Research Of High-frequency Narrow Pulse Micro-arc Oxidation Power Supply

Micro-arc oxidation (MAO) is a new technology developed on the basis of generalanodic oxidation technology. It is a emerging surface treatment technology which couldgenerate ceramic membrane on the situ of non-ferrous metals directly. Because thecombination of the ceramic membrane and substrate is metallurgical fusion, the ceramicmembrane formed on the surface has high combination strength with the base material. It canimprove the wear, heat, corrosion resistance and insulation properties of the non-ferrousmetals significantly. Because of these advantages, MAO is becoming a hotspot in the field ofinternational surface engineering technology. As for micro-arc oxidation process，the pastresearches had shown that the output frequency of Micro-arc oxidation power higher, theceramic membrane is denser and the film performance is better, but the output frequency ofcurrent micro-arc oxidation power supply are low, so this paper has designed ahigh-frequency narrow pulse Micro-arc Oxidation power supply to meet the requirements ofmicro-arc oxidation process.This paper has put forward an overall solution of the power supply, including the maincircuit of dual-inverter construct and the control system which is based on DSP according tothe control requirements. The design of power magnetic components of main circuit, theselection of power switching components, the design of high-frequency driver circuit andmain circuit PCB were completed. The control system based on the chip dsPIC33FJ64GS610was designed, including feedback sampling circuit, switching control circuit, protectioncircuit, communication interface circuit and interactive interface circuit, etc. The programs ofthe PWM, A/D sampling, PID control, LCD display, key scan, etc. were written anddebugged.This paper has built the experimental platform and debugged the power supply inconstant-voltage control mode and constant-current control mode respectively, four outputmodes of DC, DC pulse, symmetrical and asymmetrical exchanges were realized. It couldachieve a serious of output waveforms through set the waveform parameters flexibly to meeta variety of micro-arc oxidation process requirements. The power supply’s output pulsefrequency is up to20kHz, the output pulse width can be decreased to20us, and can achieve precise control of single narrow pulse energy. Some micro-arc oxidation experiments inhigh-frequency output mode has been done and a conclusion has been drew that with thefrequency increasing, the surface roughness of the film decreases, the power supply isbeneficial to micro-arc oxidation process.