PATENT DOCUMENT

Publication Number: US-10483786-B2
Application Number: US-201715473453-A
Country: US
Kind Code: B2

Title: Wireless charging systems with multicoil receivers

Abstract:
A wireless power transmitting device may have an array of transmitting coils to transmit power wirelessly to a wireless power receiving device having an array of wireless power receiving coils. The receiving device may have a rectifier that receives alternating-current signals from the wireless power receiving coils and provides corresponding rectified direct-current voltage signals to a capacitor and other circuitry. The rectifier circuitry may include bridge circuits each of which is coupled between a respective coil in the array of wireless power receiving coils and the capacitor. The wireless power transmitting coils may be arranged in a hexagonally tiled array. The wireless power receiving coils may include first, second, and third coils that are aligned with respective vertices in an equilateral triangle having sides with lengths equal to half of the center-to-center spacing of the hexagonally tiled transmitting coils.

Claims:
What is claimed is: 
     
       1. A portable electronic device that is configured to receive wireless power transmitted from an array of tiled transmitting coils in a wireless power transmitting device, wherein the tiled transmitting coils are characterized by a center-to-center spacing, the portable electronic device comprising:
 a battery; and 
 wireless power receiving circuitry that includes an array of wireless power receiving coils and that includes rectifier circuitry that is configured to rectify alternating-current wireless power signals received by the array of wireless power receiving coils and to provide a corresponding direct-current voltage to the battery, wherein the wireless power receiving coils are laterally spaced from each other in a two-dimensional array, and wherein first, second, and third wireless power receiving coils of the array of wireless power receiving coils are respectively aligned with first, second, and third vertices of an equilateral triangle that has sides with lengths equal to half of the center-to-center spacing. 
 
     
     
       2. The portable electronic device of  claim 1  further comprising a capacitor to which the direct-current voltage is provided. 
     
     
       3. The portable electronic device of  claim 2  wherein the rectifier circuitry includes first, second, and third independently selectable bridge circuits. 
     
     
       4. The portable electronic device of  claim 3  wherein the first bridge circuit is coupled between the first wireless power receiving coil and the capacitor, wherein the second bridge circuit is coupled between the second wireless power receiving coil and the capacitor, and wherein the third bridge circuit is coupled between the third wireless power receiving coil and the capacitor. 
     
     
       5. The portable electronic device of  claim 4  wherein the first bridge circuit, the second bridge circuit, and the third bridge circuit each include a pair of transistors coupled in series across the capacitor. 
     
     
       6. The portable electronic device of  claim 5  further comprising:
 a first capacitor interposed between the first wireless power receiving coil and a node between the pair of transistors in the first bridge circuit; 
 a second capacitor interposed between the second wireless power receiving coil and a node between the pair of transistors in the second bridge circuit; and 
 a third capacitor interposed between the third wireless power receiving coil and a node between the pair of transistors in the third bridge circuit. 
 
     
     
       7. The portable electronic device defined in  claim 1 , further comprising a capacitor to which the direct-current voltage is provided, wherein the rectifier circuitry comprises:
 a first bridge circuit that comprises first and second transistors coupled in series between a first plate of the capacitor and a second plate of the capacitor; 
 a second bridge circuit that comprises third and fourth transistors coupled in series between the first plate of the capacitor and the second plate of the capacitor; and 
 a third bridge circuit that comprises fifth and sixth transistors coupled in series between the first plate of the capacitor and the second plate of the capacitor, wherein the portable electronic device further comprises:
 a first capacitor having a first plate coupled to the first wireless power receiving coil and a second plate coupled to a node between the first and second transistors; 
 a second capacitor having a first plate coupled to the second wireless power receiving coil and a second plate coupled to a node between the third and fourth transistors; and 
 a third capacitor having a first plate coupled to the third wireless power receiving coil and a second plate coupled to a node between the fifth and sixth transistors. 
 
