Detection of coil coupling in an inductive charging system

• US 9,685,814 B1
• Filed: 06/13/2014
• Issued: 06/20/2017
• Est. Priority Date: 06/13/2014
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Moyer, Todd K., Bossetti, Chad A., Terlizzi, Jeffrey J.
• Primary Examiner(s): Ngo, Brian
• Application Number:
  US14/304,064
• Time in Patent Office: 1,103 Days
• Field of Search: 320104, 320108, 320162
• CPC Class Codes: G01R 31/315 by inductive methods
• 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
• CPC Class Codes: H02J 7/00034 Charger exchanging data with an electronic device, i.e. telephone, whose internal battery is under charge

Abstract

An inductive charging system can include a transmitter device and a receiver device. The transmitter device may be adapted to detect when a receiver coil in the receiver device is coupled to a transmitter coil in the transmitter device. For example, the current input into a DC-to-AC converter in the transmitter device can be measured and coil coupling detected when the current equals or exceeds a threshold value.

Claims

1. A receiver device for use in an inductive charging system, comprising:

a receiver coil operatively connected to an input of an AC-to-DC converter;

a rechargeable battery operatively connected to an output of the AC-to-DC converter;

a first resonant circuit operatively connected in series between the receiver coil and the input of the AC-to-DC converter, the first resonant circuit associated with a first resonant frequency;

a second resonant circuit operatively connected in series across leads of the first resonant circuit, the second resonant circuit associated with a second resonant frequency that is different from the first resonant frequency; and

a switch configured to;

connect the second resonant circuit across the leads of the first resonant circuit when the receiver device is receiving power; and

disconnect the second resonant circuit from the first resonant circuit when the rechargeable battery is fully charged.

3. The receiver device as in claim 1, further comprising a load operatively connected to an output of the AC-to-DC converter.

4. The receiver device as in claim 3, wherein the load comprises the rechargeable battery.

5. The receiver device as in claim 1, wherein the first and second resonant circuits each comprise a capacitor.

6. The receiver device as in claim 1, wherein the AC-to-DC converter comprises a four diode bridge circuit.

7. The receiver device as in claim 1, wherein the second resonant frequency is higher than the first resonant frequency.

2. The receiver device as in claim, further comprising a processing device for controlling a state of the switch.

8. A receiver device for use in an inductive charging system, comprising:

a receiver coil operative to receive inductive power;

a first resonant circuit operatively connected in series with the receiver coil and associated with a first resonant frequency; and

a second resonant circuit coupling an output of the first resonant circuit to a lead of the receiver coil, the second resonant circuit associated with a second resonant frequency that is higher than the first resonant frequency;

wherein;

the second resonant circuit is associated with a low-power mode of a transmitter device coupled to the receiver device.

9. The receiver device of claim 8, further comprising an electronic switch connected in series with the second resonant circuit.

10. The receiver device of claim 9, wherein the electronic switch is configured to connect or disconnect the second resonant circuit from the receiver coil.

11. The receiver device of claim 9, wherein the first resonant circuit is configured to resonate with a third resonant circuit associated with the transmitter device.

12. The receiver device of claim 11, wherein the transmitter device comprises a coil coupled in series with the third resonant circuit.

13. The receiver device of claim 12, wherein the electronic switch disables the second resonant circuit to cloak the receiver device from the transmitter device.

14. A receiver device for use in a wireless charging system, the receiver device comprising:

a processor;

a rechargeable battery in communication with the processor;

an inductive coil in communication with the processor and the rechargeable battery;

a first capacitor connected in series with a first lead of inductive coil;

a second capacitor coupling an output lead of the first capacitor to a second lead of the inductive coil; and

a switch connected in series with the second capacitor and in communication with the processor;

wherein

the processor is configured to send a signal to the switch to disconnect the second capacitor from the receiver coil when the rechargeable battery is charged beyond a threshold.

15. The receiver device of claim 14, further comprising a housing at least partially enclosing the processor and the inductive coil.

16. The receiver device of claim 14, wherein the first capacitor is configured to resonate at a first frequency with a third resonant circuit associated with a transmitter device.

17. The receiver device of claim 16, wherein the second capacitor is configured to resonant at a second frequency different from the first frequency.

18. The receiver device of claim 17, wherein the second frequency is greater than the first frequency.