The Research And Development Of Series Resonant Capacitor Charging Power Supply

For pulsed power systems utilizing capacitors as the energy storage unit, the performance of capacitor charging power supplies (CCPS) determines the stability and repeatability of the output voltage. High frequency resonant converters exhibit many advantages when used for capacitor charging, and one kind of them, series resonant converter (SRC), is employed universally to charge large-capacity capacitors.This paper presents the research and development work on series resonant CCPS applied to pulsed plasma thruster (PPT). By steady state analysis of resonant circuits working in discontinuous current mode in series resonant CCPS, three functional relationships between peak value of resonant current, peak value of resonant voltage, voltage on load capacitor and numbers of resonant periods are found and the inherent constant-current characteristic, which disappears as the current through anti-parallel diodes declines to zero, are demonstrated. Furthermore, the precise time when the constant-current characteristic changes and the voltage on the load capacitor at that moment are calculated. The truth of theoretical analysis is testified by circuit simulation. The suggestions on how to choose suitable resonant frequency when circuit characteristic impedance is known and how to choose suitable operation frequency when resonant frequency is known are made. The power switch apparatus in CCPS experience'true'zero current switching (ZCS) process by utilizing zero current resonant mode power supply controller UC3867 and thus the danger of turn-off overvoltage facing switch apparatus is avoided while the power dissipation in turn-off period is reduced. The dual-mode charging control scheme which means CCPS operates in high frequency before the charging voltage on load capacitor reaches 90% of the target voltage and operates in low frequency after that reaches reduces the possibility of over charging on the load capacitor.The system is tested and anticipated results are got. A load capacitor of 10μF is charged to 2500 V linearly within 250 ms and the repeatability of output voltage is acceptable. The repeated frequency of CCPS is 2.5 Hz when the load capacitor discharges to plasma. Some possible improvements are also proposed in the paper.