 
     
     
       8. A wireless charging system, comprising:
 a wireless power transmitting device having an array of hexagonally tiled transmitting coils; and 
 a wireless power receiving device having a two-dimensional array of wireless power receiving coils including at least first, second, and third wireless power receiving coils, wherein whenever the first wireless power receiving coil is aligned with any one of the hexagonally tiled transmitting coils, the second and third wireless power receiving coils are not aligned with any of the hexagonally tiled transmitting coils. 
 
     
     
       9. The wireless charging system of  claim 8  wherein the wireless power transmitting device is a wireless charging pad. 
     
     
       10. The wireless charging system of  claim 9  wherein the wireless power receiving device comprises a rectifier having three pairs of transistors coupled respectively to the first, second, and third wireless power receiving coils. 
     
     
       11. The wireless charging system of  claim 8  wherein the hexagonally tiled transmitting coils are characterized by a center-to-center spacing and wherein the first, second, and third wireless power receiving coils are respectively aligned with first, second, and third vertices of an equilateral triangle that has sides with lengths equal to half of the center-to-center spacing. 
     
     
       12. The wireless charging system of  claim 8 , wherein the wireless power receiving device comprises a battery, rectifier circuitry that is configured to rectify alternating-current wireless power signals received by the two-dimensional array of wireless power receiving coils and to provide a corresponding direct-current voltage to the battery, and a capacitor to which the direct-current voltage is provided, wherein the rectifier circuitry comprises:
 a first bridge circuit that comprises first and second transistors coupled in series between a first plate of the capacitor and a second plate of the capacitor; 
 a second bridge circuit that comprises third and fourth transistors coupled in series between the first plate of the capacitor and the second plate of the capacitor; and 
 a third bridge circuit that comprises fifth and sixth transistors coupled in series between the first plate of the capacitor and the second plate of the capacitor, wherein the wireless power receiving device further comprises:
 a first capacitor having a first plate coupled to the first wireless power receiving coil and a second plate coupled to a node between the first and second transistors; 
 a second capacitor having a first plate coupled to the second wireless power receiving coil and a second plate coupled to a node between the third and fourth transistors; and 
 a third capacitor having a first plate coupled to the third wireless power receiving coil and a second plate coupled to a node between the fifth and sixth transistors.

Description:
This application claims the benefit of provisional patent application No. 62/359,064, filed Jul. 6, 2016, which is hereby incorporated by reference herein in its entirety. 
    
