JP5333100B2 - RF tag - Google Patents

Description

  The present invention relates to an RF tag used for RFID applications, sensor applications, and the like, and more particularly, to a passive type RF tag.

  In recent years, RF tags (passive type or battery-less RF tags) that operate with power generated by receiving a carrier wave having a predetermined frequency (for example, 13.56 MHz) are commercially available. In general, an RF tag receives a carrier wave emitted from a reader / writer of the RF tag with an antenna, amplifies the received power by a resonance action between the reactance of the antenna and a capacitor built in the tag, and then is converted into a rectifier circuit. It operates with a direct current power source.

  FIG. 1 shows a block diagram of a configuration example of a conventional RF tag. The RF tag receives a radio wave from the reader / writer, and transmits the radio wave to the reader / writer. The resonance unit for amplifying power by resonating with the output (alternating current) of the antenna unit 201 203, a rectifying unit 205 for outputting a direct current, and a regulator 207 for stabilizing the voltage and a processing unit 209 operated by an output from the regulator 207 at the subsequent stage of the rectifying unit 205. The processing unit 209 includes a controller 211 having a data processing function and a memory 213 having a data holding function. The memory 213 is, for example, a nonvolatile memory.

  FIG. 2 is a diagram showing a part of the configuration of the conventional RF tag shown in FIG. 1 as an equivalent circuit. The RF tag includes an antenna 301 provided with a reactance as an antenna unit 201 that communicates with an antenna 401 of a reader / writer, and includes a capacitor 303 as a resonance unit 203 that is subjected to a resonance action with the reactance. A rectifier circuit 305 configured by a diode is provided as the rectifier unit 205 for converting and outputting.

  The power received by the RF tag (power generated in the RF tag) is determined by the magnitude of the radio wave output from the reader / writer 401, the distance between the reader / writer 401 and the RF tag, and the resonance action inside the RF tag. The The magnitude of the electric power is determined by these factors, and does not depend on the magnitude of the current consumed by the RF tag. That is, when the current consumed by the RF tag is large, the voltage decreases, and when the current consumed by the RF tag is small, the voltage increases.

  The received power received by the RF tag (power generated inside the RF tag) needs to be consumed by some method. That is, even when the power required for the operation of the RF tag is small, when a large amount of power is received, it is necessary to consume the surplus power by some method.

  The RF tag usually includes a rectifier circuit 305, and further includes a shunt regulator circuit 207 subsequent to the rectifier circuit 305. The shunt regulator circuit 207 has a function of keeping the voltage applied to the circuit at a constant voltage when the RF tag circuit (controller or the like) 209 consumes a current necessary for its operation. Excess power generated when the shunt regulator 207 performs step-down is consumed by a resistor provided in the shunt regulator 207 itself. Furthermore, when the input power is larger than the maximum power consumed by the shunt regulator 207, the output voltage of the rectifier circuit 305 increases, and a voltage higher than the reverse bias voltage is applied to the diode constituting the rectifier circuit 305. Current flows in the reverse bias direction of the rectifier circuit. In the RF tag, the power consumed by the resistor included in the shunt regulator 207 for making the voltage applied to the circuit constant and the power consumed by the current in the reverse bias direction of the rectifier circuit 305 result in heat. Released.

  In addition to the RF tag, in recent years, a semiconductor temperature sensor has been put into practical use and has been distributed to the market. The semiconductor temperature sensor can be formed on-chip with a semiconductor circuit having other functions, and when combined with an RF tag semiconductor, a wireless thermometer RF tag can be realized in combination with a reader / writer. With the wireless thermometer RF tag, it is possible to read temperature information detected by the semiconductor temperature sensor with a reader / writer by pasting it on a predetermined object.

  The radio thermometer RF tag can be used as a radio thermometer by attaching it to a human body. The wireless thermometer is always attached to an inpatient in the hospital, and the temperature can be read with a reader / writer at the time of temperature measurement. Time-consuming work is not necessary. Even when the patient is asleep, the body temperature can be measured simply by bringing the reader / writer close to a place where the thermometer is located. In order to use it as a wireless thermometer, it is effective to configure the RF tag as a battery-free tag and to reduce its size and thickness.

  However, in the RF tag, the power consumed by the resistor included in the shunt regulator for making the voltage applied to the circuit constant and the power consumed by the current in the reverse bias direction of the rectifier circuit result in heat. Released. Also, the RFID tag has a relatively small heat capacity. Therefore, there is a problem that the released heat affects the temperature sensor part of the RF tag with a temperature sensor (wireless thermometer RF tag). From this point of view, the radio thermometer RF tag consumes current due to the operation of its circuit, generates heat, and affects the measurement result of the temperature sensor, thereby degrading measurement accuracy. Is required to reduce Also, in order to secure a large communication distance, it is desirable that the RF tag itself consumes less power.

  In addition, when a radio thermometer RF tag is attached to a human body and used as a thermometer, if the RF tag itself generates heat, the human body may be burned, and a serious accident may also occur. For example, in the case of a wireless thermometer RF tag that uses 13.56 MHz, the automatic ticket checker at a station always emits a 13.56 MHz radio wave, so the person who attached the RF thermometer RF tag is still in the automatic ticket checker. As a result, the RF tag may resonate and generate heat.

