Abstract:
A method and system for establishing a communication link in a wireless power system from a wireless power transmitter (WPT) to a wireless power receiver (WPR) is provided. A flux modulator is operably disposed in the WPT for dynamically changing the WPT&#39;s impedance so as to modulate a magnetic field produced on the transmitter coil when a primary voltage applied to the WPT. A flux demodulator is operably disposed in the WPR for receiving and demodulating a secondary voltage induced on a receiver coil due to the modulated magnetic field on the transmitter coil. The induction of the secondary voltage on the receiver coil due to the modulated magnetic field on the transmitter coil establishes the communication link from the WPT to the WPR. The flux demodulator is configured as an analog signal processing chain or a digital signal processing block for decoding information obtained from the WPT.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of provisional patent application No. 61/673,736 titled “Transmitter To Receiver Communication Link In A Wireless Charging System”, filed in the United States Patent and Trademark Office on Jul. 20, 2012. 
         [0002]    The specification of the above referenced patent application is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND 
       [0003]    A wireless power system typically comprises a wireless power transmitter and a wireless power receiver. The wireless power transmitter transmits power wirelessly using a transmitter coil. Through the transmitter coil, the wireless power transmitter creates an electromagnetic field in a coupling region for providing energy transfer to the wireless power receiver. The wireless power receiver comprises a receiver coil that picks up the electromagnetic field. A voltage is induced in a receiver coil due to the electromagnetic field emanating from the transmitter coil. In the coupling region, power is transferred from the wireless power transmitter to the wireless power receiver. 
         [0004]    In conventional wireless power systems, there is only one way communication from the wireless power receiver to the wireless power transmitter. This communication link is used by the wireless power receiver to relay information, for example, messages to increase power being transmitted, decrease power being transmitted, maintain the same amount of power being transmitted, terminate transmission of power, etc., to the wireless power transmitter. In conventional wireless power systems, there is no communication link from the wireless power transmitter to the wireless power receiver. As a result, the transmitter cannot query and obtain any information from the receiver. 
         [0005]    With a communication link from the transmitter to the receiver, communication between the devices is bi-directional. This allows the construction of smarter, differentiated wireless power systems. For example, the transmitter can challenge and authenticate the identity of the receiver. If the receiver is a “known” device, the transmitter can turn on certain algorithms or reconfigure itself to enable higher power delivery or allow more spatial separation. The transmitter could also reconfigure the receiver to maintain stable power delivery. Therefore, there is a long felt but unresolved need for a method and system that establishes a communication link from a wireless power transmitter to a wireless power receiver. 
       SUMMARY OF THE INVENTION 
       [0006]    A method and system for establishing a communication link in a wireless power system is provided. The wireless power system comprises a wireless power transmitter and a wireless power receiver. A flux modulator is operably disposed in the wireless power transmitter to send messages to the wireless power receiver. Furthermore, a flux demodulator is operably disposed in the wireless power receiver to recover the messages sent by the flux modulator. The flux modulator is configured to dynamically change the wireless power transmitter&#39;s input impedance through a multitude of techniques, for example, an inductance change, a capacitance change, a resistance change, etc., and any combination thereof to change the current in the transmitter coil and hence modulate the transmitted magnetic flux field intensity. The modulated magnetic field of the transmitter coil induces a modulated secondary voltage on a receiver coil. The induction of the modulated secondary voltage on the receiver coil due to the modulated magnetic field on the transmitter coil establishes the communication link between the wireless power transmitter and the wireless power receiver in the wireless power system. The flux demodulator is configured to receive and demodulate the secondary voltage induced on the receiver coil for obtaining information from the wireless power transmitter. 
         [0007]    In an embodiment, the flux demodulator in the receiver is configured as an analog signal processing chain comprising a peak detector, a filter gain block, and a comparator for decoding the information obtained from the transmitter via the established communication link. In another embodiment, the flux demodulator in the receiver is configured as a digital signal processing block for decoding the information obtained from the transmitter via the established communication link. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  exemplarily illustrates a schematic diagram of a system for establishing a communication link between a transmitter and a receiver of a wireless power system. 
