REACTOR

Abstract

In the reactor in which the wiring board with the main winding formed thereon and the wiring board with the control winding formed thereon are incorporated in layers into the planer core, the magnetic flux generated by the main winding and the magnetic flux generated by the control winding are brought into the following states in order to equalize the density of the magnetic flux generated by the control current. A main winding current of high-frequency current flowing through the main winding generates an AC magnetic fluxes, each of the fluxes having a magnetic field in a direction opposite to each other so as to cancel each other out, and a control current of direct current flowing through the control winding generates a DC magnetic flux with a uniform magnetic flux density around the pair of the inner legs of which AC magnetic fluxes are cancelled out each other.

Claims

1. A reactor, comprising: a main winding substrate forming a main winding, a control winding substrate forming a control winding and a planer core, wherein the mam winding substrate and the control winding substrate are incorporated in layers into the planer core, the planer core has a center leg, a pair of inner legs arranged on both sides of the center leg, and a pair of outer legs arranged outside the inner legs, in which a main winding current of high-frequency current flowing through the main winding generates an AC magnetic flux around each of the pair of inner legs, the magnetic fluxes having a magnetic field in a direction opposite to each other so as to cancel each other out, a control current of a direct current flowing through the control winding generates a DC magnetic flux with a uniform magnetic flux density around all the legs of the core.

2. The reactor according to claim 1, wherein, the main winding substrate consists of a first main winding substrate and a second main winding substrate to hold the control winding substrate from above and below thereof, a main winding of the first main winding substrate is formed to surround the center leg and a first inner leg, which is one of the pair of the inner leg, together, a main winding of the second main winding substrate is formed to surround the center leg and a second inner leg, which is the other of the pair of the inner legs, together, and a control winding of the control winding substrate is formed to surround each of the pair of the first inner leg and the second inner leg individually.

3. The reactor according to claim 1, wherein the main winding substrate consists of a first main winding substrate and a second main winding substrate to hold the control winding substrate from above and below thereof, a main winding of the first main winding substrate is formed to surround the center leg and the pair of the inner legs together, a main winding of the second main winding substrate is formed to surround the center leg, and a control winding of the control winding substrate is formed to surround each of the pair of the inner lees individually.

4. The reactor according to claim 1, wherein the direction of the magnetic field of the magnetic flux of center leg is opposite to the direction of the magnetic field of the magnetic flux of the inner leg.

5. The reactor according to claim 1, wherein the control current becomes a variable inductance by a variable current.

6. The reactor according to claim 1, wherein the control current becomes a fixed inductance by a fixed current.

7. The reactor according to claim 1, wherein the planer core has a configuration that an EE-core or UU-core formed by arranging E-cores or U-cores with respective protruding portions facing each other is disposed laterally, or a configuration that an EI-core or UI-core formed by arranging an I-core oil the protruding portions of the E-core or U-core is disposed laterally.

8. The reactor according to claim 2, wherein the direction of the magnetic field of the magnetic flux of center leg is opposite to the direction of the magnetic field of the magnetic flux of the inner leg.

9. The reactor according to claim 3, wherein the direction of the magnetic field of the magnetic flux of center leg is opposite to the direction of the magnetic field of the magnetic flux of the inner leg.

10. The reactor according to claim 2, wherein the control current becomes a variable inductance by a variable current.

11. The reactor according to claim 3, wherein the control current becomes a variable inductance by a variable current.

12. The reactor according to claim 4, wherein the control current becomes a variable inductance by a variable current.

13. The reactor according to claim 2, wherein the control current becomes a fixed inductance by a fixed current.

14. The reactor according to claim 3, wherein the control current becomes a fixed inductance by a fixed current.

15. The reactor according to claim 4, wherein the control current becomes a fixed inductance by a fixed current.

16. The reactor according to claim 2, wherein the planer core has a configuration that an EE-core or UU-core formed by arranging E-cores or U-cores with respective protruding portions facing each other is disposed laterally, or a configuration that an EI-core or UI-core formed by arranging an I-core on the protruding portions of the E-core or U-core is disposed laterally.

17. The reactor according to claim 3, wherein the planer core has a configuration that an EE-core or UU-core formed by arranging E-cores or U-cores with respective protruding portions facing each other is disposed laterally, or a configuration that an EI-core or UI-core formed by arranging an I-core on the protruding portions of the E-core or U-core is disposed laterally.

18. The reactor according to claim 4, wherein the planer core has a configuration that an EE-core or UU-core formed by arranging E-cores or U-cores with respective protruding portions facing each other is disposed laterally, or a configuration that an EI-core or UI-core formed by arranging an I-core on the protruding portions of the E-core or U-core is disposed laterally.

19. The reactor according to claim 5, wherein the planer core has a configuration that an EE-core or UU-core formed by arranging E-cores or U-cores with respective protruding portions facing each other is disposed laterally, or a configuration that an EI-core or UI-core formed by arranging an I-core on the protruding portions of the E-core or U-core is disposed laterally.

