Non-contact power supply system

Abstract

The non-contact power supply system (10) includes a power supply device (20) that supplies power non-contactly and a power receiving device (30) that receives power non-contactly and supplies it to a load (60). The power supply device (20) has a parallel resonance circuit (22) and a drive switch element (SW0). The power receiving device (30) has a series resonance circuit (32), a rectifier circuit (33), and a control circuit (40). The control circuit (40) has a second mode in which the power supplied to the load (60) is adjusted by changing the duration of simultaneous turning-on over a plurality of cycles of the AC power generated in the series resonance circuit (32) for the second rectifier switch element (SW2) and the fourth rectifier switch element (SW4) constituting the rectifier circuit (33).

Description

Technical Field

[0001] The present disclosure relates to a non-contact power supply system composed of a power supply device and a power receiving device.

Background Art

[0002] Conventionally, various technologies have been proposed as non-contact power supply systems composed of a power supply device and a power receiving device (for example, Patent Document 1, etc.). According to the technology of Patent Document 1, in the power supply device, it is determined whether there is a vehicle equipped with a power receiving device at an appropriate position for charging the battery as a load, and the main power supply from the power supply device to the power receiving device can be started without flowing a wasteful current that does not contribute to charging the battery, thereby providing a traveling power supply system.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the technology of Patent Document 1, when the power receiving device passes over the power supply device, if the control on the power supply device side is not performed based on the feedback involving communication 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, and as a result, there is a problem that stable power cannot be supplied to the load.

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

Means for Solving the Problems

[0006] To achieve the above object, a contactless power supply system according to an aspect of the present disclosure is a contactless power supply system that supplies DC power to a load, and includes a power supply device that supplies power in a contactless manner, and a power receiving device that receives power supplied from the power supply device in a contactless manner and supplies it to the load. The power supply device has a parallel resonance circuit and a driving switch element connected to a DC power source. The parallel resonance circuit includes a first capacitor and a first coil. The power receiving device includes a series resonance circuit composed of a second capacitor and a second coil magnetically coupled to the first coil, and four rectifying switch elements, which are diodes or transistors that are connected to the series resonance circuit and rectify the alternating current generated in the series resonance circuit, and are bridge-connected to form a rectifying circuit that outputs a DC current to the load from a positive output terminal and a negative output terminal, and a control circuit that controls the rectifying circuit. The four rectifying switch elements include a first rectifying switch element connected between one end of the series resonance circuit and the positive output terminal, a second rectifying switch element connected between one end of the series resonance circuit and the negative output terminal, a third rectifying switch element connected between the other end of the series resonance circuit and the positive output terminal, and a fourth rectifying switch element connected between the other end of the series resonance circuit and the negative output terminal. Among the four rectifying switch elements, the second rectifying switch element and the fourth rectifying switch element are transistors. The control circuit changes the Among a plurality of periods T, continuous time for simultaneously turning on over a plurality of cycles the duty that is the ratio of Ton of the alternating current power generated in the series resonance circuit to adjust the power supplied to the load.

Advantages of the Invention

[0007] According to the present disclosure, there is provided a contactless power supply system that can stably supply power to a load without requiring feedback involving communication from the power receiving device to the power supply device.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2A

Figure 2B

Figure 3A

Figure 3B

Figure 4A

Figure 4B

Figure 5

Figure 6A

Figure 6B

Figure 7

Figure 8A

Figure 8B

Figure 9A

Figure 9B

Figure 10

Figure 11

Figure 12A

Figure 12B

Figure 13

Figure 14A

Figure 14B

Figure 15

Figure 16A

Figure 16B

Mode for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that all of the embodiments described below show specific examples of the present disclosure. The numerical values, circuit elements, arrangement positions and connection forms of electronic components, signal waveforms, timings, etc. shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Also, each figure is not necessarily drawn precisely. In each figure, substantially the same configuration is denoted by the same reference numeral, and overlapping descriptions are omitted or simplified. Further, "connection" means electrical connection, and includes not only the case where two circuit elements are directly connected, but also the case where two circuit elements are indirectly connected with other circuit elements inserted therebetween.

[0010] (Embodiment 1) Embodiment 1 is a non-contact power supply system composed of a power supply device and a power receiving device. In the rectifier circuit included in the power receiving device, two low-side rectifier switch elements among the four bridge-connected rectifier switch elements are constituted by transistors, and by controlling the on / off timings of these transistors, the power supplied to the load is adjusted, which is a feature.

[0011] FIG. 1 is a circuit block diagram showing the configuration of a non-contact power supply system 10 according to Embodiment 1. In this figure, a DC power supply 50 and a load 60 are also shown together. The DC power supply 50 includes, for example, a storage element or a power supply obtained by rectifying an AC power supply. The load 60 is, for example, a storage element, a motor inverter, or the like.

[0012] The non-contact power supply system 10 is a system that can stably supply power to a load without requiring feedback using communication from the power receiving device to the power supply device, and includes a power supply device 20 that supplies power non-contactly, and a power receiving device 30 that receives the power supplied from the power supply device 20 non-contactly and supplies it to the load 60.

[0013] The power feeding device 20 is a high-frequency inverter having input terminals 21a and 21b connected to a DC power source 50, a first coil L1 which is a power feeding coil connected to the DC power source 50 via the input terminals 21a and 21b and magnetically coupled to a second coil L2 which is a power receiving coil, a single-ended drive switch element SW0 connected in series to the first coil L1, and a first capacitor C1 which is a power feeding side resonance capacitor connected in parallel to the first coil L1. In this embodiment, the power feeding device 20 also has a smoothing capacitor C0. However, the smoothing capacitor C0 does not necessarily have to be provided in the power feeding device 20.

[0014] Also, the first capacitor C1 and the first coil L1 constitute a parallel resonance circuit 22.

[0015] The drive switch element SW0 is an element that switches at a predetermined frequency, for example, an NMOS transistor connected to an oscillator.

[0016] The power receiving device 30 has a series resonance circuit 32, a rectifier circuit 33, output terminals (a positive side output terminal 31a and a negative side output terminal 31b) for supplying the DC power obtained by the rectifier circuit 33 to a load 60, and a control circuit 40 for controlling 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.

[0017] The series resonance circuit 32 is a series resonance circuit that resonates at a predetermined resonance frequency, and is composed of a series connection of a second coil L2 which is a power receiving coil magnetically coupled to the first coil L1 of the power feeding device 20 and a second capacitor C2 as a power receiving side resonance capacitor.

[0018] The rectifier circuit 33 is connected to the series resonance circuit 32 and is configured by bridge-connecting four rectifying switch elements (SW1 to SW4) which are diodes or transistors that rectify the alternating current generated in the series resonance circuit 32, and outputs DC power to the load 60 from the positive output terminal 31a and the negative output terminal 31b. The four rectifying switch elements (SW1 to SW4) include a first rectifying switch element SW1 connected between one end of the series resonance circuit 32 and the positive output terminal 31a, a second rectifying switch element SW2 connected between one end of the series resonance circuit 32 and the negative output terminal 31b, a third rectifying switch element SW3 connected between the other end of the series resonance circuit 32 and the positive output terminal 31a, and a fourth rectifying switch element SW4 connected between the other end of the series resonance circuit 32 and the negative output terminal 31b.

[0019] In the present embodiment, among the four rectifying switch elements (SW1 to SW4), the first rectifying switch element SW1 and the third rectifying switch element SW3 are diodes, and the second rectifying switch element SW2 and the fourth rectifying switch element SW4 (that is, the two low-side rectifying switch elements) are transistors such as NMOS transistors and IGBTs (insulated gate bipolar transistors). In the present embodiment, the second rectifying switch element SW2 and the fourth rectifying switch element SW4 are NMOS transistors having parasitic diodes (that is, body diodes).

[0020] In the contactless power supply system 10 according to the present embodiment, among the rectifier circuit 33, the second rectifying switch element SW2 and the fourth rectifying switch element SW4 (that is, the two low-side rectifying switch elements) are configured by transistors that can be controlled by the control circuit 40, so that it is possible to stably supply power to the load without requiring feedback involving communication from the power receiving device 30 to the power supply device 20.

