Practical evaluations of resonant pole-assisted ZVS-PWM DC/DC converter with series capacitor-connected transformer parasitic parallel resonant tank

A fixed frequency phased-shifted pulse-width modulated (PWM) multiresonant inverter type DC-DC high-power converter with two high-frequency high-voltage transformer-coupled stages, which operates under the zero voltage switching (ZVS) transition principle in spite of a wide PWM-based voltage regulation processing and largely changed load conditions, is discussed. The multiresonant converter topology is composed of series capacitor-connected parallel resonant tank which makes the most of parasitic circuit components of two high-voltage transformers, and two additional quasi-resonant pole circuits. The circuit modelings of this converter system are exactly described for computer simulation. Its operating characteristics in steady state are illustrated in terms of computer-aided simulation analysis. The soft-switching operation and practical efficacy of this new converter circuit using the latest IGBTs are actually ascertained through a 50 kW-120 kV converter system operating using 20 kHz/30 kHz high-voltage transformers which is applied for driving diagnostic high-voltage X-ray tube load in medical equipment. It is proved, from a practical point of view, that the switching losses of IGBTs and their electrical dynamic stresses relating to EMI (electromagnetic interference) noise can be considerably reduced under a high-frequency switching-based phase-shift PWM control process for a wide load setting restriction