JP2008035405A - Semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor device of which forming electromagnetic coupling with an external device allows supply of electric power and delivery of information to/from the external device, and of which rising of temperature inside the device which is caused by supply of excessive power from the external device can be suppressed with a simple circuit configuration. <P>SOLUTION: In a semiconductor device (IC card) 3, a resonance circuit is constituted with a capacitive element 13 that has such characteristics as a capacitance value changes according to changes of ambient temperature and a power receiving antenna coil 11. The capacitive element 13 is installed near a constant voltage circuit 14 whose heating is relatively high. If the electric power supplied by electromagnetic coupling caused between the power receiving antenna coil 11 and a power transmitting antenna coil 6 provided to the external device (reader writer) 2 becomes excessive, an internal temperature rises especially due to heating inside the constant voltage circuit 14, which changes a capacitance value of the capacitive element 13, resulting in changes in resonance frequency of the resonance circuit. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a semiconductor device that transmits electric power and exchanges information by forming electromagnetic coupling with an external device, and more particularly, to a semiconductor device including avoidance means for preventing excessive power from being supplied from an external device. It is.

  In recent years, by forming electromagnetic coupling between a power receiving device typified by a non-contact type IC card or IC tag and a power transmitting device typified by a non-contact reader / writer, However, contactless communication systems that transmit power and exchange information have become widespread. IC cards are used, for example, in traffic ticket gate systems, financial systems, electronic passport systems, and the like, and IC tags are used, for example, in logistics systems. Such a non-contact communication system can handle a large amount of data, is highly secure, has no mechanical contact terminals, has few failures, and can be used simply by holding it, so it is easy to use and has excellent operability. There are advantages.

  Electric power for operating the power receiving apparatus (hereinafter referred to as “IC card” as appropriate) is supplied from the power transmitting apparatus (hereinafter referred to as “reader / writer” as appropriate) by electromagnetic coupling. However, there are various reader / writers from the viewpoint of power supply and communication characteristics. For example, from the viewpoint of the operating range, the antenna diameter is small and the operating range is small, the antenna diameter is large and the operating range is large, or the antenna diameter is medium, but the output magnetic field strength is set high to set the operating range. What is made comparatively large etc. are mentioned.

  The amount of power supplied from the reader / writer to the IC card includes the output magnetic field strength of the reader / writer, the distance between the reader / writer and the IC card, the antenna shapes of the reader / writer and the IC card, the power consumption of the IC card, and the overall system power consumption. Depends on impedance matching state, etc. Therefore, even if an IC card operates without any problem with one reader / writer, the temperature inside the card rises due to an excessive amount of power supplied to the other reader / writer, and the card is destroyed as the temperature rises. Problems often occur.

  One way to solve such problems is to dynamically change the resonance frequency and quality factor of the IC card (hereinafter referred to as “Q value” where appropriate) when the supply power is excessive, Conventionally, a non-contact type IC card that can avoid card destruction due to temperature rise has been provided (see, for example, Patent Document 1).

JP 2005-011009 A

  The non-contact type IC card described in Patent Document 1 increases the temperature in the IC card by dynamically changing the resonance frequency or Q value of the resonance circuit when a temperature above a predetermined level is detected by the temperature detection circuit. Suppress. As a result, the IC card is kept at a predetermined temperature or less, and the card can be prevented from being destroyed.

  However, since the non-contact type IC card described in Patent Document 1 has a configuration including a temperature detection circuit, a control circuit, and the like, the internal configuration becomes complicated, and the circuit occupation area increases, so that the card body There is a problem that the size of is enlarged.

  In view of the above problems, the present invention is a semiconductor device capable of supplying electric power by forming an electromagnetic coupling with an external device and transferring information to and from the external device, with a simple circuit configuration. It is an object of the present invention to provide a semiconductor device capable of suppressing an increase in temperature inside the device due to supply of excess power from an external device.

