Design And Research Of Ultrasonic Power Supply Based On Dynamic Impedance Matching

With the development of power electronic technology, ultrasonic technology has played an important role in the processing, cleaning, medical and other fields. While the ultrasonic power supply is the key technology of ultrasonic application, the impedance matching of ultrasonic power supply is always the key point of the research. Traditional ultrasonic power supply mostly uses static impedance matching, it makes ultrasonic power supply can’t adjust the matching network parameters when the resonance frequency drift, and it will bring some adverse consequences such as the efficiency reducing and the transducer stops vibrating. This paper put forward the concept of dynamic impedance matching, and using STM32as the main controller, an intelligent ultrasonic power experiment platform has been designed. The main research contents are as follows:Firstly, the equivalent circuit of ultrasonic transducer was analyzed. The different parameters of parallel matching network and series matching network were compared, and a simulation in MATLAB has been carried on. According to the existing problems of traditional static impedance matching, this paper put forward two dynamic matching methods; they were dynamic adjustment of matching inductance parameter and the auto-tracing of the resonant frequency. And the latter method has been chosen after compared the principle of these two dynamic matching methods.Secondly, the main scheme of ultrasonic power supply was designed, and the system was divided into plurality of sub modules. In the voltage regulation rectifier module, the thyristor was used to adjust the DC bus voltage. In the high frequency invertor module, the half bridge topology structure was used to realize the invention from DC to AC. DDS chip was used to generate high precision PWM wave and the dead time was produced by RC time-delay circuit. In order to realize the power tube can be shutdown in a high-speed, a negative bias circuit was used in the driving circuit of IR2110. In the frequency tracking module, Hall sensor was used to detect the phase of current and voltage. The phase difference signal of current and voltage was obtained after the regulate circuit, and STM32can detected the pulse width by using the PWM input function.Thirdly, according to the hardware of ultrasonic power supply, the system software has been programmed, including thyristor voltage regulation subprogram and frequency automatic tracking subprogram. The resonance frequency of ultrasonic power supply may change slowly or violently in two cases. Variable step size of frequency automatic tracking algorithm was designed, and frequency tracking can be realized rapidly and accurately.Fourthly, all of the hardware and the software were finished, and a large number of experiments were performed. And the result showed the design of ultrasonic power supply can realize frequency tracking accurately, and the goal of dynamic impedance matching was achieved primely.