JP6122402B2 - Power transmission device and wireless power transmission system - Google Patents

Power transmission device and wireless power transmission system Download PDF

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JP6122402B2
JP6122402B2 JP2014159427A JP2014159427A JP6122402B2 JP 6122402 B2 JP6122402 B2 JP 6122402B2 JP 2014159427 A JP2014159427 A JP 2014159427A JP 2014159427 A JP2014159427 A JP 2014159427A JP 6122402 B2 JP6122402 B2 JP 6122402B2
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power transmission
coil
power
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JP2016039643A (en
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山本 温
山本  温
菅野 浩
浩 菅野
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パナソニック株式会社
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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. One technique that makes such alignment unnecessary is a system called a coil array system.

  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. Such a coil array type wireless power transmission system is disclosed in, for example, Patent Documents 1 to 3 and Non-Patent Document 1.

  On the other hand, in the wireless power transmission system, there is a demand for avoiding heat generated when a foreign object such as metal approaches the coil. For example, the guidelines established by the Broadband Wireless Forum (BWF) stipulate the upper limit of temperature rise due to the proximity of metallic foreign objects such as iron, aluminum, and copper.

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, since the charging area is wide, the area where heat generation by foreign matter can occur is also wide. Therefore, in order to avoid such heat generation due to foreign matter, it is required to have a foreign matter detection function. The foreign object detection can be performed, for example, by detecting the reflection of the magnetic field due to the contamination of the foreign object. The reflection of the magnetic field can be detected based on changes in electrical characteristics such as inductance and voltage.

  However, in a configuration in which a plurality of power transmission coils are arranged, impedance characteristics (Q value) are different between the end coil and the inner coil. This complicates the setting of a threshold value for detecting the presence or absence of foreign matter. As a result, there is a risk of erroneous detection.

  The present disclosure provides a new coil array type wireless power transmission technique capable of bringing impedance characteristics of a plurality of power transmission coils closer to each other.

  In order to solve the above-described problem, a power transmission device according to an aspect of the present disclosure is a power transmission device that transmits power to a power reception device including a power reception coil in a contactless manner, and is arranged in a first direction on a surface. A plurality of power transmission coils, a parasitic element including a metal member disposed outside the plurality of power transmission coils in proximity to an end power transmission coil among the plurality of power transmission coils, and connected to the plurality of power transmission coils And a power transmission circuit that supplies AC power to the plurality of power transmission coils.

  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, the impedance characteristics of the plurality of power transmission coils can be made closer to each other.

(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. It is a figure which shows the example of Q value of the some power transmission coil in case the parasitic element is not arrange | positioned. It is a figure which shows the example of Q value of the some power transmission coil in the case where a parasitic element is arrange | positioned. (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. 3 is a flowchart showing the operation of the first embodiment. (A)-(c) is a figure which respectively shows combination Tx_1, Tx_2, and Tx_3 of a power transmission coil pair. It is a figure which shows the structural example by which the ferrite sheet was provided in the back surface side of the several power transmission coil. It is a graph which shows Q value of power transmission coil pair Tx_1, Tx_2, and Tx_3. (A) to (c) is a diagram showing combinations Tx_a, Tx_b, and Tx_c of power transmission coil pairs, respectively. It is a graph which shows Q value in each case of Drawing 9 (a)-(c). It is a graph which shows the change rate of Q value of Tx_a and Tx_b with respect to Q value of Tx_c. It is a figure which shows the example of the parasitic element comprised by the at least 1 metal wire.

  As described above, in a configuration in which a plurality of power transmission coils are arranged, impedance characteristics (Q value) are different between the end coil and the inner coil. As a result, there is a problem that the setting of a threshold value for foreign object detection becomes complicated. In order to solve this problem, in the embodiment of the present disclosure, a parasitic element including a metal member is disposed in the vicinity of the end coil.

