Variable capacity capacitor and power supply device

Abstract

A variable capacity capacitor (C1), which is used in a control circuit (73) for controlling the operation of a device (70), is provided with: 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; and a first extraction electrode layer (11) and a second extraction electrode layer (12) that face each other with the dielectric layer interposed therebetween, the first extraction electrode layer and the second extraction electrode layer being disposed at a position where the first extraction electrode layer and the second extraction electrode layer face each other 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 along a position where an electric field is generated in a direction intersecting an electric field vector generated between the first control electrode layer and the second control electrode layer. The capacitance value of the electrostatic capacitance accumulated between the first extraction electrode layer and the second control electrode layer is adjusted.

Description

Citation of related applications

[0001] This application is based on Japanese Patent Application No. 2023-14372 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 conventional capacitors, 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 a first embodiment of the present disclosure, a variable capacitance capacitor for a control circuit for controlling the operation of a device is provided. The variable capacitance capacitor includes: a first control electrode layer; a second control electrode layer opposing the first control electrode layer; a dielectric layer disposed at least between the first control electrode layer and the second control electrode layer; and a first extraction electrode layer and a second extraction electrode layer opposing each other with the dielectric layer interposed therebetween. The first extraction electrode layer and the second extraction electrode layer are disposed at positions such that, when a voltage is applied between the first control electrode layer and the second control electrode layer, an electric field is generated in a direction intersecting an electric field vector generated between the first control electrode layer and the second control electrode layer. The voltage applied between the first control electrode layer and the second control electrode layer is adjusted, thereby adjusting the capacitance value of the electrostatic capacitance accumulated between the first extraction electrode layer and the second control electrode layer.

[0008] According to this method, 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, even with the same DC voltage, the electric field applied to the dielectric layer can be increased, thereby lowering the DC voltage. In addition, since the capacitance value of the variable capacitance capacitor C1 changes according to the magnitude of the control voltage, the circuit scale can be reduced compared to the case where a circuit composed of multiple capacitors and switches is used to change the capacitance value of the capacitor.

[0009] According to a second embodiment of the present disclosure, there is provided a power supply device for supplying power to a power receiving device in a contactless manner. The power supply device includes a resonant circuit composed of a variable capacitance capacitor and a coil, and a control voltage application circuit for applying a control voltage to the variable capacitance capacitor. The variable capacitance capacitor includes: a first control electrode layer; a second control electrode layer opposite to the first control electrode layer; a dielectric layer at least disposed between the first control electrode layer and the second control electrode layer; and a first extraction electrode layer and a second extraction electrode layer opposite to each other with the dielectric layer interposed therebetween, the first extraction electrode layer and the second extraction electrode layer being disposed at positions where, when the control voltage is applied between the first control electrode layer and the second control electrode layer, an electric field is generated in a direction intersecting with an electric field vector generated between the first control electrode layer and the second control electrode layer. The control voltage application circuit is capable of performing a power supply action and a standby action. The power supply action sets the resonant circuit to a resonant state by setting the control voltage to a first control voltage and the variable capacitance capacitor to a first capacitance value when AC power of a predetermined operating frequency is applied to the resonant circuit. The standby action sets the resonant circuit to a non-resonant state by setting the control voltage to a second control voltage different from the first control voltage and the variable capacitance capacitor to a second capacitance value different from the first capacitance value when AC power of the operating frequency is applied to the resonant circuit.

