JP2003076964A - Non-contact id tag - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prolong a battery service life and to eliminate supply of unrequired power. SOLUTION: A non-contact ID tag is provided with a coil 1 receiving a command transmitted from a reader 20 and returning a response to the reader 20, a control circuit 2 performing control so as to make the coil 1 return the response and a battery 5 supplying power required for the response by the coil 1 to the control circuit 2 and the coil is induced by electromagnetic induction by the reader 20. The non-contact ID tag is provided with a switch circuit 3 performing opening/closing operations when a power supply instruction signal is outputted from the control circuit 2 so as to supply the power from the battery 5 to the control circuit 2 and the control circuit 2 outputs the power supply instruction signal at the time of judging that the power is required.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a contactless ID tag which operates by electromagnetic induction.

[0002]

2. Description of the Related Art Conventionally, as a contactless ID tag of this type,
Equipped with a coil that receives commands sent from the reader and sends back a response to the reader, a control circuit that controls the coil to send back a response, and a battery that supplies the control circuit with the power required for the response by the coil. There are so-called built-in batteries.

[0003]

In the above-mentioned conventional non-contact ID tag, the electric power required for the response by the coil is supplied from the built-in battery to the control circuit, not from the coil induced by the reader side coil. Since it can be supplied, it can be used even in a place away from the reader,
The communication distance can be extended.

However, this battery has a short battery life because it is necessary to constantly energize the control circuit from the battery, and the battery needs to be replaced frequently.

On the other hand, as a wireless tag (non-contact ID tag) capable of extending the battery life, Japanese Patent Laid-Open No. 13-606 has been proposed.
There is one disclosed in No. 1. As shown in FIG. 3, this is a tuning circuit 101 that receives transmitted radio waves.
The switching element 102 which is turned on by the output of the radio wave is provided, and the DC output of the battery 103 is supplied to each circuit of the wireless tag as a circuit power source by the conduction of the switching element 102 when the radio wave is received.

[0006] This is a battery 1 only when receiving radio waves.
Since the current output of 03 is supplied as the circuit power supply of each circuit, the battery 103 is normally disconnected from the circuit, and the battery life can be dramatically increased.

By the way, when the contactless ID tag particularly needs power, it is time to send a response to the reader, or a memory (EEPROM) built in the control circuit.
Since it is time to write data to the battery, power is supplied to the battery 103 at times other than these.
According to the method disclosed in Japanese Patent No. 3-6061, even if the electric power is supplied from the battery only when the radio wave is received, the electric power may be supplied more than necessary.

The present invention has been made by paying attention to the above points, and an object of the present invention is to prolong battery life and to avoid supply of unnecessary electric power. It is to provide a contactless ID tag.

[0009]

In order to solve the above problems, the contactless ID tag according to claim 1 receives a command transmitted from a reader and returns a response to the reader. A control circuit that controls the coil to return a response, and a battery that supplies the control circuit with the power required for the response by the coil.
In a contactless ID tag in which a coil is induced by electromagnetic induction by a reader, a switch that opens and closes when a power supply instruction signal is output from the control circuit so as to supply the power from the battery to the control circuit. A circuit is provided, and the control circuit outputs the power supply instruction signal when it determines that the power is needed.

A non-contact ID tag according to a second aspect of the present invention is the non-contact ID tag according to the first aspect, wherein the control circuit is a coil for detecting a coil voltage induced in the coil by a reader-side coil of the reader. A voltage detection circuit is provided, the coil voltage detected by the coil voltage detection circuit is compared with a preset threshold voltage, and when the coil voltage is induced but is less than the threshold voltage, the power supply instruction signal Is output.

A non-contact ID tag according to a third aspect of the present invention is the non-contact ID tag according to the second aspect, wherein a plurality of the threshold voltages are set in advance and a threshold distance to be compared with a distance to the reader is set. The threshold voltage is set to a smaller value when the distance to the reader is less than the threshold distance.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Non-contact I of the first embodiment of the present invention
The D tag will be described below with reference to FIG. This non-contact I
The D tag 10 forms the ID tag transmitting / receiving device 30 together with the reader 20. This ID tag transceiver 3
The reader 20 which is the other component of the 0 is a transmission / reception circuit 2 that executes an operation necessary for transmission / reception with the contactless ID tag 10.
0a, a coil 20b for performing transmission / reception with the coil 1 of the contactless ID tag 10 described later.

Reference numeral 1 denotes a coil, which is a coil 20b of the reader 20.
From the reader 2 while receiving the command sent from
The response is returned to the coil 20b of 0. A coil voltage is induced in the coil 1 by electromagnetic induction by the coil 20b of the reader 20, and power is supplied to a control circuit 2 described later by the induction of the coil voltage.

