PATENT DOCUMENT

Publication Number: US-10135303-B2
Application Number: US-201414281812-A
Country: US
Kind Code: B2

Title: Operating a wireless power transfer system at multiple frequencies

Abstract:
A transmitter device in an inductive energy transfer system includes a first transmitter coil operatively connected to a first resonant circuitry. A receiver device includes a first receiver coil operatively connected to a first resonant circuitry. The first transmitter coil and the first receiver coil form a first transformer. The transmitter device, the receiver device, or both the transmitter and receiver devices can also include an auxiliary coil or inductor, which may form an auxiliary transformer. Energy can be transferred from the transmitter device to the receiver device using the first transformer or the auxiliary transformer. The transfer of energy may be adaptively adjusted based on the efficiency of the energy transfer. For example, the transfer of energy can be adjusted based on the operating conditions of the load.

Claims:
We claim: 
     
       1. A receiver device operable in a power transfer mode and a low energy transfer mode in an inductive energy transfer system, the receiver device comprising:
 an AC-to-DC converter; 
 a load operatively connected to an output of the AC-to-DC converter; 
 a first receiver coil associated with the power transfer mode; 
 a first resonant circuitry associated with a first resonant frequency and coupling the first receiver coil and an input of the AC-to-DC converter; 
 an auxiliary receiver coil associated with the low energy transfer mode; 
 an auxiliary resonant circuitry coupling the auxiliary receiver coil to the input of the AC-to-DC converter; wherein the auxiliary resonant circuitry is associated with a second resonant frequency that is different from the first resonant frequency; and 
 a processing device configured to transition the receiver device to the low energy transfer mode from the power transfer mode upon determining that a current draw of the load has decreased below a threshold. 
 
     
     
       2. The receiver device as in  claim 1 , further comprising a switching device operatively connected between the first resonant circuitry and the input of the AC-to-DC converter and operatively connected between the auxiliary resonant circuitry and the input of the AC-to-DC converter. 
     
     
       3. The receiver device as in  claim 2 , wherein the processing device is operatively connected to the switching device for controlling a state of the switching device. 
     
     
       4. The receiver device as in  claim 3 , further comprising an auxiliary rectifier operatively connected to the switching device and the load. 
     
     
       5. The receiver device as in  claim 1 , wherein the load comprises a rechargeable battery. 
     
     
       6. The receiver device as in  claim 1 , wherein the first resonant circuitry and the auxiliary resonant circuitry each comprise a capacitor. 
     
     
       7. The receiver device as in  claim 1 , wherein the AC-to-DC converter comprises a diode bridge. 
     
     
       8. The receiver device as in  claim 1 , wherein the AC-to-DC converter comprises a synchronous rectifier. 
     
     
       9. The receiver device as in  claim 1 , wherein the second resonant frequency is higher than the first resonant frequency. 
     
     
       10. A transmitter device for use in an inductive energy transfer system, comprising:
 a DC-to-AC converter; 
 a first resonant circuitry associated with a first resonant frequency and a power transfer mode, the first resonant circuitry operatively connected to the DC-to-AC converter; 
 an auxiliary resonant circuitry associated with a second resonant frequency and a low energy transfer mode, wherein the second resonant frequency is different from the first resonant frequency; 
 a primary transmitter coil operatively connected to the first resonant circuitry; 
 an auxiliary transmitter coil operatively connected to the auxiliary resonant circuitry; and 
 a processing device configured to transition the transmitter device to the low energy transfer mode from the power transfer mode upon determining that a current draw of a receiver device has decreased below a threshold. 
 
     
     
       11. The transmitter device as in  claim 10 , further comprising a power supply operatively connected to the DC-to-AC converter. 
     
     
       12. The transmitter device as in  claim 10 , wherein the second resonant frequency is higher than the first resonant frequency. 
     
     
       13. The transmitter device as in  claim 10 , wherein the first resonant circuitry and the auxiliary resonant circuitry each comprise a capacitor. 
     
     
       14. The transmitter device as in  claim 10 , further comprising:
 a sense circuitry operatively connected to a load; wherein 
 the processing device is operatively connected to the sense circuitry. 
 
