JP2001222696A - Non-contact ic card and non-contact ic card communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem that a communication hindrance cause such as deterioration in modulation data, reduction in the output voltage of a voltage generating circuit or the occurrence of over-voltage has existed in a non-contact IC card. SOLUTION: The modulation circuit 40 of the non-contact IC card changes a capacitance load to perform modulation. Then the resonance frequency of a resonance circuit 3 is shifted to suppress deterioration in modulation data and reduction in the output voltage of a voltage generating circuit 33. Besides, a circuit with a configuration being the same as that of the circuit 40 is utilized and the capacitance of the resonance circuit is made to be variable by an output voltage so that the over-voltage is prevented from occurring.

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 equipped with a semiconductor integrated circuit and a non-contact type IC card communication system.

[0002]

2. Description of the Related Art Conventional non-contact type I mounted on a semiconductor integrated circuit
The technique relating to the C card will be described with reference to FIGS.

FIG. 8 is a block diagram showing a configuration of a conventional non-contact type IC card and a diagram showing transmission and reception of radio waves with a reader / writer.

[0004] In FIG. 8, a non-contact type IC card 1 comprises:
It comprises an analog circuit 2 for transmitting and receiving data by radio waves in a non-contact manner and generating a power supply voltage, a nonvolatile memory 14 for storing data, and a digital circuit 13 for controlling data to be transmitted and received.
The analog circuit 2 includes a voltage generation circuit 3 for receiving a radio wave to generate a voltage, a demodulation circuit 9 for demodulating received data, and a modulation circuit 10 for modulating transmission data.

[0005] The non-contact type IC card 1 and the reader / writer 15 transmit and receive radio waves 17 through the antenna coil 5 of the non-contact type IC card 1 and the antenna coil 16 of the reader / writer 15 which are connected to each other.
When the non-contact type IC card 1 receives the radio wave 17, an AC voltage is generated at both ends of the antenna coil 5. The generated AC voltage is converted into a DC voltage by the rectifier circuit 7 in the voltage generating circuit 3 and supplied to each block as an output voltage V.
Data transmitted and received between the non-contact type IC card 1 and the reader / writer 15 is superimposed on an AC voltage and demodulated by the demodulation circuit 9 (when the non-contact type IC card 1 receives data from the reader / writer 15). ) Or modulated by the modulation circuit 10 (when the non-contact type IC card 1 transmits data to the reader / writer 15). Non-contact type IC
Data transmitted and received between the card 1 and the reader / writer 15 is controlled by the digital circuit 13 and stored in the nonvolatile memory 14.

Here, the resonance circuit 4 and the modulation circuit 10 in the voltage generation circuit 3 will be further described with reference to FIGS.

FIG. 9 is a diagram showing a change in the output voltage of the voltage generating circuit 3 with respect to the resonance frequency of the conventional non-contact type IC card.

[0008] The resonance circuit 4 is for passing components in a predetermined frequency band, and includes an antenna coil 5 and a capacitor 6. Non-contact IC card 1 and reader / writer 15
In a non-contact IC card communication system in which communication is performed, a transmission frequency (hereinafter, simply referred to as a frequency) of a radio wave 17 transmitted from the reader / writer 15 is determined by a communication protocol (for example, ISO14443).
In the following description, the frequency of the radio wave 17 transmitted from the reader / writer 15 will be 13.56 MHz, and the resonance frequency f determined by the inductance L of the antenna coil 5 and the capacitance C of the capacitor 6 will be described.
Is adjusted to this 13.56 MHz. That is, f = 1 / 2π√LC = 13.56 MHz. Thus, the resonance frequency is set to the reader / writer 1
The voltage can be generated most efficiently when the frequency of the radio wave 17 transmitted from the radio wave 5 is adjusted to 13.56 MHz.
FIG. 9 shows this state. The vertical axis is the voltage generator 3
Output voltage V, the horizontal axis is a non-contact type IC determined by the resonance circuit 4
This is the resonance frequency f of the card 1. Resonance frequency is 13.5
At 6 MHz, the highest voltage occurs. As shown by curves (21) and (22) in the figure, the output voltage V decreases as the distance between the non-contact type IC card 1 and the reader / writer 15 increases. In a system such as a non-contact type IC card which does not have a power supply, how to efficiently generate a voltage depends on the non-contact type IC card 1.
This is a point for determining the maximum communication distance between the device and the reader / writer 15.

