Variable capacitance capacitor and power supply device

Abstract

To provide a variable capacitance capacitor capable of reducing a control voltage.SOLUTION: A variable capacitance capacitor C1 is used in a control circuit 73 for controlling an operation of a device 70. The variable capacitance capacitor includes: first control electrode layers 21; second control electrode layers 22 that face the first control electrode layers; a dielectric layer 32 that is disposed at least between the first control electrode layers and the second control electrode layers; and a first extraction electrode layer 11 and a second extraction electrode layer 12 that face each other with the dielectric layer therebetween. The first extraction electrode layer and the second extraction electrode layer are positioned so as to generate an electric field in a direction that intersects an electric field vector generated between the first control electrode layers and the second control electrode layers when a voltage is applied between the first control electrode layers and the second control electrode layers; and the voltage applied between the first control electrode layers and the second control electrode layers is adjusted to adjust a capacitance value of a capacitance stored between the first extraction electrode layer and the second control electrode layers.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a variable capacitor and a power supply device. [Background technology]

[0002] Conventionally, there is a capacitor with variable capacitance in which a dielectric layer is disposed between a pair of electrodes for applying a DC bias (for example, Patent Document 1). In the conventional capacitor, a dielectric layer is disposed between an earth electrode and a DC bias electrode, and a capacitance acquisition electrode is disposed between the earth electrode and the DC bias electrode via the dielectric layer. When a DC bias is applied between the earth electrode and the DC bias electrode, the dielectric properties of the dielectric layer change, and the capacitance of the capacitor changes. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2006-344845 A Summary of the Invention [Problem to be solved by the invention]

[0004] In a conventional capacitor, the earth electrode, the DC bias electrode, and the capacitance acquisition electrode are stacked in the same direction with a dielectric layer interposed between them, which makes it necessary to set the distance between the earth electrode and the DC bias electrode and the distance between the earth electrode and the capacitance acquisition electrode in conjunction with each other. [Means for solving the problem]

[0005] The present disclosure can be realized in the following forms.

[0006] According to a first embodiment of the present disclosure, there is provided a variable capacitor (C1) used in a control circuit (73) that controls the operation of a device (70). This variable capacitor includes a first control electrode layer (21), a second control electrode layer (22) facing the first control electrode layer, at least a dielectric layer (32) disposed between the first control electrode layer and the second control electrode layer, a first extraction electrode layer (11) facing the dielectric layer, and a second extraction electrode layer (12), the first extraction electrode layer and the second extraction electrode layer being disposed at positions that generate an electric field along a direction intersecting an electric field vector generated between the first control electrode layer and the second control electrode layer when a voltage is applied between the first control electrode layer and the second control electrode layer, and the voltage applied between the first control electrode layer and the second control electrode layer is adjusted to adjust the capacitance value of the electrostatic capacitance stored between the first extraction electrode layer and the second control electrode layer.

[0007] According to this embodiment, the direction of the electric field applied to the dielectric layer by applying a DC voltage between the first control electrode layer and the second control electrode layer can be made different from the direction of the electric field applied to the dielectric layer by applying an AC voltage between the first extraction electrode and the second extraction electrode. The distance between the first control electrode layer and the second control electrode layer and the distance between the first extraction electrode and the second extraction electrode can be set independently. Therefore, by shortening the distance between the first control electrode layer and the second control electrode layer, the electric field applied to the dielectric layer can be increased even with the same DC voltage, so that the DC voltage can be reduced. In addition, since the capacitance value of the variable capacitance capacitor C1 changes depending on the magnitude of the control voltage, the circuit size can be reduced compared to when a circuit consisting of multiple capacitors and switches is used to change the capacitance value of the capacitor.

[0008] According to a second embodiment of the present disclosure, there is provided a power supply device (70) that wirelessly supplies power to a power receiving device (80). The power supply device includes a resonant circuit (72) that includes a variable capacitor (C1) and a coil (L1), and a control voltage application circuit (76) that applies a control voltage to the variable capacitor. The variable capacitor includes a first control electrode layer (21), a second control electrode layer (22) that faces the first control electrode layer, at least a dielectric layer (32) that is disposed between the first control electrode layer and the second control electrode layer, and a first extraction electrode layer (11) and a second extraction electrode layer (12) that face each other across the dielectric layer. The first extraction electrode layer and the second extraction electrode layer are disposed at positions that generate an electric field along a direction that intersects with an electric field vector generated between the first control electrode layer and the second control electrode layer when the control voltage is applied between the first control electrode layer and the second control electrode layer. The control voltage application circuit is capable of executing a power supply operation in which the resonant circuit is set to a resonant state when AC power of a predetermined operating frequency is applied to the resonant circuit by setting the control voltage to a first control voltage and setting the variable capacitor to a first capacitance value, and a standby operation in which the resonant circuit is set to a non-resonant state when AC power of the operating frequency is applied to the resonant circuit by setting the control voltage to a second control voltage different from the first control voltage and setting the variable capacitor to a second capacitance value different from the first capacitance value.