  For example, Patent Document 1 (Japanese Patent Application Laid-Open No. 2007-114925) relates to a system including an RF tag and a reader / writer having a sensor function. In this document, in order to increase the accuracy of the sensor, the radio wave from the reader / writer is intermittently interrupted, the power supply to the element (circuit) subsequent to the rectifier circuit is interrupted, the antenna It is described that a variable capacitor is adopted as a capacity for resonating with the other coil, and the resonance frequency is changed by controlling the capacitance.

  An object of the invention of Patent Literature 1 is to suppress heat generated when an RF tag receives power supply from a reader / writer by a carrier (carrier wave) and is consumed in a circuit in the RF tag.

  In Patent Document 1, for example, the temperature rise of the tag is suppressed by intermittently interrupting the power supply from the reader / writer (Claim 1). In this case, control on the reader / writer side is necessary. Therefore, this method requires a reader / writer configuration corresponding to such control. However, in the current situation where many readers / writers that do not support such control are distributed, the effectiveness of the above-described suppression of unintended temperature rise in the market of the wireless thermometer is questionable.

  Patent Document 1 describes an invention for controlling a power supply circuit such as a regulator inside an RF tag (Claim 5). However, the power actually received by the antenna of the RF tag is consumed by some means. In the embodiment, the current supply to some or all of the circuits after the rectifier circuit is cut off, but the surplus power is consumed by the rectifier circuit, so the contribution to the suppression of the temperature rise is limited. In other words, as long as the power received by the RF tag antenna does not change, if the power supply path to the circuit in the subsequent stage of the regulator is cut, the voltage at the end of the antenna rises by that amount and reverses to the rectifier circuit that is normally composed of a diode. When a voltage exceeding the bias is applied, current flows, and heat is generated by this current.

  Further, in Patent Document 1, in the embodiment, it is described that a variable capacitor serving as a capacitor provided for resonance with the reactance of the antenna is controlled to change the resonance frequency. However, it is unclear whether the capacity will be changed.

  If the variable capacitor C1 used for resonance is provided between two terminals connected to the antenna as shown in FIG. 9 of Patent Document 1, it is significant to mechanically control the trimmer capacitor. In addition, a configuration in which a large number of small capacitors are provided as variable capacitors and a part of the switch is turned on / off by a semiconductor switch is considered, but the potential of the antenna fluctuates in both plus and minus compared to the reference ground generated by the rectifier circuit, It is difficult to configure a semiconductor switch that can be easily mounted on a tag.

  In other words, the technique disclosed in Patent Document 1 in which resonance is shifted by the variable capacitors provided at both ends of the antenna is difficult to implement with a transistor switch. Further, if resonance is shifted, power supply for operating the RF tag itself is cut off. This also turns off the power supply of the circuit that generates the signal for controlling the variable capacitor, making it difficult to control the resonance.

  The present invention has been made in view of the above-described problems. An object of this invention is to provide the RF tag which can suppress heat_generation | fever with a cheap structure.

  In one aspect, the present invention provides an antenna unit that receives a radio wave having a predetermined frequency, a resonance unit that has a resonance capacity that resonates with a current flowing through the antenna unit upon reception of the radio wave, and an output of the resonance unit. An RF tag having a rectifying unit that receives and outputs a direct current, and a processing unit that operates using the output of the rectifying unit as a power source, and further includes a voltage monitor that measures the voltage of the output of the rectifying unit, and the processing unit Includes a power supply control unit that outputs a power supply control signal for changing at least the output of the resonance unit by changing the resonance capacitance of the resonance unit based on the voltage measurement value output by the voltage monitor, and the resonance unit is included in the power supply control signal. The RF tag includes first resonance frequency changing means for changing the resonance capacitance based on the first resonance frequency changing means.

  In one aspect, the present invention provides an antenna unit that receives a radio wave having a predetermined frequency, a resonance unit that has a resonance capacity that resonates with a current flowing through the antenna unit upon reception of the radio wave, and an output of the resonance unit. An RF tag having a rectifying unit that receives and outputs a direct current, and a processing unit that operates using the output of the rectifying unit as a power source, and further includes a temperature sensor, and the processing unit measures temperature output from the temperature sensor. A power supply control unit that outputs a power supply control signal that changes the resonance capacity of the resonance unit based on the value to at least reduce the output of the resonance unit, and the resonance unit changes the resonance capacitance based on the power supply control signal. This is an RF tag comprising the resonance frequency changing means.

  In one aspect, the present invention provides an antenna unit that receives a radio wave having a predetermined frequency, a resonance unit that has a resonance capacity that resonates with a current flowing through the antenna unit upon reception of the radio wave, and an output of the resonance unit. An RF tag having a rectifying unit that receives and outputs a direct current, and a processing unit that operates using the output of the rectifying unit as a power source, and further includes a voltage monitor that measures the voltage of the output of the rectifying unit, and the processing unit Includes a power supply control unit that outputs a power supply control signal that controls disconnection and connection of the rectifier circuit of the rectifier unit based on the voltage measurement value output from the voltage monitor, and the rectifier unit includes a power supply control signal based on the power supply control signal. It is RF tag provided with the 2nd resonance frequency change means by performing a cutting | disconnection and connection.