When the non-contact type IC card 1 transmits data to the reader / writer 15, the modulation circuit 10 converts digital data output from the digital circuit 13 into analog data (converts the data into a form that can be received by the reader / writer 15). ), And includes a resistor 11 and an N-channel MOS transistor 12. The data output from the digital circuit 13 is an N-channel MO.
The data input to the gate of the S-type transistor 12
/ L, the N-channel MOS transistor 12
Turns on / off (either polarity is acceptable). That is, the current flowing through the resistor 11 connected in series with the N-channel MOS transistor 12 is turned on / off.
Therefore, the resistance load between the antenna coil 5 and the capacitance 6 of the resonance circuit 4 changes depending on the H / L of the data. Due to this change in the resistance load, the current I flowing through the antenna coil 16 of the reader / writer 15 changes, and the reader / writer 15 can recognize the data as data.

FIG. 10 shows this state.
FIG. 7 is a diagram illustrating a change in current flowing through an antenna coil of a reader / writer with respect to a resonance frequency of a conventional non-contact type IC card. The vertical axis represents the current I flowing through the antenna coil 16 of the reader / writer 15, and the horizontal axis represents the resonance frequency f of the non-contact type IC card 1 determined by the resonance circuit 4. When the MOS transistor 12 is off, the relationship between the current I and the resonance frequency f is assumed to be a curve (23). MOS transistor 1
When 2 turns on, the current I decreases and becomes a curve (24).
Regardless of ON / OFF of the MOS transistor 12,
Since the resonance frequency f is 13.56 MHz, the amount of change in the current is as indicated by the arrow (25).

In the non-contact type IC card 1 shown in FIG. 8, circuits other than the resonance circuit 4 are usually formed of a semiconductor integrated circuit. The antenna coil 5 of the resonance circuit 4 is formed by external components. The capacitance 6 of the resonance circuit 4 may be formed by a semiconductor integrated circuit or may be formed by external components.

[0012]

A non-contact type IC card has a contact distance of 0 to 2 mm and a communication distance of 0 to 10 mm.
The proximity type with a communication distance of 0 to 70 cm and the microwave with a communication distance of 0 to 10 m are roughly classified. The longer the communication distance becomes, the more difficult it becomes technically.
２2 mm), there is not much difference in characteristics as compared with contact IC cards which are already widely used, and it cannot be said that the merits of non-contact IC cards are sufficiently exhibited. Therefore, next to the contact type IC card, the proximity type non-contact type IC card (communication distance 0 to 10 cm) and the proximity type non-contact type IC card (communication distance 0 to 70 cm) are expected to spread. You.

With the spread of such non-contact type IC cards, especially in proximity type non-contact type IC cards (communication distance of 0 to 10 cm), general users are not limited to one card. Multiple cards (such as telephone cards,
It is expected that commuter passes, shopping cards, etc.) will be used in the same wallet or pass case. When using a non-contact type IC card, the biggest advantage is that the card can be processed without removing the card from the wallet or pass case. Even if multiple cards are stacked, stable communication between the reader writer and the card is possible. Desired.

However, when a plurality of cards overlap, the resonance frequency shifts to a lower side, and stable communication is hindered. This will be described with reference to FIGS.
FIG. 11 is a diagram illustrating transmission and reception of radio waves with a reader / writer when two cards are overlapped.

When there is only one card, the non-contact type IC card 1
Is, as described above, f = 1 / 2π√LC = 13.56 MHz. However, when the two cards overlap as shown in FIG. 11, if the mutual inductance between the non-contact type IC card 1 and the non-contact type IC card 21 is M, the resonance frequency is f = 1 / 2π√ (L + M) C < 13.56 MHz. That is, it becomes smaller than 13.56 MHz. Therefore, as shown in FIG. 9, the output voltage decreases. Further, as shown by an arrow (26) in FIG. 10, the amount of change in the current received by the reader / writer during data modulation is also small. These become factors that hinder stable communication, and deteriorate the communication performance.

In the non-contact type IC card, the specification of the communication distance is determined according to the application. However, when the distance to the reader / writer 15 is the longest (10 in the proximity type).
cm, 70 cm for the proximity type), so that the voltage of the voltage generation circuit 3 is output more than a specified value so that stable communication can be performed. In particular, in the case of a proximity type non-contact type IC card (communication distance 0 to 70 cm) that is promising in the field of physical distribution and FA in the future, a stable output voltage must be generated even at a distance of 70 cm. However, conversely, when approaching the reader / writer, an overvoltage is generated, which becomes a hindrance factor for stable communication and deteriorates communication performance.

