JP2016039644A - Power transmission device and wireless power transmission system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power transmission device and a radio power transmission system that can suppress reduction of the Q value caused by an array design of coils.SOLUTION: A first coil element 10a has a first winding, a first drawing line connected to one end of the first winding and a second drawing wire connected the other end of the first winding. A second coil element 10b has a second winding wound in the reverse direction to the first winding, a third drawing wire connected to one end of the second winding, and a fourth drawing wire which is connected to the other end of the second winding wire and also connected to the first drawing wire. The first and second windings are arranged so that the direction of magnetic field occurring at the center of the first winding when current flows from the second drawing wire to the first coil element is coincident with the direction of magnetic field occurring at the center of the second winding when current flows from the third drawing wire to the second coil element.SELECTED DRAWING: Figure 2

Description

  The present disclosure relates to a power transmission device and a wireless power transmission system for wireless power transmission that transmits power in a contactless manner.

  In recent years, rechargeable devices with mobility, such as portable information terminals and electric vehicles, have become widespread. Development of a wireless power transmission system for such devices is underway. As the wireless power transmission technology, methods such as an electromagnetic induction method, a magnetic field resonance method (resonance magnetic field coupling method), and an electric field coupling method are known.

  A wireless power transmission system using an electromagnetic induction method and a magnetic field resonance method includes a power transmission device including a power transmission coil and a power reception device including a power reception coil. When the power receiving coil captures the magnetic field generated by the power transmitting coil, power can be transmitted without directly contacting the electrodes.

  One of the requirements required in wireless power transmission is that it is not necessary to align the power transmission device and the power reception device. That is, it is required that highly efficient power transmission is possible without matching the position and orientation of the power receiving apparatus to a specific position and orientation. For example, as illustrated in FIGS. 1A and 1B, even if the relative position of the power receiving device 200 with respect to the power transmitting device 100 is different, it is required to maintain the power transmission efficiency so that it does not change significantly. For example, there are a moving coil method and a coil array method as a technique that eliminates such alignment.

  In the moving coil method, the motor moves the power transmission coil to a position facing the power reception coil in accordance with the position of the power reception coil. Thereby, electric power can always be transmitted in a good coupling state. However, since it is driven by a motor, there are problems in terms of thinning, quietness and reliability of the power transmission device.

  In the coil array system, the power transmission device has a coil array including a plurality of power transmission coils, and selects a power transmission coil to be energized according to the position of the power reception coil. Thereby, irrespective of the position of a receiving coil, highly efficient electric power transmission can be performed. Problems in the moving coil system in terms of thinning, quietness, and reliability of the power transmission device can be improved by eliminating the motor. Such a coil array type wireless power transmission system is disclosed in, for example, Patent Documents 1 to 3 and Non-Patent Document 1.

JP 2012-504844 A US Pat. No. 8,519,668 U.S. Pat. No. 8,629,654

Hatanaka et al. "Power Transmission of a Desk With a Cord-Free Power Supply" IEEE TRANSACTIONS OF MAGNETICS, VOL. 38, NO. 5, SEPTEMBER 2002, pp3329-3331

  In the coil array type wireless power transmission system, the Q value is lower than the case where the coil is used alone due to the interaction between adjacent coils, so that the loss is large.

  The present disclosure provides a new coil array type wireless power transmission technology capable of suppressing a decrease in Q value accompanying coil arraying.

  A coil array according to an aspect of the present disclosure includes first and second coil elements disposed adjacent to each other. The first coil element includes a first winding, a first lead connected to one end of the first winding, and a second connected to the other end of the first winding. And a lead wire. The second coil element includes a second winding wound opposite to the first winding, a third lead wire connected to one end of the second winding, and the second winding element. And a fourth lead line connected to the other end of the first winding line and connected to the first lead line. The first and second windings have a direction of a magnetic field generated at the center of the first winding when a current flows from the second lead wire to the first coil element. When a current flows from the lead wire to the second coil element, it is arranged so as to coincide with the direction of the magnetic field generated at the center of the second winding.

  The general and specific aspects described above can be implemented using systems, methods and computer programs, or can be implemented using combinations of systems, methods and computer programs.

  According to the embodiment of the present disclosure, it is possible to suppress a decrease in the Q value accompanying the array of coils.

