Piezoelectric Loudspeaker Resonance Tuning With Negative Capacitance
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Solution Overview
Problem
Existing loudspeakers face challenges in miniaturization due to increased resonant frequency, reduced bandwidth, and incompatibility with micro-fabrication methods, limiting their ability to reproduce all audio frequencies with low distortion and requiring hermetic cavities.
Innovation Solution
An electromechanical device with adjustable capacitance, utilizing piezoelectric layers and an electrical circuit with negative capacitance, allows for variable resonant frequency adjustment, compatible with micro-fabrication techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If miniaturization is applied to loudspeakers, then the size is reduced for portable devices, but the resonant frequency increases and bandwidth is reduced
Solution Approach 1:
The patent implements a variable resonant frequency electromechanical device that can dynamically adjust its resonant frequency through electrical control. This allows the loudspeaker to adapt its mechanical resonance characteristics in real-time, enabling it to maintain broad frequency bandwidth coverage even in miniaturized form by shifting resonance away from problematic frequency ranges.
Solution Approach 2:
The invention changes the resonant frequency parameter of the electromechanical device through electrical control of the variable resonant frequency circuit. This parameter adjustment capability allows the miniaturized loudspeaker to optimize its frequency response characteristics dynamically, compensating for the bandwidth limitations imposed by small size and rigid membrane structures.
2Reliability
If a hermetic cavity is used to avoid destructive interference, then acoustic performance is improved, but the apparent stiffness increases and resonant frequency increases
Solution Approach 1:
The patent employs a dynamic resonant frequency adjustment mechanism that allows the system to adapt to the stiffness introduced by the hermetic cavity. By variable resonant frequency control, the loudspeaker can compensate for the cavity-induced stiffness increase and maintain optimal frequency response across the audio band.
3Volume of moving object
If membrane surface area is reduced for miniaturization, then device size is reduced, but large displacement is necessary to achieve satisfactory pressure level
Solution Approach 1:
The variable resonant frequency electromechanical device dynamically adjusts its mechanical resonance characteristics to optimize displacement efficiency. By controlling the resonant frequency, the system can achieve larger effective displacement from the miniaturized membrane without requiring excessive mechanical travel, thereby maintaining satisfactory pressure levels in compact form.
4Ease of operation
If electromagnetic transduction is used to achieve large displacements, then performance is improved, but dimensions are incompatible with portable systems and micro-fabrication
Solution Approach 1:
The patent replaces traditional electromagnetic transduction with an electret-based electromechanical transduction system. This substitution eliminates the need for bulky permanent magnets while maintaining effective displacement capability through electret field control, enabling compatibility with miniaturized portable devices and micro-fabrication processes.
Solution Approach 2:
The invention changes the transduction mechanism from electromagnetic to electret-based, fundamentally altering the physical principles involved. This parameter change in the transduction method allows for significant size reduction while preserving the essential displacement function required for audio reproduction in portable devices.
5Ease of manufacture
If piezoelectric transduction is used for micro-fabrication compatibility, then manufacturing is improved, but displacement is not as large as electromagnetic transduction
Solution Approach 1:
The patent implements variable resonant frequency control in the electret-based electromechanical device to optimize displacement output. This dynamic adjustment capability compensates for the inherently smaller displacement of piezoelectric-like transduction mechanisms, achieving satisfactory pressure levels while maintaining micro-fabrication compatibility.
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 loudspeakers to reproduce all audio frequencies with low distortion by dynamically adjusting resonant frequency, compatible with miniaturized devices like mobile phones and tablets.
Implementation Method 1
a first piezoelectric layer, said first layer being disposed on a first part of the movable mechanical element so as to be able to actuate said movable mechanical element
Implementation Method 2
a second piezoelectric layer, said second layer being disposed on a second part of the movable mechanical element, distinct from the first part, so as to be able to convert mechanical energy associated with the movement of the movable mechanical element into electric energy
Data Source
AI summary
An electromechanical device includes at least one movable mechanical structure including at least one movable mechanical element; for each movable mechanical element of each movable mechanical structure a first piezoelectric layer, the first layer being disposed on a first part of the movable element so as to be able to actuate the movable mechanical element, and a second piezoelectric layer, the second layer being disposed on a second part of the movable element, distinct from the first part, so as to be able to convert mechanical energy associated with the movement of the movable mechanical element into electric energy, the layer forming a capacitance; the device further including an electrical circuit connected to the second piezoelectric layer in parallel with the capacitance formed by the layer and including an adjustable capacitance which can assume a negative value.