The technology of Vibrating Mesh Nebulizer (VMN) is an advanced aerosol delivery method that uses high-frequency vibration to push liquid through a precise micro-perforated mesh, creating a fine, inhalable mist.
It is highly regarded for its efficiency and gentle treatment of sensitive drugs. And it is also widely used for scent diffusing and humidifiers, with combination to other functionalities like hair dryer, window cleaner, toys, and vapes.
As the core functioning material, the high-speed vibrating of piezoelectric disc is achieved only when it is driven by an analog signal of specific voltage, frequency, and waveform that is generated by the driver board.
Therefore, one of the challenges of designing a vibrating mesh nebulizer is to generate an adequate and reliable driving signal, as required to drive a corresponding piezo mesh disk. As traditional LC oscillator circuit has large fluctuation of nebulizing rate, due to inevitable parameter variation from discrete components such as inductance.
The piezo mesh disk requires a high voltage waveform at a specific resonant frequency. The optimum frequency may vary device-to-device due to manufacturing tolerances. Further, the resonant frequency is changing as dynamic factor due to operating temperature, liquid difference and force/load on piezo disc etc. It is essentially needed for a control system to ensure the monitoring and matching to the desired dynamic resonant frequency. And the granularity of frequency-scanning/tuning is critical.
Proposal for chip model selectionIt’s for a while in the industry practice to use a common MCU (like fromTI, Microchip etc.)to handle the logic and control, combined with a boost stage and output stage/LC oscillator circuit.
In the light of above two critical factors, variation from discrete components of LC oscillator circuit and granularity of automatic frequency tuning, it is recommended to use LX8201 as chip model for VMN drive circuit.
The proposed solution is expected to have features as below:
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The LX8201 offers several features that are particularly advantageous for driving a VMN:
- Frequency Tracking: The chip incorporates a frequencytracking algorithm that automatically adjusts the output PWM frequency to match the resonant frequency of the atomizing piece. This compensates for manufacturing tolerances and frequency drift caused by temperature or load changes, ensuring optimal efficiency and consistent aerosol output. The patented algorithm can track and match the frequency with granularity <100HZ.
- Integrated Design and Protection: As a highly integrated solution, it requires minimal external components. It also includes built-in protections such as open-circuit and short-circuit detection for the atomizer, with a fast response time to prevent damage.
- Multiple Control Modes: There are several control modes, including standalone operation and slave mode, where a host MCU can start/stop atomization and receive alarm feedback via GPIO pins, offering flexibility in system design.
The typical specification it can cover for VMN as below:
Frequency Range: 90 kHz to 220 kHz
Max Output Power: 2 W
Max Drive Voltage (VP): 27 V
Max Drive Current (Is): 100 mA
Standby Current: < 20 µA
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Solution in detailAbove design with chip LX8201 works very well, and can well cover the VMN parameters including:
- Input voltage range: 3.3-5V
- Ware form: square waveform
- Frequency: 90-220kHZ (108KHZ withpiezo disc at 16mm diameter in the real case verification), automatic frequency sweeping & tuning
- Power: up to 2W
- Improved consistency of atomizing rate
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