  In one aspect, the present invention provides an antenna unit that receives a radio wave having a predetermined frequency, a resonance unit that has a resonance capacity that resonates with a current flowing through the antenna unit upon reception of the radio wave, and an output of the resonance unit. An RF tag having a rectifying unit that receives and outputs a direct current, and a processing unit that operates using the output of the rectifying unit as a power source, and further includes a temperature sensor, and the processing unit measures temperature output from the temperature sensor. A power supply control unit that outputs a power supply control signal that controls disconnection and connection of the rectifier circuit of the rectifier unit based on the value. The rectifier unit is configured to disconnect and connect the rectifier circuit based on the power supply control signal. This is an RF tag comprising the resonance frequency changing means.

  In one embodiment of the present invention, there is further provided a power control signal holding unit including a register that outputs a power control signal that receives and holds the power control signal and a holding power source that supplies power to the register. The holding power supply unit preferably stores the power supplied to the register from the direct current output from the rectification unit.

  In one embodiment of the present invention, the resonance unit, the rectification unit, and the processing unit are preferably formed in one semiconductor chip.

  In one aspect, the present invention provides an antenna unit that receives a radio wave having a predetermined frequency, a resonance unit that has a resonance capacity that resonates with a current flowing through the antenna unit upon reception of the radio wave, and an output of the resonance unit. An RF tag having a rectifying unit that receives and outputs a direct current, and a processing unit that operates using the output of the rectifying unit as a power source, and a current flowing through the antenna unit is predetermined between the antenna unit and the resonance unit. It is an RF tag having current blocking means for blocking current flowing from the antenna section to the resonance section when the size becomes larger than the value.

  In one aspect of the present invention, the current interrupting means preferably includes a current fuse.

  The present invention has an effect of providing an RF tag capable of suppressing heat generation with a low-cost configuration.

Block diagram showing the configuration of a conventional RF tag Configuration diagram showing the configuration of a conventional RF tag, a part of which is represented by an equivalent circuit Block diagram of the RF tag according to the first embodiment Configuration diagram of the RF tag according to the first embodiment, a part of which is represented by an equivalent circuit Configuration diagram of the RF tag according to the first embodiment, a part of which is represented by an equivalent circuit Configuration diagram of the RF tag according to the first embodiment, a part of which is represented by an equivalent circuit Configuration diagram of the RF tag according to the first embodiment, a part of which is represented by an equivalent circuit Configuration diagram of the RF tag according to the first embodiment, a part of which is represented by an equivalent circuit Block diagram of a modification of the RF tag according to the first embodiment Partial configuration diagram of an RF tag including a power control signal holding unit Block diagram of an RF tag according to the second embodiment Block diagram of a modification of the RF tag according to the second embodiment Block diagram of an RF tag according to the third embodiment Equivalent circuit diagram of the part related to the rectifier The figure which shows the effect to the rectification part constitution example and the resonance part by the CMOS transistor The block diagram of the RF tag modification which concerns on 3rd Embodiment Block diagram of an RF tag according to the fourth embodiment The block diagram of the RF tag modification which concerns on 4th Embodiment Block diagram of an RF tag according to the fifth embodiment Configuration diagram of an RF tag according to the fifth embodiment, a part of which is represented by an equivalent circuit

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  Embodiments described herein relate generally to an RF tag. The RF tag is an RF tag that is configured inexpensively and simply, and can suppress heat generation due to power consumption inside the RF tag. In the RF tag according to the first to fourth embodiments, the operation is controlled by the processing unit circuit that is in the subsequent stage of the rectifying unit and operates with the output from the regulator that stabilizes the output of the rectifying unit. Shows an RF tag in which heat generation is suppressed. In the RF tag according to the fifth embodiment, an RF tag in which heat generation is well suppressed without requiring the processing unit to be provided with the configuration related to the above control is shown.

  According to the first embodiment, an RF tag is provided in which the processing unit circuit controls the resonance frequency of the resonance unit based on the level of the voltage applied to the output of the rectification unit and suppresses heat generation.

  According to the second embodiment, an RF tag is provided in which the processing unit circuit controls the resonance frequency of the resonance unit based on the level of the temperature value output from the temperature sensor and suppresses heat generation.

  According to the third embodiment, an RF tag is provided in which the processing unit circuit controls connection / disconnection of the rectifying unit based on the level of the voltage applied to the output of the rectifying unit, and suppresses heat generation.

  According to the fourth embodiment, an RF tag is provided in which the processing unit circuit controls connection / disconnection of the rectifying unit based on the level of the temperature value output from the temperature sensor and suppresses heat generation.

  According to the fifth embodiment, the current blocking means arranged between the antenna unit and the resonance unit blocks the connection between the antenna unit and the resonance unit when a current of a predetermined value or more flows. An RF tag that suppresses heat generation is provided.

