CONTACTLESS POWER SUPPLY DEVICE

Abstract

Contactless power supply device (1) comprising a power transmission device (2) and a power receiving device (3) to which power is transferred from the power transmission device (2) without contact, wherein the power receiving device (3) comprises: a resonant circuit (20) comprising a receiving coil (21) which receives energy from the energy transfer device (2), and a resonant capacitor (22) which, in conjunction with the receiving coil (21), resonates with energy from the energy transfer device (2); and a rectifier circuit (25) that rectifies energy output by the resonant circuit (20), and wherein the energy transfer device (2) comprises: a transmission coil (14) that supplies energy to the energy receiving device (3); a first coil (15) which is connected in series with the transmission coil (14) and is not coupled to the receiving coil (21), even while energy is being transferred from the energy transmission device (2) to the energy receiving device (3); a first short-circuit circuit (16) that switches between short-circuiting and disconnecting both ends of the first coil (15); a power supply circuit (10) that supplies alternating current energy to the transmission coil (14) at an adjustable switching frequency, at which the transmission coil (14) does not resonate, and at an adjustable voltage; and a control circuit (19) which controls the switching frequency and the voltage of the alternating current energy supplied to the transmission coil (14) by the power supply circuit (10) and controls whether the two ends of the first coil (15) are short-circuited or disconnected via the first short-circuit circuit (16), wherein the energy receiving device (3) further comprises: a voltage detection circuit (28) that measures an output voltage of an energy output by the resonant circuit (20) and obtains a measured value of the output voltage; a determining circuit (29) which, based on the measured value of the output voltage, determines whether the contactless power supply device (1) is performing a constant voltage output operation or not, and whether the measured value of the output voltage is within a predetermined permissible voltage range or not; and a first communication device (32) which transmits a signal to the power transmission device (2) which contains determination information indicating whether the contactless power supply device (2) is performing the output operation at constant voltage or not and whether the measured value of the output voltage is within the predetermined permissible voltage range or not, wherein the power transmission device (2) further comprises: a second communication device (17) which receives the signal which contains the destination information, and wherein the control circuit (19) controls, depending on the destination information, the switching frequency and the voltage of the alternating current energy which is supplied to the transmission coil (14) by the power supply circuit (10), and controls whether the two ends of the first coil (15) are short-circuited or disconnected via the first short-circuit circuit (16).

Description

AREA

[0001] The present invention relates to a contactless power supply device. STATE OF THE ART

[0002] Until now, conventional technologies for transmitting electrical energy through space without the use of metal contacts or the like, or so-called contactless power supply technologies (also called wireless power supply technologies), have been studied.

[0003] One of the contactless power supply technologies is a method for supplying energy by electromagnetic induction. This method employs a system of primary capacitors connected in series and secondary capacitors connected in parallel (hereinafter referred to as the SP method) (see, for example, NPL 1). According to the SP method, a capacitor is connected in series with a transmission coil, which serves as part of a transformer on the primary side (power transmission side), and a capacitor is connected in parallel with a receiving coil, which serves as the other part of the transformer on the secondary side (power receiving side).

[0004] In the SP method, the output from the resonant circuit is a constant current output because the resonant circuit, formed by the receiving coil and the capacitor on the energy-receiving side, induces a parallel resonance. Therefore, it is generally more difficult to implement control in the SP method than in a method using primary and secondary capacitors connected in series (hereafter referred to as the SS method), where the output on the energy-receiving side is a constant voltage output. This is because electronic devices are generally controlled by constant voltage.

[0005] Furthermore, a technology for arranging an inductor, connected in series with the coil in the resonant circuit, on the energy receiving side has been proposed (see, for example, NPL 1 and PTL 1). Note that the method employing this technology is sometimes referred to as the SPL method. The method is also referred to herein as the SPL method. [LIST OF DOCUMENTS][PATENT LITERATURE]

[0006] [PTL 1] Japanese unexamined patent publication (Kokai) JP 2015 042 051 A [NON-PATENT LITERATURE]

[0007] [NPL 1] Watanabe et al., “Bidirectional Contactless Power Transfer System expandable from Unidirectional Systems,” The transactions of the Institute of Electrical Engineers of Japan. D, IEEJ Transactions on Industry Applications, Vol.133, No.7, pp.707-713, 2013

[0008] Other state-of-the-art documents are US 2011 / 0 254 377 A1, US 2015 / 0 229 289 A1 and US 2014 / 0 203 774 A1. SUMMARY [TECHNICAL TASK]

[0009] In a contactless power supply device where the SPL method is used, the power factor is improved because harmonic components of the transmitted energy are reduced and ideal transformer characteristics are maintained, thereby increasing energy transmission efficiency.

[0010] It is preferred that, even when the SPL method is used, the contactless power supply device is used in such a way that it performs a constant voltage output operation. Furthermore, depending on the application, an adjustable frequency range of an AC power supplied to the transmission coil is sometimes limited, even if the coupling coefficient between a transmission coil and a receiving coil is not constant.

[0011] Consequently, it is an object of the present invention to provide a contactless power supply device capable of narrowing the frequency adjustment range of an alternating current energy supplied to the transmission coil when the coupling coefficient between the transmission coil of the device on the energy transmission side and the receiving coil of the device on the energy reception side is not constant. This object is achieved by the subject matter of the independent claims. Preferred embodiments and further developments are the subject matter of the dependent claims. The invention is defined by the claims, with embodiments of the invention described below. are.

[0012] In one embodiment of the present invention, a contactless power supply device is provided, comprising a power transmission device and a power receiving device to which energy is transferred from the power transmission device without contact. In the contactless power supply device, the power receiving device includes a resonant circuit comprising a receiving coil, which receives energy from the power transmission device, and a resonant capacitor, which, in conjunction with the receiving coil, resonates with energy from the power transmission device, and a rectifier circuit, which rectifies the energy output by the resonant circuit. On the other hand, the power transmission device comprises a transmission coil, which supplies energy to the power receiving device, and a first coil, which is connected in series with the transmission coil and is not coupled to the receiving coil.even while energy is being transferred from the energy transmission device to the energy receiving device, a first short-circuit circuit that switches between short-circuiting and disconnecting the two ends of the first coil, a power supply circuit that supplies alternating current energy to the transmission coil at an adjustable switching frequency at which the transmission coil does not resonate, and at an adjustable voltage, a receiver that receives a signal containing destination information, and a control circuit that controls the switching frequency and voltage of the alternating current energy supplied to the transmission coil from the power supply circuit and controls whether the two ends of the first coil are short-circuited or disconnected via the first short-circuit circuit.

[0013] In the contactless power supply device, the energy receiving device preferably further comprises a second coil which is connected in series with the receiving coil between the resonant circuit and the rectifier circuit, and the receiving coil and the resonant capacitor of the resonant circuit are preferably connected in parallel to each other.

[0014] Alternatively, in the contactless power supply device, the receiving coil and the resonant capacitor of the resonant circuit of the power receiving device are preferably connected in series.

[0015] Furthermore, in the contactless power supply device, the energy receiving device preferably also includes a voltage sensing circuit that measures an output voltage of energy output by the resonant circuit and receives a measured value of the output voltage, a determination circuit that, based on a measured value of the output voltage, determines whether the contactless power supply device performs a constant voltage output operation or not and whether the measured value of the output voltage is within a predetermined permissible voltage range or not, and a first communication device that transmits a signal to the energy transmission device which contains determination information indicating,The device determines whether the contactless power supply performs the output process with a constant voltage and whether the measured output voltage value is within the predetermined permissible voltage range. Furthermore, the power transmission device preferably includes a second communication device that receives the signal containing the determination information. Depending on this information, the control circuit preferably controls the switching frequency and the voltage of the AC power supplied to the transmission coil by the power supply circuit, and controls whether the two ends of the first coil are short-circuited or disconnected via the first short-circuit circuit.

[0016] Furthermore, in the contactless power supply device, the control device of the power transmission device, when the determination information received from the power receiving device indicates that the contactless power supply device does not perform the output process with constant voltage, preferably controls the switching frequency of the AC energy supplied to the transmission coil by the power supply circuit, so that it is changed within a first frequency range in such a way that measured values ​​of the output voltage do not change, even if a resistance value of a load circuit connected to the rectifier circuit of the power receiving device changes.

[0017] In this case, if the determination information indicates that the contactless power supply device does not perform the constant voltage output operation, even if the control circuit changes the switching frequency of the AC energy supplied to the transmission coil by the power supply circuit over the entire first frequency range, preferably the first short-circuit circuit, thus separating the two ends of the first coil.

[0018] Furthermore, the control device of the energy transmission device in the contactless power supply device, when the determination information indicates that the contactless power supply device does not perform the constant voltage output operation, preferably controls the switching frequency of the AC energy supplied to the transmission coil by the power supply circuit, such that it is varied within a second frequency range, which differs from the first frequency range, in such a way that measured values ​​of the output voltage do not change, even if a resistance value of a load circuit connected to the rectifier circuit of the energy receiving device changes.

[0019] In this case, if the determination information indicates that the contactless power supply device does not perform the constant voltage output operation, even if the control circuit changes the switching frequency of the AC energy supplied to the transmission coil by the power supply circuit over the entire second frequency range, preferably the first short-circuit circuit, so that it short-circuits the two ends of the first coil.

[0020] Note that the first frequency range and the second frequency range are preferably defined in such a way that they partially overlap.

[0021] Furthermore, when the determination information received from the energy receiving device indicates that the contactless energy supply device is performing the output process with constant voltage and a measured value of the output voltage is not within the predetermined permissible voltage range, the control circuit of the energy transfer device in the contactless energy supply device preferably controls the voltage of the AC energy supplied to the transfer coil by the energy supply circuit in such a way that measured values ​​of the output voltage are within the predetermined permissible voltage range.

[0022] Furthermore, the energy transfer device in the contactless energy supply device preferably also includes a current sensing circuit that measures a current flowing through the transmission coil and obtains a measured value of the current, and the control circuit preferably controls the switching frequency of the alternating current energy supplied to the transmission coil by the energy supply circuit as a function of a measured value of the current, and controls whether the two ends of the first coil are short-circuited or disconnected via the first short-circuit circuit.

[0023] In this case, the control circuit of the energy transmission device, in the event that the two ends of the first coil are short-circuited, preferably monitors measured values ​​of the current while changing the switching frequency of the AC energy within a first frequency range, and thereby detects a switching frequency at which measured values ​​of the current have a local maximum, and controls the power supply circuit in such a way that an AC energy having the detected switching frequency is supplied to the transmission coil.

[0024] Furthermore, if no switching frequency at which measured current values ​​exhibit a local maximum is detected within the first frequency range, the control circuit of the energy transmission device preferably controls the first short-circuit circuit, thus disconnecting the two ends of the first coil. If the two ends of the first coil are disconnected, the control circuit monitors measured current values ​​while changing the switching frequency of the AC energy within a second frequency range, which differs from the first frequency range. It thereby detects a switching frequency at which measured current values ​​exhibit a local maximum and controls the energy supply circuit in such a way that AC energy exhibiting the detected switching frequency is supplied to the transmission coil.

[0025] Furthermore, the energy receiving device in the contactless energy supply device preferably also includes a voltage detection circuit that measures an output voltage of energy output by the resonant circuit and receives a measured value of the output voltage, and a second short-circuit circuit that is able to switch between whether the resonant circuit is short-circuited or not, and the determining circuit preferably causes the second short-circuit circuit to short-circuit the resonant circuit if the measured value of the output voltage is outside the predetermined permissible voltage range.On the other hand, the energy transmission device preferably also includes a current sensing circuit that measures a current flowing through the transmission coil and obtains a measured value of the current, and the control circuit preferably controls the switching frequency of the alternating current energy supplied to the transmission coil by the power supply circuit as a function of the measured value of the current, and controls whether the two ends of the first coil are short-circuited or disconnected via the first short-circuit circuit.

[0026] In this case, the control circuit of the energy transmission device, in the event that the two ends of the first coil are short-circuited, preferably monitors measured values ​​of the current while changing the switching frequency of the AC energy within a first frequency range, and thereby detects the switching frequency at which measured values ​​of the current have a local maximum or a phase of measured values ​​of the current and a voltage phase of the AC energy supplied to the transmission coil coincide, and controls the energy supply circuit in such a way that AC energy having the detected switching frequency is supplied to the transmission coil. [BENEFICIAL EFFECTS OF THE INVENTION]

[0027] A contactless power supply device according to the present invention has an advantageous effect of narrowing a frequency adjustment range of an alternating current energy supplied to the transmission coil when the coupling coefficient between the transmission coil of the device on the energy transmission side and the receiving coil of the device on the energy reception side is not constant. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is an equivalent circuit diagram of a contactless power supply device according to an SPL method. Fig. Figure 2 is a diagram illustrating an example of simulation results of frequency responses of an output voltage from the contactless power supply device according to the SPL method. Fig. Figure 3 is a diagram illustrating an example of simulation results of frequency responses of an input impedance of the contactless power supply device according to the SPL method. Fig. Figure 4 is a schematic view of a configuration of a contactless power supply device according to an embodiment of the present invention. Fig. Figure 5 is a diagram illustrating an example of simulation results of frequency responses of an output voltage from the contactless power supply device according to the present embodiment when the two ends of a coil connected in series with a transmission coil are short-circuited. Fig. Figure 6 is a diagram showing an example of simulation results of the frequency response of the output voltage when the voltage applied to the transmission coil is adjusted according to a coupling coefficient in the diagram. Fig. The simulation is modified as illustrated in point 5. Fig. Figure 7 is a diagram illustrating an example of simulation results of frequency responses of the output voltage of the contactless power supply device according to the present embodiment when the two ends of a coil connected in series with a transmission coil are separated and the voltage applied to the transmission coil is changed according to the coupling coefficient. Fig. Figure 8 is a diagram illustrating an example of simulation results of frequency responses of the output voltage of the contactless power supply device when the voltage applied to the transmission coil is changed according to the coupling coefficient, while the two ends of the coil connected in series with a transmission coil are short-circuited or not. Fig. Figure 9 is a process flow diagram of a control system for switching the relay between an on and an off state and the switching frequency and voltage of an alternating current energy supplied to the transmission coil, wherein the control is carried out by a control circuit. Fig. Figure 10 is a circuit diagram of an energy transmission device according to a modification. Fig. Figure 11 is a diagram illustrating an example of a relationship between the frequency responses of the output voltage and the frequency responses of an input impedance of the contactless power supply device. Fig. Figure 12 is a schematic view of a configuration of a contactless power supply device according to a further modification. Fig. 13A is a circuit diagram of an energy transmission device according to yet another modification. Fig. 13B is a circuit diagram of a power supply circuit according to yet another modification. Fig. Figure 14 is a schematic view of a configuration of a contactless power supply device according to yet another modification. Fig. 15 is an equivalent circuit diagram of the contactless power supply device according to the one in Fig. 14 illustrated modification, when the two ends of a coil which is connected in series with a transmission coil are short-circuited. Fig. Figure 16 is a diagram showing an example of simulation results of frequency responses of an output voltage from the contactless power supply device according to the in Fig. Figure 14 illustrates the modification when the two ends of the coil, which is connected in series with the transmission coil, are short-circuited. Fig. Figure 17 is a diagram showing an example of simulation results of the frequency response of the output voltage when the voltage applied to the transmission coil is adjusted according to a coupling coefficient in the diagram. Fig. The simulation is modified in 16 illustrated ways. Fig. Figure 18 is a diagram showing an example of simulation results of the frequency response of the output voltage of the contactless power supply device according to the [reference to be added]. Fig. Figure 14 illustrates the modification when the two ends of the coil, which is connected in series with the transmission coil, are separated and a voltage applied to the transmission coil is changed according to the coupling coefficient. Fig. Figure 19 is a diagram showing an example of simulation results of the frequency response of the output voltage of the contactless power supply device according to the [document / reference] in [reference]. Fig. Figure 14 illustrates the modification when the voltage applied to the transmission coil is changed according to the coupling coefficient, while the two ends of the coil connected in series with the transmission coil are short-circuited or not. Fig. Figure 20 is a diagram which shows an example of a relationship between the frequency responses of the output voltage and the frequency responses of an input impedance of the contactless power supply device according to the in Fig. 14 illustrated variations, illustrated. Fig. Figure 21 is a diagram which shows an example of a relationship between frequency responses of the output voltage of the contactless power supply device according to the one in Fig. Figure 14 illustrates the modification and frequency response of a delay of a phase of current with respect to a phase of voltage with respect to an alternating current energy applied to a transmission coil 14. Fig. Figure 22 is a schematic view of a configuration of a contactless power supply device according to yet another modification. DESCRIPTION OF EXECUTION FORMS

[0028] In the following, a contactless power supply device according to an embodiment of the present invention is described with reference to the drawings.

[0029] To better understand the contactless power supply device according to the present invention, a constant voltage output process, which is carried out by the contactless power supply device according to the SPL method, is first described.

[0030] Fig. Figure 1 is an equivalent circuit diagram of the contactless power supply device according to the SPL method. It is assumed that, in an equivalent circuit 100 in the diagram, a transmission coil of a resonant circuit on the power transmission side is coupled to a receiving coil of a resonant circuit on the power reception side to form an ideal transformer with a ratio of n:1. Crl is the capacitance of a capacitor connected in series with the transmission coil in the resonant circuit on the power transmission side. Lr and Lm are the leakage inductance and excitation inductance, respectively, of the resonant circuit on the power transmission side.Note that the inductance Lp of the transmission coil in the resonant circuit on the power transmission side is equal to (Lm + Lr), and if a coupling coefficient between the transmission coil and the receiving coil is assumed to be denoted by k, then Lr = (1 - k)Lp and Lm = kLp. Furthermore, Ri and Ris are winding resistance values ​​on the power transmission side and on the power reception side, respectively. Cp is the capacitance of a capacitor connected in parallel with the receiving coil in the resonant circuit on the power reception side. Lop is the inductance of a coil connected in series with the receiving coil. Rac is the equivalent AC resistance of a load circuit Ro and is given by Ras = (8 / π). 2 ) × Ro expressed.

