JP2012005238A - Non-contact power feeding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-contact power feeding device for improving the detection precision of presence or absence of a power reception device.SOLUTION: The non-contact power feeding device includes a power transmission device 10 transmitting current to a power reception device 50 by at least magnetic coupling. The power transmission device includes an energized power transmission coil L, detecting means 15 detecting a current state of the power transmission coil, and estimating means 15 estimating a relative distance between the power transmission device and the power reception device from a change of the detected current state.

Description

  The present invention relates to a non-contact power feeding device.

  As a non-contact (wireless) power transmission technique, a technique of transmitting power using electromagnetic coupling between a power transmission (primary side) device and a power receiving (secondary side) device is known. Then, by detecting the peak of the induced voltage of the power receiving coil, it is determined whether or not what is coupled to the power transmitting coil is the power receiving coil, in other words, whether it is a foreign substance such as a metal other than the power receiving coil ( Patent Document 1).

JP 2006-60909 A

  However, in the above prior art, the determination is made by detecting the peak of the induced voltage of the power receiving coil. Therefore, if the distance between the power transmitting coil and the power receiving coil is relatively long, the peak voltage becomes small, and whether or not the power receiving device is present. There was a problem that detection accuracy was low.

  The problem to be solved by the present invention is to improve the detection accuracy of the presence or absence of a power receiving device.

  This invention solves the said subject by estimating the relative distance of a power transmission apparatus and a power receiving apparatus from the change of the electric current state of a power transmission coil.

  According to the present invention, if the relative distance between the power transmission device and the power receiving device is estimated from the change in the current state of the power transmission coil, the change in the current state can be detected relatively large even if the relative distance is large. Increases accuracy.

It is a block diagram which shows the non-contact electric power feeding system to which one embodiment of this invention is applied. It is an electric circuit diagram which shows the non-contact electric power feeder of FIG. It is a wave form diagram which shows an example of the production | generation pulse and inverter current in the control part of FIG. It is a wave form diagram which shows the other example of the production | generation pulse and inverter current in the control part of FIG. 2 is a graph showing frequency characteristics of an output current phase with respect to an output voltage phase of the inverter of FIG. 1 for each coupling coefficient k between a power transmission coil and a power reception coil. It is a graph which shows the time waveform of the output current phase with respect to the output voltage phase of the inverter of FIG. 1 for every coupling coefficient k of a power transmission coil and a power reception coil. (A) is a graph showing the characteristics of the current phase and gain with respect to the inverter frequency when the power receiving device is removed from the system of FIG. 1 and the coupling coefficient k is 0, and (b) is the power transmission device removed from the system of FIG. The graph showing the current phase and gain characteristics from the power load side of the power receiving apparatus to the power receiving coil when the coupling coefficient k is 0, and (c) shows the current phase characteristics seen from the inverter of the system of FIG. It is a graph shown for every coupling coefficient k. It is a flowchart which shows the control procedure of the system of FIG. It is a block diagram which shows the power transmission apparatus and power receiving apparatus of the non-contact electric power feeding system to which other embodiment of this invention is applied. It is a figure which shows an example of the look-up table used with the non-contact electric power feeding system of FIG.

<< First Embodiment >>
FIG. 1 shows a non-contact power feeding system 1 to which an embodiment of the present invention is applied, which includes a power transmitting device 10 and a power receiving device 50, and is mounted on a vehicle or the like from a power transmitting device 10 installed on a power supply stand or the like. In this system, power is supplied to a load 53 such as a battery of the power receiving device 50 in a contactless manner and charged. Details of the power transmission device 10 and the power reception device 50 of FIG. 1 are shown in FIG.

The power transmission device 10 of this example includes an AC power supply unit 11 of a commercial power supply (frequency is 50 Hz in eastern Japan, frequency is 60 Hz in west Japan), a DC power supply unit 12 that converts an AC voltage transmitted from the AC power supply unit 11 into a DC voltage, The voltage type inverter unit 13, the power transmission coil (primary coil) L ₁ that supplies the high frequency power output from the voltage type inverter unit 13 to the power receiving device 50 in a contactless manner, and the power transmission coil L ₁ are provided in series to transmit power. And a primary capacitor C ₂ constituting a resonance circuit of the device 10.

As shown in FIG. 2, the DC power supply unit 12 includes a diode D ₁ and a diode D ₂ , a diode D ₃ and a diode D ₄ , a diode D ₅ and a diode D ₆ , each connected in parallel, and an intermediate connection therebetween. The three-phase output terminal of the AC power supply unit 11 is connected to the point.

The voltage type inverter unit 13 includes diodes D _{7 to} D ₁₀ connected in reverse parallel to switching elements S _{1 to} S ₄ such as MOSFETs, and a DC voltage smoothing capacitor C 1, and outputs from the DC power source unit 12. The direct current voltage is inversely converted to high frequency power of about 1 to 50 kHz.

Then, the intermediate connection point of the switching elements S ₁ and S _2, each of the intermediate connection point of the switching elements S ₃ and S _4, and the resonant circuit consisting of the power transmission coil L ₁ and the primary capacitor C ₂ Metropolitan is connected Yes.

The power receiving device 50 is provided in parallel and in series with the power receiving coil (secondary coil) L ₂ that receives high-frequency power from the power transmitting coil L ₁ of the power transmitting device 10 in a non-contact state by electromagnetic induction, and the power receiving coil L _2. It consists of secondary capacitors C ₃ and C ₄ that constitute the resonance circuit of the power receiving device 50, a rectifying unit 51 that rectifies the high-frequency power received by the power receiving coil L ₂ , a smoothing capacitor C _5, and a secondary battery. A load 53 and a relay switch 52 that cuts off / conducts power supply are provided.

In rectifier 51, a diode _{D 11} and a diode _{D 12,} respectively of the diode _{D 13} and a diode _{D 14} are connected in parallel, the respective intermediate connection points, and the receiving coil _{L 2} and the secondary capacitor _C 3, _{C 4} The output terminal of the configured resonance circuit is connected. The output terminal of the rectifying unit 51 is connected to the load 53 via the relay switch 52.

Returning to FIG. 1, the contactless power feeding system 1 of this example includes a control unit 14 that controls the voltage-type inverter unit 13 and the relay switch 52, and a load 53 such as a battery, in addition to the power transmission device 10 and the power receiving device 50 described above. A load control unit 54 that monitors the state of charge and generates a command value for charging power, and wirelessly communicates the power command value generated by the load control unit 54 to the power transmission device 10. For example, wireless communication such as Bluetooth (registered trademark) Unit 55 and charging start switch 56 for notifying power transmission device 10 that the user starts charging.

The control unit 14 includes a current phase detection unit 15 that detects the phase of the output current of the voltage type inverter unit 13 and a duty command Dt ₁ , Dt of the voltage type inverter unit 13 from the load power command generated by the load control unit 54. ₂ , a duty command generation unit (voltage amplitude command unit) 16 that generates 2 and a pulse generation unit 17 that generates a switching pulse of the voltage type inverter unit 13 from the duty commands Dt ₁ and Dt ₂ .

The voltage type inverter unit 13 is controlled by the control unit 14 as follows. That is, the duty command generation unit 16 receives the load power command from the load control unit 54 and the duty commands Dt ₁ and Dt ₂ such that the power supplied to the load 53 matches the command value from the load control unit 54. Is generated. Next, PWM modulation is performed. As shown in FIG. 3, the generated duty commands Dt ₁ and Dt ₂ are compared with the triangular wave carrier using a triangular wave carrier comparison method, and the switching elements S _{1 to} S ₄ are compared. Control pulses are generated.