           [0009]      FIG. 2  exemplarily illustrates a first embodiment of the system for establishing a communication link between a transmitter and a receiver of a wireless power system, where a flux demodulator in the receiver is configured as an analog signal processing chain. 
           [0010]      FIG. 3  exemplarily illustrates a second embodiment of the system for establishing a communication link between a transmitter and a receiver of a wireless power system, where the flux demodulator in the receiver is configured as a digital signal processing block. 
           [0011]      FIG. 4A  exemplarily illustrates a first embodiment of a flux modulator in the wireless power transmitter of the wireless power system. 
           [0012]      FIG. 4B  exemplarily illustrates a second embodiment of the flux modulator in the transmitter of the wireless power system. 
           [0013]      FIG. 5A  exemplarily illustrates a third embodiment of the flux modulator in the transmitter of the wireless power system. 
           [0014]      FIG. 5B  exemplarily illustrates a fourth embodiment of the flux modulator in the transmitter of the wireless power system. 
           [0015]      FIG. 5C  exemplarily illustrates a fifth embodiment of the flux modulator in the transmitter of the wireless power system. 
           [0016]      FIG. 5D  exemplarily illustrates a sixth embodiment of the flux modulator in the transmitter of the wireless power system. 
           [0017]      FIG. 6A  exemplarily illustrates a seventh embodiment of the flux modulator in the transmitter of the wireless power system. 
           [0018]      FIG. 6B  exemplarily illustrates an eighth embodiment of the flux modulator in the transmitter of the wireless power system. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]      FIG. 1  exemplarily illustrates a schematic diagram of a system  100  for establishing a communication link  109  between a wireless power transmitter  100   a  and a wireless power receiver  100   b  of a wireless power system. The wireless power transmitter  100   a  comprises an inverter  101 , a tuning circuit  110  and a transmitter coil  103 . The transmitter coil  103  is, for example, an inductor. The tuning circuit  110  comprises one or more of passive electronic components, for example, a resistor, a capacitor, an inductor, a magnetic device, a transducer, etc.; active electronic components, for example, a diode, a transistor such as a metal oxide semiconductor field effect transistor (MOSFET), a bipolar transistor, etc., operational amplifiers, an optoelectronic device, directional coupler, etc., and electronic switches. The inverter  101  is a switch circuit that converts an input direct current (DC) at an input voltage of Vin into an alternating current (AC) at an output voltage of Vp. The voltage Vp represents the AC primary voltage. The primary voltage Vp is applied to the tuning circuit  110  and the transmitter coil  103  of the wireless power transmitter  100   a  to wirelessly transmit power to the wireless power receiver  100   b . The AC passes through the transmitter coil  103  and emanates a varying magnetic field from the transmitter coil  103 . This magnetic field in the transmitter coil  103  induces a voltage Vs in a receiver coil  104  of the wireless power receiver  100   b  which is in close proximity of the wireless power transmitter  100   a . The voltage Vs is herein referred to as secondary voltage. An AC current is produced at the receiver coil  104  in the wireless power receiver  100   b . A rectifier block (not shown) in the wireless power receiver  105  rectifies the AC current to obtain DC. A capacitor  107  in the wireless power receiver  100   b  filters stray AC components. A pure DC output is received across a load Rload  108 . 
