Power transmission equipment and contactless power supply system

Abstract

In contactless power supply using an electric field coupling method, switching losses are reduced. [Solution] The power transmission device (2) for contactless power supply includes a power supply circuit (10) that converts DC power to AC power by zero-volt switching, an output capacitor (Co) and an output coil (Lo) connected to the power supply circuit and connected in series with each other, a first coil (L1) connected in series with the output capacitor and the output coil, and a first power transmission electrode (P1) and a second power transmission electrode (P2) connected to each other via the first coil.

Description

[Technical Field]

[0001] This disclosure relates to power transmission equipment and contactless power supply systems. [Background technology]

[0002] As the switching frequency of a power supply circuit increases, the losses during switching become greater. In Class E amplifiers, Zero-Voltage Switching (ZVS) and Zero-Voltage Derivative Switching (ZDS) are implemented. ZVS is the operation of switching a switching element on or off when the voltage applied to the switching element is zero. ZDS is the operation of switching a switching element on when the time change of the voltage applied to the switching element is zero (i.e., dV / dt = 0). In Class E amplifiers, losses during switching can be reduced.

[0003] Non-patent document 1 describes the conditions for a power supply circuit that is not contactless to operate as a Class E amplifier.

[0004] Patent Document 1 discloses a contactless power supply device that operates using ZVS. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2024-060471 [Non-patent literature]

[0006] [Non-Patent Document 1] Lujie Zhang, "Load-Independent Class-E Power Conversion", [online], April 13, 2020, Virginia Tech, [Retrieved January 14, 2025], Internet<URL:https: / / vtechworks.lib.vt.edu / items / a9238206-afb9-42f9-8fc7-f2c1900dee0a> [Overview of the project] [Problems that the invention aims to solve]

[0007] In contactless power supply, the degree of coupling between the transmitting coil and the receiving coil can change. Therefore, even if the conditions for a Class E amplifier described in Non-Patent Document 1 are met under certain conditions, there is a problem that the conditions for a Class E amplifier will no longer be met when the conditions change.

[0008] In the configuration described in Patent Document 1, power is transmitted by magnetic field coupling. Therefore, if conductive foreign matter such as metal is present between the transmitting coil and the receiving coil, there is a problem in that abnormal heat generation occurs.

[0009] One aspect of this disclosure aims to realize a power transmission device that can reduce switching losses and performs contactless power supply using an electric field coupling method. [Means for solving the problem]

[0010] A power transmission device for contactless power supply according to aspect 1 of the present disclosure comprises a DC power supply, a first power supply circuit that converts DC power supplied from the DC power supply into AC power by zero-volt switching, a first output capacitor and a first output coil connected to the first power supply circuit and connected in series with each other, a first coil connected in series with the first output capacitor and the first output coil, and a first power transmission electrode and a second power transmission electrode connected to each other via the first coil and transmitting the AC power by electric field coupling.

[0011] According to the above configuration, losses in switching can be reduced, and contactless power supply can be performed using an electric field coupling method.

[0012] In the power transmission device according to Embodiment 2 of the present disclosure, the first power supply circuit may be configured to include an input coil connected in series with the DC power supply, a switching element connected in series with the input coil, and a capacitor formed in parallel with the switching element.

[0013] In the power transmission device according to embodiment 3 of this disclosure, the capacitance may be configured to be an input capacitor connected in parallel with the switching element, as in embodiment 2 described above.

[0014] In the power transmission device according to embodiment 4 of this disclosure, in embodiment 2 described above, the switching element may be a transistor and the capacitance may be the parasitic capacitance of the transistor.

[0015] With the above configuration, the input capacitor element can be omitted, and the circuit can be simplified.

[0016] In the power transmission device according to aspect 5 of the present disclosure, the power transmission device may be configured to include a first capacitor connected in parallel with the first coil, as described in aspect 1 above.

[0017] According to the above configuration, the effects of capacity fluctuations depending on the distance between the power transmission device and the power receiving device can be reduced, thereby reducing losses in switching.

[0018] According to aspect 6 of the present disclosure, in the power transmission device according to aspect 1 described above, the power transmission device includes: a second power supply circuit that converts DC power supplied from the DC power source into AC power by zero-voltage switching and operates in an opposite phase to the first power supply circuit; a second output capacitor and a second output coil connected to the second power supply circuit and in series with each other; and a third coil connected in series to the second output capacitor and the second output coil, wherein the first power transmission electrode and the second power transmission electrode may be configured to be connected to each other via the first coil and the third coil.

[0019] According to the above configuration, a higher AC voltage can be transmitted to the power receiving device.

[0020] According to aspect 7 of the present disclosure, in the contactless power feeding system according to any one of aspects 1 to 6 described above, the contactless power feeding system includes: the power transmission device; and a power receiving device that receives the AC power from the power transmission device, wherein the power receiving device may be configured to include: a first power receiving electrode and a second power receiving electrode that are respectively electric-field coupled to the first power transmission electrode and the second power transmission electrode during power feeding; and a second coil connected between the first power receiving electrode and the second power receiving electrode.

[0021] According to aspect 8 of the present disclosure, in the contactless power feeding system according to aspect 7 described above, the contactless power feeding system may be configured to include a T-type LCL circuit connected to the first power receiving electrode.

[0022] According to the above configuration, even when the load of the power receiving device changes, switching loss can be reduced.

[0023] According to aspect 9 of the present disclosure, in the contactless power feeding system according to aspect 7 described above, the contactless power feeding system may be configured to include a T-type CLC circuit connected to the first power receiving electrode.

[0024] According to the above configuration, even when the load of the power receiving device changes, switching loss can be reduced.

[0025] In the contactless power supply system according to aspect 10 of the present disclosure, in aspect 7 described above, the power receiving device may be configured to include a second capacitor connected in parallel with the second coil.

[0026] According to the above configuration, the effects of capacity fluctuations depending on the distance between the power transmission device and the power receiving device can be reduced, thereby reducing losses in switching.

[0027] A contactless power supply system according to aspect 11 of the present disclosure, in aspect 6 above, comprises a power transmission device and a power receiving device that receives AC power from the power transmission device, wherein the power receiving device comprises a first power receiving electrode and a second power receiving electrode that are electrically coupled to the first power transmission electrode and the second power transmission electrode, respectively, a second coil connected between the first power receiving electrode and the second power receiving electrode, and an impedance adjustment circuit connected to the first power receiving electrode, wherein the impedance adjustment circuit may be configured to include a first adjustment coil connected to the first power receiving electrode, a second adjustment coil connected in series with the first adjustment coil, a third adjustment coil connected to the second power receiving electrode, a fourth adjustment coil connected in series with the third adjustment coil, and an adjustment capacitor connected between a node between the first adjustment coil and the second adjustment coil and a node between the third adjustment coil and the fourth adjustment coil.

