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 reception device (30) that receives power in a non-contact manner. The power supply device (20) has a parallel resonance circuit (22) and a drive switch element (SW0). The power reception device (30) has a series resonance circuit (32), a rectifier circuit (33), and a control circuit (40). The control circuit (40) has a first mode in which, with respect to a second rectification switch element (SW2) and a fourth rectification switch element (SW4) that constitute the rectifier circuit (33), the time from turning on to off is changed with reference to the zero-cross point of an AC current generated in the series resonance circuit (32), thereby changing the duration during which the second rectification switch element (SW2) and the fourth rectification switch element (SW4) are simultaneously turned on and adjusting the power supplied to a load (60).

Description

Non-contact power supply system

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

[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. A traveling power supply system is provided.

[0003] Japanese Patent No. 7243450

[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 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. As a result, there is a problem that power cannot be stably 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.

[0006] To achieve the above objective, a contactless power supply system according to one embodiment of the present disclosure is a contactless power supply system that supplies DC power to a load, comprising 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, 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 includes a first capacitor and a first coil, the power receiving device has a series resonant circuit composed of a second capacitor and a second coil magnetically coupled to the first coil, a rectifier circuit configured by bridge-connecting four rectifier switch elements which are diodes or transistors connected to the series resonant circuit and rectify the alternating current generated in the series resonant circuit, and outputs DC current to the load from a positive output terminal and a negative output terminal, and a control circuit that controls the rectifier circuit, wherein the four rectifier switch elements are connected in the series The control circuit includes a first rectifier switch element connected between one end of the vibration circuit and the positive output terminal, a second rectifier switch element connected between one end of the series resonant circuit and the negative output terminal, a third rectifier switch element connected between the other end of the series resonant circuit and the positive output terminal, and a fourth rectifier switch element connected between the other end of the series resonant circuit and the negative output terminal, wherein the second and fourth rectifier switch elements are transistors, and the control circuit has a first mode that adjusts the power supplied to the load by changing the duration during which the second and fourth rectifier switch elements are simultaneously on, based on the zero-crossing point of the alternating current generated in the series resonant circuit.

[0007] This disclosure provides a contactless 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.

[0008] Figure 1 is a circuit block diagram showing the configuration of the contactless power supply system according to Embodiment 1. Figure 2A is a diagram illustrating the relationship between the coupling coefficient and output power in a conventional contactless power supply system. Figure 2B is a diagram illustrating the relationship between the coupling coefficient and output power in a contactless power supply system according to Embodiment 1. Figure 3A is a diagram illustrating the relationship between the distance between the power supply device and the power receiving device, the coupling coefficient, and the output power when a conventional contactless power supply system is applied to a power supply system while driving. Figure 3B is a diagram illustrating the relationship between the distance between the power supply device and the power receiving device, the coupling coefficient, and the output power when a contactless power supply system according to Embodiment 1 is applied to a power supply system while driving. Figure 4A is a timing chart showing the operation in the first mode by the contactless power supply system according to Embodiment 1. Figure 4B is a diagram showing the current path flowing through the power receiving device in the operation in the first mode by the contactless power supply system according to Embodiment 1. Figure 5 is a diagram illustrating the adjustment of the power received in the first mode by the contactless power supply system according to Embodiment 1. Figure 6A is a timing chart showing the operation in the second mode by the contactless power supply system according to Embodiment 1. Figure 6B is a diagram showing the current path flowing through the power receiving device during operation in the second mode by the contactless power supply system according to Embodiment 1. Figure 7 is a diagram illustrating the adjustment of the power received in the second mode by the contactless power supply system according to Embodiment 1. Figure 8A is a timing chart showing an example of operation in which the contactless power supply system according to Embodiment 1 operates while switching between the first mode and the second mode. Figure 8B is a timing chart showing another example of operation in which the contactless power supply system according to Embodiment 1 operates while switching between the first mode and the second mode. Figure 9A is a circuit block diagram showing the configuration of the contactless power supply system according to Modification 1 of Embodiment 1. Figure 9B is a timing chart showing the operation of the contactless power supply system according to Modification 1 of Embodiment 1. Figure 10 is a circuit block diagram showing the configuration of the contactless power supply system according to Modification 2 of Embodiment 1. Figure 11 is a circuit block diagram showing the configuration of the contactless power supply system according to Embodiment 2. Figure 12A is a timing chart showing the operation in the first mode by the contactless power supply system according to Embodiment 2.Figure 12B is a diagram showing the current path flowing through the power receiving device during operation in the first mode by the contactless power supply system according to Embodiment 2. Figure 13 is a diagram illustrating the adjustment of the received power in the first mode by the contactless power supply system according to Embodiment 2. Figure 14A is a timing chart showing the operation in the second mode by the contactless power supply system according to Embodiment 2. Figure 14B is a diagram showing the current path flowing through the power receiving device during operation in the second mode by the contactless power supply system according to Embodiment 2. Figure 15 is a diagram illustrating the adjustment of the received power in the second mode by the contactless power supply system according to Embodiment 2. Figure 16A is a circuit block diagram showing the configuration of the contactless power supply system according to Modification 1 of Embodiment 2. Figure 16B is a timing chart showing the operation of the contactless power supply system according to Modification 1 of Embodiment 2. Figure 17 is a circuit block diagram showing the configuration of the contactless power supply system according to Embodiment 3. Figure 18A is a timing chart showing the operation in the first mode by the contactless power supply system according to Embodiment 3. Figure 18B is a diagram showing the current path flowing through the power receiving device during operation in the first mode by the contactless power supply system according to Embodiment 3. Figure 19 is a diagram illustrating the adjustment of the power received in the first mode by the contactless power supply system according to Embodiment 3. Figure 20A is a circuit block diagram showing the configuration of the contactless power supply system according to Modification 1 of Embodiment 3. Figure 20B is a timing chart showing the operation of the contactless power supply system according to Modification 1 of Embodiment 3. Figure 21 is a circuit block diagram showing the configuration of the contactless power supply system according to Modification 2 of Embodiment 3.

[0009] The embodiments of this disclosure will be described in detail below with reference to the drawings. The embodiments described below are all specific examples of this disclosure. The numerical values, circuit elements, placement and connection configurations of electronic components, signal waveforms, timings, etc., shown in the following embodiments are examples only and are not intended to limit this disclosure. Furthermore, the figures are not necessarily strictly accurate. In each figure, substantially identical components are denoted by the same reference numerals, and redundant explanations are omitted or simplified. Also, "connection" refers to an electrical connection, including 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] (Embodiment 1) Embodiment 1 is a contactless power supply system comprising a power supply device and a power receiving device, characterized in that, in the rectifier circuit of the power receiving device, two of the four bridge-connected rectifier switch elements are made of transistors, and the power supplied to the load is adjusted by controlling the on / off timing of these transistors.

[0011] Figure 1 is a circuit block diagram showing the configuration of a contactless power supply system 10 according to Embodiment 1. The DC power supply 50 and load 60 are also shown in this figure. The DC power supply 50 includes, for example, an energy storage element or a power supply obtained by rectifying an AC power supply. The load 60 is, for example, an energy storage element, a motor inverter, etc.

[0012] 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 consists of a power supply device 20 that supplies power contactlessly, and a power receiving device 30 that receives power supplied from the power supply device 20 contactlessly and supplies it to the load 60.

[0013] 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 which is a power supply coil connected to the DC power supply 50 via 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 with the first coil L1, and a first capacitor C1 which is a power supply side resonant capacitor connected in parallel with 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.

[0014] Furthermore, the first capacitor C1 and the first coil L1 form a parallel resonant circuit 22.

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

[0016] The power receiving device 30 includes a series resonant circuit 32, a rectifier circuit 33, output terminals (positive output terminal 31a and negative output terminal 31b) for supplying DC power obtained by the rectifier circuit 33 to the load 60, and a control circuit 40 for controlling the rectifier circuit 33. In this embodiment, the power receiving device 30 also includes 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 resonant circuit 32 is a series resonant circuit that resonates at a predetermined resonant 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 supply device 20, and a second capacitor C2, which is a power receiving side resonant capacitor.

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

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

[0020] In the contactless power supply system 10 according to this embodiment, the second rectifier switch element SW2 and the fourth rectifier switch element SW4 (i.e., two low-side rectifier switch elements) in the rectifier circuit 33 are composed of transistors that can be controlled by the control circuit 40. Therefore, it becomes 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 composed of, for example, a microcontroller having a processor that executes a built-in program. More specifically, the control circuit 40 controls the second rectifier switch element SW2 and the fourth rectifier switch element SW4 (i.e., two low-side rectifier switch elements) to turn on and off with reference to the zero-crossing point of the AC current generated in the series resonant circuit 32. In particular, for control from on to off, the control circuit 40 has a first mode in which it adjusts the power supplied to the load 60 by changing the time from on to off with reference to the zero-crossing point, thereby changing the duration for which the second rectifier switch element SW2 and the fourth rectifier switch element SW4 are simultaneously on.

[0022] Furthermore, the control circuit 40 has a second mode for adjusting the power supplied to the load 60 by changing the duration for which the second rectifier switch element SW2 and the fourth rectifier switch element SW4 are simultaneously turned on over multiple periods of the alternating current generated in the series resonant circuit 32 (and simultaneously turned off at other times). The control circuit 40 may operate in a mixed configuration of the first and second modes by switching between them, or it may operate only in the first mode, or only in the second mode. Which operation is performed may be determined by prior settings for the control circuit 40, or by control signals input to the control circuit 40 from an external source.

[0023] Note that Figure 1 omits the illustration of measuring instruments for measuring voltage and current at various points in the power receiving device 30. 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 the potential at the negative output terminal 31b as a reference. The values ​​measured by these ammeters and voltmeters are input to the control circuit 40 and used for control by the control circuit 40.

