| Microarc oxidation (MAO) technology is an important research content of material surface modification that belongs to the crossing field of material engineering, electrochemical and power conversion technology. The uncertainty of oxidation mechanism and weakness of related basic theory research result in the mismatch between the output characteristics of MAO pulse power supply and its load which decrease the power conversion efficiency and machining efficiency. Induced high power consumption restricted the further research and industrial popularization and application of MAO technology. To definite the load characteristic of MAO pulse power supply and design the power supply matching to its load is the basic process problem to decrease the power consumption of MAO process. This paper carried on systematic researchs of the design and load electrical characteristic of MAO pulse power supply and the matching technology between power supply and its load.Firstly, this paper researched the modeling and quantitative analysis of the load equivalent circuit of MAO pulse power supply combining of theory analysis, experimental study and numerical simulation. According to the discharge principle and characteristic in MAO process, the whole oxidation process was divided into various stages. Load circuit models of MAO pulse power supply by stages were built using electrochemical impedance spectroscopy (EIS) research method. It was concluded that the load of MAO pulse power supply is essentially the capacitive load of oxidation film that can equivalent to a network of resistance-capacity structure under current pulse.Secondly, this paper designed the MAO square-wave constant current pulse power supply and researched its output forms and parameters design. A square-wave pulse power supply whose pulse width, amplitude and frequency can be regulated independently was put forward according to the requirements of MAO pulse power supply load characteristic and process. Paralleled unit structure BUCK-type circuit with constant current characteristic was designed. By parallel current sharing technology among constant current units, problems about amplitude regulation, capacity and redundancy were solved and modularization and high power output regulation of power supply were reached. Using inductance as the component of energy storage and conversion, pulse forming circuit was structured that can regulate the output frequency and pulse width and imply power supply to output pulse current with steep-wave rising edge. According to switching losses, a passive lossy buffer soft-switching circuit was designed to achieve ZCS and ZVS and decrease the switching loss and improve the operation condition of power switch tube. At maximum 250KV level, the parameters of main circuit and comprehensive control system with soft start and protection function to over voltage, over current and load open based on PLC were designed to prove the condition for the deep research of load characteristic and the implementation of natural important industry experiment project (PECC).Thirdly, voltage characteristics of equivalent load circuit to current pulse step were analyzed and the response of pulse power supply load to its output was researched. By parameter fitting, combined with oxidation mechanism analysis, the load model of MAO square-wave pulse power supply was built and circuit parameters were quantitative characterized. Specific physical significances of various parameters were gained corresponding according variation law of equivalent circuit parameters. Simulation analysis were carried out and its result same as the response characteristic and parameter variation law under practical condition. Above research prove supports to the design of MAO pulse power supply and system efficiency optimization technically and in theory.Finally, according to load model structure and quantitative parameters based on MAO process conditions, analysis about stress efficacy of power supply pulse and the effect of power supply output form and parameters to energy conversion law was inducted. Some conclusions were gained: the rising edge steepness of pulse current has decisive influence to arcing speed, keeping current after film breakdown increase the power loss of process system and result in the material sputtering from discharge channel. Current output form with steep-wave rising edge was put forward and flyback circuit with peak current form output was regulated. By simulation and experiment, power analysis and comparison between square-wave and flyback pulse power supply were carried out, the rationality of built pulse power supply load equivalent circuit and its parameters design were checked, and the matching relationship between the load model and the output form of pulse power supply were verified also. The research in this paper provided the foundation for the optimization of MAO pulse power supply, and it provided the method for the improvement of production efficiency and energy conversion efficiency in MAO process also.
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