Power transmission equipment

Abstract

To provide a power-transmission device capable of improving power-transmission efficiency, using a plurality of coils for power-transmission.SOLUTION: A power-transmission device 2 comprises: a plurality of power-transmission coils (12-1 to 12-n) for transmitting power to a power-reception device 3 via a power-reception coil 21; at least one of power-supply circuits (11-1 to 11-n) each for supplying AC power to the plurality of power-transmission coils (12-1 to 12-n), respectively; a communication device 13 that receives a signal representing a power-reception situation from the power-reception device 3 at the power-reception device 3; and a control circuit 14 for controlling at least one of the power-supply circuits (11-1 to 11-n) so as not to supply the AC power to each of power-transmission coils unselected among the power-transmission coils (12-1 to 12-n), by selecting a power-transmission coil whose power-transmission efficiency with respect to the power-reception device 3 is highest as a power-transmission coil used for power-transmission to the power-reception device 3 to supply the AC power to the selected power-transmission coil, according to the power-reception situation.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a power transmitting device for transmitting power to a power receiving device in a contactless manner. [Background technology]

[0002] Conventionally, research has been conducted into so-called non-contact power supply (also called wireless power supply) technology, which transmits power through space without going through metal contacts or the like.

[0003] As one of such contactless power transfer technologies, a technology has been proposed in which power is transferred from a power transmitting device (hereinafter simply referred to as a power transmitting device) to a power receiving device (hereinafter simply referred to as a power receiving device) via a power transmitting coil and a power receiving coil. In particular, a technology has been proposed in which the power transmitting device is provided with multiple coils for power transfer, thereby increasing the degree of freedom in the position of the power receiving device when power is transferred (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2010-527226 Summary of the Invention [Problem to be solved by the invention]

[0005] When a power transmitting device is provided with multiple coils, the efficiency of power transmission varies depending on the relative position of the power receiving device with respect to the multiple coils and the coil actually used to supply power to the power receiving device.

[0006] Therefore, an object of the present invention is to provide a power transmission device that can improve power transmission efficiency by using a plurality of coils for power transmission. [Means for solving the problem]

[0007] According to one aspect of the present invention, there is provided a power transmission device capable of contactlessly transmitting power to a power receiving device having a power receiving coil, the power transmission device including a plurality of power transmission coils that transmit power to the power receiving device via the power receiving coils, at least one power supply circuit that supplies AC power to each of the plurality of power transmission coils, a communicator that receives a signal from the power receiving device that indicates a power reception status of the power receiving device, and a control circuit that selects, according to the power reception status, a power transmission coil from the plurality of power transmission coils that has the highest power transmission efficiency to the power receiving device as the power transmission coil to be used for power transmission to the power receiving device, supplies AC power to the selected power transmission coil from the plurality of power transmission coils, and controls the at least one power supply circuit not to supply AC power to the non-selected power transmission coils from the plurality of power transmission coils.

[0008] With this configuration, the power transmitting device transmits power using a power transmitting coil with high power transmission efficiency and does not supply power to other power transmitting coils, thereby reducing unnecessary power consumption and improving power transmission efficiency.

[0009] In this power transmitting device, the signal indicating the power receiving status preferably includes a value indicating a voltage output from the power receiving device. Furthermore, while the control circuit of the power transmitting device is not receiving the signal indicating the power receiving status from the power receiving device, it is preferable that the control circuit of the power transmitting device supplies AC power from a corresponding power supply circuit among at least one power supply circuit to each of the plurality of power transmitting coils at a predetermined cycle and at mutually different timings, and selects, from among the plurality of power transmitting coils, the power transmitting coil to which AC power was supplied when the signal indicating the power receiving status was received from the power receiving device and at least one power transmitting coil located around the power transmitting coil, the power transmitting coil that produces the highest voltage output from the power receiving device, as the power transmitting coil to be used for power transmission to the power receiving device.

[0010] With this configuration, the power transmitting device can appropriately select a power transmitting coil that has high efficiency in transmitting power to the power receiving device.

[0011] In this power transmitting device, it is preferable that the plurality of power transmitting coils are provided on a substrate, and that the substrate is supported by a support member that can adjust the position of the substrate, and that a control circuit of the power transmitting device controls the support member to adjust the position of the substrate in accordance with the power receiving status of the power receiving device so as to increase power transmission efficiency when transmitting power from a selected power transmitting coil to the power receiving device.

