Variable capacity capacitor and power supply device

Abstract

A variable capacity capacitor (1) includes: a first control electrode (21); a second control electrode (22) facing the first control electrode; a dielectric layer (32) disposed at least between the first control electrode and the second control electrode; and a first extraction electrode (11) and a second extraction electrode (12) facing each other with the dielectric layer interposed therebetween, the first extraction electrode and the second extraction electrode being disposed at a position in which the first extraction electrode and the second extraction electrode face each other when a control voltage is applied between the first control electrode and the second control electrode. And a position at which an electric field is generated along a direction intersecting an electric field vector generated between the first control electrode and the second control electrode.

Description

Citation of related applications

[0001] This application is based on Japanese Patent Application No. 2023-14374 filed on February 2, 2023, and the contents thereof are incorporated herein by reference. Technical Field

[0002] The present disclosure relates to a variable-capacity capacitor and a power supply device. Background Art

[0003] Conventionally, there are capacitors with variable capacitance (e.g., Patent Document 1) that have a dielectric layer disposed between a pair of electrodes for applying a DC bias. In conventional capacitors, a dielectric layer is disposed between a ground electrode and a DC bias electrode, and a capacitance acquisition electrode is disposed between the ground electrode and the DC bias electrode with the dielectric layer interposed therebetween. Applying a DC bias between the ground electrode and the DC bias electrode changes the dielectric properties of the dielectric layer, thereby changing the capacitance of the capacitor. Prior art literature Patent Literature

[0004] Patent Document 1: Japanese Patent Application Laid-Open No. 2006-344845 Summary of the Invention

[0005] In the capacitor described in Patent Document 1, the grounding electrode, DC bias electrode, and capacitance acquisition electrode are stacked in the same direction with dielectric layers interposed between them. Therefore, the distance between the grounding electrode and the DC bias electrode, and the distance between the grounding electrode and the capacitance acquisition electrode, must be set in tandem.

[0006] The present disclosure can be implemented in the following forms.

[0007] In one embodiment of the present disclosure, a variable-capacitance capacitor is provided. The variable-capacitance capacitor includes: a first control electrode; a second control electrode opposing the first control electrode; a dielectric layer disposed at least between the first control electrode and the second control electrode; and a first extraction electrode and a second extraction electrode opposing each other with the dielectric layer interposed therebetween, the first extraction electrode and the second extraction electrode being disposed at positions where, when a control voltage is applied between the first control electrode and the second control electrode, an electric field is generated in a direction intersecting an electric field vector generated between the first control electrode and the second control electrode.

[0008] This method allows the distance between the first and second control electrodes, and the distance between the first and second extraction electrodes, to be independently set. Therefore, by shortening the distance between the first and second control electrodes, the electric field applied to the dielectric layer can be increased even with the same control voltage, thereby reducing the control voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The above objects, other objects, features and advantages of the present disclosure will become more apparent with reference to the accompanying drawings and the following detailed description. Figure 1 This is a three-dimensional diagram of a variable capacitance capacitor. Figure 2 yes Figure 1 A cross-sectional view of the variable capacitance capacitor taken along line II-II is shown. Figure 3 It is a diagram explaining PVDF. Figure 4 is a graph showing the relationship between the control electric field and the relative dielectric constant. Figure 5 It is a perspective view of a variable capacitor according to a second embodiment. Figure 6 It is a diagram showing the results of studying the number of configurations. Figure 7 It is a cross-sectional view of a variable capacitor according to a third embodiment. Figure 8 Graph showing the results of studying the inter-electrode distance and electrode length. Figure 9 This is a circuit diagram of a contactless power supply system according to a fourth embodiment. Figure 10 is a graph showing a hysteresis curve. Figure 11 This diagram compares relaxors (Japanese: リラクサー) and ferroelectrics. DETAILED DESCRIPTION

[0010] A. First embodiment: like Figure 1 As shown, the variable capacitance capacitor 1 has a first extraction electrode layer 11 as a first extraction electrode, a second extraction electrode layer 12 as a second extraction electrode, a first control electrode layer 21 as a first control electrode, a second control electrode layer 22 as a second control electrode, a first dielectric layer 31, a second dielectric layer 32 as a dielectric layer, a first extraction electrode common layer 41 and a second extraction electrode common layer 42.

[0011] exist Figure 1In the figure, the XYZ axes are depicted as three spatial axes that are orthogonal to each other. The directions pointed by the arrows of the X-axis, Y-axis, and Z-axis represent the positive directions along the X-axis, Y-axis, and Z-axis, respectively. The positive directions along the X-axis, Y-axis, and Z-axis are the +X direction, +Y direction, and +Z direction, respectively. The directions opposite to the directions pointed by the arrows of the X-axis, Y-axis, and Z-axis are the negative directions along the X-axis, Y-axis, and Z-axis, respectively. The negative directions along the X-axis, Y-axis, and Z-axis are the -X direction, -Y direction, and -Z direction, respectively. Regardless of positive or negative, the directions along the X-axis, Y-axis, and Z-axis are referred to as the X direction, Y direction, and Z direction, respectively. The same applies to the figures and descriptions shown below.

[0012] like Figure 2 As shown, the first control electrode layer 21 and the second control electrode layer 22 are electrode layers used to adjust the capacitance of the variable capacitor 1. The first extraction electrode layer 11 and the second extraction electrode layer 12 are electrode layers used to utilize the capacitance of the variable capacitor 1. Typically, the variable capacitor 1 is used by applying a control voltage (DC voltage) between the first control electrode layer 21 and the second control electrode layer 22, and applying AC power between the first extraction electrode layer 11 and the second extraction electrode layer 12.