[0009] According to this embodiment, the direction of the electric field applied to the dielectric layer by applying a DC voltage between the first control electrode layer and the second control electrode layer can be made different from the direction of the electric field applied to the dielectric layer by applying an AC voltage between the first extraction electrode and the second extraction electrode. The distance between the first control electrode layer and the second control electrode layer and the distance between the first extraction electrode and the second extraction electrode can be set independently. Therefore, by shortening the distance between the first control electrode layer and the second control electrode layer, the electric field applied to the dielectric layer can be increased even with the same DC voltage, so that the DC voltage can be reduced. In addition, since the capacitance value of the variable capacitance capacitor C1 changes depending on the magnitude of the control voltage, the circuit scale of the resonant circuit and the control voltage application circuit can be reduced compared to using a circuit composed of multiple capacitors and switches to change the capacitance value of the capacitor. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram showing a configuration of a contactless power supply system. [Diagram 2] Circuit diagram of a wireless power supply system. [Diagram 3] FIG. [Figure 4] 4 is a cross-sectional view of the variable capacitor shown in FIG. 3 taken along line IV-IV. [Diagram 5] FIG. 13 is a graph showing the relationship between a control electric field and a relative dielectric constant. [Figure 6] FIG. [Figure 7] FIG. 11 is a circuit diagram of a power supply device according to a second embodiment. [Figure 8] FIG. 11 is a circuit diagram of a power supply device according to a third embodiment. [Figure 9] FIG. 11 is a circuit diagram of a power supply device according to a fourth embodiment. [Figure 10] FIG. 4 is a diagram showing the relationship between the start timing of application of a control voltage and a coil voltage. [Figure 11] FIG. 13 is a graph showing the dielectric properties of a dielectric layer according to the fifth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] A. First embodiment: A1. Configuration of the wireless power supply system: As shown in FIG. 1, the contactless power supply system 1 includes a power supply device 70 and a power receiving device 80. In this embodiment, the power supply device 70 is buried under a road RS. The power receiving device 80 is mounted on a vehicle VE as a moving body that travels on the road RS. When the vehicle VE is traveling, the power receiving device 80 is supplied with power from the power supply device 70. Here, traveling includes a case where the vehicle VE is moving and a case where the vehicle is stopped, such as waiting at a traffic light. The vehicle VE is configured as, for example, an electric vehicle or a hybrid vehicle.

[0012] The power supply device 70 has a primary side resonant circuit 72, which is a series resonant circuit having a primary side coil L1 and a variable capacitance capacitor C1, and an AC power source 71 that supplies power to the primary side resonant circuit 72. The AC power source 71 supplies power to the multiple primary side resonant circuits 72. The multiple primary side coils L1 are arranged along the extension direction of the road RS. The power receiving device 80 has a secondary side coil L2.

[0013] The moving body on which the power receiving device 80 is mounted is not limited to a vehicle VE traveling on the road RS, and may be, for example, an AGV (automated guided vehicle), a traveling robot, etc. The power supply device 70 may be installed not under the road RS, but on a sidewalk or parking lot adjacent to the road RS, or on a route along which the AGV travels.

[0014] A2.Circuit configuration of the non-contact power supply system: 2, in addition to the above configuration, the power supply device 70 includes a control circuit 73 and a primary side detection circuit 78. The control circuit 73 has a control voltage application circuit 76 and a primary side control circuit 77. A primary side coil L1 and a variable capacitance capacitor C1 are connected in series to configure a primary side resonant circuit 72 as a resonant circuit.

[0015] The control circuit 73 adjusts the electric field applied between the first control electrode layer 21 and the second control electrode layer 22 to adjust the capacitance value of the electrostatic capacitance stored between the first extraction electrode layer 11 and the second control electrode layer 22, thereby controlling the operation of the power supply device 70. The control voltage application circuit 76 applies a control voltage between the first control electrode layer 21 and the second control electrode layer 22. The control voltage is a voltage for changing the dielectric constant of the second dielectric layer 32. The variable capacitance capacitor C1 adjusts the resonant frequency of the primary side resonant circuit 72 by adjusting the capacitance value using the control voltage.

[0016] The AC power supply 71 includes a DC power supply 74 and an inverter 75. The inverter 75 converts the DC power supplied from the DC power supply 74 into AC power of a predetermined operating frequency and applies the AC power to the primary side resonant circuit 72. In this embodiment, the operating frequency is 85 kHz. The variable capacitance capacitor C1 has a function of making the primary side resonant circuit 72 resonate at the operating frequency and making the primary side resonant circuit 72 non-resonate at the operating frequency. In this embodiment, the variable capacitance capacitor C1 is configured to be switchable between a first capacitance value and a second capacitance value smaller than the first capacitance value. The capacitance value of the variable capacitance capacitor C1 is switched between the first capacitance value and the second capacitance value by a switching signal Sig1 output from the control voltage application circuit 76. When the primary side coil L1 and the secondary side coil L2 are magnetically coupled and the variable capacitance capacitor C1 has the first capacitance value, the primary side resonant circuit 72 resonates at the operating frequency. That is, the first capacitance value of the variable capacitor C1 is set to a value that makes the resonant frequency of the primary side resonant circuit 72 coincide with the operating frequency. On the other hand, when the variable capacitor C1 has the second capacitance value, the resonant frequency of the primary side resonant circuit 72 deviates from the operating frequency, and the primary side resonant circuit 72 is in a non-resonant state at the operating frequency.

[0017] As will be described later in detail, the control voltage application circuit 76 applies a switching signal Sig1, which is generated using AC power output from the AC power supply 71, to the variable capacitor C1.

[0018] The primary side detection circuit 78 is a magnetic sensor that detects the magnitude of the magnetic flux near the primary side coil L1, more specifically, a magnetic sensor that incorporates a coil provided near the primary side coil L1. The primary side detection circuit 78 detects the magnetic flux density and outputs a signal indicating the detected magnetic flux density to the primary side control circuit 77. The primary side control circuit 77 uses the signal output from the primary side detection circuit 78 to instruct the control voltage application circuit 76 to switch the voltage value of the switching signal Sig1 to the variable capacitance capacitor C1. Specifically, when the magnetic flux density indicated by the signal is greater than a predetermined threshold value, the primary side control circuit 77 instructs the control voltage application circuit 76 to switch the voltage value of the switching signal Sig1 to the variable capacitance capacitor C1.

