POWER MANAGEMENT IN AN ELECTROMAGNETIC TRANSPONDER

• US 20110140852A1
• Filed: 06/15/2010
• Published: 06/16/2011
• Est. Priority Date: 06/19/2009
• Status: Active Grant

• Current Assignee: STMicroelectronics SAS (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SAS (STMicroelectronics NV)
• Inventors: Wuidart, Luc
• Granted Patent: US 8,922,338 B2
• Time in Patent Office: Days
• US Class Current: 340/10.1
• 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 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs

Abstract

A method of evaluation, by an electromagnetic transponder in the field of a terminal generating a magnetic field, of power that can be extracted from this field, including the steps of: evaluating the current coupling between the transponder and the terminal; and deducing therefrom information relative to the power available in this coupling position.

Claims

1. A method of evaluation, by an electromagnetic transponder in the field of a terminal generating a magnetic field, of the power that it can extract from this field, comprising the steps of:

evaluating the current coupling between the transponder and the terminal; and

deducing therefrom data relative to the power available in this coupling position.

2. The method of claim 1, wherein:

the transponder comprises an oscillating circuit upstream of rectifying means capable of providing a D.C. voltage;

first data relative to the level of said D.C. voltage are measured and stored for a first value of the resistive load formed by circuits of the transponder on the oscillating circuit;

second data relative to the level of said D.C. voltage are measured and stored for a second value of the resistive load on the oscillating circuit; and

a position of the current coupling factor with respect to an optimum coupling position with one of the two values of the resistive load is deduced therefrom.

3. The method of claim 1, wherein said data relative to the available power are the maximum current that can be sampled from the transponder circuits under a minimum voltage.

4. The method of claim 2, wherein a variation of the resistive load between the first and second values is obtained by switching a resistive retromodulation element comprised by the transponder.

5. A method for managing the power of an electromagnetic transponder in the field of a terminal, wherein:

the available power is estimated according to claims 1; and

it is compared with the power required for the execution of a function by the transponder.

6. The method of claim 5, wherein power required for different functions are stored in the transponder.

7. The method of claim 5, wherein the execution of the function is only started by the transponder if the available power is sufficient.

8. The method of claim 5, wherein the functions executed by the transponder are adapted according to the available power.

9. The method of claim 5, wherein data relative to the required power are transmitted to the terminal to have it adapt the power of the generated field.

10. An electromagnetic transponder comprising:

an oscillating circuit upstream of a rectifying circuit capable of providing a D.C. voltage when the transponder is present in the magnetic field of a terminal; and

at least one processing unit capable of implementing the method of claim 1.

11. The transponder of claim 10, further comprising at least one switchable resistive element capable of being functionally connected in parallel on the oscillating circuit.