[0017]

According to a first aspect of the present invention, there is provided a non-contact type IC card which transmits and receives data by radio waves in a non-contact manner and generates a power supply voltage, and stores the data. And a digital circuit for controlling data to be transmitted and received, wherein the resonance frequency of a resonance circuit for passing a component of a predetermined frequency band in the analog circuit is set to a non-contact type.
The transmission data output from the digital circuit is set higher than the transmission frequency of the C card communication system, and the transmission data output from the digital circuit is modulated by changing the capacitive load by the capacitance element of the resonance circuit and the capacitance element of the modulation circuit in the analog circuit. It is characterized by performing.

According to this configuration, since the capacitance load between the antenna coil and the capacitance of the resonance circuit changes, the change of the current I flowing through the antenna coil of the reader / writer can be increased by the change of the capacitance load. .

Further, since the resonance frequency shifts during data modulation when a plurality of cards are overlapped, a decrease in the output voltage of the voltage generation circuit can be suppressed, and a decrease in the amount of change in the current received by the reader / writer can be suppressed. , And stable communication can be performed.

According to a second aspect of the present invention, there is provided the non-contact type IC card according to the first aspect, wherein two outputs of the modulation circuit are connected to the resonance circuit. One or more MOS type transistors for inputting transmission data output from the digital circuit are connected in series between two outputs.

According to this configuration, the capacitance load can be easily changed by H / L of the transmission data output from the digital circuit.

According to a third aspect of the present invention, there is provided the non-contact type IC card according to the second aspect, wherein the capacitance element connected between the two outputs of the modulation circuit includes two metal electrodes. It is characterized by being constituted by an insulating film inserted between them.

With this configuration, the capacitive element can be easily formed by a normal semiconductor process.

According to a fourth aspect of the present invention, there is provided the non-contact type IC card according to the second aspect, wherein the capacitive element connected between two outputs of the modulation circuit includes one or more MOS transistors. Characterized by being constituted by a type transistor.

With this configuration, the capacitance element can be formed with a small area, which is advantageous in cost.

According to a fifth aspect of the present invention, there is provided a non-contact type IC card which transmits and receives data by radio waves in a non-contact manner and generates a power supply voltage; a non-volatile memory for storing data; A digital circuit for controlling data to be transmitted and received, wherein the control of the capacitance of the resonance circuit in the voltage generation circuit in the analog circuit is variable depending on the magnitude of the output voltage of the rectification circuit. .

With this configuration, it is possible to reduce the occurrence of overvoltage when the non-contact type IC card approaches the reader / writer, and it is possible to perform stable communication.

According to a sixth aspect of the present invention, there is provided the non-contact type IC card according to the fifth aspect, wherein the capacitive element is further connected in parallel to the resonance circuit in which an antenna coil and a capacitor are connected in parallel. And one or more MOS transistors for inputting an output of a voltage detection circuit in the voltage generation circuit are connected in series.

According to this configuration, the capacitance load can be easily changed by H / L of the detection signal output from the voltage detection circuit.

According to a ninth aspect of the present invention, there is provided a non-contact type IC card communication system which transmits and receives data by radio waves in a non-contact manner and generates a power supply voltage, and a nonvolatile memory for storing data. And a digital circuit for controlling data to be transmitted and received, wherein a resonance frequency of a resonance circuit for passing a component of a predetermined frequency band in the analog circuit is higher than a transmission frequency of the non-contact type IC card communication system. A plurality of non-contact type IC cards for setting and modulating transmission data output from the digital circuit by changing a capacitive load by a capacitance of a resonance circuit and a capacitance of a modulation circuit in the analog circuit are simultaneously read by a plurality of readers. It is characterized by communicating with a writer.

With this configuration, it is possible to solve the problem that the resonance frequency when a plurality of cards overlap is shifted to a lower side, and to perform stable communication.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS.

(Embodiment 1) First, referring to FIGS. 1, 2 and 3, the non-contact type I in Embodiment 1 of the present invention will be described.
The operation of the C card will be described. FIG. 1 is a block diagram showing a configuration of a non-contact type IC card according to Embodiment 1 of the present invention, and a diagram showing transmission and reception of radio waves with a reader / writer. In FIG. 1, the same components as those in FIG. 8 will be described using the same reference numerals.

