Patent Publication Number: US-2020303953-A1

Title: Power receiving system and power supply system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2019-055515, filed on Mar. 22, 2019, the entire contents of which are incorporated herein by reference. 
     FIELD 
     Embodiments relate to a power receiving system and a power supply system. 
     BACKGROUND 
     In recent years, it has been proposed to install electronic devices on a shopping cart to provide various services to a user of the cart. Any battery mounted on the cart to supply power to electronic devices on the cart will need to be regularly charged. In order to charge the battery provided on a cart, various power supplying mechanisms can be used to supply power to the cart. For example, the battery can be charged in a non-contact manner when the cart is disposed in a storage position (e.g., a cart charging station). For non-contact power transmission, it is important to align the antenna on the power receiving side with the antenna on the power transmission side in order to efficiently transmit electric power. A power supplying system in which a non-contact power transmission technology is utilized includes a receiving coil located on the cart and a transmitting coil of a power transmitting system for supplying power to the receiving coil of the cart when the cart is housed in a cart storage location. 
     However, since carts are compactly housed in a storage located, it is often the case that portions of one cart overlap with portions of another cart. For example, shopping carts are configured to be stored in a nested manner. As such, the receiving coil in one such stored cart is often in close proximity to the receiving coils of the carts nested to the front and rear of the stored cart when housed in the storage position. When a receiving coil of one cart is in close proximity to the receiving coil of another cart, each transmitting coil corresponding to the receiving coils must be arranged to face and be close to the corresponding receiving coil. When two receiving coils are adjacent to a transmitting coil provided for charging one cart, the resonant frequency for receiving power from the transmitting coil may change and the transmission efficiency may decrease. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a cart on which a power receiving device to receive power from the power supply system according to the first and second embodiments is mounted. 
         FIG. 2  is a perspective view showing an example of a configuration of a power supply system according to a first embodiment. 
         FIG. 3  is a schematic diagram showing a cart carrying a power receiving system to be powered by a power supply system according to a first embodiment housed at a storage position. 
         FIG. 4  is a block diagram of a control system in a power supply system according to a first embodiment. 
         FIG. 5  is a block diagram of a power supply system according to a modification of the first embodiment. 
         FIG. 6  is a perspective view of a power supply system according to a second embodiment. 
         FIG. 7  is a schematic diagram showing a cart carrying a power receiving system to be powered by a power supply system according to a second embodiment housed at a storage position. 
         FIG. 8  is a block diagram of a control system in a power supply system according to a second embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     According to an embodiment, a power receiving system includes a first receiving coil, a second receiving coil, a receiving circuit, a switching circuit, and a shorting circuit. The first receiving coil is at a first location on the cart. The second receiving coil is at a second location different from the first location on the cart. The receiving circuit generates direct current (DC) power from the power received by the first receiving coil or the second receiving coil. The switching circuit connects one of the first and second receiving coils to the receiving circuit. The shorting circuit disables the other one of the first and second receiving coils. 
     Hereinafter, a power supply system according to certain example embodiments will be described with reference to the drawings. 
     First Embodiment 
     First, a power supply system according to a first embodiment will be described. 
     The power supply system includes a power receiving system including two power receiving units installed in each cart, and a power transmitting system including a power transmitting unit corresponding to the positions of a plurality of carts that can be housed at a storage position. The power supply system is a system for transmitting power in a non-contact manner to a receiving coil installed in each cart in accordance with the position at which the cart is housed in the storage position. The power transmitting unit of the power transmitting system transmits power in a state in which the power transmitting unit of the power receiving system is not physically connected to, or otherwise contacting, the power receiving unit. 
       FIG. 1  is a diagram illustrating an example of a configuration of a cart  1  for a power supply system according to a first embodiment. Power supplied by the power supply system is received by a power receiving system  20  mounted on the cart  1 . 
     Cart  1  is depicted as a shopping cart, but, in general, cart  1  can be any cart, mobile unit, hand truck, or moving body. The power supply system includes a power transmitting system  30  (see  FIG. 2 ) for transmitting power in a non-contact manner and a power receiving system  20  for receiving power transmitted in a non-contact manner. 
     The power receiving system  20  is a power receiving device that is mounted on the cart  1 . Power receiving system  20  includes a power receiving unit  23  that receives power transmitted in a contactless manner. For example, the power receiving system  20  charges the battery  22  mounted on the cart  1  by using the power received by the power receiving unit  23 . The power transmitting system  30  is a power transmitting device for supplying power to the power receiving system  20 . The power transmitting system  30  includes a power transmitting unit  32  that transmits power that can be received by the power receiving system  20  mounted on the cart  1 . For example, the power transmitting system  30  is configured to transmit electric power to the power receiving system  20  while the cart  1  is housed at a storage position (cart storage location). The power transmitting system  30  transmits electrical power by utilizing the power transmitting unit  32 . 
     The battery  22  is, for example, a power supply unit that supplies power to an electronic device  21  mounted on the cart  1 . In this example, it is assumed that each cart  1  is provided with a battery  22 , an electronic device  21 , and a power receiving system  20 . The battery  22  may be mounted on the cart  1  as a separate device from the electronic device  21  or may be integrated with the electronic device  21 . 
     The cart  1  comprises a cart body  11 , an electronic device  21  having a battery  22 , a power receiving unit  23 R, and a power receiving unit  23 L). The cart body  12  has a form permitting a user to store commodities therein and is able to carry stored commodities. The electronic device  21  is an apparatus for providing information to user or providing services to the user. The battery  22  is a power supply unit for operating the electronic device  21 . The power receiving units  23 R and  23 L receives electric power transmitted from an external device. The electronic device  21  charges the battery  22  by the power received by the power receiving unit  23 R or the power receiving unit  23 L. 
