JPH1125238A - IC card - Google Patents

Abstract

(57) [Summary] [PROBLEMS] A waste of an IC card in an IC card system in which a plurality of IC cards are accommodated in a reader / writer, and the IC card receives operating power transmitted from the reader / writer by a power receiving antenna. Reduction of required power, etc. are realized. SOLUTION: In an IC card 1, when receiving power transmitted from a reader / writer, a switch switching means 6 opens a switch SW1 in a processing state where power consumption is small, so that a power receiving antenna 2 The sensitivity is reduced to reduce the received power. Note that the received power control means is constituted by the switch switching means 6 and the switch SW1. For example, when performing a process that consumes a large amount of power when the switch SW1 is in the open state, the switch switching unit 6 closes the switch SW1 with the power of the battery B to receive normal power. In addition to the above configuration, an information communication antenna 3 for communicating information, a control unit 4 for controlling processing, and a memory 5 for storing data are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an IC card of an IC card system in which a plurality of IC cards are accommodated in a reader / writer, and the IC card receives operating power transmitted from the reader / writer by a power receiving antenna. In particular, the present invention relates to an IC card that reduces received power in a processing situation where power consumption is small.

[0002]

2. Description of the Related Art An IC card formed by embedding a microcomputer chip and a memory on a card substrate having a size similar to that of a credit card or the like is expected to be put to practical use in various fields such as finance, distribution, transportation, and medical care. Have been. In an IC card system using such an IC card, power is transmitted and supplied from a reader / writer (R / W) to the IC card, and information such as control codes and data is communicated between the reader / writer and the IC card. Let me.

In power transmission and information communication between a reader / writer and an IC card, a non-contact method using electromagnetic waves is employed in addition to a contact method in which terminals are brought into contact with each other. Various modes are also being studied in the non-contact method. For example, an antenna is provided in each of the IC card and the reader / writer, and power is transmitted between the reader / writer and the IC card in a non-contact manner by electromagnetic wave transmission using these antennas. For transmitting and transmitting information.

In such an IC card using the non-contact method, for example, if the distance between the reader / writer and the IC card is about several tens of centimeters to 1.5 meters, information communication and the like are performed between them. It is known that is possible. In the future, even if the distance between the reader / writer and the IC card is as large as, for example, 5 meters, it is expected that information communication and the like will be possible between them. For this reason, it is envisioned that, for example, when a plurality of persons carrying IC cards pass through the gate at the same time, processing such as authenticating each of the persons by a reader / writer provided near the gate is performed by the IC card system. ing.

Here, an example of such an IC card system is shown in FIG. The system shown in FIG. 1 includes, for example, a reader / writer 21 installed near a gate, and a plurality of IC cards 31a, 31b, 31c,... Carried by each person passing through the gate. Have been. Further, in the same drawing, the plurality of IC cards 31a, 31b, 31c,... That is, the reader / writer 21 and the IC cards 31a, 31b, 31c,... Are located at a distance where power supply and information communication can be performed therebetween.

The reader / writer 21 has an IC card 31
, 31b, 31c,... and a power transmitting antenna 22 for transmitting power to the IC cards 31a, 31b,.
And an information communication antenna 23 for communicating information between the antennas 31c,..., And a control unit 24 for controlling power transmission processing, information communication processing, and the like.
It is connected to the. Note that the control unit 24 also performs processing such as communication control with an information processing device (not shown).

The IC cards 31a, 31b, 31c,...
, For receiving the power transmitted from the power transmission antenna 22 of the reader / writer 21, and the information communication antenna 23 of the reader / writer 23, respectively. Information communication antennas 33a, 33b, 33 for communicating information between
, and these two antennas control the power receiving process, the information communication process, and the like.
34b, 34c,...

Here, the power supplied from the reader / writer 21 to the IC cards 31a, 31b, 31c,.
.. Are operating power for operating the respective IC cards 31a, 31b, 31c,. In the following, the codes indicating the plurality of IC cards 31a, 31b, 31c,... Are collectively described as an IC card 31, a power receiving antenna 32, an information communication antenna 33, and a control unit 34. .

In the above system, a separate IC card 31 is carried by each person passing through the gate.
For example, when a plurality of persons pass through a gate while walking side by side along a passage having a width of 5 meters, the reader / writer 2
1 authenticates the identifier (ID) stored in the IC card 31 of each of these persons. That is, the reader / writer 21 supplies power to the IC cards 31 near the gate accommodated by the reader / writer 21 and performs information communication with the IC cards 31 for authentication and the like. As a result, the reader / writer 21 can authenticate a plurality of persons who pass through the gate at the same time, for example, as to whether or not each person is qualified to pass through the gate. Various kinds of information can be communicated with the IC card 31 carried by the person.

[0010] In the same manner, in the above-mentioned system, for example, it is possible to authenticate each of a plurality of livestock simultaneously passing through a ranch gate, and to identify each of a plurality of luggage flowing simultaneously on a belt conveyor. Can also.
As described above, in the IC card system as described above, for example, when it is necessary to simultaneously and individually authenticate and identify a plurality of objects, these processes can be particularly effectively performed.

