Research On Digital High Voltage Power Supply System For Electron Beam Welder

The issue is one part of the project “Research on Power Supply System for Electron Beam Welder for Rail welding” of XX Company.The role of High Voltage Power Supply System is mainly used to accelerate the electron beam which is produced by Filament Power Supply System, and the performance of High Voltage Power Supply System determines the level of electron beam welding and the quality of weld. With the development of power electronic devices, the circuit topology in switching power supply, control chip and control method, the high voltage DC power supply with high frequency by digital control is becoming a hot spot of development and application.Firstly, the paper has gave a brief introduction about the Electron Beam Welder and High Voltage Power Supply System. Aiming at the applications and technical indicators, it has selected the full-bridge circuit as the main power circuit topology of the High Voltage Power Supply System, based on the theoretical analysis and comparison in DC-DC conversion circuit. And then it has selected the phase-shift control method.As the switching circuit is adopted, if the switch devices work in hard switching mode, will produce larger switching loss, and easy to produce the phenomenon such as peek voltage and over current damaged the switch devices when opening and closing. The soft switch technology can be very good to avoid the above problems, and also can improve the work efficiency.The main circuit of the High Voltage Power Supply System is powered by 380 V, 50 Hz, three-phase. Then it converts AC into DC by the Three-phase Uncontrolled Rectifier Circuit with filtering capacitor. And then, it converts the DC into 20 kHz AC by the Full-bridge Inverter Circuit with IGBT as the inverter power devices. And the Step-up Transformer converts the AC into 30 kV. Then, it converts the HF AC into a 60 kV DC for electron gun by Voltage Double Rectifier Circuit. Last, the paper has gave the parameters of these components for main circuit, and built the simulation model by using the software Simulink, and verified the correctness of the design.The DSP2812 is the core of the control circuit of the High Voltage Power Supply System. After processed the voltage signal traveling through sampling circuit, it generated the PWM pulse to drive the switch devices IGBT, to change the output voltage by changed the phase shifted angle. The paper has expounded a method which can generate the PWM pulse, and Rebuild All on CCS software platform. Then, run the program after downloaded to the DSP2812, and generated the required PWM pulse.Due to the high frequency inverter circuit, greatly reduce the volume and weight of the Step-up Transformer. With the soft switching technology, the switching loss and the peek voltage is resolved. And, with the DSP control technology, it can achieve for the purpose of adjusting the output voltage quickly and accurately.