[0012] With this configuration, the power transmitting device can optimize the position of the power transmitting coil used for power transmission relative to the power receiving device, thereby further improving power transmission efficiency. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic configuration diagram of a contactless power supply system including a power transmission device according to an embodiment of the present invention. [Figure 2] FIG. 1 is a schematic configuration diagram of a power transmission device. [Figure 3] FIG. 2 is a diagram illustrating an example of the arrangement of power transmission coils. [Figure 4] FIG. 10 is a diagram illustrating an example of the arrangement of a substrate on which each power transmission coil is provided. [Figure 5] FIG. 2 is a schematic configuration diagram of a power receiving device. [Figure 6] 10 is a diagram showing an example of the arrangement of a substrate on which each unit of a power transmitting device is provided and a support member according to a modified example. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0014] A power transmission device according to one embodiment of the present invention will be described below with reference to the drawings. The power transmission device has multiple coils (hereinafter referred to as power transmission coils) used to transmit power to a power receiving device in a contactless manner, and when the power receiving device is placed in a position where it can receive power from the power transmission device, it transmits power to the power receiving device via one of the multiple power transmission coils. In order to select a power transmission coil to use for power transmission from the multiple power transmission coils, the power transmission device receives a signal indicating a power reception status from the power receiving device and selects a power transmission coil with the highest power transmission efficiency depending on the power reception status.

[0015] FIG. 1 is a schematic diagram of a contactless power supply system including a power transmission device according to this embodiment.

[0016] As shown in FIG. 1 , the contactless power transfer system 1 includes a power transmitter 2 and a power receiver 3 to which power is transmitted from the power transmitter 2 through a space in a contactless manner. The power transmitter 2 is disposed, for example, in a predetermined building. More specifically, the power transmitter 2 is installed behind a wall, behind a ceiling, or under a floor of a room in the predetermined building, or behind an exterior wall of the predetermined building. The power transmitter 2 transmits power supplied from a commercial power source or a power supply device installed in the predetermined building to the power receiver 3 located within a power transmission range inside or outside the building, across a wall or the like in a contactless manner. The power receiver 3 is installed in a mobile device such as a smartphone or other mobile device and receives the power transmitted from the power transmitter 2. The power received by the power receiver 3 is used to charge a battery installed in the device in which the power receiver 3 is installed, or to operate the device in which the power receiver 3 is installed.

[0017] In this embodiment, the power transmitter 2 and the power receiver 3 are configured as a contactless power feeding system that does not use resonance on the power transmitter side, but instead uses a system (NS system) in which a coil and a resonant capacitor in a resonant circuit of the power receiver 3 on the power receiving side resonate in series. However, without being limited to this example, the power transmitter 2 and the power receiver 3 may be a contactless power feeding system that uses, for example, a so-called primary-series-secondary-series resonant capacitor system (SS system) or a primary-series-secondary-parallel resonant capacitor system (SP system). Alternatively, the power transmitter 2 and the power receiver 3 may be a contactless power feeding system that does not use resonance on the power transmitter side, but uses another system (NP system) in which a coil and a resonant capacitor in a resonant circuit of the power receiver 3 on the power receiving side resonate in parallel.

[0018] 2 is a schematic configuration diagram of the power transmitting device 2. The power transmitting device 2 has n (n is an integer of 2 or more) power supply circuits 11-1 to 11-n, n power transmitting coils 12-1 to 12-n, a communicator 13, and a control circuit 14. These circuits included in the power transmitting device 2 are arranged on one or more boards.

[0019] The power supply circuits 11-1 to 11-n supply AC power having a predetermined drive frequency and a predetermined voltage to the corresponding power transmission coils 12-1 to 12-n. Preferably, the power supply circuits 11-1 to 11-n are capable of changing at least one of the voltage and drive frequency of the AC power supplied to the corresponding power transmission coil. Since each of the power supply circuits 11-1 to 11-n can have the same configuration and the same function, the following description will focus on one power supply circuit 11-j (j=1,...,n).

[0020] The power supply circuit 11-j includes, for example, a full-wave rectifier circuit, a power factor correction circuit, and an inverter.

[0021] The full-wave rectifier circuit has, for example, four diodes connected in a bridge configuration, and is connected to the commercial power supply 10. The full-wave rectifier circuit rectifies the AC power supplied from the commercial power supply 10, converts it into power having a pulsating voltage, and outputs the power to the power factor correction circuit.

[0022] The power factor correction circuit converts the voltage of the power output from the full-wave rectifier circuit into DC power having a voltage according to control from the control circuit 14 and outputs it to the inverter. The configuration of the power factor correction circuit can be the same as any of various power factor correction circuits that can adjust the amplification factor of the output voltage relative to the input voltage under control from the control circuit 14.

[0023] When the power supply circuit 11-j is connected to a power supply device that supplies DC power, the power supply circuit 11-j may have a DC-DC converter instead of the power factor correction circuit. Furthermore, the DC-DC converter may be a variable DC-DC converter that can change the output voltage in accordance with the control of the control circuit 14.