[0021] The control circuit 40 is a circuit that adjusts the power supplied from the power receiving device 30 to the load 60 by controlling the rectifier circuit 33, and is configured by, for example, a microcontroller having a processor that executes a built-in program. More specifically, the control circuit 40 controls the second rectifying switch element SW2 and the fourth rectifying switch element SW4 (that is, two low-side rectifying switch elements) to turn on and off based on the zero-cross point in the alternating current generated in the series resonance circuit 32. In particular, regarding the control of turning off from on, the control circuit 40 changes the time until the point of turning off from on based on the zero-cross point, thereby changing the duration during which the second rectifying switch element SW2 and the fourth rectifying switch element SW4 are simultaneously on, and has a first mode of adjusting the power supplied to the load 60.

[0022] Furthermore, the control circuit 40 has a second mode of adjusting the power supplied to the load 60 by changing the duration during which the second rectifying switch element SW2 and the fourth rectifying switch element SW4 are simultaneously on over a plurality of cycles of the alternating current generated in the series resonance circuit 32 (at other times, they are simultaneously turned off). Note that the control circuit 40 may operate in a mixed manner by switching between the first mode and the second mode, may operate only in the first mode, or may operate only in the second mode. Which operation to perform may be determined depending on a prior setting for the control circuit 40 or a control signal input to the control circuit 40 from the outside.

[0023] Note that in FIG. 1, illustration of measuring instruments for measuring voltages and currents at various locations in the power receiving device 30 is omitted. For example, (1) an ammeter connected in series with the second coil L2 to measure the current flowing through the second coil L2, (2) an ammeter connected in series with the positive output terminal 31a to measure the current output from the positive output terminal 31a, and (3) a voltmeter connected between the positive output terminal 31a and the negative output terminal 31b to measure the potential at the positive output terminal 31a with reference to the potential at the negative output terminal 31b are provided, and the values measured by these ammeters and voltmeters are input to the control circuit 40 and used for control in the control circuit 40.

[0024] 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 resonance circuit 22, and the power receiving device 30 has a series resonance circuit 32. The significance thereof will be described with reference to FIGS. 2A to 3B.

[0025] FIG. 2A is a diagram for explaining the relationship between the coupling coefficient (Coupling coefficient k) and the output power (Output power) in a contactless power supply system according to the prior art. FIG. 2B is a diagram for explaining the relationship between the coupling coefficient and the output power in the contactless power supply system 10 according to Embodiment 1. Here, the coupling coefficient is the coupling coefficient between the power supply coil and the power receiving coil. The output power is the output power of the contactless power supply system (that is, the power supplied by the power receiving device to the load).

[0026] More specifically, in FIGS. 2A and 2B, (a) of the figure is a diagram showing the equivalent circuit of the resonance circuits included in the power supply device and the power receiving device constituting the contactless power supply system and the meanings of the respective symbols, and (b) of the figure is a graph showing the relationship between the coupling coefficient and the output power.

[0027] In the contactless power supply system according to the prior art, as shown in FIG. 2A(a), the resonance circuit included in the power supply device is a series resonance circuit connected to an AC power supply that outputs an AC voltage Vin, and includes a capacitor having a capacitance C1, a resistor having a resistance value r1, and a power supply coil having an inductance L1. On the other hand, the resonance circuit included in the power receiving device is a series resonance circuit, and includes a capacitor having a capacitance C2, a resistor having a resistance value r2, and a power receiving coil having an inductance L2, and it is assumed that a voltage Vo is output to a load having a resistance value Ro. Here, let the coupling coefficient between the power supply coil and the power receiving coil be k.

[0028] Then, the relationship between the output power Po and the coupling coefficient k becomes the curve shown in Fig. 2A(b). That is, as the coupling coefficient k approaches zero (k→0), the output power Po increases (Po→∞).

[0029] On the other hand, in the non-contact power supply system 10 according to the present embodiment, as shown in Fig. 2B(a), the resonance circuit included in the power supply device 20 is a parallel resonance circuit 22 connected to an AC power supply that outputs an AC voltage Vin, and is composed of a parallel circuit of a capacitor having a capacitance C1, a resistor having a resistance value r1, and a power supply coil having an inductance L1. On the other hand, it is assumed that the resonance circuit included in the power receiving device 30 is a series resonance circuit 32 similar to the prior art. Also, let the coupling coefficient between the power supply coil and the power receiving coil be k.

[0030] Then, the relationship between the output power Po and the coupling coefficient k becomes the curve shown in Fig. 2B(b). That is, contrary to the prior art, as the coupling coefficient k approaches zero (k→0), the output power Po decreases (Po→0).

[0031] Fig. 3A is a diagram for explaining the relationship between the distance between the power supply device and the power receiving device, the coupling coefficient, and the output power ( "bridge power transmission characteristics") when the non-contact power supply system according to the prior art is applied to a traveling power supply system. Fig. 3B is a diagram for explaining the relationship between the distance between the power supply device 20 and the power receiving device 30, the coupling coefficient, and the output power ( "single-ended power transmission characteristics") when the non-contact power supply system 10 according to Embodiment 1 is applied to a traveling power supply system. More specifically, in Figs. 3A and 3B, (a) in the figure 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; broken line; left vertical axis), and (b) in the figure is a diagram for explaining the distance (Coil position) between the power supply device and the power receiving device in the traveling power supply system.

[0032] Now, focus on a case where the distance between the power receiving device mounted on the vehicle and the power feeding device provided under the floor is increasing (i.e., the power receiving device is moving away from the power feeding device) from a state where the distance is small (i.e., the power receiving device is close to the power feeding device).

[0033] Then, in the non-contact power feeding system according to the prior art, as shown in Fig. 3A(a), when the distance between the power feeding device and the power receiving device increases from a state where the distance is small, the coupling coefficient decreases (broken line). However, from the relationship between the coupling coefficient and the output power shown in Fig. 2A(b), the output power increases conversely (solid line). Therefore, it is necessary to perform control so that excessive power is not transmitted in the power feeding device.

[0034] On the other hand, in the non-contact power feeding system 10 according to the present embodiment, as shown in Fig. 3B(a), when the distance between the power feeding device 20 and the power receiving device 30 increases from a state where the distance is small, the coupling coefficient decreases (broken line). However, from the relationship between the coupling coefficient and the output power shown in Fig. 2B(b), the output power also decreases (solid line). Therefore, when the power receiving device 30 passes by the power feeding device 20 and moves away, it is not necessary to suppress power as in the prior art.

[0035] As described above, in the non-contact power feeding system 10 according to the present embodiment, since the power feeding device 20 has the parallel resonance circuit 22, contrary to the non-contact power feeding system according to the prior art, there is a unique relationship in which the output power decreases as the coupling coefficient decreases. As a result, as the distance between the power feeding device 20 and the power receiving device 30 increases, the output power decreases. Therefore, it is possible to stably supply power to the load 60 during traveling power feeding without the need for feedback involving communication from the power receiving device 30 to the power feeding device 20.

[0036] In addition, in Figs. 2A to 3B, traveling power feeding is described as an example. However, the non-contact power feeding system 10 according to the present embodiment can be applied not only to traveling power feeding but also to other applications such as a non-contact charger for charging an electronic device equipped with a battery such as a smartphone.

[0037] Next, the operation in the first mode by the non-contact power supply system 10 according to the present embodiment will be described. FIG. 4A is a timing chart showing the operation in the first mode by the non-contact power supply system 10 according to Embodiment 1. (a) to (e) in FIG. 4A show the current Ll2 flowing through the second coil L2, the control signal (gate-source voltage Vgs) given from the control circuit 40 to the second rectifying switch element SW2, the voltage across the second rectifying switch element SW2 (drain-source voltage Vds), the control signal (gate-source voltage Vgs) given from the control circuit 40 to the fourth rectifying switch element SW4, and the voltage across the fourth rectifying switch element SW4 (drain-source voltage Vds), respectively. Also, at the top of FIG. 4A, four periods (i), (iii), (ii), and (iv) that constitute one cycle of the current Ll2 flowing through the second coil L2 are shown.