     Note, in some examples, the battery  22  may be an external power supply provided separately from the electronic device  21  rather than integrated with or housed within the electronic device  21 . The battery  22  when configured an external power supply can include a charging circuit for charging the battery with electric power from the power receiving unit  23 R or  23 L, by which the battery  22  is rechargeable. In this case, the battery  22  may be configured to supply stored electric power to the electronic device  21 . 
     The cart body  11  includes a basket  12  for storing articles such as goods and packages. The basket  12  is supported by a frame  14  provided with four casters  15  ( 15  Fr,  15 Fl,  15 Rr,  15 Rl). Four casters  15  are provided at the 4 corners of the lower part of the frame  14 . Each caster  15  ( 15 Fr,  15 Fl,  15 Rr,  15 Rl) has a wheel  13  ( 13 Fr,  13 Fl,  13 Rr,  13 Rl) that rotates in the direction of movement. The cart body  11  is moved by rolling the wheels  13  of each caster  15  along on a floor. Each caster  15  is configured so that the wheels  13  can be freely rotated to face any direction. Thus, the cart body  11  can freely move in different directions. 
     A handle  16  is provided on one side of the basket  12 . The handle  16  can be gripped by the user. The user grasps the handle  16  while moving the cart body  11 . In this example, the direction in which the basket  12  is pushed by user on the handle  16  side of the basket  12  is assumed to be the forward direction for the cart  1 . A wheel  13 Fr supported by the caster  15 Fr is thus a right front wheel, and a wheel  13 Fl supported by the caster  15 Fl is a left front wheel. A wheel  15 Rr supported by the caster  13 Rr is a right rear wheel, and a wheel  13 Rl supported by the caster  15 Rl is a left rear wheel. 
     A lower portion of the frame  14  provided at the four corners where the four casters ( 15 Fr,  15 Fl,  15 Rl,  15 Rr) are respectively provided narrows toward the forward direction end and is wider at the backward direction side. Therefore, the width between casters  15 Fr and  15 Fl supporting the front wheels is narrower than the width between casters  15 Rr and  15 Rl supporting the rear wheels. Thus, when a plurality of carts are stored in a front-to-back manner, the frame  14  of the rear cart can be housed substantially within the frame  14  of the preceding cart in the storage stack. 
     In this description, the side of the basket  12  opposite the handle  16  side is referred to as a front side, and the other side (the handle  16  side) is referred to as a back side. The basket  12  has an openable side  12   a  at the back side of the basket  12 . The openable side  12   a  swings at point on an upper end side of the openable side  12   a  to open and close. The basket  12  narrows in width towards the front side. Thus, when multiple carts  1  are pushed together (referred to as “stacked” or “nested”) in a front-to-back manner, the openable side  12   a  of a preceding cart is pushed up (open) by the front end of the next cart  1  added to the stack and portions of the stacked carts  1  are overlapped with each other. 
     The electronic device  21  is attached to the cart body  11 . In the example configuration shown in  FIG. 1 , the electronic device  21  is provided with a battery  22  and is attached to the handle  16 . The electronic device  21  is driven by electrical power from the battery  22 . In this example, the electronic device  21  is an information terminal such as a tablet computer for providing information to the cart user, or a commodity reader for acquiring information about a commodity selected and scanned by the user. The electronic device  21  may be also or instead be a charging device for charging a portable terminal (for example, a cellular phone, a smartphone, a digital camera, or the like), provided by the user or the like, using the electric power from the battery  22 . 
     In the configuration example shown in  FIG. 1 , the electronic device  21  is a tablet terminal  21 A and a commodity reader  21 B. The tablet terminal  21 A is a computer having a display unit provided with a touch panel. The tablet terminal  21 A is provided with a display portion directed toward a user who is positioned on the handle  16  side of the cart  1 . The tablet terminal  21 A displays information of a commodity (product) that has been read by the commodity reader  21 B. In some examples, the tablet terminal  21 A may also perform a settlement process (e.g., purchase of commodities via a credit card or the like) on the commodity or commodities that have been read by the commodity reader  21 B. 
     The commodity reader  21 B is an apparatus for reading information from a commodity. The commodity reader  21 B may itself have a display unit that displays information about a commodity that has been scanned by the user. In this example, the commodity reader  21 B is an RFID tag reader for reading RFID tags attached to commodities as those tagged commodities are being put in the basket  12  by the user. The commodity reader  21 B may also track the removal of tagged commodities from the basket  12 . Also, the commodity reader  21 B may, in addition to or instead of an RFID tag reader, be a scanner for reading commodity identification information such as a barcode attached to the commodity. 
     The electronic device  21  may be provided with an interface device (e.g., a dock) for connecting a portable terminal (a smartphone, a tablet terminal, or the like) provided by the user. Such a user-provided portable terminal may be used in place of a store-provided tablet terminal  21 A. The user-provided portable terminal connected to the interface device may perform substantially the same processing as that of the tablet terminal  21 A described above. The interface device may charge the user-provided portable terminal. The interface device may include a battery  22  or may be connected to a battery  22  provided separately. 
     In the present embodiment, power receiving units  23 R,  23 L are attached to the cart  1 . In the configuration example shown in  FIG. 1 , two power receiving unit  23   r,    23   l  are attached to cart body  11 . The power receiving unit  23 R is attached to the right side of the cart body  11 , and the power receiving unit  23 L is attached to the left side of the cart body  11 . The two power receiving units  23 R,  23 L have receiving coils that receive power from a transmitting coil. 
     In  FIG. 1 , the receiving coil of power receiving unit  23 R is attached to the outer side on the right side face of cart body  11 . The power receiving unit  23 R is provided above the rear wheel  13 Rr with the power receiving surface of the receiving coil facing towards the right and substantially perpendicular to the floor. According to the configuration shown in  FIG. 1 , the receiving coil of the power receiving unit  23 R can receive power output from a transmitting coil disposed on the right side of the cart body  11  when the cart  1  is housed in the storage position. 
