JPWO2016135895A1 - Resonator and wireless power transmission device - Google Patents

Abstract

A resonator and a wireless power transmission device capable of reducing a leakage electromagnetic field are provided. According to one embodiment, a resonator includes a first coil for wireless power transmission and a second coil. The second coil is magnetically coupled to the first coil and is electrically separated. At least one of the first coil and the second coil includes a magnetic core.

Description

  Embodiments described herein relate generally to a resonator and a wireless power transmission device.

  Conventionally, a resonator including a spiral type wireless power transmission coil and a magnetically coupled and electrically separated loop coil has been proposed. In the above-described conventional resonator, the magnetic field generated by the wireless power transmission coil and the magnetic flux generated by the loop coil cancel each other, thereby reducing the leakage electromagnetic field having a predetermined frequency from the wireless power transmission coil. .

  However, in the above conventional resonator, since the coupling coefficient between the wireless power transmission coil and the loop coil is small, it is necessary to enlarge the loop coil in order to reduce the leakage electromagnetic field from the wireless power transmission coil. there were. As a result, there is a problem that the leakage electromagnetic field from the loop coil increases.

JP 2012-115069 A

  A resonator and a wireless power transmission device capable of reducing a leakage electromagnetic field are provided.

  A resonator according to an embodiment includes a first coil for wireless power transmission and a second coil. The second coil is magnetically coupled to the first coil and is electrically separated. At least one of the first coil and the second coil includes a magnetic core.

The figure which shows the resonator which concerns on 1st Embodiment. The figure which shows the equivalent circuit of the resonator which concerns on 1st Embodiment. The figure which shows the frequency characteristic of input impedance. The figure which shows the frequency characteristic of the electric current of a 1st coil and a 2nd coil. The figure which shows the modification of the resonator of FIG. The figure which shows the modification of the resonator of FIG. The figure which shows the modification of the resonator of FIG. The figure which shows the modification of the resonator of FIG. The figure which shows the modification of the resonator of FIG. The figure which shows the modification of the resonator of FIG. The figure which shows the modification of the resonator of FIG. The figure which shows the modification of the resonator of FIG. The figure which shows the modification of the resonator of FIG. The figure which shows the frequency characteristic of the electric current phase of a 1st coil and a 2nd coil. The figure which shows the frequency characteristic of the electric current phase of a 1st coil and a 2nd coil. The figure explaining the positional relationship of a 1st coil and a 2nd coil. The figure which shows the frequency characteristic of the electric current of a 1st coil and a 2nd coil.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
First, the resonator according to the first embodiment will be described with reference to FIGS. The resonator according to the present embodiment is used by being mounted on a wireless power transmission device such as a wireless power transmission device or a wireless power reception device, for example.

  FIG. 1 is a diagram illustrating a resonator according to the present embodiment. As shown in FIG. 1, the resonator includes a first resonance circuit 1, a second resonance circuit 2, and a flat magnetic core 3.

The first resonance circuit 1 is a resonance circuit for wireless power transmission. The first resonance circuit 1 has a resonance frequency f ₁ (first resonance frequency). As shown in FIG. 1, the first resonance circuit 1 includes a first coil 11 and a first capacitor 12.

The first coil 11 is a solenoid type coil for wireless power transmission, and is formed by winding a winding around the magnetic core 3. The first coil 11 has an inductance _{L 1.}

The first capacitor 12 is connected to the first coil 11 and forms the first resonance circuit 1 together with the first coil 11. The first capacitor 12 has a capacitance value _{C 1.} The resonance frequency _{f 1} of the first resonance circuit _{1, f 1 = 1 / 2π (} L 1 C 1) becomes ^1/2.

When the resonator is mounted on the wireless power transmission device, the first resonance circuit 1 is connected to an AC power source 13 as shown in FIG. By the AC power supply 13 supplies AC power to the first resonance circuit 1, the first resonance circuit 1 resonates at the resonance frequency f _1. Thereby, the 1st coil 11 generates an alternating current magnetic field, and transmits electric power wirelessly to the coil by the side of power reception.