(A) And (b) is a figure which shows two examples from which the position of the power receiving apparatus 200 with respect to the power transmission apparatus 100 differs. (A) is a figure which shows the example with the same winding direction of two adjacent coil elements, (b) is a figure which shows the example whose winding directions of two adjacent coil elements are mutually opposite. It is. (A) is a perspective view which shows the power transmission apparatus 100 in embodiment with this indication, (b) is a figure which shows the 1st example by which the power receiving apparatus 200 was set | placed on the power transmission apparatus 100, ( c) is a diagram illustrating a second example in which the power receiving device 200 is placed on the power transmitting device 100. FIG. It is a figure which shows schematic structure of the wireless power transmission system in Embodiment 1 of this indication. It is a figure which shows the modification of the power transmission apparatus in Embodiment 1. FIG. It is a figure which shows an example of a power transmission circuit. FIG. 3 is a diagram illustrating a configuration of a plurality of power transmission coils 110. 3 is a flowchart showing the operation of the first embodiment. It is a figure which shows the modification of a coil array. It is a figure which shows the structure of the coil array used for verification. It is a figure which shows the structural example by which the ferrite sheet was provided in the back surface side of several coils. It is a figure which shows the coil element pair in a comparative example.

  As described above, in a configuration in which a plurality of power transmission coils are arranged, the Q value of each coil decreases due to the interaction between adjacent coils. This is due to an increase in electrical resistance due to electromagnetic coupling between adjacent coils. When the power transmission frequency is f, the coil inductance is L, and the coil electrical resistance is R, the Q value is represented by Q = 2πfL / R. For this reason, when the electrical resistance increases, the Q value decreases. As a result, the power transmission efficiency between the transmitting and receiving coils decreases. In particular, when the power transmission coil is formed by a pattern on a printed circuit board, the loss is large, and this decrease in the Q value is a problem.

  In order to solve such a problem, in the coil array according to the embodiment of the present disclosure, the winding directions of two coil elements adjacent to each other are reversed. One lead line of these coil elements is connected to each other. The connection of these lead wires is determined so that a magnetic field having the same phase is generated from the windings of the two coil elements. Here, the case of “same phase” includes not only strictly the same phase but also a case where the phase shift is less than 90 °.

  FIG. 2 is a schematic diagram illustrating an example of a coil array including two coil elements. FIG. 2A shows an example of two coil elements 10a and 10b in which windings are wound in the same direction. FIG. 2B shows an example of two coil elements 10a and 10b in which windings are wound in opposite directions. Here, in the case of a planar coil as shown in FIG. 2, “winding in opposite directions” means that one coil is wound clockwise from outside to inside, and the other coil is outside. It means that it is wound counterclockwise from the inside to the inside. In the coil element in which the winding is wound along the axial direction, one coil is wound clockwise in one direction on the axis, and the other coil is wound counterclockwise.

  In the example shown in FIG. 2A, the lead wire connected to the outer peripheral end of the first coil element 10a and the lead wire connected to the outer peripheral end of the second coil element 10b are connected to the switch (SW). It is connected. The lead wire connected to the inner peripheral end of the first coil element 10a and the lead wire connected to the inner peripheral end of the second coil element 10b are connected to each other at the same potential.

  In the example shown in FIG. 2B, the lead wire connected to the outer peripheral end of the first coil element 10a and the lead wire connected to the inner peripheral end of the second coil element 10b are connected to the switch. ing. The lead wire connected to the inner peripheral end of the first coil element 10a and the lead wire connected to the outer peripheral end of the second coil element 10b are connected to each other at the same potential. Here, the direction of the magnetic field generated at the center of the winding when a current flows from the lead wire connected to the outer peripheral end of the first coil element 10a to the first coil element 10a is the same as that of the second coil element 10b. This coincides with the direction of the magnetic field generated at the center of the winding when a current flows from the lead wire connected to the inner peripheral end to the second coil element 10b.

  According to the analysis of the present inventor, the multi-element array formed on the basis of the configuration of FIG. 2B has a Q value compared to the multi-element array formed on the basis of the normal configuration as shown in FIG. Was found to improve by 10% or more. As a result of analysis under certain conditions, the Q value decreased by 17% in the configuration of FIG. 2A compared to the case where a single coil exists, but the Q value decreased by 6 in the configuration of FIG. Only 8%. That is, the Q value was improved by 12.5%.

  Details of the conditions for suppressing the reduction of the Q value will be described below.

  As shown in FIG. 11, the inventor can independently control the connection (conduction / non-conduction) between each of the two lead wires drawn from each coil element and the lead wire of the adjacent coil. It has also been clarified that the difference in the winding direction of the coil element does not affect the Q value in the structure. An effect of the embodiment of the present disclosure is a reduction in adverse effects as a parasitic element due to a non-operating coil that is not involved in power transmission being disposed close to an operating coil. However, when adjacent non-operating coils function as in the case of so-called parasitic elements (when no adjacent lead wire has two adjacent coils), the coil element winding direction Even if the above is reversed, the effect of the present disclosure cannot be obtained.

