JP2009010128A - Semiconductor switch and persistent current switch system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor switch and a persistent current switch in which the resistance value of the whole part including a wiring part is reduced. <P>SOLUTION: A first current wiring 10 and a second current wiring 20 are constituted with a normal conducting material wiring 50 (having a cross section of 5×0.5 mm) and a superconducting material wiring 60 (Bi2223 high-temperature superconducting wire) arranged parallel thereto. In addition, a control wiring 30 is the same copper-made wire as the normal conducting material wiring 50. MOS-FET40 is an MOS-FET having an on-resistance of 1.8 MΩ at normal temperature and an on-resistance of 0.5 MΩ at a liquid nitrogen temperature. An S-terminal 42 of the MOS-FET40 is connected with the first current wiring 10 and a D-terminal 44 thereof is connected with the second current wiring 20 respectively by soft-soldering. In this case, the above connections are performed in such a manner that an edge part of the S-terminal 42 and an edge part of the D-terminal 44 are brought into contact with both the normal conducting material wiring 50 and the superconducting material wiring 60 which constitute the first current wiring 10 and the second current wiring 20. Likewise, a G-terminal 46 is connected with the control wiring 30 by soft-soldering. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a semiconductor switch that receives power supply by wiring formed of a superconducting material and a permanent current switch system using the semiconductor switch.

  In order to operate the superconducting coil in a permanent current mode in which a permanent current flows through the superconducting coil, a permanent current switch for short-circuiting the terminals of the superconducting coil is necessary. Conventionally, a thermal permanent current switch has been used as the permanent current switch.

  In this thermal permanent current switch, a permanent current switch made of a superconducting material is heated, and the superconducting material is thermally and normally conducted, thereby generating a resistance in the permanent current switch and turning it off. On the contrary, the superconducting material is cooled and turned on by superconducting transition (see, for example, Patent Document 1).

However, although the thermal permanent current switch has zero resistance when turned on, it takes time until the resistance becomes zero, that is, the switching speed is slow.
In the case of Japanese Patent Application No. 2006-012779, when a plurality of semiconductor switches are connected in parallel to form a bypass switch and connected in parallel with a thermal permanent current switch, the switching speed of the thermal permanent current switch is low. Even so, we proposed a technique to operate the superconducting coil in the permanent current mode normally.
JP-A-8-138828

  However, when a space is limited when connecting a plurality of semiconductor elements in parallel as described above, the amount of the conductor forming the wiring portion is limited for the wiring portion for connecting the plurality of semiconductors in parallel. Since it cannot be increased in proportion to the number of semiconductor elements in the space formed, it is difficult to reduce the resistance value of the wiring portion.

  In other words, even if the resistance of the semiconductor element is reduced, it is difficult to reduce the resistance caused by the wiring. Therefore, it is difficult to reduce the on-resistance of the entire semiconductor switch including the wiring portion. It was.

  The present invention has been made in view of these problems, and an object of the present invention is to provide a semiconductor switch having a reduced overall resistance value including a wiring portion and a permanent current switch system using the semiconductor switch.

  The semiconductor switch according to claim 1, which has been made to solve such a problem (2: In this column, in order to facilitate understanding of the invention, the “Best Mode for Carrying Out the Invention” column is provided as necessary. Is a semiconductor switch (2) in which the semiconductor elements (40) are connected in parallel, and is connected in parallel. Wirings (12, 22) for supplying power to the formed semiconductor element (40) are formed of a superconducting material.

In such a semiconductor switch (2), wirings (12, 22) for supplying power to the semiconductor switches (2) connected in parallel are formed of a superconducting material.
That is, electric power is supplied to the semiconductor elements (40) connected in parallel through the wires (12, 22) made of the superconducting material. In this state, when the semiconductor switch (2) is cooled to a cryogenic temperature, the superconducting state is entered, and the resistance value of the wiring portion becomes zero.

That is, in the extremely low temperature state, the resistance of the semiconductor switch (2) is only a small resistance of the semiconductor, so that the resistance value of the entire semiconductor switch (2) is reduced.
The semiconductor switch (1) according to claim 2 is a semiconductor switch (1) in which semiconductor elements (40) are connected in parallel to supply power to the semiconductor elements (40) connected in parallel. The wirings (10, 20) are formed of a normal conductive material and a superconductive material arranged in parallel with the normal conductive material.

  In such a semiconductor switch (1), wirings (10, 20) for supplying power to the semiconductor switches (1) connected in parallel are formed of a normal conductive material and a superconductive material. Moreover, the wiring (60) formed of the superconducting material is arranged in parallel with the wiring (50) formed of the normal conducting material.

