Power transmission device and non-contact power supply system

Abstract

The present invention comprises: a power transmission resonance circuit (11) that transmits power to a power receiving device (2) in a non-contact manner via a power transmission coil (110); a resonance adjustment circuit (14) that has a circuit connection coil (140) disposed so as to be magnetically coupled to the power transmission coil (110) and not magnetically coupled to a power receiving coil (200), and a variable capacitance circuit (145) connected in series with the circuit connection coil (140), and adjusts a capacitive reactance component of the power transmission resonance circuit (11) via the circuit connection coil (140); and a control device (13) that controls the operation of the resonance adjustment circuit (14) according to the resonance state of the power receiving coil (200) and the power transmission coil (110).

Description

Power transmission device and wireless power supply system

[0001] The present application relates to a power transmitting device and a contactless power supply system.

[0002] There is a contactless power transfer technology that transmits power contactlessly by magnetic coupling between coils placed apart. When the magnetic coupling between the coils is weak, the power factor can be improved by utilizing the resonance phenomenon, enabling highly efficient contactless power transfer. However, there is a risk that the power transfer efficiency will drop significantly under conditions that deviate from the resonance state. As contactless power transfer is a technology that is expected to be applied to mobile devices, it is in an environment where the electrical characteristics between the resonant coils are prone to fluctuate and the resonance conditions are easily deviated from, so resonance adjustment to satisfy the resonance conditions is extremely important.

[0003] In response to this, a contactless power transfer device has been proposed that controls a resonant circuit configured with a capacitor and a switching element on the power transmission side to control the capacitive reactance component and achieve desired circuit operation (see, for example, Patent Document 1). Also, a technology has been proposed that adjusts the resonance condition using a reactance adjustment circuit connected to a second coil of the power receiving device that is magnetically coupled to the power transmission coil (see, for example, Patent Document 2).

[0004] JP 2020-156302 A (paragraphs 0013 to 0015, 0030 to 0034, Figure 1) JP 2018-511293 A (paragraphs 0045 to 0052, Figures 1 to 2)

[0005] However, when controlling the capacitive reactance component of a resonant circuit, a control switching element must be placed in a path that is prone to large currents. Therefore, depending on the circuit configuration, efficiency can be reduced due to conduction losses in the switching element. In contrast, if the resonance conditions are adjusted using a reactance adjustment circuit connected to the second coil of the power receiving device, the increase in on-state loss can be suppressed because no semiconductor switch is placed in the path through which the resonant current flows. However, because this configuration assumes that an adjustment circuit is connected to the power receiving device, applying it to a system with multiple power receiving devices increases costs.

[0006] The present application discloses a technique for solving the above-mentioned problems, and aims to provide a resonance adjustment method that suppresses both an increase in loss and an increase in cost.

[0007] The power transmission device disclosed in the present application is characterized by comprising: a power transmission resonant circuit having a power transmission coil for magnetically coupling with a power receiving coil of a power receiving device, converting power supplied from a power source into magnetic energy and transmitting the power to the power receiving device via the power transmission coil; a circuit connection coil that is magnetically coupled with the power transmission coil and is positioned so as not to be magnetically coupled with the power receiving coil even when the power transmission coil is magnetically coupled with the power receiving coil; a resonance adjustment circuit having a variable capacitance circuit connected in series with the circuit connection coil and adjusting the capacitive reactance component of the power transmission resonant circuit via the circuit connection coil; and a control device that controls the operation of the resonance adjustment circuit depending on the resonance state between the power receiving coil and the power transmission coil.

[0008] According to the power transmission device disclosed in the present application, the capacitive reactance component is adjusted via a coil that is magnetically coupled to the power transmission coil independently of the power receiving coil, thereby making it possible to obtain a power transmission device and a contactless power supply device that achieve both suppression of increase in loss and suppression of increase in cost.