20. The reactor according to claim 6, wherein the planer core has a configuration that an EE-core or UU-core formed by arranging E-cores or U-cores with respective protruding portions facing each other is disposed laterally, or a configuration that an EI-core or UI-core formed by arranging an I-core on the protruding portions of the E-core or U-core is disposed laterally.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0057] FIG. 1 is a diagram illustrating a schematic configuration of a reactor according to the present invention;

[0058] FIG. 2 is a diagram illustrating a decrease in a footprint of the reactor according to the present invention;

[0059] FIG. 3 is a diagram illustrating a conceivable configuration example of the reactor by means of a planer core;

[0060] FIG. 4 is a diagram illustrating a first embodiment of the reactor according to the present invention;

[0061] FIG. 5 is a diagram illustrating a state of each current and a state of each magnetic flux in the first embodiment of the reactor according to the present invention;

[0062] FIG. 6 is a diagram illustrating another state of each current and another state of each magnetic flux in the first embodiment of the reactor according to the present invention;

[0063] FIG. 7 is a diagram illustrating a second embodiment of the reactor according to the present invention;

[0064] FIG. 8 is a diagram illustrating a state of each current and a state of each magnetic flux in the second embodiment of the reactor according to the present invention;

[0065] FIG. 9 is a diagram illustrating another state of each current and another state of each magnetic flux in the second embodiment of the reactor according to the present invention;

[0066] FIG. 10 is a diagram illustrating other examples of the winding pattern of a control winding of the reactor according to the present invention;

[0067] FIG. 11 is a diagram showing a configuration example of a conventional variable reactor; and

[0068] FIG. 12 is a diagram illustrating a configuration example of a reactor with a combination of a planer core and wiring boards.

BEST MODE FOR CARRYING OUT THE INVENTION

[0069] A reactor according to the present invention will be described with reference to the accompanying drawings. Now, FIG. 1 will be used to illustrate a schematic configuration of the reactor according to the present invention, FIG. 2 will be used to illustrate a decrease in a footprint of the reactor, and FIG. 3 will be used to illustrate uniform fluxes. Furthermore, FIGS. 4 to 6 are used to illustrate a first embodiment of the reactor according to the present invention, FIGS. 7 to 9 are used to illustrate a second embodiment of the reactor according to the present invention, and FIG. 10 is used to illustrate different examples of a winding pattern of a control winding.

Schematic Configuration of the Reactor According to the Present Invention

[0070] A description will be made about a schematic configuration of the reactor of the present invention by referring to FIG. 1. FIG. 1(a) shows a schematic shape of a planer core provided to the reactor, and FIGS. 1(b), 1(c) and 1(d) respectively show a first winding substrate, a control winding substrate and a second winding substrate of the reactor of the present invention. FIG. 1(e) schematically shows a state of a magnetic flux generated in the core by each winding.

[0071] In FIG. 1(a), a planer core 11 of a reactor 10 is an approximately flat-shaped member formed with a magnetic material such as ferrite, which is composed of two core members divided on a central plane. One surface of each core member has a plane shape, and the other surface has a protruding portion extending toward a direction approximately perpendicular to the plane shape, the protruding portion forming a leg of the core.

[0072] By placing opposite the protruding portions of respective two core members, a laminated core is formed. A concave part between the protruding portions forms a through hole inside the core. In the through hole, wiring boards for a first main winding substrate 14A, a second main winding substrate 14B and a control winding substrate 15 are arranged.

[0073] The planer core 11 shown in FIG. 1(a) employs four E-cores as core members. FIG. 1(a) shows a configuration example having two planer cores 11a, 11b which are formed in such a manner that the protruding portions of two E-cores are arranged to oppose to each other. The configuration example represents an EE-core employing the E-cores in this description, but may represent a UU-core employing eight U-cores.

[0074] The planer core 11 has a center leg 16a, a pair of inner legs 16b, 16c arranged on both sides of the center leg 16a, and a pair of outer legs 16d, 16e further arranged outside the inner legs 16b, 16c, and the wiring boards are disposed in the through holes between the adjacent legs.

[0075] The wiring board of the first main winding substrate 14A shown in FIG. 1(b) is provided with a winding pattern of the first main winding 12b, and the wiring board of the second main winding substrate 14B show in FIG. 1(d) is provided with a winding pattern of the second main winding 12c. In addition to that, the wiring board of the control winding substrate 15 shown in FIG. 1(c) is provided with winding patterns of the control windings 13a, 13b.

[0076] The first main winding substrate 14A, the second main winding substrate 14B and the control winding substrate 15 are provided with openings, into which the respective legs of the planer core 11 are inserted, thereby incorporating the wiring boards in layers in the planer core 11. The wiring boards shown in FIGS. 1(b), 1(c) and 1(d) have the configurations corresponding to a first embodiment of the reactor of the present invention.

[0077] The planer core 11 shown in FIG. 1(e) schematically presents the state of magnetic flux generated by a winding current flowing through each winding.

[0078] The planer core 11 is provided with the outer leg 16d, the inner leg 16b and the center leg 16a, the inner leg 16c and the outer leg 16e sequentially from one side of the core, and a magnetic flux with an AC magnetic field is generated by a high-frequency current flowing through the main windings 12b, 12c whereas a magnetic flux with a DC magnetic field is generated by a direct current flowing the control winding 13.

[0079] According to the reactor of the present invention, in the inner leg 16b and the inner leg 16c, the high-frequency current is applied to the windings of the respective main windings 12b, 12c so as to induce high-frequency components in the control winding. However, as a magnetic field is formed in each inner leg in the direction opposite to each other, the high-frequency components induced in the control winding are cancelled.

