JP2002222399A - Non-contact ic card - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the success rate of data transmission by suppressing the dropping of power voltage in the case of data transmission in a non-contact IC card for transmitting data by a load switching system. SOLUTION: In order to reduce the current consumption of a regulator 22 with the lowering of the load impedance of an antenna L2 in the case of signal transmission by the load switching system, a regulator 22 is cut off from a power source line 25 by a transistor M2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-contact type IC card which is supplied with power from the outside and transmits data to a reader / writer device by a load switching method.

[0002]

2. Description of the Related Art In recent years, IC card systems using IC cards have become widespread for use in entry / exit management systems, railway ticket gate systems, FA management systems, and the like. The IC card includes a contact type IC card having an external terminal and a non-contact type IC card having no external terminal. Non-contact type IC cards have high security because there are no external terminals, and are likely to be used more widely in the future.

FIG. 4 shows a non-contact type IC card system. The reader / writer device 1 and the IC card 2 are provided with analog interface units 1a and 2a for performing data communication using electromagnetic waves and digital units 1b and 2b for processing signals, respectively, via antenna coils L1 and L2. To perform data communication. Data subjected to processing such as error detection and error correction, data authentication and the like, and encryption and the like in the digital unit 2b is stored in the nonvolatile memory 3.

The reader / writer device 1 modulates a carrier having a predetermined frequency into a desired data sequence to generate a transmission signal, and transmits the transmission signal to the IC card 2 via the antenna coil L1. The IC card 2 receives and demodulates the transmission signal via the antenna coil L2, modulates data held therein according to the received data, and transmits the modulated data to the reader / writer device 1.

As a method of transmitting data from the IC card 2 to the reader / writer device 1, a load switching method for transmitting a signal by varying the load impedance between both ends of the antenna coil L2 of the IC card 2 has been proposed. ing.

FIG. 5 shows an analog interface section 2a of an IC card. In the modulation unit based on the load switching method, the MOS transistor switch M1 and the load resistor R1 are connected in series between both ends of the antenna coil L2, and the gate of the transistor switch M1 is controlled by the transmission data 26 to control the antenna coil M1. Data is transmitted to the reader / writer device 1 by changing the load resistance between both ends of L2.

In the case of this load switching system, the smaller the load resistance R1, the greater the degree of change in impedance, and the easier the demodulation by the reader / writer device 1 becomes. 2
Reference numeral 3 denotes a resonance capacitor, and reference numerals 21 and 22 denote a rectifying circuit for rectifying a carrier signal received via the antenna coil L2 and a regulator for stabilizing the output. The output of the regulator 22 reduces power consumption inside the IC card. Is funded.
The power supply voltage of the regulator 22 is stabilized by a regulator such as a shunt regulator.

[0008]

FIG. 6 shows the transmission data, the output voltage of the regulator 22 and the current consumption of the regulator 22 in such a configuration.

When data is transmitted from the IC card 2 to the reader / writer device 1, if both ends of the antenna coil L2 are short-circuited by the load resistor R1, the power supply to the circuit is reduced and the power supply voltage is reduced. At this time, the operation of the regulator 22 may not follow, and the power supply voltage may drop rapidly, so that data transmission may not be performed normally.

According to the present invention, in an IC card to which power is supplied in a non-contact manner and data is transmitted by a load switching method, a drop in a power supply voltage during data transmission is suppressed and a success rate of data transmission is improved. The purpose is to:

[0011]

According to a first aspect of the present invention, there is provided a non-contact type IC card which rectifies a carrier signal received via an antenna, stabilizes the signal via a regulator, and supplies necessary power. A non-contact type IC card which employs a load switching method for transmitting a signal by changing a load impedance of the antenna when transmitting to the outside, wherein the regulator is synchronized with transmission data when transmitting a signal by the load switching method. Means for controlling the current output capability of the regulator, so that the current consumption of the regulator is reduced as the load impedance of the antenna decreases.

According to this configuration, the power consumption due to the operation delay of the regulator is eliminated with respect to the power supply voltage drop due to the modulation by the load switching method, the power supply voltage drop can be suppressed, and the success rate of data transmission is improved.

According to a second aspect of the present invention, in the non-contact type IC card according to the first aspect, the regulator is realized by a shunt regulator, and the regulator and a power supply line for supplying a power supply voltage to the regulator are connected by a switch. The current output capability is controlled by controlling the operation / non-operation of the regulator by controlling the power supply / disconnection.

According to a third aspect of the present invention, in the non-contact type IC card according to the second aspect, the switch is constituted by a MOS transistor, and a gate of the MOS transistor is controlled by transmission data to operate the regulator.
The non-operation control is performed.

According to a fourth aspect of the present invention, in the non-contact IC card according to the first aspect, the regulator is realized by a shunt regulator, and controls a power supply voltage detection level used for adjusting an output voltage of the regulator. The current output capability is controlled.

