Transformer parasitic high-frequency inverter-fed DC-DC converter for medical-use X-ray power generator and its digital control

This paper describes a 32-bit RISC processor-based digital feedback control scheme for a series-parallel resonant high power DC-DC converter using its high-voltage transformer parasitic LC circuit components which is applied to medical use X-ray high-voltage generator. In this converter system, the I-PD feedback control algorithm with a nonlinear compensator for steady-state voltage regulation characteristics and an input voltage fluctuation compensator are presented. A practical estimation procedure to obtain the adequate I-PD gains specified by logarithmic interpolation from some regulation points is established under conditions of extremely wide load ranges for the medical X-ray high-voltage generator. The high speed processing hardware for the digital feedback control scheme with 20 kHz sampling frequency is also discussed, as well as the programming guidelines. Finally, the performance of this application-specific converter and the effectiveness of the proposed gain parameter estimation procedure of the I-PD compensator are demonstrated on the basis of experimental results.