Claims:1. A receiver unit (108) of a wireless power transfer system (100), the receiver unit (108) comprising:
a main receiver coil (120);
a plurality of auxiliary receiver coils (122) disposed about a central axis (208) of the main receiver coil (120); and
a receiver drive subunit (118) comprising:
a main converter (124) operatively coupled to the main receiver coil (120), wherein the main converter (124) comprises a main output terminal (504); and
a plurality of auxiliary converters (126, 502, 602, 702) operatively coupled to the plurality of auxiliary receiver coils (122), wherein the plurality of auxiliary converters (126, 502, 602, 702) is operatively coupled to each other to form an auxiliary output terminal (506), and wherein the auxiliary output terminal (506) is coupled in series to the main output terminal (504).
2. The receiver unit (108) as claimed in claim 1, wherein one auxiliary converter of the plurality of auxiliary converters (126, 502, 602, 702) is operatively coupled in parallel to another auxiliary converter of the plurality of auxiliary converters (126, 502, 602, 702).
3. The receiver unit (108) as claimed in claim 1, wherein one auxiliary converter of the plurality of auxiliary converters (126, 502, 602, 702) is operatively coupled in series to another auxiliary converter of the plurality of auxiliary converters (126, 502, 602, 702).
4. The receiver unit (108) as claimed in claim 1, wherein each of the plurality of auxiliary receiver coils (122) is operatively coupled to a corresponding auxiliary converter of the plurality of auxiliary converters (126, 502, 602, 702).
5. The receiver unit (108) as claimed in claim 1, wherein at least one of the plurality of auxiliary converters (126, 502, 602, 702) is at least one of a passive rectifier and an active rectifier.
6. The receiver unit (108) as claimed in claim 1, wherein the plurality of auxiliary receiver coils (122) is disposed on the main receiver coil (120).
7. The receiver unit (108) as claimed in claim 6, wherein the plurality of auxiliary receiver coils (122) is disposed on at least one of a first surface (202), a second surface (204), and a peripheral side (206) of the main receiver coil (120).
8. The receiver unit (108) as claimed in claim 1, wherein the plurality of auxiliary receiver coils (122) is at least one of a circular shaped, an oval shaped, a square shaped, a triangular shaped, rectangular shaped, asymmetrical shaped, symmetrical shaped, and an elliptical shaped.
9. The receiver unit (108) as claimed in claim 1, wherein the plurality of auxiliary receiver coils (122) is disposed symmetrically about the central axis (208) of the main receiver coil (120).
10. The receiver unit (108) as claimed in claim 1, wherein at least one of the main receiver coil (120) and the plurality of auxiliary receiver coils (122) is disposed on a ferrite layer (302, 210).
11. The receiver unit (108) as claimed in claim 1, wherein the receiver unit (108) is disposed on a printed circuit board (604).
12. The receiver unit (108) as claimed in claim 1, wherein the main receiver coil (120) and the plurality of auxiliary receiver coils (122) are resonant coils.
13. A wireless power transfer system (100) comprising:
a transmitter unit (106); and
a receiver unit (108) operatively coupled to the transmitter unit (106), wherein the receiver unit (108) comprises:
a main receiver coil (120);
a plurality of auxiliary receiver coils (122) disposed about a central axis (208) of the main receiver coil (120);
a receiver drive subunit (118) comprising:
a main converter (124) operatively coupled to the main receiver coil (120), wherein the main converter (124) comprises a main output terminal (504); and
a plurality of auxiliary converters (126, 502, 602, 702) operatively coupled to the plurality of auxiliary receiver coils (122), wherein the plurality of auxiliary converters (126, 502, 602, 702) is operatively coupled to each other to form an auxiliary output terminal (506), and wherein the auxiliary output terminal (506) is coupled in series to the main output terminal (504).
14. The wireless power transfer system (100) as claimed in claim 13, comprising a field focusing coil (110) disposed between the transmitter unit (106) and the receiver unit (108).
15. The wireless power transfer system (100) as claimed in claim 13, comprising a plurality of phase compensation coils configured to compensate a change in at least one of an impedance of the main receiver coil (120) and a phase angle of current flowing through the main receiver coil (120).
16. The wireless power transfer system (100) as claimed in claim 13, wherein the transmitter unit (106) comprises:
a transmitter coil (114); and
a transmitter drive subunit (112) operatively coupled to the transmitter coil (114).
17. The wireless power transfer system (100) as claimed in claim 16, wherein the plurality of auxiliary receiver coils (122) is configured to compensate a misalignment between the transmitter coil (114) and the main receiver coil (120).
18. A method of operation of a receiver unit (108) of a wireless power transfer system (100), comprising:
inducing a first voltage at at least one of a main receiver coil (120) and a plurality of auxiliary receiver coils (122) based on an alignment of the main receiver coil (120) and the plurality of auxiliary receiver coils (122) with a transmitter coil (114);
generating a second voltage at a main output terminal (504) of a main converter (124) and a third voltage at an auxiliary output terminal (506) of a plurality of auxiliary converters (126, 502, 602, 702) based on the first voltage; and
transmitting a combination of the second voltage and the third voltage to a load (508).
, Description:BACKGROUND
[0001] Embodiments of the present invention relate generally to a power transfer system and more particularly to a wireless power transfer system. In particular, the present invention relates to a receiver unit of the wireless power transfer systems.
