Development Of High Frequency Pulse-circuit Digital Power Supply For ECM Based On FPGA

As an important form of special processing, electrochemical machining has become an integral part of modern processing technology. Electrochemical machining has been widely used due to the characteristics of non-contact processing, especially in the difficult machining and complex curved surface.As the core part of pulse current electrochemical machining equipment, the quality of the pulse power determines the quality and efficiency of electrochemical machining. Experiments show that the higher the output frequency of the pulse power supply is, the better the processing quality is. Besides, the larger the output current capacity is, the higher the processing efficiency is. The progress of the high-power high-frequency pulse electrolysis power supply drives the development of electrochemical machining. Therefore, it is especially important to develop high-power high-frequency pulse current electrolytic power supplies.In view of the electrochemical machining process, the topological structure including full bridge inverter and chopper output is adopted. Full bridge inverter is to realize voltage or current regulation. At the same time, frequency and pulse width adjustment is implemented by chopper as the output level. The output current of chopper is square wave rather than triangle wave, which make up for the inadequacy of inverter. Three-phase rectifier and filter circuit at power frequency, full bridge inverter circuit, high frequency transformer, secondary high-frequency rectifier and filter circuit, chopper circuit, and the absorption buffer circuit and power driver circuit of switch tube are designed.The digital control of power supply is completed by FPGA, as the power system control center. The digital PI regulator completes voltage or current closed-loop control to realize high precision. The real-time adjustment of frequency and pulse width is implemented by the digital PWM. Touch screen is used to design a friendly human-computer interaction interface, which can not only set up but also display the power supply parameters.Based on over-voltage protection, over-current protection and temperature protection, energy release module is designed. By examining current rising rate, the damage of work-piece, tools, and the power supply caused by short circuit accident can be avoided in time.Air cooling is used to guarantee a reasonable temperature. The layout of the components is reasonable arranged. The case is made according to the actual size, so it has a compact structure and it is easy to handle.After repeated commissioning, a digital high-frequency high-power pulse electrolysis power supply has been completed. Test shows that the output is stable, waveform is good, calorific value is small, and the power supply is safe and reliable.