Comparison of triangular wave carriers is performed as follows.
The switching element S ₁ is set to “ON” when triangular wave carrier> duty command D ₂ , and is set to “OFF” when triangular wave carrier ≦ duty D ₂ . The switching element S ₂ is “ON” when triangular wave carrier ≦ duty command D ₂ , and “OFF” when triangular wave carrier> duty D ₂ . The switching element S ₃ is “ON” when triangular wave carrier> duty command D ₁ , and “OFF” when triangular wave carrier ≦ duty D ₁ . The switching element S ₄ is “ON” when triangular wave carrier ≦ duty command D ₁ and “OFF” when triangular wave carrier> duty D ₁ .

  The pulse generator 17 generates a dead time so as not to cause an arm short circuit between the switching elements S1 and S3 and between the switching elements S2 and S4. In this way, as shown in the lowermost part of FIG. 3, the output line voltage Vinv of the voltage type inverter unit 13 is changed to a rectangular wave AC, and a constant voltage output can be obtained.

  In addition to using the above-described triangular wave carrier comparison method, the voltage type inverter unit 13 is controlled, for example, in order to perform the control more simply, as shown in FIG. 4, a waveform with a duty of 50% using a rectangular pulse. Can be controlled.

Now, in the contactless power supply system 1 described above, for example with respect to the power transmission coil L ₁ of the installed power transmitting device 10 to the feeding station, to supply power operation to approximate the power receiving coil L ₂ of the power receiving apparatus 50 mounted on a vehicle In determining whether the power receiving coil L ₂ has approached the power transmitting coil L ₁ to a sufficient distance, in other words, whether the relative distance between the power receiving coil L ₂ and the power transmitting coil L ₁ has become a predetermined value or less. It is necessary to judge while driving. When receiving coil L ₂ is not close to a sufficient distance to the power transmission coil L _1, because feeding impossible or feed efficiency is reduced.

Since the above-described conventional technique is a method for detecting the peak of the induced voltage of the power receiving coil L ₂ mounted on the vehicle, the peak voltage decreases when the relative distance between the power transmitting coil L ₁ and the power receiving coil L ₂ is long. the a receiving coil L ₂ and the foreign matter other than the power receiving coil L ₂ has a problem that it is difficult to determine.

Therefore, the contactless power supply system 1 of this embodiment, instead of the power receiving device 50 side, the transmission current state of the coil L ₁ of the power transmission device 10, the output current to the specifically, the output voltage of the phase voltage-type inverter unit 13 based in the state of phase estimates the distance of the power receiving coil L ₂ for the power transmission coil L _1.

Hereinafter, a method for detecting the presence or absence (in other words, the relative distance) of the power receiving device 50 in the power transmitting device 10 will be described with reference to FIG. 5, the frequency characteristic of the output current phase for the output voltage phase of the voltage-type inverter unit 13 of the power transmission device 10 shown in FIGS. 1 and 2, each coupling coefficient k between the power transmission coil L ₁ and the power receiving coil L ₂ It is the shown graph.

According to FIG. 5, when a state where the power transmission coil L ₁ and the power receiving coil L ₂ is not at all bound magnetically (coupling coefficient k = 0), the current phase advances the phase at the frequency f _0. On the other hand, close to the power transmission coil _{L 1} and the power receiving coil _{L 2,} the magnetically coupled state (k = 0.1 to 0.5), the current phase if the coupling coefficient k = 0.1 or more delayed phase It becomes. Therefore, the power transmission coil L ₁ is excited at the frequency f ₀ , and it is determined whether the output current phase of the voltage type inverter unit 13 at that time is a lagging phase or a leading phase. (In other words, relative distance) can be detected. That is, the process proceeds or in the case of the phase does not exist receiving coil L _2, determines the relative distance is powered non distance or more, in the case of delay phase, determines that at least the power reception coil L ₂ is present in the possible feed distance To do. In this case, as shown in FIG. 5, the relative distance can be detected according to the value of the delay phase.

