Non-contact power supply system

Abstract

A non-contact power supply system (10) comprises: a power supply device (20) that supplies power in a non-contact manner; and a power receiving device (30) that receives the power supplied from the power supply device (20) in a non-contact manner and supplies the power to a load (60). The power supply device (20) has a parallel resonance circuit (22) and a driving switch element (SW0) that are connected to a direct current power supply (50). The parallel resonance circuit (22) includes a first capacitor (C1) and a first coil (L1). The power receiving device (30) has: a series resonance circuit (32) that is composed of a second capacitor (C2) and a second coil (L2) that is magnetically coupled to the first coil (L1); and a rectifier circuit (33) that is connected to the series resonance circuit (32) and includes at least one rectifying switch element (SW1 to SW4) that rectifies alternating current power generated in the series resonance circuit (32).

Description

Contactless power supply system

[0001] The present disclosure relates to a contactless power supply system including a power supply device and a power receiving device.

[0002] Conventionally, various technologies have been proposed as contactless power supply systems configured with a power supply device and a power receiving device (for example, Patent Document 1, etc.). The technology in Patent Document 1 provides a power supply system during travel in which the power supply device determines whether a vehicle equipped with a power receiving device is located in an appropriate position for charging a battery, which is a load, and can start main power supply from the power supply device to the power receiving device without flowing unnecessary current that does not contribute to charging the battery.

[0003] Patent No. 7243450

[0004] However, in the technology of Patent Document 1, when a power receiving device passes over a power supply device, unless control is performed on the power supply device side based on feedback involving communication of information from the power receiving device to the power supply device, the power transmitted from the power supply device to the power receiving device becomes unstable, resulting in a problem that power cannot be supplied stably to the load.

[0005] Therefore, an object of the present disclosure is to provide a contactless power supply system that can stably supply power to a load without requiring feedback that involves communication from a power receiving device to a power supply device.

[0006] In order to achieve the above object, a contactless power supply system according to one embodiment of the present disclosure includes a power supply device that supplies power contactlessly, and a power receiving device that contactlessly receives the power supplied from the power supply device and supplies it to a load, wherein the power supply device has a parallel resonant circuit and a drive switch element connected to a DC power source, and the parallel resonant circuit includes a first capacitor and a first coil, and the power receiving device has a series resonant circuit configured with a second capacitor and a second coil magnetically coupled to the first coil, and a rectifier circuit connected to the series resonant circuit and including at least one rectification switch element that rectifies AC power generated in the series resonant circuit.

[0007] The present disclosure provides a contactless power supply system that can stably supply power to a load without requiring communication from a power receiving device to a power supply device.

[0008] FIG. 1 is a circuit block diagram showing the configuration of a contactless power transfer system according to an embodiment. FIG. 2A is a diagram illustrating the relationship between a coupling coefficient and output power in a contactless power transfer system according to a conventional technology. FIG. 2B is a diagram illustrating the relationship between a coupling coefficient and output power in a contactless power transfer system according to an embodiment. FIG. 3A is a diagram illustrating the relationship between the distance between a power transfer device and a power receiving device, and the coupling coefficient and output power when a contactless power transfer system according to a conventional technology is applied to a moving power transfer system. FIG. 3B is a diagram illustrating the relationship between the distance between a power transfer device and a power receiving device, and the coupling coefficient and output power when a contactless power transfer system according to an embodiment is applied to a moving power transfer system. FIG. 4A is a diagram illustrating power factor control in a contactless power transfer system according to an embodiment. FIG. 4B is a diagram illustrating the relationship between the phase difference between the current and the output voltage in power factor control in a power receiving device of a contactless power transfer system according to an embodiment and the transmitted power by the contactless power transfer system. FIG. 5 is a diagram illustrating feedback control in a power receiving device of a contactless power transfer system according to an embodiment. FIG. 6A is a diagram illustrating control of stopping power supply to a load by a contactless power transfer system according to an embodiment. Fig. 6B is a diagram showing an example of timing for turning off the cutoff switch element shown in Fig. 6A. Fig. 7 is a block diagram showing a configuration of a contactless power supply system according to a modified example of the embodiment, which is composed of one power supply device and multiple power receiving devices. Fig. 8 is a circuit diagram showing a configuration of a power supply device according to a modified example provided in the contactless power supply system according to the embodiment.