  When the resonator is mounted on the wireless power receiving apparatus, the first resonance circuit 1 is connected to a load such as a battery instead of the AC power supply 13. The first coil 11 receives power wirelessly via an AC magnetic field generated by a coil on the power transmission side.

  In FIG. 1, the resonator includes the first capacitor 12, but a configuration without the first capacitor 12 is also possible. In this case, the first capacitor 12 may be prepared separately from the resonator and connected to the first coil 11.

The second resonance circuit 2 is a resonance circuit for reducing the leakage electromagnetic field from the first coil 11. The second resonance circuit 2 is electrically separated from the first resonance circuit 1 and is not connected to a power source. The second resonance circuit 2 has a resonance frequency f ₂ (second resonance frequency). As shown in FIG. 1, the second resonance circuit 2 includes a second coil 21 and a second capacitor 22.

The second coil 21 is a solenoid-type coil formed by winding a magnetic core 3 wound around, has an inductance L _2. The second coil 21 is magnetically coupled to the first coil 11 and is induced by an alternating magnetic field generated by the first coil 11 to generate an electromotive force. Due to this electromotive force, a current flows through the second resonance circuit 2, and the second coil 21 generates an alternating magnetic field.

The second capacitor 22 is connected to the second coil 21 and forms the second resonance circuit 2 together with the second coil 21. The second capacitor 21 has a capacitance value _{C 2.} Second resonance frequency _{f 2} of the resonant circuit 2 _{becomes f 2 = 1 / 2π (L} 2 C 2) 1/2.

  In FIG. 1, the resonator includes the second capacitor 22, but a configuration without the second capacitor 22 is also possible. In this case, the second capacitor 22 may be prepared separately from the resonator and connected to the second coil 21.

FIG. 2 is an equivalent circuit of the resonator shown in FIG. In FIG. 2, V ₁ is an AC voltage value applied by the AC power supply 13, I ₁ is a current value of the first resonance circuit 1, R ₁ is a resistance value of the second resonance circuit 1, and Z _in is an input viewed from the AC power supply 13. Impedance, I ₂ is a current value of the second resonance circuit 2, R ₂ is a resistance value of the second resonance circuit 2, and M ₁₂ is a mutual inductance between the first coil 11 and the second coil 12. At this time, the input impedance Z _in is expressed by the following equation.

As can be seen from Equation (1), the input impedance Z _in changes according to the resonance frequency f ₂ (= ½π (L ₂ C ₂ ) ^1/2 ) of the second resonance circuit 2. Therefore, by adjusting the resonance frequency f _2, it is possible to increase the input impedance Z ₁ of a predetermined frequency.

By adjusting the resonance frequency f _2, the input impedance Z ₁ of a frequency X is increased, since the alternating current having a frequency X is less likely to flow through the first coil 11, the AC magnetic field having a frequency of X that the first coil 11 to generate Becomes smaller.

The resonator according to the present embodiment reduces the leakage electromagnetic field from the resonator using such a principle. That is, in this embodiment, the resonance frequency f ₂ is the input impedance Z _in a predetermined frequency to reduce the leakage electromagnetic field is set to rise.

In general, the AC power supply 13 is an inverter, and the first coil 11 is driven by a rectangular wave current supplied from the inverter. The rectangular wave current mainly includes a fundamental wave current and a harmonic current. The fundamental current is set to the resonance frequency f ₁ of the first resonance circuit 1 and causes the first coil 11 to generate a magnetic field for wireless power transmission. On the other hand, the harmonic current (third harmonic, fifth harmonic, etc.) has a frequency that is an integral multiple of the fundamental current, and causes the first coil 11 to generate a leakage electromagnetic field that does not contribute to wireless power transmission.

Therefore, in this embodiment, the resonance frequency f ₂ is the input impedance Z _in of the first integer multiple of the frequency of the resonant frequency f ₁ of the resonant circuit 1 is set to rise. Thereby, the leakage electromagnetic field caused by the harmonic current from the first coil 11 can be reduced. Specifically, the resonance frequency f ₂ is set to an integral multiple of the frequency of the resonant frequency f _1.