[0009] 6A and 6B are schematic circuit diagrams showing different current paths that change when the resonance adjustment circuit operates. FIG. 6B is a diagram showing operation waveforms of each part in the resonance adjustment circuit of the power transmission device that configures the contactless power supply system according to the first embodiment. FIG. 6B is a circuit diagram showing an example of the configuration of a resonance adjustment circuit of a power transmission device that configures the contactless power supply system according to the first embodiment. FIG. 6B is a block diagram showing an example of the configuration of a resonance adjustment circuit of a power transmission device that configures the contactless power supply system according to the first embodiment. FIG. 6A is a circuit diagram showing an example of the configuration of a resonance adjustment circuit of a power transmission device that configures the contactless power supply system according to the first embodiment. FIG. 6B is a block diagram showing an example of the hardware configuration of a control device of a power transmission device that configures the contactless power supply system according to each embodiment of the present application.

[0010] 1 to 7 are diagrams for explaining the configuration and operation of a contactless power transfer system according to a first embodiment, and a power transmitting device and a power receiving device that constitute the contactless power transfer system, in which Fig. 1 is a block diagram showing a state in which a power transmitting device and a power receiving device are combined to constitute a contactless power transfer system, Fig. 2 is a circuit diagram for explaining the configuration of a power transmitting resonant circuit and a power receiving resonant circuit that perform magnetic coupling, and Fig. 3 is a circuit diagram for explaining the configuration of a power receiving device.

[0011] Fig. 4 is a block diagram illustrating the magnetic connection relationship between the power transmitting coil and circuit connection coil on the power transmitting device side and the power receiving coil on the power receiving device side, Fig. 5 is a circuit diagram showing an example configuration of a resonance adjustment circuit of the power transmitting device, Fig. 6A and Fig. 6B are schematic circuit diagrams showing different current paths that change when the resonance adjustment circuit operates, and Fig. 7 is a diagram in which the operating waveforms of the current in the power transmitting coil, the drive signals for each of the two semiconductor switches, and the adjustment capacitor voltage that constitute the resonance adjustment circuit of the power transmitting device are aligned in a synchronized vertical direction.

[0012] 1, a contactless power transfer system 3 is composed of a power transmitting device 1 that converts power supplied from an AC power source 4 into magnetic energy and outputs the magnetic energy, and a power receiving device 2 that receives the converted magnetic energy through magnetic coupling and supplies desired power to a load 5 or the like. A characteristic feature of the configuration is that a resonance adjustment circuit 14 for performing resonance adjustment is provided in a portion other than the path through which the main power of the power transmitting device 1 is transmitted. Here, before describing the characteristic configuration, a basic configuration as a contactless power transfer system will be described.

[0013] 2 , the power transmitting device 1 includes a power transmitting resonant circuit 11 that is configured with a power transmitting coil 110 and at least one power transmitting-side resonant capacitor 111 and is magnetically coupled to a power receiving resonant circuit 20 (power receiving coil 200) of the power receiving device 2. The power transmitting resonant circuit 11 may be configured to include a resonant reactor 112 separate from the power transmitting coil 110 as shown in the figure, or may be configured to include another resonant capacitor. The power transmitting coil 110 and the power transmitting-side resonant capacitor 111 are designed to achieve a resonant condition at the output frequency of the AC power source 4.

[0014] When the output waveform of the AC power supply 4 is a waveform including harmonic components such as a rectangular wave, the power transmitter resonant circuit 11 is generally designed to satisfy the resonance condition for the fundamental wave component of the output waveform, but may also be designed to resonate with respect to the harmonic components. Note that the power transmitter resonant circuit 11 shown in Fig. 2 shows one of various resonant circuit configurations and does not limit the configuration of the power transmitter resonant circuit 11.

[0015] The power receiving device 2 includes a power receiving resonant circuit 20 that is magnetically coupled to the above-mentioned power transmitting resonant circuit 11 (power transmitting coil 110) and converts magnetic energy into electrical energy, and a power receiving circuit 21 that converts the electrical energy converted by the power receiving resonant circuit 20 into power corresponding to the load 5 and outputs it.