    
     FIELD 
     This relates generally to charging systems, and, more particularly, to systems for charging electronic devices. 
     BACKGROUND 
     In a wireless charging system, a wireless charging mat may wirelessly transmit power to a portable electronic device that is placed on the mat. A portable device may have a receiving coil and rectifier circuitry for receiving wireless alternating-current (AC) power from a coil in the wireless charging mat that is overlapped by the receiving coil. The rectifier converts the received AC power into direct-current (DC) power. 
     Charging efficiency may not be as high as desired with this type of wireless charging arrangement. There may also be a relatively large amount of cost and complexity associated with forming coils in a wireless charging mat. 
     SUMMARY 
     A wireless power transmitting device may transmit power wirelessly to a wireless power receiving device. The wireless power transmitting device may be a wireless charging mat or other equipment with an array of wireless power transmitting coils. The wireless power receiving device may be a portable electronic device with a battery, an array of wireless power receiving coils that receive wireless power from the array of wireless power transmitting coils, and a rectifier that receives alternating-current signals from the wireless power receiving coils and provides corresponding rectified direct-current voltage signals to circuitry in the wireless power receiving device. 
     The wireless power receiving device may include a capacitor that receive the direct-current voltage signals and may include charging circuitry that charges a battery using these signals. The rectifier circuitry may include multiple bridge circuits each of which is coupled between a respective coil in the array of wireless power receiving coils and the capacitor. 
     The wireless power transmitting coils may be arranged in a hexagonally tiled array. The wireless power receiving coils may include first, second, and third coils that are arranged so that the second and third coils are not aligned with any of the transmitting coils when the first coil is aligned with one of the transmitting coils. The receiving coils may be aligned with respective vertices in an equilateral triangle having sides with lengths equal to half of the center-to-center spacing of the hexagonally tiled transmitting coils. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of an illustrative wireless charging system that includes a wireless power transmitting device and a wireless power receiving device in accordance with an embodiment. 
         FIG. 2  is a circuit diagram of illustrative wireless power transmitting equipment in accordance with an embodiment. 
         FIG. 3  is a circuit diagram of illustrative wireless power receiving equipment in accordance with an embodiment. 
         FIG. 4  is a diagram of an illustrative hexagonally tiled array of wireless power transmitting coils of the type that may be used in a wireless power transmitting device and an associated cluster of three laterally offset receiver coils of the type that may be used in a wireless power receiving device in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     A wireless power system may have a wireless power transmitting device such as a wireless power adapter or other wireless power transmitting equipment. The wireless power transmitting device may wirelessly transmit power to a wireless power receiving device such as a wristwatch, cellular telephone, tablet computer, laptop computer, or other electronic equipment. The wireless power receiving device may use power from the wireless power transmitting device for powering the device and for charging an internal battery. 
     An illustrative wireless power system (wireless charging system) is shown in  FIG. 1 . As shown in  FIG. 1 , wireless power system  10  may include a wireless power transmitting device such as wireless power transmitting device  12  and may include a wireless power receiving device such as wireless power receiving device  24 . 
     Power transmitting device  12  may be a stand-alone power adapter (e.g., a wireless charging mat that includes power adapter circuitry), may be a wireless charging mat that is coupled to a power adapter or other equipment by a cable, may be a portable device, may be equipment that has been incorporated into furniture, a vehicle, or other system, or may be other wireless power transfer equipment. Illustrative configurations in which wireless power transmitting device  12  is a wireless charging mat may sometimes be described herein as an example. 
