JP2016187260A - Wireless power feeding apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wireless power feeding apparatus capable of achieving wireless transmission of electric power with low loss using electric field resonance.SOLUTION: A wireless power feeding apparatus 100 includes a power supply unit 110, a power transmission coupler 120 and a power reception coupler 130, and transmits electric power from the power transmission coupler 120 to the power reception coupler 130 in a wireless manner by electric field resonance. The power supply unit 110 performs a switching operation by soft switching using a first capacitor 113 and a series resonant circuit 114. The power transmission coupler 120 is constituted by sharing the series resonant circuit 114 of the power supply unit 110. In other words, the power transmission coupler 120 is constituted by connecting a second capacitor 121 and a first coil 122 of the series resonant circuit 114 in series.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a wireless power feeder that wirelessly transmits electric power by electromagnetic resonance, and more particularly to an electric field resonance type wireless power feeder that transmits electric power by electric field resonance.

  There are many active researches on wireless power feeding technology. This originates from a technology that MIT announced in 2006 as electromagnetic resonance. The antenna (coupler) unit, which is an energy transmission / reception unit, is characterized by high transmission efficiency of 90% or more and a large transmission distance. An ISM frequency band of MHz is used as a resonance frequency for generating electromagnetic field resonance by wireless power feeding. Therefore, it is necessary to generate high-frequency power of 13 MHz, 27 MHz, or 40 MHz in the ISM frequency band in the power supply unit that supplies power to the power transmission coupler. The power supply unit is required to supply such high-frequency power with high efficiency.

  The wireless power supply apparatus includes a power supply unit that generates high-frequency power, a coupler unit that wirelessly transmits power, and a power receiving smoothing circuit (rectifier unit) that converts received power into direct current. The coupler unit includes a power transmission coupler and a power reception coupler, and is configured as a resonance circuit in which a coil (C) and a capacitor (L) are connected in series. In a system in which power transmission is performed by magnetic field resonance, the coils are enlarged and arranged to face each other, and magnetic field resonance is performed between the two coils. Further, in the system in which electric power transmission is performed by electric field resonance, capacitors are enlarged and arranged to face each other, and electric field resonance is performed between both capacitors.

  The efficiency of the wireless power feeder is obtained by multiplying the efficiency in the power supply unit, the wireless transmission efficiency in the coupler unit, and the efficiency in the power receiving smoothing circuit. The wireless power feeding method is required to improve the efficiency of each component as much as possible because the power transmission efficiency is lower than that of the wired method.

  In order to increase the efficiency of the power supply unit, it is preferable to use an RF inverter that is a circuit using a soft switching method for the power supply unit. In the power supply unit using the soft switching method, a transistor is used for switching. However, the loss in the transistor is mostly the switching loss compared to the conduction loss. Therefore, in order to reduce the switching loss, a soft switching method is adopted in which the phase is adjusted using a resonance circuit so that the voltage when current flows along with switching becomes zero.

  Patent Document 1 discloses a power supply apparatus configured to perform wireless power supply using a soft switching power supply unit. FIG. 8 shows the configuration of the wireless power feeding apparatus described in Patent Document 1. In the wireless power supply apparatus 90 shown in the figure, a method of transmitting power by magnetic field resonance is adopted. In order to increase the efficiency of power transmission by magnetic field resonance, it is preferable to increase the coils of the power transmission coupler 91 and the power reception coupler 92 and to reduce the capacitor so that a predetermined resonance frequency is obtained.

  The soft switching type power supply unit includes a series resonance circuit in which a coil and a capacitor are connected in series. On the other hand, the power transmission coupler connected to the power supply unit is also a series resonant circuit in which a coil and a capacitor are connected in series. Therefore, in Patent Document 1, one coil and one capacitor are reduced by sharing the series resonance circuit of the power supply unit and the power transmission coupler 91. That is, the coil and the capacitor used for the power transmission coupler 91 are also used for the series resonance circuit of the power supply unit. As a result, the series resonance circuit of the power supply unit is composed of a large coil and a small capacitor used for the power transmission coupler 91.