Hereinafter, the case of reducing the third leakage electromagnetic field caused by the harmonic currents having a frequency three times higher than the resonant frequency f _1. In the following description, it is assumed that the resonance frequency f ₁ (frequency of the fundamental wave current) of the first resonance circuit 1 is 85 kHz. At this time, the frequency of the third harmonic current is 255 kHz.

Figure 3 is a graph showing the frequency characteristic of the input impedance Z _in. 3, the solid line input impedance _{Z in} the case of setting the resonance frequency _{f 2} of the second resonance circuit 2 to 255KHz, a broken line indicates an input impedance _{Z in} the case where the resonator is not provided with the second coil 21. The case where the second coil 21 is not provided is equivalent to the case where the coupling coefficient k between the first coil 11 and the second coil 21 is zero.

As shown in FIG. 3, when the resonator does not include the second coil 21, the input impedance Z _in is minimum at 85 kHz (= f ₁ ) and increases gently in the frequency region of 85 kHz or higher.

On the other hand, when the resonator includes the second coil 21 and the resonance frequency f ₂ is set to 255 kHz (= 85 kHz × 3), the input impedance Z _in increases sharply at 255 kHz and changes almost at 85 kHz. Not done.

Than 3, by setting the resonance frequency _{f 2} to 255KHz, without affecting the input impedance _{Z in} of 85 kHz, it can be seen that raising the input impedance _{Z in} of 255KHz vicinity.

FIG. 4 is a diagram illustrating frequency characteristics of currents of the first coil 11 and the second coil 21. In FIG. 4, the solid line current of the first coil 11 in the case of setting the resonance frequency _{f 2} to 255KHz, dotted line current of the second coil 21 in the case of setting the resonance frequency _{f 2} to 255KHz, dashed line resonator is first The electric current of the 1st coil 11 in case the 2 coil 21 is not provided is shown.

  As shown in FIG. 4, when the resonator does not include the second coil 21, the current of the first coil 11 becomes maximum at 85 kHz, and gently decreases in the frequency region of 85 kHz or higher.

In contrast, if the resonator comprises a second coil 21, the resonance frequency _{f 2} is set to 255KHz, the current of the first coil 11 is made rapidly decreased at 255KHz, not changed almost at 85 kHz.

From FIG. 4, by setting the resonance frequency _{f 2} to 255KHz, without affecting the current of 85kHz of the first coil 11, it is understood that it is possible to reduce the 255KHz vicinity of current. That is, the harmonic current that generates the leakage electromagnetic field can be reduced without affecting the current that contributes to wireless power transmission.

As described above, in the present embodiment, by setting the resonance frequency f ₂ to an integral multiple of the resonance frequency f _1, increases the input impedance Z _in of the frequency of an integral multiple of the resonance frequency f _1, the first coil 11 The harmonic current flowing through the can be reduced. Therefore, the leakage electromagnetic field from the first coil 11 can be reduced.

As can be seen from FIG. 4, the harmonic current decreases not only in the resonance frequency f ₂ but also in the frequency region near the resonance frequency f ₂ . Therefore, the resonance frequency f _2, is set to a frequency near the frequency of an integral multiple of the resonance frequency f _1, to obtain the same effect as described above. When the first coil 11 due to a manufacturing error of the frequency shift of the second coil 21 expected respectively about 5%, a frequency near the frequency of an integral multiple of the resonance frequency f _1, for example, to an integer multiple of the frequency of the resonance frequency f ₁ On the other hand, the frequency is within 10% error.

  In the resonator according to the present embodiment, as indicated by a dotted line in FIG. 4, a current also flows through the second coil 21, and the second coil 21 generates an alternating magnetic field, which causes a leakage electromagnetic field from the resonator. Become. In general, a magnetic field generated by a solenoid type coil as shown in FIG. 1 is expressed by the following equation.

The above H _r , H _θ , and H _φ are the components of the magnetic field at a certain point in space, and E _r and E _φ are the components of the electric field. In equations (2) to (6), k is the wave number, a is the radius of the coil, I is the intensity of the current flowing through the coil, and N is the number of turns of the winding. According to the equations (2) to (6), the magnetic field strength H and the electric field strength E generated by the solenoid type coil are the square of the coil radius a, the first power of the current strength I, and the first power of the number of turns N. It turns out that it grows proportionally.