Reference numeral 2 is a control circuit, which is a circuit for controlling a response to a command transmitted from the reader 20 and is constituted by an IC and has a power supply section 2a,
It has an EEPROM 2b and a signal processing logic circuit 2c. The power supply unit 2a has a diode bridge for rectification, and is supplied with electric power by induction of a battery 5 and a coil 1 which will be described later and supplies electric power to each unit in the control circuit 2. The EEPROM 2b stores data to be a response to the reader 20 and other necessary data. The signal processing logic circuit 2c executes various signal processings such as transmission / reception with the reader 20 and output of a power supply instruction signal to the switch circuit 3 described later.

The control circuit 2 is connected between both ends of the coil 1, and is also connected between both ends of the battery 5 via a second transistor 3b of a switch circuit 3 which will be described later. Therefore, the control circuit 2 can supply power by applying a coil voltage induced by electromagnetic induction by the coil 20b of the reader 20 and power from the battery 5 by opening / closing the switch circuit 3. Has become.

A switch circuit 3 includes a first transistor 3a, a second transistor 3b, a first resistor 3c, and a second transistor 3a.
3d and a third resistor 3e.
The collector of the first transistor 3a is connected to the base of the second transistor 3b via the first resistor 3c, the emitter is connected to one end of the control circuit 2 and the coil 1, and the base is connected to the second terminal.
Are respectively connected to the control circuit 2 via the resistors 3d. The second transistor 3b has a collector for the control circuit 2, an emitter for the battery 5, and a base for the first resistor 3.
They are respectively connected to the collector of the first transistor 3a via c. In addition, this second transistor 3
b is between the base and emitter due to the third resistor 3e
It is connected. The operation of the switch circuit 3 will be described later in detail.

Reference numeral 4 denotes a capacitor, one end of which is connected to the emitter of the first transistor 3a, the control circuit 2 and one end of the coil, and the other end of which is connected to the base of the first transistor 3a and the second Is connected to the control circuit 2 through the resistor 3d. This capacitor 4 is electromagnetically induced by the coil 20b of the reader 20 and smoothes the alternating current generated in the coil 1.

Next, a flow of transmission / reception between the contactless ID tag and the reader 20 will be briefly described. First, in order to confirm whether the contactless ID tag 10 is present between the reader 20 and the contactless ID tag 10,
Transmission and reception are performed between the coils 1 and 20b. When the reader 20 reads the data written in the EEPROM 2b of the contactless ID tag 10, after confirming that the contactless ID tag 10 is present, the contactless ID
A command designating the read address of the tag 10 is transmitted from the coil of the reader 20 to the coil of the contactless ID tag 10. After this, the EEPROM of the contactless ID tag 10
The data written in 2b is read from the coil 1 of the contactless ID tag 10 so that the reader 20 can read the data.
A response is sent back to the coil 20b.

Next, the operation of the switch circuit 3 will be described. As described above, the coil 1 of the contactless ID tag 10
When a response is sent from the reader 20 to the coil 20b of the reader 20, it is necessary to excite the coil 1, so that energy must be supplied. Therefore, the control circuit 2
When the response is returned, the signal processing logic circuit 2c adjusts the output timing of the power supply instruction signal so that power is supplied from the battery 5, and is a component of the switch circuit 3. The signal is output to the base of the first transistor 3a through the second resistor 3d.

Then, the above-mentioned power supply signal becomes a base current, and the collector and emitter of the first transistor 3a become conductive, and this conduction causes the base current of the second transistor 3b to flow. Then, the second
The collector-emitter of the transistor 3b becomes conductive, and this conduction allows the battery to supply power to the control circuit 2.

In such a non-contact ID tag, when the power supply instruction signal is output from the control circuit 2, the switch circuit 3 opens and closes, and power is supplied from the battery 5 to the control circuit 2.
Since the battery 5 is supplied to the control circuit 2, it is not necessary to always supply the power from the battery 5 to the control circuit 2, and the battery life can be extended. Moreover, when the control circuit 2 determines that power is required, the power supply instruction signal is output, so that unnecessary power can be dispensed with.

When the control circuit 2 needs power, not only when a response is returned, but also when, for example, an EEP
There are times when data is written in the ROM 2b, and even in such a case, the control circuit 2 adjusts the timing at which the power supply instruction signal is output by the signal processing logic circuit 2c, and the first timing of the switch circuit 3 is adjusted. It will be output to the transistor 3a.

Next, a non-contact tag according to the second embodiment of the present invention will be described below with reference to FIG. The same elements as those in the first embodiment are designated by the same reference numerals, and only different points from the first embodiment will be described. In the first embodiment, the timing for outputting the power supply instruction signal is adjusted by the signal processing logic circuit 2c so that the power is supplied from the battery 5 at the same time as the response is returned. On the other hand, in the present embodiment, the coil voltage detection circuit 2d is provided, the coil voltage detected by the coil voltage detection circuit 2d is compared with the preset threshold voltage, and the coil voltage is induced. However, when the coil voltage is induced to such an extent that the control circuit 2 can be activated, the power supply instruction signal is changed to
The output timing is adjusted and output by the signal processing logic circuit 2c.