[0031] From the equivalent circuit 100, an F-matrix Fspl(s, k, Rac) of the contactless power supply device according to the SPL method is expressed by the following equation. [Math. 1 Fspl(s,k,Rac):=[11s⋅Grl01]⋅{1s⋅Lr(k)01}⋅[101s⋅Lm(k)1]⋅[1s⋅L r(k)01]⋅[1n2⋅Ris01]⋅[10s⋅1n2⋅Cp1]⋅[1s⋅Lop⋅n201]⋅[101n2⋅Rac1]

[0032] In the equation above, s is expressed as s = j2πf. Note that f is the frequency of an alternating current energy supplied to the resonant circuit on the energy transfer side. Furthermore, k denotes a coupling coefficient between the transmission coil and the receiving coil.

[0033] From the definition of the F-matrix, an output gain Gspl(s, k, Rac) of the contactless power supply device according to the SPL method is expressed by the following equation. [Math. 2] Gspl(s,k,Rac)=1Fspl(s,k,Rac)0.0⋅Vin2⋅1n

[0034] In the preceding equation, Vin is a voltage (amplitude) of the alternating current energy supplied to the resonant circuit on the energy transfer side, and Fspl(s, k, Rac) 0,0 represents the upper left element of the F-matrix, which is expressed by equation (1).

[0035] Fig. Figure 2 is a diagram illustrating an example of simulation results of the frequency response of an output voltage from the contactless power supply device according to the SPL method, which are calculated according to equation (2). Fig. Graph 2 shows a frequency response along the horizontal axis and an output voltage response along the vertical axis. Graph 201 represents the frequency response of the output voltage when the coupling coefficient k is set to k = 0.15 and the AC equivalent resistance of the load circuit is set to Rac. Graph 202 represents the frequency response of the output voltage when the coupling coefficient k is set to k = 0.15 and the AC equivalent resistance of the load circuit is set to (10*Rac). Graph 203 represents the frequency response of the output voltage when the coupling coefficient k is set to k = 0.3 and the AC equivalent resistance of the load circuit is set to Rac. Graph 204 represents the frequency response of the output voltage when the coupling coefficient k is set to k = 0.3 and the AC equivalent resistance of the load circuit is set to (10*Rac).Furthermore, graph 205 represents a frequency response of the output voltage when the coupling coefficient k is set to k = 0.6 and the equivalent AC resistance of the load circuit is set to Rac. Additionally, graph 206 represents a frequency response of the output voltage when the coupling coefficient k is set to k = 0.6 and the equivalent AC resistance of the load circuit is set to (10*Rac). Note that the simulation assumes Lp = 174 µH, Cr1 = Cp = 20 nF, Lop = 3Lp, Ri = Ris = 0.3 Ω, n = 1, Vin = 200 V, and Ro = 200 Ω (Rac ≅ 162.1 Ω).

[0036] As in Fig. As illustrated by points 211 to 216, there exist six combinations of frequency and output voltage where the output voltage becomes essentially constant even if the equivalent AC resistance of the load circuit changes, provided that the coupling coefficient k is constant (i.e., a constant voltage output is obtained when the coupling coefficient k is constant). Of points 211 to 216, points 211 to 213 on the low-frequency side are close to the resonant frequency of the resonant circuit on the power transfer side and are affected by the resonance of the resonant circuit on the power transfer side. Conversely, points 214 to 216 on the high-frequency side are a certain amount higher than the resonant frequency of the resonant circuit on the power transfer side and are slightly affected by the resonance of the resonant circuit on the power transfer side.Since in the SPL method the resonant circuit on the power transmission side generally also resonates, alternating current energy is necessarily supplied to the resonant circuit on the power transmission side at frequencies as illustrated by points 211 to 213 in order to cause the contactless power supply device to carry out the output process at a constant voltage.

[0037] Fig. Figure 3 is a diagram illustrating an example of simulation results for the frequency response of an input impedance Zinspl(s, k, Rac) of the contactless power supply device according to the SPL method. Fig. Figure 3 shows a frequency plotted along the horizontal axis and an input impedance plotted along the vertical axis. Graphs 301 to 304 represent frequency responses of the input impedance Zinspl(s, k, Rac) when the AC equivalent resistance of the load circuit is set to Rac and the coupling coefficients k are set to 0.001, 0.15, 0.3, and 0.6, respectively. Note that the frequency responses of the input impedance Zinspl(s, k, Rac) illustrated by graphs 301 to 304 can be changed by entering values ​​of the respective parameters, which are set in the Fig. The simulations illustrated in point 2 were used to calculate an equation for the input impedance Zinspl(s, k, Rac), which is expressed by the following equation. [Math. 3] Zinspl(s,k,Rac)=Fspl(s,k,Rac)0.0Fspl(s,k,Rac)1.0

[0038] In the preceding equation, Fspl(s, k, Rac) represents 1,0the lower left element of the F-matrix, which is expressed by equation (1).

[0039] As in Fig. As illustrated in Figure 3, the input impedance in a frequency range near the resonant frequency of the power transfer circuit decreases at frequencies where a constant voltage is output, as the coupling coefficient decreases. For example, at a frequency f1, illustrated by Figure 211, at which the contactless power supply device can perform the constant voltage output operation when the coupling coefficient k = 0.15, the input impedance has a value of less than 10 Ω at the coupling coefficient k = 0.15. This is because the energy stored in the transmission coil increases due to an increase in current flowing through the power transfer circuit as a result of resonance.Therefore, in the SPL method, supplying AC energy to the resonant circuit on the energy transfer side leads to an increase in energy loss when the coupling coefficient is low. Furthermore, as shown in points 211 to 213, the output gain does not necessarily improve even if the coupling coefficient increases.

[0040] On the other hand, the input impedance increases to a certain level in a frequency range higher than the resonant frequency of the resonant circuit on the power transfer side, and in a range where the contactless power supply device can perform the output operation with a constant voltage, even if the coupling coefficient changes (for example, a range from a frequency f3, corresponding to point 214, to a frequency f4, corresponding to point 216), and the energy loss is therefore suppressed. However, the frequency range becomes wider than a frequency range in which the resonant circuit on the power transfer side resonates, and the output operation with a constant voltage can be performed (a range from frequency f2 to frequency f1).

[0041] It is assumed that this is due to the fact that the resonant frequency of the resonant circuit on the energy receiving side varies depending on the coupling coefficient.

[0042] Consequently, the contactless energy supply device according to the embodiment of the present invention supplies energy from an energy transmission device to an energy receiving device, which has a resonant circuit that causes parallel resonance and a coil which is connected in series with a receiving coil which is included in the resonant circuit. The energy transmission device is configured to supply alternating current energy to a transmission coil at a frequency at which the transmission coil does not resonate.A coil connected in series with the transmitting coil and uncoupled with the receiving coil, even during energy transfer, is arranged on the energy transfer device. The coil's state—whether its two ends are short-circuited or not—switches depending on whether the constant-voltage output is performed within a frequency range determined by the coupling coefficient between the transmitting and receiving coils. This configuration allows the contactless power supply device to narrow the frequency range of the AC power supplied to the transmitting coil during constant-voltage output and to suppress joule loss due to an increase in current flowing through the transmitting coil.

[0043] Furthermore, the contactless power supply device measures an output voltage from the resonant circuit on the energy receiving side and controls the switching frequency and the voltage of the AC energy supplied to the transmission coil in such a way that the measured value is within a permissible voltage range at the time of the constant voltage output process, thereby maintaining the constant voltage output process even if the coupling coefficient between the transmission coil and the receiving coil or the resistance value of the load circuit changes.

[0044] Note that, as used herein, the constant voltage output process is a process in which the contactless power supply device is operated in such a manner as to maintain an output voltage within a permissible voltage range (for example, within ±10% of a predetermined voltage reference value) as determined by the specification of a load circuit connected to the contactless power supply device, and the like.

[0045] Fig. Figure 4 is a schematic view of a configuration of a contactless power supply device according to an embodiment of the present invention. As shown in Fig. As illustrated in Figure 4, a contactless power supply device 1 comprises a power transmission device 2 and a power receiving device 3, to which energy is transferred from the power transmission device 2 through space without contact. The power transmission device 2 comprises a power supply circuit 10, a transmission coil 14, a coil 15, a relay 16, a receiver 17, gate drivers 18-1 and 18-2, and a control circuit 19. The power receiving device 3, on the other hand, comprises a resonant circuit 20, which includes a receiving coil 21 and a resonant capacitor 22, a coil 23, a rectifier and smoothing circuit 24, a load circuit 27, a voltage sensing circuit 28, a constant voltage determination circuit 29, and a transmitter 32.

[0046] First, the energy transfer device 2 is described.

[0047] The power transmission device 10 supplies alternating current energy to the transmission coil 14 at an adjustable switching frequency and voltage. For this purpose, the power supply circuit 10 comprises a power source 11, a power factor improvement circuit 12, and four switching elements 13-1 to 13-4.

[0048] The energy source 11 supplies energy at a predetermined pulsating voltage. For this purpose, the energy source 11 is connected to a commercial AC power source and has a full-wave rectifier circuit to rectify the AC energy supplied by the AC power source.

[0049] The power factor enhancement circuit 12 converts the voltage of the energy output by the power source 11 into a voltage determined by the control circuit 19 for output. For this purpose, the power factor enhancement circuit 12 comprises, for example, an inductor L and a diode D connected in series from the positive electrode of the power source 11, a switching element SW, whose drain and source terminals are connected between the inductor L and the diode D, respectively, and to the negative electrode of the power source 11, and which is an n-channel MOSFET, and a smoothing capacitor C connected in parallel to the switching element SW, with the diode D positioned between them. Furthermore, the gate terminal of the switching element SW is connected to the gate driver 18-1.Furthermore, the power factor improvement circuit 12 has two resistors, R1 and R2, which are connected in series between the positive and negative electrodes of the power source 11. Resistors R1 and R2 are connected in parallel between diode D and smoothing capacitor C. The control circuit 19 measures the voltage between resistor R1 and resistor R2, which represents a voltage output from diode D.

[0050] The power factor enhancement circuit 12 performs a power factor enhancement process through the gate driver 18-1, which controls the switching element SW between an on and an off state according to a duty cycle specified by the control circuit 19, and in such a way that the trajectory of a current waveform output from the diode D matches a trajectory of voltage supplied by the power source 11. The higher the duty cycle at which the switching element SW is turned on, the higher the voltage output by the diode D.

[0051] The voltage output by the diode D is smoothed by the smoothing capacitor C and supplied to the transmission coil 14 via the four switching elements 13-1 to 13-4.

[0052] Note that the power factor improvement circuit 12 is not limited to the configuration described above and may have a different configuration which is able to set an output voltage controlled by the control circuit 19.

[0053] For the four switching elements 13-1 to 13-4, n-channel MOSFETs, for example, can be used. Of the four switching elements 13-1 to 13-4, switching element 13-1 and switching element 13-2 are connected in series between the positive and negative electrode terminals of the power source 11 via the power factor enhancement circuit 12. Furthermore, in the present embodiment, switching element 13-1 is connected to the positive electrode side of the power source 11, while switching element 13-2 is connected to the negative electrode side of the power source 11. The drain terminal of switching element 13-1 is connected to the positive electrode terminal of the power source 11 via the power factor enhancement circuit 12, and the source terminal of switching element 13-1 is connected to the drain terminal of switching element 13-2.Furthermore, the source terminal of the switching element 13-2 is connected to the terminal of the negative electrode of the power source 11 via the power factor improvement circuit 12. Additionally, the source terminal of the switching element 13-1 and the drain terminal of the switching element 13-2 are connected to one end of the transmission coil 14, and the source terminal of the switching element 13-2 is connected to the other end of the transmission coil 14 via the switching element 13-4 and the coil 15.

[0054] Similarly, of the four switching elements 13-1 to 13-4, switching element 13-3 and switching element 13-4 are connected in parallel with switching element 13-1 and switching element 13-2, and connected in series between the positive and negative electrode terminals of the power source 11 via the power factor enhancement circuit 12. Furthermore, switching element 13-3 is connected to the positive electrode side of the power source 11, while switching element 13-4 is connected to the negative electrode side of the power source 11. The drain terminal of switching element 13-3 is connected to the positive electrode terminal of the power source 11 via the power factor enhancement circuit 12, and the source terminal of switching element 13-3 is connected to the drain terminal of switching element 13-4.Furthermore, the source terminal of the switching element 13-4 is connected to the terminal of the negative electrode of the power source 11 via the power factor improvement circuit 12. Additionally, the source terminal of the switching element 13-3 and the drain terminal of the switching element 13-4 are connected to the other end of the transmission coil 14 via the coil 15.

[0055] Furthermore, the gate terminals of switching elements 13-1 to 13-4 are connected to the control circuit 19 via the gate driver 18-2. Additionally, each of the switching elements 13-1 to 13-4 can have its gate terminal connected to its own source terminal via a resistor to ensure that the switching element is turned on when the voltage to turn it on is applied. The switching elements 13-1 to 13-4 are switched between an on and an off state at an adjustable switching frequency according to a control signal from the control circuit 19.In the present embodiment, a pair of switching elements 13-1 and 13-4, and a pair of switching elements 13-2 and 13-3, are alternately switched between an on and an off state such that switching elements 13-2 and 13-3 are off while switching elements 13-1 and 13-4 are on, and conversely, switching elements 13-1 and 13-4 are off while switching elements 13-2 and 13-3 are on. This configuration causes direct current energy supplied by the power source 11 via the power factor enhancement circuit 12 to be converted into alternating current energy at the switching frequency of the switching elements and supplied to the transmission coil 14.

[0056] The transmission coil 14 transmits the alternating current energy supplied by the power supply circuit 10 to the resonant circuit 20 of the energy receiving device 3 through space.

[0057] The coil 15 is connected between the transmission coil 14 and the power supply circuit 10. In the present embodiment, one end of the coil 15 is connected to the transmission coil 14 and the other end of the coil 15 is connected to the source terminal of the switching element 13-3 and the drain terminal of the switching element 13-4 of the power supply circuit 10.

[0058] The coil 15 is an example of a first coil and is arranged such that it is not coupled to the receiving coil 21, even during energy transfer from the energy transfer device 2 to the energy receiving device 3. This configuration allows the adjustment range of the switching frequency of the AC energy supplied to the transfer coil 14 to continue the output process at a constant voltage, even if the coupling coefficient between the transfer coil 14 and the receiving coil 21 varies. Furthermore, the relay 16, when switched on, causes the two ends of the coil 15 to be short-circuited. Since the frequency response of an output voltage from the contactless power supply device 1 differs when the two ends of the coil 15 are short-circuited and when they are not (i.e.,(when they are separated), switching between short-circuiting and disconnecting the two ends of coil 15 allows the adjustment range of the switching frequency to be further narrowed.

[0059] Relay 16 is an example of a first short-circuit circuit and is arranged such that one end and its other end are each connected to one end and the other end of coil 15, i.e., connected in parallel to coil 15. Relay 16 is switched between an on and an off state by control circuit 19. When control circuit 19 switches relay 16 on, the two ends of coil 15 are short-circuited, and as a result, current begins to flow through the transmission coil 14 without flowing through coil 15. Conversely, when control circuit 19 switches relay 16 off, the two ends of coil 15 are not short-circuited (i.e., the two ends of coil 15 are not separated), and any current flowing through the transmission coil 14 also begins to flow through coil 15.

[0060] The receiver 17 is an example of a second communication device and, each time it receives a wireless signal from the transmitter 32 of the power receiving device 3, extracts determination information from the wireless signal indicating whether the contactless power supply device 1 performs the constant voltage output operation or not, and outputs this determination information to the control circuit 19. For this purpose, the receiver 17 includes, for example, an antenna for receiving a wireless signal and a communication circuit for demodulating the wireless signal according to a predetermined wireless communication standard. Note that the predetermined wireless communication standard could be, for example, ISO / IEC 15693, ZigBee (registered trademark), or Bluetooth (registered trademark).

[0061] The gate driver 18-1 receives a control signal from the control circuit 19 to switch the switching element SW of the power factor enhancement circuit 12 between an on and an off state and, according to the control signal, modifies a voltage applied to the gate terminal of the switching element SW. In other words, when the gate driver 18-1 receives a control signal to turn on the switching element SW, it applies a relatively high voltage to the gate terminal of the switching element SW such that the switching element SW is turned on. Conversely, when the gate driver 18-1 receives a control signal to turn off the switching element SW, it applies a relatively low voltage to the gate terminal of the switching element SW such that the switching element SW is turned off.This configuration causes the gate driver 18-1 to switch the switching element SW of the power factor enhancement circuit 12 between an on and an off state at times specified by the control circuit 19.

[0062] The gate driver 18-2 receives a control signal from the control circuit 19 to switch the switching elements 13-1 to 13-4 between an on and an off state and, according to the control signal, changes a voltage applied to the gate terminals of the switching elements 13-1 to 13-4. In other words, upon receiving a control signal to switch on switching elements 13-1 and 13-4, the gate driver 18-2 applies a relatively high voltage to the gate terminal of switching element 13-1 and the gate terminal of switching element 13-4, such that switching elements 13-1 and 13-4 are switched on. This process causes current to flow from the power source 11 through switching element 13-1, the transmission coil 14, and switching element 13-4.On the other hand, upon receiving a control signal to switch off switching element 13-1 and switching element 13-4, the gate driver 18-2 applies such a relatively low voltage to the gate terminal of switching element 13-1 and the gate terminal of switching element 13-4 that switching element 13-1 and switching element 13-4 are switched off and current from the power source 11 is prevented from flowing through switching element 13-1 and switching element 13-4. Similarly, the gate driver 18-2 controls a voltage applied to the gate terminals of switching element 13-2 and switching element 13-3. Therefore, when the switching element 13-1 and the switching element 13-4 are switched off and the switching element 13-2 and the switching element 13-3 are switched on, current begins to flow from the energy source 11 through the switching element 13-3, the transmission coil 14 and the switching element 13-2.

[0063] The control circuit 19, for example, includes a non-volatile memory circuit and a volatile memory circuit, an arithmetic operation circuit, and an interface circuit for connection to other circuits. Each time the control circuit 19 receives the destination information from the receiver 17, the control circuit 19 controls the switching frequency and the voltage of the alternating current energy supplied to the transmission coil 14 by the power supply circuit 10, according to the destination information.