[0038] In the first mode, when the control circuit 40 detects the zero-crossing point from the positive current to the negative current in the waveform of the current Ll2 (at the end of period (i)) (FIG. 4A(a)), it controls the second rectifying switch element SW2 to turn on from the off state until then (FIG. 4A(b)). As a result, the voltage across the second rectifying switch element SW2 becomes 0V from the voltage Vout (FIG. 4A(c)).

[0039] Subsequently, when a predetermined time δt (period (iii)) elapses from the zero-crossing point, the control circuit 40 controls the fourth rectifying switch element SW4 to turn off from the on state until then (FIG. 4A(d)). As a result, the voltage across the fourth rectifying switch element SW4 becomes the voltage Vout from 0V (FIG. 4A(e)).

[0040] Thereafter, when the control circuit 40 detects the zero-crossing point from the negative current to the positive current in the waveform of the current Ll2 (at the end of period (ii)) (FIG. 4A(a)), it controls the fourth rectifying switch element SW4 to turn on from the off state until then (FIG. 4A(d)). As a result, the voltage across the fourth rectifying switch element SW4 becomes 0V from the voltage Vout (FIG. 4A(e)).

[0041] Subsequently, when a predetermined time δt (period (iv)) elapses from the zero-crossing point, the control circuit 40 controls the second rectifying switch element SW2 to turn off from its previous on state (Fig. 4A (b)). As a result, the voltage across the second rectifying switch element SW2 changes from 0V to the voltage Vout (Fig. 4A (c)).

[0042] Taking such four periods (i) to (iv) as one cycle, the control circuit 40 repeats the on / off control for the second rectifying switch element SW2 and the fourth rectifying switch element SW4. In particular, when turning off the second rectifying switch element SW2 and the fourth rectifying switch element SW4 from on, the control circuit 40 performs control to delay by a predetermined time δt from the zero-crossing point in the waveform of the current Ll2.

[0043] When the period of the alternating current flowing through the second coil L2 is T, the duty of the predetermined time δt is Duty = δt / T. The control circuit 40 adjusts the duty to a value between 0 and 0.5 according to the magnitude of the power to be supplied to the load 60. For example, the control circuit 40 may change the duty according to the magnitude of the power required from the load 60, or may change the duty so that the potential at the positive output terminal 31a with reference to the potential at the negative output terminal 31b becomes constant.

[0044] Fig. 4B is a diagram showing the current path flowing through the power receiving device 30 in the operation in the first mode by the non-contact power supply system 10 according to the first embodiment. The thick arrows in Figs. 4B (a) to (d) respectively show the current paths flowing through the power receiving device 30 in periods (i), (iii), (ii), and (iv) in Fig. 4B.

[0045] As shown in Fig. 4B(a), in period (i), since the second rectifying switch element SW2 is off and the fourth rectifying switch element SW4 is on, current (or rather, power) is supplied from the fourth rectifying switch element SW4 to the load 60 through the second coil L2, the second capacitor C2, the first rectifying switch element SW1, and from the positive output terminal 31a.

[0046] As shown in Fig. 4B(b), in the subsequent period (iii), since the second rectifying switch element SW2 and the fourth rectifying switch element SW4 are both on at the same time, current refluxes in the current loop from the second rectifying switch element SW2 through the second capacitor C2, the second coil L2, and the fourth rectifying switch element SW4, and no current (or rather, power) is supplied from the positive output terminal 31a to the load 60.

[0047] As shown in Fig. 4B(c), in the subsequent period (ii), since the second rectifying switch element SW2 is on and the fourth rectifying switch element SW4 is off, current (or rather, power) is supplied from the second rectifying switch element SW2 to the load 60 through the second capacitor C2, the second coil L2, and the third rectifying switch element SW3, and from the positive output terminal 31a.

[0048] As shown in Fig. 4B(d), in the subsequent period (iv), since the second rectifying switch element SW2 and the fourth rectifying switch element SW4 are both on at the same time, current refluxes in the current loop from the fourth rectifying switch element SW4 through the second coil L2, the second capacitor C2, and the second rectifying switch element SW2, and no current (or rather, power) is supplied from the positive output terminal 31a to the load 60.

[0049] FIG. 5 is a diagram for explaining the adjustment of the received power (the power supplied from the power receiving device 30 to the load 60) in the first mode by the non-contact power supply system 10 according to the first embodiment. FIGS. 5(a) to 5(c) show examples of timing charts showing the operation of the power receiving device 30 when the predetermined time δt shown in FIG. 4A is changed (that is, the duty is changed), and FIG. 5(d) is a graph showing the relationship between the duty (horizontal axis; Duty) and the received power (vertical axis; Pout) when the predetermined time δt is changed. Note that in FIG. 5(d), the value of the received power (vertical axis; Pout) is the value when the DC voltage input from the DC power supply 50 to the non-contact power supply system 10 and the parameters of the circuit components constituting the non-contact power supply system 10 are under predetermined conditions.

[0050] As shown in FIG. 5(d), in the first mode, the control circuit 40 can control the received power from zero to the maximum value (about 1100 W) by adjusting the duty (Duty).

[0051] As described above, in the first mode of the first embodiment, the control circuit 40 changes the time from the on state to the off state of the second rectifying switch element SW2 and the fourth rectifying switch element SW4 with reference to the zero-crossing point of the alternating current generated in the series resonance circuit 32, thereby changing the duration during which the second rectifying switch element SW2 and the fourth rectifying switch element SW4 are simultaneously on. As a result, the power supplied to the load 60 can be adjusted without the need for feedback involving communication from the power receiving device 30 to the power supply device 20.

[0052] Next, the operation in the second mode by the non-contact power supply system 10 according to the present embodiment will be described. FIG. 6A is a timing chart showing the operation in the second mode by the non-contact power supply system 10 according to Embodiment 1. (a) to (e) in FIG. 6A correspond to (a) to (e) in FIG. 4A. In the second mode, the control circuit 40 changes the duration Ton (0 ≦ Ton ≦ T) during which the second rectifying switch element SW2 and the fourth rectifying switch element SW4 are simultaneously turned on over a plurality of periods among a plurality of periods T of the alternating current generated in the second coil L2 (note that the second rectifying switch element SW2 and the fourth rectifying switch element SW4 are simultaneously turned off during the time other than the duration Ton in the period T), thereby adjusting the power supplied from the power receiving device 30 to the load 60.

[0053] Note that the duty of the duration Ton is Duty = Ton / T. The control circuit 40 adjusts the duty to a value between zero and one according to the magnitude of the power to be supplied to the load 60. For example, the control circuit 40 may change the duty according to the magnitude of the power required from the load 60, or may change the duty so that the potential at the positive output terminal 31a with reference to the potential at the negative output terminal 31b becomes constant.

[0054] FIG. 6B is a diagram showing the current path flowing through the power receiving device 30 in the operation in the second mode by the non-contact power supply system 10 according to Embodiment 1. The thick solid lines in FIGS. 6B(a1) and 6B(a2) indicate the current path flowing through the power receiving device 30 in a state where the second rectifying switch element SW2 and the fourth rectifying switch element SW4 are simultaneously OFF (Full-OFF state). More specifically, in FIG. 6B(a1), current flows upward through the second coil L2 in the figure (that is, current flows from the parasitic diode of the fourth rectifying switch element SW4, through the second coil L2, the second capacitor C2, and the first rectifying switch element SW1), and current (in other words, power) is supplied from the positive output terminal 31a to the load 60. FIG. 6B(a2) shows a case where current flows downward through the second coil L2 in the figure (that is, current flows from the parasitic diode of the second rectifying switch element SW2, through the second capacitor C2, the second coil L2, and the third rectifying switch element SW3), and current (in other words, power) is supplied from the positive output terminal 31a to the load 60.