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that each embodiment described below represents a specific example of the present disclosure. The numerical values, shapes, materials, components, component arrangement and connection configurations, steps, and step order shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Furthermore, each figure is not necessarily an exact illustration. In each figure, substantially identical configurations are assigned the same reference numerals, and redundant explanations are omitted or simplified. Furthermore, "connection" means electrical connection, and includes not only cases where two circuit elements are directly connected, but also cases where two circuit elements are indirectly connected with another circuit element inserted between them.

[0010] 1 is a circuit block diagram showing the configuration of a contactless power supply system 10 according to an embodiment. The diagram also shows a DC power supply 50 and a load 60. The DC power supply 50 includes, for example, a power storage element or a power supply obtained by rectifying an AC power supply. The load 60 includes, for example, a power storage element or a motor inverter.

[0011] The contactless power supply system 10 is a system that can stably supply power to a load without requiring feedback using communication from a power receiving device to a power supply device, and is composed of a power supply device 20 that supplies power contactlessly, and a power receiving device 30 that contactlessly receives power supplied from the power supply device 20 and supplies it to a load 60.

[0012] The power supply device 20 is a high-frequency inverter having input terminals 21a and 21b connected to a DC power supply 50, a first coil L1 serving as a power supply coil connected to the DC power supply 50 via the input terminals 21a and 21b and magnetically coupled to a second coil L2 serving as a power receiving coil, a single-ended drive switch element SW0 connected in series to the first coil L1, and a first capacitor C1 serving as a power supply-side resonant capacitor connected in parallel to the first coil L1. In this embodiment, the power supply device 20 also has a smoothing capacitor C0. However, the smoothing capacitor C0 does not necessarily have to be provided in the power supply device 20.

[0013] The first capacitor C1 and the first coil L1 form a parallel resonant circuit 22.

[0014] The drive switch element SW0 is an element that switches at a predetermined frequency, and is, for example, an NMOS transistor connected to an oscillator.

[0015] The power receiving device 30 has a series resonant circuit 32, a rectifier circuit 33, output terminals 31 a and 31 b that supply DC power obtained by the rectifier circuit 33 to a load 60, and a control circuit 40 that controls the rectifier circuit 33. In this embodiment, the power receiving device 30 also has a smoothing capacitor C3. However, the smoothing capacitor C3 does not necessarily have to be provided in the power receiving device 30.

[0016] The series resonant circuit 32 is a series resonant circuit that resonates at a predetermined resonant frequency, and is composed of a second coil L2, which is a receiving coil that is magnetically coupled to the first coil L1 of the power supply device 20, and a second capacitor C2, which is a receiving-side resonant capacitor, connected in series.

[0017] The rectifier circuit 33 is connected to the series resonant circuit 32 and includes at least one rectifier switch element (four rectifier switch elements SW1 to SW4 in this embodiment) that rectifies the AC power generated in the series resonant circuit 32. Each of the rectifier switch elements SW1 to SW4 is, for example, an NMOS transistor, an IGBT (insulated gate bipolar transistor), or the like. In the contactless power transfer system 10 according to this embodiment, the rectifier circuit 33 is not formed of a diode or the like but is formed of at least one rectifier switch element (four rectifier switch elements SW1 to SW4 in this embodiment) that can be controlled by the control circuit 40. This makes it possible to stably supply power to a load without requiring communication from the power receiving device to the power transfer device.

[0018] The control circuit 40 is a circuit that adjusts the power supplied to the load 60 by controlling the rectification switch elements SW1 to SW4 to adjust the power factor and the like in the series resonant circuit 32, and is configured, for example, by a microcontroller or the like having a processor that executes a built-in program. The control circuit 40 controls the rectification switch elements SW1 to SW4 to adjust the power factor in the series resonant circuit 32, thereby not only adjusting the power transmitted from the power supply device 20 to the load 60 via the power receiving device 30, but also adjusting the power transmitted back from the power receiving device 30 to the power supply device 20.