[0064] For this purpose, in the present embodiment, the control circuit 19 controls the switching elements 13-1 to 13-4 in such a way that the pair of switching element 13-1 and switching element 13-4 and the pair of switching element 13-2 and switching element 13-3 are switched on alternately, and that the duration for which the pair of switching element 13-1 and switching element 13-4 is in the on state and the duration for which the pair of switching element 13-2 and switching element 13-3 is in the on state are equal to each other over a period corresponding to the switching frequency.Note that, in order to prevent the pair of switching element 13-1 and switching element 13-4 and the pair of switching element 13-2 and switching element 13-3 from being in the on state simultaneously and short-circuiting the energy source 11, the control circuit 19 can set a dead time during which both pairs of switching elements are off when the pair of switching element 13-1 and switching element 13-4 and the pair of switching element 13-2 and switching element 13-3 are switching between an on and an off state.

[0065] Furthermore, the control circuit 19, referring to a reference table in which each entry specifies a relationship between a switching frequency and a duty cycle corresponding to a voltage applied to the transmission coil 14, causes a constant voltage to be output at the switching frequency and is used in the on / off control of the switching element SW of the power factor enhancement circuit 12, selects a duty cycle corresponding to a desired switching frequency. The control circuit 19 determines the times at which the switching element SW is switched between an on and an off state based on the duty cycle and a change in the output voltage from the diode D of the power factor enhancement circuit 12, and outputs control signals representing these times to the gate driver 18-1.

[0066] Furthermore, if the receiver 17 is unable to receive a wireless signal from the power receiving device 3, it is estimated that the power receiving device 3 is not located in a position where it can receive a power input from the power transfer device 2, i.e., that the power receiving device 2 is in a standby state. Therefore, in this case, the control circuit 19 can set the duty cycle for the on / off control of the switching element SW to a minimum configurable value.Alternatively, the control circuit 19 can control the power supply circuit 10 in a so-called pulse mode. This mode involves operating the power supply circuit 10 with a duty cycle set to a preset value for the on / off control of the switching element SW for a relatively short, fixed duration (for example, several seconds), and subsequently interrupting the power supply from the power supply circuit 10 to the transmission coil 14, while the switching elements remain in the off state, for a relatively long duration (for example, several minutes). Since this control ensures that the voltage applied to the transmission coil 14 is set to a minimum definable value while the power transmission device 2 is in standby mode, energy loss can be suppressed.

[0067] Furthermore, the control circuit 19 narrows the setting range of the switching frequency by controlling a switching of the relay 16 between an on and an off state when it searches for a switching frequency at which the contactless power supply device 1 performs the output operation with constant voltage.

[0068] Note that details of the on / off control of relay 16 and the control of the switching frequency and the voltage applied to the transmission coil 14 by the control circuit 19 will be described later.

[0069] Next, the energy receiving device 3 will be described.

[0070] The resonant circuit 20 is an LC resonant circuit in which the receiving coil 21 and the resonant capacitor 22 are connected in parallel. One end of the receiving coil 21, which is contained in the resonant circuit 20, is connected to one end of the resonant capacitor 22 and, in conjunction with this, to an input terminal of the rectifier and smoothing circuit 24 via the coil 23. Furthermore, the other end of the receiving coil 21 is connected to the other end of the resonant capacitor 22 and, in conjunction with this, to the other input terminal of the rectifier and smoothing circuit 24.

[0071] The receiving coil 21 receives energy from the transmitting coil 14 by resonating with the alternating current flowing through the transmitting coil 14 of the energy transfer device 2. The receiving coil 21 outputs the received energy to the rectifier and smoothing circuit 24 via the resonant capacitor 22 and the coil 23. Note that the number of turns in the winding of the receiving coil 21 and the number of turns in the winding of the transmitting coil 14 of the energy transfer device 2 can be identical or different.

[0072] The resonant capacitor 22 is connected at one end to one end of the receiving coil 21 and, in conjunction with this, to the coil 23, and at the other end to the other end of the receiving coil 21 and the rectifier and smoothing circuit 24. The resonant capacitor 22 outputs the energy received by the receiving coil 21 to the rectifier and smoothing circuit 24 via the coil 23.

[0073] The coil 23 is an example of a second coil and is connected between the resonant circuit 20 and the rectifier and smoothing circuit 24. In the present embodiment, the coil 23 is connected at one end to the receiving coil 21 and the resonant capacitor 22 in such a way that it is in series with the receiving coil 21, and at the other end to the rectifier and smoothing circuit 24. The coil 23 outputs the energy received by the resonant circuit 20 to the rectifier and smoothing circuit 24. Note that arranging the coil 23 as in the SPL method makes it possible to suppress harmonic components of the received energy.

[0074] The rectifier and smoothing circuit 24 is an example of a rectifier circuit. It features a full-wave rectifier circuit 25, which includes four diodes connected in a bridge configuration, and a smoothing capacitor 26. It rectifies and smooths the energy received via the resonant circuit 20 and the coil 23 to convert the energy into direct current (DC) energy. The rectifier and smoothing circuit 24 outputs the DC energy to the load circuit 27.

[0075] The voltage sensing circuit 28 detects an output voltage between the two terminals of the rectifier and smoothing circuit 24. Since the output voltage between the two terminals of the rectifier and smoothing circuit 24 corresponds one-to-one to the output voltage of the resonant circuit 20, a measured value of the output voltage between the two terminals of the rectifier and smoothing circuit 24 indirectly represents a measured value of the output voltage of the resonant circuit 20. For the voltage sensing circuit 28, any of the various known voltage sensing circuits capable of detecting DC voltage can be used. The voltage sensing circuit 28 outputs a voltage detection signal, representing a measured value of the output voltage, to the constant voltage determination circuit 29.

[0076] The constant voltage determination circuit 29 determines, based on the measured output voltage value received by the voltage sensing circuit 28, whether the contactless power supply device 1 is performing the output operation at a constant voltage and whether the measured output voltage value is within a permissible voltage range when the output operation is performed at a constant voltage. The constant voltage determination circuit 29 notifies the transmitter 32 of the result of the determination. For this purpose, the constant voltage determination circuit 29 includes, for example, a memory circuit configured to store the permissible voltage range and a determination circuit 30, which includes an arithmetic operation circuit configured to compare a measured output voltage value with the permissible voltage range.

[0077] Furthermore, the constant voltage determination circuit 29 includes a switching element 31, such as a MOSFET, which is connected between the rectifier and smoothing circuit 24 and the load circuit 27. When switched off, the switching element 31 prevents current from flowing from the rectifier and smoothing circuit 24 to the load circuit 27 (i.e., Rac = ∞), while when switched on, the switching element 31 allows current to flow from the rectifier and smoothing circuit 24 to the load circuit 27. The determination circuit 30 of the constant voltage determination circuit 29 switches the switching element 31 between an on and an off state within a predetermined period while measured values ​​of the output voltage are outside the permissible voltage range.This process causes the resistance of the entire circuit, which includes the load circuit 27 connected to the rectifier and smoothing circuit 24, to change within the predetermined period. Therefore, the determining circuit 30 is able to determine whether the contactless power supply device 1 is performing the output operation with a constant voltage by determining whether the measured values ​​of the output voltage remain essentially constant while the switching element 31 is switching between an on and an off state.Therefore, while measured values ​​of the output voltage are essentially constant, even when the determining circuit 30 switches the switching element 31 between an on and an off state in a predetermined period, the transmitter 32 notifies that the contactless power supply device 1 is performing the output operation with constant voltage.

[0078] Furthermore, if measured output voltage values ​​indicate that the contactless power supply device 1 is performing the output process with a constant voltage for a certain duration that is longer than the predetermined period, the detection circuit 30 suspends the switching of the switching element 31 between an on and an off state and holds the switching element 31 in the on state. The detection circuit 30 determines whether the measured output voltage value is within the permissible voltage range or not and notifies the transmitter 32 of the result of the determination.

[0079] If the measured values ​​of the output voltage are within the permissible voltage range for a certain duration which is longer than the predetermined period, the determining circuit 30 notifies the transmitter 32 of a determination result which indicates that the contactless power supply device 1 is performing the output process with constant voltage and the measured values ​​of the output voltage are within the permissible voltage range.

[0080] Note that, according to one modification, the constant voltage determination circuit 29 may have a resistor connected in parallel with the rectifier and smoothing circuit 24 and the load circuit 27. In this case, the switching element 31 may be arranged such that it is in series with the resistor and in parallel with the load circuit 27. In this case, the determination circuit 30 switches off the switching element 31 while measured output voltage values ​​are within the permissible voltage range. Conversely, if a measured output voltage value is outside the permissible voltage range, the determination circuit 30 may, as in the embodiment described above, switch the switching element 31 between an on and an off state within the predetermined period.According to the modification, the energy supply to the load circuit 27 is maintained even if the contactless power supply device 1 does not perform the constant voltage output operation.

[0081] Furthermore, a second switching element, such as a MOSFET, can be arranged in parallel with the previously described resistor and in series with the load circuit 27, according to another modification. In this case, the determining circuit 30 switches on the second switching element while measured output voltage values ​​are within the permissible voltage range, thereby enabling energy to be supplied to the load circuit 27. Conversely, if a measured output voltage value is outside the permissible voltage range, the determining circuit 30 can switch off the second switching element and interrupt the energy supply to the load circuit 27. Even if the voltage of received energy has risen to an excessively high level while the switching frequency in the energy transfer device 2 is being set, this configuration prevents the excessively high voltage from being applied to the load circuit 27.

[0082] The transmitter 32 is an example of a first communication device and generates a wireless signal in each predetermined transmission period. This signal contains determination information indicating whether the contactless power supply device 1 is performing the constant voltage output operation and whether measured output voltage values ​​are within the permissible voltage range. This determination is based on a result received by the determination circuit 30 of the constant voltage determination circuit 29. The transmitter then transmits the wireless signal to the receiver 17 of the power transmission device 2. For this purpose, the transmitter 32 includes, for example, a communication circuit that generates a wireless signal according to a predetermined wireless communication standard and an antenna for outputting the wireless signal.Note that, as with receiver 17, the predetermined wireless communication standard can be, for example, ISO / IEC 15693, ZigBee (registered trademark) or Bluetooth (registered trademark).

[0083] One process of the contactless power supply device 1 is described in detail below.

[0084] In the present embodiment, the control circuit 19 of the energy transmission device 2 controls the switching of the relay between an on and an off state and the switching frequency and the voltage of an alternating current energy supplied to the transmission coil 14 by the energy supply circuit 10, based on determination information received by the receiver 17, in such a way that the contactless energy supply device 1 continues the output process with a constant voltage.

[0085] The contactless power supply device 1 differs from the contactless power supply device according to the SPL method in that a resonance of the resonant circuit on the power transmission side is not used and the contactless power supply device 1 has the coil 15 which is connected in series with the transmission coil 14. Therefore, the frequency response of the output voltage of the contactless power supply device 1 when the two ends of the coil 15 are short-circuited is similar to the frequency response of the output voltage of the contactless power supply device according to the SPL method when in the equivalent circuit in Fig. 1. The capacitance Cr1 of the capacitor connected in series with the transmission coil in the resonant circuit on the power transmission side is increased, thereby lowering the resonant frequency of the resonant circuit on the power transmission side to prevent the resonance of the resonant circuit on the power transmission side from affecting the power supply.

[0086] Fig. Figure 5 is a diagram illustrating an example of simulation results of the frequency response of an output voltage from the contactless power supply device 1 when the two ends of the coil 15 are short-circuited. Fig. 5 represents a frequency plotted along the horizontal axis and an output voltage plotted along the vertical axis. Note that in the simulation, the same values ​​are used as the parameter values ​​of the respective circuit elements, which are used in the Fig. The simulations used in the two illustrations are shown. Graph 501 represents the frequency response of the output voltage when the coupling coefficient k is set to k = 0.15 and the AC equivalent resistance of the load circuit 27 is set to Rac. Graph 502 represents the frequency response of the output voltage when the coupling coefficient k is set to k = 0.15 and the AC equivalent resistance of the load circuit 27 is set to (10*Rac). Graph 503 represents the frequency response of the output voltage when the coupling coefficient k is set to k = 0.3 and the AC equivalent resistance of the load circuit 27 is set to Rac. Graph 504 represents the frequency response of the output voltage when the coupling coefficient k is set to k = 0.3 and the AC equivalent resistance of the load circuit 27 is set to (10*Rac).Furthermore, graph 505 represents a frequency response of the output voltage when the coupling coefficient k is set to k = 0.6 and the AC equivalent resistance of the load circuit 27 is set to Rac. Additionally, graph 506 represents a frequency response of the output voltage when the coupling coefficient k is set to k = 0.6 and the AC equivalent resistance of the load circuit 27 is set to (10*Rac).

[0087] In Fig. 5 are, since the transmission coil 14 does not resonate, extreme values ​​of the output voltage on the low-frequency side compared to Fig. 2 in the in Fig. The frequency range illustrated in Figure 5 has disappeared. However, even in this case, for each coupling coefficient, there exists a combination of frequency and output voltage at which the output voltage becomes essentially constant (i.e., a constant voltage is output), even if the equivalent AC resistance of the load circuit 27 changes, provided that the coupling coefficient k does not change (there are three combinations, illustrated in the figure by points 511 to 513). Therefore, it follows that even if an AC power is applied to the transmission coil 14 at a switching frequency at which the transmission coil 14 does not resonate, it is possible to make the contactless power supply device 1 perform the output operation with a constant voltage, regardless of any change in the resistance value of the load circuit 27.Furthermore, although, as illustrated by points 511 to 513, output voltages differ from one another depending on the coupling coefficient when a constant voltage is output against a deviation of the resistance value of the load circuit 27, the differences in the output voltage can be reduced to an essentially constant output voltage, irrespective of the coupling coefficient, by setting a voltage applied to the transmission coil 14.

[0088] Fig. Figure 6 is a diagram showing an example of simulation results of the frequency response of the output voltage when the voltage applied to the transmission coil 14 is adjusted according to the coupling coefficient in the diagram. Fig. The simulation in section 5 illustrates how the changes are made. Fig. Graph 601 represents a frequency response along the horizontal axis and an output voltage along the vertical axis. Graph 602 shows a frequency response of the output voltage when the coupling coefficient k is set to k = 0.15, the equivalent AC resistance of the load circuit 27 is set to Rac, and the voltage applied to the transmission coil is set to Vin. Graph 602 also represents a frequency response of the output voltage when the coupling coefficient k is set to k = 0.15, the equivalent AC resistance of the load circuit 27 is set to (10*Rac), and the voltage applied to the transmission coil is set to Vin.Furthermore, graph 603 represents a frequency response of the output voltage when the coupling coefficient k is set to k = 0.3, the equivalent AC resistance of the load circuit 27 is set to Rac, and the voltage applied to the transmission coil is set to (0.47*Vin). Additionally, graph 604 represents a frequency response of the output voltage when the coupling coefficient k is set to k = 0.3, the equivalent AC resistance of the load circuit 27 is set to (10*Rac), and the voltage applied to the transmission coil is set to (0.47*Vin). Furthermore, graph 605 represents a frequency response of the output voltage when the coupling coefficient k is set to k = 0.6, the equivalent AC resistance of the load circuit 27 is set to Rac, and the voltage applied to the transmission coil is set to (0.19*Vin).Furthermore, graph 606 represents a frequency response of the output voltage when the coupling coefficient k is set to k = 0.6, the AC equivalent resistance of the load circuit 27 is set to (10* Rac) and the voltage applied to the transmission coil is set to (0.19*Vin).

[0089] Combinations of a frequency and an output voltage that correspond to the in Fig. The five illustrated points 511 to 513, where the output voltage becomes essentially constant (i.e., a constant voltage is output) even when the AC equivalent resistance of the load circuit 27 changes, provided that the coupling coefficient k does not change, are three combinations specified by points 611 to 613. The output voltages at the respective points 611 to 613 are essentially the same.

[0090] The preceding description shows that even if either the resistance value of the load circuit 27 or the coupling coefficient changes, it is possible to adjust the switching frequency and the voltage of the AC energy applied to the transmission coil 14 appropriately to keep the output voltage essentially constant.

[0091] However, note that, as in Fig. Figure 6 illustrates that the frequency at which the contactless power supply device 1 performs the constant-voltage output operation increases with increasing coupling coefficient. Furthermore, in order for the output voltage at coupling coefficient k = 0.6 to be essentially equal to the output voltage at coupling coefficient k = 0.15, the input voltage at coupling coefficient k = 0.6 must be 0.19 times the input voltage at coupling coefficient k = 0.15. Since the energy transfer, which occurs at a reduced input voltage as described above, causes the current flowing through the transmission coil 14 to increase, even if the power factor is good, there is a possibility that Joule losses will increase.

[0092] Fig. Figure 7 is a diagram illustrating an example of simulation results for the frequency response of the output voltage of the contactless power supply device 1 when the two ends of coil 15 are separated and the voltage applied to the transmission coil 14 is varied according to the coupling coefficient. Note that the simulation uses the same values ​​as the parameters of the respective circuit elements, which are used in the Fig. The simulations used in the two illustrations were identical, with the exception of the inductance of coil 15. Furthermore, the inductance of coil 15 is fixed at 250 µH. Fig. Graph 701 represents a frequency response along the horizontal axis and an output voltage along the vertical axis. Graph 701 depicts the frequency response of the output voltage when the coupling coefficient k is set to k = 0.15, the equivalent AC resistance of the load circuit 27 is set to Rac, and the voltage applied to the transmission coil 14 is set to Vin. Graph 702 also depicts a frequency response of the output voltage when the coupling coefficient k is set to k = 0.15, the equivalent AC resistance of the load circuit 27 is set to (10*Rac), and the voltage applied to the transmission coil 14 is set to Vin.Furthermore, graph 703 represents a frequency response of the output voltage when the coupling coefficient k is set to k = 0.3, the equivalent AC resistance of the load circuit 27 is set to Rac, and the voltage applied to the transmission coil 14 is set to (0.48*Vin). Additionally, graph 704 represents a frequency response of the output voltage when the coupling coefficient k is set to k = 0.3, the equivalent AC resistance of the load circuit 27 is set to (10*Rac), and the voltage applied to the transmission coil 14 is set to (0.48*Vin). Furthermore, graph 705 represents a frequency response of the output voltage when the coupling coefficient k is set to k = 0.6, the AC equivalent resistance of the load circuit 27 is set to Rac, and the voltage applied to the transmission coil 14 is set to (0.22*Vin).Furthermore, graph 706 represents a frequency response of the output voltage when the coupling coefficient k is set to k = 0.6, the AC equivalent resistance of the load circuit 27 is set to (10* Rac) and the voltage applied to the transmission coil 14 is set to (0.22*Vin).

