BATTERY CHARGER OPERATING "ALL OR NOTHING" WITH A PROTECTIVE POWER SUPPLY CIRCUIT FOR MONOLITHIC INTEGRATED CIRCUITS USING THE ANTENNA ENERGY

• US 20080150476A1
• Filed: 12/26/2007
• Published: 06/26/2008
• Est. Priority Date: 12/22/2006
• Status: Active Grant

• Current Assignee: EM Microelectronic - Marin SA (The Swatch Group AG)
• Original Assignee: EM Microelectronic - Marin SA (The Swatch Group AG)
• Inventors: Lamothe, Christian
• Granted Patent: US 7,952,323 B2
• Time in Patent Office: Days
• US Class Current: 320/107
• CPC Class Codes: G06K 19/0702 the arrangement including a battery
• 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 19/0723 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: H02J 50/20 using microwaves or radio frequency waves
• CPC Class Codes: H02J 7/00712 the cycle being controlled or terminated in response to electric parameters

Abstract

The invention concerns an integrated radiofrequency circuit (1) including an antenna (2) for receiving radiofrequency signals, a rechargeable battery (3) and a battery charger (5) using said radiofrequency signals to charge said battery. The circuit is characterized in that said battery charger is integrated in the same substrate as the integrated radiofrequency circuit and in that said battery charger includes calibrating means, a current source calibrated by said calibrating means and delivering a charge current of constant maximum intensity drawn from the received radiofrequency signals and a comparator between a reference quantity representative of the end of battery charge level and a variable quantity representative of the battery charge level supplying at output a control signal (batchend) for charging or not charging the battery.

Claims

1. An integrated radiofrequency circuit including an antenna for receiving radiofrequency signals, a rechargeable battery and a battery charger using said radiofrequency signals to charge said battery;

wherein said battery charger is integrated in the same substrate as said integrated radiofrequency circuit and wherein said battery charger includes calibrating means, a current source calibrated by said calibrating means and delivering a charge current of constant maximum intensity drawn from the received radiofrequency signals, and a comparator between a reference quantity representative of the end of battery charge level and a variable quantity representative of the battery charge level supplying at output a control signal (batchend) ordering the battery to be charged or not charged.

2. The integrated radiofrequency circuit according to claim 1, wherein said comparator is a voltage comparator between a reference voltage and a battery voltage, including linearization means for converting, on the one hand, the reference voltage into said reference quantity representative of the end of battery charge level and, on the other hand, the battery voltage into said variable quantity representative of the battery charge level.

3. The integrated radiofrequency circuit according to claim 2, wherein said reference quantity representative of the end of battery charge level can be adjusted as a function of the type of battery used.

4. The integrated radiofrequency circuit according to claim 3, wherein the end of battery charge adjustment can be programmed by means of a logic word.

5. The integrated radiofrequency circuit according to claim 3, wherein the end of charge level can be adjusted by metal mask programming.

6. The integrated radiofrequency circuit according to claim 1, wherein said calibrating means include linearization means for converting said reference voltage into a reference current independent of the level of battery charge.

7. The integrated radiofrequency circuit according to claim 6, wherein said charge current is a pulsed charge current whose maximum pulse amplitude is constant.

8. The integrated radiofrequency circuit according to claim 6, wherein said calibrating means further include a programmable resistor such that two current levels can be provided at output independent of the level of battery charge.

9. The integrated radiofrequency circuit according to claim 1, wherein it includes a logic block for controlling said battery charger and wherein said logic block is powered by said radiofrequency signals to ensure that charging starts quickly.

10. The integrated radiofrequency circuit according to claim 1, wherein it further includes a circuit for monitoring the energy available from the received radiofrequency signals including a comparator between the available energy less the energy necessary for said logic block with the energy necessary for charging the battery, delivering at output a control signal for authorising or prohibiting battery charging depending upon whether the energy is sufficient or insufficient.

11. The integrated radiofrequency circuit according to claim 1, wherein means are provided for ensuring a precise end of charge voltage.

12. The integrated radiofrequency circuit according to claim 1, wherein clear distinction means between charging and not charging the battery are provided

13. The integrated radiofrequency circuit according to claim 1, wherein a switch is provided for activating or deactivating the battery charger.

14. The integrated radiofrequency circuit according to claim 1, wherein an end of battery charge indicator is provided.

15. An active transponder according to claim 1 for communicating with an external reader