     Power receiving device  24  may be a portable electronic device such as a wristwatch, a cellular telephone, a laptop computer, a tablet computer, or other electronic equipment. Power transmitting device  12  may be coupled to a wall outlet (e.g., alternating current), may have a battery for supplying power, and/or may have another source of power. Power transmitting device  12  may have an AC-DC power converter such as power converter  14  for converting AC power from a wall outlet or other power source into DC power. DC power may be used to power control circuitry  16 . During operation, a controller in control circuitry  16  may use power transmitting circuitry  52  to transmit wireless power to power receiving circuitry  54  of device  24 . Power transmitting circuitry  52  may have switching circuitry (e.g., transistors) that are turned on and off based on control signals provided by control circuitry  16  to create AC current signals through one or more coils in coil array  42 . As the AC currents pass through coil array  42 , alternating-current electromagnetic fields (signals  44 ) are produced that are received by corresponding coil array  48  in power receiving device  24 . When the alternating-current electromagnetic fields are received by the coil array, corresponding alternating-current voltages are induced in the coil array. Rectifier circuitry such as rectifier  50  may convert received AC signals (received alternating-current voltages associated with wireless power signals) from coil array  48  into DC voltage signals for powering device  24 . The DC voltages may be used in powering components in device  24  such as a display, touch sensor components, wireless circuits, audio components, and other components and may be used in charging an internal battery in device  24 . 
     Device  12  and/or device  24  may communicate wirelessly using in-band or out-of-band communications. Device  12  may, for example, have wireless transceiver circuitry  40  that wirelessly transmits out-of-band signals to device  24  using an antenna or that wirelessly transmits in-band signals to device  24  using coil array  42 . Wireless transceiver circuitry  40  may be used to wirelessly receive out-of-band signals from device  24  using the antenna or may be used to wirelessly receive in-band signals from device  24  using coil array  42 . Device  24  may have wireless transceiver circuitry  46  that transmits out-of-band signals to device  12  using an antenna or that transmits in-band signals to device  12  using coil array  48 . Receiver circuitry in wireless transceiver  46  may use an antenna to receive in-band signals from device  12  or may use coil array  48  to receive in-band signals from device  12 . 
     During power transmission operations, coils array  48  supplies received AC voltages (i.e., receive wireless power signals) to rectifier  50 . Rectifier  50  contains rectifying components such as synchronous rectification metal-oxide-semiconductor transistors arranged in a bridge network. 
     Illustrative circuitry of the type that may be used for forming power transmitting circuitry  52  of  FIG. 1  is shown in  FIG. 2 . As shown in  FIG. 2 , power transmitting circuitry  52  may include drive circuitry such as drive circuitry  60  coupled to coils such as coil  42 ′ in coil array  42  ( FIG. 1 ). Drive circuitry  60  may receive direct-current (DC) voltage Vdc from AC-DC converter  14 . Drive circuitry  60  may have transistors such as transistors  62  (e.g., metal-oxide-semiconductor transistors or other suitable transistors). Transistors  62  may be coupled in series between a terminal that receives positive power supply voltage Vdc and a ground terminal that receives a ground voltage. Capacitor  64  may be coupled to node Nd between transistors  62 . During operation, control circuitry  16  may apply control signals such as control signal IN and complementary (inverted) signal NIN to respective gates G of transistors  62 . Control circuitry  16  may modulate signals IN and NIN so that transistors  62  produce an AC drive signal. Capacitor  64  may be used to couple the AC drive signal to a coil such as coil  42 ′ in array  42  that is coupled to transistors  62 . As the AC signal flows through coil  42 ′, wireless power signal  44  ( FIG. 1 ) is produced and can be received by coil array  48  of device  24 . 
     Coil array  42  may have an array of wireless power transmitting coils mounted under a planar surface such as a charging mat cover. The array of coils may, for example, contain wireless power transmitting coils that are tiled in a hexagonal tile pattern. Drive circuitry  60  may have a pair of transistors  62  coupled to each coil in coil array  42  and/or may have other switching circuitry (e.g., other transistor circuitry) that can be adjusted by control circuitry  16  to select which coil(s) in array  62  is being used to transmit wireless power signals  44  to device  24 . 
       FIG. 3  is a circuit diagram showing illustrative circuitry of the type that may be used in implementing power receiving circuitry  54  in device  24 . As shown in  FIG. 3 , power receiving circuitry  54  may have coil array  48 . Coil array  48  may have an array of wireless power receiving coils such as first coil  48 - 1 , second coil  48 - 2 , and third coil  48 - 3 . In general, coil array  48  may have any suitable number of coils (e.g., more than three, more than four, fewer than four, fewer than ten, or other suitable number). Configurations in which coil array  48  contains three wireless power receiving coils may sometimes be described herein as an example. 
