In-band signaling within wireless power transfer systems

• US 10,122,217 B2
• Filed: 05/11/2016
• Issued: 11/06/2018
• Est. Priority Date: 09/28/2015
• Status: Expired due to Fees

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Hrinya, Stephen, Patel, Parin
• Primary Examiner(s): Fureman, Jared
• Assistant Examiner(s): Yeshaw, Esayas
• Application Number:
  US15/152,444
• Publication Number:
  US 20170093218A1
• Time in Patent Office: 909 Days
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/80 involving the exchange of data, concerning supply or distribution of electric power, between transmitting devices and receiving devices
• CPC Class Codes: H02J 7/00034 Charger exchanging data with an electronic device, i.e. telephone, whose internal battery is under charge
• CPC Class Codes: H04B 5/24 Inductive coupling
• CPC Class Codes: H04B 5/72 for local intradevice communication
• CPC Class Codes: H04B 5/79 for data transfer in combination with power transfer

Abstract

Systems and methods for in-band communication across a wireless power interface from a load device to a source device. The load device selectively modifies the timing of switches within a voltage rectifier coupled to an output of a receive coil within the load device that receives power from a transmit coil within the source device. The source device detects changes in the power transfer (or in the relative timing of a voltage or a current) as digital information received from the load device.

Claims

1. A method of operating a wireless power transfer system comprising a source device and a load device, the method comprising:

transferring power from the source device to the load device; and

during power transfer from the source device to the load device;

determining, by the load device, a data signal comprising a series of digital bits to be communicated to the source device; and

modifying a timing, by the load device, of a switch of a synchronous rectifier within the load device to desynchronize the synchronous rectifier in a pattern corresponding to the series of digital bits.

2. The method of claim 1, wherein the modification of the timing of the switch of the synchronous rectifier is a timing adjustment and comprises delaying a turn-off of the switch until after a zero-crossing of an induced current.

3. The method of claim 2, wherein the timing adjustment comprises delaying a turn-off time of the switch so that current through the switch reverses.

4. The method of claim 2, wherein the timing adjustment is configured to suppress a voltage spike associated with current conduction through a diode within the load device.

5. The method of claim 4, wherein the diode is coupled in parallel with the switch.

6. The method of claim 4, wherein:

the switch is a transistor; and

the diode is a body diode incorporated within the transistor.

7. The method of claim 4, wherein:

the switch is a transistor; and

the diode is a Schottky diode coupled across a source and a drain of the transistor.

8. The method of claim 2, wherein the timing adjustment is performed by a timing adjuster.

9. A method for operating a wireless power transfer system that includes a source device and a load device, the method comprising:

transferring power from the source device to the load device; and

during power transfer from the source device to the load device;

determining, by the source device, whether a current threshold crossing has occurred or has not occurred within an electronic element of the source device at a time corresponding to an edge of one half-cycle of an inverter of the source device; and

buffering, by the source device, a series of digital bits corresponding to a data signal sent from the load device to the source device, each digital bit of the series of digital bits corresponding to a respective determined occurrence or a respective determined absence of occurrence of a respective current threshold crossing.

10. The method of claim 9, wherein the source device comprises a bridge inverter;

and

the operation of determining, by the source device, whether the current threshold crossing has occurred within the electronic element of the source device comprises monitoring a switch of the bridge inverter for a drop in current.

11. The method of claim 10, wherein the operation of monitoring the switch of the bridge inverter for the drop in current comprises:

measuring a current through the switch; and

comparing the current to a threshold value.

12. A method for operating a wireless power transfer system that includes a source device and a load device, the method comprising:

transferring power from the source device to the load device; and

during power transfer from the source device to the load device;

determining, by the source device, whether a phase shift has occurred in an alternating current passing through an electronic element of the source device; and

buffering, by the source device, a digital bit for each determined phase shift and a complimentary digital bit for each determined absence of phase shift.

13. The method of claim 12, wherein the source device comprises a bridge inverter;

and

the operation of determining, by the source device, that the phase shift has occurred in the alternating current passing through the electronic element of the source device comprises;

monitoring a phase of current passing through the bridge inverter for a change.

14. The method of claim 13, wherein the operation of monitoring a phase of current passing through the bridge inverter for the change comprises:

measuring a phase of alternating current passing through the bridge inverter; and

comparing the phase to a threshold value.

15. A wireless power transfer system, comprising:

a source device comprising;

a bridge inverter comprising a first set of switches;

a transmit coil coupled to an output of the bridge inverter; and

a first processor configured to monitor a first electrical characteristic of the bridge inverter during operation of the bridge inverter; and

a load device aligned with the source device, the load device comprising;

a receive coil;

a bridge rectifier coupled to an output of the receive coil, the bridge rectifier comprising a second set of switches; and

a second processor coupled to the bridge rectifier;

wherein

the second processor is configured to perform a sequence of timing modifications, each timing modification comprising a delay of a turn-off of at least one switch of the second set of switches and based, at least in part, on a digital bit of a data signal to be communicated to the source device.

16. The wireless power transfer system of claim 15, wherein the first electrical characteristic comprises a voltage spike across at least one switch of the first set of switches.

17. The wireless power transfer system of claim 15, wherein the first electrical characteristic comprises a phase shift in at least one of a voltage or a current across at least one of the switches of the first set of switches.

18. The wireless power transfer system of claim 15, wherein the first processor is configured to obtain the data signal by monitoring the first electrical characteristic.

19. The wireless power transfer system of claim 15, wherein at least one switch of the first set of switches is a transistor that incorporates a body diode.

20. The wireless power transfer system of claim 15, wherein the load device is a wearable electronic device.