WO2011083788A1 - Gradient magnetic field power supply apparatus, method for controlling the power supply apparatus, and nuclear magnetic resonance imaging apparatus using the power supply apparatus - Google Patents

Gradient magnetic field power supply apparatus, method for controlling the power supply apparatus, and nuclear magnetic resonance imaging apparatus using the power supply apparatus Download PDF

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Publication number
WO2011083788A1
WO2011083788A1 PCT/JP2011/050023 JP2011050023W WO2011083788A1 WO 2011083788 A1 WO2011083788 A1 WO 2011083788A1 JP 2011050023 W JP2011050023 W JP 2011050023W WO 2011083788 A1 WO2011083788 A1 WO 2011083788A1
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Prior art keywords
magnetic field
gradient magnetic
power supply
current
inductor
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PCT/JP2011/050023
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French (fr)
Japanese (ja)
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拓也 堂本
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株式会社 日立メディコ
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
    • G01R33/38—Systems for generation, homogenisation or stabilisation of the main or gradient magnetic field
    • G01R33/385—Systems for generation, homogenisation or stabilisation of the main or gradient magnetic field using gradient magnetic field coils
    • G01R33/3852—Gradient amplifiers; means for controlling the application of a gradient magnetic field to the sample, e.g. a gradient signal synthesizer
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/493—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode the static converters being arranged for operation in parallel

Definitions

  • the present invention relates to a gradient magnetic field power supply apparatus for a nuclear magnetic resonance imaging apparatus (hereinafter referred to as an MRI apparatus), and more particularly to a technique for preventing a gradient magnetic field power supply apparatus failure due to magnetic saturation of a core of a coupled inductor used in the gradient magnetic field power supply apparatus.
  • an MRI apparatus nuclear magnetic resonance imaging apparatus
  • bridge circuits composed of multiple switching elements are connected in parallel by magnetically coupled inductors, and used as a drive circuit for the gradient magnetic field generating coil of the MRI device. It was wound around the core for magnetic coupling. (See Patent Document 1).
  • Patent Document 1 does not consider the control method of the MRI apparatus when the magnetic flux density of the core reaches the limit (saturation magnetic flux density).
  • saturation magnetic flux density When the core reaches the saturation magnetic flux density, the inductance decreases rapidly, and an overcurrent may flow through each switching element connected to the inductor. Further, the switching element may be damaged by this overcurrent.
  • an object of the present invention is to provide a gradient magnetic field power supply device capable of preventing the destruction of the switching element due to overcurrent by detecting or preventing the magnetic saturation of the core, the control method thereof, and the gradient magnetic field power supply device. It is to provide a used MRI apparatus.
  • the present invention includes two bridge circuits having the same configuration having a plurality of switching elements, an inductor magnetically coupled using a core that connects the output ends of the two bridge circuits, and 2
  • a gradient magnetic field power supply device having a gradient magnetic field control circuit that transmits a PWM signal to one bridge circuit, and controls the PWM signal based on a difference between current values output from the two bridge circuits to the inductor.
  • a gradient magnetic field power supply device capable of preventing destruction of a switching element due to overcurrent by detecting or preventing magnetic saturation of the core and an MRI apparatus using the gradient magnetic field power supply device are provided. can do.
  • FIG. 2 is a detailed view of the gradient magnetic field power source and the gradient magnetic field generating coil shown in FIG.
  • FIG. 3 is a diagram for explaining the first embodiment.
  • FIG. 3 is a diagram for explaining the first embodiment.
  • FIG. 6 is a diagram for explaining the second embodiment.
  • FIG. 6 is a diagram for explaining Example 3;
  • FIG. 6 is a diagram for explaining Example 4;
  • FIG. 6 is a diagram for explaining the fifth embodiment.
  • FIG. 3 is a flowchart showing the operation of the first embodiment.
  • FIG. 1 is a block diagram showing the overall configuration of an embodiment of an MRI apparatus for carrying out the present invention.
  • This MRI apparatus uses a NMR phenomenon to obtain a tomographic image of a subject.
  • the MRI apparatus includes a static magnetic field generation system 2, a gradient magnetic field generation system 3, a transmission system 5, A reception system 6, a signal processing system 7, a sequencer 4, and a central processing unit (CPU) 8 are provided.
  • CPU central processing unit
  • the static magnetic field generation system 2 is a vertical magnetic field system, and generates a static magnetic field by the static magnetic field generator 26 in a direction perpendicular to the body axis in the space around the subject 1.
  • a permanent magnet type or superconducting type static magnetic field generation source is arranged.
  • the static magnetic field generator 26 includes a main magnet that generates a static magnetic field or a static magnetic field coil.
  • the gradient magnetic field generation system 3 drives a gradient magnetic field generation coil 9 that applies a gradient magnetic field in the three-axis directions of X, Y, and Z, which are the coordinate system (stationary coordinate system) of the MRI apparatus, and each gradient magnetic field generation coil.
  • the gradient magnetic field power supply device 10 is configured, and by driving the gradient magnetic field power supply device 10 of each coil according to a command from the sequencer 4 described later, gradient magnetic fields Gx, Gy, Apply Gz.
  • a slice direction gradient magnetic field pulse is applied in a direction orthogonal to the slice plane (imaging cross section) to set a slice plane for the subject 1, and the remaining two orthogonal to the slice plane and orthogonal to each other
  • a phase encoding direction gradient magnetic field pulse (Gp) and a frequency encoding direction gradient magnetic field pulse (Gf) are applied in one direction, and position information in each direction is encoded into an echo signal.
  • the sequencer 4 is a control means that repeatedly applies a high-frequency magnetic field pulse (hereinafter referred to as “RF pulse”) and a gradient magnetic field pulse in a predetermined pulse sequence, and operates under the control of the CPU 8 to collect tomographic image data of the subject 1.
  • RF pulse high-frequency magnetic field pulse
  • Various commands necessary for the transmission are sent to the transmission system 5, the gradient magnetic field generation system 3, and the reception system 6.
  • the transmission system 5 irradiates the subject 1 with RF pulses in order to cause nuclear magnetic resonance to occur in the nuclear spins of the atoms constituting the living tissue of the subject 1, and includes a high frequency oscillator 11, a modulator 12, and a high frequency amplifier. 13 and a high frequency coil (transmission coil) 14a on the transmission side.
  • the RF pulse output from the high-frequency oscillator 11 is amplitude-modulated by the modulator 12 at the timing according to the command from the sequencer 4, and the amplitude-modulated RF pulse is amplified by the high-frequency amplifier 13 and then placed close to the subject 1.
  • the high frequency coil 14a the subject 1 is irradiated with the RF pulse.
  • the receiving system 6 detects an echo signal (NMR signal) emitted by nuclear magnetic resonance of nuclear spins constituting the biological tissue of the subject 1, and receives a high-frequency coil (receiving coil) 14b on the receiving side and a signal amplifier 15 And a quadrature phase detector 16 and an A / D converter 17.
  • the NMR signal of the response of the subject 1 induced by the electromagnetic wave irradiated from the high frequency coil 14a on the transmission side is detected by the high frequency coil 14b arranged close to the subject 1 and amplified by the signal amplifier 15,
  • the signal is divided into two orthogonal signals by the quadrature phase detector 16 at the timing according to the command from the sequencer 4, and each signal is converted into a digital quantity by the A / D converter 17 and sent to the signal processing system 7.
  • the signal processing system 7 performs various data processing and display and storage of processing results, and has an external storage device such as an optical disk 19 and a magnetic disk 18 and a display 20 made up of a CRT or the like.
  • an external storage device such as an optical disk 19 and a magnetic disk 18 and a display 20 made up of a CRT or the like.
  • the CPU 8 executes processing such as signal processing and image reconstruction, and displays the tomographic image of the subject 1 as a result on the display 20, and an external storage device On the magnetic disk 18 or the like.
  • the operation unit 25 inputs various control information of the MRI apparatus and control information of processing performed by the signal processing system 7 and includes a trackball or mouse 23 and a keyboard 24.
  • the operation unit 25 is disposed close to the display 20, and the operator controls various processes of the MRI apparatus interactively through the operation unit 25 while looking at the display 20.
  • the high frequency coil 14a on the transmission side, the high frequency coil 14b on the reception side, and the gradient magnetic field generating coil 9 are connected to the subject 1 in the static magnetic field space of the static magnetic field generation system 2 in which the subject 1 is inserted. It is installed opposite.
  • the radionuclide to be imaged by the MRI apparatus is a hydrogen nucleus (proton) which is the main constituent material of the subject, as is widely used in clinical practice.
  • proton the main constituent material of the subject
  • the form or function of the human head, abdomen, limbs, etc. is imaged two-dimensionally or three-dimensionally.
  • FIG. 2 is a detailed view of the gradient magnetic field power supply device 10 and the gradient magnetic field generating coil 9 shown in FIG.
  • the gradient magnetic field power supply apparatus 10 includes an X-axis gradient magnetic field power supply apparatus 201, a Y-axis gradient magnetic field power supply apparatus 202, and a Z-axis gradient magnetic field power supply apparatus 203, and applies gradient magnetic fields in the three-axis directions of X, Y, and Z, respectively. Power is supplied to the X-axis gradient magnetic field generating coil 204, the Y-axis gradient magnetic field generating coil 205, and the Z-axis gradient magnetic field generating coil 206.
  • FIG. 3 shows an X-axis gradient magnetic field power supply apparatus 201 including an X-axis gradient magnetic field control circuit 306, a gradient magnetic field output amplifier 302, and a DC power supply 304, and an X-axis gradient magnetic field generating coil connected to the output terminal of the gradient magnetic field output amplifier 302.
  • FIG. 4 is a diagram showing the X-axis gradient magnetic field control circuit 306 in the X-axis gradient magnetic field power supply apparatus 201 shown in FIG. 3 in more detail.
  • the gradient magnetic field output amplifier 302 includes a bridge circuit 303a including a plurality of switching elements and a plurality of diodes, a bridge circuit 303b having the same configuration as the bridge circuit 303a and connected in parallel to the bridge circuit 303a, and the bridge circuit 303a.
  • the inductors L11 and L21 and inductors L12 and L22 are connected to the output terminals of the bridge circuit 303b.
  • the inductors L11 and L21 and the inductors L12 and L22 are magnetically coupled using a core, respectively.
  • the bridge circuit 303a includes switching elements SW11, SW12, SW13, SW14 and diodes D11, D12, D13, D14.
  • the switching elements SW11, SW12, SW13, and SW14 are composed of, for example, IGBT (Insulated Gate Bipolar Transistor), and MOS-FET (Metal Oxide Semiconductor Semiconductor Field Effect Transistor) or the like can be used as the switching element.
  • the diodes D11, D12, D13, and D14 are composed of, for example, FRD (Fast Recovery Diode).
  • the switching elements SW11, SW12, SW13, and SW14 are IGBTs.
  • the SW11 emitter is connected to the SW12 collector, and D11 and D12 are connected in parallel to SW11 and SW12, respectively.
  • the cathodes of D11 and D12 are connected to the collectors of SW11 and SW12, respectively, and the anodes of D11 and D12 are connected to the emitters of SW11 and SW12, respectively.
  • the emitter of SW13 is connected to the collector of SW14, and D13 and D14 are connected in parallel to SW13 and SW14, respectively.
  • the cathodes of D13 and D14 are connected to the collectors of SW13 and SW14, respectively, and the anodes of D13 and D14 are connected to the emitters of SW13 and SW14, respectively.
  • the collector of SW11 and the collector of SW13 are connected, and the emitter of SW12 and the emitter of SW14 are connected.
  • the bridge circuit 303b includes switching elements SW21, SW22, SW23, and SW24 and diodes D21, D22, D23, and D24, and has the same configuration as the bridge circuit 303a.
  • the emitter of SW21 is connected to the collector of SW22, and D21 and D22 are connected in parallel to SW21 and SW22, respectively.
  • the cathodes of D21 and D22 are connected to the collectors of SW21 and SW22, respectively, and the anodes of D21 and D22 are connected to the emitters of SW21 and SW22, respectively.
  • the emitter of SW23 is connected to the collector of SW24, and D23 and D24 are connected in parallel to SW23 and SW24, respectively.
  • the cathodes of D23 and D24 are connected to the collectors of SW23 and SW24, respectively, and the anodes of D23 and D24 are connected to the emitters of SW23 and SW24, respectively.