  FIG. 2A is a diagram illustrating an example of the Q value of each coil when such a parasitic element is not disposed. In FIG. 2A, for the sake of simplicity, each coil is drawn in a donut shape, but actually has a structure including a winding and two lead wires. Similarly in the following drawings, each coil is drawn in a simplified manner. The plurality of power transmission coils Tx <b> 1 to Tx <b> 5 are electrically connected to a power transmission circuit that supplies AC power via a lead wire (not shown). As illustrated, among the plurality of power transmission coils Tx1 to Tx5, the Q values of the coils Tx1 and Tx5 at both ends are higher than the Q values of the other coils Tx2 to Tx4. This is because, for the inner coils Tx2 to Tx4, the electrical resistance of the coils increases due to the influence of two coils adjacent to both sides. 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. Since the coils Tx1 and Tx5 at both ends are adjacent to only one coil, the effect of lowering the Q value is low. As a result, the Q values of the coils Tx1 and Tx5 on both sides are higher than the Q values of the other coils.

  FIG. 2B is a diagram illustrating an example of the Q value of each coil when the parasitic elements 180a and 180b are arranged close to the coils Tx1 and Tx5 at both ends. The parasitic elements 180a and 180b have the same structure as each power transmission coil in this example, but may be different. Each parasitic element is not supplied with power. As shown in the figure, the Q values of the coils Tx1 and Tx5 on both sides are reduced to the same values as those of the inner coils Tx2 to Tx4. This is because the parasitic coupling elements 180a and 180b and the coils Tx1 and Tx5 at both ends cause the same coupling as that between the other coils and increase the electric resistance. As a result, the Q values are substantially uniform among the plurality of power transmission coils Tx1 to Tx5, and the setting of the threshold value for foreign object detection can be made uniform. Note that only one of the parasitic elements 180a and 180b may be provided. In that case, the effect of lowering the Q value can be obtained for one of the coils at both ends.

  As described above, the power transmission device according to the embodiment of the present disclosure includes a plurality of power transmission coils arranged in the first direction on the surface, and close to the end power transmission coil among these power transmission coils. A parasitic element including a metal member disposed outside the coil and a power transmission circuit that supplies AC power to a plurality of power transmission devices are provided. The parasitic element may have the same structure as the winding of the adjacent coil, or may have a different structure. The parasitic element is coupled to the power transmission coil at the end by capacitive coupling or electromagnetic coupling, and functions to lower the Q value of the coil.

  FIG. 3 is a diagram illustrating an appearance and an 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 adjacent to the some power transmission coil 110 (this example five power transmission coils 110a-110e) arranged in a line, and the power transmission coils 110a and 110e of both ends. The two parasitic elements 180a and 180b are arranged. As an example, each power transmission coil has a shape that is short in the arrangement direction (lateral direction in the figure) and long in the 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 110b and 110c are connected to the power transmission circuit. In the state shown in FIG. 3C, only two power transmission coils 110d and 110e 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.

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

  (1) A power transmission device according to an 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 a plurality of power transmission coils arranged in a first direction on a surface; A parasitic element including a metal member disposed outside the plurality of power transmission coils in proximity to an end power transmission coil among the plurality of power transmission coils, and connected to the plurality of power transmission coils, A power transmission circuit that supplies AC power to the power transmission coil.

  (2) In one embodiment, the parasitic element is configured such that a Q value of the power transmission coil at the end is substantially equal to a Q value of a power transmission coil adjacent to the power transmission coil at the end.

  (3) In a certain embodiment, the said power transmission apparatus was arrange | positioned in the vicinity of the power transmission coil located in the edge on the opposite side to the said end among the said several power transmission coils, and the outer side of the said several power transmission coil. Another passive element including another metal member is further provided.

  (4) In one embodiment, the parasitic element and the other parasitic element are configured such that the Q values of the plurality of power transmission coils are substantially equal.

  (5) In a certain embodiment, the said parasitic element has the same shape as the power transmission coil of the said end.