     
     
       15. A method for operating an inductive energy transfer system, comprising:
 transferring power from a transmitter device to charge a battery of a receiver device using a first transformer operated in a power transfer mode; and 
 thereafter, transferring power from the transmitter device to trickle charge the battery of the receiver device using an auxiliary transformer operated in a low energy transfer mode after determining that the battery is charged beyond a threshold. 
 
     
     
       16. The method as in  claim 15 , further comprising:
 monitoring a load in the receiver device; and 
 changing to a different transfer mode based on an operating condition of the load. 
 
     
     
       17. The method as in  claim 15 , wherein the transmitter device pings the receiver device with the auxiliary transformer. 
     
     
       18. The method as in  claim 15 , further comprising monitoring transfer efficiency during the power transfer mode and adjusting at least one of a frequency and a signal level to increase the transfer efficiency. 
     
     
       19. The method as in  claim 15 , wherein the power transfer mode is associated with a first resonant frequency and the low energy transfer mode is associated with a second resonant frequency that is higher than the first resonant frequency.

Description:
TECHNICAL FIELD 
     The invention relates generally to wireless power transfer systems, and more particular to operating a wireless power transfer system at more than one band of frequencies. 
     BACKGROUND 
     Many electronic devices include one or more rechargeable batteries that require external power to recharge from time to time. Often, these devices may be charged using a similar power cord or connector, for example a universal serial bus (“USB”) connector. However, despite having common connection types, devices often require separate power supplies with different power outputs. These multiple power supplies can be burdensome to use, store, and transport from place to place. As a result, the benefits of device portability may be substantially limited. 
     Furthermore, charging cords may be unsafe to use in certain circumstances. For example, a driver of a vehicle may become distracted attempting to plug an electronic device into a vehicle charger. In another example, a charging cord may present a tripping hazard if left unattended. 
     To account for these and other shortcomings of portable electronic devices, some devices include an inductive charging device. The user may simply place the electronic device on an inductive charging surface of a charging device in order to transfer energy from the charging device to the electronic device. The charging device transfers energy to the electronic device through inductively coupling between a transmitter coil in the charging device and a receiver coil in the electronic device. But as the size of many electronic devices continues to decrease, the transmitter coil may have an inductance that is lower than desired. This lower inductance can lead to large circulating currents in the inductive charging device in the transmitter device, which can result in large power losses. In situations where a high amount of power is needed by the receiver device, the large power losses may be acceptable. But when only a small amount of power is needed on the receiver side, the losses in the transmitter coil may be unacceptable and can cause thermal problems or unacceptably large parasitic standby power, also known as vampire power. 
     SUMMARY 
     Embodiments described herein provide inductive energy transfer systems that operate at more than one band of frequencies, using an appropriate band for a desired level of delivered energy. In one aspect, a receiver device for use in an inductive energy transfer system can include a first receiver coil operatively connected to an input of an AC-to-DC converter and a first resonant circuitry operatively connected between the first receiver coil and the input of the AC-to-DC converter. An auxiliary receiver coil may be operatively connected to the input of the AC-to-DC converter. An auxiliary resonant circuitry can be operatively connected between the second receiver coil and the input of the AC-to-DC converter. The first resonant circuitry is associated with a first resonant frequency, and the second resonant circuitry is associated with a second resonant frequency that is different from the first resonant frequency. In one embodiment, the second resonant frequency is higher than the first resonant frequency. 
     In another aspect, a transmitter device for use in an inductive energy transfer system can include a DC-to-AC converter operatively connected to a first resonant circuitry and an auxiliary resonant circuitry. A first transmitter coil may be operatively connected to the first resonant circuitry. An auxiliary transmitter coil can be operatively connected to the auxiliary resonant circuitry. The first resonant circuitry is associated with a first resonant frequency, and the auxiliary resonant circuitry is associated with a second resonant frequency different from the first resonant frequency. As described earlier, the second resonant frequency is higher than the first resonant frequency in some embodiments. 