[0024] The inverter is configured as a full-bridge circuit in which four switching elements are connected in a full-bridge configuration, and converts the DC power output from the power factor correction circuit into AC power having a drive frequency corresponding to the on / off switching cycle of each switching element. The inverter then outputs the AC power to the transmitting coil 12-j.

[0025] Each switching element may be, for example, an n-channel MOSFET. The on / off of each switching element is controlled by a control circuit 14. Therefore, the control circuit 14 adjusts the on / off cycle of each switching element, thereby controlling the drive frequency of the AC power supplied to the power transmitting coil 12-j.

[0026] The inverter is not limited to the above embodiment, and may be configured as a half-bridge circuit in which two switching elements are connected in a half-bridge configuration.

[0027] Each of the power transmission coils 12-1 to 12-n is connected to a corresponding one of the power supply circuits 11-1 to 11-n, and transmits power to the power receiving device 3 by generating a magnetic field according to the AC power supplied from the corresponding power supply circuit. A capacitor for blocking DC may be provided between each power transmission coil and the corresponding power supply circuit. Furthermore, when the contactless power transfer system 1 utilizes resonance on the power transmission side, each of the power transmission coils 12-1 to 12-n may be provided with a capacitor that forms a resonance circuit together with the power transmission coil.

[0028] Fig. 3 is a diagram showing an example of the arrangement of power transmitting coils 12-1 to 12-n. As shown in Fig. 3, power transmitting coils 12-1 to 12-n are each formed to have the same size and a circular outer shape. Furthermore, power transmitting coils 12-1 to 12-n are arranged in a lattice pattern on substrate 15 such that the winding axis of each coil coincides with the normal direction of substrate 15. In this example, power transmitting coils 12-1 to 12-n are each formed by wiring on substrate 15, but this is not limiting, and power transmitting coils 12-1 to 12-n may also be formed by winding a conductor around a core provided for each power transmitting coil on substrate 15. Note that the shape of power transmitting coils 12-1 to 12-n is not limited to a circle, and may be an ellipse, a hexagon, or a rectangle. Furthermore, it is not necessary for all of the power transmitting coils 12-1 to 12-n to have the same shape, and some of the power transmitting coils 12-1 to 12-n may have a different shape from the other power transmitting coils. Furthermore, it is not necessary for all of the power transmitting coils 12-1 to 12-n to have the same size, and some of the power transmitting coils 12-1 to 12-n may have a different size from the other power transmitting coils. Furthermore, the power transmitting coils 12-1 to 12-n may be arranged in an arrangement other than a grid. For example, the power transmitting coils 12-1 to 12-n may be arranged in a staggered pattern, with adjacent rows being staggered. Alternatively, the power transmitting coils 12-1 to 12-n may be arranged in a row along a predetermined straight or curved line.

[0029] FIG. 4 is a diagram showing an example of the arrangement of a board 15 on which each power transmitting coil is provided. In this example, the board 15 is arranged along the wall 401 on the back side of a wall 401 of a room 400 in which a power receiving device 3 to which power is transferred is located. Furthermore, each of the power transmitting coils 12-1 to 12-n is provided on the surface of the board 15 facing the wall 401. That is, the board 15 is arranged so that the winding axis of each of the power transmitting coils 12-1 to 12-n is approximately aligned with the normal direction of the wall 401. Therefore, by arranging the power receiving device 3 so that the receiving coil of the power receiving device 3 and any of the power transmitting coils 12-1 to 12-n face each other across the wall 401, power can be transferred from the power transmitting device 2 to the power receiving device 3. The board 15 may be attached to the back surface of the wall 401 using a fixing member such as a screw, or may be installed near the back surface of the wall 401 by using a support member (not shown) installed near the wall 401.

[0030] Furthermore, substrate 15 may be arranged along the underside of floor 402 of room 400 so that each of power transmitting coils 12-1 to 12-n faces the underside of floor 402. Alternatively, substrate 15 may be arranged along the backside of ceiling 403 of room 400 so that each of power transmitting coils 12-1 to 12-n faces the backside of ceiling 403.

[0031] Every time the communicator 13 receives a wireless signal from the communicator of the power receiving device 3, it extracts a signal indicating the power receiving status of the power receiving device 3 from the wireless signal and outputs the signal to the control circuit 14. To this end, the communicator 13 has, for example, an antenna that receives the wireless signal in accordance with a predetermined wireless communication standard and a communication circuit that demodulates the wireless signal. Note that the predetermined wireless communication standard may be, for example, ISO / IEC 15693, ZigBee (registered trademark), or Bluetooth (registered trademark).

[0032] Control circuit 14 includes, for example, a non-volatile memory circuit, a volatile memory circuit, an arithmetic circuit, and an interface circuit for connecting to other circuits. Control circuit 14 controls power supply circuits 11-1 to 11-n based on a signal indicating the power receiving state of power receiving device 3, which signal is received from power receiving device 3 via communication device 13. Details of the control of power supply circuits 11-1 to 11-n by control circuit 14 will be described later.

