| With such advantages as small droplets and uniform atomization, ultrasonic atomization has been widely used in cleaning, spraying, atomizing cultivation and other fields. However, as a key part of ultrasonic atomization system, the cost and efficiency of atomization nozzles should be taken into consideration. In order to design an ultrasonic atomization power supply with low cost and high efficiency, this paper presented an ultrasonic atomization nozzle driving circuit with class E resonant inverter and the 15 W, 60 kHz low-frequency ultrasonic atomization driving circuit was designed and built. Besides, the class-E resonant converter satisfied the feature of zero-voltage switching and the switch current and voltage waveforms did not occur simultaneously during the switching time period, which reduced the switching losses and achieved high efficiency. Additionally, the class E resonant converter can easily achieve DC to AC inverter just by a single power transistor, and can generate excellent high-frequency sinusoidal voltage. In this paper, the basic class-E resonant inverter merged with the series resonance equivalent circuit of nozzle was used to drive the ultrasonic atomizers. With the purpose of ensuring the consistency between the nozzle impedance and output impedance of the class-E resonant converter, realizing the impedance matching circuit and achieving higher efficiency of circuit.It was analyzed that the basic circuit structure, working principles and theoretical parameters of ultrasonic atomization driving circuit under the optimal working condition. At the same time, in order to verify whether the parameters designed are correct, whether the quality factor is reasonable, whether the choke inductor current ripple impact the circuit, this paper presented two methods of stead-state modeling, which obtained steady waveforms of each elements in circuit. The first method of the steady-state modeling was proposed in the time-domain, which established two different stead state equations according to different states of the power transistor and solved the initial conditions. With both initial states for the two different time intervals available, the currents and voltages of components under the steady-state condition can be expressed for one switching cycle. The second method of the steady-state modeling was proposed in frequency-domain, the active switch with on-resistance and off-resistance between on and off states can be considered as a time-dependent resistor, the impedances of other electronic components in the ultrasonic atomizing nozzle driving circuit with class E resonant inverter can be expressed in the frequency-domain. Therefore, the main power circuit can be equivalent to the special impedance network. The voltages and currents waveforms can be obtained with basic circuit laws in the frequency-domain. Finally, the voltages and currents waveforms in the time-domain can be obtained by using the inverse Fourier transform. The second method is not only suitable the optimal steady-state analysis, also applicable to non-tuned state analysis.Although the number of components in main power circuit of low-frequency ultrasonic power supply with the class-E inverter was few, components influence each other, which were responsible for completing a variety of functions. The theoretical value of the actual circuit parameters was not completely consistent with the ones which were under ideal conditions, thus might lead to the imperfect. This paper presented waveforms of voltage across the switch under non-ideal condition, and analyzed the causes of the malfunction of circuit. |