The current phase detector 15 of the contactless power feeding system 1 of this example shown in FIG. 1 detects whether the phase of the output current described above is a lag phase or a lead phase as follows. FIG. 6 is a graph showing time waveforms of the output voltage and output current of the voltage type inverter unit 13 for each coupling coefficient k. As shown in the figure, when the sampling is performed at the timing when the output voltage of the voltage type inverter unit 13 switches from negative to positive, the current phase becomes the leading phase when the coupling coefficient k = 0, and therefore the sampling is performed. The current value is a positive value. On the other hand, when the coupling coefficient k is 0.1 or more, the current phase is a lagging phase, so the sampled current value is a negative value. Therefore, the sampled current value is a positive value, a or the receiving coil L ₂ is not present, the relative distance is determined to be feeding non distance or more. Further, if the sampled current value is negative, it is determined that at least the power reception coil L ₂ is present in the possible feed distance.

Next, a phenomenon in which the current phase is reversed when the coupling coefficient k is 0.1 or more will be described with reference to FIG. FIG. 7A shows the characteristics of the current phase and the gain with respect to the frequency of the voltage type inverter unit 13 when the power receiving device 50 is removed and the coupling coefficient k is 0. Further, FIG. 7 (b) removing the power transmission device 10, when the coupling coefficient k is set to 0, indicating the current phase and gain characteristics of the power receiving up coil L ₂ viewed from the load 53 end. FIG. 7C shows the current phase characteristics as seen from the voltage type inverter unit 13 including the power receiving device 50 for each coupling coefficient k.

As can be understood from FIG. 7, when the coupling coefficient k is 0, the phase characteristics of (a) and the phase characteristics of (c) match because the power receiving device 50 is not present. Then, as the coupling coefficient k increases, a waveform in which the phase characteristic of the power receiving device 50 is synthesized in the vicinity of f ₁ that is the resonance frequency of the power receiving device 50 is obtained.

Therefore, it is understood that a large phase change with respect to the coupling coefficient k occurs in the vicinity of the resonance frequency f ₁ on the secondary side (power receiving device 50) as a composite characteristic. For this reason, it is desirable to excite the frequency type inverter unit 13 of the power transmission device 10 with the same frequency as the resonance frequency f1 of the power reception device 50 or a frequency approximate thereto.

Here, the larger the Q value of the power receiving device 50 (the sharpness of the resonance peak of the resonance circuit), the higher the Q value near the resonance frequency f ₁ in the composite characteristic, so the Q value of the power receiving device 50 may be set higher. For example, in the non-contact power supply system 1 of FIG. 1, when detecting the power receiving device 50, the relay switch 52 is opened to interrupt power supply to the load 53. Thereby, since the loss component of the power receiving apparatus 50 becomes small, the Q value can be increased.

Note that the frequency characteristics of the power transmission device 10 do not need to have two resonance points as shown in FIG. 7A, and the resonance points may be plural or zero. Therefore, the configuration of the resonant capacitor C ₂ of the power transmission device 10 may be a series, also there may be a plurality. Further, the power receiving device 50 may change the sign any number of times as long as it has a resonance circuit configuration having a characteristic that changes the sign one or more times in the frequency characteristic. Therefore, the resonance capacitors C ₃ and C ₄ of the power receiving device 50 may have one configuration, may be in series or in parallel, and a plurality may exist.

Next, the control flow will be described.
FIG. 8 is a flowchart illustrating a sequence from when the power receiving device 50 approaches the power transmitting device 10 until the power transmitting device 10 detects the presence or absence of the power receiving device 50 until charging of the load 53 is completed. The left side of the figure shows the operation of the power transmitting apparatus 10, and the right side of the figure shows the operation of the power receiving apparatus 50. Note that the power receiving device 50 is intended to power receiving coil L ₂ in a mobile object such as an electric vehicle is mounted.

  First, in the shutdown state of step S <b> 1, the relay switch 52 shown in FIG. 1 is open, and power is not supplied to the load 53. In order to charge from here, alignment of the power transmission apparatus 10 and the power receiving apparatus 50 is started. In the case of an electric vehicle, the electric vehicle is parked on the power transmission device 10. Here, the user presses the charging start switch 56 (step S2).

  When the charging start switch 56 is pressed, the wireless communication unit 55 of the power receiving device 50 transmits a wakeup signal for activating the power transmission device 10 to the control unit 14 (S3). The power transmission device 10 receives the wake-up signal from the wireless communication unit 55 and executes the activation process (step S4).

In the next step S5～S6, or metallic foreign matters, such as empty cans on the transmitting coil L ₁ of the power transmission device 10 is not on, detects, for example, by a metal detector device like. The result of this determination, if the metallic foreign matters on the power transmission coil L ₁ is riding returns to step S1, to maintain the opening of the relay switch 52 and shuts down the power transmission device 10, that there is a foreign matter to the user Notice.

If there is no foreign matter on the transmitting coil L ₁ goes to step S7. Here, in order to detect the power receiving device 50, a minute electric power is supplied to the power transmission coil L ₁ of the power transmission device 10. As a result, the presence or absence of the power receiving device 50 is determined based on the current phase of the voltage type inverter unit 13 in the above-described procedure. The power receiving device 50, the user operates the vehicle, to continue the detection logic to the transmitting coil L ₁ and the position fits.

  When the power receiving device 50 is detected in step S9, the process proceeds to step S10, the relay switch 52 is closed to allow charging, and the load 53 is charged. If the load 53 is a battery such as a secondary battery, the charging is terminated when the SOC reaches 100%, for example (step S11).

<< Second Embodiment >>
FIG. 9 is an electric circuit diagram showing the power transmitting device 10 and the power receiving device 50 in the non-contact power feeding system to which another embodiment of the present invention is applied, and the other parts are the same as those in FIG. FIG. 10 is a diagram showing an example of a look-up table of the relationship between the current phase and the relative distance used in the non-contact power feeding system shown in FIG.

The difference between this example and the first embodiment described above is that a switching relay switch 57 is provided instead of the relay switch 52 shown in FIG. 1 and a resistor 58 having a known resistance value is provided in parallel with the load 53. The relative distance between the power transmission coil L1 and the power reception coil L2 with respect to the phase of the output current detected by the current phase detection unit 15 shown in FIG. 1 is tabulated and stored in the memory of the control unit 14.

In the switching relay switch 57 shown in FIG. 9, the power received by the power receiving device 50 is supplied to the load 53, the switching position not supplied to the resistor 58, and the power received by the power receiving device 50 is supplied to the resistor 58. This is a switch for switching to any one of switching positions not supplied to the load 53.

Look-up table of Figure 10 is for the current to the phase detector output current detected by the 15 phase was tabulated by an experiment or the like in advance and calculating the relative distance between the power transmission coil L ₁ and the power receiving coil L _2, It is stored in a memory (not shown) of the control unit 14.

  Then, in step S7 in the control flow of FIG. 8, the switching relay switch 57 is switched so that the current flowing through the power receiving device 50 flows through the resistor 58 instead of the load 53, and the processing of step S8 is executed in this state. To do. In this example, since the resistance value is switched to the known resistor 58 by the changeover relay switch 57, a lookup table may be created using the resistor 58 regardless of the state of the load 53.

That is, when the detection process is performed with the power receiving device 50 connected to the load 53, the detection value by the current phase detection unit 15 may vary depending on the state of the load 53. A lookup table is created in advance using a resistor 58 having a known value, and when the power receiving device 50 is actually detected, the detection accuracy is further improved by connecting to the resistor 58. Then, the relative distance between the power transmission coil L ₁ is the detection result and the receiving coil L ₂ by notifying the user, the user convenience is improved.

The relative distance between the power transmission coil L1 and the power reception coil L2 is not limited to the above-described positive / negative phase of the output current or a lookup table obtained in advance, for example, the amplitude of the output current in the resonance circuit of the power transmission device 10 It is also possible to provide a sensor for detecting the output and determine based on the detected amplitude value of the output current.

According to the said embodiment, there exist the following effects.
(1) Even when the coupling coefficient k between the power transmission coil L ₁ and the power reception coil L ₂ is relatively low and the voltage excited by the power reception coil L ₂ is low, the power transmission coil L ₁ and the power reception coil L ₂ it can detect the relative distance, the presence or absence of the power receiving coil L ₂ can be detected with high accuracy.

(2) For example, when the power receiving device 50 is mounted on a moving body such as an automobile, the power receiving device 50 detects the presence or absence of the power transmitting device 10 and transmits information on the presence or absence of the power receiving device 50 to the power transmitting device 10 through communication. In the case of the method, the power receiving device 50 is likely to malfunction by picking up radio waves and magnetic fields emitted from various devices installed on the ground side while moving. Since the power transmission device 10 installed in is detected, the malfunction is few and the reliability is high.

(3) This example is not a method of detecting the voltage of the power reception coil L _2, the peak voltage required in the case of determining scheme whether the receiving coil L ₂ by detecting the voltage of the power reception coil L ₂ Detection means and data processing means are unnecessary. Therefore, the cost of the apparatus can be reduced.

(4) In this example, if the resonance frequency of the power receiving device 50 and the excitation frequency of the voltage type inverter unit 13 of the power transmitting device 10 are matched, the power receiving coil L ₂ and the power transmitting coil L ₁ are close to each other, and the coupling coefficient k is In a state other than 0, the change in the phase of the output current with respect to the phase of the output voltage of the voltage type inverter unit 13 of the power transmission device 10 becomes large. Therefore, it becomes easy to detect the change, and the power receiving device 50 can be detected with high accuracy.

(5) In this example, since the current phase is reversed from the leading phase to the lagging phase depending on whether the coupling coefficient k is 0 or not, the presence or absence of the power receiving device 50 is detected with high accuracy by determining the sign of the current phase. it can.

(6) In this example, if the change characteristics of the current phase according to the relative distance between the power transmission side coil L1 and the power reception side coil L2 are tabulated in advance by experiment or calculation and stored in a memory, The user can be notified of the relative position with respect to the power transmission device 10, and convenience is improved.

(7) In this example, if the amplitude of the output current is detected and the presence / absence of the power receiving device 50 is detected based on the detected current amplitude value, the inverter unit 13 of the power transmitting device 10 has the function of detecting the voltage / current phase. Since it can be controlled by an inexpensive controller that does not have, the controller 14 can be configured at low cost.

(8) In this example, if the load 53 of the power receiving device 50 is cut off when detecting the presence or absence of the power receiving device 50, the loss component of the power receiving device 50 can be reduced and the Q value can be increased. Thereby, detection accuracy becomes higher.
(9) Further, in this example, if the load 53 of the power receiving device 50 is switched and the Q value of the power receiving device 50 is varied, the change in the phase of the output current with respect to the phase of the output voltage of the inverter unit 13 of the power transmitting device 10 is large. Become. Therefore, close to the receiving coil L ₂ and the power transmission coil L ₁ is, the accuracy of detecting that the coupling coefficient k becomes nonzero condition is further improved.

(10) In this example, when detecting the presence / absence of the power receiving device 50, the load 53 of the power receiving device 50 is switched to the resistor 58 having a known resistance value, and the Q value of the power receiving device 50 is always kept constant. a table the phase change characteristics according to the relative distance between the coil L ₁ and the power receiving coil L ₂ advance through experiments or calculation, etc., can be stored in the memory. Thus, convenience is improved since it is possible to notify the relative position of the power receiving coil L ₂ and the transmitting coil L ₁ to the user.

  In the above-described embodiment, the non-contact power feeding method using electromagnetic induction has been described. However, a non-contact power feeding method using magnetic coupling by resonance of an electromagnetic field can be applied.

  The current phase detection unit 15 corresponds to detection means and estimation means according to the present invention, the voltage type inverter unit 13 corresponds to a power converter according to the present invention, and the relay switch 52 corresponds to on / off means according to the present invention. The switching relay switch 57 corresponds to the switching means according to the present invention.