[0080] The winding pattern of the control winding 13 (13a, 13b) is provided to surround the inner legs 16b, 16c, so that the magnetic flux can be generated by the DC magnetic field on all the legs. The magnetic fluxes generated on ail the legs can be equalized by supplying control currents at an equal current value to the control winding 13 (13a, 13b).

[0081] The planer core 11 can be configured by combining the E-core of an E-shaped cross-section that has three protruding portions on its one side, the U-core of a U-shaped cross-section that has two protruding portions on its one side, and an I-core of I-shaped cross-section that has no protruding portions.

[0082] In the configuration example of FIG. 1(f), the protruding portions of two E-cores are arranged to face each other so as to configure the EE-core, and two EE-cores are arranged in the lateral direction to configure the planer core 11.

[0083] In the configuration example of FIG. 1(g), the protruding portions of two U-cores are arranged to face each other so as to configure the U-core, and four U-cores are arranged in the lateral direction to configure the planer core 11.

[0084] In the configuration example of FIG. 1(h), the I-core is placed to the protruding portion of one E-core to configure an EI-core, and two EI-cores are arranged in the lateral direction to configure the planer core 11.

[0085] In the configuration example of FIG. 1(i), the I-core is placed to the protruding portion of one U-core to configure a UI-core, and four UI-cores are arranged in the lateral direction to configure the planer core 11.

[0086] (i) Footprint of Reactor

[0087] The reactor of the present invention has a profile that two planer cores being arranged in the lateral direction, and now a description will be made about a suppression of a footprint of the core part of the reactor by the above lateral arrangement, by referring to FIG. 2. The lateral arrangement of the planer core is constituted by the legs provided to the reactor of the invention, namely, the center leg, the pair of inner legs arranged on both sides of the center leg, and the pair of outer legs arranged outside the inner legs.

[0088] FIG. 2 is a diagram illustrating the decrease in the footprint by the reactor of the present invention. FIG. 2(a) shows a configuration by adopting the wiring board of the planer core, which is the example shown in FIG. 12. A width of the core in the lateral direction is denoted by W and a length of the core in the width direction is denoted by L. The wiring board extends by ΔW from the side of the core. Since the extending areas of the wiring board (the ground pattern in the figure) on both sides with respect to the plane area S of the core are respectively ΔS, the footprint due to the planer core in FIG. 2(a) is (S+2ΔS).

[0089] FIG. 2(b) shows a configuration of the reactor of the present invention. The reactor of the invention has a shape corresponding to the configuration of FIG. 2(a) in which the planer core is divided into halves in its depth and disposed in the lateral direction. In view of the arrangement form of the core, the configuration of the reactor of the present invention corresponds to a widthwise arrangement while the configuration of the conventional reactor corresponds to a lengthwise arrangement. The configuration of FIG. 2(b) has the length of L/2 in the width direction in order to make comparison with the plane area of the core of the configuration in FIG. 2(a), thereby achieving a configuration according to the plane area S of the planer core in FIG. 2(a).

[0090] In comparison of the plane area of the core of the reactor of the present invention in FIG. 2(b) and the plane area of the core with the configuration in FIG. 2(a), the footprint of the core with the configuration in FIG. 2(a) is presented as (S+2ΔS) which is the sum of the plane area S of the core and the protruding part 2ΔS. In contrast, the footprint of the reactor of the present invention does not include the protruding part 2ΔS, and is therefore presented only with the plane area S of the core. In this way, in comparison of the footprints, the footprint of the reactor of the invention is S, whereas the footprint of the lateral arrangement configuration of the planer core is (S+2ΔS). Thus, the footprint in the reactor of the present invention is decreased by 2ΔS.

[0091] Consequently, the reactor of the present invention can be configured without increasing the number of the cores, thereby avoiding the increase in the footprint of the reactor, compared to the case of lengthwise arrangement of the planer core having the footprint that includes the plane area of the core.

[0092] Moreover, the planer core of the reactor of the present invention is configured to accommodate the wiring boards in the through holes provided inside the core, thereby decreasing magnetic field noise caused by a leakage flux. The reduction of the magnetic field noise from the core makes it possible to dispose circuit components and others adjacent to the reactor, and thus a packing density in the device can be increased in its entirety.

[0093] (ii) Suppression of Leakage Flux

[0094] In the reactor of the present invention, the main winding substrates and the control winding substrate are incorporated in layers in the planer core, so as to prevent the occurrence of a leakage flux which is a magnetic flux leaking from the reactor.

[0095] (iii) Elimination of Non-Uniform Magnetic Flux

[0096] As means for eliminating the leakage flux from the winding on the outside of the core, a side part of the planer core may be extended in the lateral direction to fit the coil of the main winding in the core. However, the configuration in which the side part of the planer core is merely extended in the lateral direction to form the core has a problem that a magnetic path of the magnetic flux passing through the core causes the non-uniformity of the magnetic flux which leads to the non-uniformity of the inductance, and thus the reactor cannot work as flux-controlled type reactor.

[0097] In order to work as the magnetic flux-controlled type reactor, it is required that the inductance in the magnetic path in the core is uniform. For the uniformity of the inductance, it is necessary that the magnetic flux densities of the AC magnetic flux and the DC magnetic flux are equal in a main magnetic path. It is also necessary that a magnetic path where the AC magnetic flux passes is applied with the DC magnetic flux as bias magnetic flux by the control current.

