Resonant power supply for Magnetic Resonance Imaging gradient drivers

This paper presents a Magnetic Resonance Imaging gradient-amplifier power-supply with a Series Resonant Converter (SRC) using an innovative optimal phase-shift control. This provides very fast response by eliminating the dynamics associated with the resonant tank. One phase leg has zero voltage switching; the other leg has both zero voltage and zero current switching. This ensures very low switching losses. The switched gradient amplifier load presents specific challenges: Multiple outputs with good cross-regulation, and very fast load-transient response. All load currents vary independently from no-load to full-load, and output voltages must be tightly regulated for all conditions. The solution presented uses post-regulators for half of the output voltages. Several post-regulator options are compared based on performance and reliability. The proposed approach has high power density and excellent performance.