     Rectifier circuitry  50  may have transistors with gates G that are controlled by control signals from control circuitry  30  to implement a synchronous rectification scheme. During operation, the transistors may be turned on and off so that received AC voltages from the received AC wireless signals are converted into DC voltage signal Vout across capacitor  82 . The DC voltage Vout may be used in powering internal circuitry  84  in device  24 . Circuitry  84  may include control circuitry  30  ( FIG. 1 ), a display, a touch sensor and other input devices, audio circuitry, cellular telephone transceiver circuitry, wireless local area network circuitry, and other wireless transceiver circuitry, a battery such as battery  86 , circuitry that directs power to battery  86  (e.g., charging circuitry to recharge battery  86  when battery  86  has become depleted), and circuitry that directs power to other components in internal circuitry  84 , etc. 
     Capacitors  70 ,  74 , and  78  may be coupled between the coils of array  48  and respective rectifier circuits such as independently selectable bridge circuits  50 - 1 ,  50 - 2 , and  50 - 3 . Capacitor  78  may be coupled between coil  48 - 1  and node ND 1  in bridge circuit  50 - 1 . Capacitor  74  may be coupled between coil  48 - 2  and node ND 2  in bridge circuitry  50 - 2 . Capacitor  70  may be coupled between coil  48 - 3  and node ND 3  in bridge circuit  50 - 3 . Bridge circuit  50 - 1  may have transistors such as a pair of transistors  80  that are coupled to each other at node ND 1 . Transistors  80  may be coupled in series across capacitor  82  of rectifier  50 . Bridge circuit  50 - 2  may have transistors such as a pair of transistors  76  that are coupled to each other at node ND 2 . Transistors  76  may be coupled in series across capacitor  82  of rectifier  50  in parallel with the pair of transistors  80 . Bridge circuit  50 - 1  may have transistors such as a pair of transistors  72  that are coupled to each other at node ND 3 . Transistors  72  may be coupled in series across capacitor  82  of rectifier  50  in parallel with the pair of transistors  80  and the pair of transistors  76 . 
     Using this rectifier arrangement, control circuitry  30  can activate bridge circuit  50 - 1 ,  50 - 2 , or  50 - 3  to switch coil  48 - 1 ,  48 - 2 , or  48 - 3  into use, respectively, in receiving wireless signals  44 . For example, if it is desired to use coil  48 - 2  to receive wireless signals  44  from device  12 , transistors  76  may be used in a synchronous rectification scheme to rectify received AC wireless signals and thereby produce DC voltage Vout on capacitor  82  at the output of rectifier  50  while transistors  72  and  80  remain off. If, as another example, it is desired to use coil  48 - 1  to receive wireless signals  44  from device  12 , control circuitry  30  may turn transistors  80  on and off to synchronously rectify the AC signals received by coil  48 - 1  and thereby produce DC voltage Vout. In this way, control circuitry  30  can switch any one of the coils in coil array  48  into use in receiving wireless power. This allows control circuitry  30  to select among multiple coils in array  48  when optimizing coupling with a corresponding coil in array  42 . 
     When device  24  is place on device  12  (e.g., on a wireless charging mat), the coils of coil array  48  overlap the coils in coil array  42 . Different coils in array  48  will overlap different portions of the charging mat and therefore will overlap different coils in coil array  42 . To optimize wireless power transfer efficiency, device  12  and  24  may determine optimum coils to use in array  42  and  48 . For example, device  12  (e.g., control circuitry  16 ) may have impedance measurement circuitry coupled to the coils of array  42  and/or device  24  (e.g., control circuitry  30 ) may have impedance measurement circuitry coupled to the coils of coil array  48 . By analyzing impedance measurements or otherwise gathering information on the coupling efficiency between each of the coils of array  42  and each of the coils of array  48 , an optimum pair of coils can be identified to support charging (e.g., an optimum transmitting coil in array  42  and an optimum receiving coil in array  48 ). 
     Device  12  and device  24  may communicate using in-band or out-of-band communications when identifying the optimum transmitting and receiving coils. For example, device  12  and device  24  may coordinate search strategies when cycling through potential transmitting and receiving coils as part of the optimum coil identification process. Once identified, these coils can be switched into use to support wireless power transfer operations. In device  12 , control circuitry  16  may use drive circuitry  60  to supply AC drive signals to the optimum transmitting coil in array  42 . In device  24 , control circuitry  30  may adjust rectifier  50  so that an appropriate bridge circuit ( 50 - 1 ,  50 - 2 , or  50 - 3 ) is used in rectifying AC voltage signals from the optimum receiving coil in array  48 . 
