PROTECTION OF AN NFC OR RFID RADIO IN THE PRESENCE OF STRONG ELECTROMAGNETIC FIELDS

• US 20150154486A1
• Filed: 12/02/2013
• Published: 06/04/2015
• Est. Priority Date: 12/02/2013
• Status: Active Grant

• Current Assignee: Qualcomm technologies international, ltd. (Qualcomm, Inc.)
• Original Assignee: Cambridge Silicon Radio Limited (Qualcomm, Inc.)
• Inventors: MCFARTHING, Anthony Lawrence, HERBERHOLZ, Rainer, WILLIAMS, Peter Andrew Rees
• Granted Patent: US 9,361,564 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06K 19/0707 the arrangement being capable of collecting energy from external energy sources, e.g. thermocouples, vibration, electromagnetic radiation G06K19/0702 takes precedence
• CPC Class Codes: G06K 19/0712 the arrangement being capable of triggering distinct operating modes or functions dependent on the strength of an energy or interrogation field in the proximity of the record carrier active means for hindering electromagnetic reading or writing G06K19/07336
• CPC Class Codes: G06K 19/0715 the arrangement including means to regulate power transfer to the integrated circuit
• CPC Class Codes: G06K 19/073 Special arrangements for circuits, e.g. for protecting identification code in memory protection against unauthorised use of computer memory G06F12/14
• CPC Class Codes: H02H 3/025 Disconnection after limiting, e.g. when limiting is not sufficient or for facilitating disconnection
• CPC Class Codes: H02H 9/04 responsive to excess voltage lightning arrestors H01C7/12, H01C8/04, H01G9/18, H01T
• CPC Class Codes: H02J 50/10 using inductive coupling
• 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 7/00308 Overvoltage protection

Abstract

Methods and devices are described, including a near-field communications (NFC) or radio frequency identification (RFID) device comprising an NFC or RFID circuit, an antenna having at least a first terminal, a first rectifier connected to the first terminal of the antenna, a switch between the first rectifier and the NFC or RFID circuit, a voltage detector for detecting a voltage in the device caused by a signal received at the antenna, and a control module for controlling the switch, wherein when the voltage exceeds a threshold magnitude, the control module controls the switch to be in an open state and, after a predetermined time period, determines whether the voltage still exceeds the threshold magnitude and, if the voltage still exceeds the predetermined magnitude, controls the switch to be in the open state.

Claims

1. A near-field communication (NFC) or radio frequency identification (RFID) device comprising:

an NFC or RFID circuit;

an antenna having at least a first terminal;

a first rectifier connected to the first terminal of the antenna;

a switch between the first rectifier and the NFC or RFID circuit;

a voltage detector for detecting a voltage in the device caused by a signal received at the antenna; and

a control module for controlling the switch, wherein when the voltage exceeds a threshold magnitude, the control module controls the switch to be in an open state and, after a predetermined time period, determines whether the voltage still exceeds the threshold magnitude and, if the voltage still exceeds the predetermined magnitude, controls the switch to be in the open state.

2. The NFC or RFID device of claim 1, wherein the antenna has a second terminal, the NFC or RFID device further comprising a second rectifier connected to the second terminal.

3. The NFC or RFID device of claim 2, wherein the switch is connected between the second terminal and the NFC circuit.

4. The NFC or RFID device of claim 2, wherein an additional switch is connected between the second terminal and the NFC or RFID circuit, the control module arranged to control the additional switch in the same manner as the switch.

5. The NFC or RFID device of claim 1, wherein the voltage detector is arranged to detect the voltage at a node between the switch and the NFC or RFID device.

6. The NFC or RFID device of claim 5, wherein the control module determines whether the voltage still exceeds the threshold magnitude by controlling the switch to gradually transition the switch to the on state and monitoring the voltage.

7. The NFC or RFID device of claim 1, wherein the voltage detector is arranged to detect the voltage at a node between the first rectifier and the switch.

8. The NFC or RFID device of claim 1, wherein the controller controls the gate voltage of the switch.

9. The NFC or RFID device of claim 8, wherein the controller controls the gate voltage via a charge pump circuit.

10. The NFC or RFID device of claim 1, wherein if the controller, after the predetermined time period, determines that the voltage still exceeds the threshold magnitude and controls the switch to be in the open state, the controller, after a further predetermined time period, determines whether the voltage still exceeds the threshold magnitude and, if the voltage still exceeds the predetermined magnitude, controls the switch to be in the open state.

11. The NFC or RFID device of claim 1, wherein the antenna comprises a first capacitor, a first inductor and a second capacitor in series between the first terminal and a second terminal.

13. The NFC or RFID device of claim 1, wherein the antenna comprises an inductor and a capacitor connected in parallel, and wherein a centre tap of the inductor is connected to ground.

14. The NFC or RFID device of claim 1, wherein the first rectifier comprises a first diode.

15. The NFC or RFID device of claim 2, wherein the second rectifier comprises a second diode.

16. The NFC or RFID device of claim 1, wherein if after the predetermined time period the voltage no longer exceeds the predetermined magnitude, the control module controls the switch to be in a closed state.

17. The NFC or RFID device of claim 1, wherein if after the predetermined time period the voltage no longer exceeds a further predetermined magnitude that is less than the predetermined magnitude, the control module controls the switch to be in a closed state.

12. The NFC or RFID device of claim 12, wherein the antenna comprises a second inductor connected between the first terminal and ground, and a third inductor connected between the second terminal and ground.

18. A method of protecting a near-field communications (NFC) or radio frequency identification (RFID) circuit, the method comprising the steps of:

rectifying a signal received at a first terminal of an antenna using a first rectifier;

detecting that a voltage caused by the signal received at an antenna has exceeded a threshold magnitude;

controlling a switch between the first rectifier and the NFC or RFID circuit to be in an open state;

after a predetermined time period, determining whether the voltage still exceeds the threshold magnitude; and

if the voltage still exceeds the predetermined magnitude, controlling the switch to be in the open state.

19. The method of claim 18, comprising, if after the predetermined time period the voltage no longer exceeds the predetermined magnitude, controlling the switch to be in a closed state.

20. The method of claim 18, comprising, if after the predetermined time period the voltage still exceeds the threshold magnitude and the switch is controlled to be in the open state, determining after a further predetermined time period whether the voltage still exceeds the threshold magnitude and, if the voltage still exceeds the predetermined magnitude, controlling the switch to be in the open state.

21. The method of claim 18, comprising rectifying the signal received at a second terminal of the antenna using a second rectifier.

22. The method of claim 21, comprising controlling an additional switch between the second rectifier and the NFC or RFID circuit in the same manner as the first switch.

23. The method of claim 18, wherein determining whether the voltage still exceeds the threshold magnitude comprises controlling the switch to gradually transition the switch to the on state and monitoring the voltage.