[0002] A wireless power transfer system includes a transmitter coil, a receiver coil, and corresponding electronic circuitry. Typically, efficiency of power transfer between the transmitter coil and the receiver coil is compromised due to misalignment between the transmitter coil and the receiver coil.
[0003] In recent times, different techniques have been proposed for overcoming the shortcomings in power transfer due to misalignment between the transmitter coil and the receiver coil. These techniques entail use of controllable switches, adaptive controllers, position sensors, and optical cameras. Use of the controllable switches, the adaptive controllers, the position sensors, and the optical cameras results in a complex power transfer system with associated power losses.
[0004] Thus, there is a need for an enhanced wireless power transfer system and an associated method.
BRIEF DESCRIPTION
[0005] In accordance with one aspect of the present specification, a receiver unit of a wireless power transfer system is presented. The receiver unit includes a main receiver coil, a plurality of auxiliary receiver coils disposed about a central axis of the main receiver coil, and a receiver drive subunit. The receiver drive subunit includes a main converter operatively coupled to the main receiver coil, where the main converter includes a main output terminal. Further, the receiver drive subunit includes a plurality of auxiliary converters operatively coupled to the plurality of auxiliary receiver coils, where the plurality of auxiliary converters is operatively coupled to each other to form an auxiliary output terminal, and where the auxiliary output terminal is coupled in series to the main output terminal.
[0006] In accordance with another aspect of the present specification, a wireless power transfer system is presented. The wireless power transfer system includes a transmitter unit, and a receiver unit operatively coupled to the transmitter unit. The receiver unit includes a main receiver coil, a plurality of auxiliary receiver coils disposed about a central axis of the main receiver coil, and a receiver drive subunit. The receiver drive subunit includes main converter operatively coupled to the main receiver coil, where the main converter includes a main output terminal; and a plurality of auxiliary converters operatively coupled to the plurality of auxiliary receiver coils, where the plurality of auxiliary converters is operatively coupled to each other to form an auxiliary output terminal, and where the auxiliary output terminal is coupled in series to the main output terminal.
[0007] In accordance with yet another aspect of the present specification, a method of operation of a receiver unit of a wireless power transfer system. The method includes inducing a first voltage at at least one of a main receiver coil and a plurality of auxiliary receiver coils based on an alignment of the main receiver coil and the plurality of auxiliary receiver coils with a transmitter coil. Further, the method includes generating a second voltage at a main output terminal of a main converter and a third voltage at an auxiliary output terminal of a plurality of auxiliary converters based on the first voltage. Furthermore, the method includes transmitting a combination of the second voltage and the third voltage to a load.
DRAWINGS
[0008] These and other features, aspects, and advantages of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
[0009] FIG. 1 is a block diagram representation of a wireless power transfer system in accordance with an embodiment of the present specification;
[0010] FIG. 2 is a schematic representation of a receiver coil of the wireless power transfer system of FIG. 1 in accordance with an embodiment of the present specification;
[0011] FIGs. 3-4 are cross-sectional representations of a portion of a wireless power transfer unit in accordance with different embodiments of the present specification;
[0012] FIG. 5 is a detailed circuit representation of a wireless power transfer system in accordance with one embodiment of the present specification;
[0013] FIG. 6 is a detailed circuit representation of a wireless power transfer system in accordance with another embodiment of the present specification;
[0014] FIG. 7 is a detailed circuit representation of a wireless power transfer system in accordance with yet another embodiment of the present specification; and
[0015] FIG. 8 is a schematic representation of a wireless power transfer unit for use in a wireless power transfer system in accordance with one embodiment of the present specification.

DETAILED DESCRIPTION
[0016] Unless defined otherwise, technical and scientific terms used herein have the same meaning as is commonly understood by one of ordinary skill in the art to which this specification belongs. The terms "first", "second", and the like, as used herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. Also, the terms "a" and "an" do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced items. The use of "including," "comprising" or "having" and variations thereof herein are meant to encompass the items listed thereafter and equivalents thereof as well as additional items. The terms "connected" and "coupled" are not restricted to physical or mechanical connections or couplings, and can include electrical connections or couplings, whether direct or indirect. Furthermore, terms "circuit" and "circuitry" and "controlling unit" may include either a single component or a plurality of components, which are active and/or passive and are connected or otherwise coupled together to provide the described function. In addition, the term operatively coupled as used herein includes wired coupling, wireless coupling, electrical coupling, magnetic coupling, radio communication, software based communication, or combinations thereof.
[0017] As will be described in detail hereinafter, various embodiments of a wireless power transfer system are disclosed. In particular, the system and method discloses employing an exemplary receiver unit having a plurality of auxiliary receiver coils disposed about a central axis of the main receiver coil. Further, the various embodiments disclose different arrangements of the auxiliary receiver coils with respect to the main receiver coil. Furthermore, the embodiments disclose the arrangement of the auxiliary receiver coils with respect to associated auxiliary converters. The exemplary receiver unit may be employed in wireless charging systems, such as but not limited to a mobile phone, a laptop, an electric vehicle, consumer electronic products, and the like.
