PATENT DOCUMENT

Publication Number: US-10998776-B2
Application Number: US-202016748467-A
Country: US
Kind Code: B2

Title: Wireless power system with in-band communications

Abstract:
A wireless power receiving device has a coil that receives wireless power signals from a wireless power transmitting device and has a rectifier that produces direct-current power across rectifier output terminals using the received wireless power signals. A load in the wireless power receiving device receives a direct-current output voltage from the rectifier output terminals. In-band communications are supported in which an amplitude-shift keying communications scheme or other communications scheme is used by a data transmitter in the wireless power receiving device to transmit in-band data through the coil. In-band data is transmitted by modulating one or more transistors that are coupled to the coil and other wireless power receiving circuitry in series with one or more capacitors and is transmitted by modulating current flow through a ballast transistor or other adjustable load that is coupled across the rectifier output terminals.

Claims:
What is claimed is: 
     
       1. A wireless power receiving device configured to wirelessly receive power during wireless power transmission from a wireless power transmitting device, comprising:
 wireless power receiving circuitry that includes a coil and rectifier, configured to:
 receive wireless power signals with the coil; and 
 supply a corresponding output voltage across rectifier output terminals; 
 
 an adjustable load coupled to the rectifier output terminals; 
 capacitance switching circuitry coupled to the wireless power receiving circuitry; and 
 control circuitry configured to:
 transmit data signals to the wireless power transmitting device, using the coil, by adjusting a capacitance coupled to the wireless power receiving circuitry with the capacitance switching circuitry; and 
 transmit data signals to the wireless power transmitting device, using the coil, by adjusting the adjustable load. 
 
 
     
     
       2. The wireless power receiving device of  claim 1  further comprising input-output devices and a battery that form a load that receives the output voltage in parallel with the adjustable load. 
     
     
       3. The wireless power receiving device of  claim 2  further comprising a current sensor, wherein the control circuitry is configured to use the current sensor to measure a current flowing through the load. 
     
     
       4. The wireless power receiving device of  claim 3  wherein the control circuitry has an in-band data transmitter and is configured to use the in-band data transmitter to transmit the data signals by modulating the capacitance with the capacitance switching circuitry in response to measuring that the current flowing through the load is greater than a threshold value. 
     
     
       5. The wireless power receiving device of  claim 3  wherein the control circuitry has an in-band data transmitter and is configured to use the in-band data transmitter to transmit the in-band data signals by modulating the adjustable load in response to measuring that the current flowing through the load is less than a predetermined value. 
     
     
       6. The wireless power receiving device of  claim 5  wherein the adjustable load comprises a transistor having source-drain terminals coupled respectively to the output terminals and having a gate that is configured to receive the data signals from the in-band data transmitter. 
     
     
       7. The wireless power receiving device of  claim 6  wherein the capacitance switching circuitry comprises at least one capacitor and at least one transistor coupled in series between the coil and ground. 
     
     
       8. The wireless power receiving device of  claim 6  wherein the capacitance switching circuitry comprises first and second capacitors coupled in series respectively with first and second transistors. 
     
     
       9. The wireless power receiving device of  claim 2  wherein the control circuitry is configured to adjust the adjustable load to pass a current while waiting for the input-output devices to begin drawing current after the wireless power transmission from the wireless power transmitting device is initiated. 
     
     
       10. A wireless power receiving device configured to wirelessly receive power during wireless power transmission from a wireless power transmitting device, comprising:
 a coil; 
 a rectifier configured to:
 rectify wireless power signals received with the coil; and 
 supply a corresponding output voltage across rectifier output terminals; 
 
 a load that receives the output voltage; 
 a ballast load coupled across the rectifier output terminals; 
 a current sensor configured to measure current flow through the load; and 
 control circuitry having a data transmitter, wherein the control circuitry is configured to:
 adjust the ballast load based on information from the current sensor; and 
 use the data transmitter to adjust current flow through the ballast load to transmit data from the coil to the wireless power transmitting device. 
 
 
     
     
       11. The wireless power receiving device of  claim 10  wherein the load comprises input-output devices and wherein the control circuitry is configured to adjust the ballast load to pass a current while waiting for the input-output devices to begin drawing current after the wireless power transmission from the wireless power transmitting device is initiated. 
     
