Gradient coil power supply and a magnetic resonance imaging system

Patent metadata

Field	Value
Publication number	US-9222997-B2
Application number	US-201113703705-A
Country	US
Kind code	B2
Filing date	Jun 14, 2011
Priority date	Jun 17, 2010
Publication date	Dec 29, 2015
Grant date	Dec 29, 2015

Abstract

A gradient coil power supply includes: at least two H-bridge circuits connected in series, wherein each H-bridge circuit supplies: voltage of a first polarity when in a first switching state, voltage of a second polarity when in a second switching state, no voltage when in a third switching state, and no voltage when in a fourth switching state; and a controller for controlling the switching of the H-bridge circuits. The controller is adapted for: receiving a gradient pulse sequence; creating a switching plan for controlling the switching of the H-bridge circuits, wherein the switching plan includes controlling the voltage output of the gradient coil power supply by alternating between the first switching state and the second switching state, and at least one H-bridge circuit being in either the third or fourth switching state for part of the switching plan to cool the H-bridge circuit; and executing the switching plan.

First claim

The invention claimed is:

1. A gradient coil power supply for a magnetic resonance imaging system, the gradient coil power supply comprising:
at least two H-bridge circuits; wherein the H-bridge circuits are connected in series; wherein each of the H-bridge circuits supplies voltage of a first polarity when in a first switching state; wherein each H-bridge circuit supplies voltage of a second polarity when the H-bridge is in a second switching state; wherein each H-bridge circuit supplies no voltage when in a third switching state; wherein each H-bridge circuit supplies no voltage when in a fourth switching state; and wherein for a predetermined amount of time current is conducted through the H-bridge circuit in the third and fourth switching states, and
a controller for controlling the switching of the H-bridge circuits, wherein the controller is adapted for:
receiving a gradient pulse sequence,
creating a switching plan for controlling the switching of each of the H-bridge circuits, wherein the switching plan comprises controlling the voltage output of the gradient coil power supply by alternating between the first switching state and the second switching state, wherein the switching plan further comprises operating at least one H-bridge circuit selected from the H-bridge circuits in either the third or fourth switching state for part of the switching plan to cool the H-bridge circuit, and
executing the switching plan.

2. The gradient coil power supply of claim 1 , wherein the switching plan further comprises switching at least one of the H-bridge circuits at a varied frequency between the first and second switching states.

3. The gradient coil power supply of claim 2 , wherein the controller is further adapted for varying the frequency to minimize the switching losses in the H-bridge circuit and increases the maximum root mean square current able to be conducted by the H-bridge circuit.

4. The gradient coil power supply of claim 2 , wherein the controller is further adapted for determining a minimum bandwidth for the gradient pulse sequence, and wherein the switching plan further comprises adjusting the varied frequency above a minimum threshold, wherein the minimum threshold is the minimum frequency to obtain the minimum bandwidth.

5. The gradient coil power supply of claim 2 , wherein the pulse sequence specifies a time dependent current with a trapezoidal shape, wherein the trapezoidal shape specifies a time period where a constant current is specified, and wherein the switching plan further comprises reducing the varied frequency during the time period.

6. The gradient coil power supply of claim 1 , wherein the switching plan further comprises fixing the H-bridge circuit in the first or second switching state for a period of time.

7. The gradient coil power supply of claim 1 , wherein the switching plan further comprises setting at least one of the H-bridge circuits to either the first or second switching state for a fixed period of time, wherein the switching plan further comprises switching the remaining H-bridge circuits at a varied frequency between the first and second switching states, and wherein the fixed period of time is longer than the period of the varied frequency.

8. The gradient coil power supply of claim 1 , wherein each H-bridge comprises a voltage supply, a first switching unit, a second switching unit, a third switching unit, and a fourth switching unit; wherein in the first switching state the first and fourth switching units are closed and the second and third switching units are open; wherein in the second switching state the second and third switching units are closed and the second and third switching units are open; wherein in the third switching state the third and fourth switching units are open and the first and second switching units are closed; and wherein in the fourth switching state the third and fourth switching units are closed and the first and second switching units are open.

9. The gradient coil power supply of claim 1 , wherein the first, second, third, and fourth switching units are insulated-gate bipolar transistor switching units.

10. The gradient coil power supply of claim 9 , wherein each of the H-bridge circuits has first and second outputs; wherein each switching unit has a first connection and a second connection; wherein the first connection of the first switching unit is connected to the first output of the H-bridge circuit; wherein the second connection of the first switching unit is connected to the first connection of the second switching unit; wherein the second connection of the second switching unit is connected to the second output of the H-bridge circuit; wherein the first connection of the third switching unit is connected to the first output of the H-bridge circuit; wherein the second connection of the third switching unit is connected to the first connection of the fourth switching unit; wherein the second connection of the fourth switching unit is connected to the second output of the H-bridge circuit; wherein each voltage supply comprises a first voltage output and a second voltage output; wherein the first voltage output is connected to the second connection of the first switching unit; and wherein the second voltage output is connected to the second output of the third switching unit.

11. A method of operating a gradient coil power supply for a magnetic resonance imaging system; wherein the gradient coil power supply comprises at least two H-bridge circuits; wherein the H-bridge circuits are connected in series; wherein the each H-bridge circuit supplies voltage of a first polarity when in a first switching state; wherein each H-bridge circuit supplies voltage of a second polarity when the H-bridge is in a second switching state; wherein each H-bridge circuit supplies no voltage when in a third switching state; wherein each H-bridge circuit supplies no voltage when in a fourth switching state; wherein for a predetermined amount of time current is conducted through the H-bridge circuit in the third and fourth switching states, and wherein the method comprises:
receiving a gradient pulse sequence,
creating a switching plan for controlling the switching of the switching units in each of the H-bridge circuits, wherein the switching plan comprises controlling the voltage output of the gradient coil power supply by alternating between the first switching state and the second switching state, wherein the switching plan further comprises operating at least one H-bridge circuit selected from the H-bridge circuits in either the third or fourth switching state for part of the switching plan to cool the H-bridge circuit, and
executing the switching plan.

12. The method of claim 11 , wherein the switching plan further comprises switching at least one of the H-bridge circuits at a varied frequency between the first and second switching states.

13. A computer program product comprising machine executable instructions for execution by a processor of a control unit of a gradient coil power supply for a magnetic resonance imaging system; wherein the gradient coil power supply comprises at least two H-bridge circuits; wherein the H-bridge circuits are connected in series; wherein each H-bridge circuit supplies voltage of a first polarity when in a first switching state; wherein the each H-bridge circuit supplies voltage of a second polarity when the H-bridge is in a second switching state; wherein each H-bridge circuit supplies no voltage when in a third switching state; wherein each H-bridge circuit supplies no voltage when in a fourth switching state; wherein for a predetermined amount of time current is conducted th

Assignees

• Ham Cornelis Leonardus Gerardus
• Koninkl Philips Nv

Inventors

• Ham Cornelis Leonardus Gerardus

Classifications

• H02M7/49

  Combination of the output voltage waveforms of a plurality of converters · CPC title

• G01R33/3852 Primary

  Gradient amplifiers; means for controlling the application of a gradient magnetic field to the sample, e.g. a gradient signal synthesizer · CPC title

• G01R33/36 Primary

  Electrical details, e.g. matching or coupling of the coil to the receiver · CPC title

• H03F3/2178

  using more than one switch or switching amplifier in parallel or in series (H03F3/2173, H03F3/2175 take precedence) · CPC title