  Further, even if the adjacent non-operating coil shares the lead wire with the active coil, the effect of the present disclosure will not be exhibited if the sharing of any lead wire can be separated by the switch element. However, in the multi-element coil array system, in principle, the number of switch elements for switching the coil to be operated tends to increase. I also want to avoid it from the viewpoint of product miniaturization. Therefore, a configuration in which one lead wire is shared between one coil element and another adjacent coil element without performing separation by a switch element is a practical configuration.

  However, in the above configuration, the magnetic field generated from the power transmission coil element in the operating state, and the magnetic field that forms a magnetic path by closing the power transmission coil element through the power receiving coil element partially links the adjacent coils. Generally, an electric current is generated when a magnetic field links coils. If the two lead wires of the non-operating coil are separated from the two lead wires of the active coil by the switch element, there is no path through which the generated current flows to the active coil. The amount is limited. For this reason, the deterioration of the Q value is limited. However, in the state where one lead wire is shared between adjacent coils, the path through which current flows is not separated by the linkage of magnetic fields. For this reason, the unintended current flowing from the adjacent coil cancels out the current flowing from the operating coil. Under such conditions, the Q value is degraded. Based on the above principle, the present disclosure provides a configuration in which a current component from an adjacent coil that is not sufficiently separated by not introducing a switch element hardly deteriorates the Q value of the entire coil array circuit. More specifically, the embodiment of the present disclosure solves the problem by adopting the winding direction of the adjacent coil that can suppress the deterioration of the Q value and the connection method of the lead wire.

  FIG. 3 is a diagram illustrating an outline of the appearance and operation of the power transmission device 100 according to an embodiment. The power transmission device 100 is a wireless charger and has a flat plate structure. As shown to Fig.3 (a), this power transmission apparatus 100 is provided with the several power transmission coil 110 (this example seven power transmission coils 110a-110g) arranged in a line. Each power transmission coil corresponds to the coil element described above. In this example, the winding directions are opposite to each other for all combinations of two adjacent power transmission coils. Specifically, when the power transmission device 100 is viewed from above, the odd-numbered power transmission coils 110a, 110c, 11e, and 110g are right-handed, and the even-numbered power transmission coils 110b, 110d, and 11f are left-handed. In FIG. 3, each power transmission coil is drawn with a rectangular broken line, but actually each coil has a rectangular winding. Each power transmission coil has a shape that is short in the arrangement direction (lateral direction in the figure) and long in a direction perpendicular to the arrangement direction. Although not shown, the power transmission device 100 also includes a power transmission circuit that supplies AC power to each power transmission coil, and a control circuit that controls a connection state between the power transmission circuit and each power transmission coil.

  When the power receiving device 200 including the power receiving coil 210 comes close to the power transmitting device 100, the control circuit electrically connects the two power transmitting coils closest to the power receiving coil 210 and the power transmitting circuit. For example, in the state shown in FIG. 3B, only two power transmission coils 110c and 110d are connected to the power transmission circuit. In the state shown in FIG. 3C, only two power transmission coils 110f and 110g are connected to the power transmission circuit.

  In this example, power is always supplied to two power transmission coils, but the number of power transmission coils that are simultaneously supplied may be other than two. The number of power transmission coils fed simultaneously may be a number smaller than the total number of power transmission coils. In this way, if the number of power transmission coils fed simultaneously is limited to a specific number, fluctuations in inductance can be suppressed. Further, if the number of power transmission coils fed simultaneously is set to a small number such as 2, it is not necessary to excessively increase the inductance of each power transmission coil, which leads to downsizing of the apparatus.

  Furthermore, since the winding directions of two adjacent power transmission coils are opposite to each other and one lead wire is connected to each other, a decrease in the Q value can be suppressed. As a result, power can be transmitted with higher efficiency than in the past.

  Hereinafter, an outline of an embodiment of the present disclosure will be described.

  (1) The coil array which concerns on 1 aspect of this indication contains the 1st and 2nd coil element arrange | positioned adjacent to each other. The first coil element includes a first winding, a first lead connected to one end of the first winding, and a second connected to the other end of the first winding. And a lead wire. The second coil element includes a second winding wound opposite to the first winding, a third lead wire connected to one end of the second winding, and the second winding element. And a fourth lead line connected to the other end of the first winding line and connected to the first lead line. The first and second windings have a direction of a magnetic field generated at the center of the first winding when a current flows from the second lead wire to the first coil element. When a current flows from the lead wire to the second coil element, it is arranged so as to coincide with the direction of the magnetic field generated at the center of the second winding.

  (2) In one embodiment, the first and second coil elements are arranged on the same plane.

