Inductive power supply with duty cycle control

• US 9,257,851 B2
• Filed: 01/23/2012
• Issued: 02/09/2016
• Est. Priority Date: 01/07/2008
• Status: Active Grant

• Current Assignee: Philips IP Ventures B.V. (Koninklijke Philips N.V.)
• Original Assignee: Access Business Group International LLC (Alticor Incorporated)
• Inventors: Baarman, David W., Mollema, Scott A., Schwannecke, Joshua K., Leppien, Thomas Jay, Burns, Kenneth Michael
• Primary Examiner(s): Fleming, Fritz M
• Application Number:
  US13/355,757
• Publication Number:
  US 20120119588A1
• Time in Patent Office: 1,478 Days
• Field of Search: 307/104, 320/108
• 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 50/402 the two or more transmitting or the two or more receiving devices being integrated in the same unit, e.g. power mats with several coils or antennas with several sub-antennas
• 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 7/00034 Charger exchanging data with an electronic device, i.e. telephone, whose internal battery is under charge
• CPC Class Codes: H02M 3/33523 with galvanic isolation between input and output of both the power stage and the feedback loop
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

An inductive power supply that maintains resonance and adjusts duty cycle based on feedback from a secondary circuit. A controller, driver circuit and switching circuit cooperate to generate an AC signal at a selected operating frequency and duty cycle. The AC signal is applied to the tank circuit to create an inductive field for powering the secondary. The secondary communicates feedback about the received power back to the primary controller. The power transfer efficiency may be optimized by maintaining the operating frequency substantially at resonance, and the amount of power transferred may be controlled by adjusting the duty cycle.

Claims

1. An inductive power supply for providing power wirelessly to a remote device, said inductive power supply comprising:

a primary circuit for controlling power transfer to the remote device according to at least one operating parameter, said primary circuit configured to adjust a duty cycle of a signal to allow variation in an amount of power transferred to the remote device;

a wireless receiver configured to receive information communicated from the remote device;

a tank circuit in electrical communication with said primary circuit, said tank circuit configured to inductively couple with the remote device;

wherein said primary circuit controls said at least one operating parameter to transfer power substantially near resonance;

wherein said primary circuit controls said duty cycle of said signal to control said amount of power transferred while controlling said at least one operating parameter to transfer power substantially near resonance; and

wherein, based on said information communicated from the remote device, said primary circuit adjusts at least one of said duty cycle to control said amount of power transferred and said at least one operating parameter to transfer power substantially near resonance.

2. The inductive power supply of claim 1 wherein said at least one operating parameter includes at least one of an operating frequency and a resonant frequency, and wherein said primary circuit is configured to maintain substantial resonance by controlling said at least one operating parameter.

3. The inductive power supply of claim 1 wherein said primary circuit continuously adjusts said at least one operating parameter to maintain substantial resonance and continuously adjusts said duty cycle based on a comparison between said amount of power transferred to said remote device and a threshold.

4. The inductive power supply of claim 1 wherein said primary circuit controls said duty cycle of said signal according to at least one of a battery charging profile and a demand by said remote device.

5. The inductive power supply of claim 1 wherein said primary circuit includes a wireless receiver for receiving feedback from said remote device.

6. The inductive power supply of claim 1 wherein said primary circuit includes:

a primary controller;

a driver circuit in electrical communication with said primary controller;

a switching circuit in electrical communication with said driver circuit; and

a sensor for sensing reflected impedance of said remote device through said inductive coupling, wherein said sensor is in electrical communication with said tank circuit and said primary controller.

7. The inductive power supply of claim 6 wherein said inductive power supply is configured to receive feedback from said remote device.

8. The inductive power supply of claim 7 wherein said switching circuit includes a pair of switches,

wherein each switch is switched on at said duty cycle and at an operating frequency, but out of phase with each other;

and

wherein, in response to said feedback, said primary controller controls said operating frequency of each of said switches to transfer power substantially near resonance; and

wherein, in response to said feedback, said primary controller controls said duty cycle of each of said switches to control said amount of power transferred substantially near resonance.

9. The inductive power supply of claim 7 wherein said primary controller adjusts said at least one operating parameter as a function of input from said sensor.

10. The inductive power supply of claim 1 further including a first controller to control said at least one operating parameter and a second controller to control said duty cycle.

11. The inductive power supply of claim 1 further including a memory storing information relating to a plurality of remote devices.

12. The inductive power supply of claim 1 wherein said duty cycle is controlled based on temperature.

13. The inductive power supply of claim 12 wherein said duty cycle is decreased in response to determining that said temperature is above a threshold.

