A Single DC Source Gradient Driver Circuit With Boosting Output Capability for MRI Applications

Abstract

Magnetic resonance imaging (MRI) systems gradient driver (GD) circuits, which drive current through gradient coils, have essential roles in imaging quality and speed. They drive large current values, higher than 1000 A, with high fidelity to the commands, low current ripples, and fast transient responses, which lead to high voltage values, larger than 2 kV, to properly drive the coils. Till now, some solutions with parallel and stacked structures have been reported to fulfill such requirements, which need several independent isolated voltages to deliver the necessary output current. Thus, other parts are generally needed to generate these voltages, separately. Here, a new GD circuit with only a single independent voltage source and output voltage boosting capability is proposed to drive such gradient coils. It reduces the semiconductor and magnetic element counts, in the MRI gradient driver power chain. It also reduces the pulsed power demand from the facility, by storing energy. The proposed circuit has been mathematically analyzed, here. A 2.34 MVA,1300A/1800 V GD circuit has been designed and simulated based on the proposed topology to verify its performance. Finally, a laboratory 700 V, 10 A scaled-down prototype converter has been implemented, based on the proposed topology to verify the given analyses and simulation results.