JP7030652B2 - Drive circuit and magnetic particle imaging device - Google Patents

Description

The present invention relates to a drive circuit and a magnetic particle imaging device that generate a magnetic field by supplying a current to a coil.

Magnetic nano-particle imaging or magnetic particle imaging (MPI) is a technique for detecting a magnetic signal from a minute magnetic particle and imaging the distribution of the magnetic particle. MPI is used to locate diseased areas by non-invasive techniques by imaging the distribution of magnetic particles injected into the body. For example, by injecting a magnetic particle having a binder that selectively binds to a cancer cell into the body, the position of the cancer cell in the body of a patient who is a subject can be identified.

Some MPI devices include an AC coil that generates an AC magnetic field, a DC coil that generates a DC magnetic field, and a detector that detects a magnetic signal from magnetic particles. The AC coil and the DC coil superimpose the DC magnetic field on the AC magnetic field in the subject. Further, in the DC magnetic field, a zero magnetic field point (FFP) in which the strength of the magnetic field becomes zero is formed. The detector detects a magnetic signal from magnetic particles on the FFP magnetized by the application of an alternating magnetic field. The MPI device obtains the distribution of magnetic particles by detecting a magnetic signal while moving the position of the FFP in the subject. Patent Document 1 discloses an MPI device that magnetizes a magnetic particle on an FFP by applying an AC magnetic field and detects a magnetic signal from the magnetic particle.

Japanese Unexamined Patent Publication No. 2008-307254

The MPI device having an AC coil and a DC coil is provided with an AC drive circuit having an AC current source for supplying an AC current to the AC coil and a DC drive circuit for supplying a DC current to the DC coil. When an AC magnetic field and a DC magnetic field are generated so that the AC magnetic field and the DC magnetic field overlap at the same location on the subject, the magnetic flux of the AC magnetic field is not a little interlinking with the DC coil. Due to the coupling between the magnetic flux of the AC magnetic field and the DC coil, an AC voltage due to the generation of induced electromotive force is applied to both ends of the DC coil. When an AC voltage is applied in addition to the DC voltage to the DC coil corresponding to the load for the DC current source, the voltage value applied to the load fluctuates. Since the voltage value fluctuates, it is difficult for the DC current source to control the current value to be constant. Therefore, in an MPI device having an AC coil and a DC coil, it is required that the influence of the induced electromotive force generated by the AC magnetic field can be reduced.

The present invention has been made in view of the above, and an object of the present invention is to obtain a drive circuit capable of reducing the influence of an induced electromotive force generated by an AC magnetic field.

In order to solve the above-mentioned problems and achieve the object, the drive circuit according to the present invention has a direct current source and a first coil connected to the first terminal of the direct current source, and the first one. It has an AC drive circuit that generates an AC magnetic field by supplying an AC current to the coil, and a DC current source and a second coil connected to the first terminal of the DC current source, to the second coil. It is provided with a direct current drive circuit that generates a direct current magnetic field by supplying a direct current of the above. The drive circuit according to the present invention has a primary coil connected in series to the first coil and connected to the second terminal of an AC current source, and a DC current connected in series to the second coil. It comprises a transformer having a secondary coil connected to a second terminal of the source. The winding direction of the first coil is the same as the winding direction of the second coil, and the winding direction of the primary coil and the winding direction of the secondary coil are opposite to each other, or the winding direction of the primary coil Is the same as the winding direction of the secondary coil, and the winding direction of the first coil and the winding direction of the second coil are opposite to each other.

According to the present invention, there is an effect that the influence of the induced electromotive force generated by the AC magnetic field can be reduced.

Schematic diagram of the main part of the MPI apparatus according to the first embodiment of the present invention. Circuit diagram of the drive circuit of the MPI device shown in FIG. A block diagram showing the configuration of an AC current source included in the drive circuit shown in FIG. A block diagram showing the configuration of a DC current source included in the drive circuit shown in FIG. The figure which shows the drive circuit which concerns on the modification of Embodiment 1. Circuit diagram of the drive circuit according to the second embodiment of the present invention Circuit diagram of the drive circuit according to the modified example of the second embodiment Schematic diagram of the main part of the MPI apparatus according to the third embodiment of the present invention. Circuit diagram of the drive circuit of the MPI device shown in FIG. A block diagram showing the configuration of a DC current source included in the drive circuit shown in FIG. Schematic block diagram of the transformer according to the fourth embodiment of the present invention. Schematic block diagram of the transformer according to the fifth embodiment of the present invention. Schematic block diagram of the transformer according to the first modification of the fifth embodiment Schematic block diagram of the transformer according to the second modification of the fifth embodiment Schematic block diagram of the transformer according to the third modification of the fifth embodiment Schematic block diagram of the transformer according to the sixth embodiment of the present invention. Schematic block diagram of the transformer according to the first modification of the sixth embodiment Schematic block diagram of the transformer according to the second modification of the sixth embodiment Schematic block diagram of the transformer according to the seventh embodiment of the present invention.

Hereinafter, the drive circuit and the magnetic particle imaging apparatus according to the embodiment of the present invention will be described in detail with reference to the drawings. The present invention is not limited to this embodiment.

Embodiment 1.
FIG. 1 is a schematic diagram of a main part of the MPI device 100 according to the first embodiment of the present invention. The MPI device 100 has an AC coil 2 which is a first coil for generating an AC magnetic field, a DC coil 3 which is a second coil for generating a DC magnetic field, and a permanent magnet 4. The permanent magnet 4 is arranged on the central axis 6 of the DC coil 3. FIG. 1 shows a magnetic field line representing a DC magnetic field generated by the DC coil 3 and a magnetic field line representing a magnetic field generated by the permanent magnet 4. A static magnetic field is formed between the DC coil 3 and the permanent magnet 4.

An FFP is formed on the central axis 6 by canceling the DC magnetic field generated by the DC coil 3 and the magnetic field generated by the permanent magnet 4. The MPI device 100 moves the position of the FFP in the subject by changing the magnetic flux density of the DC magnetic field according to the change in the amount of current supplied to the DC coil 3.

The central axis 5 of the AC coil 2 is parallel to the central axis 6. The central axis 5 may coincide with the central axis 6. The AC coil 2 superimposes an AC magnetic field in the vicinity of the FFP in the DC magnetic field. The MPI device 100 has a detector for detecting a magnetic signal. In FIG. 1, the detector is not shown. The detector may include a coil. The detector detects a magnetic signal from magnetic particles on the FFP magnetized by the application of an alternating magnetic field. The MPI device 100 obtains the distribution of magnetic particles by detecting a magnetic signal while moving the position of the FFP in the subject.