[0013] The second control electrode layer 22 is opposite to the first control electrode layer 21. The second dielectric layer 32 is arranged at least between the first control electrode layer 21 and the second control electrode layer 22. The first extraction electrode layer 11 and the second extraction electrode layer 12 are opposite to each other with the second dielectric layer 32 sandwiched therebetween. The first extraction electrode layer 11 and the second extraction electrode layer 12 are arranged at positions where, when a control voltage is applied between the first control electrode layer 21 and the second control electrode layer 22, an electric field is generated in a direction that intersects the electric field vector generated between the first control electrode layer 21 and the second control electrode layer 22. In this embodiment, the first control electrode layer 21 and the second control electrode layer 22 are opposite to each other in the X direction, which is the first direction. In addition, the first extraction electrode layer 11 and the second extraction electrode layer 12 are opposite to each other in the Z direction, which is the second direction.

[0014] like Figure 2 As shown, the variable capacitance capacitor 1 has a stacked structure. Specifically, a first dielectric layer 31 is disposed above the first extraction electrode layer 11. A first control electrode layer 21, a second control electrode layer 22, and a second dielectric layer 32 are disposed above the first dielectric layer 31. The second dielectric layer 32 covers the first and second control electrode layers 21 and 22. A second extraction electrode layer 12 is disposed above the second dielectric layer 32. The film planes of each layer are oriented in the XY direction. The stacking direction of each layer is the Z direction.

[0015] like Figure 1As shown, the first control electrode layer 21 and the second control electrode layer 22 each have a flat plate shape with its long axis in the Y direction. The first control electrode layers 21 and the second control electrode layers 22 are alternately arranged with intervals in the X direction. The -Y-direction end of each first control electrode layer 21 is electrically connected to the first extraction electrode common layer 41. The +Y-direction end of each second control electrode layer 22 is electrically connected to the second extraction electrode common layer 42.

[0016] An arrangement formed by alternately arranging the first control electrode layers 21 and the second control electrode layers 22 in the X direction with the second dielectric layer 32 interposed therebetween is also referred to as a first arrangement ST1. By alternately arranging the first control electrode layers 21 and the second control electrode layers 22, the capacitors formed between the first control electrode layers 21 and the second control electrode layers 22 are connected in parallel with each other, thereby increasing the capacitance value of the variable capacitor 1.

[0017] like Figure 2 As shown, the second dielectric layer 32 is disposed at least between the first control electrode layer 21 and the second control electrode layer 22. Specifically, the second dielectric layer 32 is disposed in the control region RG1 sandwiched between the first control electrode layer 21 and the second control electrode layer 22 in the X direction. Thus, when a control voltage (a DC voltage) is applied between the first control electrode layer 21 and the second control electrode layer 22, an electric field vector substantially parallel to the X direction is generated in the control region RG1.

[0018] The first extraction electrode layer 11 and the second extraction electrode layer 12 are opposite to each other in the Z direction with the second dielectric layer 32 sandwiched therebetween. Thus, the electric field vector generated in the control region RG1 when an AC voltage is applied between the first extraction electrode layer 11 and the second extraction electrode layer 12 intersects with the voltage vector generated in the control region RG1 when a control voltage is applied between the first control electrode layer 21 and the second control electrode layer 22. In this embodiment, the first extraction electrode layer 11 and the second extraction electrode layer 12 are opposite to each other in the Z direction. The first control electrode layer 21 and the second control electrode layer 22 are opposite to each other in the X direction. Thus, the electric field vector generated in the control region RG1 when an AC voltage is applied between the first extraction electrode layer 11 and the second extraction electrode layer 12 is approximately orthogonal to the voltage vector generated in the control region RG1 when a control voltage is applied between the first control electrode layer 21 and the second control electrode layer 22.

[0019] The relative orientation of the first extraction electrode layer 11 and the second extraction electrode layer 12 is different from the relative orientation of the first control electrode layer 21 and the second control electrode layer 22. This allows the distance between the first extraction electrode layer 11 and the second extraction electrode layer 12 and the distance between the first control electrode layer 21 and the second control electrode layer 22 to be independently set. The distance between the first control electrode layer 21 and the second control electrode layer 22 can be shortened without shortening the distance between the first extraction electrode layer 11 and the second extraction electrode layer 12. Consequently, the distance between the first extraction electrode layer 11 and the second extraction electrode layer 12 can be maintained at a level sufficient to withstand the voltage applied between the first extraction electrode layer 11 and the second extraction electrode layer 12. Furthermore, by shortening the distance between the first extraction electrode layer 11 and the second extraction electrode layer 12, the electric field applied between the first control electrode layer 21 and the second control electrode layer 22 can be increased. Consequently, the control voltage can be reduced.

[0020] Assuming that the relative orientation of the first extraction electrode layer 11 and the second extraction electrode layer 12 is the same as the relative orientation of the first control electrode layer 21 and the second control electrode layer 22, in order to adjust the relative permittivity of the dielectric, the control voltage must be greater than the voltage applied between the first extraction electrode layer 11 and the second extraction electrode layer 12. To address this issue, according to this embodiment, the distance between the first extraction electrode layer 11 and the second extraction electrode layer 12 and the distance between the first control electrode layer 21 and the second control electrode layer 22 can be independently set. Therefore, by shortening the distance between the first extraction electrode layer 11 and the second extraction electrode layer 12, the control voltage can be reduced.

[0021] Furthermore, for the reasons described above, the voltage applied to the second dielectric layer 32 can be reduced compared to a case where the first extraction electrode layer 11 and the second extraction electrode layer 12 face each other in the same direction as the first control electrode layer 21 and the second control electrode layer 22. Therefore, the distance between the first extraction electrode layer 11 and the second extraction electrode layer 12 can be shortened to a level that can withstand the voltage applied to the second dielectric layer 32. Consequently, the size of the variable capacitance capacitor 1 can be reduced. Furthermore, since the first control electrode layer 21 and the second control electrode layer 22 face each other in the X direction, an electric field can also be applied to the second dielectric layer 32 in areas outside of the control region RG1. Consequently, the area of ​​the second dielectric layer 32 where the relative dielectric constant εr varies can be expanded.