[0028] A contactless power supply system according to aspect 12 of the present disclosure, in aspect 6 above, comprises a power transmission device and a power receiving device that receives AC power from the power transmission device, wherein the power receiving device comprises a first power receiving electrode and a second power receiving electrode that are electrically coupled to the first power transmission electrode and the second power transmission electrode, respectively, a second coil connected between the first power receiving electrode and the second power receiving electrode, and an impedance adjustment circuit connected to the first power receiving electrode, wherein the impedance adjustment circuit may have a first adjustment capacitor connected to the first power receiving electrode, a second adjustment capacitor connected in series with the first adjustment capacitor, a third adjustment capacitor connected to the second power receiving electrode, a fourth adjustment capacitor connected in series with the third adjustment capacitor, and an adjustment coil connected between a node between the first adjustment capacitor and the second adjustment capacitor and a node between the third adjustment capacitor and the fourth adjustment capacitor. [Effects of the Invention]

[0029] According to one aspect of this disclosure, losses in switching can be reduced, and contactless power supply can be performed by an electric field coupling method. [Brief explanation of the drawing]

[0030] [Figure 1] This is a circuit diagram showing the configuration of a power supply circuit as an example. [Figure 2] This is a circuit diagram showing the configuration of a contactless power supply system according to one embodiment of the present disclosure. [Figure 3] This is a circuit diagram showing the configuration of an equivalent circuit of a contactless power supply system according to one embodiment of the present disclosure. [Figure 4] This circuit diagram shows the equivalent circuit and impedance Zin of a reference example employing SP-type (series-parallel) electric field coupling in a contactless power supply system. [Figure 5] This circuit diagram shows the equivalent circuit and impedance Zin of a reference example employing PS-type (parallel-series) electric field coupling in a contactless power supply system. [Figure 6]This circuit diagram shows the equivalent circuit and impedance Zin of a reference example employing SS-type (series-series) electric field coupling in a contactless power supply system. [Figure 7] This is a circuit diagram showing the configuration of a contactless power supply system according to one embodiment of the present disclosure. [Figure 8] This is a circuit diagram showing the configuration of an equivalent circuit of a contactless power supply system according to one embodiment of the present disclosure. [Figure 9] This is a circuit diagram showing the configuration of a contactless power supply system according to one embodiment of the present disclosure. [Figure 10] This is a circuit diagram showing the configuration of a contactless power supply system according to one embodiment of the present disclosure. [Figure 11] This is a circuit diagram showing the configuration of a contactless power supply system according to one embodiment of the present disclosure. [Figure 12] This is a circuit diagram showing the configuration of a contactless power supply system according to one embodiment of the present disclosure. [Figure 13] This is a circuit diagram showing the configuration of a contactless power supply system according to one embodiment of the present disclosure. [Modes for carrying out the invention]

[0031] (Reference example 1) Figure 1 is a circuit diagram showing the configuration of a reference example power supply circuit 100. The power supply circuit 100 comprises a DC power supply Vin, a switching element 11, an input coil Lin, an input capacitor Cin, an output capacitor Co, an output coil Lo, and a load Ro. The power supply circuit 100 is a Class E amplifier circuit. In the power supply circuit 100, if the characteristics of each element satisfy the conditions for operation as a Class E amplifier, ZVS and / or ZDS are possible. Unless otherwise specified, the resistance, capacitance, and inductance of each element are represented by the sign of each element.

[0032] The conditions under which the circuit operates as a Class E amplifier are described, for example, in Non-Patent Document 1. When the load resistance Ro of the power supply circuit 100 is a predetermined value, the power supply circuit 100 operates in ZVS and ZDS mode. This predetermined value depends on the characteristics of other elements. When the load resistance Ro of the power supply circuit 100 is greater than this predetermined value, the power supply circuit 100 does not operate in ZDS mode but operates in ZVS mode. Note that the load Ro is a pure resistance without a reactance component.

[0033] On the other hand, when the load resistance Ro of the power supply circuit 100 is smaller than the predetermined value, the power supply circuit 100 will not operate in either ZVS or ZDS mode. In this case, the voltage applied to the switching element 11 is not zero at the timing when the switching element 11 changes from off to on. Or, the timing at which the voltage applied to the switching element 11 becomes zero is too early compared to the timing at which the switching element 11 changes from off to on (this is also not called ZVS). In other words, in order to achieve operation in ZVS mode, the load resistance Ro of the power supply circuit 100 must be greater than or equal to the predetermined value.

[0034] Furthermore, if the reactance components of the impedance due to the output capacitor Co, output coil Lo, and load Ro fluctuate (increase or decrease) while the power supply circuit 100 is in a state where it satisfies the conditions for operating in ZVS mode, the power supply circuit 100 will no longer meet the conditions for operating in ZVS mode. Therefore, if the load Ro of the circuit fluctuates, the load Ro must be a pure resistance.

[0035] [Embodiment 1] Hereinafter, embodiments relating to one aspect of this disclosure (hereinafter also referred to as "this embodiment") will be described based on the drawings. For the sake of convenience of explanation, components having the same function as those described above will be denoted by the same reference numerals, and their descriptions may be omitted.

[0036] §1 Examples of Application Figure 2 is a circuit diagram showing the configuration of the contactless power supply system 1 of this embodiment. The contactless power supply system 1 comprises a power transmission device 2 and a power receiving device 3. The power transmission device 2 supplies power to the power receiving device 3 contactlessly by electric field coupling. The power transmission device 2 comprises a first coil L1 connected between a first power transmission electrode P1 and a second power transmission electrode P2, which transmit power by electric field coupling. The power receiving device 3 comprises a second coil L2 connected between a first power receiving electrode P3 and a second power receiving electrode P4, which receive power by electric field coupling. The contactless power supply system 1 supplies power by PP-type (parallel-parallel) electric field coupling.

[0037] In the non-contact power supply system 1, even if the capacitance between the power transmission device 2 and the power receiving device 3, formed by the load Rac and electric field coupling, fluctuates, the equivalent impedance on the receiving side of the output coil Lo remains a pure resistance. Therefore, the equivalent impedance on the receiving side of the output coil Lo corresponds to the load Ro of the power supply circuit 100 in the reference example. Thus, if the load resistance Rac of the load Rac is within a predetermined range, the non-contact power supply system 1 can operate in ZVS mode and supply power non-contactly using the electric field coupling method. Because the non-contact power supply system 1 supplies power using the electric field coupling method, it can avoid abnormal heat generation due to the presence of conductive foreign matter such as metal. In addition, in the switching element 11 of the power supply circuit 10, even if it does not operate in ZDS mode, as long as it operates in ZVS mode, switching losses are not a practical problem.

[0038] §2 Example Configuration (Configuration of power transmission device 2) The power transmission device 2 comprises a DC power supply Vin, a power supply circuit 10, an output capacitor Co, an output coil Lo, a first coil L1, a first power transmission electrode P1, and a second power transmission electrode P2. The power supply circuit 10 includes a switching element 11, a control unit 12, an input coil Lin, and an input capacitor Cin.