  • the collector of SW21 and the collector of SW23 are connected, and the emitter of SW22 and the emitter of SW24 are connected.
  • L11 and L21 are wound around the same core in different winding directions, and one side of each of L11 and L21 is connected.
  • the turn ratio between L11 and L21 is 1: 1.
  • the side of L11, L21 different from the connection is connected to the emitter of SW11 and the emitter of SW21, respectively.
  • L12 and L22 are wound around the same core in different winding directions, and one side of each of L12 and L22 is connected.
  • the turn ratio between L12 and L22 is 1: 1.
  • the side different from the connection of L12 and L22 is connected to the emitter of SW13 and the emitter of SW23, respectively.
  • the collectors of SW11, SW13, SW21, and SW23 are connected to the anode of the DC power supply 304, and the emitters of SW12, SW14, SW22, and SW24 are connected to the cathode of the DC power supply 304.
  • the connection point between L11 and L21 and the connection point between L12 and L22 are connected to both ends of the X-axis gradient magnetic field generating coil 204, respectively.
  • SW11 and SW21 are generated by the X-axis gradient magnetic field control circuit 306 that generates the PWM signal 307a and the PWM signal 307b for controlling the switching elements of the bridge circuit 303a and the bridge circuit 303b.
  • SW14 and SW24 are made conductive (hereinafter referred to as ON), and SW13 and SW23, and SW12 and SW22 are respectively opened (hereinafter referred to as OFF).
  • ON conductive
  • SW13 and SW23, and SW12 and SW22 are respectively opened (hereinafter referred to as OFF).
  • the current flowing into the X-axis gradient magnetic field generating coil 204 returns to the cathode of the DC power supply 304 through L12, SW14, L22, and SW24.
  • the direction of the voltage applied to the X-axis gradient magnetic field generating coil 204 is a forward bias
  • the X-axis gradient magnetic field control circuit 306 similarly SW11 and SW21, SW14 and SW24 are turned off, and SW13 and SW23, SW12 and SW22 are turned on, respectively.
  • the current path is self-explanatory and will not be described in detail.
  • the X-axis gradient is determined based on the current detection value Ig detected by the gradient magnetic field current detector 309 that detects the current flowing in the X-axis gradient magnetic field generating coil 204.
  • Feedback control is applied by the magnetic field control circuit 306.
  • the directions of the currents flowing through L11 and L21 are both the directions flowing with respect to the X-axis gradient magnetic field generating coil 204, and the flowing current values are also the same. is there. In this case, no magnetic flux is generated in the core used for magnetic coupling of L11 and L21.
  • a current detector 310a for detecting the current flowing through L11 and a current detector 310b for detecting the current flowing through L21 are installed. Based on the respective current detection values Ia and Ib detected by the current detector 310a and the current detector 310b, the X-axis gradient magnetic field control circuit 306 controls the operation of each switching element of the bridge circuit 303a and the bridge circuit 303b. To prevent magnetic saturation of the core.
  • the current detection value Ig detected by the gradient magnetic field current detector 309 shown in FIG. 4 is output to the calculator P401 in the X-axis gradient magnetic field control circuit 306.
  • the computing unit P401 performs computation using the current detection value Ig input by the gradient magnetic field current detector 309 and the target current value Io308 sent from the CPU 8 separately. In this calculation, a value obtained by subtracting the detected current value Ig from the target current value Io 308 (differential current value Iog) is output to the PWM regulator 402.
  • the PWM regulator 402 is based on the differential current value Iog sent from the computing unit P401, and if the differential current value Iog is positive, the PWM intermediate signal 403 that is the source of the PWM signal 307a and the PWM signal 307b is within a certain period. When the differential current value Iog is negative, the ON duty of the PWM intermediate signal 403 is decreased. If the value of the differential current value Iog is 0, feedback control is performed so that the ON duty of the PWM intermediate signal 403 is maintained as it is.
  • the feedback control of the present embodiment generates the PWM intermediate signal 403 based on the current detection value Ig and the target current value Io308, but the calculation method is not limited to this.
  • the PWM intermediate signal 403 is directly transmitted to the bridge circuit 303a and the bridge circuit 303b as the PWM signal 307a and the PWM signal 307b when the switch SW401 is ON.
  • a stop signal is transmitted to the bridge circuit 303a and the bridge circuit 303b through the PWM signal 307a and the PWM signal 307b.
  • the stop signal is set to the GND level.
  • the switch SW401 is controlled by the switch controller 400.
  • the switch controller 400 performs ON / OFF control of the SW 401 based on the calculation result output from the calculator P402.
  • the computing unit P402 uses the current detection value Ia detected by the current detector 310a that detects the current flowing through L11 and the current detection value Ib detected by the current detector 310b that detects the current flowing through L21. Perform the operation. The calculation obtains a difference between the current detection value Ia and the current detection value Ib.
  • the absolute value of the value obtained by subtracting the current detection value Ib from the current detection value Ia is defined as a differential current absolute value Iab.
  • the difference between current detection value Ia and current detection value Ib is usually Does not occur.
  • the magnetic flux generated in the core is proportional to the difference between the currents flowing through L11 and L21, a value corresponding to the magnetic flux density applied to the core can be obtained by obtaining the differential current value Iab.
  • the switch SW400 is turned OFF by the switch controller 400 based on the calculated differential current absolute value Iab. Is done. Normally, the current flowing through L11 and L12 is a large current of several hundred amperes, whereas the differential current absolute value Iab required for causing the core to undergo magnetic saturation is about several amperes.
  • the PWM signal 307a and the PWM signal 307b transmit a stop signal to the bridge circuit 303a and the bridge circuit 303b, thereby preventing magnetic saturation of the core.
  • the stop signal can hold the signal and completely stop the operation of the bridge circuit 303a and the bridge circuit 303b, but the bridge circuit only during the period when the magnetic saturation is likely to occur without holding the stop signal. It is also possible to stop 303a and the bridge circuit 303b and start the operation again after eliminating the magnetic saturation of the core. It is also possible to stop the imaging of the MRI apparatus by transmitting the stop signal to the CPU 8. In addition, even when imaging is continued, it is possible to notify that there was an instantaneous abnormal operation during operation.
  • step 901 the current detection value Ia and the current detection value Ib are detected by the current detector 310a and the current detector 310b.
  • step 902 the calculator P402 calculates the difference between the current detection value Ia and the current detection value Ib.
  • the process proceeds to step 903, and when it is less than the certain value, the process proceeds to step 904.
  • Step 903 the switch SW400 is turned OFF by the switch controller 400, and the operations of the bridge circuit 303a and the bridge circuit 303b are stopped.
  • step 904 the switch SW401 is turned ON by the switch controller 400.
  • step 905 the current detection value Ig is detected by the gradient magnetic field current detector 309.
  • Step 906 the calculator P401 calculates the difference between the target current value Io308 and the current detection value Ig. If the differential current value Iog obtained by calculation is less than 0, the process proceeds to step 907. If it is 0, the process proceeds to step 908. If it is greater than 0, the process proceeds to step 909.
  • step 907 a signal obtained by reducing the ON duty of the current PWM intermediate signal 403 is output to the bridge circuit 303a and the bridge circuit 303b, and the process returns to step 901.
  • step 908 the current PWM intermediate signal 403 with the ON duty maintained is output to the bridge circuit 303a and the bridge circuit 303b, and the process returns to step 901.
  • step 909 a signal obtained by increasing the ON duty of the current PWM intermediate signal 403 is output to the bridge circuit 303a and the bridge circuit 303b, and the process returns to step 901.
  • each bridge circuit is changed to each inductor. Based on the difference between the output current values, magnetic saturation of the core used for magnetic coupling of the inductors L11 and L21 can be prevented in advance.
  • an MRI apparatus that suitably uses the X-axis gradient magnetic field power supply apparatus 201 can be provided.
  • the case where there is feedback control by the gradient magnetic field current detector 309 is shown, but even when there is no feedback control by the gradient magnetic field current detector 309, the magnetic field of the core used for magnetic coupling of the inductors L11 and L21 is shown. Saturation can be prevented beforehand.
  • a predetermined PWM signal is transmitted to the bridge circuit 303a and the bridge circuit 303b by the CPU 8 through the switch SW401.
  • a second embodiment of the present invention will be described with reference to FIG.
  • the X-axis gradient magnetic field control circuit 501 shown in FIG. 5 is partially different from the X-axis gradient magnetic field control circuit 306 in the X-axis gradient magnetic field power supply apparatus 201 shown in the first embodiment. A part of the description common to the first embodiment will be omitted.
  • the PWM regulator 402 in the X-axis gradient magnetic field control circuit 501 shown in FIG. 5 outputs a PWM intermediate signal 403 to the PWMa regulator 503a and the PWMb regulator 503b.
  • the computing unit P502 outputs the differential current value Iab to the PWMa adjuster 503a and the PWMb adjuster 503b.
  • the PWMa adjuster 503a and the PWMb adjuster 503b output the PWM signal 504a and the PWM signal 504b to the bridge circuit 303a and the bridge circuit 303b based on the input PWM intermediate signal 403 and the differential current value Iab, respectively.
  • the PWM signal 504a and the PWM signal 504b are control signals for controlling each switching element of the bridge circuit 303a and the bridge circuit 303b.
  • the PWMa adjuster 503a decreases the ON duty of the PWM intermediate signal 403 input by the PWM adjuster 402, and outputs the PWM signal 504a to the bridge circuit 303a.
  • the differential current value Iab input to the PWMa regulator 503a is negative, the ON duty of the PWM intermediate signal 403 input by the PWM regulator 402 is increased and output to the bridge circuit 303a as the PWM signal 504a.
  • the PWM intermediate signal 403 input by the PWM adjuster 402 is not increased or decreased, and the PWM intermediate signal 403 is directly used as the PWM signal 504a.
  • the bridge circuit 303a To the bridge circuit 303a.
  • the PWMb regulator 503b increases the ON duty of the PWM intermediate signal 403 inputted by the PWM regulator 402 when the differential current value Iab inputted by the arithmetic unit P502 is positive, as opposed to the PWMa regulator 503a.
  • the signal 504b is output to the bridge circuit 303b.
  • the differential current value Iab input to the PWMb regulator 503b is negative, the ON duty of the PWM intermediate signal 403 input by the PWM regulator 402 is decreased and output to the bridge circuit 303b as the PWM signal 504b.
  • the differential current value Iab is 0, the PWM intermediate signal 403 is output to the bridge circuit 303b as the PWM signal 504b, similarly to the control method in the case of the PWMa adjuster 503a.
  • the PWM signal 504a and the PWM signal 504b are independently controlled and adjusted based on the difference between the currents flowing through the inductors L11 and L21, respectively. Magnetic saturation of the core used for magnetic coupling of the inductors L11 and L21 can be prevented.
  • Example 3 of the present invention will be described with reference to FIG.
  • two current detectors are used to calculate the difference value between the currents Ia and Ib flowing through the inductors L11 and L21.
  • a single current detector 605 detects a difference value between currents flowing through the inductors L11 and L21.
  • the current detector 605 is composed of a toroidal coil. The current detector 605 performs current detection in a state where the directions of the currents Ia and Ib flowing through the inductors L11 and L21 are different from each other when outputting current from the bridge circuit 303a and the bridge circuit 303b to the inductors L11 and L21. .
  • the current value detected by the current detector 605 is zero. However, if a difference occurs between the currents Ia and Ib flowing through the inductors L11 and L21, the current detector 605 detects the difference. Assuming that the difference is the difference current value Iab2, when the difference current value Iab2 shows a certain value or more, the switch controller 600 turns off the switch SW601 based on this value. As a result, the PWM signal 604a and the PWM signal 604b transmit a stop signal to the bridge circuit 303a and the bridge circuit 303b, thereby preventing magnetic saturation of the core.
  • the difference value between the currents Ia and Ib flowing through the inductors L11 and L21 can be detected by the single current detector 605, thereby reducing the cost. Can be achieved.
  • the difference value is detected by a single current detector 605, detection with higher accuracy is possible.
  • Example 4 of the present invention will be described with reference to FIG.
  • FIG. 7 shows an example of means for directly detecting the magnetic flux of the core 701 used for magnetic coupling of the inductors L11 and L21.
  • the magnetic flux of the core 701 is directly detected by the Hall element 703 installed in the gap 702 of the core 701.
