Inductively coupled power receiver and method of operation

• US 9,124,113 B2
• Filed: 07/07/2009
• Issued: 09/01/2015
• Est. Priority Date: 07/07/2008
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: PowerbyProxi Limited (Apple Inc.)
• Inventors: Hu, Patrick Aiguo, Si, Ping, Mishriki, Fady, Bhargava, Kunal
• Primary Examiner(s): Berhane, Adolf
• Assistant Examiner(s): Quddus, Nusrat
• Application Number:
  US12/991,054
• Publication Number:
  US 20110090723A1
• Time in Patent Office: 2,247 Days
• Field of Search: 323/220, 323/223, 323/226, 323/232, 363/21.02, 363/21.04, 363/47, 363/74, 363/97, 363/110, 363/127
• US Class Current: 1/1
• CPC Class Codes: H02J 50/10 using inductive coupling
• CPC Class Codes: H02J 50/12 of the resonant type

Abstract

A contactless power receiver is provided with a dynamically tuned pick up coil. The power transfer capacity of this power receiver is dynamically tuned using semiconductor devices that are operated in linear mode over part of their operation. The semiconductor devices are driven by a controller that is configured to implement a range of control strategies depending on system requirements. The semiconductor device may be used by itself or in conjunction with reactive elements to dynamically tune the pick up coil. In some implementations the contactless power receiver maybe configured to work with a consumer electronic or a wireless sensor device. The contactless power receiver can be integrated with the energy storage component of the device to provide a retrofit solution for existing products. The device can then be placed in vicinity of a planar magnetic field generated by a charging pad.

Claims

1. A contactless power receiver suitable for use in a near field inductively coupled power transfer system including:

a. a pick up coil;

b. a metal-oxide-semiconductor filed-effect transistor (MOSFET) for controlling current flow through the pick up coil; and

c. a control circuit which drives the MOSFET in linear mode over at least part of its range of operation to tune the pick up coil based on a voltage output of the contactless power receiver, the control circuit comprising;

an operational amplifier operatively connected to a gate of the MOSFET, the operational amplifier comparing the voltage output of the contactless power receiver to a reference voltage; and

a resistive feedback arrangement for establishing dynamic gain of the operational amplifier;

wherein driving the MOSFET in linear mode comprises configuring the operational amplifier by the dynamic gain established by the resistive feedback arrangement to drive the MOSFET to switch between OFF and ON-ohmic region by controlling a gate drive voltage of the MOSFET to be in the ohmic region of the MOSFET.

2. The power receiver as claimed in claim 1 wherein the control circuit drives the MOSFET to achieve essentially pure resistive tuning of the power receiver.

3. The power receiver as claimed in claim 1 wherein the control circuit drives the MOSFET in association with a capacitor resulting in capacitive tuning of the power receiver.

4. The power receiver as claimed in claim 1 wherein the control circuit drives the MOSFET in association with an inductor resulting in inductive tuning of the power receiver.

5. The power receiver as claimed in claim 1 wherein the control circuit drives the MOSFET in association with a capacitor and inductor resulting in hybrid tuning of the power receiver.

6. The power receiver as claimed in claim 1 wherein at least one other semiconductor device in addition to the MOSFET is used in parallel to tune the pick up coil.

7. The power receiver as claimed in claim 1 wherein the control circuit further includes at least one of a comparator, a microcontroller, a microcontroller with a look up table and a gate array logic device.

8. The power receiver as claimed in claim 1 wherein the power receiver is integrated with an energy storage device.

9. The power receiver of claim 1 wherein the power receiver is incorporated into an electronic device.

10. The power receiver as claimed in claim 1 wherein the MOSFET and control circuit are incorporated into an integrated circuit.

17. A system for use with electronic devices including

a. a power transmitter including a drive circuit energizing a coil generating a magnetic field;

and

b. a power receiver as claimed in claim 1 wherein the power receiver is connected to an electronic device either through an energy storage device or directly.

18. The system as claimed in claim 17 wherein the electronic device is a consumer electronic device.

19. The system as claimed in claim 17 wherein the contactless power receiver is placed in a planar magnetic field generated by a charging pad.

11. In a contactless power system suitable for use in a near field inductively coupled power transfer system in which a power transmitter transmits power via a magnetic field to a pick up coil of a power receiver, a method of tuning the pick up coil over at least part of the range of operation of the power receiver by:

using a control circuit to drive metal-oxide-semiconductor filed-effect transistor (MOSFET) of the power receiver in linear mode to vary the resistance applied across the pick-up coil based on a voltage output of the contactless power receivers;

wherein the control circuit comprises an operational amplifier operatively connected to a gate of the MOSFET, the operational amplifier comparing the voltage output of the contactless power receiver to a reference voltage; and

a resistive feedback arrangement for establishing dynamic gain of the operational amplifier;

and wherein driving the MOSFET in linear mode comprises configuring the operational amplifier by the dynamic gain established by the resistive feedback arrangement to drive the MOSFET to switch between OFF and ON-ohmic region by controlling a gate drive voltage of the MOSFET to be in the ohmic region of the MOSFET.

12. A method as claimed in claim 11 wherein at least one other semiconductor device in addition to the MOSFET is operated in linear mode to vary the resistance applied across the pick up coil.

13. A method as claimed in claim 11 wherein at least one other semiconductor device and the MOSFET are provided in parallel with the pick up coil and the other semiconductor device modulated in linear mode for fine tuning.

14. A method as claimed in claim 13 wherein the other semiconductor device operates in switch mode.

15. A method as claimed in claim 13 wherein the other semiconductor device operates in full conduction mode.

16. The method as claimed in claim 11 wherein control strategies used to tune the power receiver include one of a Schmitt trigger, proportional control, integral control and differential control.

20. A contactless power receiver suitable for use in a near field inductively coupled power transfer system including:

a. pick up coil inputs;

b. a metal-oxide-semiconductor filed-effect transistor (MOSFET) connected to the pick up coil inputs; and

c. a control circuit which when in use with a pick up coil connected to the pick up coil inputs drives at the MOSFET in linear mode over at least part of its range of operation to tune the pick up coil at the pick up coil inputs based on a voltage output of the contactless power receiver, the control circuit comprising;

an operational amplifier operatively connected to a gate of the MOSFET, the operational amplifier comparing the voltage output of the contactless power receiver to a reference voltage; and

a resistive feedback arrangement for establishing dynamic gain of the operational amplifier;

wherein driving the MOSFET in linear mode comprises configuring the operational amplifier by the dynamic gain established by the resistive feedback arrangement to drive the MOSFET to switch between OFF and ON-ohmic region by controlling a gate drive voltage of the MOSFET to be in the ohmic region of the MOSFET.