Resonant system for wireless power transmission to multiple receivers

• US 9,231,412 B2
• Filed: 12/20/2011
• Issued: 01/05/2016
• Est. Priority Date: 12/29/2010
• Status: Active Grant

• Current Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Original Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Inventors: Lisi, Gianpaolo, Socci, Gerard G., Djabbari, Ali, Kiaei, Ali, Bahai, Ahmad R. S., Morroni, Jeffrey Anthony
• Primary Examiner(s): Amrany, Adi
• Application Number:
  US13/330,891
• Publication Number:
  US 20120169137A1
• Time in Patent Office: 1,477 Days
• Field of Search: 307/104
• US Class Current: 1/1
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/40 using two or more transmitting or receiving devices H02J50/50 takes precedence
• CPC Class Codes: H02J 50/60 responsive to the presence of foreign objects, e.g. detection of living beings
• 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 50/90 involving detection or optimisation of position, e.g. alignment
• CPC Class Codes: H02J 7/0048 Detection of remaining charge capacity or state of charge [SOC]
• CPC Class Codes: H02J 7/00714 in response to battery charging or discharging current

Abstract

In a wireless power transfer system with multiple receivers, receiver management may be necessary to effectively provide power to the multiple receivers. In one implementation, receiver management includes sweeping or stepping the transmitter resonant and/or operating frequency. In another implementation, receiver management includes receiver self-management, in which the receiver load current duty cycle is controlled to maintain receiver voltage even in the presence of multiple receivers. In another implementation, receiver management includes receiver self-management, in which one or more receivers use a time-sharing heuristic to identify when other receivers are charging and wait to begin receiving a transfer of power until another receiver has stopped receiving a transfer of power.

Claims

1. A method suitable for wireless power transfer from a transmitter including a resonant circuit with a power transfer coil through magnetic coupling to multiple receivers each including a power transfer coil, the method useable in a first receiver configured to receive a transfer of energy wirelessly from the transmitter unit, comprising:

the first receiver configured to receive a transfer of energy wirelessly from a source based on an adaptive time share heuristic, including

initializing an energy transfer detection period with a predefined duration;

reinitializing the energy transfer detection period if the first receiver determines that another receiver is starting to receive a transfer of energy from the transmitter based on a decrease in coil voltage of the receiver power transfer coil;

determining an end of the energy transfer detection period if either;

the predefined duration ends, and the first receiver does not determine that another receiver starts receiving a transfer of energy from the transmitter based on a decrease in coil voltage of the receiver power transfer coil, or

if the first receiver determines that another receiver stops receiving a transfer of energy from the transmitter based on an increase in coil voltage of the receiver power transfer coil; and

at the end of the energy transfer detection period, initiating a wait period with a random or pseudo-random duration; and

at the end of the wait period, if the first receiver determines that, during the wait period, no other receiver started to receive a transfer of energy from the transmitter, the first receiver starting to receive a transfer of energy from the transmitter.

2. The method of claim 1, further comprising:

the first receiver stopping the receiving of a transfer of energy from the transmitter at the end of a predefined charge period.

3. The method of claim 2, wherein the transmitter is configured to detect when the first receiver starts and stops receiving a transfer of energy.

4. The method of claim 3, wherein the transmitter is configured to detect when the first receiver starts or stops receiving a transfer of energy by detecting a decrease or increase, respectively, of the coil voltage on the transmitter power transfer coil.

5. The method of claim 3, wherein the transmitter is configured to turn off at least a part circuitry in the transmitter based on either determining that an average idle voltage crosses an idle voltage threshold, or determining that at least one limit of an idle voltage range crosses an idle threshold.

6. The method of claim 3, wherein the transmitter is configured to determine if a metal object is in proximity to the transmitter based on either determining that an average idle voltage crosses an idle voltage threshold, or determining that at least one limit of an idle voltage range crosses an idle threshold the transmitter determining, if the average idle voltage crosses an excess threshold, that a metal object is in proximity to the transmitter.