[0093] In this case, although a deviation in the output voltage increases due to a change in the resistance value of the load circuit 27, there exists a frequency at which the deviation in the output voltage is suppressed for each coupling coefficient, as illustrated by points 711 to 713. Furthermore, it is evident that adjusting the voltage of the AC power supplied to the transmission coil 14 also allows the output voltage to be kept essentially constant, regardless of the coupling coefficient. Moreover, the frequency at which a constant voltage is output is lower with respect to the same coupling coefficient than that in the case where the two ends of the coil 15 are short-circuited.Furthermore, the gain for the same coupling coefficient is lower than in the case where the two ends of the coil 15 are short-circuited, because inductance components that do not contribute to energy transfer increase on the energy transfer side.

[0094] Therefore, it is evident that searching for a switching frequency at which the contactless power supply device 1 performs the output operation with constant voltage in the case that the two ends of the coil 15 are short-circuited when the coupling coefficient is relatively low, and searching for a switching frequency at which the contactless power supply device 1 performs the output operation with constant voltage in the case that the two ends of the coil 15 are disconnected when the coupling coefficient is increased to a certain level, makes it possible to narrow the adjustment range of the switching frequency.

[0095] Fig. Figure 8 is a diagram illustrating an example of simulation results of the frequency response of the output voltage of the contactless power supply device 1 when, while switching between whether the two ends of the coil 15 are short-circuited or not, the voltage applied to the transmission coil 14 is changed according to the coupling coefficient. Fig. Graph 801 shows a frequency response along the horizontal axis and an output voltage along the vertical axis on the left. A phase response is also shown along the vertical axis on the right. Graph 801 represents the frequency response of the output voltage when, with the two ends of the first coil 15 short-circuited, the coupling coefficient k is set to k = 0.15, and the voltage applied to the transmission coil 14 is set to Vin. Graph 802 represents the frequency response of the output voltage when, with the two ends of the first coil 15 short-circuited, the coupling coefficient k is set to k = 0.35, and the voltage applied to the transmission coil 14 is set to (0.4 * Vin).Furthermore, graph 803 represents a frequency response of the output voltage when, in the case that the two ends of the first coil 15 are disconnected, the coupling coefficient k is set to k = 0.36, and the voltage applied to the transmission coil 14 is set to Vin. Furthermore, graph 804 represents a frequency response of the output voltage when, in the case that the two ends of the first coil 15 are disconnected, the coupling coefficient k is set to k = 0.6, and the voltage applied to the transmission coil 14 is set to (0.56*Vin). Finally, graph 805 represents a frequency response of the phase delay of current with respect to the voltage applied to the transmission coil 14 when the two ends of the coil 15 are short-circuited and the coupling coefficient k is set to k = 0.15.Furthermore, graph 806 represents a frequency response of a phase delay of current with respect to the voltage applied to the transmission coil 14 when the two ends of the coil 15 are disconnected and the coupling coefficient k is set to k = 0.6. Note that in the simulation, the following were assumed: an inductance of the transmission coil 14 Lp = 174 µH, a capacitance of the resonant capacitor 22 Cp = 20 nF, an inductance of the coil 23 Lop = 2200 µH, an inductance of the coil 15 L1 = 250 µH, winding resistances Ri = Ris = 0.1 Ω, n = 1, a voltage Vin = 260 V applied to the transmission coil 14, and a resistance of the load circuit 27 Ro = 220 Ω.

[0096] Furthermore, frequency f1 is a frequency at which, when the two ends of coil 15 are short-circuited and the coupling coefficient k is set to k = 0.15, the output voltage becomes essentially constant, even if the resistance of the load circuit 27 changes; that is, the contactless power supply device 1 performs the output operation with a constant voltage. Similarly, frequency f2 is a frequency at which, when the two ends of coil 15 are short-circuited and the coupling coefficient k is set to k = 0.35, the contactless power supply device 1 performs the output operation with a constant voltage. Additionally, frequency f3 is a frequency at which, when the two ends of coil 15 are disconnected and the coupling coefficient k is set to k = 0.36, the contactless power supply device 1 performs the output operation with a constant voltage.Furthermore, the frequency f4 is a frequency at which, when the two ends of the coil 15 are separated and the coupling coefficient k is set with k = 0.6, the contactless power supply device 1 performs the output operation with constant voltage.

[0097] As illustrated by graphs 801 to 804, it is evident that even if the coupling coefficient varies, it allows for a reasonable adjustment of the switching frequency and the voltage of the alternating current energy applied to the transmission coil 14 to keep the output voltage essentially constant.

[0098] Furthermore, it is evident that, since a frequency range from frequency f1 to frequency f2 and a frequency range from frequency f3 to frequency f4 partially overlap, the adjustment range of the switching frequency at which the contactless power supply device 1 performs the output process with constant voltage is greater compared to the cases which in Fig. 6 and Fig. Figure 7 illustrates how the switching can be performed between whether the two ends of the coil 15 are short-circuited or not.

[0099] Note that the lower limit of the setting range of a switching frequency, in the case where the two ends of coil 15 are disconnected (i.e., a second frequency range), can be set, for example, to a frequency at which the voltage of the AC energy supplied to the transmission coil 14 is essentially the same as the voltage of the AC energy supplied to the transmission coil 14 when the coupling coefficient is at the minimum of its expected values. Furthermore, the upper limit of the setting range of a switching frequency, in the case where the two ends of coil 15 are short-circuited (i.e.,a first frequency range) be set to a switching frequency at which the output operation is carried out with constant voltage in the case that the two ends of the coil 15 are short-circuited, if the coupling coefficient is essentially equal to a coupling coefficient which corresponds to the lower limit of the setting range of the switching frequency in the case that the two ends of the coil 15 are separated.

[0100] Furthermore, to improve energy transmission efficiency, it is preferred that the power supply circuit 10 and the transmission coil 14 of the energy transmission device 2 operate with soft switching (inductive process). For the power supply circuit 10 and the transmission coil 14 to operate with soft switching, it is preferred that the phase of the current flowing through the transmission coil 14 is delayed with respect to the phase of any voltage applied to it. This configuration allows, for example, current to flow from the source terminal to the drain terminal of the switching element 13-1 when the switching element 13-1 and the switching element 13-4 are switched on, and thus enables the power supply circuit 10 and the transmission coil 14 to operate with soft switching, thereby suppressing the occurrence of switching losses.

[0101] In the present embodiment, as illustrated by graphs 805 and 806, the phase delays at frequencies where the contactless power supply device 1 performs the constant voltage output operation have positive values, regardless of the coupling coefficient. Therefore, it is evident that the contactless power supply device 1, according to the present embodiment, is capable of causing the power supply circuit 10 and the transmission coil 14 to operate with soft switching.

[0102] Consequently, in order to achieve the output process with constant voltage, the control circuit 19 controls the switching of the relay 16 between an on and an off state and the switching frequency and the voltage of the alternating current energy which is applied to the transmission coil 14, as described below.

[0103] If information contained in a wireless signal received by the power receiving device 3 via the receiver 17 indicates that the contactless power supply device 1 will not perform the constant voltage output operation, the control circuit 19 switches on the relay 16 (i.e., short-circuits the two ends of the coil 15) and subsequently increases the switching frequency from the lower limit of a predetermined frequency range (for example, frequency f1 in the case where the two ends of the coil 15 are short-circuited). Fig. 8) to the upper limit of the frequency that allows a constant voltage output (for example, frequency f2). If a constant voltage output is not reached, even if the switching frequency reaches the upper limit of the frequency that allows a constant voltage output when the two ends of the first coil 15 are short-circuited, the control circuit 19 switches off the relay 16, thereby disconnecting the two ends of the coil 15. The control circuit 19 subsequently increases the switching frequency when the two ends of the coil 15 are disconnected from the lower limit of the frequency that allows a constant voltage output when the two ends of the coil 15 are disconnected (for example, frequency f3). Fig. 8), to the upper limit of the frequency that allows a constant voltage output (for example, frequency f4 in Fig. 8).

[0104] Alternatively, when changing the switching frequency, the control circuit 19 can first switch off the relay 16 and subsequently reduce the switching frequency, if the two ends of the coil 15 are disconnected, from the upper limit of the frequency that allows a constant voltage output to the lower limit of the frequency that allows a constant voltage output. If a constant voltage output is not achieved, even if the switching frequency reaches the lower limit of the frequency that allows a constant voltage output in the case of the two ends of the coil 15 being disconnected, the control circuit 19 can switch on the relay 16, thereby short-circuiting the two ends of the coil 15 and subsequently reducing the switching frequency from the upper limit to the lower limit of the frequency that allows a constant voltage output.

[0105] It is preferred that, in order for the constant voltage determination circuit 29 of the energy receiving device 3 to be able to check whether the output voltage has become substantially constant or not, the control circuit 19 changes the switching frequency stepwise in such a way that the same switching frequency is maintained for a duration which is longer than the period in which the determination circuit 30 of the constant voltage determination circuit 29 switches the switching element 31 between an on and an off state.

[0106] Furthermore, it is preferred that, while the switching frequency is being set, the control circuit 19 reduces the voltage applied to the transmission coil 14 to a lower limit voltage. This configuration prevents the voltage of the energy supplied to the energy receiving device 3 from rising excessively.

[0107] If the determination information contained in the wireless signal received by the power receiving device 3 via the receiver 17 indicates that measured output voltage values, although outside the permissible voltage range, are essentially constant even when the resistance value of the load circuit 27 changes (i.e., the output operation is performed at a constant voltage), the control circuit 19 subsequently maintains a constant switching frequency. Next, the control circuit 19, referring to the reference table, where each entry specifies a relationship between a switching frequency and a duty cycle, determines a duty cycle that ensures a constant voltage is output at the switching frequency, independent of the coupling coefficient, and is used in the on / off control of the switching element SW of the power factor enhancement circuit 12.The control circuit 19 controls the gate driver 18-1 such that the switching element SW of the power factor enhancement circuit 12 is switched between an on and an off state according to the duty cycle. This process causes the voltage applied to the transmission coil 14 to be adjusted such that the output voltage from the resonant circuit 20 is within the permissible voltage range, i.e., a constant voltage is output regardless of the coupling coefficient. If the determination information contained in a wireless signal received by the power receiving device 3 via the receiver 17 indicates that the measured values ​​of the output voltage are within the permissible voltage range, the control circuit 19 maintains the switching frequency and the voltage of the AC power supplied to the transmission coil 14 constant.

[0108] Note that instead of determining a duty cycle with reference to the reference table described above, the control circuit 19 can gradually change the duty cycle until the determination information contained in a wireless signal received by the energy receiving device 3 via the receiver 17 indicates that measured values ​​of the output voltage are within the permissible voltage range.

[0109] Fig. Figure 9 is a process flow diagram of a control system for switching the relay 16 between an on and an off state and the switching frequency and the voltage of the alternating current energy applied to the transmission coil 14, wherein the control is carried out by the control circuit 19.

[0110] If information received by the energy receiving device 3 indicates that a constant voltage output operation will not be performed, the control circuit 19 controls the power supply circuit 10 to reduce the voltage of an AC energy supplied to the transmission coil 14 to a predetermined value (step S101). The control circuit 19 then switches on the relay 16, thereby short-circuiting the two ends of the coil 15 (step S102).

[0111] The control circuit 19 controls the power supply circuit 10 to gradually increase the switching frequency from the lower limit to the upper limit of a switching frequency setting range when both ends of the coil 15 are short-circuited (step S103). Based on information received from the power receiving device 3, the control circuit 19 determines whether or not the output operation is to be performed with a constant voltage at any given switching frequency (step S104).

[0112] If it is specified that the output operation is performed with constant voltage at any switching frequency (Yes in step S104), the control circuit 19 controls the power supply circuit 10 to increase the voltage of the AC power supplied to the transmission coil 14 until an output voltage from the resonant circuit 20 of the energy receiving device 3 is within a predetermined permissible voltage range (step S105).

[0113] On the other hand, if it is not specified that the output operation is to be carried out with constant voltage at any switching frequency (No in step S104), the control circuit 19 switches off the relay 16, thereby short-circuiting the two ends of the coil 15 (step S106). The control circuit 19 controls the power supply circuit 10 to gradually increase the switching frequency from the lower limit to the upper limit of a switching frequency setting range in the event that the two ends of the coil 15 are disconnected (step S107). The control circuit 19 determines, with reference to setting information received from the power receiving device 3, whether or not it is specified that the output operation is to be carried out with constant voltage at any switching frequency (step S108).

[0114] If it is specified that the output operation is performed with constant voltage at any switching frequency (Yes in step S108), the control circuit 19 controls the power supply circuit 10 to increase the voltage of the AC power supplied to the transmission coil 14 until the output voltage from the resonant circuit 20 of the power receiving device 3 is within the predetermined permissible voltage range (step S105).

[0115] On the other hand, if it is not specified that the output operation is performed with constant voltage at an arbitrary switching frequency (No in step S108), the control circuit 19 determines whether the control has entered an infinite loop or not (step S109). For example, if the switching of relay 16 between an on and an off state (steps S102 and S105) is repeated a predetermined number of times (for example, three or five times) or more without achieving the output operation with constant voltage, the control circuit 19 determines that the control has entered an infinite loop.

[0116] If the control has not entered an infinite loop (No in step S109), the control circuit 19 continues processing step S102. On the other hand, if the control has entered an infinite loop (Yes in step S109), the contactless power supply device 1 is unable to perform the output operation with a constant voltage within the set switching frequency range, i.e., within an expected range of a coupling coefficient. Therefore, the control circuit 19 suspends the power supply from the power supply circuit 10 to the transmission coil 14, thereby suspending the power transfer from the power transmission device 2 to the power receiving device 3 (step S110).Note that a foreign object made of metal near the transmission coil 14 and the receiving coil 21 is considered the reason why the contactless power supply device 1 is unable to perform the output operation with a constant voltage within the expected range of the coupling coefficient. Therefore, in step S110, the control circuit 19 can output an anomaly signal indicating that a foreign object made of metal has been detected to another device via an interface not shown.

[0117] After step S105 or S110, the control circuit 19 terminates the switching of the relay 16 between an on and an off state and the control of the switching frequency and the voltage of the alternating current energy supplied to the transmission coil 14.

[0118] As previously described, the contactless power supply device can narrow the adjustment range of the switching frequency of alternating current energy supplied to the transmission coil when the constant voltage output operation is carried out in an environment where the coupling coefficient does not remain constant, by arranging a coil connected in series with the transmission coil of the power transfer device and not coupled to the receiving coil, even at the time of power transmission, and by short-circuiting or disconnecting the two ends of the coil.Furthermore, the contactless power supply device suppresses an increase in current flowing through the transmission coil by supplying the transmission coil with AC energy at a switching frequency where the transmission coil is not resonating, thus ensuring that the input impedance remains at a certain magnitude even as the coupling coefficient decreases. Therefore, the contactless power supply device is able to suppress energy loss even when the coupling coefficient between the transmission coil and the receiving coil is low. Additionally, the contactless power supply device monitors an output voltage from the resonant circuit of the receiving device and controls the switching frequency and the voltage of the AC energy supplied to the transmission coil according to this output voltage.This configuration allows the contactless power supply device to perform the output process with constant voltage, even if the coupling coefficient between the transmission coil and the receiving coil changes or the resistance value of the load circuit changes.

[0119] According to a modification, a switching element can be used to control the disconnection or short-circuiting of the two ends of a coil 15 which is connected in series with a transmission coil 14.

[0120] Fig. Figure 10 is a circuit diagram of an energy transfer device 2 according to the modification. In the modification, as in the embodiment described above, the transfer coil 14 and the coil 15, which is not coupled to a receiving coil 21 during energy transfer, are connected in series with a power supply circuit 10. Note that the configuration of the power supply circuit 10 can be identical to that of the power supply circuit 10 in the embodiment described above. Two switching elements 161 and 162, connected in series, are connected in parallel with the coil 15. Note that the switching elements 161 and 162 are another example of the first short-circuit circuit. For each of the switching elements 161 and 162, for example, an n-channel MOSFET can be used.The source terminal of switching element 161 and the source terminal of switching element 162 are connected together, the drain terminal of switching element 161 is connected to one end of coil 15, and the drain terminal of switching element 162 is connected to the other end of coil 15. Because of this configuration, switching off both switching elements 161 and 162 prevents current from flowing through parasitic diodes of the switching elements, thus isolating the two ends of coil 15. Furthermore, each of the gate terminals of switching elements 161 and 162 is connected to a gate driver (not shown).

[0121] A control circuit 19 is capable of short-circuiting the two ends of the coil 15 by simultaneously switching on the switching elements 161 and 162 via the gate driver. Conversely, the control circuit 19 is capable of disconnecting the two ends of the coil 15 by simultaneously switching off the switching elements 161 and 162 via the gate driver.

[0122] Furthermore, the inventors have found that if the resistance value of the load circuit of the energy receiving device has a preset value, the input impedance of the contactless power supply device according to the embodiment described above has a local minimum value at a frequency at which the contactless power supply device performs the output process with constant voltage.

[0123] Fig. Figure 11 is a diagram illustrating an example of the relationship between the frequency response of an output voltage and the frequency response of an input impedance of the contactless power supply device according to the SPL method. In the upper diagram in Fig. Figure 11 shows a frequency plotted along the horizontal axis and an output voltage plotted along the vertical axis. Additionally, the lower diagram shows... Fig. Figure 11 shows a frequency plotted along the horizontal axis and an input impedance plotted along the vertical axis. Note that the simulation uses the same values ​​as the parameters of the respective circuit elements, which are used in the Fig. The simulations used in the two illustrations were used. In the upper diagram, graph 1101 represents the same graph as graph 203 in the previous diagram. Fig. 2) a frequency response of the output voltage from the contactless power supply device 1 when the coupling coefficient k is set to k = 0.3 and the AC equivalent resistance of the load circuit 27 is set to Rac. Furthermore, graph 1102 (the same as graph 204 in Fig. 2) A frequency response of the output voltage of the contactless power supply device 1 when the coupling coefficient k is set to k = 0.3 and the AC equivalent resistance of the load circuit 27 is set to (10*Rac). Furthermore, graph 1111 in the lower diagram represents a frequency response of the input impedance of the contactless power supply device 1 when the coupling coefficient k is set to k = 0.3 and the AC equivalent resistance of the load circuit 27 is set to Rac. Additionally, graph 1112 represents a frequency response of the input impedance of the contactless power supply device 1 when the coupling coefficient k is set to k = 0.3 and the AC equivalent resistance of the load circuit 27 is set to (100*Rac).

