INDUCTIVE POWER TRANSFER SYSTEM AND METHOD

• US 20100123451A1
• Filed: 11/14/2008
• Published: 05/20/2010
• Est. Priority Date: 11/14/2008
• Status: Active Grant

• Current Assignee: Nera Innovations Limited (Atlantic IP Services Limited)
• Original Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Inventors: Freer, Benjamin
• Granted Patent: US 7,825,537 B2
• Time in Patent Office: Days
• US Class Current: 323/356
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/80 involving the exchange of data, concerning supply or distribution of electric power, between transmitting devices and receiving devices

Abstract

An inductive power transfer system includes a base unit comprising a first inductive element for providing input power to a second inductive element of a target unit providing output power, a positioning structure provided on at least one of the base unit and the target unit for removably positioning the second inductive element at a predetermined orientation and distance relative to the first inductive element, a switch element configured for selectively applying a time varying electric current to the first inductive element to produce a time varying magnetic field for inducing an electric current in the second inductive element, and a control circuit for monitoring one parameter indicative of an efficiency of power transfer and automatically selectively adjusting at least one characteristic of the time varying electric current responsive to the parameter to maximize an efficiency of power transfer from the base unit to the target unit.

Claims

1. A method for inductively transferring power from a base unit providing input power, to a target unit providing output power, where the base unit and the target unit are electrically isolated, comprising:

positioning a second inductive element of said target unit within a predetermined distance of a first inductive element of said base unit;

applying a time varying electric current to said first inductive element to produce a time varying magnetic field, said time varying magnetic field induces an electric current in said second inductive element;

monitoring at least one parameter indicative of an efficiency of power transfer from said base unit to said target unit;

automatically adjusting at least one characteristic of said time varying electric current responsive to said parameter to maximize an efficiency of power transfer from said base unit to said target unit.

2. The method according to claim 1, wherein said characteristic comprises at least one of a frequency of said time varying current and a duty cycle of said time varying current.

3. The method according to claim 1, further comprising producing said time varying electric current by switching a DC voltage source using an electronically controlled switch element.

4. The method according to claim 3, further comprising communicating said time varying electric current to a load in said base unit, and selecting said parameter to be a measured current or voltage associated with said load.

5. The method according to claim 4, wherein said selectively controlling step further comprises comparing said measured current or voltage to a constant reference value.

6. The method according to claim 1, further comprising producing said time varying magnetic field with a DC to DC type switching mode power supply circuit.

7. The method according to claim 6, further comprising utilizing said first inductive element as a primary energy storage component in said DC to DC conversion process of said switching mode power supply circuit.

8. The method according to claim 1, wherein said automatically adjusting step further comprises automatically adjusting said characteristic to induce an oscillation in said second inductive element at a frequency to be approximately equal to a self-resonant frequency of said second inductive element.

9. The method according to claim 1, further comprising responsive to a re-positioning of said second inductive element from a first position to a second position, automatically selectively re-adjusting said characteristic to maximize said efficiency, wherein said first position differs from said second position with regard to at least one characteristic selected from the group consisting of distance and orientation relative to said primary inductor.

10. The method according to claim 1, further comprising responsive to a substitution of a target unit with a different target unit, automatically selectively re-adjusting said characteristic to maximize said efficiency.

11. The method according to claim 1, further comprising rectifying an output current induced in said second inductive element to produce a DC output.

12. An inductive power transfer system, comprising:

a base unit comprising a first inductive element configured for providing input power to a second inductive element of a target unit providing output power, said base unit electrically isolated from said target unit;

positioning structure provided on at least one of said base unit and said target unit for removably positioning said second inductive element at a predetermined orientation and distance relative to said first inductive element;

a switch element configured for selectively applying a time varying electric current to said first inductive element to produce a time varying magnetic field, said time varying magnetic field inducing an electric current in said second inductive element;

a control circuit configured for monitoring at least one parameter indicative of an efficiency of power transfer from said base unit to said target unit, and automatically adjusting at least one characteristic of said time varying electric current responsive to said parameter to maximize an efficiency of power transfer from said base unit to said target unit.

13. The system of claim 12, wherein said characteristic comprises at least one of a frequency of said time varying current and a duty cycle of said time varying current.

14. The system of claim 12, wherein said switch element is electronically controlled, and wherein said switch element is configured for coupling and decoupling a DC voltage source to said first inductive element to produce said time varying current.

15. The system of claim 14, further comprising a load circuit coupled to said first inductive element, and where said parameter comprises a current or voltage associated with said load.

16. The system of claim 15, wherein said control circuit automatically selectively adjusts said characteristic based on a comparison of said measured current or voltage to a constant reference value.

17. The system of claim 12, wherein said base unit further comprises a DC to DC type switching mode power supply, said DC to DC type switching mode power supply circuit producing said time varying magnetic field.

18. The system of claim 15, where said first inductive element comprises a primary energy storage component of said DC to DC type switching mode power supply circuit.

19. The system of claim 12, wherein said control circuit is further configured during said selectively adjusting for automatically selectively adjusting said frequency to be approximately equal to a self-resonant frequency of said second inductive element.

20. The system of claim 12, wherein said control circuit is further configured during said selectively adjusting for automatically selectively re-adjusting said frequency to maximize said efficiency responsive to a re-positioning of said second inductive element from a first position to a second position, wherein said first position differs from said second position with regard to at least one characteristic selected from the group consisting of distance and orientation relative to said primary inductor.

21. The system of claim 12, wherein said control circuit is further configured during said selectively adjusting for automatically selectively re-adjust said frequency to maximize said efficiency responsive to a substitution of a target unit with a different target unit.

22. The system of claim 12, wherein said target unit further comprises rectifying element for to produce a DC output by rectifying an output current induced in said second inductive element.

23. A DC-DC converter, comprising:

a input circuit for receiving a DC input voltage;

an output circuit electrically coupled to said input circuit, said output circuit comprising a load sub-circuit electrically coupled to a converter sub-circuit, said converter sub-circuit comprising at least a first inductive element and at least one switch element having a switch control node, said switch control node responsive to a first control voltage for selectively alternating said switch element between an open state and a closed state; and

a control circuit having an input node electrically coupled to a node within said load sub-circuit and an output node electrically coupled to said switch control node, said control circuit generating at said output node a periodic voltage signal adjustable to one or more operating frequencies based on a difference between a second control voltage at said input node and a reference voltage;

wherein an inductance and a physical arrangement of said first inductive element is selected for said first inductive element to generate a permeating magnetic field that at least partially permeates a second inductive element electrically isolated from said first inductive element, wherein said permeating magnetic field induces a substantially self-resonant oscillation in said second inductive element for at least one of said operating frequencies, and wherein said control circuit is further configured to adjust said periodic voltage signal to adjust an internal voltage level at said internal node to minimize said difference.

24. The DC-DC converter of claim 23, wherein said inductive element comprises at least a first inductor.

25. The DC-DC converter of claim 24, wherein a first directional vector defining a first inductor coil axis of said first inductor and a second directional vector defining a second inductor coil axis of said second inductive element are substantially parallel.

26. The DC-DC converter of claim 24, wherein said one of said operating frequencies is at least 1 MHz, and wherein said first inductor has an inductance of at least 100 nH.

27. The DC-DC converter of claim 23, wherein said first inductive element and said switch element are electrically coupled in series between said input circuit and said load sub-circuit, and wherein said converter sub-circuit further comprises a rectifier element electrically coupled to a common node between said first inductive element and said switch element.