[0039] The power supply circuit 10 is connected to a DC power supply Vin. The power supply circuit 10 converts the DC power supplied from the DC power supply Vin into AC power by zero-volt switching (ZVS).

[0040] The input coil Lin is connected in series with the DC power supply Vin. One end of the input coil Lin is connected to the anode of the DC power supply Vin.

[0041] The switching element 11 is connected in series with the input coil Lin. One end of the switching element 11 is connected to the other end of the input coil Lin. The other end of the switching element 11 is connected to the negative terminal of the DC power supply Vin. For example, the switching element 11 is a transistor.

[0042] The control unit 12 is a circuit that controls the on / off (non-conductive) state of the switching element 11. The control unit 12 switches the switching element 11 on / off at a predetermined switching frequency f. The predetermined switching frequency f may be, for example, 1 MHz or higher, and may be a frequency included in the ISM band (for example, 6.78 MHz).

[0043] The input capacitor Cin is connected in parallel to the switching element 11. The input capacitor Cin constitutes a capacitance formed in parallel with the switching element 11. One end of the input capacitor Cin is connected to one end of the switching element 11. The other end of the input capacitor Cin is connected to the other end of the switching element 11.

[0044] The output capacitor Co and output coil Lo are connected to the power supply circuit 10 and are connected in series with each other. One end of the output capacitor Co is connected to the other end of the input coil Lin and one end of the switching element 11. One end of the output coil Lo is connected to the other end of the output capacitor Co. The arrangement of the output capacitor Co and the output coil Lo may be reversed.

[0045] The first coil L1 is connected in series with the output capacitor Co and the output coil Lo. One end of the first coil L1 is connected to the other end of the output coil Lo. The other end of the first coil L1 is connected to the negative terminal of the DC power supply Vin.

[0046] The first power transmission electrode P1 is connected to one end of the first coil L1. The first power transmission electrode P1 forms a capacitance with the first power receiving electrode P3 of the power receiving device 3. The second power transmission electrode P2 is connected to the other end of the first coil L1. The second power transmission electrode P2 forms a capacitance with the second power receiving electrode P4 of the power receiving device 3. The first power transmission electrode P1 and the second power transmission electrode P2 are, for example, flat plate electrodes. The first power transmission electrode P1 and the second power transmission electrode P2 are connected to each other via the first coil L1. The first power transmission electrode P1 and the second power transmission electrode P2 transmit AC power to the power receiving device 3 by electric field coupling. The frequency of the AC voltage applied to the first power transmission electrode P1 is the predetermined switching frequency f. As a result, the first power transmission electrode P1 and the second power transmission electrode P2 supply power to the power receiving device 3 without contact.

[0047] (Configuration of power receiving device 3) The power receiving device 3 comprises a first power receiving electrode P3, a second power receiving electrode P4, a second coil L2, and a load Rac. The second coil L2 is connected between the first power receiving electrode P3 and the second power receiving electrode P4.

[0048] The first receiving electrode P3 is connected to one end of the second coil L2. The second receiving electrode P4 is connected to the other end of the second coil L2. The first receiving electrode P3 and the second receiving electrode P4 are flat plate electrodes. The first receiving electrode P3 and the second receiving electrode P4 are connected to each other via the second coil L2. During power supply, the first receiving electrode P3 is electrically coupled to the first transmitting electrode P1. During power supply, the second receiving electrode P4 is electrically coupled to the second transmitting electrode P2. The first receiving electrode P3 and the second receiving electrode P4 receive an AC voltage from the power transmission device 2.

[0049] The load Rac is connected between the first receiving electrode P3 and the second receiving electrode P4. The first receiving electrode P3 and the second receiving electrode P4 supply power to the load Rac by outputting an AC voltage. The power supplied from the power transmission device 2 to the power receiving device 3 via a non-contact method is used by the load Rac. The load Rac may be any load device. For example, the load Rac may be a load device that includes a secondary battery that is charged by the power supply.

[0050] (Equivalent circuit) Figure 3 is a circuit diagram showing the configuration of the equivalent circuit 1a of the contactless power supply system 1 of this embodiment. During power supply, the power transmission device 2 and the power receiving device 3 are in close proximity to each other. During power supply, the first power transmission electrode P1 and the first power receiving electrode P3 are in close proximity to each other and facing each other, and the second power transmission electrode P2 and the second power receiving electrode P4 are in close proximity to each other. Therefore, a capacitance is formed between the first power transmission electrode P1 and the first power receiving electrode P3. A capacitance is also formed between the second power transmission electrode P2 and the second power receiving electrode P4. However, the capacitance formed is not limited to these. Since the first power transmission electrode P1, the second power transmission electrode P2, the first power receiving electrode P3, and the second power receiving electrode P4 are in close proximity to each other, a capacitance can be formed between each of them. The capacitance value of the capacitance formed between each electrode Pm and Pn is represented as Cmn. For example, let C12 be the capacitance value formed between the first power transmission electrode P1 and the second power transmission electrode P2, and let C13 be the capacitance value formed between the first power transmission electrode P1 and the first power receiving electrode P3.

[0051] In the non-contact power supply system 1, the equivalent circuit 1a shown in Figure 3 is obtained by replacing the capacitance between these electrodes with a π-type equivalent circuit. In the equivalent circuit 1a, a capacitance value Cm exists between one end of the first coil L1 and one end of the second coil L2. A capacitance value C1-Cm exists in parallel with the first coil L1, and a capacitance value C2-Cm exists in parallel with the second coil L2. Here, the capacitance values ​​Cm, C1, and C2 in the equivalent circuit 1a are expressed as follows.

[0052] Cm=(C24C13-C14C23) / (C13+C14+C23+C24) C1=C12+(C13+C14)(C23+C24) / (C13+C14+C23+C24) C2=C34+(C13+C23)(C14+C24) / (C13+C14+C23+C24) Capacity values ​​C13, C14, C23, and C24 change depending on the distance between the power transmission device 2 and the power receiving device 3. Therefore, capacity values ​​Cm, C1, and C2 also change depending on the distance between the power transmission device 2 and the power receiving device 3. Capacity values ​​C12 and C34 do not change depending on the distance between the power transmission device 2 and the power receiving device 3, and are determined by the structure of the power transmission device 2 and the power receiving device 3. If the distance between the power transmission device 2 and the power receiving device 3 during power supply is assumed to be constant, then capacity values ​​Cm, C1, and C2 can be considered constant during power supply.

[0053] The resistance, capacitance, and inductance of each element are represented by the sign of each element. The inductance L1 of the first coil L1 is set so that the capacitance C1 and the first coil L1 resonate at the predetermined switching frequency f when power is supplied. Similarly, the inductance L2 of the second coil L2 is set so that the capacitance C2 and the second coil L2 resonate at the predetermined switching frequency f when power is supplied. Therefore, when the switching element 11 is operating at the predetermined switching frequency f, the combined impedance of the first coil L1 and the capacitance C1 in parallel with the first coil L1 becomes infinite, and the first coil L1 and capacitance C1 can be ignored. Similarly, the second coil L2 and capacitance C2 can be ignored. Therefore, it is equivalent to having a π-type circuit consisting of capacitance Cm and two negative capacitances -Cm between the output coil Lo and the load Rac.