  In order to achieve the above object, a semiconductor device according to the present invention is a semiconductor device capable of supplying power by forming an electromagnetic coupling with an external device and transferring information to and from the external device. A resonance circuit constituted by an impedance control unit including a power transmission antenna coil included in the external device and a power reception antenna coil for forming the electromagnetic coupling, and at least a capacitive element, the impedance control unit, A first characteristic is that a temperature-dependent impedance element whose impedance value changes according to a change in ambient temperature is provided.

  According to the first characteristic configuration of the semiconductor device according to the present invention, the temperature-dependent impedance element having the characteristic that the impedance value changes according to the change of the ambient temperature is used as one of the components of the resonance circuit. As the ambient temperature changes, the impedance value of the element changes, thereby changing the resonance frequency of the resonance circuit. Therefore, for example, in order to perform highly efficient power supply in the initial state, the frequency of the carrier wave transmitted from the external device is set to a value that is the same as or close to the resonance frequency of the resonance circuit in the initial state (room temperature). Therefore, when the internal temperature rises due to heat generated by resistance loss etc. inside the semiconductor device due to excessive power supply from the external device, the impedance value automatically changes due to temperature change. As a result, the resonance frequency of the resonance circuit changes, so that the frequency of the carrier wave moves away from the resonance frequency of the resonance circuit, and the impedance value inside the resonance circuit increases, thereby decreasing the current value flowing inside the resonance circuit. To do. Therefore, the amount of heat generated inside the circuit is automatically reduced, and circuit breakdown due to overheating can be avoided.

  Furthermore, since the amount of heat generation is reduced by reducing the amount of current at this time, the internal temperature of the semiconductor device is lowered, and the impedance value is changed accordingly, so that the resonance frequency of the resonance circuit again becomes the carrier wave of the external device. As the frequency approaches, the amount of power supplied increases. In this way, the resonance frequency of the resonance circuit changes as the impedance value of the temperature dependent impedance element changes according to the temperature change inside the semiconductor device, and the resonance frequency repeats approaching and separating from the frequency of the carrier wave. Thus, it is possible to prevent the amount of supplied power from being reduced more than necessary while preventing an excessive temperature rise.

  In particular, by using a temperature-dependent impedance element whose impedance value changes according to a change in ambient temperature, a temperature detection circuit for separately detecting the temperature inside the semiconductor device, or changing the impedance value according to the temperature. Therefore, an excessive temperature rise inside the circuit can be suppressed with a simple circuit configuration without increasing the circuit scale.

  The semiconductor device according to the present invention further includes a constant voltage circuit for obtaining a predetermined voltage from the power supplied from the external device, in addition to the first characteristic configuration. The second characteristic is that the impedance value is changed due to an increase in ambient temperature due to heat radiation from the constant voltage circuit by being installed in the vicinity of the constant voltage circuit.

  According to the second characteristic configuration of the semiconductor device according to the present invention, the impedance control unit is easily affected by a temperature rise accompanying heat radiation from the constant voltage circuit which is a circuit that generates relatively large heat inside the semiconductor device. For this reason, when the temperature inside the semiconductor device rises due to excessive power supply, the impedance value of the impedance control unit changes in a relatively short time due to the influence of the temperature rise. Accordingly, the resonance frequency of the resonance circuit changes in a relatively short time. Therefore, for example, in order to perform high-efficiency power supply in the initial state, when the frequency of the carrier wave transmitted from the external device is set to a value that is the same as or close to the resonance frequency of the resonance circuit under the initial state (room temperature), When power is excessively supplied, heat is generated inside the constant voltage circuit, and when the temperature near the constant voltage circuit rises due to this, the impedance value changes in a relatively short time with this temperature rise. As a result, the resonance frequency of the resonance circuit changes. Since this resonance frequency changes in a direction away from the value of the carrier frequency set as the initial state, the power supplied to the semiconductor device is reduced accordingly, and the temperature inside the semiconductor device is reduced. The rise is suppressed. In other words, when the temperature inside the semiconductor device rises due to an excess of supplied power, it is possible to realize a temperature rise suppressing action in a relatively short time.