  • the switches SW401 and SW601 are turned off by the switch controller 400 and the switch controller 600 shown in the first or third embodiment, and the bridge circuit 303a and the bridge circuit 303b are stopped.
  • the magnetic saturation of the core 701 can be reliably prevented by directly detecting the magnetic flux of the core 701 of the magnetically coupled inductors L11 and L21.
  • Example 5 of the present invention will be described with reference to FIG.
  • FIG. 8 shows an example of means for detecting a value corresponding to the magnetic flux of the core 801 used for magnetic coupling of the inductors L11 and L21.
  • Inductor L3 is wound around core 801 as a third winding separately from inductors L11 and L21.
  • a value corresponding to the magnetic flux generated in the core 801 can be obtained.
  • the bridge circuit 303a and the bridge circuit 303b are stopped as in the fourth embodiment.
  • magnetic saturation of the core 801 can be easily prevented by providing the inductor L3 having the high-impedance resistor 802 in the core 701 of the magnetically coupled inductors L11 and L21.
  • the Example of this invention is not limited to these.
  • the magnetic saturation prevention of the core used for the magnetic coupling of the inductors L11 and L21 in the X-axis gradient magnetic field power supply apparatus 201 has been described.
  • the device 203 can be used.
  • a magnetic saturation prevention function is added to the X-axis gradient magnetic field power supply device 201, the Y-axis gradient magnetic field power supply device 202, and the Z-axis gradient magnetic field power supply device 203, if any one of the abnormalities occurs, the MRI apparatus You can also stop shooting.

Abstract

Disclosed is a gradient magnetic field power supply apparatus wherein switching elements in two bridge circuits are prevented from breaking due to an excess current generated by magnetic saturation of a core, said two bridge circuits supplying power to a gradient magnetic field generating coil, being connected by means of inductors magnetically coupled using the core, and having the same configuration. Also disclosed is an MRI apparatus using such gradient magnetic field power supply apparatus. Current values outputted to the inductors from the two bridge circuits are detected, and on the basis of the detected current values, the difference between the current values is calculated, and on the basis of the calculated difference value, the switching elements in the bridge circuits are controlled.

Description

傾斜磁場電源装置およびこの制御方法、並びにこれを用いた核磁気共鳴イメージング装置Gradient magnetic field power supply apparatus, control method thereof, and nuclear magnetic resonance imaging apparatus using the same
　本発明は、核磁気共鳴イメージング装置(以後、MRI装置という)の傾斜磁場電源装置に関し、特に傾斜磁場電源装置に用いる結合インダクタのコアの磁気飽和による傾斜磁場電源装置の故障を未然に防止する技術に関する。 The present invention relates to a gradient magnetic field power supply apparatus for a nuclear magnetic resonance imaging apparatus (hereinafter referred to as an MRI apparatus), and more particularly to a technique for preventing a gradient magnetic field power supply apparatus failure due to magnetic saturation of a core of a coupled inductor used in the gradient magnetic field power supply apparatus. About.
　従来の傾斜磁場電源装置では、複数のスイッチング素子で構成されたブリッジ回路を、それぞれ磁気結合したインダクタによって並列接続し、MRI装置の傾斜磁場発生コイルの駆動用回路として使用しており、インダクタは効率的に磁気結合させるためにコアに巻きつけていた。(特許文献1参照)。 In a conventional gradient magnetic field power supply device, bridge circuits composed of multiple switching elements are connected in parallel by magnetically coupled inductors, and used as a drive circuit for the gradient magnetic field generating coil of the MRI device. It was wound around the core for magnetic coupling. (See Patent Document 1).
特開平6-60286号公報JP-A-6-60286
　しかしながら、特許文献1では、コアの磁束密度が限界(飽和磁束密度)に達した場合のMRI装置の制御方法等については考慮されていなかった。コアが飽和磁束密度に達した場合、インダクタンスが急激に低下し、インダクタに接続される各スイチング素子に過電流が流れることがある。さらに、この過電流によってスイッチング素子が破損する可能性がある。 However, Patent Document 1 does not consider the control method of the MRI apparatus when the magnetic flux density of the core reaches the limit (saturation magnetic flux density). When the core reaches the saturation magnetic flux density, the inductance decreases rapidly, and an overcurrent may flow through each switching element connected to the inductor. Further, the switching element may be damaged by this overcurrent.
　そこで、本発明の目的は、コアの磁気飽和を検知又は未然に防止することで、過電流によるスイッチング素子の破壊を防ぐことが可能な傾斜磁場電源装置およびこの制御方法、並びに傾斜磁場電源装置を用いたMRI装置を提供することである。 Therefore, an object of the present invention is to provide a gradient magnetic field power supply device capable of preventing the destruction of the switching element due to overcurrent by detecting or preventing the magnetic saturation of the core, the control method thereof, and the gradient magnetic field power supply device. It is to provide a used MRI apparatus.
　上記目的を達成するために、本発明は、複数のスイチング素子を有する同一構成の2つのブリッジ回路と、2つのブリッジ回路の出力端同士を接続するコアを用いて磁気結合させたインダクタと、2つのブリッジ回路にPWM信号を送信する傾斜磁場制御回路と、を有する傾斜磁場電源装置であって、2つのブリッジ回路からインダクタに出力される各々の電流値の差分に基づいてPWM信号を制御する。 To achieve the above object, the present invention includes two bridge circuits having the same configuration having a plurality of switching elements, an inductor magnetically coupled using a core that connects the output ends of the two bridge circuits, and 2 A gradient magnetic field power supply device having a gradient magnetic field control circuit that transmits a PWM signal to one bridge circuit, and controls the PWM signal based on a difference between current values output from the two bridge circuits to the inductor.
　本発明によれば、コアの磁気飽和を検知又は未然に防止することで、過電流によるスイッチング素子の破壊を防ぐことが可能な傾斜磁場電源装置およびその傾斜磁場電源装置を用いたMRI装置を提供することができる。 According to the present invention, a gradient magnetic field power supply device capable of preventing destruction of a switching element due to overcurrent by detecting or preventing magnetic saturation of the core and an MRI apparatus using the gradient magnetic field power supply device are provided. can do.
本発明を実施するMRI装置のブロック図。The block diagram of the MRI apparatus which implements this invention. 図1に示した傾斜磁場電源と傾斜磁場発生コイルの詳細図。FIG. 2 is a detailed view of the gradient magnetic field power source and the gradient magnetic field generating coil shown in FIG. 実施例1を説明するための図。FIG. 3 is a diagram for explaining the first embodiment. 実施例1を説明するための図。FIG. 3 is a diagram for explaining the first embodiment. 実施例2を説明するための図。FIG. 6 is a diagram for explaining the second embodiment. 実施例3を説明するための図。FIG. 6 is a diagram for explaining Example 3; 実施例4を説明するための図。FIG. 6 is a diagram for explaining Example 4; 実施例5を説明するための図。FIG. 6 is a diagram for explaining the fifth embodiment. 実施例1の動作を示したフローチャート図。FIG. 3 is a flowchart showing the operation of the first embodiment.
　以下、添付図面に従って本発明のMRI装置の静磁場均一度測定方法、静磁場均一度調整方法、及びMRI装置の好ましい実施形態について詳説する。なお、発明の実施形態を説明するための全図において、同一機能を有するものは同一符号を付け、その繰り返しの説明は省略する。 Hereinafter, preferred embodiments of the method for measuring the static magnetic field uniformity, the method for adjusting the static magnetic field uniformity of the MRI apparatus, and the MRI apparatus according to the present invention will be described in detail according to the accompanying drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiments of the invention, and the repetitive description thereof is omitted.
　最初に本発明を実施するMRI装置の概略について説明する。図1は、本発明を実施するMRI装置の一実施例の全体構成を示すブロック図である。このMRI装置は、NMR現象を利用して被検体の断層画像を得るもので、図1に示すように、MRI装置は静磁場発生系2と、傾斜磁場発生系3と、送信系5と、受信系6と、信号処理系7と、シーケンサ4と、中央処理装置(CPU)8とを備えて構成される。 First, an outline of an MRI apparatus for carrying out the present invention will be described. FIG. 1 is a block diagram showing the overall configuration of an embodiment of an MRI apparatus for carrying out the present invention. This MRI apparatus uses a NMR phenomenon to obtain a tomographic image of a subject.As shown in FIG. 1, the MRI apparatus includes a static magnetic field generation system 2, a gradient magnetic field generation system 3, a transmission system 5, A reception system 6, a signal processing system 7, a sequencer 4, and a central processing unit (CPU) 8 are provided.
　静磁場発生系2は、垂直磁場方式であり、被検体1の周りの空間にその体軸と直交する方向に、静磁場発生装置26により静磁場を発生させるもので、被検体1の周りに永久磁石方式又は超電導方式の静磁場発生源が配置されている。静磁場発生装置26には静磁場を発生させる主磁石、又は静磁場コイルがある。 The static magnetic field generation system 2 is a vertical magnetic field system, and generates a static magnetic field by the static magnetic field generator 26 in a direction perpendicular to the body axis in the space around the subject 1. A permanent magnet type or superconducting type static magnetic field generation source is arranged. The static magnetic field generator 26 includes a main magnet that generates a static magnetic field or a static magnetic field coil.
　傾斜磁場発生系3は、MRI装置の座標系(静止座標系)であるX，Y，Zの3軸方向に傾斜磁場を印加する傾斜磁場発生コイル9と、それぞれの傾斜磁場発生コイルを駆動する傾斜磁場電源装置10とから成り、後述のシ－ケンサ4からの命令に従ってそれぞれのコイルの傾斜磁場電源装置10を駆動することにより、X，Y，Zの3軸方向に傾斜磁場Gx，Gy，Gzを印加する。撮影時には、スライス面(撮影断面)に直交する方向にスライス方向傾斜磁場パルス(Gs)を印加して被検体1に対するスライス面を設定し、そのスライス面に直交して且つ互いに直交する残りの2つの方向に位相エンコード方向傾斜磁場パルス(Gp)と周波数エンコード方向傾斜磁場パルス(Gf)を印加して、エコー信号にそれぞれの方向の位置情報をエンコードする。 The gradient magnetic field generation system 3 drives a gradient magnetic field generation coil 9 that applies a gradient magnetic field in the three-axis directions of X, Y, and Z, which are the coordinate system (stationary coordinate system) of the MRI apparatus, and each gradient magnetic field generation coil. The gradient magnetic field power supply device 10 is configured, and by driving the gradient magnetic field power supply device 10 of each coil according to a command from the sequencer 4 described later, gradient magnetic fields Gx, Gy, Apply Gz. At the time of imaging, a slice direction gradient magnetic field pulse (Gs) is applied in a direction orthogonal to the slice plane (imaging cross section) to set a slice plane for the subject 1, and the remaining two orthogonal to the slice plane and orthogonal to each other A phase encoding direction gradient magnetic field pulse (Gp) and a frequency encoding direction gradient magnetic field pulse (Gf) are applied in one direction, and position information in each direction is encoded into an echo signal.
　シーケンサ4は、高周波磁場パルス(以下、「RFパルス」という)と傾斜磁場パルスをある所定のパルスシーケンスで繰り返し印加する制御手段で、CPU8の制御で動作し、被検体1の断層画像のデータ収集に必要な種々の命令を送信系5、傾斜磁場発生系3、および受信系6に送る。 The sequencer 4 is a control means that repeatedly applies a high-frequency magnetic field pulse (hereinafter referred to as “RF pulse”) and a gradient magnetic field pulse in a predetermined pulse sequence, and operates under the control of the CPU 8 to collect tomographic image data of the subject 1. Various commands necessary for the transmission are sent to the transmission system 5, the gradient magnetic field generation system 3, and the reception system 6.