  The RF tag according to the embodiment of the present invention has a function of suppressing heat generation in any form, and can be simply configured with an inexpensive semiconductor switch. Therefore, the RF tag is advantageous in terms of cost and compact configuration. Note that the RF tag according to the embodiment of the present invention can be configured as an RFIC tag including one or a plurality of semiconductor integrated circuits in any form.

  In any form, the RF tag according to the embodiment of the present invention can constitute a radio thermometer RF tag in combination with a semiconductor temperature sensor, and can be used as a medical thermometer as a radio thermometer. This is advantageous in terms of compactness of the configuration, and is advantageous in that there is no risk of burns to the human body due to its own heat generation.

  The RF tag according to the embodiment of the present invention can be used in the physical distribution field as an RFID tag in any form. Regarding such applications, the RF tag according to the embodiment of the present invention is advantageous in that there is no possibility of causing an accident such as a fire due to its own heat generation.

<First Embodiment>
FIG. 3 is a block diagram showing the configuration of the RF tag according to the first embodiment. The RF tag includes an antenna unit 101 that receives a carrier wave from a reader / writer (not shown), a resonance unit 103 that has a capacitance that resonates with the reactance of the antenna unit 101 (resonance capacitance), and an alternating current that is output from the resonance unit 103. The voltage rectifier 105 for supplying the direct current to the subsequent stage, the voltage at the output of the rectifier 105 is measured, and the measurement result is output to the power supply controller 115 of the processing unit 109 described later, and the output of the rectifier 105 is output. A regulator 107 that receives direct current and stabilizes and outputs a voltage (for example, constant voltage), and a processing unit 109 that operates by receiving the output of the regulator 107 are provided. The processing unit 109 controls the capacity of the resonance unit 103 based on the voltage measurement value output from the controller 111 that controls the operation of the RF tag, for example, a memory 113 that stores and holds data, such as a nonvolatile memory, and the voltage monitor 106. A power control unit 115 for controlling is provided.

  The resonance unit 103 includes first resonance frequency changing means 103a. The first resonance frequency changing unit 103a changes the capacitance of the resonance unit 103 based on the power supply control signal 117 output from the power supply control unit 115 included in the processing unit 109, and thereby resonates with the reactance of the antenna unit 101. Adjust the degree of action.

  When the antenna unit 101 receives a carrier wave from a reader / writer (not shown), a resonance action occurs between the antenna unit 101 and the resonance unit 103, and power amplified by the resonance action is sent to the rectification unit 105. The rectifying unit 105 converts alternating current applied to the power into direct current and outputs the direct current. Here, the voltage monitor 106 sends the voltage value obtained by monitoring the voltage applied to the output of the rectifying unit 105 to the power supply control unit 115 of the control unit 109. The power supply control unit 115 changes the signal level of the power supply control signal 117 and operates the first resonance frequency changing unit 103a of the resonance unit 103 when the voltage value becomes a predetermined value or more. When the capacity of the resonance unit 103 is changed by the action of the first resonance frequency changing unit 103a, the degree of the resonance action is reduced, and the power supplied to the rectifying unit 105 is reduced. In this way, the power generated inside the RF tag is suppressed, and the amount of heat generated inside the RF tag is reduced.

FIG. 4A is an equivalent circuit diagram illustrating an example of the resonance unit 103 and the first resonance frequency changing unit 103a. The resonating unit 103 has a variable capacitor 3. Then, the first resonance frequency changing unit 103a changes the capacity of the variable capacitor 3 based on the power control signal 117 output from the processing unit 109 (the power control unit 115). By changing the capacity of the variable capacitor 3, the degree of resonance with the reactance 1 of the antenna unit 101 is changed, and by doing so, the magnitude of power supplied to the rectifying unit 5 is changed.
FIG. 4B is a diagram showing an example in which the variable capacitor 3 of FIG. 4A is built in a semiconductor chip as a semiconductor circuit. When the variable capacitor 3 is configured as a semiconductor circuit, the variable capacitor 3 (FIG. 4a) can be configured by a variable capacitor 3c whose capacitance value is changed by voltage. In this case, the first resonance frequency changing unit 103a controls the voltage of the variable capacitor 3c based on the power supply control signal output from the processing unit 109 (the power supply control unit), thereby resonating the unit 103 (FIG. 3). Change the capacity.

  FIG. 5a is a diagram showing another example in which the variable capacitor 3 of FIG. 4a is configured as a semiconductor circuit. When the variable capacitor 3 is configured as a semiconductor circuit, the variable capacitor 3 (FIG. 4a) can be configured as a capacitor 3a having a plurality of fixed capacitances and a switch 3b connected to the capacitor 3a. In this case, the first resonance frequency changing unit 103a controls the on / off of the plurality of switches 3b based on the power supply control signal output from the processing unit 109 (the power supply control unit), so that the resonance unit 103 ( The capacity of FIG. 3) is changed.

The capacitor 3a and the switch 3b in FIG. 5a can be incorporated in a semiconductor chip as a semiconductor circuit. In this case, when the switch 3b is formed of a transistor, it may be configured such that a differential potential difference is applied between the source and the drain.
FIG. 5B is a diagram showing an example in which the variable capacitor 3a and the switch 3b of FIG. 5A are easier to manufacture at a lower cost when configured as a semiconductor circuit. The capacitor 3a and the switch 3b in FIG. 5b can be configured with a capacitor and a switch having a lower withstand voltage than those in FIG. 5a. When a capacitor with a lower withstand voltage can be used, the capacitor configured on the semiconductor can make the interlayer film thinner, increase the capacitance per area, and as a result, the chip area can be reduced and manufactured at low cost. It is.

