Abstract:
Multiple coil systems and methods are disclosed in which transmitter and receiver inductors, or coils, are coupled in a configuration for wirelessly transferring data and/or power among them. In preferred implementations, the systems and methods are used for transmitting data using pairs of coupled coils. One preferred aspect of the invention is that the coils are not permanently affixed in physical proximity to one another, but can be moved and/or interchanged.

Description:
PRIORITY ENTITLEMENT 
       [0001]    This application is entitled to priority based on Provisional Patent Application Ser. No. 61/418,501 filed on Dec. 1, 2010, which is incorporated herein for all purposes by this reference. This application and the Provisional patent application have at least one common inventor. 
     
    
     TECHNICAL FIELD 
       [0002]    The invention relates to coupled inductor systems. More particularly, the invention relates to multiple coil systems for use in wireless data transfer applications. In preferred embodiments, the invention relates to the wireless transmission of data among coupled inductor coils. In preferred embodiments employed in wireless power transfer applications, the invention relates to the more efficient utilization of energy resources. 
       BACKGROUND OF THE INVENTION 
       [0003]    Existing power transmission systems utilize coupled inductor coils to transfer power wirelessly. Some of the systems known in the art also transmit data as well as power. Typically such systems use high-inductance coils (on the order of micro-Henries) and switch at low frequencies (hundreds of kHz). These systems are somewhat effective for transmitting power for apparatus such as battery chargers, AC/DC converters, and remote devices, but are not capable of transmitting high-bandwidth data. Effective implementation of wireless data transmission systems using coupled inductors faces several challenges. Among them is the problem of tuning the elements of the system to optimize transmission frequency in the presence of parasitic elements that cause ringing or otherwise distort the data signal. Additional problems encountered include, managing the peak currents in the inductors, and reliably sending and receiving data in the presence of active inductive power transmission. Another significant challenge is maintaining maximum bandwidth in the presence of varying system conditions such as temperature, coil misalignment, and coil separation. 
         [0004]    Due to these and other problems and potential problems, improved coupled inductor data and/or power transmission systems would be useful and advantageous contributions to the arts. 
       SUMMARY OF THE INVENTION 
       [0005]    In carrying out the principles of the present invention, in accordance with preferred embodiments, the invention provides advances in the arts with novel apparatus directed to the transfer of data and/or power using inductive couplings. In preferred embodiments, systems include capabilities for data and/or power transfer. Preferably, the coupled coils of systems of the invention are not permanently physically interconnected. 
         [0006]    According to aspects of the invention, examples of preferred embodiments include multiple coil systems having at least a primary coil, and a secondary coil for coupling with the primary coil. The primary and secondary coils are preferably not permanently physically affixed to one another and are interchangeable, e.g., a secondary coil can preferably be removed and replaced with a different secondary coil. When positioned in proximity, the primary and secondary coils are electromagnetically, but not physically, coupled such that one or more signals may be passed between the coils. 
         [0007]    According to aspects of the invention, in examples of preferred embodiments, a multiple coil system for wireless data transmission includes multiple primary side coils connected such that they may be driven independently with a driver signal. One or more suitable secondary coils are positioned in proximity to the primary coils for receiving the signal inductively so that the signal may be wirelessly transferred from one or more of the primary coils to one or more secondary coil. 
         [0008]    According to aspects of the invention, in examples of preferred embodiments, systems for wireless data transmission includes multiple primary coils connected with circuitry for sensing secondary coil proximity and for operating to responsively transmit a signal to detected secondary coils located in proximity with the primary coils. 
         [0009]    According to aspects of the invention, preferred embodiments of a system for multiple coil wireless data transmission include at least one coil equipped with switchable taps that may be selected for changing the frequency characteristics of the coil. 
         [0010]    According to another aspect of the invention, preferred embodiments of a system for multiple coil wireless data transmission include at least one coil connected with a switchable capacitor network that may be used for selectively changing the frequency characteristics of the coil. 