　送信系5は、被検体1の生体組織を構成する原子の原子核スピンに核磁気共鳴を起こさせるために、被検体1にRFパルスを照射するもので、高周波発振器11と変調器12と高周波増幅器13と送信側の高周波コイル(送信コイル)14aとから成る。高周波発振器11から出力されたRFパルスをシーケンサ4からの指令によるタイミングで変調器12により振幅変調し、この振幅変調されたRFパルスを高周波増幅器13で増幅した後に被検体1に近接して配置された高周波コイル14aに供給することにより、RFパルスが被検体1に照射される。 The transmission system 5 irradiates the subject 1 with RF pulses in order to cause nuclear magnetic resonance to occur in the nuclear spins of the atoms constituting the living tissue of the subject 1, and includes a high frequency oscillator 11, a modulator 12, and a high frequency amplifier. 13 and a high frequency coil (transmission coil) 14a on the transmission side. The RF pulse output from the high-frequency oscillator 11 is amplitude-modulated by the modulator 12 at the timing according to the command from the sequencer 4, and the amplitude-modulated RF pulse is amplified by the high-frequency amplifier 13 and then placed close to the subject 1. By supplying to the high frequency coil 14a, the subject 1 is irradiated with the RF pulse.
　受信系6は、被検体1の生体組織を構成する原子核スピンの核磁気共鳴により放出されるエコー信号(NMR信号)を検出するもので、受信側の高周波コイル(受信コイル)14bと信号増幅器15と直交位相検波器16と、A/D変換器17とから成る。送信側の高周波コイル14aから照射された電磁波によって誘起された被検体1の応答のNMR信号が被検体1に近接して配置された高周波コイル14bで検出され、信号増幅器15で増幅された後、シーケンサ4からの指令によるタイミングで直交位相検波器16により直交する二系統の信号に分割され、それぞれがA／D変換器17でディジタル量に変換されて、信号処理系7に送られる。 The receiving system 6 detects an echo signal (NMR signal) emitted by nuclear magnetic resonance of nuclear spins constituting the biological tissue of the subject 1, and receives a high-frequency coil (receiving coil) 14b on the receiving side and a signal amplifier 15 And a quadrature phase detector 16 and an A / D converter 17. After the NMR signal of the response of the subject 1 induced by the electromagnetic wave irradiated from the high frequency coil 14a on the transmission side is detected by the high frequency coil 14b arranged close to the subject 1 and amplified by the signal amplifier 15, The signal is divided into two orthogonal signals by the quadrature phase detector 16 at the timing according to the command from the sequencer 4, and each signal is converted into a digital quantity by the A / D converter 17 and sent to the signal processing system 7.
　信号処理系7は、各種データ処理と処理結果の表示及び保存等を行うもので、光ディスク19、磁気ディスク18等の外部記憶装置と、CRT等からなるディスプレイ20とを有する。受信系6からのデータがCPU8に入力されると、CPU8が信号処理、画像再構成等の処理を実行し、その結果である被検体1の断層画像をディスプレイ20に表示すると共に、外部記憶装置の磁気ディスク18等に記録する。 The signal processing system 7 performs various data processing and display and storage of processing results, and has an external storage device such as an optical disk 19 and a magnetic disk 18 and a display 20 made up of a CRT or the like. When data from the receiving system 6 is input to the CPU 8, the CPU 8 executes processing such as signal processing and image reconstruction, and displays the tomographic image of the subject 1 as a result on the display 20, and an external storage device On the magnetic disk 18 or the like.
　操作部25は、MRI装置の各種制御情報や上記信号処理系7で行う処理の制御情報を入力するもので、トラックボール又はマウス23、及び、キーボード24から成る。この操作部25はディスプレイ20に近接して配置され、操作者がディスプレイ20を見ながら操作部25を通してインタラクティブにMRI装置の各種処理を制御する。 The operation unit 25 inputs various control information of the MRI apparatus and control information of processing performed by the signal processing system 7 and includes a trackball or mouse 23 and a keyboard 24. The operation unit 25 is disposed close to the display 20, and the operator controls various processes of the MRI apparatus interactively through the operation unit 25 while looking at the display 20.
　なお、図1において、送信側の高周波コイル14aと受信側の高周波コイル14bと傾斜磁場発生コイル9は、被検体1が挿入される静磁場発生系2の静磁場空間内に、被検体1に対向して設置されている。 In FIG. 1, the high frequency coil 14a on the transmission side, the high frequency coil 14b on the reception side, and the gradient magnetic field generating coil 9 are connected to the subject 1 in the static magnetic field space of the static magnetic field generation system 2 in which the subject 1 is inserted. It is installed opposite.
　現在MRI装置の撮像対象核種は、臨床で普及しているものとしては、被検体の主たる構成物質である水素原子核(プロトン)である。プロトン密度の空間分布や、励起状態の緩和時間の空間分布に関する情報を画像化することで、人体頭部、腹部、四肢等の形態または、機能を2次元もしくは3次元的に撮像する。 Currently, the radionuclide to be imaged by the MRI apparatus is a hydrogen nucleus (proton) which is the main constituent material of the subject, as is widely used in clinical practice. By imaging information on the spatial distribution of proton density and the spatial distribution of relaxation time in the excited state, the form or function of the human head, abdomen, limbs, etc. is imaged two-dimensionally or three-dimensionally.
　図2は図1に示した傾斜磁場電源装置10と傾斜磁場発生コイル9の詳細図である。　
　傾斜磁場電源装置10は、X軸傾斜磁場電源装置201、Y軸傾斜磁場電源装置202、Z軸傾斜磁場電源装置203とから成り、それぞれX，Y，Zの3軸方向に傾斜磁場を印加するX軸傾斜磁場発生コイル204、Y軸傾斜磁場発生コイル205、Z軸傾斜磁場発生コイル206に対し電源を供給する。 FIG. 2 is a detailed view of the gradient magnetic field power supply device 10 and the gradient magnetic field generating coil 9 shown in FIG.
The gradient magnetic field power supply apparatus 10 includes an X-axis gradient magnetic field power supply apparatus 201, a Y-axis gradient magnetic field power supply apparatus 202, and a Z-axis gradient magnetic field power supply apparatus 203, and applies gradient magnetic fields in the three-axis directions of X, Y, and Z, respectively. Power is supplied to the X-axis gradient magnetic field generating coil 204, the Y-axis gradient magnetic field generating coil 205, and the Z-axis gradient magnetic field generating coil 206.
　本発明の実施例について図3及び図4を用いて説明する。　
　図3はX軸傾斜磁場制御回路306と傾斜磁場出力アンプ302と直流電源304とから成るX軸傾斜磁場電源装置201と、傾斜磁場出力アンプ302の出力端に接続されるX軸傾斜磁場発生コイル204について示した図である。図4は図3に示したX軸傾斜磁場電源装置201内のX軸傾斜磁場制御回路306についてさらに詳細に示した図である。図3に示す、傾斜磁場出力アンプ302はX軸傾斜磁場発生コイル204に印加する電圧をX軸傾斜磁場制御回路306によって制御される。 An embodiment of the present invention will be described with reference to FIGS.
FIG. 3 shows an X-axis gradient magnetic field power supply apparatus 201 including an X-axis gradient magnetic field control circuit 306, a gradient magnetic field output amplifier 302, and a DC power supply 304, and an X-axis gradient magnetic field generating coil connected to the output terminal of the gradient magnetic field output amplifier 302. FIG. FIG. 4 is a diagram showing the X-axis gradient magnetic field control circuit 306 in the X-axis gradient magnetic field power supply apparatus 201 shown in FIG. 3 in more detail. The gradient magnetic field output amplifier 302 shown in FIG.
　傾斜磁場出力アンプ302は、複数のスイッチング素子と複数のダイオードから成るブリッジ回路303aと、ブリッジ回路303aと同一の構成からなり、且つブリッジ回路303aに並列接続されるブリッジ回路303bと、これらブリッジ回路303a、ブリッジ回路303bの各々出力端に接続されたインダクタL11、L21及びインダクタL12、L22から成る。ここで、インダクタL11とL21、インダクタL12とL22はそれぞれコアを用いて磁気結合されている。ブリッジ回路303aは、スイッチング素子SW11、SW12、SW13、SW14と、ダイオードD11、D12、D13、D14から構成される。スイッチング素子SW11、SW12、SW13、SW14は例えばIGBT(Insulated Gate Bipolar Transistor)で構成され、他にもMOS-FET(Metal Oxide Semiconductor Field Effect Transistor)等が該スイッチング素子として使用することができる。また、ダイオードD11、D12、D13、D14は例えばFRD(Fast Recovery Diode)で構成される。本実施例ではスイッチング素子SW11、SW12、SW13、SW14をIGBTとする。 The gradient magnetic field output amplifier 302 includes a bridge circuit 303a including a plurality of switching elements and a plurality of diodes, a bridge circuit 303b having the same configuration as the bridge circuit 303a and connected in parallel to the bridge circuit 303a, and the bridge circuit 303a. The inductors L11 and L21 and inductors L12 and L22 are connected to the output terminals of the bridge circuit 303b. Here, the inductors L11 and L21 and the inductors L12 and L22 are magnetically coupled using a core, respectively. The bridge circuit 303a includes switching elements SW11, SW12, SW13, SW14 and diodes D11, D12, D13, D14. The switching elements SW11, SW12, SW13, and SW14 are composed of, for example, IGBT (Insulated Gate Bipolar Transistor), and MOS-FET (Metal Oxide Semiconductor Semiconductor Field Effect Transistor) or the like can be used as the switching element. The diodes D11, D12, D13, and D14 are composed of, for example, FRD (Fast Recovery Diode). In this embodiment, the switching elements SW11, SW12, SW13, and SW14 are IGBTs.
　SW11のエミッタはSW12のコレクタに接続され、SW11、SW12にはそれぞれD11、D12が並列接続される。D11、D12のカソードはそれぞれSW11、SW12のコレクタに、D11、D12のアノードはそれぞれSW11、SW12のエミッタに接続される。同様にSW13のエミッタはSW14のコレクタに接続され、SW13、SW14にはそれぞれD13、D14が並列接続される。D13、D14のカソードはそれぞれSW13、SW14のコレクタに、D13、D14のアノードはそれぞれSW13、SW14のエミッタに接続される。 The SW11 emitter is connected to the SW12 collector, and D11 and D12 are connected in parallel to SW11 and SW12, respectively. The cathodes of D11 and D12 are connected to the collectors of SW11 and SW12, respectively, and the anodes of D11 and D12 are connected to the emitters of SW11 and SW12, respectively. Similarly, the emitter of SW13 is connected to the collector of SW14, and D13 and D14 are connected in parallel to SW13 and SW14, respectively. The cathodes of D13 and D14 are connected to the collectors of SW13 and SW14, respectively, and the anodes of D13 and D14 are connected to the emitters of SW13 and SW14, respectively.
　SW11のコレクタとSW13のコレクタは接続され、SW12のエミッタとSW14のエミッタは接続される。ブリッジ回路303bはスイッチング素子SW21、SW22、SW23、SW24と、ダイオードD21、D22、D23、D24から成り、ブリッジ回路303aと同様の構成である。SW21のエミッタはSW22のコレクタに接続され、SW21、SW22にはそれぞれD21、D22が並列接続される。D21、D22のカソードはそれぞれSW21、SW22のコレクタに、D21、D22のアノードはそれぞれSW21、SW22のエミッタに接続される。同様にSW23のエミッタはSW24のコレクタに接続され、SW23、SW24にはそれぞれD23、D24が並列接続される。 The collector of SW11 and the collector of SW13 are connected, and the emitter of SW12 and the emitter of SW14 are connected. The bridge circuit 303b includes switching elements SW21, SW22, SW23, and SW24 and diodes D21, D22, D23, and D24, and has the same configuration as the bridge circuit 303a. The emitter of SW21 is connected to the collector of SW22, and D21 and D22 are connected in parallel to SW21 and SW22, respectively. The cathodes of D21 and D22 are connected to the collectors of SW21 and SW22, respectively, and the anodes of D21 and D22 are connected to the emitters of SW21 and SW22, respectively. Similarly, the emitter of SW23 is connected to the collector of SW24, and D23 and D24 are connected in parallel to SW23 and SW24, respectively.