Here, the reader / writers 21 and I
An example of a circuit configuration for performing power transmission of the C card 31 will be described in more detail with reference to FIG. As shown in the figure, the reader / writer 21 converts an AC current generated from an AC power supply 25 under the control of a control unit 24 into an amplifier (AMP).
26, and outputs the amplified AC current to the power transmitting antenna 22 composed of, for example, a coil.
As a result, an electromagnetic wave is generated in the coil of the power transmitting antenna 22, and the generated electromagnetic wave supplies power to the IC card 31 accommodated by the reader / writer 21.

That is, in the IC card 31, an electromotive force is generated in the power receiving antenna 32 composed of, for example, a coil due to the electromagnetic induction by the electromagnetic wave from the reader / writer 21, and the alternating current obtained by the electromotive force is generated. After the current is rectified by the diode D1, the current is smoothed by the capacitor C5. The DC voltage obtained in this manner is stabilized by the series regulator 36 and the capacitor C6, and is adjusted to a voltage suitable for operating the control unit 34 and the like. Supplied.

Further, the IC card 31 can be formed by using a parallel regulator. FIG. 9 shows an example of a circuit configuration of the IC card 31 in this case. In this circuit configuration, an alternating current obtained by an electromotive force generated in the power receiving antenna 32 is rectified by a diode D2, and then smoothed by a capacitor C7. It is stabilized by 37 and supplied to the control unit 34, the memory 35 and the like.

In the circuit configuration shown in FIG. 8, since the current supplied to the control unit 34 passes through the series regulator 36, the control unit 34
It is known that a voltage drop by the regulator 36 occurs in the power transmitted to the power supply. Therefore, IC
In general, in the card 31, for example, in order to supply more power to the control unit 34 even when the power transmitted from the reader / writer 21 is reduced,
A circuit configuration using the parallel regulator 37 shown in FIG. 9 is often used.

That is, in the parallel regulator 37,
When the voltage input to the regulator 37 decreases, no current flows, so that the series regulator 36
Power can be more efficiently supplied to the control unit 34 as compared with the case where. In the parallel regulator 37, when excessive power is supplied from the reader / writer 21 and the voltage input to the regulator 37 increases,
In order to stabilize the output voltage, excess power is lost as heat, and in such a case, the power from the reader / writer 21 is wastefully consumed.

As described above, the circuit configuration of the IC card 31 has been described with reference to FIGS. 8 and 9. In any of the cases shown in FIGS. When the power supplied to 31 decreases,
Since sufficient power is no longer supplied to the control unit 34 and the like, it is necessary to transmit a sufficient amount of power from the reader / writer 21 to operate the IC card 31. The amount of power consumed by the IC card 31 varies depending on the status of the processing performed by the control unit 34 and the like. In general, the process of waiting for reception of a signal from the reader / writer 21 transmits a signal to the reader / writer 21. The amount of power consumed is smaller than that of the processing for rewriting the contents of the memory 35 or the like.

[0017]

However, in the above-described IC card system, for example, electric power may be simultaneously supplied from a reader / writer to a plurality of IC cards, and the reader / writer needs to operate all of these IC cards. Since sufficient power had to be supplied, very large power had to be transmitted from the reader / writer. For this reason, problems such as an increase in the cost of the power transmitted from the reader / writer,
There was a problem that wasted power was increased. Similarly, since it is necessary to provide the reader / writer with a power supply for large power, an antenna for transmitting power, and the like, it is difficult to reduce the size and cost of the reader / writer.

More specifically, it is known that the efficiency of power transmission from a reader / writer to an IC card is generally on the order of several percent to several tens percent.
The amount of power actually transmitted from the reader / writer to the IC card is W. In this case, for example, when power is simultaneously supplied from a reader / writer to N IC cards, a power amount of about W / N is supplied to each IC card. Here, the amount of power of about W / N must be a sufficient amount of power to operate the IC card, and the amount of power received by the IC card is between the IC card and the reader / writer. Since it depends on the distance and the like, there is a case where a very large power must be supplied from the reader / writer as described above.

In addition, when a process that consumes a large amount of power is performed by an IC card, it is easy for the power to be supplied insufficiently. Even if a process that consumes a large amount of power is performed by all the IC cards performed, there is a problem that an excessive amount of power must be transmitted, which is sufficient. That is, for example, IC
Even when the card is performing processing with low power consumption, excess power exceeding the power required for the processing may be supplied from the reader / writer. For example, there is a problem that the used power is wastefully consumed as heat in the IC card. As described above, a plurality of I
It was difficult to supply necessary and sufficient electric power to each of the C cards.

The present invention has been made in order to solve such a conventional problem. When the operating power transmitted from the reader / writer is received by the power receiving antenna, the received power is reduced according to the processing situation. IC that can be controlled
The purpose is to provide the card. More specifically,
It is an object of the present invention to provide an IC card capable of reducing received power in a processing situation where power consumption is small. More specifically, the above-described IC card is applied to an IC card system in which a plurality of IC cards are accommodated in a reader / writer and the IC card receives operating power transmitted from the reader / writer through its power receiving antenna. Then, for example, it is possible to reduce the amount of power wasted in the system by causing each IC card to receive necessary and sufficient power.

