Hybrid Magnetic-Piezo Speaker Drive With One Audio Amplifier
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Solution Overview
Problem
Existing sound production methods in portable electronic devices face challenges in achieving a suitable combination of small size, good efficiency at all audio frequencies, and affordable controlling electronics, particularly with piezoelectric vibrators requiring high voltage amplifiers.
Innovation Solution
A common audio amplifier is used to drive both a magnetic and a piezoelectric vibrator, with the magnetic vibrator generating low-frequency vibrations and the piezoelectric vibrator generating high-frequency vibrations, utilizing their complementary frequency properties without frequency division filtering, and optionally using a filter bank and limiting impedance to protect the amplifier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a piezoelectric vibrator is used for sound production, then high-frequency sound efficiency is improved, but the controlling electronics become complex and expensive due to high voltage amplifier requirements
Solution Approach 1:
The patent combines a magnetic vibrator and a piezoelectric vibrator into a single sound production system, where the magnetic vibrator handles low-frequency sounds and the piezoelectric vibrator handles high-frequency sounds. This merging allows the system to achieve high-frequency efficiency while using a common audio amplifier, avoiding the need for separate high voltage amplifiers and reducing electronic complexity.
Solution Approach 2:
The common audio amplifier serves multiple functions by driving both the magnetic vibrator and the piezoelectric vibrator simultaneously. This multi-functionality eliminates the need for specialized high voltage amplifiers, simplifying the controlling electronics while maintaining efficient sound production across the full audio frequency range.
2Device complexity
If a magnetic vibrator is used for sound production, then the electronics remain simple and affordable, but efficiency at high audio frequencies deteriorates
Solution Approach 1:
The patent segments the audio frequency range by assigning different vibrators to different frequency bands: the magnetic vibrator handles low-frequency sounds where it excels, and the piezoelectric vibrator handles high-frequency sounds where it provides superior efficiency. This segmentation allows each component to operate in its optimal range, achieving overall high-frequency efficiency while keeping the electronics simple through the use of a common amplifier.
3Productivity
If piezoelectric material is used without metal support, then the piezoelectric properties are maximized, but the material becomes fragile and difficult to manufacture
Solution Approach 1:
The patent uses composite material structure by combining piezoelectric material with a metal strip support. The metal strip provides mechanical strength and ease of manufacturing, while the piezoelectric material maintains its functional properties. This composite approach allows the piezoelectric vibrator to be both efficient and manufacturable, resolving the contradiction between maximizing piezoelectric properties and ensuring structural integrity.
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 approach achieves efficient sound production across all audio frequencies with compact components, reducing the need for high voltage amplifiers and simplifying the electronics, while maintaining sound quality and reliability.
Implementation Method 1
The vibrations are generated by supplying an electrical signal to the induction coil, whereby its varying magnetic field together with the fields of the permanent magnets generates forces that displace the parts of the magnetic vibrator relative to each other
Implementation Method 2
An electrical signal supplied to the piezoelectric material causes in the material quick, reversible deformations, which cause the cover part to vibrate all over so as to function as an acoustic element
Data Source
AI summary
An arrangement for producing sound in an electronic device comprises a magnetic vibrator comprising a first part and a second part provided with permanent magnets, and at least one induction coil. The arrangement further comprises a piezoelectric vibrator comprising piezoelectric material for generating audio-frequency vibrations resulting from deformations of the material by supplying to said material a second electrical signal. The magnetic vibrator and the piezoelectric vibrator have a common audio amplifier. Said first and second electrical signal are supplied from the same audio output to the magnetic vibrator and the piezoelectric vibrator.