Therefore, in order to reduce the leakage electromagnetic field from the second coil 21, the radius and the number of turns of the second coil 21 may be reduced. When the second coil 21 is miniaturized, the inductance L ₂ of the second coil 21 is decreased, although the coupling coefficient between the first coil 11 and second coil 21 is lowered, the resonator of this embodiment, Since the 1st coil 11 and the 2nd coil 21 have the common magnetic body core 3, the fall of a coupling coefficient is suppressed.

According to the electromagnetic field simulation, when the resonator shown in FIG. 1 does not include the magnetic core 3, the inductance L ₂ is 0.53 μH and the coupling coefficient is 0.16, whereas the resonator is the magnetic core 3. when equipped with the inductance _{L 2} is 1.54MyuH, the coupling coefficient becomes 0.53.

  Thus, since the first coil 11 and the second coil 21 include the magnetic core 3 in the resonator according to the present embodiment, the second coil 21 can be reduced in size while maintaining the coupling coefficient. Therefore, the leakage electromagnetic field from the second coil 21 can also be reduced.

  5 to 13 are diagrams showing modifications of the resonator according to the present embodiment.

  In the resonator shown in FIG. 5, the magnetic core 3 is cylindrical. In the resonator shown in FIG. 6, the magnetic core 3 has a quadrangular prism shape, and the first coil 11 and the second coil 21 are spiral coils. Thus, the shape of the magnetic core 3 is not limited to a flat plate shape, and may be an arbitrary shape such as a cylindrical shape or a quadrangular prism shape.

  In the resonator of FIG. 7, the first coil 11 includes the magnetic core 3, and the second coil 21 includes the magnetic core 3 ′. Thus, the 1st coil 11 and the 2nd coil 21 may be provided with a separate magnetic core, respectively. Further, only one of the first coil 11 and the second coil 21 may include the magnetic core 3. In either case, the coupling coefficient between the first coil 11 and the second coil 21 is larger than when both the first coil 11 and the second coil 21 are not provided with a magnetic core. Therefore, the second coil 21 can be downsized, and the leakage electromagnetic field from the second coil 21 can be reduced.

  In the resonator shown in FIG. 8, the first coil 11 and the second coil 21 have a common cylindrical magnetic core 3, and the radius of the second coil 21 is smaller than the radius of the first coil 11. In the resonator shown in FIG. 9, the first coil 11 and the second coil 21 have a common flat magnetic core 3, and the radius of the second coil 21 is smaller than the radius of the first coil 11. Furthermore, in the resonator of FIG. 10, the first coil 11 and the second coil 21 are provided with separate flat magnetic cores 3 and 3 ′, respectively, and the radius of the second coil 21 is smaller than the radius of the first coil 11. It has become.

  Thus, the leakage electromagnetic field from the second coil 21 can be reduced by making the radius of the second coil 21 smaller than the radius of the first coil 11. This is the same when the number of turns of the second coil 21 is less than the number of turns of the first coil 11.

  In the resonator shown in FIG. 11, the second coil 21 includes the cylindrical magnetic core 3, and the radius of the second coil 21 is smaller than the radius of the first coil 11. The first coil 11 is a spiral coil formed on the bottom surface of the magnetic core 3. Thus, one of the first coil 11 and the second coil 21 may be a spiral coil.

  The resonator shown in FIG. 12 includes two second resonance circuits 2. Each second resonance circuit 2 in FIG. 12 includes a second coil 21 and a second capacitor 22 connected to the second coil 21. The resonator shown in FIG. 13 includes four second resonance circuits 2. Each second resonance circuit 2 in FIG. 13 includes a second coil 21 having a smaller radius than the first coil, and a second capacitor 22 connected to the second coil 21.

As described above, the resonator according to this embodiment may include a plurality of second resonance circuits 2. In this case, first the resonance frequency f ₂ of the second resonance circuit 2 is set to three times the frequency of the resonant frequency f _1, the resonance frequency f ₁ of the two resonance frequencies f ₂ eyes of the second resonant circuit 2 It is preferable that the resonance frequency f2 of each second resonance circuit ₂ is set to a different frequency. Thus, increasing the input impedance Z _in of the plurality of frequencies, to reduce the harmonic current flowing in the first coil 11, it is possible to reduce the leakage electromagnetic field from the resonator. The resonance frequency f ₂ of the second resonance circuit 2, for example, by adjusting the capacitance value C ₂ of the second capacitor 22 included in the second resonant circuit 2 are respectively settable.

(Second Embodiment)
Next, a resonator according to the second embodiment will be described with reference to FIGS. The configuration of the resonator according to this embodiment is the same as that of the first embodiment. In the first embodiment, the leakage electromagnetic field from the resonator is reduced by increasing the input impedance Z _in , but in this embodiment, the leakage electromagnetic field from the first coil 11 and the second coil 21 is canceled. As a result, the leakage electromagnetic field from the resonator is reduced. Therefore, resonator according to this embodiment, the resonator according to the first embodiment, setting of the resonance frequency f ₂ of the second coil 21 are different.

Hereinafter, the procedure for setting the resonance frequency f _2. In the following description, the positive direction of the current of the second coil 21 is the same as the direction of the magnetic field generated by the first coil 11 when a positive current flows through the first coil 11. 21 is a direction to be generated.

  In the resonator according to this embodiment, when currents having the same phase flow through the first coil 11 and the second coil 21, the first coil 11 and the second coil 21 generate magnetic fields having the same phase. On the other hand, when an antiphase current flows through the first coil 11 and the second coil 21, the first coil 11 and the second coil 21 generate an antiphase magnetic field. When the first coil 11 and the second coil 21 generate magnetic fields with opposite phases, the magnetic fields of the two cancel each other, so that the leakage electromagnetic field from the resonator is reduced.

The resonator according to the present embodiment reduces the leakage electromagnetic field from the resonator using such a principle. That is, in this embodiment, the resonance frequency f ₂ is set so that the current phase of the first coil 11 and second coil 21 of a predetermined frequency to reduce the leakage electromagnetic field is reversed phases. Thereby, the magnetic fields generated by the first coil 11 and the second coil 21 cancel each other, and the leakage electromagnetic field from the resonator can be reduced. Specifically, the resonance frequency f ₂ is set to a frequency lower than a frequency of an integral multiple of the resonance frequency f _1.

Hereinafter, the case of reducing the third leakage electromagnetic field caused by the harmonic currents having a frequency three times higher than the resonant frequency f _1. In the following description, it is assumed that the resonance frequency f ₁ (frequency of the fundamental wave current) of the first resonance circuit 1 is 85 kHz. At this time, the frequency of the third harmonic current is 255 kHz.

Figure 14 is a graph showing the frequency characteristic of the current phase of the first coil 11 and second coil 21 in the case of setting the resonance frequency _{f 2} to 255KHz. 14, the solid line resonance frequency current phase of the first coil 11 when the _{f 2} is set to 255KHz, the dotted line current phase of the second coil 21 in the case of setting the resonance frequency _{f 2} to 255KHz, dashed line resonator There current phase of the first coil 11 when not provided with the second coil 21, a chain line shows the current phase difference between the first coil 11 in the case of setting the resonance frequency f ₂ to 255kHz and the second coil 21.

As shown in FIG. 14, if you set the resonant frequency _{f 2} to 255KHz, the first coil 11 and the current phase is opposite phase (current phase difference 180 °) of the second coil 21 in the frequency region higher than 255KHz, and the more 255KHz In the low frequency region, the current phases of the first coil 11 and the second coil 21 are the same phase (current phase difference 0 °).

Further, 255 kHz is an inflection point that changes from the same phase to the opposite phase, and the current phase is not completely opposite in the frequency region of 255 kHz and its vicinity. For this reason, the magnetic field does not cancel out at 255 kHz, and the leakage electromagnetic field from the resonator cannot be reduced. Than 14, in order to reduce the leakage electromagnetic field by canceling the magnetic field, the resonance frequency f _2, it can be seen that it is necessary to set to a frequency lower than the frequency of the leakage electromagnetic field to be reduced.

Figure 15 is a graph showing the frequency characteristic of the current phase of the first coil 11 and second coil 21 in the case of setting the resonance frequency _{f 2} to 197KHz. In FIG. 15, the solid line indicates the current phase of the first coil 11 when the resonance frequency f ₂ of the second resonance circuit 2 is set to 197 kHz, and the dotted line indicates the current of the second coil 21 when the resonance frequency f ₂ is set to 197 kHz. phase, the broken line resonator current phase of the first coil 11 when not provided with the second coil 21, the current of the one-dot chain line and the first coil 11 in the case of setting the resonance frequency f ₂ to 197kHz and the second coil 21 Indicates the phase difference.

As shown in FIG. 15, if you set the resonant frequency _{f 2} to 197KHz, the current phase of the first coil 11 and second coil 21 is in the opposite phase (current phase difference 180 °) in the frequency region higher than 197KHz I understand that. According to FIG. 15, it is a frequency region of about 230 kHz or more that is completely in antiphase. Therefore, by setting the resonance frequency _{f 2} to 197KHz, the magnetic field of 255kHz is offset to reduce the leakage electromagnetic field from the resonator.

Thus, the resonance frequency f _2, by setting the frequency slightly lower than the frequency to reduce the leakage electromagnetic field, it is possible to reduce the leakage electromagnetic field from resonator due to harmonic currents. Further, the entire higher frequency range than the resonance frequency f ₂ which current phase is opposite phase, it is possible to reduce the leakage electromagnetic field.

However, the first coil 11 depending on the positional relationship of the second coil 21, the resonance frequency f _2, it is necessary to set to a frequency higher than the frequency of the leakage electromagnetic field to be reduced. FIG. 16 is a diagram for explaining the positional relationship between the first coil 11 and the second coil 21. In FIG. 16, the arrow 31 indicates the direction of the current flowing through the first coil 11, the broken line 32 indicates the magnetic field generated by the current flowing through the first coil 11, the broken line 32 arrow indicates the direction of the magnetic field 32, and the arrow 33 indicates the second direction by the magnetic field 32. The direction of current excited in the coil 21 and the arrow 34 indicate the direction of current excited in the second coil 21 ′ by the magnetic field 32.

As shown in FIG. 16, the current direction 31 of the first coil 11 and the current direction 33 of the second coil 21 coincide with each other. If the first coil 11 and second coil 21 are arranged in such a positional relationship, as described above, the resonance frequency f _2, may be set to a frequency lower than the frequency of the leakage electromagnetic field to be reduced.

On the other hand, the current direction 31 of the first coil 11 and the current direction 34 of the second coil 21 ′ are opposite to each other. When the first coil 11 and the second coil 21 ′ are arranged in such a positional relationship, the in-phase region shown in FIG. 14 is in the opposite phase, and the opposite phase region is in the same phase. 11 and the phase relationship between the second coil 21 'is inverted. Therefore, the resonance frequency f _2, it is necessary to set to a frequency higher than the frequency of the leakage electromagnetic field to be reduced.

The resonance frequency f _2, is either set to either frequency or higher frequency lower than the frequency of the leakage electromagnetic field to be reduced, be determined according to the direction of the current in the second coil 21 is excited by the current of the first coil 11 Good.

  The effect of reducing the leakage electromagnetic field according to the present embodiment is maximized when the strength of the magnetic field generated by the first coil 11 is equal to the strength of the magnetic field generated by the second coil. As described above, the strength of the magnetic field generated by each coil is proportional to the square of the radius a of each coil, the first power of the current intensity I, and the first power of the number of turns N. For this reason, for example, when the first coil 11 and the second coil 21 have the same radius and the same number of turns as in the resonator of FIG. 1, the leakage electromagnetic field reduction effect is maximized when the current intensity I is equal.