1 ... non-contact power supply system 10 ... power transmission apparatus 11 ... AC power supply unit 12 ... DC power supply 13 ... voltage type inverter unit D ₁ to D _{10 ...} diodes C _1, C 2 _... capacitors S ₁ to S ₄ ... MOSFET
L ₁ ... Power transmission coil 14 ... Control unit 15 ... Current phase detection unit 16 ... Duty command generation unit 17 ... Pulse generation unit 50 ... Power reception device L ₂ ... Power reception coil D _{11 to} D ₁₄ ... Diode C _{3 to} C ₅ ... Capacitor 51 ... rectifier 52 ... relay switch 53 ... load 54 ... load controller 55 ... wireless communicator 56 ... charge start switch 57 ... switching relay switch 58 ... resistance load

Claims (12)

A non-contact power feeding device including a power transmitting device that transmits current by at least magnetic coupling to a power receiving device,
The power transmission device is:
A power transmission coil to be energized;
Detecting means for detecting a current state of the power transmission coil;
A non-contact power feeding device comprising: an estimation unit configured to estimate a relative distance between the power transmission device and the power reception device from a detected change in a current state. The contactless power supply device according to claim 1,
A power converter for energizing the power transmission coil;
The detection means detects the phase of the output current with respect to the phase of the output voltage of the power converter,
The non-contact power feeding apparatus according to claim 1, wherein the estimating means estimates the relative distance based on the detected phase of the output current. In the non-contact electric power feeder of Claim 2,
The contactless power feeding device according to claim 1, wherein an excitation frequency of the power converter is set to the same frequency as a resonance frequency of the power receiving device. In the non-contact electric power feeder of Claim 2 or 3,
The non-contact power feeding apparatus according to claim 1, wherein the estimating means estimates the relative distance according to whether the phase of the detected output current is a positive value or a negative value. In the non-contact electric power feeder of Claim 2 or 3,
A storage unit storing a lookup table indicating a relationship between the relative distance and the phase of the output current;
The non-contact power feeding apparatus according to claim 1, wherein the estimating means estimates the relative distance based on the detected phase of the output current and the lookup table. In the non-contact electric power feeder of Claim 2 or 3,
The detecting means detects an amplitude of the output current;
The non-contact power feeding apparatus, wherein the estimating means estimates the relative distance based on the detected amplitude of the output current. A non-contact power feeding device that transmits current from a power transmission device to a power receiving device by at least magnetic coupling,
The power transmission device is:
A power transmission coil to be energized;
Detecting means for detecting a current state of the power transmission coil;
An estimation means for estimating a relative distance between the power transmission device and the power reception device from the detected change in the current state,
The power receiving device is:
A non-contact power feeding apparatus comprising a power receiving coil having at least one resonance frequency and receiving a current transmitted from the power transmitting coil. In the non-contact electric power feeder of Claim 7,
The power transmission device further includes a power converter for energizing the power transmission coil,
The contactless power feeding device according to claim 1, wherein an excitation frequency of the power converter is set to the same frequency as a resonance frequency of the power receiving coil. In the non-contact electric power feeder of Claim 7 or 8,
The non-contact power feeding device, wherein the power receiving device includes on / off means for supplying or cutting off the received power to a power load connected to the power receiving device. In the non-contact electric power feeder of Claim 7 or 8,
The power receiving apparatus includes a switching unit that switches received power between a power load connected to the power receiving apparatus and a predetermined power load provided in the power receiving apparatus. The contactless power supply device according to claim 10,
The non-contact power feeding apparatus according to claim 1, wherein the predetermined power load is a resistor having a predetermined resistance value. A non-contact power feeding method for transmitting a current from a power transmission device to a power reception device by at least magnetic coupling,
Detecting a current state of a power transmission coil of the power transmission device;
And a step of estimating a relative distance between the power transmitting device and the power receiving device from the detected change in the current state.

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