[0022] The second dielectric layer 32 has anisotropic dielectric properties. Here, anisotropic dielectric properties mean that, when a control voltage is applied to the second dielectric layer 32, the relative dielectric constant εr when an AC voltage is applied varies depending on the direction of the electric field vector generated by the AC voltage. Because the second dielectric layer 32 has anisotropic dielectric properties, when the direction of the control voltage and the AC voltage are applied differ, the relative dielectric constant εr varies significantly depending on the magnitude of the control voltage, as described in detail below.

[0023] In this embodiment, the first dielectric layer 31 and the second dielectric layer 32 comprise a ferroelectric material of the same material. Specifically, the first dielectric layer 31 and the second dielectric layer 32 comprise PVDF (polyvinylidene fluoride). Alternatively, the first dielectric layer 31 and the second dielectric layer 32 may comprise a ferroelectric polymer such as a fluororesin such as P(VDF-TrFE) (polyvinylidene fluoride-trifluoroethylene). Since the first dielectric layer 31 comprises a ferroelectric, the first dielectric layer 31 can also function as a variable capacitance capacitor.

[0024] As another form of the first dielectric layer 31 and the second dielectric layer 32 , the first dielectric layer 31 and the second dielectric layer 32 may also include dielectrics made of different materials.

[0025] like Figure 3 As shown, PVDF molecules have hydrogen atoms and fluorine atoms bonded to their carbon chains. Since hydrogen atoms are positively charged and fluorine atoms are negatively charged, PVDF molecules have an electric dipole moment. When PVDF molecules aggregate through intermolecular forces, the directions in which the carbon chains of each PVDF molecule extend are consistent. The hydrogen atoms and fluorine atoms are located in a direction perpendicular to the direction in which the carbon chains extend. Therefore, spontaneous polarization occurs in PVDF crystals. When an electric field is applied to the PVDF crystals, the polarization direction changes by rotating about the X-axis, which is the direction in which the carbon chains extend, as the central axis. Therefore, even when a control voltage is applied, the direction of polarization changes by applying an AC voltage between the first extraction electrode layer 11 and the second extraction electrode layer 12. Therefore, by using PVDF in the second dielectric layer 32, a variable capacitance capacitor 1 can be provided in which the relative dielectric constant εr changes significantly when the voltage value of the control voltage changes.

[0026] Figure 4 This graph shows the relationship between the magnitude of the control electric field Ed generated by applying a control voltage between the first control electrode layer 21 and the second control electrode layer 22 and the relative dielectric constant εr when an AC voltage is applied between the first extraction electrode layer 11 and the second extraction electrode layer 12. The variable capacitance capacitor 1 has dielectric characteristics with two peaks in the relative dielectric constant εr.

[0027] A ferroelectric material spontaneously polarizes when the control electric field is 0 V / m. When the control electric field increases to the counterelectric field Ec, the polarization becomes zero, and the relative dielectric constant εr reaches its maximum. Near the counterelectric field Ec, the dipole moment tends to move in the direction corresponding to the AC voltage applied between the first extraction electrode layer 11 and the second extraction electrode layer 12, thus increasing the relative dielectric constant εr.

[0028] When the control electric field Ed is greater than the counter electric field Ec, the relative dielectric constant εr decreases. This is probably because the electric dipole is restricted by the control electric field Ed and is less likely to move in response to the AC voltage.

[0029] In this embodiment, the direction of the control electric field Ed intersects the direction of the electric field caused by the applied AC voltage. Therefore, even in the region where the control electric field Ed is smaller than the coercive electric field Ec, a peak in the relative permittivity εr appears. It is believed that the application of the control electric field Ed facilitates the movement of the electric dipole in response to the applied AC voltage compared to the case where the control electric field Ed is not applied.

[0030] The dielectric characteristics of the variable capacitance capacitor 1 include an auxiliary region, a polarization reversal region, and a saturation region. When a control voltage is applied to the auxiliary region, the polarization movement of the second dielectric layer 32 is assisted. Specifically, the auxiliary region is a region where the control electric field Ed is smaller than the counterelectric field Ec, and the relative dielectric constant εr is greater than the relative dielectric constant ε1 and smaller than the relative dielectric constant ε2. Here, the relative dielectric constant ε1 is the relative dielectric constant εr when the control electric field Ed is zero. The relative dielectric constant ε2 is the minimum point between the two peak values ​​of the relative dielectric constant εr.

[0031] When a control voltage in the polarization reversal region, including a voltage corresponding to the counterelectric field Ec, is applied, the polarization of the second dielectric layer 32 is more easily reversed by the AC voltage than in the auxiliary region. Specifically, the polarization reversal region is a region where the control electric field Ed is within the electric field range including the counterelectric field Ec and the dielectric constant εr is greater than the peak value ε3 of the relative dielectric constant εr in the auxiliary region.

[0032] When a control voltage in the saturation region is applied, the polarization movement of the second dielectric layer 32 is restricted. Specifically, the saturation region is a region where the control electric field Ed is greater than the counter electric field Ec and vice versa.

[0033] As described above, applying the control electric field Ed in the auxiliary region facilitates polarization movement compared to when no control electric field Ed is applied. Therefore, applying the control electric field Ed in the auxiliary region to the variable capacitor 1 can increase the capacitance of the variable capacitor 1 compared to when no control electric field Ed is applied.

[0034] Furthermore, by applying the control electric field Ed in the polarization reversal region, the polarization can be more easily moved than in the auxiliary region. Therefore, by applying the control electric field Ed in the polarization reversal region to the variable capacitor 1, the electrostatic capacitance of the variable capacitor 1 can be made larger than the electrostatic capacitance when the control electric field Ed is applied in the auxiliary region.