[0055] Also, the thick solid lines in FIGS. 6B(b1) and 6B(b2) indicate the current path flowing through the power receiving device 30 in a state where the second rectifying switch element SW2 and the fourth rectifying switch element SW4 are simultaneously ON (Full-ON state). More specifically, in FIG. 6B(b1), current flows downward through the second coil L2 in the figure (that is, current circulates in a current loop including the second rectifying switch element SW2, the second capacitor C2, the second coil L2, and the fourth rectifying switch element SW4), and current (in other words, power) is not supplied from the positive output terminal 31a to the load 60. FIG. 6B(b2) shows a case where current flows upward through the second coil L2 in the figure (that is, current circulates in a current loop including the fourth rectifying switch element SW4, the second coil L2, the second capacitor C2, and the second rectifying switch element SW2), and current (in other words, power) is not supplied from the positive output terminal 31a to the load 60.

[0056] FIG. 7 is a diagram for explaining the adjustment of the received power (the power supplied from the power receiving device 30 to the load 60) in the second mode by the non-contact power supply system 10 according to the first embodiment. Here, a graph showing the relationship between the duty (horizontal axis; Duty) when the duration Ton in FIG. 6A is changed (that is, the duty is changed) and the received power (vertical axis; Pout) is shown. In FIG. 7, the value of the received power (vertical axis; Pout) is a value calculated under the same predetermined conditions as when the received power in the first mode shown in FIG. 5(d) is calculated.

[0057] As shown in FIG. 7, also in the second mode, similar to the first mode, the control circuit 40 can control the received power from zero to the maximum value (about 1100 W) by adjusting the duty (Duty).

[0058] As described above, in the second mode of the first embodiment, the control circuit 40 changes the duration during which the second rectifying switch element SW2 and the fourth rectifying switch element SW4 are simultaneously turned on over a plurality of cycles of the alternating current generated in the series resonance circuit 32, so that the power supplied to the load 60 can be adjusted without requiring feedback involving communication from the power receiving device 30 to the power supply device 20.

[0059] FIG. 8A is a timing chart showing an operation example in which the non-contact power supply system 10 according to the first embodiment operates while switching between the first mode and the second mode. In the example shown in this figure, under the control of the control circuit 40, the non-contact power supply system 10 operates while alternately switching between the first mode and the full-ON state of the second mode.

[0060] When the period obtained by combining the period of the first mode and the duration Ton in the full-ON state of the second mode is defined as the period T, the duty (Duty) of the full-ON state of the second mode is Duty = Ton / T. The control circuit 40 can adjust the power supplied to the load 60 by changing the duty.

[0061] FIG. 8B is a timing chart showing another operation example in which the contactless power supply system 10 according to Embodiment 1 operates while switching between the first mode and the second mode. In the example shown in this figure, under the control of the control circuit 40, the contactless power supply system 10 first operates in the first mode, then operates in the Full-ON state of the second mode, then operates in the first mode again, and then operates while alternately switching between the Full-ON state and the Full-OFF state of the second mode.

[0062] As described above, in the first mode, within one cycle of the alternating current generated in the series resonance circuit 32, the second rectifying switch element SW2 and the fourth rectifying switch element SW4 are turned on and off, whereas in the second mode, the second rectifying switch element SW2 and the fourth rectifying switch element SW4 are turned on and off in units of a plurality of cycles of the alternating current generated in the series resonance circuit 32. Therefore, in the first mode, there is an advantage that the adjustment of the received power can be performed at a higher speed than in the second mode. Therefore, the control circuit 40 can select and operate in a suitable mode based on the requirement regarding the adjustment speed of the received power required for the contactless power supply system 10.

[0063] FIG. 9A is a circuit block diagram showing the configuration of a contactless power supply system 10a according to Modification 1 of Embodiment 1. The difference from Embodiment 1 is that the first rectifying switch element SW1 and the third rectifying switch element SW3 constituting the rectifying circuit 33a provided in the power receiving device 30a are constituted by transistors such as NMOS transistors instead of diodes. The control circuit 40 performs synchronous rectification control on the first rectifying switch element SW1 and the third rectifying switch element SW3 in addition to the control for the second rectifying switch element SW2 and the fourth rectifying switch element SW4 in Embodiment 1 (that is, the control in the first mode and the second mode).

[0064] FIG. 9B is a timing chart showing the operation of the non-contact power supply system 10a according to Modification 1 of Embodiment 1. Here, a timing chart when the non-contact power supply system 10a operates in the first mode is shown. (a) to (i) in FIG. 9B are, respectively, the current Ll2 flowing through the second coil L2, the control signal (gate-source voltage Vgs) given from the control circuit 40 to the second rectifying switch element SW2, the voltage across both ends of the second rectifying switch element SW2 (drain-source voltage Vds), the control signal (gate-source voltage Vgs) given from the control circuit 40 to the first rectifying switch element SW1, the voltage across both ends of the first rectifying switch element SW1 (drain-source voltage Vds), the control signal (gate-source voltage Vgs) given from the control circuit 40 to the fourth rectifying switch element SW4, the voltage across both ends of the fourth rectifying switch element SW4 (drain-source voltage Vds), the control signal (gate-source voltage Vgs) given from the control circuit 40 to the third rectifying switch element SW3, and the waveforms of the voltage across both ends of the third rectifying switch element SW3 (drain-source voltage Vds).

[0065] Among (a) to (i) in FIG. 9B, (a), (b), (c), (f), and (g) in FIG. 9B showing the timing charts of the second coil L2, the second rectifying switch element SW2, and the fourth rectifying switch element SW4 are the same as (a) to (e) in FIG. 4A in Embodiment 1, respectively.

[0066] In this modification, the first rectifying switch element SW1 (transistor) turns on and off at the same timing as the on and off of the first rectifying switch element SW1 (diode) shown in FIG. 4B in Embodiment 1 by synchronous rectification by the control circuit 40 (FIG. 9B (d) and (e)). Similarly, the third rectifying switch element SW3 (transistor) turns on and off at the same timing as the on and off of the third rectifying switch element SW3 (diode) shown in FIG. 4B in Embodiment 1 by synchronous rectification by the control circuit 40 (FIG. 9B (h) and (i)).

[0067] As described above, in this modified example, the first rectifying switch element SW1 and the third rectifying switch element SW3 that constitute the rectifying circuit 33a included in the power receiving device 30a are configured by transistors, and turn on and off at the same timing as the on and off of the corresponding diodes in the first embodiment. This is the same not only in the first mode but also in the second mode. In this modified example, since the first rectifying switch element SW1 and the third rectifying switch element SW3 are configured by transistors, the power losses in the first rectifying switch element SW1 and the third rectifying switch element SW3 are reduced compared to the first embodiment configured by diodes.

[0068] FIG. 10 is a circuit block diagram showing the configuration of a non-contact power feeding system 10b according to a second modified example of the first embodiment. In this modified example, in the rectifying circuit 33b included in the power receiving device 30b, two high-side rectifying switch elements (SW1 and SW3) out of the four rectifying switch elements (SW1 to SW4) connected in a bridge are configured by transistors, and the power supplied to the load is adjusted by controlling the on / off timing of these transistors.

[0069] More specifically, in this modified example, unlike the first embodiment, the first rectifying switch element SW1 and the third rectifying switch element SW3 (that is, the two high-side rectifying switch elements) that constitute the rectifying circuit 33b are configured by transistors (here, NMOS transistors having parasitic diodes), and the second rectifying switch element SW2 and the fourth rectifying switch element SW4 are configured by diodes instead of transistors. Then, instead of controlling the second rectifying switch element SW2 and the fourth rectifying switch element SW4 in the first embodiment, the control circuit 40 performs the same control as in the first embodiment (that is, the control in the first mode and the second mode) on the first rectifying switch element SW1 and the third rectifying switch element SW3.

