SWEEP FREQUENCY MODE FOR MULTIPLE MAGNETIC RESONANT POWER TRANSMISSION

• US 20140266027A1
• Filed: 04/17/2013
• Published: 09/18/2014
• 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
• Granted Patent: US 9,627,915 B2
• Time in Patent Office: Days
• US Class Current: 320/108
• 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

b. a controller coupled to the coil and to the sweep frequency generator, wherein when one or more portable electronic devices to be charged are positioned within the variable magnetic field the power transmission pad is configured to determine a number of portable electronic devices positioned within the variable magnetic field and to adjust a power transmission level of a power transmission signal according to the determined number.

2. The system of claim 1 wherein the power transmission pad is further configured to determine a resonant frequency for each portable electronic device corresponding to a maximum energy transfer from the power transmission pad to the portable electronic device, and to determine a frequency of the power transmission signal using the determined resonant frequency of each portable electronic device.

3. A system for wireless power transmission comprising:

a. one or more portable electronic devices to be charged; and

b. a power transmission pad configured to generate a variable magnetic field, further wherein when the one or more portable electronic devices are positioned within the variable magnetic field the power transmission pad is configured to determine a number of portable electronic devices positioned within the variable magnetic field and to adjust a power transmission level of a power transmission signal according to the determined number.

4. The system of claim 3 wherein the power transmission pad is further configured to determine a resonant frequency for each portable electronic device corresponding to a maximum energy transfer from the power transmission pad to the portable electronic device, and to determine a frequency of the power transmission signal using the determined resonant frequency of each portable electronic device.

5. 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. one or more 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 one or more portable electronic devices are positioned within the variable magnetic field generated by the power transmission pad, the controller is configured to determine a number of portable electronic devices positioned within the variable magnetic field, to adjust a power transmission level of a power transmission signal according to the determined number, to determine a resonant frequency for each portable electronic device corresponding to a maximum energy transfer from the power transmission pad to the portable electronic device, and to determine a frequency of the power transmission signal using the determined resonant frequency of each portable electronic device.

6. The system of claim 5 wherein the frequency is an average of the determined resonant frequency for each portable electronic device.

7. The system of claim 5 wherein the power transmitter and the controller comprise a power source manager configured to adjust the power transmission level and the frequency of the power transmission signal according to the number of portable electronic devices currently being charged.

8. The system of claim 5 wherein when one of the one or more portable electronic devices is positioned within the variable magnetic field generated by the power transmission pad, a handshake protocol is performed between the portable electronic device and the power transmission pad, further 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.

9. 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 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.

10. The system of claim 9 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 frequency of the power transmission signal by determining the resonant 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 frequency of the power transmission signal using the determined resonant frequency of each portable electronic device.

11. The system of claim 5 wherein each portable electronic device includes a resonant tank comprising the second coil, and the resonant frequency corresponding to the maximum energy transfer comprises a resonant frequency of the resonant tank.

12. The system of claim 5 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.

13. The system of claim 12 wherein the charge level status signal comprises a power transmission termination signal when the battery is fully charged.

14. The system of claim 12 wherein the charge level status signal is transmitted to the power transmitter via the second coil and the first coil.

15. The system of claim 5 wherein each portable electronic device further comprises a battery charger coupled to the power receiver.

16. The system of claim 5 wherein determining the resonant 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 resonant frequency.

17. The system of claim 5 wherein determining the resonant 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 resonant frequency.

18. The system of claim 5 wherein determining the resonant 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 resonant frequency.

19. The system of claim 5 wherein determining the resonant 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 resonant frequency.

20. The system of claim 5 wherein the one or more portable electronic devices are configured to provide communication signals to each other.

21. A method of wireless power transmission between a power transmission pad and one or more 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 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;

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

e. transmitting the power transmission signal from the power transmission pad to the one or more portable electronic devices.

22. The method of claim 21 wherein when one of the one or more portable electronic devices is positioned within the variable magnetic field generated by the power transmission pad, a handshake protocol is performed between the portable electronic device and the power transmission pad, further 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.

23. The method of claim 21 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.

24. The method of claim 21 further comprising:

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

g. determining a resonant frequency of each portable electronic device according to the measured system characteristics;

h. determining a frequency of the power transmission signal using the determined resonant frequency of each portable electronic device;

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

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

25. The method of claim 24 wherein the frequency is an average of the determined resonant frequency for each portable electronic device.

26. The system of claim 24 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 resonant 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 frequency of the power transmission signal using the determined resonant frequency of each portable electronic device.

27. The method of claim 24 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 when the charge current exceeds a threshold level for a specific frequency it is determined that the specific frequency is the resonant frequency.

28. The method of claim 24 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.

29. The method of claim 24 wherein the system characteristic comprises an impedance on the power transmission pad and determining the resonant 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 resonant frequency.

30. The method of claim 24 wherein the system characteristic comprises an impedance on the power transmission pad and determining the resonant 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 resonant frequency.

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

32. The method of claim 21 further comprising monitoring a charge level of a portable electronic device battery, and generating a charge level status signal.

33. The method of claim 32 wherein the charge level status signal comprises a power transmission termination signal when the battery is fully charged.

34. The method of claim 32 further comprising transmitting the charge level status signal from the portable electronic device to the power transmission pad.

35. The method of claim 21 further comprising providing communication signals between the one or more portable electronic devices.