In FIG. 1, a non-contact type IC card 31
Is composed of an analog circuit 32 for transmitting and receiving data wirelessly and generating a power supply voltage, a non-volatile memory 14 for storing data, and a digital circuit 13 for controlling data to be transmitted and received. I have. The analog circuit 32 includes a voltage generation circuit 33 that receives a radio wave and generates a voltage, and a circuit 9 that demodulates received data.
And a circuit 40 for modulating transmission data.

The non-contact type IC card 31 and the reader / writer 15 are connected to the non-contact type IC card 3
The transmission and reception of the radio wave 17 are performed through the antenna coil 35 of the first and the antenna coil 16 of the reader / writer 15. When the non-contact type IC card 31 receives the radio wave 17,
An AC voltage is generated at both ends of the antenna coil 35. The generated AC voltage is converted into a DC voltage by the rectifier circuit 7 in the voltage generation circuit 33 and supplied to each block as an output voltage V. Data transmitted and received between the non-contact type IC card 31 and the reader / writer 15 is superimposed on an AC voltage and demodulated by the demodulation circuit 9 (when the non-contact type IC card 31 receives data from the reader / writer 15). ),
Alternatively, modulation by the modulation circuit 40 (the non-contact type IC card 31
Is transmitted to the reader / writer 15). Data transmitted and received between the non-contact type IC card 31 and the reader / writer 15 is controlled by the digital circuit 13 and stored in the nonvolatile memory 14.

Here, the resonance circuit 34 and the modulation circuit 40 in the voltage generation circuit 33 will be further described with reference to FIGS.

The resonance circuit 34 is provided for passing a component in a predetermined frequency band, and includes an antenna coil 35 and a capacitor 3
6. The frequency of the radio wave 17 transmitted from the reader / writer 15 is determined by a communication protocol (for example, 13.56 MHz in ISO14443, and hereinafter the frequency of the radio wave 17 transmitted from the reader / writer 15 is 13.56 MHz). As described in the art, the resonance frequency f determined by the inductance L of the antenna coil 35 and the capacitance C of the capacitor 36 is set to 13.56 MHz. That is, f = 1 / 2π√LC = 13.56 MHz.

Non-contact type I in Embodiment 1 of the present invention
In the C card, the inductance L of the antenna coil 35 is
The resonance frequency f determined by the capacitance C36 of the capacitor 35 and the capacitance 36 is adjusted to a higher side than 13.56 MHz. That is, f = 1 / 2π√L35 × C36> 13.56 MHz.

Therefore, the output voltage of the voltage generating circuit 33 is slightly lower than when the resonance frequency f is adjusted to 13.56 MHz. FIG. 2 shows this state.

FIG. 2 shows a voltage generation circuit 3 for the resonance frequency of the non-contact type IC card according to the first embodiment of the present invention.
FIG. 3 is a diagram showing a change in output voltage of No. 3; The vertical axis represents the output voltage V of the voltage generation circuit 33, and the horizontal axis represents the resonance frequency f of the non-contact type IC card 1 determined by the resonance circuit. The output voltage V of the voltage generation circuit 33 is the starting point of the arrow (1) when there is one non-contact type IC card and the starting point of the arrow (2) when there are plural non-contact type IC cards.

That is, since the resonance frequency f when one non-contact type IC card is set to the higher side, for example, f
Is adjusted to 15.5 MHz, f when the number of non-contact type IC cards is two is reduced as described above, and 1
It becomes 4.5 MHz. When the transistors 41 and 42 change from the off state to the on state, the arrow (1) and the arrow (2) move in the direction of the arrow, so that the resonance frequency decreases and moves to the 13.56 MHz side. When the output voltage is 3 V when the resonance frequency is 13.56 MHz, the output voltage when one non-contact type IC card is 2.5 V
Thus, the output voltage when two non-contact type IC cards are 2.7 V is obtained. When a plurality of non-contact type IC cards are used, the output voltage is higher than that when one non-contact type IC card is used.

Here, in order to adjust the resonance frequency f to the higher side, the inductance L of the antenna coil 35 and the capacitance 3
This is achieved by adjusting with a capacitance C of 6. That is, L or C is set to be small. Normal,
Since the antenna coil is externally mounted and the capacitance is externally mounted or built in the chip, it can be easily implemented.