[0019] In addition to the above configuration, the power receiving device 80 has a secondary resonant circuit 81, a rectifier 82, and a battery 83. A secondary coil L2 and a secondary capacitor C2 are connected in series to form the secondary resonant circuit 81. The rectifier 82 converts AC power output from the secondary resonant circuit 81 into DC power and supplies it to the battery 83. The battery 83 is charged by the supplied DC power.

[0020] When the primary coil L1 and the secondary coil L2 are magnetically coupled, the resonant frequency of the primary resonant circuit 72 and the resonant frequency of the secondary resonant circuit 81 are set to be substantially the same. This allows contactless power supply to the power receiving device 80 by magnetic field resonance between the primary coil L1 and the secondary coil L2.

[0021] A3. Standby and power transmission states: The state in which the variable capacitor C1 is set to a first capacitance value, a transmission current flows through the primary coil L1, and power is being supplied is called a power supply state. The state in which the variable capacitor C1 is set to a second capacitance value, a standby current smaller than the transmission current flows through the primary coil L1, and power is not being supplied is called a standby state.

[0022] The primary coils L1 are arranged in the direction in which the road RS extends, and the secondary coils L2 receive power from the nearest primary coil L1 in a non-contact manner. In a standby state, a standby current flows through the primary coil L1, causing the primary coil L1 to generate magnetic flux. The power receiving device 80 includes a magnetic sensor (not shown). When the power receiving device 80 approaches the target primary resonant circuit 72, the magnetic sensor detects the magnetic flux generated by the primary coil L1. When the power receiving device 80 detects the magnetic flux, it passes an AC current through the secondary coil L2 to generate magnetic flux. When the magnetic flux generated by the secondary coil L2 is detected by the primary detection circuit 78, the primary control circuit 77 commands the control voltage application circuit 76 to switch the voltage value of the switching signal Sig1. The variable capacitance capacitor C1 switches the capacitance value from the second capacitance value to the first capacitance value using the voltage value of the switching signal Sig1. This causes the primary side resonant circuit 72 to enter a resonant state, and power supply begins.

[0023] The method by which the power supply device 70 detects the presence of the secondary coil L2 is not limited to the above. As another embodiment, the power supply device 70 may detect a current flowing through the primary coil L1 and detect an increase in the current, or may detect a voltage of the primary coil L1 and detect an increase in the voltage.

[0024] A4. Structure of a variable capacitor: 3, the variable capacitor C1 has a first extraction electrode layer 11, a second extraction electrode layer 12, a first control electrode layer 21, a second control electrode layer 22, a first dielectric layer 31, a second dielectric layer 32, a first extraction electrode common layer 41, and a second extraction electrode common layer 42. The first extraction electrode layer 11 and the second extraction electrode layer 12 are also collectively referred to as an extraction electrode layer 10. The first control electrode layer 21 and the second control electrode layer 22 are also collectively referred to as a control electrode layer 20.

[0025] In FIG. 3, three mutually orthogonal spatial axes, the XYZ axes, are depicted. The directions in which the X-axis, Y-axis, and Z-axis arrows point indicate 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 in which the X-axis, Y-axis, and Z-axis arrows point 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. The directions along the X-axis, Y-axis, and Z-axis, regardless of whether they are positive or negative, are called the X direction, Y direction, and Z direction, respectively. The same applies to the following figures and explanations.

[0026] As shown in Fig. 4, the first control electrode layer 21 and the second control electrode layer 22 are electrode layers for adjusting the capacitance of the variable capacitor C1. The first extraction electrode layer 11 and the second extraction electrode layer 12 are electrode layers for utilizing the capacitance of the variable capacitor C1. Typically, the variable capacitor C1 is used by applying a control voltage, which is a DC voltage, to 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.

[0027] The variable capacitor C1 further has a first terminal ACp, a second terminal ACn, a third terminal DCp, and a fourth terminal DCn for electrically connecting to an external circuit. The first terminal ACp is electrically connected to the first extraction electrode layer 11. The second terminal ACn is electrically connected to the second extraction electrode layer 12. The third terminal DCp is electrically connected to the first control electrode layer 21. The fourth terminal DCn is electrically connected to the second control electrode layer 22.

[0028] The second control electrode layer 22 faces the first control electrode layer 21. The second dielectric layer 32 is disposed 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 face each other with the second dielectric layer 32 in between. The first extraction electrode layer 11 and the second extraction electrode layer 12 are disposed at positions that generate an electric field along a direction intersecting with an electric field vector generated between the first control electrode layer 21 and the second control electrode layer 22 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 control electrode layer 21 and the second control electrode layer 22 face each other in the X direction. Also, the first extraction electrode layer 11 and the second extraction electrode layer 12 face each other in the Z direction.

[0029] As shown in Fig. 4, the variable capacitor C1 has a laminated structure. Specifically, a first dielectric layer 31 is disposed on a 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 on the first dielectric layer 31. The second dielectric layer 32 covers the first control electrode layer 21 and the second control electrode layer 22. A second extraction electrode layer 12 is disposed on the second dielectric layer 32. The film surface direction of each layer is the XY direction. The lamination direction in which each layer is laminated is the Z direction.

[0030] 3, the first control electrode layer 21 and the second control electrode layer 22 each have a flat plate shape with a long axis in the Y direction. The first control electrode layer 21 and the second control electrode layer 22 are alternately arranged at 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.