[0054] Let Zin be the impedance of the circuit on the load Rac side (right side in Figure 3) from the output coil Lo. The impedance Zin is the equivalent load resistance corresponding to the load Ro of the power supply circuit 100, which is a Class E amplifier. In equivalent circuit 1a, the impedance Zin is expressed by the following equation, where ω is the angular frequency (ω = 2πf).

[0055] Zin = 1 / ((ωCm)) 2 Rac) ···(1) The load Rac is a pure resistance. The impedance Zin consists only of the real part and can be considered a pure resistance without a reactance component. Therefore, the circuit configuration of the equivalent circuit 1a of the non-contact power supply system 1 is the same as the circuit configuration of a Class E amplifier. In other words, the non-contact power supply system 1 is capable of ZVS and / or ZDS if the characteristics of each element satisfy the conditions for operation as a Class E amplifier. The impedance Zin in the equivalent circuit 1a corresponds to the load when the non-contact power supply system 1 is considered as a Class E amplifier. Therefore, if the load resistance Rac of the load Rac is within a predetermined range, the non-contact power supply system 1 can operate in ZVS mode and provide power non-contact by electric field coupling.

[0056] Furthermore, in the contactless power supply system 1, the capacitance value Cm appears in the denominator of the right-hand side of equation (1) representing the impedance Zin. Therefore, in the contactless power supply system 1, as the capacitance value Cm decreases, the impedance Zin of the equivalent circuit 1a increases. Thus, for example, it is sufficient that ZVS operation is achieved at the upper limit of the capacitance value Cm during power supply. Even if the power receiving device 3 moves away from the power transmitting device 2 while ZVS operation is achieved during power supply, ZVS operation can continue. It is easy to structurally limit the capacitance value Cm so that it does not increase above the upper limit.

[0057] (Regarding the no-load condition) As explained in Reference Example 1, in order to achieve operation in ZVS at least in the non-contact power supply system 1 of Embodiment 1, the impedance Zin of the equivalent circuit 1a, which corresponds to Ro in a Class E amplifier, must be greater than or equal to a predetermined value. In the equivalent circuit 1a, from equation (1), as the load resistance Rac of the load Rac increases, the impedance Zin decreases. Therefore, for example, when the power receiving device 3 is in an unloaded state (load resistance ≈ ∞), the non-contact power supply system 1 will no longer be able to maintain operation in ZVS. The non-contact power supply system 1 may stop the output operation of the power transmitting device 2 depending on the load of the power receiving device 3.

[0058] (Reference example 2) Figure 4 is a circuit diagram showing the equivalent circuit and impedance Zin of Reference Example 2, which employs SP-type (series-parallel) electric field coupling in the non-contact power supply system 1. Here, only the portion on the load Rac side from the output coil Lo is shown. Zm represents the impedance on the load Rac side from the capacitance C1. The first coil L1 is arranged in series with the first power transmission electrode P1 (not shown). In the case of the SP type, the impedance Zin has an imaginary part (j is the imaginary unit). The imaginary part includes Rac. That is, the reactance component of the impedance Zin changes with changes in the load resistance Rac, which is a pure resistance. Therefore, even if the conditions for operation in ZVS are met in a certain state, if the load resistance Rac changes even slightly, the conditions for operation in ZVS will be deviated.

[0059] (Reference example 3) Figure 5 is a circuit diagram showing the equivalent circuit and impedance Zin of Reference Example 3, which employs PS-type (parallel-series) field coupling in the contactless power supply system 1. Here, only the part on the load Rac side from the output coil Lo is depicted. Zo represents the impedance due to capacitance C2, second coil L2, and load Rac. The second coil L2 is arranged in series with the load Rac. In the case of the PS type, the impedance Zin has an imaginary part. The imaginary part includes Rac. Therefore, even in the circuit of Reference Example 3, if the load resistance Rac changes even slightly, it will deviate from the conditions for operation with ZVS.

[0060] (Reference example 4) Figure 6 is a circuit diagram showing the equivalent circuit and impedance Zin of Reference Example 4, which employs SS-type (series-series) electric field coupling in the non-contact power supply system 1. Here, only the portion on the load Rac side from the output coil Lo is shown. The first coil L1 is arranged in series with the first power transmission electrode P1 (not shown). The second coil L2 is arranged in series with the load Rac. In the case of the SS type, the impedance Zin has an imaginary part. The imaginary part includes Rac. Therefore, even in the circuit of Reference Example 4, if the load resistance Rac changes even slightly, it will deviate from the conditions for operation with ZVS.

[0061] [Embodiment 2] Other embodiments of this disclosure are described below. For the sake of convenience, components having the same function as those described in the above embodiments are denoted by the same reference numerals, and their descriptions are not repeated.

[0062] Figure 7 is a circuit diagram showing the configuration of the contactless power supply system 1b of this embodiment. The contactless power supply system 1b comprises a power transmission device 2 and a power receiving device 3b. The power receiving device 3b comprises a first power receiving electrode P3, a second power receiving electrode P4, a second coil L2, an impedance adjustment circuit 30, and a load Rac. The second coil L2 is connected between the first power receiving electrode P3 and the second power receiving electrode P4.

[0063] The impedance adjustment circuit 30 is connected between the first receiving electrode P3 and the load Rac. The impedance adjustment circuit 30 has a first adjustment coil Lr1, a second adjustment coil Lr2, and an adjustment capacitor Cr. The impedance adjustment circuit 30 is a T-type LCL circuit. One end of the first adjustment coil Lr1 is connected to the first receiving electrode P3. The second adjustment coil Lr2 is connected in series with the first adjustment coil Lr1. One end of the second adjustment coil Lr2 is connected to the other end of the first adjustment coil Lr1. The other end of the second adjustment coil Lr2 is connected to the load Rac. One end of the adjustment capacitor Cr is connected to the node between the first adjustment coil Lr1 and the second adjustment coil Lr2. The other end of the adjustment capacitor Cr is connected to the second receiving electrode P4. The inductance of the first adjustment coil Lr1 and the inductance of the second adjustment coil Lr2 are the same Lr. The first adjustment coil Lr1 and the second adjustment coil Lr2, and the adjustment capacitor Cr satisfy the condition for resonance at the predetermined switching frequency f. 2 LrCr = 1.

[0064] Figure 8 is a circuit diagram showing the configuration of the equivalent circuit 1c of the contactless power supply system 1b of this embodiment. Here, the impedance Zo to the right of the second coil L2 is expressed as follows.

