Optimal trajectory based start-up control of LCC resonant converter for X-ray generator applications

Abstract

LCC series–parallel resonant converter (LCC-SPRC) is the preferred high voltage DC power supply (HVPS) topology for medical X-ray imaging generator applications, due to its advantage in wide operating ranges, and full-range soft switching capability. In this paper, an Input-Single-Output-Series (ISOS) type LCC-SPRC which utilizes the cascaded twelve-level rectifier as the interface with a 140 kV X-ray tube, is presented. However, the existing control strategies cannot meet the requirements of high-voltage generator output voltage response time for real industrial practice. By modeling LCC-SPRC with state plane trajectory analysis (SPTA), the start-up trajectory curve is precisely predicted. By adjusting the current limit band further, the operating mode can be improved to stabilize the initial state, regulating the state variables onto the optimized trajectory locus within the shortest time cycle. Experiment results based on a 140kV/42kW setup are presented to indicate the correctness and feasibility of the proposed method.

Keywords

• X-ray high voltage generator
• LCC resonant converter
• State plane trajectory analysis
• Trajectory control