FIG. 17 is a diagram illustrating frequency characteristics of currents of the first coil 11 and the second coil 21. 17, the solid line current of the first coil 11 in the case of setting the resonance frequency _{f 2} to 197KHz, dotted line current of the second coil 21 in the case of setting the resonance frequency _{f 2} to 197KHz, dashed line resonator is first 2 current of the first coil 11 when not provided with a coil 21, a chain line shows the real current in the case of setting the resonance frequency f ₂ to 197KHz. The actual current referred to here is a current obtained by adding the current of the first coil 11 and the current of the second coil 21 in consideration of the phase difference, and substantially contributes to the generation of a leakage electromagnetic field from the resonator. Current.

As shown in FIG. 17, by setting the resonance frequency _{f 2} to 197KHz, the current of the first coil 11 and second coil 21 has a peak at 85kHz and approximately 220 kHz. Further, the current of the first coil 11 decreases rapidly at 197 kHz. This is because the impedance Z _{in at} 197 kHz increases as described in the first embodiment.

As described above, if you set the resonant frequency _{f 2} to 197KHz, the current phase is completely opposite phase at about 230 kHz. For this reason, as shown in FIG. 17, it can be seen that the substantial current is greatly reduced in the frequency region of about 230 kHz or more.

  Moreover, according to FIG. 17, the current intensity of the 1st coil 11 and the 2nd coil 21 becomes equal at 255 kHz, and a real current is the minimum. That is, the effect of reducing the leakage electromagnetic field is maximized at 255 kHz.

Thus, the resonance frequency f ₂ is the frequency at which the reduction effect of the leakage electromagnetic field is maximum is preferably set to be an integral multiple of the frequency of the resonant frequency f _1. The frequency at which the leakage electromagnetic field reduction effect is maximized can be obtained by experiment or electromagnetic field simulation.

  Note that the present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the components without departing from the scope of the invention in the implementation stage. Moreover, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiments. Further, for example, a configuration in which some components are deleted from all the components shown in each embodiment is also conceivable. Furthermore, you may combine suitably the component described in different embodiment.

1: first resonance circuit, 2: second resonance circuit, 3: magnetic core, 11: first coil, 12: first capacitor, 13: AC power supply, 21: second coil, 22: second capacitor

Claims (14)

A first coil for wireless power transmission;
A second coil that is magnetically coupled to and electrically separated from the first coil;
With
At least one of the first coil and the second coil is a resonator including a magnetic core. The resonator according to claim 1, wherein at least one of the first coil and the second coil is a solenoid type coil including the magnetic core. A first capacitor connected to the first coil and forming a first resonant circuit having a first resonant frequency;
A second capacitor connected to the second coil and forming a second resonant circuit having a second resonant frequency;
The resonator according to claim 1 or 2, further comprising: The resonator according to claim 3, wherein the second resonance frequency is set to a frequency within an error of 10% with respect to a frequency that is an integral multiple of the first resonance frequency. The resonator according to claim 3, wherein the second resonance frequency is set to a frequency different from a predetermined frequency for reducing a leakage electromagnetic field. 5. The resonator according to claim 3, wherein the second resonance frequency is set to a frequency that is higher than the frequency of the first resonance frequency and lower than a predetermined frequency that reduces a leakage electromagnetic field. The resonator according to claim 3 or 4, wherein the second resonance frequency is set to a frequency higher than a predetermined frequency for reducing a leakage electromagnetic field. 4. The resonator according to claim 3, wherein the second resonance frequency is set so that current intensities of the first coil and the second coil are equal to each other at an integer multiple of the first resonance frequency. The resonator according to any one of claims 1 to 8, comprising a plurality of the second coils. The resonator according to claim 9, comprising a plurality of second capacitors connected to the second coil and forming a second resonance circuit having a second resonance frequency. The resonator according to claim 10, wherein the plurality of second resonance circuits have different second resonance frequencies. The resonator according to any one of claims 1 to 11, wherein the first coil and the second coil are solenoid coils in which a winding is wound around the same magnetic core. The resonator according to any one of claims 1 to 12, wherein the first coil and the second coil have different radii. A wireless power transmission device comprising the resonator according to claim 1.

Images