  (6) In one embodiment, the parasitic element has a shape in which the power transmission coil at the end is cut in half.

  (7) In one embodiment, the parasitic element is configured by at least one metal wire extending in a second direction perpendicular to the first direction on the surface.

  (8) In an embodiment, the distance between the parasitic element and the power transmission coil at the end is substantially equal to the distance between the power transmission coil adjacent to the power transmission coil at the end and the power transmission coil at the end. equal.

  (9) In one embodiment, a length of the parasitic element in a second direction perpendicular to the first direction on the surface is equal to a length of each power transmission coil in the second direction.

  (10) In one embodiment, the power transmission device is a control circuit that controls a connection state between the power transmission circuit and each power transmission coil, and according to a relative position of the power reception coil with respect to the plurality of power transmission coils. And a control circuit that switches connection states between the power transmission circuit and the plurality of power transmission coils so that the AC power is supplied to a predetermined number of adjacent power transmission coils selected from the plurality of power transmission coils.

  (11) In one embodiment, the control circuit detects a foreign object close to the plurality of power transmission coils based on a change in electrical characteristics in the power transmission circuit.

  (12) In an embodiment, a wireless power transmission system according to another aspect of the present disclosure includes a power transmission device and a power reception device having a power reception coil. The power transmission device is disposed outside the plurality of power transmission coils, in proximity to a power transmission coil at an end of the plurality of power transmission coils arranged in a first direction on the surface and the plurality of power transmission coils. A parasitic element including a metal member, and a power transmission circuit connected to the plurality of power transmission coils and supplying AC power to the plurality of power transmission coils.

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

(Embodiment 1)
[1. overall structure]
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 series and parallel resonant 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 110, a plurality of switches 130, a resonance capacitor 120, a power transmission circuit 140, and a control circuit 150. The power transmission device 100 further includes two parasitic elements 180a and 180b disposed in proximity to both ends of the plurality of power transmission coils 110. The parasitic elements 180a and 180b are not connected to other elements. 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.

  The power transmission coil 110 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 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 (for example, 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 control circuit 150 can be realized by a combination of a CPU and a memory storing a computer program, for example. 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, foreign objects such as metal adjacent to the power transmission coil 110 are also 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.

[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 outside the predetermined range, the control circuit 150 determines whether or not 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 AC for several cycles only once every 1 millisecond 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. Effect verification]
Next, the result of verifying the effect of the parasitic element in the present embodiment will be described.

  FIG. 7 shows a configuration in which a parasitic element is not provided as a comparative example. Here, the Q value when power was supplied to two adjacent power transmission coils among the four power transmission coils 110 was measured. The measurement was performed for the three combinations Tx_1, Tx_2, and Tx_3 of the power transmission coil pairs shown in FIGS. Each coil is formed by a coil pattern on the substrate. 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 coil is 5, the width of the coil pattern is 0.5 mm, and the gap between the patterns is 0 0.2 mm, the inductance of Tx_1 to Tx_3 was set to a constant value of 3.1 μH, and the transmission frequency was set to 120 kHz. As shown in FIG. 8, a ferrite sheet having a relative magnetic permeability of 120, 60 mm × 80 mm × 1 mm is provided on the back surface of the plurality of coils 110 (the surface on the side where the power receiving coil does not face).

  FIG. 9 shows the Q values of the power transmission coil pairs Tx_1, Tx_2, and Tx_3. As illustrated, the Q value of the coil pairs Tx_1 and Tx_3 at both ends is maintained higher than that of the inner coil pair Tx_2. This is because the influence of coupling with surrounding coils is relatively small in the coils at both ends. As described above, in such a situation, there is a problem that the setting of a threshold value for detecting a foreign object becomes complicated.

