Electronic power supply for magnetic gradient coils used in magnetic resonance imaging - where coil current is supplied by amplifier with feed-back loop containing phase equaliser with variable frequency control according to change in amplifier load impedance

摘要

The gradient magnetic field power supply for a gradient coil (3) has an amplifier (401) for supplying the coil with current and a feed-back loop (413) between the amplifier output and input terminals. A phase equaliser with a variable frequency response is included in the feed-back circuit. A frequency response controller (414) varies the frequency response according to the change in an amplifier load impedance. The phase equaliser can consist of two phase equalising circuits each with its own frequency response with provision for changeover from one circuit to the other.