[0035] Furthermore, by applying the control electric field Ed in the saturation region, polarization can be made less likely to move. Therefore, by applying the control electric field Ed in the saturation region to the variable capacitor 1, the capacitance of the variable capacitor 1 can be made smaller than the capacitance without the control electric field Ed in the auxiliary region. Therefore, by adjusting the magnitude of the control electric field Ed, the capacitance of the variable capacitor 1 can be set to the target capacitance value.

[0036] As described above, PVDF rotates around the extension direction of the carbon chain as the central axis. Therefore, as shown in the present application, when an AC voltage is applied in a direction different from the direction of the control electric field Ed, the polarization easily moves. Therefore, the dielectric properties of the second dielectric layer 32 are anisotropic. Moreover, the relative dielectric constant εr of the second dielectric layer 32 changes according to the magnitude of the control electric field Ed, thereby providing a variable capacitance capacitor 1 with a good variable rate. Here, the variable rate refers to the change in the relative dielectric constant relative to the change in the applied electric field.

[0037] According to the first embodiment described above, the first extraction electrode layer 11 and the second extraction electrode layer 12 are positioned so as to generate an electric field in a direction intersecting the electric field vector generated when the control voltage is applied. This allows the distance between the first extraction electrode layer 11 and the second extraction electrode layer 12, and the distance between the first control electrode layer 21 and the second control electrode layer 22 to be independently set. Consequently, the control voltage can be reduced.

[0038] Furthermore, second dielectric layer 32 has a dielectric property whereby its relative permittivity εr is greater when the control voltage of the auxiliary region is applied than when no control voltage is applied. Therefore, by applying the control voltage of the auxiliary region to second dielectric layer 32, the capacitance of variable capacitor 1 can be increased compared to when no control voltage is applied.

[0039] Furthermore, second dielectric layer 32 has a dielectric property such that when a control voltage in the saturation region is applied, the relative dielectric constant εr is smaller than when no control voltage is applied. Therefore, by applying a control voltage in the saturation region to second dielectric layer 32, the capacitance of variable capacitor 1 can be reduced compared to when no control voltage is applied.

[0040] Furthermore, the second dielectric layer 32 has a dielectric property whereby the relative dielectric constant εr is greater when the control voltage in the polarization reversal region is applied than when no control voltage is applied. Therefore, by applying the control voltage in the polarization reversal region to the second dielectric layer 32, the capacitance of the variable capacitor 1 can be increased compared to when no control voltage is applied.

[0041] Furthermore, the first control electrode layer 21 and the second control electrode layer 22 face each other in the X direction, while the first extraction electrode layer 11 and the second extraction electrode layer 12 face each other in the Z direction, which is perpendicular to the X direction. Consequently, the control electric field Ed can be uniformly applied to the second dielectric layer 32 regardless of the direction of the electric field generated by the AC voltage applied between the first extraction electrode layer 11 and the second extraction electrode layer 12.

[0042] Furthermore, the dielectric properties of the second dielectric layer 32 are anisotropic. Therefore, a variable capacitor 1 can be provided in which, when an AC voltage is applied in a direction different from the control voltage, the capacitance value changes according to the voltage value of the control voltage. Furthermore, the second dielectric layer 32 comprises a ferroelectric polymer. This inclusion of the ferroelectric polymer enables a variable capacitor 1 with a good capacitance variability.

[0043] B. Second embodiment: like Figure 5 As shown in FIG. 1 , the variable capacitor 201 of this embodiment includes a first arrangement body ST1 and a second arrangement body ST2 . Components identical to those of the first embodiment are denoted by the same reference numerals, and detailed descriptions thereof are omitted as appropriate.

[0044] The second arrangement body ST2 is configured such that the first arrangement body ST1 is arranged in the Z direction. The first extraction electrode layers 11 and the second extraction electrode layers 12 are alternately arranged in the Z direction. The plurality of first extraction electrode layers 11 are electrically connected to a first extraction electrode common layer (not shown). The plurality of second extraction electrode layers 12 are electrically connected to a second extraction electrode common layer (not shown). By stacking the first arrangement body ST1 in the Z direction, the capacitors formed between adjacent first extraction electrode layers 11 and second extraction electrode layers 12 are connected in parallel, thereby increasing the capacitance of the variable capacitor 201.

[0045] When the size of the variable capacitor 1 is fixed, the capacitance value of the variable capacitor 1 and the electric field resistance of the variable capacitor 1 are in a trade-off relationship. Figure 6In the case of the first arrangement body ST1 shown, if the first arrangement number of the first arrangement body ST1 is n1 and the applied voltage is V1, the capacitance value C1 is expressed by the following equation (1) using the formula for a parallel plate capacitor. Here, the first arrangement number refers to the number of pairs of first control electrode layers 21 and second control electrode layers 22. That is, when the number of layers of the first control electrode layers 21 and the second control electrode layers 22 is the same, the first arrangement number is equal to (2×n-1) when the number of layers is n. C1=ε0·ε r ·S1 / (D / n1)·n1 =ε0·ε r ·S1·n1 2 / D· · · (1) The parameters of formula (1) are as follows. ε0: Vacuum dielectric constant ε r : Relative dielectric constant of dielectric S1: Area of ​​the capacitor formed by the first control electrode layer and the second control electrode layer D: Length in the stacking direction In addition, the inter-electrode distance d1, which is the distance between the first control electrode layer 21 and the second control electrode layer 22, is d1=W / n1 In addition, the electric field E1 applied to the dielectric in the first arrangement ST1 is expressed by the following formula (2). E1=V1 / (W / n1) =V1·n1 / W··· (2) According to equations (1) and (2), increasing the first number of configurations, n1, increases the capacitance, but also the applied electric field. The magnitude of the applied electric field is limited to the electric field that can be applied to the dielectric, i.e., the withstand electric field. Therefore, the first number of configurations, n1, is determined by the withstand electric field of the dielectric.