     In the configuration example shown in  FIG. 1 , the receiving coil of power receiving unit  23 L is attached to the outer side on the left side surface of cart body  11 . The power receiving unit  23 L is provided above the rear wheel  13 Rl with the power receiving surface of the receiving coil facing to the left and substantially perpendicular to the floor. According to the configuration shown in  FIG. 1 , the receiving coil of the power receiving unit  23 L can receive power output from a transmitting coil disposed on the left side of the cart body  11  when the cart  1  is housed in the storage position. 
     The present disclosure is not limited to a configuration in which a power receiving system includes a plurality of power receiving units, nor is the present disclosure limited to a cart  1  configuration including only two receiving coils or only one on the left side or only one on the right side. In general, so long as at least two receiving coils of different carts do not overlap with each other when two carts are stored together (stacked). For example, in some examples, a receiving coil may be provided on either of the left and right sides of the carts  1 , and another receiving coil may be provided on the bottom surface of the cart body  11  of each cart  1 . Two receiving coils may be provided on each cart  1  in two different positions such as on one side (left/right) and on the bottom side. 
     In the present embodiment, two power receiving units  23 R and  23 L mounted on each cart  1  are able to receive electric power via either one of them. As will be described later, a power transmitting system transmits power from a transmitting coil disposed on one side of each cart  1  when housed in the storage position. Correspondingly, in each cart  1 , a receiving coil of the power receiving unit facing the transmitting coil is enabled, and a receiving coil of the power receiving unit on the side where the transmitting coil is not disposed is disabled. 
     The power receiving coil of power receiving unit  23  opposite the transmitting coil provides power to electronic device  21  or battery  22 . In contrast, disabled receiving coils of the cart  1  will not adversely affect the contactless power transmission from adjacent transmitting coils disposed opposite to the other receiving coil. The configuration of the control system of a power receiving system including the two power receiving units  23  will be described below. 
     Next, the configuration of the power supply system according to the first embodiment will be described. 
       FIG. 2  is a perspective view showing a state in which carts  1  mounted with a power receiving system are housed at a storage position equipped with a power supply system according to the first embodiment. 
     Each cart  1  carrying a power receiving system  20  is housed at a predetermined storage position (also referred to as a cart storage location). In  FIG. 2 , two carts  1  ( 1 A,  1 B) are housed at a storage position, but, in general, more than two carts  1  can be housed in a nested manner (stacked) at the storage position. When a plurality of carts  1  are nested together, the receiving coil in each cart  1  is at a predetermined position so as not to overlap with the receiving coils of the other adjacently stacked carts. 
     The housing position is provided with four guide rails ( 31 Rr,  31 Rl,  31 Fr,  31 Fl) for guiding the respective wheels ( 13 Rr,  13 Rl,  13 Fr,  13 Fl) of the four casters ( 15 Rr,  15 Rl,  15 Fr,  15 Fl) of each cart  1 . Guide rails ( 31 Rr,  31 Rl,  31 Fr,  31 Fl) are guide devices for guiding each cart  1  to a predetermined position in a cart storage location. In the example shown in  FIG. 2 , one pair of guide rails  31 Rr,  31 Rl correspond to the rear wheels of the cart  1  and one pair of guide rails  31 Fr,  31 Fl correspond to the front wheels of the cart  1  are provided. However, the guide rails are not limited to the configuration in which the four guide rails are arranged, and, in general, any number of guide rails may be utilized as long as each cart  1  is guided to a separate predetermined position in the cart storage location. For example, the arrangement of guide rails may omit any one or two of the four depicted guide rails  31 Rr,  31 Rl,  31 Fr, and  31 Fl. 
     In the storage position, each cart  1  is housed in a state where a wheel is moved along a guide rail and the front and rear carts in the stack (nesting) overlap each other. The front side of the basket  12  in the cart  1  is, as described, an openable side  12   a  which swings opened and closed. Further, the basket  12  is formed to have a smaller surface on the distal end side than the proximal end side on which the openable side  12   a  is formed. Thus, when the front side of the basket  12  of the rear cart  1 B is pushed into the openable side  12   a  of the cart  1 A, the openable side  12   a  of the cart  1 A is pushed towards the front direction and upward. When the rear cart  1 B is pushing up the openable side  12   a  of the front cart  1 A, the basket  12  of the cart  1 B overlaps with the basket  12  of the cart  1 A. 
     The frame  14  of each cart  1  is formed such that its back end side is wider than its front end side. Therefore, casters  15 Fr,  15 Fl supporting front wheels  13 Fr,  13 Fl of cart  1  closer in to each other than casters  15 Rr,  15 Rl supporting rear wheels  13 Rr,  13 Rl. Thus, when a plurality of carts  1  are stacked, the frame  14  of the rear cart  1 B overlaps with the frame  14  of the front cart  1 A. 
     As described above, a plurality of carts  1  ( 1 A,  1 B) are housed overlapped with each other when housed in a cart storage location. The amount of possible overlap of each cart  1  depends on the particular shapes of the frame  14  and the basket  12  of each cart  1 . When the interval between the front and rear of each cart  1  stored in a stacked state at the storage position is a predetermined distance, the interval at which the receiving coil of each power receiving unit  23 R,  23 L of each cart  1  is also at a predetermined distance. However, in this example, it is assumed that power receiving units  23 R of stacked carts  1  do not overlap with each other. In this embodiment, it is assumed that the receiving coil of each cart  1  will be adjacent to the receiving coil of the adjacent carts  1  in the stack, as depicted in  FIG. 2 . 
     Power transmitting units  32 R,  32 L supply power that can be received by power receiving units  23 R,  23 L in a non-contact manner. Each power transmitting unit  32 R,  32 L has a transmitting coil and a transmitting circuit. The transmitting coil of a power transmitting unit  32 R,  32 L is provided at a position that opposes a receiving coil of a power receiving unit  23 R,  23 L in each cart  1  when housed in the storage position. In the power supply system according to the first embodiment, transmitting coils of power transmitting unit  32 R,  32 L are alternately arranged on the right side and the left side of the carts  1  housed at the storage position as shown in  FIG. 2 . 
