Dual energy X-ray computer tomography (CT) offers enhanced imaging and reduced radiation dose. A conventional technique is using two tubes, each energized by its high voltage power supply (HVPS) at different voltage levels. This approach is straightforward but costly. An alternative is using a single tube fed by an HVPS capable of generating these same voltages with fast transitions from one state to another. A conventional HVPS with exceptionally fast dynamics is less costly than a modulator employing a set of HV switches. Such an HVPS is described in this paper. Key technology includes an all-solid-state modular IGBT-based HV converter with energy-dosing inverters operating at up to 70 kHz. The inverters' output voltages are phase-shifted, which yields low ripple and fast risetime combined with low stored energy. Controls provide standard operating features and means of communicating with the outside world. Digital processing enables predictive control for generating clean transitions from one state to another in a wide range of load/line conditions. The HVPS incorporates also two filament power supplies and a high-speed starter. Results of extensive testing with both resistive loads and X-ray tubes are presented. The developed techniques can also be used in other applications requiring low-cost generation of high-power HV pulses submillisecond-to many seconds-long.Index Terms -Computer tomography, dual energy, X-ray, high voltage power supply, pulsed power, power modulator, energy dosing.
MAIN DESIGN PARAMETERSA typical CT HVPS for medical applications has a peak power of about 100 kW, but average power of only 5 kW. Relatively low average power is an important factor of Manuscript Alex Pokryvailo (M'05-SM'07) was born in Vyborg, Russia. He received the M.Sc. and Ph.D. degrees in electrical engineering from the Leningrad Polytechnic Institute in 1975 and 1987, respectively. Formerly with Soreq NRC, Israel, now he is with Spellman High Voltage Electronics Corp., serving as Director of Research. His current and recent experience relates to design of HV high-power switch-mode power supplies, Pulsed Power, with emphasis on high-current opening and closing switches and magnetic design, fast diagnostics, and corona discharges. Previously, he studied switching arcs, designed SF6-insulated switchgear, made research in the area of interaction of flames with electromagnetic fields, etc. He has published over 120 papers, two textbooks (in Hebrew), and more than 20 patents pertaining to HV technology.Costel Carp (M'05) was born in Romania. He earned his BTek degree from Polytechnic Institute Iasi, Romania, in 1986, and has been with Spellman High Voltage Electronics Corporation since 2002. His main field of expertise is power electronics, with emphasis on high voltage, high-power supplies for industrial and medical applications.Cliff Scapellati (M'92), photograph and biography not available at the time of publication.