  FIG. 6 is a diagram illustrating an example in which the resonance unit 103 and the first resonance frequency changing unit 103a (both of FIG. 3) are configured as semiconductor circuits. In this example, the resonance unit 103 includes a capacitor (capacitor) 3c and a plurality of capacitors 3d connected in series in parallel with the capacitor 3c with a ground potential interposed therebetween. The first resonance frequency changing unit 103a is configured as a transistor switch 3e disposed between the capacitor 3d and the ground potential. A power control signal 117 from the processing unit 109 is connected to the transistor switch 3e. The power source control signal 117 switches on / off of the transistor switch 3e (for example, when the switch 3e is turned on), the resonance frequency of the resonance unit 103 changes, and the degree of resonance with the reactance 1 is reduced. The power generated in the RF tag is reduced.

  The power control signal 117 can take, for example, a low level (L) and a high level (H). If the transistor switch 3e is an N-ch transistor, the capacitance 3c and the plurality of capacitances 3d so that the combined capacitance of the capacitance 3c and the plurality of capacitances 3d resonates well with the reactance 1 when the power control signal 117 is at the L level. A value should be set. When the power control signal 117 is at the H level, the combined capacitance changes and the resonance frequency shifts, so that the power generated in the RF tag can be reduced. If the power is reduced, the power consumed in the RF tag is naturally reduced, and the heat generation amount of the RF tag can be suppressed.

  In addition, when changing the capacity | capacitance (resonance capacity | capacitance of the capacity | capacitance 3c and the capacity | capacitance 3d) of the resonance part 103 with the transistor switch 3e, as above-mentioned, the structure capacity | capacitance is increased by turning on the transistor switch 3e. However, conversely, the combined capacitance may be reduced by turning on the transistor switch 3e.

  In the present embodiment, the power supply control signal 117 for shifting (changing) the resonance frequency is converted into a direct current signal (AC) generated by the resonance action of the antenna unit 101 and the resonance unit 103 by the rectification unit 105, Further, it is generated in the processing unit 109 that operates with an output that has been made a constant voltage by the regulator 107. Therefore, the RF tag according to the present embodiment can suppress the heat generation of the RF tag regardless of the specifications of the reader / writer, that is, without controlling the power of the carrier generated by the reader / writer. Is possible.

  As described above, in the present embodiment, the resonance frequency of the resonance unit 103 is changed by switching the on / off state of the transistor switch 3e, the power generated inside the RF tag is reduced, and heat generation is suppressed. I am trying. Therefore, even when the electromagnetic field output from the reader / writer is large and the amount of heat generated by the power consumption inside the RF tag is large, the power generated inside the RF tag is small. It is possible to suppress the heat generation amount.

<Modification of First Embodiment>
FIG. 7 is a block diagram showing a configuration of an RF tag according to a modification of the first embodiment. In addition to the configuration of the RF tag according to the first embodiment shown in FIG. 3, the RF tag according to the present modification further receives the power supply control signal 117 and holds the power supply for the register 123 and the power supply for the register 123. A power control signal holding unit 121 including a power source unit 125 for power supply.

  In the first embodiment described with reference to FIGS. 3 to 6, the magnitude of the power generated from the carrier wave received by the antenna unit 101 by shifting the resonance frequency of the resonance unit 103 (FIG. 3). To suppress the heat generated. On the other hand, the power that can be used by the RF tag is decreased by shifting the resonance frequency of the resonance unit 103, so that the power control unit 115 of the processing unit 109 sets the power control signal 117 for shifting the resonance frequency to a desired level. It may be difficult to maintain (for example, H level). When the power supply control signal 117 cannot maintain a predetermined level (for example, H level), the resonance frequency of the resonance unit 103 (FIG. 3) returns to the original level, and the generated power is restored to its original magnitude. Then, the voltage monitor 106 detects the voltage rise again, and the power control signal 117 becomes a predetermined level (for example, H level). In this manner, a situation in which the power control signal 117 frequently alternates between the H level and the L level appears, and the heat generation suppressing effect may be impaired.

  Therefore, in this modification, a configuration for holding the power control signal 117 is added to the configuration between the first resonance frequency changing unit 103a and the power control unit 115, and the configuration is supplied to the processing unit 109. In this case, the signal level of the power control signal 117 is stabilized when the power to be reduced is reduced.

  FIG. 8 is an equivalent circuit diagram showing the configuration of the power supply control signal holding unit 121 (FIG. 7) in this modification. Thus, the power supply control signal holding unit 121 is provided with the register 23 (123) that holds the level of the power supply control signal 117. Then, as the holding power supply unit 125 that is the power supplied to the register 23, the electrical energy held in the capacitor 25 a when the voltage level of the power supply supplied to the capacitor 25 a and the processing unit 109 is lowered to the processing unit 109. A diode 25b (a backflow prevention diode) is provided to prevent outflow. In the present modification, the signal level held by the register 123 is used as the power control signal 117 supplied to the first resonance frequency changing unit 103a.