[0033] Next, the details of the power receiving device 3 will be described.

[0034] 5 is a schematic configuration diagram of the power receiving device 3. The power receiving device 3 includes a power receiving coil 21, a resonant capacitor 22, a power receiving circuit 23, a control circuit 24, and a communication device 25.

[0035] The power receiving coil 21 forms a resonant circuit together with the resonant capacitor 22, and receives power from the power transmitting coils 12-1 to 12-n by resonating with the AC current flowing through the power transmitting coils 12-1 to 12-n of the power transmitting device 2. For this purpose, the resonant capacitor 22 is connected in series with the power receiving coil 21. The resonant capacitor 22 may also be connected in parallel with the power receiving coil 21. The AC power output from the resonant circuit formed by the power receiving coil 21 and the resonant capacitor 22 is output to the power receiving circuit 23. The number of turns of the power receiving coil 21 and the number of turns of the power transmitting coils 12-1 to 12-n of the power transmitting device 2 may be the same as or different from each other. The shape and size of the power receiving coil 21 and the shape and size of the power transmitting coils 12-1 to 12-n of the power transmitting device 2 may be the same as or different from each other.

[0036] The power receiving circuit 23 converts AC power from the resonant circuit formed by the power receiving coil 21 and the resonant capacitor 22 into DC power and outputs the DC power to a load circuit (not shown) connected to the power receiving circuit 23. The load circuit is a circuit provided in the device incorporating the power receiving device 3, such as a charger for charging the battery of the device incorporating the power receiving device 3. Furthermore, the power receiving circuit 23 detects the power receiving status from the power transmitting device 2, in particular the output voltage from the power receiving circuit 23. To this end, the power receiving circuit 23 has a rectifying and smoothing circuit and a voltage detection circuit.

[0037] The rectifying and smoothing circuit has a full-wave rectifying circuit with switching elements such as four bridge-connected diodes or MOSFETs, and a smoothing capacitor, and rectifies and smoothes the power received via the power receiving coil 21 to convert it into DC power. The rectifying and smoothing circuit then outputs the DC power to the load circuit.

[0038] The voltage detection circuit measures the output voltage between both terminals on the output side of the rectifying and smoothing circuit (i.e., the output voltage of the power receiving circuit 23, hereinafter sometimes simply referred to as the output voltage) at predetermined intervals. Since the output voltage between both terminals of the rectifying and smoothing circuit corresponds one-to-one to the output voltage of the resonant circuit consisting of the power receiving coil 21 and the resonant capacitor 22, the measured value of the output voltage between both terminals of the rectifying and smoothing circuit indirectly becomes the measured value of the output voltage of the resonant circuit. The voltage detection circuit can be, for example, any of various well-known voltage detection circuits capable of detecting DC voltage. The voltage detection circuit then outputs the measured value of the output voltage to the control circuit 24.

[0039] The control circuit 24 includes, for example, a non-volatile memory circuit, a volatile memory circuit, an arithmetic circuit, and an interface circuit for connecting to other circuits. The control circuit 24 compares the measured value of the output voltage from the power receiving circuit 23 with a predetermined threshold at predetermined intervals. When the measured value of the output voltage exceeds the predetermined threshold, the control circuit 24 determines that power transmitted from the power transmitting device 2 has been detected. The control circuit 24 then generates a signal representing the power receiving status and outputs the signal to the communicator 25. The control circuit 24 includes a value representing the output voltage from the power receiving device 3, such as the most recent measured value of the output voltage, in the signal representing the power receiving status. Furthermore, the control circuit 24 may include, in the signal representing the power receiving status, information representing a predetermined tolerance range that the output voltage must satisfy, along with the most recent measured value of the output voltage. Alternatively, the control circuit 24 may include, in the signal representing the power receiving status, a signal value representing whether the most recent measured value of the output voltage is within the predetermined tolerance range, below the tolerance range, or above the tolerance range. Furthermore, the control circuit 24 may include, in the signal representing the power receiving status, a signal value representing that power transmission is unnecessary, such as a signal representing that charging is completed, received from a load circuit (not shown).Alternatively, the control circuit 24 may include, in the signal representing the power receiving status, a signal value representing that power transmission needs to be resumed, such as a signal representing that charging is resumed, received from a load circuit (not shown).

[0040] When the communicator 25 receives a signal indicating the power receiving status from the control circuit 24, it generates a wireless signal including the signal indicating the power receiving status and transmits the wireless signal to the communicator 13 of the power transmitting device 2. To this end, the communicator 25 has, for example, a communication circuit that generates a wireless signal in accordance with a predetermined wireless communication standard and an antenna that outputs the wireless signal. Note that the predetermined wireless communication standard, like the communicator 13, can be, for example, ISO / IEC 15693, ZigBee (registered trademark), or Bluetooth (registered trademark).