[0024] Next, the operation of the contactless power supply system 10 according to this embodiment, configured as described above, will be explained. First, in the contactless power supply system 10 according to this embodiment, the power supply device 20 has a parallel resonant circuit 22 and the power receiving device 30 has a series resonant circuit 32, and the significance of this will be explained using Figures 2A to 3B.

[0025] Figure 2A is a diagram illustrating the relationship between the coupling coefficient k and output power in a conventional contactless power supply system. Figure 2B is a diagram illustrating the relationship between the coupling coefficient and output power in a 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. Output power is the output power of the contactless power supply system (i.e., the power supplied to the load by the power receiving device).

[0026] More specifically, in Figures 2A and 2B, Figure (a) shows the equivalent circuits of the resonant circuits of the power supply and power receiving devices that constitute the contactless power supply system, and the meaning of each symbol, while Figure (b) shows the flags indicating the relationship between the coupling coefficient and the output power.

[0027] In a conventional non-contact power supply system, as shown in Figure 2A(a), the resonant circuit of the power supply device is a series resonant circuit connected to an AC power source that outputs an AC voltage of voltage Vin, and consists of a capacitor having capacitance C1, a resistor having resistance r1, and a power supply coil having inductance L1. On the other hand, the resonant circuit of the power receiving device is a series resonant circuit and consists of a capacitor having capacitance C2, a resistor having resistance r2, and a power receiving coil having inductance L2, and outputs a voltage Vo to a load with resistance Ro. Here, the coupling coefficient between the power supply coil and the power receiving coil is k.

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

[0029] On the other hand, in the contactless power supply system 10 according to this embodiment, as shown in Figure 2B(a), the resonant circuit of the power supply device 20 is a parallel resonant circuit 22 connected to an AC power supply that outputs an AC voltage of voltage Vin, and is composed of a parallel circuit of a capacitor having capacitance C1, a resistor having resistance r1, and a power supply coil having inductance L1, while the resonant circuit of 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 supply coil and the power receiving coil is denoted as k.

[0030] Then, the relationship between the output power Po and the coupling coefficient k is the curve shown in Figure 2B(b). In other words, contrary to the conventional technology, as the coupling coefficient k approaches zero (k→0), the output power Po decreases (Po→0).

[0031] Figure 3A is a diagram illustrating 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 a conventional contactless power supply system is applied to a power supply system while driving. Figure 3B is a diagram illustrating 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 contactless power supply system 10 according to Embodiment 1 is applied to a power supply system while driving. More specifically, in Figures 3A and 3B, Figure (a) is a graph showing the relationship between the distance between the power supply device and the power receiving device (Coil position), the coupling coefficient (Coupling coefficient k; solid line; right vertical axis), and the output power (Output power; dashed line; left vertical axis), and Figure (b) is a diagram illustrating the distance between the power supply device and the power receiving device (Coil position) in a power supply system while driving.

[0032] Now, let's focus on the case where the distance between the power receiving device mounted on the vehicle and the power supply device located under the floor increases from a small distance (i.e., the power receiving device is close to the power supply device) to a larger distance (i.e., the power receiving device is moving away from the power supply device).

[0033] In conventional contactless power supply systems, as shown in Figure 3A(a), the coupling coefficient decreases as the distance between the power supply device and the power receiving device increases from a small state (dashed line). However, as shown in Figure 2A(b), the relationship between the coupling coefficient and output power shows that the output power actually increases (solid line). Therefore, it becomes necessary to control the power supply device to prevent excessive power transmission.

[0034] In contrast, in the contactless power supply system 10 according to this embodiment, as shown in Figure 3B(a), the coupling coefficient decreases as the distance between the power supply device 20 and the power receiving device 30 increases from a small state (dashed line), but the output power also decreases (solid line) as shown in the relationship between the coupling coefficient and output power in Figure 2B(b). Therefore, when the power receiving device 30 passes the power supply device 20 and moves away from it, there is no need to suppress power as in the conventional technology.

[0035] Thus, in the contactless power supply system 10 according to this embodiment, because the power supply device 20 has a parallel resonant circuit 22, there is a unique relationship in which the output power decreases as the coupling coefficient decreases, contrary to the contactless power supply system of the prior art. As a result, the output power decreases as the distance between the power supply device 20 and the power receiving device 30 increases, so power can be stably supplied to the load 60 during power supply while driving without requiring feedback involving communication from the power receiving device 30 to the power supply device 20.

[0036] Although Figures 2A to 3B illustrate the example of power supply while driving, the contactless power supply system 10 according to this embodiment can be applied not only to power supply while driving, but also to other applications such as contactless chargers for charging electronic devices equipped with batteries, such as smartphones.

[0037] Next, the operation of the contactless power supply system 10 according to this embodiment in the first mode will be described. Figure 4A is a timing chart showing the operation of the contactless power supply system 10 according to Embodiment 1 in the first mode. Figures 4A(a) to (e) 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 second rectifier switch element SW2, the voltage across the second rectifier switch element SW2 (drain-source voltage Vds), the control signal (gate-source voltage Vgs) given from the control circuit 40 to the fourth rectifier switch element SW4, and the voltage across the fourth rectifier switch element SW4 (drain-source voltage Vds), respectively. Also, the upper part of Figure 4A shows four periods (i), (iii), (ii), and (iv) that constitute one cycle of the current Ll2 flowing through the second coil L2.

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

[0039] Next, after a predetermined time δt (period (iii)) has elapsed from the zero-crossing point, the control circuit 40 controls the fourth rectifier switch element SW4 to switch it from on to off (Figure 4A(d)). As a result, the voltage across the fourth rectifier switch element SW4 changes from 0V to voltage Vout (Figure 4A(e)).

[0040] Subsequently, when the control circuit 40 detects the zero-crossing point from negative current to positive current in the waveform of current Ll2 (Figure 4A(a)) (at the end of period (ii)), it controls the fourth rectifier switch element SW4 to turn it on from its previous off state (Figure 4A(d)). As a result, the voltage across the fourth rectifier switch element SW4 changes from voltage Vout to 0V (Figure 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] Using 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, 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 remains 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 Embodiment 1. The thick solid lines 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 power, in other words) is supplied from the fourth rectifying switch element SW4 to the load 60 through the second coil L2, the second capacitor C2, and the first rectifying switch element SW1 and from the positive output terminal 31a.

[0046] As shown in (b) of FIG. 4B, in the subsequent period (iii), since the second rectifying switch element SW2 and the fourth rectifying switch element SW4 are turned on simultaneously, a current refluxes through 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 (c) of FIG. 4B, in the subsequent period (ii), since the second rectifying switch element SW2 is turned on and the fourth rectifying switch element SW4 is turned off, current (or rather, power) is supplied from the second rectifying switch element SW2, through the second capacitor C2, the second coil L2, and the third rectifying switch element SW3, and from the positive output terminal 31a to the load 60.

[0048] As shown in (d) of FIG. 4B, in the subsequent period (iv), since the second rectifying switch element SW2 and the fourth rectifying switch element SW4 are turned on simultaneously, a current refluxes through 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 feeding system 10 according to Embodiment 1. FIGS. 5(a) to 5(c) show examples of timing charts indicating the operations 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. In FIG. 5(d), the value of the received power (vertical axis; Pout) is the value under the condition that the DC voltage input from the DC power supply 50 to the non-contact power feeding system 10 and the parameters of the circuit components constituting the non-contact power feeding system 10 are set to predetermined conditions.

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

[0051] As described above, in the first mode of Embodiment 1, the control circuit 40 changes the time from when the second rectifier switch element SW2 and the fourth rectifier switch element SW4 are turned on, based on the zero-crossing point of the AC current generated in the series resonant circuit 32, thereby changing the duration during which the second rectifier switch element SW2 and the fourth rectifier switch element SW4 are simultaneously turned on. This makes it possible to adjust the power supplied to the load 60 without requiring feedback involving communication from the power receiving device 30 to the power supply device 20.

[0052] Next, the operation of the contactless power supply system 10 according to this embodiment in the second mode will be described. Figure 6A is a timing chart showing the operation of the contactless power supply system 10 according to Embodiment 1 in the second mode. Figures 6A(a) to (e) correspond to Figures 4A(a) to (e). In the second mode, the control circuit 40 adjusts the power supplied from the power receiving device 30 to the load 60 by changing the duration Ton (0 ≤ Ton ≤ T) over multiple periods of the multiple periods T in the alternating current generated in the second coil L2 for the second rectifier switch element SW2 and the fourth rectifier switch element SW4 (while simultaneously turning off the second rectifier switch element SW2 and the fourth rectifier switch element SW4 during periods T other than the duration Ton).

[0053] The duty cycle for a duration of Ton is given by Duty Cycle = Ton / T. The control circuit 40 adjusts the duty cycle to a value between zero and 1, depending on the amount of power to be supplied to the load 60. For example, the control circuit 40 may change the duty cycle according to the amount of power required from the load 60, or it may change the duty cycle so that the potential at the positive output terminal 31a remains constant, with the potential at the negative output terminal 31b as the reference.

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

[0055] Furthermore, the thick arrows in (b1) and (b2) of Figure 6B indicate the current path flowing through the power receiving device 30 when the second rectifier switch element SW2 and the fourth rectifier switch element SW4 are simultaneously turned on (Full-ON state). More specifically, Figure 6B(b1) shows the case where current flows downward in the second coil L2 (i.e., current flows back into the current loop including the second rectifier switch element SW2, the second capacitor C2, the second coil L2, and the fourth rectifier switch element SW4), and current (in other words, power) is not supplied to the load 60 from the positive output terminal 31a. Figure 6B(b2) shows the case where current flows upward in the second coil L2 (i.e., current flows back into the current loop including the fourth rectifier switch element SW4, the second coil L2, the second capacitor C2, and the second rectifier switch element SW2), and current (in other words, power) is not supplied to the load 60 from the positive output terminal 31a.