[0065] Zo=(ωLr) 2 / Rac Therefore, the impedance Zin to the right of the output coil Lo is expressed as follows:

[0066] Zin = Rac / ((ωLr) 2 (ωCm) 2 ) ···(2) The load Rac is a pure resistance. The impedance Zin consists only of the real part and can be considered a pure resistance without a reactance component. Furthermore, in the contactless power supply system 1b, unlike in embodiment 1, an impedance adjustment circuit 30 is provided, so the load resistance Rac appears in the numerator of equation (2) which represents the impedance Zin. Therefore, in the contactless power supply system 1b, unlike in embodiment 1, when the load resistance Rac of the load Rac of the power receiving device 3b increases, the impedance Zin of the equivalent circuit 1c increases.

[0067] In order to achieve ZVS operation, the impedance Zin of the equivalent circuit 1c corresponding to the load resistance Ro of the load Ro of the power supply circuit 100 must be greater than or equal to a predetermined value. Therefore, for example, it is sufficient for ZVS operation to be achieved at the lower limit of the load resistance Rac of the load Rac of the power receiving device 3b during power supply (the state in which the load is largest). Even if the load resistance Rac of the load Rac of the power receiving device 3b increases (the load of the power receiving device 3b decreases) while power supply is in a state in which ZVS operation is achieved, ZVS operation can be continued.

[0068] For example, in lithium-ion secondary batteries, charging is performed with a constant current or constant voltage depending on the charge level. When the charge level is high, charging is performed with a constant voltage until the load resistance becomes zero (load resistance ≈ ∞). If the load Rac is such a secondary battery, the load resistance Rac of the load Rac increases as the charge level increases.

[0069] According to the contactless power supply system 1b, if the load Rac is a secondary battery, even if the charge level increases, the impedance Zin increases, allowing operation in ZVS to continue. The lower limit of the load resistance Rac (upper limit of the load) is usually determined by the specifications and can also be limited by the circuit.

[0070] Furthermore, in the contactless power supply system 1b, the capacitance value Cm appears in the denominator of the right-hand side of equation (2) representing the impedance Zin. Therefore, in the contactless power supply system 1b, as the capacitance value Cm decreases, the impedance Zin of the equivalent circuit 1c increases. Even if the power receiving device 3b moves away from the power transmitting device 2 while ZVS operation is being realized during power supply, ZVS operation can continue.

[0071] Thus, the contactless power supply system 1b can continue operating in ZVS mode even if there are fluctuations in the distance between the power transmission device 2 and the power receiving device 3b, or in the load of the power receiving device 3b, during power supply. Therefore, the contactless power supply system 1b can reduce switching losses even when the power supply conditions change. This enables efficient contactless power supply at high frequencies.

[0072] An example of the procedure for setting the parameters of each element is described below. The procedure for determining the parameters (Lin, Cin, Co, Lo, Zin) of each element for the equivalent circuit 1c shown in Figure 8 to operate in ZVS is well known (see Non-Patent Literature 1). Here, the lower limit of Zin that must be satisfied is determined. In the non-contact power supply system 1b, the minimum value of the load resistance Rac is determined from the specifications of the load Rac. Cm, C1, and C2 are determined from the area of ​​each electrode and the positional relationship during power supply. L1 and L2 are determined so as to satisfy the resonance condition with C1 and C2. Also, Lr and Cr are determined so as to satisfy the resonance condition. At this time, under the condition that Cm is at its maximum and the load resistance Rac is at its minimum, Lr is determined so that the output voltage to the load Rac becomes the desired voltage, within the range in which Zin obtained from equation (2) is greater than the lower limit mentioned above.

[0073] [Embodiment 3] Another embodiment of the present disclosure will be described below. For convenience of description, members having the same functions as the members described in the above embodiments are denoted by the same reference numerals, and the description thereof will not be repeated.

[0074] FIG. 9 is a circuit diagram showing a configuration of a non-contact power feeding system 1d of the present embodiment. The non-contact power feeding system 1d includes a power transmission device 2 and a power reception device 3d. The power reception device 3d includes a first power reception electrode P3, a second power reception electrode P4, a second coil L2, an impedance adjustment circuit 30, a rectifier circuit 31, a smoothing capacitor 32, and a load 33.

[0075] The impedance adjustment circuit 30 outputs an AC voltage to the rectifier circuit 31. The rectifier circuit 31 performs full-wave rectification on the AC voltage and outputs the voltage to the smoothing capacitor 32. The smoothing capacitor 32 is connected between output terminals of the rectifier circuit 31. The smoothing capacitor 32 smoothes the voltage output from the rectifier circuit 31. The smoothing capacitor 32 outputs the smoothed DC output voltage to the load 33. The load 33 may be any DC load device. The load 33 may be, for example, a load device including a secondary battery that is charged by power feeding.

[0076] Let the load resistance of the load 33 be Rdc. The load resistance Rac in Embodiment 2 is an equivalent load resistance when the rectifier circuit 31, the smoothing capacitor 32, and the load 33 are regarded as one load. The following relationship holds between the load resistance Rdc and the load resistance Rac.

[0077] Rac=(8 / π 2 )Rdc That is, the non-contact power feeding system 1d can also be represented by the equivalent circuit 1c shown in FIG. 8, and the following holds.

[0078] Zin=(8 / π 2 )Rdc / ((ωLr) 2 (ωCm) 2 ) ···(3) In the non-contact power supply system 1d, as in the non-contact power supply system 1b, operation in ZVS can continue even if there are fluctuations in the distance between the power transmission device 2 and the power receiving device 3d, or in the load of the power receiving device 3d, during power supply. Therefore, the non-contact power supply system 1d can reduce switching losses even when the power supply conditions change.

[0079] [Embodiment 4] Other embodiments of this disclosure are described below. For the sake of convenience, components having the same function as those described in the above embodiments are denoted by the same reference numerals, and their descriptions are not repeated.

[0080] The capacitance values ​​C1 and C2 appearing in the equivalent circuit 1c (Figure 8) of the aforementioned non-contact power supply system 1b may change depending on the distance between the power transmission device 2 and the power receiving device 3d during power supply. If the capacitance values ​​C1 and C2 change significantly, they may deviate from the resonance conditions with the first coil L1 and the second coil L2. As a result, operation in ZVS may not be maintained.

[0081] Figure 10 is a circuit diagram showing the configuration of the contactless power supply system 1e of this embodiment. The contactless power supply system 1e comprises a power transmission device 2e and a power receiving device 3e. The power transmission device 2e comprises a DC power supply Vin, a power supply circuit 10, an output capacitor Co, an output coil Lo, a first coil L1, a first capacitor C1', a first power transmission electrode P1, and a second power transmission electrode P2. The first capacitor C1' is connected in parallel with the first coil L1.

[0082] The power receiving device 3e comprises a first power receiving electrode P3, a second power receiving electrode P4, a second coil L2, a second capacitor C2', an impedance adjustment circuit 30, and a load Rac. The second capacitor C2' is connected in parallel with the second coil L2.