　D23、D24のカソードはそれぞれSW23、SW24のコレクタに、D23、D24のアノードはそれぞれSW23、SW24のエミッタに接続される。SW21のコレクタとSW23のコレクタは接続され、SW22のエミッタとSW24のエミッタは接続される。L11、L21はそれぞれ異なった向きの巻き線方向で同一のコアに巻かれ、L11、L21のそれぞれの片側同士を接続している。L11とL21の巻数比は1：1である。また、L11、L21の該接続とは異なる側は、それぞれSW11のエミッタとSW21のエミッタに接続される。同様にL12、L22はそれぞれ異なった向きの巻き線方向で同一のコアに巻かれ、L12、L22のそれぞれの片側同士を接続している。 The cathodes of D23 and D24 are connected to the collectors of SW23 and SW24, respectively, and the anodes of D23 and D24 are connected to the emitters of SW23 and SW24, respectively. The collector of SW21 and the collector of SW23 are connected, and the emitter of SW22 and the emitter of SW24 are connected. L11 and L21 are wound around the same core in different winding directions, and one side of each of L11 and L21 is connected. The turn ratio between L11 and L21 is 1: 1. Further, the side of L11, L21 different from the connection is connected to the emitter of SW11 and the emitter of SW21, respectively. Similarly, L12 and L22 are wound around the same core in different winding directions, and one side of each of L12 and L22 is connected.
　L12とL22の巻数比は1：1である。L12、L22の該接続とは異なる側は、それぞれSW13のエミッタとSW23のエミッタに接続される。コアを用いることにより互いのインダクタよる磁気結合は容易になされる。SW11、SW13、SW21、SW23のコレクタは直流電源304の陽極に接続され、SW12、SW14、SW22、SW24のエミッタは直流電源304の陰極に接続される。L11とL21の接続箇所とL12とL22の接続箇所はそれぞれX軸傾斜磁場発生コイル204の両端に接続される。 The turn ratio between L12 and L22 is 1: 1. The side different from the connection of L12 and L22 is connected to the emitter of SW13 and the emitter of SW23, respectively. By using the core, the magnetic coupling by the inductors can be easily performed. The collectors of SW11, SW13, SW21, and SW23 are connected to the anode of the DC power supply 304, and the emitters of SW12, SW14, SW22, and SW24 are connected to the cathode of the DC power supply 304. The connection point between L11 and L21 and the connection point between L12 and L22 are connected to both ends of the X-axis gradient magnetic field generating coil 204, respectively.
　X軸傾斜磁場発生コイル204に電圧を印加したい場合は、ブリッジ回路303a及びブリッジ回路303bの各スイッチング素子を制御するPWM信号307a及びPWM信号307b生成するX軸傾斜磁場制御回路306によって、SW11とSW21、SW14とSW24をそれぞれ導通(以下ON)させ、SW13とSW23、SW12とSW22はそれぞれ開放(以下OFF)させる。これにより、直流電源304の陽極からSW11、L11及びSW21、L21を通じそれぞれX軸傾斜磁場発生コイル204に電流が流れる。 When it is desired to apply a voltage to the X-axis gradient magnetic field generating coil 204, SW11 and SW21 are generated by the X-axis gradient magnetic field control circuit 306 that generates the PWM signal 307a and the PWM signal 307b for controlling the switching elements of the bridge circuit 303a and the bridge circuit 303b. SW14 and SW24 are made conductive (hereinafter referred to as ON), and SW13 and SW23, and SW12 and SW22 are respectively opened (hereinafter referred to as OFF). As a result, current flows from the anode of the DC power supply 304 to the X-axis gradient magnetic field generating coil 204 through SW11, L11 and SW21, L21.
　X軸傾斜磁場発生コイル204に流れ込んだ電流はL12、SW14及びL22、SW24を通じ直流電源304の陰極に戻る。この場合にX軸傾斜磁場発生コイル204に印加される電圧の向きを順バイアスとすると、X軸傾斜磁場発生コイル204に逆バイアスを印加したい場合は、同様にX軸傾斜磁場制御回路306によって、SW11とSW21、SW14とSW24をそれぞれOFFさせ、SW13とSW23、SW12とSW22はそれぞれOＮをさせることで実施可能である。電流経路については自明であるので特に詳説しない。 The current flowing into the X-axis gradient magnetic field generating coil 204 returns to the cathode of the DC power supply 304 through L12, SW14, L22, and SW24. In this case, assuming that the direction of the voltage applied to the X-axis gradient magnetic field generating coil 204 is a forward bias, if it is desired to apply a reverse bias to the X-axis gradient magnetic field generating coil 204, the X-axis gradient magnetic field control circuit 306 similarly SW11 and SW21, SW14 and SW24 are turned off, and SW13 and SW23, SW12 and SW22 are turned on, respectively. The current path is self-explanatory and will not be described in detail.
　ブリッジ回路303a、ブリッジ回路303bの各スイッチング素子の制御に際しては、X軸傾斜磁場発生コイル204に流れる電流を検出する傾斜磁場電流検出器309によって検出される電流検出値Igに基づいて、X軸傾斜磁場制御回路306によりフィードバック制御がかけられる。ここで、X軸傾斜磁場発生コイル204に順バイアスを印加する際、L11及びL21を流れる電流の向きは、共にX軸傾斜磁場発生コイル204に対して流れる向きであり、流れる電流値も同一である。この場合、L11とL21の磁気結合に用いているコアに磁束は発生しない。 When controlling the switching elements of the bridge circuit 303a and the bridge circuit 303b, the X-axis gradient is determined based on the current detection value Ig detected by the gradient magnetic field current detector 309 that detects the current flowing in the X-axis gradient magnetic field generating coil 204. Feedback control is applied by the magnetic field control circuit 306. Here, when a forward bias is applied to the X-axis gradient magnetic field generating coil 204, the directions of the currents flowing through L11 and L21 are both the directions flowing with respect to the X-axis gradient magnetic field generating coil 204, and the flowing current values are also the same. is there. In this case, no magnetic flux is generated in the core used for magnetic coupling of L11 and L21.
　L11とL21がそれぞれ異なった向きの巻き線方向で同一のコアに巻いているためである。しかし、SW11とSW21のどちらか一方に異常が発生した場合等は、L11とL21に流れる電流値に差が生じる。この場合、L11とL21を巻いているコアに磁束が発生する。この様な状態が続くとコアの磁束密度が限界に達し(飽和磁束密度)、L11とL21によるインタクタンス成分がほぼ0[H]となる。SW11とSW22が共にONにして使用するような場合、SW11からL11、L21、SW22の経路で過電流が流れ各素子の破壊に繋がる。 This is because L11 and L21 are wound around the same core in different winding directions. However, when an abnormality occurs in one of SW11 and SW21, a difference occurs in the value of the current flowing through L11 and L21. In this case, a magnetic flux is generated in the core around L11 and L21. If such a state continues, the core magnetic flux density reaches the limit (saturated magnetic flux density), and the inductance component by L11 and L21 becomes almost 0 [H]. When both SW11 and SW22 are turned on and used, overcurrent flows through the path from SW11 to L11, L21, and SW22, leading to the destruction of each element.
　そこで、L11に流れる電流を検出する電流検出器310aと、L21に流れる電流を検出する電流検出器310bと、を設置する。電流検出器310a及び電流検出器310bにより検出される各々の電流検出値Ia及びIbに基づいて、X軸傾斜磁場制御回路306は、ブリッジ回路303a及びブリッジ回路303bの各スイッチング素子の動作を制御し、コアの磁気飽和を未然に防止する。 Therefore, a current detector 310a for detecting the current flowing through L11 and a current detector 310b for detecting the current flowing through L21 are installed. Based on the respective current detection values Ia and Ib detected by the current detector 310a and the current detector 310b, the X-axis gradient magnetic field control circuit 306 controls the operation of each switching element of the bridge circuit 303a and the bridge circuit 303b. To prevent magnetic saturation of the core.
　ここで、X軸傾斜磁場制御回路306の制御方法について、電流検出値Igによるフィードバック制御と共に図4を用いて説明する。 Here, a control method of the X-axis gradient magnetic field control circuit 306 will be described with reference to FIG. 4 together with feedback control by the current detection value Ig.
　図4に示す傾斜磁場電流検出器309により検出した電流検出値Igは、X軸傾斜磁場制御回路306内の演算器P401に出力される。演算器P401は、傾斜磁場電流検出器309によって入力された電流検出値Igと、別途CPU8から送られてくる目標電流値Io308と、を用いて演算を行う。該演算では目標電流値Io308から電流検出値Igを引いた値(差分電流値Iog)をPWM調整器402に出力する。PWM調整器402は演算器P401から送られてきた差分電流値Iogに基づいて、差分電流値Iogの値が正ならばPWM信号307a及びPWM信号307bの元となるPWM中間信号403の一定期間内にONをしている時間(ONデューティー)を増加させ、差分電流値Iogの値が負ならばPWM中間信号403のONデューティーを減少させる。差分電流値Iogの値が0ならばPWM中間信号403のONデューティーは現状維持とするフィードバック制御をかける。本実施例のフィードバック制御は、電流検出値Igと目標電流値Io308に基づいてPWM中間信号403を生成するものであるが、その演算方法はこれに限定されるものではない。 The current detection value Ig detected by the gradient magnetic field current detector 309 shown in FIG. 4 is output to the calculator P401 in the X-axis gradient magnetic field control circuit 306. The computing unit P401 performs computation using the current detection value Ig input by the gradient magnetic field current detector 309 and the target current value Io308 sent from the CPU 8 separately. In this calculation, a value obtained by subtracting the detected current value Ig from the target current value Io 308 (differential current value Iog) is output to the PWM regulator 402. The PWM regulator 402 is based on the differential current value Iog sent from the computing unit P401, and if the differential current value Iog is positive, the PWM intermediate signal 403 that is the source of the PWM signal 307a and the PWM signal 307b is within a certain period. When the differential current value Iog is negative, the ON duty of the PWM intermediate signal 403 is decreased. If the value of the differential current value Iog is 0, feedback control is performed so that the ON duty of the PWM intermediate signal 403 is maintained as it is. The feedback control of the present embodiment generates the PWM intermediate signal 403 based on the current detection value Ig and the target current value Io308, but the calculation method is not limited to this.
　PWM中間信号403は、スイッチSW401がONの場合はそのままPWM信号307aとPWM信号307bとして、ブリッジ回路303a及びブリッジ回路303bに送信される。スイッチSW401がOFFの場合はPWM信号307a及びPWM信号307bを通じブリッジ回路303a及びブリッジ回路303bに停止する信号を送信する。停止信号は例えばGNDレベルとする。PWM信号307a及びPWM信号307bのライン上にプルダウン抵抗をGND間に挿入する(特に図示しない)ことで、スイッチSW401がOFFになった場合、PWM信号307a及びPWM信号307bをGNDレベルに維持することが出来る。 The PWM intermediate signal 403 is directly transmitted to the bridge circuit 303a and the bridge circuit 303b as the PWM signal 307a and the PWM signal 307b when the switch SW401 is ON. When the switch SW401 is OFF, a stop signal is transmitted to the bridge circuit 303a and the bridge circuit 303b through the PWM signal 307a and the PWM signal 307b. For example, the stop signal is set to the GND level. By inserting a pull-down resistor between GND of the PWM signal 307a and PWM signal 307b (not shown in particular), when the switch SW401 is turned OFF, the PWM signal 307a and PWM signal 307b are maintained at the GND level. I can do it.
　次に、スイッチSW401の動作について説明する。スイッチSW401はスイッチ制御器400によって制御される。スイッチ制御器400は、演算器P402から出力されてくる演算結果に基づいてSW401のON/OFF制御を行う。演算器P402は、L11に流れる電流を検出する電流検出器310aにより検出された電流検出値Iaと、L21に流れる電流を検出する電流検出器310bにより検出された電流検出値Ibと、を用いて演算を行う。該演算は、電流検出値Iaと電流検出値Ibとの差分を求める。 Next, the operation of the switch SW401 will be described. The switch SW401 is controlled by the switch controller 400. The switch controller 400 performs ON / OFF control of the SW 401 based on the calculation result output from the calculator P402. The computing unit P402 uses the current detection value Ia detected by the current detector 310a that detects the current flowing through L11 and the current detection value Ib detected by the current detector 310b that detects the current flowing through L21. Perform the operation. The calculation obtains a difference between the current detection value Ia and the current detection value Ib.
