Capacitive Sensing in Micro-Speakers with Inset Plate
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Solution Overview
Problem
Micro-speakers in consumer electronics face reliability issues due to wire breakage from flexing during sound production, limiting their audio performance and durability, especially in compact devices like smartphones and laptops.
Innovation Solution
A micro-speaker design featuring a flexible circuit sound radiating surface with capacitive displacement sensing, using a voice coil made of low-tensile strength material and external wiring of higher tensile strength, connected via a flexible printed circuit board to minimize mechanical stress and enhance reliability and acoustic sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wires are used to connect the voice coil to external components, then electrical connections are established, but wire breakage occurs due to flexing during vibration
Solution Approach 1:
The patent replaces the mechanical wire connection system with a capacitive sensing system. Instead of using physical wires that flex and break during diaphragm vibration, the invention uses electrical fields to detect diaphragm position and transmit signals. The capacitive sensor detects changes in capacitance caused by diaphragm displacement, eliminating the need for flexible wire connections that are prone to breakage.
Solution Approach 2:
The patent introduces a capacitive sensor as an intermediary between the voice coil and external components. This sensor acts as a mediator that detects diaphragm position through electrical field changes rather than direct mechanical contact. The sensor includes a fixed electrode and a movable electrode that couples to the diaphragm, creating an intermediate detection mechanism that avoids the wire flexing problem.
2Measurement precision
If the second conductive plate is positioned close to the voice coil for capacitive sensing, then displacement detection sensitivity is improved, but parasitic capacitance increases
Solution Approach 1:
The patent applies local quality by creating an asymmetric capacitive sensing structure where the first capacitive sensor has a fixed electrode and the second capacitive sensor has a movable electrode that couples to the diaphragm. This local differentiation in electrode configuration allows the system to achieve both high sensitivity through close positioning and reduced parasitic capacitance through the specific movable electrode design that moves with the diaphragm.
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 design improves acoustic sensitivity, reduces parasitic capacitance, and enhances reliability by minimizing wire flexing and mechanical fatigue, resulting in improved audio performance and durability for compact electronic devices.
Implementation Method 1
a capacitive displacement sensor for sensing a movement of the sound radiating surface. The capacitive displacement sensor may include a first conductive plate fixedly positioned over the sound radiating surface and a second conductive plate coupled to the sound radiating surface
Implementation Method 2
The moving coil motor may include a diaphragm, voice coil and magnet assembly positioned within a frame. The input of an electrical audio signal to the moving coil motor causes the diaphragm to vibrate and output sound
Data Source
AI summary
A speaker assembly including a sound radiating surface suspended over a magnet assembly, a suspension member for suspending the sound radiating surface over the magnet assembly, a voice coil extending from a bottom side of the sound radiating surface, and a capacitive displacement sensor for sensing a movement of the sound radiating surface. The capacitive displacement sensor including a first conductive plate fixedly positioned over the sound radiating surface and a second conductive plate coupled to the sound radiating surface and vertically aligned with the first conductive plate, and wherein the second conductive plate is confined to an area that is entirely radially inward of the voice coil.