JP3591982B2 - Power supply for magnetic resonance imaging system - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a power supply device used for a magnetic resonance imaging apparatus (hereinafter, referred to as an “MRI apparatus”), and is particularly suitable for various power supplies required for generating a static magnetic field, a gradient magnetic field, and a high-frequency magnetic field requiring large power. Regarding power supply.
[0002]
[Prior art]
An MRI apparatus applies a high-frequency magnetic field in a pulsed manner to a test object placed in a static magnetic field, detects a magnetic resonance signal generated by the test object, and reconstructs a spectrum or an image based on the detected signal. The MRI apparatus has a superconducting or normal conducting coil for generating a static magnetic field as a magnetic field generating coil, a gradient magnetic field coil for generating a gradient magnetic field superimposed on the static magnetic field, and a high frequency coil for generating a high frequency magnetic field. Have been. These magnetic field generating coils are provided with a switching power supply for controlling the magnitude and timing of an applied current in order to generate a magnetic field having a predetermined magnetic strength.
[0003]
FIG. 6 shows a configuration of a switching power supply for generating a gradient magnetic field, particularly as a switching power supply for generating a magnetic field of such an MRI apparatus. This switching power supply includes four switching elements 51 to 54, reactors 55 and 56, and capacitors 57 and 58 for smoothing the output of the switching power supply. As a switching element electric field An effect type transistor (MOSFET) is adopted, the switching elements 51 and 52 and the switching elements 53 and 54 are respectively connected in series to the DC power supply 50, and the switching elements 51 and 52 and the switching elements 53 and 54 are connected in parallel. A bridge circuit composed of four connected arms is configured. The reactor 55 and the capacitor 57 are connected in parallel with the switching element 52, and the reactor 56 and the capacitor 58 are connected in parallel with the switching element 54. The smoothing circuit smoothes the voltages VL 'and VR' on the drain side of the switching elements 52 and 54, respectively. Is composed. One output terminal of this switching power supply is connected to a connection point between reactor 55 and capacitor 57, and the other output terminal is connected to a connection point between reactor 56 and capacitor 58, respectively.
[0004]
The switching power supply is alternately driven at a constant period so that the switching elements 52 and 53 are off when the switching elements 51 and 54 are on, and the switching elements 52 and 53 are on when the switching elements 51 and 54 are off. . At this time, on the other hand, for example, if the time during which the switching elements 51 and 54 are turned on is long and the on time of the switching elements 52 and 53 is shortened, the switching element 52 viewed from the neutral point (not shown) of the DC power supply 50 is assumed. And the drain-side voltages VL ′ and VR ′ of the output terminals 54 and 54 have rectangular waveforms as shown in FIG. 7, respectively, and are smoothed by the reactor 55 and the capacitor 57 and the reactor 56 and the capacitor 58 to obtain the output terminal voltage VLA. 'And VRA' are DC voltages as indicated by chain lines. However, since the voltage at the output terminal is a DC voltage including a ripple of the switching frequency, the output current IL ′ supplied to the magnetic field coil has a DC voltage slightly including the ripple of the same frequency as VLA ′ and VRA ′ as indicated by the solid line. It becomes a current.
[0005]
Since the ripple of the output current becomes an image noise in the MRI apparatus, it is necessary to set the effective value to, for example, about several mA or less. Therefore, a method of suppressing the cutoff frequency of the smoothing circuit including the reactor and the capacitor, and A method of increasing the switching frequency of the switch is adopted.
[0006]
[Problems to be solved by the invention]
However, in the former case, if the cutoff frequency is reduced, the response of the output current to the current command value to be applied to the magnetic field generating coil is delayed, making it difficult to obtain a high-speed, high-quality image. The latter uses a switch capable of high-speed switching, such as a MOSFET, and can be operated at a frequency of, for example, about 80 kHz to 100 kHz. Generally, a high-speed switching element such as a MOSFET has a withstand voltage of about 500 V and a rated current of about 100 A. And cannot cope with higher voltage and current capacity.