[0018] FIG. 1 is a block diagram representation of a wireless power transfer system 100 in accordance with an embodiment of the present specification. The wireless power transfer system 100 includes a wireless power transfer unit 102 and a power source 104. In one embodiment, the wireless power transfer unit 102 includes a transmitter unit 106, a receiver unit 108, and a field focusing coil 110. In one embodiment, the transmitter unit 106 is magnetically coupled to the receiver unit 108 via the field focusing coil 110. The field focusing coil 110 is configured to focus magnetic field from the transmitter unit 106 to the receiver unit 108. In another embodiment, the field focusing coil 110 may not be present in the wireless power transfer unit 102.
[0019] The transmitter unit 106 includes a transmitter (Tx) drive subunit 112 coupled to a transmitter (Tx) coil 114. In one embodiment, the transmitter drive subunit 112 may be a converter. The transmitter drive subunit 112 includes a plurality of switches. The plurality of switches includes semiconductor switches, such as an insulated gate bipolar transistor, a metal oxide semiconductor field effect transistor, a field-effect transistor, an injection enhanced gate transistor, an integrated gate commutated thyristor, a gallium nitride based switch, a silicon carbide based switch, a gallium arsenide based switch, diodes, or the like. In one embodiment, the transmitter coil 114 may be a wound copper wire.
[0020] Further, the receiver unit 108 includes a receiver (Rx) coil 116 and a receiver (Rx) drive subunit 118. In accordance with aspects of the present specification, the receiver coil 116 includes a main receiver coil 120 and a plurality of auxiliary receiver coils 122. The plurality of auxiliary receiver coils 122 is disposed about the central axis of the main receiver coil 120. The plurality of auxiliary receiver coils 122 may also be interchangeably referred to herein as an array of auxiliary receiver coils.
[0021] The exemplary receiver unit 108 may form a part of a two-coil wireless power transfer system, three-coil wireless power transfer system, and a four-coil wireless power transfer system. As will be appreciated, the two-coil wireless power transfer system includes only the receiver unit and the transmitter unit. Further, the three-coil power transfer system includes a field focusing coil in addition to the receiver unit and the transmitter unit. The four-coil power transfer system includes a phase compensation coil in addition to the receiver unit, the field focusing coil, and the transmitter unit.
[0022] In one embodiment, the main receiver coil 120 and the plurality of auxiliary receiver coils 122 are resonant coils. In particular, each of the main receiver coil 120 and the plurality of auxiliary receiver coils 122 may be coupled to a corresponding capacitor. In one specific embodiment, the main receiver coil 120 and the plurality of auxiliary receiver coils 122 are compatible with a Wireless Power Consortium (WPC) standard (Qi) that is defined in a frequency range of 100 kHz to 200 kHz.
[0023] Further, the receiver drive subunit 118 includes a main converter 124 and a plurality of auxiliary converters 126. The main receiver coil 120 is coupled to the main converter 124. The main converter 124 includes a main output terminal and is configured to rectify a voltage induced at the main receiver coil 120 during operation.
[0024] Further, auxiliary receiver coils 122 are coupled to the auxiliary converters 126. The auxiliary converters 126 are configured to rectify a voltage induced at the auxiliary receiver coils 122 during operation. In one embodiment, each auxiliary receiver coil 122 is coupled to a corresponding auxiliary converter 126. In one embodiment, at least one of the plurality of auxiliary converters 126 is a passive rectifier. In one specific embodiment, the passive rectifier is a diode rectifier.
[0025] Furthermore, the plurality of auxiliary converters 126 is coupled to each other to form an auxiliary output terminal. In accordance with aspects of the present specification, the main output terminal of the main converter 124 is coupled to the auxiliary output terminal in series. Further, a load is coupled across the main output terminal and the auxiliary output terminal.
[0026] It may be noted that conventional wireless power transfer systems may typically include a single receiver coil. This receiver coil contributes towards supply of a voltage to a load, such as a battery. In one scenario, if the receiver coil is not aligned with a transmitter coil, in order to induce a desired voltage in the receiver coil, the current in the transmitter coil has to be higher than the current in the transmitter coil, when the receiver coil is aligned with the transmitter coil. As a result, efficiency of the conventional wireless power transfer system is compromised. Shortcomings of the conventional wireless power transfer systems can be circumvented using the exemplary wireless power transfer system 100.
[0027] As noted hereinabove, the exemplary receiver unit 108 includes the auxiliary receiver coils 122 in addition to the main receiver coil 120. The combination of the main receiver coil 120 and the auxiliary receiver coils 122 is configured to provide desired voltage to the load, via the corresponding main and auxiliary converters 124, 126, even in an event of misalignment of the main receiver coil 120 with respect to the transmitter coil 114.
[0028] In particular, during operation of the wireless power transfer system 100, power provided from the power source 104 is converted to another form by the transmitter drive subunit 112 and provided to the transmitter coil 114. Accordingly, the transmitter coil 114 is energized and a magnetic field is generated at the transmitter coil 114. The magnetic field at the transmitter coil 114 induces a voltage at the main receiver coil 120 and the plurality of auxiliary receiver coils 122 based on alignment of the main receiver coil 120 and the plurality of auxiliary receiver coils 122 with respect to the transmitter coil 114.
[0029] The voltage induced at the main receiver coil 120 and the plurality of auxiliary receiver coils 122 is transmitted to the main converter 124 and the plurality of auxiliary converters 126, respectively. A rectified voltage is generated at the main output terminal of the main converter 124 and a rectified voltage is generated at the auxiliary output terminal of the plurality of auxiliary converters 126. In accordance with aspects of the present specification, a combination of the voltage obtained at the main output terminal and the voltage obtained at the auxiliary output terminal is provided to the load (not shown in FIG. 1).