[0070] Specifically, in the first mode, the control circuit 40 controls the first rectifying switch element SW1 and the third rectifying switch element SW3 (i.e., the two high-side rectifying switch elements) to be turned on and off based on the zero-crossing point of the alternating current generated in the series resonance circuit 32. In particular, for the control of turning off from on, by changing the time until the point of turning off from on based on the zero-crossing point, the duration during which the first rectifying switch element SW1 and the third rectifying switch element SW3 are simultaneously turned on is changed, thereby adjusting the power supplied to the load 60.

[0071] Also, in the second mode, the control circuit 40 adjusts the power supplied to the load 60 by changing the duration during which the first rectifying switch element SW1 and the third rectifying switch element SW3 (i.e., the two high-side rectifying switch elements) are simultaneously turned on over a plurality of cycles of the alternating current generated in the series resonance circuit 32 (and are simultaneously turned off at other times). Note that the control circuit 40 may operate in a mixed manner by switching between the first mode and the second mode, or may operate only in the first mode, or may operate only in the second mode. Which operation to perform may be determined depending on a prior setting for the control circuit 40 or a control signal input to the control circuit 40 from the outside.

[0072] Also, in this modification example as well, similar to Modification Example 1 of Embodiment 1, the second rectifying switch element SW2 and the fourth rectifying switch element SW4 that constitute the rectifying circuit 33b provided in the power receiving device 30b may be constituted by transistors such as NMOS transistors instead of diodes. In that case, in addition to the control for the first rectifying switch element SW1 and the third rectifying switch element SW3 (i.e., the two high-side rectifying switch elements) in Modification Example 2 (i.e., the control in the first mode and the second mode), the control circuit 40 performs synchronous rectification control on the second rectifying switch element SW2 and the fourth rectifying switch element SW4.

[0073] As described above, the contactless power supply system 10 according to Embodiment 1 is a contactless power supply system that supplies DC power to the load 60, and includes a power supply device 20 that supplies power in a contactless manner, and a power receiving device 30 that receives the power supplied from the power supply device 20 in a contactless manner and supplies it to the load 60. The power supply device 20 has a parallel resonance circuit 22 and a driving switch element SW0 connected to a DC power supply 50. The parallel resonance circuit 22 includes a first capacitor C1 and a first coil L1. The power receiving device 30 includes a series resonance circuit 32 composed of a second capacitor C2 and a second coil L2 magnetically coupled to the first coil L1, and four rectifying switch elements (SW1 to SW4), which are diodes or transistors that are connected to the series resonance circuit 32 and rectify the alternating current generated in the series resonance circuit 32, are bridge-connected. The power receiving device 30 also has a rectifying circuit 33 that outputs a DC current to the load 60 from a positive output terminal 31a and a negative output terminal 31b, and a control circuit 40 that controls the rectifying circuit 33. The four rectifying switch elements (SW1 to SW4) include a first rectifying switch element SW1 connected between one end of the series resonance circuit 32 and the positive output terminal 31a, a second rectifying switch element SW2 connected between one end of the series resonance circuit 32 and the negative output terminal 31b, a third rectifying switch element SW3 connected between the other end of the series resonance circuit 32 and the positive output terminal 31a, and a fourth rectifying switch element SW4 connected between the other end of the series resonance circuit 32 and the negative output terminal 31b. Among the four rectifying switch elements (SW1 to SW4), the second rectifying switch element SW2 and the fourth rectifying switch element SW4 are transistors. The control circuit 40 adjusts the power supplied to the load 60 by changing the duration of simultaneously turning on the second rectifying switch element SW2 and the fourth rectifying switch element SW4 over a plurality of cycles of the alternating power generated in the series resonance circuit 32.

[0074] As a result, (1) the power supply device 20 has a parallel resonance circuit 22, the power receiving device 30 has a series resonance circuit 32, and (2) in the power receiving device 30, the control circuit 40 controls the low-side second rectifying switch element SW2 and the fourth rectifying switch element SW4 constituting the rectifying circuit 33 in a second mode over a plurality of cycles of the AC power generated in the series resonance circuit 32. Thus, it is possible to adjust the power supplied to the load 60 and stably supply power to the load 60 without requiring feedback involving communication from the power receiving device 30 to the power supply device 20.

[0075] Here, among the four rectifying switch elements (SW1 to SW4), the first rectifying switch element SW1 and the third rectifying switch element SW3 may be diodes. As a result, the second mode is realized by simple switching control only for the two low-side rectifying switch elements (the second rectifying switch element SW2 and the fourth rectifying switch element SW4) among the four rectifying switch elements (SW1 to SW4) constituting the rectifying circuit 33.

[0076] Moreover, the non-contact power supply system 10b according to Modification Example 2 of Embodiment 1 is a non-contact power supply system that supplies DC power to the load 60, and includes a power supply device 20 that supplies power non-contact and a power receiving device 30 that receives the power supplied from the power supply device 20 non-contact and supplies it to the load 60. The power supply device 20 has a parallel resonance circuit 22 and a driving switch element SW0 connected to a DC power supply 50. The parallel resonance circuit 22 includes a first capacitor C1 and a first coil L1. The power receiving device 30 includes a series resonance circuit 32 composed of a second capacitor C2 and a second coil L2 magnetically coupled to the first coil L1, and four rectifying switch elements (SW1 to SW4), which are diodes or transistors that are connected to the series resonance circuit 32 and rectify the alternating current generated in the series resonance circuit 32, are bridge-connected. The rectifying circuit 33 outputs a DC current to the load 60 from the positive output terminal 31a and the negative output terminal 31b, and has a control circuit 40 that controls the rectifying circuit 33. The four rectifying switch elements (SW1 to SW4) include a first rectifying switch element SW1 connected between one end of the series resonance circuit 32 and the positive output terminal 31a, a second rectifying switch element SW2 connected between one end of the series resonance circuit 32 and the negative output terminal 31b, a third rectifying switch element SW3 connected between the other end of the series resonance circuit 32 and the positive output terminal 31a, and a fourth rectifying switch element SW4 connected between the other end of the series resonance circuit 32 and the negative output terminal 31b. Among the four rectifying switch elements (SW1 to SW4), the first rectifying switch element SW1 and the third rectifying switch element SW3 are transistors. The control circuit 40 adjusts the power supplied to the load 60 by changing the duration of simultaneously turning on the first rectifying switch element SW1 and the third rectifying switch element SW3 over a plurality of cycles of the alternating power generated in the series resonance circuit 32.

[0077] As a result, (1) the power supply device 20 has a parallel resonance circuit 22, and the power receiving device 30b has a series resonance circuit 32, and (2) in the power receiving device 30b, the control circuit 40 controls the high-side first rectifying switch element SW1 and the third rectifying switch element SW3 constituting the rectifying circuit 33b in a second mode over a plurality of cycles of the AC power generated in the series resonance circuit 32. Therefore, it is possible to adjust the power supplied to the load 60 and stably supply power to the load 60 without requiring feedback involving communication from the power receiving device 30b to the power supply device 20.

[0078] Here, among the four rectifying switch elements (SW1 to SW4), the second rectifying switch element SW2 and the fourth rectifying switch element SW4 may be diodes. As a result, the second mode is realized by simple switching control only for the two high-side rectifying switch elements (the first rectifying switch element SW1 and the third rectifying switch element SW3) among the four rectifying switch elements (SW1 to SW4) constituting the rectifying circuit 33b.

[0079] Also, like the non-contact power supply system 10a according to Modification 1 of Embodiment 1, all of the four rectifying switch elements (SW1 to SW4) may be transistors. As a result, the rectifying circuit 33a is composed of four transistors corresponding to a full bridge, and has the same circuit configuration as a synchronous rectification type.

[0080] (Embodiment 2) Embodiment 2 is a non-contact power supply system composed of a power supply device and a power receiving device. The rectifying circuit included in the power receiving device constitutes a half-wave rectifying circuit. Among the two rectifying switch elements constituting the half-wave rectifying circuit, the rectifying switch element connected to both ends of the series resonance circuit is composed of a transistor, and the on / off timing of the transistor is controlled to adjust the power supplied to the load.