[0124] As in Fig. As illustrated in Figure 11, the input impedance exhibits a local minimum value at a frequency f0, at which the contactless power supply device 1 performs the output operation at constant voltage, when the AC equivalent resistance of the load circuit 27 is set to Rac. In other words, the current flowing through the transmission coil 14 exhibits a local maximum value at frequency f0.

[0125] Therefore, according to a modification, the control circuit of the power transmission device can determine whether the contactless power supply device performs the output process at constant voltage or not, based on a frequency response of current flowing through the transmission coil.

[0126] Fig. Figure 12 is a schematic view of a configuration of a contactless power supply device according to the modification. As in Fig. As illustrated in Figure 12, a contactless power supply device 41 comprises a power transmission device 42 and a power receiving device 43, to which energy is transferred from the power transmission device 42 through space without contact. The power transmission device 42 comprises a power supply circuit 50, a transmission coil 54, a capacitor 55, a coil 56, a current sensing circuit 57, a receiver 58, a relay 59, a gate driver 60, and a control circuit 61.On the other hand, the energy receiving device 43 has a resonant circuit 70, which includes a receiving coil 71 and a resonant capacitor 72, a coil 73, a rectifier and smoothing circuit 74, which includes a full-wave rectifier circuit 75 and a smoothing capacitor 76, a load circuit 77, a voltage sensing circuit 78, a constant voltage determination circuit 79, a fixed load circuit 82 and a transmitter 83.

[0127] The contactless power supply device 41 differs from the one described in the energy transmission device 42 with respect to the energy transmission device 42. Fig. Figure 4 illustrates the contactless power supply device 1 in the configuration of the power supply circuit 50, in that it includes the capacitor 55 and the current sensing circuit 57, and in part a control system implemented by the control circuit 61. Furthermore, the contactless power supply device 41 differs from the contactless power supply device 1 with respect to the energy receiving device 43, in that it includes the fixed load circuit 82. Therefore, the differences described above and the related facts are explained below.

[0128] The energy transmission device 50 supplies alternating current energy to the transmission coil 54 at an adjustable switching frequency and voltage. For this purpose, the energy supply circuit 50 comprises a variable voltage energy source 51, a DC-DC converter 52, and three switching elements 53-1 to 53-3.

[0129] The variable voltage power source 51 is a power source that supplies direct current (DC) energy and is capable of adjusting the DC voltage according to the control circuit 61. Note that the variable voltage power source 51 can have any number of different circuit configurations capable of adjusting the input voltage. While the contactless power supply device 41 performs the constant voltage output operation, the DC energy supplied by the variable voltage power source 51 is converted into alternating current (AC) energy by the switching elements 53-1 and 53-2 and supplied to the transmission coil 54.On the other hand, the direct current energy supplied by the variable voltage energy source 51, while the switching frequency is adjusted for the contactless power supply device 41 to carry out the constant voltage output operation, is supplied to the transmission coil 54 via the DC converter 52 and the switching element 53-3.

[0130] The input terminal of the DC-DC converter 52 is connected to the positive electrode of the variable voltage power source 51, and the output terminal of the DC-DC converter 52 is connected to one end of the capacitor 55 via a diode D and the switching element 53-3. The DC-DC converter 52 reduces the voltage of the DC power supplied by the variable voltage power source 51 to a predetermined voltage (for example, 5 V).

[0131] While the switching frequency for the contactless power supply device 41 is set to carry out the output operation with constant voltage, the voltage output by the DC converter 52 is supplied to the transmission coil 54 via the diode D, the switching element 53-3 and the capacitor 55.

[0132] For each of the switching elements 53-1 to 53-3, for example, an n-channel MOSFET can be used. Switching elements 53-1 and 53-2 are connected in series between the positive and negative terminals of the variable voltage power source 51. Furthermore, switching element 53-1 is connected to the positive terminal of the variable voltage power source 51, while switching element 53-2 is connected to the negative terminal of the variable voltage power source 51. The drain terminal of switching element 53-1 is connected to the positive terminal of the variable voltage power source 51, and the source terminal of switching element 53-1 is connected to the drain terminal of switching element 53-2. In addition, the source terminal of the switching element 53-1 and the drain terminal of the switching element 53-2 are connected to one end of the transmission coil 54 via the capacitor 55.Furthermore, the source terminal of the switching element 53-2 is connected to the terminal of the negative electrode of the variable voltage energy source 51 and the other end of the transmission coil 54 via the current sensing circuit 57 and the coil 56.

[0133] Furthermore, the drain terminal of the switching element 53-3 is connected to the output terminal of the DC-DC converter 52, and the source terminal of the switching element 53-3 is connected to one end of the transmission coil 54 via the capacitor 55. The gate terminals of the switching elements are connected to the gate driver 60.

[0134] While the contactless power supply device 41 performs the constant voltage output operation, the gate driver 60 holds the switching element 53-3 in the off state according to a control signal from the control circuit 61. Furthermore, the gate driver 60 alternately switches the switching elements 53-1 and 53-2 between an on and an off state at a switching frequency at which the constant voltage output operation is performed, according to a control signal from the control circuit 61. In other words, when the switching element 53-1 is on and the switching element 53-2 is off, current flows to the transmission coil 54 in conjunction with energy supplied to the capacitor 55 from the variable voltage power source 51 through the switching element 53-1, and the capacitor 55 is charged.On the other hand, when the switching element 53-1 is switched off and the switching element 53-2 is switched on, the capacitor 55 is discharged and current flows from the capacitor 55 to the transmission coil 54.

[0135] Furthermore, while the switching frequency for the contactless power supply device 41 is being set to perform the constant voltage output operation, the gate driver 60 holds the switching element 53-1 in the off state according to a control signal from the control circuit 61 and alternately switches the switching element 53-3 and the switching element 53-2 between an on and an off state at the switching frequency according to a control signal from the control circuit 61.

[0136] The capacitor 55 is connected between the transmission coil 54 and the power supply circuit 50. The capacitor 55 supplies alternating current energy to the transmission coil 54 at the switching frequency by repeatedly charging and discharging in response to the switching elements changing between an on and an off state at the switching frequency. It is preferred that the capacitance of the capacitor 55 is set such that the resonant frequency of the transmission coil 54 and the capacitor 55 is lower than the resonant frequency of the resonant circuit 70 of the power receiving device 43 and lower than the lower limit of the frequency of a frequency range in which the switching frequency is set, so that the transmission coil 54 and the capacitor 55 do not operate as a resonant circuit in the frequency range in which the switching frequency is set.

[0137] The current sensing circuit 57 is connected between the transmission coil 54 and the power supply circuit 50 and measures the current flowing through the transmission coil 54. The current sensing circuit 57 outputs a measured current value to the control circuit 61. Note that the current sensing circuit 57 can be connected to the transmission coil 54 in parallel with the capacitor 55, in conjunction with a deflection capacitor (not shown) connected in series with the current sensing circuit 57. In this case, the current sensing circuit 57 is able to indirectly measure the current flowing through the transmission coil 54.

[0138] Furthermore, the constant voltage determination circuit 79 of the energy receiving device 43 has a determination circuit 80 and a switching element 81, each of which is similar to the determination circuit 30 and the switching element 31 according to the embodiment described above.

[0139] While measured output voltage values ​​from the resonant circuit 70, as measured by the voltage sensing circuit 78, are within the permissible voltage range, i.e., the contactless power supply device 40 operates at a constant voltage output, the determining circuit 80 of the constant voltage determining circuit 79 switches on the switching element 81, thereby causing the output voltage from the resonant circuit 70 to be supplied to the load circuit 77 via the rectifier and smoothing circuit 74. Conversely, if measured output voltage values ​​are outside the permissible voltage range, the determining circuit 80 switches off the switching element 81, preventing the output voltage from the resonant circuit 70 from being supplied to the load circuit 77.

[0140] The fixed load circuit 82 is connected in parallel to the load circuit 77 with the rectifier and smoothing circuit 74 and, while the switching frequency is being set, provides the energy receiving device 43 with a load that is essentially the same as a load that serves as a reference for the load circuit 77 (in the case of the in Fig. (9 illustrated simulation, for example Rac). For this purpose, the fixed load circuit 82 is connected in parallel to the load circuit 77 via the rectifier and smoothing circuit 74 and includes a resistor R1 with a resistance value corresponding to the load that serves as the reference for the load circuit 77. Resistor R1 is connected in series with a switching element SW1, which is an n-channel MOSFET. Furthermore, the fixed load circuit 82 includes a resistor R2 and a switching element SW2, which is an npn bipolar transistor, between the two output terminals of the rectifier and smoothing circuit 74. These are connected in series from the positive electrode side in that order. Additionally, resistor R2 and switching element SW2 are connected in parallel with resistor R1.The gate terminal of switching element SW1 is connected between resistor R2 and one end (in this example, the collector terminal) of switching element SW2. Furthermore, the base terminal of switching element SW2 is connected to the positive electrode terminal of the rectifier and smoothing circuit 74 via resistor R3 and a reverse-biased Zener diode ZD.

[0141] While the contactless power supply device 41 performs the output operation at a constant voltage, the output voltage from the resonant circuit 70 is higher than the breakdown voltage of the Zener diode ZD. Consequently, current is supplied to the base terminal of the switching element SW2 via the Zener diode ZD and the resistor R3, thus turning on the switching element SW2. As a result, the voltage applied to the gate terminal of the switching element SW1 decreases, and the switching element SW1 is thereby turned off. Therefore, the output voltage from the resonant circuit 70 is not applied across the resistor R1.

[0142] On the other hand, the energy supplied to the energy receiving device 43 by the energy transmission device 42 also decreases, since, while the switching frequency is being adjusted so that the contactless power supply device 41 performs the output operation with a constant voltage, the voltage of the energy supplied to the transmission coil 54 by the DC converter 52 is low. Therefore, the output voltage from the resonant circuit 70 also decreases to a voltage lower than the breakdown voltage of the Zener diode ZD. As a result, the switching element SW2 is switched off, and in connection with this, the voltage applied to the gate terminal of the switching element SW1 increases, thereby switching the switching element SW1 on. Therefore, the output voltage from the resonant circuit 70 is applied to the resistor R1.As a result, a fixed load of resistor R1 is provided to the energy receiving device 43.

[0143] The following describes a process of the control circuit 61 of the energy transfer device 42 according to the modification. While the contactless energy supply device 41 performs the output process with constant voltage, the control circuit 61, as in the previously described embodiment, controls the variable voltage energy source 51 of the energy supply circuit 50 in order to supply the transmission coil 54 with DC voltage at a voltage according to the switching frequency, in such a way that a measured value of the output voltage from the resonant circuit 70 of the energy receiving device 43 lies within a predetermined permissible range.In addition, the control circuit 61 keeps the switching element 53-3 in the off state and, in conjunction with this, switches the switching elements 53-1 and 53-2 between an on and an off state at a switching frequency with which the output process is carried out with constant voltage via the gate driver 60.

[0144] On the other hand, if information contained in a wireless signal received by the energy receiving device 43 via the receiver 58 indicates that the contactless power supply device 41 is not performing the constant voltage output operation, the control circuit 61 holds the switching element 53-1 in the off state and, in conjunction with this, alternately switches the switching elements 53-3 and 53-2 between an on and an off state via the gate driver 60, thereby causing energy to be supplied to the transmission coil 54 from the DC-DC converter 52. Furthermore, the control circuit 61 controls the variable voltage power source 51 in such a way that the voltage supplied to the transmission coil 54 from the DC-DC converter 52 has a predetermined value.Through this control, the control circuit 61 reduces the energy supplied to the energy receiving device 43 by the energy transfer device 42 to a level at which voltage is applied to the resistor R1 of the fixed load circuit 82 of the energy receiving device 43.

[0145] The control circuit 61 monitors measured values ​​of the current flowing through the transmission coil 54, which are measured by the current sensing circuit 57, while the switching frequency is changed, and detects a switching frequency at which the measured current values ​​exhibit a local maximum. In this way, if, within a set range of the switching frequency, no local maximum value is detected from the measured current values ​​when the two ends of the coil 56 are short-circuited (i.e., the measured current values ​​do not increase or decrease monotonically within the set range of the switching frequency as the switching frequency increases), the control circuit 61 activates the relay 59 to disconnect the two ends of the coil 56.Subsequently, the control circuit 61 can detect a switching frequency within a set range at which the measured current values ​​exhibit a local maximum when the two ends of the coil 56 are disconnected. Conversely, if no local maximum value is detected in the measured current values ​​within the set range when the two ends of the coil 56 are disconnected, the control circuit 61 activates the relay 59 to short-circuit the two ends of the coil 56. Subsequently, the control circuit 61 can detect a switching frequency within the set range at which the measured current values ​​exhibit a local maximum when the two ends of the coil 56 are short-circuited.

[0146] The switching frequency at which the measured values ​​of the current flowing through the transmission coil 54 exhibit a local maximum is a frequency at which the input impedance of the contactless power supply device 41 exhibits a local minimum value, i.e., a frequency at which the contactless power supply device 41 performs the output operation with a constant voltage, as in Fig. Figure 11 illustrates the frequency f0. Therefore, when a switching frequency is detected at which the measured values ​​of the current flowing through the transmission coil 54 exhibit a local maximum, the control circuit 61 controls the switching of the switching elements 53-1 and 53-2 between an on and an off state via the gate driver 60 at the switching frequency in such a way that energy is supplied to the transmission coil 54 from the variable voltage power source 51. In addition, the control circuit 61 switches off the switching element 53-3. This process enables the control circuit 61 to cause the contactless power supply device 41 to perform the output operation at a constant voltage.Furthermore, as described above, the control circuit 61 controls the variable voltage energy source 51 of the power supply circuit 50 in order to supply the transmission coil 54 with a DC voltage at a voltage according to the switching frequency in such a way that measured values ​​of the output voltage from the resonant circuit 70 of the energy receiving device 43 are within a predetermined permissible range.

[0147] According to the modification, the control circuit of the energy transmission device is able to detect a switching frequency at which the contactless energy supply device performs the output process with constant voltage by monitoring the current flowing through the transmission coil.

[0148] According to a further modification, the power supply circuit that supplies alternating current energy to the transmission coil can have a circuit configuration in the power transmission device that differs from that described above and its modifications, insofar as the power supply circuit is a circuit that can variably adjust the switching frequency and the voltage applied to the transmission coil.

[0149] Fig. 13A and Fig. 13B are each circuit diagrams of power supply circuits according to the modification.

[0150] A power supply circuit 110, which is in Fig. Figure 13A illustrates a power source 11, a power factor enhancement circuit 12, two switching elements 13-1 and 13-2, and a capacitor 131 connected in series with a transmission coil 14 to block a direct current. Note that in this modification, n-channel MOSFETs, for example, can also be used for the switching elements. Furthermore, the power factor enhancement circuit 12 can be configured identically to the power factor enhancement circuit 12 in the embodiment described above.

[0151] In this modification, switching element 13-1 and switching element 13-2 are connected in series between the positive and negative electrode terminals of the power source 11. Furthermore, switching element 13-1 is connected to the positive electrode side of the power source 11, while switching element 13-2 is connected to the negative electrode side of the power source 11. The drain terminal of switching element 13-1 is connected to the positive electrode terminal of the power source 11 via the power factor enhancement circuit 12, and the source terminal of switching element 13-1 is connected to the drain terminal of switching element 13-2. Additionally, the source terminal of switching element 13-2 is connected to the negative electrode terminal of the power source 11 via the power factor enhancement circuit 12.Furthermore, the source terminal of switching element 13-1 and the drain terminal of switching element 13-2 are connected to one end of the transmission coil 14 via capacitor 131, and the source terminal of switching element 13-2 is connected to the other end of the transmission coil 14 via a coil 15 or a relay 16. Additionally, the gate terminals of the switching elements are connected to a gate driver 18-2.

[0152] In this modification, the gate driver 18-2 can alternately switch the switching element 13-1 and the switching element 13-2 between an on and an off state according to a control signal from a control circuit. In other words, when the switching element 13-1 is on and the switching element 13-2 is off, the capacitor 131 is charged with current flowing from the power source 11 via the power factor enhancement circuit 12 and the switching element 13-1, and in connection with this, current also flows to the transmission coil 14 via the coil 15 or the relay 16. Conversely, when the switching element 13-1 is off and the switching element 13-2 is on, the capacitor 131 is discharged and current flows from the capacitor 131 via the transmission coil 14 and the coil 15 or the relay 16.In this modification, the control circuit can therefore control the switching frequency at which the switching element 13-1 and the switching element 13-2 are switched between an on and an off state via the gate driver 18-2, depending on determination information received from an energy receiving device 3.

[0153] A power supply circuit 120, which is in Fig. As illustrated in Figure 13B, the power supply circuit 120, like the power supply circuit 110, has a power source 11, a power factor enhancement circuit 12, two switching elements 13-1 and 13-2, and a capacitor 131 connected in series with a transmission coil 14. Note, however, that in the power supply circuit 120, compared to the power supply circuit 110, one end of the transmission coil 14 is connected to the positive electrode terminal of the power source 11 via the capacitor 131 and the power factor enhancement circuit 12, and the other end of the transmission coil 14 is connected to the source terminal of the switching element 13-1 and the drain terminal of the switching element 13-2 via the coil 15 or the relay 16.

[0154] In this modification, the gate driver 18-2 can also only switch the switching element 13-1 and the switching element 13-2 alternately between an on and an off state according to a control signal from the control circuit.

[0155] Note that with regard to the power supply circuit 110, which is in Fig. 13A is illustrated, and the power supply circuit 120, which is in Fig. As illustrated in Figure 13B, it is preferred that the capacitance of the capacitor 131 is set in such a way that the resonant frequency of the transmission coil 14 and the capacitor 131 is lower than the resonant frequency of a resonant circuit 20 of the energy receiving device 3, and than the lower limit of the frequency of the frequency range in which the switching frequency is set such that the transmission coil 14 and the capacitor 131 are not operated as a resonant circuit within a frequency range in which the switching frequency is set.