[0010] According to this method, 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, thereby lowering the DC voltage. In addition, since the capacitance value of the variable capacitance capacitor C1 changes according to the magnitude of the control voltage, the circuit scale of the resonant circuit and the control voltage application circuit can be reduced compared to the case where a circuit composed of multiple capacitors and switches is used to change the capacitance value of the capacitor. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] 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 Schematic diagram showing the structure of a contactless power supply system. Figure 2 This is a circuit diagram of a contactless power supply system. Figure 3 This is a three-dimensional diagram of a variable capacitance capacitor. Figure 4 yes Figure 3 The IV-IV line cross-sectional view of the variable capacitance capacitor shown. Figure 5 is a graph showing the relationship between the control electric field and the relative dielectric constant. Figure 6 This is a circuit diagram of a power supply unit. Figure 7 This is a circuit diagram of a power supply device according to a second embodiment. Figure 8 This is a circuit diagram of a power supply device according to a third embodiment. Figure 9 This is a circuit diagram of a power supply device according to a fourth embodiment. Figure 10 This is a diagram showing the relationship between the control voltage application start timing and the coil voltage. Figure 11 Graphs showing dielectric properties of a dielectric layer according to the fifth embodiment. DETAILED DESCRIPTION

[0012] A. First embodiment: A1. Structure of contactless power supply system: like Figure 1As shown, 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 beneath the road RS. The power receiving device 80 is mounted on a vehicle VE, which is a moving object traveling on the road RS. While the vehicle VE is traveling, the power receiving device 80 receives power from the power supply device 70. Traveling includes both the vehicle VE moving and the vehicle stopping, for example, at a traffic light. The vehicle VE is, for example, an electric vehicle or a hybrid vehicle.

[0013] The power supply device 70 includes a primary-side resonant circuit 72, which is a series resonant circuit comprising a primary-side coil L1 and a variable capacitor C1; and an AC power supply 71, which supplies power to the primary-side resonant circuit 72. The AC power supply 71 supplies power to the multiple primary-side resonant circuits 72. The multiple primary-side coils L1 are arranged along the direction in which the road RS extends. The power receiving device 80 includes a secondary-side coil L2.

[0014] Furthermore, the mobile object equipped with the power receiving device 80 is not limited to a vehicle VE traveling on the road RS, and may also be, for example, an AGV (automated guided vehicle), a traveling robot, etc. Furthermore, the power supply device 70 may be installed not below the road RS but on a sidewalk or parking lot adjacent to the road RS, or on the path of an AGV.

[0015] A2. Circuit structure of contactless power supply system: like Figure 2 As shown, power supply device 70 includes, in addition to the above-described configuration, a control circuit 73 and a primary-side detection circuit 78. Control circuit 73 includes a control voltage application circuit 76 and a primary-side control circuit 77. Primary-side coil L1 and variable-capacitance capacitor C1 are connected in series to form a primary-side resonant circuit 72, which serves as a resonant circuit.

[0016] The control circuit 73 controls the operation of the power supply device 70 by adjusting the electric field applied between the first control electrode layer 21 and the second control electrode layer 22, thereby adjusting the capacitance value of the electrostatic capacitance accumulated between the first extraction electrode layer 11 and the second control electrode layer 22. 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 used to change the dielectric constant of the second dielectric layer 32. The variable capacitor C1 adjusts the resonant frequency of the primary-side resonant circuit 72 by adjusting its capacitance value using the control voltage.

[0017] 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 at a predetermined operating frequency and applies it to the primary resonant circuit 72. In this embodiment, the operating frequency is 85 kHz. The variable capacitor C1 has the function of causing the primary resonant circuit 72 to enter a resonant state at the operating frequency and to enter a non-resonant state at the operating frequency. In this embodiment, the variable 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 capacitor C1 is switched between the first and second capacitance values ​​by a switching signal Sig1 output from the control voltage application circuit 76. When the primary coil L1 and the secondary coil L2 are magnetically coupled and the variable capacitor C1 is at the first capacitance value, the primary resonant circuit 72 enters a resonant state at the operating frequency. In other words, the first capacitance value of the variable capacitor C1 is set to a value that causes the resonant frequency of the primary resonant circuit 72 to coincide with the operating frequency. In contrast, 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 therefore the primary-side resonant circuit 72 enters a non-resonant state at the operating frequency.

[0018] As will be described in detail later, the control voltage application circuit 76 applies a switching signal Sig1 generated using the AC power output from the AC power supply 71 to the variable capacitance capacitor C1 .