　ここで、電流検出値Iaから電流検出値Ibを引いた値の絶対値を差分電流絶対値Iabとする。X軸傾斜磁場制御回路306によって、SW11とSW21、SW14とSW24をそれぞれON、SW13とSW23、SW12とSW22をそれぞれOFFした場合、通常、電流検出値Iaと電流検出値Ibとの間に差は生じない。しかし、各スイッチング素子間のばらつきや、各スイッチング素子の一部に異常等が発生した場合などは、電流検出値Iaと電流検出値Ibとの間で値に差が生じる場合がある。この様な場合、L11とL21の磁気結合に用いているコアに磁束が発生している。 Here, the absolute value of the value obtained by subtracting the current detection value Ib from the current detection value Ia is defined as a differential current absolute value Iab. When SW11 and SW21, SW14 and SW24 are turned ON, SW13 and SW23, and SW12 and SW22 are turned OFF by X-axis gradient magnetic field control circuit 306, the difference between current detection value Ia and current detection value Ib is usually Does not occur. However, there may be a difference in the value between the current detection value Ia and the current detection value Ib when there is a variation between the switching elements or when an abnormality or the like occurs in a part of each switching element. In such a case, magnetic flux is generated in the core used for magnetic coupling of L11 and L21.
　コアに発生する磁束は、L11及びL21に流れる電流の差分に比例することから、差分電流値Iabを求めることでコアにかかる磁束密度に相当する値を得る事ができる。演算器P402により算出された差分電流絶対値Iabがコアが磁気飽和を起こす一定以上の値を示した場合、該算出された差分電流絶対値Iabに基づいてスイッチ制御器400により、スイッチSW401はOFFされる。通常L11、L12に流れる電流は数百アンペアという大電流であるのに対し、コアが磁気飽和を起こすために必要な差分電流絶対値Iabは数アンペア程度である。 Since the magnetic flux generated in the core is proportional to the difference between the currents flowing through L11 and L21, a value corresponding to the magnetic flux density applied to the core can be obtained by obtaining the differential current value Iab. When the differential current absolute value Iab calculated by the arithmetic unit P402 indicates a value greater than or equal to a certain value at which the core causes magnetic saturation, the switch SW400 is turned OFF by the switch controller 400 based on the calculated differential current absolute value Iab. Is done. Normally, the current flowing through L11 and L12 is a large current of several hundred amperes, whereas the differential current absolute value Iab required for causing the core to undergo magnetic saturation is about several amperes.
　これにより、PWM信号307a及びPWM信号307bは、ブリッジ回路303a及びブリッジ回路303bに対し停止信号を送信し、コアの磁気飽和を未然に防止することができる。また、該停止信号はその信号を保持して完全にブリッジ回路303a及びブリッジ回路303bの動作を停止させる事も出来るが、停止信号を保持せずに磁気飽和を起こしそうになった期間のみブリッジ回路303a及びブリッジ回路303bを停止させ、コアの磁気飽和解消後に再び動作を開始させる事も出来る。また、該停止信号をCPU8に送信し、MRI装置の撮像を停止する事も可能である。また撮像を継続した場合に置いても，動作中に瞬間的な異常動作があった事を知らせる事も出来る。 Thereby, the PWM signal 307a and the PWM signal 307b transmit a stop signal to the bridge circuit 303a and the bridge circuit 303b, thereby preventing magnetic saturation of the core. Further, the stop signal can hold the signal and completely stop the operation of the bridge circuit 303a and the bridge circuit 303b, but the bridge circuit only during the period when the magnetic saturation is likely to occur without holding the stop signal. It is also possible to stop 303a and the bridge circuit 303b and start the operation again after eliminating the magnetic saturation of the core. It is also possible to stop the imaging of the MRI apparatus by transmitting the stop signal to the CPU 8. In addition, even when imaging is continued, it is possible to notify that there was an instantaneous abnormal operation during operation.
　次に、本実施例の動作を図9のフローチャートに基づいて説明する。 Next, the operation of this embodiment will be described based on the flowchart of FIG.
　まず、ステップ901では、電流検出器310a及び電流検出器310bにより、電流検出値Iaと電流検出値Ibを検出する。次に、ステップ902では、演算器P402により、電流検出値Iaと電流検出値Ibの差分を演算する。演算により求めた差分電流絶対値Iabが一定値以上の場合ステップ903に進み、一定値未満の場合ステップ904に進む。ステップ903ではスイッチ制御器400により、スイッチSW401がOFFされ、ブリッジ回路303a及びブリッジ回路303bの動作を停止される。次に、ステップ904では、スイッチ制御器400により、スイッチSW401がONされる。次に、ステップ905では、傾斜磁場電流検出器309により、電流検出値Igを検出する。次に、ステップ906では、演算器P401により、目標電流値Io308と電流検出値Igの差分を演算する。演算により求めた差分電流値Iogが0未満の場合は、ステップ907に進み、0の場合は、ステップ908に進み、0より大きい場合は、ステップ909に進む。ステップ907では、現状のPWM中間信号403のONデューティーを減少させた信号をブリッジ回路303a及びブリッジ回路303bに出力し、ステップ901に戻る。ステップ908では、現状のPWM中間信号403のONデューティーを維持させた信号をブリッジ回路303a及びブリッジ回路303bに出力し、ステップ901に戻る。ステップ909では、現状のPWM中間信号403のONデューティーを増加させた信号をブリッジ回路303a及びブリッジ回路303bに出力し、ステップ901に戻る。 First, in step 901, the current detection value Ia and the current detection value Ib are detected by the current detector 310a and the current detector 310b. Next, in step 902, the calculator P402 calculates the difference between the current detection value Ia and the current detection value Ib. When the differential current absolute value Iab obtained by the calculation is greater than or equal to a certain value, the process proceeds to step 903, and when it is less than the certain value, the process proceeds to step 904. In Step 903, the switch SW400 is turned OFF by the switch controller 400, and the operations of the bridge circuit 303a and the bridge circuit 303b are stopped. Next, in step 904, the switch SW401 is turned ON by the switch controller 400. Next, at step 905, the current detection value Ig is detected by the gradient magnetic field current detector 309. Next, in Step 906, the calculator P401 calculates the difference between the target current value Io308 and the current detection value Ig. If the differential current value Iog obtained by calculation is less than 0, the process proceeds to step 907. If it is 0, the process proceeds to step 908. If it is greater than 0, the process proceeds to step 909. In step 907, a signal obtained by reducing the ON duty of the current PWM intermediate signal 403 is output to the bridge circuit 303a and the bridge circuit 303b, and the process returns to step 901. In step 908, the current PWM intermediate signal 403 with the ON duty maintained is output to the bridge circuit 303a and the bridge circuit 303b, and the process returns to step 901. In step 909, a signal obtained by increasing the ON duty of the current PWM intermediate signal 403 is output to the bridge circuit 303a and the bridge circuit 303b, and the process returns to step 901.
　以上説明した様に本実施例のX軸傾斜磁場電源装置201によれば、磁気結合したインダクタL11及びL21によって並列接続されたブリッジ回路303a及びブリッジ回路303bにおいて、各々のブリッジ回路から各々のインダクタに出力される電流値の差分に基づいてインダクタL11及びL21の磁気結合に用いるコアの磁気飽和を未然に防止することができる。また、X軸傾斜磁場電源装置201を好適に用いたMRI装置を提供することができる。また、本実施例では傾斜磁場電流検出器309によるフィードバック制御がある場合を示したが、傾斜磁場電流検出器309によるフィードバック制御がない場合においても、インダクタL11及びL21の磁気結合に用いるコアの磁気飽和を未然に防止することができる。この場合、ブリッジ回路303a及びブリッジ回路303bにはCPU8により所定のPWM信号がスイッチSW401を通し送信される。 As described above, according to the X-axis gradient magnetic field power supply apparatus 201 of the present embodiment, in each of the bridge circuit 303a and the bridge circuit 303b connected in parallel by the magnetically coupled inductors L11 and L21, each bridge circuit is changed to each inductor. Based on the difference between the output current values, magnetic saturation of the core used for magnetic coupling of the inductors L11 and L21 can be prevented in advance. In addition, an MRI apparatus that suitably uses the X-axis gradient magnetic field power supply apparatus 201 can be provided. Further, in this embodiment, the case where there is feedback control by the gradient magnetic field current detector 309 is shown, but even when there is no feedback control by the gradient magnetic field current detector 309, the magnetic field of the core used for magnetic coupling of the inductors L11 and L21 is shown. Saturation can be prevented beforehand. In this case, a predetermined PWM signal is transmitted to the bridge circuit 303a and the bridge circuit 303b by the CPU 8 through the switch SW401.
　本発明の実施例2について、図5を用いて説明する。　
　実施例1で示したX軸傾斜磁場電源装置201内のX軸傾斜磁場制御回路306に対し、図5に示すX軸傾斜磁場制御回路501は構成が一部異なっている。実施例1と共通部分については一部説明を省略する。 A second embodiment of the present invention will be described with reference to FIG.
The X-axis gradient magnetic field control circuit 501 shown in FIG. 5 is partially different from the X-axis gradient magnetic field control circuit 306 in the X-axis gradient magnetic field power supply apparatus 201 shown in the first embodiment. A part of the description common to the first embodiment will be omitted.
　図5に示すX軸傾斜磁場制御回路501内のPWM調整器402は、PWMa調整器503aとPWMb調整器503bに対しPWM中間信号403を出力する。また、演算器P502は、PWMa調整器503aとPWMb調整器503bに対し差分電流値Iabを出力する。PWMa調整器503aとPWMb調整器503bは、それぞれ入力されたPWM中間信号403と差分電流値Iabに基づいて、PWM信号504aとPWM信号504bをブリッジ回路303a及びブリッジ回路303bに出力する。PWM信号504a、PWM信号504bは、ブリッジ回路303a及びブリッジ回路303bの各スイチング素子を制御する制御信号である。 The PWM regulator 402 in the X-axis gradient magnetic field control circuit 501 shown in FIG. 5 outputs a PWM intermediate signal 403 to the PWMa regulator 503a and the PWMb regulator 503b. The computing unit P502 outputs the differential current value Iab to the PWMa adjuster 503a and the PWMb adjuster 503b. The PWMa adjuster 503a and the PWMb adjuster 503b output the PWM signal 504a and the PWM signal 504b to the bridge circuit 303a and the bridge circuit 303b based on the input PWM intermediate signal 403 and the differential current value Iab, respectively. The PWM signal 504a and the PWM signal 504b are control signals for controlling each switching element of the bridge circuit 303a and the bridge circuit 303b.
　次にPWMa調整器503a及びPWMb調整器503bの動作について詳説する。PWMa調整器503aは、演算器P502によって入力された差分電流値Iabがプラスの場合、PWM調整器402によって入力されたPWM中間信号403のONデューティーを減少させ、PWM信号504aとしてブリッジ回路303aに出力する。反対に、PWMa調整器503aに入力された差分電流値Iabがマイナスの場合は、PWM調整器402によって入力されたPWM中間信号403のONデューティーを増加させ、PWM信号504aとしてブリッジ回路303aに出力する。また、PWMa調整器503aに入力された差分電流値Iabが0の場合は、PWM調整器402によって入力されたPWM中間信号403のONデューティーの増減は行わず、そのままPWM中間信号403をPWM信号504aとしてブリッジ回路303aに出力する。 Next, the operation of the PWMa adjuster 503a and the PWMb adjuster 503b will be described in detail. When the differential current value Iab input by the calculator P502 is positive, the PWMa adjuster 503a decreases the ON duty of the PWM intermediate signal 403 input by the PWM adjuster 402, and outputs the PWM signal 504a to the bridge circuit 303a. To do. On the contrary, when the differential current value Iab input to the PWMa regulator 503a is negative, the ON duty of the PWM intermediate signal 403 input by the PWM regulator 402 is increased and output to the bridge circuit 303a as the PWM signal 504a. . When the differential current value Iab input to the PWMa adjuster 503a is 0, the PWM intermediate signal 403 input by the PWM adjuster 402 is not increased or decreased, and the PWM intermediate signal 403 is directly used as the PWM signal 504a. To the bridge circuit 303a.