[0019] Furthermore, when stopping the power supply to the load 60, the control circuit 40 operates (turns off) the cutoff switch elements such as the rectification switch elements SW1 to SW4 to cut off the current. Furthermore, the control circuit 40 can also control the output voltage, output current, or output power supplied to the load to be constant by feedback control in the power receiving device 30. Details will be described later using the drawings.

[0020] Next, the operation of the contactless power supply system 10 according to the present embodiment configured as described above will be described. First, in the contactless power supply system 10 according to the present embodiment, the power supply device 20 has a parallel resonant circuit 22, and the power receiving device 30 has a series resonant circuit 32. The significance of these features will be described with reference to FIGS. 2A to 3B.

[0021] 2A is a diagram illustrating the relationship between a coupling coefficient k and output power in a contactless power transfer system according to a conventional technique. FIG. 2B is a diagram illustrating the relationship between the coupling coefficient k and output power in a contactless power transfer system 10 according to an embodiment. Here, the coupling coefficient is the coupling coefficient between the power transfer coil and the power receiving coil. The output power is the output power of the contactless power transfer system (i.e., the power supplied by the power receiving device to the load).

[0022] More specifically, in Figures 2A and 2B, (a) in the figure is a diagram showing the equivalent circuit of the resonant circuit of the power supply device and the power receiving device that make up the contactless power supply system and the meaning of each symbol, and (b) in the figure is a flag that indicates the relationship between the coupling coefficient and the output voltage.

[0023] 2A(a), in a contactless power transfer system according to the related art, the resonant circuit included in the power transfer device is a series resonant circuit connected to an AC power supply that outputs an AC voltage of Vin, and is composed of a capacitor having a capacitance C1, a resistor having a resistance value r1, and a power transfer coil having an inductance L1, while the resonant circuit included in the power receiving device is a series resonant circuit that is composed of a capacitor having a capacitance C2, a resistor having a resistance value r2, and a power receiving coil having an inductance L2, and outputs a voltage Vo to a load with a resistance value Ro. Here, the coupling coefficient between the power transfer coil and the power receiving coil is denoted by k.

[0024] 2A(b) shows the relationship between the output power Po and the coupling coefficient k. In other words, as the coupling coefficient k approaches zero (k→0), the output power Po increases (Po→∞).

[0025] 2B(a), in the contactless power transfer system 10 according to the embodiment, the resonant circuit included in the power transfer device 20 is a parallel resonant circuit 22 connected to an AC power supply that outputs an AC voltage of Vin, and is configured as a parallel circuit of a capacitor having a capacitance C1, a resistor having a resistance value r1, and a power transfer coil having an inductance L1, while the resonant circuit included in the power receiving device 30 is a series resonant circuit 32 similar to that of the prior art. Furthermore, the coupling coefficient between the power transfer coil and the power receiving coil is k.

[0026] 2B(b) shows the relationship between the output power Po and the coupling coefficient k. In other words, contrary to the prior art, as the coupling coefficient k approaches zero (k→0), the output power Po decreases (Po→0).

[0027] 3A is a diagram illustrating the relationship between the distance between a power supply device and a power receiving device, the coupling coefficient, and the output power ("bridge power transmission characteristics") when a contactless power supply system according to the prior art is applied to a moving power supply system. FIG. 3B is a diagram illustrating the relationship between the distance between a power supply device 20 and a power receiving device 30, the coupling coefficient, and the output power ("single-ended power transmission characteristics") when a contactless power supply system 10 according to an embodiment is applied to a moving power supply system. More specifically, in FIGS. 3A and 3B, (a) is a graph showing the relationship between the distance (coil position) between the power supply device and the power receiving device, the coupling coefficient (coupling coefficient k; solid line; right vertical axis), and the output power (output power; dashed line; left vertical axis), and (b) is a diagram illustrating the distance (coil position) between the power supply device and the power receiving device in a moving power supply system.