[0007]
In recent years, a large current power supply is required as a magnetic field power supply of an MRI apparatus in order to obtain an image useful for diagnosis in a short time. In such an MRI apparatus, a switch withstand voltage is about 1200 V and an output current is about 400 to 600 A. Power supply unit is required. However, a high-speed switching element represented by a MOSFET has a problem that it is difficult to achieve a higher-speed response and a larger capacity because the voltage to be used is limited by the rated current of the switching element as described above. Was.
[0008]
On the other hand, a power supply for an MRI apparatus in which a switching power supply is connected in series to a magnetic field coil has been proposed (such as OM Mueller et al., Literature name "Quasi-linear IGBT inverter topologies", literature name Proceedings of APEC '). 94 vol.1 P253-9 or vol.2 P1077, 1994). In this power supply device, the voltage applied to the magnetic field coil is distributed to the plurality of switching power supplies, so that an element having a relatively low withstand voltage can be used as the switching element. However, even in this case, the problem that a ripple having the same frequency as the operating frequency of the used switching element occurs cannot be solved.
[0009]
Therefore, an object of the present invention is to provide a low ripple current power supply suitable for a high-voltage, large-capacity magnetic field, regardless of the type of switching element used. It is another object of the present invention to provide a power supply device having a low ripple current without using a high-speed switching element such as a MOSFET.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, a power supply device for an MRI apparatus according to the present invention includes a switching power supply having a switching element and a magnetic field generation apparatus for a magnetic resonance imaging apparatus having a control circuit for controlling the switching element in the switching power supply. A power supply device for a magnetic resonance imaging apparatus connected to a coil, comprising a plurality of the switching power supplies, a plurality of switching power supply groups configured by connecting the switching power supplies in parallel, and connecting these switching power supply groups in series. Current control means connected to the output side of each switching power supply to prevent current from flowing to another switching power supply, and a plurality of voltage storage means connected in series with the magnetic field generating coil on the output side of each switching power supply group. , Which detects the current applied to the magnetism generating coil and feeds it back to the control circuit Detecting means or / and, in which a voltage detecting means for feedback by detecting the output voltage of each voltage storage means.
[0011]
Alternatively, a power supply device for an MRI apparatus according to the present invention includes a switching power supply having a switching element and a control circuit for controlling the switching element in the switching power supply. A power supply device for a resonance imaging apparatus, comprising: a plurality of switching power supplies, a plurality of switching power supplies, a plurality of switching power supply groups configured by connecting the switching power supplies in series, and the switching power supply groups connected in parallel. A plurality of voltage storage means connected in series with the magnetic field generating coil on the output side of the power supply; current control means for preventing current from flowing to another switching power supply on the output side of each switching power supply group; Current detection means for detecting the applied current and feeding it back to the control circuit, or And it is obtained by a voltage detecting means for feedback by detecting the output voltage of each voltage storage means.
[0012]
Preferably, in such a power supply device for a magnetic resonance imaging apparatus, the control circuit is connected to the current detection means and / or the voltage detection means, and specifies a current to be applied to the magnetic generation coil and / or each voltage storage means. Compares the specified voltage to be output with the current or / and voltage detected by the current detecting means and / or the voltage detecting means, and sets the phase of the switching element in each switching power supply such that the difference between the two becomes zero. The drive control is performed by shifting.
[0013]
As described above, the power supply device of the present invention can distribute the voltage applied to the magnetic field coil to the plurality of switching power supplies by connecting the switching power supply group in which the plurality of switching power supplies are connected in parallel, so that the switching element Even if the switch withstand voltage and the current capacity of one switching power supply are small due to the limitation of the rated current and the withstand voltage of the switching power supply, the output current of the whole power supply device can be increased, and the magnetic field for MRI apparatus requiring a large current capacity Applicable to generating coils. Also, since the input voltage of each switching power supply can be kept low, a high-speed switching element such as a MOSFET can be used in spite of a large current capacity, and a power supply device which has a quick response of the output current and a small ripple can be obtained. Can be
[0014]
Further, by providing the current control means on the output side where the switching power supplies are connected in parallel, it is possible to prevent the current from flowing from another switching power supply. Furthermore, by making the output voltage of each switching power supply variable and providing the voltage storage means on the output side where the switching power supply groups are connected in series, the voltage applied to the magnetic generating coil can be freely changed.
