Sweep frequency mode for multiple magnetic resonant power transmission

• US 9,627,915 B2
• Filed: 04/17/2013
• Issued: 04/18/2017
• Est. Priority Date: 03/15/2013
• Status: Active Grant

• Current Assignee: Flextronics America LLC (Flextronics International Limited)
• Original Assignee: Flextronics America LLC (Flextronics International Limited)
• Inventors: Telefus, Mark
• Primary Examiner(s): Rodas, Richard Isla
• Assistant Examiner(s): Henze-Gongola, David V
• Application Number:
  US13/865,038
• Publication Number:
  US 20140266027A1
• Time in Patent Office: 1,462 Days
• Field of Search: 320108
• CPC Class Codes: H02J 50/10 using inductive coupling
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/20 using microwaves or radio frequency waves
• CPC Class Codes: H02J 50/40 using two or more transmitting or receiving devices H02J50/50 takes precedence
• 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: H02M 3/28 using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
• CPC Class Codes: H02M 3/335 using semiconductor devices only
• CPC Class Codes: H04B 5/79 for data transfer in combination with power transfer

Abstract

A power transmission pad is configured to provide wireless power transmission to multiple portable electronic devices where each device is orientation-free relative to the pad. The power transmission pad is also configured to be power adaptive by changing the power transmission level depending on the number of devices being concurrently charged. Each device, is placed within the magnetic field for the purpose of charging the device battery. The power transmission pad includes a sweep frequency generator for generating power transmissions across a frequency spectrum. The number of devices to be charged is determined as well as an optimal frequency for maximum energy transfer to each device. A single combined optimal frequency is determined using the optimal frequencies determined for each individual device. The sweep frequency generator is locked to the single combined optimal frequency and a power transmission level is set according to the number of devices.

Claims

1. A power transmission pad for wireless power transmission comprising:

a. a coil;

b. a power transmitter having a sweep frequency generator coupled to the coil to provide a frequency varying signal through the coil, thereby generating a variable magnetic field; and

c. a controller coupled to the coil and to the sweep frequency generator, wherein when a plurality of portable electronic devices to be charged are positioned within the variable magnetic field a handshake protocol is performed between each of the portable electronic devices and the power transmission pad, wherein the power transmission pad is configured to determine the number of portable electronic devices positioned within the variable magnetic field by counting a number of handshake protocols and to adjust a power transmission level of a power transmission signal according to the determined number, wherein the power transmission pad is further configured to determine an optimal device frequency from the frequency varying signal for each portable electronic device where the optimal device frequency corresponds to a frequency where a maximum energy transfer occurs from the power transmission pad to the portable electronic device, and to determine an optimal system frequency of the power transmission signal using the determined optimal device frequency of each portable electronic device, wherein the optimal system frequency is an average of the determined optimal device frequency for each portable electronic device.

2. A system for wireless power transmission comprising:

a. a plurality of portable electronic devices to be charged; and

b. a power transmission pad configured to generate a frequency varying signal that results in a variable magnetic field, further wherein when the plurality of portable electronic devices are positioned within the variable magnetic field a handshake protocol is performed between each of the portable electronic devices and the power transmission pad, wherein the power transmission pad is configured to determine the number of portable electronic devices positioned within the variable magnetic field by counting a number of handshake protocols and to adjust a power transmission level of a power transmission signal according to the determined number, wherein the power transmission pad is further configured to determine an optimal device frequency from the frequency varying signal for each portable electronic device where the optimal device frequency corresponds to a frequency where a maximum energy transfer occurs from the power transmission pad to the portable electronic device, and to determine an optimal system frequency of the power transmission signal using the determined optimal device frequency of each portable electronic device, wherein the optimal system frequency is an average of the determined optimal device frequency for each portable electronic device.