[0016] The power receiving resonant circuit 20 is composed of a power receiving coil 200 and at least one power receiving-side resonant capacitor 201, and may also include a resonant reactor or resonant capacitor separate from the power receiving coil 200. The power receiving coil 200 and the power receiving-side resonant capacitor 201 are designed to achieve a resonant condition at the output frequency of the AC power source 4 via the power transmitting coil 110. When the output waveform of the AC power source 4 is a waveform that includes harmonic components, such as a rectangular wave, the power receiving resonant circuit 20 is generally designed to satisfy the resonant condition for the fundamental wave component of the output waveform, but may also be designed to resonate with respect to the harmonic components.

[0017] The receiving resonant circuit 20 shown in Figure 2 is configured such that one receiving-side resonant capacitor 201 is connected in series to the receiving coil 200, but this shows one of various resonant circuit configurations and does not limit the configuration of the resonant circuit.

[0018] 3, the power receiving circuit 21 is configured with a rectifier circuit 210 and a filter 211, and a load 5 is connected to the output terminal of the power receiving circuit 21. The rectifier circuit 210 is configured with, for example, four diode elements connected in a full bridge configuration, and receives AC power output from the power receiving resonant circuit 20 and outputs DC power.

[0019] The filter 211 is, for example, a C filter configured with a capacitor, and attenuates high-frequency components contained in the voltage and current output from the rectifier circuit 210. Depending on the system configuration, a different filter configuration may be applied, such as an LC filter configured with a capacitor and a reactor. The load 5 is, for example, a motor that consumes power or a battery for storing electricity. Alternatively, the load may be configured to include a power converter for adjusting the voltage or current of the load.

[0020] The AC power supply 4 is a power supply that outputs a high-frequency current or voltage. It may include a power converter such as an inverter or a DC / DC converter, and the output waveform may be a waveform including multiple frequency components, such as a rectangular wave.

[0021] 1 , the power transmitter 1 of the contactless power transfer system 3 of the present application will be described in detail, assuming the basic configuration of the contactless power transfer system described above. The power transmitter 1 includes the above-described power transmitter resonant circuit 11, a resonance adjustment circuit 14 that is magnetically connected to the power transmitter resonant circuit 11 independently of the power receiving coil 200 and adjusts the resonance of the power transmitter resonant circuit 11, and a control device 13 that controls the operation of the resonance adjustment circuit 14. The power transmitter 1 also includes current detection means 12 that detects a current in a power transmitting side circuit, and the control device 13 controls the operation of the resonance adjustment circuit 14 in accordance with the detected current output from the current detection means 12.

[0022] 4 , the power transmitting coil 110 of the power transmitting resonance circuit 11 is composed of a main coil portion 110m that is magnetically coupled to the power receiving coil 200 and a sub-coil portion 110s that is not magnetically coupled to the power receiving coil 200 but is magnetically coupled to the circuit connection coil 140 of the resonance adjustment circuit 14. In other words, in the contactless power transfer system 3 of the present application, one power receiving device 2 (power receiving coil 200) and one resonance adjustment circuit 14 (circuit connection coil 140) are configured to be magnetically connected to different portions of one power transmitting coil 110.

[0023] Meanwhile, current detection means 12 is arranged in the circuit to detect the current flowing through the power transmitting coil 110, and the obtained current information is input to the control device 13. Based on the obtained current information, the control device 13 generates a control signal for controlling the resonance adjustment circuit 14. The power receiving device 2 and the resonance adjustment circuit 14 are in a state where they are not magnetically coupled to each other, or are in a state where they are very weakly coupled (for example, the coupling coefficient between the power transmitting coil 110 and the power receiving coil 200 is 0.01 or less).