[0056] Figure 7 illustrates the adjustment of the received power (power supplied from the power receiving device 30 to the load 60) in the second mode by the contactless power supply system 10 according to Embodiment 1. Here, a graph is shown showing the relationship between the duty cycle (horizontal axis; Duty) and the received power (vertical axis; Pout) when the duration Ton in Figure 6A is changed (i.e., the duty cycle is changed). Note that in Figure 7, the value of the received power (vertical axis; Pout) is the value calculated under the same predetermined conditions as when the received power in the first mode shown in Figure 5(d) was calculated.

[0057] As shown in Figure 7, in the second mode as in the first mode, the control circuit 40 can control the received power from zero to the maximum value (approximately 1100W) by adjusting the duty cycle.

[0058] As described above, in the second mode of Embodiment 1, the control circuit 40 can adjust the power supplied to the load 60 without requiring feedback involving communication from the power receiving device 30 to the power supply device 20 by changing the duration for which the second rectifier switch element SW2 and the fourth rectifier switch element SW4 are simultaneously turned on over multiple periods in the alternating current generated in the series resonant circuit 32.

[0059] Figure 8A is a timing chart showing an example of operation in which the contactless power supply system 10 according to Embodiment 1 operates while switching between a first mode and a second mode. In the example shown in this figure, under the control of the control circuit 40, the contactless power supply system 10 operates while alternately switching between the first mode and the full-ON state of the second mode.

[0060] If the period T is the sum of the duration of the first mode and the duration Ton of the full-ON state in the second mode, then the duty cycle of the full-ON state in the second mode is Duty Cycle = Ton / T. The control circuit 40 can adjust the power supplied to the load 60 by changing the duty cycle.

[0061] Figure 8B is a timing chart showing another example of operation in which the contactless power supply system 10 according to Embodiment 1 operates while switching between a first mode and a 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 second mode in a Full-ON state, then operates again in the first mode, and then operates while alternately switching between the second mode's Full-ON state and Full-OFF state.

[0062] As described above, in the first mode, the second rectifier switch element SW2 and the fourth rectifier switch element SW4 are turned on and off within one cycle of the alternating current generated in the series resonant circuit 32, whereas in the second mode, the second rectifier switch element SW2 and the fourth rectifier switch element SW4 are turned on and off in units of multiple cycles of the alternating current generated in the series resonant circuit 32. Therefore, the first mode has the advantage of being able to adjust the received power at a faster speed compared to the second mode. Thus, the control circuit 40 can select and operate in a suitable mode based on the requirements for the speed of adjustment of the received power required for the contactless power supply system 10.

[0063] Figure 9A is a circuit block diagram showing the configuration of a contactless power supply system 10a according to a modification 1 of Embodiment 1. The difference from Embodiment 1 is that the first rectifier switch element SW1 and the third rectifier switch element SW3, which constitute the rectifier circuit 33a of the power receiving device 30a, are made of transistors such as NMOS transistors instead of diodes. In addition to controlling the second rectifier switch element SW2 and the fourth rectifier switch element SW4 in Embodiment 1 (i.e., control in the first mode and the second mode), the control circuit 40 performs synchronous rectification control on the first rectifier switch element SW1 and the third rectifier switch element SW3.

[0064] Figure 9B is a timing chart showing the operation of the contactless power supply system 10a according to a modified example 1 of Embodiment 1. Here, the timing chart is shown for when the contactless power supply system 10a operates in the first mode. Figures 9B(a) to (i) show the waveforms of the current Ll2 flowing through the second coil L2, the control signal (gate-source voltage Vgs) applied from the control circuit 40 to the second rectifier switch element SW2, the voltage across the second rectifier switch element SW2 (drain-source voltage Vds), the control signal (gate-source voltage Vgs) applied from the control circuit 40 to the first rectifier switch element SW1, the voltage across the first rectifier switch element SW1 (drain-source voltage Vds), the control signal (gate-source voltage Vgs) applied from the control circuit 40 to the fourth rectifier switch element SW4, the voltage across the fourth rectifier switch element SW4 (drain-source voltage Vds), the control signal (gate-source voltage Vgs) applied from the control circuit 40 to the third rectifier switch element SW3, and the voltage across the third rectifier switch element SW3 (drain-source voltage Vds).

[0065] Of Figures 9B(a) to (i), Figures 9B(a), (b), (c), (f), and (g) which show the timing charts of the second coil L2, the second rectifier switch element SW2, and the fourth rectifier switch element SW4, are the same as Figures 4A(a) to (e) in Embodiment 1.

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

[0067] As described above, in this modified example, the first rectifier switch element SW1 and the third rectifier switch element SW3 that constitute the rectifier circuit 33a of the power receiving device 30a are composed of transistors and switch on and off at the same timing as the corresponding diodes in Embodiment 1. This is true not only for the first mode but also for the second mode. In this modified example, since the first rectifier switch element SW1 and the third rectifier switch element SW3 are composed of transistors, power loss in the first rectifier switch element SW1 and the third rectifier switch element SW3 is reduced compared to Embodiment 1, in which they are composed of diodes.

[0068] Figure 10 is a circuit block diagram showing the configuration of a contactless power supply system 10b according to a modified example 2 of Embodiment 1. This modified example is characterized in that, in the rectifier circuit 33b of the power receiving device 30b, two of the four bridge-connected rectifier switch elements (SW1 to SW4), the two high-side rectifier switch elements (SW1 and SW3), are made of 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 Embodiment 1, the first rectifier switch element SW1 and the third rectifier switch element SW3 (i.e., two high-side rectifier switch elements) constituting the rectifier circuit 33b are composed of transistors (here, NMOS transistors with parasitic diodes) instead of diodes, and the second rectifier switch element SW2 and the fourth rectifier switch element SW4 are composed of diodes instead of transistors. The control circuit 40 then performs the same control on the first rectifier switch element SW1 and the third rectifier switch element SW3 as in Embodiment 1 (i.e., control in the first mode and the second mode), instead of controlling the second rectifier switch element SW2 and the fourth rectifier switch element SW4 as in Embodiment 1.

[0070] Specifically, in the first mode, the control circuit 40 controls the first rectifier switch element SW1 and the third rectifier switch element SW3 (i.e., two high-side rectifier switch elements) to turn on and off based on the zero-crossing point of the AC current generated in the series resonant circuit 32. In particular, for the control from on to off, the control circuit 40 changes the duration during which the first rectifier switch element SW1 and the third rectifier switch element SW3 are simultaneously on by changing the time from on to off with respect to the zero-crossing point, thereby adjusting the power supplied to the load 60.

[0071] In the second mode, the control circuit 40 adjusts the power supplied to the load 60 by changing the duration for which the first rectifier switch element SW1 and the third rectifier switch element SW3 (i.e., two high-side rectifier switch elements) are simultaneously turned on over multiple periods of the alternating current generated in the series resonant circuit 32 (and simultaneously turned off at other times). The control circuit 40 may operate in a mixed configuration of the first and second modes by switching between them, or it may operate only in the first mode, or only in the second mode. Which operation is performed may be determined by prior settings for the control circuit 40, or by control signals input to the control circuit 40 from an external source.

[0072] Furthermore, in this modified example, as in Modification 1 of Embodiment 1, the second rectifier switch element SW2 and the fourth rectifier switch element SW4 constituting the rectifier circuit 33b of the power receiving device 30b may be composed of transistors such as NMOS transistors instead of diodes. In that case, the control circuit 40 performs synchronous rectification control on the second rectifier switch element SW2 and the fourth rectifier switch element SW4, in addition to controlling the first rectifier switch element SW1 and the third rectifier switch element SW3 (i.e., two high-side rectifier switch elements) in Modification 2 (i.e., control in the first mode and the second mode).

[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 a load 60, and comprises a power supply device 20 that supplies power without contact, and a power receiving device 30 that receives power supplied from the power supply device 20 without contact and supplies it to the load 60, the power supply device 20 has a parallel resonant circuit 22 and a drive switch element SW0 connected to a DC power supply 50, the parallel resonant circuit 22 includes a first capacitor C1 and a first coil L1, and the power receiving device 30 includes a second capacitor C2 and The system includes a series resonant circuit 32 composed of a first coil L1 and a second coil L2 that is magnetically coupled, a rectifier circuit 33 configured by bridging four rectifier switch elements (SW1 to SW4), which are diodes or transistors connected to the series resonant circuit 32 and rectify the alternating current generated in the series resonant circuit 32, and outputting a direct 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 rectifier circuit 33, and four rectifier switch elements (SW1 to SW4 ) includes a first rectifier switch element SW1 connected between one end of the series resonant circuit 32 and the positive output terminal 31a, a second rectifier switch element SW2 connected between one end of the series resonant circuit 32 and the negative output terminal 31b, a third rectifier switch element SW3 connected between the other end of the series resonant circuit 32 and the positive output terminal 31a, and a fourth rectifier switch element SW4 connected between the other end of the series resonant circuit 32 and the negative output terminal 31b, and of the four rectifier switch elements (SW1 to SW4), the The second rectifier switch element SW2 and the fourth rectifier switch element SW4 are transistors, and the control circuit 40 has a first mode in which it adjusts the power supplied to the load 60 by changing the time from when the second rectifier switch element SW2 and the fourth rectifier switch element SW4 are turned on simultaneously, based on the zero-crossing point of the alternating current generated in the series resonant circuit 32.

[0074] As a result, (1) the power supply device 20 has a parallel resonant circuit 22 and the power receiving device 30 has a series resonant circuit 32, and (2) in the power receiving device 30, the control circuit 40 controls the second rectifier switch element SW2 and the fourth rectifier switch element SW4 of the low side that constitute the rectifier circuit 33 in the first mode, so that the power supplied to the load 60 can be adjusted and power can be supplied to the load 60 stably without requiring feedback involving communication from the power receiving device 30 to the power supply device 20.