[0098] A description will now be made about the non-uniformity in the magnetic flux densities of the AC magnetic flux and the DC magnetic flux, and about the non-uniformity in the bias magnetic flux due to the DC magnetic flux in the configuration example.

Non-Uniformity in Magnetic Flux Density of AC Magnetic Flux

[0099] FIG. 3 shows a conceivable configuration example of the reactor with the planer core. In the schematic configuration in FIG. 3(a), the planer core extends both sides by the lengths of WB and WC to place the main windings, shown with the solid lines, in the core. The broken line in FIG. 3(a) depicts the coil of the control winding. FIGS. 3(b) and 3(c) show the states of the AC magnetic fluxes generated by the main windings.

[0100] FIG. 3(b) shows the states of the AC magnetic fluxes generated by the main windings, and FIG. 3(c) shows the states of the equivalent magnetic fluxes. The core has a center leg a, inner legs b and c. The first main windings and the second winding are wound around the inner legs b and c respectively. The arrows in FIGS. 3(b) and 3(c) present examples of the AC magnetic fluxes generated by the alternating current flowing through the main windings. Since the magnetic fluxes around the center leg a have the magnetic flux directions opposite to each other depending on the first main winding and the second main winding, these fluxes balance out each other and are cancelled out. As shown in the state of the equivalent magnetic flux in FIG. 3(c), the magnetic fluxes around the center leg a are cancelled out, thereby forming magnetic paths for the AC magnetic fluxes, namely a magnetic path passing the outer magnetic path d and the inner magnetic path b, a magnetic path passing the inner legs b and c, and a magnetic path passing the inner leg c and the outer leg e. Of these magnetic paths, the outer magnetic path has the path length of l.sub.1 while the inner magnetic path has the path length of l.sub.2, and the path length l.sub.2 is longer than the path length l.sub.1. A magnetic flux density B can be expressed as B=μ*N*I/l, where μ is a magnetic flux coefficient, N is the number of turns of the coil, I is a current and l is the path length, and an inductance L of each magnetic path is expressed as L=μ*S*N.sup.2/l, where S is a cross-sectional area and N is the number of turns of the winding. These relational expressions for the magnetic flux density B and the inductance L show that the magnetic flux densities B and the inductances L of the magnetic paths having different path lengths l differ from one another.

[0101] In this way, the reactor having the configuration shown in FIG. 3(a) causes the non-uniformity in the magnetic flux density of the AC magnetic fluxes and the inductances in the magnetic paths.

Non-Uniformity in Bias Magnetic Flux by DC Magnetic Flux

[0102] FIG. 3(d) shows a state of the DC magnetic flux generated by the control windings. The control windings are wound around the center leg a to apply the direct current to the control windings, so that magnetic fluxes are generated on the magnetic path passing the inner leg b and the center leg a and the magnetic path passing the inner leg c and the center leg a. Since two magnetic fluxes flow through the center leg a, the magnetic flux density through the center leg a gets higher than that through each of the inner leg b and the inner leg c. Consequently, in the reactor with the configuration of FIG. 3(a), the magnetic flux density of the bias magnetic flux generated in each magnetic path becomes non-uniform.

[0103] FIG. 3(e) shows a state of a magnetic flux obtained by combining magnetic fluxes of the control winding and a magnetic flux of the control winding. Since no DC magnetic flux is generated on the outer legs d and e by the control windings, a magnetic path, in which the bias magnetic flux is not applied to the AC magnetic flux generated by the main magnetic flux, is formed.

[0104] On the other hand, FIGS. 3(f) and 3(g) respectively show the configurations of the reactor of the present invention and the states of the magnetic fluxes thereof. FIG. 3(f) shows the schematic configuration of the reactor of the invention, in which the wiring boards of the main windings and the wiring board of the control winding are disposed inside the core of the reactor. FIG. 3(g) shows the state of a magnetic flux obtained by combining magnetic fluxes of the control winding and a magnetic flux of the control winding generated by the reactor of the present invention. The DC magnetic flux is also generated on the outer legs d and e by the control winding so as to apply the bias magnetic flux to all AC magnetic fluxes formed by the main magnetic flux. Consequently, in the reactor having the planer core to which the wiring boards are incorporated in layers, the densities of the magnetic fluxes generated by the control current of the control winding become uniform, while the inductance of the reactor is set according to the control current of the current winding.

[0105] In the reactor according to the present invention that is configured by incorporating in layers the wiring boards respectively having the main winding formed thereon and the wiring board having the control winding formed thereon into the planer core, (a) the magnetic fluxes generated by the main windings and (b) the magnetic flux generated by the control winding are respectively made to be in the following states, so as to enable to make a uniform magnetic flux densities by the control current uniform.

[0106] (a) When a high-frequency current is applied to the main windings, a high-frequency component is induced in the control winding, and the inducement of the high-frequency component causes a drawback that the high-frequency current is applied to a control circuit, and a drawback that an excessive voltage is generated across the control winding. In order to prevent these drawbacks, the magnetic fluxes are brought to the state in which the high-frequency component is not induced in the control winding during the production of the magnetic fluxes by the main windings.

[0107] (b) The control winding is formed around the legs of the core from which the high-frequency component is removed.

[0108] The uniform magnetic flux density can generate uniform inductances on the main windings that are wound around the legs, thereby enabling to vary inductances in the reactor depending on the control current. Main winding currents of the high-frequency current flowing the main windings generates AC magnetic fluxes of which magnetic field directions are opposite to each other in a pair of the inner legs, and then the magnetic fluxes cancel each other out.