[0024] This makes the resonance adjustment circuit 14 independent of the power receiving coil 200 and substantially magnetically coupled only with the power transmitting coil 110, preventing the system from becoming complicated. Also, the number of power receiving devices 2 and the number of resonance adjustment circuits 14 can be set independently. As a result, it becomes easy to accommodate system changes, such as changing from a system that supplies power to a single power receiving device 2 to a system that supplies power to multiple power receiving devices 2.

[0025] The resonance adjustment circuit 14 is composed of a circuit connection coil 140 that is magnetically coupled to the secondary coil portion 110s, and a variable capacitance circuit 145 that outputs a signal from the circuit connection coil 140 to the control device 13 and changes the capacitance of the capacitor based on a control signal from the control device 13. Furthermore, as shown in FIG. 5, it is provided with operation detection means 144 that detects the electrical operation of the circuit connection coil 140.

[0026] The variable capacitance circuit 145 is composed of a bidirectional switch 141 that can cut off current in both directions, and an adjustment capacitor 142 whose equivalent capacitance changes depending on the operation of the bidirectional switch 141. The bidirectional switch 141 and the adjustment capacitor 142 are connected in series to the circuit connection coil 140, and the bidirectional switch 141 and the adjustment capacitor 142 are connected in parallel with each other.

[0027] The bidirectional switch 141 is configured with, for example, two semiconductor switches 141 a and 141 b, and is configured to be able to interrupt current in both directions by connecting the two semiconductor switches 141 a and 141 b in series in opposite directions. The semiconductor switches 141 a and 141 b may be replaced with different configurations or different circuit components as long as they function as a bidirectional switch.

[0028] The operation detection means 144 is composed of a voltage detection means 144a that detects the voltage applied to the circuit connection coil 140, or a current detection means 144b that detects the current flowing through the circuit connection coil 140. The voltage detection means 144a and the current detection means 144b are installed so as to be able to detect the voltage applied to the circuit connection coil 140 and the current flowing through the circuit connection coil 140, respectively, and information on the detected voltage and current is input to the control device 13.

[0029] The drive signals for the semiconductor switches 141a and 141b are generated by the control device 13 based on current information for the power transmitting coil 110 and voltage and current information for the circuit connection coil 140. Note that, although both the voltage and current of the circuit connection coil 140 are detected and input to the control device 13 in Fig. 5, it is also possible to eliminate one of the detection means and generate the drive signals for the semiconductor switches 141a and 141b based on information on either the voltage or the current.

[0030] Next, we will explain the change in the current path in the variable capacitance circuit 145 when the resonance adjustment circuit 14 is in operation. The adjustment capacitor 142 is controlled to switch between a circuit connection state and a circuit cutoff state according to the voltage and current generated across the circuit connection coil 140 and the on / off states of the semiconductor switches 141a and 141b. By controlling the switching between the two states, the circuit connection state and the circuit cutoff state, it is possible to control the equivalent capacitor capacitance.

[0031] Fig. 6A shows the current path when the adjustment capacitor 142 is in a circuit connection state. In the circuit connection state, the current is interrupted by the bidirectional switch 141, and the adjustment capacitor 142 is connected to the power transmitting resonant circuit 11 via the circuit connection coil 140, affecting the adjustment capacitor 142 as a reactance element. Fig. 6B shows the current path when the adjustment capacitor 142 is in a disconnected state. In the disconnected state, both ends of the circuit connection coil 140 are short-circuited via the bidirectional switch 141, and the adjustment capacitor 142 is not connected to the power transmitting resonant circuit 11, so it does not function as a reactance element. In this way, by switching the connection state of the adjustment capacitor 142 by controlling the operation of the bidirectional switch 141, it is possible to change the magnitude of the reactance component magnetically coupled with the power transmitting coil 110.