  That is, electric power is supplied to each semiconductor element (40) connected in parallel by the wiring (50) of the normal conducting material and the wiring (60) of the superconducting material connected in parallel. When the semiconductor switch (1) is cooled to an extremely low temperature in this state, the resistance value is reduced because the semiconductor elements (40) are connected in parallel. In addition, the superconducting material wiring (60) connected in parallel to the normal conducting material wiring (50) is also cooled to a cryogenic state and is in a superconducting state, so that the resistance value becomes zero.

That is, in the extremely low temperature state, the resistance of the semiconductor switch (1) is only a small resistance of the semiconductor, so that the resistance value of the entire semiconductor switch (1) is reduced.
When a plurality of semiconductor elements (40) are connected in parallel to form a semiconductor switch (1, 2), the plurality of semiconductor elements (40) may be disposed on the substrate (70). In that case, as described in claim 3, wiring for supplying electric power formed of a superconducting material may be laminated on the substrate (70) on which the semiconductor element (40) is arranged.

  When the wiring formed of the superconducting material is laminated on the substrate (70) in this manner, the crystal orientation of the laminated superconducting material becomes good and the critical current density increases, so that the width of the laminated surface can be reduced. Further, since the area of the wiring portion of the superconducting material is reduced, the degree of freedom in selecting the arrangement position when the semiconductor element (40) is arranged on the substrate (70) is increased. Therefore, mounting of the semiconductor element (40) onto the substrate (70) is facilitated, and the mounting density can be increased.

  The semiconductor element (40) used for the semiconductor switch (1, 2) is preferably a MOS-FET as described in claim 4. When MOS-FETs are connected in parallel and at a very low temperature, the resistance value is lower than that of other semiconductor elements (40), so that a high-performance semiconductor switch (1, 2) can be obtained.

  The permanent current switch system (5) according to claim 5 includes a permanent current switch (84) and the semiconductor switch according to any one of claims 1 to 4 connected in parallel to the permanent current switch (84). And a control means (92) for controlling on / off of the permanent current switch (84) and the semiconductor switch (1, 2).

  In such a permanent current switch system (5), the current flowing through the permanent current switch by the semiconductor switch (1, 2) according to any one of claims 1 to 4 connected in parallel to the permanent current switch (84). Can be bypassed. Therefore, since the switching speed of the semiconductor switch (1, 2) is faster than the switching speed of the permanent current switch (84), the switching speed of the entire permanent current switch system (5) is made higher than the switching speed of the permanent current switch (84). Can be fast.

  Moreover, since the resistance value of the semiconductor switch (1) including the wiring portion is low, loss such as heat generated by the bypass current flowing through the semiconductor switch (1) is reduced, and an efficient permanent current switch system (5) is obtained. Can do.

Embodiments to which the present invention is applied will be described below with reference to the drawings. The embodiment of the present invention is not limited to the following embodiment, and can take various forms as long as they belong to the technical scope of the present invention.
[First Embodiment]
(Configuration of semiconductor switch 1)
FIG. 1 is a diagram showing an outline of a connection state of the semiconductor switch 1. The semiconductor switch 1 is a switch formed by connecting MOS-FETs 40 in parallel, and includes a first current wiring 10, a second current wiring 20, a control wiring 30, and a MOS-FET 40 as shown in FIG.

The first current wiring 10 and the second current wiring 20 have the same configuration, and include a normal conductive material wiring 50 and a superconducting material wiring 60 arranged in parallel thereto.
The normal conducting material wiring 50 is a copper wire having a cross section of 5 × 0.5 mm, and the superconducting material wiring 60 is a Bi2223 high temperature superconducting wire having the same cross sectional dimension. The control wiring 30 is the same copper wire as the normal conductive material wiring 50.

The MOS-FET 40 is a MOS-FET having an on-resistance of 1.8 mΩ at room temperature and an on-resistance of 0.5 mΩ at liquid nitrogen temperature.
The MOS-FET 40 includes a source terminal 42 (hereinafter also abbreviated as S terminal 42), a drain terminal 44 (hereinafter also abbreviated as D terminal 44) and a gate terminal 46 (hereinafter also abbreviated as G terminal 46). Have.

  The S terminal 42 is connected to the first current wiring 10 by soldering. At the time of this connection, the end portion of the S terminal 42 is connected so as to be in contact with both the normal conducting material wiring 50 and the superconducting material wiring 60 constituting the first current wiring 10.

  The D terminal 44 is connected to the second current wiring 20 by soldering. At the time of this connection, the end of the D terminal 44 is connected so as to be in contact with both the normal conducting material wiring 50 and the superconducting material wiring 60 constituting the second current wiring 20.

Similarly, the G terminal 46 is connected to the control wiring 30 by soldering.
(Operation of semiconductor switch 1)
In the semiconductor switch 1, the S terminal 42 of the MOS-FET 40 is connected to the first current wiring 10, and the D terminal 44 is connected to the second current wiring 20. Then, the control wiring 30 is connected to the G terminal 46, and an on / off command signal is input to the G terminal 46 from a control device 92 (to be described later) via the control wiring 30, and between the source and the drain by the on / off command signal. Is short-circuited / opened, that is, turned on / off.

(Performance of semiconductor switch 1)
When the semiconductor switch 1 as described above was immersed in liquid nitrogen and the resistance value of each part was measured, the following values (1) to (4) were obtained.

(1) Resistance of normal conductive material wiring 50 of first current wiring 10 and second current wiring 20: 22.0 μΩ
(2) Resistance of the superconducting material wiring 60 of the first current wiring 10 and the second current wiring 20: 1.5 μΩ
(3) Resistance of MOS-FET 40: 4.5 μΩ
(4) Total resistance of the semiconductor switch 1: 6.0 μΩ
(Application example of semiconductor switch 1)
Next, an application example of the semiconductor switch 1 will be described with reference to FIG. FIG. 2 is a schematic configuration diagram of a superconducting coil system 80 using the semiconductor switch 1 as a bypass switch.

  As shown in FIG. 2, the superconducting coil system 80 includes a superconducting coil 82, a permanent current switch system 5, a first changeover switch 86, a second changeover switch 88, and a DC power supply 90.

  The superconducting coil 82 stores electric power as magnetic energy, and is formed of a Bi2223 high-temperature superconducting wire. The superconducting coil 82 is cooled with liquid nitrogen, liquid helium, or the like to be in a superconducting state.

The permanent current switch system 5 includes a thermal permanent current switch 84, a semiconductor switch 1, a first current wire 10, a second current wire 20, and a control device 92.
The thermal permanent current switch 84 is a superconducting material provided with a heater (not shown), and is used in a state of being cooled to a cryogenic temperature together with the superconducting coil 82. In other words, if the superconducting material is not heated by the heater, it is cooled and is in a very low temperature state. Therefore, a permanent current flows in a superconducting state with zero resistance. This state is called on.

  Conversely, if heated by a heater, the superconducting state breaks down, resistance is generated, and the permanent current is interrupted. This state is called off. The on / off of the thermal permanent current switch, that is, control of heating / non-heating of the heater is performed by an on / off command signal from the control device 92.

  Further, both ends of the thermal-type permanent current switch 84 are connected to both ends of the superconducting coil 82 as shown in FIG. 2, and both ends of the superconducting coil 82 are short-circuited when the switch is turned on. And a permanent current is caused to flow through the superconducting coil 82. On the contrary, when it is off, the closed circuit is opened and the permanent current flowing through the superconducting coil 82 is cut off.

  The semiconductor switch 1 is connected in parallel with the thermal permanent current switch 84, that is, the S terminal 42 and the D terminal 44 of the MOS-FET 40 are respectively connected to both ends of the thermal permanent current switch 84.

  A control line from the control device 92 is connected to the G terminal 46 of the MOS-FET 40 constituting the semiconductor switch 1, and an on / off command signal is input from the control device 92 to the gate via the control line. The source / drain is short-circuited / opened, that is, turned on / off by the / off command signal.

  The semiconductor switch 1 composed of the MOS-FET has a switching speed faster than that of the thermal permanent current switch 84, and the resistance value is lowered by being parallelized or cooled as described above. It has characteristics.

  One end of the superconducting coil 82 is connected to the positive terminal of the DC power supply 90 via the first current wire 10 and the first changeover switch 86, and the other end is connected to the DC via the second current wire 20 and the second changeover switch 88. The negative terminal of the power supply 90 is connected.

  The first changeover switch 86 and the second changeover switch 88 are switches for supplying / cutting off the current supplied from the DC power supply 90 to the superconducting coil 82 based on the on / off command signal from the control device 92.

  The first changeover switch 86 and the second changeover switch 88 are turned on in response to an on command signal from the control device 92, supply current from the DC power supply 90 to the superconducting coil 82, and are turned off in response to the off command signal. The current from the power supply 90 is cut off.

  The DC power supply 90 is a device for supplying a current to the superconducting coil 82, and is connected to a plus terminal and a minus terminal by the first current wiring 10 and the second current wiring 20 via the first changeover switch 86 and the second changeover switch 88. Are connected to both ends of the superconducting coil 82.

  The control device 92 outputs an on / off command signal to the thermal permanent current switch 84, the semiconductor switch 1, the first changeover switch 86, and the second changeover switch 88, and the thermal permanent current switch 84, the semiconductor switch 1, the first switch The changeover switch 86 and the second changeover switch 88 are turned on / off.

  The cooling unit 94 is a container for cooling the superconducting coil 82, the thermal permanent current switch 84, and the semiconductor switch 1. Then, the inside is filled with a cooling medium such as liquid nitrogen or liquid helium, and the superconducting coil 82, the thermal permanent current switch 84, and the semiconductor switch 1 are immersed in the cooling medium to be cooled so as to be in a superconducting state. .

The cooling medium of the cooling unit 94 is cooled by a cooling device (not shown), for example, a pulse tube cooling device, and cools the superconducting coil 82 and the like into a superconducting state.
(Resolving instability of superconducting coil system 80)
As an example of a method of using the semiconductor switch 1, in the superconducting coil system 80, when the thermal permanent current switch 84 generates heat due to an accidental event and the superconducting circuit becomes unstable, the instability is eliminated. This will be described with reference to FIG.

  FIG. 3 is an operation explanatory diagram for explaining the operation of the superconducting coil system 80 when the instability of the superconducting coil system 80 is eliminated. In FIG. 3, the control device 92 is omitted.

  In the superconducting coil system 80, a permanent current flows as shown by a broken line in FIG. In this state, heat is generated due to some accident, and when the thermal permanent current switch 84 is heated and temporarily turned off, that is, in a state where resistance is generated, a large current is generated in the superconducting coil system 80. Since it flows, the heating is further promoted by Joule heating in the resistance generated by the thermal permanent current switch 84.

  In other words, if the thermal permanent current switch 84 generates heat due to an accident, a resistance is generated, and the thermal permanent current switch 84 enters a cycle where it is further heated by the resistance. That is, it is difficult to return to the on state.

Therefore, when the thermal permanent current switch 84 generates heat due to an accident, the current flowing in the superconducting circuit is rapidly attenuated.
Therefore, when the thermal permanent current switch 84 generates heat due to an accident, an ON command signal is output from the control device 92 to the semiconductor switch 1 and the semiconductor switch 1 is turned ON. Then, the resistance value of the semiconductor switch 1 configured by connecting the MOS-FETs 40 in parallel is smaller than the resistance value generated in the thermal permanent current switch 84 due to heat generation, as shown in FIG. Most of the current flows through the semiconductor switch 1 (a current having a value inversely proportional to the resistance flows).

  That is, since almost no current flows through the thermal permanent current switch 84, heat generation due to Joule heating is eliminated. Therefore, if an accidental reason for causing the thermal permanent current switch 84 to generate heat is eliminated and the cooling capacity exceeds the amount of heat generated by the thermal permanent current switch 84, the thermal permanent current switch 84 is cooled below a predetermined temperature. The thermal permanent current switch 84 can be quickly recovered from the superconducting state, that is, the ON state.

After the thermal permanent current switch 84 is restored to the ON state in this way, an OFF command signal is output from the control device 92 to the semiconductor switch 1, and the semiconductor switch 1 is turned OFF.
(Characteristics of semiconductor switch 1)
In the semiconductor switch 1 as described above, the first current wiring 10 and the second current wiring 20 which are wirings for supplying power to the semiconductor switches 1 connected in parallel are the normal conductive material wiring 50 and the superconducting material wiring 60. Formed with. In addition, the superconducting material wiring 60 formed of a superconducting material is arranged in parallel with the normal conducting material wiring 50 formed of a normal conducting material.

  That is, electric power is supplied to the MOS-FET 40 by the normal conductive material wiring 50 and the superconductive material wiring 60 connected in parallel. In this state, when the semiconductor switch 1 is cooled to an extremely low temperature, the resistance value of the MOS-FET 40 is reduced. In addition, the superconducting material wiring 60 connected in parallel with the normal conducting material wiring 50 is also cooled to a very low temperature state and becomes a superconducting state, so that the resistance value becomes zero.

That is, in the extremely low temperature state, the resistance of the semiconductor switch 1 is only a small resistance of the semiconductor, so that the resistance value of the entire semiconductor switch 1 is reduced.
Further, a MOS-FET 40 is used for the semiconductor switch 1. When the MOS-FETs 40 are connected in parallel and at a very low temperature, the resistance value is lower than that of other semiconductor elements, so that a high-performance semiconductor switch 1 can be obtained.

