INDUCTIVE POWER SUPPLY WITH DUTY CYCLE CONTROL

• US 20120119588A1
• Filed: 01/23/2012
• Published: 05/17/2012
• 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
• Granted Patent: US 9,257,851 B2
• Time in Patent Office: Days
• US Class Current: 307/104
• 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 generating a signal at an operating frequency and a duty cycle;

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

wherein said inductive power supply receives feedback from said remote device;

wherein, in response to said feedback, said primary circuit controls said operating frequency of said signal to optimize power transfer efficiency between said inductive power supply and said remote device; and

wherein, in response to said feedback, said primary circuit controls said duty cycle of said signal to control said amount of power transferred to said remote device.

2. The inductive power supply of claim 1 wherein said primary circuit maintains said operating frequency of said signal substantially at resonance.

3. The inductive power supply of claim 1 wherein said primary circuit continuously adjusts said operating frequency 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 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.

6. The inductive power supply of claim 5 wherein said switching circuit includes a pair of switches,

wherein each switch is switched on at said duty cycle and at said 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.

7. The inductive power supply of claim 5 wherein said primary controller adjusts said operating frequency of said signal as a function of input from said sensor.

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

9. An inductive power supply system comprising:

an inductive power supply including;

a primary circuit for generating a signal at an operating frequency and a duty cycle; and

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

a remote device separable from said inductive power supply for receiving power from said inductive power supply, said remote device including;

a secondary energized by said inductive field,

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 inductive power supply;

wherein, in response to said feedback, said primary circuit controls said operating frequency of said signal to optimize power transfer efficiency between said inductive power supply and said remote device; and

wherein, in response to said feedback, said primary circuit controls said duty cycle of said signal to control said amount of power transferred to said remote device.

10. The inductive power supply system of claim 9 wherein said primary circuit maintains said operating frequency of said signal substantially at resonance.

11. The inductive power supply system of claim 9 wherein said primary circuit continuously adjusts said operating frequency 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.

12. The inductive power supply system of claim 9 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.

13. The inductive power supply system of claim 9 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.

14. The inductive power supply system of claim 13 wherein said switching circuit includes a pair of switches,

wherein each switch is switched at said duty cycle and at said 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.

15. The inductive power supply system of claim 13 wherein said primary controller adjusts said operating frequency of said signal as a function of input from said sensor.

16. The inductive power supply system of claim 9 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.

17. A method for transferring power from an inductive power supply to a remote device, said method comprising:

setting an initial operating frequency of a signal in said inductive power supply;

setting an initial duty cycle of said signal in said inductive power supply;

applying said signal to a tank circuit for transferring an amount of power from said inductive power supply to a remote device;

receiving, in said inductive power supply, feedback from said remote device;

adjusting, in response to said feedback, said operating frequency of said signal to optimize power transfer efficiency between said inductive power supply and said remote device;

adjusting, in response to said feedback, said duty cycle of said signal to control said amount of power transferred to said remote device.

18. The method for transferring power of claim 17 wherein said adjusting said duty cycle includes:

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

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

19. The method for transferring power of claim 17 wherein at least one of said setting an initial operating frequency and adjusting said operating frequency includes sweeping a frequency range, determining an amount of power transferred to said remote device for each operating frequency, and selecting an operating frequency where said amount of power transferred to said remote device is relatively high compared to other frequencies within said frequency range.

20. The method for transferring power of claim 17 wherein at least one of said setting an initial operating frequency and adjusting said operating frequency includes sweeping a frequency range and selecting said operating frequency closest to resonance.