[0075] Here, the control circuit 40 may further have a second mode for adjusting the power supplied to the load 60 by changing the duration for which the second rectifier switch element SW2 and the fourth rectifier switch element SW4 are simultaneously turned on over multiple periods in the alternating current generated in the series resonant circuit 32. This allows the power supplied to the load 60 to be adjusted in the same way as in the first mode, using the second mode which requires slower switching control than the first mode.

[0076] Furthermore, of the four rectifier switch elements (SW1 to SW4), the first rectifier switch element SW1 and the third rectifier switch element SW3 may be diodes. As a result, the first and second modes can be realized by simple switching control of only the two low-side rectifier switch elements (the second rectifier switch element SW2 and the fourth rectifier switch element SW4) of the four rectifier switch elements (SW1 to SW4) that constitute the rectifier circuit 33.

[0077] Furthermore, the non-contact power supply system 10b according to the modified example 2 of Embodiment 1 is a non-contact power supply system that supplies DC power to a load 60, and comprises a power supply device 20 that supplies power in a non-contact manner, and a power receiving device 30b that receives power supplied from the power supply device 20 in a non-contact manner and supplies it to the load 60, the power supply device 20 having a parallel resonant circuit 22 and a drive switch element SW0 connected to a DC power supply 50, the parallel resonant circuit 22 including a first capacitor C1 and a first coil L1, and the power receiving device 30b having a second capacitor The device comprises a series resonant circuit 32 composed of C2 and a second coil L2 that is magnetically coupled to a first coil L1, a rectifier circuit 33b configured by bridging four rectifier switch elements (SW1 to SW4), which are diodes or transistors connected to the series resonant circuit 32 and rectify the alternating current generated in the series resonant circuit 32, and outputting 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 rectifier circuit 33b, and four rectifier switch elements (SW1 to SW4) SW4) includes a first rectifier switch element SW1 connected between one end of the series resonant circuit 32 and the positive output terminal 31a, a second rectifier switch element SW2 connected between one end of the series resonant circuit 32 and the negative output terminal 31b, a third rectifier switch element SW3 connected between the other end of the series resonant circuit 32 and the positive output terminal 31a, and a fourth rectifier switch element SW4 connected between the other end of the series resonant circuit 32 and the negative output terminal 31b. Of the four rectifier switch elements (SW1 to SW4), The first rectifier switch element SW1 and the third rectifier switch element SW3 are transistors, and the control circuit 40 has a first mode in which it adjusts the power supplied to the load 60 by changing the time from when the first rectifier switch element SW1 and the third rectifier switch element SW3 are turned on simultaneously, based on the zero-crossing point of the alternating current generated in the series resonant circuit 32.

[0078] As a result, (1) the power supply device 20 has a parallel resonant circuit 22 and the power receiving device 30b has a series resonant circuit 32, and (2) in the power receiving device 30b, the control circuit 40 controls the high-side first rectifier switch element SW1 and the third rectifier switch element SW3 constituting the rectifier circuit 33b in the first mode, so that the power supplied to the load 60 can be adjusted and power can be supplied to the load 60 stably without requiring feedback involving communication from the power receiving device 30b to the power supply device 20.

[0079] Here, the control circuit 40 may further have a second mode for adjusting the power supplied to the load 60 by changing the duration for which the first rectifier switch element SW1 and the third rectifier switch element SW3 are simultaneously turned on over multiple periods of the alternating current generated in the series resonant circuit 32. This allows the power supplied to the load 60 to be adjusted in the same way as in the first mode, using the second mode which requires slower switching control than the first mode.

[0080] Furthermore, of the four rectifier switch elements (SW1 to SW4), the second rectifier switch element SW2 and the fourth rectifier switch element SW4 may be diodes. As a result, the first and second modes can be realized by simple switching control of only the two high-side rectifier switch elements (first rectifier switch element SW1 and third rectifier switch element SW3) of the four rectifier switch elements (SW1 to SW4) that constitute the rectifier circuit 33b.

[0081] Furthermore, as in the non-contact power supply system 10a according to Modification 1 of Embodiment 1, the four rectifier switch elements (SW1 to SW4) may all be transistors. As a result, the rectifier circuit 33a is composed of four transistors corresponding to a full bridge, resulting in the same circuit configuration as a synchronous rectifier type.

[0082] (Embodiment 2) Embodiment 2 is a contactless power supply system comprising a power supply device and a power receiving device, characterized in that the rectifier circuit provided in the power receiving device constitutes a half-wave rectifier circuit, and of the two rectifier switch elements constituting the half-wave rectifier circuit, the rectifier switch element connected to both ends of the series resonant circuit is made of a transistor, and the power supplied to the load is adjusted by controlling the on / off timing of the transistor.

[0083] Figure 11 is a circuit block diagram showing the configuration of the contactless power supply system 10c according to Embodiment 2. The contactless power supply system 10c according to this embodiment includes a power supply device 20 and a power receiving device 30c, and basically has the same configuration as the contactless power supply system 10 according to Embodiment 1. However, in this embodiment, in the rectifier circuit 33c, which is a half-wave rectifier circuit provided in the power receiving device 30c, of the two rectifier switch elements (SW5 and SW6) that constitute the half-wave rectifier circuit, the fifth rectifier switch element SW5 connected to both ends of the series resonant circuit 32 is composed of a transistor (here, an NMOS transistor with a parasitic diode), and the other sixth rectifier switch element SW6 is composed of a diode.

[0084] Furthermore, the control circuit 40 provided in the power receiving device 30c performs the same control on the fifth rectifier switch element SW5 as in the first embodiment (i.e., control in the first mode and the second mode), instead of controlling the second rectifier switch element SW2 and the fourth rectifier switch element SW4 in the first embodiment.

[0085] More specifically, in the first mode, the control circuit 40 changes the duration for which current flows back into the current loop between the fifth rectifier switch element SW5 and the series resonant circuit 32 by changing the time from when it is turned on to when it is turned off, with reference to the zero-crossing point of the alternating current generated in the series resonant circuit 32, thereby adjusting the power supplied to the load 60.

[0086] In the second mode, the control circuit 40 adjusts the power supplied to the load 60 by changing the duration for which the fifth rectifier switch element SW5 is simultaneously turned on over multiple periods of the alternating current generated in the series resonant circuit 32 (and simultaneously turned off at other times). The control circuit 40 may operate in a mixed configuration of the first and second modes by switching between them, or it may operate only in the first mode or only in the second mode. Which operation is performed may be determined by prior settings for the control circuit 40 or by control signals input to the control circuit 40 from an external source.

[0087] Figure 12A is a timing chart showing the operation of the non-contact power supply system 10c according to Embodiment 2 in the first mode. Figures 12A(a) to (c) 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 rectifier switch element SW5, and the voltage across the fifth rectifier switch element SW5 (drain-source voltage Vds), respectively. The upper part of Figure 12A also shows three periods (i), (ii) and (iii) that constitute one cycle of the current Ll2 flowing through the second coil L2.

[0088] In the first mode, when the control circuit 40 detects a zero-crossing point from positive to negative current in the waveform of the current Ll2 (Figure 12A(a)) (at the end of period (i)), it controls the fifth rectifier switch element SW5 to turn it on from its previous off state (Figure 12A(b)). As a result, the voltage across the fifth rectifier switch element SW5 changes from voltage Vout to 0V and remains so during period (ii) (Figure 12A(c)).

[0089] Next, when the control circuit 40 detects the zero-crossing point from negative current to positive current in the waveform of current Ll2 (Figure 12A(a)) (end of period (ii)), after a predetermined time δt (period (iii)) has elapsed from that zero-crossing point, the control circuit 40 controls the fifth rectifier switch element SW5 to turn it off from its previous on state (Figure 12A(b)). As a result, the voltage across the fifth rectifier switch element SW5 changes from 0V to voltage Vout (Figure 12A(c)).

[0090] The control circuit 40 repeatedly performs on / off control of the fifth rectifier switch element SW5, with these three periods (i) to (iii) forming one cycle. In particular, when the control circuit 40 switches the fifth rectifier switch element SW5 from on to off, it performs a control that delays the zero-crossing point in the waveform of the current Ll2 by a predetermined time δt.

[0091] Furthermore, if the period of the alternating current flowing through the second coil L2 is T, the duty cycle for a predetermined time δt is given by Duty Cycle = δt / T. The control circuit 40 adjusts the duty cycle to a value between zero and 0.5, depending on the magnitude of the power to be supplied to the load 60. For example, the control circuit 40 may change the duty cycle according to the magnitude of the power required by the load 60, or it may change the duty cycle so that the potential at the positive output terminal 31a remains constant, with the potential at the negative output terminal 31b as the reference.

[0092] Figure 12B is a diagram showing the current path flowing through the power receiving device 30c during operation in the first mode by the non-contact power supply system 10c according to Embodiment 2. The thick arrows in (a) to (c) of Figure 12B indicate the current path flowing through the power receiving device 30c during periods (i), (ii), and (iii) in Figure 12B, respectively.

[0093] As shown in Figure 12B(a), during period (i), the fifth rectifier switch element SW5 is off, so current (in other words, power) is supplied to the load 60 from the positive output terminal 31a via the second coil L2, the second capacitor C2, and the sixth rectifier switch element SW6.

[0094] As shown in Figure 12B(b), during the following period (ii), the direction of the current flowing through the second coil L2 is reversed, and the fifth rectifier switch element SW5 is turned on. As a result, current flows back into the current loop through the second coil L2, the second capacitor C2, and the fifth rectifier switch element SW5, and no current (in other words, power) is supplied to the load 60 from the positive output terminal 31a.

[0095] As shown in Figure 12B(c), in the following period (iii), the direction of the current flowing through the second coil L2 is reversed, but since the fifth rectifier switch element SW5 remains ON, current flows back into the current loop through the second capacitor C2, the second coil L2, and the fifth rectifier switch element SW5, and no current (in other words, power) is supplied to the load 60 from the positive output terminal 31a.