[0046] Similarly, for the second arrangement body ST2, if the second arrangement number of the second arrangement body ST2 is set to n2 and the applied voltage is set to V2, the capacitance value C2 is also expressed by the following formula (3). C2=ε0·ε r ·S2 / H·n2 2 · · · (3) The parameters of formula (3) are as follows. S2: Area of ​​the capacitor formed by the first extraction electrode layer and the second extraction electrode layer H: Length in the stacking direction In addition, the electric field E2 applied to the dielectric in the second arrangement body ST2 is expressed by the following formula (4). E2=V2·n2 / H··· (4) The inventors studied the optimal values ​​of the first arrangement number n1 and the second arrangement number n2 when the size of the variable capacitor 1 is fixed. The values ​​used for the study are as follows. Width of variable capacitor (W: length in the Y direction): 20 mm Depth of variable capacitor (D: length in the X direction): 20 mm Height of variable capacitor (H: length in the Z direction): 2 mm First capacitance value (large capacitance value): 300nF Second capacitance value (smaller capacitance value): 60nF Control voltage (V1): 10V AC voltage (V2): 200V (effective value) The results of the study show that when the first arrangement number n1 is greater than or equal to 20,000 and the second arrangement number n2 is greater than or equal to 100, the electric field withstand condition can be satisfied and the target capacitance value can be obtained. Figure 6 The electric field E1 when the first arrangement number n1 is 20000 and the electric field E2 when the second arrangement number n2 is 100 are shown. By transforming the formula (3) to obtain "H = ε0·ε r ·S2·n2 2 Substituting / C2" into "H" in equation (4), the electric field E2 is expressed by the following equation (5). E2=C2·V2 / (ε0· ε r ·S2·n2) · · · (5) Therefore, if Figure 6 As shown, when the capacitance value C2, the voltage V2, the area S2, and the second configuration number n2 are set to fixed values, the larger the relative dielectric constant εr, the smaller the electric field E2.

[0047] Here, when P(VDF-TrFE) is used as the dielectric, the relative dielectric constant εr that satisfies the target capacitance value is "20". Figure 6 Point PO represents the electric field withstand capability of P(VDF-TrFE) when the relative dielectric constant εr is 20. Figure 6 As shown, when the first arrangement number n1 is 20,000 and the second arrangement number n2 is 100, both the electric field E1 and the electric field E2 are smaller than the dielectric's electric field withstand condition, thus satisfying the dielectric's electric field withstand condition.

[0048] According to the second embodiment described above, since the variable capacitor 201 includes the first arrangement body ST1 and the second arrangement body ST2, the capacitance value of the variable capacitor 201 can be increased compared to capacitors that do not have a structure in which the electrodes are arranged alternately. Furthermore, since the orientation of the first control electrode layer 21 and the second control electrode layer 22 of the first arrangement body ST1 differs from the orientation of the first extraction electrode layer 11 and the second extraction electrode layer 12 of the second arrangement body ST2, a variable capacitor 201 that satisfies both the electric field withstand capability and the capacitance value can be provided. Furthermore, by setting the first arrangement number n1 to 20,000 or greater and the second arrangement number n2 to 100 or greater, a variable capacitor 201 having a target capacitance value can be provided.

[0049] C. Third embodiment: like Figure 7 As shown, the relative orientation of the first extraction electrode layer 11 and the second extraction electrode layer 12, and the relative orientation of the first control electrode layer 21 and the second control electrode layer 22, of the variable capacitor 301 of the third embodiment differ from those of the first embodiment. Components identical to those of the aforementioned embodiments are denoted by the same reference numerals, and detailed descriptions are omitted as appropriate.

[0050] like Figure 7 As shown, the variable capacitance capacitor 301 includes, in addition to the first extraction electrode layer 11, the second extraction electrode layer 12, the first control electrode layer 21, the second control electrode layer 22, and the second dielectric layer 32, a first insulating layer 51 and a second insulating layer 52. The first insulating layer 51 is disposed above the first control electrode layer 21. The first extraction electrode layer 11, the second extraction electrode layer 12, and the second dielectric layer 32 are disposed above the first insulating layer 51. The first extraction electrode layer 11 and the second extraction electrode layer 12 are opposed to each other in the X direction, sandwiching the second dielectric layer 32. The second insulating layer 52 is disposed above the second dielectric layer 32. The second insulating layer 52 covers the first extraction electrode layer 11, the second dielectric layer 32, and the second extraction electrode layer 12. The second control electrode layer 22 is disposed above the second insulating layer 52. The first control electrode layer 21 and the second control electrode layer 22 are opposed to each other in the Z direction, sandwiching the second dielectric layer 32.

[0051] In this embodiment, the first insulating layer 51 and the second insulating layer 52 are made of the same material. For example, an oxide film such as aluminum oxide (Al2O3) or silicon dioxide (SiO2) can be used as the first insulating layer 51 and the second insulating layer 52. Alternatively, in other embodiments, the first insulating layer 51 and the second insulating layer 52 may be made of different materials.

[0052] By disposing the first insulating layer 51 between the second dielectric layer 32 and the first control electrode layer 21, and disposing the second insulating layer 52 between the second dielectric layer 32 and the second control electrode layer 22, the electric field generated when the control voltage is applied can be uniformly applied to the second dielectric layer 32. This is because the arrangement of the first insulating layer 51 and the second insulating layer 52 can suppress the influence of the electric field generated by the application of the AC voltage between the first control electrode layer 21 and the second control electrode layer 22.