       FIG. 4  is a top view of coils  42 ′ in coil array  42  and coils  48 - 1 ,  48 - 2 , and  48 - 3  in coil array  48  in an illustrative scenario in which device  24  has been placed on top of device  12 . As shown in  FIG. 4 , coils  42 ′ may be arranged in a hexagonally tiled array. Each tile in the hexagonal array may contain a respective one of coils  42 ′. Coils  48 - 1 ,  48 - 2 , and  48 - 3  may be arranged in a pattern that does not allow all three of these coils to simultaneously align with three of coils  42 ′, regardless of how device  42  is placed on device  12 . For example, the coils of array  48  may be laterally offset from each other so that each coil in array  48  is aligned with a respective vertex  90  of an equilateral triangle such as triangle  92  of  FIG. 4 . Triangle  92  has sides of length d/2, where d is the center-to-center distance of the hexagonally tiled transmitting coils in array  42 . With this type of arrangement, whenever a first receiver coil such as coil  48 - 1  is aligned with a given transmitter coil  42 ′ in one of the hexagonally tiled regions of array  42 , the second and third coils of coil array  48  (coils  48 - 2  and  48 - 3 , respectively) are not aligned with any of the other transmitter coils  42 ′ in coil array  42 . 
     The use of partly overlapping laterally offset receiver coils in coil array  48  such as the illustrative three coils  48 - 1 ,  48 - 2 , and  48 - 3  of coil array  48  of  FIG. 4  is illustrative. Array  48  may be formed from other numbers of coils (e.g., more than three receiver coils, fewer than five receiver coils, etc.) and/or different lateral offset patterns may be used. The two-dimensional array of coils  48 - 1 ,  48 - 2 , and  48 - 3  of  FIG. 4  (e.g., coils that are not all arranged in a straight line and that are laterally offset from each other in a two-dimensional pattern that ensures that whenever a first receiver coil such as coil  48 - 1  is aligned with a given transmitter coil  42 ′, second coil  48 - 2  and third coil  48 - 3  will not be aligned with any of the other transmitter coils  42 ′) helps ensure that there will be satisfactory coupling between at least one of these three coils and a corresponding one of the transmitter coils in array  42 , even when device  24  is placed in a variety of different orientations. A two-dimensional array of the type shown in  FIG. 4  in which each receiver coil is located at the vertex of an equilateral triangle such as triangle  92  of  FIG. 4  helps reduce the likelihood that all three receiver coils will be poorly aligned with the hexagonally tiled coils of array  42 , thereby ensuring that there is at least one transmitter coil and receiver coil that overlap sufficiently well to support efficient wireless power transfer between device  12  and device  24 . The two-dimensional array of coils in coil array  48  of  FIG. 4  is also compact and does not involve placement of receiving coils far apart at potentially non-overlapping positions with respect to each other. If desired, receiver coils may be placed farther apart at other triangle vertex locations in a tiled array of triangles  92 , while still ensuring that the receiver coils are positioned at a variety of locations relative to the hexagonal tiles of array  42 . The configuration of coil array  48  of  FIG. 4  is illustrative. 
     Coils  42 ′ in array  42  and coils  48 - 1 ,  48 - 2 ,  48 - 3  in array  48  may be implemented using one or more loops of wire, using one or more loops of metal traces on a printed circuit or other suitable substrate, or may be formed from other looped signal paths. The coils may have circular outlines (footprints when viewed from above), may have hexagonal outlines, may have rectangular outlines, or may have other suitable shapes. The coils may have 2-100 turns, more than 5 turns, more than 15 turns, more than 30 turns, fewer than 75 turns, fewer than 50 turns, or other suitable numbers of turns. The coils may have diameters of 5 mm or more, 10 mm or more, 15 mm or more, 20 mm or more, 30 mm or more, 50 mm or more, 100 mm or less, 60 mm or less, 35 mm or less, or other suitable diameters. The frequency of the AC wireless signals in system  10  (e.g., signals  44 ) may be 100 kHz to 10 MHz, more than 200 kHz, more than 500 kHz, more than 1 MHz, more than 5 MHz, less than 20 MHz, less than 10 MHz, less than 1 MHz, or other suitable frequency. 
     The foregoing is merely illustrative and various modifications can be made to the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20170329
Publication Date: 20191119
Grant Date: 20191119
Priority Date: 20160706
Inventors: MOUSSAOUI, ZAKI
DAYAL, ROHAN
QIU, WEIHONG
Assignee: APPLE INC
CPC Classifications: [{"code": "H01F38/14", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J50/90", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/90", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/40", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01F38/14", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/90", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/345", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/345", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J7/025", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J7/345", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J50/40", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F38/14", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J2310/22", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J50/005", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 60911194