[0083] In this embodiment, the inductance L1 of the first coil L1 is set such that the capacitance C1'+C1 and the first coil L1 resonate at the predetermined switching frequency f during power supply. 2 L1(C1'+C1)=1. Furthermore, the inductance L2 of the second coil L2 is set so that the capacitance C2'+C2 and the second coil L2 resonate at the predetermined switching frequency f during power supply. ω 2 L2(C2'+C2)=1.

[0084] In the non-contact power supply system 1e, even if C1 changes, the rate of change of (C1'+C1) is smaller than the rate of change of C1. Therefore, the first coil L1 is less likely to deviate from the resonance condition, and the effects of changes in capacitance value C1 can be suppressed. The same effect can be obtained for the second capacitor C2'. The non-contact power supply system 1e can operate more stably in ZVS during power supply.

[0085] [Embodiment 5] Other embodiments of this disclosure are described below. For the sake of convenience, components having the same function as those described in the above embodiments are denoted by the same reference numerals, and their descriptions are not repeated.

[0086] Figure 11 is a circuit diagram showing the configuration of the contactless power supply system 1f of this embodiment. The contactless power supply system 1f comprises a power transmission device 2e and a power receiving device 3f. The power receiving device 3f comprises a first power receiving electrode P3, a second power receiving electrode P4, a second coil L2, a second capacitor C2', an impedance adjustment circuit 30f, and a load Rac.

[0087] The impedance adjustment circuit 30f is connected between the first power receiving electrode P3 and the load Rac. The impedance adjustment circuit 30f includes a first adjustment capacitor Cr1, a second adjustment capacitor Cr2, and an adjustment coil Lr. The impedance adjustment circuit 30f is a T-type CLC circuit. One end of the first adjustment capacitor Cr1 is connected to the first power receiving electrode P3. One end of the second adjustment capacitor Cr2 is connected to the other end of the first adjustment capacitor Cr1. The other end of the second adjustment capacitor Cr2 is connected to the load Rac. One end of the adjustment coil Lr is connected to the node between the first adjustment capacitor Cr1 and the second adjustment capacitor Cr2. The other end of the adjustment coil Lr is connected to the second power receiving electrode P4. The capacitance value of the first adjustment capacitor Cr1 and the capacitance value of the second adjustment capacitor Cr2 are the same Cr. The first adjustment capacitor Cr1, the second adjustment capacitor Cr2, and the adjustment coil Lr satisfy the condition for resonance at the predetermined switching frequency f.

[0088] In the non-contact power supply system 1f, similar to embodiment 2, an impedance adjustment circuit 30f is provided, so that when the load resistance Rac of the load Rac of the power receiving device 3f increases, the impedance Zin increases. Therefore, even if the load resistance Rac of the load Rac of the power receiving device 3f increases while power supply is in operation in ZVS mode, ZVS operation can be continued.

[0089] [Embodiment 6] Other embodiments of this disclosure are described below. For the sake of convenience, components having the same function as those described in the above embodiments are denoted by the same reference numerals, and their descriptions are not repeated.

[0090] Figure 12 is a circuit diagram showing the configuration of the contactless power supply system 1g of this embodiment. The contactless power supply system 1g comprises a power transmission device 2g and a power receiving device 3g. The power transmission device 2g comprises a DC power supply Vin, a first power supply circuit 10a, a first output capacitor Coa, a first output coil Loa, a first coil L1, a second power supply circuit 10b, a second output capacitor Cob, a second output coil Lob, a third coil, a first power transmission electrode P1, and a second power transmission electrode P2.

[0091] The first power supply circuit 10a and the second power supply circuit 10b are each connected to a DC power supply Vin. The first power supply circuit 10a includes a first switching element 11a, a control unit 12, a first input coil Lina, and a first input capacitor Cina. The second power supply circuit 10b includes a second switching element 11b, a second input coil Linb, and a second input capacitor Cinb. The configurations of the first power supply circuit 10a and the second power supply circuit 10b are the same as those of the power supply circuit 10 in Embodiment 1. However, the control unit 12 may control both the first switching element 11a and the second switching element 11b of the first power supply circuit 10a. The first power supply circuit 10a and the second power supply circuit 10b convert the DC power supplied from the DC power supply Vin into AC power by zero-volt switching (ZVS).

[0092] The control unit 12 is a circuit that controls the on / off (conductive) / non-conductive state of the first switching element 11a and the second switching element 11b. The control unit 12 switches the on / off state of the first switching element 11a and the second switching element 11b at a predetermined switching frequency f. The control unit 12 alternately repeats periods in which the first switching element 11a is on and the second switching element 11b is off, and periods in which the first switching element 11a is off and the second switching element 11b is on. The on / off phases of the first switching element 11a and the second switching element 11b are shifted by π from each other. That is, the second power supply circuit 10b operates in opposite phase to the first power supply circuit 10a.

[0093] The first output capacitor Coa and the first output coil Loa are connected to the first power supply circuit 10a and are connected in series with each other. The arrangement of the first output capacitor Coa and the first output coil Loa may be reversed.

[0094] The first coil L1 is connected in series with the first output capacitor Coa and the first output coil Loa. One end of the first coil L1 is connected to the first output coil Loa. The other end of the first coil L1 is connected to the negative terminal of the DC power supply Vin. The first power transmission electrode P1 is connected to one end of the first coil L1.

[0095] The second output capacitor Cob and the second output coil Lob are connected to the second power supply circuit 10b and are connected in series with each other. The arrangement of the second output capacitor Cob and the second output coil Lob may be reversed.

[0096] The third coil L3 is connected in series with the second output capacitor Cob and the second output coil Lob. One end of the third coil L3 is connected to the second output coil Lob. The other end of the third coil L3 is connected to the negative terminal of the DC power supply Vin. The second power transmission electrode P2 is connected to one end of the third coil L3.

[0097] The first power transmission electrode P1 and the second power transmission electrode P2 are connected to each other via the first coil L1 and the third coil L3.

[0098] The inductances L1 and L3 of the first coil L1 and the third coil L3 are set such that, during power supply, the capacitance C1 and the combined inductance L1+L3 of the first coil L1 and the third coil L3 resonate at the predetermined switching frequency f. 2 (L1+L3)C1=1.

[0099] The power receiving device 3g comprises a first power receiving electrode P3, a second power receiving electrode P4, a second coil L2, an impedance adjustment circuit 30g, and a load Rac. The impedance adjustment circuit 30g is connected between the first power receiving electrode P3 and the load Rac. The impedance adjustment circuit 30g has a first adjustment coil Lr1, a second adjustment coil Lr2, a third adjustment coil Lr3, a fourth adjustment coil Lr4, and an adjustment capacitor Cr.

[0100] One end of the third adjustment coil Lr3 is connected to the second receiving electrode P4. The fourth adjustment coil Lr4 is connected in series with the third adjustment coil Lr3. One end of the fourth adjustment coil Lr4 is connected to the other end of the third adjustment coil Lr3. The load Rac is connected between the other end of the second adjustment coil Lr2 and the other end of the fourth adjustment coil Lr4. One end of the adjustment capacitor Cr is connected to the node between the first adjustment coil Lr1 and the second adjustment coil Lr2. The other end of the adjustment capacitor Cr is connected to the node between the third adjustment coil Lr3 and the fourth adjustment coil Lr4.