7. A transmitter circuit suitable for wireless power transfer to multiple receiver circuits, each configured to receive power transfer wirelessly from the transmitter circuit, the transmitter circuit comprising:

an alternating current (AC) power supply, and

a resonant circuit including a power transfer coil, and configured to receive power from the AC power supply;

the transmitter circuit configured to generate a magnetic field from the power transfer coil for transmitting power through magnetic coupling to the multiple receiver circuits;

each receiver circuit including a power transfer coil, and configured to receive power transfer based on an adaptive time share heuristic including;

initializing a power transfer detection period with a predefined duration;

reinitializing the power transfer detection period if the receiver circuit determines that another receiver circuit is receiving power transfer from the transmitter circuit based on a decrease in coil voltage of the receiver power transfer coil;

determining an end of the power transfer detection period if either;

the predefined duration ends, and the receiver circuit does not determine that another receiver circuit is receiving power transfer based on a decrease in coil voltage of the receiver power transfer coil, or

the receiver circuit determines that another receiver circuit stops receiving power transfer based on an increase in coil voltage of the receiver power transfer coil;

at the end of the power transfer detection period, initiating a wait period with a random or pseudo-random duration; and

at the end of the wait period, if the receiver circuit does not determine that another receiver circuit is receiving power transfer from the transmitter circuit based on a decrease in coil voltage of the receiver power transfer coil, initiating power transfer to the receiver circuit based on magnetic coupling from the transmitter power transfer coil through the receiver power transfer coil.

8. The transmitter circuit of claim 7, wherein the receiver circuit terminates power transfer from the transmitter circuit after a predefined charge period.

9. The transmitter circuit of claim 8,

the transmitter circuit further configured to detect when the receiver initiates and terminates power transfer.

10. The transmitter circuit of claim 9,

the transmitter circuit is further configured to detect when the receiver circuit initiates or terminates power transfer by detecting a decrease or increase, respectively, of the coil voltage on the transmitter power transfer coil.

11. The transmitter circuit of claim 9,

the transmitter circuit further configured to turn off at least a part circuitry in the transmitter based on either determining that an average idle voltage crosses an idle voltage threshold, or determining that at least one limit of an idle voltage range crosses an idle threshold.

12. The transmitter circuit of claim 9,

the transmitter further configured to determine if a metal object is in proximity to the transmitter based on either determining that an average idle voltage crosses an idle voltage threshold, or determining that at least one limit of an idle voltage range crosses an idle threshold.

13. A receiver circuit suitable for use in a wireless power transfer system including a transmitter circuit and multiple receiver circuits, the transmitter circuit including a resonant circuit with a power transfer coil and configured to generate a magnetic field for transmitting power through magnetic coupling, the receiver circuit comprising:

a power transfer coil; and

power transfer circuitry configured to receive power transfer through the power transfer coil based on an adaptive time share heuristic;

the adaptive time share heuristic including;

initializing a power transfer detection period with a predefined duration;

reinitializing the power transfer detection period if the receiver circuit determines that another receiver circuit is receiving power transfer from the transmitter circuit based on a decrease in coil voltage of the receiver power transfer coil;

determining an end of the power transfer detection period if either;

the predefined duration ends, and the receiver circuit does not determine that another receiver circuit is receiving power transfer based on a decrease in coil voltage of the receiver power transfer coil, or

the receiver circuit determines that another receiver circuit stops receiving power transfer based on an increase in coil voltage of the receiver power transfer coil;

at the end of the power transfer detection period, initiating a wait period with a random or pseudo-random duration; and

at the end of the wait period, if the receiver circuit does not determine that another receiver circuit is receiving power transfer from the transmitter circuit based on a decrease in coil voltage of the receiver power transfer coil, initiating power transfer to the receiver circuit based on magnetic coupling from the transmitter power transfer coil through the receiver power transfer coil.

14. The receiver circuit of claim 13,

the receiver circuit is configured to terminate power transfer from the transmitter circuit after a predefined charge period.

15. The receiver circuit of claim 14, wherein the transmitter circuit is configured to detect when the receiver initiates and terminates power transfer.

16. The receiver circuit of claim 15, wherein the transmitter circuit is further configured to detect when the receiver circuit initiates or terminates power transfer by detecting a decrease or increase, respectively, of the coil voltage on the transmitter power transfer coil.

17. The receiver circuit of claim 15, wherein the transmitter circuit is further configured to turn off at least a part circuitry in the transmitter based on either determining that an average idle voltage crosses an idle voltage threshold, or determining that at least one limit of an idle voltage range crosses an idle threshold.

18. The receiver circuit of claim 15, wherein the transmitter circuit is further configured to determine if a metal object is in proximity to the transmitter based on either determining that an average idle voltage crosses an idle voltage threshold, or determining that at least one limit of an idle voltage range crosses an idle threshold.