[0028] Now, let us focus on the case where the distance between the power receiving device mounted on the vehicle and the power supply device installed under the floor starts small (i.e., the power receiving device is close to the power supply device) and then increases (i.e., the power receiving device is moving away from the power supply device).

[0029] In the conventional contactless power transfer system, as shown in (a) of Fig. 3A, when the distance between the power transfer device and the power receiving device increases from a small state, the coupling coefficient decreases (dashed line), but the output power increases (solid line) due to the relationship between the coupling coefficient and the output power shown in (b) of Fig. 2A. This creates a need for control so that the power transfer device does not transmit excessive power.

[0030] In contrast, in the contactless power supply system 10 according to the embodiment, as shown in (a) of Fig. 3B, when the distance between the power supply device 20 and the power receiving device 30 increases from a small state, the coupling coefficient decreases (dashed line), but the output power also decreases (solid line) according to the relationship between the coupling coefficient and output power shown in (b) of Fig. 2B. Therefore, when the power receiving device 30 passes by the power supply device 20 and moves away, there is no need to suppress power as in the conventional technology.

[0031] As described above, in the contactless power supply system 10 according to the embodiment, the power supply device 20 has the parallel resonant circuit 22, and therefore, contrary to the contactless power supply system according to the conventional technology, there is a unique relationship in which the output power decreases as the coupling coefficient decreases. As a result, the output power decreases as the distance between the power supply device 20 and the power receiving device 30 increases, and therefore, power can be stably supplied to the load 60 during power supply while traveling.

[0032] 2A to 3B have been described using an example of power supply while driving, the contactless power supply system 10 according to the embodiment can be applied not only to power supply while driving but also to other applications such as a contactless charger that charges electronic devices equipped with a battery, such as a smartphone, as will be described later.

[0033] 4A is a diagram illustrating power factor control in the contactless power transfer system 10 according to the embodiment. More specifically, (a) of FIG. 4A illustrates definitions of the current I2 flowing through the series resonant circuit 32 of the power receiving device 30, the output voltage V2 of the series resonant circuit 32, and the output voltage Vo of the power receiving device 30. (b) of FIG. 4A is a timing chart illustrating an example of signal waveforms and state changes at various points in the power receiving device 30. (b) of FIG. 4A illustrates the current I2 (b1) flowing through the series resonant circuit 32, the on / off states (b2) of the rectifying switch elements SW1 to SW4, the output voltage V2 (b3) of the series resonant circuit 32, and the current I2 flowing through the series resonant circuit 32 and the output voltage V2 (b4) of the series resonant circuit 32.

[0034] In the contactless power transfer system 10 according to the embodiment, for the purpose of power factor control, an ammeter for measuring the current I2 flowing through the series resonant circuit 32 may be inserted at the position marked with an asterisk in (a) of Fig. 4A to provide the power factor control, or a voltmeter for measuring the output voltage V2 of the series resonant circuit 32 may be provided at the position of the output voltage V2 in (a) of Fig. 4A. The measurement results of the ammeter or voltmeter are output to the control circuit 40, and the control circuit 40 performs power factor control.

[0035] In the timing chart shown in (b) of FIG. 4A, the control circuit 40 performs on / off control of the rectifier switch elements SW1 to SW4 (see (b2) of FIG. 4A) at a timing delayed by phase φ (approximately 40 degrees) from the zero crossing of the current I2 (see (b1) of FIG. 4A), thereby showing an example in which the output voltage V2 delayed by phase φ from the zero crossing of the current I2 appears with a swing width of +Vo and −Vo (see (b3) and (b4) of FIG. 4A).

[0036] The control circuit 40 detects the current I2 flowing through the series resonant circuit 32, or detects the output voltage V2 of the series resonant circuit 32, and controls the on / off timing of the rectifier switch elements SW1 to SW4 based on the phase of the detected current I2 or output voltage V2, thereby adjusting the phase difference between the current I2 and the output voltage V2, and as a result, adjusting the power factor in the series resonant circuit 32 and adjusting the power (i.e., active power) supplied from the power receiving device 30 to the load 60.