  (3) In one embodiment, the coil array includes a plurality of coil elements including the first and second coil elements arranged in a line on the plane.

  (4) In one embodiment, the length of each coil element in the arrangement direction of the plurality of coil elements is smaller than the length of each coil element in a direction perpendicular to the arrangement direction on the plane.

  (5) In one embodiment, the coil array is provided on a printed board.

  (6) In one embodiment, each coil element is a multilayer wiring coil.

  (7) In an embodiment, there is no overlap between adjacent coil elements included in the coil array.

  (8) A power transmission device according to another aspect of the present disclosure is a power transmission device that transmits power in a non-contact manner to a power reception device including a power reception coil, and is described in any one of the items (1) to (7). A coil array; and a power transmission circuit connected to the plurality of coil elements included in the coil array and supplying AC power to the plurality of coil elements.

  (9) In an embodiment, the power transmission device further includes a control circuit that controls a connection state between the power transmission circuit and each coil element, and the control circuit includes the power receiving coil for the plurality of coil elements. The connection state of the power transmission circuit and the plurality of coil elements is switched so that the AC power is supplied to at least one coil element selected from the plurality of coil elements according to the relative position.

  (10) In one embodiment, the control circuit connects a certain number of coil elements selected from the plurality of coil elements to the power transmission circuit when performing power transmission.

  (11) In an embodiment, the control circuit connects two coil elements selected from the plurality of coil elements to the power transmission circuit when performing power transmission.

  (12) In one embodiment, two lead lines of each coil element are connected to the power transmission circuit so that a magnetic field having the same phase is generated from the two coil elements selected by the control circuit.

  (13) A power receiving device according to another aspect of the present disclosure is a power receiving device that receives power in a non-contact manner from a power transmitting coil including a power transmitting coil, and the coil according to any one of the items (1) to (7) An array, and a power receiving circuit that supplies AC power received by the coil array to a load.

  (14) A wireless power transmission system according to another aspect of the present disclosure includes the power transmission device according to any one of the items (8) to (13) and a power reception device having a power reception coil.

  (15) A power reception device according to another aspect of the present disclosure includes the power transmission device including at least one power transmission coil, and the power reception device described in the item (13).

  Hereinafter, more detailed embodiments of the present disclosure will be described.

(Embodiment 1)
[1. Constitution]
FIG. 4A is a block diagram illustrating a schematic configuration of the wireless power transmission system according to the first embodiment of the present disclosure. The wireless power transmission system includes a power transmission device 100 and a power reception device 200. Power is transmitted from the plurality of power transmission coils 110 in the power transmission device 100 to the power reception coils 210 in the power reception device 200 in a contactless manner.

  The power receiving device 200 includes a power receiving coil 210, capacitors 220a and 220b, a power receiving circuit 220, and a secondary battery 230. The power receiving coil 210 and the capacitors 220a and 220b constitute a parallel resonance circuit. The power receiving circuit 220 rectifies and outputs the AC power received by the power receiving coil 210. The secondary battery 230 is charged with the DC power output from the power receiving circuit 220. The energy stored in the secondary battery 230 is consumed by a load (not shown).

  The power receiving circuit 220 may include various circuits such as a rectifier circuit, a frequency conversion circuit, a constant voltage / constant current control circuit, and a modulation / demodulation circuit for communication. It is configured to convert the received AC energy into DC energy or low frequency AC energy available to the load. Various sensors for measuring the voltage / current output from the power receiving coil 210 may be included in the power receiving circuit 220.

  The power transmission device 100 includes a plurality of power transmission coils (coil arrays) 110, a plurality of switches 130, a resonance capacitor 120, a power transmission circuit 140, and a control circuit 150. The plurality of switches 130 are connected to the plurality of power transmission coils 110, respectively. Here, “connected” means connected so as to be electrically conductive. The plurality of power transmission coils 110 are connected in parallel to the power transmission circuit 140 via the plurality of switches 130. One end of each power transmission coil is connected to one electrode of the capacitor 120. The other electrode of the capacitor 120 is connected to the power transmission circuit 140. Each of the plurality of switches 130 is connected to a terminal of the plurality of power transmission coils 110 where the capacitor 120 is not connected. This is because the voltage fluctuation is large between the capacitor 120 and the plurality of power transmission coils 110. As shown in FIG. 4B, another resonance capacitor 121 may be connected between the switch 130 and the power transmission circuit 140. By providing the two capacitors 120 and 121 at both ends of each coil, the voltage applied to each coil can be reduced. Thereby, a switch with a low withstand voltage can be used.