  By configuring the power supply control signal holding unit 121 in this way, the signal level of the register 123 is kept constant while sufficient power is stored in the holding power supply unit 125, and heat generation is continuously suppressed. A sufficient heat dissipation effect can be expected. Eventually, the electrical energy stored in the holding power supply unit 125 gradually decreases due to the leakage current, the register 123 cannot maintain the signal level, and the level of the power control signal 117 returns (for example, to the L level). The resonance frequency 103 (FIG. 7) is restored. Note that since the size of the capacitor 25a of the holding power supply unit 125 is related to the length of time that the register 123 can maintain the signal level, the time for heat dissipation, the time interval for suppressing heat generation, and the like are taken into consideration. And may be determined as appropriate.

<Second Embodiment>
FIG. 9 is a block diagram showing a configuration of an RF tag according to the second embodiment. The RF tag according to the present embodiment has a configuration in which the voltage monitor 106 (FIG. 3) is omitted from the configuration of the RF tag according to the first embodiment shown in FIG. 3, and a temperature sensor 131 is added instead. The temperature sensor 131 may be a semiconductor temperature sensor and may be configured integrally with the processing unit 109a.

  The output of the temperature sensor 131, that is, the temperature measurement value is input to the power supply control unit 115a. The power supply control unit 115a switches the power supply control signal 117 to a predetermined level (for example, H level) when the temperature measurement value is equal to or higher than a predetermined temperature value.

  Thus, in the RF tag according to the present embodiment, by the control operation by the temperature sensor 131 and the power supply control unit 115a that is operated by the electric power that has been converted to direct current by the rectification unit 105 and constant voltage by the regulator 107, The resonance frequency of the resonance unit 103 is changed according to the temperature, and thus heat generation of the RF tag is suppressed.

<Modification of Second Embodiment>
FIG. 10 is a block diagram illustrating a configuration of an RF tag according to a modification of the second embodiment. The RF tag according to this modification has a configuration in which a power control signal holding unit 121 having a register 123 and a holding power supply unit 125 is further added to the RF tag (second embodiment) shown in FIG. .

  As described above, the RF tag according to the present modification also has the signal level of the power supply control signal 117 when the power supplied to the processing unit 109 is reduced, similarly to the RF tag according to the modification of the first embodiment. Stabilization is planned. Note that the configuration of the register 121 and the holding power supply unit 125 may be the same as the configuration shown in FIG. 8 in connection with the modification of the first embodiment.

<Third Embodiment>
FIG. 11 is a block diagram showing a configuration of an RF tag according to the second embodiment. The RF tag according to the present embodiment is the same as that of the RF tag according to the first embodiment shown in FIG. 3 except that the rectifier 105 is based on the power control signal 117 instead of the first resonance frequency changing means 103a. It has a configuration in which a second resonance frequency changing means 105a that operates by cutting off or connecting the rectifier circuit is added. The second resonance frequency changing unit 105a may be configured integrally with the rectifier circuit 105 as a semiconductor circuit.

  The second resonance frequency changing unit 105a shorts the rectifier circuit of the rectifier 105 when the power control signal 117 output from the power controller 115 of the processor 109 is at a predetermined level (for example, H level). By invalidating part of the resonance capacitance of the resonance unit 103 and changing the resonance capacitance value, the degree of resonance action is reduced, and the power supplied to the rectification unit 105 is reduced. In this way, the power generated inside the RF tag is suppressed, and the amount of heat generated inside the RF tag is reduced.

  FIG. 12A is an equivalent circuit diagram of the rectifying circuit of the rectifying unit 105. When the rectifier circuit represented in this way is mounted using CMOS transistors, each element may be configured as shown in FIG. For example, the transistor 105a configuring the rectifier circuit is configured by an NMOS transistor and has a gate grounded. Even if the drain is at a higher potential than the ground potential or at a lower potential, the difference is within the threshold voltage of the NMOS transistor, but the drain is off, but the drain potential is lower than the ground potential by exceeding the threshold voltage. If so, it turns on and functions as a diode.

  FIG. 13 is a diagram showing a configuration in which second resonance frequency changing means 105a is added to the rectifier circuit shown in FIG. 12 (b). As described above, the second resonance frequency changing unit 105a can be configured by connecting the power supply control signal 117 to one or a plurality of gates constituting the diode of the rectifier circuit. In this case, the rectifier circuit 105 is short-circuited when the power supply control signal 117 is active (for example, H level). As a result, both ends of the part 103b of the capacitor in the resonance unit 103 are short-circuited. Be changed.

  As described above, in the RF tag according to this embodiment, the potential of the gate of the transistor functioning as a diode of the rectifier circuit and the signal (alternating current) generated by the resonance action of the antenna unit 101 and the resonance unit 103 are converted into the rectification unit. Control is performed by a power supply control signal 117 generated in the processing unit 109 which is turned into a direct current at 105 and operates with an output having a constant voltage output by the regulator 107. The power control signal 117 changes based on whether or not the voltage applied to the output of the rectifying unit 105 is equal to or higher than a predetermined value. Therefore, this RF tag can suppress the heat generation of the RF tag by changing the resonance frequency in accordance with the level of the output voltage of the rectifying unit 105.