[0015]
Similarly, a voltage applied to the magnetic field coil can be distributed to a plurality of switching power supplies by connecting a plurality of switching power supplies connected in series to a switching power supply group connected in series. Can be applied to a magnetic field generating coil for an MRI apparatus that requires a large amount of current. In addition, since the input voltage of each switching power supply can be kept low, a high-speed switching element such as a MOSFET can be used despite its large current capacity.
[0016]
Further, a voltage storage means is provided on the output side where the switching power supplies are connected in series, and further, the output voltage of each switching power supply can be made variable to prevent a current from flowing from another switching power supply. Further, by making the output voltage of each switching power supply variable, the voltage applied to the magnetism generating coil can be freely changed. As described above, by providing the current control means on the output side where the switching power supply groups are connected in parallel, the voltage applied to the magnetism generating coil can be freely varied.
[0017]
In addition, by operating each switching power supply slightly out of phase by the control circuit, even when each switching power supply is operated at a low switching frequency, the ripple included in the final output current obtained by combining these output currents is obtained. Can have a high frequency and a low frequency, and as a result, the noise of the image of the MRI apparatus due to the ripple can be reduced. Further, since a low ripple current can be obtained without using a high-speed switching element such as a MOSFET, a large-capacity semiconductor switch such as a bipolar transistor, a gate turn-off thyristor, or an insulated gate bipolar transistor (IGBT) can be used. it can. Thereby, the capacity can be further increased.
[0018]
Further, the control circuit compares the current command value with the output current of the power supply device detected by the current detection means, and controls the switching power supplies so that the difference between the two becomes zero, thereby changing the phase of each switching power supply. A desired output current can always be obtained even when the operation is shifted. Further, the control circuit compares the voltage command value with the output voltage of each voltage storage means detected by the voltage detection means, and controls the switching power supply so that the difference between the two becomes zero, thereby controlling each switching power supply. Even when the operation is performed with the phase shifted, the output voltage may always be a desired output voltage. Furthermore, such control of the switching power supply may be performed by both current and voltage.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described.
[0020]
FIG. 1 is a diagram showing an embodiment of a power supply 10 for an MRI apparatus according to the present invention. The power supply 10 comprises four switching power supplies 11 to 14 and current control means respectively connected to the output sides of these switching power supplies. , And the switching power supplies 11 and 12 connected in parallel and the switching power supplies 13 and 14 connected in parallel respectively constitute a switching power supply group, and these switching power supply groups are connected in series. It is connected to a magnetic field generating coil 40 which is a load connected to the output side of the power supply device 10 for the MRI apparatus. The output side of a switching power supply group composed of switching power supplies 11 and 12 connected in parallel is connected to a capacitor 31 as voltage storage means. Similarly, a capacitor 32 as voltage storage means is connected to an output side of a switching power supply group including switching power supplies 13 and 14 connected in parallel. The capacitors 31 and 32 are connected in series to the magnetic field generating coil 40, and the sum of the voltages stored in the capacitors 31 and 32 is applied to the magnetic field generating coil 40.
[0021]
Further, a current detecting means 41 for detecting a current flowing in the magnetic field generating coil 40 and a control circuit 30 for controlling the driving of each of the switching power supplies 11 to 14 are provided. The control circuit 30 receives a specified current value to be applied to the magnetic field generating coil 40 and a current value detected by the current detection means 41, and controls the switching power supplies 11 so that the difference between the two becomes zero. To 14 are driven and controlled.
