Sweep frequency for multiple magnetic resonant power transmission using alternating frequencies

• US 9,369,000 B2
• Filed: 04/17/2013
• Issued: 06/14/2016
• 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): DIAO, M BAYE
• Application Number:
  US13/865,077
• Publication Number:
  US 20140266029A1
• Time in Patent Office: 1,154 Days
• Field of Search: 320/108, 307/104, 455/41.1, 455/41.2
• US Class Current: 1/1
• 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. The sweep frequency generator is set to cycle through the optimal frequencies determined for each device.

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 multiple portable electronic devices to be charged are positioned within the variable magnetic field, the power transmission pad is configured to determine resonant frequencies for the multiple portable electronic devices each corresponding to a maximum energy transfer from the power transmission pad to a corresponding one of the multiple portable electronic devices, and to cycle a frequency of a power transmission signal through the determined resonant frequencies of the multiple portable electronic devices, wherein the resonant frequencies are determined by sweeping transmission frequencies of the frequency varying signal across a sweep frequency spectrum, monitoring a characteristic of the pad or of the multiple portable electronic devices in response to the variable magnetic field, and selecting specific frequencies according to the monitored characteristic.

2. The system of claim 1 wherein the power transmission pad is further configured to determine a numeric total of the multiple portable electronic devices positioned within the variable magnetic field and to adjust a power transmission level of the power transmission signal according to the determined numeric total.

3. A system for wireless power transmission comprising:

a. multiple portable electronic devices to be charged; and

b. a power transmission pad configured to generate a variable magnetic field, wherein when the multiple portable electronic devices are positioned within the variable magnetic field, the power transmission pad is configured to determine resonant frequencies for the multiple portable electronic devices each corresponding to a maximum energy transfer from the power transmission pad to a corresponding one of the multiple portable electronic devices, and to cycle a frequency of a power transmission signal through the determined resonant frequencies of the multiple portable electronic devices, wherein the resonant frequencies are determined by sweeping transmission frequencies of the variable magnetic field across a sweep frequency spectrum, monitoring a system characteristic in response to the variable magnetic field, and selecting the resonant frequencies corresponding to greatest changes in values of the system characteristic, highest values of the system characteristic among monitored values of the system characteristic, or values of the system characteristic exceeding corresponding threshold value levels.

4. The system of claim 3 wherein the power transmission pad is further configured to determine a numeric total of portable electronic devices positioned within the variable magnetic field and to adjust a power transmission level of the power transmission signal according to the determined numeric total.

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; and

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 numeric total 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 numeric total, to determine a resonant frequency for each of the one or more portable electronic devices each corresponding to a maximum energy transfer from the power transmission pad to a corresponding one of the one or more portable electronic devices, and to cycle a frequency of the power transmission signal through the determined resonant frequencies of the one or more portable electronic devices, wherein when one of the one or more portable electronic devices becomes fully charged, is removed from the 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 numeric total of portable electronic devices to be charged, and to adjust the power transmission level according to the determined updated numeric total.

6. 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 numeric total of portable electronic devices currently being charged.

7. 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 numeric total of portable electronic devices positioned within the variable magnetic field by counting a number of handshake protocols.

8. The system of claim 5 wherein when one of the one or more portable electronic devices becomes fully charged, is removed from the variable magnetic field, or a new portable electronic device is positioned within the variable magnetic field, the power transmission pad is further configured to cycle the frequency of the power transmission signal through the determined resonant frequencies of the updated numeric total of portable electronic devices.

9. The system of claim 5 wherein each of the one or more portable electronic devices includes a resonant tank comprising one of the one or more second coils, and the resonant frequency for one of the one or more portable electronic devices corresponding to the maximum energy transfer comprises a resonant frequency of its corresponding resonant tank.

10. 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.

11. The system of claim 10 wherein the charge level status signal comprises a power transmission termination signal when the battery is fully charged.

12. The system of claim 10 wherein the charge level status signal is transmitted to the power transmitter via the second coils corresponding to the portable electronic device battery and the first coil.

13. The system of claim 5 wherein each of the one or more portable electronic devices further comprises a corresponding battery charger coupled to the power receiver.

14. The system of claim 5 wherein determining the resonant frequency for one of the one or more portable electronic devices 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 for the portable electronic device.

15. The system of claim 5 wherein determining the resonant frequency for one of the one or more portable electronic devices 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 for the portable electronic device.

16. The system of claim 5 wherein determining the resonant frequency for one of the one or more portable electronic devices 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 for the portable electronic device.

17. The system of claim 5 wherein determining the resonant frequency for one of the one or more portable electronic devices 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 for the portable electronic device.

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

19. A method of wireless power transmission between a power transmission pad and multiple 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 of the multiple portable electronic devices with a corresponding second coil;

b. generating a variable magnetic field by applying the sweep frequency generator to the first coil;

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

d. determining a resonant frequency of each of the multiple portable electronic devices according to the measured one or more system characteristics;

e. cycling a frequency of a power transmission signal through the determined resonant frequencies of the multiple portable electronic devices; and

f. transmitting the power transmission signal from the power transmission pad to the multiple portable electronic devices.

20. The method of claim 19 further comprising:

g. determining a numeric total of portable electronic devices positioned within the variable magnetic field; and

h. adjusting a power transmission level of a power transmission signal according to the determined numeric total.

21. The method of claim 20 wherein when one of the multiple 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 numeric total of portable electronic devices positioned within the variable magnetic field by counting a number of handshake protocols.

22. The method of claim 20 wherein when one of the multiple portable electronic devices becomes fully charged, is removed from the 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 numeric total of portable electronic devices to be charged, and to adjust the power transmission level according to the determined updated numeric total.

23. The system of claim 19 wherein when one of the multiple portable electronic devices becomes fully charged, is removed from the variable magnetic field, or a new portable electronic device is positioned within the variable magnetic field, the power transmission pad is further configured to cycle the frequency of the power transmission signal through the determined resonant frequencies of the remaining portable electronic devices.

24. The method of claim 19 wherein the one or more system characteristics comprise a charge current of one of the multiple portable electronic devices and determining the resonant frequency of the portable electronic device 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 of the portable electronic device.

25. The method of claim 19 wherein the one or more system characteristics comprise a charge current of one of the multiple portable electronic devices and determining the resonant frequency of the portable electronic device 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 of the portable electronic device.

26. The method of claim 19 wherein the one or more system characteristics comprise an impedance on the power transmission pad and determining the resonant frequency of one of the multiple portable electronic devices 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.

27. The method of claim 19 wherein the one or more system characteristics comprise an impedance on the power transmission pad and determining the resonant frequency of one of the multiple portable electronic devices 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.

28. The method of claim 19 wherein each of the multiple portable electronic devices includes a resonant tank comprising one of the second coils, and the determined resonant frequency for each of the multiple portable electronic devices corresponds to a resonant frequency of a corresponding resonant tank.

29. The method of claim 19 further comprising monitoring a charge level of a portable electronic device battery, and generating a charge level status signal.

30. The method of claim 29 wherein the charge level status signal comprises a power transmission termination signal when the battery is fully charged.

31. The method of claim 29 further comprising transmitting the charge level status signal from the portable electronic device corresponding to the portable electronic device battery to the power transmission pad.

32. The method of claim 19 further comprising providing communication signals between the multiple portable electronic devices.