Protection of an NFC or RFID radio in the presence of strong electromagnetic fields

• US 9,361,564 B2
• Filed: 12/02/2013
• Issued: 06/07/2016
• Est. Priority Date: 12/02/2013
• Status: Active Grant

• Current Assignee: Qualcomm technologies international, ltd. (Qualcomm, Inc.)
• Original Assignee: Qualcomm technologies international, ltd. (Qualcomm, Inc.)
• Inventors: McFarthing, Anthony Lawrence, Herberholz, Rainer, Williams, Peter Andrew Rees
• Primary Examiner(s): Le, Thien M
• Assistant Examiner(s): Habib, Asifa
• Application Number:
  US14/093,895
• Publication Number:
  US 20150154486A1
• Time in Patent Office: 918 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 including a first terminal and a second terminal;

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

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

a second switch coupled between the second terminal and the NFC or RFID circuit;

a second rectifier coupled to the second terminal of the antenna;

a voltage detector configured to detect a voltage in the device caused by a signal received at the antenna; and

a controller, coupled to the first and second switches, and configured to;

when the voltage exceeds a first threshold magnitude, cause the first switch to be in an open state;

wait for a first time period;

after the first time period lapses, determine whether the voltage exceeds a second threshold magnitude that is less than the first threshold magnitude;

based on the voltage exceeding the second threshold magnitude after the first time period lapses, cause the switch to remain in the open state; and

based on the voltage not exceeding the second threshold magnitude after the first time period lapses, cause the switch to be in a closed state; and

control the second switch in the same manner as the first switch.

2. The NFC or RFID device of claim 1, wherein the first switch is coupled between the second terminal and the NFC or RFID circuit.

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

4. The NFC or RFID device of claim 3, wherein the controller is configured to determine whether the voltage exceeds the second threshold magnitude by gradually transitioning the first switch to the on state and monitoring the voltage.

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

6. The NFC or RFID device of claim 1, wherein the controller is configured to control a gate voltage of the switch.

7. The NFC or RFID device of claim 6, wherein the controller is configured to control the gate voltage via a charge pump circuit.

8. The NFC or RFID device of claim 1, wherein the controller is further configured to:

after the first time period lapses, determine that the voltage exceeds the second threshold magnitude and that the switch is in the open state;

after a further time period, determine that the voltage still exceeds the second threshold magnitude; and

control the switch to remain in the open state based on the determination that the voltage exceeds the second threshold magnitude.

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

10. The NFC or RFID device of claim 9, wherein the antenna further comprises:

a second inductor connected between the first terminal and ground; and

a third inductor connected between the second terminal and ground.

11. 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.

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

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

14. The NFC or RFID device of claim 1, wherein the controller is further configured to:

after the first time period lapses, determine that the voltage still exceeds the second threshold magnitude; and

control the switch to remain in the open state based on the determination that the voltage still exceeds the second threshold magnitude.

15. 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 the antenna has exceeded a first threshold magnitude;

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

waiting for a first time period;

after the first time period lapses, determining whether the voltage exceeds a second threshold magnitude that is less than the first threshold magnitude;

based on the voltage exceeding the second threshold magnitude after the first time period lapses, controlling the first switch to remain in the open state;

based on the voltage not exceeding the second threshold magnitude after the first time period lapses, cause the switch to be in a closed state;

rectifying the signal received at a second terminal of the antenna using a second rectifier; and

controlling a second switch coupled between the second rectifier and the NFC or RFID circuit in the same manner as the first switch.

16. The method of claim 15, further comprising:

after the first time period lapses, determining that the voltage no longer exceeds the second threshold magnitude; and

controlling the first switch to be in a closed state based on the determination that the voltage no longer exceeds the second threshold magnitude.

17. The method of claim 15, further comprising:

after the first time period lapses, determining that the voltage still exceeds the second threshold magnitude and that the first switch is in the open state;

after a further time period, determining that the voltage still exceeds the second threshold magnitude; and

controlling the first switch to remain in the open state based on the determination that the voltage still exceeds the second threshold magnitude.

18. The method of claim 15, wherein determining whether the voltage exceeds the second threshold magnitude comprises gradually transitioning the first switch to the on state and monitoring the voltage.