[0030] It should be noted herein that if a central axis of the transmitter coil 114 is aligned with a central axis of the main receiver coil 120, the main receiver coil 120 is aligned with the transmitter coil 114. When the main receiver coil 120 is aligned with the transmitter coil 114, the main receiver coil 120 has a maximum magnetic coupling with the transmitter coil 114. In the event of maximum magnetic coupling between the transmitter coil 114 and the main receiver coil 120, a higher voltage is induced across the main receiver coil 120 compared to a voltage induced at the main receiver coil 120 during a misaligned condition of the main receiver coil 120 with respect to the transmitter coil 114. In such a scenario, the voltage induced across the auxiliary receiver coils 122 is a considerably lower value. However, a cumulative voltage across the main output terminal of the main converter 124 and the auxiliary output terminal of the auxiliary converters 126 is a relatively higher value, for example, ‘X’ volts.
[0031] In another scenario where the main receiver coil 120 is misaligned with respect to the transmitter coil 114, at least one of the auxiliary receiver coils 122 may be in alignment with the transmitter coil 114. It should be noted herein that if a central axis of the transmitter coil 114 is aligned with a central axis of the auxiliary receiver coil 122, the transmitter coil 114 is aligned with the auxiliary receiver coil 122. In such a scenario, a voltage induced at the particular auxiliary receiver coil 122, which is in alignment with the transmitter coil 114, is higher than a voltage induced in the other auxiliary coils 122. Here again, a cumulative voltage across main terminal of the main converter 124 and the auxiliary terminal of the auxiliary converters 126 is a higher value, for example, ‘Y’ volts, where ‘Y’ volts is approximately equal to ‘X’ volts. The cumulative voltage ‘Y’ volts is induced without a significant increase in a magnitude of the current flowing in the transmitter coil 114. Thus, even during a misaligned condition of the main receiver coil 120 with respect to the transmitter coil 114, a desired voltage required is provided to the load without a significant increase in the magnitude of the current flowing in the transmitter coil 114. Accordingly, an efficiency of power transfer in the wireless power transfer system 100 is not compromised even in the event of misalignment of the main receiver coil 120 with respect to the transmitter coil 114.
[0032] Additionally, in conventional wireless power transfer systems, communication between a receiver coil and a transmitter coil is hindered if the receiver coil is misaligned with respect to the transmitter coil. In accordance with the embodiment of the present specification, use of the of the auxiliary receiver coils 122, enhances communication between the receiver unit 108 and the transmitter unit 106 compared to a conventional wireless power transfer system having a receiver unit devoid of auxiliary receiver coils.
[0033] It may be noted that in a typical wireless power transfer system, a transmitter unit is configured to communicate with a receiver unit. In particular, the receiver unit sends configuration and control feedback signals to the transmitter unit, about a status of the receiver unit such that the transmitter unit can determine whether to transmit power to the receiver unit. In one embodiment, the status of the receiver unit may be a presence of the receiver unit proximate to the transmitter unit. In conventional wireless power transfer systems, when a receiver coil is misaligned with respect to a transmitter coil, communication between the receiver unit and the transmitter unit is affected and hence, the transmitter unit fails to receive the feedback signals from the receiver unit. Lack of communication between the receiver unit and the transmitter unit causes the transmitter unit to stop supply of power to the receiver unit. In accordance with the exemplary embodiment of the present invention, use of auxiliary receiver coils 122 aids in continuous communication between the receiver unit 108 and the transmitter unit 106 even when the main receiver coil 120 is in a misaligned condition with respect to the transmitter coil 106. In accordance with aspects of the present specification, even if the main receiver coil 120 is misaligned with respect to the transmitter coil 106, at least one of the auxiliary receiver coils 122 is aligned with the transmitter coil 114. Hence, the receiver unit 108 continues to send feedback signals to the transmitter unit 106. This aids in maintaining continuity in communication between the transmitter unit 106 and the receiver unit 108.
[0034] The configuration of the receiver unit 108 is described in greater detail with respect to FIG. 2 and arrangement of the receiver unit 108 with respect to the transmitter unit 106 is described in greater detail with respect to FIGs. 3-7.
[0035] Referring to FIG. 2, a schematic representation of a receiver coil 116 in accordance with an embodiment of the present specification is presented. In particular, FIG. 2 is a top view of the receiver coil 116. The receiver coil 116 includes the main receiver coil 120 and the plurality of auxiliary receiver coils 122.
[0036] The main receiver coil 120 has a first surface 202 and a second surface 204. The first surface 202 is opposite to the second surface 204. Further, the main receiver coil 120 has a peripheral side 206, an inner edge 205, and an outer edge 207.
[0037] Reference numeral 208 is representative of a central axis of the main receiver coil 120. The central axis 208 is an axis passing through a center and perpendicular to a x-y plane of the main receiver coil 120.
[0038] In the illustrated embodiment, the main receiver coil 120 is a flat structure. Specifically, the main receiver coil 120 is square shaped, or rectangular shaped, or oval shaped, or circular shaped, or quadrilateral shaped, or the like. A center portion of the main receiver coil 120 is hollow. The main receiver coil 120 is disposed directly on a ferrite layer 210. Specifically, the second surface 204 is in direct contact with the ferrite layer 210. In another embodiment, the first surface 202 may be in direct contact with the ferrite layer 210.