  Each power transmission coil can be, for example, a thin flat coil formed of a substrate pattern. It is not necessary to be composed of a single conductor pattern, and for example, as shown in FIG. 18 of Patent Document 3, a plurality of stacked conductor patterns may be connected in series. . A coil having such a configuration is referred to as a “multilayer wiring coil”. In addition, a winding coil using a copper wire, a litz wire, a twisted wire, or the like can be used. The Q value of each power transmission coil can be set to 100 or more, for example, but may be set to a value smaller than 100. The capacitors 120, 220a, and 220b may be provided as necessary. The self-resonant characteristic of each coil may be used in place of these capacitors.

  The configuration in which the effect of the coil array of the present embodiment is maximized is related to a physical arrangement relationship between a plurality of adjacent coils. That is, when there is an overlap between two adjacent coils, a high effect can be obtained with a configuration in which the ratio of the crossing area to the coil area is, for example, 0.5 or less. This is because the effect is enhanced when the magnetic flux passing through the non-intersecting portion of the adjacent coil pair is stronger than the magnetic flux passing through the crossing portion of the adjacent coil pair. For example, this condition includes a case where there is no overlap between adjacent coils. In consideration of the reduction in the thickness of the charger and the reduction in cost by limiting the number of wiring layers of the multilayer printed circuit board, it is preferable to arrange the layers forming a plurality of adjacent coils in the same plane.

  The power transmission circuit 140 may be, for example, a full bridge type inverter or an oscillation circuit such as a class D or class E. FIG. 5 shows an example in which the power transmission circuit 140 is configured with a full-bridge inverter as an example. The power transmission circuit 140 may have various sensors for measuring a modulation / demodulation circuit for communication and voltage / current. The power transmission circuit 140 is connected to an external direct current (DC) power supply 300. DC power input from the DC power supply 300 is converted into AC power and output. This AC power is sent to the space by two power transmission coils selected from the plurality of power transmission coils 110.

  The frequency at the time of electric power transmission is set to the same value as the resonance frequency of the power transmission resonator comprised by the power transmission coil 110 and the capacitor 120, for example. However, it is not limited to this, For example, you may set to the value within the range of about 85-115% of the resonance frequency. The frequency band of power transmission can be set to a value within the range of 100 kHz to 200 kHz, for example, but may be set to a value outside this range.

  The power source 130 includes a commercial power source, a primary battery, a secondary battery, a solar cell, a fuel cell, a USB (Universal Serial Bus) power source, a high-capacity capacitor (eg, an electric double layer capacitor), a voltage converter connected to the commercial power source, Or it may be a combination thereof.

  The control circuit 150 is a processor that controls the operation of the entire power transmission apparatus 100. The power transmission circuit 150 can be realized by, for example, a combination of a CPU and a memory storing a computer program. The control circuit 150 may be a dedicated integrated circuit configured to realize the operation of the present embodiment. The control circuit 150 performs power transmission control (power transmission state adjustment) by the power transmission circuit 140 and controls the open / closed states of the plurality of switches 130.

  The control circuit 150 further detects the relative position of the power receiving coil 210 with respect to the plurality of power transmitting coils 110. In addition to this, a foreign object such as a metal adjacent to the power transmission coil 110 may be detected. The detection of the position of the power receiving coil 210 and the detection of foreign matter can be performed based on measured values of parameters that vary with changes in impedance such as voltage, current, frequency, and inductance on the circuit. More specifically, the control circuit 150 turns on the plurality of switches 130 in order by a certain number (for example, two), and measures any of the above parameters each time. When a value deviating from the specified range is measured, it can be determined that the power receiving coil 210 or a foreign object exists in the vicinity of the power transmitting coil that is feeding at that time. In order to enable such detection, the control circuit 150 may include a detection circuit (not shown). In the present disclosure, detection of the power receiving coil 210 and detection of foreign matter are not limited to a specific method, and can be performed by any known method.

  The control circuit 150 in the present embodiment selects two power transmission coils to be used for power transmission according to the relative position of the power reception coil 210 with respect to the plurality of power transmission coils 110. And the conduction | electrical_connection state of the some switch 130 is switched so that alternating current power may be supplied from the power transmission circuit 140 only to two selected power transmission coils. As a result, AC energy is sent from the two selected power transmission coils to the space.

  The control circuit 150 may include a communication circuit that performs communication with the power receiving apparatus 200. For example, information indicating fluctuations in the impedance of the load of the power receiving device 200 can be obtained by the communication circuit. Based on the information, the control circuit 150 can instruct the power transmission circuit 140 to change the power transmission parameter so that, for example, a constant voltage is supplied to the load. Such power transmission parameters can be, for example, frequency, phase difference between a pair of switching elements of the inverter, or input voltage of the inverter. When adjusting the input voltage, the power transmission circuit 140 may include a DC / DC converter between the DC power supply 300 and the inverter. By changing these power transmission parameters, the voltage supplied to the load can be changed.