3. A system for wireless power transmission comprising:

a. a power transmission pad comprising;

i. a first coil;

ii. a power transmitter having a sweep frequency generator coupled to the first coil to provide a frequency varying signal through the first coil, thereby generating a variable magnetic field; and

iii. a controller coupled to the first coil and to the sweep frequency generator;

b. a plurality of portable electronic devices to be charged, each portable electronic device comprising;

i. a second coil; and

ii. a power receiver coupled to the second coil and configured to receive energy transferred from the power transmission pad via the second coil, wherein when the plurality of portable electronic devices are positioned within the variable magnetic field generated by the power transmission pad, a handshake protocol is performed between each of the portable electronic devices and the power transmission pad, wherein the power transmission pad is configured to determine the number of portable electronic devices positioned within the variable magnetic field by counting a number of handshake protocols, to adjust a power transmission level of a power transmission signal according to the determined number, to determine an optimal device frequency from the frequency varying signal for each portable electronic device where the optimal device frequency corresponds to a frequency where a maximum energy transfer occurs from the power transmission pad to the portable electronic device for a present orientation of the portable electronic device relative to the power transmission pad, and to determine an optimal system frequency of the power transmission signal using the determined optimal device frequency of each portable electronic device, wherein the optimal system frequency is an average of the determined optimal device frequency for each portable electronic device.

4. The system of claim 3 wherein the power transmitter and the controller comprise a power source manager configured to adjust the power transmission level and the optimal system frequency of the power transmission signal according to the number of portable electronic devices currently being charged.

5. The system of claim 3 wherein when one of the one or more portable electronic devices becomes fully charged, is removed from variable magnetic field, or a new portable electronic device is positioned within the variable magnetic field, the power transmission pad is configured to re-calibrate the power transmission level by determining an updated number of portable electronic devices to be charged, and to adjust the power transmission level according to the determined updated number.

6. The system of claim 5 wherein when one of the one or more portable electronic devices becomes fully charged, is removed from variable magnetic field, or a new portable electronic device is positioned within the variable magnetic field, the power transmission pad is further configured to re-calibrate the optimal system frequency of the power transmission signal by determining the optimal device frequency for each portable electronic device corresponding to the maximum energy transfer from the power transmission pad to the portable electronic device, and to determine the optimal system frequency of the power transmission signal using the determined optimal device frequency of each portable electronic device.

7. The system of claim 3 wherein each portable electronic device includes a resonant tank comprising the second coil, and the optimal device frequency corresponding to the maximum energy transfer comprises a resonant frequency of the resonant tank.

8. The system of claim 3 wherein the power receiver further comprises a power management block configured to monitor a charge level of a portable electronic device battery, and configured to generate a charge level status signal.

9. The system of claim 8 wherein the charge level status signal comprises a power transmission termination signal when the battery is fully charged.

10. The system of claim 8 wherein the charge level status signal is transmitted to the power transmitter via the second coil and the first coil.

11. The system of claim 3 wherein each portable electronic device further comprises a battery charger coupled to the power receiver.

12. The system of claim 3 wherein determining the optimal device frequency comprises monitoring a charge current of the portable electronic device while the sweep frequency generator sweeps the transmission frequencies across a sweep frequency spectrum, and when the charge current exceeds a threshold level for a specific frequency it is determined that the specific frequency is the optimal device frequency.

13. The system of claim 3 wherein determining the optimal device frequency comprises monitoring a charge current of the portable electronic device while the sweep frequency generator sweeps the transmission frequencies across a sweep frequency spectrum, and selecting a specific frequency corresponding to the highest charge current as the optimal device frequency.

14. The system of claim 3 wherein determining the optimal device frequency comprises monitoring an impedance on the power transmission pad while the sweep frequency generator sweeps the transmission frequencies across a sweep frequency spectrum, wherein a change in the impedance corresponds to an energy transfer to the portable electronic device, and when the change in impedance exceeds a threshold level for a specific frequency it is determined that the specific frequency is the optimal device frequency.

15. The system of claim 3 wherein determining the optimal device frequency comprises monitoring an impedance on the power transmission pad while the sweep frequency generator sweeps the transmission frequencies across a sweep frequency spectrum, wherein a change in the impedance corresponds to an energy transfer to the portable electronic device, and selecting a specific frequency corresponding to a greatest change in impedance as the optimal device frequency.

16. The system of claim 3 wherein the one or more portable electronic devices are configured to provide communication signals to each other.