[0039] According to aspects of the present specification, the plurality of auxiliary receiver coils 122 is disposed about the central axis 208. In the illustrated embodiment, four auxiliary receiver coils 122 are disposed on the main receiver coil 120. Specifically, the plurality of auxiliary receiver coils 122 is disposed on at least one of the first surface 202 and the second surface 204 of the main receiver coil 120. In another embodiment, the auxiliary receiver coils 122 are disposed partially on the main receiver coil 120. In yet another embodiment, the auxiliary receiver coils 122 are disposed proximate to the along the outer edge 207 proximate to the main receiver coil 120. The number of auxiliary receiver coils 122 may vary depending on the application.
[0040] Furthermore, in one embodiment, all the auxiliary receiver coils 122 are equidistant from the central axis 208. In another embodiment, each auxiliary receiver coil of the plurality of auxiliary receiver coils 122 is disposed at a different distance from the central axis 208. In yet another embodiment, the auxiliary receiver coils 122 are symmetrically disposed about the central axis 208. In yet another embodiment, the auxiliary receiver coils 122 are unsymmetrically disposed about the central axis 208. In yet another embodiment, the plurality of auxiliary receiver coils 122 may be arranged concentric to the main receiver coil 120. In yet another embodiment, the auxiliary receiver coils 122 are in a different plane with respect to each other and the main receiver coil 120. In yet another embodiment, one auxiliary receiver coil 122 overlaps another auxiliary receiver coil 122.
[0041] The auxiliary receiver coils 122 may be square shaped, rectangular shaped, oval shaped, circular shaped, quadrilateral shaped, or the like. The auxiliary receiver coils 122 are symmetrically shaped or unsymmetrically shaped. In the illustrated embodiment, a center portion of each of the auxiliary receiver coils 122 is hollow.
[0042] Although the illustrated embodiment shows only four auxiliary receiver coils 122 disposed on the main receiver coil 120, number of auxiliary and main receiver coils may vary depending on the application. Further, although the illustrated embodiment shows auxiliary receiver coils 122 distributed sparsely about the central axis 208, in one embodiment, the auxiliary receiver coils 122 may be distributed densely about the central axis 208.
[0043] FIGs. 3-4 are cross-sectional representations 300, 400 of a portion of a wireless power transfer unit 102 in accordance with aspects of the present specification. In particular, FIGs. 3 and 4 are cross-sectional representations of the transmitter unit 106 and the receiver unit 108 of the wireless power transfer unit 102. More particularly, FIGs. 3-4 depict the transmitter coil 114 and the receiver coil 116. The orientation of the wireless power transfer unit 102 is for illustrative purpose and should not be construed as limitation of the embodiment
[0044] In particular, in the embodiment of FIG. 3, the transmitter coil 114 is disposed on a corresponding ferrite layer 302. Reference numeral 304 is representative of a central axis of the transmitter coil 114. The central axis 304 of the transmitter coil 114 passes through a center of the transmitter coil 114 and is in perpendicular to a x-y plane of the transmitter coil 114. The receiver coil 116 includes the main receiver coil 120 and the auxiliary receiver coils 122. An interface layer 306 is disposed between the receiver coil 116 and the transmitter coil 114. The interface layer 306 may be made of a non-magnetic insulation material, such as teflon, any polymer, plastic, ceramic, mylar, and the like.
[0045] Further, the main receiver coil 120 is disposed on a corresponding ferrite layer 210. The auxiliary receiver coils 122 are disposed about the central axis 208 on the main receiver coil 120. In the illustrated embodiment, the auxiliary receiver coils 122 are disposed between the main receiver coil 120 and the interface layer 306.
[0046] Furthermore, the central axis 304 is aligned with the central axis 208. Accordingly, the main receiver coil 120 is aligned with the transmitter coil 114. When the main receiver coil 120 is aligned with the transmitter coil 114, the main receiver coil 120 has maximum magnetic coupling with the transmitter coil 114 compared to the auxiliary receiver coils 122. Hence, a higher voltage is induced across the main receiver coil 120 compared to a voltage induced across the auxiliary receiver coils 122. Although the embodiment of FIG. 3 represents the transmitter coil 114 aligned with the main receiver coil 120, in another embodiment, the main receiver coil 120 may be misaligned with respect to the transmitter coil 114 and at least one of the auxiliary receiver coils 122 may be aligned with respect to the transmitter coil 114.
[0047] Referring now to FIG. 4, the transmitter coil 114 is disposed on the ferrite layer 302. The auxiliary receiver coils 122 are disposed on a corresponding ferrite layer 210. Further, the main receiver coil 120 is disposed on the auxiliary receiver coils 122 such that the auxiliary receiver coils 122 are sandwiched between the ferrite layer 210 and the main receiver coil 120. The main receiver coil 120 is disposed between the auxiliary receiver coils 122 and the interface layer 306.
