PATENT DOCUMENT

Publication Number: US-10734840-B2
Application Number: US-201715422345-A
Country: US
Kind Code: B2

Title: Shared power converter for a wireless transmitter device

Abstract:
A transmitter device is configured to transfer energy to multiple receiver devices. The transmitter device includes multiple transmitter coils, and a shared power converter is coupled to each transmitter coil. The shared power converter includes a leading half bridge and multiple trailing half bridges. Each transmitter coil is coupled between the leading half bridge and a respective one of the trailing half bridges. The shared power converter is dynamically configurable in that the leading half bridge may be coupled to multiple trailing half bridges when energy is to be transferred wirelessly to two or more receiver devices. The leading half bridge simultaneously operates with each trailing half bridge as an independent full-bridge phase shift inverter. A signal supplied to each transmitter coil is independently regulated by controlling a phase shift of a respective trailing half bridge with respect to the leading half bridge.

Claims:
What is claimed is: 
     
       1. A shared power converter circuit for a wireless energy transfer system, the shared power converter circuit comprising:
 a leading half bridge coupled between first and second input nodes of the shared power converter circuit and having a first intermediate node; 
 multiple transmitter coils, each coupled to the first intermediate node; and 
 multiple trailing half bridges coupled between the first and second input nodes, each trailing half bridge having a respective intermediate node coupled to a distinct one of the multiple transmitter coils; wherein 
 the leading half bridge is configured to simultaneously operate with each trailing half bridge as an independent full-bridge phase shift inverter by:
 applying a first voltage at the first intermediate node; 
 applying a second voltage at the respective intermediate node of a one of the multiple trailing half bridges; and 
 controlling a phase shift of the second voltage with respect to the first voltage; wherein 
 a one of the multiple transmitter coils is between the first intermediate node and a second intermediate node. 
 
 
     
     
       2. The shared power converter circuit of  claim 1 , wherein the leading half bridge comprises:
 a first switching element connected to the first intermediate node; and 
 a second switching element connected to the first intermediate node. 
 
     
     
       3. The shared power converter circuit of  claim 2 , wherein each trailing half bridge comprises:
 a third switching element connected to the second intermediate node; and 
 a fourth switching element connected to the second intermediate node. 
 
     
     
       4. A wireless transmitter device, comprising:
 a first transmitter coil; 
 a second transmitter coil; 
 a shared power converter coupled to the first and second transmitter coils, the shared power converter comprising: 
 a leading half bridge comprising:
 a first switching element coupled between a power supply and a first intermediate node; and 
 a second switching element coupled between a ground and the first intermediate node; 
 
 a first trailing half bridge comprising:
 a third switching element coupled between the power supply and a second intermediate node; and 
 a fourth switching element coupled between the ground and the second intermediate node, wherein the first transmitter coil is coupled between the first and second intermediate nodes; 
 
 a second trailing half bridge comprising:
 a fifth switching element coupled between the power supply and a third intermediate node; and 
 a sixth switching element coupled between the ground and the third intermediate node, wherein the second transmitter coil is coupled between the first and third intermediate nodes; and 
 
 a processing device coupled to the shared power converter and configured to operate the shared power converter as a full bridge to transfer energy from the first transmitter coil by:
 causing a first switch signal and a second switch signal to be respectively transmitted to the first switching element and the second switching element of the leading half bridge; and 
 causing a third switch signal and a fourth switch signal to be respectively transmitted to the third switching element and the fourth switching element of the first trailing half bridge; wherein 
 
 the first and second switch signals produce a first voltage signal at the first intermediate node; 
 the third and fourth switch signals produce a second voltage signal at the second intermediate node; and 
 a phase of the second voltage signal is independent of a phase of the first voltage signal. 
 
     
     
       5. The wireless transmitter device of  claim 4 , wherein:
 the full bridge comprises a first full bridge; and 
 the processing device is further configured to operate the shared power converter as a second full bridge to transfer energy from the second transmitter coil by: 
 causing a fifth switch signal and a sixth switch signal to be respectively transmitted to the fifth switching element and the sixth switching element of the second trailing half bridge, wherein: 
 the fifth and sixth switch signals produce a third voltage signal at the third intermediate node; and 
 a phase of the third voltage signal is independent of the phase of the first voltage signal. 
 
     
     
       6. The wireless transmitter device of  claim 5 , wherein the processing device is configured to create the first and the second full bridges simultaneously. 
     
     
       7. The wireless transmitter device of  claim 4 , further comprising a memory coupled to the processing device, the memory configured to store one or more switch signal characteristics for at least:
 the first and second switch signals; or 
 the third and fourth switch signals. 
 
     
     
       8. The wireless transmitter device of  claim 7 , further comprising a signal generator coupled to the processing device, wherein the processing device is further configured to cause the one or more switch signal characteristics to be transmitted to the signal generator, and based on the received one or more switch signal characteristics, the signal generator is configured to:
 produce the first and second switch signals and respectively transmit the first and second switch signals to the first switching element and the second switching element of the leading half bridge; or 
 produce the third and fourth switch signals and respectively transmit the third and fourth switch signals to the third switching element and the fourth switching element of the first trailing half bridge. 
 
     
     
       9. The wireless transmitter device of  claim 4 , further comprising:
 first transmitter resonant circuitry coupled between the first trailing half bridge and the first transmitter coil; and 
 second transmitter resonant circuitry coupled between the second trailing half bridge and the second transmitter coil. 
 
     
     
       10. A method of operating a wireless transmitter device that is coupled to or includes a shared power converter comprising a leading half bridge and multiple trailing half bridges, wherein a respective transmitter coil is coupled between the leading half bridge and each of the multiple trailing half bridges, the method comprising:
 detecting a receiver device on a transmitting surface of the wireless transmitter device; and 
 forming a full bridge in the shared power converter to transfer energy from the respective transmitter coil to the receiver device, wherein forming the full bridge comprises:
 transmitting a first set of switch signals to the leading half bridge; and 
 transmitting a second set of second switch signals to a respective trailing half bridge that is coupled to the respective transmitter coil, wherein the second set of switch signals is phase-shifted independently with respect to the first set of switch signals. 
 
 
     
     
       11. The method of  claim 10 , further comprising:
 determining one or more switch signal characteristics for the second set of switch signals prior to transmitting the first and second sets of switch signals, wherein the one or more switch signal characteristics comprises a phase difference of the second set of switch signals with respect to a phase of the first set of switch signals; and 
 transmitting the one or more switch signal characteristics to a signal generator that is coupled to the leading half bridge and to each of the multiple trailing half bridges, wherein the signal generator produces the first set of switch signals and produces the second set of switch signals based on the one or more switch signal characteristics. 
 
     
     
       12. The method of  claim 11 , further comprising determining a receiver device type for the receiver device prior to determining the one or more switch signal characteristics. 
     
     
       13. The method of  claim 10 , further comprising:
 prior to detecting the receiver device on the transmitting surface, detecting an object on the transmitting surface; 
 determining if the object is the receiver device; and 
 forming the full bridge to transfer energy to the receiver device only when the object is the receiver device. 
 
     
     
       14. The method of  claim 10 , wherein the shared power converter is one of multiple shared power converters and the method comprises:
 determining a location of the receiver device on the transmitting surface; and 
 identifying a respective one of the multiple shared power converters to receive the first and second sets of switch signals based on the determined location. 
 
     
     
       15. The method of  claim 10 , further comprising:
 determining if the transfer of energy is to stop; and 
 stop transmitting the first and second sets of switch signals when the transfer of energy is to stop. 
 
     
     
       16. A method of operating a wireless transmitter device that includes or is coupled to a shared power converter, the shared power converter comprising a leading half bridge, first and second trailing half bridges, a first transmitter coil coupled between the leading half bridge and the first trailing half bridge, and a second transmitter coil coupled between the leading half bridge and the second trailing half bridge, the method comprising:
 detecting a first receiver device on a transmitting surface of the wireless transmitter device; 
 forming a first full bridge in the shared power converter to transfer energy from the first transmitter coil to the first receiver device, wherein forming the first full bridge comprises:
 transmitting a first set of switch signals to the leading half bridge; and 
 transmitting a second set of switch signals to the first trailing half bridge, wherein the second set of switch signals is phase-shifted independently with respect to the first set of switch signals; 
 
 detecting a second receiver device on the transmitting surface of the wireless transmitter device; and 
 forming a second full bridge in the shared power converter to transfer energy from the second transmitter coil to the second receiver device, wherein forming the second full bridge comprises:
 transmitting a third set of switch signals to the second trailing half bridge, wherein the third set of switch signals is phase-shifted independently with respect to the first set of switch signals. 
 
 
     
     
       17. The method of  claim 16 , wherein the third set of switch signals is phase-shifted with respect to the first set of switch signals and with respect to the second set of switch signals. 
     