       FIG. 3  is a diagram illustrating a relationship between a receiving coil and a transmitting coil provided in each cart  1  in the power supply system according to the first embodiment, from a perspective looking downwards from above the cart storage location. 
       FIG. 3  schematically shows the positional relationship between the receiving coils of five carts  1  housed at the storage position and the transmitting coils at the storage position. In the power transmitting system according to the first embodiment, a transmitting coil (first transmitting coil) of a power transmitting unit  32 R is disposed on the right side of every other cart  1  (the odd numbered positions at the storage position. A transmitting coil (second transmitting coil) of a power transmitting unit  32 L is disposed on the left side surface of every other cart  1  (the even numbered positions) at the storage position. 
     In the example shown in  FIG. 3 , the transmitting coil of a power transmitting unit  32 R is arranged to face the receiving coil of a power receiving unit  23 R provided on the right side surface of the carts  1  at the first, third, and fifth positions in the stack. The transmitting coil of a power transmitting unit  32 L is arranged to face the receiving coil of a power receiving unit  23 L provided on the left side surface of carts  1  at the second and fourth positions in the stack. Accordingly, the power transmitting system is configured such that the transmitting coils are alternately arranged along both sides of the plurality of carts at the storage position. 
     Next, the configuration of the control system of the power supply system according to the first embodiment will be described. 
       FIG. 4  is a block diagram showing an example of a configuration of a control system in a power supply system according to a first embodiment. 
     The power supply system is a system for transmitting electric power in a non-contact manner, and comprises a power receiving system  20  and a power transmitting system  30 . The power receiving system  20  is a system in which a power receiving unit  23 R,  23 L receives power in a non-contact manner, and supplies the received power to the battery  22  or the electronic device  21 . The power transmitting system  30  is a system for transmitting power to the power receiving units  23 R,  23 L mounted on each cart  1  in a non-contact manner. The power transmitting system  30  includes a plurality of power transmitting units  32 R,  32 L disposed along guide rails at the storage position. Direct current (DC) power is supplied to each power transmitting unit  32 R,  32 L via an alternating (AC) adapter or the like which is connected to a commercial power supply. 
     In the configuration shown in  FIG. 4 , each power transmitting unit  32  ( 32 R,  32 L) in power transmitting system includes a transmission circuit  48  ( 48 R or  48 L, respectively) and a transmitting coil  47  ( 47 R or  47 L, respectively). The power transmitting unit  32  may be provided with a control circuit for controlling each circuit. The control circuit may be implemented, for example, as a processor for executing the arithmetic processing and a memory for storing the program executed by the processor. The power transmitting unit  32  may include a power supply circuit for converting a voltage from an external AC power supply to a voltage suitable for the operation of each circuit. Further, the power transmitting unit  32  may include a display unit such as an indicator switching the displayed colors according to the present operating state. 
     Each transmission circuit  48  generates power that is output from a transmitting coil  47 . The transmission circuit  48  supplies the generated power to the transmitting coil  47  for transmission. The transmission circuit  48  generates AC power by switching DC power supplied from a power supply. A transmitting coil  47  outputs power receivable by a corresponding power receiving unit  23 R,  23 L in response to the power supplied from the transmission circuit  48 . The transmitting coil  47  has a planar surface for transmitting electric power. The transmitting coil  47  is disposed to face the power receiving surface of a power receiving unit  23 R,  23 L. 
     The transmitting coil  47  is connected in series or parallel with a capacitor to form a resonant circuit (transmission resonant circuit). The transmitting coil  47  in the power transmitting resonance circuit generates a magnetic field corresponding to the AC power provided from the transmission circuit  48 . The transmitting coil  47  may be configured as, for example, a wound structure in which an insulated electric wire is wound in coil or the like, or may be as a coil pattern on a printed circuit board or the like. 
     Next, a description will be given of the power receiving system  20 . 
     In the example configuration shown in  FIG. 4 , a power receiving system  20  mounted on each cart  1  includes two power receiving units  23 R,  23 L and a controller  40 . Each power receiving unit  23 R,  23 L has a receiving coil ( 45 R or  45 L, respectively and a shorting circuit  46  ( 46 R,  46 L). The controller  40  includes a switching circuit  41 , a receiving circuit  42 , and a control circuit  43 . Also, the power receiving system  20  may be provided with a display for displaying an operating state. 
     In the example configuration shown in  FIG. 4 , power receiving unit  23 R includes receiving coil  45 R and shorting circuit  46 R, and power receiving unit  23 L includes receiving coil  45 L and shorting circuit  46 L. 
     Each power receiving coil  45 R,  45 L includes a coil to receive power transmitted from a transmitting coil  47 R,  47 L. A coil for power reception may be configured as a wound structure in which insulated electric wires are wound, or may a coil pattern formed on a printed circuit board. For example, a receiving coil  45 R,  45 L comprises a resonant circuit (a power receiving resonant circuit) including a capacitor in series or in parallel. When shorting circuit  46 R,  46 L is not short-circuited, each receiving coil  45 R,  45 L electromagnetically couples with an adjacent transmitting coil  47  to generate an induced current by the magnetic field output from transmitting coil  47 . Thus, receiving coil  45 R,  45 L receives power from transmitting coil  47  as AC power. 
     Each power receiving coil  45 R,  45 L functions as an AC power supply while receiving AC power from transmitting coil  47 . When the magnetic field resonance system is used for the power transmission, the self-resonant frequency of the power receiving resonance circuit (the active one of receiving coil  45 R or  45 L) is substantially the same as the frequency at which the power transmitting unit  32 R or  32 L transmits power. As a result, power transmission efficiency is improved when the transmitting coil ( 45 R or  45 L) and the transmitting coil  47  are electromagnetically coupled to each other. 