[0032] 7 shows an example of operational waveforms in the resonance adjustment circuit 14 when switching between the two states, the circuit connected state and the circuit cutoff state, is controlled. In FIG. 7, the top row shows the outline of the current waveform (coil current I0) of the circuit connection coil 140 that is magnetically coupled to the sub-coil portion 110s of the power transmission coil 110. Moving downward, the diagram shows the outline of the waveform of the drive signal Sda of the semiconductor switch 141a, the waveform of the drive signal Sdb of the semiconductor switch 141b, and the voltage waveform (capacitor voltage V2) of the adjustment capacitor 142, in that order.

[0033] The current waveform of circuit connection coil 140 and the voltage waveform of adjustment capacitor 142 are positive in the directions indicated by the arrows in Figures 6A and 6B. The waveform example in Figure 7 is based on an assumed resonant system in which the current of power transmission coil 110 is a sine wave, and coil current I0 is depicted as a sine waveform. For drive signal Sda of semiconductor switch 141a and drive signal Sdb of semiconductor switch 141b, 1 represents the on state and 0 represents the off state.

[0034] The drive signals Sda and Sdb are synchronized with the current waveform of the circuit connection coil 140, and are output after adjusting the control phase αc so that the signal has the same frequency as the current waveform of the transmitting coil 110. The voltage waveform of the adjustment capacitor 142 includes a period during which the voltage is zero, and the length of this period during which the voltage is zero can be adjusted by controlling the phase relationship between the current waveform of the transmitting coil 110 and the drive signals Sda and Sdb of the semiconductor switches 141a and 141b.

[0035] The dashed line in the voltage waveform of the adjustment capacitor 142 represents the outline of the fundamental wave component Wf. Since the fundamental wave component Wf is determined by the length of the period during which the capacitor voltage V2 is zero, the capacitor voltage V2 can be controlled by controlling the length of the zero period. In other words, the effective value of the capacitance, which is the impedance component of the adjustment capacitor 142, can be adjusted.

[0036] The current of the power transmitting coil 110 in an ideal state (resonant state) is determined by design. For example, the ideal current value of the power transmitting coil 110 is determined based on the circuit constant of the power transmitting resonant circuit 11. The drive signals Sda and Sdb of the semiconductor switches 141a and 141b are determined by comparing the ideal current value of the power transmitting coil 110 with the current value of the power transmitting coil 110 obtained by the current detection means 12.

[0037] Specifically, when the current value of the power transmitting coil 110 obtained from the current detection means 12 is larger than the ideal current value (design value) of the power transmitting coil 110, the period during which the capacitor voltage V2 is 0 is reduced to reduce the current value of the power transmitting coil 110. On the other hand, when the current value of the power transmitting coil 110 obtained from the current detection means 12 is smaller than the design value, the period during which the capacitor voltage V2 is 0 is increased to increase the current value of the power transmitting coil 110. By controlling in this manner, the current of the power transmitting coil 110 can be kept constant, enabling stable operation.

[0038] In other words, the resonance state is grasped from the information within the power transmission device 1, and the resonance state of the magnetic coupling between the power transmission coil 110 and the power receiving coil 200 is optimized using the information within the power transmission device 1, thereby improving the efficiency of contactless power supply.

[0039] In the example of Figure 7, the drive signals Sda and Sdb of the semiconductor switches 141a and 141b are depicted as complementary signals, but there may be periods when both are on and periods when both are off, and the time ratio between on and off does not necessarily have to be 1:1.

[0040] As described above, according to the power transmitting device 1 of the first embodiment, the resonance adjustment circuit 14 is arranged so as to be magnetically coupled to the power transmitting coil 110, independently of the power receiving coil 200. Furthermore, since resonance adjustment is performed based on information about the current flowing through the power transmitting coil 110, it is possible to adjust the resonance state in accordance with the operation of the power transmitting resonance circuit 11. Furthermore, since the resonance adjustment circuit 14 is configured to be indirectly connected to the power transmitting coil 110, it is possible to prevent the resonance current flowing through the power transmitting coil 110 from flowing into the resonance adjustment circuit 14, thereby suppressing an increase in conduction loss associated with the resonance current. Furthermore, since this configuration does not require information about devices on the power receiving side, it is possible to easily accommodate an increase or decrease in the number or arrangement of power receiving devices 2.