[0101] The inductances of the first adjustment coil Lr1, the second adjustment coil Lr2, the third adjustment coil Lr3, and the fourth adjustment coil Lr4 are all the same Lr. The first adjustment coil Lr1, the second adjustment coil Lr2, the third adjustment coil Lr3, and the fourth adjustment coil Lr4, along with the adjustment capacitor Cr, satisfy the condition for resonance at the predetermined switching frequency f. 2ω 2 LrCr = 1.

[0102] The contactless power supply system 1g can achieve zero-volt switching, similar to Embodiment 2. Therefore, even when the power supply conditions change, switching losses can be reduced. Thus, the contactless power supply system 1g that performs differential input may be configured by providing two sets of switching elements (11a, 11b), input coils (Lina, Linb), and input capacitors (Cina, Cinb) in parallel with each other. This makes it possible to double the voltage between the first power transmission electrode P1 and the second power transmission electrode P2 compared to the contactless power supply system 1b of Embodiment 2. Therefore, the contactless power supply system 1g is suitable when the load Rac of the power receiving device 3g requires high power.

[0103] In the non-contact power supply system 1g, similar to Embodiment 2, an impedance adjustment circuit 30g is provided, so that when the load resistance Rac of the load Rac of the power receiving device 3g increases, the impedance Zin increases. Therefore, even if the load resistance Rac of the load Rac of the power receiving device 3g increases while power supply is in operation in ZVS mode, ZVS operation can be continued.

[0104] [Embodiment 7] Other embodiments of this disclosure are described below. For the sake of convenience, components having the same function as those described in the above embodiments are denoted by the same reference numerals, and their descriptions are not repeated.

[0105] Figure 13 is a circuit diagram showing the configuration of the contactless power supply system 1h of this embodiment. The contactless power supply system 1h comprises a power transmission device 2g and a power receiving device 3h. The power receiving device 3g comprises a first power receiving electrode P3, a second power receiving electrode P4, a second coil L2, an impedance adjustment circuit 30h, and a load Rac.

[0106] The impedance adjustment circuit 30h is connected between the first power receiving electrode P3 and the load Rac. The impedance adjustment circuit 30h includes a first adjustment capacitor Cr1, a second adjustment capacitor Cr2, a third adjustment capacitor Cr3, a fourth adjustment capacitor Cr4, and an adjustment coil Lr. The impedance adjustment circuit 30h is the same as the impedance adjustment circuit 30g of Embodiment 6, but with the coil and capacitors swapped.

[0107] The capacitance values ​​of the first adjustment capacitor Cr1, the second adjustment capacitor Cr2, the third adjustment capacitor Cr3, and the fourth adjustment capacitor Cr4 are all the same Cr. The first adjustment capacitor Cr1, the second adjustment capacitor Cr2, the third adjustment capacitor Cr3, and the fourth adjustment capacitor Cr4, along with the adjustment coil Lr, satisfy the condition for resonance at the predetermined switching frequency f. (1 / 2)ω 2 LrCr = 1.

[0108] The same effects as those of the contactless power supply system 1g of Embodiment 6 can be obtained with the contactless power supply system 1h.

[0109] [Variation] Instead of the input capacitor Cin, the parasitic capacitance of the switching element, which is a transistor, may be used as a capacitance formed in parallel with the switching element.

[0110] In addition, in the non-contact power supply systems 1g and 1h, a first capacitor C1' and / or a second capacitor C2' may be provided, similar to embodiments 4 and 5. The first capacitor C1' is connected between the first power transmission electrode P1 and the second power transmission electrode P2, and is connected in parallel to the first coil L1 and the third coil. The second capacitor C2' is connected between the first power receiving electrode P3 and the second power receiving electrode P4, and is connected in parallel to the second coil L2.

[0111] In addition, in the contactless power supply systems 1e and 1f, one of the first capacitor C1' and the second capacitor C2' may be omitted.

[0112] The load Rac in the above-described embodiment may actually be a circuit including a rectifier circuit and a DC load, as in Embodiment 3.

[0113] 〔summary〕 A power transmission device for contactless power supply according to aspect 1 of the present disclosure comprises a DC power supply, a first power supply circuit that converts DC power supplied from the DC power supply into AC power by zero-volt switching, a first output capacitor and a first output coil connected to the first power supply circuit and connected in series with each other, a first coil connected in series with the first output capacitor and the first output coil, and a first power transmission electrode and a second power transmission electrode connected to each other via the first coil and transmitting the AC power by electric field coupling.

[0114] In the power transmission device according to Embodiment 2 of the present disclosure, the first power supply circuit may be configured to include an input coil connected in series with the DC power supply, a switching element connected in series with the input coil, and a capacitor formed in parallel with the switching element.

[0115] In the power transmission device according to embodiment 3 of this disclosure, the capacitance may be configured to be an input capacitor connected in parallel with the switching element, as in embodiment 2 described above.

[0116] In the power transmission device according to embodiment 4 of this disclosure, in embodiment 2 described above, the switching element may be a transistor and the capacitance may be the parasitic capacitance of the transistor.

[0117] In any of the above embodiments 1 to 4, the power transmission device according to embodiment 5 of the present disclosure may be configured to include a first capacitor connected in parallel with the first coil.

[0118] The power transmission device according to embodiment 6 of the present disclosure may be configured such that, in any of embodiments 1 to 4 above, it includes a second power supply circuit that converts DC power supplied from the DC power source into AC power by zero-volt switching and operates in opposite phase to the first power supply circuit, a second output capacitor and a second output coil connected to the second power supply circuit and connected in series with each other, and a third coil connected in series with the second output capacitor and the second output coil, and the first power transmission electrode and the second power transmission electrode are connected to each other via the first coil and the third coil.

[0119] A contactless power supply system according to aspect 7 of the present disclosure may be configured in any of aspects 1 to 6 above, comprising: a power transmission device; a power receiving device that receives AC power from the power transmission device, wherein the power receiving device comprises: a first power receiving electrode and a second power receiving electrode that are electrically coupled to the first power transmission electrode and the second power transmission electrode, respectively, during power supply; and a second coil connected between the first power receiving electrode and the second power receiving electrode.

[0120] The contactless power supply system according to aspect 8 of this disclosure may be configured to include a T-shaped LCL circuit connected to the first power receiving electrode in aspect 7 described above.

[0121] The contactless power supply system according to aspect 9 of this disclosure may be configured to include a T-shaped CLC circuit connected to the first power receiving electrode in aspect 7 described above.

[0122] In the contactless power supply system according to aspect 10 of the present disclosure, in any of the above aspects 7 to 9, the power receiving device may be configured to include a second capacitor connected in parallel with the second coil.