The reason why the power supply instruction signal is output when the coil voltage is induced is as follows.
That is, in the state where the coil 1 is not induced at all,
Since the coil 1 is not transmitting / receiving with the coil 20b of the reader 20, the power is supplied at such a time because unnecessary power is supplied. The threshold voltage compared to the coil voltage is EEPR
It is written in the OM 2b in advance.

In such a contactless ID tag, the coil voltage detection circuit 2d provided in the control circuit 2 compares the coil voltage with a preset threshold voltage, and the coil voltage is less than the threshold voltage. Since the power supply instruction signal is output when the control circuit 2 is not supplied with sufficient power, it is possible to reliably obtain the effect that unnecessary power can be dispensed with. .

Next, the contactless ID according to the third embodiment of the present invention.
The tags are described below. The same elements as those in the second embodiment are designated by the same reference numerals, and only different points from the second embodiment will be described. The third embodiment is basically the same as the second embodiment, except that a plurality of threshold voltages are set in advance and a threshold distance to be compared with the distance to the reader 20 is set. When the distance between and is less than the threshold distance, the threshold voltage is switched to a smaller value. The threshold distance compared to the distance to the reader 20 is
It is written in the EEPROM 2b in advance.

The distance between the reader 20 and
In addition, for example, it is possible to perform measurement by providing a distance measuring device of infrared type or ultrasonic type, and the value measured by the distance measuring device provided in the reader 20 is transmitted from the reader 20 so that non-contact It is input to the control circuit 2 of the ID tag.

In such a contactless ID tag, a plurality of threshold voltages are set in advance and a threshold distance to be compared with the distance to the reader 20 is set, and the distance to the reader 20 is the threshold distance. When the distance is less than the threshold voltage, the threshold voltage is switched to a smaller value. Therefore, when the distance to the reader 20 is short and a large amount of power is not required to return the response, the power supply is limited. As a result, it is possible to reliably obtain the effect of being able to dispense with supplying unnecessary power.

[0029]

According to the non-contact ID tag of claim 1, when the power supply instruction signal is output from the control circuit, the switch circuit is opened and closed to supply power from the battery to the control circuit. Therefore, it is not necessary to constantly supply electric power from the battery to the control circuit, and the battery life can be extended. Moreover, since the power supply instruction signal is output when the control circuit determines that power is needed, unnecessary power can be dispensed with.

In addition to the effect of the non-contact ID tag according to claim 1, the non-contact ID tag according to claim 2 is characterized in that the coil voltage detection circuit provided in the control circuit detects a coil voltage and a preset threshold voltage. When the coil voltage is induced but the voltage is less than the threshold voltage and sufficient power is not supplied to the control circuit, the power supply instruction signal is output. The effect of the non-contact ID tag according to the first aspect of the present invention is that it can be dispensed with without supplying.

In the non-contact ID tag according to a third aspect of the present invention, a plurality of threshold voltages are set in advance and a threshold distance to be compared with the distance to the reader is set, and the distance to the reader is less than the threshold distance. At this time, the threshold voltage is switched to a smaller value, so that the power supply is limited when the distance to the reader is short and a large amount of power is not required to send back a response. As a result, the effect of the non-contact ID tag according to claim 1 that can be dispensed with without supplying unnecessary electric power can be surely exhibited.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a first embodiment of the present invention.

FIG. 2 is a circuit diagram of a second embodiment of the present invention.

FIG. 3 is a circuit diagram of what is disclosed in JP-A-13-6061.

[Explanation of symbols]

1 coil 2 control circuit 2d coil voltage detection circuit 3 switch circuit 5 batteries 10 Non-contact ID tag 20 leader

Continued front page    (72) Inventor Hidefumi Tanaka             1048, Kadoma, Kadoma-shi, Osaka Matsushita Electric Works Co., Ltd.             Inside the company F-term (reference) 5B035 AA06 BB09 CA13 CA23                 5K012 AB12 AC06 AC08 AC10 AE13

Claims (3)

[Claims] 1. A coil for receiving a command transmitted from a reader and returning a response to the reader, a control circuit for controlling the coil to return a response, and a control circuit for controlling the electric power required for the response by the coil. A non-contact ID tag in which a coil is induced by electromagnetic induction by a reader, and a power supply instruction signal is output from the control circuit to supply the power to the control circuit from the battery. A contactless ID tag, characterized in that a switch circuit that opens and closes at times is provided, and the control circuit outputs the power supply instruction signal when it is determined that the power is required. 2. The control circuit is provided with a coil voltage detection circuit for detecting a coil voltage induced in the coil by a reader-side coil of the reader, and preset with the coil voltage detected by the coil voltage detection circuit. The contactless ID tag according to claim 1, wherein the power supply instruction signal is output when the coil voltage is induced but less than the threshold voltage by comparing the generated threshold voltage. 3. A plurality of the threshold voltages are set in advance, a threshold distance to be compared with the distance to the reader is set, and when the distance to the reader is less than the threshold distance, The contactless ID tag according to claim 2, wherein the threshold voltage is switched to a smaller value.