The modulation circuit 40 includes a non-contact type IC card 31
Is for converting digital data output from the digital circuit 13 into analog data (converting data so that the reader / writer 15 can receive the data) when transmitting data to the reader / writer 15. Transistors 41 and 42 are connected in series. The capacitor 43 is composed of two metal electrodes and an insulating film inserted between them. The data output from the digital circuit 13 is input to the gates of the P-channel MOS transistors 41 and 42, and the P-channel MOS transistor 4 is changed according to the H / L of the data.
1 and 42 turn on / off. Therefore, the capacitor 43 connected in series with the P-channel MOS transistors 41 and 42 is turned on / off. Here, the polarity may be either. That is, the P-channel MOS transistors 41 and 42 are for connecting the capacitor 43 to the capacitor 36 in parallel or disconnecting the capacitor 43, and may be configured by N-channel MOS transistors. Further, it is also possible to configure with one MOS type transistor.

Here, the two outputs of the modulation circuit, that is, the drains (or sources) of the P-channel MOS transistors 41 and 42 are connected in parallel to the antenna coil 35 and the capacitor 36 of the resonance circuit 34.

The transmission data (H / L) transmitted from the digital circuit 13 is modulated by the modulation circuit 40 and changes in the current I flowing through the antenna coil 35 to the antenna coil 16 of the reader / writer 15. It will be recognized as. Here, in the transmission data (H / L) transmitted from the digital circuit of the non-contact type IC card according to the first embodiment of the present invention, the capacitance load between the antenna coil 35 of the resonance circuit 34 and the capacitance 36 changes. Therefore, the current I flowing through the antenna coil 16 of the reader / writer 15 is
Changes.

FIG. 3 shows this state, and shows a change in the value of the current flowing through the antenna coil of the reader / writer when the non-contact type IC card according to Embodiment 1 of the present invention is used. The vertical axis represents the current I flowing through the antenna coil 16 of the reader / writer 15, and the horizontal axis represents the resonance frequency f of the non-contact type IC card 31 determined by the resonance circuit 34. When the transistors 41 and 42 are off, the current I
If the relationship between and the resonance frequency f is a curve (3),
When the transistors 41 and 42 are turned on, the current I decreases,
A curve (4) results.

In the case of a resistive load which is a conventional non-contact type IC card, the resonant frequency f is constant irrespective of the on / off state of the transistor 12 because it is composed of one resistor 11 and one transistor 12. However, in the case of the capacitive load which is the non-contact type IC card of the present invention, when the transistors 41 and 42 are turned on, the capacitance 36 and the capacitance 43 are connected in parallel, so that the resonance frequency f shifts to a lower side.
That is, assuming that the capacitance of the capacitor 43 is C43, f = 1 / 2π√L35 × (C36 + C43) <1 / 2π
√L35 × C36. Therefore, the current I flowing through the antenna coil 16 of the reader / writer 15 is
Changes from off to on when the number of non-contact type IC cards is one, as shown by an arrow (5) in FIG. 3, and when there are a plurality of non-contact type IC cards, the arrow in FIG. It changes like (7). For example, assuming that the resonance frequency when the transistors 41 and 42 are off when the number of non-contact type IC cards is one is 15.5 MHz, the resonance frequency when the operation of the transistors 41 and 42 is changed to the on state is 15M.
Hz. Further, when the number of non-contact type IC cards is two and the resonance frequency when the transistors 41 and 42 are off is 14.5 MHz, the resonance frequency when the transistors 41 and 42 change to the on state changes to 14 MHz.

The change amounts of the current I are indicated by arrows (6) and (8) in FIG. 3, respectively. The amount of change in the current I of the non-contact type IC card according to the conventional configuration,
When there is one C card, the arrow (25) shown in FIG.
5 mA, and the arrow (2
6) is 0.4 mA, whereas the change amount of the current I of the non-contact type IC card according to the first embodiment of the present invention, that is, when there is one non-contact type IC card, the arrow shown in FIG. 6) is 0.7 mA, and when there are two non-contact type IC cards, the arrow (8) becomes 0.6 mA.

As described above, in the non-contact type IC card 31 of the present invention, when one card is used, the amount of change in the current flowing through the reader / writer can be increased as compared with the conventional case. Although there is an effect that the reader / writer can more reliably recognize data even when one card is used, the effect can be further enhanced when communicating with a plurality of cards.

That is, when it is assumed that a plurality of cards are used at the same time, even if the resonance frequency f of the non-contact type IC card is shifted in advance to a higher side, since the modulation circuit is constituted by a capacitive load, the transmission data , That is, when the transistors 41 and 42 of the modulation circuit 40 change on and off, the resonance frequency f shifts to a lower side. Therefore, the output voltage of the voltage generation circuit 33 is almost the same as when the resonance frequency f is adjusted to 13.56 MHz.
Further, the current change arrows (6) and (8) for the reader / writer 15 to recognize as data are larger than the arrows (25) and (26) shown in FIG. Card 31 and reader / writer 15
Stable communication is possible between

In the non-contact type IC card 31 shown in FIG. 1, circuits other than the resonance circuit 34 are usually formed of a semiconductor integrated circuit. Antenna coil 35 of resonance circuit 34
Is formed of external components. The capacitance 36 of the resonance circuit 34 may be formed by a semiconductor integrated circuit or may be formed by external components.

(Embodiment 2) Next, Embodiment 2 of the present invention will be described with reference to FIG. FIG. 4 is a modulation circuit diagram of the contactless IC card according to Embodiment 2 of the present invention.

The difference between the semiconductor integrated circuit of the non-contact type IC card according to the first embodiment of the present invention and the second embodiment of the present invention lies in the configuration of the capacitive element of the modulation circuit 40. That is, the modulation circuit 40 in the non-contact type IC card 31 according to the first embodiment is constituted by two metal electrodes as a capacitor and an insulating film inserted between them. Reference numeral 40 denotes a P-channel MOS transistor as a capacitor.

In FIG. 4, the capacitance element of the modulation circuit 40 according to the second embodiment is formed using the gate oxide film capacitance of two P-channel MOS transistors. The gate of the P-channel MOS transistor 51 is connected to the source (or drain) of the P-channel MOS transistor 41. The source and drain of the P-channel MOS transistor 51 are connected to the source (or drain) of the P-channel MOS transistor 42.
It is connected to the. The gate of the P-channel MOS transistor 52 is connected to the source (or drain) of the P-channel MOS transistor 42,
The source and drain of the channel MOS transistor 52 are connected to the source (or drain) of the P-channel MOS transistor 41. With such a configuration, the operation is the same as that described with reference to FIGS. 1, 2, and 3.

As described in the first embodiment of the present invention, the P-channel MOS transistors 41 and 42 can be constituted by N-channel MOS transistors. In this case, P-channel MOS transistors 51 and 52 are also formed of N-channel MOS transistors.

Normally, the semiconductor integrated circuit portion of the non-contact type IC card according to the present invention is manufactured by using a CMOS process. Therefore, at the same time as forming the CMOS gate circuit, forming a MOS transistor instead of the capacitor 43 composed of the two metal electrodes shown in FIG. 1 and an insulating film inserted between them can reduce the area and cost. It is economically advantageous.

(Third Embodiment) Next, a third embodiment of the present invention will be described with reference to FIGS. FIG.
FIG. 7 is a block diagram showing a configuration of a non-contact type IC card according to Embodiment 3 of the present invention and a diagram showing transmission and reception of radio waves with a reader / writer.

The difference between the prior art and the semiconductor integrated circuit of the non-contact type IC card according to the third embodiment of the present invention is as follows.
The circuit configuration used in the modulation circuit 40 in the non-contact type IC card 31 in the first embodiment is put into a resonance circuit as it is, and the gate of a P-channel MOS transistor is replaced with a voltage detection circuit instead of the output of the digital circuit 13. 8 is input and the modulation circuit 10 is provided separately.

In FIG. 5, a resonance circuit 64 receives the output of the voltage detection circuit 8 in the voltage generation circuit 63 in parallel with the capacitance 67 in addition to the antenna coil 5 and the capacitance 6 described in the background art. P-channel MOS transistors 65 and 66 are connected in series. The voltage detection circuit 8 outputs H until the output voltage V of the voltage generation circuit 63 reaches a certain voltage level (for example, 5 V). At this time, P-channel MOS transistors 65 and 6
Reference numeral 6 denotes an off state, that is, the capacitor 67 is in an off state. Therefore, the resonance frequency f is f = 1 / 2π√LC = 13.56 MHz.

When the output voltage V of the voltage generation circuit 63 reaches a certain voltage level (for example, 5 V), the output of the voltage detection circuit 8 outputs L. At this time, P-channel MOS transistors 65 and 66 are on, that is, capacitor 67 is on. Therefore, assuming that the capacitance of the capacitor 67 is C67, the resonance frequency f becomes f = １ ／ π√L (C + C67) <13.56 MHz, and shifts from 13.56 MHz to a lower side.

FIG. 6 shows this state, and shows a change in the output voltage of the voltage generating circuit with respect to the resonance frequency of the non-contact type IC card according to the third embodiment of the present invention. When the non-contact type IC card 61 is approached from a distance to the reader / writer 15, the output voltage V of the voltage generation circuit 63 follows a locus as indicated by an arrow (14). Thus, according to this configuration, the occurrence of overvoltage when the non-contact type IC card approaches the reader / writer can be reduced, and stable communication can be performed.

Note that the P-channel MOS transistors 65 and 66 can be constituted by N-channel MOS transistors. In this case, the output of the voltage detection circuit 8 is inverted or the output of the voltage detection circuit 8 is And the resonance frequency f is set to 13.5 with the capacitor 67 turned on.
The resonance frequency f may be shifted from 13.56 MHz to a higher side when the capacitance 67 is turned off in accordance with 6 MHz.

(Fourth Embodiment) Next, a fourth embodiment of the present invention will be described with reference to FIG.

FIG. 7 shows a resonance circuit of the non-contact type IC card according to the fourth embodiment of the present invention.

The difference between the third embodiment of the present invention and the semiconductor integrated circuit of the non-contact type IC card according to the fourth embodiment of the present invention lies in the configuration of the capacitance element of the modulation circuit 40. That is, the resonance circuit 64 in the non-contact type IC card 61 according to the third embodiment is constituted by two metal electrodes as a capacitor and an insulating film inserted between them. Reference numeral 40 denotes a P-channel MOS transistor as a capacitor.

In FIG. 7, the capacitance element of the resonance circuit 64 in the fourth embodiment is configured using the gate oxide film capacitance of two P-channel MOS transistors. The gate of the P-channel MOS transistor 71 is connected to the source (or drain) of the P-channel MOS transistor 65, and the source and drain of the P-channel MOS transistor 71 are the source (or drain) of the P-channel MOS transistor 66.
It is connected to the. The gate of the P-channel MOS transistor 72 is connected to the source (or drain) of the P-channel MOS transistor 66,
The source and the drain of the channel MOS transistor 72 are connected to the source (or drain) of the P-channel MOS transistor 65. With such a configuration, the operation is the same as that described with reference to FIGS.

As described in the third embodiment of the present invention, the P-channel MOS transistors 65 and 66 can be constituted by N-channel MOS transistors. In this case, P-channel MOS transistors 71 and 72 are also formed of N-channel MOS transistors.

Normally, the semiconductor integrated circuit portion of the non-contact type IC card according to the present invention is manufactured by using a CMOS process. Therefore, at the same time when the CMOS gate circuit is formed, it is possible to reduce the area and cost by forming a MOS transistor instead of the capacitor 67 formed of the two metal electrodes shown in FIG. 1 and the insulating film interposed therebetween. It is economically advantageous.

[0069]

As described above, in the non-contact type IC cards according to the first and second embodiments of the present invention, the modulation circuit comprises:
A reader / writer and a plurality of non-contact I / Os are used to perform modulation by changing a capacitive load according to H / L of transmission data output from a digital circuit and to change a resonance frequency.
Stable communication is possible with the C card. By using this circuit, it is possible to realize a proximity type (communication distance of 0 to 10 cm) non-contact type IC card which is expected to be widely used in the near future.

Further, in the non-contact type IC card according to the third and fourth embodiments of the present invention, the capacitance of the resonance circuit can be changed by the output voltage of the voltage generating circuit, and the non-contact type IC card is close to the reader / writer. Overvoltage can be reduced and stable communication can be performed. By using this circuit, the proximity type (communication distance 0 to 70c
m), a non-contact type IC card can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a non-contact type IC card according to Embodiment 1 of the present invention, and a diagram illustrating transmission and reception of radio waves with a reader / writer.

FIG. 2 is a diagram showing a change in an output voltage of a voltage generation circuit with respect to a resonance frequency of the non-contact type IC card according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a change in a current flowing through an antenna coil of a reader / writer with respect to a resonance frequency of the non-contact type IC card according to the first embodiment of the present invention.

FIG. 4 is a block diagram of a modulation circuit of the non-contact type IC card according to the second embodiment of the present invention.

FIG. 5 is a block diagram illustrating a configuration of a non-contact type IC card according to Embodiment 3 of the present invention and a diagram illustrating transmission and reception of radio waves with a reader / writer.

FIG. 6 is a diagram showing a change in an output voltage of a voltage generation circuit with respect to a resonance frequency of the non-contact type IC card according to the third embodiment of the present invention.

FIG. 7 is a block diagram of a resonance circuit of the non-contact type IC card according to the fourth embodiment of the present invention.