[0123] A contactless power supply system according to aspect 11 of the present disclosure, in aspect 6 above, comprises a power transmission device and a power receiving device that receives AC power from the power transmission device, wherein the power receiving device comprises a first power receiving electrode and a second power receiving electrode that are electrically coupled to the first power transmission electrode and the second power transmission electrode, respectively, a second coil connected between the first power receiving electrode and the second power receiving electrode, and an impedance adjustment circuit connected to the first power receiving electrode, wherein the impedance adjustment circuit may be configured to include a first adjustment coil connected to the first power receiving electrode, a second adjustment coil connected in series with the first adjustment coil, a third adjustment coil connected to the second power receiving electrode, a fourth adjustment coil connected in series with the third adjustment coil, and an adjustment capacitor connected between a node between the first adjustment coil and the second adjustment coil and a node between the third adjustment coil and the fourth adjustment coil.

[0124] A contactless power supply system according to aspect 12 of the present disclosure, in aspect 6 above, comprises a power transmission device and a power receiving device that receives AC power from the power transmission device, wherein the power receiving device comprises a first power receiving electrode and a second power receiving electrode that are electrically coupled to the first power transmission electrode and the second power transmission electrode, respectively, a second coil connected between the first power receiving electrode and the second power receiving electrode, and an impedance adjustment circuit connected to the first power receiving electrode, wherein the impedance adjustment circuit may have a first adjustment capacitor connected to the first power receiving electrode, a second adjustment capacitor connected in series with the first adjustment capacitor, a third adjustment capacitor connected to the second power receiving electrode, a fourth adjustment capacitor connected in series with the third adjustment capacitor, and an adjustment coil connected between a node between the first adjustment capacitor and the second adjustment capacitor and a node between the third adjustment capacitor and the fourth adjustment capacitor.

[0125] This disclosure is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of this disclosure. [Explanation of symbols]

[0126] 1, 1b, 1d, 1e, 1f, 1g, 1h Contactless power supply system 1a, 1c Equivalent Circuits 2, 2e, 2g power transmission equipment 3, 3b, 3d, 3e, 3f, 3g, 3h Power receiving device 10, 10a, 10b power supply circuit, first power supply circuit, second power supply circuit 11, 11a, 11b Switching element, first switching element, second switching element 12 Control Unit 30, 30f, 30g, 30h Impedance Adjustment Circuit 31 Rectifier circuit 32 Smoothing Capacitors 33, Rac, Ro load C1 First capacitor C2 Second capacitor Cin, Cina, Cinb Input capacitor, 1st input capacitor, 2nd input capacitor Co, Coa, Cob: Output capacitor, 1st output capacitor, 2nd output capacitor Cr Adjustment Capacitor Cr1~Cr4 First adjustment capacitor~Fourth adjustment capacitor L1 First Coil L2 Second Coil L3 Third Coil Lin, Lina, Linb Input coil, 1st input coil, 2nd input coil Lo, Loa, Lob output coil, 1st output coil, 2nd output coil Lr adjustment coil Lr1~Lr4 1st adjustment coil~4th adjustment coil P1 First power transmission electrode P2 Second power transmission electrode P3 First receiving electrode P4 Second receiving electrode Vin DC power supply

Claims

1. DC power supply and A first power supply circuit that converts DC power supplied from the DC power supply into AC power by zero-volt switching, A first output capacitor and a first output coil are connected to the first power supply circuit and connected in series with each other. A first coil connected in series with the first output capacitor and the first output coil, A power transmission device for contactless power supply, comprising a first power transmission electrode and a second power transmission electrode connected to each other via the first coil, which transmit the AC power by electric field coupling.

2. The first power supply circuit is, An input coil connected in series with the DC power supply, A switching element connected in series with the input coil, The power transmission device according to claim 1, further comprising a capacitor formed in parallel with the switching element.

3. The power transmission device according to claim 2, wherein the capacitance is an input capacitor connected in parallel with the switching element.

4. The switching element is a transistor, The power transmission device according to claim 2, wherein the capacitance is the parasitic capacitance of the transistor.

5. The power transmission device according to claim 1, wherein the power transmission device comprises a first capacitor connected in parallel with the first coil.

6. A second power supply circuit that converts the DC power supplied from the DC power supply into AC power by zero-volt switching and operates in opposite phase to the first power supply circuit, A second output capacitor and a second output coil are connected to the second power supply circuit and connected in series with each other, The device comprises a second output capacitor and a third coil connected in series with the second output coil, The power transmission device according to claim 1, wherein the first power transmission electrode and the second power transmission electrode are connected to each other via the first coil and the third coil.

7. A power transmission device according to any one of claims 1 to 6, The system includes a power receiving device that receives the AC power from the power transmission device, The power receiving device is During power supply, the first receiving electrode and the second receiving electrode are electrically coupled to the first transmitting electrode and the second transmitting electrode, respectively. A non-contact power supply system comprising a second coil connected between the first power receiving electrode and the second power receiving electrode.

8. The contactless power supply system according to claim 7, comprising a T-shaped LCL circuit connected to the first power receiving electrode.

9. The contactless power supply system according to claim 7, comprising a T-shaped CLC circuit connected to the first power receiving electrode.

10. The contactless power supply system according to claim 7, wherein the power receiving device comprises a second capacitor connected in parallel with the second coil.

11. The power transmission device according to claim 6, The system includes a power receiving device that receives the AC power from the power transmission device, The power receiving device is During power supply, the first receiving electrode and the second receiving electrode are electrically coupled to the first transmitting electrode and the second transmitting electrode, respectively. A second coil connected between the first and second power receiving electrodes, The system comprises an impedance adjustment circuit connected to the first power receiving electrode, The impedance adjustment circuit described above is A first adjustment coil connected to the first power receiving electrode, A second adjustment coil connected in series with the first adjustment coil, A third adjustment coil connected to the second power receiving electrode, A fourth adjustment coil connected in series with the third adjustment coil, A contactless power supply system having a node between the first adjustment coil and the second adjustment coil, and an adjustment capacitor connected between the node between the third adjustment coil and the fourth adjustment coil.

12. The power transmission device according to claim 6, The system includes a power receiving device that receives the AC power from the power transmission device, The power receiving device is During power supply, the first receiving electrode and the second receiving electrode are electrically coupled to the first transmitting electrode and the second transmitting electrode, respectively. A second coil connected between the first and second power receiving electrodes, The system comprises an impedance adjustment circuit connected to the first power receiving electrode, The impedance adjustment circuit described above is A first adjustment capacitor connected to the first power receiving electrode, A second adjusting capacitor connected in series with the first adjusting capacitor, A third adjustment capacitor connected to the second power receiving electrode, A fourth adjustment capacitor connected in series with the third adjustment capacitor, A contactless power supply system having a node between the first adjustment capacitor and the second adjustment capacitor, and an adjustment coil connected between the node between the third adjustment capacitor and the fourth adjustment capacitor.

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