[0016]

FIG. 1 is a block diagram showing an embodiment of the present invention.
This will be described with reference to FIG. FIG. 1 shows an analog interface section 2a of an IC card 2 in a non-contact type IC card system for transmitting data to a reader / writer device by a load switching method.

As a load switching type modulation circuit, a MOS transistor switch M1 and a load resistor R1 are connected in series between both ends of an antenna coil. Data is transmitted to the reader / writer device by changing the load resistance.

The difference from the conventional circuit shown in FIG. 5 is that a MOS transistor is connected in series between the power supply line and the regulator 22.
The point is that the transistor switch (M2) is inserted. By controlling the gate of M2 by supplying an inverted signal of the transmission data via the inverter 24, the operation / non-operation of the regulator 22 is controlled.

FIG. 2 shows transmission data, the gate voltage of the transistor switch M2, the output voltage of the regulator 22, and the current consumption of the regulator 22 in the case of the configuration shown in FIG.

When the transmission data is "L" and the modulation transistor switch M1 is off, the regulator 22
Is performing normal operation. When the transmission data is "H" and the modulation transistor switch M1 is turned on, the transistor switch M2 is turned off and at the same time the regulator 2 is turned on.
Since the power supply line 2 is separated from the power supply line 25 and is in a non-operation state, current consumption due to operation delay is eliminated, and a power supply voltage drop can be suppressed to a minimum.

FIG. 3 shows an example of controlling the current output capability of the regulator by controlling the power supply voltage detection level used for adjusting the output voltage of the shunt regulator.
The comparator 41 compares the comparison reference level with the power supply voltage detection level generated by the resistance division, and controls the current flowing through the transistor M3 based on the output to stabilize the power supply voltage. When transmitting the data "L", the MOS transistor switch M4 is turned on in synchronization with the load resistance between the antenna and the coil L2 being turned on, the resistor R2 is short-circuited, and the power supply voltage detection level is reduced.
The current flowing through the transistor M3 is suppressed, so that a power supply voltage drop can be suppressed.

The regulator 22 may be controlled by a bipolar transistor, or a capacitor may be used instead of a resistor as an impedance for load switching.

[0023]

As described above, the non-contact type IC card of the present invention is configured to rectify a carrier wave signal received via an antenna, stabilize the signal via a regulator, and cover necessary power, and In a non-contact type IC card adopting a load switching method in which a signal is transmitted by varying the load impedance of the antenna at the time of transmission, the current output capability of the regulator is synchronized with transmission data at the time of signal transmission by the load switching method. Since the control means is provided to reduce the current consumption of the regulator as the load impedance of the antenna decreases, the power supply voltage drop during data transmission can be suppressed, and the success rate of data transmission can be improved. .

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an analog interface unit according to an embodiment of a non-contact type IC card of the present invention.

FIG. 2 is a diagram showing voltage, current, and signal waveforms of respective parts during load switching according to the embodiment;

FIG. 3 is a configuration diagram of a regulator according to the embodiment.

FIG. 4 is an overall configuration diagram of a non-contact type IC card system.

FIG. 5 is a configuration diagram of an analog interface unit of a conventional contactless IC card.

FIG. 6 is a diagram showing the voltages of various parts during load switching according to the conventional example;
Current and signal waveform diagrams

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Reader / writer apparatus 1a Analog interface section of reader / writer apparatus 1b Digital section of reader / writer apparatus 2 IC card 2a Analog interface section of IC card 2b Digital section of IC card 3 Non-volatile memory 21 Rectifier circuit 22 Regulator 23 Resonant capacitance 24 Inverter 25 Power supply line 41 Comparator L1 Reader / writer device antenna L2 IC card antenna M1 Data transmission control MOS transistor switch M2 Regulator control MOS transistor switch M3 Shunt regulator MOS transistor M4 Power supply voltage detection MOS transistor switch for level control R1 Load switching load resistor R2 Power supply voltage level detection resistor

Claims (4)

[Claims] The present invention is configured to rectify a carrier signal received via an antenna and to stabilize the signal via a regulator to cover necessary power. When transmitting to the outside, the load impedance of the antenna is varied to transmit a signal. Load to be transmitted
In a non-contact type IC card employing a switching system, means for controlling a current output capability of the regulator in synchronization with transmission data at the time of signal transmission by a load switching system is provided. A non-contact type IC card configured to reduce current consumption of the non-contact type IC card. The regulator is realized by a shunt regulator, and controls the operation / non-operation of the regulator by controlling connection / disconnection of the regulator and a power supply line for supplying a power supply voltage to the regulator by a switch. And controlling the current output capability by performing the control.
The non-contact IC card described in the above. 3. The non-contact IC card according to claim 2, wherein the switch is constituted by a MOS transistor, and controls the operation / non-operation of the regulator by controlling the gate of the MOS transistor with transmission data. 4. The non-contact IC card according to claim 1, wherein the regulator is realized by a shunt regulator, and controls a current output capability by controlling a power supply voltage detection level used for adjusting an output voltage of the regulator.