FIG. 2 is a circuit diagram of the drive circuit 1 included in the MPI device 100 shown in FIG. The drive circuit 1 includes an AC drive circuit 7 having an AC current source 9 and an AC coil 2, and a DC drive circuit 8 having a DC current source 10 and a DC coil 3. The AC coil 2 is connected to the first terminal T1 of the AC current source 9. The AC drive circuit 7 generates an AC magnetic field by supplying an AC current to the AC coil 2. The DC coil 3 is connected to the first terminal T3 of the DC current source 10. The direct current drive circuit 8 generates a direct current magnetic field by supplying a direct current to the direct current coil 3.

FIG. 3 is a block diagram showing a configuration of an AC current source 9 included in the drive circuit 1 shown in FIG. The AC current source 9 includes an AC current generation circuit 14 that generates an AC current, a current detector 15 that detects an effective value of the generated AC current, and a control unit 16 that controls the AC current generation circuit 14. The control unit 16 adjusts the current output from the AC current generation circuit 14 so that the effective value detected by the current detector 15 matches the preset command value. In this way, the alternating current source 9 performs feedback control for keeping the effective value of the alternating current constant. The current detector 15 may detect a frequency or a strain rate in addition to the current value.

FIG. 4 is a block diagram showing a configuration of a DC current source 10 included in the drive circuit 1 shown in FIG. The direct current source 10 includes a direct current generation circuit 17 that generates a direct current, a current detector 18 that detects the current value of the generated direct current, and a control unit 19 that controls the direct current generation circuit 17. The direct current generation circuit 17 has a converter such as a linear regulator or a switching regulator. The converter produces direct current from a commercial power source. The control unit 19 adjusts the current output from the DC current generation circuit 17 so that the current value detected by the current detector 18 matches the preset command value. In this way, the DC current source 10 performs feedback control for keeping the current value of the DC current constant. According to the configurations shown in FIGS. 3 and 4, the AC current source 9 and the DC current source 10 are independently controlled so that the waveforms of the currents follow the respective commands.

The MPI device 100 creates an AC magnetic field and a DC magnetic field so that the AC magnetic field and the DC magnetic field overlap at the same location on the subject. In the first embodiment, as shown in FIG. 1, the magnetic flux of the AC magnetic field is interlinked with the DC coil 3. Although the AC coil 2 and the DC coil 3 are spatially arranged at different positions, they are magnetically coupled to each other by interlinking the magnetic flux of the AC magnetic field with the DC coil 3. The configuration of the drive circuit 1 can be regarded as a transformer in which the AC coil 2 is the primary winding and the DC coil 3 is the secondary winding and has a constant coupling coefficient. In the example shown in FIG. 1, it is assumed that the winding direction of the AC coil 2 and the winding direction of the DC coil 3 are the same.

The drive circuit 1 includes a transformer 11 having a primary coil 12 and a secondary coil 13. The primary coil 12 and the secondary coil 13 are insulated from each other. The primary coil 12 is connected in series with the AC coil 2 and is connected to the second terminal T2 of the AC current source 9. The secondary coil 13 is connected in series with the DC coil 3 and is connected to the second terminal T4 of the DC current source 10. The winding direction of the primary coil 12 and the winding direction of the secondary coil 13 are opposite to each other. When the winding direction of the AC coil 2 and the winding direction of the DC coil 3 are opposite to each other, the polarity of the primary coil 12 and the polarity of the secondary coil 13 are the same.

By supplying a direct current to the direct current coil 3, a potential difference due to the resistance component of the direct current coil 3 is generated at both ends of the direct current coil 3. Further, when the magnetic flux of the AC magnetic field interlinks with the DC coil 3, an induced electromotive force is generated at both ends of the DC coil 3. In addition to the DC voltage, an AC voltage due to an induced electromotive force is applied to the DC coil 3. Seen from the DC current source 10, although the DC current is supplied to the DC coil 3 which is a load, an AC voltage is applied to the load in addition to the DC voltage. Since the AC coil 2 generates a strong magnetic force that can be exerted on the magnetic particles in the body of the subject, a strong AC voltage is applied to the DC coil 3 by the AC magnetic field generated by the AC coil 2.

As described above, the direct current source 10 performs feedback control for keeping the current value of the direct current constant. Assuming that an AC voltage component corresponding to the AC voltage of the DC coil 3 is included in the output voltage of the DC current source 10, the adjustment of the output voltage according to the voltage fluctuation of the DC coil 3 due to the AC voltage is the DC current source. Required at 10. In this case, the adjustment range of the output voltage required for the DC current source 10 may be insufficient with the voltage fluctuation range that can be realized by a normal converter that converts the DC voltage into an AC voltage. A special element needs to be added to the DC current source 10 in order to include a strong AC voltage component in the output voltage and to enable a wider voltage fluctuation range than that of a normal converter. Due to the addition of special elements, the configuration of the DC current source 10 becomes complicated and large, and the cost of the DC current source 10 increases. Further, as the frequency of the AC voltage becomes higher, it becomes difficult to realize the DC current source 10 which can include a strong AC voltage component in the output voltage and expand the voltage fluctuation range.

In the first embodiment, the transformer 11 functions to cancel the AC voltage due to the induced electromotive force. In the following description, the function for canceling the AC voltage due to the induced electromotive force may be referred to as a voltage compensation function. The transformer 11 generates an AC voltage in the secondary coil 13 by applying an AC voltage to the primary coil 12. The secondary coil 13 generates an AC voltage having the same voltage level as the AC voltage generated by the DC coil 3. It occurs in the secondary coil 13 because the winding direction of the AC coil 2 and the winding direction of the DC coil 3 are the same, and the polarity of the primary coil 12 and the polarity of the secondary coil 13 are opposite to each other. The polarity of the AC voltage to be generated is opposite to the polarity of the AC voltage generated by the DC coil 3. By generating an AC voltage in the secondary side coil 13 having an AC voltage having the same voltage level as the voltage value due to the induced electromotive force and having a polarity opposite to the polarity of the AC voltage due to the induced electromotive force, the drive circuit 1 is subjected to. Both AC voltages are offset.

Since it is not necessary to include the AC voltage component in the output voltage of the DC current source 10, the configuration of the DC current source 10 may be any configuration capable of outputting the DC voltage caused by the resistance component of the DC coil 3. As a result, the DC current source 10 can use a normal converter, and the configuration can be simplified and miniaturized, and cost reduction can be realized.

Next, the conditions of the drive circuit 1 for realizing the voltage compensation function by the transformer 11 will be described. As described above, the AC coil 2 and the DC coil 3 are magnetically coupled. The inductance of the AC coil 2 is L _ac , the inductance of the DC coil 3 is L _dc , the mutual inductance of the transformer that regards the AC coil 2 as the primary winding and the DC coil 3 as the secondary winding is _Mc , and the coupling coefficient of the transformer. If is k _c , the following equation (1) holds.