[0041] The operation of the control circuit 14 of the power transmitting device 2 will be described in detail below.

[0042] The control circuit 14 operates the power supply circuits 11-1 to 11-n in a standby mode while the communicator 13 is not receiving a wireless signal from the power receiving device 3. In the standby mode, the control circuit 14 sets an active period for each of the power supply circuits 11-1 to 11-n, during which the circuits are active at a predetermined cycle and at different timings. That is, the control circuit 14 supplies AC power to the corresponding power transmitting coil only from the power supply circuit 11-1 to 11-n that is in the active period. That is, during the active period, the control circuit 14 switches on / off each switching element of the inverter of the power supply circuit that is in the active period at a switching cycle corresponding to a predetermined drive frequency. Furthermore, the control circuit 14 controls the power factor correction circuit or DC-DC converter of the power supply circuit that is in the active period to set the voltage of the AC power supplied to the corresponding power transmitting coil to a predetermined standby voltage. The standby voltage is set to a relatively low voltage that allows the power receiving device 3 to detect the power received from any of the power transmitting coils when the power receiving device 3 is located within a range where it can receive power from that power transmitting coil. In addition, the control circuit 14 turns off each switching element of the inverter of the power supply circuit during a rest period other than an operating period, thereby stopping the power supply from that power supply circuit to the corresponding power transmitting coil.

[0043] The order of the power supply circuits to be activated is set, for example, as follows. That is, when the power transmitting coils 12-1 to 12-n are arranged two-dimensionally, the order of the power supply circuits to be activated is set so that AC power is supplied to the power transmitting coils 12-1 to 12-n in raster scan order. For example, in the example shown in FIG. 3(a), the power supply circuit 11-1 that supplies AC power to the power transmitting coil 12-1 located at the upper left is activated first. Next, the power supply circuit 11-2 that supplies AC power to the power transmitting coil 12-2 located immediately to the right of the power transmitting coil 12-1 is activated. Then, after the power supply circuit that supplies AC power to the power transmitting coil located at the right end of the top row is activated, the power supply circuit that supplies AC power to the power transmitting coil located at the left end of the second row from the top is activated. The power supply circuits are activated one by one in this order, and finally the power supply circuit 11-n that supplies AC power to the power transmitting coil 12-n located at the bottom right is activated. Then, the power supply circuits 11-1 and 11-2 are activated in order.

[0044] The order in which the power supply circuits are activated is not limited to the above. For example, the power supply circuits corresponding to the power transmission coils located in odd-numbered columns or odd-numbered rows in the arrangement of the power transmission coils may be activated in order, followed by the power supply circuits corresponding to the power transmission coils located in even-numbered columns or even-numbered rows. Alternatively, the power supply circuits corresponding to the power transmission coils in a vertical column may be activated in order from top to bottom, and once the power supply circuit corresponding to the bottom-most power transmission coil is activated, the power supply circuits corresponding to the power transmission coils in adjacent vertical columns may be activated in the same order. Furthermore, when the power transmission coils 12-1 to 12-n are arranged in a line along a predetermined straight or curved line, the power supply circuits may be activated one by one, starting from the power transmission coil located at either end to the power transmission coil located at the other end.

[0045] When communicator 13 starts receiving a wireless signal from communicator 25 of power receiving device 3, control circuit 14 assumes that power receiving device 3 is located within a range where it can receive power from any of the power transmitting coils. Therefore, control circuit 14 operates power supply circuits 11-1 to 11-n in a search mode. In the search mode, control circuit 14 controls each power supply circuit to determine which of power transmitting coils 12-1 to 12-n will be used to supply power to power receiving device 3.

[0046] To this end, the control circuit 14 identifies the power supply circuit that was active when the communicator 13 received the wireless signal as the power supply circuit that serves as the search reference point. This is because it is estimated that the power receiving device 3 received power from a power transmitting coil that received AC power from the power supply circuit that was active when the communicator 13 received the wireless signal. The control circuit 14 then selects a power transmitting coil to be used for power transmission from among the power transmitting coil that receives AC power from the power supply circuit that serves as the search reference point and at least one power transmitting coil located around the power transmitting coil. Specifically, the control circuit 14 sequentially activates the power supply circuits corresponding to each power transmitting coil located around the power transmitting coil that receives AC power from the power supply circuit that serves as the search reference point. For example, the control circuit 14 activates the power supply circuits corresponding to each power transmitting coil located around the power transmitting coil that receives AC power from the power supply circuit that serves as the search reference point in clockwise or counterclockwise order. At this time, the control circuit 14 refers to the layout information indicating the layout of the power transmitting coils 12-1 to 12-n and the power supply circuits that supply AC power to each of the power transmitting coils, and identifies the power transmitting coil to which AC power is supplied from the identified power supply circuit and each of the power transmitting coils located around it. Note that the layout information may be stored in a memory included in the control circuit 14.