     
       12. The wireless power receiving device of  claim 11  further comprising capacitance switching circuitry coupled to the coil, wherein the control circuitry is configured to use the data transmitter to transmit data to the wireless power transmitting device by using the capacitance switching circuitry to adjust a capacitance coupled to the coil. 
     
     
       13. The wireless power receiving device of  claim 10  further comprising at least one capacitor and at least one transistor coupled to the coil in series, wherein the control circuitry is configured to:
 transmit data from the coil to the wireless power transmitting device by adjusting the transistor that is coupled in series with the capacitor in response to measuring with the current sensor that a current flowing through the load is greater than a predetermined threshold value. 
 
     
     
       14. The wireless power receiving device of  claim 13  wherein the control circuitry is configured to:
 use the data transmitter to adjust current flow through the ballast load to transmit data from the coil to the wireless power transmitting device in response to measuring with the current sensor that the current flowing through the load is less than the predetermined threshold value. 
 
     
     
       15. The wireless power receiving device of  claim 10  wherein the load includes a battery. 
     
     
       16. A wireless power receiving device configured to wirelessly receive power during wireless power transmission from a wireless power transmitting device, comprising:
 a coil; 
 a rectifier that is configured to rectify wireless power signals received with the coil and that is configured to supply a corresponding output voltage across rectifier output terminals; 
 a load that includes a display and a battery and that receives the output voltage; 
 a first transistor coupled to the rectifier output terminals; 
 a capacitor; 
 a second transistor coupled to the coil in series with the capacitor; 
 control circuitry having a data transmitter, wherein the control circuitry is configured to:
 use the data transmitter to transmit data signals through the coil by adjusting current flow through the first transistor; and 
 use the data transmitter to transmit data signals through the coil by adjusting the second transistor. 
 
 
     
     
       17. The wireless power receiving device of  claim 16  further comprising a current sensor configured to measure current flow through the load, wherein the control circuitry is configured to:
 use the data transmitter to transmit data signals through the coil by adjusting current flow through the first transistor in response to measuring with the current sensor that the current flowing through the load is less than a predetermined value. 
 
     
     
       18. The wireless power receiving device of  claim 17  wherein the control circuitry is configured to:
 use the data transmitter to transmit data signals through the coil by adjusting the second transistor in response to measuring with the current sensor that the current flowing through the load is more than the predetermined value. 
 
     
     
       19. The wireless power receiving device of  claim 16  further comprising a current sensor configured to measure current flow through the load, wherein the first transistor forms an adjustable load, and wherein the control circuitry is configured to:
 adjust the adjustable load based on information from the current sensor. 
 
     
     
       20. The wireless power receiving device of  claim 19  wherein the control circuitry is configured to adjust the adjustable load to: 1) pass a fixed ballast current while waiting for the load to begin drawing current after the wireless power transmission from the wireless power transmitting device is initiated and 2) pass less than the fixed ballast current after the load begins drawing current. 
     
     
       21. The wireless power receiving device of  claim 16  wherein the data transmitter has a first output coupled to a gate of the first transistor and a second output coupled to a gate of the second transistor and wherein the data transmitter is configured to transmit amplitude-shift keying data signals through the coil using the first transistor and is configured to transmit amplitude-shift keying data signals through the coil using the second transistor.

Description:
This application claims the benefit of provisional patent application No. 62/832,795, filed Apr. 11, 2019, which is hereby incorporated by reference herein in its entirety. 
    
    
     FIELD 
     This relates generally to power systems, and, more particularly, to wireless power systems for charging electronic devices. 
     BACKGROUND 
     In a wireless charging system, a wireless charging mat wirelessly transmits power to a portable electronic device that is placed on the mat. The portable electronic device has a coil and rectifier circuitry. The coil of the portable electronic device receives alternating-current wireless power signals from a coil in the wireless charging mat. The rectifier circuitry converts the received signals into direct-current power. 
     SUMMARY 
     A wireless power system has a wireless power transmitting device and a wireless power receiving device. The wireless power receiving device has a coil that receives wireless power signals from the wireless power transmitting device and has a rectifier that produces direct-current power across rectifier output terminals using the received wireless power signals. A load in the wireless power receiving device receives a direct-current output voltage from the rectifier output terminals. 
     The system supports in-band communications in which an amplitude-shift keying communications scheme or other communications scheme is used by a data transmitter in the wireless power receiving device to transmit in-band data through the coil. 
     Capacitor switching circuitry or other switchable circuitry for adjusting the impedance of the wireless power receiving circuitry in the wireless power receiving device may be coupled to the coil. A ballast load such as a ballast transistor or other adjustable load may be coupled across the rectifier output terminals. A current source may monitor current flow through the load. 
     During start-up operations, the ballast load may be used to shunt a current between the rectifier output terminals. This ensures that a minimum amount of current passes between the rectifier output terminals while the wireless power receiving device is receiving power, even if the load of the wireless power receiving device is not yet passing current. Once current begins flowing through the load, the ballast load may be turned off or the amount of current passing through the ballast transistor may otherwise be reduced. 
     When it is desired to transmit in-band data, the data transmitter may supply control signals to the ballast transistor or to one or more transistors in the capacitor switching circuitry. This transmits data through the coil to a data receiver in the wireless power transmitting device. 
     The components that are modulated to transmit the in-band data can be selected based on load conditions. For example, in response to determining that light loading conditions are present (e.g., the current flowing through the load is less than a predetermined threshold value), the data transmitter can transmit in-band data by modulating the ballast transistor. In response to determining that heavy loading conditions are present (e.g., the current flowing through the load is more than the predetermined threshold value), the data transmitter can transmit in-band data by modulating one or more transistors in the capacitor switching circuitry. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of an illustrative wireless charging system that includes a wireless power transmitting device and a wireless power receiving device in accordance with an embodiment. 
         FIG. 2  is a circuit diagram of wireless power transmitting and receiving circuitry in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     A wireless power system includes a wireless power transmitting device such as a wireless charging mat. The wireless power transmitting device wirelessly transmits power to a wireless power receiving device such as a wristwatch, cellular telephone, tablet computer, laptop computer, or other electronic equipment. The wireless power receiving device uses power from the wireless power transmitting device for powering the device and for charging an internal battery. 
     The wireless power transmitting device communicates with the wireless power receiving device and obtains information on the characteristics of the wireless power receiving device. In some embodiments, the wireless power transmitting device has multiple power transmitting coils. In such embodiments, the wireless power transmitting device uses information from the wireless power receiving device and measurements made in the wireless power transmitting device to determine which coil or coils in the transmitting device are magnetically coupled to wireless power receiving devices. Coil selection is then performed in the wireless power transmitting device. Wireless power is transmitted from the wireless power transmitting device to the wireless power receiving device using selected coil(s) to charge a battery in the wireless power receiving device and/or to power other load circuitry. 
     When it is desired for the wireless power transmitting device to send information to the wireless power receiving device, the wireless power transmitting device transmits data to the wireless power receiving device by modulating the frequency of the alternating-current wireless power signal that is being transmitted to the wireless power receiving device. This frequency modulation is sometimes referred to as frequency-shift keying (FSK) modulation. In the wireless power receiving device, an FSK demodulator can demodulate the frequency of the received alternating-current wireless power signal and can thereby receive the data transmitted from the wireless power transmitting device. 
     When it is desired for the wireless power receiving device to send information to the wireless power transmitting device, the wireless power receiving device transmits data to the wireless power transmitting device by modulating components in the wireless power receiving device. This modulation causes fluctuations in the impedance of the wireless power receiving circuitry seen by the transmitted wireless power signal. Modulation of the impedance of the receiving circuitry in this way modulates the amplitude (and phase) of the transmitted wireless power signal and results in detectable changes in the alternating-current being used to drive the wireless power transmitting coil. This type of modulation is sometimes referred to as amplitude-shift keying (ASK). Using FSK and ASK communications and/or other in-band and/or out-of-band communications, the devices in the wireless power transmitting system can coordinate operation. 
     An illustrative wireless power system (wireless charging system) is shown in  FIG. 1 . As shown in  FIG. 1 , wireless power system  8  includes a wireless power transmitting device such as wireless power transmitting device  12  and includes a wireless power receiving device such as wireless power receiving device  24 . Wireless power transmitting device  12  includes control circuitry  16 . Wireless power receiving device  24  includes control circuitry  30 . Control circuitry in system  8  such as control circuitry  16  and control circuitry  30  is used in controlling the operation of system  8 . This control circuitry may include processing circuitry associated with microprocessors, power management units, baseband processors, digital signal processors, microcontrollers, and/or application-specific integrated circuits with processing circuits. The processing circuitry implements desired control and communications features in devices  12  and  24 . For example, the processing circuitry may be used in selecting coils, determining power transmission levels, processing sensor data and other data, processing user input, handling negotiations between devices  12  and  24 , sending and receiving in-band and out-of-band data, making measurements, and otherwise controlling the operation of system  8 . 
     Control circuitry in system  8  may be configured to perform operations in system  8  using hardware (e.g., dedicated hardware or circuitry), firmware and/or software. Software code for performing operations in system  8  is stored on non-transitory computer readable storage media (e.g., tangible computer readable storage media) in control circuitry  8 . The software code may sometimes be referred to as software, data, program instructions, instructions, or code. The non-transitory computer readable storage media may include non-volatile memory such as non-volatile random-access memory (NVRAM), one or more hard drives (e.g., magnetic drives or solid state drives), one or more removable flash drives or other removable media, or the like. Software stored on the non-transitory computer readable storage media may be executed on the processing circuitry of control circuitry  16  and/or  30 . The processing circuitry may include application-specific integrated circuits with processing circuitry, one or more microprocessors, a central processing unit (CPU) or other processing circuitry. 
     Power transmitting device  12  may be a stand-alone power adapter (e.g., a wireless charging mat that includes power adapter circuitry), may be a wireless charging mat that is coupled to a power adapter or other equipment by a cable, may be a portable device, may be equipment that has been incorporated into furniture, a vehicle, or other system, may be a removable battery case, or may be other wireless power transfer equipment. Illustrative configurations in which wireless power transmitting device  12  is a wireless charging mat are sometimes described herein as an example. 
     Power receiving device  24  may be a portable electronic device such as a wristwatch, a cellular telephone, a laptop computer, a tablet computer, an accessory such as an earbud, or other electronic equipment. Power transmitting device  12  may be coupled to a wall outlet (e.g., an alternating current power source), may have a battery for supplying power, and/or may have another source of power. Power transmitting device  12  may have an alternating-current (AC) to direct-current (DC) power converter such as AC-DC power converter  14  for converting AC power from a wall outlet or other power source into DC power. DC power may be used to power control circuitry  16 . During operation, a controller in control circuitry  16  uses power transmitting circuitry  52  to transmit wireless power to power receiving circuitry  54  of device  24 . Power transmitting circuitry  52  may have switching circuitry (e.g., inverter circuitry  61  formed from transistors) that is turned on and off based on control signals provided by control circuitry  16  to create AC current signals through one or more wireless power transmitting coils such as transmit coils  36 . Coils  36  may be arranged in a planar coil array (e.g., in configurations in which device  12  is a wireless charging mat). 
     As the AC currents pass through one or more coils  36 , alternating-current electromagnetic (e.g., magnetic) fields (signals  44 ) are produced that are received by one or more corresponding receiver coils such as coil  48  in power receiving device  24 . When the alternating-current electromagnetic fields are received by coil  48 , corresponding alternating-current currents are induced in coil  48 . Rectifier circuitry such as rectifier  50 , which contains rectifying components such as synchronous rectification metal-oxide-semiconductor transistors arranged in a bridge network, converts received AC signals (received alternating-current signals associated with electromagnetic signals  44 ) from coil  48  into DC voltage signals for powering device  24 . 
     The DC voltage produced by rectifier  50  (sometime referred to as rectifier output voltage Vrect) can be used in charging a battery such as battery  58  and can be used in powering other components in device  24 . For example, device  24  may include input-output devices  56  such as a display, touch sensor, communications circuits, audio components, sensors, light-emitting diode status indicators, other light-emitting and light detecting components, and other components and these components (which form a load for device  24 ) may be powered by the DC voltages produced by rectifier  50  (and/or DC voltages produced by battery  58 ). 
     Device  12  and/or device  24  may communicate wirelessly using in-band or out-of-band communications. Device  12  may, for example, have wireless transceiver circuitry  40  that wirelessly transmits out-of-band signals to device  24  using an antenna. Wireless transceiver circuitry  40  may be used to wirelessly receive out-of-band signals from device  24  using the antenna. Device  24  may have wireless transceiver circuitry  46  that transmits out-of-band signals to device  12 . Receiver circuitry in wireless transceiver  46  may use an antenna to receive out-of-band signals from device  12 . In-band transmissions between devices  12  and  24  may be performed using coils  36  and  48 . 
     It is desirable for power transmitting device  12  and power receiving device  24  to be able to communicate information such as received power, states of charge, and so forth, to control wireless power transfer. However, the above-described technology need not involve the transmission of personally identifiable information in order to function. Out of an abundance of caution, it is noted that to the extent that any implementation of this charging technology involves the use of personally identifiable information, implementers should follow privacy policies and practices that are generally recognized as meeting or exceeding industry or governmental requirements for maintaining the privacy of users. In particular, personally identifiable information data should be managed and handled so as to minimize risks of unintentional or unauthorized access or use, and the nature of authorized use should be clearly indicated to users. 
     During wireless power transfer operations, wireless transceiver circuitry  40  can use one or more coils  36  to transmit in-band signals to wireless transceiver circuitry  46  that are received by wireless transceiver circuitry  46  using coil  48 . Any suitable modulation scheme may be used to support in-band communications between device  12  and device  24 . With one illustrative configuration, frequency-shift keying (FSK) is used to convey in-band data from device  12  to device  24  and amplitude-shift keying (ASK) is used to convey in-band data from device  24  to device  12 . Power may be conveyed wirelessly from device  12  to device  24  during these FSK and ASK transmissions. Other types of in-band communications may be used, if desired. 
     During wireless power transmission operations, circuitry  52  supplies AC drive signals to one or more coils  36  at a given power transmission frequency. The power transmission frequency may be, for example, a predetermined frequency of about 125 kHz, about 200 kHz, at least 80 kHz, at least 100 kHz, less than 500 kHz, less than 300 kHz, or other suitable wireless power frequency. In some configurations, the power transmission frequency may be negotiated in communications between devices  12  and  24 . In other configurations, the power transmission frequency may be fixed. 
     During wireless power transfer operations, while power transmitting circuitry  52  is driving AC signals into one or more of coils  36  to produce signals  44  at the power transmission frequency, wireless transceiver circuitry  40  uses FSK modulation to modulate the power transmission frequency of the driving AC signals and thereby modulate the frequency of signals  44 . As shown in  FIG. 2 , FSK modulator  40 T may modulate the drive frequency fd that is being supplied by controller  16 M to input  74  of inverter  61 . In this way, FSK data is transmitted from device  12  to device  24 . In device  24 , coil  48  is used to receive signals  44 . Power receiving circuitry  54  uses the received signals on coil  48  and rectifier  50  to produce DC power. At the same time, wireless transceiver circuitry  46  (e.g., FSK demodulator  46 R) uses FSK demodulation to extract the transmitted in-band data from signals  44 . This approach allows FSK data (e.g., FSK data packets) to be transmitted in-band from device  12  to device  24  with coils  36  and  48  while power is simultaneously being wirelessly conveyed from device  12  to device  24  using coils  36  and  48 . 
     In-band communications between device  24  and device  12  uses ASK modulation and demodulation techniques. Wireless transceiver circuitry  46  transmits in-band data to device  12  by using capacitance switching circuitry (e.g., one or more transistors in transceiver  46  that are coupled coil  48  in series with one or more capacitors) or by using an adjustable load (e.g., a ballast load transistor) to modulate the impedance of power receiving circuitry  54  (e.g., coil  48 ). This, in turn, modulates the amplitude of signal  44  and the amplitude of the AC signal passing through coil(s)  36 . Wireless transceiver circuitry  40  monitors the amplitude of the AC signal passing through coil(s)  36  and, using ASK demodulation, extracts the transmitted in-band data from these signals that was transmitted by wireless transceiver circuitry  46 . The use of ASK communications allows ASK data bits (e.g., ASK data packets) to be transmitted in-band from device  24  to device  12  with coils  48  and  36  while power is simultaneously being wirelessly conveyed from device  12  to device  24  using coils  36  and  48 . The use of ASK modulation in device  24  can affect both the phase and magnitude of the received signals in device  12 , so ASK demodulation operations may, if desired, be performed using data receiver circuitry that is sensitive to both changes in magnitude and changes in phase. As an example, IQ (in-phase and quadrature) receiver circuitry in the data receiver of device  12  may be used in receiving ASK data transmitted from device  24 . 
     Control circuitry  16  has external object measurement circuitry  41  (sometimes referred to as foreign object detection circuitry or external object detection circuitry) that detects external objects on a charging surface associated with device  12 . Circuitry  41  can detect foreign objects such as coils, paper clips, and other metallic objects and can detect the presence of wireless power receiving devices  24 . During object detection and characterization operations, external object measurement circuitry  41  can be used to make measurements on coils  36  to determine whether any devices  24  are present on device  12 . 
     In an illustrative arrangement, measurement circuitry  41  of control circuitry  16  contains signal generator circuitry (e.g., oscillator circuitry for generating AC probe signals at one or more probe frequencies, a pulse generator, etc.) and signal detection circuitry (e.g., filters, analog-to-digital converters, impulse response measurement circuits, etc.). During measurement operations, switching circuitry in device  12  may be adjusted by control circuitry  16  to switch each of coils  36  into use. As each coil  36  is selectively switched into use, control circuitry  16  uses the signal generator circuitry of signal measurement circuitry  41  to apply a probe signal to that coil while using the signal detection circuitry of signal measurement circuitry  41  to measure a corresponding response. Measurement circuitry  43  in control circuitry  30  and/or in control circuitry  16  may also be used in making current and voltage measurements. 
     The characteristics of each coil  36  depend on whether any foreign objects overlap that coil (e.g., coins, wireless power receiving devices, etc.) and also depend on whether a wireless power receiving device with a coil such as coil  48  of  FIG. 1  is present, which could increase the measured inductance of any overlapped coil  36 . Signal measurement circuitry  41  is configured to apply signals to the coil and measure corresponding signal responses. For example, signal measurement circuitry  41  may apply an alternating-current probe signal while monitoring a resulting signal at a node coupled to the coil. As another example, signal measurement circuitry  41  may apply a pulse to the coil and measure a resulting impulse response (e.g., to measure coil inductance). Using measurements from measurement circuitry  41 , the wireless power transmitting device can determine whether an external object is present on the coils. If, for example, all of coils  36  exhibit their expected nominal response to the applied signals, control circuitry  16  can conclude that no external devices are present. If one of coils  36  exhibits a different response (e.g., a response varying from a normal no-objects-present baseline), control circuitry  16  can conclude that an external object (potentially a compatible wireless power receiving device) is present. Configurations in which an array of temperature sensors, optical sensors, and/or other sensors are used to help identify objects on the charging surface of device  12  may also be used. 
     Control circuitry  30  has measurement circuitry  43 . In an illustrative arrangement, measurement circuitry  43  of control circuitry  30  contains signal generator circuitry (e.g., oscillator circuitry for generating AC probe signals at one or more probe frequencies, a pulse generator, etc.) and signal detection circuitry (e.g., filters, analog-to-digital converters, impulse response measurement circuits, etc.). During measurement operations, device  24  may use measurement circuitry  43  to make measurements to characterize device  24  and the components of device  24 . For example, device  24  may use measurement circuitry  43  to measure the inductance of coil  48  (e.g., signal measurement circuitry  43  may be configured to measure signals at coil  48  while supplying coil  48  with signals at one or more frequencies (to measure coil inductances), signal pulses (e.g., so that impulse response measurement circuitry in the measurement circuitry can be used to make inductance and Q factor measurements), etc. Measurement circuitry  43  may also make measurements of the output voltage of rectifier  50 , the output current of rectifier  50 , etc. 
       FIG. 2  is a circuit diagram of illustrative wireless charging circuitry for system  8 . As shown in  FIG. 2 , circuitry  52  may include an inverter such as inverter  61  or other drive circuit that produces wireless power signals that are transmitted through an output circuit that includes one or more coils  36  and capacitors such as capacitor  70 . Control signals for inverter  61  are provided by control circuitry  16  at control input  74 . A single coil  36  is shown in the example of  FIG. 2 , but multiple coils  36  may be used, if desired. During wireless power transmission operations, transistors in inverter  61  are driven by AC control signals from control circuitry  16  (e.g., controller  16 M supplies drive signals for inverter  61  at input  74  at a desired alternating-current drive frequency fd). This causes the output circuit formed from coil  36  and capacitor  70  to produce alternating-current electromagnetic fields (signals  44 ) that are received by wireless power receiving circuitry  54  using a wireless power receiving circuit formed from coil  48  and one or more capacitors  72  in device  24 . Rectifier  50  converts received power from AC to DC and supplies a corresponding direct current output voltage Vrect across rectifier output terminals  76  for powering load circuitry (load  106 ) in device  24  (e.g., for charging battery  58 , for powering a display and/or other input-output devices  56 , and/or for powering other circuitry in load  106 ). Data can be transmitted from device  12  to device  24  using frequency shift keying (FSK) or other suitable modulation scheme. For example, data can be transmitted by using FSK modulator (data transmitter)  40 T to control controller  16 M and thereby modulate frequency fd. This data can be received in device  24  by using FSK demodulator  46 R (data receiver RX) to perform FSK demodulation operations. 
     Circuitry  54  has voltage regulator circuitry that helps stabilize the voltage Vrect during operation of system  8 . The voltage regulator circuitry may include a voltage sensor such as voltage sensor  98  that monitors the voltage Vrect and an adjustable load such as ballast load  100  that is coupled between output terminals  76  (e.g., a transistor that has first and second source-drain terminals coupled respectively to the positive and ground terminals  76  and that has a gate that receives a control signal from ASK modulator  46 T) and that is used to shunt current between terminals  76  (e.g., to help stabilize voltage Vrect). Ballast load  100 , which may sometimes be referred to as a ballast transistor, adjustable load, adjustable ballast load transistor, adjustable current load, or adjustable ballast load, is used to help ensure that there is always a minimum current flowing between output terminals  76 , even if the components in load  106  have not yet been activated (e.g., during start-up). For example, ballast load  100  may be adjusted to draw a predetermined current (e.g., 50 mA) when device  24  initially receives power (e.g., before the battery charging circuitry for battery  58 , the display, and/or other input-output devices  56  of load  106  start to draw significant current). 
     Current sensor  104  may be used to detect current flow through load  106 . When it is determined that current is flowing to load  106  (e.g., battery  58  is being charged and/or other load components such as a display, communications circuitry, control circuitry, and other devices are drawing current), control circuitry  30  of device  24  can apply a control signal to the gate or other control terminal of ballast load  100  that turns ballast load  100  off or otherwise reduces the current flow through ballast load  100  (e.g., to reduce undesired power consumption due to current flow through ballast load  100 ). In this way, ballast load  100  serve as a ballast that helps to ensure sufficient loading is present during modes of operation in which load  106  is not drawing significant current. Ballast load  100  draws current when load  106  is inactive and is not drawing current. When load  106  is active and is drawing current, ballast load  100  is turned off or otherwise is adjusted to draw less current than when load  106  is inactive. 
     Wireless transceiver circuitry  46  of device  24  may include a data transmitter such as data transmitter  46 T. During in-band communications (e.g., ASK communications) between device  24  and device  12 , control circuitry  30  can modulate components in device  24  to modulate the impedance of the wireless power receiving circuitry of device  24  that is seen by the wireless power transmitting circuitry of device  12 . For example, device  24  may use data transmitter  46 T to apply control signals to the gate of ballast load  100  and/or to the gate of one or more transistors in capacitance switching circuitry or other switching circuitry coupled to coil  48 . As shown in  FIG. 2 , device  24  may have capacitance switching circuitry formed from transistors such as transistors  94  and  96  that are coupled in series with capacitors  90  and  92 , respectively, and that are coupled to the power receiving circuitry formed from coil  48  and capacitors  72 . During in-band transmission, control circuitry  30  can apply control signals (e.g., transmitted data signals) to the gates of transistors such as transistors  94  and  96 . Transistors  94  and  96  may be coupled to the input circuit of device  24  that is formed from coil  48  and capacitors  72  using respective capacitors  90  and  92  and may form capacitance switching circuitry (capacitance modulation circuitry) that can be used to modulate the capacitance coupled to wireless power receiving circuitry  54 . 