[0022]
Here, the reactors 20 to 27 used as current control means may switch one switching power supply to another switching power supply when the timing for driving the switching power supply is slightly deviated, especially when the driving is performed with a phase shifted as described later. This is to prevent current from flowing around the power supply.
[0023]
As the switching power supplies 11 to 14 in this embodiment, those used as a conventional power supply device as shown in FIG. 6 can be employed as the switching power supply. FIG. 2 shows an example of a suitable switching power supply. The switching power supply 11 uses a large-capacity semiconductor switching element having an withstand voltage of about 600 V and a switching frequency of about 20 kHz, and an insulated gate bipolar transistor (IGBT) as the switching elements 61 to 64, excluding the switching elements. Are the same as those in FIG. Briefly, a set of switching elements 61 and 62 connected in series to the DC power supply 60 and a set of switching elements similarly connected in series to the DC power supply and parallel to the switching elements 61 and 62 are provided. The switching elements 63 and 64 constitute a four-arm bridge circuit. The reactor 65 and the capacitor 67 for smoothing the voltage on the collector side of the switching element 62 and the voltage on the collector side of the switching element 64 are smoothed. And a condenser 68 for performing the operation. A connection point between the reactor 65 and the capacitor 67 is connected to one output terminal of the switching power supply, and a connection point between the reactor 66 and the capacitor 68 is similarly connected to the other output terminal. Is connected to the magnetic field generating coil 40 via the reactors 20 and 21 and the capacitor 31 as shown in FIG. Although only the switching power supply 11 is shown in FIG. 2, the switching power supplies 12 to 14 have exactly the same configuration.
[0024]
The switching power supply having such a configuration is repeatedly driven at a predetermined cycle so that the switching elements 61 and 64 and the switching elements 62 and 63 are alternately turned on and off similarly to the switching power supply of FIG. At this time, for example, by increasing the on-time of the switching elements 61 and 64 and shortening the on-time of the switching elements 62 and 63, the voltage VLA1 of the output terminal of the switching power supply 11 is increased as described in FIG. And VRA1 are DC voltages having different polarities from each other. The voltages VLA1 and VRA1 are obtained by smoothing the voltages VL1 and VR1 on the collector side of the switching elements 62 and 64 as viewed from the neutral point (not shown) of the DC power supply 60 in FIG. 2 by using a reactor and a capacitor. It is smoothed by a circuit. As a result, the output of the switching power supply becomes a DC current IL1.
[0025]
By the way, in the embodiment shown in FIG. 1, each of the switching power supplies 11 to 14 configured as described above is connected to the magnetic field generating coil 40 via a reactor and a capacitor. 14 is driven by the control circuit 30 by shifting the phase of the switch. In this embodiment, as shown in FIG. 3, the phase is shifted by 90 degrees corresponding to the provision of four switching power supplies. In the drawing, solid-line rectangular waveforms VL1 to VL4 indicate voltages on the collector side of the switching elements 62 of the switching power supplies 11 to 14, and chain-line waveforms VLA1 to VLA4 indicate voltages smoothed by the reactor and the capacitor. Waveform IL indicates an output current of power supply device 10 in which currents IL1 to IL4 output from switching power supplies 11 to 14 are finally combined. Here, as a result of the switching power supplies being connected in parallel, the output current IL from the power supply device 10 is larger than the currents IL1 to IL4 output from the switching power supplies 11 to 14.
[0026]
In order to shift the switching phase, the control circuit 30 shifts the timing of applying the gate voltage of the switching element of each of the switching power supplies 11 to 14 and detects the current command value to be applied to the magnetic field generating coil 40 and the current detecting means 41. Then, the voltage applied to the switching element of each switching power supply is controlled so that the difference between the two becomes zero. Thus, even when the switching currents are shifted in phase, the output current IL having a predetermined current command value flows through the magnetic field generating coil 40. In addition, as the current detecting means 41, a known current detector such as a low resistance or Hall element detector can be used in addition to the current transformer.
