Voltage and power limiter for an electromagnetic transponder

• US 9,361,489 B2
• Filed: 06/15/2015
• Issued: 06/07/2016
• Est. Priority Date: 07/02/2014
• Status: Active Grant

• Current Assignee: STMicroelectronics SAS (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SAS (STMicroelectronics NV)
• Inventors: Battista, Marc, Bas, Gilles, Tailliet, Francois
• Primary Examiner(s): ODOM, CURTIS B
• Application Number:
  US14/739,814
• Publication Number:
  US 20160004890A1
• Time in Patent Office: 358 Days
• US Class Current: 1/1
• CPC Class Codes: G06K 19/0715 the arrangement including means to regulate power transfer to the integrated circuit
• CPC Class Codes: G06K 7/10158 methods and means used by the interrogation device for reliably powering the wireless record carriers using an electromagnetic interrogation field
• CPC Class Codes: H04B 1/18 Input circuits, e.g. for coupling to an antenna or a transmission line coupling networks between antennas or lines and receivers independent of the nature of the receiver H03H

Abstract

An electromagnetic transponder including a resonant circuit; a rectifying bridge having input terminals connected across the resonant circuit and having rectified output terminals providing an electronic circuit power supply voltage; and a device for limiting the voltage across the resonant circuit, connected between the input terminals of the rectifying bridge.

Claims

1. An electromagnetic transponder comprising:

a resonant circuit;

a rectifying bridge having input terminals electrically coupled across the resonant circuit and having rectified output terminals configured to provide a voltage for powering an electronic circuit; and

a limiter configure to limit a voltage across the resonant circuit, electrically coupled between the input terminals of the rectifying bridge, wherein the limiter includes a detection circuit configured to compare the voltage across the resonant circuit with a threshold that is adjustable between first and second values, the second value being greater than the first value.

2. The transponder of claim 1, wherein the limiter comprises an adjustable impedance element electrically coupled between the input terminals of the rectifying bridge, the detection circuit being configured to adjust an impedance of the adjustable impedance element.

3. The transponder of claim 2, wherein the limiter includes a filter interposed between the detection circuit and the adjustable impedance element.

4. The transponder of claim 3, wherein the filter has a first time constant when the voltage across the resonant circuit decreases and a second time constant when the voltage across the resonant circuit increases, the first time constant being at least ten times greater than the second time constant.

5. The transponder of claim 2, wherein the limiter includes a charge pump circuit configured to provide a boosted control voltage for adjusting the adjustable impedance element.

6. The transponder of claim 1, further comprising a control circuit configured to set the threshold at the second value when the transponder is in a retromodulation mode.

7. The transponder of claim 1, wherein the voltage across the resonant circuit in which the detection circuit is configured to compare with the threshold is a peak voltage.

8. A device comprising:

a resonant circuit;

a rectifying bridge configured to rectify a voltage across the resonant circuit; and

a limiter configure to limit the voltage across the resonant circuit, electrically coupled between the input terminals of the rectifying bridge, wherein the limiter includes a detection circuit configured to compare the voltage across the resonant circuit with a threshold that is adjustable between first and second values, the second value being greater than the first value.

9. The device of claim 8, wherein the limiter comprises an adjustable impedance element electrically coupled between the input terminals of the rectifying bridge, the detection circuit being configured to adjust an impedance of the adjustable impedance element.

10. The device of claim 9, wherein the limiter includes a filter interposed between the detection circuit and the adjustable impedance element.

11. The device of claim 10, wherein the filter has a first time constant when the voltage across the resonant circuit decreases and a second time constant when the voltage across the resonant circuit increases, the first time constant being at least ten times greater than the second time constant.

12. The device of claim 9, wherein the limiter includes a charge pump circuit configured to provide a boosted control voltage for adjusting the adjustable impedance element.

13. The device of claim 8, further comprising a control circuit configured to set the threshold at the second value when the device is in a retromodulation mode.

14. The device of claim 8, wherein the voltage across the resonant circuit in which the detection circuit is configured to compare with the threshold is a peak voltage.