JP6358410B2 - Coil antenna, power transmission device and power reception device - Google Patents

Description

  The present invention relates to a wireless power transmission system that wirelessly transmits power from a power transmission device to a power reception device.

  In recent years, research and development for improving power transmission efficiency and reducing the size of devices in a wireless power transmission system have become active.

  In a magnetic field coupling type wireless power transmission system, magnetic field coupling is performed in a state where a coil antenna of a power transmission device and a coil antenna of a power reception device are arranged close to each other. Therefore, when the positional relationship between the coil antenna of the power transmission device and the coil antenna of the power reception device changes, the power transmission efficiency changes according to the deviation.

  Patent Document 1 discloses a coil antenna in which the coil conductors of the coil antenna are wound so that the interval between the coil conductors is dense on the outside of the coil conductor and sparse on the inside in order to suppress fluctuations in power transmission efficiency due to the above-described positional deviation. It is shown.

Japanese Patent Laying-Open No. 2015-95656

  In general, when the coil conductors are wound so as to be closely spaced, inductance and parasitic capacitance per unit length of the coil conductors are increased. As a result, the self-resonant frequency generated in the coil conductor is lowered. When the self-resonant frequency coincides with or is close to the power transmission frequency, no current flows through the entire coil conductor of the coil antenna, and the coil antenna does not emit magnetic flux. That is, since the self-resonance generated in the coil conductor of the coil antenna does not contribute to power transmission, the power transmission efficiency of the system is significantly reduced when the self-resonance frequency coincides with or is close to the power transmission frequency.

  The above-described problem is not limited to the coil antenna wound so that the coil conductor is dense outside and outside the winding range, as shown in Patent Document 1, but the area occupied by the coil antenna is reduced. For the sake of simplicity, the same occurs even when the interval between the coil conductors is reduced as a whole. Therefore, the miniaturization of the coil antenna is limited by the self-resonant frequency.

  An object of the present invention is to provide a coil antenna suitable for miniaturization, a power transmission device including the coil antenna, and a power reception device that suppress a decrease in power transmission efficiency.

(1) The coil antenna of the present invention is a coil antenna used for coupling a power transmitting device and a power receiving device that constitute a wireless power transmission system,
A plurality of coil conductors wound around a winding axis;
The plurality of coil conductors have parallel portions connected in parallel and wound in parallel,
When the plurality of coil conductors constituting the parallel portion are connected in series, the self-resonant frequency due to the inductance and capacitor generated in the coil conductor is f0, the self-resonant frequency of the coil antenna is f1, and the voltage / current transmitted by the power transmission device When the frequencies are represented by f2, f2 <f1 and f0 ≦ 2f2, respectively.

  With the above configuration, in the parallel portion of the coil conductors, the coil conductors are adjacent to each other at substantially the same potential portion, so that effective parasitic capacitance does not occur, and the self-resonant frequency of the coil antenna can be maintained high. That is, the self-resonant frequency can be used in a relationship that does not coincide with or close to the frequency for power transmission, while having a portion where the interval between the coil conductors is close.

  In addition, the inductance of the coil conductor when the coil conductors of the parallel part are connected in series and the self-resonance frequency f0 due to the capacitor are not more than twice the frequency f2 of the voltage / current transmitted by the power transmission device. Since the space between the coil conductors is narrow, a small coil antenna is configured while maintaining a high self-resonance frequency.

(2) It is preferable that the said coil conductor has a part where the space | interval between mutually adjacent coil conductors is a sparse part, and a dense part, and the said parallel part is comprised by the said dense part. Thereby, the parasitic capacitance between the parallel portions of the coil conductors (that is, the parasitic capacitance that affects the self-resonant frequency of the coil antenna) can be relatively reduced, and the size can be further reduced accordingly.

(3) In the above (2), it is preferable that the dense portion is located farther from the sparse portion in the radial direction from the winding shaft. Thereby, the coupling coefficient with the coil antenna of the coupling partner can be stabilized within a wide range of the relative positional relationship with the coil antenna of the coupling partner.