[0096] Figure 13 is a diagram illustrating the adjustment of the received power (power supplied from the power receiving device 30c to the load 60) in the first mode by the contactless power supply system 10c according to Embodiment 2. Figures 13(a) to (c) show examples of timing charts that show the operation of the power receiving device 30c when a predetermined time δt shown in Figure 12A is changed (i.e., the duty cycle is changed), and Figure 13(d) is a graph that shows the relationship between the duty cycle (horizontal axis; Duty) and the received power (vertical axis; Pout) when a predetermined time δt is changed.

[0097] In Figure 13(d), the value of the received power (vertical axis; Pout) is the value calculated under the same predetermined conditions as when the received power in the first mode shown in Figure 5(d) in Embodiment 1 was calculated. As can be seen by comparing Figure 13(d) and Figure 5(d), in Embodiment 2, the maximum value of the received power is halved compared to Embodiment 1.

[0098] As shown in Figure 13(d), in the first mode, the control circuit 40 can control the received power from zero to a maximum value (approximately 550W) by adjusting the duty cycle.

[0099] As described above, in the first mode of the second embodiment, the control circuit 40 changes the time from when the fifth rectifier switch element SW5 is turned on to when it is turned off, with reference to the zero-crossing point of the alternating current generated in the series resonant circuit 32. This changes the time during which current flows back into the current loop passing through the fifth rectifier switch element SW5 and the series resonant circuit 32, thereby allowing the power supplied to the load 60 to be adjusted without requiring feedback involving communication from the power receiving device 30c to the power supply device 20.

[0100] Next, the operation of the contactless power supply system 10c according to this embodiment in the second mode will be described. Figure 14A is a timing chart showing the operation of the contactless power supply system 10c according to Embodiment 2 in the second mode. Figures 14A(a) to (c) correspond to Figures 12A(a) to (c). In the second mode, the control circuit 40 adjusts the power supplied from the power receiving device 30c to the load 60 by changing the duration Ton (0 ≤ To ≤ T) over multiple periods of the multiple periods T in the alternating current generated in the second coil L2 for the fifth rectifier switch element SW5 (note that the fifth rectifier switch element SW5 is turned off during periods T other than the duration Ton).

[0101] The duty cycle for a duration of Ton is given by Duty Cycle = Ton / T. The control circuit 40 adjusts the duty cycle to a value between zero and 1, depending on the amount of power to be supplied to the load 60. For example, the control circuit 40 may change the duty cycle according to the amount of power required from the load 60, or it may change the duty cycle so that the potential at the positive output terminal 31a remains constant, with the potential at the negative output terminal 31b as the reference.

[0102] Figure 14B is a diagram showing the current path flowing through the power receiving device 30c during operation in the second mode by the non-contact power supply system 10c according to Embodiment 2. The thick arrows in (a1) and (a2) of Figure 14B indicate the current path flowing through the power receiving device 30c when the fifth rectifier switch element SW5 is in the off state (Full-OFF state). More specifically, Figure 14B(a1) shows the case where current flows upward in the second coil L2 (i.e., current flows from the second coil L2 to the second capacitor C2 and the sixth rectifier switch element SW6), and current (in other words, power) is supplied to the load 60 from the positive output terminal 31a. Figure 14B(a2) shows the case where current flows downward in the second coil L2 (i.e., current flows back into the current loop including the parasitic diode of the second capacitor C2, the second coil L2, and the fifth rectifier switch element SW5), and current (in other words, power) is not supplied to the load 60 from the positive output terminal 31a.

[0103] Furthermore, the thick arrows in (b1) and (b2) of Figure 14B indicate the current path flowing through the power receiving device 30c when the fifth rectifier switch element SW5 is in the ON state (Full-ON state). More specifically, (b1) of Figure 14B shows the case where current flows upward in the second coil L2 (i.e., current flows back into the current loop including the fifth rectifier switch element SW5, the second capacitor C2, and the second coil L2), and current (in other words, power) is not supplied to the load 60 from the positive output terminal 31a. (b2) of Figure 14B shows the case where current flows downward in the second coil L2 (i.e., current flows back into the current loop including the second coil L2, the second capacitor C2, and the fifth rectifier switch element SW5), and current (in other words, power) is not supplied to the load 60 from the positive output terminal 31a.

[0104] Figure 15 is a diagram illustrating the adjustment of the received power (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 is shown showing the relationship between the duty cycle (horizontal axis; Duty) and the received power (vertical axis; Pout) when the duration Ton in Figure 14A is changed (i.e., the duty cycle is changed).

[0105] In Figure 15, the value of the received power (vertical axis; Pout) is the value calculated under the same predetermined conditions as when the received power in the second mode shown in Figure 7 in Embodiment 1 was calculated. As can be seen by comparing Figure 15 and Figure 7, in the second mode as well as in the first mode, the maximum value of the received power in Embodiment 2 is half that of Embodiment 1.

[0106] As shown in Figure 15, in the second mode as in the first mode, the control circuit 40 can control the received power from zero to the maximum value (approximately 550W) by adjusting the duty cycle.

[0107] As described above, in the second mode of Embodiment 2, the control circuit 40 changes the duration for which the fifth rectifier switch element SW5 is turned on over multiple periods of the alternating current generated in the series resonant circuit 32, thereby changing the time for which current flows back into the current loop passing through the fifth rectifier switch element SW5 and the series resonant circuit 32. This makes it possible to adjust the power supplied to the load 60 without requiring feedback involving communication from the power receiving device 30c to the power supply device 20.

[0108] Furthermore, 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. Alternatively, under the control of the control circuit 40, the contactless power supply system 10c may initially operate in the first mode, then operate in the Full-ON state of the second mode, then operate again in the first mode, and then operate while alternately switching between the Full-ON state and the Full-OFF state of the second mode.

[0109] In the first mode, the fifth rectifier switch element SW5 is switched on and off within one cycle of the alternating current generated in the series resonant circuit 32, whereas in the second mode, the fifth rectifier switch element SW5 is switched on and off in units of multiple cycles of the alternating current generated in the series resonant circuit 32. Therefore, the first mode has the advantage of being able to adjust the received power at a faster speed compared to the second mode. Thus, the control circuit 40 can select and operate in a suitable mode based on the requirements for the speed of adjustment of the received power required for the contactless power supply system 10c.

[0110] Figure 16A is a circuit block diagram showing the configuration of a contactless power supply system 10d according to a modification 1 of Embodiment 2. The difference from Embodiment 2 is that the sixth rectifier switch element SW6, which constitutes the rectifier circuit 33d of the power receiving device 30d, is made of a transistor such as an NMOS transistor instead of a diode. In addition to controlling the fifth rectifier switch element SW5 in Embodiment 2 (i.e., control in the first and second modes), the control circuit 40 also performs synchronous rectification control on the sixth rectifier switch element SW6.

[0111] Figure 16B is a timing chart showing the operation of a contactless power supply system 10d according to a modified example 1 of Embodiment 2. Here, the timing chart is shown for when the contactless power supply system 10d operates in the first mode. Figures 16B(a) to (e) 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 rectifier switch element SW5, the voltage across the fifth rectifier switch element SW5 (drain-source voltage Vds), the control signal (gate-source voltage Vgs) given from the control circuit 40 to the sixth rectifier switch element SW6, and the voltage across the sixth rectifier switch element SW6 (drain-source voltage Vds), respectively.

[0112] Of Figures 16B(a) to (e), Figures 16B(a), (b), and (c), which show the timing charts of the second coil L2 and the fifth rectifier switch element SW5, are the same as Figures 12A(a) to (c) in Embodiment 2.

[0113] In this modified example, the sixth rectifier switch element SW6 (transistor) is switched on and off at the same timing as the sixth rectifier switch element SW6 (diode) shown in Figure 12B in Embodiment 2, by synchronous rectification by the control circuit 40 (Figures 16B(d) and (e)).

[0114] Thus, in this modified example, the sixth rectifier switch element SW6 constituting the rectifier circuit 33d of the power receiving device 30d is composed of a transistor and switches on and off at the same timing as the corresponding diode in Embodiment 2. This is true not only for the first mode but also for the second mode. In this modified example, since the sixth rectifier switch element SW6 is composed of a transistor, the power loss in the sixth rectifier switch element SW6 is reduced compared to Embodiment 2, in which it is composed of a diode.

[0115] As described above, the contactless power supply system 10c according to Embodiment 2 is a contactless power supply system that supplies DC power to a load 60, and comprises a power supply device 20 that supplies power without contact, and a power receiving device 30c that receives power supplied from the power supply device 20 without contact and supplies it to the load 60. The power supply device 20 has a parallel resonant circuit 22 and a driving switch element SW0 connected to a DC power supply 50, and the parallel resonant circuit 22 includes a first capacitor C1 and a first coil L1. The power receiving device 30c is configured by connecting a series resonant circuit 32 composed of a second capacitor C2 and a second coil L2 that is magnetically coupled to the first coil L1, and two rectifier switch elements (SW5 and SW6), which are diodes or transistors connected to the series resonant circuit 32 and half-wave rectify the AC current generated in the series resonant circuit 32. The circuit includes a rectifier circuit 33c 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 rectifier circuit 33c. The two rectifier switch elements (SW5 and SW6) include a fifth rectifier switch element SW5 connected between both ends of the series resonant circuit 32, and a sixth rectifier switch element SW6 connected between one end of the series resonant circuit 32 and the positive output terminal 31a. Of the two rectifier switch elements (SW5 and SW6), the fifth rectifier switch element SW5 is a transistor, and the control circuit 40 has a first mode in which it adjusts the power supplied to the load 60 by changing the time from when the fifth rectifier switch element SW5 is turned on to when it is turned off, with reference to the zero-crossing point of the AC current generated in the series resonant circuit 32.