Japanese Patent No. 5069726

  However, when electromagnetic resonance is performed at a high frequency in the ISM frequency band, a large loss is generated in the coil due to the skin effect and the proximity effect. In the wireless power feeder described in Patent Document 1, it is necessary to use a large coil for the power transmission coupler 91 in order to perform power transmission by magnetic field resonance. Therefore, there arises a problem that the loss in the coil is further increased.

  In addition, an air-core coil is used as the coil of the power transmission coupler 91. However, the air-core coil has a particularly large loss because the magnetic field divergence is large. In order to reduce the loss, there is a method using a coil having a ferrite core instead of the air-core coil. However, since the permeability of the ferrite decreases from 1 MHz to the high frequency side, the loss can be reduced at 2 MHz or more. Can not. Since high-frequency power in the MHz band is supplied to the power transmission coupler 91, even if a coil having a ferrite core is used as the coil of the power transmission coupler 91, loss cannot be reduced.

  Further, in the wireless power feeding apparatus adopting magnetic field resonance as in Patent Document 1, since the leakage magnetic flux from the power transmission coupler 91 and the power reception coupler 92 is large, a magnetic shield for shielding this is necessary. However, magnetic shields are extremely difficult and costly compared to electric field shields, and wireless power feeding by magnetic field resonance has a problem that large power cannot be supplied to reduce leakage magnetic flux.

  The present invention has been made to solve these problems, and an object of the present invention is to provide a wireless power feeder capable of wirelessly transmitting power with low loss using electric field resonance.

A first aspect of the wireless power feeding device of the present invention is a wireless power feeding device that wirelessly transmits power from a power transmission coupler having the same resonance frequency to a power reception coupler, the transistor that performs a switching operation at the resonance frequency, and the transistor A power supply unit comprising: a first capacitor connected in parallel; a series resonance circuit that resonates at the resonance frequency by connecting a second capacitor and a first coil in series; The second capacitor and the first coil are shared, and electric power is transmitted by causing electric field resonance between the second capacitor and a third capacitor included in the power receiving coupler. And

  In another aspect of the wireless power supply apparatus of the present invention, the power supply unit generates power at the resonance frequency by a soft switching method and supplies the power to the power transmission coupler.

  In another aspect of the wireless power feeding apparatus of the present invention, the second capacitor is larger than a dimension capable of transmitting power at a predetermined transmission efficiency by electric field resonance with respect to the third capacitor, and the first coil Is characterized in that the loss is reduced by reducing the size so as to achieve the resonance frequency with the second capacitor.

  In another aspect of the wireless power supply apparatus of the present invention, the resonance frequency is a frequency in an ISM frequency band.

  According to the present invention, it is possible to provide a wireless power feeding apparatus capable of wirelessly transmitting electric power with low loss using electric field resonance.

It is a block diagram which shows the structure of the wireless electric power feeder of 1st Embodiment of this invention. It is a block diagram which shows the structure of the conventional power supply part which operate | moves by a soft switching system. It is a block diagram which shows the structure of the conventional power transmission / reception coupler part which employ | adopted the electric field resonance system. It is a block diagram which shows the structure of the conventional power transmission / reception coupler part which employ | adopted the magnetic field resonance system. It is a block diagram which shows the detailed structure of the conventional power transmission / reception coupler part of a magnetic field resonance system. It is a block diagram which shows the structure of the wireless electric power feeder which connected the conventional electric field resonance system power transmission / reception coupler part to the conventional power supply part. It is a block diagram which shows the structure of the wireless electric power feeder which connected the power transmission / reception coupler part of the conventional magnetic field resonance system to the conventional power supply part. It is a block diagram which shows the structure of the conventional wireless electric power feeder.