[0109] That is to say, in the inducement of the high-frequency component in the control winding by the high-frequency currents of two main windings, the high-frequency component induced in the control winding due to the flow of the high-frequency current of one of the main windings and the high-frequency component induced in the control winding due to the flow of the high-frequency current in the other main winding are the same in strength, but these components are in the direction opposite to each other. Consequently, the high-frequency components generated by the respective windings cancel each other, so as to remove them.

[0110] Although the high-frequency components are induced in the control winding due to the flow of the high-frequency currents in each main winding, the generation of the magnetic fields in opposite directions on the legs can cancel the high-frequency components induced in the control winding.

[0111] As a result, it can prevent the high-frequency current from flowing into the control circuit from the control winding. In addition to that, the cancellation of the high-frequency component of the control winding can suppress the local generation of the excessive voltage across the control winding.

[0112] The control current of the direct current flowing the control winding generates the DC magnetic flux with the uniform magnetic flux density around all the legs including the pair of the inner legs in which the AC magnetic fluxes have been cancelled out. By making the magnetic flux density of the DC magnetic flux generated by the control winding uniform in all the legs of the core, it is possible to equalize the variation of the inductances with respect to the main windings.

[0113] The wiring boards provided to the reactor of the present invention are the main winding substrates and the control winding substrate, which are stacked on top of each other. The main winding substrate consists of the first main winding substrate and the second main winding substrate. The control winding substrate may be sandwiched from above and below thereof by the first main winding substrate and the second main winding substrate, or may be disposed on either side of the layer of the first main winding substrate and the second main winding substrate.

[0114] The wiring board provided to the reactor of the present invention is configured by sandwiching the control winding substrate with two main winding substrates to thereby enhance the degree of bond of the magnetic fields between the main windings and the control winding.

First Embodiment of Reactor

[0115] with reference to FIGS. 4 to 6, a first embodiment of the reactor according the present invention will be described. FIG. 4 shows a schematic diagram of the first embodiment of the reactor of the invention. In this figure, the same reference signs are assigned to the parts in common with those in FIG. 1.

[0116] FIG. 4(a) shows a schematic configuration of the planer core 11 of the reactor 10. This planer core 11 has the same configuration as that in FIG. 1(a) and employs four E-cores as core members, in which the protruding portions of two E-cores are arranged facing each other so as to form two planer cores 11a, 11b. Although FIG. 4(a) shows a configuration of an EE-core employing the E-cores, this configuration may be a UU-core employing the U-cores.

[0117] The planer core 11 comprises the center leg 16a, a pair of inner legs 16b, 16c arranged on both sides of the center leg 16a, and a pair of outer legs 16d, 16e further arranged outside the inner legs 16b, 16c. Through holes are formed between the adjacent legs, into which the wiring boards of the first main winding substrate 14A, the second main winding substrate 14B and the control winding substrate 15 are arranged.

[0118] FIG. 4(b) shows the wiring boards of the first main winding substrate 14A, the second main winding substrate 14B and the control winding substrate 15. FIG. 4(c) shows the winding patterns respectively created on the wiring boards of the first main winding substrate 14A, the second main winding substrate 14B and the control winding substrate 15.

[0119] The first main winding substrate 14A is provided with the winding pattern of the first main winding 12b, and also with two openings, into which the inner leg 16b and the center leg 16a are inserted. The winding pattern is formed to surround the two openings.

[0120] The second main winding substrate 14B is provided with the winding pattern of the second main winding 12c, and also with two openings, into which the inner leg 16c and the center leg 16a are inserted. The winding pattern is formed to surround the two openings.

[0121] The control winding substrate 15 is provided with the winding patterns of the control windings 13a, 13b, and also with three openings, into which the inner leg 16b, the inner leg 16c and the center leg 16a are inserted. The winding patterns are formed to surround the openings for inserting the inner leg 16b and the inner leg 16c among the three openings.

[0122] The first main winding 12b and the second main winding 12c are supplied with high-frequency currents brunched from a high-frequency power source, not shown, so as to generate AC magnetic fluxes flowing around each leg, namely the center leg 16a, the inner legs 16b, 16c, and the outer legs 16d, 16e, of the planer core 11. On the other hand, the control windings 13a, 13b are supplied with direct currents to generate a DC magnetic fluxes flowing around each leg, namely the center leg 16a, the inner legs 16b, 16c, and the outer legs 16d, 16e, of the planer core 11.

[0123] FIG. 5 shows a state of currents flowing the winding of each wiring board and states of fluxes induced by the current. FIG. 5(a) shows a schematic configuration of the planer core 11 of the reactor 10 that is the same as that of FIG. 5(a). FIG. 5(b) shows the states of the currents and the states of the magnetic fluxes of the first main winding substrate 14A, the second main winding substrate 14B and the control winding substrate 15.