[0037] 4B is a diagram showing the relationship ("power receiving side control (voltage-current phase difference control)") between the phase difference φ between the current I2 and the output voltage V2 in power factor control in the power receiving device 30 of the contactless power transfer system 10 according to the embodiment and the transmitted power (received power) by the contactless power transfer system 10. The horizontal axis represents the phase difference φ between the current I2 and the output voltage V2, and the vertical axis represents the received power by the contactless power transfer system 10 (i.e., the active power supplied from the power receiving device 30 to the load 60).

[0038] As shown in Figure 4B, when the phase difference between the current I2 and the output voltage V2 is 0 degrees, the transmitted power is maximum, when the phase difference is 90 degrees the transmitted power is zero, and when the phase difference exceeds 90 degrees the transmitted power becomes a negative value, that is, power is transmitted backward from the power receiving device 30 to the power supply device 20.

[0039] As described above, according to the contactless power supply system 10 according to the embodiment, the control circuit 40 controls the on / off timing of the rectifying switch elements SW1 to SW4 to adjust the power factor in the series resonant circuit 32, and can adjust the transmission power supplied from the power receiving device 30 to the load 60, and can adjust the transmission power reversely transmitted from the power receiving device 30 to the power supply device 20. Furthermore, power factor control enables both current control and voltage control, and it is possible to adjust the voltage, current, or power supplied to the load 60, such as a storage element, without requiring feedback control involving communication from the power receiving device to the power supply device, which is required in conventional technology, and without having a DCDC converter on the output side.

[0040] Fig. 5 is a diagram illustrating feedback control in the power receiving device 30 of the contactless power transfer system 10 according to the embodiment. Fig. 5(a) shows an example in which the contactless power transfer system 10 supplies power to an inverter 61 that supplies AC power to a motor 62 as a load, and Fig. 5(b) shows an example in which the contactless power transfer system 10 supplies power with a constant current or voltage to a load 60.

[0041] As shown in (a) of FIG. 5, in the contactless power supply system 10 according to the embodiment, the control circuit 40 obtains feedback information about the voltage at the output terminals 31 a and 31 b and controls the rectifier circuit 33, thereby making it possible to supply a constant voltage to the inverter 61 without requiring a DCDC converter or the like for constant voltage control on the output side of the rectifier circuit 33.

[0042] Furthermore, as shown in (b) of FIG. 5, according to the contactless power supply system 10 of the embodiment, the control circuit 40 controls the rectifier circuit 33 by obtaining feedback information about the voltage at the output terminals 31 a and 31 b, or controls the rectifier circuit 33 by obtaining feedback information about the current value flowing through the output terminals 31 a and 31 b, thereby making it possible to supply a constant voltage or a constant current to the load 60 without requiring a DCDC converter or the like for constant voltage control or constant current control on the output side of the rectifier circuit 33.

[0043] In addition, a voltmeter may be provided to measure the voltage between the output terminals 31a and 31b in order to obtain feedback information about the voltage at the output terminals 31a and 31b, and an ammeter may be provided to measure the current flowing between the output terminals 31a and 31b in order to obtain feedback information about the current value flowing through the output terminals 31a and 31b.

[0044] As described above, according to the contactless power supply system 10 of the embodiment, the rectifier circuit 33 is configured with at least one rectification switch element SW1 to SW4. Therefore, the control circuit 40 controls the rectification switch elements SW1 to SW4 based on feedback information about the output voltage or the output current, and thereby, it is possible to stably supply power of a constant voltage or a constant current to the load without requiring communication for feedback from the power receiving device to the power supply device (in other words, while the power supply device continues to operate at a fixed frequency).

[0045] Although the constant voltage control or constant current control has been described as an example in FIG. 5, the output control by the control circuit 40 is not limited to these, and for example, constant power control may also be performed.