[0021]

In order to achieve the above object, in an IC card according to the present invention, when an operating power transmitted from a reader / writer is received by a power receiving antenna, a received power control means controls power consumption. The sensitivity of the power receiving antenna is reduced in a processing situation where the power consumption is small, thereby reducing the received power. The IC card according to the present invention accommodates a plurality of IC cards in a reader / writer,
The present invention is suitable for application to an IC card system in which an IC card receives operating power transmitted from a reader / writer by using a power receiving antenna.

Therefore, in the IC card, when a process that consumes a small amount of power is performed, for example, waiting for reception from a reader / writer, the sensitivity of the power receiving antenna is reduced, thereby reducing the received power. As a result, power that is large enough to perform such low power consumption processing is received. Further, in the IC card, when a process that consumes a large amount of power such as a transmission process to a reader / writer is performed, the sensitivity of the power receiving antenna cannot be reduced, and such a process that consumes a large amount of power is performed. Large enough power is received.

As described above, in the IC card, for example, necessary and sufficient power is received, so that the power wasted by the IC card can be reduced. Further, for example, when such an IC card is applied to the above-mentioned IC card system, necessary and sufficient electric power can be simultaneously supplied from the reader / writer to each of the plurality of IC cards. Can be reduced. Further, since the power wasted by the IC card is reduced, in the above-mentioned IC card system, for example, the magnitude of the power transmitted simultaneously from the reader / writer can be reduced, thereby reducing the size of the reader / writer. Cost reduction and the like can be realized.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment according to the present invention will be described with reference to the drawings. FIG. 1 shows a configuration example of an IC card 1 according to a first embodiment of the present invention.
Has a power receiving antenna 2 for receiving power,
An information communication antenna 3 for communicating information, a control unit (controller) 4 for controlling and executing various processes,
A memory 5 for storing data, a switch SW1 for opening and closing a circuit connection, and a battery B for supplying power to the switch SW1 are provided.

In this embodiment and the second to sixth embodiments to be described later, this IC card 1 accommodates a plurality of IC cards in a reader / writer, and transmits the IC card from the reader / writer through its power receiving antenna. Provided in an IC card system for receiving the operating power obtained. Note that this IC
As for the configuration of the card system, only the internal configuration of the IC card 1 is different from that of the system shown in FIG. 7, and the description of the configuration of the reader / writer is omitted. The circuit configuration for rectifying, smoothing, and stabilizing the power received by the power receiving antenna 2 of the IC card 1 is also the same as, for example, the case shown in FIGS. Examples and second to sixth to be described later
The description is omitted in the embodiment.

The power receiving antenna 2 is composed of, for example, a coil wound a plurality of times in a tubular shape. One end of the coil is connected to the control unit 4 via a conductor, and the other end is connected to the switch SW1. The control unit 4 is connected to the control unit 4 via the control unit 4. In addition, the power receiving antenna 2 non-contactly receives the power transmitted as an electromagnetic wave from the reader / writer. The information communication antenna 3 is composed of, for example, a coil wound a plurality of times in a tubular shape, and both ends of the coil are connected to the control unit 4. As a result, the information communication antenna 3 transmits and receives information as electromagnetic waves to and from the reader / writer in a non-contact manner.

The control section 4 comprises a CPU and the like, and stores a control program for performing various processes such as information communication. Accordingly, the control unit 4 performs, for example, information transmission processing and information reception processing on the information communication antenna 3.
, And a process of writing data to the memory 5. Further, the control unit 14 is provided with a switch switching means 6 for switching the open / close state of the switch SW1 according to the status of the processing, and the details of this means 6 will be described later.

The memory 5 is a means for storing data, for example, an EEPR whose storage contents can be rewritten.
OM (Electrically Erasable Programmable ROM)
It is composed of The switch SW1 is provided between the other end of the power receiving antenna 2 and the control unit 4 as described above, and is a unit for switching a connection state of a circuit therebetween.

When the switch SW1 is closed (switch O
When N is set, both ends of the power receiving antenna 2 are connected to the control unit 14, whereby the power received by the power receiving antenna 2 is supplied to the control unit 14, the memory 5, and the like. On the other hand, when the switch SW1 is open (the switch OF
In the case of F), the circuit between the other end of the power receiving antenna 2 and the control unit 14 is cut off, so that the power receiving antenna 2 does not receive power.

The battery B is a means for supplying electric power to the switch switching means 6 and the switch SW1. For example, a minute power supply, a capacitor for storing electric power, or a weak electric power from a coil is obtained by an electromagnetic wave from a reader / writer. It is composed of circuits and the like. Here, the battery B is used when the switch SW1 is closed when the switch SW1 is open. That is,
When the switch SW1 is open, the power receiving antenna 2
Power is not received by the switch switching means 6
Switches the switch SW1 using the power of the battery B. Therefore, the battery B only needs to store, for example, a small amount of electric power sufficient to perform such a switching process.

Here, as described above, in this embodiment,
When the switch SW1 is opened, the power receiving antenna 2
The connection between the other end and the control unit 4 is released,
In this case, the sensitivity of the power receiving antenna 2 becomes substantially zero, and no power is received. For this reason, in the present embodiment, it is set in the switch switching means 6 to open the switch SW1 in a state where no processing is performed. The switch switching means 6 is set to close the switch SW1 when performing some processing.