　PWMb調整器503bは、PWMa調整器503aとは反対に演算器P502によって入力された差分電流値Iabがプラスの場合、PWM調整器402によって入力されたPWM中間信号403のONデューティーを増加させ、PWM信号504bとしてブリッジ回路303bに出力する。反対に、PWMb調整器503bに入力された差分電流値Iabがマイナスの場合は、PWM調整器402によって入力されたPWM中間信号403のONデューティーを減少させ、PWM信号504bとしてブリッジ回路303bに出力する。差分電流値Iabが0の場合は、PWMa調整器503aの場合の制御方法と同様に、PWM中間信号403をPWM信号504bとしてブリッジ回路303bに出力する。 The PWMb regulator 503b increases the ON duty of the PWM intermediate signal 403 inputted by the PWM regulator 402 when the differential current value Iab inputted by the arithmetic unit P502 is positive, as opposed to the PWMa regulator 503a. The signal 504b is output to the bridge circuit 303b. On the other hand, if the differential current value Iab input to the PWMb regulator 503b is negative, the ON duty of the PWM intermediate signal 403 input by the PWM regulator 402 is decreased and output to the bridge circuit 303b as the PWM signal 504b. . When the differential current value Iab is 0, the PWM intermediate signal 403 is output to the bridge circuit 303b as the PWM signal 504b, similarly to the control method in the case of the PWMa adjuster 503a.
　以上説明した様に本実施例のX軸傾斜磁場電源装置201によれば、インダクタL11及びL21に流れる電流の差分に基づいてPWM信号504a、PWM信号504bをそれぞれ独立に制御し調整することで、インダクタL11及びL21の磁気結合に用いるコアの磁気飽和を防止することができる。 As described above, according to the X-axis gradient magnetic field power supply apparatus 201 of the present embodiment, the PWM signal 504a and the PWM signal 504b are independently controlled and adjusted based on the difference between the currents flowing through the inductors L11 and L21, respectively. Magnetic saturation of the core used for magnetic coupling of the inductors L11 and L21 can be prevented.
　本発明の実施例3について、図6を用いて説明する。 Example 3 of the present invention will be described with reference to FIG.
　図6に示すX軸傾斜磁場制御回路601は実施例1で示したX軸傾斜磁場制御回路306と一部異なっている。実施例1と共通部分については一部説明を省略する。 6 is partially different from the X-axis gradient magnetic field control circuit 306 shown in the first embodiment. A part of the description common to the first embodiment will be omitted.
　実施例1及び実施例2では、インダクタL11及びL21に流れる電流IaとIbの差分値を演算するために、2つの電流検出器、電流検出器310a及び電流検出器310bを用いていた。これに対し、実施例3では図6に示すように単一の電流検出器605によりインダクタL11及びL21に流れる電流の差分値を検出する。電流検出器605はトロイダルコイルで構成される。電流検出器605は、ブリッジ回路303a、ブリッジ回路303bからインダクタL11、L21に共に電流を出力する場合において、インダクタL11、L21に流れる電流Ia、Ibの向きを互いに異にした状態で電流検出を行う。インダクタL11及びL21に流れる電流Ia、Ibが同一の値の場合は、電流検出器605により検出される電流値は0である。しかし、インダクタL11及びL21に流れる電流Ia、Ibに差が生じた場合は、電流検出器605によりその差分が検出される。該差分を差分電流値Iab2とすると、差分電流値Iab2が一定値以上を示した場合、この値に基づいてスイッチ制御器600により、スイッチSW601はOFFされる。これにより、PWM信号604a及びPWM信号604bは、ブリッジ回路303a及びブリッジ回路303bに対し停止信号を送信し、コアの磁気飽和を未然に防止することができる。 In the first and second embodiments, two current detectors, the current detector 310a and the current detector 310b are used to calculate the difference value between the currents Ia and Ib flowing through the inductors L11 and L21. On the other hand, in the third embodiment, as shown in FIG. 6, a single current detector 605 detects a difference value between currents flowing through the inductors L11 and L21. The current detector 605 is composed of a toroidal coil. The current detector 605 performs current detection in a state where the directions of the currents Ia and Ib flowing through the inductors L11 and L21 are different from each other when outputting current from the bridge circuit 303a and the bridge circuit 303b to the inductors L11 and L21. . When the currents Ia and Ib flowing through the inductors L11 and L21 have the same value, the current value detected by the current detector 605 is zero. However, if a difference occurs between the currents Ia and Ib flowing through the inductors L11 and L21, the current detector 605 detects the difference. Assuming that the difference is the difference current value Iab2, when the difference current value Iab2 shows a certain value or more, the switch controller 600 turns off the switch SW601 based on this value. As a result, the PWM signal 604a and the PWM signal 604b transmit a stop signal to the bridge circuit 303a and the bridge circuit 303b, thereby preventing magnetic saturation of the core.
　以上説明した様に本実施例のX軸傾斜磁場電源装置201によれば、インダクタL11及びL21に流れる電流IaとIbの差分値を単一の電流検出器605により検出することが出来るためコスト低下を図ることができる。また、単一の電流検出器605で差分値を検出するため、より精度の高い検出が可能となる。 As described above, according to the X-axis gradient magnetic field power supply apparatus 201 of the present embodiment, the difference value between the currents Ia and Ib flowing through the inductors L11 and L21 can be detected by the single current detector 605, thereby reducing the cost. Can be achieved. In addition, since the difference value is detected by a single current detector 605, detection with higher accuracy is possible.
　本発明の実施例4について、図7を用いて説明する。 Example 4 of the present invention will be described with reference to FIG.
　図7は、インダクタL11及びL21の磁気結合に用いたコア701の磁束を直接検出する手段の一例を示している。コア701のギャップ702に設置したホール素子703により、コア701の磁束を直接検出している。該検出した磁束が一定値以上となった場合、実施例1又は実施例3で示したスイッチ制御器400、スイッチ制御器600により、スイッチSW401、SW601をOFFしブリッジ回路303a及びブリッジ回路303bを停止させる。 FIG. 7 shows an example of means for directly detecting the magnetic flux of the core 701 used for magnetic coupling of the inductors L11 and L21. The magnetic flux of the core 701 is directly detected by the Hall element 703 installed in the gap 702 of the core 701. When the detected magnetic flux exceeds a certain value, the switches SW401 and SW601 are turned off by the switch controller 400 and the switch controller 600 shown in the first or third embodiment, and the bridge circuit 303a and the bridge circuit 303b are stopped. Let
　以上説明した様に本実施例では磁気結合したインダクタL11及びL21のコア701の磁束を直接検出することで、コア701の磁気飽和を確実に防止する事が出来る。 As described above, in this embodiment, the magnetic saturation of the core 701 can be reliably prevented by directly detecting the magnetic flux of the core 701 of the magnetically coupled inductors L11 and L21.
　本発明の実施例5について、図8を用いて説明する。 Example 5 of the present invention will be described with reference to FIG.
　図8は、インダクタL11及びL21の磁気結合に用いたコア801の磁束に相当する値を検出する手段の一例を示している。インダクタL11及びL21とは別にコア801に3次巻線としてインダクタL3を巻く。インダクタL3にはL11やL12のインダクタンスに影響を及ぼさないような高いインピーダンス、例えば数メガオームの抵抗802を接続する。この抵抗802に発生する電圧又は電流を検出する事により、コア801に発生している磁束に相当する値を得る事が出来る。該検出した電圧又は電流値が一定値以上となった場合、実施例4と同様に、ブリッジ回路303a及びブリッジ回路303bを停止させる。 FIG. 8 shows an example of means for detecting a value corresponding to the magnetic flux of the core 801 used for magnetic coupling of the inductors L11 and L21. Inductor L3 is wound around core 801 as a third winding separately from inductors L11 and L21. A high impedance that does not affect the inductance of L11 or L12, for example, a resistor 802 of several megaohms, is connected to the inductor L3. By detecting the voltage or current generated in the resistor 802, a value corresponding to the magnetic flux generated in the core 801 can be obtained. When the detected voltage or current value exceeds a certain value, the bridge circuit 303a and the bridge circuit 303b are stopped as in the fourth embodiment.
　以上説明した様に本実施例では磁気結合したインダクタL11及びL21のコア701に高インイーダンスの抵抗802を備えたインダクタL3を備えることで容易にコア801の磁気飽和を防止する事が出来る。 As described above, in this embodiment, magnetic saturation of the core 801 can be easily prevented by providing the inductor L3 having the high-impedance resistor 802 in the core 701 of the magnetically coupled inductors L11 and L21.
　以上、本発明の実施例を述べたが、本発明はこれらに限定されるものではない。本実施例では、X軸傾斜磁場電源装置201内のインダクタL11及びL21の磁気結合に用いるコアの磁気飽和防止について記載したが、同一の手法をY軸傾斜磁場電源装置202、Z軸傾斜磁場電源装置203に使用できることは言うまでもない。また、X軸傾斜磁場電源装置201、Y軸傾斜磁場電源装置202、Z軸傾斜磁場電源装置203、全てに磁気飽和防止機能を付加した場合、いずれか一つに異常が発生した場合、MRI装置の撮影を停止することも出来る。 As mentioned above, although the Example of this invention was described, this invention is not limited to these. In the present embodiment, the magnetic saturation prevention of the core used for the magnetic coupling of the inductors L11 and L21 in the X-axis gradient magnetic field power supply apparatus 201 has been described. Needless to say, the device 203 can be used. In addition, when a magnetic saturation prevention function is added to the X-axis gradient magnetic field power supply device 201, the Y-axis gradient magnetic field power supply device 202, and the Z-axis gradient magnetic field power supply device 203, if any one of the abnormalities occurs, the MRI apparatus You can also stop shooting.
　1　被検体、2　静磁場発生系、3　傾斜磁場発生系、4　シーケンサ、5　送信系、6　受信系、7　信号処理系、8　中央処理装置(CPU)、9　傾斜磁場発生コイル、10　傾斜磁場電源装置、11　高周波発振器、12　変調器、13　高周波増幅器、14a　高周波コイル(送信コイル)、14b　高周波コイル(受信コイル)、15　信号増幅器、16　直交位相検波器、17　Ａ／Ｄ変換器、18　磁気ディスク、19　光ディスク、20　ディスプレイ、23　トラックボール又はマウス、24　キーボード、25　操作部、26　静磁場発生装置、201　X軸傾斜磁場電源装置、202　Y軸傾斜磁場電源装置、203　Z軸傾斜磁場電源装置、204　X軸傾斜磁場発生コイル、205　Y軸傾斜磁場発生コイル、206　Z軸傾斜磁場発生コイル、302　傾斜磁場出力アンプ、303a、303b　ブリッジ回路、304　直流電源、306、501、601　X軸傾斜磁場制御回路、307a、307b、504a、504b、604a、604b　PWM信号、308　目標電流値Io、309　傾斜磁場電流検出器、310a、310b、605　電流検出器、400、600　スイッチ制御器、402　PWM調整器、403　PWM中間信号、503a　PWMa調整器、503b　PWMb調整器、701、801　コア、702　ギャップ、703　ホール素子、802　抵抗 1 subject, 2 static magnetic field generation system, 3 gradient magnetic field generation system, 4 sequencer, 5 transmission system, 6 reception system, 7 signal processing system, 8 central processing unit (CPU), 9 gradient magnetic field generation coil, 10 gradient magnetic field power supply Equipment, 11 high frequency oscillator, 12 modulator, 13 high frequency amplifier, 14a high frequency coil (transmitting coil), 14b high frequency coil (receiving coil), 15 signal amplifier, 16 quadrature phase detector, 17 A / D converter, 18 magnetic disk , 19 optical disk, 20 display, 23 trackball or mouse, 24 keyboard, 25 operation unit, 26 static magnetic field generator, 201 X-axis gradient magnetic field power supply, 202 Y-axis gradient magnetic field power supply, 203 Z-axis gradient magnetic field power supply, 204 X-axis gradient magnetic field generation coil, 205 Y-axis gradient magnetic field generation coil, 206 Z-axis gradient magnetic field generation coil, 302 Gradient magnetic field output amplifier, 303a, 303b bridge circuit, 304 DC power supply, 306, 501 601 X-axis gradient magnetic field control circuit, 307a, 307b, 504a, 504b, 604a, 604b PWM signal, 308 target current value Io, 309 gradient magnetic field current detector, 310a, 310b, 605 current detector, 400, 600 switch controller , 402 PWM regulator, 403 PWM intermediate signal, 503a PWMa regulator, 503b PWMb regulator, 701, 801 core, 702 gap, 703 Hall element, 802 resistance

Claims (13)

  1. 　複数のスイチング素子を有する同一構成の2つのブリッジ回路と、前記2つのブリッジ回路の出力端同士を接続するコアを用いて磁気結合させたインダクタと、前記2つのブリッジ回路にPWM信号を送信する傾斜磁場制御回路と、を有する傾斜磁場電源装置において、前記2つのブリッジ回路から前記インダクタに出力される各々の電流値の差分に基づいて前記PWM信号のONデューティーを制御することを特徴とする傾斜磁場電源装置。 Two bridge circuits having the same configuration having a plurality of switching elements, an inductor magnetically coupled using a core connecting the output ends of the two bridge circuits, and a gradient for transmitting a PWM signal to the two bridge circuits In the gradient magnetic field power supply device having a magnetic field control circuit, the gradient magnetic field is characterized in that the ON duty of the PWM signal is controlled based on the difference between the current values output from the two bridge circuits to the inductor. Power supply.
