Research And Design Of A Non-contact System For Ultrasonic Decomposition

Taking advantage of thermal effect and cavitation, ultrasonic decomposition is widely applied in the fields of cell disruption, enzyme catalysis and other biomedical area in the recent years. However, when dealing with different biological samples, ultrasonic equipment has defects of simplex working state, bad adaptability to load and low processing efficiency; Changes of temperature and viscosity in biological samples lead to a drift of resonance frequency of load, therefore ultrasonic system will work in an inharmonic state. Under the circumstance, power consumption and heat generation will increase; Meanwhile, output amplitude will decrease. So the technology of ultrasonic biological decomposition has limitations in dealing with different samples.According to the defects of traditional ultrasonic power supply and new requirements of ultrasonic biological decomposition, this paper takes the methods of direct digital synthesis, D class power amplifier, phase transformation and frequency tracking; Then a self-adaption ultrasonic decomposition system is designed to track the dynamic parameters. Taking advantage of ultrasonic cavitation and tube bath brings the system a character of non-contact and non-pollution. To adapt to different samples, technology of direct digital synthesis is applied to control output frequency in a relatively wide range. Adding D class power amplifier simplifies the main circuit of power inverter. Based on simulation and research of characteristics of transducer, features of physical change and multiple peaks of frequency are taken into consideration when samples of dynamic parameters is taken. By PI adjustment, rough positioning of range of resonance frequency is realized; accurate way of reducing value of phase difference associates with PI adjustment. The two ensure that the load works in a resonance state in a relatively shortest time. The intensity of work is controlled by amplitude adjustment circuit from 0 to 100% in 256 levels. The system reaches a resonance state by searching and reducing the phase difference between feedback voltage and current. Experiments shows that the self-adaption ultrasonic decomposition system has a power factor of 92% and reaches a maximum output value of 400 W.