[0047] The control circuit 14 monitors the measured value of the output voltage from the power receiving device 3, which is included in the received signal indicating the power receiving status. The control circuit 14 then identifies the power supply circuit and the power transmitting coil (hereinafter sometimes referred to as the corresponding power transmitting coil) that were active when the measured value was highest as the power supply circuit and the power transmitting coil to which AC power is supplied from that power supply circuit as the next search reference point. The control circuit 14 then repeats the above process to identify the power supply circuit and the corresponding power transmitting coil that were active when the measured value of the output voltage from the power receiving device 3 was highest. It is estimated that using the power transmitting coil with the highest measured output voltage for power transmission will maximize power transmission efficiency. Therefore, the control circuit 14 selects the identified power supply circuit and the corresponding power transmitting coil as the power supply circuit and the power transmitting coil to be used for power transmission to the power receiving device 3. By selecting the power supply circuit and the power transmitting coil to be used for power transmission to the power receiving device 3 in this manner, the control circuit 14 can appropriately select a power transmitting coil with high power transmission efficiency. The control circuit 14 may identify the power transmitting coil with the highest measured output voltage value by other methods, without being limited to the above example. For example, the control circuit 14 may first receive a signal indicating the power receiving status, and then sequentially supply AC power to all of the power transmitting coils from the corresponding power supply circuits. The control circuit 14 may then record the measured output voltage value included in the received signal indicating the power receiving status for each power transmitting coil to which AC power is supplied, thereby identifying the power transmitting coil to which AC power was supplied when the measured output voltage value was highest.

[0048] When the power supply circuit and power transmitting coil to be used for power transmission to the power receiving device 3 are selected, the control circuit 14 operates the selected power supply circuit in power transmission mode and sets the other power supply circuits to sleep mode. For the power supply circuit in power transmission mode, the control circuit 14 switches on / off each switching element of the inverter of the power supply circuit in power transmission mode at a switching period corresponding to the drive frequency while receiving a wireless signal from the power receiving device 3 or until a signal indicating the power receiving status included in the wireless signal received from the power receiving device 3 indicates that power transmission is unnecessary. Furthermore, the control circuit 14 controls the power factor correction circuit or DC-DC converter of the power supply circuit in power transmission mode to adjust the voltage of the AC power supplied from the power transmission circuit to the corresponding power transmitting coil so that the measured output voltage falls within a predetermined tolerance range. In other words, if the measured output voltage is lower than the predetermined tolerance range, the control circuit 14 controls the power factor correction circuit or DC-DC converter so that the voltage of the AC power supplied to the power transmitting coil is increased. Conversely, if the measured value of the output voltage is higher than the predetermined tolerance range, the control circuit 14 controls the power factor correction circuit or the DC-DC converter so as to lower the voltage of the AC power supplied to the power transmitting coil.

[0049] Furthermore, the degree of coupling between the power transmitting coil and the power receiving coil 21 of the power receiving device 3 changes depending on the relative positions of the power transmitting coil and the power receiving coil 21 used for power transmission. The drive frequency at which power transmission efficiency is high also changes depending on the degree of coupling. Therefore, the control circuit 14 may change the drive frequency of the AC power supplied from the power transmission circuit to the corresponding power transmitting coil by changing the on / off switching cycle of each switching element of the inverter of the selected power supply circuit. The control circuit 14 may then control the drive frequency so that the measured value of the output voltage included in the received signal indicating the power receiving status is maximized.

[0050] Furthermore, the control circuit 14 turns off each switching element of the inverter of the power supply circuit in the pause mode so that AC power is not supplied to the power transmitting coil from that power supply circuit. By setting the power supply circuit that is not used for power transmission in the pause mode in this way, the control circuit 14 can reduce the wasteful consumption of power that is not used for power transmission.

[0051] Even if the control circuit 14 controls the voltage of AC power supplied from a power supply circuit in the power transmission mode, the measured value of the output voltage from the power receiving device 3, which is included in the wireless signal received from the power receiving device 3, may not reach a predetermined tolerance range. In such a case, the control circuit 14 may also operate in the power transmission mode a power supply circuit that supplies AC power to a power transmitting coil adjacent to a power transmitting coil corresponding to the power supply circuit in the power transmission mode. In this case, the control circuit 14 may increase the number of power supply circuits operating in the power transmission mode until the measured value of the output voltage from the power receiving device 3 falls within the predetermined tolerance range. This allows power to be supplied to the power receiving device 3 from multiple power transmitting coils, making it easier to ensure that the output voltage from the power receiving device 3 falls within the predetermined tolerance range.