  FIG. 10 is a diagram for explaining a verification result when the parasitic element 180 is arranged at one end. FIG. 10A shows a comparative example in which power is supplied to two end coil pairs Tx_a in a configuration without the parasitic element 180. FIG. 10B illustrates an example in which power is supplied to two end coil pairs Tx_b in a configuration in which a parasitic element 180 is disposed adjacent to the end coil. FIG. 10C shows a comparative example in which power is supplied to two internal coil pairs Tx_c in a configuration without the parasitic element 180.

  The parasitic element 180 illustrated in FIG. 10B has a shape in which the power transmission coil 110 is cut in half. That is, the parasitic element 180 is composed of five divided metal wires and does not form a closed loop. The length of the parasitic element 180 in the direction perpendicular to the arrangement direction of the plurality of power transmission coils 110 is 50 mm, which is the same as that of each power transmission coil. The distance (gap distance) between the parasitic element 180 and the coil at the end is 0.2 mm, as is the distance between the other coils.

  FIG. 11 is a graph showing the Q value in each case of FIGS. It can be seen that the Q value of Tx_b provided with the parasitic element 180 is closer to the Q value of Tx_c than the Q value of Tx_a.

  FIG. 12 is a graph showing the rate of change of the Q values of Tx_a and Tx_b with respect to the Q value of Tx_c. The Q value of Tx_b is suppressed to a change rate of about 0.7% from the Q value of Tx_c. This rate of change does not significantly affect the threshold setting. From the above results, it was verified that the Q value of the end coil can be made closer to the Q value of the internal coil by providing the parasitic element 180.

  As described above, according to the present embodiment, by providing the parasitic element in the vicinity of the end coil, the impedance characteristic (Q value) of the end coil can be brought close to the impedance characteristics of other coils. . As a result, the foreign object detection threshold can be set to a constant value regardless of the selected power transmission coil, so that the foreign object detection accuracy is improved.

  In the present embodiment, the parasitic element has the same shape as the power transmission coil or a shape obtained by cutting the power transmission coil in half. However, the shape of the parasitic element is not limited to these examples. The parasitic element may be configured by at least one metal wire, for example, as shown in FIG. Even such a metal wire can be used as a parasitic element because coupling can occur between adjacent end coils. As described above, the parasitic element can be configured by at least one metal wire extending in the second direction perpendicular to the arrangement direction (first direction) on the arrangement surface of the plurality of power transmission coils.

  The parasitic element does not need to be arranged on a line in the arrangement direction of the plurality of power transmission coils, and may be close to the end coil. Here, “proximity” means close to the extent of changing the Q value of the coil at the end. The length of the gap between the parasitic element and the end coil is determined, for example, such that the Q value of the end coil is substantially equal to the Q value of the adjacent coil. Here, “substantially equal” for the Q value means that the rate of change of the Q value falls within 2%. The distance between the parasitic element and the end coil (gap distance) can be set substantially equal to the distance between the end coil and the adjacent coil. Here, “substantially equal” in distance means that the difference is within 30%.

  The material of the parasitic element is not limited to a specific material as long as it is a metal. The same material as the power transmission coil (for example, copper wire on the substrate) may be used, or another metal may be used. For example, a nonmagnetic metal such as copper can be suitably used as the metal member in the parasitic element.

  In the present embodiment, the plurality of power transmission coils 110 are arranged in one dimension, but may be arranged in two dimensions. Even if it is such an arrangement | sequence, said relationship should just be satisfy | filled about the group of power transmission coils arranged in a certain direction. That is, among the plurality of power transmission coils arranged in two dimensions, a parasitic element including a metal member may be provided in the vicinity of the end coil.

  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.

