Solid state power supply for high impedance NMR magnets

Abstract

We present design and construction details of an all solid-state power supply suitable for dc electromagnets in the impedance range 500–1300 Ω. Current is limited to a conservative 2 A. Current control is implemented through a series element consisting of cascaded, water-cooled power transistors isolated and regulated to operate at equally spaced voltage intervals within the transistor voltage rating. Current regulation is estimated to be a few parts in 105 for a 10% voltage or load change. Conversion of existing tube-type power supplies to this configuration is detailed.