[0124] In FIG. 5, with respect to the direction of each current flow, the direction of the current flowing forward in the figure is indicated by a circle with an inner black circle (.circle-solid.), while the direction of the current flowing backward in the figure is indicated by a circle with an inner cross (x) mark, and with respect to the magnetic flux directions, the direction of the magnetic flux flowing forward in the figure is indicated by a square with an inner black circle (.circle-solid.), while the direction of the magnetic flux flowing backward in the figure is indicated by a square with an inner cross (x) mark. [0125] State of a magnetic flux generated by the main winding:

[0126] In the first main winding substrate 14A, the high-frequency current flowing the main winding 12b generates magnetic fluxes around the outer leg 16d, the inner leg 16b, the center 16a and the inner leg 16c. In the second main winding substrate 14B, the high-frequency current flowing the main winding 12c generates magnetic fluxes around the inner leg 16b, the center leg 16a, the inner leg 16c and the outer leg 16e.

[0127] When the high-frequency current of the main winding 12b flows in the direction shown by an arrow, a magnetic flux in the direction shown in the figure is generated around each leg. Around the inner leg 16b, a magnetic flux that flows in the backward magnetic flux direction in the figure is generated by the high-frequency current flowing the main winding 12b, a magnetic flux that flows in the forward magnetic flux direction in the figure is generated by the high-frequency current flowing the main winding 12c. As two fluxes generated around the inner leg 16b flow in the directions opposite to each other, both fluxes are cancelled out each other when the number of turns and the current value of the main winding 12b and the main winding 12c are equal. Similarly, a magnetic flux that flows in the forward magnetic flux direction in the figure and another magnetic flux that flows in the backward magnetic flux direction backward in the figure are generated around the inner leg 16c respectively by the high-frequency current flowing the main winding 12b and the high-frequency current flowing the main winding 12c. Since the two magnetic fluxes generated around the inner leg 16c flow in the directions opposite to each other, both magnetic fluxes are cancelled out each other when the number of turns and the current value of the main winding 12b and the main winding 12c are equal.

[0128] Furthermore, around the center leg 16a, a magnetic flux flowing in the backward magnetic flux direction in the figure is generated by the high-frequency current flowing the main winding 12b, and also another magnetic flux flowing in the backward magnetic flux direction in the figure is generated by the high-frequency current flowing the main winding 12c.

[0129] FIG. 5(c) shows the states of magnetic fluxes generated by high-frequency currents, in which the magnetic fluxes generated around the inner leg 16b and the inner leg 16c by the high-frequency currents are cancelled out each other. [0130] State of a magnetic flux generated by the control winding:

[0131] On the control winding substrate 15, a direct current flowing through the control winding 13a generates magnetic fluxes around the outer leg 16d, the inner leg 16b and the center leg 16a, and a direct current flowing the control winding 13b generates magnetic fluxes around the center leg 16a, the inner leg 16c and the outer leg 16e. In FIG. 5, when the direct currents of the control windings 13a, 13b flow in the direction indicated with arrows, respectively, a magnetic flux flowing in the direction shown in the figure is generated around each leg.

[0132] Around the inner leg 16b and the inner leg 16c, magnetic fluxes flowing in the backward magnetic flux direction in the figure are generated by the direct currents respectively flowing the control windings 13a, 13b. Since the AC magnetic fluxes generated by the high-frequency current around the inner leg 16b and the inner leg 16c are cancelled out each other, no current is induced by the AC magnetic flux in the control windings 13a, 13b, thereby preventing the flow of the high-frequency current and the generation of an excessive voltage in the control circuit, not shown.

[0133] FIG. 5(d) shows a state of a magnetic flux generated by a direct current, in which a state of a DC magnetic flux with a uniform flux density is generated around all the legs of the core, including the inner legs 16b, 16c and the center leg 16a, by the direct current.

[0134] Thus, in the configuration of the first embodiment, the wiring boards are incorporated in layers into the planer core 11, so that the winding patterns of the first main winding 12b and the second main winding 12c surround together the center 16a. In addition to that, in the inner leg 16b, the magnetic fields generated by the main winding currents flowing through the first main winding 12b and the second main winding 12c are in the opposing directions, and thereby the magnetic fluxes are cancelled out each other. Correspondingly, in the inner leg 16c, the magnetic fields generated by the main winding currents flowing the first main winding 12b and the second main winding 12c are in the opposing directions, and thereby the magnetic fluxes are cancelled out each other.

[0135] FIG. 6 schematically shows a state of a magnetic flux around each legs of the planer core, FIGS. 6(a) and 6(b) respectively showing states of magnetic fluxes generated by the first main winding and the second main winding, FIG. 6(c) showing a state in which the magnetic fluxes generated by the two main windings are combined, FIG. 6(d) showing a state of a magnetic flux generated by the control winding, FIG. 6(e) showing a state in which the magnetic fluxes generated by the two main windings and the control winding are combined.

[0136] The magnetic flux generated by the first main winding flows, as shown in FIG. 6(a), through a path around the outer leg 16d and the inner leg 16b and also through a path around the center leg 16a and the inner leg 16c, and the magnetic flux generated by the second main winding flows, as shown in FIG. 6(b), through a path around the inner leg 16b and the center leg 16a and also through a path around the inner leg 16c and the outer leg 16e. In the inner legs 16b, 16c, AC magnetic fluxes generated by the two main windings cancel each other out. An arrow shown by a broken line in FIG. 6(c) presents a cancellation state.

[0137] A DC magnetic flux generated by the control winding flows, as shown in FIG. 6(d), through the inner leg 16b and the inner leg 16c, between which the AC magnetic fluxes are cancelled out, so that a uniform magnetic flux density is formed in the center leg 16a and the outer legs 16d, 16e.