As described above, the switch switching means 6 switches the switch SW1 in a situation where a process with small power consumption is performed by the control unit 4 or the like (a situation where no power is consumed in this embodiment, that is, a situation where no process is performed). Is switched to the open state, thereby lowering the sensitivity of the power receiving antenna 2 and lowering the received power. Also, the switch switching means 6
For example, when the switch SW1 is in the open state, the control unit 4
For example, when a process that consumes a large amount of power is performed, or when a larger amount of power is required than when the device is in the open state (in this embodiment, when any process that consumes power is performed).
Then, the switch SW1 is switched to the closed state, so that the power received by the power receiving antenna 2 becomes a normal power amount (that is, the power amount not reduced as described above).

In this embodiment, the switch switching means 6
By switching the open / close state of the switch SW1 in accordance with the above setting, the reception power control means for reducing the sensitivity of the power reception antenna in the processing situation where the power consumption is small, thereby reducing the reception power is configured. Thus, the IC card 1 can switch between receiving and not receiving power from the reader / writer according to the processing situation.

FIG. 2 shows an IC according to a second embodiment of the present invention.
1 shows an example of the configuration of a card 11.
Has a power receiving antenna 2 for receiving power,
An information communication antenna 3 for communicating information, a control unit 4 for controlling and executing various processes, a memory 5 for storing data, and a switch SW2 for opening and closing a circuit connection;
A resistor R is provided. Here, since the configurations of the power receiving antenna 2, the information communication antenna 3, the control unit 4, and the memory 5 are the same as those in the first embodiment, the description thereof is omitted. Further, the present embodiment is different from the first embodiment in the configuration for lowering the sensitivity of the power receiving antenna 2, and the description of other configurations and communication processing is omitted.

In the IC card 11 according to the present embodiment, one end of the power receiving antenna 2 is connected to the control unit 4 via a conductor, and between the other end and the control unit 4, A switch SW2 for opening and closing the connection is provided. A resistor R is provided between the other end of the power receiving antenna 2 and the control unit 4 in parallel with the switch SW2. When the switch SW2 is opened, the other end of the power receiving antenna 2 is connected to the control unit 14 via the resistor R. As a result, the same effect as that of the series regulator can be obtained. For example, the processing efficiency can be improved as compared with the case where the voltage is stabilized by the parallel regulator. Can be.

Here, the value of the resistor R is r,
Further, the above description will be described more specifically by taking as an example a case where the values of the load resistances applied to both ends of the power receiving antenna 2 when the influence of the resistance R is removed are the same r. That is, when the other end of the power receiving antenna 2 and the control unit 4 are connected via the resistor R, the magnitude of the total resistance applied to both ends of the power receiving antenna 2 becomes 2r. The amount of current flowing to the control unit 4 is 1 /
It becomes 2. Also, since the magnitude of the voltage generated by the electromagnetic induction is the same as when there is no resistor R, the amount of power consumed by the IC card 11 is 1 / compared to the case without the resistor R.
It becomes 2.

In the above case, the voltage generated by the electromagnetic induction is divided into 1/2 by the original load resistance and the resistance R, and the resistance R consumes power as heat or the like. However, the amount of power actually supplied to the control unit 4 and the like is １ ／ of that when no resistor R is provided. As described above, when the switch SW2 is opened, the power receiving antenna 22
, The resistance value applied to both ends of the antenna 2 increases, thereby reducing the amount of power received by the antenna 2.

When the switch SW2 is closed, the power receiving antenna 2 is connected via the switch SW2.
Is connected to the control unit 4, for example, power can be transmitted from the power receiving antenna 2 to the control unit 4 and the like without loss. Power that has not been reduced as described above) is received.

In the present embodiment, the switch switching means 6 switches the switch SW2 to the open state in a situation where a process with small power consumption is performed by the control unit 4 or the like, thereby lowering the sensitivity of the power receiving antenna 2. As a result, the received power is reduced. Further, the switch switching means 6 is provided, for example, when a process that consumes a large amount of power is performed by the control unit 4 or the like when the switch SW2 is open, or when a larger amount of power is required than when the switch SW2 is open. For example, the switch SW2 is switched to the closed state, so that normal power is received by the power receiving antenna 2 and supplied to the control unit 4 and the like.

Here, the processing that consumes a relatively small amount of power in the control unit 4 or the like of the IC card 11 includes, for example, processing of receiving information from a reader / writer, processing of waiting for a command from the reader / writer, and the like. . Here, the command waiting state is, for example, accommodated in a reader / writer,
When the own ID is transmitted to the reader / writer and is identified, the state in which the reader / writer is waiting for the communication by designating the own ID and, for example, the reader / writer Is stored in, that is, when it is in a position where power supply and information communication can be performed with the reader / writer,
This is a state in which there is no communication request from the reader / writer, and the apparatus is on standby.

In this command waiting state, the capability of a circuit such as a CPU inside the IC card 11 can be reduced, so that, for example, a process for receiving information from a reader / writer is performed. Power consumption can be further reduced. In addition, for example, a command transmitted from the reader / writer to the IC card 11 can be communicated at a lower speed than in the case of normal information communication, and this command can be easily identified by composing a pulse or tone modulation of a fixed period. The IC card 11
In this case, a circuit for receiving received information, a CPU for detecting a signal from a reader / writer, or the like can be operated at a low speed to further reduce power consumption.