  In addition to the second characteristic configuration described above, the semiconductor device according to the present invention is characterized in that the resonance circuit has an impedance value of the temperature-dependent impedance element due to an increase in ambient temperature due to heat radiation from the constant voltage circuit. Thus, the third characteristic is that the value of the resonance frequency in the resonance circuit is changed in a direction away from the value of the frequency of the carrier wave transmitted by the external device.

  According to the third characteristic configuration of the semiconductor device according to the present invention, the resonance frequency changes in a direction away from the carrier frequency value as the temperature rises, so that the power supplied from the external device to the inside of the semiconductor device decreases. As a result, the amount of heat generated due to resistance loss or the like inside the semiconductor device is reduced, and an increase in internal temperature is suppressed.

  The semiconductor device according to the present invention has a characteristic in which the temperature-dependent impedance element has a capacitance value that changes in accordance with a change in ambient temperature, in addition to any one of the first to third characteristic configurations. The fourth feature is that a temperature-dependent capacitive element is included.

  At this time, the impedance control unit may be configured by only the temperature-dependent capacitive element, and a resonance circuit may be configured by the temperature-dependent capacitive element and the power receiving antenna coil. In this case, since the capacitive element constituting the resonance circuit has a characteristic of changing the capacitance value according to the change in the ambient temperature, the internal temperature rises with a simple circuit configuration without increasing the circuit scale. Can be suppressed

  Further, in the semiconductor device according to the present invention, in addition to the fourth characteristic configuration, the capacitance value of the temperature-dependent capacitive element decreases as the ambient temperature increases within a range higher than a predetermined temperature. A fifth characteristic is that the capacitor is composed of an F-characteristic capacitor having characteristics.

  In particular, when the predetermined temperature is about room temperature, a high capacitance value can be realized at room temperature, so that the Q value of the resonance circuit can be increased. Furthermore, by setting the frequency of the carrier wave transmitted from the external device at this time to a value that is the same as or close to the resonance frequency of the resonance circuit at room temperature, sufficient power is supplied at room temperature. When the excessive temperature is supplied and the internal temperature rises, the capacitance value changes (decreases), and the resonance frequency changes in a direction away from the carrier frequency, so that the power supplied to the semiconductor device decreases, As a result, an increase in internal temperature can be suppressed.

  In addition to any one of the first to fifth characteristic configurations, the temperature-dependent impedance element has a characteristic that an inductance value changes according to a change in ambient temperature. The sixth feature is that a temperature-dependent inductive element is included.

  In this case, even if the capacitive element constituting the resonance circuit does not have a temperature dependency that changes the capacitance value according to a change in the ambient temperature, the resonance frequency of the resonance circuit is caused by an increase in the internal temperature. Can be changed.

  The semiconductor device according to the present invention has, in addition to any one of the first to sixth feature configurations, a seventh feature that the semiconductor device is an IC card or an IC tag.

  At this time, as in the case of the IC card and the IC tag, the name of the semiconductor device is not limited as long as it is a semiconductor device using RFID (Radio Frequency IDentification) technology. That is, RFID cards, RFID tags, RFID chips, and the like are similarly within the scope of the semiconductor device according to the present invention.

  According to the configuration of the present invention, as one of the components of the resonance circuit, a temperature-dependent impedance element having a characteristic that an impedance value changes according to a change in the ambient temperature is used. The impedance value of the element changes, thereby changing the resonance frequency of the resonance circuit. Therefore, for example, in order to perform highly efficient power supply in the initial state, the frequency of the carrier wave transmitted from the external device is set to a value that is the same as or close to the resonance frequency of the resonance circuit in the initial state (room temperature). When the internal temperature rises due to heat generation due to resistance loss etc. inside the semiconductor device due to excessive power supplied from the external device, the impedance value automatically changes due to temperature change, Along with this, the resonance frequency of the resonance circuit changes, so that the frequency of the carrier wave moves away from the resonance frequency of the resonance circuit, and the impedance value inside the resonance circuit increases, thereby reducing the current value flowing inside the resonance circuit. . Therefore, the amount of heat generated inside the circuit is automatically reduced, and circuit breakdown due to overheating can be avoided.