     The receiving coils  45 R,  45 L are configured so that a power receiving surface for receiving electric power is flat. The receiving coils  45 R,  45 L are installed in the cart body  11  in a position and a direction corresponding to the transmission surface of a respective transmitting coil  47  at the housing position. In the configuration example shown in  FIG. 2 , each receiving coil  45 R,  45 L is disposed on a side surface of the cart body  11  with the power receiving surface substantially perpendicular to the floor surface. Accordingly, each receiving coil  47 R or  45 L of each cart  1  faces the power transmitting surface of a transmitting coil  47  at the storage position which is also substantially perpendicular to the floor surface. 
     In the configuration shown in  FIG. 4 , a shorting circuit  46 R or  46 L is respectively connected to each receiving coil  45 R,  45 L. Each shorting circuit  46 R,  46 L is a circuit for disabling reception of power from the transmitting coils  47 . Shorting circuits  46 R,  46 L disable receiving coils  45 R,  45 L by shorting the receiving coils. More particularly in this example, the shorting circuits  46 R,  46 L disable the respective receiving coils  45 R,  45 L by shorting the receiving coils to ground. The shorting circuit  46 R,  46 L short-circuits and disables the respective receiving coil  45 R,  45 L in response to a control signal from a control circuit  43  of a controller  40 . 
     Each controller  40  includes a switching circuit  41 , a receiving circuit  42 , and a control circuit  43 . In the configuration example shown in  FIG. 4 , the controllers  40  are provided separately from the power receiving unit  23 R and the power receiving unit  23 L in each power receiving system  20 . A controller  40  is attached to each cart  11  main body. In other examples, the controller  40  may be integrated with either the power receiving unit  23 R or the power receiving unit  23 L. The switching circuit  41  of the controller  40  is connected to receiving coils  45 R and  45 L. The control circuit  43  of each controller  40  is also connected to shorting circuit  46 R of power receiving unit  23 R and shorting circuit  46 L of power receiving unit  23 L. 
     A receiving coil  45 R,  45 L, which is not shorted by the shorting circuit  46 , can receive power from the transmitting coil  47 . An active one of the receiving coils  45 R,  45 L supplies power to the receiving circuit  42  via the switching circuit  41 . The switching circuit  41  connects either the receiving coil  45 R or the receiving coil  45 L to the receiving circuit  42 . The switching circuit  41  includes a switching circuit for turning on the appropriate one of the receiving coil  45 R or the receiving coil  45 L. 
     The receiving circuit  42  converts power received from the receiving coil  45 R or receiving coil  45 L as connected by the switching circuit  41  into electric power that can be supplied to the battery  22  or the electronic device  21 . For example, the receiving circuit  42  rectifies the received power supplied from the receiving coils  45 R,  45 L, and converts this received power into a direct current. The receiving circuit  42  is realized by a circuit including a rectifying bridge constituted by diodes. In this example, a pair of input terminals of the rectifier bridge are connected to a receiving coil  45 R or  45 L via switching circuit  41 . The receiving circuit  42  in this example full-wave rectifies the received power and outputs DC power from the pair of output terminals. 
     The control circuit  43  controls the operation of each circuit in the power receiving system  20 . The control circuit  43  may be comprised by a microcomputer or the like. The control circuit  43  outputs a signal indicating which one of shorting circuit  46 R or  46 L is to be shorting the respective one of the receiving coils  45 R or  45 L. Thus, the control circuit  43  performs control to short-circuit the receiving coil  45 R or  45 L which is not to receive power. The control circuit  43  also outputs a signal indicating to switching circuit  41  which one of receiving coil  45 R or  45 L is to receive power. Thus, control circuit  43  functions to connect to receiving circuit  42  to the active one of the two receiving coils  45 R and  45 L. 
     The control circuit  43  can operate to identify which one of receiving coil  45 R or  45 L is actually receiving power from a transmitting coil  47  when the cart  1  is housed at the storage position. The control circuit  43  can switch the switching circuit  41  as appropriate based on detecting which receiving coil  45 R,  45 L has received power from transmitting coil  47 . 
     When the active receiving coil  45 R or  45 L is identified, the control circuit  43  operates to short-circuit the receiving coil  45 L or  45 R that is not to receive power by control of the corresponding shorting circuit  46 L or  46 R. Control circuit  43  also sets switching circuit  41  to connect the active receiving coil  45 R or  45 L to receiving circuit  42 . In this context, “active” refers to a receiving coil that is presently receiving power from a transmitting coil. 
     When the receiving coil  45 R receives power from the transmitting coil  47 R, control circuit  43  shorts receiving coil  45 L with shorting circuit  46 L. The receiving coil  45 L is shorted and the control circuit  43  connects the receiving coil  45 R to the receiving circuit  42  by way of the switching circuit  41 . Thus, the control circuit  43  can realize the control for disabling a non-active receiving coil  45 R or  45 L for which no transmitting coil  47  is adjacent. 
     As described above, according to the power supply system of the first embodiment, when the cart  1  is housed at the cart storage position (see  FIG. 2 ), the receiving coil ( 45 R or  45 L) which is not adjacent to a transmitting coil  47  is short-circuited, and it thus is possible to prevent coupling between adjacent receiving coils ( 45 R or  45 L) on different carts  1  when multiple carts are stacked at the cart storage position. As a result, the power receiving system  20  provided in the carts  1  housed at the storage position can more efficiently receive power from the power transmitting system  30  at the storage position. 
     Modification of the First Embodiment 
     Next, a modification of the first embodiment will be described. 