         [0020]    The system  100  for establishing a peak flux modulation based communication link  109  between the wireless power transmitter  100   a  and the wireless power receiver  100   b  of the wireless power system comprises a flux modulator  102  operably disposed in the wireless power transmitter  100   a  and a flux demodulator  106  operably disposed in the wireless power receiver  100   b . The flux modulator  102  utilizes the transmitter coil  103  of the wireless power transmitter  100   a  to send information in the form of messages to the flux demodulator  106 . The flux demodulator  106  utilizes the receiver coil  104  of the wireless power receiver  100   b  to recover the messages transmitted by the flux modulator  102 . The flux modulator  102  is configured to dynamically change the wireless power transmitter&#39;s  100   a  input impedance through a multitude of techniques, for example, an inductance change, a capacitance change, a resistance change, etc., and any combination thereof to change the current in the transmitter coil  103  and hence modulate the transmitted magnetic flux intensity. This represents a flux modulation performed at the wireless power transmitter  100   a . The input to the flux demodulator  106  is the secondary voltage, Vs, induced on the receiver coil  104 , as a result of flux emanating from the transmitter coil  103 . The modulated magnetic field on the transmitted coil  103  induces a modulated secondary voltage on a receiver coil  104 . The induction of a modulated secondary voltage on the receiver coil  104  proportional to the modulated magnetic field on the transmitter coil  103  establishes the communication link  109  from the wireless power transmitter  100   a  to the wireless power receiver  100   b  in the wireless power system. 
         [0021]    The flux demodulator  106  in the wireless power receiver  100   b  is configured to receive and demodulate the secondary voltage induced on the receiver coil  104  for obtaining information, for example, in the form of messages from the wireless power transmitter  100   a . The messages sent by the wireless power transmitter  100   a  are, for example, packet based messages, symbol based messages, etc., or any combination thereof. The system  100  disclosed herein allows the wireless power transmitter  100   a  to communicate with the wireless power receiver  100   b , via the established communication link  109  for multiple applications, for example, authentication, exchange of diagnostic information, synchronization, etc. 
         [0022]      FIG. 2  exemplarily illustrates a first embodiment of the system  100  for establishing a communication link  109  between a wireless power transmitter  100   a  and a wireless power receiver  100   b  of a wireless power system, where the flux demodulator  106  in the wireless power receiver  100   b  is configured as an analog signal processing chain. The analog signal processing chain decodes the information obtained from the wireless power transmitter  100   a  via the established communication link  109  exemplarily illustrated in  FIG. 1 . The analog signal processing chain in the flux demodulator  106  processes the secondary voltage to obtain an analog representation of a message transmitted by the flux modulator  102 . The flux demodulator  106  configured as the analog signal processing chain comprises a peak detector  106   a , a filter gain block  106   b , and a comparator  106   c . The voltage induced across the receiver coil  104 , Vs, is fed as an input to the peak detector  106   a . The peak detector  106   a  determines the peak of the AC value and converts the peak of the AC value into a DC value that stays at the peak of the AC value. The filter gain block  106   b  removes unwanted frequency components from the DC signal and enhances the desired frequency components. The comparator  106   c  compares the input voltages and provides a digital data output to indicate the largest of the input voltages. 
         [0023]      FIG. 3  exemplarily illustrates a second embodiment of the system  100  for establishing a communication link  109  between a wireless power transmitter  100   a  and a wireless power receiver  100   b  of a wireless power system, where the flux demodulator  106  is configured as a digital signal processing block  106   d . The digital signal processing block  106   d  converts the secondary voltage, Vs, induced across the receiver coil  104  that is directly fed as input to the digital signal processing block  106   d , into digital data. That is, the digital signal processing block  106   d  decodes the information obtained from the wireless power transmitter  100   a  via the established communication link  109  exemplarily illustrated in  FIG. 1 . The digital signal processing block  106   d  processes the secondary voltage to obtain a digital representation of the message transmitted by the flux modulator  102 . The digital signal processing block  106   d  recovers the message sent by the wireless power transmitter  100   a.    
