Electronic circuit for contactless tag, and contactless tag

• US 20040227002A1
• Filed: 03/29/2004
• Published: 11/18/2004
• Est. Priority Date: 04/01/2003
• Status: Active Grant

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Watanabe, Shinichiro
• Granted Patent: US 7,142,117 B2
• Time in Patent Office: Days
• US Class Current: 235/491
• CPC Class Codes: G06K 19/0701 at least one of the integrated circuit chips comprising an arrangement for power management
• 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

An electronic circuit for a contactless tag includes a rectification circuit that rectifies an induced electromotive force caused by bringing an antenna coil into close proximity to a reader/writer to generate a rectified voltage and a secondary battery. A charging/discharging circuit is provided that charges according to the rectified voltage and discharges the secondary battery.

Claims

1. An electronic circuit for a contactless tag, comprising:

means for rectifying an induced electromotive force caused by bringing an antenna coil into close proximity to a reader/writer to generate a rectified voltage;

a secondary battery; and

means for being charged according to the rectified voltage and for discharging the secondary battery.

2. The electronic circuit for a contactless tag according to claim 1, wherein the means for charging and discharging comprises:

a capacitor that stores a charge according to the rectified voltage;

a resistor through which the capacitor supplies a discharge voltage to the secondary battery so as to charge the secondary battery, the resistor acting as a time-constant resistor; and

a diode that prevents the charge charged in the capacitor from flowing to a portion other than the secondary battery.

3. The electronic circuit for a contactless tag according to claim 2, wherein the capacitor is a device serving as an electric double-layer capacitor or a capacitor whose internal resistance is much smaller than that of the secondary battery and whose electrostatic capacitance is large.

4. The electronic circuit for a contactless tag according to claim 2, wherein the diode is defined as a first diode and the capacitor is defined as a first capacitor, and

the means for charging and discharging further comprises:

a second diode connected in series to the first diode; and

a second capacitor connected in parallel to the first capacitor between the first diode and the second diode, and the second capacitor has a smaller capacitance than the first capacitor.

5. A contactless tag using the electronic circuit according to claim 1.

6. The electronic circuit for a contactless tag according to claim 1, further comprising a transceiving device for data communication with the reader/writer.

7. The electronic circuit for a contactless tag according to claim 6, wherein the transceiving device includes the antenna coil.

8. The electronic circuit for a contactless tag according to claim 6, wherein the transceiving device includes a resonance circuit.

9. The electronic circuit for a contactless tag according to claim 1, wherein the secondary battery is a paper type battery.

10. The electronic circuit for a contactless tag according to claim 1, wherein the secondary battery has an internal resistor.

11. The electronic circuit for a contactless tag according to claim 1, further comprising a detection circuit that detects a drop in the rectified voltage.

12. The electronic circuit for a contactless tag according to claim 1, further comprising an electrophoretic display.

13. The electronic circuit for a contactless tag according to claim 12, wherein the electrophretic display includes a writing voltage, a current and a display holding time.

17. The electronic circuit for a contactless tag according to claim 2, wherein the diode is defined as a first diode and the capacitor is defined as a first capacitor, and

the charging/discharging circuit further comprises:

a second diode connected in series to the first diode; and

a second capacitor connected in parallel to the first capacitor between the first diode and the second diode, and the second capacitor has a smaller capacitance than the first capacitor.

14. An electronic circuit for a contactless tag, comprising:

a rectification circuit that rectifies an induced electromotive force caused by bringing an antenna coil into close proximity to a reader/writer to generate a rectified voltage;

a secondary battery; and

a charging/discharging circuit that charges according to the rectified voltage and that discharges the secondary battery.

15. The electronic circuit for a contactless tag according to claim 14, wherein the charging/discharging circuit comprises:

a capacitor that stores a charge according to the rectified voltage;

a resistor through which the capacitor supplies a discharge voltage to the secondary battery so as to charge the secondary battery, the resistor acting as a time-constant resistor; and

a diode that prevents the charge charged in the capacitor from flowing to a portion other than the secondary battery.

16. The electronic circuit for a contactless tag according to claim 15, wherein the capacitor is a device serving as an electric double-layer capacitor or a capacitor whose internal resistance is much smaller than that of the secondary battery and whose electrostatic capacitance is large.

18. The electronic circuit for a contactless tag according to claim 14, further comprising a transceiving device for data communication with the reader/writer.

19. The electronic circuit for a contactless tag according to claim 18, wherein the transceiving device includes the antenna coil.

20. A method for manufacturing an electronic circuit for a contactless tag comprising:

rectifying an induced electromotive force caused by bringing an antenna coil into close proximity to a reader/writer to generate a rectified voltage;

providing a secondary voltage; and

charging a charge/discharge circuit according to a rectified voltage and discharging the secondary battery.