[0116] As a result, (1) the power supply device 20 has a parallel resonant circuit 22 and the power receiving device 30c has a series resonant circuit 32, and (2) in the power receiving device 30c, the control circuit 40 controls the fifth rectifier switch element SW5 constituting the rectifier circuit 33c in the first mode, so that the power supplied to the load 60 can be adjusted and power can be supplied to the load 60 stably without requiring feedback involving communication from the power receiving device 30c to the power supply device 20.

[0117] Here, the control circuit 40 may further have a second mode in which it adjusts the power supplied to the load 60 by changing the duration for which the fifth rectifier switch element SW5 is turned on over multiple periods in the alternating current generated in the series resonant circuit 32. This allows the power supplied to the load 60 to be adjusted in the same way as in the first mode, using the second mode which requires slower switching control than the first mode.

[0118] Furthermore, of the two rectifier switch elements (SW5 and SW6), the sixth rectifier switch element SW6 may be a diode. As a result, the first and second modes can be realized by simple switching control of only the fifth rectifier switch element SW5 among the two rectifier switch elements (SW5 and SW6) that constitute the rectifier circuit 33c.

[0119] Furthermore, as in the non-contact power supply system 10d according to the modified example 1 of Embodiment 2, both of the two rectifier switch elements (SW5 and SW6) may be transistors. As a result, the rectifier circuit 33d is composed of two transistors for half-wave rectification, resulting in the same circuit configuration as a synchronous rectifier type.

[0120] (Embodiment 3) Embodiment 3 is a contactless power supply system comprising a power supply device and a power receiving device, characterized in that, in the rectifier circuit of the power receiving device, two of the four rectifier switch elements connected in bridge configuration, a pair of high-side and low-side (i.e., constituting a totem pole) rectifier switch elements connected in series, are made of transistors, and the power supplied to the load is adjusted by controlling the on / off timing of these transistors.

[0121] Figure 17 is a circuit block diagram showing the configuration of a contactless power supply system 10e according to Embodiment 3. The contactless power supply system 10e according to this embodiment comprises a power supply device 20 and a power receiving device 30e, and basically has the same configuration as the contactless power supply system 10 according to Embodiment 1. However, in this embodiment, in the rectifier circuit 33e provided in the power receiving device 30e, of the four rectifier switch elements (SW1 to SW4) that are bridge-connected, two rectifier switch elements (i.e., the third rectifier switch element SW3 and the fourth rectifier switch element SW4) connected in series (i.e., the high-side and low-side, i.e., forming a totem pole) are composed of transistors (here, NMOS transistors with parasitic diodes), and the other two rectifier switch elements (i.e., the first rectifier switch element SW1 and the second rectifier switch element SW2) are composed of diodes.

[0122] Furthermore, the control circuit 40 provided in the power receiving device 30e controls the third rectifier switch element SW3 and the fourth rectifier switch element SW4 in the same first mode as in Embodiment 1, instead of controlling the second rectifier switch element SW2 and the fourth rectifier switch element SW4 in Embodiment 1. More specifically, in the first mode, the control circuit 40 controls the third rectifier switch element SW3 and the fourth rectifier switch element SW4, which constitute a totem pole, by changing the time from on to off and from off to on, with reference to the zero-crossing point of the AC current generated in the series resonant circuit 32. This changes the duration for which current is returned to the current loop passing through the two high-side or low-side rectifier switch elements and the series resonant circuit 32, thereby adjusting the power supplied to the load 60.

[0123] Figure 18A is a timing chart showing the operation of the contactless power supply system 10e according to Embodiment 3 in the first mode. Figures 18A(a) to (e) show the waveforms of the current Ll2 flowing through the second coil L2, the control signal (gate-source voltage Vgs) applied from the control circuit 40 to the third rectifier switch element SW3, the voltage across the third rectifier switch element SW3 (drain-source voltage Vds), the control signal (gate-source voltage Vgs) applied from the control circuit 40 to the fourth rectifier switch element SW4, and the voltage across the fourth rectifier switch element SW4 (drain-source voltage Vds), respectively. The upper part of Figure 18A also shows four periods (i), (iii), (ii), and (iv) that constitute one cycle of the current Ll2 flowing through the second coil L2.

[0124] In the first mode, when the control circuit 40 detects a zero-crossing point from positive to negative current in the waveform of the current Ll2 (Figure 18A(a)) (at the end of period (i)), it controls the third rectifier switch element SW3 to turn on from its previous off state (Figure 18A(b)) and the fourth rectifier switch element SW4 to turn off from its previous on state (Figure 18A(d)) after a predetermined time δt (period (iii)) has elapsed from that zero-crossing point. As a result, the voltage across the third rectifier switch element SW3 changes from voltage Vout to 0V (Figure 18A(c)), and the voltage across the fourth rectifier switch element SW4 changes from 0V to voltage Vout (Figure 18A(e)).

[0125] Subsequently, when the control circuit 40 detects the zero-crossing point from negative current to positive current in the waveform of current Ll2 (Figure 18A(a)) (end of period (ii)), it controls the third rectifier switch element SW3 to turn it off from its previous on state (Figure 18A(b)) and controls the fourth rectifier switch element SW4 to turn it on from its previous off state (Figure 18A(d)) after a predetermined time δt (period (iv)) has elapsed since that zero-crossing point. As a result, the voltage across the third rectifier switch element SW3 changes from 0V to voltage Vout (Figure 18A(c)), and the voltage across the fourth rectifier switch element SW4 changes from voltage Vout to 0V (Figure 18A(e)).

[0126] The control circuit 40 repeatedly performs on / off control of the third rectifier switch element SW3 and the fourth rectifier switch element SW4, with these four periods (i) to (iv) forming one cycle. In particular, the control circuit 40 controls the third rectifier switch element SW3 and the fourth rectifier switch element SW4 by delaying the zero-crossing point of the current Ll2 waveform by a predetermined time δt when switching them from on to off and from off to on.

[0127] Furthermore, if the period of the alternating current flowing through the second coil L2 is T, the duty cycle for a predetermined time δt is, as in Embodiment 1, duty cycle = δt / T. The control circuit 40 adjusts the duty cycle to a value of zero or more and 0.5 or less, according to the magnitude of the power to be supplied to the load 60. For example, the control circuit 40 may change the duty cycle according to the magnitude of the power required from the load 60, or it may change the duty cycle so that the potential at the positive output terminal 31a remains constant, with the potential at the negative output terminal 31b as a reference.

[0128] Figure 18B is a diagram showing the current path flowing through the power receiving device 30e during operation in the first mode by the contactless power supply system 10e according to Embodiment 3. The thick arrows in (a) to (d) of Figure 18B indicate the current path flowing through the power receiving device 30e during periods (i), (iii), (ii), and (iv) in Figure 18B, respectively.

[0129] As shown in Figure 18B(a), during period (i), the third rectifier switch element SW3 is off and the fourth rectifier switch element SW4 is on. Therefore, current (in other words, power) is supplied from the fourth rectifier switch element SW4 to the load 60 via the second coil L2, the second capacitor C2, and the first rectifier switch element SW1, through the positive output terminal 31a.

[0130] As shown in Figure 18B(b), in the following period (iii), the direction of the current flowing through the second coil L2 is reversed, causing current to flow back from the second rectifier switch element SW2 through the second capacitor C2, the second coil L2, and the fourth rectifier switch element SW4 into the current loop, and no current (in other words, power) is supplied to the load 60 from the positive output terminal 31a.

[0131] As shown in Figure 18B(c), during the following period (ii), the third rectifier switch element SW3 is turned on and the fourth rectifier switch element SW4 is turned off. As a result, current (in other words, power) is supplied from the second rectifier switch element SW2 to the load 60 via the second capacitor C2, the second coil L2, and the third rectifier switch element SW3, through the positive output terminal 31a.

[0132] As shown in Figure 18B(d), during the following period (iv), the third rectifier switch element SW3 is turned on and the fourth rectifier switch element SW4 is turned off. As a result, current flows back from the third rectifier switch element SW3 through the current loop via the second coil L2, the second capacitor C2, and the first rectifier switch element SW1, and no current (in other words, power) is supplied to the load 60 from the positive output terminal 31a.

[0133] Figure 19 is a diagram illustrating the adjustment of the received power (power supplied from the power receiving device 30e to the load 60) in the first mode by the contactless power supply system 10e according to Embodiment 3. Figures 19(a) to (c) show examples of timing charts that show the operation of the power receiving device 30e when a predetermined time δt shown in Figure 18A is changed (i.e., the duty cycle is changed), and Figure 19(d) is a graph that shows the relationship between the duty cycle (horizontal axis; Duty) and the received power (vertical axis; Pout) when a predetermined time δt is changed. Note that in Figure 19(d), the value of the received power (vertical axis; Pout) is the value calculated under the same predetermined conditions as when the received power in the first mode shown in Figure 5(d) in Embodiment 1 was calculated.

[0134] As shown in Figure 19(d), in the first mode, the control circuit 40 can control the received power from zero to a maximum value (approximately 1100W) by adjusting the duty cycle.

[0135] As described above, in the first mode of Embodiment 3, the control circuit 40 changes the time from on to off and from off to on for the third rectifier switch element SW3 and the fourth rectifier switch element SW4, with reference to the zero-crossing point of the AC current generated in the series resonant circuit 32. This changes the duration for which current is returned to the current loop passing through the two high-side or low-side rectifier switch elements and the series resonant circuit 32, thereby adjusting the power supplied to the load 60 without requiring feedback involving communication from the power receiving device 30e to the power supply device 20.

