Stability Analysis And Research Of High-power Ultrasonic Welding Power

Ultrasonic welding(Ultrasonic welding,USW)equipment is mainly composed of an ultrasonic welding power supply and a piezoelectric transducer system.The stability of high-power ultrasonic welding power supply is currently one of the main reasons affecting the quality of ultrasonic welding.The main task of this paper is to study how to improve the output stability of the ultrasonic power supply and the consistency of long-term processing,with focusing on the stability of the DC bus voltage of the ultrasonic power supply and the accuracy of energy calculation.The specific research content is as follows:This paper analyzes the factors that affect the stability of the ultrasonic power supply output,and the relationship between the stability of the ultrasonic power supply and that of welding quality.Through detailed theoretical analysis and experimental verification,it is shown that the DC bus voltage fluctuation,energy measurement error,working mode,frequency tracking,frequency output accuracy and other factors have a certain impact on the stability of the ultrasonic power supply.The Saber simulation of the rectifier filter circuit showed that the larger the load,the greater the ripple of the DC voltage output.And experiments have verified that output voltage fluctuations could lead to fluctuations in output amplitude.A 3.5 k W power factor correction system was designed.The relationship model between rectifier filtering and output ripple was established to illustrate the relationship between output voltage and load.The processing experiment of ultrasonic power supply with power factor correction module was simulated to test the consistency of the output voltage,current and power of the transducer,and compared it with the power without power factor correction module.The metal welding joint experiment on the ultrasonic power supply with the power factor correction module was carried out to judge the welding quality by tensile shear force,microstructure,and residual teeth area in the pulled metal.In this paper,there are two different design schemes for the output energy measurement of the ultrasonic power supply.One is to directly calculate the power through the DSP,and the other is to use a combination of hardware multipliers and DSP software algorithms.And the errors of the output energy of the ultrasonic power supply calculated by the two methods were compared.A lot of processing experiments have been done for the ultrasonic welding power supply of the two schemes and the error and output consistency of the output energy were compared.Welding experiments with different power levels were carried out for the second scheme,and the data from the experiment was linearly analyzed.The results showed that: in terms of the consistency of output voltage and current,when the output power was about 1150 W,the output voltage,current,and power fluctuations of the ultrasonic power supply with power factor correction module accounted for 2%,7.2%,and 2.98% of the average respectively,while the number of that without power factor correction module were 24.26%,32%,and 6.1%.For the ultrasonic welding experiment of multi-layer copper/copper nickel-plated metal joints,through observation of the microstructure,in the welded joints of the ultrasonic welding power supply with power factor correction module,the concave flat surface was gloss and there were no obvious weld penetration,cracks,etc.,while in some welded joints without power factor correction module there were some perforation and desoldering.Use DSP to directly calculate and use the hardware multiplier AD633 to measure the power error,It is found that the error calculated directly with DSP is 3-4 times that of the hardware multiplier.With the same set energy,the difference between the maximum value and the minimum value of the actual output energy of the energy scheme directly calculated by using DSP is 3 times that of the scheme with the hardware multiplier AD633.Therefore,both the power factor correction module and the hardware multiplier energy measurement unit significantly improve the stability of the ultrasonic power supply.