         [0011]    According to an additional aspect of the invention, an example of a preferred multiple coil data transfer system according to the invention includes at least one primary coil connected to a circuit for transmitting data. A secondary coil is provided, along with a circuit for receiving data. In the system, at least one primary coil and at least one secondary coil are adapted for inductively coupling for data transfer. In order to facilitate this, the primary side includes circuitry for selecting at least one primary coil for transmitting data based on sensed proximity to a secondary coil. 
         [0012]    The invention has advantages including but not limited to one or more of, improved coupled coil system bandwidth, improved data integrity, and reduced costs. These and other potential advantageous, features, and benefits of the present invention can be understood by one skilled in the arts upon careful consideration of the detailed description of representative embodiments of the invention in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The present invention will be more clearly understood from consideration of the following detailed description and drawings in which: 
           [0014]      FIG. 1  is a simplified schematic diagram of a coupled inductor system illustrating an example of a preferred embodiment of the invention; 
           [0015]      FIG. 2  is a schematic diagram of an example of a preferred embodiment of a multiple coil system according to the invention; and 
           [0016]      FIG. 3  is a simplified schematic view illustrating an example of a preferred embodiment of a multiple coil system according to the invention. 
       
    
    
       [0017]    References in the detailed description correspond to like references in the various drawings unless otherwise noted. Descriptive and directional terms used in the written description such as right, left, back, top, bottom, upper, side, et cetera, refer to the drawings themselves as laid out on the paper and not to physical limitations of the invention unless specifically noted. The drawings are not to scale, and some features of embodiments shown and discussed are simplified or amplified for illustrating principles and features, as well as anticipated and unanticipated advantages of the invention. 
       DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0018]    The present patent application is related to U.S. patent application Ser. No. 13/045,493 which shares at least one common inventor with the present application and has a common assignee. Said related application is hereby incorporated herein for all purposes by this reference. 
         [0019]    It has been determined that data may be transferred efficiently among coupled coils. Generally, using inductive coupling, a primary coil is positioned in proximity to a secondary coil. The primary and secondary coils are properly oriented and positioned so that they may be electromagnetically coupled in order to facilitate a transfer of energy between them. Generally, one primary coil is used with one secondary coil, and secondary side systems are designed to resonate at a particular frequency. This allows for more efficient transfer of energy at that particular frequency. The inventors have reduced to practice a novel and useful improved coupled inductor data transmission system using multiple inductor coils, on the order of 10&#39;s to 100&#39;s of nano-Henries, switched at high frequencies, on the order of 10&#39;s to 100&#39;s of MHz. The multiple coils of the system can be dynamically coupled based on operational considerations. 
         [0020]    The systems of the invention can be utilized for high bandwidth wireless data transmission as well as for wireless power transmission. Preferably, the primary and secondary coils are not permanently physically connected with one another. Each of the coils is preferably connected with additional circuitry designed for particular functionality. For example, the primary coil may be associated with data signal transmitting circuitry, and the secondary coil may be associated with corresponding data receiving circuitry. The respective coils typically reside in electronic apparatus or systems of various kinds. For example, the primary coil may reside within a battery charger or power inverter apparatus, and the secondary coil may reside in communication, computer, battery, imaging, or other portable apparatus, to cite a few examples. The respective coils are positioned within their respective apparatus such that, in operation, they may be placed in physical proximity for inductive coupling such that the coils are in communication with one another for the exchange data, and in some cases power. The system drives the primary coil on one side to transmit, and receives at the secondary coil on the other side. Such systems can be utilized for high bandwidth communication as well as power transfer across the inductive coupling between the primary and secondary coils. Transmitter, receiver, or transceiver apparatus may be used as desired for the particular implementation, using available communications equipment in combination with the multiple coil data transmission system. 