[0046] 6A is a diagram illustrating control of stopping power supply to a load 60 by a contactless power supply system 10 according to an embodiment. In the contactless power supply system 10, for control of stopping power supply to the load 60, (1) a first cutoff switch element SW5 (marked with a star in the figure) for cutting off the current flowing through the series resonant circuit 32 may be provided, or (2) a current flowing through a rectifier circuit 33 in which second cutoff switch elements SW6a to SW6d (marked with a star in the figure) are added to the rectifier elements constituting the rectifier circuit 33 may be cut off, the rectifier switch elements SW1 to SW4 constituting the rectifier circuit 33 may be configured as bidirectional switches, or when the rectifier switch elements SW1 to SW4 constituting the rectifier circuit 33 are switch elements such as IGBTs without parasitic diodes, each of the rectifier switch elements SW1 to SW4 may function as the second cutoff switch elements SW6a to SW6d (marked with a star in the figure) for cutting off the current flowing through the rectifier circuit 33. Alternatively, (3) a third cutoff switch element SW7 or SW8 (marked with a star in the drawing) for cutting off the current output from the rectifier circuit 33 may be provided.

[0047] The control circuit 40 may control the current to be interrupted by operating at least one of the first shutoff switch element SW5, the second shutoff switch elements SW6a to SW6d, and the third shutoff switch elements SW7 and SW8 when stopping the power supply to the load 60. Specifically, when stopping the power supply to the load 60, the control circuit 40 may (1) control the first shutoff switch element SW5 to be turned off, or (2) control the two second shutoff switch elements SW6a and SW6c connected to the positive output terminal 31a to be turned off, or (3) control the two second shutoff switch elements SW6b and SW6d connected to the negative output terminal 31b to be turned off, or (4) control the third shutoff switch element SW7 or SW8 to be turned off.

[0048] 6B is a diagram showing an example of the timing at which the shutoff switch elements SW5, SW6a to SW6d, and SW7 shown in FIG. 6A are shut off. As shown in this diagram, when the control circuit 40 stops the power supply to the load 60, it shuts off the current by turning off at least one of the first shutoff switch element SW5, the second shutoff switch elements SW6a to SW6d, and the third shutoff switch element SW7 at the timing of the zero crossing of the current I2 flowing through the series resonant circuit 32. Note that when shutting off SW8, there is no need to consider the timing at which it is shut off, and it may be shut off at any timing.

[0049] Fig. 7 is a block diagram showing the configuration of a contactless power supply system 10a according to a modified example of the embodiment, which is configured with one power supply device 20 and multiple power receiving devices 30 and 30a. In Fig. 7, the power supply device 20 is provided on the lower side of the figure, with an insulating plate 70 sandwiched between them, and the two power receiving devices 30 and 30a are provided on the upper side of the figure.

[0050] The power supply device 20 is a device that receives DC power from a DC power supply 50 and supplies the power in a wireless manner, and is identical to the power supply device 20 in Fig. 1. The power receiving device 30 is a device that receives the power supplied from the power supply device 20 in a wireless manner and supplies it to a load 60, and is identical to the power receiving device 30 in Fig. 1. The other power receiving device 30a is a device that receives the power supplied from the power supply device 20 in a wireless manner and supplies it to a load 60a, and is a power receiving device that has the same structure (power receiving coil L2a, etc.) as the power receiving device 30.

[0051] When the contactless power transfer system 10a is applied to an in-motion power transfer system, the insulating plate 70 corresponds to the floor or rails on which a vehicle equipped with a power receiving device travels, or when the contactless power transfer system 10a is applied to a contactless charger that charges an electronic device equipped with a battery, such as a smartphone, the insulating plate 70 corresponds to a housing that covers the power transfer device 20. Furthermore, the insulating plate 70 does not necessarily have to be present.

[0052] 7, two power receiving devices 30 and 30a simultaneously receive power from one power supply device 20 and supply power to loads. Even in such a contactless power supply system 10a, communication from the power receiving device 30 to the power supply device 20 is not required, and the power supply to the loads 60 and 60a can be controlled independently in each of the multiple power receiving devices 30 and 30a, thereby enabling a stable power supply to the loads.