     
       18. The method of  claim 16 , wherein the first and second full bridges are formed simultaneously. 
     
     
       19. The method of  claim 16 , further comprising prior to transmitting the second set of switch signals:
 determining one or more first switch signal characteristics for the second set of switch signals, wherein the one or more first switch signal characteristics comprises a phase difference of the second set of switch signals with respect to a phase of the first set of switch signals; and 
 generating the second set of switch signals based on the determined one or more first switch signal characteristics. 
 
     
     
       20. The method of  claim 16 , further comprising prior to transmitting the third set of switch signals:
 determining one or more second switch signal characteristics for the third set of switch signals, wherein the one or more second switch signal characteristics comprises a phase difference of the third set of switch signals with respect to a phase of the first set of switch signals; and 
 generating the third set of switch signals based on the determined one or more second switch signal characteristics. 
 
     
     
       21. The method of  claim 16 , wherein transmitting the first set of switch signals to the leading half bridge comprises reading the first set of switch signals from a memory. 
     
     
       22. The method of  claim 16 , wherein transmitting the second set of switch signals to the first trailing half bridge comprises reading the second set of switch signals from a memory. 
     
     
       23. The method of  claim 16 , wherein transmitting the third set of switch signals to the second trailing half bridge comprises reading the third set of switch signals from a memory. 
     
     
       24. A power adapter, comprising:
 a leading half bridge coupled between first and second input nodes, the leading half bridge comprising:
 a first switching element coupled between the first input node and a first intermediate node; and 
 a second switching element coupled between the first intermediate node and the second input node; 
 
 a first trailing half bridge coupled between the first and the second input nodes, the first trailing half bridge comprising:
 a third switching element coupled between the first input node and a second intermediate node; and 
 a fourth switching element coupled between the second intermediate node and the second input node, wherein a first load is coupled between the first intermediate node and the second intermediate node; and 
 
 a second trailing half bridge coupled between the first and the second input nodes, the second trailing half bridge comprising:
 a fifth switching element coupled between the first input node and a third intermediate node; and 
 a sixth switching element coupled between the third intermediate node and the second input node, wherein a second load is coupled between the first intermediate node and the third intermediate node; wherein the power adapter is configured to: 
 
 apply a first switching signal to the first switching element and a second switching signal to the second switching element; 
 apply a third switching signal to the third switching element and a fourth switching signal to the fourth switching element; and 
 apply a fifth switching signal to the fifth switching element and a sixth switching signal to the sixth switching element, the fifth and sixth switching signals having a phase independent of a phase of the first and second switching signals. 
 
     
     
       25. The power adapter of  claim 24 , wherein the first load and the second load each comprise a transmitter coil.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Patent Application No. 62/380,337, filed on Aug. 26, 2016, and entitled “A Shared Power Converter For A Wireless Transmitter Device,” which is incorporated by reference as if fully disclosed herein. 
    
    
     FIELD 
     The described embodiments relate generally to wireless energy transfer systems. More particularly, the present embodiments relate to a wireless transmitter device with a shared power converter for use with multiple transmitter coils. 
     BACKGROUND 
     Some electronic devices are configured to receive power wirelessly. A user may place the electronic device on a charging surface of a wireless charging device to transfer power from the charging device to the electronic device. The charging device transfers power to the electronic device through inductively coupling between a transmitter coil in the charging device and a receiver coil in the electronic device. 
     Some wireless charging devices are constructed to only transfer energy to a particular electronic device. This can increase the cost to a user who uses wireless charging for multiple electronic devices. Because each electronic device may operate only with a particular charging device, a user may be required to purchase multiple charging devices. 
     SUMMARY 
     Embodiments described herein relate to a transmitter device that is configured to transfer energy to multiple receiver devices using a shared power converter. The shared power converter includes a single leading half bridge and multiple trailing half bridges. The shared power converter can be coupled to multiple transmitter coils, with each transmitter coil coupled between the single leading half bridge and a respective one of the multiple trailing half bridges. The shared power converter is dynamically configurable in that the leading half bridge may be coupled to one or more of the multiple trailing half bridges when energy is to be transferred wirelessly to a single receiver device, or the leading half bridge may be simultaneously coupled to multiple trailing half bridges when energy is to be transferred wirelessly to multiple receiver devices. When the leading half bridge is coupled to a respective trailing half bridge, the leading half bridge and the respective trailing half bridge form an independent full bridge. The amount of energy that is transferred by the transmitter coil coupled between the leading half bridge and the respective trailing half bridge can be regulated by controlling a relative phase offset or difference between the switch signals that are received by the respective trailing half bridge and the switch signals that are received by the leading half bridge. 
     In one aspect, a shared power converter circuit for a wireless energy transfer system includes a leading half bridge coupled between first and second input nodes of the shared power converter circuit and multiple trailing half bridges coupled between the first and second input nodes of the shared power converter circuit. The leading half bridge has a first intermediate node that is coupled to multiple transmitter coils. Each trailing half bridge has a second intermediate node that is coupled to a respective one of the multiple transmitter coils. The leading half bridge is configured to simultaneously operate with each trailing half bridge as an independent full bridge phase shift inverter. An alternating current (AC) signal (e.g., AC voltage) supplied to each transmitter coil is independently regulated by controlling a phase shift of a respective trailing half bridge with respect to the leading half bridge. 
     In another aspect, a wireless transmitter device includes a first transmitter coil, a second transmitter coil, a shared power converter coupled to the first and second transmitter coils, and a processing device coupled to the shared power converter. The shared power converter further includes a leading half bridge, a first trailing half bridge, and a second trailing half bridge. The leading half bridge includes a first switching element coupled to a first intermediate node and a second switching element coupled to the first intermediate node. The first trailing half bridge includes a third switching element coupled to a second intermediate node and a fourth switching element coupled to the second intermediate node. The second trailing half bridge includes a fifth switching element connected to a third intermediate node and a sixth switching element connected to the third intermediate node. The first transmitter coil is coupled between the first and second intermediate nodes, and the second transmitter coil is coupled between the first and third intermediate nodes. The processing device is configured to assemble the shared power converter into a full bridge for wireless energy transfer from the first transmitter coil. The processing device is configured to cause first and second switch signals to be transmitted to the leading half bridge, and to cause third and fourth switch signals to be transmitted to the first trailing half bridge. The first and second switch signals have a first phase and the third and fourth switch signals have a second phase that is different from the first phase. 
     In yet another aspect, a shared power converter is included in, or coupled to, a wireless transmitter device. The shared power converter can include a leading half bridge and first and second trailing half bridges. A first transmitter coil is coupled between the leading half bridge and the first trailing half bridge. A second transmitter coil is coupled between the leading half bridge and the second trailing half bridge. A method of operating the wireless transmitter device may include detecting a first receiver device on a transmitting surface of the transmitter device and forming a first full bridge in the shared power converter to transfer energy from the first transmitter coil to the first receiver device. The first full bridge is formed by transmitting a first set of switch signals to the leading half bridge, and transmitting a second set of switch signals to the first trailing half bridge. The second set of switch signals is phase-shifted with respect to the first set of switch signals. Additionally, a second receiver device may be detected on the transmitting surface of the transmitter device and a second full bridge formed in the shared power converter to transfer energy from the second transmitter coil to the second receiver device. The second full bridge is formed by transmitting a third set of switch signals to the second trailing half bridge, where the third set of switch signals is phase-shifted with respect to the first set of switch signals. In some embodiments, the third set of switch signals is phase-shifted with respect to the first set of switch signals and with respect to the second set of switch signals. The first and second full bridges can be formed sequentially or simultaneously (either at the same time or with some overlap in time). 
     In another aspect, a shared power converter is included in, or coupled to, a wireless transmitter device. The shared power converter includes a leading half bridge and multiple trailing half bridges. A transmitter coil is coupled between the leading half bridge and each respective one of the multiple trailing half bridges. A method of operating the wireless transmitter device includes detecting a receiver device on a transmitting surface of the transmitter device and forming a full bridge in the shared power converter to transfer energy from a respective transmitter coil to the receiver device. The operation of forming the full bridge includes transmitting a first set of switch signals to the leading half bridge, and transmitting a second set of switch signals to a respective trailing half bridge that is coupled to the respective transmitter coil. The second set of switch signals is phase-shifted with respect to the first set of switch signals. 
     In yet another aspect, a power adapter includes a leading half bridge coupled between first and second input nodes, a first trailing half bridge coupled between the first and the second input nodes, and a second trailing half bridge coupled between the first and the second input nodes the leading half bridge. The leading half bridge includes a first switching element coupled between the first input node and a first intermediate node, and a second switching element coupled between the first intermediate node and the second input node. The first trailing half bridge includes a third switching element coupled between the first input node and a second intermediate node, and a fourth switching element coupled between the second intermediate node and the second input node. The second trailing half bridge includes a fifth switching element coupled between the first input node a third intermediate node, and a sixth switching element coupled between the third intermediate node and the second input node. A first load is coupled between the first intermediate node and the second intermediate node and a second load is coupled between the first intermediate node and the third intermediate node. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure will be readily understood by the following detailed description in conjunction with the accompanying drawings, wherein like reference numerals designate like structural elements, and in which: 
         FIG. 1  shows an example transmitter device that is configured to transfer energy wirelessly to one or more receiver devices; 
         FIG. 2  shows an example wireless energy transfer system; 
         FIG. 3  depicts an example schematic diagram of a shared power converter that is suitable for use in the transmitter device shown in  FIG. 1 ; 
         FIG. 4A  shows example voltage levels of a first node signal that can be produced at the first intermediate node in the shared power converter shown in  FIG. 3 ; 
         FIG. 4B  depicts example voltage levels of a second node signal that can be produced at the second intermediate node in the shared power converter shown in  FIG. 3 ; 
         FIG. 4C  illustrates example voltage levels of an AC coil signal that is received by the first transmitter coil shown in  FIG. 3 , and is based on the first and second node signals shown in  FIGS. 4A-4B ; 
         FIG. 5A  shows example voltage levels of a first node signal that can be produced at the first intermediate node in the shared power converter shown in  FIG. 3 ; 
         FIG. 5B  depicts example voltage levels of a third node signal that can be produced at the third intermediate node in the shared power converter shown in  FIG. 3 ; 
         FIG. 5C  depicts example voltage levels of an AC coil signal that is received by the second transmitter coil shown in  FIG. 3 , and is based on the first and third node signals shown in  FIGS. 5A-5B ; 
         FIG. 6  shows a flowchart of a first method of operating a wireless transmitter device that includes or is coupled to a shared power converter; 
         FIG. 7  depicts a flowchart of a second method of operating a wireless transmitter device that includes or is coupled to a shared power converter; and 
         FIG. 8  shows a flowchart of a method of operating a wireless transmitter device that includes or is coupled to multiple shared power converters. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to representative embodiments illustrated in the accompanying drawings. It should be understood that the following descriptions are not intended to limit the embodiments to one preferred embodiment. To the contrary, it is intended to cover alternatives, modifications, and equivalents as can be included within the spirit and scope of the described embodiments as defined by the appended claims. 
     The following disclosure relates to a shared power converter that is configurable to convert an input signal into multiple alternating current (AC) signals that are used by one or more components in receiver devices. For example, the shared power converter may be used to convert a direct current (DC) signal into an AC signal or to convert a first AC signal into a second AC signal. In one embodiment, the shared power converter may be included in a wireless transmitter device. In another embodiment, the shared power converter can be included in a power adapter that couples a wireless transmitter device to a power source, such as a wall outlet. 
     In the embodiments described herein, the shared power converter is coupled to, or included in, an inductive or resonant wireless transmitter device that is configured to transfer energy to multiple receiver devices. The wireless transmitter device includes multiple transmitter coils, with at least one transmitter coil associated with each receiver device. In some embodiments, each receiver device is associated with a respective one of the transmitter coils when energy is transferred to multiple receiver devices. 
     The shared power converter is coupled to each transmitter coil. The shared power converter includes a leading half bridge and multiple trailing half bridges. Each transmitter coil is coupled between the leading half bridge and a respective one of the multiple trailing half bridges. The shared power converter is dynamically configurable in that the leading half bridge may be coupled to select trailing half bridges when energy is to be transferred wirelessly to multiple receiver devices. For example, the transmitter device can transfer energy wirelessly to two receiver devices by selectively activating two individual transmitter coils. Each transmitter coil is selectively enabled by configuring the shared power converter into two full bridges, e.g., by coupling the leading half bridge with two respective trailing half bridges. Energy can be transferred to the two receiver devices sequentially, simultaneously, or with some overlap in time. 
     In a particular embodiment, the leading half bridge includes two switching elements or semiconductor switches that are each connected to a first node. Each trailing half bridge also includes two switching elements or semiconductor switches that are each connected to a distinct second node. A transmitter coil is coupled between the first node in the leading half bridge and the second node in a respective trailing half bridge. In a non-limiting embodiment, each switching element is a metal-oxide semiconductor field-effect transistor. Other embodiments can use a different type of switching element, such as, for example, a bi-polar transistor, a diode, or any other suitable electronic switch. 
     In some embodiments, a processing device is coupled to the shared power converter. The processing device is adapted to cause switch signals to be received by the leading half bridge and to cause switch signals to be received by one or more trailing half bridges. A full bridge is created when the primary half bridge is coupled to a trailing half bridge. Thus, the shared power converter can be assembled and reassembled to produce one or more full bridges for wireless energy transfer. 
     In some embodiments, the switch signals that are received by the leading half bridge and the switch signals that are received by the trailing half bridges are used to select which trailing bridges are coupled to the leading half bridge to create a full bridge. In other words, the switch signals are used to configure and reconfigure the shared power converter for wireless energy transfer. Which trailing half bridge is coupled to the leading half bridge can be determined based at least in part on the characteristics of the transmitter coil coupled to a trailing half bridge. Characteristics of a transmitter coil include, but are not limited to, the number of windings, the DC resistance, the maximum DC signal, the electromagnetic interference, the magnetic saturation flux density, the Curie temperature, and so on. 
     In some embodiments, a switch can be coupled between the leading half bridge and each trailing half bridge. The shared power converter is configured into one or more full bridges by closing one or more respective switches to couple the leading half bridge to respective trailing half bridges. 
     For example, in one embodiment, a full H Bridge is produced when the leading half bridge is coupled to a trailing half bridge. The H Bridge is used to produce a coil signal (e.g., a current) that passes through a transmitter coil bi-directionally (e.g., an AC coil signal). The AC coil signal generates one or more time-varying magnetic fields around the transmitter coil. Energy is transferred to receiver device when the time-varying magnetic field(s) extend to, and interact with, a receiver coil in the receiver device. The time-varying magnetic field(s) induce an alternating voltage across the receiver coil, which in turn produces an AC signal in the receiver coil. The AC signal in the receiver coil can be used for various operations or functions, such as to charge a battery and/or to transmit and/or receive communication or control signals. 
     In some embodiments, the processing device is coupled to a signal generator. The signal generator is configured to produce the switch signals for the leading and trailing half bridges. In a non-limiting example, the processing device may access one or more switch signal characteristics that are stored in a memory. The processing device can cause the switch signal characteristic(s) to be transmitted to the signal generator to cause the signal generator to produce at least one switch signal that includes the received at least one switch signal characteristic. Example switch signal characteristics include, but are not limited to, a frequency or a frequency difference, an amplitude or an amplitude difference, and/or a phase or a phase difference. The generated switch signals are then received by the leading half bridge and at least one trailing half bridge to create a full bridge for wireless energy transfer. 
     The switch signal characteristic(s) can be determined based at least in part on the characteristics of a respective transmitter coil (e.g., number of windings, DC resistance, maximum DC signal, the electromagnetic interference, magnetic saturation flux density, Curie temperature, and the like). Additionally or alternatively, the one or more switch signal characteristics can be determined based at least in part on the characteristics of the receiver coil in the receiver device and/or the energy transfer specifications for the receiver device. 
     Additionally or alternatively, the processing device can access a memory to cause switch signals that are stored in the memory to be transmitted to the leading half bridge and/or one or more respective trailing half bridges. The switch signals received by the leading half bridge and by at least one particular trailing half bridge create a full bridge for wireless energy transfer. 
     The reconfigurable shared power converter reduces the number of components in a transmitter device, which may reduce the complexity and the cost of a transmitter device. Conventional wireless transmitter devices couple a power converter to each transmitter coil, which increases the number of components in the transmitter device. In contrast to a conventional transmitter device, a shared power converter can be coupled simultaneously to two or more transmitter coils to transfer energy from each transmitter coil. Thus, the shared power converter reduces the number of components in a transmitter device. In many examples, fewer components translate into reduced complexity and cost. 
     Additionally, the shared power converter allows the transfer of energy to each receiver device to be defined or customized for each receiver device. The switch signal characteristics of the switch signals that are received by a respective trailing half bridge can be modified or controlled with respect to the switch signals that are received by the leading half bridge. For example, the switch signals received by a trailing half bridge may be phase-shifted with respect to the switch signals that are received by the leading half bridge. Additionally, the amplitudes and/or frequencies of the switch signals that are received by the trailing half bridge can differ from the amplitudes and/or frequencies of the switch signals that are received by the leading half bridge. When two or more trailing half bridges are coupled to the leading half bridge, the switch signals received by each trailing half bridge can have a different phase, amplitude, and/or frequency with respect to the phase, amplitude, and/or frequency of the switch signals received by the leading half bridge. Through constructive and destructive interferences, a unique or individualized AC coil signal may be received by a transmitter coil, allowing the transfer of energy to be regulated and customized for each receiver device. 
     As used herein, the terms “connected” and “coupled” are generally intended to be construed broadly to cover direct connections and indirect connections. In the context of the present invention, the terms “connected” and “coupled” are intended to cover circuits, components, and/or devices that are connected such that an electrical parameter passes from one to another. Example electrical parameters include, but are not limited to, voltages, currents, magnetic fields, control signals, and/or communication signals. Thus, the terms “coupled” and “connected” include circuits, components, and/or devices that are coupled directly together or through one or more intermediate circuits, components, and/or devices. 
     These and other embodiments are discussed below with reference to  FIGS. 1-8 . However, those skilled in the art will readily appreciate that the detailed description given herein with respect to these Figures is for explanatory purposes only and should not be construed as limiting. 
       FIG. 1  depicts one example of a transmitter device that is configured to transfer energy wirelessly to one or more receiver devices. In the illustrated embodiment, a first receiver device  100  and a second receiver device  102  are placed on a transmitting surface  104  of a transmitter device  106 . The transmitter device  106  is configured to transfer energy wirelessly to the first and second receiver devices  100 ,  102  sequentially, simultaneously, or partially overlapping in time. 
     In some embodiments, the transmitter device  106  is configured to convert a DC signal into a first AC signal. The first AC signal is used by the transmitter device  106  to generate one or more time-varying or oscillating magnetic fields that are used to transfer energy wirelessly from one or more transmitter coils (not shown) in the transmitter device  106  to one or more receiver coils  112  in the first receiver device  100  when the first receiver device  100  is placed on or near the transmitting surface  104  of the transmitter device  106 . 
     Additionally, the transmitter device  106  is configured to convert the DC signal into a second AC signal. The second AC signal may be the same signal as the first AC signal or a different signal compared to the first AC signal. The second AC signal is used by the transmitter device  106  to generate one or more time-varying or oscillating magnetic fields that are used to transfer energy wirelessly from one or more transmitter coils (not shown) in the transmitter device  106  to one or more receiver coils  114  in the second receiver device  102  when the second receiver device  102  is placed on or near the transmitting surface  104  of the transmitter device  106 . 
     In some embodiments, the DC-to-AC conversion stage can be omitted from the transmitter device  106 . For example, a power adapter (not shown) that couples a wireless transmitter device to a power source, such as a wall outlet, may be configured to convert a first AC signal into a second AC signal. In a non-limiting example, the power converter can convert a high voltage, low frequency AC signal into a low voltage, high frequency AC signal. The low voltage, high frequency AC signal may be received by the transmitter coil(s) to generate one or more time-varying magnetic fields that are used to transfer energy wirelessly from the transmitter coil(s) in the transmitter device  106  to the receiver coil(s)  112 ,  114  in the first and second receiver devices  100 ,  102 , respectively. 
     The transmitter device  106  can be implemented as any suitable transmitter device. Example transmitter devices include, but are not limited to, a wireless charging pad, a wireless charging station, clothing or a fashion accessory that is configured to wirelessly charge a receiver device, a wireless charging dock, and a wireless charging cover or door that can be removably attached to the housing of the receiver device (e.g., a wireless charging cover that replaces a battery door). 
     Similarly, the first and second receiver devices  100 ,  102  may each be configured as any suitable receiver device. For example, a receiver device may be a cellular or smart phone, a gaming device, a remote control, a tablet or laptop computing device, a digital media player, a wearable electronic device (e.g., a watch), a kitchen or household appliance, a motor vehicle, and so on. 
     Embodiments described herein relate to a transmitter device that includes multiple transmitter coils for transferring energy to multiple receiver devices. As described earlier, energy can be transferred to two or more receiver devices simultaneously, at different times, or with some overlap in time. The transmitter device is coupled to, or includes, a shared power converter that permits the transmitter device to control and customize the transfer of energy to each receiver device. As will be described in more detail in conjunction with  FIG. 3 , the shared power converter includes a leading half bridge that can be coupled to at least one trailing half bridge to transfer energy to one or more receiver devices. 
       FIG. 2  shows an example wireless energy transfer system. The system  200  includes a transmitter device  202  and three receiver devices  204 ,  206 ,  208 . For simplicity, only the receiver device  204  is shown in detail. However, those skilled in the art will recognize that the other receiver devices  206 ,  208  can be configured similarly to the receiver device  204 . Additionally, the receiver devices  204 ,  206 ,  208  may each include additional components, circuits, and/or functionality. For example, a receiver device can include a display and/or a touch-sensitive display, network ports, one or more input devices (e.g., trackpad, microphone, button, etc.), and/or one or more output devices (e.g., speakers, haptic device, etc.). 
     In the illustrated embodiment, a shared power converter  210  in the transmitter device  202  receives a DC signal on a signal line  212 . The signal line  212  can represent a power cable that is connected to a power adapter, a connection to a battery, or a connection (e.g., a USB cable) to another electronic device. In other embodiments, the transmitter device  202  may be configured to receive an AC signal by connecting an AC-to-DC power converter between the signal line  212  and the shared power converter  210 . 
     The shared power converter  210  is configurable to inductively couple each transmitter coil  226 ,  228 ,  230  in the transmitter device  202  to a respective receiver coil  232 ,  234 ,  236  in one or more of the receiver devices  204 ,  206 ,  208 . In particular, the shared power converter  210  can be assembled into multiple signal converters (e.g., multiple DC-to-AC power converters). In the illustrated embodiment, the shared power converter  210  is configured into three signal converters  214 ,  216 ,  218  (e.g., three DC-to-AC power converters). Each signal converter  214 ,  216 ,  218  converts a DC signal into an AC coil signal that is used to transfer energy to the receiver devices  204 ,  206 ,  208 , respectively. 
     As will be described in more detail later, the switch signals that are received by a signal converter  214 ,  216 ,  218  can be used to modify, define, or customize the characteristics of an AC coil signal that is received by a respective transmitter coil  226 ,  228 ,  230 . The characteristics of the AC coil signal include the phase, the frequency, and/or the amplitude of the AC coil signal. The AC coil signal is used to control and/or adjust the time-varying magnetic field(s) produced by a transmitter coil  226 ,  228 ,  230 , which in turn regulates and adjusts the amount of energy transferred to a receiver coil  232 ,  234 ,  236  in a receiver device  204 ,  206 ,  208 , respectively. 
     The signal converters  214 ,  216 ,  218  can be any suitable type of a DC-to-AC power converter. In one embodiment, each signal converter  214 ,  216 ,  218  is constructed as an H Bridge power converter. An H Bridge power converter includes four switching elements that are selectively activated (e.g., turned on or opened) and deactivated (e.g., turned off or closed) to convert a DC signal into an AC signal. Any suitable switching element can be used. An example shared power converter is described in conjunction with  FIG. 3 . 
     The output of each signal converter  214 ,  216 ,  218  is coupled to a respective transmitter resonant circuitry  220 ,  222 ,  224 . Each transmitter resonant circuitry  220 ,  222 ,  224  may include one or more electrical components (e.g., resistors, capacitors, inductors) that are used to determine a resonating frequency for the transmitter device  202  when energy is transferred to at least one receiver device  204 ,  206 ,  208 . The output of each transmitter resonant circuitry  220 ,  222 ,  224  is coupled to a respective transmitter coil  226 ,  228 ,  230  that is selectively energized with an AC coil signal for energy transfer. 
     As described earlier, each receiver device  204 ,  206 ,  208  includes a receiver coil  232 ,  234 ,  236 . In  FIG. 2 , the receiver coil  232  inductively couples with the transmitter coil  226  to transfer energy to the receiver device  204 . Similarly, the receiver coil  234  inductively couples with the transmitter coil  228  for energy transfer, and the receiver coil  236  inductively couples with the transmitter coil  230  for energy transfer. Each transmitter coil  226 ,  228 ,  230  can have the same or different characteristics (e.g., number of windings, DC resistance, maximum DC signal, the electromagnetic interference, magnetic saturation flux density, Curie temperature, and the like). Similarly, each receiver coil  232 ,  234 ,  236  may have the same or different characteristics. 
     As shown in the receiver device  204 , the receiver coil  232  is coupled to receiver resonant circuitry  238 . Like the transmitter resonant circuitry, the receiver resonant circuitry  238  can include one or more electrical components (e.g., resistors, capacitors, inductors) that are used to determine a resonating frequency for the receiver device  204  when energy is transferred to the receiver device  204 . The transfer of energy from the transmitter device  202  to the receiver device  204  can be more efficient when the transmitter device  202  and the receiver device  204  resonant at a common frequency. 
     An output of the receiver resonant circuitry  238  is coupled to an AC-to-DC power converter  240 . Any suitable type of AC-to-DC power converter may be used. For example, the AC-to-DC power converter  240  can be constructed as a diode bridge in one embodiment. 
     A load  242  is coupled to the output of the AC-to-DC power converter  240 . The load  242  represents a rechargeable battery and/or one or more components that use the energy received from the receiver coil  232 . 
     Energy is transferred from the transmitter coil  226  to the receiver coil  232  by passing an AC coil signal through the transmitter coil  226  to produce one or more time-varying or oscillating magnetic fields (energy transfer represented by arrow  244 ). Because the AC coil signal is an alternating signal, the direction(s) of the magnetic field(s) changes based on the direction of the AC coil signal through the transmitter coil  226 . Energy is transferred to the receiver device  204  when the time-varying magnetic fields extend to, and interact with, the receiver coil  232 . The time-varying magnetic fields induce an AC voltage across the receiver coil  232 , which in turn produces an AC signal in the receiver coil  232 . The AC signal is received by the AC-to-DC power converter  240 , which converts the AC signal into a DC signal. The DC signal is then received by the load  242  (e.g., to charge the battery). 
     Additionally or alternatively, the transferred energy can be used to transmit communication signals between the transmitter device  202  and the receiver device  204  (communication signals represented by arrow  246 ). For example, the receiver device  204  may use load modulation to transfer communication signals (e.g., control and/or status data) from the receiver device  204  to the transmitter device  202 . As one example, the receiver device  204  can apply a controlled pulsed load across the receiver coil  232 , which results in an amplitude modulation of the voltage on the transmitter coil  226 . The transmitter device  202  (e.g., or a processing device  248  in the transmitter device  202 ) can detect and demodulate the amplitude modulation. 
     Additionally or alternatively, the receiver device  204  may transfer a brief burst of energy (a “ping”) to the transmitter device  202  to inform the transmitter device  202  of the presence of the receiver device  204 . Additionally or alternatively, the receiver device  204  may transfer a ping to the transmitter device  202  to determine if the transmitter device  202  is ready to transmit energy. 
     Additionally or alternatively, the transmitter device  202  can use phase shift keying, frequency modulation and the like to transmit communication signals from the transmitter device  202  to the receiver device  204 . Additionally or alternatively, the transmitter device  202  may transfer a ping to the receiver device  204  to determine if the receiver device  204  is ready to receive energy and/or to determine a location of the receiver device  204  on the transmitting surface of the transmitter device  202 . 
     A processing device  248  in the transmitter device  202  can be connected to a signal generator  250  and/or to the shared power converter  210 . Although not shown in  FIG. 2 , the processing device  248  may be coupled to other components (e.g., a display, memory) in the transmitter device  202 . The processing device  248  may control and/or monitor the operation of the shared power converter  210  and/or the signal generator  250 . As one example, when the shared power converter  210  is configured as an H Bridge, the processing device  248  may control the activation (e.g., turning on or opening) and the deactivation (e.g., turning off or closing) of the switching elements in the H Bridge. 
     In some embodiments, the processing device  248  can cause one or more switch signal characteristics that are stored in memory  252  to be transmitted to the signal generator  250 . The one or more switch signal characteristics include, but are not limited to, a frequency, a frequency difference, a phase, a phase difference, an amplitude difference, and amplitude of a switch signal. The signal generator  250  is configured to produce switch signals based on the received switch signal characteristic(s). The processing device  248  may be configured to determine which signal converter(s)  214 ,  216 ,  218  should receive the switch signals when energy is to be transferred to one or more of the receiver devices  204 ,  206 ,  208 . 
     The memory  252  can store electronic data that can be used by the transmitter device  202 . For example, the memory  252  can store electrical data or content such as, for example, device settings and user preferences, timing and control signals, switch signals, switch signal characteristics, data structures or databases, documents and applications, identifying data for one or more receiver devices, and so on. The memory  252  can be configured as any type of memory. By way of example only, the memory  252  can be implemented as random access memory, read-only memory, Flash memory, removable memory, or other types of storage elements, or combinations of such devices. 
     A processing device  254  in the receiver device  204  can be coupled to the AC-to-DC power converter  240  and/or the load  242 . Although not shown in  FIG. 2 , the processing device  254  may be connected to other components (e.g., a display, memory) in the receiver device  204 . The processing device  254  may control or monitor the operation of the AC-to-DC power converter  240  and/or the load  242 . As one example, the processing device  254  may monitor the charge level on the load  242  when the load  242  is a rechargeable battery. 
     The processing devices  248 ,  254  can be implemented as any electronic device capable of processing, receiving, or transmitting data or instructions. For example, the processing devices  248 ,  254  can each be a microprocessor, a central processing unit (CPU), an application-specific integrated circuit (ASIC), a digital signal processor (DSP), or combinations of such devices. As described herein, the term “processing device” is meant to encompass a single processor or processing unit, multiple processors, multiple processing units, or other suitably configured computing element or elements. 
     Communication circuitry  256  in the transmitter device  202  may be coupled to the processing device  248  in the transmitter device  202 . Similarly, communication circuitry  258  in the receiver device  204  can be coupled to the processing device  254  in the receiver device  204 . The communication circuitry  256 ,  258  can be coupled to one another to establish a communication channel  260  between the transmitter device  202  and the receiver device  204 . As described earlier, energy transfer can be used for communication between the transmitter and receiver devices  202 ,  204 . The communication channel  260  is an additional or alternate communication mechanism that is separate from the transfer of energy. The communication channel  260  can be used to convey information from the transmitter device  202  to the receiver device  204 , and vice versa. The communication channel  260  may be implemented as a wired link and/or as a wireless link. The communication channel  260  may be configured as any suitable communication channel, such as, for example, Near Field Communication, Bluetooth, and/or Infrared communication channels. 
     In some embodiments, the transmitter device  202  and/or the receiver device  204  may each include one or more sensors  262 ,  264 , respectively. The sensor(s)  262  in the transmitter device  202  are coupled to the processing device  248 , and the sensor(s)  264  in the receiver device  204  are coupled to the processing device  254 . Each sensor in the sensors  262 ,  264  may be positioned substantially anywhere on or in the transmitter device  202  and/or the receiver device  204 , respectively. The sensor(s)  262 ,  264  can be configured to sense substantially any type of characteristic, such as, but not limited to, images, pressure, light, heat, force, touch, temperature, movement, and so on. For example, the sensor(s)  262 ,  264  may each be an image sensor, a temperature sensor, a light or optical sensor, a touch or proximity sensor, an accelerometer, an environmental sensor, a gyroscope, a magnet, and so on. 
     As will be described in more detail later, one or more sensors  262  in the transmitter device  202  can be configured to detect the presence or absence of the receiver device  204  on or near the transmitting surface of the transmitter device  202 . Additionally or alternatively, at least one sensor  262  may be configured to determine a location and/or an orientation of the receiver device  204  on the transmitting surface. For example, one or more proximity sensors can be used to determine whether an object is in contact with the transmitting surface, and an image and/or magnetic sensor(s) may be used to determine if the object is the receiver device  204 . Additionally, an image sensor and/or one or more magnetic sensor(s) can be used to identify the receiver device  204 , which allows the transmitter device  202  (e.g., the processing device  248 ) to determine the switch signal characteristics to transmit to the signal generator  250 . Alternatively, the identity of the receiver device  204  may be used by the processing device  248  to cause particular switch signals to be transmitted to a respective signal converter  214 ,  216 ,  218 . 
     With respect to the receiver device  204 , the one or more sensors  264  in the receiver device  204  may be configured to detect or obtain data regarding the receiver device  204 . For example, one or more sensors  264  can be used to determine an orientation of the receiver device  204  on the transmitting surface of the transmitter device  202 . The orientation of the receiver device  204  may be horizontal (e.g., flat on the transmitting surface) or vertical (e.g., resting on a side of the housing on the transmitting surface). In some embodiments, the receiver device  204  can transmit data to the transmitter device  202  regarding the orientation of the receiver device  204 . 
     The receiver device  206  is shown with the receiver coil  234  connected to circuitry  266  and a load  268  connected to the circuitry  266 . The receiver device  208  is depicted with the receiver coil  236  connected to circuitry  270  and a load  272  connected to the circuitry  270 . As described earlier, each circuitry  266 ,  270  and load  268 ,  272  can be configured similarly to the circuitry (receiver resonant circuitry  238 , AC-to-DC power converter  240 , communication circuitry  258 , processing device  254 , and/or sensor(s)  264 ) and load  242  shown in the receiver device  204 . Alternatively, in some embodiments, at least one receiver device  206  and/or  208  can be configured with different circuitry and/or load. 
     Although only one shared power converter  210 , processing device  248 , signal generator  250 , communication circuitry  256 , memory  252 , and sensors  262  are shown in  FIG. 2 , a transmitter device  202  can include multiple shared power converters, processing devices, communication circuitry, memories, sensors, and/or signal generators. Each signal converter (e.g.,  214 ,  216 ,  218 ) in a shared power converter can be connected to a respective signal generator, transmitter resonant circuitry, and/or transmitter coil. 
     Similarly, in some embodiments, the receiver devices  204 ,  206 ,  208  may include multiple receiver coils, resonant circuitry, AC-to-DC power converters, loads, communication circuitry, processing devices, and/or sensors. In some embodiments, each receiver coil can be connected to a respective receiver resonant circuitry and an AC-to-DC power converter. Alternatively, two or more receiver coils may share an AC-to-DC power converter and resonant circuitry. 
     In some embodiments, the shared power converter  210  can be disposed in a power adapter that is coupled to the transmitter device  202 . Additionally, the power adapter may include the signal generator  250 , the memory  252 , and a processing device. In such embodiments, the signal converters  214 ,  216 ,  218  can be configured to convert a first AC signal into a second AC signal. Each signal converter  214 ,  216 ,  218  may be coupled to a respective transmitter coil  226 ,  228 ,  230 . A transmitter coil  226 ,  228 ,  230  can receive a converted second AC signal when energy is to be transferred to a respective receiver coil  232 ,  234 ,  236 . For example, in one embodiment, at least one signal converter  214 ,  216 ,  218  may be configured to convert a high voltage, low frequency AC signal into a low voltage, high frequency AC signal. 
       FIG. 3  depicts an example schematic diagram of a shared power converter that is suitable for use in the transmitter device shown in  FIG. 1 . The shared power converter  300  includes a leading half bridge  302  and multiple trailing half bridges  304 ,  306 ,  308 . Although  FIG. 3  depicts three trailing half bridges  304 ,  306 ,  308 , the shared power converter can include two or more trailing half bridges. The leading half bridge  302  and the trailing half bridges  304 ,  306 ,  308  are each coupled between a first input node (e.g., a voltage source Vdd) and a second input node (e.g., a reference voltage source (e.g., ground)). 
     The leading half bridge  302  includes a first switching element  309  connected to a first intermediate node (NODE  1 ) and a second switching element  310  connected to the first intermediate node (NODE  1 ). The first trailing half bridge  304  includes a third switching element  312  connected to a second intermediate node (NODE  2 ) and a fourth switching element  314  connected to the second intermediate node (NODE  2 ). A first LC resonant circuit  316  is connected between the first intermediate node (NODE  1 ) and the second intermediate node (NODE  2 ). In the illustrated embodiment, the first LC resonant circuit  316  includes a first transmitter coil  318  connected in series with a first capacitor  320 . The first capacitor  320  represents the transmitter resonant circuitry shown in  FIG. 2  (e.g., transmitter resonant circuitry  220 ). 
     The second trailing half bridge  306  includes a fifth switching element  322  connected to a third intermediate node (NODE  3 ) and a sixth switching element  324  connected to the third intermediate node (NODE  3 ). A second LC resonant circuit  326  is connected between the first intermediate node (NODE  1 ) and the third intermediate node (NODE  3 ). As shown in  FIG. 3 , the second LC resonant circuit  326  includes a second transmitter coil  328  connected in series with a second capacitor  330 . Like the first capacitor  320 , the second capacitor  330  represents the transmitter resonant circuitry shown in  FIG. 2  (e.g., transmitter resonant circuitry  222 ). 
     The third trailing half bridge  308  includes a seventh switching element  332  connected to a fourth intermediate node (NODE  4 ) and an eighth switching element  334  connected to the fourth intermediate node (NODE  4 ). A third LC resonant circuit  336  is connected between the first intermediate node (NODE  1 ) and the fourth intermediate node (NODE  4 ). In the illustrated embodiment, the third LC resonant circuit  336  includes a third transmitter coil  338  (e.g., a third load) connected in series with a third capacitor  340 . The third capacitor  340  represents the transmitter resonant circuitry shown in  FIG. 2  (e.g., transmitter resonant circuitry  224 ). 
     The first, second, and third LC resonant circuits  316 ,  326 ,  336  may each be configured differently in other embodiments. For example, the second capacitor  330  in the second LC resonant circuit  326  can be connected in series with the second transmitter coil  328  and another capacitor connected in parallel with the second transmitter coil  328 . 
     Alternatively, the first, second, and third LC resonant circuits  316 ,  326 ,  336  can each be configured as a different type of resonant circuit. For example, the first resonant circuit  316  can be configured as an RLC resonant circuit. A resistor may be connected in series with the first transmitter coil  318  and a capacitor connected in parallel with the first transmitter coil  318 . 
     In one embodiment, all of the components shown in  FIG. 3  are included in a transmitter device. In another embodiment, the leading half bridge  302  and the first, second, and third trailing half bridges  304 ,  306 ,  308  are included in a power adapter that is coupled to the transmitter device and the first, second, and third LC resonant circuits  316 ,  326 ,  336  are included in the transmitter device. In yet another embodiment, the leading half bridge  302 , the first, second, and third trailing half bridges  304 ,  306 ,  308 , and the first, second, and third capacitors  320 ,  330 ,  340  are included in a power adapter that is coupled to the transmitter device and the first, second, and third transmitter coils  318 ,  328 ,  338  are included in the transmitter device. 
     In  FIG. 3 , each switching element  309 ,  310 ,  312 ,  314 ,  322 ,  324 ,  332 ,  334  is a metal-oxide-semiconductor field-effect transistor (MOSFET), although this is not required. Other embodiments can use a different type of switching element or semiconductor switch, such as a bi-polar transistor, a diode, or any other suitable electronic switch. 
     One or more signal generators (e.g., signal generator  250  in  FIG. 2 ) may be coupled to respective switching elements  309 ,  310 ,  312 ,  314 ,  322 ,  324 ,  332 ,  334 . In the illustrated embodiment, one or more signal generators can be coupled to a respective gate G 1 , G 2 , G 3 , G 4 , G 5 , G 6 , G 7 , and/or G 8  of the switching elements  309 ,  310 ,  312 ,  314 ,  322 ,  324 ,  332 ,  334 . 
     As described earlier, the switch signals are used to configure or assemble the shared power converter for wireless energy transfer. Which trailing half bridge(s)  304 ,  306 ,  308  is used to form a full bridge with the leading half bridge  302  is determined at least in part by which trailing half bridge(s)  304 ,  306 ,  308  receives switch signals. An AC coil signal is generated and applied across a respective LC resonant circuit  316 ,  326 ,  336  by alternately opening (e.g., turned off or deactivated) and closing (e.g., turned on or activated) the switching elements in the leading half bridge  302  and in the respective trailing half bridge  304 ,  306 ,  308 . 
     Other factors or considerations can influence which trailing half bridge  304 ,  306 ,  308  is used to form a full bridge with the leading half bridge  302 . For example, the location of a receiver device on the transmitting surface of a transmitter device can be considered when determining which trailing half bridge(s)  304 ,  306 ,  308  is coupled to the leading half bridge  302 . 
     For example, with respect to the leading half bridge  302  and the first trailing half bridge  304 , the first and fourth switching elements  309 ,  314  are closed while the second and third switching elements  310 ,  312  are open, and the first and fourth switching elements  309 ,  314  are open while the second and third switching elements  310 ,  312  are closed to produce an AC coil signal. In particular, the switch signals that are initially received by the first, second, third, and fourth switching elements  309 ,  310 ,  312 ,  314  cause the first and fourth switching elements  309 ,  314  to close and the second and third switching elements  310 ,  312  to open, which allows a signal (e.g., current) to pass from the first input node (e.g., Vdd), through the first switching element  309 , through the first LC resonant circuit  316 , and through the fourth switching element  314  to the second input node (e.g., ground). Thus, the signal passes through the first LC resonant circuit  316  in one direction. Thereafter, the switch signals that are received by the first, second, third, and fourth switching elements  309 ,  310 ,  312 ,  314  cause the first and fourth switching elements  309 ,  314  to open and the second and third switching elements  310 ,  312  to close, which permits a signal (e.g., current) to pass from the first input node, through the third switching element  312 , through the first LC resonant circuit  316 , and through the second switching element  310  to the second input node. Thus, the signal passes through the first LC resonant circuit in an opposite direction. In this manner, an AC coil signal is received by the first transmitter coil  318 , which causes the first transmitter coil  318  to generate one or more time-varying or oscillating magnetic fields. 
     A similar process can be used to alternately open and close the first and sixth switching elements  309 ,  324  and the second and fifth switching elements  310 ,  322  to cause the second transmitter coil  328  to produce one or more time-varying magnetic fields. Additionally, the first and eighth switching elements  309 ,  334  and the second and seventh switching elements  310 ,  332  may be alternately opened and closed to cause the third transmitter coil  338  to generate one or more time-varying magnetic fields. 
     As described earlier, the switch signals can be used to modify, define, or customize the characteristics of the AC coil signal that is received by a respective transmitter coil  318 ,  328 ,  338 . The characteristics of the AC coil signal include the phase, the frequency, and/or the amplitude of the AC coil signal. The AC coil signal is used to control and/or adjust the one or more time-varying magnetic fields that develop around a transmitter coil, which in turn regulates and adjusts the amount of energy transferred to a receiver coil in a receiver device. 
       FIGS. 4A-4C  are described in conjunction with the leading half bridge  302  and the first trailing half bridge  304  shown in  FIG. 3 .  FIG. 4A  shows example voltage levels of a first node signal that can be produced at the first intermediate node (NODE  1 ), while  FIG. 4B  depicts example voltage levels of a second node signal that can be produced at the second intermediate node (NODE  2 ) in the shared power converter shown in  FIG. 3 .  FIG. 4C  illustrates the voltage levels of an AC coil signal that is received by the first transmitter coil  318  shown in  FIG. 3  based on the first and second node signals shown in  FIGS. 4A-4B . As described earlier, the AC coil signal is used to control the transfer of energy from the first transmitter coil  318 . 
     In a non-limiting example, a first square wave switch signal is received by the first switching element  309 , a second square wave switch signal is received by the second switching element  310 , a third square wave switch signal is received by the third switching element  312 , and a fourth square wave switch signal is received by the fourth switching element  314 . The third and fourth square wave switch signals have a phase difference or offset with respect to the phase of the first and second square wave switch signals. As described earlier, the first, second, third, and fourth square wave switch signals alternately open and close the first, second, third, and fourth switching elements  309 ,  310 ,  312 ,  314 . 
     Based on the above example, the voltage levels in the first node signal  400  (see  FIG. 4A ) represent the voltage levels at the first intermediate node (NODE  1 ) and the voltage levels in the second node signal  402  ( FIG. 4B ) represent the voltage levels at the second intermediate node (NODE  2 ). The AC coil signal  404  represents the voltage levels across the first transmitter coil  318  based on the first and second node signals  400 ,  402  (e.g., NODE  1 -NODE  2 ). The second node signal  402  is phase-shifted with respect to the first node signal  400  because the third and fourth square wave switch signals received by the third and fourth switching elements  312 ,  314  are phase-shifted with respect to the first and second square wave switch signals received by the first and second switching elements  309 ,  310 . Due to constructive and destructive interferences between the first node signal  400  and the second node signal  402 , the AC coil signal  404  includes three voltage levels that vary over time, which adjusts the one or more time-varying magnetic fields produced by the first transmitter coil  318 . The amount of energy that is transferred by the first transmitter coil  318  is regulated through the variations in the AC coil signal  404 . 
     In particular, the voltage levels of the AC coil signal  404  can be produced as follows. At time t 1 , the voltage level of the second node signal  402  transitions from a first voltage level to a low voltage level (e.g., ground), while the voltage level of the first node signal  400  is at a low voltage level (e.g., ground). Accordingly, the voltage level of the AC coil signal  404  transitions from a negative first voltage level to a second voltage level (e.g., zero). The amount of energy transferred from the transmitter coil  318  transitions from a first quantity of energy to a second quantity of energy (e.g., zero) when the voltage level of the AC coil signal  404  transitions to the second voltage level. 
     At time t 2 , the voltage level of the first node signal  400  transitions from the low voltage level to a first voltage level, while the voltage level of the second node signal  402  remains at the low voltage level. Accordingly, at time t 2 , the voltage level of the AC coil signal  404  transitions from the second voltage level to a positive third voltage level. The amount of energy transferred from the first transmitter coil  318  can transition from the first quantity of energy to a second quantity of energy when the voltage level of the AC coil signal  404  transitions to the positive second voltage level. 
     At time t 3 , the voltage level of the second node signal  402  transitions from the low voltage level to the first voltage level, while the voltage level of the first node signal  400  remains at the first voltage level. Accordingly, at time t 3 , the voltage level of the AC coil signal  404  transitions from the positive second voltage level to the first voltage level. 
     At time t 4 , the voltage level of the first node signal  400  transitions from the first voltage level to the low voltage level, while the voltage level of the second node signal  402  remains at the first voltage level. Accordingly, at time t 4 , the voltage level of the AC coil signal  404  transitions from the second voltage level to first negative voltage level. 
     The transitions in the first and second node signals  400 ,  402  repeat over time to produce the repeating waveform of the AC coil signal  404 . Based on the AC coil signal  404 , the energy transferred from the first transmitter coil  318  varies over time. Thus, the amount of energy that is transferred from the transmitter coil  318  can be controlled through the different voltage levels in the AC coil signal  404  and the timing of the transitions in the voltage levels of the AC coil signal  404 . 
     The voltage levels in the first node signal  400 , the second node signal  402 , and the AC coil signal  404  can each be any suitable voltage level. The voltage levels in the first node signal  400  may differ from the voltage levels in the second node signal  402 . Additionally, the switch signals are not limited to square waves. A switch signal can have any suitable waveform. 
       FIGS. 5A-5C  are described in conjunction with the leading half bridge  302  and the second trailing half bridge  306  shown in  FIG. 3 .  FIG. 5A  shows example voltage levels of a first node signal that can be produced at the first intermediate node (NODE  1 ), and  FIG. 5B  depicts example voltage levels of a third node signal that can be produced at the third intermediate node (NODE  3 ) in the shared power converter shown in  FIG. 3 .  FIG. 5C  illustrates the voltage levels of an AC coil signal that is received by the second transmitter coil  328  shown in  FIG. 3  based on the first and second node signals shown in  FIGS. 5A-5B . 
     In a non-limiting example, a first square wave switch signal is received by the first switching element  309 , a second square wave switch signal is received by the second switching element  310 , a fifth square wave switch signal is received by the fifth switching element  322 , and a sixth square wave switch signal is received by the sixth switching element  324 . The fifth and sixth square wave switch signals received by the fifth and sixth switching elements  322 ,  324  in the second trailing half bridge  306  are phase-shifted with respect to the first and second square wave switch signals that are received by the first and second switching elements  309 ,  310  in the leading half bridge  302 . As described earlier, the first, second, fifth, and sixth square wave switch signals alternately open and close the first, second, fifth, and sixth switching elements  309 ,  310 ,  322 ,  324 . 
     The voltage levels produced in first node signal  500  represent the voltage levels at the first intermediate node (NODE  1 ) and the voltage levels in the third node signal  502  represent the voltage levels at the third intermediate node (NODE  3 ). The third node signal  502  is phase-shifted with respect to the first node signal  500  because the fifth and sixth square wave switch signals received by the fifth and sixth switching elements  322 ,  324  are phase-shifted with respect to the first and second square wave switch signals received by the first and second switching elements  309 ,  310 . 
     The AC coil signal  504  represents the voltage levels across the second transmitter coil  328  based on the first and third node signals  500 ,  502  (e.g., NODE  1 -NODE  3 ). Due to constructive and destructive interferences between the first node signal  500  and the third node signal  502 , the AC coil signal  504  includes three voltage levels that vary over time, which adjusts the one or more time-varying magnetic fields produced by the second transmitter coil  328 . The amount of energy that is transferred by the second transmitter coil  328  is controlled through the variations in the AC coil signal  504 . 
     In the illustrated embodiment, the voltage levels and the transitions between the voltage levels in the first node signal  500  are similar to the voltage levels and the transitions between the voltage levels in the first node signal  400  shown in  FIG. 4 . The voltage levels in the third node signal  502  are similar to the voltage levels in the second node signal  402  (see  FIG. 4B ), but the transitions between the voltage levels in the third node signal  502  occur later in time compared to voltage levels in the second node signal  402 . In other words, the transitions between the voltage levels in the third node signal  502  occur after the transitions between the voltage levels in the second node signal  402 . 
     Accordingly, the amount of time the AC coil signal  504  is at the negative first voltage level is greater than the amount of time the AC coil signal  404  ( FIG. 4B ) is at the negative first voltage level. The amount of time the AC coil signal  504  (see  FIG. 5C ) is at the second voltage level (e.g., zero) is less than the amount of time the AC coil signal  404  is at the second voltage level. Finally, the amount of time the AC coil signal  504  is at the positive third voltage level is greater than the amount of time the AC coil signal  404  ( FIG. 4B ) is at the positive third voltage level. Thus, the time spent transferring energy by the second transmitter coil  328  is greater than the time spent transferring energy by the transmitter coil  318 . 
     The amount of energy transferred by a transmitter coil can be regulated by phase-shifting the switch signals that are received by a trailing half bridge with respect to the switch signals received by the leading half bridge. In the embodiment shown in  FIGS. 4 and 5 , the switch signals received by the trailing half bridges  304 ,  306  can be phase-shifted by a different amount of time, thereby allowing the amount of energy transferred by the first and second transmitter coils  318 ,  328  to be customized for particular receiver devices. For example, one receiver device may be configured to receive a greater amount of energy for a longer time period than another receiver device. 
     The voltage levels in the first node signal  500 , the third node signal  502 , and the AC coil signal  504  can each be any suitable voltage level. The voltage levels in the first node signal  500  may differ from the voltage levels in the third node signal  502 . Additionally, the switch signals are not limited to square waves. A switch signal can have any suitable waveform. 
     Those skilled in the art will recognize that when the resonant circuitry in a transmitter device (e.g., transmitter resonant circuitry  220  in  FIG. 2 ) and the resonant circuitry in a receiver device (e.g., receiver resonant circuitry  238 ) are tuned to resonant at a common frequency, the current received by a transmitter coil will be a sine wave waveform. The voltage waveform (e.g., AC coil signal  404  or  504 ) output to the transmitter coil does not significantly change the current waveform. 
       FIG. 6  depicts a flowchart of a first method of operating a wireless transmitter device that is coupled to, or includes, a shared power converter. Initially, as shown in block  600 , a receiver device is placed on a transmitting surface of a transmitter device. One or more switch signal characteristics are then determined at block  602 . As described earlier, the switch signals characteristic(s) include a phase (or phase difference), an amplitude or amplitude difference, and/or a frequency (or frequency difference) of at least one set of switch signals (e.g., the switch signals received by a trailing half bridge). For example, to customize or regulate the transfer of energy, the switch signals received by the switching elements in a trailing half bridge can be phase-shifted with respect to the switch signals received by the switching elements in the leading half bridge. Additionally, in some embodiments, the amplitude and/or frequency of the switch signals received by a trailing half bridge can differ from the switch signals received by a leading half bridge. 
     The switch signal characteristic(s) can be determined based at least in part on the characteristics of a respective transmitter coil (e.g., number of windings, DC resistance, maximum DC signal, the electromagnetic interference, magnetic saturation flux density, Curie temperature, and the like). Additionally or alternatively, the one or more switch signal characteristics can be determined based at least in part on the characteristics of the receiver coil in the receiver device and/or the energy transfer specifications for the receiver device. 
     Next, as shown in block  604 , the switch signals are transmitted to the switching elements in the leading half bridge and the switch signals are transmitted to the switching elements in a particular one of the trailing half bridges. Together the leading half bridge and the trailing half bridge form a full bridge, allowing energy to be transferred to the receiver device. 
       FIG. 7  depicts a flowchart of a second method of operating a wireless transmitter device that is coupled to, or includes, a shared power converter. Initially, as shown in block  700 , a determination is made as to whether an object is detected on a transmitting surface of a transmitter device. The presence of the object may be determined using a variety of methods. In one embodiment, one or more sensors in the transmitter device (e.g., sensors  262  in  FIG. 2 ) can be used to detect the presence of an object on the transmitting surface. For example, a processing device (e.g., processing device  248  in  FIG. 2 ) can receive output signals from one or more proximity sensors. The processing device may be configured to process or analyze the signals to determine whether an object is in contact with the transmitting surface. 
     Additionally or alternatively, light sensors may be used to detect the presence of an object. In such embodiments, a transmitting surface can include apertures or openings that allow light to be received by light sensors within the transmitter device. When an object is placed on the transmitting surface, the object can block one or more openings and prevent a light sensor (or sensors) from receiving light. A processing device can receive output signals from the light sensors that represent the amount of detected light. The processing device may be configured to process the output signals and, based on the output signals from the blocked light sensor(s) indicating an absence of light, determine an object is in contact with the transmitting surface. 
     Additionally or alternatively, an image sensor can capture images of the transmitting surface. A processing device may be configured to analyze the images to determine when an object is near or in contact with the transmitting surface of the transmitter device. 
     Returning to block  700 , the process waits at block  700  when it is determined an object is not in contact with the transmitting surface. When it is determined an object is in contact with the transmitting surface, the method passes to block  702  where a determination is made as to whether the object is a receiver device. Any suitable technique can be used to determine if the object is a receiver device. For example, in one embodiment, both the receiver device and the transmitter device can include one or more conductive electrodes. At least one conductive electrode in the receiver device may be positioned over a corresponding conductive electrode (or electrodes) in the transmitter device to form one or more capacitive sensors. The capacitance of each capacitive sensor can be detected by the transmitter device (e.g., by the processing device  248 ) and used to determine the object is a receiver device. 
     Additionally or alternatively, the transmitter device may transfer a first ping (e.g., a short burst of energy) to the receiver device and the receiver device can transmit a second ping to the transmitter device in response to the received first ping. Additionally or alternatively, a communication channel (e.g., communication channel  260  in  FIG. 2 ) can be established between the transmitter and receiver devices. A communication signal that is transmitted from the receiver device to the transmitter device can be used to determine the object is a receiver device. 
     The process returns to block  700  if it is determined an object is not a receiver device. When it is determined the object is a receiver device, the method passes to block  704  where the type of receiver device is determined. For example, one receiver device type can be a cellular phone and another receiver device type may be a watch. In some embodiments, the receiver device type can specify a make or model of a receiver device. 
     In some embodiments, the receiver device can self-identify to the transmitter device. For example, in the example provided above where one or more conductive electrodes in the receiver device are positioned over corresponding conductive electrodes in the transmitter device, the location(s) of the capacitive sensor(s) can be used to identify the receiver device type. Different types of receiver devices and/or different models of receiver devices can position the conductive electrodes at different locations within the receiver device so a particular pattern of capacitive sensors is formed when a receiver device is placed on the transmitting surface. 
     In some embodiments, a communication channel (e.g., communication channel  260  in  FIG. 2 ) can be established between the transmitter and receiver devices. A receiver device can transmit one or more communication signals to the transmitter device to inform the transmitter device of the receiver device type. 
     Additionally or alternatively, one or more sensors in the transmitter device can be used to determine the receiver device type. For example, images of the receiver device that are captured by an image sensor can be analyzed by a processing device to determine the receiver device type. In some embodiments, a surface of the housing of a receiver device may include a pattern (e.g., a bar code or graphic) and an image of the pattern can be captured by an image sensor. A processing device can analyze the image to determine a receiver device type. 
     In some embodiments, one or more magnetic sensors in the transmitter device can detect a particular pattern of magnetic structures in the receiver device, where the pattern identifies the receiver device type. 
     After the receiver device type is determined at block  704 , the method continues at block  706  where one or more switch signal characteristics are determined based on the receiver device type. Next, as shown in block  708 , the switch signals are transmitted to the switching elements in the leading half bridge and the switch signals are transmitted to the switching elements in a particular one of the trailing half bridges. Together the leading half bridge and the trailing half bridge form a full bridge, allowing energy to be transferred to the receiver device. 
     A determination may be made at block  710  as to whether the transfer of energy is to continue or stop. For example, a processing device in the receiver device (e.g., processing device  254 ) may monitor the charge level on a rechargeable battery. When the battery is charged to a sufficient level (e.g., full charge level), the processing device can cause a communication signal to be transmitted to the transmitter device instructing the transmitter device to stop transferring energy. The communication signal can be transmitted through a communication channel (e.g., communication channel  260  in  FIG. 2 ), through load modulation, and/or by causing the receiver device to transfer a ping to the transmitter device. 
     The method waits at block  710  when the transfer of energy is to continue. When the transfer of energy is to stop, the process passes to block  712  where the transmission of the switch signals to the leading and trailing half bridges ceases, which in turn ends the transfer of energy. The method then returns to block  700 . 
     In some embodiments, a transmitter device can include multiple shared power converters. For example, a large charging mat can include multiple shared power converters. Rather than energizing the entire transmitting surface to transfer energy to a receiver device, only a section of the transmitting surface can be used to transfer energy to a receiver device. Accordingly, only the transmitter coil(s) in the section receive AC coil signal(s). This can reduce the amount of power consumed by a transmitter device. 
       FIG. 8  shows a flowchart of a method of operating a wireless transmitter device that is coupled to or includes multiple shared power converters. Initially, as shown in block  800 , the location of a receiver device can be determined. Any suitable technique can be used to determine the location of a receiver device. For example, in one embodiment, a transmitter device can include a touch-sensitive layer below the transmitting surface. The touch-sensitive layer is configured to detect multiple touch or contact events and the locations of the touch events. In a non-limiting example, a touch-sensitive layer is a capacitive touch-sensitive layer that is coupled to a processing device. Based on output signals that represent capacitance values, a processing device can determine both touch events and the locations of the touch events. 
     Additionally or alternatively, a processing device in the receiver device can cause the receiver device to transmit a ping to the transmitter device that indicates the location of the receiver device on the transmitting surface. 
     In some embodiments, one or more magnetic sensors in the transmitter device can detect a magnetic structure (or structures) in the receiver device, which can be used to determine the location of the receiver device on the transmitting surface. 
     Once the location of the receiver device on the transmitting surface is determined, one or more shared power converters that can be used to transfer energy to the receiver device are identified (block  802 ). Switch signals are then transmitted to the leading half bridge and a respective trailing half bridge in each identified shared power converter to transfer energy to the receiver device (block  804 ). 
     The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the described embodiments. However, it will be apparent to one skilled in the art that the specific details are not required in order to practice the described embodiments. Thus, the foregoing descriptions of the specific embodiments described herein are presented for purposes of illustration and description. They are not targeted to be exhaustive or to limit the embodiments to the precise forms disclosed. It will be apparent to one of ordinary skill in the art that many modifications and variations are possible in view of the above teachings.

Metadata:
Filing Date: 20170201
Publication Date: 20200804
Grant Date: 20200804
Priority Date: 20160826
Inventors: QIU, WEIHONG
MOUSSAOUI, ZAKI
DAYAL, ROHAN
Assignee: APPLE INC
CPC Classifications: [{"code": "H02J50/402", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/402", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/12", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J50/12", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J50/12", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J7/025", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J50/40", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 61243402