Research Of YAG Welding Laser Discharge System Based On DSP

Laser welding has been widely used in cutting-edge technology fields such as energy,optoelectronics,communications and defense industry with the advantages of precision,high efficiency,safety,and easy automation.Among various laser welding machines,the YAG laser welding technology is the most mature and the most widely used.As some welding parts get smaller and smaller as well as more and more Ingenious,it's higher requirements for the performance of welding lasers.Nowadays,the biggest defect of the traditional YAG laser welding machine is the low stability of the laser in the low power mode(eg,the output laser energy is less than 1 J),which can not reach the quality requirements of the welding parts.This will cause the product to have inconsistent solder joints during welding that some have a small energy and others are large.According to the analysis result,the main reason was that the output power of laser power supply was inconsistent in one pulse time.The traditional analog discharge control system cannot accurately capture the compensation time and has low control accuracy,resulting in low stability of output current and output voltage.Therefore,it is necessary to ensure the consistency of the laser power supply's output power over the same pulse time.This paper proposes the use of digital processing chip(DSP)control system to replace the traditional analog discharge control system.In order to verify the above method,the digital discharge control platform was theoretically analyzed from the aspects of power main circuit design,loop control design,functional circuit design and software design,and a small and medium prototype was made.The experimental results of the prototype show that the energy stability of digital control system reach 98%,which is 4% of stability better than the traditional laser welding machine(about 94%),to meet the technical requirements.The main tasks of this topic are as follows:(1)In this paper,the output beam type of YAG welding laser is introduced first.The components of the laser power supply are briefly described and the necessity of its digitization is proposed.(2)Proposed a Buck converter as the power main circuit of the laser power discharge system,and analyzed the working principle of the Buck converter in one pulse time.The buck converter operates in CCM mode during the pulse time and uses PWM control.In addition,the parameters of each component in the power main circuit were calculated,providing a basis for the prototype design.(3)Used the small signal analysis method to theoretically analyze the loop compensation network of the discharge control and design the feedback control loop of the Buck circuit.To realize a dual-loop control,an inner current loop is used to control the xenon lamp current because of the xenon lamp load has a negative resistance characteristic,and the voltage outer loop is used to control the main circuit output voltage.The compensation network function obtained in the design is converted into a time domain function and discretized to provides a theoretical basis for the design of the digital compensation network of the digital control system.(4)Set up the functional circuit and software control platform of the discharge control system so as to realize the normal operation of the machine.The discharge control system needs signal connection and data communication with other systems,and collect each electrical signal in the power main circuit and convert to digital signal with the analog-to-digital conversion.CCS software is used as a development platform for C language programming to implement timing control of the entire discharge system and feedback closed-loop control of the power main circuit.(5)Produced an experimental prototype and adjusted each compensation network parameter.It has been verified that the stability of the output laser energy in a plurality of pulse times has been significantly improved to meet the design requirements.