     In the first embodiment, a receiving coil  45 R or  45 L which receives power from the transmitting coil  47  is identified, and the receiving coil  45 R or  45 L which does not receive power is short-circuited, but determining which receiving coil  45 R or  45 L is to be short-circuited may be specified by another method. For example, in the first modification, it is assumed that the power receiving system  20  mounted on each cart  1  has a radio unit  50 . With this modification, power receiving system  20  can acquire information indicating which receiving coil  45  or  45 L will be active by signal or communication from a power receiving system  20  of the cart  1  that has already been stored at the storage position at the stacking position immediately ahead of the present cart  1  being added to the stack, and thus determines which receiving coil  45  or  45 L is to be short-circuited (non-active) according to such a communication from the already stacked/stored cart  1 . 
       FIG. 5  is a block diagram showing an example of a configuration of a power receiving system  20  according to a modification of the first embodiment. 
     In the modification shown in  FIG. 5 , a radio unit  50  (also referred to as a wireless communication circuit  50 ) is provided in the power receiving system  20  according to the first embodiment. Since configurations other than the radio unit  50  are similar to those of the first embodiment described above, detailed description thereof will not be repeated. 
     The radio unit  50  has a function of communicating with a radio unit  50  mounted on another cart  1 . For example, the radio unit  50  of a cart  1  communicates with a radio unit  50  on a cart  1  housed in front of the cart  1  at the storage position. Thus, the control circuit  43  can acquire information via radio unit  50  indicating whether an already stored cart  1  is receiving power on receiving coil  45 R or  45 L. The control circuit  43  controls to receive power at the receiving coil ( 45 R or  45 L) on the side opposite to the active receiving coil  45 R or  45 L on the already stacked cart  1 . 
     In another example, the radio unit  50  may have a function of wirelessly communicating with a power transmitting unit  32  ( 32 R,  32 L) of power transmitting system  30 . In this case, transmitting system  30  may be provided with a radio unit for performing wireless communication. Thus, control circuit  43  of power receiving system  20  may control elements based on setting information obtained by communication with a power transmitting unit  32 . The wireless communication between power receiving system  20  and power transmitting unit  32  may be realized by, for example, a wireless communication circuit that performs wireless communication at the same frequency as the frequency used for power transmission by using load modulation or the like. 
     As described above, the power supply system according to the modification of the first embodiment and the first embodiment includes a power receiving system  20  to be attached to a cart  1  and a power transmitting system  30  to be disposed at a storage position for the cart  1 . The power receiving system  20  has a first receiving coil ( 23 R or  23 L) attached to a first location on the cart  1  and a second receiving coil ( 23 L or  23 R) attached to a second location on the cart  1 . The power transmitting system  30  includes a plurality of transmitting coils  47  alternately positions that will be opposite to the first places on stacked carts  1  at the storage position and second places on stacked carts  1  at the storage position. The carts  1  operate to short-circuit the one of the receiving coils ( 23 R or  23 L) that is not adjacent to a transmission coil  47  of the power transmitting system at the storage position. 
     Accordingly, in the power supply system according to the first embodiment, when a cart  1  is housed in the storage position, a receiving coil ( 23 R or  23 L) for which a transmitting coil  47  is not provided adjacent thereto can be short-circuited (disabled), and it is thus possible to prevent the inadvertent coupling between adjacent receiving coils ( 23 R or  23 L) on stacked carts  1 . As a result, the power receiving systems  20  can more efficiently receive power from a power transmitting system  30  at the storage position. 
     Second Embodiment 
       FIG. 6  is a perspective view showing a configuration example of a power receiving system  20 ′ and a power transmitting system  30 ′ constituting the power supply system according to the second embodiment. 
     The arrangement shown in  FIG. 6  differs from the configuration shown in  FIG. 2  in the disposition of power transmitting units at the storage location. In the configuration shown in  FIG. 6 , power transmitting system  30 ′ has power transmitting units  32 R′,  32 L′ at each cart storage position at the storage location. That is each cart storage position as a power transmitting unit  32 R′ and  32 L′ rather than having power transmitting units  32 R and  32 R alternating along the stacking direction of carts  1  at the storage location (see  FIG. 2 ). Other than positioning and inclusion of power transmitting units  32 R′ and  32 L′ at the storage position of the carts  1 , the second embodiment is similar to the first embodiment. 
     Each cart  1 A,  1 B is provided with power receiving units  23 R′,  23 L′ on respective side surfaces of the cart body  11 , similar to the configurations shown in  FIGS. 1 and 2 . The two power receiving units  23 R′,  23 L′ constitute a power receiving system  20 ′ (see  FIG. 8 ) which is mounted on each cart  1 . Each cart  1 A,  1 B when housed in a nested state at a storage position (a cart storage location) as described in the first embodiment, positions the power receiving units  23 R′,  23 L′ at predetermined positions along storage position (see  FIG. 7 ). 
     In the power transmitting system  30 ′ according to the second embodiment, power transmitting units  32 R′ are arranged side by side along the guide rail  31 Rr on the outer side of the guide rail  31 Rr. Power transmitting units  32 L′ are also arranged side by side along the guide rail  31 Rl on the outer side of the guide rail  31 Rl. Power transmitting coils of the power transmitting unit  32 R′ and transmitting coils of the power transmitting unit  32 L′ are arranged at intervals corresponding to the distance between the carts housed at the housing position (storage location). Power transmitting unit  32 R′ and power transmitting unit  32 L′ are respectively located on the left and right sides of each individual cart  1  housed at the storage position function. The power transmitting system  30 ′ is a system for supplying power to a plurality of carts  1  housed at a cart storage location. 
     The power transmitting units  32 R′,  32 L′ supply power that can be received by a corresponding power receiving unit  23 R′,  23 L′ in a non-contact manner. Each power transmitting unit  32 R′,  32 L′ has a transmitting coil and a transmission circuit, etc. similarly to described in the first embodiment. In the power transmitting system  30 ′ according to the second embodiment, transmitting coils of the power transmitting unit  32 R′ and transmitting coil of the power transmitting unit  32 L′ are disposed on both the left and right sides of each cart  1  stacked at the storage position. In the power transmitting system  30 ′, the power transmitting unit  32 R′ and the power transmitting unit  32 L′ corresponding to the a cart  1  are controlled as one set of power transmitting devices for a respective power receiving systems  20 ′ of a stacked cart  1 . 