[0156] Furthermore, in the embodiment or modification described above, which is described in Fig. Figure 10 illustrates a capacitor 131 connected in series with the transmission coil 14 and the coil 15 to block a direct current, as in the modification shown in Fig. 13A illustrates how it should be arranged.

[0157] Furthermore, in the Fig. 4 illustrated embodiment and the one in Fig. 13A and Fig. Figure 13B illustrated variations using a variable voltage energy source instead of the energy source and power factor improvement circuit, as shown in Fig. 12 illustrates how to use it. Conversely, in the Fig. 12 illustrated modifications, the energy source and the power factor improvement circuit in the Fig. In the embodiment illustrated in Figure 4, a variable voltage energy source can be used instead. Furthermore, in the embodiment shown in Fig. In the 12 illustrated modification, the variable voltage energy source 51 is configured in such a way that it is able to supply energy to the transmission coil 54 at a predetermined voltage while the switching frequency is being adjusted. In this case, the DC converter 52 and the switching element 53-3 can be omitted.

[0158] Furthermore, if it is possible to connect the receiver 17 of the energy transmission device 2 and the transmitter 32 of the energy receiving device 3 to each other in a wired manner, each of the receiver 17 and the transmitter 32 can have a communication circuit capable of transmitting a signal containing destination information in a wired manner.

[0159] Note that the switching frequency at which the contactless power supply device 1 performs the constant voltage output operation lies within a frequency range where output gain decreases with increasing switching frequency. Therefore, according to a further modification, a determining circuit 30 of a constant voltage determining circuit 29 in a power receiving device 3, when a contactless power supply device 1 does not perform the constant voltage output operation, can notify a transmitter 32 of the average value of measured output voltage values ​​during the last predetermined duration (for example, a duration one to three times longer than the switching time of a switching element 31 between an on and an off state). The transmitter 32 can incorporate the average value of measured output voltage values ​​into its determination information.

[0160] In this case, a control circuit 19 of a power transmission device 2 can change the switching frequency in relatively large steps as the average value of measured output voltage increases with increasing switching frequency. Conversely, if the average value of measured output voltage decreases with increasing switching frequency, the control circuit 19 can change the switching frequency in relatively small steps. This configuration allows the control circuit 19 to reduce the time required to find a switching frequency at which the contactless power supply device 1 performs the output operation at a constant voltage.

[0161] According to yet another modification, the receiving coil and the resonant capacitor, which comprises the resonant circuit of the energy receiving device, can be connected in series, as in the SS method.Since in this case the contactless power supply device is able to perform the output operation with constant voltage, the contactless power supply device, as in the embodiment or variations described above, is able to narrow an adjustment range of the switching frequency of alternating current energy supplied to the transmission coil when the output operation is performed with constant voltage in an environment in which the coupling coefficient does not remain constant, by arranging a coil that is connected in series with the transmission coil of the power transmission device and is not coupled to the receiving coil, even at the time of an energy transmission, and by short-circuiting or disconnecting the two ends of the coil.

[0162] Fig. Figure 14 is a schematic view of a configuration of a contactless power supply device according to the modification. As in Fig. As illustrated in Figure 14, a contactless power supply device 4 according to the modification comprises a power transmission device 2 and a power receiving device 44, to which energy is transferred from the power transmission device 2 through space without contact. The power transmission device 2 comprises a power supply circuit 10, a transmission coil 14, a coil 15, a relay 16, a receiver 17, gate drivers 18-1 and 18-2, and a control circuit 19. On the other hand, the energy receiving device 44 has a resonant circuit 20, which includes a receiving coil 21 and a resonant capacitor 22, a rectifier and smoothing circuit 24, which includes a full-wave rectifier circuit 25 and a smoothing capacitor 26, a load circuit 27, a voltage detection circuit 28, a determining circuit 30 and a switching element 31, which form a constant voltage determining circuit, and a transmitter 32.The contactless power supply device 4, which is in . Fig. Figure 14 illustrates this, and it differs from the contactless power supply device 1, which is shown in Figure 14. Fig. Figure 4 illustrates the difference in the configuration of the resonant circuit 20 contained in the energy receiving device 44, and in that the energy receiving device 44 does not include the coil 23. Therefore, the differences described above and the related facts are explained below. Regarding the other components forming the contactless energy supply device 4, see the description of corresponding components forming the contactless energy supply device 1 according to the embodiment described above.

[0163] In this modification, the receiving coil 21 and the resonant capacitor 22 of the resonant circuit 20 are connected in parallel. Energy received via the receiving coil 21 is output to the rectifier and smoothing circuit 24 via the resonant capacitor 22. Since the contactless power supply device 4, according to this modification as described above, has a similar configuration to that of the SS method, it is able to perform the output process with a constant voltage. Furthermore, in this example, because the resonant circuit 20 operates in series resonance (unlike the contactless power supply device according to the SPL method), the coil 23 can be omitted. Note that, unlike the SS method, the contactless power supply device 4 does not need to utilize the resonance of the transmission coil 14 on the power transmission side.In other words, the control circuit 19 of the energy transmission device 2, as in the embodiment described above, can control the power supply circuit 10 to supply alternating current energy to the transmission coil 14 at a switching frequency at which the transmission coil 14 does not resonate.

[0164] Fig. Figure 15 is an equivalent circuit diagram of the contactless power supply device 4 according to the modification when the two ends of the coil 15 are short-circuited. It is assumed that in an equivalent circuit 200 in the circuit diagram, the transmission coil 14 on the power transmission side, coupled to the receiving coil 21 of the resonant circuit 20 on the power reception side, forms an ideal transformer with a ratio of n:1. Lr and Lm are, respectively, the leakage inductance and excitation inductance of the transmission coil 14 of the power transmission device 2. Note that an inductance Lp of the transmission coil 14 is equal to (Lm + Lr) and, assuming that a coupling coefficient between the transmission coil 14 and the receiving coil 21 is denoted by k, Lr = (1 - k)Lp and Lm = kLp. Furthermore, Ri and Ris are each a winding resistance value of the energy transmission device 2 and a winding resistance value of the energy receiving device 44.Cp is the capacitance of a resonant capacitor 22, which is connected in series with the receiving coil 21 in the resonant circuit 20 of the energy receiving device 44. L1 is an inductance of the coil 15. Note that if the two ends of the coil 15 are short-circuited via the relay 16, L1 = 0. Rac is an AC equivalent resistance of a resistance value Ro of the load circuit 27 and is given by Ras = (8 / π). 2 ) × Ro expressed.

[0165] From the equivalent circuit 200, an F-matrix Fspl(s, k, Rac) of the contactless power supply device 4 is expressed according to the modification by the following equation. [Math. 4] Fp(s,Rac,k,L1)=[1s⋅L101]⋅[1Ri01]⋅[1s⋅(1−k)⋅Lp01]⋅[101s⋅ k⋅Lp1]⋅[1n2⋅Ris01]⋅[1n2⋅Ris01]⋅[1n2s⋅Cp01]⋅[101n2⋅Rac1] In the equation above, s is expressed as s = j2πf. Note that f is a frequency of an alternating current energy supplied to the transmission coil 14. Furthermore, k denotes a coupling coefficient between the transmission coil 14 and the receiving coil 21.

[0166] From the definition of the F-matrix, an output gain Gspl(s, k, Rac) of the contactless power supply device 4 is expressed by the following equation. [Math. 5] Gspl(s,k,Rac)=1Fspl(s,k,Rac)0.0⋅Vin2⋅1n

[0167] In the equation above, Vin is a voltage (amplitude) of the alternating current energy supplied to the transmission coil 14, and Fspl(s, k, Rac) 0,0 represents the upper left element of the F-matrix, which is expressed by equation (4).

[0168] Fig. Figure 16 is a diagram illustrating an example of simulation results of the frequency response of an output voltage from the contactless power supply device 4 according to the modification when the two ends of the coil 15 are short-circuited, the frequency responses being calculated according to equation (5). Fig. Graph 1601 represents a frequency response along the horizontal axis and an output voltage along the vertical axis. Graph 1602 represents a frequency response of the output voltage when the coupling coefficient k is set to k = 0.15 and the AC equivalent resistance of the load circuit 27 is set to Rac. Graph 1603 represents a frequency response of the output voltage when the coupling coefficient k is set to k = 0.3 and the AC equivalent resistance of the load circuit 27 is set to Rac. Furthermore, graph 1604 represents a frequency response of the output voltage when the coupling coefficient k is set to k = 0.3 and the AC equivalent resistance of the load circuit 27 is set to (10*Rac).Furthermore, graph 1605 represents a frequency response of the output voltage when the coupling coefficient k is set to k = 0.6 and the equivalent AC resistance of the load circuit 27 is set to Rac. Additionally, graph 1606 represents a frequency response of the output voltage when the coupling coefficient k is set to k = 0.6 and the equivalent AC resistance of the load circuit 27 is set to (10*Rac). Note that the simulation assumes Lp = 174 µH, Cp = 20 nF, Ri = Ris = 0.1 Ω, n = 1, Vin = 300 V, and Ro = 10 Ω (Rac - 8.1 Ω).

[0169] As in Fig. As illustrated by points 1611 to 1613, in the modification there also exists for each coupling coefficient a combination of a frequency and an output voltage at which the output voltage becomes essentially constant even if the AC equivalent resistance Rac of the load circuit 27 changes under the condition that the coupling coefficient k is constant (i.e. a constant voltage is output when the coupling coefficient k is constant).In other words, it turns out that in the present embodiment, although no capacitor connected in series with or in parallel to the transmission coil 14 is included and the transmission coil 14 does not resonate, it is possible, as with the contactless power supply device according to the SS method, to cause the contactless power supply device 4 to carry out the output process with constant voltage against a change in the resistance value of the load circuit 27.Furthermore, although, as illustrated by points 1611 to 1613, the output voltages differ depending on the coupling coefficient when a constant voltage is applied against a variation in the resistance value of the load circuit 27, the differences in the output voltages can be reduced to an essentially constant output voltage, regardless of the coupling coefficient, by adjusting a voltage applied to the transmission coil 14. Note that, unlike the contactless power supply device according to the SS method, the contactless power supply device 4 according to the modification is able, by not utilizing resonance on the power transmission side, to prevent the input impedance from decreasing excessively, especially when the coupling coefficient is low, and thereby suppresses energy loss.

[0170] Fig. Figure 17 is a diagram showing an example of simulation results of the frequency response of the output voltage when the voltage applied to the transmission coil 14 is adjusted according to the coupling coefficient in the Fig. The simulation is modified in 16 illustrated examples. Fig. Graph 1701 represents a frequency response along the horizontal axis and an output voltage along the vertical axis. Graph 1701 depicts the frequency response of the output voltage when the coupling coefficient k is set to k = 0.15, the equivalent AC resistance of the load circuit 27 is set to Rac, and the voltage applied to the transmission coil 14 is set to Vin. Graph 1702 also depicts a frequency response of the output voltage when the coupling coefficient k is set to k = 0.15, the equivalent AC resistance of the load circuit 27 is set to (10*Rac), and the voltage applied to the transmission coil 14 is set to Vin.Furthermore, graph 1703 represents a frequency response of the output voltage when the coupling coefficient k is set to k = 0.3, the equivalent AC resistance of the load circuit 27 is set to Rac, and the voltage applied to the transmission coil 14 is set to (0.5*Vin). Additionally, graph 1704 represents a frequency response of the output voltage when the coupling coefficient k is set to k = 0.3, the equivalent AC resistance of the load circuit 27 is set to (10*Rac), and the voltage applied to the transmission coil 14 is set to (0.5*Vin). Furthermore, graph 1705 represents a frequency response of the output voltage when the coupling coefficient k is set to k = 0.6, the AC equivalent resistance of the load circuit 27 is set to Rac, and the voltage applied to the transmission coil 14 is set to (0.25*Vin).Furthermore, graph 1706 represents a frequency response of the output voltage when the coupling coefficient k is set to k = 0.6, the AC equivalent resistance of the load circuit 27 is set to (10* Rac) and the voltage applied to the transmission coil 14 is set to (0.25*Vin).

[0171] Combinations of a frequency and an output voltage that correspond to the in Fig. The 16 illustrated points 1611 to 1613, where the output voltage becomes essentially constant (i.e., a constant voltage is output) even when the AC equivalent resistance Rac of the load circuit 27 changes, provided that the coupling coefficient k does not change, are three combinations illustrated by points 1711 to 1713. The output voltages at the respective points 1711 to 1713 are essentially the same.

[0172] The description shows that in the modification, even if either the resistance value of the load circuit 27 or the coupling coefficient varies, it is possible to adjust the switching frequency and the voltage of the AC energy applied to the transmission coil 14 appropriately, thus keeping the output voltage essentially constant.

[0173] Note that, as in Fig. Figure 17 illustrates that the frequency at which the contactless power supply device, according to the modification, performs the constant-voltage output operation increases with increasing coupling coefficient. Furthermore, in order for the output voltage at coupling coefficient k = 0.6 to be substantially equal to the output voltage at coupling coefficient k = 0.15, the input voltage at coupling coefficient k = 0.6 must be 0.25 times the input voltage at coupling coefficient k = 0.15. Since the energy transfer, which occurs at a reduced input voltage as described above, causes the current flowing through the transmission coil 14 to increase, even if the power factor is good, there is a possibility that Joule losses will increase.

[0174] Fig. Figure 18 is a diagram illustrating an example of simulation results of the frequency response of the output voltage of the contactless power supply device 4 according to the modification when the two ends of the coil 15 are separated and the voltage applied to the transmission coil 14 is changed according to the coupling coefficient. Note that in the simulation, the same values ​​are used as the values ​​of parameters of the respective circuit elements, which are used in the Fig. The simulations used in the 16 illustrations were used, with the exception of the inductance of coil 15. Furthermore, the inductance of coil 15 is fixed at 200 µH. Fig. Graph 1801 represents a frequency response along the horizontal axis and an output voltage along the vertical axis. Graph 1801 depicts the frequency response of the output voltage when the coupling coefficient k is set to k = 0.15, the equivalent AC resistance of the load circuit 27 is set to Rac, and the voltage applied to the transmission coil 14 is set to Vin. Graph 1802 also depicts a frequency response of the output voltage when the coupling coefficient k is set to k = 0.15, the equivalent AC resistance of the load circuit 27 is set to (10*Rac), and the voltage applied to the transmission coil 14 is set to Vin.Furthermore, graph 1803 represents a frequency response of the output voltage when the coupling coefficient k is set to k = 0.3, the equivalent AC resistance of the load circuit 27 is set to Rac, and the voltage applied to the transmission coil 14 is set to (0.5*Vin). Additionally, graph 1804 represents a frequency response of the output voltage when the coupling coefficient k is set to k = 0.3, the equivalent AC resistance of the load circuit 27 is set to (10*Rac), and the voltage applied to the transmission coil 14 is set to (0.5*Vin). Furthermore, graph 1805 represents a frequency response of the output voltage when the coupling coefficient k is set to k = 0.6, the AC equivalent resistance of the load circuit 27 is set to Rac, and the voltage applied to the transmission coil 14 is set to (0.25*Vin).Furthermore, graph 1806 represents a frequency response of the output voltage when the coupling coefficient k is set to k = 0.6, the AC equivalent resistance of the load circuit 27 is set to (10* Rac) and the voltage applied to the transmission coil 14 is set to (0.25*Vin).

[0175] In the case where the two ends of coil 15 are separated, i.e., current flowing through the transmission coil 14 also flows through coil 15, which is connected in series with the transmission coil 14, there is a frequency for each coupling coefficient at which the output voltage becomes essentially constant, even if the equivalent AC resistance of the load circuit 27 varies, as specified by points 1811 to 1813. Furthermore, it is evident that adjusting the voltage of the AC energy supplied to the transmission coil 14 also allows the output voltage to be kept essentially constant in this case, regardless of the coupling coefficient.Furthermore, the frequency at which a constant voltage is output for the same coupling coefficient decreases compared to the case where the two ends of coil 15 are short-circuited. Consequently, any deviation in the frequency at which the output voltage becomes essentially constant with respect to a change in the coupling coefficient becomes small. Additionally, the gain for the same coupling coefficient is lower than in the case where the two ends of coil 15 are short-circuited, due to the increase in inductance components on the energy transfer side that do not contribute to energy transfer.

[0176] Therefore, it is evident that in the modification, searching for a switching frequency at which the contactless power supply device 4 performs the output operation with constant voltage in the case that the two ends of the coil 15 are short-circuited when the coupling coefficient is relatively low, and searching for a switching frequency at which the contactless power supply device 4 performs the output operation with constant voltage in the case that the two ends of the coil 15 are disconnected when the coupling coefficient is increased to a certain level, also makes it possible to narrow the adjustment range of the switching frequency.

[0177] Fig. Figure 19 is a diagram illustrating an example of simulation results of the frequency response of the output voltage of the contactless power supply device 4 according to the modification when, while switching between whether the two ends of the coil 15 are short-circuited or not, the voltage applied to the transmission coil 14 is changed according to the coupling coefficient. Fig. Graph 1901 shows a frequency response along the horizontal axis and an output voltage along the vertical axis on the left. A phase response is also shown along the vertical axis on the right. Graph 1901 represents the frequency response of the output voltage when, with the two ends of the first coil 15 short-circuited, the coupling coefficient k is set to k = 0.15, and the voltage applied to the transmission coil 14 is set to Vin. Graph 1902 represents the frequency response of the output voltage when, with the two ends of the first coil 15 short-circuited, the coupling coefficient k is set to k = 0.32, and the voltage applied to the transmission coil 14 is set to (0.47*Vin).Furthermore, graph 1903 represents a frequency response of the output voltage when, in the case that the two ends of the first coil 15 are disconnected, the coupling coefficient k is set to k = 0.32, and the voltage applied to the transmission coil 14 is set to Vin. Furthermore, graph 1904 represents a frequency response of the output voltage when, in the case that the two ends of the first coil 15 are disconnected, the coupling coefficient k is set to k = 0.6, and the voltage applied to the transmission coil 14 is set to (0.54*Vin). Finally, graph 1905 represents a frequency response of a phase delay of current with respect to the voltage applied to the transmission coil 14 when the two ends of the coil 15 are disconnected and the coupling coefficient k is set to k = 0.15.Furthermore, graph 1906 represents a frequency response of a phase delay of current with respect to the voltage applied to the transmission coil 14 when the two ends of the coil 15 are short-circuited and the coupling coefficient k is set to k = 0.15. Additionally, graph 1907 represents a frequency response of a phase delay of current with respect to the voltage applied to the transmission coil 14 when the two ends of the coil 15 are disconnected and the coupling coefficient k is set to k = 0.6.

