Series resonant ZCS–PFM DC–DCconverter with multistage rectified voltage multiplierand dual-mode PFM control scheme for medical-use high-voltage X-ray power generator

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 cannot 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 a series resonant inverter-linked multistage DC voltage multiplier instead of a 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 shown that the proposed converter control scheme of the two-step selective changed frequency selection switching is more effective for improving the output voltage responses. The 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.