(4) In said (1), it is preferable that the space | interval of the coil conductor of the said parallel part is narrower than the space | interval of the said parallel part and the other parallel part adjacent to the said parallel part. As a result, the parasitic capacitance can be further reduced without increasing the area occupied by the coil conductor.

(5) In said (1), it is preferable that the space | interval of the coil conductor of the said parallel part near outer periphery is narrower than the space | interval of the coil conductor of the said parallel part near inner periphery. As a result, the parasitic capacitance can be further reduced without increasing the area occupied by the coil conductor.

(6) In said (1), it is preferable that the space | interval of the said adjacent parallel parts is narrower on the outer periphery side than on the inner periphery side. As a result, the parasitic capacitance can be further reduced without increasing the area occupied by the coil conductor.

(7) In any one of (1) to (6), the frequency f0 is preferably equal to or less than the frequency f2. As a result, the coil conductors in the parallel portion are further narrowed to form a smaller coil antenna.

(8) In any one of (1) to (7), the frequency f2 is preferably in the HF band. Although the HF band is a frequency band suitable for power transmission, this HF band is also a frequency band in which the self-resonant frequency of the coil antenna is likely to be close. According to the present invention, since the self-resonant frequency can be maintained high, problems due to the self-resonant frequency of the coil antenna being close to the frequency of the voltage / current transmitted by the power transmission device can be avoided.

(9) A power transmission device of the present invention is a power transmission device in a wireless power transmission system that wirelessly transmits power from a power transmission device to a power reception device,
A coil antenna used for coupling with the power receiving device;
The coil antenna is
Comprising a coil conductor wound around a winding axis;
The coil conductor has a parallel portion connected in parallel and wound in parallel;
When the coil conductors of the parallel part are connected in series, the self-resonance frequency due to the inductance and the capacitor generated in the coil conductor is f0, the self-resonance frequency of the coil antenna is f1, and the frequency of the voltage / current transmitted by the power transmission device is f2. When expressed respectively, f2 <f1 and f0 ≦ 2f2.

  With the above configuration, it is possible to configure a power transmission device that is small and has high power transmission efficiency.

(10) The power receiving device of the present invention is a power receiving device in a wireless power transmission system that wirelessly transmits power from the power transmitting device to the power receiving device,
A coil antenna used for coupling with the power transmission device;
The coil antenna is
Comprising a coil conductor wound around a winding axis;
The coil conductor has a parallel portion connected in parallel and wound in parallel;
When the coil conductors of the parallel part are connected in series, the self-resonance frequency due to the inductance and the capacitor generated in the coil conductor is f0, the self-resonance frequency of the coil antenna is f1, and the frequency of the voltage / current transmitted by the power transmission device is f2. When expressed respectively, f2 <f1 and f0 ≦ 2f2.

  With the above configuration, it is possible to configure a power receiving device that is small and has high power transmission efficiency.

  ADVANTAGE OF THE INVENTION According to this invention, the fall of electric power transmission efficiency is suppressed and the coil antenna suitable for size reduction, a power transmission apparatus provided with it, and a power receiving apparatus are obtained.