  A wireless power supply apparatus according to a preferred embodiment of the present invention will be described in detail with reference to the drawings. In addition, about each structural part which has the same function, the same code | symbol is attached | subjected and shown for simplification of illustration and description.

(First embodiment)
A wireless power feeder according to a first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram illustrating a configuration of a wireless power supply apparatus 100 according to the present embodiment. The wireless power feeding apparatus 100 includes a power supply unit 110 that generates AC power having a predetermined resonance frequency (fc), a power transmission coupler 120 that inputs AC power from the power supply unit 110 and transmits power wirelessly, and wirelessly transmits power from the power transmission coupler 120. And a power receiving smoothing circuit (rectifying unit) 140 that smoothes AC power received by the power receiving coupler 130 into DC power.

  When power having a resonance frequency fc is supplied from the power supply unit 110, the power transmission coupler 120 wirelessly transmits the supplied power to the power reception coupler 130 by performing electric field resonance with the power reception coupler 130. The power receiving coupler 130 outputs the power received from the power transmission coupler 120 to the power receiving smoothing circuit 140, and the power receiving smoothing circuit 140 smoothes the power to DC power. Further, power is supplied to the load 20 connected to the power reception smoothing circuit 140.

  The power supply unit 110 includes a pulse generation unit 111 that outputs a control signal (pulse signal) at a resonance frequency fc, a transistor 112 that performs a switching operation according to the control signal input from the pulse generation unit 111, and a first transistor connected in parallel to the transistor 112. 1 capacitor 113 and a series resonance circuit 114 are provided. The series resonance circuit 114 is configured by connecting the second capacitor 121 and the first coil 122 in series, and is configured to resonate at the resonance frequency fc.

  The transistor 112 has a gate terminal 112a connected to the pulse generator 111 and a source terminal 112b grounded. The drain terminal 112c is connected to the external power supply (Vdd) 10 via the choke coil 115.

  The power supply unit 110 includes the transistor 112, the first capacitor 113, and the series resonance circuit 114 as described above, and thus can perform a switching operation by a soft switching method. As a result, loss in the power supply unit 110 can be reduced.

  The wireless power supply apparatus 100 according to the present embodiment is characterized in that the power transmission coupler 120 is configured by sharing the series resonance circuit 114 of the power supply unit 110. That is, the power transmission coupler 120 of the present embodiment is configured by the second capacitor 121 and the first coil 122 of the series resonance circuit 114. The power receiving coupler 130 is configured by connecting a third capacitor 131 and a second coil 132 in series.

  FIG. 2 shows the configuration of a conventional power supply unit that operates in the soft switching system. The power supply unit 30 shown in the figure includes a pulse generation unit 31, a transistor 32, a capacitor 33, and a series resonance circuit 34, similar to the power supply unit 110 of the present embodiment. The capacitor 35 and the coil 36 are connected in series. The drain terminal of the transistor 32 is connected to the external power supply 10 via the choke coil 37.

  FIG. 3 shows the configuration of a conventional power transmission / reception coupler unit employing the electric field resonance method. A conventional power transmission / reception coupler unit 40 using an electric field resonance system includes a power transmission coupler 43 configured by connecting a capacitor 41 and a coil 42 in series, a power reception coupler 46 configured by connecting a capacitor 44 and a coil 45 in series, and It has. The power transmission coupler 43 wirelessly transmits the power supplied from the power supply 11 to the power reception coupler 46 by electric field resonance. The power receiving coupler 46 supplies the received power to the load 20.

  For comparison with the electric field resonance type power transmission / reception coupler unit 40, FIG. 4 shows a configuration of a conventional power transmission / reception coupler unit employing the magnetic field resonance method. A conventional power transmission / reception coupler unit 50 using a magnetic field resonance method includes a power transmission coupler 53 configured by connecting a capacitor 51 and a coil 52 in series, and a power reception coupler 56 configured by connecting a capacitor 54 and a coil 55 in series. It has. The power transmission coupler 53 wirelessly transmits the power supplied from the power supply 11 to the power reception coupler 56 by magnetic field resonance. The power receiving coupler 56 supplies the received power to the load 20.