         [0024]      FIG. 4A  exemplarily illustrates a first embodiment of the flux modulator  102  in the wireless power transmitter  100   a  of the wireless power system. The transmitter coil  103  comprises a primary coil  103   a  and a communication modulation coil  103   b  connected in parallel. The communication modulation coil  103   b  may be enclosed within the primary coil  103   a  or vice versa or the coils  103   a  and  103   b  may be placed distinctly away from each other. The primary coil  103   a  is represented as L TX  and the communication modulation coil  103   b  is represented as L MOD . The flux modulator control module  102   a  in the flux modulator  102  is configured to change the wireless power transmitter&#39;s  100   a  input impedance (as seen by the power source) by selecting the primary coil  103   a  or both the primary coil  103   a  and the communication modulation coil  103   b  using a switch S 1 . If switch S 1  is open, current passes though the primary coil L TX    103   a  only, and the amount of flux generated in the transmitter coil  103  is transmitted to the receiver coil  104  at the wireless power receiver  100   b . If switch S 1  is closed, the primary coil L TX    103   a  and the communication modulation coil L MOD    103   b  are connected in parallel. The effective inductance of the transmitter coil  103  decreases, thereby affecting the current and the amount of flux generated in the transmitter coil  103  that is transmitted to the receiver coil  104  at the wireless power receiver  100   b . The change in effective inductance changes the current through the transmitter coil  103   a  which in turn modulates the intensity of the magnetic field produced by the wireless power transmitter  100   a . By opening and closing switch S 1 , the flux modulator control module  102   a  modulates the flux thereby creating the communication channel from the wireless power transmitter  100   a  to the wireless power receiver  100   b.    
         [0025]      FIG. 4B  exemplarily illustrates a second embodiment of the flux modulator  102  in the wireless power transmitter  100   a  of the wireless power system. The transmitter coil  103  comprises a primary coil  103   a  and a communication modulation coil  103   b  connected in series. The communication modulation coil  103   b  may be enclosed within the primary coil  103   a  or vice versa or the coils  103   a  and  103   b  may be placed distinctly away from each other. The primary coil  103   a  is represented as L TX  and the communication modulation coil  103   b  is represented as L MOD . The flux modulator control module  102   a  in the flux modulator  102  is configured to change the wireless power transmitter&#39;s  100   a  input impedance (as seen by the power source) by selecting the primary coil  103   a  or both the primary coil  103   a  and the communication modulation coil  103   b . If switch S 1  is closed, current passes through the primary coil L TX    103   a  and the amount of flux generated in the transmitter coil  103  is transmitted to the receiver coil  104  at the wireless power receiver  100   b . If switch S 1  is open, the communication modulation coil L MOD    103   b  and the primary coil L TX    103   a  are connected in series. The effective inductance increases, thereby affecting the current and the amount of flux generated in the transmitter coil  103  that is transmitted to the receiver coil  104  at the wireless power receiver  100   b . The change in effective primary inductance changes the current through the transmitter coil  103   a  which in turn modulates the intensity of the magnetic field produced by the wireless power transmitter  100   a . By opening and closing switch S 1 , the flux modulator control module  102   a  modulates the flux thereby creating the communication channel from the wireless power transmitter  100   a  to the wireless power receiver  100   b.    
         [0026]      FIG. 5A  exemplarily illustrates a third embodiment of the flux modulator  102  in the wireless power transmitter  100   a  of the wireless power system. The tuning circuit  110  is in series with the transmitter coil  103 . The tuning circuit  110  comprises a primary capacitor and a communication modulation capacitor that is connected in parallel with the primary capacitor. The primary capacitor is represented as C TX  and the communication modulation capacitor is represented as C MOD . The flux modulator control module  102   a  in the flux modulator  102  is configured to change the wireless power transmitter&#39;s  100   a  input impedance (as seen by the power source) by selecting the primary capacitor or both the primary capacitor and the communication modulation capacitor. If switch S 1  is open, the impedance of the tuning circuit  110  is (−j/W*C TX ). If switch S 1  is closed, the impedance of the tuning circuit  110  changes to (−j/W*(C TX+ C MOD )). This change in impedance of the tuning circuit  110  changes the impedance of the wireless power transmitter  100   a  and hence, the current that passes through the primary coil L TX    103 . The change in current through the transmitter coil  103  in turn modulates the intensity of the magnetic flux field produced by the wireless power transmitter  100   a  that is transmitted to the receiver coil  104  at the wireless power receiver  100   b . By opening and closing switch S 1 , the flux modulator control module  102   a  modulates the flux thereby creating the communication channel from the wireless power transmitter  100   a  to the wireless power receiver  100   b.    
