepped portion of the center pole increases while a second facing area of the second electrode to the side circumferential face defined by the stepped portion of the center pole decreases by a same amount as an increased amount of the first facing area.