[0048] In the illustrated embodiment, the central axis 208 of the main receiver coil 120 is misaligned with respect to the central axis 304 of the transmitter coil 114. The misalignment of the central axis 208 with respect to the central axis 304 is represented by reference numeral 308. In this embodiment, the auxiliary receiver coil A3 is aligned with respect to the transmitter coil 114. Accordingly, the auxiliary receiver coil A3 has a maximum magnetic coupling with the transmitter coil 114 compared to the main receiver coil 120 and the auxiliary receiver coil A2 with the transmitter coil 114. Thus, a voltage induced across the auxiliary receiver coil A3 is higher than a voltage induced across the auxiliary receiver coil A2. Further, in this embodiment, a voltage induced across the main receiver coil 120 is lower compared to a voltage induced across the main receiver coil 120, which is aligned with respect to the transmitter coil 114. However, a combination of a voltage induced at the auxiliary receiver coil A3 and a voltage induced at the main receiver coil 120 is provided to the corresponding converters for rectification and subsequently, to a load (not shown in FIG. 4). Thus, a desired voltage is provided to the load irrespective of aligned or misaligned conditions of the main receiver coil 120 with respect to the transmitter coil 114. It may be noted that in this scenario, the current in the transmitter coil 114 does not increase substantially. As a result, transfer of desired power to the load is achieved.
[0049] Although the illustrated embodiment of FIG. 4 represents the transmitter coil 114 misaligned with respect to the main receiver coil 120, in another embodiment, the main receiver coil 120 may be aligned with respect to the transmitter coil 114 and the auxiliary receiver coils 122 may be misaligned with respect to the transmitter coil 114.
[0050] FIG. 5 is a detailed circuit representation of a wireless power transfer system 500 in accordance with one embodiment of the present specification. The wireless power transfer system 100 includes the power source 104, the transmitter unit 106, the receiver unit 108, and a load 508. The power source 104 is coupled to the transmitter unit 106. The transmitter unit 106 is magnetically coupled to the receiver unit 108. Further, the receiver unit 108 is electrically coupled to the load 508.
[0051] The receiver unit 108 includes the receiver drive subunit 118 and the receiver coil 116. The exemplary receiver coil 116 includes the main receiver coil 120 and the plurality of auxiliary receiver coils 122. The plurality of auxiliary receiver coils 122 is represented as A1, A2, A3, and A4.
[0052] The receiver drive subunit 118 includes the main converter 124 and the plurality of auxiliary converters 502. The plurality of auxiliary converters 502 are represented as R1, R2, R3, and R4. In one embodiment, the main converter 124 and the plurality of auxiliary converters 502 are passive rectifiers. In particular, the main converter 124 and the plurality of auxiliary converters 502 are full bridge passive diode rectifiers. The main converter 124 includes a main output terminal 504. The plurality of auxiliary converters 502 is coupled to each other to form an auxiliary output terminal 506. In the illustrated embodiment, the plurality of auxiliary converters 502 is coupled to each other in parallel. The main converter 124 is coupled in series with the plurality of auxiliary converters 502. In particular, the main output terminal 504 is coupled in series with the auxiliary output terminal 506. Further, the load 508 is coupled across the main output terminal 504 and the auxiliary output terminal 506.
[0053] In particular, the power source 104 is coupled to the transmitter drive subunit 112. In one embodiment, the power source 104 is a direct current (DC) power source. During operation, the DC power provided by the power source 104 is converted to an alternating current (AC) power by the transmitter drive subunit 112. As a result, current flows through the transmitter coil 114 and a magnetic field is generated. Hence, the transmitter coil 114 is magnetically coupled to the receiver coil 116.
[0054] A voltage is induced across the receiver coil 116 due to the magnetic coupling between the transmitter coil 114 and the receiver coil 116. Specifically, a voltage is induced across the main receiver coil 120 and the auxiliary receiver coils 122 based on alignment with the transmitter coil 114. The voltage induced across the main receiver coil 120 and the auxiliary receiver coils 122 may be alternately referred to as the first voltage. For ease of representation, the first voltage induced across the main receiver coil 120 is represented as Vrx and the first voltage induced across the plurality of auxiliary coils A1, A2, A3, and A4 are represented as V1, V2, V3, and V4, respectively. Further, the first voltage induced at the main receiver coil 120 is rectified and an output voltage Va is obtained at the main output terminal 504. The output voltage Va obtained at the main output terminal 504 is also referred to as a second voltage. The first voltages induced at the auxiliary receiver coils 122 are rectified and an output voltage Vb is obtained at the auxiliary output terminal 506. The output voltage Vb obtained at the auxiliary output terminal 506 is also referred to as a third voltage. Further, a combination of the second and third voltages Va and Vb is provided to the load 508. In one embodiment, the sum of the voltages Va and Vb is provided to the load 508.
[0055] In an embodiment, when the main receiver coil 120 is aligned with the transmitter coil 114, the main receiver coil 120 has maximum magnetic coupling with the transmitter coil 114 compared to auxiliary receiver coils 122 (as depicted in FIG. 3). Hence, the voltage Vrx is greater than voltages V1, V2, V3, or V4. In one embodiment, the voltages V1, V2, V3, and V4 have a negligible value. The voltage Vrx is rectified by the main converter 124 and a voltage Va is generated at the main output terminal 504. Further, at least one of the voltages V1, V2, V3, and V4 is rectified and a voltage Vb is obtained at the auxiliary output terminal 506. Since the voltages V1, V2, V3, and V4 have a negligible value, the voltage Vb has a lower value. The value of voltage Vb is lesser than the value of voltage Va. A combination of the voltages Va and Vb is provided to the load 508. Thus, a desired voltage is provided to the load 508.