         [0027]      FIG. 5B  exemplarily illustrates a fourth embodiment of the flux modulator  102  in the wireless power transmitter  100   a  of the wireless power system. The tuning circuit  110  is in series with the transmitter coil  103 . The tuning circuit  110  comprises a primary capacitor and a communication modulation capacitor that is connected in series with the primary capacitor. The primary capacitor is represented as C TX  and the communication modulation capacitor is represented as C MOD . The flux modulator control module  102   a  in the flux modulator  102  is configured to change the wireless power transmitter&#39;s  100   a  input impedance (as seen by the power source) by selecting the primary capacitor or both the primary capacitor and the communication modulation capacitor. If switch S 1  is open, the impedance of the tuning circuit  110  is the primary capacitor in series with the communication modulation capacitor which is (−j/W*C new ) where Cnew is (C TX *C MOD  (C TX +C MOD )) If switch S 1  is closed, the impedance of the tuning circuit  110  changes to (−j/W*C TX ). This change in impedance of the tuning circuit  110  changes the impedance of the wireless power transmitter  100   a  and hence, the current that passes through the primary coil L TX    103 . The change in current through the transmitter coil  103  in turn modulates the intensity of the magnetic flux field produced by the wireless power transmitter  100   a  that is transmitted to the receiver coil  104  at the wireless power receiver  100   b . By opening and closing switch S 1 , the flux modulator control module  102   a  modulates the flux thereby creating the communication channel from the wireless power transmitter  100   a  to the wireless power receiver  100   b.    
         [0028]      FIG. 5C  exemplarily illustrates a fifth embodiment of the flux modulator  102  in the wireless power transmitter  100   a  of the wireless power system. The tuning circuit  110  is in parallel with the transmitter coil  103 . The tuning circuit  110  comprises a primary capacitor and a communication modulation capacitor that is connected in series with the primary capacitor. The primary capacitor is represented as C TX  and the communication modulation capacitor is represented as C MOD . The flux modulator control module  102   a  in the flux modulator  102  is configured to change the wireless power transmitter&#39;s  100   a  input impedance (as seen by the power source) by selecting the primary capacitor or both the primary capacitor and the communication modulation capacitor. If switch S 1  is open, the impedance of the tuning circuit  110  is the primary capacitor in series with the communication modulation capacitor which is (−j/W*Cnew) where Cnew is (C TX *C MOD /(C TX +C MOD )). If switch S 1  is closed, the impedance of the tuning circuit  110  changes to (−j/W*C TX ). This change in impedance of the tuning circuit  110  changes the impedance of the wireless power transmitter  100   a  and hence, the current that passes through the primary coil L TX    103 . The change in current through the transmitter coil  103  in turn modulates the intensity of the magnetic flux field produced by the wireless power transmitter  100   a  that is transmitted to the receiver coil  104  at the wireless power receiver  100   b . By opening and closing switch S 1 , the flux modulator control module  102   a  modulates the flux thereby creating the communication channel from the wireless power transmitter  100   a  to the wireless power receiver  100   b.    