  As a configuration of the magnetic field resonance type power transmission / reception coupler unit, more specifically, a configuration including four coils shown in FIG. 5 is used. The power transmission / reception coupler unit 60 shown in FIG. 5 includes a power transmission coupler 64 including an exciting coil 61, a power transmission coil 62 and a capacitor 63, and a power reception coupler 68 including a power reception coil 65, a capacitor 66 and a load coil 67. Electric power is transmitted between the power transmission coil 62 and the power reception coil 65 by magnetic field resonance, and the excitation coil 61 and the power transmission coil 62 and the power reception coil 65 and the load coil 67 are coupled by electromagnetic induction.

  In the power transmission / reception coupler section 40 shown in FIG. 3, in order to cause electric field resonance between the power transmission coupler 43 and the power reception coupler 46, the dimensions of the capacitors 41 and 44 are made larger and opposed to each other. By increasing the dimensions of the capacitors 41 and 44, the transmission efficiency by electric field resonance can be increased. In order to set the resonance frequency of the power transmission coupler 43 and the power reception coupler 46 to fc, the dimensions of the capacitors 41 and 44 are increased, and the dimensions of the coils 42 and 45 are decreased.

  On the other hand, in the power transmission / reception coupler unit 50 shown in FIG. 4, the dimensions of the coils 52, 55 are increased and faced to make magnetic resonance between the power transmission coupler 53 and the power reception coupler 56. By increasing the dimensions of the coils 52 and 55, the transmission efficiency by magnetic field resonance can be increased. In order to set the resonance frequency of the power transmission coupler 53 and the power reception coupler 56 to fc, the dimensions of the coils 52 and 55 are increased, and the dimensions of the capacitors 51 and 54 are decreased. In the power transmission / reception coupler section 60 shown in FIG. 5, the dimensions of the power transmission coil 62 and the power reception coil 65 that perform magnetic field resonance are increased.

  When electromagnetic resonance is performed at a high frequency of MHz or higher, a large loss occurs due to the skin effect and proximity effect in the coil. Therefore, in the magnetic field resonance type power transmission / reception coupler unit 50 that needs to increase the size of the coil, the coil A large loss occurs at 52 and 55. On the other hand, in the electric field resonance type power transmission / reception coupler section 40, since the coils 42 and 45 having small dimensions are used, the loss in the coils 42 and 45 can be reduced. Further, the loss in the capacitor is extremely small compared to the coil. Since the wireless power feeding apparatus 100 according to the present embodiment employs the same electric field resonance method as that of the power transmission / reception coupler unit 40, the loss in the power transmission coupler 120 and the power reception coupler 130 can be reduced.

  FIG. 6 shows a configuration of a wireless power feeding apparatus in which the electric field resonance type power transmission / reception coupler unit 40 shown in FIG. 3 is connected to the conventional power source unit 30 operating in the soft switching mode shown in FIG. As shown in the figure, in the conventional configuration, the series resonance circuit 34 including the capacitor 35 and the coil 36 is connected in series with the series resonance circuit including the capacitor 41 and the coil 42 of the power transmission coupler 43. . The wireless power supply apparatus 100 according to the present embodiment is configured such that one series resonance circuit 114 shares such series connection of two series resonance circuits. As a result, the number of capacitors and coils can be reduced to reduce costs, and loss can be reduced by reducing the number of coils.