  In particular, by using a temperature-dependent impedance element whose impedance value changes according to a change in ambient temperature, a temperature detection circuit for separately detecting the temperature inside the semiconductor device, or changing the impedance value according to the temperature. Therefore, an excessive temperature rise inside the circuit can be suppressed with a simple circuit configuration without increasing the circuit scale.

  Hereinafter, embodiments of a semiconductor device according to the present invention (hereinafter, referred to as “the present device” as appropriate) will be described with reference to the drawings.

  The device of the present invention is a semiconductor device capable of supplying power by forming electromagnetic coupling with an external device, and capable of transferring information to and from the external device, and is supplied with excess power from the external device. It is characterized by having an avoiding means for preventing this. In the following, a non-contact type IC card is assumed as an embodiment of the device of the present invention (hereinafter simply referred to as “IC card”), and a non-contact type reader / writer (hereinafter simply referred to as “IC card”) as an embodiment of the external device. In the following description, it is assumed that power and information can be exchanged with a reader / writer.

<First Embodiment>
Hereinafter, a first embodiment of the device of the present invention (hereinafter referred to as “this embodiment” as appropriate) will be described with reference to FIGS.

  FIG. 1 is a block diagram showing a schematic configuration of an information communication system including the device of the present invention in this embodiment. An information communication system 1 shown in FIG. 1 includes a reader / writer 2 and an IC card 3.

  The reader / writer 2 includes an oscillator 4, a matching circuit 5, and a power transmission antenna coil 6.

  The oscillator 4 is configured to output a voltage waveform having a predetermined frequency. The matching circuit 5 is configured by a circuit including a capacitive element therein. The matching circuit 5 forms an antenna circuit together with the antenna coil 6 for power transmission, and the communication path and power transmission between the reader / writer 2 and the IC card 3. In order to perform impedance matching with the antenna coil 6, the impedance value is controlled.

  The IC card 3 includes a power receiving antenna coil 11, a rectifier circuit 12, a capacitive element 13, a constant voltage circuit 14, and an internal logic circuit 15.

  The power receiving antenna coil 11 forms a parallel resonance circuit (hereinafter simply referred to as “resonance circuit”) together with the capacitive element 13. As will be described later, the capacitive element 13 has a temperature dependency that changes a capacitance value in accordance with a change in ambient temperature. When the distance between the power receiving antenna coil 11 and the power transmitting antenna coil 6 is within a predetermined range, an electromagnetic coupling EMC is formed between the coils. At this time, when a voltage waveform having a predetermined frequency is output from the oscillator 4, an electromagnetic wave is transmitted from the power transmitting antenna coil 6, and a voltage is induced at both ends of the power receiving antenna coil 11 by electromagnetic coupling EMC. The magnitude of the induced voltage becomes maximum when the resonance frequency related to the resonance circuit is equal to the carrier wave frequency transmitted from the power transmission antenna coil 6, and becomes smaller as the resonance frequency becomes farther from the carrier wave frequency.

  The reader / writer 2 superimposes a data signal related to information transmitted to the IC card 3 on a carrier wave caused by a voltage waveform output from the oscillator 4 and supplies the signal to the power receiving antenna coil 11. That is, in the power receiving antenna coil 11, in addition to the voltage component related to the carrier wave, the voltage component related to the data signal given from the reader / writer 2 is also induced. The induced voltage is full-wave rectified by the rectifier circuit 12, adjusted to a predetermined voltage value by the constant voltage circuit 14, and supplied to the internal logic circuit 15. The internal logic circuit 15 includes, for example, an IC chip, a memory, a modulation circuit, a demodulation circuit, and the like.

  The capacitive element 13 is an element having a temperature dependency in which the capacitance value is determined according to the ambient temperature, and an example of the characteristic is shown in FIG. As an example of the capacitive element 13, FIG. 2 shows the ambient temperature of the element when a multilayer ceramic capacitor having a temperature dependency called F characteristic is adopted among the multilayer ceramic capacitors made of ferroelectric ceramics as a raw material. It is the graph which showed the relationship of the capacitance value, A horizontal axis represents ambient temperature and a vertical axis | shaft represents the capacitance value, respectively.