     The first transmitter and the first receiver coils form a first transformer. The auxiliary transmitter coil and the auxiliary receiver coil form an auxiliary transmitter. The auxiliary transformer can be used to transfer lesser amounts of energy at higher frequencies and the first transformer may be used to transfer greater amounts of energy at lower frequencies. 
     In some embodiments, an inductive energy transfer system can include an auxiliary transmitter coil but not an auxiliary receiver coil. An auxiliary transmitter coil can couple inductively with a first receiver coil to transfer energy. The auxiliary transmitter coil and the first receiver coil form an auxiliary transformer. 
     In other embodiments, an inductive energy transfer system can include an auxiliary receiver coil but not an auxiliary transmitter coil. An auxiliary receiver coil can couple inductively with a first transmitter coil to transfer energy. The auxiliary receiver coil and the first transmitter coil form an auxiliary transformer. 
     In another aspect, a method for operating an inductive energy transfer system can include transferring energy from a transmitter device to a receiver device using a first transformer in a power transfer mode, and transferring energy from the transmitter device to the receiver device using an auxiliary transformer in a low energy transfer mode. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the invention are better understood with reference to the following drawings. The elements of the drawings are not necessarily to scale relative to each other. Identical reference numerals have been used, where possible, to designate identical features that are common to the figures. 
         FIG. 1  illustrates one example of inductive energy transfer system; 
         FIG. 2  depicts a simplified block diagram of one example of the inductive energy transfer system  100  shown in  FIG. 1 ; 
         FIG. 3  illustrates a simplified block diagram of an example of a first inductive energy transfer system transfers energy more efficiently; 
         FIG. 4  depicts a simplified block diagram of an example of a second inductive energy transfer system that transfer energy more efficiently; 
         FIG. 5  illustrates an example power metal oxide semiconductor field-effect transistor (MOSFET) bridge; 
         FIG. 6  depicts a simplified block diagram of an example of a third inductive energy transfer system that transfer energy more efficiently; and 
         FIG. 7  is a flowchart of a method for operating an inductive energy transfer system. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments described herein provide inductive energy transfer systems that operate at more than one band of frequencies, using an appropriate band for a desired level of delivered energy. Energy can be transferred inductively from a transmitter device to a receiver device to charge a battery or to operate the receiver device. Additionally or alternatively, communication or control signals can be transmitted inductively between the transmitter and receiver devices. For example, while charging, high frequency pulses can be added on top of the inductive charging frequency to enable both charging and communication. Alternatively, the transferred energy can be used solely for communication. Thus, the terms “energy”, “signal”, or “signals” are meant to encompass transferring energy for wireless charging, transferring energy as communication and/or control signals, or both wireless charging and the transmission of communication and/or control signals. 
     A transmitter device in an inductive energy transfer system includes a first transmitter coil operatively connected to a first resonant circuitry. A receiver device includes a first receiver coil operatively connected to a first resonant circuitry. The first transmitter coil and the first receiver coil form a first transformer. The transmitter device, the receiver device, or both the transmitter and receiver devices can also include an auxiliary coil or inductor, which may form an auxiliary transformer. Energy can be transferred from the transmitter device to the receiver device using the first transformer or the auxiliary transformer. The transfer of energy may be adaptively adjusted based on the efficiency of the energy transfer. For example, the transfer of energy can be adjusted based on the operating conditions of the load. 
     In some embodiments, the transmitter device can transfer a short burst of energy to the receiver device to determine if the first receiver coil is coupled to the first transmitter coil. This short burst of energy is known as a ping. The transmitter device may transmit a ping and wait for a response from the receiver device. If no response is received, the transmitter device waits for a given period of time before sending another ping. If a response is received, the transmitter device can transfer energy to the receiver device to charge a battery and/or to transmit one or more communication signals to the receiver device. In one embodiment, the transmitter device can ping the receiver device using an auxiliary transformer. The auxiliary transformer can be energized with a signal having a higher frequency to ping the receiver device with a lower amount of energy. If the receiver device transmits a response, the transmitter device can energize the first transmitter coil with a signal having a lower frequency to transfer a higher amount of energy to the receiver device. Additionally or alternatively, energy can be transferred using the auxiliary transformer for other purposes. For example, the auxiliary transformer can be used to transfer power for trickle charging and the first transformer may transfer energy for power charging. 