Second Embodiment of Reactor

[0138] A second embodiment of the reactor has the same configuration as that of the first embodiment, except the configuration of the main winding substrate, to thereby bringing the magnetic fluxes into the state similar to that of the first embodiment. With reference to FIGS. 7 to 9, the second embodiment of the reactor of the present invention will be described. FIG. 7 schematically shows the second embodiment of the reactor of the invention. In this figure, the same reference signs are assigned to the parts in common with those in FIG. 1 and FIGS. 4 to 6.

[0139] FIG. 7(a) shows a schematic configuration of the planer core 11 of the reactor 10. The planer core 11 has the configuration similar to that shown in FIG. 4(a), which configuration has the center leg 16a, the pair of the inner legs 16b, 16c arranged on both sides of the center leg 16a, and further has the pair of the outer legs 16d, 16e disposed outside the inner legs 16b, 16c. The adjacent legs are provided with through holes between them, into which the wiring boards of the first main winding substrate 14A, the second main winding substrate 14B and the control winding substrate 15 are respectively placed.

[0140] FIG. 7(b) shows the wiring boards of the first main winding substrate 14A, the second main winding substrate 14B and the control winding substrate 15, and FIG. 7(c) shows the winding patterns formed on the wiring boards of the first main winding substrate 14A, the second main winding substrate 14B and the control winding substrate 15, respectively.

[0141] On the first main winding substrate 14A, the winding pattern of the first main winding 12b is formed, and three openings are provided to insert the inner legs 16b, 16c and the center leg 16a therein. The winding pattern is formed to surround these three openings.

[0142] On the second main winding substrate 14B, the winding pattern of the first main winding 12c is formed, and an opening is provided to insert the center leg 16a therein. The winding pattern is formed to surround this opening.

[0143] On the control winding substrate 15, the winding patterns of the control windings 13a, 13b are formed, and three openings are provided to insert therein the inner leg 16b and inner leg 16c as well as the center leg 16a. The winding patterns are formed to surround the opening among three openings into where the inner leg 16b and the inner leg 16c are inserted. The configuration of the control winding substrate 15 is the same as that in the first embodiment.

[0144] The first main winding 12b and the second main winding 12c are supplied with high-frequency currents branched from a high-frequency power source, not shown, so as to generate AC magnetic fluxes flowing through each leg, namely the center leg 16a, the inner legs 16b, 16c and the outer legs 16d, 16e, of the planer core 11. On the other hand, the control windings 13a, 13b are supplied with the direct current to thereby generate DC magnetic fluxes with the same magnetic flux density around all the legs of the planer core 11, including the center leg 16a and the inner legs 16b, 16c.

[0145] FIG. 8 shows a state of current flowing the winding of each wiring board and a state of a magnetic flux induced by the current. FIG. 8 (a) shows a schematic configuration of the planer core 11 of the reactor 10 that is the same as that of FIG. 7 (a). FIG. 8 (b) shows the states of the currents and the states of the magnetic fluxes of the first main winding substrate 14A, the second main winding substrate 14B and the control winding substrate 15.

[0146] FIG. 8 also uses the same symbols as those in the first embodiment which denote the direction of the current and the direction of the magnetic flux. [0147] State of a magnetic flux generated by the main winding:

[0148] On the first main winding substrate 14A, fluxes are generated around the outer leg 16d, the inner leg 16b, the inner leg 16c and the outer 16e by a high-frequency current flowing the main winding 12b, and in the second main winding substrate 14B, fluxes are generated around the inner leg 16b, center leg 16a and the inner leg 16c by a high-frequency current flowing the main winding 12c.

[0149] When the high-frequency current of the main winding 12b flows in the direction indicated by an arrow, a magnetic flux flowing in the direction shown in the figure is generated around each leg. Around the inner leg 16b, a magnetic flux flowing in the backward magnetic flux direction in the figure is generated by the high-frequency current flowing through the main winding 12b, and another magnetic flux flowing in the forward magnetic flux direction in the figure is also generated by the high-frequency current flowing in the main winding 12c. Since these two magnetic fluxes generated around the inner leg 16b flow in the directions opposite to each other, both magnetic fluxes are cancelled out each other if the number of turns and the current value of the main winding 12b and the main winding 12c are equal. Correspondingly, around the inner leg 16c, a magnetic flux flowing in the backward magnetic flux direction in the figure is generated by the high-frequency current flowing the main winding 12b, and another flux flowing in the forward magnetic flux direction in the figure is also generated by the high-frequency current flowing in the main winding 12c. Since these two magnetic fluxes generated around the inner leg 16c flow in the directions opposite to each other, both magnetic fluxes cancel each other out if the number of turns and the current value of the main winding 12b and the main winding 12c are equal.

[0150] In addition to that, around the center leg 16a, a magnetic flux flowing in the backward magnetic flux direction in the figure is generated by the high-frequency current flowing the main winding 12c.

[0151] FIG. 8(c) shows a state of a magnetic flux generated by a high-frequency current, in which state the magnetic fluxes generated by the high-frequency current around the inner leg 16b and the inner leg 16c are cancelled out each other. [0152] State of a magnetic flux generated by the control winding:

[0153] On the control winding substrate 15, magnetic fluxes are generated around the outer leg 16d, the inner leg 16b and the center leg 16a by a direct current flowing in the control winding 13a, and also magnetic fluxes are generated around the center leg 16a, the inner leg 16c and the outer leg 16e by a direct current flowing the control winding 13b. The states of the magnetic fluxes generated by the control windings in the second embodiment are similar to the states of the magnetic fluxes generated by the control windings in the first embodiment. In FIG. 8, when the direct currents of the control windings 13a, 13b flow in the direction indicated by arrows, a magnetic flux flowing in the direction shown in the figure is generated around each leg.