FIG. 1 is a plan view of a coil antenna 10 according to the first embodiment. FIG. 2 is a plan view illustrating the coil conductors 11 and 12 of the coil antenna 10 with different line types. FIG. 3 is an equivalent circuit diagram of the coil antenna 10. FIG. 4 is a circuit diagram of a wireless power transmission system 301 according to the second embodiment. FIG. 5 is a perspective view showing the configuration of the power transmission coil antenna Lt and the power reception coil antenna Lr of the wireless power transmission system 301. FIG. 6 is a perspective view showing another configuration of the power transmission coil antenna Lt and the power reception coil antenna Lr of the wireless power transmission system 301. FIGS. 7A and 7B are comparative examples, and are plan views of a coil antenna 10S in which coil conductors in parallel portions of the coil antenna 10 of the first embodiment are connected in series. FIG. 8 is an equivalent circuit diagram of the coil antenna 10S shown in FIG. FIG. 9 is a cross-sectional view of a coil antenna in which a plurality of coil conductors are arranged in different layers of a base material. FIG. 10 is a plan view of a coil antenna 30 according to the third embodiment. FIG. 11 is a plan view illustrating the coil conductors 11, 12, and 13 of the coil antenna 30 with different line types. FIG. 12 is a comparative example, and is a plan view of a coil antenna 30 </ b> S in which coil conductors in parallel portions of the coil antenna 30 are connected in series. FIG. 13 is a plan view of a coil antenna 40 according to the fourth embodiment. FIG. 14 is a plan view illustrating the coil conductors 11 and 12 of the coil antenna 40 with different line types.

  Hereinafter, several specific examples will be given with reference to the drawings to show a plurality of modes for carrying out the present invention. In each figure, the same reference numerals are assigned to the same portions. In consideration of ease of explanation or understanding of the main points, the embodiments are shown separately for convenience, but the components shown in different embodiments can be partially replaced or combined. In the second and subsequent embodiments, description of matters common to the first embodiment is omitted, and only different points will be described. In particular, the same operation effect by the same configuration will not be sequentially described for each embodiment.

<< First Embodiment >>
In the first embodiment, the structure and operation of an example of a coil antenna will be described with reference to the drawings.

  FIG. 1 is a plan view of a coil antenna 10 according to the first embodiment. The coil antenna 10 is a coil antenna used for coupling a power transmission device and a power reception device that constitute a wireless power transmission system, and is provided in either or both of the power transmission device and the power reception device.

  The coil antenna 10 includes an insulating base material 19 and a coil conductor formed on the base material 19.

  The coil antenna 10 includes coil conductors 11 and 12 wound around a winding axis. The winding axes of the coil conductors 11 and 12 are oriented in a direction perpendicular to the surface of the base material 19. A point o in FIG. 1 is a point through which the winding axis passes.

  FIG. 2 is a plan view illustrating the coil conductors 11 and 12 with different line types.

  The coil conductor 11 constitutes a rectangular spiral coil having a first end T11 and a second end T21. Further, the coil conductor 12 constitutes a rectangular spiral coil having a first end T12 and a second end T22. The first end T11 of the coil conductor 11 and the first end T12 of the coil conductor 12 are connected to each other and used as a terminal T1 (see FIG. 1). Similarly, the second end T21 of the coil conductor 11 and the second end T22 of the coil conductor 12 are connected to each other and used as a terminal T2 (see FIG. 1). Terminals T1 and T2 of the coil antenna 10 are connected to an external circuit. Therefore, the coil conductors 11 and 12 are connected in parallel.

  In this example, the coil conductors 11 and 12 are entirely composed of parallel portions from the first ends T11 and T12 to the second ends T21 and T22. In FIG. 1, parallel parts PP1a, PP1b, PP1c, PP1d indicate parallel parts of the outer peripheral part along the four sides. The parallel parts PP2a, PP2b, PP2c, PP2d indicate intermediate parallel parts along the four sides. The parallel parts PP3a, PP3b, PP3c, PP3d indicate parallel parts of the inner peripheral part along the four sides.

  In FIG. 2, the inter-line distance dp1 is the distance between the coil conductor 11 and the coil conductor 12 at the outer peripheral part, the inter-line distance dp2 is the inter-line distance between the coil conductor 11 and the coil conductor 12, and the inter-line distance dp3 is the inner peripheral part. The distance between the coil conductor 11 and the coil conductor 12 in FIG. Further, the capacitance Cp1 is a line capacitance generated between the coil conductor 11 and the coil conductor 12 in the outer peripheral portion, the capacitance Cp2 is a line capacitance generated between the coil conductor 11 and the coil conductor 12 in the intermediate portion, and the capacitance Cp3 is an internal capacitance. Line capacities generated between the coil conductor 11 and the coil conductor 12 in the periphery are respectively shown.