[0056] In another embodiment, the auxiliary receiver coil A3 is aligned with the transmitter coil 114 and the main receiver coil 120 is not in alignment with the transmitter coil 114 (as depicted in FIG. 4). In this scenario, the other auxiliary coils A1, A2, and A4 are also not in alignment with the transmitter coil 114. The auxiliary receiver coil A3 has a maximum magnetic coupling with the transmitter coil 114. Thus, the voltage induced across the auxiliary receiver coil A3 is higher than the voltage induced across other auxiliary receiver coils A1, A2, and A4. In particular, the voltage V3 is greater than voltages V1, V2, or V4.
[0057] Furthermore, the auxiliary converters R1, R2, R3, and R4 are configured to rectify the voltages induced across auxiliary receiver coils A1, A2, A3, and A4, respectively. If the auxiliary converters R1, R2, R3, and R4 are coupled in parallel, the voltages at the output of each auxiliary converter aid in determination of activation and/or deactivation of diodes of the auxiliary converters R1, R2, R3, and R4. Specifically, the voltages at the output of each auxiliary converter enable to determine which converter among the auxiliary converters R1, R2, R3, and R4 is operational. In one example, when the voltage V3 is greater than voltages V1, V2, or V4, the voltage at the output of the auxiliary converter R3 is greater than the voltages at the outputs of the auxiliary converters R1, R2, and R4. If the voltage at the output of the auxiliary converter R3 is greater than the voltage at the output of the auxiliary converters R1, R2, and R4, the voltage at the output of the auxiliary converter R3 reverse biases the diodes of the auxiliary converters R1, R2, and R4. Therefore, the auxiliary converters R1, R2, and R4 are in a deactivated state and do not contribute towards rectification of the voltages V1, V2, and V4, respectively. Hence, the current flowing through the auxiliary receiver coils A1, A2, and A4 is zero, thereby preventing power losses. In this scenario, only the auxiliary converter R3 is operational and the voltage Vb obtained at the auxiliary output terminal 506 is equal to the voltage rectified by the auxiliary converter R3. Specifically, in this example, voltage V3 is rectified by auxiliary converter R3 to obtain the voltage Vb at the auxiliary output terminal 506.
[0058] In accordance with aspects of the present specification, the activation and deactivation of the diodes of the auxiliary converters R1, R2, R3, and R4 are performed without use of controllers. Specifically, the particular auxiliary converter having the maximum input voltage is activated and the remaining auxiliary converters are deactivated resulting in lower power losses.
[0059] Although in the illustrated embodiment, each auxiliary receiver coil is coupled to a corresponding auxiliary converter, in other embodiments, a plurality of auxiliary receiver coils may be coupled to one auxiliary converter. Also, although the example of FIG.5 depicts use of passive diode rectifiers, use of other types of auxiliary converters and main converters are envisaged. In one embodiment, the auxiliary converters and the main converters may be active rectifiers.
[0060] FIG. 6 is a detailed circuit representation of a wireless power transfer system 600 of FIG. 1, in accordance with another embodiment of the present specification. The wireless power transfer system 100 includes the power source 104, the transmitter unit 106, the receiver unit 108, and the load 508. The transmitter unit 106 includes the transmitter drive subunit 112 coupled to the transmitter coil 114. The receiver unit 108 includes the main receiver coil 120, the main converter 124, the plurality of auxiliary receiver coils 122, and the plurality of auxiliary converters 602. The main receiver coil 120 is coupled to the main converter 124. Further, the plurality of auxiliary receiver coils 122 is coupled to the plurality of auxiliary converters 602. The auxiliary converters 602 are represented as R1, R2, R3, and R4. The auxiliary receiver coils 122 are represented as A1, A2, A3, and A4. In the illustrated embodiment, the auxiliary receiver coil A1 is coupled to the auxiliary converter R1, and in a similar manner, the auxiliary receiver coils A2, A3, and A4 are coupled to auxiliary converters R2, R3, and R4, respectively.
[0061] Further, the auxiliary converter R1 is coupled in series with auxiliary converter R3. Further, the auxiliary converter R2 is coupled in series with the auxiliary converter R4. Furthermore, a combination of the auxiliary converters R1 and R3 is coupled across the auxiliary converters R2 and R4 in parallel to form an auxiliary output terminal 506. The main converter 124 is coupled in series with the plurality of auxiliary converters 602, such that the main output terminal 504 of the main converter 124 is in series with the auxiliary output terminal 506. Further, the main converter 124 and the plurality of auxiliary converters 602 are coupled across the load 508. Additionally, the main receiver coil 120, the main converter 124, the auxiliary receiver coils 122, and the auxiliary converters 602 are disposed on a single printed circuit board 604.
[0062] In the presently contemplated configuration, a voltage Vrx is induced across the main receiver coil 120. The voltage Vrx is rectified by the main converter 124 and the voltage Va is obtained at the main output terminal 504. In a similar manner, voltages V1, V2, V3, and V4 are induced across the auxiliary receiver coils A1, A2, A3, and A4. The auxiliary converters R1, R2, R3, and R4 are configured to rectify the voltages V1, V2, V3, and V4, respectively.