         [0029]      FIG. 5D  exemplarily illustrates a sixth embodiment of the flux modulator  102  in the wireless power transmitter  100   a  of the wireless power system. The tuning circuit  110  is in parallel with the transmitter coil  103 . The tuning circuit  110  comprises a primary capacitor and a communication modulation capacitor that is connected in parallel with the primary capacitor. The primary capacitor is represented as C TX  and the communication modulation capacitor is represented as C MOD . The flux modulator control module  102   a  in the flux modulator  102  is configured to change the wireless power transmitter&#39;s  100   a  input impedance (as seen by the power source) by selecting the primary capacitor or both the primary capacitor and the communication modulation capacitor. If switch S 1  is open, the impedance of the tuning circuit  110  is (−j/W*C TX ). If switch S 1  is closed, the impedance of the tuning circuit  110  changes to (−j/W*(C TX+ C MOD )). This change in impedance of the tuning circuit  110  changes the impedance of the wireless power transmitter  100   a  and hence, the current that passes through the primary coil L TX    103 . The change in current through the transmitter coil  103  in turn modulates the intensity of the magnetic flux field produced by the wireless power transmitter  100   a  that is transmitted to the receiver coil  104  at the wireless power receiver  100   b . By opening and closing switch S 1 , the flux modulator control module  102   a  modulates the flux thereby creating the communication channel from the wireless power transmitter  100   a  to the wireless power receiver  100   b.    
         [0030]      FIG. 6A  exemplarily illustrates a seventh embodiment of the flux modulator  102  in the wireless power transmitter  100   a  of the wireless power system. The tuning circuit  110  is in series with the transmitter coil  103 . The tuning circuit  110  comprises a primary capacitor and a communication modulation resistor that is connected in series with the primary capacitor. The primary capacitor is represented as C TX  and the communication modulation resistor is represented as R MOD . The flux modulator control module  102   a  in the flux modulator  102  is configured to change the wireless power transmitter&#39;s  100   a  input impedance (as seen by the power source) by selecting the primary capacitor or both the primary capacitor and the communication modulation resistor. If switch S 1  is open, the impedance of the tuning circuit  110  is (−j/W*C TX ) where W is the operating angular frequency of the system. If switch S 1  is closed, the impedance of the tuning circuit  110  changes to (R MOD −j/(W*C TX )). This change in impedance of the tuning circuit  110  changes the impedance of the wireless power transmitter  100   a  and hence, the current that passes through the primary coil L TX    103 . The change in current through the transmitter coil  103  in turn modulates the intensity of the magnetic flux field produced by the wireless power transmitter  100   a  that is transmitted to the receiver coil  104  at the wireless power receiver  100   b . By opening and closing switch S 1 , the flux modulator control module  102   a  modulates the flux thereby creating the communication channel from the wireless power transmitter  100   a  to the wireless power receiver  100   b.    
         [0031]      FIG. 6B  exemplarily illustrates an eighth embodiment of the flux modulator  102  in the wireless power transmitter  100   a  of the wireless power system. In this embodiment, a communication modulation resistor R MOD  with a switch S 1  across it is placed between the input power source Vin and the inverter  101 . The flux modulator control module  102   a  in the flux modulator  102  is configured to change the wireless power transmitter&#39;s  100   a  input impedance (as seen by the power source) by including or bypassing the communication modulation resistor in the current path. If switch S 1  is closed, the communication modulation resistor is excluded from the current path. If switch S 1  is open, the communication modulation resistor is included in the current path. The inclusion and exclusion of the communication modulation resistor changes the impedance of the wireless power transmitter  100   a  and hence, the current that passes through the primary coil L TX    103 . The change in current through the transmitter coil  103  in turn modulates the intensity of the magnetic flux field produced by the wireless power transmitter  100   a  that is transmitted to the receiver coil  104  at the wireless power receiver  100   b . By opening and closing switch S 1 , the flux modulator control module  102   a  modulates the flux thereby creating the communication channel from the wireless power transmitter  100   a  to the wireless power receiver  100   b.    
         [0032]    The foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present invention disclosed herein. While the invention has been described with reference to various embodiments, it is understood that the words, which have been used herein, are words of description and illustration, rather than words of limitation. Further, although the invention has been described herein with reference to particular means, materials, and embodiments, the invention is not intended to be limited to the particulars disclosed herein; rather, the invention extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims. Those skilled in the art, having the benefit of the teachings of this specification, may affect numerous modifications thereto and changes may be made without departing from the scope and spirit of the invention in its aspects.