Patent ID: 6448775
Filing Date: 2002-09-10
Classification: G01R

Abstract:
A gradient amplifier for a magnetic resonance apparatus, said gradient amplifier comprising:a controller for current control having an output; a modulator stage having an input connected to said output of said controller, and having a plurality of outputs; an output stage having a plurality of inputs respectively connected to the outputs of said modulator stage, said output stage generating a gradient amplifier output voltage supplied to a gradient coil and thereby producing a coil current in said gradient coil; said controller comprising a comparator for comparing a reference value of said coil current to an actual value of said coil current, said comparator having at first input supplied with said reference value, a second input supplied with an actual value of said coil current, an output at which a comparison result is present, and a proportional control branch connected to said comparator output, said proportional control branch having an output, and an integral control branch connected to said proportional control branch output, said integral control branch having an output, an adder having inputs, and the respective outputs of said integral control branch and said proportional control branch being connected to the respective inputs of said adder via scaling resistors; and a differential control stage which emits a voltage for relieving said closed loop controller which is proportional to a slope of a pulse edge of said coil current, said differential control stage having an input connected to said first input of said comparator and an output connected to an input of said adder, and said adder combining the respective outputs of said integral control branch, said proportional control branch and said voltage emitted by said differential control stage.