       FIG. 7  is a diagram illustrating a positional relationship between a power transmitting units  32 R′,  32 R′ and each cart  1  according to the second embodiment.  FIG. 7  schematically shows the positional relationship between the receiving coils of five carts  1  housed/stacked at the storage position and the transmitting coils at the storage position. In the power transmitting system according to the second embodiment, transmitting coils of the power transmitting units  32 R′ are arranged on the right side of the cart body  11  and transmitting coils of the power transmitting units  32 L′ are disposed on the left side of the cart body  11 , for all carts at the storage position. 
     In the example shown in  FIG. 7 , a power transmitting unit  32 R′ and a power transmitting unit  32 L′ corresponding to the each cart  1  are controlled such that either one of the power transmitting unit  1  R′ or the power transmitting unit  1  L′ performs the power transmission. For example, a plurality of power transmitting units  32 R′ arranged side by side along the right side of the storage position are controlled so as to transmit power to every other one of the carts  1  stacked at the storage position. 
     In other words, among a plurality of transmitting coils  32 R′, power is transmitted to every other cart  1 , and not every transmitting coil  32 R′ is active, with non-active transmitting coils  32 R′ being short-circuited. On the other hand, transmitting coils  32 L′ op opposite an active transmitting coil  32 R′ do not transmit power (is short-circuited) and only transmitting coils  32 L′ disposed opposite a non-active transmitting coil  32 R′ will be active. 
     A transmitting coil  75 R (or  75 L) of power transmitting unit  32 R′ (or  32 L′) that is not active is short-circuited based on control by a control circuit  73 . Opposed pairs of power transmitting units  32 R′ and  32 L′ are controlled so only one of the pair is active at a time. The other of the pair is non-active, that is short-circuited when other one of the pair of power transmitting units  32 R′ and  32 L′ transmits power. That is, in the second embodiment, the transmitting coils arranged at the left ( 75 L) and right ( 75 R) sides are controlled such that only every other coil along a side is active the other directly adjacent coils on the same side are short-circuited (non-active). 
     Next, the configuration of the control system of the power supply system according to the second embodiment will be described. 
       FIG. 8  is a block diagram showing an example of a configuration of a control system in a power supply system according to a second embodiment. 
     As shown in  FIG. 8 , a power transmitting unit  32 R′ a power transmitting unit  32 L′, and controller  70  form a power transmitting device corresponding to the power receiving system  20 ′ of a cart  1 . The power transmitting system  30 ′ can perform power transmission to a plurality of carts  1  housed at a storage position. The power transmitting unit  32 R′ and the power transmitting unit  32 L′ corresponding to a single cart  1  are controlled by a single controller  70 . In power transmitting system  30 ′, each controller  70  is communicatively coupled to each other controller  70 . 
     In the configuration shown in  FIG. 8 , a power transmitting unit  32 R′ includes a transmitting coil  75 R, and shorting circuit  76 R and power transmitting unit  32 L′ includes a transmitting coil  75 L, and a shorting circuit  76 L. The controller  70  includes a switching circuit  71 , a transmission circuit  72 , and a control circuit  73 . 
     In the example configuration shown in  FIG. 8 , power transmitting unit  32 R′ includes transmitting coil  75 R and shorting circuit  76 R. The power transmitting unit  32 L′ has a transmitting coil  75 R and a shorting circuit  76 R. The transmitting coils  75 R,  75 L output power that can be received by the receiving coils  23 R′,  23 L′ of the power receiving units  20 ′. The transmitting coils  75 R,  75 L are formed so that each has a power transmitting surface for transmitting electric power that is flat. The transmitting coil  75 R,  75 L is disposed so that it faces a receiving coil  23 R′,  23 L′ in a state that such that it is substantially perpendicular to the floor surface. For example, a transmitting coil  75 R,  75 L constitutes a transmission resonant circuit when connecting in series or in parallel with a capacitor. For example, a coil for electric power transmission may be configured as a wound structure in which an insulated electric wire is wound in a pattern or may be a coil pattern formed as wiring pattern on a printed circuit board or the like. Active transmitting coils  75 R,  75 L generate a magnetic field corresponding to AC power from the transmission circuit  72 . 
     The transmitting coils  75 R,  75 L are at a position opposite a receiving coil  23 R′,  23 L′ on a cart  1  when the cart  1  is at a housing position. 
     In the configuration shown in  FIG. 8 , a shorting circuit  76 R or  76 L is respectively connected to each transmitting coil  75 R or  75 L. Each shorting circuit  76 R,  76 L is a circuit for disabling a corresponding transmitting coil  75 R,  75 L. For example, the shorting circuit  76 R may disable a transmitting coil  75 R by grounding the transmitting coil  75 R. The shorting circuit  76 R,  76 L shorts and disables a transmitting coil  75 R,  75 L in response to a control signal from the control circuit  73 . 
     Each controller  70  includes a switching circuit  71 , a transmission circuit  72 , and a control circuit  73 . In the configuration example shown in  FIG. 8 , the controller  70  is provided separately from the power transmitting unit  32 R′ and the power transmitting unit  32 L′. In other examples, the controller  70  may be integrated with either the power transmitting unit  32 R′ or the power transmitting unit  32 L′. The switching circuit  71  in the controller  70  connects to the transmitting coil  75 R and the transmitting coil  75 L. The control circuit  73  of the controller  70  is connected to the shorting circuit  76 R of the power transmitting unit  32 R′ and the shorting circuit  76 L of the power transmitting unit  32 L′. 