[0052] Furthermore, if the measured value of the output voltage from the power receiving device 3 falls below the predetermined tolerance range after it has once fallen within the predetermined tolerance range, the control circuit 14 may assume that the power receiving device 3 has moved. Therefore, the control circuit 14 may use the power supply circuit operating in the power transmission mode as a search reference point and optimally apply the search mode to each power supply circuit.

[0053] Furthermore, when the signal indicating the power receiving status included in the wireless signal received from the power receiving device 3 indicates that power transmission is no longer necessary, the control circuit 14 returns each power supply circuit to the standby mode and stores in memory the identification information of the power supply circuit that was used for power transmission. Thereafter, when the signal indicating the power receiving status included in the wireless signal received from the power receiving device 3 indicates that power transmission needs to be resumed, the control circuit 14 operates each power supply circuit in the search mode, using the power supply circuit that was previously used for power transmission and that was stored in memory as the search reference point.

[0054] Furthermore, when the control circuit 14 is no longer able to receive a wireless signal from the power receiving device 3, it returns each power supply circuit to the standby mode and terminates power transmission to the power receiving device 3.

[0055] As described above, the power transmitting device has multiple power transmitting coils. When the power receiving device is positioned so that it can receive power from the power transmitting device, the power transmitting device transmits power to the power receiving device via one of the multiple power transmitting coils. In this case, the power transmitting device receives a signal indicating the power receiving status from the power receiving device and, depending on the power receiving status, selects the power transmitting coil from the multiple power transmitting coils that provides the highest power transmission efficiency as the power transmitting coil to be used for power transmission. Therefore, the power transmitting device can increase the flexibility of the position of the power receiving device during power transmission and improve power transmission efficiency. Therefore, even if the position of the power receiving device changes because it needs to be moved due to building renovations, for example, the power receiving device can still receive power from the power transmitting device. Thus, the power transmitting device eliminates the need for construction work on the equipment for supplying power to the power receiving device even if the position of the device changes.

[0056] According to a modification, the substrate 15 on which the plurality of power transmitting coils 12-1 to 12-n are provided may be supported by a support member that can adjust the position or inclination of the substrate 15. The control circuit 14 may then control the support member to adjust the position or inclination of the substrate 15, thereby changing the position or inclination of the power transmitting coils used for power transmission so as to further improve the efficiency of power transmission to the power receiving device 3.

[0057] 6 is a diagram showing an example of the arrangement of a substrate 15 on which components of the power transmission device 2, such as a plurality of power transmission coils, are provided and a support member according to this modification. In this modification, the substrate 15 on which components of the power transmission device 2 are provided is supported by a support member 16 configured as an XY stage. Actuators 163 and 164 that drive two axes 161 and 162 of the support member 16, respectively, are connected to the control circuit 14.

[0058] In the search mode, the control circuit 14 selects the power transmitting coil that maximizes the measured value of the output voltage from the power receiving device 3 and the power supply circuit that supplies AC power to the power transmitting coil. The control circuit 14 then controls the actuators 163 and 164 on the axes 161 and 162 of the support member 16 to change the position of the power transmitting coil to which AC power is supplied by a predetermined distance in each of the vertical and horizontal directions while supplying AC power only from the identified power supply circuit. The control circuit 14 then identifies the direction in which the measured value of the output voltage from the power receiving device 3 increases, and changes the position of the power transmitting coil to which AC power is supplied in the identified direction to identify the position where the measured value of the output voltage from the power receiving device 3 is maximized. The control circuit 14 then stops the actuators 163 and 164 so that the power transmitting coil is fixed at the identified position. Thereafter, the control circuit 14 operates the identified power supply circuit in the power transmission mode, as in the above embodiment.

[0059] According to this modification, the power transmitting device can optimize the position of the power transmitting coil used for power transmission in relation to the position of the power receiving device, thereby further improving power transmission efficiency.

[0060] In addition, if the support member 16 is a tilting stage that can change the tilt of the substrate 15, the control circuit 14 may control the support member 16 to adjust the tilt of the substrate 15 so that the measured value of the output voltage from the power receiving device 3 is the highest when any of the power supply circuits is operating in the search mode.

[0061] Alternatively, one or several of the power transmitting coils 12-1 to 12-n may be provided on different substrates. In this case, each substrate may be supported by a different support member. In this case, the control circuit 14 may control the position or tilt of only the support member on which the power transmitting coil to which AC power is supplied from the power supply circuit operating in the search mode is provided.

