Analysis and design of voltage maintaining method for series resonant capacitor charging power supply

High energy density high-voltage metallized film capacitor is one of the most suitable energy storage elements in pulsed power system, such as Electromagnetic Gun (EMG) system. But the voltage drop at high voltage is an inherent problem of metallized film capacitor, which will affect the launching precision of EMG system. To improve the launching precision, this paper mainly focuses on the voltage maintaining method of capacitor charging power supply (CCPS). Based on the traditional series resonant CCPS, a voltage maintaining method is proposed, which feeds energy to capacitor to compensate voltage drop during launching delay. The scheme is simple and easy to implement. It also can switch smoothly from fast charging stage to micro power charging maintaining stage. Furthermore, for the portable CCPS fed by lithium ion battery, the charging voltage maintaining precision is deteriorated by the common-mode voltage. So a common-mode voltage restraining circuit is proposed and analyzed in detail. A 4kV 1.0kJ/s CCPS prototype was constructed. The experimental results of the prototype show that, the CCPS has approximate maintaining accuracy of 0.1%.