     In some embodiments, an AC-to-DC converter in the receiver device can be implemented as a bridge rectifier. Other embodiments can construct the AC-to-DC converter as a synchronous rectifier. In a synchronous rectifier, the diodes in a bridge rectifier may be replaced with transistors, such as power metal oxide semiconductor field-effect transistors (MOSFETs). A processing device can turn each respective MOSFET on or off. Typically, a power MOSFET includes a body diode between the drain and the source of the MOSFET. It may be more efficient in some embodiments to turn off the synchronous rectifier and use the body diodes as a bridge rectifier when the load is lighter; namely, when the load is drawing less current. 
     Referring now to  FIG. 1 , there is shown a top view of one example of an inductive energy transfer system. The inductive energy transfer system  100  includes a charging device  102  and an electronic device  104 . In the illustrated embodiment, the charging device  102  is depicted as a charging dock and the electronic device as a smart telephone. The electronic device and/or the charging device can be implemented as different devices in other embodiments. For example, the electronic device  104  can be a digital media player, a wearable electronic or communication device, a health monitoring device, a tablet computing device, and any other type of electronic device that includes one or more inductive charging coils. As another example, the charging device  102  may be adapted to be inserted into a charging port in an electronic device. 
     The electronic device  104  is placed on a charging surface  106  of the charging device  102  when charge is to be transferred to the electronic device. The charging device  102  may be connected to a power source through a power cord (e.g., a wall outlet) or through a connector such as a Universal Serial Bus (USB) connector (not shown). The charging device  102  includes one or more inductive charging coils that transfer energy to one or more inductive charging coils in the electronic device  104 . In this manner, the charging device  102  is a transmitter device with a transmitter coil or coils and the electronic device  104  is a receiver device with one or more receiver coils. Energy can be transferred, for example, to charge a battery in the electronic device  104  or to operate the electronic device. Additionally or alternatively, control and/or communication signals can be transferred wirelessly between the charging device  102  and the electronic device  104 . 
       FIG. 2  depicts a simplified block diagram of one example of the inductive energy transfer system  100  shown in  FIG. 1 . The transmitter device  102  includes a power supply  200  operably connected to a DC-to-AC converter  202 . Any suitable type of a DC-to-AC converter may be used. For example, the DC-to-AC converter can be constructed as an H bridge in one embodiment. The DC-to-AC converter  202  is operatively connected to transmitter resonant circuitry  204 . The transmitter resonant circuitry  204  is operatively connected to a first transmitter coil  206 . 
     The receiver device  104  can include a first receiver coil  208  operably connected to receiver resonant circuitry  210 . The receiver resonant circuitry  210  is operatively connected to an AC-to-DC converter  212 . Any suitable type of AC-to-DC converter may be used. For example, the AC-to-DC converter can be constructed as a diode bridge in one embodiment. 
     A load  214  is operably connected to the output of the AC-to-DC converter  212 . The load  214  is a rechargeable battery in one embodiment. A different type of load can be used in other embodiments. 
     The first transmitter coil  206  and the first receiver coil  208  together form a first transformer  216 . The first transformer  216  transfers power or energy through inductive coupling between the first transmitter coil  206  and the first receiver coil  208  (energy transfer represented by arrow  218 ). Essentially, energy is transferred from the first transmitter coil  206  to the first receiver coil  208  through the creation of a varying magnetic flux by the AC signal in the first transmitter coil  206  that induces a current in the first receiver coil  208 . The AC signal induced in the first receiver coil  208  is received by the AC-to-DC converter  212  that converts the AC signal into a DC signal. In embodiments where the load  214  is a rechargeable battery, the DC signal is used to charge the battery. Additionally or alternatively, the transferred energy can be used to transmit communication signals to or from the receiver device (communication signals represented by arrow  220 ). 