  As shown in the graph of FIG. 2, the multilayer ceramic capacitor having F characteristics has a maximum capacitance value near 20 ° C. (room temperature), and the capacitance value increases as the ambient temperature rises within a range higher than room temperature. It turns out that it falls.

  When the capacitive element 13 having temperature dependence as shown in FIG. 2 is used as a constituent element of the resonance circuit, the capacitance value changes according to the ambient temperature of the capacitive element 13, and accordingly, the resonance frequency is Will change.

  When each element value of the resonance circuit is set so that the resonance frequency is equal to or close to the carrier wave transmitted from the power transmission antenna coil 6 at room temperature, it is induced at both ends of the power reception antenna coil 11 at the room temperature. The voltage value to be increased increases, and sufficient power can be supplied to the internal logic circuit 15 in the subsequent stage. On the other hand, in some cases, it is assumed that excessive power is supplied. In such a case, heat is generated due to resistance loss or the like in the IC card 3 (particularly, the constant voltage circuit 14). 3 The temperature inside increases. FIG. 3 is a graph showing the relationship between the power supplied to the IC card 3 and the temperature associated with the IC card 3, with the horizontal axis representing the magnitude of the supplied power and the vertical axis representing the temperature. Yes. As shown in FIG. 3, it can be seen that the temperature associated with the inside of the IC card 3 increases as the amount of supplied power increases. When the internal temperature of the IC card 3 increases, the ambient temperature of the capacitive element 13 increases accordingly, and the capacitance value of the capacitive element 13 decreases as shown in FIG.

  When the capacitance value of the capacitive element 13 decreases, the resonance frequency of the resonance circuit set near the carrier frequency at room temperature changes in a direction away from the carrier frequency. As a result, the voltage induced at both ends of the power receiving antenna coil 11 decreases and the amount of power supplied decreases, so that heat generation inside the IC card 3 is suppressed. Thereafter, when the temperature related to the inside of the IC card 3 starts to decrease, the ambient temperature of the capacitive element 13 decreases, so that the capacitance value of the capacitive element 13 increases again as shown in FIG. As a result, the resonance frequency of the resonance circuit again approaches the frequency of the carrier wave.

  Thereafter, under a predetermined repetition time, the capacitance value of the capacitive element 13 repeatedly increases and decreases, and accompanying this, the change in which the resonance frequency approaches the carrier frequency and the change in the distance away from the carrier frequency are repeated. It becomes. Such a repetition is automatically performed, so that the power necessary for the operation can be received from the reader / writer 2 while suppressing a temperature rise due to excessive power being supplied into the IC card 3. Can do. Note that the cycle time of repeated increase and decrease of the resonance frequency depends on the heat radiation characteristics inside the IC card 3. That is, when the heat dissipation characteristics inside the IC card 3 are good (heat dissipation is performed quickly), the cycle time is shortened. On the other hand, when the heat dissipation characteristics are poor (the time required for heat dissipation is long), the cycle time is lengthened. .

  FIG. 4 is a graph illustrating the relationship between the supplied power supplied from the reader / writer 2 and the received power actually received by the IC card 3, where the vertical axis represents the received power and the horizontal axis represents the supplied power. Yes. As shown in FIG. 4, in a range where the supplied power is relatively small (for example, when the distance between the reader / writer 2 and the IC card 3 is long), the IC card 3 receives power as the supplied power increases. Although the power also increases, within a range where the supplied power exceeds a predetermined value (for example, when the distance between the reader / writer 2 and the IC card 3 is within a predetermined value), the received power is within the predetermined range. Saturates inside. As described above, as the internal temperature of the IC card 3 rises, the resonance frequency is separated from the carrier frequency supplied from the reader / writer 2, so that sufficient power is not supplied to the IC card 3. It is because. In other words, this means that the internal temperature of the IC card 3 does not rise above a predetermined value, and this automatically causes a circuit breakdown to occur as the internal temperature of the IC card 3 rises. Can be prevented.