[0136] Figure 20A is a circuit block diagram showing the configuration of a contactless power supply system 10f according to a modification 1 of Embodiment 3. The difference from Embodiment 3 is that the first rectifier switch element SW1 and the second rectifier switch element SW2, which constitute the rectifier circuit 33f of the power receiving device 30f, are made of transistors such as NMOS transistors instead of diodes. In addition to controlling the third rectifier switch element SW3 and the fourth rectifier switch element SW4 in Embodiment 3 (i.e., control in the first mode), the control circuit 40 performs synchronous rectification control on the first rectifier switch element SW1 and the second rectifier switch element SW2.

[0137] Figure 20B is a timing chart showing the operation of the contactless power supply system 10f according to a modified example 1 of Embodiment 3. Here, the timing chart is shown for when the contactless power supply system 10f operates in the first mode. Figures 20B(a) to (i) show the waveforms of the current Ll2 flowing through the second coil L2, the control signal (gate-source voltage Vgs) applied from the control circuit 40 to the third rectifier switch element SW3, the voltage across the third rectifier switch element SW3 (drain-source voltage Vds), the control signal (gate-source voltage Vgs) applied from the control circuit 40 to the first rectifier switch element SW1, the voltage across the first rectifier switch element SW1 (drain-source voltage Vds), the control signal (gate-source voltage Vgs) applied from the control circuit 40 to the fourth rectifier switch element SW4, the voltage across the fourth rectifier switch element SW4 (drain-source voltage Vds), the control signal (gate-source voltage Vgs) applied from the control circuit 40 to the second rectifier switch element SW2, and the voltage across the second rectifier switch element SW2 (drain-source voltage Vds).

[0138] Of Figures 20B(a) to (i), Figures 20B(a), (b), (c), (f), and (g), which show the timing charts of the second coil L2, the third rectifier switch element SW3, and the fourth rectifier switch element SW4, are the same as Figures 18A(a) to (e) in Embodiment 3.

[0139] In this modified example, the first rectifier switch element SW1 (transistor) is switched on and off by synchronous rectification by the control circuit 40 at the same timing as the on and off of the first rectifier switch element SW1 (diode) shown in Figure 18B in Embodiment 3 (Figures 20B(d) and (e)). Similarly, the second rectifier switch element SW2 (transistor) is switched on and off by synchronous rectification by the control circuit 40 at the same timing as the on and off of the second rectifier switch element SW2 (diode) shown in Figure 18B in Embodiment 3 (Figures 20B(h) and (i)).

[0140] As described above, in this modified example, the first rectifier switch element SW1 and the second rectifier switch element SW2 that constitute the rectifier circuit 33f of the power receiving device 30f are composed of transistors and switch on and off at the same timing as the corresponding diodes in Embodiment 3. In this modified example, since the first rectifier switch element SW1 and the second rectifier switch element SW2 are composed of transistors, the power loss in the first rectifier switch element SW1 and the second rectifier switch element SW2 is reduced compared to Embodiment 3, in which diodes are used.

[0141] Figure 21 is a circuit block diagram showing the configuration of a contactless power supply system 10g according to a modified example 2 of Embodiment 3. In this modified example, the rectifier circuit 33g provided in the power receiving device 30g is characterized in that, of the four rectifier switch elements (SW1 to SW4) that are bridge-connected, the two first rectifier switch elements SW1 and the second rectifier switch element SW2 on the left side that constitute a totem pole are made of transistors, and the power supplied to the load is adjusted by controlling the on / off timing of these transistors.

[0142] More specifically, in this modified example, unlike Embodiment 3, the first rectifier switch element SW1 and the second rectifier switch element SW2 (i.e., the totem pole on the left side) constituting the rectifier circuit 33g are composed of transistors (in this case, NMOS transistors with parasitic diodes) instead of diodes, and the third rectifier switch element SW3 and the fourth rectifier switch element SW4 are composed of diodes instead of transistors. The control circuit 40 then performs the same control on the first rectifier switch element SW1 and the second rectifier switch element SW2 as in Embodiment 3 (i.e., control in the first mode), instead of controlling the third rectifier switch element SW3 and the fourth rectifier switch element SW4 as in Embodiment 3.

[0143] Specifically, in the first mode, the control circuit 40 changes the time from when the first rectifier switch element SW1 and the second rectifier switch element SW2 (i.e., the left-side totem pole) are switched on and off, using the zero-crossing point of the alternating current generated in the series resonant circuit 32 as a reference. This changes the duration for which current is returned to the current loop passing through the two rectifier switch elements (high-side or low-side) and the series resonant circuit 32, thereby adjusting the power supplied to the load 60.

[0144] Furthermore, in this modified example, as in Modification Example 1 of Embodiment 3, the third rectifier switch element SW3 and the fourth rectifier switch element SW4 constituting the rectifier circuit 33g provided in the power receiving device 30g may be composed of transistors such as NMOS transistors instead of diodes. In that case, the control circuit 40 performs synchronous rectification control on the third rectifier switch element SW3 and the fourth rectifier switch element SW4, in addition to controlling the first rectifier switch element SW1 and the second rectifier switch element SW2 (i.e., the totem pole on the left side) in Modification Example 2 (i.e., control in the first mode).

[0145] As described above, the contactless power supply system 10e according to Embodiment 3 is a contactless power supply system that supplies DC power to a load 60, comprising a power supply device 20 that supplies power without contact, and a power receiving device 30e that receives power supplied from the power supply device 20 without contact and supplies it to the load 60, the power supply device 20 having a parallel resonant circuit 22 and a drive switch element SW0 connected to a DC power supply 50, the parallel resonant circuit 22 including a first capacitor C1 and a first coil L1, and the power receiving device 30e having a second capacitor C2 and The device comprises a series resonant circuit 32 composed of a first coil L1 and a second coil L2 that is magnetically coupled, a rectifier circuit 33e configured by bridging four rectifier switch elements (SW1 to SW4), which are diodes or transistors connected to the series resonant circuit 32 and rectify the alternating current generated in the series resonant circuit 32, and outputting a direct 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 rectifier circuit 33e, and the four rectifier switch elements (SW1 to SW4) The series resonant circuit 32 includes a first rectifier switch element SW1 connected between one end of the series resonant circuit 32 and the positive output terminal 31a, a second rectifier switch element SW2 connected between one end of the series resonant circuit 32 and the negative output terminal 31b, a third rectifier switch element SW3 connected between the other end of the series resonant circuit 32 and the positive output terminal 31a, and a fourth rectifier switch element SW4 connected between the other end of the series resonant circuit 32 and the negative output terminal 31b, and of the four rectifier switch elements (SW1 to SW4), the third rectifier switch element SW4 The switch element SW3 and the fourth rectifier switch element SW4 are transistors, and the control circuit 40 has a first mode in which it adjusts the power supplied to the load 60 by changing the time from when the third rectifier switch element SW3 and the fourth rectifier switch element SW4 are simultaneously on, based on the zero-crossing point of the alternating current generated in the series resonant circuit 32, and the time from when they are turned on to when they are turned off.

[0146] As a result, (1) the power supply device 20 has a parallel resonant circuit 22 and the power receiving device 30e has a series resonant circuit 32, and (2) in the power receiving device 30e, the control circuit 40 controls the totem poles on the right side that constitute the rectifier circuit 33e (third rectifier switch element SW3 and fourth rectifier switch element SW4) in the first mode, so that the power supplied to the load 60 can be adjusted and power can be supplied to the load 60 stably without requiring feedback involving communication from the power receiving device 30e to the power supply device 20.

[0147] Here, of the four rectifier switch elements (SW1 to SW4), the first rectifier switch element SW1 and the second rectifier switch element SW2 may be diodes. As a result, the first mode is realized by simple switching control of only the two rectifier switch elements (third rectifier switch element SW3 and fourth rectifier switch element SW4) on the right side of the totem pole, out of the four rectifier switch elements (SW1 to SW4) that constitute the rectifier circuit 33e.

[0148] The non-contact power supply system 10g according to the modified example 2 of Embodiment 3 is a non-contact power supply system that supplies DC power to a load 60, comprising a power supply device 20 that supplies power in a non-contact manner, and a power receiving device 30g that receives power supplied from the power supply device 20 in a non-contact manner and supplies it to the load 60, wherein the power supply device 20 has a parallel resonant circuit 22 and a drive switch element SW0 connected to a DC power supply 50, the parallel resonant circuit 22 includes a first capacitor C1 and a first coil L1, and the power receiving device 30g includes a second capacitor C2, The system includes a series resonant circuit 32 composed of a first coil L1 and a second coil L2 that is magnetically coupled, a rectifier circuit 33g configured by bridging four rectifier switch elements (SW1 to SW4), which are diodes or transistors connected to the series resonant circuit 32 and rectify the alternating current generated in the series resonant circuit 32, and outputting a direct 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 rectifier circuit 33g, and the four rectifier switch elements (SW1 to SW4) The series resonant circuit 32 includes a first rectifier switch element SW1 connected between one end of the series resonant circuit 32 and the positive output terminal 31a, a second rectifier switch element SW2 connected between one end of the series resonant circuit 32 and the negative output terminal 31b, a third rectifier switch element SW3 connected between the other end of the series resonant circuit 32 and the positive output terminal 31a, and a fourth rectifier switch element SW4 connected between the other end of the series resonant circuit 32 and the negative output terminal 31b, and of the four rectifier switch elements (SW1 to SW4), the first rectifier switch element is The switch element SW1 and the second rectifier switch element SW2 are transistors, and the control circuit 40 has a first mode in which it adjusts the power supplied to the load 60 by changing the time from on to off and from off to on with respect to the first rectifier switch element SW1 and the second rectifier switch element SW2, with respect to the zero-crossing point of the AC current generated in the series resonant circuit 32 as the reference, thereby changing the duration during which the first rectifier switch element SW1 and the second rectifier switch element SW2 are simultaneously on.