[0053] Fig. 8 is a circuit diagram showing a configuration of a power supply device 20a according to a modified example provided in the contactless power supply system according to the embodiment. That is, the contactless power supply system according to the present disclosure may have the power supply device 20a shown in Fig. 8 instead of the power supply device 20 shown in Fig. 1.

[0054] 1 , the power supply device 20a according to the modified example shown in Fig. 8 is a high-frequency inverter having input terminals 21a and 21b connected to a DC power supply 50, a first coil L1 serving as a power supply coil connected to the DC power supply 50 via the input terminals 21a and 21b and magnetically coupled to a second coil L2 serving as a power receiving coil, a single-ended drive switch element SW0 connected in series to the first coil L1, and a first capacitor C1 serving as a power supply-side resonant capacitor connected in series to the first coil L1 and connected in parallel to the single-ended drive switch element SW0 to form a parallel resonant circuit. The circuit consisting of the first coil L1 and the first capacitor C1 is an example of a parallel resonant circuit 22a connected to the DC power supply 50.

[0055] Even in the contactless power supply system including the power supply device 20a according to the modified example shown in FIG. 8, the same effects as those of the contactless power supply system 10 according to the above embodiment can be achieved.

[0056] As described above, the contactless power supply system 10 according to the above embodiment includes the power supply device 20 that supplies power contactlessly, and the power receiving device 30 that contactlessly receives the power supplied from the power supply device 20 and supplies it to the load 60. The power supply device 20 has a parallel resonant circuit 22 and a drive switch element SW0 that are connected to a DC power supply 50. The parallel resonant circuit 22 includes a first capacitor C1 and a first coil L1. The power receiving device 30 has a series resonant circuit 32 that is configured with a second capacitor C2 and a second coil L2 that is magnetically coupled to the first coil L1, and a rectifier circuit 33 that is connected to the series resonant circuit 32 and includes at least one rectification switch element SW1 to SW4 that rectifies the AC power generated in the series resonant circuit 32.

[0057] As a result, the power supply side is configured with the parallel resonant circuit 22, the power receiving side is configured with the series resonant circuit 32, and the rectifier circuit 33 is configured with at least one rectifying switch element SW1 to SW4, thereby realizing the contactless power supply system 10 that can stably supply power to the load without requiring feedback involving communication from the power receiving device to the power supply device. Therefore, the circuit scale and implementation costs of the contactless power supply system 10 are suppressed, enabling miniaturization and cost reduction.

[0058] Here, the power receiving device 30 may further include at least one of a first shutoff switch element SW5 for shutting off the current flowing through the series resonant circuit 32, second shutoff switch elements SW6a to SW6d for shutting off the current flowing through the rectifier circuit 33, and a third shutoff switch element SW7 for shutting off the current output from the rectifier circuit 33, and a control circuit 40 that controls the operation of at least one of the first shutoff switch element SW5, the second shutoff switch elements SW6a to SW6d, and the third shutoff switch element SW7 to shut off the current when stopping the power supply to the load 60. This makes it possible to stop the power supply to the load 60 with simple control.

[0059] The power receiving device 30 may further include a control circuit 40 that adjusts the power supplied to the load 60 by controlling at least one of the rectifying switch elements SW1 to SW4 to adjust the power factor in the series resonant circuit 32. This enables power control of the power transmitted by the wireless power transfer system 10 through control in the power receiving device 30. Furthermore, power factor control enables current control and voltage control, and the power receiving device 30 can adjust the power supplied to the load 60 without having a DCDC converter. Furthermore, the control circuit 40 can also perform reverse power transmission from the power receiving device 30 to the power transfer device 20 by controlling at least one of the rectifying switch elements SW1 to SW4 to adjust the power factor in the series resonant circuit 32.

[0060] Furthermore, the contactless power supply system 10a according to the modified example includes, as power receiving devices, a plurality of power receiving devices 30 and 30a that contactlessly receive power supplied from the power supply device 20 and supply the power to a load. Since feedback involving communication from the power receiving device to the power supply device is not performed, the power supply side does not adjust the transmitted power according to the load. In other words, the plurality of power receiving devices 30 and 30a can independently control the power supply to the load, enabling a stable power supply.