[0178] Furthermore, frequency f1 is a frequency at which, when the two ends of coil 15 are short-circuited and the coupling coefficient k is set to k = 0.15, the output voltage becomes essentially constant, even if the resistance of the load circuit 27 changes; that is, the contactless power supply device 4 performs the output operation with a constant voltage. Similarly, frequency f2 is a frequency at which, when the two ends of coil 15 are short-circuited and the coupling coefficient k is set to k = 0.32, the contactless power supply device 4 performs the output operation with a constant voltage. Additionally, frequency f3 is a frequency at which, when the two ends of coil 15 are disconnected and the coupling coefficient k is set to k = 0.32, the contactless power supply device 4 performs the output operation with a constant voltage.Furthermore, the frequency f4 is a frequency at which, when the two ends of the coil 15 are separated and the coupling coefficient k is set to k = 0.6, the contactless power supply device 4 performs the output process with a constant voltage. Note that in the simulation, the same values ​​as the values ​​of parameters of the respective circuit elements, which are used in the [reference], are also used. Fig. The simulations used in the 16 illustrations were used, with the exception of the inductance of coil 15. Furthermore, the inductance of coil 15 is fixed at 200 µH.

[0179] As illustrated by graphs 1901 to 1904, it is evident that even if the coupling coefficient varies, it allows for a proper adjustment of the switching frequency and the voltage of the alternating current energy applied to the transmission coil 14 to keep the output voltage essentially constant.

[0180] Furthermore, it is evident that, since a frequency range from frequency f1 to frequency f2 and a frequency range from frequency f3 to frequency f4 partially overlap, the adjustment range of the switching frequency at which the contactless power supply device 4 performs the output process with constant voltage is greater compared to the cases which in Fig. 17 and Fig. Figure 18 illustrates how the switching can be performed between whether the two ends of the coil 15 are short-circuited or not.

[0181] Note that the lower limit of the setting range of a switching frequency, in the case where the two ends of coil 15 are disconnected (i.e., a second frequency range), can be set, for example, to a frequency at which the voltage of the AC energy supplied to the transmission coil 14 is essentially the same as the voltage of the AC energy supplied to the transmission coil 14 when the coupling coefficient is at the minimum of its expected values. Furthermore, the upper limit of the setting range of a switching frequency, in the case where the two ends of coil 15 are short-circuited (i.e.,a first frequency range) be set to a switching frequency at which the output operation is carried out with constant voltage in the case that the two ends of the coil 15 are short-circuited, if the coupling coefficient is essentially equal to a coupling coefficient which corresponds to the lower limit of the setting range of the switching frequency in the case that the two ends of the coil 15 are separated.

[0182] As described above, to improve energy transmission efficiency, it is preferred that the power supply circuit 10 and the transmission coil 14 of the energy transmission device 2 operate with soft switching (inductive process). For the power supply circuit 10 and the transmission coil 14 to operate with soft switching, it is preferred that the phase of the current flowing through the transmission coil 14 is delayed with respect to the phase of the applied voltage. This configuration allows, for example, current to flow from the source terminal to the drain terminal of the switching element 13-1 when the switching element 13-1 and the switching element 13-4 are switched on, and thus enables the power supply circuit 10 and the transmission coil 14 to operate with soft switching, thereby suppressing the occurrence of switching losses.

[0183] In the modified version, as illustrated by graphs 1905 to 1907, the phase delays at frequencies where the contactless power supply device 4 performs the output operation with constant voltage exhibit positive values, regardless of the coupling coefficient. Therefore, it is evident that the contactless power supply device 4 is capable of causing the power supply circuit 10 and the transmission coil 14 to operate with soft switching.

[0184] Consequently, in order to achieve the output process with constant voltage, the control circuit 19 of the energy transmission device 2, in the modification, can, for example, switch the relay 16 between an on and an off state and the switching frequency and the voltage of the alternating current energy applied to the transmission coil 14, according to the process flow diagram shown in Fig. Figure 9 illustrates how to control.

[0185] Note that the energy transmission device according to the in Fig. 10 illustrated modifications in the modification can also be used instead of the energy transmission device 2.

[0186] Furthermore, the inventors discovered that in the contactless power supply device 4, which is in Fig. Figure 14 illustrates that if the resistance value of the load circuit connected to the resonant circuit on the energy receiving side is a negligibly small value, the current flowing through the transmission coil also has a local maximum value, and the phase of the voltage of an alternating current energy applied to the transmission coil coincides with the phase of the current flowing through the transmission coil at a frequency of the alternating current energy at which the contactless power supply device performs the output process at constant voltage.

[0187] Fig. Figure 20 is a diagram which shows an example of a relationship between frequency responses of the output voltage of the contactless power supply device 4, which is in Fig. Figure 14 illustrates the frequency response of the input impedance of the contactless power supply device 4. The diagram above shows the frequency response of the input impedance of the contactless power supply device 4. Fig. In diagram 20, a frequency is plotted along the horizontal axis and an output voltage is plotted along the vertical axis. Additionally, in the lower diagram... Fig. Figure 20 shows a frequency plotted along the horizontal axis and an input impedance plotted along the vertical axis. Note that the simulation uses the same values ​​as the parameters of the respective circuit elements, which are used in the Fig. The 16 illustrated simulations were used. In the upper diagram, graph 2001 represents (the same as graph 1601 in Fig. 16) a frequency response of the output voltage from the contactless power supply device 4 when the two ends of the coil 15 are short-circuited, the coupling coefficient k is set to k = 0.15, and the AC equivalent resistance of the load circuit 27 is set to Rac. Furthermore, graph 2002 (the same as graph 1602 in Fig. 16) a frequency response of the output voltage of the contactless power supply device 4 when the two ends of the coil 15 are short-circuited, the coupling coefficient k is set to k = 0.15, and the AC equivalent resistance of the load circuit 27 is set to (10*Rac). Furthermore, graph 2011 in the lower diagram represents a frequency response of the input impedance of the contactless power supply device 4 when the two ends of the coil 15 are short-circuited, the coupling coefficient k is set to k = 0.15, and the AC equivalent resistance of the load circuit 27 is set to Rac. Furthermore, graph 2012 represents a frequency response of the input impedance of the contactless power supply device 4 when the two ends of the coil 15 are short-circuited, the coupling coefficient k is set to k = 0.15 and the AC equivalent resistance of the load circuit 27 is set to (0.1 *Rac).Furthermore, graph 2013 represents a frequency response of the input impedance of the contactless power supply device 4 when the ends of the coil 15 are short-circuited, the coupling coefficient k is set to k = 0.15 and the AC equivalent resistance of the load circuit 27 is set to (0.01 *Rac).

[0188] As in Fig. As illustrated in Figure 20, the frequency at which the input impedance has a local minimum value, because the equivalent AC resistance Rac of the load circuit 27 is smaller, is closer to a frequency f0 at which the contactless power supply device 4 performs the output operation at constant voltage. In particular, if the equivalent AC resistance of the load circuit 27 is set to (0.01 * Rac), the input impedance has a local minimum value at frequency f0. In other words, the current flowing through the transmission coil 14 has a local maximum value at frequency f0. Moreover, since the coil 15 is not coupled to the receiving coil 21, the previously described situation also applies in a case where the two ends of the coil 15 are separated, i.e., the current flowing through the transmission coil 14 also flows through the coil 15.

[0189] Fig. Figure 21 is a diagram which shows an example of a relationship between frequency responses of the output voltage of the contactless power supply device 4, which is in Fig. 14 illustrates, and frequency responses of a delay of the phase of current with respect to the phase of voltage with respect to an alternating current energy applied to the transmission coil 14. In the upper diagram in Fig. In diagram 21, a frequency is plotted along the horizontal axis and an output voltage is plotted along the vertical axis. Additionally, in the lower diagram... Fig. Figure 21 shows a frequency plotted along the horizontal axis and a phase delay plotted along the vertical axis. Note that in the diagram, a positive phase delay indicates that the current phase is delayed relative to the voltage phase. Furthermore, the simulation also used the same values ​​as the parameters of the respective circuit elements, which were used in the Fig. The simulations used in the 16 illustrations were used. In the upper diagram, graph 2101 represents the same graph as graph 1601 in the previous diagram. Fig. 16) a frequency response of the output voltage from the contactless power supply device 4 when the two ends of the coil 15 are short-circuited, the coupling coefficient k is set to k = 0.15, and the AC equivalent resistance of the load circuit 27 is set to Rac. Furthermore, graph 2102 (the same as graph 1602 in Fig. 16) a frequency response of the output voltage from the contactless power supply device 4 when the two ends of the coil 15 are short-circuited, the coupling coefficient k is set to k = 0.15 and the AC equivalent resistance of the load circuit 27 is set to (10*Rac).

[0190] Furthermore, graph 2111 in the lower diagram represents a frequency response of a phase delay of current relative to the phase of voltage with respect to the AC energy applied to the transmission coil 14 when the two ends of the coil 15 are short-circuited, the coupling coefficient k is set to k = 0.15, and the AC equivalent resistance of the load circuit 27 is set to Rac. Additionally, graph 2112 represents a frequency response of a phase delay of current relative to the phase of voltage with respect to the AC energy applied to the transmission coil 14 when the two ends of the coil 15 are short-circuited, the coupling coefficient k is set to k = 0.15, and the AC equivalent resistance of the load circuit 27 is set to (10*Rac).Furthermore, graph 2113 represents a frequency response of a phase delay of current relative to the phase of voltage with respect to the AC energy applied to the transmission coil 14 when the ends of the coil 15 are short-circuited, the coupling coefficient k is set to k = 0.15, and the AC equivalent resistance of the load circuit 27 is set to (0.1 * Rac). Additionally, graph 2114 represents a frequency response of a phase delay of current relative to the phase of voltage with respect to the AC energy applied to the transmission coil 14 when both ends of the coil 15 are short-circuited, the coupling coefficient k is set to k = 0.15, and the AC equivalent resistance of the load circuit 27 is set to (0.01 * Rac).

[0191] As in Fig. As illustrated in Figure 21, the frequency at which the phase delay of current with respect to the phase of voltage with respect to the AC energy applied to the transmission coil 14 is 0, since the AC equivalent resistance Rac of the load circuit 27 is smaller, is closer to a frequency f0 at which the contactless power supply device 4 performs the output operation at constant voltage. In particular, if the AC equivalent resistance of the load circuit 27 is set to (0.01 * Rac), the phase delay of current with respect to the phase of voltage with respect to the AC energy applied to the transmission coil 14 at frequency f0 is essentially 0, i.e., the power factor becomes essentially 1.In other words, if the AC equivalent resistance of the load circuit 27 is set to (0.01 * Rac), the phase delay of the current relative to the phase of the voltage with respect to the AC energy applied to the transmission coil 14 at frequencies higher than the frequency f0 will have positive values, meaning that so-called inductive driving is carried out. Therefore, in a frequency band where the phase delay lies in the range of 0° to 90°, the contactless power supply device 4 is able to cause the power supply circuit 10 and the transmission coil 14 to operate with soft switching.On the other hand, the phase delay of the current relative to the phase of the voltage with respect to the AC energy applied to the transmission coil 14 is negative at frequencies lower than the frequency f0, indicating capacitive driving. Therefore, in a frequency band where the phase delay lies between 0° and -90°, the power supply circuit 10 and the transmission coil 14 are forced to operate with hard switching, resulting in a decrease in power transmission efficiency. Furthermore, since the coil 15 is not coupled to the receiving coil 21, the previously described situation also applies if the two ends of the coil 15 are disconnected, meaning that the current flowing through the transmission coil 14 also flows through the coil 15.

[0192] Therefore, according to a modification, the control circuit of the power transmission device can determine whether the contactless power supply device performs the output process at constant voltage or not, based on a frequency response of current flowing through the transmission coil.

[0193] Fig. Figure 22 is a schematic view of a configuration of a contactless power supply device according to the modification. As in Fig. Figure 22 illustrates a contactless power supply device 5 comprising a power transmission device 42 and a power receiving device 45, to which energy is transferred from the power transmission device 42 through space without contact. The contactless power supply device 5, which is shown in Fig. Figure 22 illustrates this, and it differs from the contactless power supply device 4, which is shown in Figure 4. Fig. 14 is illustrated in that it is the energy transmission device 42, which is in Fig. Figure 12 illustrates that, instead of the energy transmission device 2, the energy receiving device 45 has a relay 33 and an energy charging circuit 34 instead of the switching element 31. Both a receiver 58 of the energy transmission device 42 and a transmitter 32 of the energy receiving device 45 operate as a communication device that can be used for both transmitting and receiving a wireless signal, and in part of a processing operation carried out by a determining circuit 30. Therefore, the differences and related facts described above are explained below on the energy receiving device side. Regarding the energy transmission device 42, see the description in relation to the one in Figure 12. Fig. 12 illustrated modification. See also the description of corresponding forming components in the preceding described embodiment with regard to the forming components which are not those exhibiting the preceding differences of the energy receiving device 45.

[0194] In the energy receiving device 45, the relay 33 is an example of a second short-circuit circuit, wherein one end of it is connected between a resonant capacitor 22 of a resonant circuit 20 and one end of the input side of a rectifier and smoothing circuit 24, and the other end of it is connected between the resonant circuit 20 and the other end of the input side of the rectifier and smoothing circuit 24. In the present embodiment, the relay 33 is normally off, and the determining circuit 30, which controls the relay 33 to turn it on, causes the relay 33 to be turned on. When the relay 33 is turned on, the resonant circuit 20 is short-circuited. Therefore, the impedance of circuits connected to the resonant circuit 20 becomes negligible.

[0195] The energy charging circuit 34 is charged with energy output via the rectifier and smoothing circuit 24 and provides energy to the destination circuit 30, which is used by the destination circuit 30 to keep the relay 33 in the on state. For this purpose, the energy charging circuit 34 includes, for example, a capacitor, one end of which is connected to the output terminal on the positive electrode side of the rectifier and smoothing circuit 24 via a diode arranged in such a way that it is forward-biased, and the other end of the capacitor is grounded. While energy is supplied to the energy receiving device 45 from the energy transfer device 42, the capacitor of the energy charging circuit 34 is charged with energy output by the rectifier and smoothing circuit 24.Furthermore, if the contactless power supply device 5 does not perform the output process with constant voltage and the relay 33 is switched on and energy is therefore no longer output by the rectifier and smoothing circuit 24, the determining circuit 30 keeps the relay 33 in the on state using energy obtained from the discharging capacitor of the energy charging circuit 34.

[0196] Note that the energy charging circuit 34 may include a circuit other than the capacitor capable of charging energy. For example, the energy charging circuit 34 may include a battery instead of the capacitor. In this case, energy charged by the energy charging circuit 34 can be used to power the determining circuit 30 and the transmitter 32.

[0197] The determining circuit 30 determines, based on a measured output voltage value received by a voltage sensing circuit 28, whether the contactless power supply device 5 is performing the output operation at a constant voltage and whether the measured output voltage value is within a permissible voltage range when the output operation is performed at a constant voltage. The determining circuit 30 notifies the transmitter 32 of the result of the determination.

[0198] Furthermore, in the modified version, while measured values ​​of the output voltage are outside the permissible voltage range, the determining circuit 30 keeps the relay 33 in the on state, thereby short-circuiting the two ends of the resonant circuit 20 and maintaining the state in which the two ends of the resonant circuit 20 are short-circuited until the energy transmission device 42 receives detection information indicating that a switching frequency at which the contactless energy supply device 5 performs the output process with constant voltage has been detected.This configuration causes the impedance of circuits connected to the resonant circuit 20 to have a negligibly small value, while the control circuit 61 of the power transmission device 42 sets the switching frequency and the voltage of the alternating current energy applied to the transmission coil 54, at which the contactless power supply device 5 is able to perform the output operation at a constant voltage.

[0199] Furthermore, when the detection information is received from the power transmission device 42 via the transmitter 32, the detection circuit 30 switches off the relay 33, thereby disconnecting the two ends of the resonant circuit 20. This process causes the impedance of the circuits connected to the resonant circuit 20 to have a value corresponding to the resistance value of the load circuit 27. Additionally, when measured output voltage values ​​are within the permissible voltage range, i.e., when the contactless power supply device 5 is performing the output operation with a constant voltage, the detection circuit 30 maintains the state in which the relay 33 is in the off position, meaning that the two ends of the resonant circuit 20 are disconnected. The detection circuit 30 notifies the transmitter 32 of a detection result indicating that the measured output voltage values ​​are within the permissible voltage range.

[0200] The following describes a process of the control circuit 61 of the energy transfer device 42 according to the modification. While the contactless energy supply device 5 performs the output process with a constant voltage, the control circuit 61, as in the previously described embodiment, controls a variable voltage energy source 51 of an energy supply circuit 50 in order to supply the transmission coil 54 with DC voltage at a voltage according to the switching frequency, in such a way that a measured value of the output voltage from the resonant circuit 20 of the energy receiving device 45 lies within a predetermined permissible range.In addition, the control circuit 61 keeps a switching element 53-3 in the off state and, in conjunction with this, switches switching elements 53-1 and 53-2 between an on and an off state at a switching frequency at which the output process is carried out with constant voltage via a gate driver 60.

[0201] On the other hand, if information contained in a wireless signal received by the energy receiving device 45 via the transmitter 32 indicates that the contactless power supply device 5 is not performing the constant voltage output operation, the control circuit 61 holds the switching element 53-1 in the off state and, in conjunction with this, alternately switches the switching elements 53-3 and 53-2 between an on and an off state via the gate driver 60, thereby causing energy to be supplied to the transmission coil 54 from the DC-DC converter 52. Furthermore, the control circuit 61 controls the variable voltage power source 51 in such a way that the voltage supplied to the transmission coil 54 from the DC-DC converter 52 has a predetermined value.Through this control, the control circuit 61 reduces the energy supplied to the energy receiving device 45 by the energy transmission device 42 to a level at which the energy receiving device 45 does not malfunction.