[0041] Embodiment 2 In this embodiment 2, a voltage division compensation capacitor is added to the variable capacitance circuit described in embodiment 1. Fig. 8 is a circuit diagram corresponding to Fig. 5 of embodiment 1, illustrating an example of the configuration of a resonance adjustment circuit, for explaining the configuration and operation of a power transmission device constituting a contactless power transfer system according to embodiment 2. Note that apart from the addition of the voltage division compensation capacitor and the associated operation, the present embodiment is the same as embodiment 1, and therefore a description of the similar parts will be omitted, and Figs. 1 to 4 used in the description of embodiment 1 will be used.

[0042] 8, in the second embodiment, a voltage division compensation capacitor 143 is connected in series to the circuit connection coil 140. Therefore, the voltage generated across the circuit connection coil 140 is divided between the parallel circuit of the adjustment capacitor 142 and bidirectional switch 141, and the voltage division compensation capacitor 143. As in the first embodiment, by controlling the operation of the bidirectional switch 141, the adjustment capacitor 142 is switched between the circuit connection state and the circuit disconnection state, thereby changing the equivalent capacitance and adjusting the resonance.

[0043] In this case, what differs from the first embodiment is the voltage applied to the bidirectional switch 141 when the bidirectional switch 141 is off. Since the voltage division compensation capacitor 143 is always present in the current path flowing through the resonance adjustment circuit 14, the voltage applied to the bidirectional switch 141 is a value obtained by subtracting the voltage divided by the voltage division compensation capacitor 143 from the voltage generated across the circuit connection coil 140.

[0044] Therefore, compared to the configuration of embodiment 1, a lower voltage is applied to the semiconductor switches 141a and 141b that make up the bidirectional switch 141, and the voltage rating required for the semiconductor switches can also be lowered. MOS-FETs (Metal-Oxide-Semiconductor Field-Effect Transistors), which are commonly used semiconductor switches, have a trade-off between voltage rating and on-resistance, and by replacing them with semiconductor switches with a lower voltage rating, the on-resistance can be reduced, thereby reducing losses.

[0045] As described above, according to the power transmitting device 1 of the second embodiment, the resonance adjustment circuit 14 includes the voltage division compensation capacitor 143, and therefore the semiconductor switches 141 a and 141 b can be replaced with elements with a lower withstand voltage than when the same voltage is applied to the circuit connection coil 140. As a result, by using semiconductor switches with a small on-resistance, it is possible to reduce conduction loss, resulting in an improvement in efficiency.

[0046] In each of the above embodiments, the control device 13 may be configured with a processor 130 and a storage device 131, as shown in FIG. 9 , which is an example of hardware. The storage device is not shown, but may include a volatile storage device such as a random access memory and a non-volatile auxiliary storage device such as a flash memory. Alternatively, a hard disk auxiliary storage device may be used instead of the flash memory. The processor 130 executes a program input from the storage device 131. In this case, the program is input from the auxiliary storage device to the processor 130 via the volatile storage device. The processor 130 may output data such as calculation results to the volatile storage device of the storage device 131, or may store the data in the auxiliary storage device via the volatile storage device. The processor 130 may have a communication function, or may include a communication unit (not shown).

[0047] Although various exemplary embodiments and examples are described in this application, the various features, aspects, and functions described in one or more embodiments are not limited to the application of a particular embodiment, but may be applied to the embodiments alone or in various combinations. Therefore, countless variations not illustrated are contemplated within the scope of the technology disclosed in this specification. For example, this includes cases where at least one component is modified, added, or omitted, or where at least one component is extracted and combined with components of another embodiment.

