Precision gradient amplifier with multiple output voltage levels
AssigneeKoninklijke Philips Electronics N.V.
InventorsDaniel T. Trabbic, Thomas R. McBride
Life of this patent
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Abstract
A controlled power supply (201, 222) drives a magnetic field gradient coil (161) of a magnetic resonance imaging apparatus (10). A gradient amplifier (201) includes a plurality of switching power regulators (50, 52, 54, 56) which are electrically connected in series. A bipolar circuit (70) receives power from the series connected switching power regulators (50, 52, 54, 56) and delivers the power at a selected polarity to the gradient coil (161). A control circuit (221) delivers phase staggered pulse width modulated control signals (A, B, C, D) to the switching power regulators (50, 52, 54, 56).
Claims22
A controlled power supply for driving a magnetic field gradient coil of a magnetic resonance imaging apparatus, the power supply including:
- a plurality of switching power regulators electrically connected in series to deliver power to the gradient coil;
- and
- a control circuit that delivers phase staggered pulse width modulated control signals to the switching power regulators, the control circuit including:
- phase shifting circuits that each introduce a different selected phase shift to an a.c. carrier signal to define phase staggered a.c. carrier signals,
- pulse width modulation circuits that each receive one of the phase staggered a.c. carrier signals and produce a pulse train at a frequency and phase selected by the received phase staggered a.c. carrier signal, and
- a feedback controller communicating with the pulse width modulation circuits to control a pulse width of pulses of the pulse trains based on a set point and a feedback signal from the magnetic field gradient coil.
A controlled power supply for driving a magnetic field gradient coil of a magnetic resonance imaging apparatus, the power supply including:
- a plurality of switching power regulators electrically connected in series and configured to deliver power to the gradient coil wherein the switching power regulators each include high speed field effect transistors;
- and
- a control circuit configured to deliver phase staggered pulse width modulated control signals to the switching power regulators wherein the power supply having a total number of switching power regulators is N, and the switching power regulators each include high speed field effect transistors having a rating below Vrated and exceeding Vrated/where Vrated is a maximum voltage amplitude delivered to the gradient coil.
A method for applying controlled power to a magnetic field gradient coil of a magnetic resonance imaging apparatus, the method including:
- generating phase staggered pulse width modulated control signals from a single pulse width modulated control signal, the phase staggered pulse width modulated control signals all having the same pulse width;
- producing a plurality of switched power outputs each of which is switched by one of the phase staggered pulse width modulated control signals applied to a field effect transistor;
- combining the switched power outputs in series;
- applying the series combined switched power outputs to the gradient coil;
- measuring the current through the ma magnetic field gradient coil;
- and
- feedback controlling the single pulse width modulated control signal based on the measured current through the magnetic field gradient coil.
Dependencies are inferred from the claim text.