  2. 　前記インダクタに傾斜磁場発生コイルを接続し、前記インダクタから前記傾斜磁場発生コイルに流れる電流を検出する傾斜磁場電流検出器を備えると共に、前記傾斜磁場制御回路が、前記傾斜磁場電流検出器からの電流検出値によるフィードバック制御を、前記PWM信号の元となるPWM中間信号に反映させることを特徴とする請求項1記載の傾斜磁場電源装置。 The gradient magnetic field generating coil is connected to the inductor, and a gradient magnetic field current detector for detecting a current flowing from the inductor to the gradient magnetic field generating coil is provided, and the gradient magnetic field control circuit includes a current from the gradient magnetic field current detector. 2. The gradient magnetic field power supply device according to claim 1, wherein feedback control based on a detected value is reflected in a PWM intermediate signal that is a source of the PWM signal.
  3. 　前記傾斜磁場制御回路は、前記2つのブリッジ回路から前記インダクタに出力される各々の電流値を検出する2つの電流検出器を用いて前記電流値の差分を検出することを特徴とする請求項2記載の傾斜磁場電源装置。 3. The gradient magnetic field control circuit detects a difference between the current values using two current detectors that detect respective current values output from the two bridge circuits to the inductor. The gradient magnetic field power supply device described.
  4. 　前記傾斜磁場制御回路は、前記2つのブリッジ回路の内、一方のブリッジ回路から前記インダクタに流れる電流値が、他方のブリッジ回路から前記インダクタに流れる電流値より大きい場合、前記一方のブリッジ回路に出力するPWM信号のONデューティーを下げ、または、前記他方のブリッジ回路に出力するPWM信号のONデューティーを上げることを特徴とする請求項1記載の傾斜磁場電源装置。 The gradient magnetic field control circuit outputs to one of the two bridge circuits when a current value flowing from one bridge circuit to the inductor is larger than a current value flowing from the other bridge circuit to the inductor. 2. The gradient magnetic field power supply device according to claim 1, wherein the ON duty of the PWM signal to be reduced is decreased or the ON duty of the PWM signal output to the other bridge circuit is increased.
  5. 　前記傾斜磁場制御回路は、前記2つのブリッジ回路から前記インダクタに共に電流を出力する場合、前記電流の向きを互いに異なる状態して単一の電流検出器を用いて前記電流値の差分を検出することを特徴とする請求項2記載の傾斜磁場電源装置。 When the gradient magnetic field control circuit outputs a current from the two bridge circuits to the inductor, the gradient direction control circuit detects the difference between the current values using a single current detector with the directions of the currents being different from each other. 3. The gradient magnetic field power supply device according to claim 2, wherein
  6. 　前記傾斜磁場制御回路は、前記単一の電流検出器で電流値に差分が生じ、且つ該差分が一定値を超えた場合、PWM信号を用いて、前記2つのブリッジ回路を停止することを特徴とする請求項5記載の傾斜磁場電源装置。 The gradient magnetic field control circuit uses the PWM signal to stop the two bridge circuits when a difference occurs in the current value in the single current detector and the difference exceeds a certain value. 6. The gradient magnetic field power supply device according to claim 5.
  7. 　複数のスイチング素子を有する同一構成の2つのブリッジ回路と、前記、2つのブリッジ回路の出力端同士を接続するコアを用いて磁気結合させたインダクタと、前記2つのブリッジ回路にPWM信号を送信する傾斜磁場制御回路と、を有する傾斜磁場電源装置において、前記コアの磁束に基づいて前記PWM信号のONデューティーを制御することを特徴とする傾斜磁場電源装置。 Two bridge circuits having the same configuration having a plurality of switching elements, an inductor magnetically coupled using a core connecting the output ends of the two bridge circuits, and a PWM signal to the two bridge circuits A gradient magnetic field power supply device having a gradient magnetic field control circuit, wherein the ON duty of the PWM signal is controlled based on the magnetic flux of the core.
  8. 　前記コアにギャップを儲け前記ギャップ間にホール素子を設置すると共に前記ホール素子により前記コアの磁束を検出することを特徴とする請求項7記載の傾斜磁場電源装置。 8. The gradient magnetic field power supply device according to claim 7, wherein a gap is formed in the core, a Hall element is installed between the gaps, and a magnetic flux of the core is detected by the Hall element.
  9. 　前記コアに抵抗を備えた巻線を設置し、前記抵抗にかかる電圧、または、前記抵抗に流れる電流を検出することで前記コアの磁束を間接的に検出することを特徴とする請求項7記載の傾斜磁場電源装置。 8. The magnetic flux of the core is indirectly detected by installing a winding having a resistance in the core and detecting a voltage applied to the resistance or a current flowing through the resistance. Gradient magnetic field power supply device.
  10. 　被検体に、均一な磁場空間を発生するための静磁場発生コイルと、傾斜磁場を発生するための傾斜磁場発生コイルと、前記被検体に磁気共鳴を誘起するための高周波磁場発生コイルと、前記被検体の磁気共鳴信号を検出するための受信コイルと、を備える核磁気共鳴イメージング装置において、請求項1記載の傾斜磁場電源装置を用いることを特徴とする核磁気共鳴イメージング装置。 A static magnetic field generating coil for generating a uniform magnetic field space in the subject; a gradient magnetic field generating coil for generating a gradient magnetic field; a high-frequency magnetic field generating coil for inducing magnetic resonance in the subject; 6. A nuclear magnetic resonance imaging apparatus comprising: a receiving coil for detecting a magnetic resonance signal of a subject; and the gradient magnetic field power supply apparatus according to claim 1.
  11. 　被検体に、均一な磁場空間を発生するための静磁場発生コイルと、傾斜磁場を発生するための傾斜磁場発生コイルと、前記被検体に磁気共鳴を誘起するための高周波磁場発生コイルと、前記被検体の磁気共鳴信号を検出するための受信コイルと、を備える核磁気共鳴イメージング装置において、請求項7記載の傾斜磁場電源装置を用いることを特徴とする核磁気共鳴イメージング装置。 A static magnetic field generating coil for generating a uniform magnetic field space in the subject; a gradient magnetic field generating coil for generating a gradient magnetic field; a high-frequency magnetic field generating coil for inducing magnetic resonance in the subject; 8. A nuclear magnetic resonance imaging apparatus comprising: a receiving coil for detecting a magnetic resonance signal of a subject; and the gradient magnetic field power supply apparatus according to claim 7.
  12. 　複数のスイチング素子を有する同一構成の2つのブリッジ回路と、前記2つのブリッジ回路の出力端同士を接続するコアを用いて磁気結合させたインダクタと、前記2つのブリッジ回路にPWM信号を送信する傾斜磁場制御回路と、前記インダクタに傾斜磁場発生コイルを接続し、前記インダクタから前記傾斜磁場発生コイルに流れる電流を検出する傾斜磁場電流検出器と、前記2つのブリッジ回路から前記インダクタに出力される各々の電流値を検出する2つの電流検出器を備えた傾斜磁場電源装置の制御方法であって、
    　前記傾斜磁場制御回路は、前記2つのブリッジ回路から前記インダクタを通し傾斜磁場発生コイルに電力を供給するステップと、前記傾斜磁場発生コイルに流れる電流を検出し、その値に基づいて前記PWM信号の元となるPWM中間信号を生成するステップと、前記生成したPWM中間信号を前記2つのブリッジ回路からインダクタに出力される各々の電流値の差分に基づいて制御し、前記PWM信号を生成するステップと、前記生成したPWM信号を前記2つのブリッジ回路に出力するステップと、を備えることを特徴とする傾斜磁場電源装置の制御方法。     Two bridge circuits having the same configuration having a plurality of switching elements, an inductor magnetically coupled using a core connecting the output ends of the two bridge circuits, and a gradient for transmitting a PWM signal to the two bridge circuits A magnetic field control circuit, a gradient magnetic field generating coil connected to the inductor, a gradient magnetic field current detector for detecting a current flowing from the inductor to the gradient magnetic field generating coil, and each of the two bridge circuits output to the inductor A method of controlling a gradient magnetic field power supply device comprising two current detectors for detecting a current value of
    The gradient magnetic field control circuit supplies power to the gradient magnetic field generating coil from the two bridge circuits through the inductor, detects a current flowing through the gradient magnetic field generation coil, and based on the value, detects the PWM signal. A step of generating an original PWM intermediate signal, a step of controlling the generated PWM intermediate signal based on a difference between respective current values output from the two bridge circuits to an inductor, and generating the PWM signal; And a step of outputting the generated PWM signal to the two bridge circuits.
  13. 　前記PWM信号を生成するステップにおいて、前記2つのブリッジ回路の内、一方のブリッジ回路から前記インダクタに流れる電流値が、他方のブリッジ回路から前記インダクタに流れる電流値より大きい場合、前記一方のブリッジ回路に出力するPWM信号のONデューティーを下げ、または、前記他方のブリッジ回路に出力するPWM信号のONデューティーを上げることを特徴とする請求項12に記載の傾斜磁場電源装置の制御方法。 In the step of generating the PWM signal, when one of the two bridge circuits has a current value flowing from one bridge circuit to the inductor larger than a current value flowing from the other bridge circuit to the inductor, the one bridge circuit 13. The control method of a gradient magnetic field power supply device according to claim 12, wherein the ON duty of the PWM signal output to the second bridge circuit is decreased or the ON duty of the PWM signal output to the other bridge circuit is increased.
PCT/JP2011/050023 2010-01-06 2011-01-05 Gradient magnetic field power supply apparatus, method for controlling the power supply apparatus, and nuclear magnetic resonance imaging apparatus using the power supply apparatus WO2011083788A1 (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20130088234A1 (en) * 2010-06-17 2013-04-11 Koninklijke Philips Electronics N.V. Gradient coil power supply and a magnetic resonance imaging system
CN107102368A (en) * 2017-05-02 2017-08-29 吉林大学 A kind of closed-loop control near-earth water source exploration device and detection method
EP3352353A1 (en) * 2017-01-24 2018-07-25 General Electric Company Direct flux control power converter

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000245710A (en) * 1999-03-03 2000-09-12 Hitachi Medical Corp Power source device and magnetic resonance imaging device using it
WO2004103173A1 (en) * 2003-05-26 2004-12-02 Hitachi Medical Corporation Magnetic resonance imaging device
WO2007004565A1 (en) * 2005-07-01 2007-01-11 Hitachi Medical Corporation Power source device, and magnetic resonance imaging apparatus using the device
JP2007014361A (en) * 2005-07-05 2007-01-25 Hitachi Medical Corp Power device and magnetic resonance imaging system using the same

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000245710A (en) * 1999-03-03 2000-09-12 Hitachi Medical Corp Power source device and magnetic resonance imaging device using it
WO2004103173A1 (en) * 2003-05-26 2004-12-02 Hitachi Medical Corporation Magnetic resonance imaging device
WO2007004565A1 (en) * 2005-07-01 2007-01-11 Hitachi Medical Corporation Power source device, and magnetic resonance imaging apparatus using the device
JP2007014361A (en) * 2005-07-05 2007-01-25 Hitachi Medical Corp Power device and magnetic resonance imaging system using the same

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20130088234A1 (en) * 2010-06-17 2013-04-11 Koninklijke Philips Electronics N.V. Gradient coil power supply and a magnetic resonance imaging system
US9222997B2 (en) * 2010-06-17 2015-12-29 Koninklijke Philips N.V. Gradient coil power supply and a magnetic resonance imaging system
EP3352353A1 (en) * 2017-01-24 2018-07-25 General Electric Company Direct flux control power converter
US10050531B1 (en) 2017-01-24 2018-08-14 General Electric Company Direct flux control power converter
CN107102368A (en) * 2017-05-02 2017-08-29 吉林大学 A kind of closed-loop control near-earth water source exploration device and detection method

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