  The power transmission device 100 may include elements other than the above-described components. For example, you may provide the display element which displays the detection result of the receiving coil 210 or a foreign material by the control circuit 150. FIG. Such a display element may be a light source such as an LED. Further, an oscillating circuit for detecting foreign matter and a detection coil may be provided.

  Further, the configuration of the power receiving device 200 is not limited to that illustrated in FIG. 4A. As long as it has the receiving coil 210 which receives at least one part of the energy sent from the power transmission coil 110, the structure may be arbitrarily designed.

  FIG. 6 is a diagram schematically showing the configuration of a plurality of power transmission coils (coil arrays) 110 in the present embodiment. Although four power transmission coils are shown here for simplicity, the number of power transmission coils may be five or more. The windings of two adjacent power transmission coils are wound in opposite directions. In the odd-numbered coil from the left, the lead wire from the outer peripheral end is connected to the switch. In the even-numbered coil from the left, the lead wire from the inner peripheral end is connected to the switch. The lead wire from the inner peripheral end of the odd-numbered coil from the left and the lead wire from the outer peripheral end of the even-numbered coil from the left are connected to each other and connected to one terminal of the power transmission circuit 140 via the capacitor 120. Is done. Each switch is connected to the other terminal of the power transmission circuit 140.

  In the present embodiment, the number of power transmission coils that are fed simultaneously is two. FIG. 6 shows a state where power is supplied only to the two coils located in the center. Each coil is fed so that a magnetic field having the same phase is generated from two adjacent coil elements. In other words, the power transmission circuit 140 supplies power to the coil element pairs wound in the opposite directions in opposite phases. The connection of each lead line is determined so that the above relationship is satisfied even if the combination of the coil element pairs to be fed changes.

  With such a configuration, a decrease in the Q value of each coil element pair is suppressed, and highly efficient power transmission is realized. Even when the number of coil elements is five or more, the same effect can be obtained if the above-described conditions are satisfied.

[2. Operation]
Next, an example of the operation of the power transmission device 100 of this embodiment will be described with reference to the flowchart of FIG.

  When the power transmission device 100 is turned on, the control circuit 150 first performs foreign object detection processing (step S100). The foreign object detection process is performed, for example, by detecting a physical quantity (parameter) such as an input inductance or a voltage of the power transmission coil 110 and determining whether the value exceeds a predetermined range. If this parameter exceeds a predetermined range, it can be estimated that there is a foreign object. In that case, the control circuit 150 displays a warning without performing power transmission. If no foreign object is detected, the control circuit 150 assigns 1 to the variable N (step S101). A variable N represents the number of the power transmission coil 110. The control circuit 150 selects the Nth and N + 1th power transmission coils as power transmission coils to be fed (step S102). At this time, the control circuit 150 turns on only two switches connected to the two selected power transmission coils. Thereafter, the power transmission circuit 140 sets the power transmission parameter to a position detection value and oscillates for a certain period of time (step S103). The parameters set here may include, for example, the frequency, the phase shift amount between the switching element pairs of the inverter, or the input voltage of the inverter. The power transmission circuit 140 oscillates with these parameters set to values suitable for detecting the position of the power receiving coil. Next, the control circuit 150 determines whether or not monitor values such as current, voltage, and impedance flowing in the circuit are within a predetermined range (step S104). If the monitor value is within the predetermined range, the power transmission circuit 140 stops the output (step S108). Subsequently, the control circuit 150 determines whether or not the variable N is equal to a value obtained by subtracting 1 from the number Nmax of the power transmission coils (step S109). If N is not equal to Nmax−1, the control circuit 150 substitutes N + 1 for the variable N (step S110). Thereafter, steps S102 to S104 and S108 to S110 are repeated until the monitor value falls within a predetermined range or N = Nmax-1.

  If it is determined in step S109 that N = Nmax−1, the power transmitting apparatus 100 waits until a predetermined time has elapsed (S111). This case is a case where a large change in the monitor value was not detected although the determination was completed for all the power transmission coils 110. At this time, since it is considered that the power receiving coil 210 does not exist nearby, the power transmitting apparatus 100 waits for a predetermined time and then executes step S101 again.

  If it is determined in step S104 that the monitor value is within the predetermined range, the control circuit 150 determines whether communication with the power receiving apparatus 200 has been established (step S105). When communication is established, the power transmission circuit 140 performs power transmission with the parameter value for power transmission (step S106). This parameter value is a value suitable for power transmission, and is set according to the load (for example, secondary battery) of the power receiving apparatus 200. The control circuit 150 executes the operation of step S105 every predetermined time during power transmission to check whether communication is interrupted.