The processing that consumes a relatively large amount of power in the control unit 4 or the like of the IC card 11 includes, for example, processing of calculating and processing information received from a reader / writer by a CPU or the like, and processing of a memory 5 such as an EEPROM. And a process of transmitting a response signal to the reader / writer. That is, in the processing of the received information by the CPU or the like,
For example, the amount of calculation is particularly large when information encrypted by a reader / writer is decrypted, and when this decryption is performed at a relatively high speed, a large amount of power is consumed. In the process of writing data to the memory 5, for example, EEPRO
Particularly when M is used as the memory 5, a large amount of power is consumed. Further, in the transmission process to the reader / writer, a large amount of power is consumed as power for transmitting and outputting, power consumed by a circuit for controlling the transmission process, and the like.

In the present embodiment, based on the above, the switch switching means 6 causes the switch SW2 to be in the open state in a processing state where the power consumption is small, for example, the reception processing or the processing in the command waiting state. Is set. The switch switching means 6 is set to close the switch SW2 in a processing situation where the power consumption is large, such as processing of received information, processing of writing to the memory 5, and processing of information transmission.

In this embodiment, the switch switching means 6
By switching the open / close state of the switch SW2 in accordance with the above setting, the reception power control means for lowering the sensitivity of the power reception antenna in a processing situation where the power consumption is small, thereby reducing the reception power is configured. As described above, the IC card 11 can control the amount of power received from the reader / writer according to the processing situation.

FIG. 3 shows an IC according to a third embodiment of the present invention.
2 shows a configuration example of the card 12. Note that the present embodiment is different from the second embodiment only in the configuration for lowering the sensitivity of the power receiving antenna 2, and thus the description of other circuit configurations, communication processing, and the like will be omitted. IC shown in the figure
In the card 12, as described above, the coil constituting the power receiving antenna 2 is wound a plurality of times, for example, in a tubular shape, and one end of the coil is connected to the control unit 4 via a conductor. At the other end, a switch SW3 for switching the number of turns of a coil used for power reception is provided between the power reception antenna 2 and the control unit 4.

That is, one end of the power receiving antenna 2 is connected to the control unit 4 via a conductor, and the other end of the power receiving antenna 2 is connected to the points a and b in FIG. It is configured to be able to connect to the control unit 4 by switching between points. For example, switch S
When the point a and the control unit 4 are connected by W3, the number of turns of the coil used for power reception becomes n. Further, for example, when the point b and the control unit 4 are connected by the switch SW3, the number of turns of the coil used for power reception is m, which is smaller than the above n.

Here, since the induced electromotive force generated in the coil is generally proportional to the number of turns of the coil, the point b is connected to the control unit 4 when the point a is connected to the control unit 4. More power is received by the power receiving antenna 2 as compared with the case where the power is received. In this embodiment, the switch switching means 6 switches the switch SW3 to the point b in a situation where the processing with small power consumption is performed by the control unit 4 or the like, thereby reducing the sensitivity of the power receiving antenna 2 and performing reception. Reduce power. In addition, the switch switching means 6 is used, for example, when a process that consumes a large amount of power is performed by the control unit 4 when the switch SW3 is connected to the point b, or when the switch SW3 is connected to the point b. Switch SW3 is switched to point a when
Normal power (that is, received power when the number of turns of the coil is n) is received by the power receiving antenna 2 and supplied to the control unit 4 and the like.

For this reason, the switch switching means 6 is set to switch the switch SW3 to the point b in a processing situation where the power consumption is small, for example, a reception processing or a processing in a command waiting state. The switch switching means 6 is set to switch the switch SW3 to the point a in a processing situation where the power consumption is large, such as processing of received information, processing of writing to the memory 5, and processing of transmitting information. In this embodiment, the switch switching means 6
By switching the switch SW3 in accordance with the above setting, the reception power control means for reducing the sensitivity of the power reception antenna in a processing situation where the power consumption is small, and thereby reducing the reception power is configured. Thus, IC
The card 12 can control the amount of power received from the reader / writer in accordance with the status of processing.

FIG. 4 shows an IC according to a fourth embodiment of the present invention.
An example of the configuration of the card 13 is shown. Note that the present embodiment is different from the second embodiment only in the configuration for lowering the sensitivity of the power receiving antenna 2, and thus the description of other circuit configurations, communication processing, and the like will be omitted. IC shown in the figure
In the card 13, both ends of the power receiving antenna 2 are connected to the control unit 4 via conductors, and a capacitor C1 is connected to the control unit 4 in parallel with the power receiving antenna 2. Further, a circuit including a capacitor C2 and a switch SW4 is provided in parallel with both the power receiving antenna 2 and the capacitor C1 for the control unit 4. Here, the switch SW4 is means for opening and closing the connection between the capacitor C2 and one end of the power receiving antenna 2.

By opening and closing the switch SW4, the frequency (resonance frequency) of the electromagnetic wave most efficiently received by the power receiving antenna 2 can be switched. That is, generally, a Q value is known as a quantity representing the goodness of the resonance circuit, and the greater the Q value, the larger the electromotive force generated in the resonance circuit. In general, the Q value is known as a value obtained by multiplying a value obtained by dividing energy stored in the resonance circuit by energy lost in one cycle by a predetermined coefficient.