For the transformer 11, if the inductance of the primary coil 12 is L _p , the inductance of the secondary coil 13 is L _s , the mutual inductance of the transformer 11 is M _t , and the coupling coefficient of the transformer 11 is _kt , the following equation ( 2) holds.

Conditions when the same AC current flows through the AC coil 2 and the primary side coil 12 and the voltage level of the AC voltage generated in the DC coil 3 becomes equal to the voltage level of the AC voltage generated in the secondary side coil 13. Is expressed by the following equation (3) or equation (4).
M _c = M _t ... (3)
k _c ²・ L _dc・ L _ac = k _t ²・ L _p・ L _s・ ・ ・ (4)

Assuming L _p = L _ac and kt ₌ 1, the following equation (5) holds.
L _s = k _c ²・ L _dc・ ・ ・ (5)

The drive circuit 1 includes an AC current source 9 and a DC current source 10 capable of feedback control, and can realize a voltage compensation function by the transformer 11 by satisfying the conditions shown in the equations (1) to (5).

As described above, since a strong AC voltage is applied to the DC coil 3, the relative positions of the AC coil 2 and the DC coil 3 change, in other words, the coupling coefficient k _c changes. As a result, the induced electromotive force generated in the DC coil 3 changes significantly. In order to realize the voltage compensation function by the transformer 11 when the induced electromotive force changes, the drive circuit 1 may fine-tune the AC voltage applied to the secondary coil 13. The fine adjustment of the AC voltage can be performed by a mechanism provided in the transformer 11 or outside the transformer 11 in the drive circuit 1. The fine adjustment of the AC voltage will be described with reference to embodiments 6 and 7 described later.

FIG. 5 is a diagram showing a drive circuit 1A according to a modified example of the first embodiment. The drive circuit 1A, which is a modification of the drive circuit 1, has a transformer 11A to which the primary coil 12 and the secondary coil 13 are connected, instead of the transformer 11 shown in FIG. The transformer 11A is a so-called autotransformer in which the primary side coil 12 and the secondary side coil 13 are shared, and is also called an auto transformer. Since the winding direction of the primary side coil 12 and the winding direction of the secondary side coil 13 are the same, the winding direction of the AC coil 2 and the winding direction of the DC coil 3 are opposite to each other. The drive circuit 1A can reduce the influence of the induced electromotive force generated by the AC magnetic field, similarly to the drive circuit 1 described above.

The central axis 5 of the AC coil 2 and the central axis 6 of the DC coil 3 are not limited to the case where they are parallel to each other. The central axis 5 and the central axis 6 may not be perpendicular to each other and may have an angle other than 90 degrees. The central axis 5 and the central axis 6 may intersect each other or may be in a twisted position. If the central axis 5 and the central axis 6 are perpendicular to each other, the magnetic flux of the AC magnetic field does not interlink with the DC coil 3, so that no induced electromotive force is generated in the DC coil 3. However, when the central axis 5 and the central axis 6 are perpendicular to each other, the position of the FFP is fixed at a certain point, and the FFP cannot be moved. In the MPI device 100 according to the first embodiment, the position of the FFP can be appropriately set by making the central axis 5 parallel to the central axis 6 or forming an angle other than 90 degrees.

The MPI device 100 can detect a magnetic signal with a high degree of freedom by appropriately setting the position of the FFP. By detecting the magnetic signal while moving the FFP, the distribution of magnetic particles can be obtained at high speed. The MPI device 100 can reduce the influence of the dielectric electromotive force due to the magnetic flux of the AC magnetic field and the DC coil 3 by the transformer 11 and can obtain the distribution of the magnetic particles at high speed with a high degree of freedom. Further, since the position of the FFP can be appropriately set in the MPI device 100, the degree of freedom in design for creating a detection algorithm or improving the detection accuracy can be improved.

According to the first embodiment, by including the transformer 11, the drive circuit 1 can cancel the AC voltage generated in the DC coil 3 by the induced electromotive force. As a result, the drive circuit 1 and the MPI device 100 have the effect of being able to reduce the influence of the induced electromotive force generated by the AC magnetic field.

Embodiment 2.
FIG. 6 is a circuit diagram of the drive circuit 20 according to the second embodiment of the present invention. The drive circuit 20 is provided in the MPI device 100 in place of the drive circuit 1 according to the first embodiment. The drive circuit 20 has an AC drive circuit 21 provided in place of the AC drive circuit 7 shown in FIG. The AC drive circuit 21 has an AC current source 22 provided in place of the AC current source 9 shown in FIG. The AC current source 22 is provided with a configuration for making the waveform of the AC current closer to a sine wave by reducing unnecessary harmonics included in the fundamental wave of the AC current. In the second embodiment, the same components as those in the first embodiment are designated by the same reference numerals, and the configurations different from those in the first embodiment will be mainly described.

The AC current source 22 has a single-phase inverter 23 provided in place of the AC current generation circuit 14 shown in FIG. The single-phase inverter 23 shown in FIG. 6 is a full-bridge inverter. The single-phase inverter 23 includes a direct current source, a capacitor, and a switching element constituting a full-bridge circuit. The single-phase inverter 23 may be a half-bridge having a simpler configuration than a full-bridge inverter, or a three-level inverter having a more complicated configuration than a full-bridge inverter.

A current detector 15 is connected to the output terminal T5 of the single-phase inverter 23. Further, the AC current source 22 has a control unit that adjusts the current output from the single-phase inverter 23 so that the current value detected by the current detector 15 matches a preset command value. In FIG. 6, the control unit is not shown.

The alternating current source 22 has a reactor 24 and a capacitor 25. The reactor 24 and the capacitor 25 form a resonance circuit. The reactor 24 is connected to the output terminal T5 via the current detector 15. One terminal of the capacitor 25 is connected between the reactor 24 and the first terminal T1. The other terminal of the capacitor 25 is connected between the input terminal T6 of the single-phase inverter 23 and the second terminal T2. The AC coil 2 and the primary coil 12, which are loads, are connected in parallel to the capacitor 25, so that the capacitor 25 constitutes a parallel resonant circuit.

The purpose of providing the AC current source 22 in the AC drive circuit 21 is to pass an AC current, which is a sinusoidal current having a large amount of current and less distortion, to the AC coil 2 and the primary side coil 12, which are loads. The large amount of current is such that the AC coil 2 can generate a strong magnetic force that can be applied to the magnetic particles in the body of the subject. The AC current source 22 amplifies the amount of current between the capacitor 25 and the AC coil 2 and the primary coil 12 by resonance by appropriately setting the resonance frequency of the capacitor 25 or the value of the capacitor. As a result, the AC current source 22 can pass a large amount of AC current to the AC coil 2 and the primary side coil 12 even when the amount of current output from the single-phase inverter 23 is extremely small.