     The transmitting coil  75 R,  75 L, which is not shorted by a corresponding shorting circuit  76 R or  76 L, outputs power. The active transmitting coil  75 R,  75 L outputs power supplied from transmission circuit  72  connected via a switching circuit  71 . The switching circuit  71  connects either one of the transmitting coil  75 R or the transmitting coil  75 L to the transmission circuit  72 . The switching circuit  71  can turn on either of the transmitting coil  75 R or the transmitting coil  75 L. 
     The control circuit  73  controls the operation of the power transmitting system  30 ′. The control circuit  73  may comprise, for example, a microcomputer or the like. The control circuit  73  outputs a signal indicating a shorting circuit  76 R or  76 L is to short circuit one of a transmitting coil  75 R or  75 L. Thus, the control circuit  73  short-circuits the non-active one of transmitting coil  75 R or  75 L. The control circuit  73  outputs a signal to the switching circuit  71  indicating which one of the transmitting coil  75 R or  75 L is to be active for power transmission to the power receiving system  20 ′. Thus, the control circuit  73  controls which one of transmitting coil  75 R or  75 L is to be connected to the transmission circuit  72  from among the two transmitting coils  75 R and  75 L. 
     The control circuit  73  specifies which transmitting coil  75 R or  75 L. is to be used for actually transmitting power. The control circuit  73  controls which transmitting coil  75 R or  75 L is to be active such that adjacent transmission coils  75 R (and transmission coils  75 L) are not active. The control circuit  73  communicates with at least one other control circuit  73  for an adjacent cart position of the power transmitting system  30 ′ so adjacent transmitting coils  75 R (and transmitting coils  75 ) are not active. 
     Control circuit  73  also functions to short the non-active one of the transmitting coils  75 L,  75 R by controlling each of the shorting circuits  76 L,  76 R as appropriate. The control circuit  73  also sets the switching circuit  71  to connect the active one of the transmitting coil  75 R or  75 L to the transmission circuit  72 . For example, when power is to be transmitted from transmitting coil  75 R, control circuit  73  shorts transmitting coil  75 L by using shorting circuit  76 L and connects the transmitting coil  75 R to the transmission circuit  72  by using the switching circuit  71 . 
     Next, a description will be given of the power receiving system  20 ′. 
     In the example configuration shown in  FIG. 8 , the power receiving system  20 ′ that is mounted on each cart  1  includes two power receiving units ( 23 R′,  23 L′) and a controller  60 . Each power receiving unit  23 R′,  23 L′ includes a receiving coil. The controller  60  includes a switching circuit  61  and a power receiving circuit  62 . 
     In  FIG. 8 , receiving coils  23 R′,  23 L′) receive power transmitted from transmitting coils  75 R,  75 L. For example, each receiving coil  23 R′,  23 L′ is connected in series or in parallel with a capacitor. The receiving coil  23 R′,  23 L′ is electromagnetically coupled to an active transmitting coil  75 R,  75 L, and generates an induced current by the magnetic field output from the active transmitting coil  75 R,  75 L. Thus, the receiving coil  23 R′,  23 L′ receives power from the transmitting coil  75 R,  75 L as AC power. 
     In the example configuration shown in  FIG. 8 , each controller  60  includes a switching circuit  61  and a power receiving circuit  62 . Also, the present disclosure relates to a method of manufacturing the same. In  FIG. 8 , the controller  60  is provided separately from the power receiving unit  23 R′ and the power receiving unit  23 L′. However, the controller  60  may be integrally provided with either the power receiving unit  23 R′ or the power receiving unit  23 L′. 
     The switching circuit  61  can be controlled to connect the power receiving circuit  62  to either the receiving coil  23 R′ or the receiving coil  23 L′. 
     The receiving circuit  62  converts power received via the receiving coil  23 R′ or receiving coil  23 L′ to power that can be supplied to battery  22  or electronic device  21 . For example, the receiving circuit  62  rectifies received power to convert the received power to direct current, similarly to the receiving circuit  42 . 
     In general, the configuration of the power receiving system  20 ′ may be configured in a manner similar to that as shown in  FIG. 4  or  FIG. 5  (e.g., a radio unit  50  may be incorporated). That is, in the power receiving system  20 ′ according to the second embodiment, a shorting circuit may be connected to each receiving coil, and a control circuit ( 73 ) for controlling the shorting circuits  76 R,  76 L and the switching circuit ( 71 ) may be provided. Thus, a receiving coil  76 R or  76 L which does not receive power can be short-circuited to be disabled. 
     As described above, the power supply system according to the second embodiment includes a power receiving system  20 ′ to be attached to a cart and a power transmitting system  30 ′ to be disposed at the storage location of the carts  1 . The power receiving system has a first receiving coil ( 23 R′ or  23 L′) attached to a first location of each cart  1  and a second receiving coil ( 23 L′ or  23 R′) attached to a second location of the cart  1 . The power receiving system  20 ′ receives power from a transmitting coil of the power transmitting system  30 ′ at position corresponding to either the first location or the second location on the cart  1 . 
     The power transmitting system  30 ′ has transmitting coils at positions opposite to each first location of all carts  1  that can be housed (stacked) in the cart storage location and also transmitting coils opposite to each second location of all carts  1  housed in the cart storage location. In the power transmitting system  30 ′, transmitting coils are controlled to transmit electric power such that, at most, only every other one of the transmitting coils along a side of the carts  1  housed in the cart storage location are active simultaneously. In addition, in the power transmitting system  30 ′, those transmitting coils that are not active are short-circuited. 
     The power transmitting system according to the second embodiment alternates active and non-active transmitting coils such that adjacent carts  1  are charged on opposite sides of the storage location. As a result, it is possible to inhibit the coupling between coils for adjacent carts  1 . As a result, receiving coils provided in the carts  1  housed at the storage location can more efficiently receive power from transmitting coils of the power transmitting system  30 ′ at the storage location. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the present disclosure. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the present disclosure. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the present disclosure.