Novel digital control topology of a high power resonant DC-DC converter for X-ray high-voltage applications

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 a medical use X-ray high-voltage generator. In the converter system, I-PD feedback control algorithm with a nonlinear compensator for steady-state voltage regulation characteristics and an input voltage fluctuation compensator are presented in this paper. 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 as the medical use X-ray high-voltage generator. High speed processing hardware for the digital feedback control scheme with 20 kHz sampling frequency are also discussed as well as programming guidelines. Finally, the performances 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.