         [0021]    In the coupled inductor system according to the invention, a signal from a primary side driver is transmitted through a primary side coil to a secondary coil. If a data receiving circuit or load is connected to the secondary coil, the electric current from the secondary coil can be used to transmit data and/or to power the load. An example of a preferred embodiment of a coupled inductor system for wireless data transfer according to the invention is shown in  FIG. 1 . The system  100  includes a primary side  102  for providing one or more signals to a secondary side  104  receiver. The primary side  102  has multiple primary coils  106   a ,  106   b ,  106   c , and driver circuitry  108 . By using several primary coils  106  instead of a single coil, the size of each coil can be kept small and a large total area for inductive coupling can still be provided. The secondary side  104  has one, and preferably multiple coils  110   a ,  110   b ,  110   c , for receiving signals from the primary side  102 . In a system  100  with multiple primary coils  106 , the primary coils preferably can be driven all simultaneously, one at a time, or in selected combinations. One or both sides (primary and secondary) of systems constructed in accordance with the invention can be built with multiple selectable coils. 
         [0022]    In operation, with multiple coils arrayed in the system  100 , as in this example using multiple primary side coils  106  and multiple secondary side coils  110 , it is possible, using the primary side circuitry  108 , to detect the presence and location of a secondary side coil  110  by using appropriate sensors arranged to sense changes in the current on the primary side coils  106 . Proximity sensing preferably detects activity on a coil  106  by technology and techniques known in the arts. Activity on the coil  106  can be detected by rectifying the signal on the coil terminals and detecting the input power, for example. This detected power can be compared to a known threshold to determine whether the coil  106  is being driven by another coupled coil  110 . Alternatively, the system  100  can be configured to sense the presence of a signal on the coil  106 . Activity on the coil(s)  106  may be detected with or without first rectifying the signal. For example, coil activity can be sensed either from one terminal to ground or between the terminals. Upon detection of the position of a secondary side  104  receiving coil, e.g.  110 ( a ), in proximity suitable for inductive coupling, then the appropriate transmitting coil or coils, e.g.,  106 ( a ), closest to and/or best aligned with the detected receiving coil  110 ( a ) can be driven. In the event multiple transmitting coils can favorably be driven, each may be driven with a different drive strength selected to increase the overall the signal integrity in the system  100 . It is within the scope of the invention to use the systems described and shown for transmitting power in addition to, or in some instances, instead of data. 
         [0023]    An example of a preferred embodiment of a coupled inductor system for wireless data transfer according to the invention is shown in  FIG. 2 . The system  200  includes a primary side  202  for providing one or more signals to a secondary side  204  receiver. The primary side  202  has driver circuitry  208  for driving one or more primary coil  206 . The primary coil(s)  206  have one or more selectable tap points  210  activated by a switch  212  such that the effective size, and thus the frequency and resonance quality, or Q, of the primary coil(s)  206  can be changed dynamically. By manipulating the switch(es), e.g.,  212  and changing the tap point  210 , the radius of the coil  206  is changed based on a sense of the data integrity, coupling coefficient, or other system parameter detected by the primary side driver circuitry  208 . This system  200  may be implemented using multiple coils  206  having one or more alternative tap points  210  such that various combinations may be selected dynamically according to operational requirements. 