[0154] Around the inner leg 16b and the inner leg 16c, magnetic fluxes flowing in the backward magnetic flux direction in the figure are generated by the direct currents flowing the control windings 13a, 13b. Since the AC magnetic fluxes generated by the high-frequency currents around the inner leg 16b and the inner leg 16c are cancelled out each other, no current is induced by the AC magnetic fluxes in the control windings 13a, 13b, thereby preventing the flow of the high-frequency current and the generation of an excessive voltage in the control circuit, not shown.

[0155] FIG. 8(d) shows a state of a magnetic flux generated by a direct current, in which a state of a DC magnetic flux with a uniform flux density is generated around all the legs, including the inner legs 16b, 16c and the center leg 16a, by the direct current.

[0156] Thus, in the configuration of the second embodiment, the wiring boards are incorporated in layers into the planer core 11, so that the magnetic fields generated in the inner leg 16b by the main winding currents flowing through the first main winding 12b and the second main winding 12c are in the opposing directions, and thereby the magnetic fluxes cancel each other out. Correspondingly, in the inner leg 16c, the magnetic fields generated by the main winding currents flowing through the first main winding 12b and the second main winding 12c are in the opposing directions, and thereby the magnetic fluxes cancel each other out.

[0157] FIG. 9 schematically shows a state of a magnetic flux around each leg of the planer core, in which FIGS. 9(a) and 9(b) respectively show the states of the magnetic fluxes generated by the first main winding and the second main winding, FIG. 9(c) shows a state where the magnetic fluxes generated by the two main windings are combined, FIG. 9(d) shows a state of a magnetic flux generated by the control winding, and FIG. 9(e) shows a state where the magnetic fluxes generated by the two main windings and the control winding are combined.

[0158] The magnetic flux generated by the first main winding flows, as shown in FIG. 9(a), through a path around the outer leg 16d and the inner leg 16b and also through a path around the inner leg 16c and the outer leg 16e, and the magnetic flux generated by the second main winding flows, as shown in FIG. 9(b), through a path around the inner leg 16b and the center leg 16a and also through a path around the center leg 16a and the inner leg 16c. In the inner legs 16b, 16c, the AC magnetic fluxes generated by the two main windings cancel each other out. Arrows shown in FIG. 9(c) by broken lines present cancellation state.

[0159] The DC magnetic flux generated by the control winding flows, as shown in FIG. 9(d), around the inner leg 16b and the inner leg 16c, between which the AC magnetic fluxes have been cancelled out, so that a magnetic flux with a uniform flux density is generated around each of the center leg 16a and the outer legs 16d, 16e.

Winding Pattern of Control Winding

[0160] The winding pattern of the control winding may have a configuration different from those presented in the first embodiment and the second embodiment.

[0161] FIG. 10(a) shows the winding patterns of the control windings presented in the first and second embodiments. These winding patterns are formed in such a way that the winding is coiled around the inner leg 16b the number of predetermined times in the clockwise direction in the figure, and is then coiled around the inner leg 16c the number of predetermined times in the clockwise direction in the figure.

[0162] FIG. 10(b) shows another configuration of the winding pattern of the control winding. This winding pattern is formed in such a way that the winding is coiled around the inner leg 16b once in the clockwise direction in the figure, and is further coiled around the inner leg 16c once in the clockwise direction in the figure, and then goes back to the inner leg 16b to be coiled once around the inner legs 16b and 16c. This winding pattern of coiling the winding around two inner legs is repeated the number of the predetermined times.

[0163] In either case of the winding pattern in FIG. 10(a) and the winding pattern in FIG. 10(b), the equivalent magnetic fluxes can be generated around all the legs.

[0164] The descriptions about the above embodiments and its variations present some examples of the reactor according to the present invention. The invention is therefore not limited to the above embodiments, and can be changed in various ways based on the purport of the invention which will not be excluded from the scope of the invention.

INDUSTRIAL APPLICABILITY

[0165] The reactor of the present invention is to an impedance matching device and similar.

REFERENCE SIGNS LIST

[0166] 10 Reactor [0167] 11, 11a, 11b Planer Core [0168] 12b, 12c Main Winding [0169] 13a, 13b Control Winding [0170] 14A First Main Winding Substrate [0171] 14B Second Main Winding Substrate [0172] 15 Control Winding Substrate [0173] 16a Center Leg [0174] 16b, 16cInner Leg [0175] 16d, 16e Outer Leg [0176] 100 Variable Reactor [0177] 101a, 101b Core [0178] 102a, 102b Main Winding [0179] 103 Control Winding [0180] 110 Planer Transmitter [0181] 111 Planer EE-Core [0182] 111a, 111b E-core [0183] 112 Planer UU-Core [0184] 112a, 112b, 112c, 112d U-Core [0185] 121 Planer Core [0186] 121a Center Leg [0187] 121b, 121c Side Leg [0188] 122 Main Winding [0189] 123 Control Winding [0190] 124 Main winding Substrate [0191] 125 Control Winding Substrate [0192] 126a, 126b, 126c Opening