[0048] For example, in Fig. 1, the AC power supply 4 is depicted so as to be interpreted as a system power supply separate from the power transmission device 1, but this is not limited thereto. In order to supply desired AC power to the power transmission resonant circuit 11, a power conversion device that converts an AC system power supply or a DC power supply into predetermined AC power may be used as the AC power supply 4. In other words, the AC power supply 4 may be used as a device that constitutes the power transmission device 1. Also, although an example in which the power receiving device 2 outputs DC to the load 5 has been described, this is not limited thereto and the power receiving device 2 may also output AC.

[0049] As described above, the power transmitter 1 of the present application is configured to include a power transmitter resonant circuit 11 having a power transmitter coil 110 for magnetically coupling with the power receiver coil 200 of the power receiver 2, converting power supplied from a power source (AC power source 4) into magnetic energy and transmitting the power to the power receiver 2 via the power transmitter coil 110, a circuit connection coil 140 that is magnetically coupled with the power transmitter coil 110 and arranged so as not to be magnetically coupled with the power receiver coil 200 even when the power transmitter coil 110 is magnetically coupled to the power receiver coil 200, a resonance adjustment circuit 14 having a variable capacitance circuit 145 connected in series with the circuit connection coil 140 and adjusting the capacitive reactance component of the power transmitter resonant circuit 11 via the circuit connection coil 140, and a control device 13 that controls the operation of the resonance adjustment circuit 14 in accordance with the resonance state between the power receiver coil 200 and the power transmitter coil 110. This allows the capacitive reactance component to be adjusted in a circuit on the power transmitter 1 side that is separate from the path through which the resonant current flows, thereby achieving both suppression of loss and cost increases.

[0050] The control device 13 controls the operation of the resonance adjustment circuit 14 based on at least one of the values ​​of the voltage applied to the circuit connection coil 140 and the current flowing through the circuit connection coil 140, and the current flowing through the transmission coil 110. Therefore, the resonance state can be maintained using only the information within the transmission device 1, and therefore costs can be reduced even when applied to a system having a reception device 2.

[0051] The control device 13 increases or decreases the reactance component of the resonance adjustment circuit 14 so that the current in the power transmission coil 110 becomes a predetermined value, so that the resonant state can be reliably maintained using only the information within the power transmission device 1 .

[0052] In this case, when the current in the transmission coil 110 is larger than a predetermined design value, the control device 13 reduces the current in the transmission coil 110 by increasing the reactance component of the resonance adjustment circuit 14, and when the current in the transmission coil 110 is smaller than the predetermined design value, the control device 13 increases the current in the transmission coil 110 by decreasing the reactance component of the resonance adjustment circuit 14, thereby more reliably maintaining the resonance state.

[0053] The variable capacitance circuit 145 is provided with a parallel circuit of an adjustment capacitor 142 and an open / close switch (bidirectional switch 141), and the control device 13 is configured to change the capacitive reactance component (of the power transmission resonant circuit 11) by controlling the opening and closing operation of the open / close switch (bidirectional switch 141), thereby making it possible to adjust the capacitive reactance component with a simple operation.

[0054] If the open / close switch is a bidirectional switch 141 made up of two semiconductor switches connected in series in opposite directions, it is possible to form an open / close switch that is easy to drive and control, has a low rated current, and has little loss.

[0055] If the variable capacitance circuit 145 is provided with a voltage division compensation capacitor 143 connected in series to the parallel circuit (of the adjustment capacitor 142 and the bidirectional switch 141), the voltage applied to the open / close switch (bidirectional switch 141) can be further reduced, allowing the use of an open / close switch with an even lower rated current and less loss.

[0056] The control device 13 operates the open / close switch (bidirectional switch 141) in synchronization with the current in the circuit connection coil 140, so that the capacitance of the adjustment capacitor 142 can be reliably changed while reducing switching loss.

