APPARATUS FOR WIRELESSLY CHARGING ENERGY STORAGE ELEMENTS

• US 20130300357A1
• Filed: 05/09/2013
• Published: 11/14/2013
• Est. Priority Date: 05/10/2012
• Status: Active Grant

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Mercier, Patrick P., Chandrakasan, Anantha P.
• Granted Patent: US 9,293,942 B2
• Time in Patent Office: Days
• US Class Current: 320/108
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 7/00 Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries

Abstract

An apparatus for wirelessly charging an energy storage element is disclosed. The apparatus includes a coil, a set of capacitors, a set of switches and a rectifier. The coil, which has multiple taps, is capable of being energized by a charger via inductive coupling. The capacitors are connected to the coil at various taps. The switches selectively connect the rectifier to at least one of the capacitors to charge the energy storage element that is connected to the rectifier.

Claims

1. An apparatus for wirelessly charging an energy storage element, said apparatus comprising:

a rectifier configured to connect to said energy storage element;

a coil capable of being energized by a charger via inductive coupling, wherein said coil includes a plurality of taps for supplying various inductances;

a plurality of capacitors connected to said coil at said plurality of taps; and

a plurality of switches for selectively connecting said rectifier to at least one of said plurality of capacitors for charging said energy storage element.

2. The apparatus of claim 1, wherein said apparatus further includes a resistance measuring circuit for measuring instantaneous resistance of said energy storage element.

3. The apparatus of claim 2 wherein said apparatus further includes a switch selection circuit for controlling said plurality of switches to preform selective connections of said rectifier to at least one of said plurality of capacitors based on instantaneous resistances measured by said resistance measuring circuit.

4. The apparatus of claim 1, wherein said rectifier includes four diodes connected in a bridge configuration.

5. The apparatus of claim 1, wherein said energy storage element is a rechargeable battery.

6. The apparatus of claim 1, wherein said energy storage element is a capacitor.

7. The apparatus of claim 1, wherein said charger includes a charger coil, a power amplifier, and a power supply for energizing said charger coil via said power amplifier.

8. The apparatus of claim 7, wherein said power amplifier is a class-D amplifier.

9. A method for wirelessly charging an energy storage element, said method comprising:

connecting a rectifier to said energy storage element;

providing a coil capable of being energized by a charger via inductive coupling, wherein said coil includes a plurality of taps for supplying various inductances;

connecting a plurality of capacitors to said coil at said plurality of taps; and

selectively connecting said rectifier to at least one of said plurality of capacitors for charging said energy storage element.

10. The method of claim 9, wherein said method further includes measuring instantaneous resistance of said energy storage element.

11. The method of claim 10, wherein said selectively connecting further includes controlling a plurality of switches for selective connecting said rectifier to at least one of said plurality of capacitors based on said measured instantaneous resistances.