Development Of Intelligent Digital Ultrasonic Power Supply

With the maturity of ultrasonic transducer manufacturing technology and the application of power ultrasonic technology,ultrasonic plastic welding technology has been widely used because of its high efficiency,safety and cleanliness.In the process of ultrasonic transducer working,due to aging,heating and load mutation,the resonant frequency will change,so that the transducer working in the state of detuning,resulting in unstable output power,welding quality can not be uniform and stable guarantee.Therefore,it is very important to study the ultrasonic power supply with the function of adaptive frequency tracking and power regulation.This paper mainly focuses on the ultrasonic plastic welding power supply in the frequency tracking direction of self-adaptive adjustment,smooth power adjustment,power rapid discharge and convenient man-machine interface and other issues were systematically studied,developed a rated power of 2k W ultrasonic prototype.Firstly,the main power circuit of ultrasonic power supply is designed according to the design requirements of ultrasonic power supply.Fully-bridge inverter is designed with Insulated Gate Bipolar Transistor as switch tube.The LC resonant matching circuit is designed according to the characteristics of the transducer.According to the requirement of impedance matching,the high frequency transformer and magnetic bias suppression circuit are designed to ensure the high efficiency of power output.Relay is used to design the corresponding discharge circuit to ensure the safety after power loss.Then the control and drive system of the ultrasonic power supply is designed.The main control system with STM32F767 as the main controller is designed to control and adjust the working state of the ultrasonic power supply.The IGBT full bridge drive circuit was designed by using the Infineon isolation driver chip 2ED020I12-FA to drive the IGBT safely and reliably.At the same time,the analog and digital mixed acquisition circuit is designed to realize the acquisition of voltage and current effective values and phase difference information,and to provide feedback quantity for feedback control.Secondly,the maximum electrorheological variable step size sweep algorithm is used to scan the resonant frequency rapidly.A direction adaptive variable step size frequency tracking algorithm is designed to solve the problem that the direction cannot be automatically adjusted in the process of frequency tracking.The compound power control algorithm is used to adjust the power by means of phase-shifting and power modulation.And use the touch screen to develop the corresponding man-machine interface to achieve convenient operation and control of the ultrasonic power supply.Finally,the system control model is built in Matlab/Simulink,and the Phase Shift Pulse Width Modulation and the composite power control algorithm are simulated and analyzed.By building the actual verification platform,the actual test of the whole system is carried out,and the correctness of the design is verified.