14. An inductive power supply system comprising:

an inductive power supply including;

a primary circuit for controlling power transfer according to at least operating parameter, said primary circuit configured to adjust a duty cycle of a signal to control an amount of power transferred;

a wireless receiver configured to receive information via a communication link; and

a tank circuit in electrical communication with said primary circuit, wherein said primary circuit applies said signal to said tank circuit to transfer said amount of power; and

a remote device separable from said inductive power supply, said remote device for inductively coupling with said inductive power supply to receive said power from said inductive power supply, said remote device including;

a secondary energized by said inductive coupling,

a load in electrical communication with said secondary,

a sensor in electrical communication with said secondary,

a secondary controller in electrical communication with said sensor, and

a communication device in electrical communication with said secondary controller for sending feedback to said wireless receiver of said inductive power supply;

wherein said primary circuit controls said at least one operating parameter to maintain power transfer substantially near resonance;

wherein, in response to said feedback, said primary circuit controls said duty cycle of said signal to control said amount of power transferred while controlling said at least one operating parameter to transfer power substantially near resonance; and

wherein, based on said information communicated from said remote device, said primary circuit adjusts at least one of said duty cycle to control said amount of power transferred and said at least one operating parameter to transfer power substantially near resonance.

15. The inductive power supply system of claim 14 wherein said at least one operating parameter includes at least one of an operating frequency and a resonant frequency.

16. The inductive power supply system of claim 15 further comprising a memory for storing information, wherein said information includes at least one of a resonant frequency, a maximum operating frequency, a minimum operating frequency, a current usage, a minimum duty cycle, a maximum duty cycle and wireless communication protocol of said remote device.

17. The inductive power supply system of claim 14 wherein said primary circuit continuously adjusts said at least one operating parameter to maintain substantial resonance and continuously adjusts said duty cycle based on a comparison between said amount of power transferred to said remote device and a threshold.

18. The inductive power supply system of claim 14 wherein said primary circuit controls said duty cycle of said signal according to at least one of a battery charging profile and a demand communicated to said inductive power supply by said remote device.

19. The inductive power supply system of claim 14 wherein said primary circuit controls said duty cycle of said signal based on temperature.

20. The inductive power supply of claim 19 wherein said duty cycle is decreased in response to said temperature being above a threshold.

21. The inductive power supply system of claim 14 wherein said primary circuit includes:

a primary controller;

a driver circuit in electrical communication with said primary controller;

a switching circuit in electrical communication with said driver circuit; and

a sensor for sensing reflected impedance of said remote device, wherein said sensor is in electrical communication with said tank circuit and said primary controller.

22. The inductive power supply system of claim 21 wherein said switching circuit includes a pair of switches,

wherein each switch is switched at said duty cycle and at an operating frequency, but out of phase with each other;

and

wherein, in response to said feedback, said primary controller controls said operating frequency of each of said switches; and

wherein, in response to said feedback, said primary controller controls said duty cycle of each of said switches.

23. The inductive power supply system of claim 21 wherein said primary controller adjusts said at least one operating parameter as a function of input from said sensor.

24. The inductive power supply system of claim 14 wherein said primary circuit includes a wireless receiver and said remote device includes a wireless transmitter, wherein said wireless receiver receives said feedback from said wireless transmitter.

25. A method for wirelessly supplying power to a remote device, comprising the steps of:

placing a remote device in sufficient proximity to an inductive power supply to establish an inductive coupling between the remote device and the inductive power supply;

in the inductive power supply, operating the inductive power supply according to at least one operating parameter to transfer power to the remote device via the inductive coupling between the remote device and the inductive power supply;

receiving, in the inductive power supply, information communicated from the remote device;

controlling the at least one operating parameter of the inductive power supply to transfer power substantially near resonance;

controlling a duty cycle of a switching circuit in the inductive power supply in order to control an amount of power transferred to the remote device while controlling the at least one operating parameter to transfer power substantially near resonance; and

adjusting, based on the information communicated from the remote device, at least one of the duty cycle to control the amount of power transferred and the at least one operating parameter to transfer power substantially near resonance.

26. The method of claim 25 further comprising:

in the remote device, taking measurements of a characteristic of power wirelessly received from the inductive power supply;

receiving, in the inductive power supply, communication from the remote device;

determining, based on the measurements, at least one of (a) an operating frequency for transferring power substantially near resonance and (b) the amount of power to transfer to the remote device.

27. The method of claim 26 further comprising wherein said determining step includes storing information indicative of a power transfer efficiency at one or more of the at least one operating parameters;

and

selecting an initial at least one operating parameter as the at least one operating parameter having the greatest power transfer efficiency.

28. The method of claim 25 wherein the step of controlling a duty cycle of a switching circuit includes controlling the duty cycle to transfer power at a first power level selected to be low enough to avoid over-powering the remote device.

29. The method of claim 25 wherein said determining step includes determining an initial duty cycle based on the measurements.

30. The method of claim 25 further comprising the step of selecting an initial duty cycle of at or less than 20% to avoid delivering too much power to the remote device.

31. The method of claim 25 further comprising receiving, in the inductive power supply, feedback from the remote device.

32. The method of claim 25 wherein said step of controlling a duty cycle includes:

decreasing the duty cycle in response to a determination that the power transferred to the remote device is above a threshold; and

increasing the duty cycle in response to a determination that the power transferred to the remote device is below a threshold.

33. The method of claim 25 wherein said step of controlling a duty cycle includes adjusting the duty cycle based on temperature.

34. The method of claim 33 wherein said duty cycle is decreased in response to determining that the temperature is above a threshold.