In this embodiment, when the switch SW4 is opened and only the capacitor C1 is connected to the power receiving antenna 2, it is configured to resonate with an electromagnetic wave transmitted from the reader / writer. That is, in this case, the resonance frequency coincides with the frequency of the electromagnetic wave from the reader / writer, the Q value increases, and the power receiving antenna 2
The generated electromotive force increases. When the switch SW4 is closed and both the capacitor C1 and the capacitor C2 are connected to the power receiving antenna 2, the resonance frequency is shifted so that the frequency does not match the frequency of the electromagnetic wave from the reader / writer. Have been. Therefore, in this case, the amount of power received by the power receiving antenna 2 is reduced as compared with the case where the switch SW4 is opened.

That is, the switch switching means 6 switches the switch SW4 to the closed state in a state where the processing with small power consumption is performed by the control unit 4 or the like, thereby reducing the sensitivity of the power receiving antenna 2 and performing reception. Reduce power. Further, the switch switching means 6 includes, for example, a switch SW
The switch SW4 is switched to the open state when the control unit 4 or the like performs a process that consumes a large amount of power when the control unit 4 is in the closed state, or when a larger amount of power is required than in the closed state, Thus, normal power (that is, power when the resonance frequency is not shifted) is received by the power receiving antenna 2 and supplied to the control unit 4 and the like.

For this reason, the switch switching means 6 is set to switch the switch SW4 to the closed state in a processing state where the power consumption is small, for example, a reception processing or a processing in a command waiting state. The switch switching means 6 is set to switch the switch SW4 to the open state in a processing situation where the power consumption is large, such as processing of received information, processing of writing to the memory 5, and processing of transmitting information. In this embodiment, the switch switching means 6 switches the switch SW4 in accordance with the above setting, thereby reducing the sensitivity of the power receiving antenna in a processing situation where the power consumption is small, and thereby reducing the received power. Control means is configured.

As described above, the IC card 13 can control the amount of electric power received from the reader / writer according to the processing situation. Contrary to the above configuration, when the switch SW4 is closed and both the capacitor C1 and the capacitor C2 are connected to the antenna 2 for power reception, the resonance frequency due to the parallel capacitance of these capacitors changes from the reader / writer. It may be configured to match the frequency of the electromagnetic wave. In this case, when the switch SW4 is opened and only the capacitor C1 is connected to the power receiving antenna 2, the resonance frequency shifts and the amount of power received by the power receiving antenna 2 decreases.

FIG. 5 shows an IC according to a fifth embodiment of the present invention.
2 shows a configuration example of the card 14. Note that the present embodiment is different from the second embodiment only in the configuration for lowering the sensitivity of the power receiving antenna 2, and thus the description of other circuit configurations, communication processing, and the like will be omitted. IC shown in the figure
In the card 14, both ends of the power receiving antenna 2 are connected to the control unit 4 via conductors, and the capacitor C3 is connected to the control unit 4 in parallel with the power receiving antenna 2.
And a circuit including the switch SW5. Here, the switch SW5 is means for opening and closing the connection between the capacitor C3 and one end of the power receiving antenna 2.

That is, by opening and closing the switch SW5, the frequency (resonance frequency) of the electromagnetic wave most efficiently received by the power receiving antenna 2 can be switched as in the case of the fourth embodiment. In this embodiment,
When the switch SW5 is closed and the capacitor C3 is connected to the power receiving antenna 2, the Q value is increased by resonating with an electromagnetic wave transmitted from the reader / writer. Further, when the switch SW5 is opened and the capacitor C3 is no longer connected to the power receiving antenna 2, the resonance frequency is shifted so that it does not match the frequency of the electromagnetic wave from the reader / writer.

That is, the switch switching means 6 switches the switch SW5 to the open state in a state where the processing with small power consumption is performed by the control unit 4 or the like, thereby reducing the sensitivity of the power receiving antenna 2 and performing reception. Reduce power. Further, the switch switching means 6 includes, for example, a switch SW
The switch SW5 is switched to the closed state when the control unit 4 or the like performs a process that consumes a large amount of power when the control unit 5 is in the open state, or when a larger amount of power is required than in the open state, Thus, normal power (that is, power when the resonance frequency is not shifted) is received by the power receiving antenna 2 and supplied to the control unit 4 and the like.

For this reason, the switch switching means 6 is set to switch the switch SW5 to the open state in a processing situation where the power consumption is small, for example, a reception processing or a processing in a command waiting state. Further, the switch switching means 6 is set to switch the switch SW5 to the closed state in a processing situation where a large amount of power is consumed, such as processing of received information, processing of writing to the memory 5, and processing of transmitting information. In this embodiment, the switch switching means 6 switches the switch SW5 in accordance with the above setting, thereby reducing the sensitivity of the power receiving antenna in a processing situation where the power consumption is small, and thereby reducing the received power. Control means is configured.

As described above, the IC card 14 can control the amount of power received from the reader / writer in accordance with the status of processing. Contrary to the above configuration, when the switch SW5 is opened and the capacitor C3 is no longer connected to the power receiving antenna 2, the resonance frequency is configured to match the frequency of the electromagnetic wave from the reader / writer. You may. In this case, when the switch SW5 is closed and the capacitor C3 is connected to the power receiving antenna 2, the resonance frequency shifts and the received power decreases.