     In some embodiments, the leakage inductance of a transformer can be significant. Thus, the transmitter and receiver resonant circuitry  204  and  210  may be included in the inductive energy transfer system  100  to cancel some or all of the leakage inductance when the capacitance and inductance values are near the resonant frequency (frequency f R1 ). Any suitable type of resonant circuitry can be used. In some embodiments, the transmitter resonant circuitry  204  is a resonant capacitor connected in series between the DC-to-AC converter  202  and the first transmitter coil  206 . The receiver resonant circuitry  210  is a resonant capacitor connected in series between the first receiver coil  208  and the AC-to-DC converter  212 . 
     Generally, the operating conditions of a load may vary over time, which can adversely impact transfer efficiency. For example, when the load is a rechargeable battery, the battery draws a higher current when charging and less current when charged or nearly charged (e.g., trickle charging). Therefore, it can be desirable to vary the transfer of energy based on the operating conditions of the load, which results in a more efficient transfer of energy. For example, the frequency and/or the amount of energy being transferred can be adjusted when the operating conditions of the load change. 
       FIG. 3  illustrates a simplified block diagram of an example of a first inductive energy transfer system that transfers energy more efficiently. The inductive energy transfer system  300  is similar to the embodiment shown in  FIG. 2 , with the addition of a sense circuit and a processing device in the receiver device  304  and in the transmitter device  302 . The load and/or the efficiency of energy transfer can be monitored continuous, periodically, or at select times and adjustments made accordingly to improve efficiency. This way the efficiency curve may be optimized over a wider range of load currents or conditions in real time or near real time. 
     The transmitter device  302  can include a sense circuit  306  operatively connected to the transmitter coil  206  and a processing device  308  operatively connected to the sense circuit. The processing device  308  may also be operatively connected to the power supply  200  and/or to the DC-to-AC converter  202 . The sense circuit  306  can monitor or measure the current in the first transmitter coil  206 . The processing device  308  may analyze the measurements to determine whether the receiver device  304  has transmitted a communication signal to the transmitter device  302 . For example, the receiver device  304  can request the transmitter device to transfer more or less energy. The processing device  308  can adaptively adjust one or more settings in the transmitter device based on received communication and/or control signals from the receiver device. For example, the processing device  308  may adjust the signal level and/or frequency of the signal that is received by the first transmitter coil. 
     The receiver device  304  can include a sense circuit  310  operatively connected to the load  214  and a processing device  312  connected to the sense circuit  310 . The processing device  312  may also be connected to the DC-to-AC converter  212 . The sense circuit  310  can sense or measure the state or operations of the load, such as the current input into the load. The processing device  312  may analyze the measurements to determine whether an operating condition of the load has changed and if so, transmit a communication signal to the transmitter device  302 . For example, the receiver device  304  can request the transmitter device to transfer more or less energy. Additionally or alternatively, the receiver device  304  can transmit a signal indicating the battery is charged, and in response the transmitter device may enter a low power or sleep state. 
     The processing devices  308 ,  312  can each be implemented as any electronic device capable of processing, receiving, or transmitting data or instructions. For example, the processing device  308  can be a microprocessor, a central processing unit (CPU), an application-specific integrated circuit (ASIC), a digital signal processor (DSP), or combinations of multiple 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. 
     Referring now to  FIG. 4 , there is shown a simplified block diagram of an example of a second inductive energy transfer system that transfers energy more efficiently. The inductive energy transfer system  400  is similar to the embodiment shown in  FIG. 3 , with the addition of an auxiliary transmitter and/or auxiliary receiver coil and corresponding auxiliary resonant circuitry. The auxiliary transmitter coil and/or auxiliary receiver coil can transfer energy at a frequency (frequency f R2 ) that is different from the frequency f R1  of the first transformer  216 . In some embodiments, the auxiliary coil(s) and corresponding resonant circuitry are optimized to be efficient at higher frequencies (f R1 &lt;f R2 ). The auxiliary coil(s) can be used to transfer lesser amounts of energy at higher frequencies (e.g., when the load is lighter), while the first transmitter and receiver coils may be used to transfer greater amounts of energy at lower frequencies. 
     In some embodiments, the transmitter device  402  can include auxiliary resonant circuitry  406  operatively connected between the output of the DC-to-AC converter  202  and an auxiliary transmitter coil  408 . And the receiver device  404  may include an auxiliary receiver coil  410  operatively connected to auxiliary resonant circuitry  412 . The first resonant circuitry  210  or the auxiliary resonant circuitry  412  is operatively connected to the AC-to-DC converter  212  through a switching device  414 . Any suitable type of switching device can be used and may include one or more switching devices. The processing device  312  is operatively connected to the switching device  414  through the signal line  416  to control the state of the switching device (i.e., to connect auxiliary resonant circuitry or to connect first resonant circuitry to AC-to-DC converter  212 ). 
     The auxiliary transmitter coil  408  and the auxiliary receiver coil  410  together form an auxiliary transformer  416 . As described earlier, in one embodiment the first transformer  216  is used to transfer a greater amount of energy at lower frequencies and the auxiliary transformer  416  transfers a lesser amount of energy at higher frequencies. As one example, the auxiliary transmitter coil  408  may be constructed as a small coil of a relatively thin wire having a high number of turns. When energized at a higher frequency, the impedance of the inductor is higher so a lower amount of current flows through the coil and a higher output voltage is produced. However, less energy may be transferred to the auxiliary receiver coil  410  due to a higher output resistance. At higher frequencies, the lower amount of energy can transfer more efficiently than with the first transformer  216  when the load is lighter. As described earlier, a load is “lighter” when the load is drawing less current. 
     Other inductive energy transfer systems can include the auxiliary transmitter coil but not the auxiliary receiver coil. For example, an auxiliary transmitter coil can couple inductively with a first receiver coil to transfer energy at a frequency that is different from first resonant frequency f R1 . The auxiliary transmitter coil and the first receiver coil form an auxiliary transformer. Alternatively, an inductive energy transfer system may include an auxiliary receiver coil but not an auxiliary transmitter coil. The first transmitter coil can couple inductively with an auxiliary receiver coil to transfer energy at a frequency that is different from first resonant frequency f R1 ). The auxiliary receiver coil and the first transmitter coil form an auxiliary transformer. As described earlier, the auxiliary transformer may be used to ping the receiver device periodically or at select times in some embodiments. 
     As one example, the first transformer  216  can transfer energy at 250-400 kHz while the auxiliary transformer may transfer energy at 750 kHz-1 MHz. In some embodiments, the auxiliary transmitter coil  408  can be used to ping the receiver device periodically and the first transmitter coil  206  can be used to charge a battery in the receiver device. As described earlier, the sense circuit  310  and the processing device  312  in the receiver device  404  can be used to determine when to transfer energy with the auxiliary transformer  416  based on the load conditions. The receiver device  404  can transmit a communication signal to the transmitter device  402  informing the transmitter device of the operating condition of the load and/or to transfer energy using the auxiliary transformer  416 . The sense circuit  306  and the processing device  308  in the transmitter device  402  receives the communication signal and the processing device  308  can adjust the operation of the DC-to-AC converter  202  so that a higher frequency signal is received by the auxiliary transmitter  402 . 
     Thus, the inductive energy transfer system  400  can have different operating modes. A first mode can transfer a higher amount of energy at lower frequencies using the first transformer  216 . A second mode can transfer a lower amount of energy at higher frequencies using the auxiliary transformer  416 . The second mode allows the transmitter device  402  to ping the receiver device  404  periodically without consuming a lot of power. For example, when the transmitter device  402  is in a low power or sleep state, the transmitter device  402  may wake up periodically to transmit a ping to detect the presence of the receiver device, to determine if the receiver device needs more power, and/or to see if the receiver device has a status update. 
     As described previously, any suitable type of AC-to-DC converter can be used in a receiver device. In some embodiments, the AC-to-DC converter  212  in the receiver device  404  can be implemented as a diode bridge. Other embodiments can construct the AC-to-DC converter  212  as a synchronous rectifier. In a synchronous rectifier, the diodes in the diode bridge may be replaced with transistors, such as power metal oxide semiconductor field-effect transistors (MOSFETs).  FIG. 5  illustrates an example MOSFET bridge. A MOSFET bridge can function as an AC-to-DC converter, such as AC-to-DC converter  212  in the receiver device. The processing device  312  may turn each respective MOSFET on or off. Typically, a power MOSFET  500  includes a body diode  502  between the drain and the source of the MOSFET (see  FIG. 5 ). With a lighter load, it may be more efficient to turn off the synchronous rectifier and use the body diodes  502  as a diode bridge. 