  In FIG. 2, the line distance da1 is the distance between the parallel part PP1a at the outer peripheral part and the parallel part PP2a at the intermediate part, and the line distance da2 is between the parallel part PP2a at the intermediate part and the parallel part PP3a at the inner peripheral part. Is the interval. The capacitance Ca1 is a parasitic capacitance generated at the line distance da1 portion, and the capacitance Ca2 is a parasitic capacitance generated at the line distance da2 portion.

  FIG. 3 is an equivalent circuit diagram of the coil antenna 10. Here, the inductors L11a and L11b are inductors that represent inductance generated in the coil conductor 11 in a lumped constant circuit. Similarly, the inductors L12a and L12b are inductors that represent inductance generated in the coil conductor 12 in a lumped constant circuit. Capacitors Cpa and Cpb are capacitors that represent the line capacitance generated between the coil conductor 11 and the coil conductor 12 in a lumped constant circuit.

  As shown in FIGS. 1 and 2, the coil conductors 11 and 12 of the coil antenna 10 are configured in parallel from the first ends T11 and T12 to the second ends T21 and T22. The potential difference at 12 adjacent positions is almost zero. That is, the potential difference between the coil conductors 11 and 12 is almost zero regardless of the position from the first ends T11 and T12 to the second ends T21 and T22. Therefore, the voltage applied to the line-to-line capacitances (parasitic capacitances) Cpa and Cpb is almost 0, and resonance does not substantially occur in the LC circuits of the inductors L12a and L12b and the capacitors Cpa and Cpb. Therefore, the parallel portions PP1a, PP1b, PP1c, PP1d, PP2a, PP2b, PP2c, PP2d, PP3a, PP3b, PP3c, PP3d shown in FIG. Self-resonance at the portion does not substantially occur.

  The self-resonant frequency of the coil antenna 10 is determined by the inductance of the parallel part and the parasitic capacitances Ca1 and Ca2 between adjacent parallel parts. Since the inductance of the parallel part is a parallel connection circuit of the two coil conductors 11 and 12, the combined inductance is small. In addition, since the regions of the parasitic capacitances Ca1 and Ca2 generated between the parallel portions are small (not generated between all the lines but only between the parallel portions), the total parasitic capacitance is small. Therefore, the self-resonant frequency of the coil antenna is set higher than that of the coil antenna provided with one spiral coil conductor having the same number of turns.

  7A and 7B are plan views of a coil antenna 10S of a comparative example. The coil antenna shown in FIG. 7A is obtained by connecting a plurality of coil conductors constituting a parallel portion of the coil antenna 10 of this embodiment in series. 7B, the winding order of the coil conductor is changed from the coil antenna 10S shown in FIG. 7A, and the number of turns of the coil conductor is the same as that of the coil antenna 10 shown in FIGS. In the same manner, the coil conductor is configured to form one rectangular spiral.

  FIG. 8 is an equivalent circuit diagram of the coil antenna 10S shown in FIG. Here, the inductors La, Lb, Lc, and Ld are inductors that represent inductance generated in the coil conductor in a lumped constant circuit. Capacitors Ca, Cb, Cc, and Cd are capacitors that represent parasitic capacitance generated between coil conductor lines in a lumped constant circuit. The self-resonant frequency of the coil antenna 10S is determined by the inductors La, Lb, Lc, Ld and the capacitors Ca, Cb, Cc, Cd. Therefore, the self-resonant frequency decreases as the number of turns of the coil conductor increases and the distance between the lines decreases.

  In the present invention, in order to avoid a decrease in the self-resonant frequency without increasing the size of the coil antenna, the interval between the coil conductors constituting the parallel portion and the interval between the parallel portion and the parallel portion is determined. Is important. In the present invention, the above relationship is defined as follows.