[0031] A structure formed by alternately arranging the first control electrode layer 21 and the second control electrode layer 22 with the second dielectric layer 32 therebetween in the X direction is also referred to as a first structure ST1. By alternately arranging the first control electrode layer 21 and the second control electrode layer 22, the capacitors formed between the first control electrode layer 21 and the second control electrode layer 22 are connected in parallel with each other, so that the capacitance value of the variable capacitor C1 can be increased.

[0032] 4, 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 a control region RG1 sandwiched between the first control electrode layer 21 and the second control electrode layer 22 in the X direction. As a result, when a control voltage that is a DC voltage is applied between the first control electrode layer 21 and the second control electrode layer 22, an electric field vector that is approximately parallel to the X direction is generated in the control region RG1.

[0033] The first extraction electrode layer 11 and the second extraction electrode layer 12 face each other in the Z direction with the second dielectric layer 32 interposed therebetween. As a result, an 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 roughly intersects with a 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, an 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 roughly intersects with a 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.

[0034] The direction in which the first extraction electrode layer 11 and the second extraction electrode layer 12 face each other is different from the direction in which the first control electrode layer 21 and the second control electrode layer 22 face each other. 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 set independently. 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. Therefore, by shortening the distance between the first control electrode layer 21 and the second control electrode layer 22 while maintaining the distance between the first extraction electrode layer 11 and the second extraction electrode layer 12 that can withstand the voltage applied 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. Therefore, the control voltage can be reduced.

[0035] In this embodiment, the first dielectric layer 31 and the second dielectric layer 32 contain a ferroelectric material of the same material. In particular, the first dielectric layer 31 and the second dielectric layer 32 contain PVDF (polyvinylidene fluoride). Alternatively, the first dielectric layer 31 and the second dielectric layer 32 may contain a ferroelectric polymer such as a fluororesin such as P(VDF-TrFE) (poly(vinylidene fluoride-trifluoroethylene)). The first dielectric layer 31 containing a ferroelectric material can also function as a variable capacitance capacitor.

[0036] As another embodiment of the first dielectric layer 31 and the second dielectric layer 32, the first dielectric layer 31 and the second dielectric layer 32 may include dielectric materials different from each other.

[0037] In the PVDF molecule, hydrogen atoms and fluorine atoms are bonded to the carbon chain. Since the hydrogen atoms are positively charged and the fluorine atoms are negatively charged, the PVDF molecule has a dipole moment. When the PVDF molecules are aggregated by intermolecular forces, the carbon chains of the PVDF molecules are aligned in the same direction. The hydrogen atoms and the fluorine atoms are located perpendicular to the direction in which the carbon chains extend. Therefore, the PVDF crystal is spontaneously polarized. When an electric field is applied to the PVDF crystal, the direction of polarization changes so as to rotate around 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 when an AC voltage is applied between the first extraction electrode layer 11 and the second extraction electrode layer 12. Therefore, by using PVDF for the second dielectric layer 32, it is possible to provide a variable capacitance capacitor C1 whose relative dielectric constant changes when the voltage value of the control voltage is changed.

[0038] 5 is a diagram showing 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 capacitor C1 has dielectric characteristics in which the relative dielectric constant εr has two peaks.

[0039] Ferroelectrics are spontaneously polarized when the control electric field is zero V / m. When the control electric field is increased to the coercive electric field Ec, the polarization becomes zero and the relative dielectric constant εr becomes maximum. In the vicinity of the coercive electric field Ec, the dipole moment tends to move in a direction corresponding to the AC voltage applied between the first extraction electrode layer 11 and the second extraction electrode layer 12, so it is considered that the relative dielectric constant εr becomes large.

[0040] When the control electric field Ed becomes larger than the coercive electric field Ec, the relative dielectric constant εr becomes smaller. This is thought to be because the electric dipoles are restrained by the control electric field Ed and are less likely to move in response to the AC voltage.

[0041] In this embodiment, the direction of the control electric field Ed and the direction of the electric field caused by the application of an AC voltage intersect. In addition, the PVDF contained in the second dielectric layer 32 rotates with the carbon chain as the axis of rotation. Therefore, even in the region of the control electric field Ed smaller than the coercive electric field Ec, a peak of the relative dielectric constant εr appears. It is considered that this is because the application of the control electric field Ed makes it easier for the electric dipoles to move in response to the application of the AC voltage than when the control electric field Ed is not applied.

[0042] The dielectric characteristics of the variable capacitor C1 include an assist region, a polarization inversion region, and a saturation region. When a control voltage for the assist region is applied, the movement of the polarization of the second dielectric layer 32 is assisted. Specifically, the assist region is a region where the control electric field Ed is smaller than the coercive electric field Ec, and the relative dielectric constant εr is larger 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 two peaks of the relative dielectric constant εr.

[0043] When a control voltage for the polarization inversion region including the voltage of the coercive electric field Ec is applied, the polarization of the second dielectric layer 32 is more likely to be inverted in response to the AC voltage than in the assist region. Specifically, the polarization inversion region is an electric field range in which the control electric field Ed includes the coercive electric field Ec, and is a region in which the relative dielectric constant εr is larger than the peak value ε3 of the relative dielectric constant εr in the assist region.

[0044] When a control voltage in the saturation region is applied, the movement of the polarization of the second dielectric layer 32 is constrained. Specifically, the saturation region is a region in which the control electric field Ed is greater than the coercive electric field Ec, and the control electric field Ed is greater than the coercive electric field Ec.

[0045] As described above, by applying the control electric field Ed in the assist region, the polarization can be made to move more easily than when the control electric field Ed is not applied. Therefore, by applying the control electric field Ed in the assist region to the variable capacitor C1, the capacitance of the variable capacitor C1 can be made larger than the capacitance when the control electric field Ed is not applied.

[0046] Moreover, by applying the control electric field Ed in the polarization inversion region, the polarization can be made to move more easily than in the assist region. Therefore, by applying the control electric field Ed in the polarization inversion region to the variable capacitor C1, the capacitance of the variable capacitor C1 can be made larger than the capacitance when the control electric field Ed in the assist region is applied.

[0047] Moreover, by applying the control electric field Ed in the saturation region, the polarization can be made less likely to move. Therefore, by applying the control electric field Ed in the saturation region to the variable capacitor C1, the capacitance of the variable capacitor C1 can be made smaller than the capacitance when the control electric field Ed in the assist region is not applied. Therefore, according to the variable capacitor C1, the capacitance value of the variable capacitor C1 can be set to a target capacitance value by adjusting the magnitude of the control electric field Ed.

[0048] A5. Circuit configuration of the control voltage application circuit: As shown in FIG. 6, the control voltage application circuit 76 includes a rectifier 79, a smoothing capacitor C10, and a switch SW. The rectifier 79 rectifies the AC current output from the AC power supply 71, and outputs a DC voltage to the wiring N1 and the wiring N2. For example, a diode bridge circuit can be used as the rectifier 79. The voltage applied to the wiring N1 is higher than the voltage applied to the wiring N2. The switch SW is disposed on the wiring N1. The switch SW is, for example, a transistor. The smoothing capacitor C10 is connected between the wiring N1 and the wiring N2. The switching signal Sig1 is specifically a voltage between the wiring N1 and the wiring N2.

[0049] The wiring N1 is connected to a third terminal DCp of the variable capacitor C1. The wiring N2 is connected to a fourth terminal DCn of the variable capacitor C1. The wiring connected to one output terminal of the inverter 75 is connected to a first terminal ACp of the variable capacitor C1. The wiring connected to the other output terminal of the inverter 75 is connected to a second terminal ACn of the variable capacitor C1.

[0050] The primary side control circuit 77 outputs a signal to the control voltage application circuit 76 to set the switch SW to an open state or a conductive state. Specifically, when the power supply device 70 is set to a power supply state, the primary side control circuit 77 outputs a signal to set the switch SW to an open state. When the signal is input from the primary side control circuit 77, the control voltage application circuit 76 performs a supply operation to set the switch SW to an open state. In the supply operation, the control voltage application circuit 76 sets the control voltage to zero volts as a first control voltage. As a result, the control voltage Vd applied between the first control electrode layer 21 and the second control electrode layer 22 of the variable capacitance capacitor C1 becomes zero volts. The capacitance value of the variable capacitance capacitor C1 is set to a first capacitance value when the relative dielectric constant εr of the second dielectric layer 32 is the relative dielectric constant ε1. Therefore, the primary side resonant circuit 72 is in a resonant state.

[0051] On the other hand, when the power supply device 70 is set to a standby state, the primary side control circuit 77 outputs a signal to set the switch SW to a conductive state. When the control voltage application circuit 76 receives a signal from the primary side control circuit 77, the control voltage application circuit 76 performs a standby operation to set the switch SW to a conductive state. In the standby operation, the control voltage application circuit 76 sets the control voltage to a voltage value that becomes the control electric field Ed of the saturation region as the second control voltage. As a result, the control electric field Ed applied between the first control electrode layer 21 and the second control electrode layer 22 of the variable capacitance capacitor C1 becomes an electric field of the saturation region. The capacitance value of the variable capacitance capacitor C1 is set to a second capacitance value in the case of the relative dielectric constant εr of the saturation region of the second dielectric layer 32. As described above, the second capacitance value is smaller than the first capacitance value. As a result, the primary side resonant circuit 72 is in a non-resonant state.

[0052] According to the first embodiment described above, the first extraction electrode layer 11 and the second extraction electrode layer 12 are arranged at positions that generate an electric field along a direction intersecting with an electric field vector generated when a 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 set independently. This allows the control voltage to be reduced. In addition, the variable capacitance capacitor C1 is used in a control voltage application circuit 76 that adjusts the control electric field Ed applied between the first control electrode layer 21 and the second control electrode layer 22 in the non-contact power supply system 1 to adjust the capacitance value of the electrostatic capacitance stored between the first extraction electrode layer 11 and the second control electrode layer 22, thereby controlling the operation of the non-contact power supply system 1. This allows the circuit size to be reduced compared to a case where the circuit is configured with a plurality of capacitors and switches in order to change the capacitance value of the capacitance component of the primary side resonance circuit 72. In addition, the circuit size can be reduced compared to a capacitor whose capacitance value is changed mechanically.

[0053] Moreover, the variable capacitor C1 is used to adjust the resonant frequency of the primary side resonant circuit 72 to control the operation of the primary side resonant circuit 72. This allows the circuit size to be smaller than a circuit configuration having multiple capacitors to change the capacitance value of the capacitance component of the primary side resonant circuit 72.

[0054] The control voltage application circuit 76 executes a power supply operation in which the primary side resonant circuit 72 is set to a resonant state by setting the control voltage Vd to zero volts, and a standby operation in which the primary side resonant circuit 72 is set to a non-resonant state by setting the control voltage to a voltage in the saturation region. The variable capacitance capacitor C1 is set to a first capacitance value by setting the control voltage Vd to zero volts, and is set to a second capacitance value by setting the control voltage Vd to the voltage value of the control electric field Ed in the saturation region. In the power supply device 70 that performs contactless power supply using magnetic field resonance, whether or not the power supply device is caused to supply power can be controlled by setting the primary side resonant circuit 72 to a resonant state or a non-resonant state. The variable capacitance capacitor C1 according to this embodiment can be suitably applied to such a power supply device 70.

[0055] Moreover, the second capacitance value is smaller than the first capacitance value, which makes it possible to reduce the impedance of the primary-side resonant circuit 72 in the standby state of the contactless power supply system 1, thereby reducing the current flowing through the primary-side coil L1.

[0056] B. Second embodiment: 7, the power supply device 70 according to the second embodiment differs from the first embodiment in the configuration of a control voltage application circuit 276. The same components as those in the above embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted as appropriate.

[0057] The control voltage application circuit 276 according to this embodiment includes a rectifier 79, a smoothing capacitor C10, and a DC-DC converter 100. The DC-DC converter 100 steps down or steps up the DC voltage output from the rectifier 79, and outputs it to the wiring N1 and the wiring N2. The control voltage output by the control voltage application circuit 276 is the same as that in the first embodiment. When stepping down or stepping up the voltage, the control voltage application circuit 276 outputs a voltage that is linear with respect to time. This suppresses abrupt fluctuations in current, thereby suppressing surge voltage.

[0058] C. Third embodiment: 8, a power supply device 70 according to a third embodiment differs from the above-described embodiments in the configuration of a control voltage application circuit 376. The same components as those in the above-described embodiments are given the same reference numerals, and detailed descriptions thereof will be omitted as appropriate.

[0059] The control voltage application circuit 376 according to this embodiment includes a capacitor C30, a first diode D1, a second diode D2, a smoothing capacitor C10, and a DC-DC converter 100. The capacitor C30, the first diode D1, the second diode D2, and the smoothing capacitor C10 form a half-wave voltage doubler rectifier circuit. This makes it possible to output a large control voltage Vd. The control voltage output by the control voltage application circuit 376 is the same as that in the first embodiment.

[0060] D. Fourth embodiment: 9, a power supply device 70 according to a fourth embodiment differs from the above-described embodiments in the configuration of a control voltage application circuit 476. The same components as those in the above-described embodiments are denoted by the same reference numerals, and detailed description thereof will be omitted as appropriate.

[0061] The control voltage application circuit 476 according to this embodiment is connected to both terminals of the primary coil L1. The control voltage application circuit 476 converts the coil voltage, which is an AC voltage applied to the primary coil L1, into a DC voltage and supplies it to the wiring N1 and the wiring N2.

[0062] As shown in FIG. 10, when switching from a power supply operation to a standby operation, the control voltage application circuit 476 starts the standby operation from around time t1 when the voltage of the coil voltage is zero volts. Specifically, the control voltage application circuit 476 starts applying the control voltage Vd in the saturation region between the third terminal DCp and the fourth terminal DCn from around time t1. Here, around time t1 refers to a period around time t1 when the voltage of the AC power becomes 10% or less of the maximum voltage value of the AC power. In this embodiment, the control voltage application circuit 476 performs the standby operation from time t1. As a result, the control electric field Ed is applied to the second dielectric layer 32 of the variable capacitor C1 in a state where the second dielectric layer 32 is not easily affected by the electric field caused by the application of the AC power, so that the control electric field can be effectively applied to the second dielectric layer 32.

[0063] According to the fourth embodiment described above, the control voltage is applied to the variable capacitor C1 when the voltage of the AC power applied to the primary coil L1 is close to zero volts. As a result, the control electric field Ed is applied to the second dielectric layer 32 in a state where the second dielectric layer 32 is not easily affected by the electric field caused by the application of the AC power, so that the control electric field can be applied to the second dielectric layer 32 effectively.

[0064] E. Fifth embodiment: As shown in FIG. 11, in this embodiment, the second dielectric layer 32 has a dielectric characteristic in which the relative dielectric constant εr at a temperature higher than the phase transition temperature Tc as the operating temperature is smaller than the relative dielectric constant εr at the phase transition temperature Tc. Specifically, when the temperature of the second dielectric layer 32 becomes higher than the phase transition temperature Tc, the relative dielectric constant εr decreases. In this embodiment, the dielectric used for the second dielectric layer 32 is manufactured so that the phase transition temperature Tc is a value smaller than the operating temperature when the power supply device 70 is in an abnormal state. As a result, when the control circuit 73 becomes abnormally high temperature, the capacitance value of the variable capacitance capacitor C1 decreases. Therefore, it becomes difficult for a current to flow through the primary side resonant circuit 72, and the primary side resonant circuit 72 can be protected.

[0065] According to the fifth embodiment described above, the second dielectric layer 32 has a dielectric characteristic in which the relative dielectric constant εr decreases at a temperature higher than the phase transition temperature Tc. In an abnormal state of the power supply device 70, the capacitance value of the variable capacitor C1 decreases, so that the current flowing through the primary coil L1 can be reduced to protect the primary resonant circuit 72.

[0066] F. Other Embodiments: (F1) In the first embodiment, the second dielectric layer 32 includes a ferroelectric polymer. In another embodiment, the second dielectric layer 32 may include an inorganic ferroelectric such as barium titanate (BaTiO3). The relative dielectric constant εr of an inorganic ferroelectric also changes depending on the magnitude of the control voltage. For this reason, it can be used as the dielectric layer of the variable capacitor C1. It is even better if the inorganic ferroelectric is polarized in a plurality of directions. This is because, even when the direction in which the control voltage is applied is different from the direction in which the AC voltage is applied, the relative dielectric constant changes depending on the magnitude of the control voltage, and therefore it is possible to provide a variable capacitor C1 with a good variability.

[0067] (F2) In the first embodiment, the control voltage application circuit 76 applies a control voltage in the saturation region when the power supply device 70 is in a standby state, and does not apply a control voltage when the power supply device 70 is in a power transmission state. As another embodiment, the control voltage application circuit 76 may apply a control voltage in the polarization inversion region or the assist region when the power supply device 70 is in a standby state, and may not apply a control voltage when the power supply device 70 is in a power transmission state.

[0068] (F3) In the first embodiment, the primary resonant circuit 72 has a variable capacitor C1 connected in series to the primary coil L1, and the secondary resonant circuit 81 has a secondary capacitor C2 connected in series to the secondary coil L2, which is a so-called SS type circuit configuration. The circuit configuration of the primary resonant circuit 72 and the secondary resonant circuit 81 are not limited to the SS type. (a) For example, the primary resonant circuit 72 may have a so-called PS type circuit configuration in which the variable capacitor C1 is connected in parallel to the primary coil L1, and the secondary resonant circuit 81 may have a secondary capacitor C2 connected in series to the secondary coil L2. (b) Also, in addition to the variable capacitor C1 connected in series to the primary coil L1, the secondary resonant circuit 81 may have a so-called P-SS type circuit configuration in which two secondary capacitors C2 are connected in series to each of the terminals of the secondary coil L2. (c) The primary resonant circuit 72 may also include a closed circuit in which a coil and a capacitor are connected in series. The coil of this closed circuit is arranged in a position where it can be magnetically coupled to the secondary coil L2 when the primary coil L1 and secondary coil L2 are magnetically coupled. (d) The capacitor of the closed circuit may be connected in parallel to the coil instead of in series. (e) The primary resonant circuit 72 may also include a coil connected in series to the primary coil L1, and a capacitor connected in parallel to the coil. This coil is arranged in a position where it can be magnetically coupled to the secondary coil L2 when the primary coil L1 and secondary coil L2 are magnetically coupled.

[0069] (F4) In the above first embodiment, the variable capacitor C1 is applied to the power supply device 70. The device to which the variable capacitor C1 is applied is not limited to the power supply device 70. For example, the variable capacitor C1 can be used in a device that includes a circuit for converting a frequency.

[0070] The present disclosure is not limited to the above-mentioned embodiments and modifications, and can be realized in various configurations without departing from the spirit of the present disclosure. For example, the technical features in the embodiments and modifications corresponding to the technical features in each aspect described in the Summary of the Invention column can be appropriately replaced or combined in order to solve some or all of the above-mentioned problems or to achieve some or all of the above-mentioned effects. Furthermore, if a technical feature is not described as essential in this specification, it can be appropriately deleted.

[0071] Other forms: The features of the present disclosure are as follows: (Form 1) A variable capacitor (C1) used in a control circuit (73) that controls the operation of a device (70), A first control electrode layer (21); a second control electrode layer (22) facing the first control electrode layer; a dielectric layer (32) disposed at least between the first control electrode layer and the second control electrode layer; a first extracting electrode layer (11) and a second extracting electrode layer (12) facing each other with the dielectric layer interposed therebetween, the first extraction electrode layer and the second extraction electrode layer are disposed at positions that generate an electric field along a direction intersecting an electric field vector generated between the first control electrode layer and the second control electrode layer when a voltage is applied between the first control electrode layer and the second control electrode layer; A variable capacitance capacitor in which a voltage applied between the first control electrode layer and the second control electrode layer is adjusted to adjust a capacitance value of the electrostatic capacitance stored between the first extraction electrode layer and the second control electrode layer. (Form 2) The variable capacitor according to aspect 1, The device further includes a resonant circuit (72) formed of the variable capacitor and a primary coil (L1), the control circuit further includes a control voltage application circuit (76, 276, 376, 476) that applies a control voltage between the first control electrode layer and the second control electrode layer to change the dielectric constant of the dielectric layer; The variable capacitor adjusts a capacitance value using the control voltage, thereby adjusting a resonant frequency of the resonant circuit. (Form 3) The variable capacitor according to aspect 2, the device is a power supply device that wirelessly supplies power to a power receiving device, The control voltage application circuit includes: a power supply operation of setting the resonant circuit to a resonant state when AC power having a predetermined operating frequency is applied to the resonant circuit by setting the control voltage to a first control voltage; a standby operation of setting the resonant circuit to a non-resonant state when the AC power of the operating frequency is applied to the resonant circuit by setting the control voltage to a second control voltage different from the first control voltage; The variable capacitor is set to a first capacitance value when the first control voltage is applied, and is set to a second capacitance value different from the first capacitance value when the second control voltage is applied. (Form 4) A variable capacitor according to aspect 3, the resonant circuit is a series resonant circuit, The second capacitance value is smaller than the first capacitance value. (Form 5) The variable capacitor according to aspect 3 or 4, A variable capacitor, in which application of the second control voltage begins from approximately the time point when the voltage of the AC power applied to the primary coil is zero volts. (Form 6) 6. The variable capacitor according to any one of aspects 1 to 5, A variable capacitor, wherein the dielectric layer has a dielectric characteristic in which the relative dielectric constant at a temperature higher than a predetermined operating temperature is smaller than the relative dielectric constant at the operating temperature. (Form 7) A power supply device (70) that wirelessly supplies power to a power receiving device (80), a resonant circuit (72) consisting of a variable capacitor (C1) and a primary coil (L1); a control voltage application circuit (76) that applies a control voltage to the variable capacitor; The variable capacitor is A first control electrode layer (21); a second control electrode layer (22) facing the first control electrode layer; a dielectric layer (32) disposed at least between the first control electrode layer and the second control electrode layer; a first extracting electrode layer (11) and a second extracting electrode layer (12) facing each other with the dielectric layer interposed therebetween, the first extraction electrode layer and the second extraction electrode layer are disposed at positions that generate an electric field along a direction intersecting an electric field vector generated between the first control electrode layer and the second control electrode layer when the control voltage is applied between the first control electrode layer and the second control electrode layer, The control voltage application circuit includes: a power supply operation of setting the control voltage to a first control voltage and setting the variable capacitor to a first capacitance value, thereby setting the resonant circuit to a resonant state when AC power having a predetermined operating frequency is applied to the resonant circuit; a standby operation of setting the resonant circuit to a non-resonant state when the AC power of the operating frequency is applied to the resonant circuit by setting the control voltage to the second control voltage different from the first control voltage and setting the variable capacitor to a second capacitance value different from the first capacitance value. [Explanation of symbols]

[0072] 11...first extraction electrode layer, 12...second extraction electrode layer, 21...first control electrode layer, 22...second control electrode layer, 32...second dielectric layer, 70...power supply device, 73...control circuit, 76, 276, 376, 476...control voltage application circuit, C1...variable capacitor, L1...primary coil

Claims

1. A variable capacitor (C1) used in a control circuit (73) that controls the operation of a device (70), A first control electrode layer (21); a second control electrode layer (22) facing the first control electrode layer; a dielectric layer (32) disposed at least between the first control electrode layer and the second control electrode layer; a first extracting electrode layer (11) and a second extracting electrode layer (12) facing each other with the dielectric layer interposed therebetween; the first extraction electrode layer and the second extraction electrode layer are disposed at positions that generate an electric field along a direction intersecting an electric field vector generated between the first control electrode layer and the second control electrode layer when a voltage is applied between the first control electrode layer and the second control electrode layer, a voltage applied between the first control electrode layer and the second control electrode layer is adjusted to adjust a capacitance value of an electrostatic capacitance stored between the first extraction electrode layer and the second control electrode layer; The device is a power supply device that has a resonant circuit (72) formed of the variable capacitor and a primary coil (L1) and wirelessly supplies power to a power receiving device, the control circuit has a control voltage application circuit (76, 276, 376, 476) that applies a control voltage between the first control electrode layer and the second control electrode layer to change the dielectric constant of the dielectric layer, The control voltage application circuit includes: a power supply operation of setting the resonant circuit in a resonant state when AC power having a predetermined operating frequency is applied to the resonant circuit by setting the control voltage to a first control voltage; a standby operation of setting the resonant circuit to a non-resonant state when the AC power of the operating frequency is applied to the resonant circuit by setting the control voltage to a second control voltage different from the first control voltage; The variable capacitor is adjusting a capacitance value using the control voltage to adjust a resonant frequency of the resonant circuit; a first capacitance value is set when the first control voltage is applied, and a second capacitance value different from the first capacitance value is set when the second control voltage is applied; A variable capacitor, wherein application of the second control voltage begins approximately at a point in time when the voltage of the AC power applied to the primary coil is zero volts.

2. 2. The variable capacitor according to claim 1, the resonant circuit is a series resonant circuit, The second capacitance value is smaller than the first capacitance value.

3. A variable capacitor (C1) used in a control circuit (73) that controls the operation of an apparatus (70), A first control electrode layer (21); a second control electrode layer (22) facing the first control electrode layer; a dielectric layer (32) disposed at least between the first control electrode layer and the second control electrode layer; a first extracting electrode layer (11) and a second extracting electrode layer (12) facing each other with the dielectric layer interposed therebetween; the first extraction electrode layer and the second extraction electrode layer are disposed at positions that generate an electric field along a direction intersecting an electric field vector generated between the first control electrode layer and the second control electrode layer when a voltage is applied between the first control electrode layer and the second control electrode layer, a voltage applied between the first control electrode layer and the second control electrode layer is adjusted to adjust a capacitance value of an electrostatic capacitance stored between the first extraction electrode layer and the second control electrode layer; A variable capacitor, wherein the dielectric layer has a dielectric characteristic in which the relative dielectric constant at a temperature higher than a predetermined operating temperature is smaller than the relative dielectric constant at the operating temperature.

4. A power supply device (70) that wirelessly supplies power to a power receiving device (80), a resonant circuit (72) consisting of a variable capacitor (C1) and a primary coil (L1); a control voltage application circuit (76) that applies a control voltage to the variable capacitor; The variable capacitor is A first control electrode layer (21); a second control electrode layer (22) facing the first control electrode layer; a dielectric layer (32) disposed at least between the first control electrode layer and the second control electrode layer; a first extracting electrode layer (11) and a second extracting electrode layer (12) facing each other with the dielectric layer interposed therebetween; the first extraction electrode layer and the second extraction electrode layer are disposed at positions that generate an electric field along a direction intersecting an electric field vector generated between the first control electrode layer and the second control electrode layer when the control voltage is applied between the first control electrode layer and the second control electrode layer, The control voltage application circuit includes: a power supply operation of setting the control voltage to a first control voltage and setting the variable capacitor to a first capacitance value, thereby setting the resonant circuit to a resonant state when AC power having a predetermined operating frequency is applied to the resonant circuit; a standby operation of setting the resonant circuit to a non-resonant state when the AC power of the operating frequency is applied to the resonant circuit by setting the control voltage to a second control voltage different from the first control voltage and setting the variable capacitor to a second capacitance value different from the first capacitance value, The power supply device, wherein application of the second control voltage begins from approximately a point in time when the voltage of the AC power applied to the primary coil is zero volts.

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