[0057] Alternatively, the control device 13 can reliably change the capacitance of the adjustment capacitor 142 by operating the open / close switch (bidirectional switch 141) so that the current flowing through the transmission coil 110 matches the frequency.

[0058] Furthermore, the contactless power supply system 3 of the present application is configured to include the above-mentioned power transmission device 1 and one or more power receiving devices 2 that receive power from the power transmission device 1 contactlessly. Therefore, even if the power receiving devices 2 are replaced or increased or decreased, the capacitive reactance component can be adjusted in a circuit on the power transmission device 1 side that is separate from the path through which the resonant current flows, thereby making it possible to suppress both increases in loss and increases in costs.

[0059] 1: Power transmitting device, 11: Power transmitting resonance circuit, 110: Power transmitting coil, 110m: Main coil portion, 110s: Sub-coil portion, 12: Current detecting means, 13: Control device, 14: Resonance adjustment circuit, 140: Circuit connecting coil, 141: Bidirectional switch (open / close switch), 142: Adjustment capacitor, 143: Voltage division compensation capacitor, 145: Variable capacitance circuit, 2: Power receiving device, 20: Power receiving resonance circuit, 200: Power receiving coil, 21: Power receiving circuit, 3: Contactless power transfer system, 4: AC power supply (power supply), 5: Load.

Claims

1. a power transmitting resonant circuit having a power transmitting coil for magnetically coupling with a power receiving coil of a power receiving device, converting power supplied from a power source into magnetic energy, and transmitting the power to the power receiving device via the power transmitting coil; a circuit connection coil that is magnetically coupled to the power transmitting coil and that is arranged so as not to be magnetically coupled to the power receiving coil even when the power transmitting coil is magnetically coupled to the power receiving coil; and a resonance adjustment circuit that has a variable capacitance circuit that is connected in series to the circuit connection coil and adjusts a capacitive reactance component of the power transmitting resonance circuit via the circuit connection coil; a control device that controls an operation of the resonance adjustment circuit in accordance with a resonance state between the power receiving coil and the power transmitting coil; A power transmitting device comprising:

2. The power transmitting device according to claim 1, characterized in that the control device controls the operation of the resonant adjustment circuit based on at least one of the values ​​of the voltage applied to the circuit connection coil and the current flowing through the circuit connection coil and the current flowing through the power transmitting coil.

3. 3. The power transmitting device according to claim 1, wherein the control device controls an operation of the resonance adjustment circuit so that a current in the power transmitting coil becomes a predetermined value.

4. The power transmission device according to claim 3, characterized in that when the current in the power transmission coil is larger than a predetermined design value, the control device reduces the current in the power transmission coil by increasing the reactance component of the resonant adjustment circuit, and when the current in the power transmission coil is smaller than the predetermined design value, the control device increases the current in the power transmission coil by reducing the reactance component.

5. The variable capacitance circuit is provided with a parallel circuit of an adjustment capacitor and an open / close switch, 3. The power transmitting device according to claim 1, wherein the control device changes the capacitive reactance component by controlling an opening and closing operation of the opening and closing switch.

6. 6. The power transmitting device according to claim 5, wherein the open / close switch is a bidirectional switch including two semiconductor switches connected in series in opposite directions.

7. 6. The power transmitting device according to claim 5, wherein the variable capacitance circuit includes a voltage division compensation capacitor connected in series to the parallel circuit.

8. The power transmitting device according to claim 5 , wherein the control device operates the open / close switch in synchronization with a current in the circuit connection coil.

9. The power transmitting device according to claim 5 , wherein the control device operates the open / close switch so that a frequency of the current flowing through the power transmitting coil coincides with a frequency of the current flowing through the power transmitting coil.

10. The power transmitting device according to claim 1 or 2, one or more of the power receiving devices that receive power from the power transmitting device in a non-contact manner; A non-contact power supply system equipped with the above.