Further, the resonance circuit can be regarded as a filter circuit capable of extracting a specific frequency component from the input current. The AC current source 22 can appropriately control the resonance by the resonance circuit to cut unnecessary harmonics included in the fundamental wave of the AC current and obtain an AC current which is a sinusoidal current with less distortion. The reactor 24 acts between a square wave, which is the output of the single-phase inverter 23, and a sine wave, which is the output of the capacitor 25 at the time of resonance, and controls the current of the single-phase inverter 23.

Next, the conditions of the resonance circuit for obtaining an AC current having a large current amount and a small distortion by the AC current source 22 will be described. Assuming that the inductance of the reactor 24 is L _b and the combined capacitance of the capacitance of the capacitor 25 and the capacitance of the reactor 24 is L _res , the following equation (6) holds. L _ac is the inductance of the AC coil 2, and L _p is the inductance of the primary coil 12.

Assuming that the capacitance of the capacitor 25 is _Cres , f ₀ , which is the resonance frequency of the resonance circuit, is expressed by the following equation (7).

By matching the frequency of the alternating current output by the single-phase inverter 23 to f ₀ , the amount of current by the alternating current source 22 is maximized. Further, by matching the frequency of the alternating current output by the single-phase inverter 23 to f ₀ , the power factor of the reactor 24 and the capacitor 25, which are the loads for the single-phase inverter 23, is maximized, that is, the drive efficiency is maximized. This minimizes the distortion of the sinusoidal current due to the harmonics.

Since the AC current source 22 shown in FIG. 6 has resistance components (not shown) in each of the single-phase inverter 23, the reactor 24, and the capacitor 25, the amount of current at resonance in the resonance circuit is not infinite. However, if the resistance component on the circuit is sufficiently small and the Q value in the resonance circuit becomes too high, the Q value may be lowered by installing a resistor in parallel with the capacitor 25. Thereby, the AC current source 22 can improve the controllability of the resonance circuit.

By adjusting the frequency of the single-phase inverter 23 according to the equations (6) and (7), the AC current source 22 can easily adjust the resonance circuit while fixing other conditions in the resonance circuit. From the viewpoint of detection by the MPI device 100, it may be desired to fix the frequency of the single-phase inverter 23. In this case, the AC current source 22 may adjust the resonance circuit by fixing the frequency of the single-phase inverter 23 and adjusting other conditions in the resonance circuit. For example, the capacitor 25 may be provided with a mechanism for adjusting the capacitance. Alternatively, a capacitor whose capacitance can be adjusted may be connected in parallel with the capacitor 25. The capacity of the AC coil 2 or the capacity of the reactor 24 may be variable. Alternatively, a reactor having a variable capacity may be connected in series with the reactor 24. As a result, the AC current source 22 can adjust the resonance circuit by fixing the frequency of the single-phase inverter 23.

FIG. 7 is a circuit diagram of the drive circuit 20A according to the modified example of the second embodiment. The drive circuit 20A, which is a modification of the drive circuit 20, is provided with an AC current source 22A instead of the AC current source 22 shown in FIG. The AC current source 22A includes a single-phase inverter 23 and a capacitor 25A connected to the single-phase inverter 23 and connected in series with the AC coil 2 and the primary coil 12. In the AC current source 22A, the AC coil 2 and the primary side coil 12, which are loads, are connected in series with the capacitor 25A, so that the capacitor 25A constitutes a series resonance circuit. The AC current source 22A is not provided with the reactor 24.

The above-mentioned alternating current source 22 including a parallel resonant circuit is advantageous for passing a large amount of alternating current. On the other hand, the AC current source 22A including the series resonant circuit is advantageous for applying a high voltage to the load. The AC current source 22 and the AC current source 22A can be appropriately selected in consideration of the specifications of the AC coil 2, the configuration and specifications of the single-phase inverter 23, and the like. The drive circuit 20A is advantageous from the viewpoint of power supply efficiency because it can reduce the distortion of the sinusoidal current due to the harmonics.

The drive circuit 20 may be provided with a configuration for removing switching noise due to the single-phase inverter 23. For example, the drive circuit 20 removes switching noise by a method such as removal of a noise component by using a lock-in amplifier, filtering at the timing when the noise component is generated, and shielding of spatial conduction of noise. Is also good. By removing the switching noise, the MPI device 100 can reduce the influence of the presence of the switching noise on the detection of the magnetic signal.

According to the second embodiment, the drive circuit 20 includes the single-phase inverter 23 and the capacitor 25 constituting the resonance circuit, so that an alternating current having a large current amount and a small distortion can be obtained.

Embodiment 3.
FIG. 8 is a schematic diagram of a main part of the MPI device 101 according to the third embodiment of the present invention. The MPI device 101 is provided with a DC coil 31, which is a third coil, in place of the permanent magnet 4 shown in FIG. In the third embodiment, the same components as those of the first and second embodiments are designated by the same reference numerals, and the configurations different from those of the first and second embodiments will be mainly described.

The central axis of the DC coil 31 coincides with the central axis 6 of the DC coil 3. FIG. 8 shows a magnetic field line representing a DC magnetic field generated by the DC coil 3 and a magnetic field line representing a magnetic field generated by the DC coil 31. A static magnetic field is formed between the DC coil 3 and the DC coil 31. The MPI device 101 can spatially freely change the strength of the static magnetic field by adjusting the direct current flowing through the direct current coil 31. The DC coil 31 shown in FIG. 8 is spatially arranged at a position separated from the AC coil 2. In the third embodiment, the magnetic flux of the AC magnetic field not only interlinks with the DC coil 3 but also interlinks with the DC coil 31.

FIG. 9 is a circuit diagram of the drive circuit 30 included in the MPI device 101 shown in FIG. The drive circuit 30 includes an AC drive circuit 7 having an AC current source 9 and an AC coil 2. Further, the drive circuit 30 includes a DC drive circuit 8 which is a first DC drive circuit having a DC current source 10 which is a first DC current source and a DC coil 3. The direct current drive circuit 8 generates a first direct current magnetic field by supplying a direct current to the direct current coil 3. Further, the drive circuit 30 includes a DC drive circuit 32 which is a second DC drive circuit having a DC current source 33 which is a second DC current source and a DC coil 31. The DC coil 31 is connected to the first terminal T7 of the DC current source 33. The direct current drive circuit 32 generates a second direct current magnetic field by supplying a direct current to the direct current coil 31.