  In the present embodiment, an F characteristic monolithic ceramic capacitor has been described as an example of the capacitive element 13. However, if the element has a characteristic in which a capacitance value changes according to a change in ambient temperature, The capacitor is not limited. Further, by installing the capacitive element 13 in the vicinity of a circuit (for example, the constant voltage circuit 14) that generates a relatively large amount of heat among the circuits related to the inside of the C card 3, the internal temperature of the IC card 3 increases. The effect which suppresses can be heightened.

<Second Embodiment>
Hereinafter, a second embodiment of the device of the present invention (hereinafter referred to as “this embodiment” as appropriate) will be described with reference to FIG. The present embodiment differs from the first embodiment only in that an impedance control unit 21 whose impedance value changes in accordance with a change in ambient temperature is used instead of the capacitive element 13, and other configurations are different. The elements are identical. Below, only a different point from 1st Embodiment is demonstrated, and the description is abbreviate | omitted about the same part.

  FIG. 5 is a block diagram showing a schematic configuration of an information communication system 1a including the device of the present invention in the present embodiment. The IC card 3a shown in FIG. 5 includes an impedance control unit 21 including impedance elements Z1 and Z2. The impedance element Z1 is an element having a capacitance component, and is connected in parallel with the power receiving antenna coil 11. The impedance element Z2 is an element having an inductance component, and is connected in series with the power receiving antenna coil 11. These impedance elements Z1 and Z2 and the power receiving antenna coil 11 form a resonance circuit.

  Further, at least one of the impedance element Z1 and the impedance element Z2 has a temperature dependency that changes an impedance value (a capacitance value in the impedance element Z1 and an inductance value in the impedance element Z2) according to a change in ambient temperature. It shall be formed with the material which has. At this time, when a material having temperature dependency is used as the impedance element Z1, the F ceramic multilayer ceramic capacitor exemplified as an example in the first embodiment may be adopted. In addition, when using a material having temperature dependency as the impedance element Z2, for example, an SMD inductor having an inductance value having temperature characteristics (MLF series manufactured by TDK) or a chip inductor having temperature characteristics similar to that is employed. It doesn't matter. In the following description, the case where both impedance elements Z1 and Z2 are made of a temperature-dependent material will be described as an example (in FIG. 5, the arrow symbol indicating that the impedance is variable is indicated by the impedance element). Z1 and Z2).

  In such a configuration, the impedance element Z1 and the impedance element Z1 and the impedance element Z1 so that the power transmitted from the power transmission antenna coil 6 is transmitted to the IC card 3a as efficiently as possible, that is, in a state close to impedance matching, at room temperature. By setting each element value of Z2, the voltage value induced at both ends of the power receiving antenna coil 11 becomes large at room temperature. At this time, as described above in the first embodiment, in some cases, it is assumed that excessive power is supplied to the subsequent circuit. In such a case, heat generated due to resistance loss or the like inside the IC card 3a. Occurs, and the temperature inside the IC card 3a rises.

  When the temperature inside the IC card 3a rises, the impedance values of the impedance elements Z1 and Z2 having temperature dependence change, and thereby the impedance value of the IC card 3a changes. That is, the impedance of the IC card 3a, which has been set to a state close to impedance matching at room temperature, changes in a direction away from the impedance matching state. As a result, the voltage induced at both ends of the power receiving antenna coil 11 is reduced and the amount of supplied power is reduced, so that heat generation inside the IC card 3a is suppressed.

  That is, also in the present embodiment, as in the first embodiment, an increase in the internal temperature of the IC card 3a can be automatically suppressed.

  Also in this embodiment, the impedance control unit 21 is installed in the vicinity of a circuit (for example, the constant voltage circuit 14) that generates a relatively large amount of heat among the circuits related to the IC card 3a. The effect which suppresses the raise of internal temperature can be heightened.