[0149] As a result, (1) the power supply device 20 has a parallel resonant circuit 22 and the power receiving device 30g has a series resonant circuit 32, and (2) in the power receiving device 30g, the control circuit 40 controls the left-side totem pole (first rectifier switch element SW1 and second rectifier switch element SW2) constituting the rectifier circuit 33g in the first mode, so that the power supplied to the load 60 can be adjusted and power can be supplied to the load 60 stably without requiring feedback involving communication from the power receiving device 30g to the power supply device 20.

[0150] Here, of the four rectifier switch elements (SW1 to SW4), the third rectifier switch element SW3 and the fourth rectifier switch element SW4 may be diodes. As a result, the first mode is realized by simple switching control of only the two rectifier switch elements (first rectifier switch element SW1 and second rectifier switch element SW2) on the left side of the totem pole, out of the four rectifier switch elements (SW1 to SW4) that constitute the rectifier circuit 33g.

[0151] The contactless power supply system described herein has been explained above based on Embodiments 1 to 3 and its modifications. However, this disclosure is not limited to Embodiments 1 to 3 and its modifications. Within the scope of this disclosure, various modifications that a person skilled in the art could conceive of are applied to Embodiments 1 to 3 and its modifications, as well as other forms constructed by combining some of the components of Embodiments 1 to 3 and its modifications, are also included within the scope of this disclosure, as long as they do not depart from the spirit of this disclosure.

[0152] For example, in the above embodiment, the power supply device 20 is equipped with one switch element (driving switch element SW0), but if it is a single-ended inverter having a parallel resonant circuit, it may further be equipped with switch elements for other purposes. For example, the power supply device 20 may be equipped with a switch element that turns the power supply from the DC power supply 50 on and off.

[0153] Furthermore, although the power supply coil L1 and the power receiving coil L2 were single coils in the above embodiment, they may be composed of multiple coils connected in series or in parallel.

[0154] The contactless power supply system described herein can stably supply power to a load without requiring feedback involving communication from a power receiving device to a power supply device. It can be used, for example, in a power supply system while driving, or as a contactless charger for charging electronic devices equipped with batteries such as smartphones.

[0155] 10, 10a-10g Contactless power supply system 20 Power supply device 21a, 21b Input terminals 22 Parallel resonant circuit 30, 30a-30g Power receiving device 31a Positive output terminal 31b Negative output terminal 32 Series resonant circuit 33, 33a-33g Rectifier circuit 40 Control circuit 50 DC power supply 60 Load C0, C3 Smoothing capacitors C1 First capacitor (power supply side resonant capacitor) C2 Second capacitor (power receiving side resonant capacitor) L1 First coil (power supply coil) L2 Second coil (power receiving coil) SW0 Drive switch element SW1 First rectifier switch element SW2 Second rectifier switch element SW3 Third rectifier switch element SW4 Fourth rectifier switch element SW5 Fifth rectifier switch element SW6 Sixth rectifier switch element

Claims

1. A contactless power supply system for supplying DC power to a load, comprising: 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, 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 includes a first capacitor and a first coil, the power receiving device has a series resonant circuit composed of a second capacitor and a second coil magnetically coupled to the first coil, a rectifier circuit configured by bridging four rectifier switch elements which are diodes or transistors connected to the series resonant circuit and rectifying the alternating current generated in the series resonant circuit, and outputs DC current to the load from a positive output terminal and a negative output terminal, and a control circuit that controls the rectifier circuit, The four rectifier switch elements include a first rectifier switch element connected between one end of the series resonant circuit and the positive output terminal, a second rectifier switch element connected between one end of the series resonant circuit and the negative output terminal, a third rectifier switch element connected between the other end of the series resonant circuit and the positive output terminal, and a fourth rectifier switch element connected between the other end of the series resonant circuit and the negative output terminal, wherein the second and fourth rectifier switch elements are transistors, and the control circuit has a first mode of adjusting the power supplied to the load by changing the duration during which the second and fourth rectifier switch elements are simultaneously on, with reference to the zero-crossing point of the alternating current generated in the series resonant circuit.

2. The contactless power supply system according to claim 1, wherein the control circuit further has a second mode for adjusting the power supplied to the load by changing the duration for which the second rectifier switch element and the fourth rectifier switch element are simultaneously turned on over multiple periods in the alternating current generated in the series resonant circuit.

3. The contactless power supply system according to claim 1 or 2, wherein, of the four rectifier switch elements, the first rectifier switch element and the third rectifier switch element are diodes.

4. A contactless power supply system for supplying DC power to a load, comprising: 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, 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 includes a first capacitor and a first coil, the power receiving device has a series resonant circuit composed of a second capacitor and a second coil magnetically coupled to the first coil, a rectifier circuit configured by bridging four rectifier switch elements which are diodes or transistors connected to the series resonant circuit and rectifying the alternating current generated in the series resonant circuit, and outputs a DC current to the load from a positive output terminal and a negative output terminal, and a control circuit that controls the rectifier circuit. The four rectifier switch elements include a first rectifier switch element connected between one end of the series resonant circuit and the positive output terminal, a second rectifier switch element connected between one end of the series resonant circuit and the negative output terminal, a third rectifier switch element connected between the other end of the series resonant circuit and the positive output terminal, and a fourth rectifier switch element connected between the other end of the series resonant circuit and the negative output terminal, wherein the first and third rectifier switch elements are transistors, and the control circuit has a first mode that adjusts the power supplied to the load by changing the duration during which the first and third rectifier switch elements are simultaneously on, based on the zero-crossing point of the alternating current generated in the series resonant circuit.

5. The contactless power supply system according to claim 4, wherein the control circuit further has a second mode for adjusting the power supplied to the load by changing the duration for which the first rectifier switch element and the third rectifier switch element are simultaneously turned on over multiple periods in the alternating current generated in the series resonant circuit.

6. The contactless power supply system according to claim 4 or 5, wherein, of the four rectifier switch elements, the second rectifier switch element and the fourth rectifier switch element are diodes.

7. A contactless power supply system for supplying DC power to a load, comprising: 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, 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 includes a first capacitor and a first coil, the power receiving device has a series resonant circuit composed of a second capacitor and a second coil magnetically coupled to the first coil, a rectifier circuit configured by bridging four rectifier switch elements which are diodes or transistors connected to the series resonant circuit and rectifying the alternating current generated in the series resonant circuit, and outputs a DC current to the load from a positive output terminal and a negative output terminal, and a control circuit that controls the rectifier circuit. The four rectifier switch elements include a first rectifier switch element connected between one end of the series resonant circuit and the positive output terminal, a second rectifier switch element connected between one end of the series resonant circuit and the negative output terminal, a third rectifier switch element connected between the other end of the series resonant circuit and the positive output terminal, and a fourth rectifier switch element connected between the other end of the series resonant circuit and the negative output terminal, wherein the third and fourth rectifier switch elements are transistors, and the control circuit has a first mode of adjusting the power supplied to the load by changing the time from on to off and from off to on with respect to the third and fourth rectifier switch elements, with respect to the zero-crossing point of the AC current generated in the series resonant circuit as the reference, thereby changing the duration during which the third and fourth rectifier switch elements are simultaneously on.

8. The contactless power supply system according to claim 7, wherein, of the four rectifier switch elements, the first rectifier switch element and the second rectifier switch element are diodes.

9. A contactless power supply system for supplying DC power to a load, comprising: 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, 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 includes a first capacitor and a first coil, the power receiving device has a series resonant circuit composed of a second capacitor and a second coil magnetically coupled to the first coil, a rectifier circuit configured by bridging four rectifier switch elements which are diodes or transistors connected to the series resonant circuit and rectifying the alternating current generated in the series resonant circuit, and outputs DC current to the load from a positive output terminal and a negative output terminal, and a control circuit that controls the rectifier circuit, The four rectifier switch elements include a first rectifier switch element connected between one end of the series resonant circuit and the positive output terminal, a second rectifier switch element connected between one end of the series resonant circuit and the negative output terminal, a third rectifier switch element connected between the other end of the series resonant circuit and the positive output terminal, and a fourth rectifier switch element connected between the other end of the series resonant circuit and the negative output terminal, wherein the first and second rectifier switch elements are transistors, and the control circuit has a first mode that adjusts the power supplied to the load by changing the duration during which the first and second rectifier switch elements are simultaneously on, based on the zero-crossing point of the alternating current generated in the series resonant circuit.

10. The contactless power supply system according to claim 9, wherein, of the four rectifier switch elements, the third rectifier switch element and the fourth rectifier switch element are diodes.

11. The contactless power supply system according to claim 1, 2, 4, 5, 7, or 9, wherein the four rectifier switch elements are transistors.

12. A contactless power supply system for supplying DC power to a load, comprising: 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, 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 includes a first capacitor and a first coil, the power receiving device has a series resonant circuit composed of a second capacitor and a second coil magnetically coupled to the first coil, a rectifier circuit configured by connecting two rectifier switch elements which are diodes or transistors that half-wave rectify the AC current generated in the series resonant circuit and output a DC current to the load from a positive output terminal and a negative output terminal, and a control circuit that controls the rectifier circuit, wherein the two rectifier switch elements include a fifth rectifier switch element connected between both ends of the series resonant circuit and a sixth rectifier switch element connected between one end of the series resonant circuit and the positive output terminal, A contactless power supply system comprising: of the two rectifier switch elements, the fifth rectifier switch element is a transistor; and the control circuit has a first mode of adjusting the power supplied to the load by changing the time from when the fifth rectifier switch element is turned on to when it is turned off, with reference to the zero-crossing point of the alternating current generated in the series resonant circuit; 13. The contactless power supply system according to claim 12, wherein the control circuit further has a second mode for adjusting the power supplied to the load by changing the duration for which the fifth rectifier switch element is turned on over multiple periods in the alternating current generated in the series resonant circuit.

14. The contactless power supply system according to claim 12 or 13, wherein the sixth rectifier switch element among the two rectifier switch elements is a diode.

15. The contactless power supply system according to claim 12 or 13, wherein the two rectifier switching elements are transistors.

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