[0081] FIG. 11 is a circuit block diagram showing the configuration of the non-contact power supply system 10c according to Embodiment 2. The non-contact power supply system 10c according to the present embodiment includes a power supply device 20 and a power receiving device 30c, and basically has the same configuration as the non-contact power supply system 10 according to Embodiment 1. However, in the present embodiment, in the rectifier circuit 33c which is a half-wave rectifier circuit included in the power receiving device 30c, among the two rectifying switch elements (SW5 and SW6) constituting the half-wave rectifier circuit, the fifth rectifying switch element SW5 connected to both ends of the series resonance circuit 32 is constituted by a transistor (here, an NMOS transistor having a parasitic diode), and the other sixth rectifying switch element SW6 is constituted by a diode.

[0082] Then, instead of controlling the second rectifying switch element SW2 and the fourth rectifying switch element SW4 in Embodiment 1, the control circuit 40 included in the power receiving device 30c performs the same control as in Embodiment 1 (that is, control in the first mode and the second mode) on the fifth rectifying switch element SW5.

[0083] More specifically, in the first mode, the control circuit 40 changes the time until the turn-off point with respect to the fifth rectifying switch element SW5 based on the zero-cross point in the alternating current generated in the series resonance circuit 32, thereby changing the duration of the current reflux in the current loop passing through the fifth rectifying switch element SW5 and the series resonance circuit 32, and thereby adjusting the power supplied to the load 60.

[0084] In the second mode, the control circuit 40 changes the duration of turning on simultaneously over a plurality of cycles in the alternating current generated in the series resonance circuit 32 with respect to the fifth rectifying switch element SW5 (and turns off simultaneously at other times), thereby adjusting the power supplied to the load 60. Note that the control circuit 40 may operate in a mixed manner by switching between the first mode and the second mode, may operate only in the first mode, or may operate only in the second mode. Which operation to perform may be determined depending on the prior setting for the control circuit 40 or a control signal input to the control circuit 40 from the outside.

[0085] Figure 12A is a timing chart showing the operation in the first mode by the non-contact power supply system 10c according to Embodiment 2. (a) to (c) of Figure 12A show the waveforms of the current Ll2 flowing through the second coil L2, the control signal (gate-source voltage Vgs) given from the control circuit 40 to the fifth rectifying switch element SW5, and the voltage across both ends of the fifth rectifying switch element SW5 (drain-source voltage Vds), respectively. Also, at the top of Figure 12A, three periods (i), (ii), and (iii) constituting one cycle of the current Ll2 flowing through the second coil L2 are shown.

[0086] In the first mode, when the control circuit 40 detects the zero-crossing point from the positive current to the negative current in the waveform of the current Ll2 (at the end of period (i)) in Figure 12A(a), the control circuit 40 controls the fifth rectifying switch element SW5 to turn on from the off state until then (Figure 12A(b)). As a result, the voltage across both ends of the fifth rectifying switch element SW5 becomes 0V from the voltage Vout and continues in period (ii) (Figure 12A(c)).

[0087] Subsequently, when the control circuit 40 detects the zero-crossing point from the negative current to the positive current in the waveform of the current Ll2 (at the end of period (ii)) in Figure 12A(a), and when a predetermined time δt (period (iii)) has elapsed from that zero-crossing point, the control circuit 40 controls the fifth rectifying switch element SW5 to turn off from the on state until then (Figure 12A(b)). As a result, the voltage across both ends of the fifth rectifying switch element SW5 becomes from 0V to the voltage Vout (Figure 12A(c)).

[0088] Taking such three periods (i) to (iii) as one cycle, the control circuit 40 repeats the on-off control for the fifth rectifying switch element SW5. In particular, when turning off the fifth rectifying switch element SW5 from the on state, the control circuit 40 performs control to delay by a predetermined time δt from the zero-crossing point in the waveform of the current Ll2.

[0089] When the period of the alternating current flowing through the second coil L2 is T, the duty of a predetermined time δt is Duty = δt / T. The control circuit 40 adjusts the duty to a value between zero and 0.5, inclusive, according to the magnitude of the power to be supplied to the load 60. For example, the control circuit 40 may change the duty according to the magnitude of the power required by the load 60, or may change the duty so that the potential at the positive output terminal 31a with reference to the potential at the negative output terminal 31b becomes constant.

[0090] FIG. 12B is a diagram showing the current path flowing through the power receiving device 30c in the operation in the first mode by the non-contact power supply system 10c according to Embodiment 2. The thick arrow lines in FIGS. 12B(a) to 12B(c) respectively show the current paths flowing through the power receiving device 30c during periods (i), (ii), and (iii) in FIG. 12B.

[0091] As shown in FIG. 12B(a), in period (i), since the fifth rectifying switch element SW5 is off, current (in other words, power) is supplied from the positive output terminal 31a to the load 60 through the second coil L2, the second capacitor C2, and the sixth rectifying switch element SW6.

[0092] As shown in FIG. 12B(b), in the subsequent period (ii), the direction of the current flowing through the second coil L2 is reversed and the fifth rectifying switch element SW5 is turned on, so current flows back through the current loop passing through the second coil L2, the second capacitor C2, and the fifth rectifying switch element SW5, and no current (in other words, power) is supplied from the positive output terminal 31a to the load 60.

[0093] As shown in FIG. 12B(c), in the subsequent period (iii), the direction of the current flowing through the second coil L2 is reversed, but since the fifth rectifying switch element SW5 remains on, current flows back through the current loop passing through the second capacitor C2, the second coil L2, and the fifth rectifying switch element SW5, and no current (in other words, power) is supplied from the positive output terminal 31a to the load 60.

[0094] FIG. 13 is a diagram for explaining the adjustment of the received power (the power supplied from the power receiving device 30c to the load 60) in the first mode by the non-contact power supply system 10c according to the second embodiment. FIGS. 13(a) to 13(c) show examples of timing charts showing the operations of the power receiving device 30c when the predetermined time δt shown in FIG. 12A is changed (that is, the duty is changed), and FIG. 13(d) is a graph showing the relationship between the duty (horizontal axis; Duty) and the received power (vertical axis; Pout) when the predetermined time δt is changed.

[0095] Note that in FIG. 13(d), the value of the received power (vertical axis; Pout) is a value calculated under the same predetermined conditions as when calculating the received power in the first mode shown in FIG. 5(d) in the first embodiment. As can be seen by comparing FIG. 13(d) with FIG. 5(d), in the second embodiment, the maximum value of the received power is half that in the first embodiment.

[0096] As shown in FIG. 13(d), in the first mode, the control circuit 40 can control the received power from zero to the maximum value (about 550 W) by adjusting the duty (Duty).

[0097] As described above, in the first mode of the second embodiment, the control circuit 40 changes the time until the fifth rectifying switch element SW5 is turned off with reference to the zero-crossing point of the alternating current generated in the series resonance circuit 32 with respect to the fifth rectifying switch element SW5, thereby changing the time during which the current refluxes in the current loop passing through the fifth rectifying switch element SW5 and the series resonance circuit 32. As a result, the power supplied to the load 60 can be adjusted without requiring feedback involving communication from the power receiving device 30c to the power supply device 20.

[0098] Next, the operation in the second mode by the non-contact power supply system 10c according to the present embodiment will be described. FIG. 14A is a timing chart showing the operation in the second mode by the non-contact power supply system 10c according to Embodiment 2. (a) to (c) in FIG. 14A correspond to (a) to (c) in FIG. 12A. In the second mode, the control circuit 40 changes the duration Ton (0 ≦ Ton ≦ T) during which the fifth rectifying switch element SW5 is turned on over a plurality of periods among a plurality of periods T of the alternating current generated in the second coil L2 (note that the fifth rectifying switch element SW5 is turned off during the time other than the duration Ton in the period T), thereby adjusting the power supplied from the power receiving device 30c to the load 60.