FIG. 10 is a block diagram showing a configuration of a DC current source 33 included in the drive circuit 30 shown in FIG. The direct current source 33 includes a direct current generation circuit 37 that generates a direct current, a current detector 38 that detects the current value of the generated direct current, and a control unit 39 that controls the direct current generation circuit 37. The direct current generation circuit 37 has a converter such as a linear regulator or a switching regulator. The converter produces direct current from a commercial power source. The control unit 39 adjusts the current output from the DC current generation circuit 37 so that the current value detected by the current detector 38 matches the preset command value. In this way, the DC current source 33 performs feedback control for keeping the current value of the DC current constant. The DC current source 33 is controlled independently of the AC current source 9 and the DC current source 10.

The drive circuit 30 has a transformer 11 which is a first transformer and a transformer 34 which is a second transformer. The transformer 34 has a primary coil 35 and a secondary coil 36. The primary coil 35 and the secondary coil 36 are insulated from each other. The primary coil 35 is connected between the primary coil 12 of the transformer 11 and the second terminal T2. The secondary coil 36 is connected between the DC coil 31 and the second terminal T8 of the DC current source 33.

By supplying a direct current to the direct current coil 31, a potential difference due to the resistance component of the direct current coil 31 is generated at both ends of the direct current coil 31. Further, when the magnetic flux of the AC magnetic field interlinks with the DC coil 31, an induced electromotive force is generated at both ends of the DC coil 31. In the third embodiment, the AC voltage due to the induced electromotive force is generated in each of the DC coil 3 and the DC coil 31.

In the drive circuit 30 according to the third embodiment, the AC voltage generated in the DC coil 3 by the induced electromotive force is canceled by the transformer 11, and the AC voltage generated in the DC coil 31 by the induced electromotive force is canceled by the transformer 34. The transformer 34 generates an AC voltage in the secondary coil 36 by applying an AC voltage to the primary coil 35. The secondary coil 36 generates an AC voltage having the same voltage level as the AC voltage generated by the DC coil 31. It occurs in the secondary side coil 36 because the winding direction of the AC coil 2 and the winding direction of the DC coil 3 are the same, and the polarity of the primary side coil 35 and the polarity of the secondary side coil 36 are opposite to each other. The polarity of the AC voltage to be generated is opposite to the polarity of the AC voltage generated by the DC coil 31. By generating an AC voltage in the secondary side coil 36 that has an AC voltage at the same voltage level as the voltage level due to the induced electromotive force and a polarity opposite to the polarity of the AC voltage due to the induced electromotive force, the drive circuit 1 is subjected to. Both AC voltages are offset. Thereby, the voltage compensation function by the transformer 34 can be realized.

Since it is not necessary to include the AC voltage component in the output voltage of the DC current source 33, the configuration of the DC current source 33 may be any configuration as long as it can output the DC voltage caused by the resistance component of the DC coil 31. As a result, the DC current source 33 can use a normal converter, and the configuration can be simplified and miniaturized, and cost reduction can be realized.

When the MPI device 101 is provided with an AC coil and a DC coil other than the AC coil 2 and the DC coils 3 and 31 shown in FIG. 9, other than the interlinking between the AC magnetic field by the AC coil 2 and the DC coils 3 and 31. Chaining can occur. The MPI device 101 is configured to realize the same voltage compensation function as that of the third embodiment for each DC coil for the chaining generated in addition to the chaining between the AC magnetic field by the AC coil 2 and the DC coils 3 and 31. May be provided. In this case as well, the MPI device 101 has an induced electromotive force due to the voltage compensation function of each DC coil even when a more complicated magnetic field is formed by adding the AC coil and the DC coil to the configuration of the third embodiment. The effect of

The DC coil 31 may be arranged so as to be superimposed on the AC coil 2 in addition to being arranged at a position spatially separated from the AC coil 2. In this case, the AC coil 2 and the DC coil 31 can be regarded as being combined into a single coil. The synthesized coil, which is such a synthesized coil, forms a magnetic field in which an AC magnetic field is synthesized with a DC magnetic field. Therefore, the composite coil can fulfill the functions of the DC coil and the AC coil. Further, the synthetic coil can individually adjust the strength of the AC magnetic field and the strength of the DC magnetic field by controlling the AC current source 9 and the DC current source 33. The MPI device 101 is provided with a synthetic coil in place of the AC coil 2 and the DC coil 31, so that the configuration of the device can be simplified and downsized. The voltage compensation function of the third embodiment can be applied to a drive circuit 30 for driving a coil in which an alternating current is superimposed on a direct current, as in the case where a synthetic coil is provided.

According to the third embodiment, the drive circuit 30 is provided with transformers 11 and 34 for each of the DC coils 3 and 31, so that the AC voltage generated by the induced electromotive force can be canceled for each of the DC coils 3 and 31. Become. As a result, the drive circuit 30 and the MPI device 101 have the effect of being able to reduce the influence of the induced electromotive force generated by the AC magnetic field.

In the above embodiments 1 to 3, the transformer 11 is used so that an alternating current is passed through the primary coil 12 and a direct current is passed through the secondary coil 13. An example of the configuration of the transformer 11 will be described in the fourth and fifth embodiments shown below. The transformer 11 according to the fourth and fifth embodiments may be provided in any of the drive circuits 1, 20, and 30 according to the first to third embodiments. The transformer 34 according to the third embodiment may have the same configuration as the transformer 11 according to the fourth and fifth embodiments.

Embodiment 4.
FIG. 11 is a schematic configuration diagram of the transformer 11B according to the fourth embodiment of the present invention. The transformer 11B, which is one of the configuration examples of the transformer 11, is a solenoid type transformer having a winding wound around a linear central axis, and is an air-core transformer having no core. In the fourth embodiment, the same components as those of the first to third embodiments are designated by the same reference numerals, and the configurations different from those of the first to third embodiments will be mainly described. The broken line shown in FIG. 11 indicates that the transformer 11B is not provided with a core. The solenoid type transformer has an advantage that it is easier to form a winding than the toroidal type transformer described later.

Here, the definitions of core and air core will be described. In each embodiment, the core means a core made of a magnetic material, that is, a core made of an iron-based material or a magnetic material such as ferrite having a magnetic permeability sufficiently larger than 1. An air core means that there is no core made of these magnetic materials. Therefore, the air core includes not only the case where the central axis side of the winding is hollow or only air, but also the case where a material other than the magnetic material is present on the central axis side of the winding. For example, a transformer in which a winding is wound around a cylinder made of a non-magnetic material such as paper or plastic corresponds to an air-core transformer. Further, in order to increase the saturation magnetic flux density of the magnetic material which is the core, it is often performed to insert a gap in the core. In this case, a magnetic circuit is composed of a magnetic material portion and a non-magnetic material portion. In a normal core, the gap is extremely small, and the proportion of the core, that is, the non-magnetic material, is sufficiently small. If the proportion of the non-magnetic material in the core is sufficiently large, for example, if the length of the non-magnetic material exceeds half of the total magnetic path length, it may be regarded as an air core.

The central axis of the primary coil 12 and the central axis of the secondary coil 13 coincide with each other. The central shaft 44 is the central shaft of the primary coil 12 and the secondary coil 13. Since a direct current flows through the secondary coil 13, an AC magnetic field is formed on the central axis 44 side of the secondary coil 13 in a state where a strong direct current bias is applied to the secondary coil 13. If an iron core, which is a normally used core, is provided in the transformer 11B, magnetic flux saturation may occur in the core due to the application of a strong DC bias. Due to the saturation of the magnetic flux in the core, it becomes difficult for the transformer 11B to fulfill the voltage compensation function due to the generation of the AC voltage in the secondary coil 13. Further, the magnetic flux saturation can be suppressed by increasing the size of the core, but in this case, the configuration of the transformer 11B becomes large.

In the fourth embodiment, by making the transformer 11B an air core, the transformer 11B can avoid the problem of magnetic flux saturation. The air-core transformer 11B is effective when a large direct current flows through the primary coil 12 or the secondary coil 13. The transformer 11B can avoid a situation in which the voltage compensation function cannot be fulfilled due to magnetic flux saturation. According to the fourth embodiment, the transformer 11B has an effect that the voltage compensation function can be realized by a small configuration. Note that the transformer 11B may be a single-winding transformer in which the primary coil 12 and the secondary coil 13 are shared, similar to the transformer 11A shown in FIG.

Embodiment 5.
FIG. 12 is a schematic configuration diagram of the transformer 11C according to the fifth embodiment of the present invention. The transformer 11C, which is one of the configuration examples of the transformer 11, is a solenoid type transformer and has a core 41 around which the primary coil 12 and the secondary coil 13 are wound. In the fifth embodiment, the same components as those in the first to fourth embodiments are designated by the same reference numerals, and the configurations different from those in the first to fourth embodiments will be mainly described.

The central axis of the core 41, which is an iron core, coincides with the central axis 44 of the primary coil 12 and the secondary coil 13. The transformer 11C has a core 41 and a permanent magnet 42 that applies a DC magnetic field to the core 41. The permanent magnet 42 is arranged to face one end of the core 41 in the direction of the central axis 44. Here, the permanent magnet 42 is assumed to generate a DC magnetic field having a strength capable of canceling the DC magnetic field generated by the DC current flowing through the secondary coil 13. The transformer 11C can avoid the occurrence of magnetic flux saturation in the core 41 by canceling the DC magnetic field generated by the secondary coil 13 with the DC magnetic field generated by the permanent magnet 42. Since it is not necessary to increase the size of the core 41 in order to suppress the saturation of the magnetic flux, the transformer 11C can be configured in a small size.

In the fifth embodiment, the transformer 11C is provided with the permanent magnet 42 together with the core 41, so that it is possible to avoid a situation in which the voltage compensation function cannot be fulfilled due to magnetic flux saturation. According to the fifth embodiment, the transformer 11C has an effect that the voltage compensation function can be realized by a small configuration.

The transformer 11C is not limited to the one having one permanent magnet 42 arranged facing the end of the core 41. The transformer 11C may have two permanent magnets 42. One of the two permanent magnets 42 is arranged to face one end of the core 41. The other one of the two permanent magnets 42 is located opposite the other end of the core 41. Further, the arrangement of the permanent magnets 42 can be appropriately changed. In the following modification, an example of arrangement of the permanent magnets 42 will be described.

FIG. 13 is a schematic configuration diagram of the transformer 11D according to the first modification of the fifth embodiment. The transformer 11D, which is one of the configuration examples of the transformer 11, has a magnetic circuit 43 which is a closed magnetic path including a core 41 and a permanent magnet 42. The permanent magnet 42 constitutes a part of the magnetic circuit 43. The transformer 11D advances the magnetic flux generated by the permanent magnet 42 to the core 41 through the magnetic circuit 43. The transformer 11D according to the first modification can also cancel the DC magnetic field generated by the secondary coil 13 by the DC magnetic field generated by the permanent magnet 42. The transformer 11D has an advantage that the leakage flux to the outside of the transformer 11D can be reduced by making the permanent magnet 42 a part of the magnetic circuit 43.

FIG. 14 is a schematic configuration diagram of the transformer 11E according to the second modification of the fifth embodiment. The transformer 11E, which is one of the configuration examples of the transformer 11, has a permanent magnet 42 which is a core. The transformer 11E according to the second modification can also cancel the DC magnetic field generated by the secondary coil 13 by the DC magnetic field generated by the permanent magnet 42.

In the transformers 11C, 11D, 11E according to the fifth embodiment, the strength of the permanent magnet 42 is set so as to be able to cancel the DC magnetic field of the secondary coil 13. The transformers 11C, 11D, 11E are provided with a mechanism for adjusting the relative position between the secondary coil 13 and the permanent magnet 42, and the adjustment by such a mechanism cancels the DC magnetic field on the central axis 44 side of the secondary coil 13. It may be possible. In this case as well, the transformers 11C, 11D, and 11E can avoid the situation where the voltage compensation function cannot be achieved due to the saturation of the magnetic flux. Further, the transformers 11C, 11D, and 11E are readjusted to cancel the DC magnetic field by making fine adjustments by such a mechanism when the amount of DC current flowing through the secondary coil 13 changes. be able to. Note that the transformers 11C, 11D, and 11E may be single-winding transformers in which the primary coil 12 and the secondary coil 13 are shared, similar to the transformer 11A shown in FIG.

The transformer 11 is not limited to the solenoid type transformer, and may be a toroidal type transformer. FIG. 15 is a schematic configuration diagram of the transformer 11F according to the third modification of the fifth embodiment. The transformer 11F, which is one of the configuration examples of the transformer 11, is a toroidal type transformer. In a toroidal transformer, the winding is wound around an annular core. In the transformer 11F, the primary coil 12 and the secondary coil 13 are wound along an annulus. In FIG. 15, in order to distinguish between the primary side coil 12 and the secondary side coil 13, the primary side coil 12 is shown by a long-dot chain line, and the secondary side coil 13 is shown by a solid line. In the example shown in FIG. 15, the primary coil 12 and the secondary coil 13 are alternately wound. In a toroidal transformer, the inside of the torus shape formed by the annular winding is the core. The transformer 11F may be an air core.

The toroidal type transformer has an advantage that the leakage flux to the outside of the transformer 11 can be reduced as compared with the solenoid type transformer. The transformer 11F reduces the leakage flux to the outside of the transformer 11F and makes it possible to confine the magnetic flux inside the torus shape. As a result, the transformer 11F can efficiently generate an AC voltage in the secondary coil 13.

Next, a configuration example of the transformer 11 that enables fine adjustment of the AC voltage applied to the secondary coil 13 will be described in the following embodiments 6 and 7. The transformer 34 according to the third embodiment may have the same configuration as the transformer 11 according to the sixth and seventh embodiments.

Embodiment 6.
FIG. 16 is a schematic configuration diagram of the transformer 11G according to the sixth embodiment of the present invention. The transformer 11G, which is one of the configuration examples of the transformer 11, adjusts the voltage value of the AC voltage applied to the secondary coil 13 by moving the contact 51 of the secondary coil 13. In the sixth embodiment, the same components as those of the first to fifth embodiments are designated by the same reference numerals, and the configurations different from those of the first to fifth embodiments will be mainly described.

The transformer 11G is provided in the drive circuit 1 according to the first embodiment. The transformer 11 G is not limited to the drive circuit 1, and may be provided in the other drive circuits 20 and 30 according to the first to third embodiments. Further, although FIG. 16 shows a solenoid type transformer 11G having a core 41, the transformer 11G can be configured in the same manner as the transformer 11 described in the fourth and fifth embodiments. In FIG. 16, components unnecessary for explanation, such as the permanent magnet 42, are not shown.

The contact 51 can be moved by a mechanism provided in the transformer 11G or outside the transformer 11G in the drive circuit 1. The contact 51 is movable in the direction of the central axis 44. The transformer 11G changes the number of turns of the secondary coil 13 by adjusting the position of the contact 51 in the direction of the central axis 44. The inductance of the secondary coil 13, which is L _s in the above equation (4), is increased by changing the turns ratio of the primary coil 12 and the secondary coil 13 due to the change in the number of turns of the secondary coil 13. Change. The transformer 11G adjusts the AC voltage of the secondary coil 13 by adjusting the boost ratio between the primary coil 12 and the secondary coil 13 due to the change in the inductance of the secondary coil 13. In FIG. 16, the mechanism for moving the contact 51 is not shown.

The drive circuit 1 performs feedback control for making the current value of the DC current constant in the DC current source 10 shown in FIG. 4, and adjusts the position of the contact 51 to generate an AC voltage in the secondary coil 13. The voltage level of can be adjusted. The drive circuit 1 can fulfill the voltage compensation function by adjusting the secondary coil 13 to generate an AC voltage having the same voltage level as the AC voltage generated by the DC coil 3. Further, the drive circuit 1 can easily fine-tune the voltage level of the AC voltage by moving the contact 51.

The voltage level applied to the load may fluctuate due to changes in the conditions of the DC coil 3 and the primary coil 12, which are loads for the DC current source 10. The change in load conditions is a change in the electrical characteristics of the drive circuit 1, such as a change in the relative position between the AC coil 2 and the DC coil 3, or a change in the inductance of the AC coil 2, the DC coil 3 or the transformer 11G . It is a change to be obtained. However, depending on the situation, the voltage fluctuation range of the load may exceed the fluctuation range that can be dealt with by the feedback control by the DC current source 10. An example of such a situation is a case where the induced electromotive force generated in the DC coil 3 is extremely large with respect to the DC voltage applied to the load by the DC current source 10.

According to the sixth embodiment, the drive circuit 1 is AC by adjusting the position of the contact 51 even when the load has a fluctuation of the voltage level exceeding the fluctuation range that can be dealt with by the control of the DC current source 10. The voltage level of the voltage can be adjusted. The transformer 11G changes the inductance of the secondary coil 13 by changing the width of the secondary coil 13 in the direction of the central axis 44 instead of changing the number of turns of the secondary coil 13. Is also good.

FIG. 17 is a schematic configuration diagram of the transformer 11H according to the first modification of the sixth embodiment. The transformer 11H, which is one of the configuration examples of the transformer 11, is a single-winding transformer in which the primary coil 12 and the secondary coil 13 are shared, similar to the transformer 11A shown in FIG. The transformer 11 H has a winding 52 that functions as a primary coil 12 and a secondary coil 13. The potential at one end of the winding 52 is the common potential between the primary coil 12 and the secondary coil 13. The one end of the winding 52 is shared as an input terminal of the primary coil 12 and an input terminal of the secondary coil 13. The other end of the winding 52 is an output terminal of the primary coil 12. The contact 51 is movably provided between one end and the other end of the winding 52. The contact 51 is an output terminal which is a terminal on the low pressure side of the secondary coil 13. The transformer 11H has the same configuration as the Slidac®. In this way, in the single-winding transformer, the number of turns of the secondary coil 13 can be changed by moving the contact 51 between one end and the other end of the winding 52.

FIG. 18 is a schematic configuration diagram of the transformer 11I according to the second modification of the sixth embodiment. The transformer 11I, which is one of the configuration examples of the transformer 11, _adjusts the coupling coefficient, which is kt in the above equation (4), by changing the relative positions of the primary coil 12 and the secondary coil 13. .. The transformer 11I adjusts the AC voltage of the secondary coil 13 by adjusting the coupling coefficient of the transformer 11I.

The transformer 11I shown in FIG. 18 changes the position of the secondary coil 13 in the direction of the central axis 44. By moving the secondary coil 13 closer to the primary coil 12, the coupling coefficient increases. Further, the coupling coefficient is also increased by superimposing a part of the secondary side coil 13 on a part of the primary side coil 12 from the state where the secondary side coil 13 is separated from the primary side coil 12. Further, by moving the secondary coil 13 away from the primary coil 12, the coupling coefficient is reduced. The transformer 11I is not limited to the movement of the secondary coil 13, and the coupling coefficient may be adjusted by the movement of the primary coil 12.

The transformer 11I is not limited to the change in the relative position between the primary coil 12 and the secondary coil 13 in the direction of the central axis 44, and the distance between the central axis of the primary coil 12 and the central axis of the secondary coil 13 is set. The coupling coefficient may be adjusted by changing it. When the transformer 11I is an air-core transformer, the relative positions of the primary side coil 12 and the secondary side coil 13 can be easily changed so as to greatly change the coupling coefficient.

The transformers 11G, 11H, 11I according to the sixth embodiment adjust the AC voltage of the secondary coil 13 by changing at least one of the number of turns, the inductance, and the coupling coefficient of the secondary coil 13. be able to. The transformers 11G, 11H, and 11I may adjust the AC voltage of the secondary coil 13 by appropriately combining changes in the number of turns, changes in inductance, and changes in the coupling coefficient.

Embodiment 7.
FIG. 19 is a schematic configuration diagram of the transformer 11J according to the seventh embodiment of the present invention. The transformer 11J is one of the configuration examples of the transformer 11. The secondary coil 13 of the transformer 11J has a main winding 53 and an auxiliary winding 54 for adjusting the AC voltage. In the seventh embodiment, the same components as those in the first to sixth embodiments are designated by the same reference numerals, and the configurations different from those in the first to sixth embodiments will be mainly described.