[0027]
Here, the voltage waveform at the output terminal of each switching power supply is a DC waveform including a ripple having the same frequency as the switching frequency as shown by chain lines VLA1 to VLA4 in FIG. 3, but these phases are shifted by 90 degrees. Thereby, the voltage of the output terminal as the whole power supply device 10 in FIG. 1 is increased in frequency, and the ripple of the output current IL flowing through the magnetic field generating coil 40 can be reduced. Therefore, even when a switching element having a low operating frequency is used as a power supply for an MRI apparatus such as an IGBT having a switching frequency of 20 kHz, the ripple frequency of the actual output can be increased to 80 kHz and the ripple can be reduced. Therefore, the power supply device 10 can be suitably used as a power supply for an MRI apparatus requiring a frequency of 80 kHz.
[0028]
In this way, the DC currents output from switching power supplies 11 and 12 are connected to capacitor 31 via reactors 20 to 23, so that DC voltage V1 is obtained at the output terminal of capacitor 31. Similarly, the DC current output from the switching power supplies 13 and 14 is connected to the capacitor 32 via the reactors 24 to 27, so that a DC voltage V2 is obtained at the output terminal of the capacitor 32. This DC voltage can be varied from -V01 to + V01 when the input voltage of the switching power supply 11 is V01. Accordingly, the output voltage VL of the power supply device 10, which is the sum of the respective output voltages V1 and V2 of the capacitors 31 and 32, can be freely varied between-(V1 + V2) and + (V1 + V2). That is, a voltage higher than the output voltage of each of the switching power supplies 11 to 14 can be obtained.
[0029]
Next, another embodiment of the present invention will be described. The power supply device shown in FIG. 1 obtains an output as the whole power supply device by connecting a plurality of switching power supply groups in which a plurality of switching power supplies are connected in parallel to obtain an output as a whole, as shown in FIG. In the power supply device of another embodiment, several switching power supply groups in which a plurality of switching power supplies are connected in series are connected in parallel to obtain an output of the power supply device as a whole. The configuration of this power supply device will be briefly described with reference to FIG. 4. This power supply device 10 also includes four switching power supplies 11 to 14 as in the above-described embodiment, but includes a switching power supply 11 connected in series. The switching power supply 12 and the switching power supplies 13 and 14 connected in series form a switching power supply group. Capacitors 71 to 74, which are voltage storage means, are connected to the output sides of the switching power supplies 11 to 14, respectively. The output side of a switching power supply group including switching power supplies 11 and 12 connected in series is connected to a current control means. Reactors 81 and 82 are connected, and reactors 83 and 84 are connected to the output side of a switching power supply group including switching power supplies 13 and 14 connected in series. When the reactors 81 and 83 are connected and the reactors 82 and 84 are connected, the switching power supply group including the switching power supplies 11 and 12 and the switching power supply group including the switching power supplies 13 and 14 generate magnetism in parallel. Connected to coil 40. 1, the power supply device 10 also includes a current detection means 41 for detecting a current flowing through a magnetic field generating coil 40 connected to the output side of the power supply device 10 for an MRI apparatus, and switching power supplies 11 to 14. And a control circuit 30 for controlling driving.
[0030]
In the power supply device 10 according to this embodiment, the switching power supplies 11 to 14 described above can be applied in exactly the same manner, and the functions of the reactors 81 to 84, the capacitors 71 to 74, the current detecting means 41, and the control circuit 30 are the same as those described above. This is the same as the embodiment. That is, the control circuit 30 shifts the timing of applying the gate voltage of the switching element of each of the switching power supplies 11 to 14, and adjusts the current command value to be applied to the magnetic field generating coil 40 and the current value detected by the current detection unit 41. And the voltage applied to the switching element of each switching power supply is controlled so that the difference between the two becomes zero. The reactor prevents the current from sneaking by driving the switching power supply by shifting the phase in this way, and further smoothes the output current together with the capacitor.