[0053] The inventors studied the optimal values ​​of the inter-electrode distance Lc between the first extraction electrode layer 11 and the second control electrode layer 22 of the variable capacitance capacitor 301 and the length of the second control electrode layer 22 , that is, the electrode length Le. Figure 8 The variable capacitance region Rcv shown is a region where the relative dielectric constant εr changes and the capacitance value becomes variable by applying a control voltage between the first control electrode layer 21 and the second control electrode layer 22. The fixed capacitance region Rcf is a region where it is difficult to apply an electric field even when a control voltage is applied, so that the relative dielectric constant εr does not change, that is, a region where the capacitance value is fixed. The capacitor formed in the variable capacitance region Rcv is called a variable capacitance capacitor Cv, and the capacitor formed in the fixed capacitance region Rcf is called a fixed capacitance capacitor Cf. Between the first extraction electrode layer 11 and the second extraction electrode layer 12, a capacitor is formed by connecting the fixed capacitance capacitor Cf, the variable capacitance capacitor Cv, and the fixed capacitance capacitor Cf in series. The capacitance value of the capacitor formed between the first extraction electrode layer 11 and the second extraction electrode layer 12, that is, the composite capacitance Cs, is expressed by the following formula (6). Cs=1 / (1 / Cf+1 / Cv+1 / Cf) · · · (6) In equation (6), "Cf" represents the capacitance value of the fixed-capacitance capacitor Cf, and "Cv" represents the capacitance value of the variable-capacitance capacitor Cv.

[0054] Figure 8 The horizontal axis of the graph is the variable rate of the variable capacitance capacitor Cv, and the vertical axis is the variable rate of the combined capacitance Cs. The variable rate is the change in capacitance relative to the change in the electric field, that is, (ΔC / ΔE). Figure 8 This is a graph plotting the variable rate calculated by setting the distance between the first extraction electrode layer 11 and the second extraction electrode layer 12, i.e. (Lc+Le+Lc), to a fixed value and changing the ratio of the inter-electrode distance Lc to the electrode length Le. Figure 8 As shown in FIG. 1 , the smaller the ratio of the inter-electrode distance Lc to the electrode length Le, the greater the variable rate of the combined capacitance Cs can be.

[0055] D. Fourth embodiment: Figure 9The variable capacitor 1 of the fourth embodiment shown is used in a power supply device 70 included in a contactless power supply system 400. The same components as those in the above-described embodiments are denoted by the same reference numerals, and detailed descriptions thereof are omitted as appropriate.

[0056] like Figure 9 As shown, contactless power supply system 400 includes a power supply device 70 and a power receiving device 80. In this embodiment, power supply device 70 is buried beneath the road. Power receiving device 80 is installed on a vehicle traveling on the road. While the vehicle is traveling, power receiving device 80 receives power from power supply device 70. Traveling includes both the vehicle VE moving and the vehicle stopping, for example, at a traffic light.

[0057] Furthermore, the mobile object on which the power receiving device 80 is mounted is not limited to a vehicle traveling on a road, and may be, for example, an AGV (Automated Guided Vehicle) or a traveling robot.

[0058] The power supply device 70 includes an AC power supply 71, multiple primary-side resonant circuits 72, and multiple control voltage application circuits 76. The AC power supply 71 supplies power to the multiple primary-side resonant circuits 72. The primary-side resonant circuits 72 are series resonant circuits comprising a primary coil L1 and a variable capacitor 1. The multiple primary coils L1 are arranged along the road's extension direction. The control voltage application circuit 76 changes the capacitance of the variable capacitor 1 by varying the value of the control voltage applied to the variable capacitor 1.

[0059] Power receiving device 80 includes a secondary resonant circuit 81 and a power receiving circuit 83. Secondary resonant circuit 81 is a series resonant circuit including a secondary coil L2 and a capacitor 82. Power receiving circuit 83 utilizes received power. Power receiving circuit 83 includes a rectifier circuit and a battery (not shown).

[0060] AC power source 71 applies AC power at a predetermined operating frequency to primary resonant circuit 72. In this embodiment, the operating frequency is 85 kHz. Variable capacitor 1 has the function of causing primary resonant circuit 72 to resonate at the operating frequency and to enter a non-resonant state at the operating frequency. In this embodiment, variable capacitor 1 is configured to be switchable between a first capacitance value and a second capacitance value, which is smaller than the first capacitance value. The capacitance value of variable capacitor 1 is switched between the first and second capacitance values ​​based on a control voltage output from control voltage application circuit 76. When primary coil L1 and secondary coil L2 are magnetically coupled and variable capacitor 1 is at the first capacitance value, primary resonant circuit 72 is resonant at the operating frequency. In other words, the first capacitance value of variable capacitor 1 is set to a value that matches the resonant frequency of primary resonant circuit 72 with the operating frequency. In contrast, when variable capacitor 1 is at the second capacitance value, the resonant frequency of primary resonant circuit 72 deviates from the operating frequency, causing primary resonant circuit 72 to enter a non-resonant state at the operating frequency. Since the second capacitance value is smaller than the first capacitance value, when the variable capacitor 1 is set to the second capacitance value, the impedance of the primary-side resonant circuit 72 increases, and the current flowing through the primary-side coil L1 decreases.

[0061] The state in which the variable capacitor 1 is set to a first capacitance value and a power transmission current flows through the primary coil L1 to supply power is called the power supply state. The state in which the variable capacitor 1 is set to a second capacitance value and a standby current smaller than the power transmission current flows through the primary coil L1 to not supply power is called the standby state.

[0062] When the primary coil L1 and the secondary coil L2 are magnetically coupled, the resonant frequency of the primary resonant circuit 72 is set to be substantially the same as the resonant frequency of the secondary resonant circuit 81. This allows contactless power supply to the power receiving device 80 through magnetic field resonance between the primary coil L1 and the secondary coil L2.

[0063] The primary coils L1 are arranged along the direction of the road, and the secondary coils L2 receive contactless power from the nearest primary coil L1. In the standby state, the standby current flows through the primary coils L1, generating magnetic flux in the primary coils L1. The power receiving device 80 has a magnetic sensor (not shown). When the power receiving device 80 approaches the primary resonant circuit 72 of the object, the magnetic sensor detects the magnetic flux generated by the primary coil L1. When the power receiving device 80 detects the magnetic flux, it causes an alternating current to flow through the secondary coils L2 to generate magnetic flux. The power supply device 70 has a magnetic sensor (not shown). Then, when the magnetic sensor detects the magnetic flux generated by the secondary coils L2, the control voltage application circuit 76 changes the voltage value of the control voltage and switches the variable capacitor 1 to the first capacitance value. As a result, the primary resonant circuit 72 enters a resonant state, and power supply begins.

