Research On Pulse Power Supply Used In Mircoarc Oxidation

Microarc oxidation is a kind of surface treatment technology which makes ceramic coatings on the surface of the metal and its alloy. The ceramic coatings generated by microarc oxidation have good properties of insulation and agaist high temperature, corrosion and abrasion, which makes it have broad application prospects in the fields of aerospace, aviation, automotive, electronics, shipbuilding, etc. At present, microarc oxidation has been a research hotspot. The power supply is an important factor constraining the development of microarc oxidation, and this paper focuses on the power supply used in microarc oxidation.The requirements of the power supply used in microarc oxidation include high output voltage and high output current, so the topology is usually full-bridge. The paper chose the full-bridge phase-shifted converter with the primary side of the transformer series with saturated conductor and blocking capacitor as the study object and analyzes the working principle by detailed. By comparing the effects of several control modes used in switching power supply, this paper ultimately chose average current conrol mode. The average current control mode has good performances on dynamic response and agaist interference without slope compensation.This paper established the small-signal model based on the converter taking the duty loss into account. And on the basis of the model, this paper designed the current and voltage regulators in order. The compensated control system has good steady and dynamic characteristics.The digital power supply is the development direction. This paper built the control system based on digital signal processor TMS320F2812 and presented a relatively simple phase-shifted scheme and soft-start method. According to the current relationships of the inductor and the primary side of the transformer, sampling the current of the primary side of transformer to get the average current of the inductor eliminated the need for Hall elements which saves resources and reduces cost.At last, the chopper circuit, sampling circuit and driving circuit were also designed. Combined the DC-DC power supply with the chopper circuit, an experiment was carrid out. The experiment verifies that the digital power supply works well. It can realize soft switching in a wide range. And the chooper circuit can output asymmetric pulse waves in both positive and negative directions with the frequency and duty cycle adjustable which can satisfy the requirements of microarc oxidation. The theoretical analysis is verified correctly.