FIG. 6 shows an IC according to a sixth embodiment of the present invention.
An example of the configuration of the card 15 is shown. Note that the present embodiment is different from the second embodiment only in the configuration for lowering the sensitivity of the power receiving antenna 2, and thus the description of other circuit configurations, communication processing, and the like will be omitted. IC shown in the figure
In the card 15, one end of the power receiving antenna is connected to the control unit 4 via a conductor, and the other end of the power receiving antenna 2 is connected to the points c and d in FIG.
It is configured to be switchable between points. That is, when the switch SW6 is switched to the point c, the number of turns of the coil of the power receiving antenna 2 used for power reception becomes p, and when the switch SW6 is switched to the point d, the power used for power reception is The number of windings of the coil of the receiving antenna 2 is q, which is a number different from p described above.

The switch SW6 and the control unit 4
And a capacitor C4 is connected between the conductor connecting the power receiving antenna and the one end of the power receiving antenna 2. Here, in general, when the number of turns of the coil is different, the magnitude of the inductance of the coil is different. Therefore, the resonance frequency of the circuit is different between the case where the number of turns of the coil of the power receiving antenna 2 is p and the case where the number of turns is q. Are different. That is, the switch S
By opening and closing W6, the frequency (resonance frequency) of the electromagnetic wave most efficiently received by the power receiving antenna 2 can be switched, as in the case of the fourth embodiment.

In this embodiment, when the switch SW6 is connected to the point c and the number of turns of the coil of the power receiving antenna 2 becomes p, the Q value is resonated with the electromagnetic wave transmitted from the reader / writer. It is configured to be large. Also, when the switch SW6 is connected to the point d and the number of turns of the coil of the power receiving antenna 2 becomes q, the resonance frequency shifts and does not match the frequency of the electromagnetic wave from the reader / writer.

That is, the switch switching means 6 switches the switch SW6 to the point d in a situation where the control unit 4 or the like performs a process with small power consumption, thereby lowering the sensitivity of the power receiving antenna 2 and performing reception. Reduce power. Further, the switch switching means 6 includes, for example, a switch SW
The switch is used when a large amount of power is consumed by the control unit 4 or the like when the terminal 6 is connected to the point d, or when a larger amount of power is required than when the terminal 6 is connected to the point d. The SW 6 is switched to the point c so that the power receiving antenna 2 receives normal power (that is, power when the resonance frequency is not shifted) and supplies the power to the control unit 4 and the like.

For this reason, the switch switching means 6 is set to switch the switch SW6 to the point d in a processing situation where the power consumption is small, for example, a reception processing or a processing in a command waiting state. The switch switching means 6 is set to switch the switch SW6 to the point c in a processing situation where the amount of power consumption is large, such as processing of received information, processing of writing to the memory 5, and processing of information transmission. In this embodiment, the switch switching means 6
By switching the switch SW6 in accordance with the above setting, the reception power control means for lowering the sensitivity of the power receiving antenna in a processing situation where the power consumption is small and thereby reducing the reception power is configured.

As described above, the IC card 15 can control the amount of power received from the reader / writer in accordance with the status of processing. Note that, contrary to the above configuration, when the switch SW6 is switched to the point d, the resonance frequency may be configured to match the frequency of the electromagnetic wave from the reader / writer. In this case, when the switch SW6 is switched to the point c, the resonance frequency shifts and the received power decreases.

As shown in the fourth to sixth embodiments, for example, by switching the inductance of the coil of the power receiving antenna 2 and the capacitance of the capacitor connected to the antenna 2, the power receiving antenna 2 Can be switched, whereby the amount of power received by the antenna 2 can be controlled. In the above, as a preferred mode, whether or not the resonance frequency of the circuit is made to coincide with the frequency of the electromagnetic wave from the reader / writer is switched. However, such a switching method is not necessarily used. In other words, the closer these frequencies are, the higher the received power becomes,
If the configuration can be switched to a different resonance frequency depending on the processing situation, the received power amount can be controlled thereby.

As shown in the first to sixth embodiments,
In the IC card according to the present invention, the sensitivity of the power receiving antenna can be reduced in a processing situation where the power consumption is small, and thus the received power can be reduced. By controlling the received power according to the processing status in this way, the IC card receives necessary and sufficient power from the reader / writer, so that the power received by the IC card is not wasted.

For example, for a reader / writer, a plurality of ICs
In an IC card system accommodating cards, necessary and sufficient electric power can be supplied to a plurality of IC cards accommodated by a reader / writer. For this reason,
If the number of IC cards accommodated in the reader / writer is the same, it is only necessary to transmit less power from the reader / writer than in the conventional case. Thus, for example, the magnitude of the power transmitted simultaneously from the reader / writer is reduced. Can be smaller.

More specifically, for example, when a plurality of IC cards are stored in a reader / writer,
When information transmission processing, memory rewriting processing, and the like are being performed by the C card, other IC cards are generally in a state of waiting for an instruction from the reader / writer, and are in a processing state of low power consumption. . In such a case, for example, by reducing the reception power in the other IC card based on not receiving an operation request from the reader / writer, sufficient power is received by the specific IC card. Can be guaranteed. In this way, an IC card performing a process that consumes a large amount of power can be supplied with more sufficient power than other IC cards that do not require much power, thereby increasing the amount of power consumption. It is possible to stabilize the operation of the IC card that is performing the process, and to ensure that the process is performed.