[0031]
In this manner, even if a plurality of switching power supplies are connected as shown in FIG. 1 or connected as shown in FIG. A ripple DC current can be obtained as an output.
[0032]
In the above-described embodiments of FIGS. 1 and 4, both use four switching power supplies, but the number of switching power supplies is not limited to four, and any number of switching power supplies may be used. In this case, by further increasing the number of switching power supplies connected in parallel, a power supply device with a larger current output can be configured.
[0033]
In the embodiment shown in FIGS. 1 and 4, the switching power supplies 11 to 14 are connected in parallel, so that the output current of one switching power supply is prevented from flowing into another switching power supply. Although the reactors 20 to 27 and the reactors 81 to 84 are used, such a current control means may be a resistor instead of the reactor, other switches or diodes, and the like. These combinations may be used. Also, in FIGS. 1 and 4, the reactor is connected to both of the two output terminals, but this is not necessarily required to be on both sides, and may be on one side.
[0034]
In the above embodiment, the case where the phases of the switches of each switching power supply are shifted at equal intervals has been described, but the shift intervals do not necessarily have to be equal. The phases may be unequal, and the phases of some switching power supplies may be the same. Even when the phases of the switches of a plurality of switching power supplies are not shifted, it is possible to increase the current capacity of the power supply device by providing a plurality of switching power supplies in parallel. However, by shifting the phase, the ripple of the main current of the power supply can be made higher in frequency. Therefore, use a high-withstand-voltage, high-current element such as an IGBT whose safe operating frequency is relatively low as a switching element. This is suitable for not only low ripple but also large capacity. When a high-speed switching element such as a MOSFET is used, the frequency of the ripple can be further increased.
[0035]
Further, the switching power supply in the present invention is not limited to the embodiment shown in FIG. 2, and the number of power supplies and switches, types of switching elements, configuration of a smoothing circuit, and the like can be arbitrarily changed. For example, FIG. 2 exemplifies a switching power supply composed of one power supply and a four-arm switch. However, the switching power supply may be composed of two power supplies and a two-arm switch, or a power supply composed of one switch. Furthermore, it can be applied in any switch Introduction Besides bipolar transistor also of the IGBT, a gate turn-off thyristor as a switching element.
[0036]
Further, in the embodiment shown in FIG. 2, a reactor and a capacitor are used as a smoothing circuit (filter). However, such a smoothing circuit may be provided not on each switching power supply but on a power supply device side. It can be provided not only for each switching power supply but also for the power supply itself. As such an example, a switching power supply 11 'as shown in FIG. 5 in which a reactor and a capacitor in the switching power supply are removed is shown. This switching power supply 11 'uses an IGBT as a switching element as in the embodiment shown in FIG. 2, and one of its output terminals is directly connected to the connection point of the switching elements 61 and 62, and the other is connected to the switching element 63, It is directly connected to 64 connection points. Therefore, since the output current IL1 of the switching power supply 11 'is not smoothed, a smoothing circuit is provided on the output side in a power supply device having a plurality of such switching power supplies 11' as shown in FIG. 1 or FIG. Must have. In the embodiment shown in FIG. 1, the reactors 20 to 27 and capacitors 31 and 32 provided on the output side of the switching power supply function as current control means and voltage accumulation means for preventing current from flowing around, respectively, and a smoothing circuit. Therefore, the output IL of the power supply device 10 can be converted to a direct current. The same applies to the embodiment shown in FIG. 4, and the capacitors 71 to 74 and the reactors 81 to 84 also contribute to smoothing.
[0037]
Further, in the embodiment of FIGS. 1 and 4, the drive control of each switching power supply by the control circuit 30 is performed based on the current value, but the voltage detection means (FIG. 1) for detecting the output voltages of the capacitors 31 and 32 and the capacitors 71 to 74 (Not shown), and inputs a voltage designation value to be output by each voltage storage means and a detection value detected by the voltage detection means to the control circuit 30, and drives each switching power supply so that the difference between the two becomes zero. You may make it control. In this case, each voltage command value may be equally divided for each switching power supply, or may be different for each switching power supply, and can be set arbitrarily. For this purpose, in the above embodiment, one control circuit 31 may be provided independently for each switching power supply for control. Further, the drive control of the switching power supply may be performed by both the current and the voltage.