<Modification of Third Embodiment>
FIG. 14 is a block diagram illustrating a configuration of an RF tag according to a modification of the third embodiment. The RF tag according to this modification has a configuration in which a power supply control signal holding unit 121 having a register 123 and a holding power supply unit 125 is further added to the RF tag (third embodiment) shown in FIG. .

  As described above, the RF tag according to the present modification also has the power supply control signal 117 when the power supplied to the processing unit 109 is reduced, similarly to the RF tag according to the modification of the first and second embodiments. The signal level is stabilized. Note that the configuration of the register 121 and the holding power supply unit 125 may be the same as the configuration shown in FIG. 8 in connection with the modification of the first embodiment.

<Fourth embodiment>
FIG. 15 is a block diagram showing a configuration of an RF tag according to the fourth embodiment. The RF tag according to the present embodiment has a configuration in which the voltage monitor 106 (FIG. 11) is omitted from the configuration of the RF tag according to the third embodiment shown in FIG. 11, and a temperature sensor 131 is added instead. The temperature sensor 131 may be a semiconductor temperature sensor and may be configured integrally with the processing unit 109a.

  The output of the temperature sensor 131, that is, the temperature measurement value is input to the power supply control unit 115a. The power supply control unit 115a switches the power supply control signal 117 to a predetermined level (for example, H level) when the temperature measurement value is equal to or higher than a predetermined temperature value.

  Thus, in the RF tag according to the present embodiment, by the control operation by the temperature sensor 131 and the power supply control unit 115a that is operated by the electric power that has been converted to direct current by the rectification unit 105 and constant voltage by the regulator 107, The resonance frequency of the resonance unit 103 is changed according to the temperature, and thus heat generation of the RF tag is suppressed.

<Modification of Fourth Embodiment>
FIG. 16 is a block diagram illustrating a configuration of an RF tag according to a modification of the fourth embodiment. The RF tag according to the present modification has a configuration in which a power control signal holding unit 121 having a register 123 and a holding power supply unit 125 is further added to the RF tag (fourth embodiment) shown in FIG. .

  As described above, the RF tag according to the present modification is also the same as the RF tag according to the modification of the first, second, and third embodiments when the power supplied to the processing unit 109 is reduced. The signal level of the power control signal 117 is stabilized. Note that the configuration of the register 121 and the holding power supply unit 125 may be the same as the configuration shown in FIG. 8 in connection with the modification of the first embodiment.

<Fifth embodiment>
FIG. 17 is a block diagram showing a configuration of an RF tag according to the fifth embodiment. The RF tag has a function of blocking the flow when the magnitude of current between the antenna unit 101 that receives a carrier wave from a reader / writer (not shown) and the antenna unit 101 and the resonance unit 103 exceeds a predetermined value. The current interrupting means 102, the resonance unit 103 having a capacity that resonates with the reactance of the antenna unit 101, the AC output from the resonance unit 103 is rectified, the DC is supplied to the subsequent stage, and the output of the rectification unit 105 is output. A regulator 107 that receives direct current and stabilizes and outputs a voltage (for example, constant voltage), and a processing unit 109 that operates by receiving the output of the regulator 107 are provided. The processing unit 109 includes a controller 111 and a memory 113.

  FIG. 18 is a diagram showing an RF tag current interrupting means 102 according to the fifth embodiment in an equivalent circuit. As described above, the current interrupting means 102 includes the current fuse 2 that disconnects the electrical connectivity when the magnitude of the current flowing through the antenna 1 exceeds a predetermined value. Since the electrical connectivity between the antenna 1 and the capacitor 3 is cut off by the action of the current fuse 2, the current flow after the capacitor 3 is eliminated, and the heat generation of the RF tag is suppressed.

  The RF tag according to the present embodiment has a very simple configuration by providing the current fuse 2 between the antenna unit 101 (antenna 1) and the resonance unit 103 (capacitor 3) as the current interrupting means 102, and has an extremely simple configuration. It is possible to reliably prevent excessive heat generation. For example, when a wireless thermometer is constructed by adding a semiconductor temperature sensor to an RF tag and affixing it to a human body, it is effective as an absolute safety measure for preventing burns.

  Note that any of the RF tags according to the embodiments of the present invention can be configured in combination with a semiconductor temperature sensor or the like to form a wireless thermometer RF tag. The radio thermometer RF tag can also be used as a radio thermometer used as a medical device in contact with a human body. The RF tag according to this embodiment has a function of suppressing excessive heat generation, and is very useful from the viewpoint of burn prevention or the like when used as a wireless thermometer.

  In the RF tag according to the first to fourth embodiments of the present invention, the controller 111 included in the processing unit 109 receives a command from the reader / writer and sends it to the power control unit 115 (or 115a). It is also possible to configure to issue an instruction to change the signal level of the power control signal 117. With this configuration, the RF tag suppresses heat generation according to instructions from the reader / writer in addition to heat generation suppression control based on the level of the output voltage of the rectifier 105 and / or the temperature inside the RF tag. It is also possible to control.

