Dual battery configuration and method of using the same to provide a long-term power solution in a programmable smart card
View Patent ↗A smart card package includes two on-board batteries for providing uninterrupted power to a programmed, volatile memory unit. The first battery is a non-rechargeable battery with sufficient capacity to provide power to the volatile on-board memory during an initial storage period between programming the memory and deployment of the smart card. This initial storage period may be, for example, approximately two years. The second battery is a rechargeable battery that will be charged by the host device in which the smart card is deployed. The second, rechargeable battery can provide power to the volatile memory throughout the life of the card, after the first, non-rechargeable battery is dead. Specifically, the second, rechargeable battery can provide power to the non-volatile memory when needed during, for example, any subsequent storage period or during movement of the smart card between host devices.
1. A smart card comprising:
processing and memory circuitry;
an interface for electrically connecting said smart card to a host device, said interface comprising a power line for receiving power from said host device;
a primary battery disposed in said smart card for providing power to said processing and memory circuitry; and
a secondary rechargeable battery disposed in said smart card for providing power to said processing and memory circuitry;
recharging circuitry for recharging said secondary battery with power from said host device; and
means for preventing said primary and secondary batteries from charging each other including a first diode preventing discharge of said secondary battery into said primary battery and a second diode preventing discharge of said primary battery into said secondary battery.
2. The smart card of claim 1 , wherein said primary battery is non-rechargeable.
3. The smart card of claim 2 , wherein said primary battery is a lithium battery.
4. The smart card of claim 1 , further comprising access control data for a cable television system stored in said processing and memory circuitry.
5. A method of providing power to processing and memory circuitry of a smart card said method comprising:
providing a charged primary battery and a charged secondary battery in said smart card prior to initial installation of said smart card in a host device;
determining whether said primary or secondary battery has a higher voltage prior to initial installation of said smart card in said host device; and
providing power to said processing and memory circuitry with whichever battery has said higher voltage prior to initial installation of said smart card in said host device.
6. The method of claim 5 , wherein said primary battery is a lithium battery.
7. The method of claim 5 , further comprising:
installing said smart card in a host device;
electrically connecting said smart card to said host device and providing power to said smart card from said host device; and
charging said secondary battery with power from said host device.
8. The method of claim 7 , further comprising providing power to said processing and memory circuitry with said secondary battery when said smart card is removed from said host device.
9. The method of claim 7 , further comprising:
charging said secondary battery prior to installation of said smart card in a host device; and
powering said processing and memory circuitry with said secondary battery after depletion of said primary battery.
10. The method of claim 7 , further comprising preventing discharge of said secondary battery into said primary battery.
11. The method of claim 7 , further comprising preventing discharge of said primary battery into said secondary battery.
12. The method of claim 7 , further comprising storing access control data for a cable television system in said processing and memory circuitry of said smart card.
13. The method of claim 5 , further comprising charging said secondary rechargeable battery with power from said host device when said smart card is installed in said host device.
14. The method of claim 5 , wherein said primary battery is non-rechargeable.
15. The method of claim 5 , further comprising periodically determining whether said primary or secondary battery has a higher voltage prior to installation of said smart card in said host device; and providing power to said processing and memory circuitry with whichever battery has said higher voltage prior to installation of said smart card in said host device.
16. The method of claim 5 , further comprising switching which of the two said batteries provides power to said processing and memory circuitry when a voltage of the battery supplying power drops below a voltage of the battery not supplying power.
17. The method of claim 5 , further comprising, if said primary and secondary batteries have an equal voltage, supplying power to said processing and memory circuitry with both said primary and secondary batteries.
18. A method of providing power to processing and memory circuitry of a smart card said method comprising:
providing power to said processing and memory circuitry with a primary non-rechargeable battery disposed in said smart card prior to installation of said smart card in a host device;
charging a secondary battery prior to initial installation of said smart card in a host device; and
powering said processing and memory circuitry with said secondary battery prior to initial installation of said smart card in a host device.
19. The method of claim 18 , wherein said primary battery is a lithium battery.
20. The method of claim 18 , further comprising:
charging said secondary rechargeable battery with power from said host device when said smart card is installed in said host device; and
providing power to said processing and memory circuitry with said secondary battery when said primary battery is depleted and said smart card is removed from said host device.
21. The method of claim 18 , further comprising:
preventing discharge of said secondary battery into said primary battery; and
preventing discharge of said primary battery into said secondary battery.
22. The method of claim 18 , further comprising storing access control data for a cable television system in said processing and memory circuitry of said smart card.