[0099] Note that the duty of the duration Ton is Duty = Ton / T. The control circuit 40 adjusts the duty to a value between zero and one according to the magnitude of the power to be supplied to the load 60. For example, the control circuit 40 may change the duty according to the magnitude of the power required from the load 60, or may change the duty so that the potential at the positive output terminal 31a with reference to the potential at the negative output terminal 31b becomes constant.

[0100] FIG. 14B is a diagram showing the current path flowing through the power receiving device 30c in the operation in the second mode by the non-contact power supply system 10c according to Embodiment 2. The thick arrows in FIGS. 14B(a1) and (a2) indicate the current path flowing through the power receiving device 30c in a state where the fifth rectifying switch element SW5 is off (Full-OFF state). More specifically, in FIG. 14B(a1), current flows upward through the second coil L2 in the figure (that is, current flows from the second coil L2 to the second capacitor C2 and the sixth rectifying switch element SW6), and current (in other words, power) is supplied from the positive output terminal 31a to the load 60. FIG. 14B(a2) shows a case where current flows downward through the second coil L2 in the figure (that is, current refluxes in a current loop including the second capacitor C2, the second coil L2, and the parasitic diode of the fifth rectifying switch element SW5), and current (in other words, power) is not supplied from the positive output terminal 31a to the load 60.

[0101] Also, the thick arrows in FIGS. 14B(b1) and (b2) indicate the current path flowing through the power receiving device 30c in a state where the fifth rectifying switch element SW5 is on (Full-ON state). More specifically, in FIG. 14B(b1), current flows upward through the second coil L2 in the figure (that is, current refluxes in a current loop including the fifth rectifying switch element SW5, the second capacitor C2, and the second coil L2), and current (in other words, power) is not supplied from the positive output terminal 31a to the load 60. FIG. 14B(b2) shows a case where current flows downward through the second coil L2 in the figure (that is, current refluxes in a current loop including the second coil L2, the second capacitor C2, and the fifth rectifying switch element SW5), and current (in other words, power) is not supplied from the positive output terminal 31a to the load 60.

[0102] FIG. 15 is a diagram for explaining the adjustment of the received power (the power supplied from the power receiving device 30c to the load 60) in the second mode by the non-contact power supply system 10c according to Embodiment 2. Here, a graph showing the relationship between the duty (horizontal axis; Duty) when the duration Ton in FIG. 14A is changed (that is, the duty is changed) and the received power (vertical axis; Pout) is shown.

[0103] Note that in FIG. 15, the value of the received power (vertical axis; Pout) is a value calculated under the same predetermined conditions as when calculating the received power in the second mode shown in FIG. 7 in Embodiment 1. As can be seen by comparing FIG. 15 and FIG. 7, also in the second mode, similar to the first mode, in Embodiment 2, the maximum value of the received power is half that in Embodiment 1.

[0104] As shown in FIG. 15, also in the second mode, similar to the first mode, the control circuit 40 can control the received power from zero to the maximum value (about 550 W) by adjusting the duty (Duty).

[0105] As described above, in the second mode of Embodiment 2, the control circuit 40 changes the duration for turning on the fifth rectifying switch element SW5 over a plurality of cycles of the alternating current generated in the series resonance circuit 32, thereby changing the time during which the current refluxes in the current loop passing through the fifth rectifying switch element SW5 and the series resonance circuit 32. As a result, without the need for feedback involving communication from the power receiving device 30c to the power supply device 20, the power supplied to the load 60 can be adjusted.

[0106] Note that the contactless power supply system 10c according to Embodiment 2 may operate while switching between the first mode and the second mode, similar to Embodiment 1. For example, under the control of the control circuit 40, the contactless power supply system 10c may operate while alternately switching between the first mode and the full-ON state of the second mode. Also, under the control of the control circuit 40, the contactless power supply system 10c may first operate in the first mode, then operate in the full-ON state of the second mode, then operate in the first mode again, and then operate while alternately switching between the full-ON state and the full-OFF state of the second mode.

[0107] In the first mode, within one cycle of the alternating current generated in the series resonance circuit 32, the fifth rectifying switch element SW5 turns on and off, while in the second mode, the fifth rectifying switch element SW5 turns on and off in units of a plurality of cycles of the alternating current generated in the series resonance circuit 32. Therefore, the first mode has the advantage that the received power can be adjusted at a higher speed compared to the second mode. Thus, the control circuit 40 can select and operate in a suitable mode based on the requirements regarding the adjustment speed of the received power required for the contactless power supply system 10c.

[0108] FIG. 16A is a circuit block diagram showing the configuration of a contactless power supply system 10d according to Modification 1 of Embodiment 2. The difference from Embodiment 2 is that the sixth rectifying switch element SW6 constituting the rectifying circuit 33d provided in the power receiving device 30d is constituted by a transistor such as an NMOS transistor instead of a diode. The control circuit 40 performs synchronous rectification control on the sixth rectifying switch element SW6 in addition to the control on the fifth rectifying switch element SW5 in Embodiment 2 (that is, the control in the first mode and the second mode).

[0109] FIG. 16B is a timing chart showing the operation of the non-contact power feeding system 10d according to Modification 1 of Embodiment 2. Here, a timing chart when the non-contact power feeding system 10d operates in the first mode is shown. (a) to (e) of FIG. 16B show waveforms of the current Ll2 flowing through the second coil L2, the control signal (gate-source voltage Vgs) given from the control circuit 40 to the fifth rectifying switch element SW5, the voltage across both ends of the fifth rectifying switch element SW5 (drain-source voltage Vds), the control signal (gate-source voltage Vgs) given from the control circuit 40 to the sixth rectifying switch element SW6, and the voltage across both ends of the sixth rectifying switch element SW6 (drain-source voltage Vds), respectively.

[0110] Among (a) to (e) of FIG. 16B, (a), (b), and (c) of FIG. 16B showing the timing charts of the second coil L2 and the fifth rectifying switch element SW5 are the same as (a) to (c) of FIG. 12A in Embodiment 2, respectively.

[0111] In this modification, the sixth rectifying switch element SW6 (transistor) of the power receiving device 30d turns on and off at the same timing as the on and off of the sixth rectifying switch element SW6 (diode) shown in FIG. 12B of Embodiment 2 by synchronous rectification by the control circuit 40 (FIG. 16B (d) and (e)).

[0112] As described above, in this modification, the sixth rectifying switch element SW6 constituting the rectifying circuit 33d provided in the power receiving device 30d is composed of a transistor and turns on and off at the same timing as the on and off of the corresponding diode in Embodiment 2. This is the same not only in the first mode but also in the second mode. In this modification, since the sixth rectifying switch element SW6 is composed of a transistor, the power loss in the sixth rectifying switch element SW6 is reduced as compared with Embodiment 2 in which it is composed of a diode.

[0113] As described above, the non-contact power supply system 10c according to Embodiment 2 is a non-contact power supply system that supplies DC power to the load 60, and includes a power supply device 20 that supplies power non-contact and a power receiving device 30c that receives the power supplied from the power supply device 20 non-contact and supplies it to the load 60. The power supply device 20 has a parallel resonance circuit 22 and a driving switch element SW0 connected to the DC power supply 50. The parallel resonance circuit 22 includes a first capacitor C1 and a first coil L1. The power receiving device 30c includes a second capacitor C2 and a series resonance circuit 32 composed of a second coil L2 magnetically coupled to the first coil L1, and two rectifying switch elements that are connected to the series resonance circuit 32 and are diodes or transistors that half-wave rectify the alternating current generated in the series resonance circuit 32. A rectifying circuit 33c that outputs a DC current to the load 60 from the positive output terminal 31a and the negative output terminal 31b, and a control circuit 40 that controls the rectifying circuit 33c. The two rectifying switch elements include a fifth rectifying switch element connected between both ends of the series resonance circuit 32 and a sixth rectifying switch element connected between one end of the series resonance circuit 32 and the positive output terminal 31a. Among the two rectifying switch elements, the fifth rectifying switch element is a transistor, and the control circuit 40 adjusts the power supplied to the load 60 by changing the duration of turning on the fifth rectifying switch element SW5 constituting the rectifying circuit 33c over a plurality of cycles of the alternating current power generated in the series resonance circuit 32.