  The self-resonant frequency (that is, the coil antenna) due to the inductance and the capacitor generated in the coil conductor when a plurality of coil conductors constituting the parallel portion of the coil antenna 10 shown in FIG. 1 are connected in series as shown in FIG. When the self-resonant frequency of 10S is represented by f0, the self-resonant frequency of the coil antenna 10 is represented by f1, and the voltage / current frequency transmitted by the power transmission device is represented by f2, f2 <f1 and f0 ≦ 2f2. Further, f0 ≦ f2 may be satisfied.

  According to the present embodiment, as already described, since the self-resonant frequency is not lowered even if the space between the parallel portions is narrowed, the space between the parallel portions is narrowed between the parallel portions and the parallel portions. By expanding this, the capacitance component, which is the first variable that determines the self-resonance frequency, can be reduced. Further, since the inductance of the coil conductor is also reduced, the inductive component that is the second variable that determines the self-resonant frequency can be reduced. As a result, the self-resonance frequency can be increased. In addition, the coil antenna can be miniaturized under the same self-resonant frequency.

  In the coil antenna 10 of the present embodiment, the coil conductors adjacent to each other have a sparse part and a dense part, and the parallel part is composed of a dense part. That is, the space between the coil conductors in the parallel portion is narrow, and the interval between the parallel portion and the parallel portion is wide. In other words, the interval between the coil conductors in the parallel portion is narrower than the interval between the parallel portion and another parallel portion adjacent to the parallel portion. Thus, the parasitic capacitances Ca1 and Ca2 can be further reduced without increasing the occupied area of the coil conductors 11 and 12. In the present embodiment, the line-to-line distances dp1 and da1 are configured such that dp1 <da1.

  In the coil antenna 10 of the present embodiment, the dense portion is located farther from the sparse portion in the radial direction from the winding axis. That is, the dense part is located closer to the outer periphery, and the sparse part is located closer to the inner periphery, so that the coupling coefficient with the coupling partner coil antenna is wide in a wide range of relative positional relationship with the coupling partner coil antenna. Stabilized. In other words, the interval between adjacent parallel portions is narrower on the outer periphery than on the inner periphery. In the coil conductors constituting the parallel part, the distance between the coil conductors in the parallel part near the outer periphery is narrower than the distance between the coil conductors in the parallel part near the inner periphery.

  In the present embodiment, the distances dp1, dp2, and dp3 between the lines have a relationship of dp1 ≦ dp2 ≦ dp3, and the distances between the lines da1 and da2 have a relationship of da1 ≦ da2.

  In the example shown above, the coil antenna is formed by forming the coil conductor with the conductor pattern on the insulating base material. However, the base material is not essential, and the same coil antenna is formed by the wire-shaped coil conductor. May be. Further, the substrate may be a wiring board on which a circuit other than the coil antenna is configured.

  Moreover, the coil conductor by a conductor pattern may be arrange | positioned in the layer from which a base material differs. Here, FIG. 9 shows a partial cross-sectional view of a coil antenna having a structure in which coil conductors are arranged in different layers of a base material. Thus, for example, the coil conductors in the parallel portion may be arranged in different layers of the base material to constitute a multilayer substrate. In this case, the line-to-line distances dp1, dp2, and dp3 are distances including an interlayer distance component.

<< Second Embodiment >>
The second embodiment shows an example of a wireless power transmission system.

  FIG. 4 is a circuit diagram of a wireless power transmission system 301 according to the second embodiment. The wireless power transmission system 301 includes a power transmission device 101 and a power reception device 201.

  The power transmission device 101 includes a power transmission coil antenna Lt and a resonance capacitor Ct connected in series to the power transmission coil antenna Lt. The power transmission coil antenna Lt and the resonance capacitor Ct constitute a resonance circuit 110. The power transmission device 101 includes an inverter circuit 111 that converts the DC input voltage Vi into an AC voltage and applies the AC voltage to the resonance circuit 110. Inverter circuit 111 includes switching elements Q1 and Q2, a capacitor C11, a diode D1, and a drive circuit 112. The drive circuit 112 alternately drives the switching elements Q1 and Q2 on / off at the HF band operating frequency (eg, 6.78 MHz). The resonance frequency of the resonance circuit 110 is the operating frequency or a frequency in the vicinity thereof.

