Inductive Powering Surface for Powering Portable Devices

• US 20090001941A1
• Filed: 06/29/2007
• Published: 01/01/2009
• Est. Priority Date: 06/29/2007
• Status: Abandoned Application

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Xia, Zenglin, Hsu, Feng-Hsiung
• Application Number:
  US11/771,952
• Publication Number:
  US 20090001941A1
• Time in Patent Office: Days
• US Class Current: 323/211
• 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 7/0044 specially adapted for holding portable devices containing batteries H02J7/0045 takes precedence

Abstract

Systems and methods for an inductive powering surface for powering portable devices are described. In one aspect, a powering device includes the inductive powering surface. The inductive powering surface includes multiple primary coils, an impedance auto-match circuit and other control circuits. The impedance auto-match circuit selectively energizes the primary coils to transfer power via inductive coupling to the secondary coil(s) in a portable device. The impedance auto-match circuit is configured to detect voltage and current phase differences over caused by positioning of the portable device on the inductive powering surface. The impedance auto-match circuit calibrates a power factor of the inductive powering surface to transfer an objectively maximized power load via inductive coupling to the portable device.

Claims

1. A powering device comprising:

an inductive powering surface, the inductive powering surface comprising an impedance auto-match circuit and other control circuits coupled to primary power coils, the impedance auto-match circuit and the other control circuits for selectively energizing the primary coils to transfer power via inductive coupling to secondary coil(s) in a portable device; and

wherein the impedance auto-match circuit is configured to detect voltage and current phase differences over time to calibrate a power factor to transfer an optimized power load to the secondary coil(s) to power the portable device.

2. The powering device of claim 1, wherein the power factor is based on a ratio of real power and apparent power, real power being actual load power, apparent power being a product of current and voltage associated with the circuit, the circuit comprising the primary power coils and inductively coupled secondary circuits associated with the portable device.

3. The powering device of claim 1, wherein the voltage and current phase differences are a result of changes in inductance of power coil(s) responsive to movement of the portable device over the inductive powering surface.

4. The powering device of claim 1, wherein the inductive powering surface comprises a radio leakage shield, the radio leakage shield comprises a thin metal sheet mounted outside of secondary ferrite and primary ferrite.

5. The powering device of claim 1, wherein responsive to determining that phase difference between current and voltage do not match, the impedance auto-match circuit is configured to calibrate the power factor via a non-fixed value capacitor matrix.

6. The powering device of claim 1, wherein the voltage and current phase differences are determined by a logical circuit that outputs a rectangular signal to a switches controller, the rectangular signal having a duty cycle proportional to a determined voltage and current phase difference, the switches controller turning on and off respective ones of multiple capacitors to minimize phase difference between current and voltage.

7. The powering device of claim 6, wherein the switches controller is a microcontroller or a complex programmable logic device.

8. The powering device of claim 6, wherein values associated with the multiple capacitors are scaled.

9. The powering device of claim 6, wherein a number of capacitors in the multiple capacitors are configurable.

10. The powering device of claim 6, wherein the multiple capacitors are in series with a load.

11. The powering device of claim 6, wherein the multiple capacitors are in parallel with a load.

12. The powering device of claim 6, wherein the logical circuit minimizes phase difference between current and voltage by:

(a) adjusting capacitance in increasing direction from a middle value;

(b) responsive to the adjusting;

if phase difference increases, moving capacitance in a decreasing direction to minimize the phase difference until the phase difference begins to decrease when one compensation capacitance is applied; and

if the phase difference decreases, continuing to adjust capacitance in the increasing direction to minimize the phase difference until the phase difference begins to decrease when one compensation capacitance is applied;

(c) maintaining associated switches state to provide power to the secondary coil(s); and

(d) if phase difference changes responsive to a change in load inductance, and if phase difference change is larger than a pre-defined threshold, rescanning and re-determining minimum phase difference by (a) and (b).

13. A method to provide inductive power to a portable device, the method comprising:

selectively energizing, by an impedance auto-match circuit in an inductive powering surface, primary coils in the inductive powering surface to provide power via inductive coupling to secondary coil(s) in a portable device; and

wherein the power is based on detected voltage and current phase differences caused at least in part by positioning of the portable device on different respective areas of the inductive powering surface.

14. The method of claim 13, wherein the power is based on a ratio of real power and apparent power, real power being capacity of a circuit for performing work over time, apparent power being a product of current and voltage associated with a circuit comprising the primary power coils.

15. The method of claim 13, wherein selectively energizing the primary coils further comprises:

determining that phase difference between current and voltage are minimized;

calibrating capacitors in a capacitor matrix to minimize voltage-current phase difference; and

wherein the calibrating results in an optimized power factor.

16. The method of claim 13, wherein the detected voltage and current phase differences are determined by a logical circuit that outputs a rectangular signal to a switches controller, the rectangular signal having a duty cycle proportional to a determined voltage and current phase difference, the switches controller turning on and off respective ones of multiple capacitors to minimize phase difference between current and voltage in the inductive powering surface.

17. The method of claim 16, wherein values associated with the multiple capacitors are scaled.

18. The method of claim 16, wherein a number of capacitors in the multiple capacitors are configurable.

19. The method of claim 16, wherein the logical circuit minimizes phase difference between current and voltage by:

(a) adjusting capacitance in increasing direction from a middle value;

(b) responsive to the adjusting;

if phase difference increases, moving capacitance in a decreasing direction to minimize the phase difference until the phase difference begins to decrease when one compensation capacitance is applied; and

if the phase difference decreases, continuing to adjust capacitance in the increasing direction to minimize the phase difference until the phase difference begins to decrease when one compensation capacitance is applied;

(c) maintaining associated switches state to provide power to the secondary coil(s); and

(d) if phase difference changes responsive to a change in load inductance, and if phase difference change is larger than a pre-defined threshold, rescanning and re-determining minimum phase difference by (a) and (b).

20. A method implemented by a powering device, the method comprising:

selectively activating primary coils adjacent to secondary coil(s) in a portable device to transfer power via inductive coupling to the secondary coil(s), the portable device being detected in association with a surface of the powering device;

measuring phase difference between current and voltage in the surface;

controlling compensation capacitors in the surface based on the phase difference to calibrate a power factor for the surface, the power factor being calibrated to maximize power transfer via inductive coupling between the primary coils and the secondary coil(s); and

while the primary coils are in adjacent association with the secondary coil(s);

(a) re-measuring the phase difference between the current and the voltage; and

(b) if the phase difference is larger than a pre-defined threshold, re-controlling compensation capacitors using the phase difference to re-calibrate the power factor to to maximize inductive power transfer between the primary coils and the secondary coil(s); and

wherein power transferred via inductive coupling to the secondary coil(s) allows for operation of the portable device.