FIG. 8 is a block diagram showing a configuration of a conventional non-contact type IC card and a diagram showing transmission and reception of radio waves to and from a reader / writer.

FIG. 9 is a diagram showing a change in an output voltage of a voltage generation circuit with respect to a resonance frequency of a conventional non-contact type IC card.

FIG. 10 is a diagram showing a change in a current flowing through an antenna coil of a reader / writer with respect to a resonance frequency of a conventional non-contact type IC card.

FIG. 11 is a diagram showing transmission / reception of radio waves to / from a reader / writer when two non-contact type IC cards are overlapped;

[Explanation of symbols]

 REFERENCE SIGNS LIST 15 reader / writer 16 antenna coil 17 radio wave 31 non-contact IC card 32 analog circuit 33 voltage generation circuit 34 resonance circuit 35 antenna coil 36 capacitance 40 modulation circuit 41 P-channel MOS transistor 42 P-channel MOS transistor 43 capacitance 51 P-channel MOS Type transistor 52 P-channel MOS transistor 61 Non-contact type IC card 62 Analog circuit 63 Voltage generation circuit 64 Resonance circuit 65 P-channel MOS transistor 66 P-channel MOS transistor 67 Capacity 71 P-channel MOS transistor 72 P-channel MOS transistor

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Tatsumi Kado, Inventor 1-1, Kochicho, Takatsuki-shi, Osaka Matsushita Electronics Co., Ltd. F-term (reference) 2C005 MA29 MB05 NA08 TA22 5B035 BB09 CA23 CA35 5K012 AB05 AB18 AB19 AC09 AE13

Claims (9)

[Claims] An analog circuit for transmitting and receiving data by radio waves in a non-contact manner and generating a power supply voltage, a nonvolatile memory for storing data, and a digital circuit for controlling data to be transmitted and received. The resonance frequency of a resonance circuit for passing a component of a predetermined frequency band in the analog circuit is set higher than the transmission frequency of a non-contact type IC card communication system, and transmission data output from the digital circuit is A non-contact type IC card wherein modulation is performed by changing a capacitive load by a capacitive element of a resonance circuit and a capacitive element of a modulation circuit in the analog circuit. 2. The two outputs of the modulation circuit are connected to the resonance circuit, and between the two outputs of the modulation circuit, one input for inputting transmission data output from the capacitance element and the digital circuit. 2. The non-contact IC card according to claim 1, wherein one or more MOS transistors are connected in series. 3. The capacitor according to claim 2, wherein the capacitor connected between two outputs of the modulation circuit is formed of two metal electrodes and an insulating film inserted between the two metal electrodes. Contact type IC card. 4. The non-contact type IC card according to claim 2, wherein said capacitive element connected between two outputs of said modulation circuit comprises one or more MOS transistors. 5. An analog circuit for transmitting and receiving data wirelessly and generating a power supply voltage by radio waves, a nonvolatile memory for storing data, and a digital circuit for controlling data to be transmitted and received. A non-contact type IC card, wherein the control of the capacitance element of the resonance circuit in the voltage generation circuit in the analog circuit is variable depending on the magnitude of the output voltage of the rectification circuit. 6. One or more MOS type for inputting an output of a voltage detecting circuit in the voltage generating circuit and a capacitive element in parallel to the resonance circuit in which an antenna coil and a capacitive element are connected in parallel. The non-contact type IC card according to claim 5, wherein the transistors are connected in series. 7. The capacitor according to claim 6, wherein the capacitance element connected in parallel with the antenna coil and the capacitance of the resonance circuit is constituted by two metal electrodes and an insulating film inserted between them. Non-contact type IC card. 8. A capacitor connected in parallel with an antenna coil and a capacitor of the resonance circuit includes at least one MOS transistor.
7. The non-contact type IC card according to claim 6, comprising a type transistor. 9. An analog circuit for transmitting and receiving data wirelessly and generating a power supply voltage by radio waves, a nonvolatile memory for storing data, and a digital circuit for controlling data to be transmitted and received. The resonance frequency of a resonance circuit for passing a component of a predetermined frequency band in the analog circuit is set higher than the transmission frequency of the non-contact type IC card communication system, and transmission data output from the digital circuit is A non-contact type IC card wherein a plurality of non-contact type IC cards for performing modulation by changing a capacitive load by a capacitance of a resonance circuit and a capacitance of a modulation circuit in the analog circuit simultaneously communicate with a reader / writer. Card communication system.