  The power receiving device 201 includes a power receiving coil antenna Lr and a resonance capacitor Cr connected in parallel to the power receiving coil antenna Lr. The power receiving coil antenna Lr and the resonance capacitor Cr constitute a resonance circuit 210. The power receiving coil antenna Lr and the power transmitting coil antenna Lt are mainly magnetically coupled. The power receiving apparatus 201 includes a rectifying / smoothing circuit 211 that converts an AC voltage generated in the resonance circuit 210 into a DC voltage, and a load Ro that is driven by the DC output voltage converted by the rectifying / smoothing circuit 211. The rectifying / smoothing circuit 211 includes a rectifying circuit 212 using a diode bridge circuit, smoothing capacitors C21 and C22, and a voltage regulator circuit 213.

  The resonant circuit 210 resonates in parallel at the operating frequency or a frequency in the vicinity thereof. The resonant voltage of the resonant circuit 210 is full-wave rectified by the rectifier circuit 212, smoothed and stabilized by the smoothing capacitors C21 and C22, and the voltage regulator circuit 213, and a predetermined constant voltage Vo is supplied to the load Ro.

  5 and 6 are perspective views showing configurations of the power transmission coil antenna Lt and the power reception coil antenna Lr. In the example shown in FIG. 5, the power transmission coil antenna Lt is the coil antenna (coil antenna 10) having the structure shown in the first embodiment, and the power reception coil antenna Lr is a normal coil antenna. In the example shown in FIG. 6, the power receiving coil antenna Lr is the coil antenna (coil antenna 10) having the structure shown in the first embodiment, and the power transmitting coil antenna Lt is a normal coil antenna. In any case, the “ordinary coil antenna” is a coil conductor having a simple loop shape or spiral shape.

  Note that both the coil antenna for power transmission and the coil antenna for power reception may be the coil antenna having the structure shown in the first embodiment. In either case, the power transmission coil antenna and the power reception coil antenna are mainly magnetically coupled, and power is transmitted mainly via the magnetic field.

  The self-resonant frequency due to the inductance and capacitor generated in the coil conductor when the coil conductors in the parallel part of the coil antenna 10 are connected in series is f0, the self-resonant frequency of the coil antenna 10 is f1, and When the frequencies are represented by f2, f2 <f1 and f0 ≦ 2f2. Further, f0 ≦ f2 may be satisfied. The coil conductor can be wound more densely so that f0 ≦ f2. Here, the frequency f2 is 6.78 MHz as described above.

  Thus, the coil antenna of the present invention can be used for either a power transmission coil antenna or a power reception coil antenna.

  In the coil antenna 10 of the present embodiment, in the radial direction from the winding axis, a portion where the distance between the coil conductors is dense is located near the outer periphery, and a sparse portion is located closer to the inner periphery. In general, the two coil antennas have the highest degree of coupling when their winding axes coincide and face each other, and the degree of coupling tends to decrease as the position deviates from the position. However, in the coil antenna of this embodiment, the number of coil conductors that are close to each other in a face-to-face state increases as the relative positional relationship with the coil antenna of the coupling partner is shifted. As a result, the tendency of the degree of coupling to decrease due to a shift in the relative positional relationship is suppressed, and the coupling coefficient with the coupling partner coil antenna is stabilized in a wide range of the relative positional relationship with the coupling partner coil antenna.

<< Third Embodiment >>
FIG. 10 is a plan view of a coil antenna 30 according to the third embodiment. The coil antenna 30 is a coil antenna used for coupling a power transmission device and a power reception device that constitute a wireless power transmission system, and is provided in either or both of the power transmission device and the power reception device.

  The coil antenna 10 includes an insulating base material 19 and a coil conductor formed on the base material 19.