[0202] While the control circuit 61 changes the switching frequency, it monitors measured values ​​of the current flowing through the transmission coil 54, which is measured by a current sensing circuit 57, and detects a switching frequency at which the measured current values ​​exhibit a local maximum. In this way, if, within a set range of the switching frequency, no local maximum value is detected from the measured current values ​​(i.e., the measured current values ​​do not increase or decrease monotonically with increasing switching frequency within the set range of the switching frequency), the control circuit 61 activates the relay 59 to disconnect the two ends of the coil 56.Subsequently, the control circuit 61 can detect a switching frequency within a set range at which the measured current values ​​exhibit a local maximum when the two ends of the coil 56 are disconnected. Conversely, if no local maximum value is detected in the measured current values ​​within the set range when the two ends of the coil 56 are disconnected, the control circuit 61 activates the relay 59 to short-circuit the two ends of the coil 56. Subsequently, the control circuit 61 can detect a switching frequency within the set range at which the measured current values ​​exhibit a local maximum when the two ends of the coil 56 are short-circuited.

[0203] Note that the control circuit 61 can detect a switching frequency at which a measured current value is greater than or equal to a predetermined threshold, as well as a switching frequency at which a measured current value exhibits a local maximum. Note that the predetermined threshold may, for example, be set to a value corresponding to the current flowing through the transmission coil 54 at a switching frequency that is shifted by a predetermined acceptable error range from the switching frequency at which the current flowing through the transmission coil 54 exhibits a local maximum.

[0204] The switching frequency at which the measured values ​​of the current flowing through the transmission coil 54 exhibit a local maximum is a frequency at which the input impedance of the contactless power supply device 5 exhibits a local minimum value, i.e., a frequency at which the contactless power supply device 5 performs the output operation with a constant voltage, as in Fig. Figure 20 illustrates the frequency f0. Therefore, when a switching frequency is detected at which the measured values ​​of the current flowing through the transmission coil 54 exhibit a local maximum, the control circuit 61 controls the switching of the switching elements 53-1 and 53-2 between an on and an off state via the gate driver 60 at the switching frequency in such a way that energy is supplied to the transmission coil 54 from the variable voltage power source 51. In addition, the control circuit 61 switches off the switching element 53-3. This process enables the control circuit 61 to cause the contactless power supply device 5 to perform the output process at a constant voltage.The control circuit 61 notifies the receiver 58 of detection information indicating that a switching frequency at which the contactless power supply device 5 performs the output process with constant voltage has been detected, and causes the receiver 58 to transmit a wireless signal containing the detection information to the transmitter 32 of the power receiving device 45.

[0205] The control circuit 61 then controls the variable voltage energy source 51 of the power supply circuit 50 to supply the transmission coil 54 with a DC voltage at a voltage corresponding to the switching frequency, such that a measured value of the output voltage from the resonant circuit 20 of the energy receiving device 45 lies within a predetermined permissible range. In this way, the control circuit 61 can determine a voltage of energy supplied by the variable voltage energy source 51, for example, by referring to a reference table in which each entry specifies a relationship between a switching frequency and a voltage of energy supplied by the variable voltage energy source 51. Such a reference table is, for example, pre-stored in a memory contained within the control circuit 61.

[0206] Furthermore, instead of referring to the reference table described above, the control circuit 61 can gradually change the voltage of the energy supplied by the variable voltage energy source 51 until the determination information contained in a wireless signal received by the energy receiving device 45 via the receiver 58 indicates that a measured value of the output voltage is within the permissible voltage range.

[0207] According to the modification, the control circuit of the energy transmission device is able to detect a switching frequency at which the contactless energy supply device performs the output process with constant voltage by monitoring the current flowing through the transmission coil.

[0208] According to a modification, while the control circuit 61 can change the switching frequency, it can monitor measured values ​​of current flowing through a transmission coil 54, which is measured by a current sensing circuit 57, and detect a switching frequency at which the phase delay of the current relative to the phase of the voltage with respect to an AC energy applied to the transmission coil 54 is 0. In this case, the control circuit 61 can identify the phase of the voltage with respect to the AC energy applied to the transmission coil 54 based on, for example, the times at which switching elements 53-3 and 53-2 are switched between an on and an off state, and a time constant defined based on the inductance of the transmission coil 54 and a coil 56, as well as the capacitance of a capacitor 55.On the other hand, the control circuit 61 can determine the phase of current flowing through the transmission coil 54 on the basis of a temporal change in the measured values ​​of the current flowing through the transmission coil 54, which is measured by the current sensing circuit 57.

[0209] As in Fig. As illustrated in Figure 21, the frequency at which the phase delay of the current relative to the phase of the voltage with respect to the AC energy applied to the transmission coil 54 is zero is a frequency at which a contactless power supply device 5 performs the output operation at a constant voltage. Therefore, when a switching frequency at which the phase delay of the current relative to the phase of the voltage with respect to the AC energy applied to the transmission coil 54 is zero is detected, as in the preceding description, the control circuit 61 can control the switching of the switching elements 53-1 and 53-2 between an on and an off state at the detected switching frequency via a gate driver 60 in such a way that energy is supplied to the transmission coil 54 from a variable voltage power source 51 and the switching element 53-3 is held in the off state.Note that the control circuit 61 in the modification can also detect a switching frequency at which the absolute value of a difference between the phase of voltage and the phase of current with respect to the AC energy applied to the transmission coil 54 is less than or equal to a predetermined threshold, as well as a switching frequency at which the delay of the phase of current with respect to the phase of voltage with respect to the AC energy applied to the transmission coil 54 is 0.

[0210] In this case, if, within a set range of switching frequencies, the phase delay of the current relative to the phase of the voltage with respect to the AC energy applied to the transmission coil 54 is not zero when both ends of the coil 56 are short-circuited, the control circuit 61 can also control the relay 59 to disconnect the two ends of the coil 56. Subsequently, the control circuit 61 can detect a switching frequency at which the phase delay of the current relative to the phase of the voltage with respect to the AC energy applied to the transmission coil 54 is zero, within a set range of switching frequencies, when both ends of the coil 56 are disconnected.Conversely, if, within the switching frequency setting range, the phase delay of the current relative to the phase of the voltage with respect to the AC energy applied to the transmission coil 54 is not zero when the two ends of the coil 56 are disconnected, the control circuit 61 can control the relay 59 to short-circuit the two ends of the coil 56. Subsequently, within the switching frequency setting range, the control circuit 61 can detect a switching frequency at which the phase delay of the current relative to the phase of the voltage with respect to the AC energy applied to the transmission coil 54 is zero, when the two ends of the coil 56 are short-circuited.

[0211] According to a further modification, the power supply circuit that supplies alternating current energy to the transmission coil can have a circuit configuration in the power transmission device that differs from that described above and its modifications, insofar as the power supply circuit is a circuit that can variably adjust the switching frequency and the voltage applied to the transmission coil.

[0212] Furthermore, the energy transmission device in the Fig. 14 illustrated modification and the energy transmission device in the in Fig. 22 illustrated the modification of the power supply circuit 110, which is in Fig. 13A is illustrated, or the power supply circuit 120, which is in Fig. 13B illustrates how to use it.

[0213] As described above, a person skilled in the art can make various modifications suitable for the embodiments without deviating from the scope of the present invention. REFERENCE MARK LIST 1, 4, 5, 41 Contactless power supply device 2.42 Energy transmission device 10, 110, 120 Power supply circuit 11 Energy source 12 Power Factor Improvement Circuit 51 Variable voltage energy source 52 DC converters 13-1 to 13-4, 53-1 to 53-3 switching element 14, 54 Transmission coil 55 Capacitor 15, 56 coil 16, 59 relays 57 Current sensing circuit 17, 58 recipients 18-1, 18-2, 60 Gate Drivers 19, 61 Control circuit 3, 43, 44, 45 Energy receiving device 20, 70 Resonance circuit 21, 71 Receiving coil 22, 72 Resonant capacitor 23, 73 coil 24, 74 Rectifier and smoothing circuit 25, 75 Full-wave rectifier circuit 26, 76 Smoothing capacitor 27, 77 load switching 28, 78 Voltage detection circuit 29, 79 Constant voltage determination circuit 30, 80 Determination circuit 31, 81 Switching element 82 Circuit with fixed load 32, 83 channels 111 Alternating current power source 131 Capacitor 161, 162 Switching element

Claims

[1] Contactless power supply device (1) comprising a power transmission device (2) and a power receiving device (3) to which power is transferred from the power transmission device (2) without contact, wherein the power receiving device (3) comprises: a resonant circuit (20) comprising a receiving coil (21) which receives energy from the energy transfer device (2), and a resonant capacitor (22) which, in conjunction with the receiving coil (21), resonates with energy from the energy transfer device (2); and a rectifier circuit (25) that rectifies energy output by the resonant circuit (20), and wherein the energy transfer device (2) comprises: a transmission coil (14) that supplies energy to the energy receiving device (3); a first coil (15) which is connected in series with the transmission coil (14) and is not coupled to the receiving coil (21), even while energy is being transferred from the energy transmission device (2) to the energy receiving device (3); a first short-circuit circuit (16) that switches between short-circuiting and disconnecting both ends of the first coil (15); a power supply circuit (10) that supplies alternating current energy to the transmission coil (14) at an adjustable switching frequency, at which the transmission coil (14) does not resonate, and at an adjustable voltage; and a control circuit (19) which controls the switching frequency and the voltage of the alternating current energy supplied to the transmission coil (14) by the power supply circuit (10) and controls whether the two ends of the first coil (15) are short-circuited or disconnected via the first short-circuit circuit (16), wherein the energy receiving device (3) further comprises: a voltage detection circuit (28) that measures an output voltage of an energy output by the resonant circuit (20) and obtains a measured value of the output voltage; a determining circuit (29) which, based on the measured value of the output voltage, determines whether the contactless power supply device (1) is performing a constant voltage output operation or not, and whether the measured value of the output voltage is within a predetermined permissible voltage range or not; and a first communication device (32) which transmits a signal to the power transmission device (2) which contains determination information indicating whether the contactless power supply device (2) is performing the output operation at constant voltage or not and whether the measured value of the output voltage is within the predetermined permissible voltage range or not, wherein the power transmission device (2) further comprises: a second communication device (17) which receives the signal which contains the destination information, and wherein the control circuit (19) controls, depending on the destination information, the switching frequency and the voltage of the alternating current energy which is supplied to the transmission coil (14) by the power supply circuit (10), and controls whether the two ends of the first coil (15) are short-circuited or disconnected via the first short-circuit circuit (16). [2] Contactless power supply device (1) according to claim 1, wherein the energy receiving device (3) further comprises: a second coil (23) which is connected in series with the receiving coil (21) between the resonant circuit (20) and the rectifier circuit (25), and the receiving coil (21) and the resonant capacitor (22) of the resonant circuit (20) are connected in parallel to each other. [3] Contactless power supply device (1) according to claim 1, wherein the receiving coil (21) and the resonant capacitor (22) of the resonant circuit (20) of the power receiving device (3) are connected in series. [4] Contactless power supply device (1) according to claim 1, wherein the control circuit (19), when the determination information indicates that the contactless power supply device (1) does not perform the constant voltage output operation in the event that the two ends of the first coil (15) are short-circuited, controls the switching frequency of the alternating current energy supplied to the transmission coil (14) by the power supply circuit (10) such that it is changed within a first frequency range in such a way that measured values ​​of the output voltage do not change, even if a resistance value of a load circuit (27) connected to the rectifier circuit (25) of the energy receiving device (3) changes. [5] Contactless power supply device (1) according to claim 4, wherein the control circuit (19), when the determination information indicates that the contactless power supply device (1) does not perform the constant voltage output operation, even if the control circuit (19) changes the switching frequency of the AC energy supplied to the transmission coil (14) by the power supply circuit (10) over the entire first frequency range, controls the first short-circuit circuit (16) so that it disconnects the two ends of the first coil (15). [6] Contactless power supply device according to claim 1, wherein the control circuit (19), when the determination information indicates that the contactless power supply device (1) does not perform the constant voltage output operation, controls the switching frequency of the alternating current energy supplied to the transmission coil (14) by the power supply circuit (10) such that it is changed within a second frequency range, which differs from the first frequency range, in such a way that measured values ​​of the output voltage do not change, even if a resistance value of a load circuit (27) connected to the rectifier circuit (25) of the energy receiving device (3) changes. [7] Contactless power supply device (1) according to claim 6, wherein the control circuit (19), when the determination information indicates that the contactless power supply device (1) does not perform the constant voltage output operation, even if the control circuit (19) changes the switching frequency of the AC energy supplied to the transmission coil (14) by the power supply circuit (10) over the entire second frequency range, controls the first short-circuit circuit (16) so that it short-circuits the two ends of the first coil (15). [8] Contactless power supply device according to claim 6 or 7, wherein the first frequency range and the second frequency range are defined in such a way that they partially overlap each other. [9] Contactless power supply device according to any one of claims 4 to 8, wherein the control circuit (19), when the determination information indicates that the contactless power supply device (1) performs the output process with constant voltage and a measured value of the output voltage is not within the predetermined permissible voltage range, controls the voltage of the AC energy supplied to the transmission coil (14) by the power supply circuit (10) in such a way that measured values ​​of the output voltage are within the predetermined permissible voltage range. [10] Contactless power supply device (41) comprising a power transmission device (42) and a power receiving device (43) to which power is transferred from the power transmission device (42) without contact, wherein the power receiving device (43) comprises: a resonant circuit (70) comprising a receiving coil (71) which receives energy from the energy transfer device (42), and a resonant capacitor (72) which, in conjunction with the receiving coil (71), resonates with energy from the energy transfer device (42); and a rectifier circuit (75) that rectifies energy output by the resonant circuit (70), and wherein the energy transfer device (42) comprises: a transmission coil (54) that supplies energy to the energy receiving device (43); a first coil (56) which is connected in series with the transmission coil (54) and is not coupled to the receiving coil (71), even while energy is being transferred from the energy transmission device (42) to the energy receiving device (43); a first short-circuit circuit (59) that switches between short-circuiting and disconnecting both ends of the first coil (56); a power supply circuit (50) that supplies alternating current energy to the transmission coil (54) at an adjustable switching frequency, at which the transmission coil (54) does not resonate, and at an adjustable voltage; and a control circuit (61) which controls the switching frequency and the voltage of the alternating current energy supplied to the transmission coil (54) by the power supply circuit (50) and controls whether the two ends of the first coil (56) are short-circuited or disconnected via the first short-circuit circuit (59), wherein the power transmission device (42) further comprises: a current sensing circuit (57) that measures a current flowing through the transmission coil (54) and obtains a measured value of the current, and the control circuit (61) controls the switching frequency of the alternating current energy supplied to the transmission coil (54) by the power supply circuit (50) depending on the measured value of the current and controls whether the two ends of the first coil (56) are short-circuited or disconnected via the first short-circuit circuit (59). [11] Contactless power supply device (41) according to claim 10, wherein the control circuit (61), in the case that the two ends of the first coil (56) are short-circuited, monitors measured values ​​of the current while changing the switching frequency of the AC energy within a first frequency range, and thereby detects a switching frequency at which measured values ​​of the current have a local maximum, and controls the power supply circuit (50) in such a way that an AC energy having the detected switching frequency is supplied to the transmission coil (54). [12] Contactless power supply device (41) according to claim 11, wherein the control circuit (61), when no switching frequency at which measured current values ​​exhibit a local maximum is detected within the first frequency range, controls the first short-circuit circuit (59) so that it disconnects the two ends of the first coil (56), and, in the event that the two ends of the first coil (56) are disconnected, monitors measured current values ​​while changing the switching frequency of the AC power within a second frequency range which differs from the first frequency range, and thereby detects a switching frequency at which measured current values ​​exhibit a local maximum and controls the power supply circuit (50) in such a way that AC power having the detected switching frequency is supplied to the transmission coil (54). [13] Contactless power supply device (5) comprising a power transmission device (42) and a power receiving device (45) to which power is transferred from the power transmission device (42) without contact, wherein the power receiving device (45) comprises: a resonant circuit (20) comprising a receiving coil (21) which receives energy from the energy transfer device (42), and a resonant capacitor (22) which, in conjunction with the receiving coil (21), resonates with energy from the energy transfer device (42); and a rectifier circuit (25) that rectifies energy output by the resonant circuit (20), and wherein the energy transfer device (42) comprises: a transmission coil (54) that supplies energy to the energy receiving device (45); a first coil (56) which is connected in series with the transmission coil (54) and is not coupled to the receiving coil (21), even while energy is being transferred from the energy transmission device (42) to the energy receiving device (45); a first short-circuit circuit (59) that switches between short-circuiting and disconnecting both ends of the first coil (56); a power supply circuit (50) that supplies alternating current energy to the transmission coil (54) at an adjustable switching frequency, at which the transmission coil (54) does not resonate, and at an adjustable voltage; and a control circuit (61) which controls the switching frequency and the voltage of the alternating current energy supplied to the transmission coil (54) by the power supply circuit (50) and controls whether the two ends of the first coil (56) are short-circuited or disconnected via the first short-circuit circuit (59), wherein the energy receiving device (45) further comprises: a voltage sensing circuit (28) that measures an output voltage of energy output by the resonant circuit (20) and obtains a measured value of the output voltage; and a second short-circuit circuit (33) capable of switching between whether the resonant circuit (20) is short-circuited or not when the measured value of the output voltage is outside the predetermined permissible voltage range, the determining circuit (30) causing the second short-circuit circuit (33) to short-circuit the resonant circuit (20), the power transfer device (42) further comprising: a current sensing circuit (57) that measures a current flowing through the transmission coil (54) and obtains a measured value of the current, and the control circuit (61) controls the switching frequency of the alternating current energy supplied to the transmission coil (54) by the power supply circuit (50) depending on the measured value of the current and controls whether the two ends of the first coil (56) are short-circuited or disconnected via the first short-circuit circuit (59). [14] Contactless power supply device according to claim 13, wherein the control circuit (61), in the case that the two ends of the first coil (56) are short-circuited, monitors measured values ​​of the current while changing the switching frequency of the AC energy within a first frequency range, and thereby detects a switching frequency at which measured values ​​of the current have a local maximum or a phase of measured values ​​of the current and a voltage phase of the AC energy supplied to the transmission coil (54) coincide, and controls the power supply circuit (50) in such a way that AC energy having the detected switching frequency is supplied to the transmission coil (54).

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