[0061] While the contactless power supply system according to the present disclosure has been described above based on the embodiments and modifications, the present disclosure is not limited to these embodiments and modifications. As long as they do not deviate from the gist of the present disclosure, various modifications that a person skilled in the art could conceive of to the present embodiments and modifications, and other forms constructed by combining some of the components in the embodiments and modifications, are also included within the scope of the present disclosure.

[0062] For example, a contactless power supply system having the configuration for power factor control shown in FIG. 4A may be added with the configuration for power supply stop control shown in FIG. 6A , and further configured as one power supply device and multiple power receiving devices as shown in FIG. 7 .

[0063] In the above embodiment, the power supply device 20 includes one switch element (drive switch element SW0), but the power supply device 20 may include a switch element for other purposes as long as the power supply device 20 is a single-ended inverter having a parallel resonant circuit. For example, the power supply device 20 may include a switch element that turns on and off the power supply from the DC power supply 50.

[0064] Furthermore, in the above embodiment, the power supply coil L1 and the power receiving coil L2 are each a single coil, but they may be configured as a plurality of coils connected in series or in parallel.

[0065] INDUSTRIAL APPLICABILITY The contactless power supply system according to the present disclosure can be used as a power supply system for when the vehicle is moving, a contactless charger for charging an electronic device equipped with a battery such as a smartphone, and the like.

[0066] REFERENCE SIGNS LIST 10, 10a Wireless power supply system 20, 20a Power supply device 21a, 21b Input terminal 22, 22a Parallel resonant circuit 30, 30a Power receiving device 31a, 31b Output terminal 32 Series resonant circuit 33 Rectifier circuit 40 Control circuit 50 DC power supply 60, 60a Load 61 Inverter 62 Motor C0, C3 Smoothing capacitor C1 First capacitor (power supply side resonant capacitor), capacitance (example) C2 Second capacitor (power receiving side resonant capacitor), capacitance (example) L1 First coil (power supply coil), inductance (example) L2, L2a Second coil (power receiving coil), inductance (example) SW0 Drive switch element SW1 to SW4 Rectification switch elements SW5 First cutoff switch element SW6a to SW6d Second cutoff switch element SW7, SW8 Third cutoff switch element

Claims

1. A contactless power supply system comprising: a power supply device that supplies power contactlessly; and a power receiving device that contactlessly receives the power supplied from the power supply device and supplies it to a load, wherein the power supply device has a parallel resonant circuit and a drive switch element connected to a DC power source, the parallel resonant circuit including a first capacitor and a first coil, and the power receiving device has a series resonant circuit consisting of a second capacitor and a second coil magnetically coupled to the first coil, and a rectifier circuit connected to the series resonant circuit and including at least one rectification switch element that rectifies AC power generated in the series resonant circuit.

2. The contactless power supply system according to claim 1, wherein the power receiving device further comprises at least one of a first cutoff switch element for cutting off the current flowing through the series resonant circuit, a second cutoff switch element for cutting off the current flowing through the rectifier circuit, and a third cutoff switch element for cutting off the current output from the rectifier circuit, and a control circuit that, when power supply to the load is to be stopped, operates at least one of the first cutoff switch element, the second cutoff switch element, and the third cutoff switch element to cut off the current.

3. The contactless power transfer system according to claim 1, wherein the power receiving device further includes a control circuit that adjusts the power supplied to the load by controlling the at least one rectifying switch element to adjust the power factor in the series resonant circuit.

4. The contactless power supply system according to claim 3, wherein the power receiving device adjusts the power supplied to the load without having a DCDC converter.

5. The contactless power supply system according to claim 3, wherein the control circuit controls the at least one rectifying switch element to adjust the power factor in the series resonant circuit, thereby transmitting power from the power receiving device to the power supply device.

6. The contactless power supply system according to claim 1, wherein the power receiving device comprises a plurality of power receiving devices that contactlessly receive power supplied from the power supply device and supply the power to a load.

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