DESCRIPTION OF SYMBOLS 100 Power transmission apparatus 110 Power transmission coil 120, 121 Capacitor 130 Switch 140 Power transmission circuit 150 Control circuit 180 Parasitic element 200 Power receiving apparatus 210 Power receiving coil 220 Capacitor 230 Secondary battery 300 DC power supply

Claims (12)

  1. A power transmission device that transmits power in a contactless manner to a power reception device including a power reception coil,
    A plurality of power transmission coils arranged in a first direction along a certain surface ;
    Among the plurality of power transmission coils, a parasitic element including a nonmagnetic metal member disposed outside the plurality of power transmission coils in the vicinity of an end power transmission coil,
    A power transmission circuit connected to the plurality of power transmission coils and supplying AC power to the plurality of power transmission coils;
    A power transmission device comprising:
  2.   2. The power transmission device according to claim 1, wherein the parasitic element is configured such that a Q value of the power transmission coil at the end is substantially equal to a Q value of a power transmission coil adjacent to the power transmission coil at the end. .
  3. Another parasitic element including a non-magnetic metal member disposed outside the plurality of power transmission coils in the vicinity of the power transmission coil located at the end opposite to the end of the plurality of power transmission coils. The power transmission device according to claim 1, further comprising:
  4.   The power transmission device according to claim 3, wherein the parasitic element and the other parasitic element are configured such that Q values of the plurality of power transmission coils are substantially equal.
  5.   5. The power transmission device according to claim 1, wherein the parasitic element has the same shape as the power transmission coil at the end.
  6.   5. The power transmission device according to claim 1, wherein the parasitic element has a shape in which a power transmission coil at the end is cut in half.
  7.   5. The power transmission device according to claim 1, wherein the parasitic element is configured by at least one metal wire extending in a second direction perpendicular to the first direction on the surface. .
  8.   The distance between the parasitic element and the power transmission coil at the end is substantially equal to the distance between the power transmission coil adjacent to the power transmission coil at the end and the power transmission coil at the end. The power transmission device according to any one of the above.
  9.   The length of the parasitic element in a second direction perpendicular to the first direction on the surface is equal to the length of each power transmission coil in the second direction. The power transmission device described.
  10.   A control circuit that controls a connection state between the power transmission circuit and each power transmission coil, and a certain number of adjacent ones selected from the plurality of power transmission coils according to a relative position of the power reception coil with respect to the plurality of power transmission coils The power transmission device according to claim 1, further comprising a control circuit that switches a connection state between the power transmission circuit and the plurality of power transmission coils so that the AC power is supplied to the power transmission coil.
  11.   The power transmission device according to any one of claims 1 to 10, wherein the control circuit detects a foreign object close to the plurality of power transmission coils based on a change in electrical characteristics in the power transmission circuit.
  12. A power transmission device according to any one of claims 1 to 11 ,
    A power receiving device having a power receiving coil;
    Wireless power transmission system comprising a.
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Cited By (2)

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US10289142B2 (en) 2011-02-01 2019-05-14 Fu Da Tong Technology Co., Ltd. Induction type power supply system and intruding metal detection method thereof
US10312748B2 (en) 2011-02-01 2019-06-04 Fu Da Tong Techology Co., Ltd. Signal analysis method and circuit

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KR20190096027A (en) * 2018-02-08 2019-08-19 엘지전자 주식회사 Cooking appliance

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JP4318044B2 (en) * 2005-03-03 2009-08-19 ソニー株式会社 Power supply system, the power supply apparatus and method, receiving apparatus and method, recording medium, and program
JP5188211B2 (en) * 2008-03-07 2013-04-24 キヤノン株式会社 Power supply apparatus and power supply method
JP5478326B2 (en) * 2010-03-30 2014-04-23 パナソニック株式会社 Contactless power supply system
JP2012016125A (en) * 2010-06-30 2012-01-19 Panasonic Electric Works Co Ltd Non-contact power supply system, and metal foreign substance detector of non-contact power supply system
JP5906457B2 (en) * 2011-12-05 2016-04-20 パナソニックIpマネジメント株式会社 Contactless power supply

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10289142B2 (en) 2011-02-01 2019-05-14 Fu Da Tong Technology Co., Ltd. Induction type power supply system and intruding metal detection method thereof
US10312748B2 (en) 2011-02-01 2019-06-04 Fu Da Tong Techology Co., Ltd. Signal analysis method and circuit

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