  If it is determined in step S105 that communication has not been established, the power transmission circuit 140 stops output (step S107). In this case, it waits until a predetermined time elapses (step S111). Thereafter, the operation of step S101 is executed again.

  With the above operation, power can be transmitted using the two power transmission coils closest to the power reception coil 210 only when the proximity of the power reception coil 210 is detected. Detection of the power receiving coil 210 can be performed by, for example, intermittent oscillation (intermittent operation) that oscillates alternating current for several cycles only once every 1 mm seconds to several seconds. Since the operation is switched to the continuous operation only when the power receiving coil 210 is detected, an increase in power consumption can be suppressed. The operating frequency of the power transmission circuit 140 in this detection operation may be the same as or different from the power transmission frequency.

  According to the present embodiment, the number of power transmission coils used for power transmission is always limited to a certain number (two in the above example). Further, the plurality of power transmission coils are arranged in a line, and the length of each power transmission coil in the arrangement direction is smaller than the length of the power reception coil. For this reason, size reduction of a power transmission apparatus and highly efficient electric power transmission are realizable.

  In the above-described embodiment, the number of power transmission coils used for power transmission is always maintained at a constant number, but such an operation is not necessarily required. For example, the number of power transmitting coils to be fed may be changed according to the size of the power receiving coil. When the width Dwt of the power transmission coil is, for example, 1/3 or less of the width Dwr of the power reception coil, the three power transmission coils face the power reception coil. In such a case, power may be supplied to three power transmission coils instead of two.

[3. Modified example]
FIG. 8 is a diagram illustrating a modification of the plurality of power transmission coils 110. As illustrated, the plurality of power transmission coils 110 are not necessarily connected to the switch. There may be coils in the system that are not fed, such as coils at both ends. Even in this case, one lead wire of the coil that is not fed and the coil that is fed are connected to each other. These lead wires are connected to a ground terminal, for example. Thus, only two coils may be fed. Even when power is supplied to three or more coils, coils that are not supplied with power may be arranged at both ends.

  The coil array of the present disclosure can be used not only as a plurality of power transmission coils 110 in the power transmission device 100 but also as power reception coils in the power reception device 200. Even when the coil array of the present disclosure is used as a power receiving coil, it is possible to suppress a decrease in the Q value, thereby improving the transmission efficiency.

  In the configuration in which the power transmission device 100 or the power reception device 200 includes a foreign object detection coil in addition to the power transmission or power reception coil, the coil array of the present disclosure may be used as the foreign object detection coil.

[4. Effect verification]
Next, the result of verifying the effect of the coil array in this embodiment will be described.

  FIG. 9 shows the configuration of the coil array 110 used for verification. Four coil patterns were formed in two layers by a printed circuit board manufacturing process. The length of each coil in the arrangement direction is 12 mm, the length of each coil in the direction perpendicular to the arrangement direction is 50 mm, the number of turns of each layer of each coil is 5 (total 10 times), and the width of the coil pattern is 0.5 mm. The gap between patterns was 0.2 mm. The winding of each coil is led from the surface layer to the back layer by a via on the inner peripheral end side, and two lead wires are drawn from the outer peripheral end of each layer. As shown in FIG. 10, a ferrite sheet having a relative permeability of 120, 60 mm × 80 mm × 1 mm is provided on the back surface of the coil array 110 (the surface on the side where the receiving coil does not face). The inductance, coupling coefficient, and Q value of the coil element pair Tx when AC power having a frequency of 120 kHz was supplied to the two central coils were measured. The measurement was performed in the comparative example in which the coil winding directions are all the same and in the example in which the winding directions of two adjacent coils are opposite. In each example, a magnetic field having the same phase was generated from the two central coils. The measurement results are shown in Table 1 below.

  As can be seen from Table 1, in the example, the Q value was improved by 12.5% compared to the comparative example.

  Next, the case where a switch was provided on both of the two lead lines in each of the two coil elements to be fed and the case where the coils at both ends shown in FIG. 9 were not arranged were also verified. Table 2 below shows the results for each of these cases.

  In Table 2, models 1 and 2 represent the comparative example and the example in Table 1, respectively. Models 3 and 4 represent examples in which switches are provided on both of the two lead lines in each of the two coil elements to be fed. The models 3 and 4 correspond to the configuration shown in FIG. 11, for example. In these models, one lead wire of two coils is not connected, but is connected to a switch instead. In model 3, the winding directions of two adjacent coils are the same, and in model 4, the winding directions of the two adjacent coils are opposite. Models 5 and 6 represent examples in which the coils at both ends shown in FIG. 9 are not arranged. In model 5, the winding directions of two adjacent coils are the same, and in model 6, the winding directions of the two adjacent coils are opposite.

