Two-Paralleled Bridge Type High Frequency PWM Chopper with Multi-Loop Current Feedback Tracking Scheme for Gradient Magnetic Field Controller.

This paper deals the digital optimal current control scheme to improve MRI (Magnetic Resonant Imaging) Gradient-Magnetic Coil (GC) current control implementation. The GC current needs high precision control specifications so as to take clear images with MRI. The novel MRi-GC current control amplifier has the high-frequency PWM chopper circuit with a multi-parallel input structure. The GC current control circuit can prevent the current ripple amplitude and realize high precision GC current controls, but the control system is hard to design because the GC current control circuit has the multi-input and multi-output structure and required high precision control abilities. Therefore, the digital optimal control scheme has tried to apply for the GC current control. The optimal controller is skillful at the design of multi-input and multi-output systems. The novel controller will actualize the high precision GC current controllability because Error System newly includes the GC current error parameter so as to decide the multiinputs. In this paper, we discuss the novel controller with computer simulations that it can expect the high precision GC current control to improve the image quality of MRI systems.