Non-contacting RF-ID card for wide voltage range input

• US 5,652,423 A
• Filed: 06/16/1995
• Issued: 07/29/1997
• Est. Priority Date: 06/21/1994
• Status: Expired due to Term

• Current Assignee: Sony Chemicals Corp. (Dexerials Corporation)
• Original Assignee: Sony Chemicals Corp. (Dexerials Corporation)
• Inventors: Fujimoto, Masahiro, Orihara, Katsuhisa, Yanagibori, Susumu, Saitoh, Shoshichi
• Primary Examiner(s): Hajec, Donald T.
• Assistant Examiner(s): LEE, MICHAEL GUNYOUNG
• Application Number:
  US08/491,077
• Time in Patent Office: 774 Days
• Field of Search: 235/491, 235/492, 235/487, 235/451, 235/439, 235/449, 902/26
• US Class Current: 235/492
• 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: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer

Abstract

A battery-free non-contacting information card of a relatively simple arrangement which prevents an IC chip or the like from being destroyed by an excess voltage. This non-contacting information card includes a resonance circuit (3) for receiving a carrier signal (e.g., FSK signal) modulated on the basis of information supplied from a card reader/writer (2), an information processing system (5), (6), (7) for obtaining information from the carrier signal and a rectifier system (13) for obtaining a voltage by rectifying the carrier signal, wherein the non-contacting information card can be operated by the voltage obtained at the output side of the rectifier circuit (13). The resonance circuit (3) includes a variable capacitive element (3d). A resonance frequency of the resonance circuit (3) is varied by varying the capacity value of the variable capacitive element (3d) in response to the voltage value obtained at the output side of the rectifier circuit (13) to thereby make the voltage value obtained at the output side of the rectifier circuit (13) substantially constant.

Claims

1. An improved non-contacting information card including a resonance circuit for receiving a carrier signal modulated on the basis of information supplied from a card reader/writer, information processing means for obtaining information from said carrier signal, and rectifier means for rectifying said carrier signal to provide a voltage, said non-contacting information card being operated by said voltage obtained at an output side of said rectifier means, the improvement comprising:

a variable capacitive element connected in said resonance circuit; and

voltage feedback means connected to the output side of said rectifier means and to said variable capacitive element, wherein a resonance frequency of said resonance circuit is controlled by varying a capacity value of said variable capacitive element in response to said voltage at the output side of said rectifier means, and said variable capacitive element is formed of a vari-cap diode reversely biased by a connection to said voltage at the output side of said rectifier means, thereby preventing destruction of said non-contacting information card by excess voltage by making said voltage at the output side of said rectifier means substantially constant.