[0064] The method by which the power supply device 70 detects the presence of the secondary coil L2 is not limited to the above. Alternatively, the power supply device 70 may detect the current flowing through the primary coil L1 and detect an increase in the current, or detect the voltage across the primary coil L1 and detect an increase in the voltage.

[0065] like Figure 10 As shown, in the power supply state, the control voltage application circuit 76 sets the control voltage to 0V. As a result, the control electric field Ed applied to the second dielectric layer 32 becomes 0V / m. Moreover, the capacitance value of the variable capacitance capacitor 1 is set to the first capacitance value. In addition, the relative dielectric constant εr is represented by the change in polarization relative to the change in electric field, that is, the slope of the hysteresis curve. In the standby state, the control voltage application circuit 76 sets the control voltage to a voltage value in the saturation region. As a result, since the relative dielectric constant εr becomes smaller than that in the power supply state, the capacitance value of the variable capacitance capacitor 1 becomes a second capacitance value smaller than the capacitance value in the power supply state. In the case of the standby state, since the area in the hysteresis curve becomes smaller, it can be set to low loss.

[0066] According to the fourth embodiment described above, the variable capacitor 1 is used in the power supply device 70. When the power supply device 70 is in the standby state, the control voltage application circuit 76 applies a voltage in the saturation region, thereby reducing the capacitance value of the variable capacitor 1 compared to the capacitance value in the power supply state. This reduces the loss in the variable capacitor 1 in the standby state.

[0067] E. Other implementation methods: (E1)In the above first embodiment, the second dielectric layer 32 includes a ferroelectric polymer. As other embodiments, the second dielectric layer 32 may also include an inorganic ferroelectric such as barium titanate (BaTiO3). Similar to the ferroelectric polymer, the relative dielectric constant εr of the inorganic ferroelectric changes according to the magnitude of the control voltage. Therefore, the variable capacitance capacitor 1 can be provided. It is more preferable if the inorganic ferroelectric has anisotropic dielectric properties. This is because even when the direction of the applied control voltage and the direction of the applied AC voltage are different, the relative dielectric constant changes according to the magnitude of the control voltage, so that the variable capacitance capacitor 1 with a good variable rate can be provided. In addition, since the three axes of the crystal structure of barium titanate can be polarized respectively, the dielectric properties of barium titanate are anisotropic.

[0068] (E2)In the above first embodiment, the second dielectric layer 32 includes a ferroelectric polymer. As other embodiments, the second dielectric layer 32 may also include a relaxor ferroelectric (Japanese: 強誘電体リラクサー). As shown in Figure 11 , a relaxor ferroelectric is a polymer in which regions where the polarizations of molecules are locally consistent are formed. Since a relaxor ferroelectric can locally change the direction of polarization, it has the property of polarization movement under a small electric field. By using a relaxor ferroelectric as the second dielectric layer 32, the variable rate of the capacitance of the variable capacitance capacitor 1 can be increased. In addition, since the area of the hysteresis curve is smaller than that of the ferroelectric, the variable capacitance capacitor 1 with low loss can be provided. Specific examples of relaxor ferroelectrics are copolymers based on P(VDF-TrFE) and copolymerized with a third monomer such as CTFE or CFE, such as P(VDF-TrFE-CTFE) or P(VDF-TrFE-CTE). In addition, a relaxor ferroelectric can be produced by creating defects, for example, by irradiating an electron beam on a ferroelectric polymer such as P(VDF-TrFE).

[0069] (E3)In the above fourth embodiment, the control voltage application circuit 76 applies a control voltage in the saturation region in the standby state of the power supply device 70 and does not apply a control voltage in the power transmission state of the power supply device 70. As another method, the control voltage application circuit 76 may also apply a control voltage in the polarization reversal region or the auxiliary region in the standby state of the power supply device 70 and does not apply a control voltage in the power transmission state of the power supply device 70.

[0070] (E4) In the first embodiment described above, the first control electrode layer 21 and the second control electrode layer 22 are alternately arranged in the X direction. As another embodiment, a configuration may be configured such that one first control electrode layer 21 and one second control electrode layer 22 are provided. Furthermore, in the first embodiment, the first extraction electrode layer 11 and the second extraction electrode layer 12 are opposed in the Z direction, and the first control electrode layer 21 and the second control electrode layer 22 are opposed in the X direction. The opposing directions are not limited to these. For example, a configuration may be configured such that the first extraction electrode layer 11 and the second extraction electrode layer 12 are opposed in the X direction, and the first control electrode layer 21 and the second control electrode layer 22 are opposed in the Z direction.

[0071] The present disclosure is not limited to the above-mentioned embodiments and variations, and can be implemented through various structures within the scope of the above-mentioned subject matter. For example, the technical features in the embodiments and variations corresponding to the technical features in the various methods described in the Summary of the Invention section can be appropriately replaced or combined to solve part or all of the above-mentioned technical problems or achieve part or all of the above-mentioned effects. In addition, as long as the above-mentioned technical features are not described as necessary structures in this specification, they can be appropriately deleted.