[0063] Rectified voltages at the outputs of the auxiliary converters R1 and R3 are represented as Vx and rectified voltages at the outputs of the auxiliary converters R2 and R4 are represented as Vy. If the voltage Vx is greater than the voltage Vy, diodes of the auxiliary converters R2 and R4 are reverse biased. In this scenario, the auxiliary converters R2 and R4 do not rectify the voltages V2 and V4 and only the auxiliary converters R1 and R3 rectify the voltages V1 and V3, respectively. Hence, the current flowing in the auxiliary receiver coils A2 and A4 is zero.
[0064] Further, an output voltage Vb is obtained at the auxiliary output terminal 506. In one example, the rectified voltage Vb is equal to the voltage Vx. A combination of the voltage Va at the main output terminal 504 and the voltage Vb at the auxiliary output terminal 506 is provided to the load 508. In one embodiment, a sum of voltages Va and Vb may be provided to the load 508.
[0065] FIG. 7 is a detailed circuit representation of a wireless power transfer system 700 in accordance with yet another embodiment of the present specification. The wireless power transfer system 100 includes the power source 104, the transmitter unit 106, the receiver unit 108, and the load 508. The transmitter unit 106 includes the transmitter drive subunit 112 coupled to the transmitter coil 114. The receiver unit 108 includes the main receiver coil 120, the main converter 124, the plurality of auxiliary receiver coils 122, and the plurality of auxiliary converters 702. The main receiver coil 120 is coupled to the main converter 124. The plurality of auxiliary receiver coils 122 is coupled to the plurality of auxiliary converters 702. For ease of representation, the plurality of auxiliary converters 702 are represented as HR1, HR2, HR3, and HR4.
[0066] In the example of FIG. 7, each of the main converter 124 and the plurality of auxiliary converters 702 is a center tapped full-wave diode rectifier. The main converter 124 includes two diodes and a center tap terminal 704 which is a contact at a point of the main receiver coil 120, preferably at the mid-point of the main receiver coil 120. Similarly, each of the plurality of auxiliary converters 702 includes two diodes and a center-tap terminal 706 which is a contact at a point of the corresponding auxiliary receiver coil 122. The two diodes of each of the converters 124 and 702 are connected to the opposite ends of the corresponding coils 120, 122.
[0067] In accordance with the illustrated embodiments of FIGS. 5-7, the number of diodes in the plurality of auxiliary converters 702 is half the number of diodes in the plurality of auxiliary converters 502 or 602. Power losses are reduced since the plurality of auxiliary converters 702 have reduced number of diodes.
[0068] As noted hereinabove, a voltage is induced across the main receiver coil 120 and the plurality of auxiliary receiver coils 122 based on alignment with the transmitter coil 114. The voltage induced across the main receiver coil 120 is represented as Vrx. The main converter 124 rectifies the voltage Vrx and a voltage Va is obtained at the main output terminal 504. In a similar manner, the auxiliary converters HR1, HR2, HR3, and HR4 rectify the voltage induced at the auxiliary receiver coils 122. Accordingly, a rectified voltage Vb is generated at the auxiliary output terminal 506. Further, a combination of voltages Va and Vb is provided to the load 508.
[0069] FIG. 8 is a schematic representation of a wireless power transfer unit 800 in accordance with one embodiment of the present specification. The wireless power transfer unit 800 includes the transmitter unit 106 and the receiver unit 108. In the illustrated embodiment, the transmitter unit 106 has the plurality of transmitter coils 114. The receiver unit 108 is disposed in a mobile phone 802. The receiver unit 108 includes the receiver coil 116 having the main receiver coil 120 and the plurality of auxiliary receiver coils 122. The plurality of auxiliary receiver coils 122 is disposed about the central axis 208 of the main receiver coil 120. Specifically, the plurality of auxiliary receiver coils 122 disposed on the main receiver coil 120. The main receiver coil 120 and the plurality of auxiliary receiver coils 122 are coupled to the load (not shown in FIG. 8) via the corresponding converters (not shown in FIG. 8). In one embodiment, the load is a battery or a battery charger of the mobile phone 802.
[0070] A voltage is induced across the main receiver coil 120 and the plurality of auxiliary receiver coils 122 based on the alignment of the main receiver coil 120 and the plurality of auxiliary receiver coils 122 with respect to the transmitter coil 114. Further, the voltage induced at the receiver coil 116, is rectified and provided to the load. In particular, the voltages at the main receiver coil 120 and the plurality of auxiliary receiver coils 122 are rectified by the main converter (not shown in FIG. 8) and the plurality of auxiliary converters (not shown in FIG. 8), respectively. Further, the rectified voltages obtained at the main output terminal (not shown in FIG. 8) and the auxiliary output terminal (not shown in FIG. 8) is provided to the load, such as the battery. Accordingly, the battery of the receiver unit 108 is charged.
[0071] In accordance with the embodiments discussed herein, the arrangement of the main receiver coil and the plurality of auxiliary receiver coils aids in enhancing communication with the transmitter coil and allows efficient power transfer between the transmitter coil and the receiver coils even in the event of misalignment of the main receiver coil with the transmitter coil. Further, the arrangement of the auxiliary converters aids in activation and deactivation of the diodes of the auxiliary converters without use of controllers. Furthermore, the exemplary wireless power transfer system adjusts misalignments between the transmitter unit and the receiver unit without employing sensors or any other detection techniques, such as camera.
[0072] While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof.