Contactless communication medium and electronic device using the same

Patent metadata

Field	Value
Publication number	US-10333354-B2
Application number	US-201715442250-A
Country	US
Kind code	B2
Filing date	Feb 24, 2017
Priority date	Mar 1, 2016
Publication date	Jun 25, 2019
Grant date	Jun 25, 2019

Abstract

A contactless communication medium, includes: a coil sensitive to a magnetic field; a rectifying circuit configured to rectify an alternating power energy generated in the coil; a smoothing circuit configured to smooth a rectified output outputted from the rectifying circuit to generate a DC voltage; an output terminal connected to the smoothing circuit; a voltage detecting circuit configured to compare an output voltage extracted from the output terminal with a reference voltage; a switch configured to operate in response to an output from the voltage detection circuit and to attenuate the alternating power energy generated in the coil when the output voltage reaches a predetermined value; and a load connected to the output terminal, wherein impedance of the load has a value such that the output voltage has a predetermined value when an effective value of the magnetic field applied to the coil is 12 A/m or more.

First claim

What is claimed is:

1. A contactless communication medium, comprising:
a coil sensitive to a magnetic field;
a rectifying circuit configured to rectify an alternating power energy generated in the coil;
a smoothing circuit configured to smooth a rectified output outputted from the rectifying circuit to generate a DC voltage;
an output terminal connected to the smoothing circuit;
a voltage detecting circuit configured to compare an output voltage extracted from the output terminal with a reference voltage;
a switch configured to operate in response to an output from the voltage detection circuit and to attenuate the alternating power energy generated in the coil when the output voltage reaches a predetermined value; and
a load connected to the output terminal,
wherein an impedance of the load has a value such that the output voltage has a predetermined value when an effective value of the magnetic field applied to the coil is 12 A/m or more.

2. The contactless communication medium of claim 1 , wherein the load is connected in parallel or in series to the smoothing circuit such that a discharge time constant of the smoothing circuit has a value based on the impedance of the load.

3. The contactless communication medium of claim 2 , wherein the load is a fixed resistor.

4. The contactless communication medium of claim 2 , wherein the load is a variable resistor.

5. The contactless communication medium of claim 1 , wherein the load is within a range of 30 to 500 Ω.

6. The contactless communication medium of claim 1 , wherein sensitivity of the coil to the magnetic field is attenuated when the effective value of the magnetic field is 13.6 A/m (rms) or more.

7. The contactless communication medium of claim 6 , wherein the sensitivity of the coil to the magnetic field is attenuated when the effective value of the magnetic field is 18 A/m (rms) or more.

8. The contactless communication medium of claim 7 , wherein the sensitivity of the coil to the magnetic field is attenuated when the effective value of the magnetic field is 28.8 A/m (rms) or more.

9. The contactless communication medium of claim 1 , wherein the effective value of the magnetic field conforms to the specification of ISO14443.

10. The contactless communication medium of claim 1 , wherein 12 A/m (rms), which is the effective value of the magnetic field, is applied to PICC1 of ISO14443.

11. The contactless communication medium of claim 6 , wherein 13.6 A/m (rms), which is the effective value of the magnetic field, is applied to PICC3 of ISO14443.

12. The contactless communication medium of claim 7 , wherein 18 A/m (rms), which is the effective value of the magnetic field, is applied to PICC6 of ISO14443.

13. The contactless communication medium of claim 8 , wherein 28.8 A/m (rms), which is the effective value of the magnetic field, is applied to PICC6 of ISO14443.

14. The contactless communication medium of claim 1 , wherein the output voltage is 3V.

15. The contactless communication medium of claim 1 , further comprising a functional circuit connected to the output terminal, wherein a source voltage of the functional circuit is the output voltage output from the output terminal.

16. The contactless communication medium of claim 15 , wherein a maximum rated source voltage of the functional circuit is equal to or less than the output voltage.

17. The contactless communication medium of claim 1 , wherein a capacitor is connected in parallel or in series to the coil to form a resonance circuit, and
wherein an inductance of the coil and a capacitance of the capacitor have values respectively such that the resonance frequency of the resonance circuit is within a range of 100 KHz to 27.12 MHz.

18. The contactless communication medium of claim 17 , wherein, when a magnitude of the inductance of the coil is l 2 and the capacitance of the capacitor is c 2 , l 2 ·c 2 as a product of l 2 and c 2 is within a range of 1.72×10 −17 (s 2 ) to 8.27×10 −16 (s 2 ).

19. The contactless communication medium of claim 18 , wherein the capacitance c 2 is within a range of 3 to 170 pF.

20. The contactless communication medium of claim 18 , wherein the inductance l 2 is within a range of 0.5 to 100 μH.

21. The contactless communication medium of claim 20 , wherein the inductance l 2 is within a range of 0.9 to 50 μH.

22. The contactless communication medium of claim 1 , wherein the rectifying circuit is constituted with a full-wave rectifying circuit or a half-wave rectifying circuit formed of diode elements.

23. The contactless communication medium of claim 22 , wherein the diode elements are configured with any one of PN junction diodes, Schottky barrier diodes, and MOS transistors.

24. An electronic device configured to write or read information into or from the contactless communication medium of claim 1 that performs contactless communication with the contactless communication or supply a driving current to the coil of the contactless communication medium.

25. The electronic device of claim 24 , wherein the electronic device is applied to any one of a Qi scheme, an A4WP scheme, an NFC scheme, and a PMA scheme.

Assignees

• Rohm Co Ltd

Inventors

• Yoshii Yusuke

Classifications

• H04B5/0075

  Electricity · mapped topic

• Y02B70/1475

  Cross-Sectional Technologies · mapped topic

• H02M3/335

  using semiconductor devices only · CPC title

• H02M3/33592

  having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer · CPC title

• H02J50/12 Primary

  of the resonant type · CPC title