As described above, in the above-described IC card system, it is possible to reduce wasted power and the like, so that it is possible to reduce the cost of power and to transmit large power from the reader / writer. Since it is not necessary to reduce the size of the reader / writer, the size and cost of the reader / writer can be reduced. Also, for example, when transmitting the same amount of power from the reader / writer as in the conventional case, a larger number of IC cards can be accommodated by the reader / writer simultaneously than in the conventional case.

As a configuration for lowering the sensitivity of the power receiving antenna provided in the IC card, there are first to sixth
The configuration is not limited to that shown in the embodiment, and any configuration may be used. In short, any configuration may be used as long as the received power can be reduced in a processing situation where power consumption is small.

In the first to sixth embodiments, the information transmitting antenna for transmitting information and the information receiving antenna for receiving information are commonly used as the information communication antenna in the IC card. Although an example has been described, for example, the information transmitting antenna and the information receiving antenna may be configured separately. In the first to sixth embodiments, I
In the C card, an example is shown in which the power receiving antenna and the information communication antenna are configured separately.
For example, a configuration in which a power receiving antenna and an information communication antenna, an information transmitting antenna, and an information receiving antenna are shared may be used.

In the second to sixth embodiments, unlike the first embodiment, the power supplied to the IC card does not become zero regardless of the switching state of the switches SW2 to SW6. As described in the second to sixth embodiments, the battery does not have to be provided in the IC card.

When the reader / writer simultaneously communicates information with a plurality of IC cards as in the above-described IC card system, congestion control can be performed to avoid interference. As a method of congestion control, for example, a method of changing the frequency of a signal transmitted from each IC card, or time division so that response signals transmitted from each IC card to a reader / writer do not overlap at the same time. A method or the like is used. Here, as a specific example of the latter congestion control using time division, for example, a unique identifier (ID) is provided for each IC card,
After receiving a signal from the reader / writer, each card transmits a response signal to the reader / writer using its own ID when a random time obtained by random number generation processing or the like has elapsed.

As a result, when the response signals from two or more IC cards do not overlap at the same time,
The reader / writer can receive a response signal from one IC card, confirm the ID thus received, and notify the corresponding IC card that the ID has been received. Further, in the IC card notified of the recognition of its own ID by the reader / writer, transmission of the signal to the reader / writer is temporarily stopped.

By repeating such processing, 2
The probability that response signals from more than one IC card overlap at the same time gradually decreases. As a result, the reader / writer can recognize the IDs of all the IC cards accommodated by the reader / writer. it can. And
After the reader / writer recognizes the IDs of all the IC cards in this manner, the reader / writer can perform information communication with a specific IC card by designating these IDs.

[0077]

As described above, the IC according to the present invention is
According to the card, when the operating power transmitted from the reader / writer is received by the power receiving antenna, the sensitivity of the power receiving antenna is controlled according to the processing situation, so that the received power is controlled according to the processing situation. Can be controlled. More specifically, since the sensitivity of the power receiving antenna is reduced in a processing situation where the power consumption is small, the received power can be reduced in a processing situation where the power consumption is small. For this reason, the IC card according to the present invention accommodates a plurality of IC cards in a reader / writer,
The present invention is applied to an IC card system in which an IC card receives operating power transmitted from a reader / writer by its power receiving antenna. For example, the power transmitted from the reader / writer is obtained by causing each IC card to receive necessary and sufficient power. , And the amount of power wasted in the system can be reduced.

[Brief description of the drawings]

FIG. 1 is a configuration example of an IC card according to a first embodiment of the present invention.

FIG. 2 is a configuration example of an IC card according to a second embodiment of the present invention.

FIG. 3 is a configuration example of an IC card according to a third embodiment of the present invention.

FIG. 4 is a configuration example of an IC card according to a fourth embodiment of the present invention.

FIG. 5 is a configuration example of an IC card according to a fifth embodiment of the present invention.

FIG. 6 is a configuration example of an IC card according to a sixth embodiment of the present invention.

FIG. 7 is an example of an IC card system.

FIG. 8 is a configuration example of an IC card according to a conventional example.

FIG. 9 is a configuration example of an IC card according to a conventional example.

[Explanation of symbols]

1, 11, 12, 13, 14, 15, ... IC card, S
W1, SW2, SW3, SW4, SW5, SW6 switch, 2 antenna for power reception, 3 antenna for information communication, 4 control unit, 5 memory, B
Battery, 6. switch switching means, R, resistor,
C1, C2, C3, C4, capacitors,

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Takahiro Watanabe, Inventor Kokusai Denki Co., Ltd., 3-14-20 Higashinakano, Nakano-ku, Tokyo (72) Inventor Manabu Manabu 3--14-20, Higashinakano, Nakano-ku, Tokyo Kokusai Electric (72) Inventor Isao Sone 3--14-20 Higashinakano, Nakano-ku, Tokyo Kokusai Electric Co., Ltd.

Claims (1)

[Claims] 1. An IC card in an IC card system in which a plurality of IC cards are accommodated in a reader / writer and the IC card receives operating power transmitted from the reader / writer by a power receiving antenna, the power consumption is small. An IC card, comprising: a reception power control unit that lowers the sensitivity of a power reception antenna in a processing situation, thereby reducing reception power.