  As can be seen from the results of models 3 and 4 in Table 2, in the configuration in which the switch is connected to both of the two lead wires, the Q value can be improved even if the directions of two adjacent windings are reversed. I couldn't. The model 3 has a Q value similar to that of the model 2 (example). However, it is not preferable to provide a large number of switches because the cost increases. In the embodiment, a high Q value can be maintained without providing many switches.

  As can be seen from the results of Models 5 and 6 in Table 2, when the coils at both ends were not arranged, the Q value did not improve so much even if the direction of the winding was reversed. Therefore, the rule relating to the coil winding direction and the lead wire connection, which is a feature of the configuration of the present disclosure, is applied not only to the coil in the operating state but also to the non-operating coil arranged in the periphery. It can be said that the improvement effect is particularly high in the configuration.

  As described above, in the embodiment of the present disclosure, the windings of two adjacent coil elements are wound in opposite directions. Further, one lead line is connected to each other, for example, a ground terminal. With such a configuration, a decrease in the Q value can be suppressed, so that transmission efficiency can be increased.

  The foreign object detection device and the wireless power transmission system according to the present disclosure can be widely applied to, for example, applications that charge or supply power to electric vehicles, AV devices, batteries, medical devices, and the like.

10a, 10b Coil element 100 Power transmission device 110 Power transmission coil 120, 121 Capacitor 130 Switch 140 Power transmission circuit 150 Control circuit 200 Power reception device 210 Power reception coil 220 Capacitor 230 Secondary battery 300 DC power source

Claims (15)

A coil array including first and second coil elements disposed adjacent to each other,
The first coil element is:
A first winding;
A first lead wire connected to one end of the first winding;
A second lead wire connected to the other end of the first winding;
Have
The second coil element is
A second winding wound opposite to the first winding;
A third lead wire connected to one end of the second winding;
A fourth lead wire connected to the other end of the second winding, the fourth lead wire connected to the first lead wire;
Have
The first and second windings have a direction of a magnetic field generated at the center of the first winding when a current flows from the second lead wire to the first coil element. Arranged so as to coincide with the direction of the magnetic field generated at the center of the second winding when a current flows from the lead wire to the second coil element;
Coil array.   The coil array according to claim 1, wherein the first and second coil elements are arranged on the same plane.   The coil array according to claim 2, wherein the coil array includes a plurality of coil elements including the first and second coil elements arranged in a line on the plane.   The coil according to any one of claims 1 to 3, wherein a length of each coil element in the arrangement direction of the plurality of coil elements is smaller than a length of each coil element in a direction perpendicular to the arrangement direction on the plane. array.   The coil array according to claim 1, wherein the coil array is provided on a printed circuit board.   The coil array according to any one of claims 1 to 5, wherein each coil element is a multilayer wiring coil.   The coil array according to any one of claims 1 to 6, wherein there is no overlap between adjacent coil elements included in the coil array. A power transmission device that transmits power in a contactless manner to a power reception device including a power reception coil,
A coil array according to any one of claims 1 to 7;
A power transmission circuit connected to a plurality of coil elements included in the coil array and supplying AC power to the plurality of coil elements;
A power transmission device comprising: A control circuit for controlling a connection state between the power transmission circuit and each coil element;
The control circuit is configured so that the AC power is supplied to at least one coil element selected from the plurality of coil elements according to a relative position of the power receiving coil with respect to the plurality of coil elements. Switch the connection state with multiple coil elements,
The power transmission device according to claim 8.   The power transmission device according to claim 9, wherein the control circuit connects a certain number of coil elements selected from the plurality of coil elements to the power transmission circuit when performing power transmission.   The power transmission device according to claim 9 or 10, wherein the control circuit connects two coil elements selected from the plurality of coil elements to the power transmission circuit when performing power transmission.   12. The power transmission device according to claim 11, wherein two lead lines of each coil element are connected to the power transmission circuit such that a magnetic field having the same phase is generated from the two coil elements selected by the control circuit. . A power receiving device that receives power in a contactless manner from a power transmission coil including a power transmission coil,
A coil array according to any one of claims 1 to 7;
A power receiving circuit for supplying alternating current power received by the coil array to a load;
A power receiving apparatus comprising: A power transmission device according to any one of claims 8 to 13,
A power receiving device having a power receiving coil;
A wireless power transmission system comprising: A power transmission device having at least one power transmission coil;
A power receiving device according to claim 13;
A wireless power transmission system comprising:

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