[0038]
【The invention's effect】
As described above, according to the present invention, a plurality of switching power supplies connected in parallel are further connected in series as a power supply apparatus of the MRI apparatus, or a plurality of switching power supplies connected in series are further connected in parallel with each other. By connecting the current control means and the voltage accumulating means to the output side, a high-voltage, large-capacity power supply device can be configured, and furthermore, it is possible to prevent the sneak current of each switching power supply. The output voltage of the switching power supply can be freely varied. Further, according to the present invention, by operating a plurality of switching power supplies with shifted phases, it is possible to reduce ripples and increase the frequency, so that high voltage and high voltage can be obtained without using a high-speed switching element such as a MOSFET. A high-current, fast-response output current response and low-ripple power supply device can be provided.
[Brief description of the drawings]
FIG. 1 is a block diagram showing one embodiment of a power supply device of the present invention.
FIG. 2 is a circuit diagram showing one embodiment of a switching power supply used in the power supply device of the present invention.
FIG. 3 is a diagram showing switching waveforms and output currents of the power supply device of FIG.
FIG. 4 is a block diagram showing another embodiment of the power supply device of the present invention.
FIG. 5 is a circuit diagram showing another embodiment of the switching power supply used in the power supply device of the present invention.
FIG. 6 is a block diagram showing a conventional power supply device.
FIG. 7 is a diagram showing a switching waveform and an output current in a conventional device.
[Explanation of symbols]
10 Power supply for MRI system
11-14 Switching power supply
30 control circuit
20-27, 81-84 reactor (current control means)
31, 32, 71-71 Capacitor (voltage storage means)
40 magnetic coil
41 Current detection means.

Claims (3)

A power supply device for a magnetic resonance imaging apparatus connected to a magnetic field generating coil of a magnetic resonance imaging apparatus including a switching power supply having a switching element and a control circuit for controlling the switching element in the switching power supply,
A plurality of the switching power supplies are provided, and a plurality of switching power supply groups configured by connecting two or more of the switching power supplies in parallel and the switching power supply groups are connected in series,
A current control means for preventing a current from flowing to another switching power supply on an output side of each switching power supply; a plurality of voltage accumulating means connected in series with the magnetic field generating coil on an output side of each switching power supply group; Current detecting means for detecting a current applied to the magnetism generating coil and feeding it back to the control circuit; and / or voltage detecting means for detecting and feeding back the output voltage of each voltage storage means. Power supply for magnetic resonance imaging apparatus. A power supply device for a magnetic resonance imaging apparatus connected to a magnetic field generating coil of a magnetic resonance imaging apparatus including a switching power supply having a switching element and a control circuit for controlling the switching element in the switching power supply,
A plurality of the switching power supplies are provided, and a plurality of switching power supply groups configured by connecting two or more of the switching power supplies in series and the switching power supply groups are connected in parallel,
A plurality of voltage storage means connected in series with the magnetic field generating coil on an output side of each switching power supply; a current control means for preventing a current from flowing to another switching power supply on an output side of each switching power supply group; Current detecting means for detecting a current applied to the magnetism generating coil and feeding it back to the control circuit; and / or voltage detecting means for detecting and feeding back the output voltage of each voltage storage means. Power supply for magnetic resonance imaging apparatus. The control circuit is connected to the current detection means and / or the voltage detection means, and specifies a current value to be applied to the magnetism generating coil and / or a voltage specification value to be output by each voltage storage means. And / or comparing the current and / or voltage detected by the means and / or the voltage detecting means, and controlling the driving by shifting the phase of the switching element in each switching power supply so that the difference between the two becomes zero. A power supply device for a magnetic resonance imaging apparatus according to claim 1.

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