High-Power High-Performance Low-Cost Capacitor Charger Concept and Implementation

A 20-kJ/s 10-kV 1-kHz repetition rate capacitor charger design and testing are described. The goal of the development was to combine high performance and versatility with low-cost design and good manufacturability. This goal was met using an energy-dosing converter topology with smart controls adapting the switching frequency in such a way as to ensure zero-current switching for all possible scenarios, keeping maximum duty cycle for high power. The switching is accomplished at a frequency of up to 55 kHz, employing relatively slow insulated-gate bipolar transistors with low conduction losses. High efficiency allows all-air cooled design that fits into a 19" × 10" × 24" rack. Design guidelines are reviewed. Comprehensive PSpice models accounting for numerous parasitic parameters and mimicking controls for the frequency variation were developed and simulation results are presented. Worst-case repeatability analysis has been performed. Both PSpice simulations and analytical tools predicted pulse-to-pulse repeatability of 0.3%; the measured figures are 0.8% and 1% for short- and long-term operations, respectively, at peak charging and repetition rates. Typical current and voltage traces and results of thermal runs are presented.