         [0024]    An additional example of another preferred embodiment of a multiple coil coupled inductor system for wireless power transfer according to the invention is shown in  FIG. 3 . The system  300  includes a primary side  302  for providing one or more signals to a secondary side  304  receiver. The primary side  302  has driver circuitry  308  for driving one or more primary coil  306 . The primary coil(s)  306  are connected with a network  310  of one or more selectable capacitors which may be activated by switch(es), e.g.,  312 , such that the frequency and Q of the primary coil(s)  306  can be changed dynamically. By manipulating the switch(es), e.g.,  312  and changing the effective configuration of the capacitor network  310 , the resonant qualities of the coils may be changed based on a sense of the data integrity, coupling coefficient, or other system parameter detected by the primary side driver circuitry  308 . This system  300  may be implemented using multiple coil(s)  306  having one or more alternative capacitor networks  310  for the dynamic implementation of combinations designed to match operational requirements. An additional feature of the invention includes the capability of driving two or more coils/resonant capacitors in parallel. Each coil/resonant capacitor setup can be used to provide a different filter frequency. This feature may be implemented on either, or both of, the primary side and the secondary side 
         [0025]    One or both sides (primary and secondary) of systems implementing the invention can be built with multiple coils, selectable taps or capacitor networks as shown in and described with respect to  FIGS. 1 through 3 , or suitable combinations thereof. The systems of the invention facilitate data transmission, and in some cases power transmission, using multiple coils in configurations through which the system can be adapted to changes in operating conditions, including the presence or absence of a secondary side, or misalignment of primary and secondary coils. Preferably, the systems of the invention have the capability of receiving both data and power on the same lines. This can be done simultaneously or serially. The system can change the transmission frequency when switching between power and data transmission. For example, the system can operate at the resonant frequency of the system for power transmission and change to a different frequency for data transmission. In a system with power and data both present, either the power or the data signal may be used for mode selection, configuration, and/or proximity sensing. When both data and power are transmitted through separate coils of a system, the physical locations of the data and power coils relative to each other can be critical. The relative positions of the coils coupled for transmission of data and power can be changed by selecting coils, and/or taps, and/or capacitor networks as described herein. General advantages may be realized by increasing or decreasing inductive coupling between transmitter and receiver, improving data integrity, or aiding in alignment of transmitting and receiving coils. 
         [0026]    Physical proximity sensing by monitoring the current behavior on the primary coil(s) may be used to optimize overall system behavior. For example, the system can be put into an ultra-low power mode when there is no detection of a secondary coil in suitable proximity suitable for signal transfer. When the system detects the proximity of a secondary coil, then the system can enter into a more active mode such as a signal transfer mode. The system configuration and/or operation can also be changed based on the proximity of one or more secondary coil. For example, if the system uses a periodic ping to search for a receiver, then the ping frequency can be increased when proximity is detected. In some applications this will reduce the time required for the system to come up and complete configuration. 
         [0027]    There are advantages to utilizing inductive multiple coil data and power transmission simultaneously. In a system which transmits both power and data, the power loop can be regulated using communication through the inductive data path. This path has higher bandwidth than other communication techniques such as modulating the power signal. Providing a high speed data path also enables additional functionality. Using the high speed data path for power control permits higher bandwidth and faster response times. Since the coupled coils are physically separated, they can be used to transmit data across an isolation barrier. This can be implemented in several different physical configurations. For example, the primary and secondary coils may be stacked vertically with an isolation barrier between them. The coils may be co-planar, either interleaved or not interleaved. In any implementation, the transmitting and receiving circuitry may be implemented separately or monolithically on a single piece of silicon. Using coils for data transmission is inherently a localized field communication. Consequently, this technology can be used for a variety of secure data transfer needs. These secure data transfer needs include, but are not limited to, payment transactions, personal identification, access control, asset tracking and management, transportation and logistics, animal identification, and inventory systems. 
         [0028]    While the making and using of various exemplary embodiments of the invention are discussed herein, it should be appreciated that the present invention provides inventive concepts which can be embodied in a wide variety of specific contexts. It should be understood that the multiple coil system of invention may be practiced with coupled inductor systems having communications and power transfer functionality, such as in battery chargers, power converters, portable electronics, and the like. For purposes of clarity, detailed descriptions of functions, components, and systems familiar to those skilled in the applicable arts are not included. The methods and apparatus of the invention provide one or more advantages including but not limited to, data transfer capabilities, managed power transfer capabilities, and enhanced energy utilization and conservation attributes. While the invention has been described with reference to certain illustrative embodiments, those described herein are not intended to be construed in a limiting sense. For example, variations or combinations of steps or materials in the embodiments shown and described may be used in particular cases without departure from the invention. Various modifications and combinations of the illustrative embodiments as well as other advantages and embodiments of the invention will be apparent to persons skilled in the arts upon reference to the drawings, description, and claims.