[0019] The primary-side detection circuit 78 is a magnetic sensor that detects the magnitude of the magnetic flux near the primary-side coil L1. Specifically, it is a magnetic sensor with a built-in coil positioned near the primary-side coil L1. The primary-side detection circuit 78 detects the magnetic flux density and outputs a signal representing 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, if the magnetic flux density indicated by the signal is greater than a predetermined threshold, 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.

[0020] In addition to the above-described configuration, power receiving device 80 further includes a secondary resonant circuit 81, a rectifier 82, and a battery 83. The secondary coil L2 and the secondary capacitor C2 are connected in series to form the secondary resonant circuit 81. The rectifier 82 converts the AC power output from the secondary resonant circuit 81 into DC power and supplies it to the battery 83. The supplied DC power charges the battery 83.

[0021] 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.

[0022] A3. Standby state and power supply state: The state in which the variable capacitor C1 is set to a first capacitance value and a transmission current flows through the primary coil L1, thereby providing power is called the power supply state. The state in which the variable capacitor C1 is set to a second capacitance value and a standby current smaller than the transmission current flows through the primary coil L1, thereby not providing power, is called the standby state.

[0023] The primary coils L1 are arranged along the direction of extension of the road RS, 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 target, the magnetic sensor detects the magnetic flux generated by the primary coil L1. Upon detecting the magnetic flux, the power receiving device 80 causes an alternating current to flow through the secondary coils L2, generating magnetic flux. When the magnetic flux generated by the secondary coils L2 is detected by the primary detection circuit 78, the primary control circuit 77 instructs the control voltage application circuit 76 to switch the voltage value of the switching signal Sig1. The variable capacitance capacitor C1 switches its capacitance from the second capacitance value to the first capacitance value using the voltage value of the switching signal Sig1. As a result, the primary resonant circuit 72 enters a resonant state, and power supply begins.

[0024] 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.

[0025] A4. Structure of variable capacitance capacitor: like Figure 3 As shown, the variable capacitance capacitor C1 includes 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 collectively referred to as the extraction electrode layer 10. The first control electrode layer 21 and the second control electrode layer 22 are collectively referred to as the control electrode layer 20.

[0026] exist Figure 3In 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.

[0027] like Figure 4 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 capacitance capacitor C1. The first extraction electrode layer 11 and the second extraction electrode layer 12 are electrode layers used to utilize the capacitance of the variable capacitance capacitor C1. Typically, the variable capacitance capacitor C1 is used to apply a control voltage (DC voltage) between the first control electrode layer 21 and the second control electrode layer 22, and to apply AC power between the first extraction electrode layer 11 and the second extraction electrode layer 12.

[0028] Variable capacitor C1 further includes a first terminal ACp, a second terminal ACn, a third terminal DCp, and a fourth terminal DCn for electrical connection 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.

[0029] 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. In addition, the first extraction electrode layer 11 and the second extraction electrode layer 12 are opposite to each other in the Z direction.

[0030] like Figure 4As shown, the variable capacitance capacitor C1 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.

[0031] like Figure 3 As 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.

[0032] A structure 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 structure 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 C1.

[0033] like Figure 4 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.

[0034] The first extraction electrode layer 11 and the second extraction electrode layer 12 face each other in the Z direction, sandwiching the second dielectric layer 32. Consequently, 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 approximately 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 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.

[0035] 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. Therefore, the distance between the first control electrode layer 21 and the second control electrode layer 22 can be shortened while maintaining a 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. This increases the electric field applied between the first control electrode layer 21 and the second control electrode layer 22. Consequently, the control voltage can be reduced.

[0036] 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.

[0037] 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 include dielectrics made of different materials.

[0038] PVDF molecules have hydrogen and fluorine atoms bound to their carbon chains. Since hydrogen atoms are positively charged and fluorine atoms are negatively charged, PVDF molecules have a 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 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 polarization direction 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 C1 can be provided whose relative dielectric constant changes when the voltage value of the control voltage changes.

[0039] Figure 5This 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. Variable capacitor C1 has dielectric characteristics with two peaks in the relative dielectric constant εr.

[0040] 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 shift in the direction corresponding to the AC voltage applied between the first extraction electrode layer 11 and the second extraction electrode layer 12, so the relative dielectric constant εr is expected to increase.

[0041] 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.

[0042] In this embodiment, the direction of the control electric field Ed intersects the direction of the electric field caused by the applied AC voltage. Furthermore, the polarization direction of the PVDF contained in the second dielectric layer 32 rotates about the carbon chain. Therefore, even in regions where the control electric field Ed is smaller than the counter-electric field Ec, a peak in the relative permittivity εr is observed. 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 absence of the control electric field Ed.

[0043] The dielectric characteristics of variable capacitance capacitor C1 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.

[0044] 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 than in the auxiliary region due to the AC voltage. 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.

[0045] 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.

[0046] 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 C1 can increase the capacitance of the variable capacitor C1 compared to when no control electric field Ed is applied.

[0047] Furthermore, by applying the control electric field Ed in the polarization reversal region, the polarization can be moved more easily than in the auxiliary region. Therefore, by applying the control electric field Ed in the polarization reversal 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 auxiliary region is applied.

[0048] Furthermore, by applying the control electric field Ed in the saturation region, polarization can be made less likely to shift. 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 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 C1 can be set to the target capacitance value.

[0049] A5. Circuit structure of control voltage application circuit: like Figure 6 As shown, 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 wiring N2. A diode bridge circuit, for example, can be used as the rectifier 79. The voltage applied to wiring N1 is higher than the voltage applied to wiring N2. A switch SW is provided in wiring N1. Switch SW is, for example, a transistor. A smoothing capacitor C10 is connected between wiring N1 and wiring N2. Specifically, the switching signal Sig1 is the voltage between wiring N1 and wiring N2.

[0050] Wiring N1 is connected to the third terminal DCp of the variable capacitor C1. Wiring N2 is connected to the fourth terminal DCn of the variable capacitor C1. Wiring connected to one output terminal of the inverter 75 is connected to the first terminal ACp of the variable capacitor C1. Wiring connected to the other output terminal of the inverter 75 is connected to the second terminal ACn of the variable capacitor C1.

[0051] 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 conducting state. Specifically, when the power supply device 70 is set to the power supply state, the primary-side control circuit 77 outputs a signal to set the switch SW to an open state. When a 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. During the supply operation, the control voltage application circuit 76 sets the control voltage to zero volts, which is the 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 is zero volts. The capacitance value of the variable capacitance capacitor C1 is set to the first capacitance value when the relative dielectric constant εr of the second dielectric layer 32 is the relative dielectric constant ε1. As a result, the primary-side resonant circuit 72 enters a resonant state.

[0052] In contrast, when the power supply device 70 is set to the standby mode, the primary-side control circuit 77 outputs a signal to turn on the switch SW. Upon receiving a signal from the primary-side control circuit 77, the control voltage application circuit 76 performs a standby operation to turn on the switch SW. During the standby operation, the control voltage application circuit 76 sets the control voltage to a voltage value that provides a control electric field Ed in the saturation region, which is the second control voltage. Consequently, the control electric field Ed applied between the first control electrode layer 21 and the second control electrode layer 22 of the variable capacitor C1 is in the saturation region. The capacitance of the variable capacitor C1 is set to the second capacitance value when the relative dielectric constant εr of the second dielectric layer 32 is in the saturation region. As described above, the second capacitance value is smaller than the first capacitance value. Consequently, the primary-side resonant circuit 72 enters a non-resonant state.

[0053] 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. Furthermore, the variable capacitance capacitor C1 is used in the control voltage application circuit 76, which controls the operation of the contactless power supply system 1 by adjusting the control electric field Ed applied between the first control electrode layer 21 and the second control electrode layer 22 and the capacitance accumulated between the first extraction electrode layer 11 and the second control electrode layer 22. This reduces the circuit size compared to a configuration using multiple capacitors and switches to change the capacitance of the primary-side resonant circuit 72. Furthermore, it can be more compact than a capacitor whose capacitance value is mechanically changed.

[0054] The variable capacitor C1 is used to adjust the resonant frequency of the primary resonant circuit 72 and to control the operation of the primary resonant circuit 72. This reduces the circuit size compared to a circuit configuration having multiple capacitors to change the capacitance value of the primary resonant circuit 72. Furthermore, the control voltage application circuit 76 sets the control voltage Vd to zero volts to perform a power supply operation, setting the primary-side resonant circuit 72 to a resonant state. It also sets the control voltage to a voltage in the saturation region to perform a standby operation, setting the primary-side resonant circuit 72 to a non-resonant state. The variable capacitance capacitor C1 is set to a first capacitance value by setting the control voltage Vd to zero volts, and 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 a power supply device 70 that uses magnetic field resonance for contactless power supply, whether the power supply device performs power supply operation 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 of this embodiment is ideally suited for use in such a power supply device 70.

[0055] The second capacitance value is smaller than the first capacitance value. Thus, in the standby state of the contactless power supply system 1, the impedance of the primary-side resonant circuit 72 can be reduced, thereby reducing the current flowing through the primary-side coil L1.

[0056] B. Second embodiment: Figure 7 The power supply device 70 of the second embodiment shown is different from the first embodiment in the configuration of the control voltage application circuit 276. The same components as those in the above embodiment are denoted by the same reference numerals, and detailed descriptions thereof are omitted as appropriate.

[0057] The control voltage application circuit 276 of 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 wiring N1 and wiring N2. The control voltage output by the control voltage application circuit 276 is the same as that of the first embodiment. When stepping down or stepping up the voltage, the control voltage application circuit 276 outputs a voltage linearly with respect to time. This suppresses abrupt current fluctuations and thus suppresses surge voltages.

[0058] C. Third embodiment: Figure 8 The power supply device 70 of the third embodiment shown is different from the above-described embodiments in the configuration of the control voltage application circuit 376. The same configurations as those in the above-described embodiments are denoted by the same reference numerals, and detailed descriptions thereof are omitted as appropriate.

[0059] The control voltage application circuit 376 of this embodiment includes a capacitor C30, a first diode D1, a second diode D2, a smoothing capacitor C10, and a DC-DC converter 100. Capacitor C30, first diode D1, second diode D2, and smoothing capacitor C10 form a half-wave voltage-doubling rectifier circuit. This circuit can output a relatively high control voltage Vd. The control voltage output by the control voltage application circuit 376 is the same as that of the first embodiment.

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

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

[0062] like Figure 10 As shown, when the control voltage application circuit 476 switches from power supply operation to standby operation, it begins standby operation around time t1, when the coil voltage reaches zero volts. Specifically, the control voltage application circuit 476 applies a saturation-region control voltage Vd between the third terminal DCp and the fourth terminal DCn starting around time t1. Here, "around time t1" refers to the period around time t1, when the voltage of the AC power reaches 10% or less of its maximum value. In this embodiment, the control voltage application circuit 476 begins standby operation at time t1. This allows the control electric field Ed to be applied to the second dielectric layer 32 of the variable capacitor C1 while the layer is less susceptible to the electric field caused by the applied AC power. Consequently, the control electric field can be effectively applied to the second dielectric layer 32.

[0063] According to the fourth embodiment described above, the variable capacitor C1 begins applying the control voltage when the voltage of the AC power applied to the primary coil L1 is near zero volts. This allows the control electric field Ed to be applied to the second dielectric layer 32 while the layer is less susceptible to the electric field caused by the applied AC power. Therefore, the control electric field can be effectively applied to the second dielectric layer 32.

[0064] E. Fifth embodiment: like Figure 11As shown, in this embodiment, the second dielectric layer 32 has dielectric properties where the relative dielectric constant εr at temperatures higher than the phase transition temperature Tc, which serves as the operating temperature, is smaller than the relative dielectric constant εr at the phase transition temperature Tc. Specifically, the relative dielectric constant εr of the second dielectric layer 32 decreases as the temperature rises above the phase transition temperature Tc. In this embodiment, the dielectric used for the second dielectric layer 32 is fabricated so that the phase transition temperature Tc is lower than the operating temperature when the power supply device 70 enters an abnormal state. Consequently, if the control circuit 73 reaches a high temperature due to an abnormality, the capacitance value of the variable capacitor C1 decreases. Consequently, current is less likely to flow through the primary resonant circuit 72, protecting the primary resonant circuit 72.

[0065] According to the fifth embodiment described above, the second dielectric layer 32 has dielectric properties such that the relative permittivity εr decreases at temperatures higher than the phase transition temperature Tc. Since the capacitance of the variable capacitor C1 decreases during an abnormal state of the power supply device 70, the current flowing through the primary coil L1 can be reduced, thereby protecting the primary resonant circuit 72.

[0066] F. Other implementation methods: (F1) In the first embodiment described above, the second dielectric layer 32 includes a ferroelectric polymer. In other embodiments, the second dielectric layer 32 may also include an inorganic ferroelectric such as barium titanate (BaTiO3). Even for an inorganic ferroelectric, the relative dielectric constant εr will change according to the magnitude of the control voltage. Therefore, it can be used as a dielectric layer of a variable capacitance capacitor C1. It can also be an inorganic ferroelectric that is polarized in multiple directions. This is because, even when the direction of applying the control voltage is different from the direction of applying the AC voltage, the relative dielectric constant will change according to the magnitude of the control voltage, thereby providing a variable capacitance capacitor C1 with a good variable rate.

[0067] (F2) In the first embodiment described above, the control voltage application circuit 76 applies the control voltage in the saturation region when the power supply device 70 is in the standby state, and does not apply the control voltage when the power supply device 70 is in the power transmission state. Alternatively, the control voltage application circuit 76 may apply the control voltage in the polarization reversal region or the auxiliary region when the power supply device 70 is in the standby state, and not apply the control voltage when the power supply device 70 is in the power transmission state.

[0068] (F3) In the first embodiment described above, the primary-side resonant circuit 72 has a primary-side coil L1 connected in series with a variable-capacitance capacitor C1, and the secondary-side resonant circuit 81 has a secondary-side coil L2 connected in series with a secondary-side capacitor C2, a so-called SS-type circuit configuration. The circuit configurations of the primary-side resonant circuit 72 and the secondary-side resonant circuit 81 are not limited to the SS-type configuration. (a) For example, the primary-side resonant circuit 72 may have a variable-capacitance capacitor C1 connected in parallel with the primary-side coil L1, and the secondary-side capacitor C2 connected in series with the secondary-side coil L2 in the secondary-side resonant circuit 81, a so-called PS-type circuit configuration. (b) Alternatively, in addition to the variable-capacitance capacitor C1 connected in series with the primary-side coil L1, a capacitor connected in parallel with the primary-side coil L1 may be included, and in the secondary-side resonant circuit 81, two secondary-side capacitors C2 are connected in series with each of the two terminals of the secondary-side coil L2, a so-called P-SS-type circuit configuration. (c) Alternatively, the primary-side resonant circuit 72 may include a closed circuit in which a coil and a capacitor are connected in series. The coil of the closed circuit is positioned so that it can magnetically couple with the secondary coil L2 when the primary coil L1 and the secondary coil L2 are magnetically coupled. (d) Furthermore, the capacitor of the closed circuit may be connected in parallel with the coil, rather than in series. (e) Alternatively, the primary resonant circuit 72 may include a coil connected in series with the primary coil L1 and a capacitor connected in parallel with the coil. The coil is positioned so that it can magnetically couple with the secondary coil L2 when the primary coil L1 and the secondary coil L2 are magnetically coupled.

[0069] (F4) In the first embodiment described above, the variable capacitor C1 is used in 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 having a built-in frequency conversion circuit.

[0070] 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 various 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 essential structures in this specification, they can be appropriately deleted.

[0071] Other ways: The features of the present disclosure are as follows. (Method 1) A variable capacitance capacitor, wherein the variable capacitance capacitor (C1) is used in a control circuit (73) for controlling the operation of a device (70), comprising: a first control electrode layer (21); a second control electrode layer (22) opposite to the first control electrode layer; a dielectric layer (32) disposed at least 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) are opposite to each other with the dielectric layer sandwiched therebetween. The first extraction electrode layer and the second extraction electrode layer are arranged at positions where, when a voltage is applied between the first control electrode layer and the second control electrode layer, an electric field is generated in a direction intersecting with an electric field vector generated between the first control electrode layer and the second control electrode layer. The voltage applied between the first control electrode layer and the second control electrode layer is adjusted, thereby adjusting the capacitance value of the electrostatic capacitance accumulated between the first extraction electrode layer and the second control electrode layer. (Method 2) In the variable capacitance capacitor described in embodiment 1, The device further comprises a resonant circuit (72) composed of the variable capacitance capacitor and the primary side coil (L1). The control circuit further includes a control voltage applying circuit (76, 276, 376, 476) for applying a control voltage between the first control electrode layer and the second control electrode layer for changing the dielectric constant of the dielectric layer. The variable capacitance capacitor adjusts the resonant frequency of the resonant circuit by adjusting the capacitance value using the control voltage. (Method 3) In the variable capacitance capacitor described in embodiment 2, The above device is a power supply device that supplies power to a power receiving device in a contactless manner. The control voltage application circuit can perform power supply and standby operations. The power supply operation sets the resonant circuit to a resonant state by setting the control voltage to a first control voltage and applying AC power of a predetermined operating frequency to the resonant circuit. The standby operation is performed by setting the control voltage to a second control voltage different from the first control voltage, and setting the resonant circuit to a non-resonant state when the AC power of the operating frequency is applied to the resonant circuit. The variable capacitance 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. (Method 4) In the variable capacitance capacitor described in embodiment 3, The above resonant circuit is a series resonant circuit. The second capacitance value is smaller than the first capacitance value. (Method 5) In the variable capacitance capacitor described in embodiment 3 or 4, The second control voltage is applied starting from around the time when the voltage of the AC power applied to the primary side coil reaches zero volts. (Method 6) In the variable capacitance capacitor according to any one of aspects 1 to 5, The dielectric layer has a dielectric property in which a relative dielectric constant at a temperature higher than a predetermined operating temperature is smaller than a relative dielectric constant at the operating temperature. (Method 7) A power supply device (70) supplies power to a power receiving device (80) in a contactless manner, the power supply device comprising: a resonant circuit (72) composed of a variable capacitance capacitor (C1) and a primary side coil (L1); and a control voltage applying circuit (76) for applying a control voltage to the variable capacitance capacitor; The variable capacitance capacitor includes: a first control electrode layer (21); a second control electrode layer (22) opposite to the first control electrode layer; a dielectric layer (32) disposed at least 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) are opposite to each other with the dielectric layer sandwiched therebetween. The first extraction electrode layer and the second extraction electrode layer are arranged at positions where, when the control voltage is applied between the first control electrode layer and the second control electrode layer, an electric field is generated in a direction intersecting with an electric field vector generated between the first control electrode layer and the second control electrode layer. The control voltage application circuit can perform power supply and standby operations. The power supply operation sets the resonant circuit to a resonant state by setting the control voltage to a first control voltage and the variable capacitor to a first capacitance value, when AC power of a predetermined operating frequency is applied to the resonant circuit. The standby operation is performed by setting the control voltage to the second control voltage different from the first control voltage, setting the variable capacitance capacitor to the second capacitance value different from the first capacitance value, and setting the resonant circuit to a non-resonant state when the AC power of the operating frequency is applied to the resonant circuit. The control circuit and method thereof described in the present disclosure may also be implemented by a special-purpose computer, which is provided by constituting a processor and a memory, and the above-mentioned processor is programmed to perform one or more functions embodied by a computer program. Alternatively, the control circuit and method thereof described in the present disclosure may be implemented by a special-purpose computer, which is provided by constituting a processor by one or more special-purpose hardware logic circuits. Alternatively, the control unit and the method of the control unit described in the present disclosure may be implemented by one or more special-purpose computers, which are constituted by a combination of a processor and a memory programmed to perform one or more functions and a processor constituted by one or more hardware logic circuits. In addition, the computer program may also be stored in a non-temporary tangible recording medium readable by a computer as an instruction executed by a computer. 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 capacitance capacitor, wherein the variable capacitance capacitor (C1) is used in a control circuit (73) for controlling the operation of a device (70), comprising: a first control electrode layer (21); a second control electrode layer (22) opposite to the first control electrode layer; a dielectric layer (32) at least arranged between the first control electrode layer and the second control electrode layer; A first extraction electrode layer (11) and a second extraction electrode layer (12) are opposite to each other with the dielectric layer interposed therebetween, The first extraction electrode layer and the second extraction electrode layer 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 layer and the second control electrode layer when a voltage is applied between the first control electrode layer and the second control electrode layer. The voltage applied between the first control electrode layer and the second control electrode layer is adjusted, and the capacitance value of the electrostatic capacitance accumulated between the first extraction electrode layer and the second control electrode layer is adjusted.

2. The variable capacitance capacitor according to claim 1, wherein The device further comprises a resonant circuit (72) including the variable capacitance capacitor and a primary coil (L1). The control circuit further includes a control voltage applying circuit (76, 276, 376, 476) for applying a control voltage between the first control electrode layer and the second control electrode layer for changing the dielectric constant of the dielectric layer. The variable capacitance capacitor adjusts the resonance frequency of the resonance circuit by adjusting a capacitance value using the control voltage.

3. The variable capacitance capacitor according to claim 2, wherein: The device is a power supply device that supplies power to a power receiving device in a contactless manner. The control voltage application circuit can perform power supply operation and standby operation, The power supply operation sets the resonant circuit to a resonant state by setting the control voltage to a first control voltage when AC power of a predetermined operating frequency is applied to the resonant circuit. The standby operation sets the resonant circuit to a non-resonant state by setting the control voltage to a second control voltage different from the first control voltage when the AC power of the operating frequency is applied to the resonant circuit. The variable capacitance 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.

4. The variable capacitance capacitor according to claim 3, wherein: The resonant circuit is a series resonant circuit, The second capacitance value is smaller than the first capacitance value.

5. The variable capacitance capacitor according to claim 3 or 4, wherein: Application of the second control voltage begins around a time point when the voltage of the AC power applied to the primary side coil reaches zero volts.

6. The variable capacitance capacitor according to claim 1, wherein: The dielectric layer has a dielectric property in which a relative dielectric constant at a temperature higher than a predetermined operating temperature is smaller than a relative dielectric constant at the operating temperature.

7. A power supply device, the power supply device (70) supplying power to a power receiving device (80) in a contactless manner, the power supply device comprising: a resonant circuit (72), the resonant circuit comprising a variable capacitance capacitor (C1) and a primary side coil (L1); as well as a control voltage applying circuit (76) for applying a control voltage to the variable capacitance capacitor, The variable capacitance capacitor comprises: a first control electrode layer (21); a second control electrode layer (22) opposite to the first control electrode layer; a dielectric layer (32) at least arranged between the first control electrode layer and the second control electrode layer; A first extraction electrode layer (11) and a second extraction electrode layer (12) are opposite to each other with the dielectric layer interposed therebetween, The first extraction electrode layer and the second extraction electrode layer 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 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 can perform power supply operation and standby operation, The power supply operation sets the resonant circuit to a resonant state by setting the control voltage to a first control voltage and the variable capacitor to a first capacitance value when AC power of a predetermined operating frequency is applied to the resonant circuit. The standby action sets the resonant circuit to a non-resonant state by setting the control voltage to a second control voltage different from the first control voltage, setting the variable capacitance capacitor to a second capacitance value different from the first capacitance value, and applying the AC power of the operating frequency to the resonant circuit.

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