[0072] Other ways: The features of the present disclosure are as follows. (Method 1) A variable-capacity capacitor, the variable-capacity capacitor (1, 201, 301) comprising: a first control electrode (21); a second control electrode (22) opposite to the first control electrode; a dielectric layer (32) disposed at least between the first control electrode and the second control electrode; and A first extraction electrode (11) and a second extraction electrode (12) facing each other with the dielectric layer interposed therebetween, The first extraction electrode and the second extraction electrode are arranged at positions where an electric field is generated in a direction intersecting with an electric field vector generated between the first control electrode and the second control electrode when a control voltage is applied between the first control electrode and the second control electrode. (Method 2) In the variable capacitance capacitor described in embodiment 1, The dielectric layer has a dielectric property in which a relative dielectric constant when the control voltage for assisting the movement of polarization is applied is greater than a relative dielectric constant when the control voltage is not applied. (Method 3) In the variable capacitance capacitor according to embodiment 1 or 2, The dielectric layer has a dielectric property in which a relative dielectric constant when the control voltage in a saturation region for restricting movement of polarization is applied is smaller than a relative dielectric constant when the control voltage is not applied. (Method 4) In the variable capacitance capacitor according to any one of aspects 1 to 3, The dielectric layer has a dielectric property in which a relative dielectric constant when the control voltage including a polarization reversal region having a voltage value of a resistive electric field is applied is greater than a relative dielectric constant when the control voltage is not applied. (Method 5) In the variable capacitance capacitor according to any one of aspects 1 to 4, The first control electrode and the second control electrode face each other in a first direction, and the first extraction electrode and the second extraction electrode face each other in a second direction orthogonal to the first direction. (Method 6) In the variable capacitance capacitor according to any one of aspects 1 to 5, the variable capacitance capacitor includes: a first arrangement body (ST1) in which the first control electrodes and the second control electrodes are alternately arranged with the dielectric layer interposed therebetween; and The first control electrodes and the second control electrodes are alternately arranged across the first arrangement body (ST2). (Method 7) In the variable capacitance capacitor described in embodiment 6, The number of the first arrangement bodies is greater than or equal to 20,000, and the number of the second arrangement bodies is greater than or equal to 100. (Method 8) In the variable capacitance capacitor according to any one of aspects 1 to 7, The dielectric properties of the dielectric layer are anisotropic. (Method 9) In the variable capacitance capacitor according to any one of aspects 1 to 8, The dielectric layer includes any one of a ferroelectric polymer and an inorganic ferroelectric. (Method 10) In the variable capacitance capacitor according to any one of aspects 1 to 9, The dielectric layer includes a relaxor-type ferroelectric. (Method 11) A power supply device, The power supply device (70) comprises a variable capacitance capacitor according to any one of the embodiments 1 to 10. The dielectric layer comprises a ferroelectric. The power supply device comprises: a resonant circuit (72) composed of the variable capacitance capacitor and a primary side coil (L1); and a control voltage applying circuit (76) for applying the control voltage between the first control electrode and the second control electrode. The control voltage application circuit applies a voltage in a saturation region for limiting movement of polarization in a standby state of the power supply device. Although the present disclosure is described based on embodiments, it should be understood that the present disclosure is not limited to the above-described embodiments and structures. The present disclosure also includes various modifications and variations within the scope of equivalents. In addition, various combinations and methods, and further combinations and methods that include only one element, or more or less than the above elements, also fall within the scope and concept of the present disclosure.

Claims

1. A variable-capacity capacitor, comprising: a first control electrode (21); a second control electrode (22) opposite to the first control electrode; a dielectric layer (32) disposed at least between the first control electrode and the second control electrode; as well as A first extraction electrode (11) and a second extraction electrode (12) facing each other with the dielectric layer interposed therebetween, The first extraction electrode and the second extraction electrode are arranged at positions where an electric field is generated in a direction intersecting with an electric field vector generated between the first control electrode and the second control electrode when a control voltage is applied between the first control electrode and the second control electrode.

2. The variable capacitance capacitor according to claim 1, wherein The dielectric layer has a dielectric property in which a relative dielectric constant when the control voltage for assisting the movement of polarization is applied is greater than a relative dielectric constant when the control voltage is not applied.

3. The variable capacitance capacitor according to claim 1, wherein The dielectric layer has a dielectric characteristic in which a relative dielectric constant when the control voltage of a saturation region for limiting movement of polarization is applied is smaller than a relative dielectric constant when the control voltage is not applied.

4. The variable capacitance capacitor according to claim 1, wherein The dielectric layer has a dielectric characteristic in which a relative dielectric constant when the control voltage including a polarization reversal region having a voltage value of a resistive electric field is applied is greater than a relative dielectric constant when the control voltage is not applied.

5. The variable capacitance capacitor according to claim 1, wherein The first control electrode and the second control electrode are opposed to each other in a first direction, and the first extraction electrode and the second extraction electrode are opposed to each other in a second direction orthogonal to the first direction.

6. The variable capacitance capacitor according to claim 1, wherein: The variable capacitance capacitor comprises: a first arrangement body (ST1) in which the first control electrodes and the second control electrodes are alternately arranged with the dielectric layer interposed therebetween; and A second arrangement body (ST2) in which the first control electrodes and the second control electrodes are alternately arranged with the first arrangement body interposed therebetween.

7. The variable capacitance capacitor according to claim 6, wherein: The number of the first arrangement bodies is greater than or equal to 20,000, and the number of the second arrangement bodies is greater than or equal to 100.

8. The variable capacitance capacitor according to claim 1, wherein The dielectric property of the dielectric layer is anisotropic.

9. The variable capacitance capacitor according to claim 1, wherein: The dielectric layer includes any one of a ferroelectric polymer and an inorganic ferroelectric.

10. The variable capacitance capacitor according to claim 1, wherein The dielectric layer includes a relaxor-type ferroelectric.

11. A power supply device, comprising the variable capacitance capacitor according to claim 1. The dielectric layer comprises a ferroelectric, The power supply device comprises: a resonance circuit (72) including the variable capacitance capacitor and a primary side coil (L1); and a control voltage applying circuit (76) for applying the control voltage between the first control electrode and the second control electrode. The control voltage application circuit applies a voltage in a saturation region for limiting movement of polarization in a standby state of the power supply device.

Images