High-frequency ZVS PWM power amplifier system with high-precision magnetic-field current tracking control scheme

In order to minimize switching losses and stresses, reduce EMI and RFI noises, and realize the snubberless configuration, soft-switched PWM power conversion circuits and systems using new power semiconductor devices have attracted recent interest. The authors have proposed a novel topology with an auxiliary Transformer-assisted Quasi-Resonant Commutated Pole (TQRCP) circuit which can operate under a principle of Zero-Voltage Switching (ZVS) transition without initial resonant current control loop. In this paper, a high-frequency ZVS-PWM power amplifier which incorporates auxiliary TQRCP circuits into the bridge legs is developed for a magnetic-field current tracking control system. The control implementation for achieving a precise magnetic-field current tracking realization with low ripple factor is introduced into the switched-mode PWM power amplifier and its design is considered for efficient generation of gradient-magnetic-fields in Magnetic Resonance Imaging (MRI) machines.