[0114] Thereby, (1) the power supply device 20 has the parallel resonance circuit 22 and the power receiving device 30c has the series resonance circuit 32, and (2) in the power receiving device 30c, the control circuit 40 controls the fifth rectifying switch element SW5 constituting the rectifying circuit 33c in the second mode over a plurality of cycles of the alternating current power generated in the series resonance circuit 32. Therefore, the power supplied to the load 60 can be adjusted without requiring feedback involving communication from the power receiving device 30c to the power supply device 20, and the power can be stably supplied to the load 60.

[0115] Here, among the two rectifying switch elements, the sixth rectifying switch element may be a diode. As a result, among the two rectifying switch elements (SW5 and SW6) constituting the rectifying circuit 33c, the second mode is realized by simple switching control only for the fifth rectifying switch element SW5.

[0116] Also, like the non-contact power supply system 10d according to the first modification of the second embodiment, both of the two rectifying switch elements may be transistors. As a result, the rectifying circuit 33d is composed of two transistors for half-wave rectification, and has the same circuit configuration as the synchronous rectification type.

[0117] As described above, the non-contact power supply system according to the present disclosure has been described based on the first and second embodiments and the modifications. However, the present disclosure is not limited to these first and second embodiments and the modifications. As long as the gist of the present disclosure is not deviated from, various modifications conceived by those skilled in the art applied to the first and second embodiments and the modifications, and other forms constructed by combining some components in the first and second embodiments and the modifications are also included in the scope of the present disclosure.

[0118] For example, in the above embodiment, the power supply device 20 includes one switch element (driving switch element SW0). However, as long as it is a single-ended inverter having a parallel resonance circuit, it may further include switch elements for other uses. 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.

[0119] Also, in the above embodiment, the power supply coil L1 and the power receiving coil L2 are single coils, but may be composed of a plurality of coils connected in series or in parallel.

Industrial Applicability

[0120] The non-contact power supply system according to the present disclosure can be used, for example, in a traveling power supply system or a non-contact charger for charging an electronic device equipped with a battery such as a smartphone, as a non-contact power supply system that can stably supply power to a load without requiring feedback involving communication from a power receiving device to a power supply device.

Explanation of Signs

[0121] 10, 10a, 10b, 10c, 10d Non-contact power supply system 20 Power supply device 21a, 21b Input terminals 22 Parallel resonance circuit 30, 30a, 30b, 30c, 30d Power receiving device 31a Positive output terminal 31b Negative output terminal 32 Series resonance circuit 33, 33a, 33b, 33c, 33d Rectifier circuit 40 Control circuit 50 DC power supply 60 Load C0, C3 Smoothing capacitors C1 First capacitor (power supply side resonance capacitor) C2 Second capacitor (power receiving side resonance capacitor) L1 First coil (power supply coil) L2 Second coil (power receiving coil) SW0 Driving switch element SW1 First rectifying switch element SW2 Second rectifying switch element SW3 Third rectifying switch element SW4 Fourth rectifying switch element SW5 Fifth rectifying switch element SW6 Sixth rectifying switch element

Claims

1. A non-contact power supply system for supplying DC power to a load, comprising: a power supply device for non-contact power supply; a power receiving device for non-contact receiving of the power supplied from the power supply device and supplying it to the load, wherein the power supply device has a parallel resonance circuit and a driving switch element connected to a DC power source, the parallel resonance circuit includes a first capacitor and a first coil, the power receiving device includes: a series resonance circuit composed of a second capacitor and a second coil magnetically coupled to the first coil; a rectifier circuit for outputting a DC current to the load from a positive output terminal and a negative output terminal, the rectifier circuit being configured by bridge-connecting four rectifying switch elements which are diodes or transistors connected to the series resonance circuit and rectifying the alternating current generated in the series resonance circuit; a control circuit for controlling the rectifier circuit; the four rectifying switch elements include a first rectifying switch element connected between one end of the series resonance circuit and the positive output terminal, a second rectifying switch element connected between one end of the series resonance circuit and the negative output terminal, a third rectifying switch element connected between the other end of the series resonance circuit and the positive output terminal, and a fourth rectifying switch element connected between the other end of the series resonance circuit and the negative output terminal; among the four rectifying switch elements, the second rectifying switch element and the fourth rectifying switch element are transistors; the control circuit adjusts the power supplied to the load by changing the duty, which is the ratio of the duration Ton of simultaneous turning-on over a plurality of periods among a plurality of periods T of the alternating power generated in the series resonance circuit, for the second rectifying switch element and the fourth rectifying switch element; a non-contact power supply system.

2. Among the four rectifying switch elements, the first rectifying switch element and the third rectifying switch element are diodes; The non-contact power supply system according to Claim 1.

3. A non-contact power supply system for supplying DC power to a load, comprising: a power supply device for non-contact power supply; a power receiving device for non-contact receiving of the power supplied from the power supply device and supplying it to the load, wherein the power supply device has a parallel resonance circuit and a driving switch element connected to a DC power source, the parallel resonance circuit includes a first capacitor and a first coil, the power receiving device includes: A series resonance circuit composed of a second capacitor and a second coil magnetically coupled to the first coil, Four rectifying switch elements, which are diodes or transistors connected to the series resonance circuit and rectifying the alternating current generated in the series resonance circuit, are bridge-connected to form a rectifying circuit that outputs a direct current to the load from a positive output terminal and a negative output terminal, A control circuit for controlling the rectifying circuit, The four rectifying switch elements include a first rectifying switch element connected between one end of the series resonance circuit and the positive output terminal, a second rectifying switch element connected between one end of the series resonance circuit and the negative output terminal, a third rectifying switch element connected between the other end of the series resonance circuit and the positive output terminal, and a fourth rectifying switch element connected between the other end of the series resonance circuit and the negative output terminal, Among the four rectifying switch elements, the first rectifying switch element and the third rectifying switch element are transistors, The control circuit adjusts the power supplied to the load by changing the duty, which is the ratio of the duration Ton during which the first rectifying switch element and the third rectifying switch element are simultaneously turned on over a plurality of periods among a plurality of periods T of the alternating power generated in the series resonance circuit, A non-contact power supply system.

4. Among the four rectifying switch elements, the second rectifying switch element and the fourth rectifying switch element are diodes, The non-contact power supply system according to claim 3.

5. The four rectifying switch elements are transistors, The non-contact power supply system according to claim 1 or 3.

6. A non-contact power supply system for supplying direct current power to a load, comprising A power supply device for non-contact power supply, A power receiving device for non-contact receiving of power supplied from the power supply device and supplying it to the load, The power supply device has a parallel resonance circuit and a driving switch element connected to a direct current power source, The parallel resonance circuit includes a first capacitor and a first coil, The power receiving device is A series resonance circuit composed of a second capacitor and a second coil magnetically coupled to the first coil, Two rectifying switch elements, which are diodes or transistors connected to the series resonance circuit and half-wave rectify the alternating current generated in the series resonance circuit, are connected to form a rectifying circuit that outputs a direct current to the load from a positive output terminal and a negative output terminal, and a control circuit for controlling the rectifying circuit. The two rectifying switch elements include a fifth rectifying switch element connected between both ends of the series resonance circuit and a sixth rectifying switch element connected between one end of the series resonance circuit and the positive output terminal. Among the two rectifying switch elements, the fifth rectifying switch element is a transistor. The control circuit adjusts the power supplied to the load by changing the duty, which is the ratio of the duration Ton during which the fifth rectifying switch element is turned on over a plurality of periods among a plurality of periods T in the alternating current power generated in the series resonance circuit, with respect to the fifth rectifying switch element. Non-contact power supply system. **Claim 7** Among the two rectifying switch elements, the sixth rectifying switch element is a diode. The non-contact power supply system according to claim 6. **Claim 8** The two rectifying switch elements are transistors. The non-contact power supply system according to claim 6.

Images