     By turning on and off transistors  94  and  96  (e.g., by turning these transistors on together and off together to represent either digital data ones or digital data zeros), the capacitances associated with capacitors  94  and  96  are alternately connected and disconnected from the input circuitry of wireless power receiving circuit  54  and the impedance of coil  48  seen by wireless power transmitting circuitry  52  of device  12  is varied accordingly. The modulation of the input impedance of circuitry  52  modulates the flow of wireless power from coil  36  to coil  48  and thereby modulates the magnitude of the voltage (and, if desired, the phase of the voltage) of the signal on node  102  in device  12 . 
     The magnitude of the voltage (and, if desired, the phase of the voltage) on node  102  may also be modulated by modulating the amount of current passing through ballast load  100  (e.g., by using transmitter  46 T to adjust the control signal voltage on the gate of a transistor serving as ballast load  100 , which also affects the input impedance of circuitry  52 ). 
     Wireless transceiver circuitry  40  of device  12  includes data receiver  40 R (e.g., a receiver that measures changes in the amplitude and/or phase of the signal on node  102 ). During operation, ASK data that is transmitted by ASK modulator (data transmitter)  46 T passes as in-band data from coil  48  to coil  36  and is received by ASK demodulator (data receiver)  40 R. 
     In some operating conditions (e.g., certain values of coil inductance, load conditions, electromagnetic coupling between coils, etc.), the transmission of in-band data by modulating the capacitance coupled between circuitry  54  and ground using transistors  94  and  96  may result in more ripple in voltage Vrect than desired, particularly during light loading. This can give rise to excessive Vrect values and undesired triggering of overvoltage protection circuitry in device  24 . In scenarios in which the communications frequency of the in-band communications data lies in the audible frequency range (e.g., at 2 kHz, etc.), this may also give rise to a risk of undesired audible buzzing. 
     Modulation of the current that flows through ballast load  100 , on the other hand, always causes Vrect to swing lower and thereby avoids potential issues with overvoltage protection circuit triggering. The modulation current amplitude associated with ballast load  100  can also be dynamically adjusted by transmitter  46 T (e.g., the modulation depth achieved when using ballast load  100  can be programmed by control circuitry  30 ). This allows in-band signal strength to be increased if needed to ensure satisfactory communications and to otherwise be decreased to help minimize power loss. Ballast load  100  may also be used for load ballasting, so ballast load  100  can serve dual purposes in device  24 —e.g., to help with 1) load ballasting and 2) modulating load current to transmit in-band data. This dual use of ballast load  100  can reduce hardware costs. 
     When ballast load  100  is turned on, current flows through ballast load  100 , which consumes power, so the use of capacitor-based impedance modulation (using, e.g., transistors  94  and  96  or other switching circuitry to adjust the capacitance coupled to coil  48 ) can be helpful in high load conditions where Vrect ripple is not likely to be excessive and overvoltage protection is not likely to be triggered due to ripple. The use of ballast load  100  (e.g., the use of load modulation which causes the voltage on Vrect to drop and not to swing upward) for in-band data communications can be helpful in low (light) load conditions where system  8  is more sensitive to potentially triggering overvoltage protection due to Vrect ripple. The use of ballast load  100  in this light loading conditions may allow the use of higher Vrect operating voltages. 
     Based on these considerations, device  24  can therefore use load modulation with ballast load  100  for in-band communications under light loading conditions (when the current through load  106  is detected by current sensor  104  as being below a predetermined threshold current value) and can use capacitance modulation with capacitance switching circuitry (e.g., using transistors  94  and  96 ) for in-band communications under heavy loading conditions (when control circuitry  30  determines from the load current measurements of sensor  104  that the load current is above the predetermined threshold current value). 
     In device  12 , data receiver  40 R can be used to demodulate in-band data that is transmitted by device  24  in both light loading and heavy loading conditions. Any suitable receiver circuitry can be included in receiver  40 R to measure changes to the magnitude (and, if desired, phase) of the voltage on node  102 . This circuitry may, for example, include IQ demodulation circuitry. 
     The foregoing is merely illustrative and various modifications can be made to the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20200121
Publication Date: 20210504
Grant Date: 20210504
Priority Date: 20190411
Inventors: CHEN, WEIYUN
TERRY, STEPHEN C.
Assignee: APPLE INC
CPC Classifications: [{"code": "H02J50/80", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J7/02", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/10", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04Q2213/03", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J50/80", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J2207/20", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04Q9/00", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/12", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J50/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/80", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J7/02", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04Q2213/03", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04Q9/00", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 72747457