High power current pulse power supply for Micro-arc oxidation

This paper presents the design and construction of a current pulse power supply used for Micro-arc Oxidation (MAO), which is a novel technology capable of depositing ceramic coatings on the surface of valve metal and their alloys. The load of MAO changes acutely during oxidation process and the load transfers from capacitive characteristic to resistant characteristic. So the current pulse power supply is more suitable for MAO than the voltage pulse power supply, which is commercially available. A double switch flyback converter is incorporated into the current pulse power supply because it is capable of outputting the current pulse with a steep front edge by using the coupling inductance and energy can flow back to the power system through energy feedback channel. The control system of the current pulse power supply uses peak current control to regulate pulse energy and ensure that the energy of each pulse is uniform even though input voltage fluctuates. Frequency auto-adjustment control is used to maintain the power supply works in Critical-DCM or DCM mode to satisfy the load demand. A prototype with a peak electrical power up to 2MW, which is made up of ten units, has been constructed and tested. The pulses have a repetition rate up to 4kHz. The experimental results show that the current pulse power supply improves efficiency of energy.