[0062] According to another modification, one or more of the power transmitting coils 12-1 to 12-n to be used for power transmission may be preset via another device. In this case, a wireless signal including preset information specifying the power transmitting coil to be used for power transmission is transmitted from a device such as a mobile terminal capable of communicating with the communicator 13. The control circuit 14 refers to the preset information included in the wireless signal received via the communicator 13 and selects the power transmitting coil to be used for power transmission and a power supply circuit that supplies AC power to the power transmitting coil. The control circuit 14 operates only the identified power supply circuit in standby mode and sets the other power supply circuits to sleep mode until it is able to receive a wireless signal from the power receiving device 3. Then, upon receiving a wireless signal from the power receiving device 3, the control circuit 14 operates the selected power supply circuit in power transmission mode.

[0063] Note that two or more power transmitting coils may be specified in the preset information. In this case, when a wireless signal is received from the power receiving device 3, only the power supply circuits corresponding to the specified power transmitting coils may be operated in search mode to identify the power transmitting coils and power supply circuits that will ultimately be used for power transmission.

[0064] According to this modification, the power transmitting coil and the power supply circuit to be used for power transmission are specified in advance, which shortens the time until power transmission to the power receiving device becomes possible. Furthermore, the power transmitting device can limit the power supply circuits to operate in standby mode, which reduces power consumption when power transmission is not being performed.

[0065] According to yet another modification, the power transmitter 2 may be configured so that AC power is supplied to two or more power transmitting coils from one power supply circuit. In this case, a 1-input, m-output (m is an integer greater than or equal to 2) switch may be provided between the power supply circuit and the power transmitting coil to which AC power is supplied from the power supply circuit. The control circuit 14 may control the switch to switch the power transmitting coil to which AC power is supplied from the power supply circuit.

[0066] According to this modification, the number of power supply circuits can be made smaller than the number of power transmission coils, thereby reducing the circuit scale of the power transmission device.

[0067] As described above, those skilled in the art can make various modifications to the embodiments within the scope of the present invention. [Explanation of symbols]

[0068] 1. Contactless power supply system 2. Power transmission equipment 10 Commercial power supply 11-1~11-n Power supply circuit 12-1~12-n Transmission coils 13 Communication Device 14 Control circuit 15 PCB 16 Support member 161, 162 axes 163, 164 Actuator 3 Power receiving device 21 Receiving coil 22 Resonant Capacitor 23 Receiving circuit 24 Control circuit 25 Communication Device

Claims

1. A power transmitting device capable of contactlessly transmitting power to a power receiving device having a power receiving coil, a plurality of power transmitting coils that transmit power to the power receiving device via the power receiving coil; at least one power supply circuit that supplies AC power to each of the plurality of power transmitting coils; a communication device that receives a signal indicating a power receiving state of the power receiving device from the power receiving device; a control circuit that selects, according to the power receiving state, a power transmitting coil from among the plurality of power transmitting coils that has the highest power transmission efficiency to the power receiving device as a power transmitting coil to be used for power transmission to the power receiving device, supplies AC power to the selected power transmitting coil from among the plurality of power transmitting coils, and controls the at least one power supply circuit not to supply AC power to the power transmitting coils that are not selected from among the plurality of power transmitting coils; and the plurality of power transmitting coils are arranged two-dimensionally, the signal representing the power receiving status includes a measured value of a voltage output from the power receiving device and information representing a predetermined tolerance range that the output voltage should satisfy; the control circuit controls the control circuit to supply AC power from a corresponding one of the at least one power supply circuit to each of the plurality of power transmitting coils in a raster scan order at a predetermined cycle and at timings different from each other while the control circuit is not receiving a signal indicating the power receiving state from the power receiving device; Among the plurality of power transmission coils, from among the power transmission coil to which AC power was supplied when the signal indicating the power receiving state was received from the power receiving device and at least one power transmission coil located around the power transmission coil, a power transmission coil that produces the highest voltage output from the power receiving device is selected as a power transmission coil to be used for power transmission to the power receiving device; and the control circuit refers to the signal indicating the power receiving state, and controls the power supply circuit to adjust the voltage of the AC power supplied to the selected power transmitting coil among the plurality of power transmitting coils so that the measured value falls within the allowable range. Power transmission equipment.

2. the plurality of power transmitting coils are provided on a substrate, and the substrate is supported by a support member that is capable of adjusting a position of the substrate; The power transmission device according to claim 1, wherein the control circuit controls the support member to adjust the position of the substrate so as to increase power transmission efficiency when transmitting power from the selected power transmission coil to the power receiving device, depending on the power receiving status.

3. The power transmission device described in claim 1, wherein the control circuit controls the power supply circuit to supply AC power to a transmission coil adjacent to the selected transmission coil among the plurality of transmission coils if the measured value does not reach the allowable range even after adjusting the voltage of the AC power supplied to the selected transmission coil.

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