     Alternatively, a separate auxiliary AC-to-DC converter or rectifier  600  in the receiver device  604  can be connected to the auxiliary receiver coil  410  (see  FIG. 6 ). The processing device  312  is connected to a switching device  602  through signal line  606  to control the state of the switching device  602 . When contacts  2  and  4  of the switching device  602  are electrically connected together, the load  214  may be connected to the primary receiver coil  208  through the AC-to-DC converter  212  and the resonant circuitry  210 . Alternatively, the load  214  may be connected to the primary receiver coil  208  through the auxiliary rectifier  500  and the resonant circuitry  210  when contacts  2  and  3  are electrically connected together. Then again, the load  214  can be connected to the auxiliary receiver coil  410  through the AC-to-DC converter  212  and the auxiliary resonant circuitry  412  when contacts  1  and  4  are electrically connected together. Conversely, the load  214  may be connected to the auxiliary receiver coil  410  through the auxiliary rectifier  600  and the auxiliary resonant circuitry  412  when contacts  1  and  3  are electrically connected together. Thus, energy can be transferred to the load using one of several paths in the receiver device  604 , with the selection of the path being based on the operating conditions of the load. The selected path can change in real time or near real time as the operating conditions of the load vary over time. 
     Referring now to  FIG. 7 , there is shown a flowchart of a method for operating an inductive energy transfer system. Initially, a determination may be made as to whether the inductive energy transfer system is to operate in a low energy transfer mode (block  700 ). As described earlier, a low energy transfer mode can be used when the load is lighter (i.e., not drawing much current). In one embodiment, a lesser amount of energy is transfer to the load at a higher frequency. 
     If the inductive energy transfer system is to operate in the low energy transfer mode, the process passes to block  702  where the auxiliary transformer transfers energy from the transmitter device to the receiver device in the low energy transfer mode. If the inductive energy transfer system will not operate in the low energy transfer mode, the method continues at block  704  where the first transformer transfers energy from the transmitter device to the receiver device. In one embodiment, the first transformer transfers a higher amount of energy at a lower frequency compared to the auxiliary transformer. This mode may be called a power transfer mode. 
     The process passes to block  706  after block  702  or after block  704 . In block  706 , one or more operations in the receiver device is monitored. For example, in one embodiment, the current input into the load is monitored to determine whether or not the transfer of energy needs to be adjusted. The frequency of the energy transfer is adjusted at block  708  if the operations in the receiver indicate the frequency of the power transfer should be modified. The load and/or the efficiency of energy transfer can be monitored continuous, periodically, or at select times and adjustments made accordingly to improve efficiency. As described earlier, the efficiency curve may be optimized over a wider range of load currents or conditions in real time or near real time. 
     A determination may then be made at block  710  as to whether the mode of energy transfer should change. If not, the method waits and the efficiency of the energy transfer is monitored continuous, periodically, or at select times. If the mode of energy transfer is to change, the method returns to block  700 . 
     Various embodiments have been described in detail with particular reference to certain features thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the disclosure. And even though specific embodiments have been described herein, it should be noted that the application is not limited to these embodiments. In particular, any features described with respect to one embodiment may also be used in other embodiments, where compatible. Likewise, the features of the different embodiments may be exchanged, where compatible.

Metadata:
Filing Date: 20140519
Publication Date: 20181120
Grant Date: 20181120
Priority Date: 20140519
Inventors: MOYER, TODD K.
TERLIZZI, JEFFREY J.
ALVES, Jeffrey M.
Assignee: APPLE INC
CPC Classifications: [{"code": "H02J50/80", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/02", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/40", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J50/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J5/005", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/025", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J5/00", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/402", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/12", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J50/402", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/02", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/80", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J5/00", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/12", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 54539308