  The coil antenna 10 includes coil conductors 11, 12, and 13 wound around a winding axis. The winding axes of the coil conductors 11, 12, 13 are oriented in a direction perpendicular to the surface of the base material 19. Point o in FIG. 10 is a point through which the winding axis passes.

  FIG. 11 is a plan view illustrating the coil conductors 11, 12, and 13 with different line types.

  The coil conductor 11 constitutes a rectangular spiral coil having a first end T11 and a second end T21. The coil conductor 12 constitutes a rectangular spiral coil having a first end T12 and a second end T22. Further, the coil conductor 13 constitutes a rectangular spiral coil having a first end T13 and a second end T23. The first end T11 of the coil conductor 11, the first end T12 of the coil conductor 12, and the first end T13 of the coil conductor 13 are connected to each other and used as a terminal T1 (see FIG. 10). Similarly, the second end T21 of the coil conductor 11, the second end T22 of the coil conductor 12, and the second end T23 of the coil conductor 13 are connected to each other and used as a terminal T2 (see FIG. 10). Terminals T1 and T2 of the coil antenna 30 are connected to an external circuit. Therefore, the coil conductors 11, 12, and 13 are connected in parallel.

  FIG. 12 is a comparative example, and is a plan view of a coil antenna 30 </ b> S in which coil conductors in parallel portions of the coil antenna 30 are connected in series. This coil antenna 30S has the same number of turns of the coil conductor as the coil antenna 30 shown in FIGS. 10 and 11, but the coil conductor has a simple rectangular spiral shape. In this case, the number of turns of the coil conductor is increased and the line spacing is narrowed, so that the self-resonant frequency is lowered. However, in the coil antenna 30 of the third embodiment, the self-resonant frequency can be increased as compared with the coil antenna 30S.

  As shown in this embodiment, the number of coil conductors connected in parallel is not limited to two, but may be three, or four or more.

<< Fourth Embodiment >>
FIG. 13 is a plan view of a coil antenna 40 according to the fourth embodiment. The coil antenna 40 is a coil antenna used for coupling a power transmission device and a power reception device that constitute a wireless power transmission system, and is provided in either or both of the power transmission device and the power reception device.

  The coil antenna 40 includes an insulating base material 19 and a coil conductor formed on the base material 19.

  The coil antenna 40 includes coil conductors 11 and 12 wound around a winding axis. The winding axes of the coil conductors 11 and 12 are oriented in a direction perpendicular to the surface of the base material 19. A point o in FIG. 13 is a point through which the winding axis passes.

  FIG. 14 is a plan view illustrating the coil conductors 11 and 12 with different line types.

  The coil conductor 11 constitutes a spiral coil having a first end T11 and a second end T21. Further, the coil conductor 12 constitutes a spiral coil having a first end T12 and a second end T22. The first end T11 of the coil conductor 11 and the first end T12 of the coil conductor 12 are connected to each other and used as a terminal T1 (see FIG. 13). Similarly, the second end T21 of the coil conductor 11 and the second end T22 of the coil conductor 12 are connected to each other and used as a terminal T2 (see FIG. 13). Terminals T1 and T2 of the coil antenna 10 are connected to an external circuit. Therefore, the coil conductors 11 and 12 are connected in parallel.

  Since the coil antenna 40 of the fourth embodiment also has the coil conductors connected in parallel, the self-resonant frequency can be increased.

  As shown in the present embodiment, the coil conductor may have a circular spiral shape, and the shape of the spiral is not limited to this. Moreover, the shape which combined the straight line and the curve may be sufficient.

  Finally, the description of the above embodiment is illustrative in all respects and not restrictive. Those skilled in the art can make modifications and changes as appropriate. The scope of the present invention is shown not by the above embodiments but by the claims. Furthermore, the scope of the present invention includes modifications from the embodiments within the scope equivalent to the claims.