  You may combine the structure concerning the RF tag by the 1st thru | or 5th embodiment concerning this invention. For example, by providing the voltage monitor 106 and the temperature sensor 131, it is possible to perform complex heat generation suppression control based on the output voltage of the rectifier circuit 105 and the temperature inside the RF tag. In this case, the heat generation suppression control may be executed when both the output voltage of the rectifier circuit 105 and the internal temperature of the RF tag exceed a predetermined value, or the output voltage of the rectifier circuit 105 and the internal temperature of the RF tag may be controlled. You may make it perform heat_generation | fever suppression control, when either one exceeds predetermined value.

  In the RF tag according to the embodiment of the present invention, when an excessive electric power that leads to an excessive temperature rise is received by the resonance capacitor and the switch formed on the semiconductor, the RF tag itself detects it, or the reader / The resonance frequency of the RF tag can be shifted by a command from the writer. By shifting the resonance frequency, the received power received by the tag from the reader / writer is reduced, and by reducing the power consumption of the tag, it is possible to reduce heat generation from the RF tag itself.

  In the RF tag according to the embodiment of the present invention, the power received from the reader / writer increases, the RF tag generates excessive heat, and the temperature of the RF tag itself rises, and the temperature sensor built in the RF tag detects. When the temperature exceeds a certain value, it is possible to suppress heat generation by performing a control operation for reducing the received power.

  In the RF tag according to the embodiment of the present invention, even when the received power when the resonance frequency is changed is smaller than the power that maintains the signal level of the signal instructing the change of the resonance frequency, The state in which the frequency is shifted is maintained for a certain period of time, and it is possible to contribute to heat dissipation until the resonance frequency returns to the original state.

  In the RF tag according to the embodiment of the present invention, when the RF capacitor itself receives excessive electric power that leads to an excessive temperature rise due to the resonance capacitor and the switch configured on the CMOS type semiconductor, it is detected by the RF tag itself, or By receiving a command from the reader / writer, a part of the transistors of the RF tag rectifier circuit is short-circuited, so that the received power received by the RF tag from the reader / writer is reduced and the power consumption of the RF tag is reduced. It becomes possible to reduce the heat generation from itself.

  In the RF tag according to the embodiment of the present invention, it is possible to prevent burns due to excessive current flowing through the antenna and heat generation of the RF tag (wireless thermometer) attached to the human body. In addition, when an RF tag is attached to an article other than a human body for physical distribution management or the like, it is possible to prevent fire and smoke generation due to heat generation.

  The present invention provides an RF tag that can be used for applications such as a radio thermometer and RFID.

DESCRIPTION OF SYMBOLS 1 ... Antenna 2 ... Current fuse 3 ... Capacitor (capacitance)
3a: Capacitor (capacitance)
3b ... Switch 3c ... Capacitor (capacitance)
3d ... Capacitor (capacitance)
3e ... Transistor switch 5 ... Rectifier circuit 23 ... Register 25a ... Capacitor (capacitance)
25b ... Backflow prevention diode 117 ... Power supply control signal 301 ... Antenna 303 ... Resonance capacitor 305 ... Rectifier circuit 401 ... Antenna (reader / writer)

JP 2007-114925 A

Claims (4)

An antenna unit for receiving radio waves having a predetermined frequency;
A resonance unit having a resonance capacity that resonates with a current flowing through the antenna unit in response to reception of the radio wave;
A rectifying unit that receives the output of the resonance unit and outputs a direct current;
An RF tag having a processing unit that operates using the output of the rectifying unit as a power source,
Furthermore, it has a voltage monitor that measures the voltage of the output of the rectifying unit,
The processing unit includes a power control unit that outputs a power control signal that controls disconnection and connection of the rectifier circuit of the rectifier based on a voltage measurement value output from the voltage monitor,
The rectifying unit includes an RF tag that includes second resonance frequency changing means for disconnecting and connecting the rectifier circuit based on the power control signal. An antenna unit for receiving radio waves having a predetermined frequency;
A resonance unit having a resonance capacity that resonates with a current flowing through the antenna unit in response to reception of the radio wave;
A rectifying unit that receives the output of the resonance unit and outputs a direct current;
An RF tag having a processing unit that operates using the output of the rectifying unit as a power source,
In addition, it has a temperature sensor
The processing unit includes a power control unit that outputs a power control signal that controls disconnection and connection of the rectifying circuit of the rectifying unit based on a temperature measurement value output from the temperature sensor,
The rectifying unit includes an RF tag that includes second resonance frequency changing means for disconnecting and connecting the rectifier circuit based on the power control signal. And a power control signal holding unit including a register that outputs and holds a power control signal that receives and holds the power control signal, and a holding power supply unit that supplies power to the register,
The RF tag according to claim 1 , wherein the holding power supply unit stores electric power supplied to the register from a direct current output from the rectifying unit. The RF tag according to any one of claims 1 to 3, wherein the resonance unit, the rectification unit, and the processing unit are formed in one semiconductor chip.

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