  For comparison with the configuration of FIG. 6, FIG. 7 shows a configuration of a wireless power feeding apparatus in which the magnetic resonance type power transmission / reception coupler unit 50 shown in FIG. 4 is connected to the conventional power source unit 30 shown in FIG. . Even in this case, the series resonance circuit 34 including the capacitor 35 and the coil 36 is connected in series with the series resonance circuit including the capacitor 51 and the coil 52 of the power transmission coupler 53. In the configuration of Patent Document 1 shown in FIG. 8, such a series connection of two series resonance circuits is configured to be shared by one series resonance circuit 34. As a result, the number of capacitors and coils can be reduced. However, in the magnetic field resonance method, the coils 52 and 55 need to be enlarged.

  Note that the wireless power feeding device 90 described in Patent Document 1 is a half-bridge power feeding circuit that directly supplies an alternating current to a power transmission coil without using an exciting coil, and is connected in series to the power transmission coil 62 shown in FIG. The capacitor 63 is shared with the capacitor 35 and the coil 36 of the series resonance circuit 34.

  According to the wireless power supply apparatus of the present embodiment, by sharing the series resonance circuit of the power supply unit that operates in the soft switching system and the power transmission coupler, the number of capacitors and coils can be reduced and the cost can be reduced. Moreover, by performing wireless transmission by the electric field resonance method, the coil of the power transmission / reception coupler can be reduced in size, and the loss due to the coil can be greatly reduced. Furthermore, the magnetic flux leakage from the power transmission / reception coupler can be greatly reduced by downsizing the coil. On the other hand, when it is necessary to reduce the leakage of the electric field and the leakage of electromagnetic waves by increasing the capacitor of the power transmission / reception coupler, it can be easily shielded with a metal plate or the like.

  The degree to which the power loss is reduced by sharing the series resonant circuit 114 and the power transmission coupler 120 of the power supply unit 110 will be described using simulation results. As an example, when 500 W is applied from the external power supply 10, a loss of 85 W occurs in the conventional configuration in which the series resonance circuit 114 and the power transmission coupler 120 of the power supply unit 110 are separately provided. On the other hand, in the present embodiment in which the series resonant circuit 114 and the power transmission coupler 120 are shared, the loss is 62 W with respect to 500 W applied, and it is possible to reduce the 23 W loss from the conventional configuration. It has become.

  Note that the description in the present embodiment shows an example of the wireless power supply apparatus according to the present invention, and the present invention is not limited to this. The detailed configuration and detailed operation of the wireless power supply apparatus in this embodiment can be changed as appropriate without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 100 Wireless power supply device 110 Power supply part 111 Pulse generation part 112 Transistor 112a Gate terminal 112b Source terminal 112c Drain terminal 113 1st capacitor | condenser 114 Series resonance circuit 115 Choke coil 120 Power transmission coupler 121 2nd capacitor 122 1st coil 130 Power reception coupler 131 Third capacitor 132 Second coil 140 Power receiving smoothing circuit

Claims (4)

A wireless power feeder that wirelessly transmits power from a power transmission coupler having the same resonance frequency to a power reception coupler,
A transistor that performs a switching operation at the resonance frequency, a first capacitor connected in parallel to the transistor, a series resonance circuit that resonates at the resonance frequency by connecting a second capacitor and a first coil in series, A power supply unit comprising:
The power transmission coupler is configured to share the second capacitor and the first coil,
A wireless power feeder, wherein electric power is transmitted by causing electric field resonance between the second capacitor and a third capacitor included in the power receiving coupler. The wireless power feeder according to claim 1, wherein the power supply unit generates power of the resonance frequency by a soft switching method and supplies the power to the power transmission coupler. The second capacitor is larger than a dimension capable of transmitting power at a predetermined transmission efficiency by electric field resonance with respect to the third capacitor, and the first coil is disposed between the second capacitor and the second capacitor. The wireless power feeding apparatus according to claim 1, wherein the loss is reduced by reducing a dimension so as to be a resonance frequency. The wireless power feeding apparatus according to claim 1, wherein the resonance frequency is a frequency in an ISM frequency band.

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