Near field communications (NFC) device power harvesting and power supply selection

• US 8,559,872 B2
• Filed: 01/23/2009
• Issued: 10/15/2013
• Est. Priority Date: 01/23/2008
• Status: Active Grant

• Current Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Original Assignee: Broadcom Innovision Limited (Broadcom, Inc.)
• Inventors: Butler, Paul
• Primary Examiner(s): NGUYEN, TUAN HOANG
• Application Number:
  US12/863,617
• Publication Number:
  US 20100291871A1
• Time in Patent Office: 1,726 Days
• Field of Search: 455/41.1, 455/41.2, 455/127.1, 455/129, 455/343.1, 455/571, 455/572, 455/573, 455/574
• US Class Current: 455/41.1
• CPC Class Codes: G06K 19/0701 at least one of the integrated circuit chips comprising an arrangement for power management
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• CPC Class Codes: G11C 5/142 Contactless power supplies, e.g. RF, induction, or IR
• CPC Class Codes: H04B 1/1607 Supply circuits converters H02M; filters therefor H02M1/14; voltage stabilisers G05F1/46
• CPC Class Codes: H04B 5/26 using coils
• CPC Class Codes: H04B 5/28 using the near field of leaky cables, e.g. of leaky coaxial cables
• CPC Class Codes: H04B 5/72 for local intradevice communication
• CPC Class Codes: H04B 5/79 for data transfer in combination with power transfer

Abstract

A near field RF communicator has an antenna circuit (102) to couple with the H field of an RF magnetic field and a power supply deriver (301) to derive a rectified auxiliary power supply from the received magnetic field. Rectification may be performed using an actively switched rectifier (502) having a passive mode of operation. A sub regulation system (506) is provided to regulate the auxiliary power supply to inhibit the possibility of temporally varying power requirements of the near field RF communicator or its host causing an apparent load modulation of a signal that is transmitted or received by the communicator.

Claims

1. A communication device, comprising:

an antenna circuit;

a controller; and

first and second power supplies, wherein the first power supply comprises;

a rectifier configured to supply a rectified voltage derived from a magnetic field received by the antenna circuit;

a charge storing element configured to store the rectified voltage; and

a regulator configured to regulate the rectified voltage, and

wherein the controller is further configured to control operation of the second power supply in accordance with a level of the magnetic field and to inhibit the first and second power supplies from operating at the same time.

2. The communication device of claim 1, further comprising:

a sensor configured to provide a sensor output that is a measure of an intensity of the magnetic field, wherein the controller is further configured to control the operation of the second power supply in accordance with the sensor output.

3. The communication device of claim 2, further comprising:

a switch configured to couple the rectifier to the regulator or to decouple the rectifier from the regulator in response to a command from the controller.

4. The communication device of claim 3, wherein the controller is further configured to provide a first command to the switch to couple the rectifier to the regulator when the sensor output is greater than or equal to a threshold or to provide a second command to the switch to decouple the rectifier from the regulator when the sensor output is less than the threshold.

5. The communication device of claim 1, further comprising:

a first switch configured to couple the rectifier to the regulator or to decouple the rectifier from the regulator; and

a second switch configured to couple the first power supply to the regulator or to decouple the first power supply from the regulator.

6. The communication device of claim 5, wherein the first switch is further configured to only couple the rectifier to the regulator when the second switch is arranged to decouple the first power supply from the regulator.

7. The communication device of claim 5, wherein the first switch is further configured to only decouple the rectifier from the regulator when the second switch is arranged to couple the first power supply to the regulator.

8. The communication device of claim 5, wherein the regulator is further configured to regulate the rectified voltage to provide a regulated voltage, and further comprising:

a second charge storing element to store the regulated voltage; and

a third switch configured to couple the first power supply to the second charge storing element or to decouple the first power supply from the second charge storing element.

9. The communication device of claim 8, wherein the third switch is further configured to only couple the first power supply to the second charge storing element when the second switch is arranged to couple the first power supply to the regulator.

10. The communication device of claim 1, further comprising:

a second regulator configured to regulate a signal derived from the magnetic field received by the antenna circuit.

11. A communication device, comprising:

a rectifier configured to supply a rectified voltage derived from a magnetic field;

a sensor configured to provide a sensor output that is a measure of an intensity of the magnetic field;

a switch configured to provide the rectified voltage when in a first state or to not provide the rectified voltage when in a second state; and

a controller configured to cause the switch to enter into the first state when the sensor output is greater than or equal to a threshold or to cause the switch to enter into the second state when the sensor output is less than the threshold.

12. The communication device of claim 11, further comprising:

an antenna circuit configured to inductively receive a signal from the magnetic field and to convert the signal into a current,

wherein the rectifier is further configured to rectify the current to supply the rectified voltage.

13. The communication device of claim 11, further comprising:

NFC functionality,

wherein the switch is further configured to provide the rectified voltage to the NFC functionality when in the first state or to not provide the rectified voltage to the NFC functionality when in the second state.

14. The communication device of claim 13, wherein the NFC functionality comprises at least one of:

a demodulator;

a signal generator;

a driver, or

a data store.

15. The communication device of claim 11, further comprising:

NFC functionality; and

a second switch configured to provide power to the NFC functionality when the switch is in the second state or to not provide the power to the NFC functionality when the switch is in the first state.

16. The communication device of claim 15, wherein the NFC functionality comprises at least one of:

a demodulator;

a signal generator;

a driver, or

a data store.

17. The communication device of claim 15, further comprising:

a battery configured to provide the power to the second switch.

18. A communication device, comprising:

a first power supply;

a second power supply;

NFC functionality; and

a controller configured to couple the first power supply to the NFC functionality when an intensity of a magnetic field is less than a threshold and to couple the second power supply to the NFC functionality when the intensity of the magnetic field is greater than or equal to the threshold.

19. The communication device of claim 18, wherein the second power supply comprises:

a rectifier configured to supply a rectified voltage derived from the magnetic field;

a sensor configured to provide a sensor output that is a measure of the intensity of the magnetic field; and

a switch configured to provide the rectified voltage to the NFC functionality when in a first state or to not provide the rectified voltage to the NFC functionality when in a second state,

wherein the controller is further configured to cause the switch to enter into the first state when the sensor output is greater than or equal to the threshold or to cause the switch to enter into the second state when the sensor output is less than the threshold.

20. The communication device of claim 19, further comprising:

an antenna circuit configured to inductively receive a signal from the magnetic field and to convert the signal to a current.

21. The communication device of claim 20, further comprising:

a charge storing element configured to store the rectified voltage; and

a second regulator configured to regulate the rectified voltage.