Series resonant high-voltage PFM DC-DC converter with voltage multiplier based a two-step frequency switching control for medical-use X ray power generator

Abstract

In general, high-voltage DC power supplies employing a variety of high-frequency inverters are implemented for constant value control schemes. In particular, their good transient and steady-state performances can not be achieved under wide load variations for a medical-use high voltage X ray generator ranging from 20 kV to 150 kV in the output voltage and from 0.5 mA to 1250 mA, respectively. A high-voltage DC power supply designed for X ray power generator applications is considered, which uses series resonant inverter-linked multistage DC voltage multiplier instead of conventional high voltage diode module rectifier connected to the secondary-side of a high-voltage transformer. A constant on-time/variable frequency control scheme of this converter operating at zero-current soft switching mode is described. Introducing the capacitor-diode cascaded multistage voltage multiplier, the secondary turn numbers, and secondary-side stray capacitance of the high-voltage high-frequency transformer as well as the rectifier diode voltage ratings can be greatly reduced. It is proven that the proposed converter control scheme of the 2 step changed frequency selection switching is more effective for improving output voltage responses. A series resonant high-frequency transformer-linked voltage-multiplying rectifier is evaluated for an X ray high voltage generator on the basis of simulation analysis and observed data in experiment.