[Second Embodiment]
Next, the semiconductor switch 2 having a superconducting film formed on the substrate 70 will be described with reference to FIG. FIG. 4 is a diagram showing a schematic configuration of the semiconductor switch 2 in which a superconducting film is formed on the substrate 70. As shown in FIG. 4, the semiconductor switch 2 includes a first current path 12, a second current path 22, a control line 32, a MOS-FET 40, and a substrate 70.

The substrate 70 is formed by depositing the first current path 12, the second current path 22, and the control line 32 on a substantially rectangular sapphire plate 72.
The first current path 12 and the second current path 22 are thin films of high-temperature superconducting material such as yttrium, and are deposited on the surface of the substrate 70 such as magnesium oxide or sapphire.

  The first current path 12 is formed along edges of two long sides other than one side of the short side of the substantially rectangular sapphire plate 72 and the other short side (that is, three sides of the sapphire plate 72). The second current path 22 is formed at the center of the sapphire plate 72 from the edge of the short side where the first current path 12 is not formed toward the other short side.

  Two control lines 32 are formed on the sapphire plate 72 in the long side direction between the first current path 12 and the second current path 22, and each of the two control lines 32 has a first current path. In the vicinity of the edge of the short side where 12 is not formed, a connection part for external connection in the short side direction is formed.

  The MOS-FET 40 is the same as that in the first embodiment, and the S terminal 42, the first current path 12, the D terminal 44, the second current path 22, the G terminal 46, and the control line 32 are high-temperature superconducting materials or short lengths. These are connected by wire bonding of a high conductivity normal conducting material.

  In such a semiconductor switch 2, the first current path 12 and the second current path 22, which are wirings for supplying power to the semiconductor switches 2 connected in parallel, are formed of a superconducting material.

  That is, electric power is supplied to the MOS-FETs 40 connected in parallel through the superconducting material film (the first current path 12 and the second current path 22). In this state, when the semiconductor switch 2 is cooled to an extremely low temperature, the resistance value of the superconducting material portion becomes zero.

That is, in the extremely low temperature state, the resistance of the semiconductor switch 2 is only a small resistance of the semiconductor, so that the resistance value of the entire semiconductor switch 2 is reduced.
In addition, since the first current path 12 and the second current path 22 of the superconducting material can be narrowed, the degree of freedom in selecting the arrangement position when the MOS-FET 40 is arranged on the substrate 70 is increased. Mounting on 70 becomes easy and the mounting density can be increased.

1 is a diagram showing an outline of a connection state of a semiconductor switch 1. FIG. It is a schematic block diagram of the superconducting coil system 80 which used the semiconductor switch 1 as a bypass switch. It is operation | movement explanatory drawing for demonstrating the action | operation of the superconducting coil system 80 at the time of eliminating the instability of a superconducting circuit. 2 is a diagram showing a schematic configuration of a semiconductor switch 2 in which a superconducting film is formed on a substrate 70. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1,2 ... Semiconductor switch, 5 ... Permanent current switch system, 10 ... 1st current wiring, 12 ... 1st current path, 20 ... 2nd current wiring, 22 ... 2nd current path, 30 ... Control wiring, 32 ... Control 40 ... MOS-FET, 42 ... Source terminal (S terminal), 44 ... Drain terminal (D terminal), 46 ... Gate terminal (G terminal), 50 ... Normal conductor wiring, 60 ... Superconducting material wiring, 70 ... Substrate, 72 ... sapphire plate, 80 ... superconducting coil system, 82 ... superconducting coil, 84 ... thermal permanent current switch, 86 ... first changeover switch, 88 ... second changeover switch, 90 ... DC power supply, 92 ... control device, 94: Cooling section.

Claims (5)

A semiconductor switch formed by connecting semiconductor elements in parallel,
A semiconductor switch, wherein a wiring for supplying electric power to the semiconductor elements connected in parallel is formed of a superconducting material. A semiconductor switch formed by connecting semiconductor elements in parallel,
A semiconductor switch characterized in that a wiring for supplying electric power to the semiconductor elements connected in parallel is formed of a superconducting material arranged in parallel with the normal conducting material and the normal conducting material. The semiconductor switch according to claim 1 or 2,
The semiconductor element is disposed on a substrate;
A wiring for supplying electric power formed of the superconducting material is laminated on a substrate on which the semiconductor element is disposed. In the semiconductor switch in any one of Claims 1-3,
The semiconductor switch, wherein the semiconductor element is a MOS-FET. A permanent current switch;
The semiconductor switch according to any one of claims 1 to 4, wherein the semiconductor switch is connected in parallel to the permanent current switch;
Control means for controlling on / off of the permanent current switch and the semiconductor switch;
A permanent current switch system comprising:

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