C11... Capacitors C21, C22... Smoothing capacitors Ca, Cb, Cc, Cd... Capacitors Ca1, Ca2... Parasitic capacitances Cp1, Cp2, Cp3. ... line distances dp1, dp2, dp3 ... line distances L11a, L11b, L12a, L12b ... inductors La, Lb, Lc, Ld ... inductor Lr ... power receiving coil antenna Lt ... power transmitting coil antennas PP1a, PP1b, PP1c, PP1d , PP2a, PP2b, PP2c, PP2d, PP3a, PP3b, PP3c, PP3d ... Parallel portions Q1, Q2 ... Switching elements Ro ... Loads T1, T2 ... Terminals T11, T12 ... First end T21, T22 ... Second end 10, 30 , 40 ... Coil antenna 10S, 30 ... Coil antenna 11, 12, 13 ... Coil conductor 19 ... Insulating substrate 101 ... Power transmission device 110 ... Resonance circuit 111 ... Inverter circuit 112 ... Drive circuit 201 ... Power reception device 210 ... Resonance circuit 211 ... Rectification smoothing circuit 212 ... Rectification circuit 213 ... Voltage regulator circuit 301 ... Wireless power transmission system

Claims (10)

In a coil antenna used for coupling a power transmitting device and a power receiving device constituting a wireless power transmission system,
A plurality of coil conductors wound around a winding axis;
The plurality of coil conductors have parallel portions connected in parallel and wound in parallel,
When the plurality of coil conductors constituting the parallel portion are connected in series, the self-resonant frequency due to the inductance and capacitor generated in the coil conductor is f0, the self-resonant frequency of the coil antenna is f1, and the voltage / current transmitted by the power transmission device A coil antenna, wherein f2 <f1 and f0 ≦ 2f2 when the frequencies are represented by f2. The coil conductor has a sparse part and a dense part between adjacent coil conductors,
The coil antenna according to claim 1, wherein the parallel portion includes the dense portion.   The coil antenna according to claim 2, wherein the dense portion is located farther than the sparse portion in a radial direction from the winding axis.   The coil antenna according to claim 1, wherein an interval between the coil conductors of the parallel part is narrower than an interval between the parallel part and another parallel part adjacent to the parallel part.   The coil antenna according to claim 1, wherein an interval between the coil conductors in the parallel portion near the outer periphery is narrower than an interval between the coil conductors in the parallel portion near the inner periphery.   The coil antenna according to claim 1, wherein an interval between the adjacent parallel portions is narrower on the outer periphery side than on the inner periphery side.   The coil antenna according to any one of claims 1 to 6, wherein the frequency f0 is equal to or less than the frequency f2.   The coil antenna according to any one of claims 1 to 7, wherein the frequency f2 is an HF band. A power transmission device in a wireless power transmission system that wirelessly transmits power from a power transmission device to a power reception device,
A coil antenna used for coupling with the power receiving device;
The coil antenna is
Comprising a coil conductor wound around a winding axis;
The coil conductor has a parallel portion connected in parallel and wound in parallel;
When the coil conductors of the parallel part are connected in series, the self-resonance frequency due to the inductance and the capacitor generated in the coil conductor is f0, the self-resonance frequency of the coil antenna is f1, and the frequency of the voltage / current transmitted by the power transmission device is f2. A power transmission device characterized by satisfying f2 <f1 and f0 ≦ 2f2, respectively. A power receiving device in a wireless power transmission system that wirelessly transmits power from a power transmitting device to a power receiving device,
A coil antenna used for coupling with the power transmission device;
The coil antenna is
Comprising a coil conductor wound around a winding axis;
The coil conductor has a parallel portion connected in parallel and wound in parallel;
When the coil conductors of the parallel part are connected in series, the self-resonance frequency due to the inductance and the capacitor generated in the coil conductor is f0, the self-resonance frequency of the coil antenna is f1, and the frequency of the voltage / current transmitted by the power transmission device is f2. A power receiving device characterized by f2 <f1 and f0 ≦ 2f2, respectively.

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