17. A method of wireless power transmission between a power transmission pad and a plurality of portable electronic devices to be charged, the method comprising:

a. configuring the power transmission pad with a first coil and a sweep frequency generator, and each portable electronic device with a second coil;

b. generating a frequency varying signal that results in a variable magnetic field by applying the sweep frequency generator to the first coil;

c. determining a number of portable electronic devices positioned within the variable magnetic field by counting a number of handshake protocols which are performed between each of the portable electronic devices and the power transmission pad when the portable electronic devices are positioned within the variable magnetic field;

d. adjusting a power transmission level of a power transmission signal according to the determined number;

e. transmitting the power transmission signal from the power transmission pad to the plurality of portable electronic devices;

f. measuring one or more system characteristics in response to the variable magnetic field;

g. determining an optimal device frequency of each portable electronic device according to the measured system characteristics, wherein the optimal device frequency corresponds to a frequency where a maximum energy transfer occurs from the power transmission pad to the portable electronic device;

h. determining an optimal system frequency of the power transmission signal using the determined optimal device frequency of each portable electronic device, wherein the optimal system frequency is an average of the determined optimal device frequency for each portable electronic device;

i. locking an energy transmission frequency of the power transmission pad to the determined optimal system frequency; and

j. transmitting the power transmission signal from the power transmission pad to the portable electronic device using the locked energy transmission frequency.

18. The method of claim 17 wherein when one of the one or more portable electronic devices becomes fully charged, is removed from variable magnetic field, or a new portable electronic device is positioned within the variable magnetic field, the power transmission pad is configured to re-calibrate the power transmission level by determining an updated number of portable electronic devices to be charged, and to adjust the power transmission level according to the determined updated number.

19. The method of claim 17 wherein when one of the one or more portable electronic devices becomes fully charged, is removed from variable magnetic field, or a new portable electronic device is positioned within the variable magnetic field, the power transmission pad is further configured to re-calibrate the locked energy transmission frequency by determining the optimal device frequency for each portable electronic device corresponding to the maximum energy transfer from the power transmission pad to the portable electronic device, and to determine the optimal system frequency of the power transmission signal using the determined optimal device frequency of each portable electronic device.

20. The method of claim 17 wherein the system characteristic comprises a charge current of the portable electronic device and determining the optimal device frequency comprises monitoring the charge current of the portable electronic device while the sweep frequency generator sweeps the transmission frequencies across a sweep frequency spectrum, and when the charge current exceeds a threshold level for a specific frequency it is determined that the specific frequency is the optimal device frequency.

21. The method of claim 17 wherein the system characteristic comprises a charge current of the portable electronic device and determining the resonant frequency comprises monitoring the charge current of the portable electronic device while the sweep frequency generator sweeps the transmission frequencies across a sweep frequency spectrum, and selecting a specific frequency corresponding to the highest charge current as the resonant frequency.

22. The method of claim 17 wherein the system characteristic comprises an impedance on the power transmission pad and determining the optimal device frequency comprises monitoring the impedance on the power transmission pad while the sweep frequency generator sweeps the transmission frequencies across a sweep frequency spectrum, wherein a change in the impedance corresponds to an energy transfer to the portable electronic device, and when the change in impedance exceeds a threshold level for a specific frequency it is determined that the specific frequency is the optimal device frequency.

23. The method of claim 17 wherein the system characteristic comprises an impedance on the power transmission pad and determining the optimal device frequency comprises monitoring the impedance on the power transmission pad while the sweep frequency generator sweeps the transmission frequencies across a sweep frequency spectrum, wherein a change in the impedance corresponds to an energy transfer to the portable electronic device, and selecting a specific frequency corresponding to a greatest change in impedance as the optimal device frequency.

24. The method of claim 17 wherein each portable electronic device includes a resonant tank comprising the second coil, and the determined optimal device frequency corresponds to a resonant frequency of the resonant tank.

25. The method of claim 17 further comprising monitoring a charge level of a portable electronic device battery, and generating a charge level status signal.

26. The method of claim 25 wherein the charge level status signal comprises a power transmission termination signal when the battery is fully charged.

27. The method of claim 25 further comprising transmitting the charge level status signal from the portable electronic device to the power transmission pad.

28. The method of claim 17 further comprising providing communication signals between the one or more portable electronic devices.