| Resistance welding is a common welding method in the field of electronic manufacturing.With the development of the miniaturization of electronic devices,the energy control precision and response speed of micro-scale welding process are required to be improved.High-frequency welding power supply is beneficial to improve the control response speed,output energy control precision,reduce the volume of equipment,energy conservation and emission reduction.However,the high frequency of power supply can lead to the increase of switching loss of power tube and loss of transformer duty cycle.Aiming at the development of a high precision resistance spot welding power supply for the manufacture of microelectronic devices,this paper focuses on the design and simulation of high-frequency inverter power supply,prototype trial-manufacture and testing,power supply process adaptability and quality control.(1)Based on PSpice and MATLAB,the modeling and simulation of 25 k Hz inverter resistance spot welding power supply are completed.PSpice model of main circuit is constructed by parameter extraction method,and open-loop simulation test is carried out.The mathematical model of the main circuit is established,the system stability is analyzed by using The Bode diagram,and the Simulink controller is designed and optimized based on the zero-pole compensation method.Through PSpice and Simulink joint closed-loop simulation,the feasibility of the power supply design scheme is verified.The simulation results show that the power supply scheme can meet the output requirements of the design index.(2)On the basis of the simulation model,the main circuit and control system of the power supply are studied,and the output performance of the prototype is tested and analyzed.The key technical problems such as soft switch technology of full bridge inverter circuit,design of high frequency transformer and synchronous rectification technology are studied emphatically.A full digital power supply control system is designed based on STM32H745 controller.The finite bipolar method can realize the high frequency soft switching of inverter circuit,and the synchronous rectifier technology can reduce the loss of secondary rectifier diode switching.The output waveform of power supply has the advantages of fast current rise,low overshoot and small ripple.(3)Based on the developed power supply prototype,the micro-spot welding experimental platform is constructed,the micro-spot welding process of micro-wire and copper foil sheet is studied,and the welding quality of micro-spot welding is monitored based on process information.The experimental results of aluminum wire-copper foil process show that better tensile strength can be obtained by using 25 k Hz spot welding power source.Based on electrical signals in the welding process,the dynamic change curve of electrode dynamic resistance is obtained to predict the electrode burning loss state,and the welding quality is evaluated in the continuous welding process according to various statistical information such as root mean square value,mean value,standard deviation and mean-standard deviation graph. |
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