The main winding 53 is a portion of the AC voltage adjustment that is excluded from the subject of changes for the adjustment of the inductance or coupling coefficient. The main winding 53 is fixed to the structure of the transformer 11J in a wound state. The auxiliary winding 54 is connected in series with the main winding 53. The auxiliary winding 54 is a portion of the AC voltage adjustment that is subject to change for adjustment of inductance or coupling coefficient. The auxiliary winding 54 is movable for adjusting the inductance or coupling coefficient.

Due to the adjustment of the inductance or coupling coefficient, the structural changes required for the secondary coil 13 are limited. According to the seventh embodiment, the transformer 11J can adjust the AC voltage of the secondary coil 13 even if the auxiliary winding 54 for adjusting the inductance or the coupling coefficient is provided separately from the main winding 53. can.

The AC coil 2 and the DC coil 3 are spatially arranged at different positions and are magnetically coupled to each other. The MPI devices 100 and 101 having the AC coil 2 and the DC coil 3 are provided with the drive circuits 1, 20 and 30 and the transformer 11 according to the first to seventh embodiments, so that the induced electromotive force generated by the AC magnetic field is provided. The impact of this can be reduced by a low-cost, simple and compact configuration. The drive circuits 1, 20, 30 and the transformer 11 are a drive circuit in which a coil that generates an AC magnetic field and a coil that generates a DC magnetic field are magnetically coupled, or a case where a DC current and an AC current are superimposed. It can be widely applied to a drive circuit in which a current having a similar current waveform is passed through one coil. The drive circuits 1, 20, 30 and the transformer 11 may be applied to devices other than the MPI devices 100, 101.

The configuration shown in the above-described embodiment shows an example of the content of the present invention, can be combined with another known technique, and is one of the configurations as long as it does not deviate from the gist of the present invention. It is also possible to omit or change the part.

1,1A, 20,20A, 30 drive circuit, 2 AC coil, 3,31 DC coil, 4,42 permanent magnet, 5,6,44 central axis, 7,21 AC drive circuit, 8,32 DC drive circuit, 9,22,22A AC current source, 10,33 DC current source, 11,11A, 11B, 11C, 11D, 11E, 11F, 11G, 11H, 11I, 11J, 34 transformer, 12,35 primary side coil, 13, 36 Secondary side coil, 14 AC current generation circuit, 15, 18, 38 current detector, 16, 19, 39 control unit, 17, 37 DC current generation circuit, 23 single-phase inverter, 24 reactor, 25, 25A capacitor, 41 core, 43 magnetic circuit, 51 contacts, 52 windings, 53 main windings, 54 auxiliary windings, 100,101 MPI device, T1, T3, T7 first terminal, T2, T4, T8 second terminal, T5 output terminal, T6 input terminal.

Claims (16)

An AC drive circuit having an AC current source and a first coil connected to the first terminal of the AC current source and generating an AC magnetic field by supplying an AC current to the first coil.
A DC drive circuit having a DC current source and a second coil connected to the first terminal of the DC current source and generating a DC magnetic field by supplying a DC current to the second coil.
A primary coil connected in series with the first coil and connected to the second terminal of the AC current source, and a second coil connected in series with the second coil and connected to the second terminal of the DC current source. A transformer with a secondary coil connected to the terminal of
Equipped with
The winding direction of the first coil is the same as the winding direction of the second coil, and the winding direction of the primary coil and the winding direction of the secondary coil are opposite to each other, or
The winding direction of the primary coil is the same as the winding direction of the secondary coil, and the winding direction of the first coil and the winding direction of the second coil are opposite to each other . Drive circuit. The drive circuit according to claim 1, wherein the transformer generates an AC voltage in the secondary coil, which can cancel the AC voltage generated in the second coil by the AC magnetic field. The alternating current source controls to keep the effective value of the alternating current constant.
The drive circuit according to claim 1 or 2, wherein the direct current source controls to keep the current value of the direct current constant. The invention according to any one of claims 1 to 3, wherein the central axis of the first coil and the central axis of the second coil are parallel to each other or have an angle other than 90 degrees. Drive circuit. The alternating current source is
With a single-phase inverter,
A capacitor connected to the single-phase inverter and connected in parallel to the first coil and the primary coil,
The drive circuit according to any one of claims 1 to 4, wherein the drive circuit comprises. The alternating current source is
With a single-phase inverter,
A capacitor connected to the single-phase inverter and connected in series with the first coil and the primary coil,
The drive circuit according to any one of claims 1 to 4, wherein the drive circuit comprises. The first DC drive circuit, which is the DC drive circuit having the first DC current source, which is the DC current source, and generating the first DC magnetic field, which is the DC magnetic field.
A second coil having a second direct current source and a third coil connected to the second direct current source, and generating a second direct current magnetic field by supplying the direct current to the third coil. DC drive circuit and
The first transformer, which is the transformer, and
Between the primary coil connected between the primary coil of the first transformer and the second terminal of the AC current source, and between the third coil and the second DC current source. A second transformer with a connected secondary coil, and
Equipped with
The winding direction of the first coil is the same as the winding direction of the second coil, and the winding direction of the primary coil of the second transformer and the winding direction of the secondary coil of the second transformer. Are opposite to each other or
The winding direction of the primary coil of the second transformer is the same as the winding direction of the secondary coil of the second transformer, and the winding direction of the first coil and the winding direction of the second coil. The drive circuit according to any one of claims 1 to 6, wherein the two are opposite to each other . The second transformer is characterized in that an AC voltage capable of canceling the AC voltage applied to the third coil by the AC magnetic field is generated in the secondary coil of the second transformer. The drive circuit according to claim 7. The drive circuit according to any one of claims 1 to 6, wherein the transformer is an air-core transformer. The transformer is
The core around which the primary coil and the secondary coil are wound,
A permanent magnet that applies a DC magnetic field to the core,
The drive circuit according to any one of claims 1 to 6, wherein the drive circuit comprises. The drive circuit according to any one of claims 1 to 6, wherein the transformer is a toroidal type transformer. The drive circuit according to any one of claims 1 to 6, wherein the transformer adjusts a voltage value of an AC voltage generated in the secondary coil. The drive circuit according to claim 12, wherein the transformer adjusts the voltage value by moving the contact of the secondary coil. The drive circuit according to claim 12, wherein the transformer adjusts the voltage value by changing the inductance of the secondary coil. The drive circuit according to claim 12, wherein the transformer adjusts the voltage value by changing the coupling coefficient of the secondary coil. A magnetic particle imaging apparatus comprising the drive circuit according to any one of claims 1 to 15.

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