  In the first embodiment described above, when the ambient temperature rises, the resonance frequency changes, and when the resonance frequency is separated from the carrier frequency, the power supplied decreases, or in the second embodiment described above, the ambient frequency Even if the impedance of the IC card 3a changes as the temperature rises and the power supplied by moving away from the impedance matching state decreases, the data signal superimposed on the carrier wave is the IC card 3 (3a). Is preferably transmitted accurately. For this reason, the temperature dependency of the capacitive element having temperature dependency or the impedance element having temperature dependency is a characteristic that changes the capacitance value or the impedance value due to a change in ambient temperature, while the change causes a change in communication characteristics. On the other hand, it is preferable that the characteristics hardly change.

  Here, various factors such as modulation rate, modulation depth, and waveform dullness at the time of modulation can be cited as factors for determining the quality of communication characteristics. The determination factors depend on the method of the demodulation circuit mounted on the IC card. Is different. In the following, the case where the modulation rate is used as an element for determining the quality of communication characteristics will be described as an example.

  In the first embodiment described above, the parameter that changes depending on the ambient temperature is only the capacitance value of the capacitive element 13, so if the resonance frequency changes, the change in the modulation factor is automatically determined accordingly, and is selected. There is no room for it.

  FIG. 6 is a circuit diagram for numerical calculation in which the information communication system 1 in the first embodiment shown in FIG. 1 is modeled for numerical calculation.

  An information communication system model circuit (hereinafter, abbreviated as “model circuit” where appropriate) 1 s that models the information communication system 1 shown in FIG. 1 is a circuit that models each component constituting the information communication system 1. Composed. That is, the model circuit 1s includes a reader / writer model 2s that models the reader / writer 2, an IC card model 3s that models the IC card 3, and an electromagnetic coupling model EMCs that models electromagnetic coupling EMC (inductor with inductance 0.071 μH). 37).

  The reader / writer model 2s includes an oscillator model 4s including an AC voltage source 31 and a resistor 32 having a resistance value of 50Ω, a matching circuit model 5s including a capacitor 33 having a capacitance value of 10 pF and a capacitor 34 having a capacitance value of 59 pF, and a resistor. A power transmission antenna coil model 6s including a resistor 35 having a value of 1Ω and an inductor 36 having an inductance of 1.929 μH is provided. On the other hand, the IC card model 3s has a power receiving antenna coil model 11s composed of an inductor 38 having an inductance of 0.929 μH, a capacitive element model 13s composed of a capacitor C1, and a load composed of a resistor 39 having a resistance value of 1 kΩ. A model 22s is provided. The load model 22s is a model in which a load composed of the rectifier circuit 12, the constant voltage circuit 14, and the internal logic circuit 15 is integrated. The circuit element values constituting the model circuit 1s are merely examples for modeling.

  The results of numerical calculation using the model circuit 1s illustrated in FIG. 6 are shown below.

  First, the following three states are defined as conditions for simulation and comparison of the results. That is, the first state in which a desired voltage is applied from the reader / writer 2 on the supply side, the second state in which excessive power is supplied from the reader / writer 2 on the supply side, and the IC card 3 associated with the excessive power supply. The internal temperature rises, whereby the capacitance value of the capacitive element 13 changes to define the third states in which the resonance frequency of the IC card 3 changes. Then, in order to model each of the first to third states in the model circuit 1s, necessary numerical values related to elements constituting the model circuit 1s are set. That is, in order to model the first state, a voltage of 12 V is supplied from the AC voltage source 31 included in the reader / writer model 2s, so that the voltage across the load model 22s on the IC card model 3s side in the unmodulated state is 2. The case where it becomes about 3V-2.5V is assumed. Further, in order to model the second state, a voltage of 30 V (excess voltage compared with the first state) is supplied from the AC voltage source 31 of the reader / writer model 2s, so that the card side at the time of non-modulation Assume that the voltage across the load model 22s is 5.8V (a value greater than the voltage across the load model 22s in the first state). Further, in order to model the third state, a voltage of 30 V (an excessive voltage compared to the first state) is supplied from the AC voltage source 31 included in the reader / writer model 2s, whereby the capacitive element model 13s. By changing the capacitance value as compared with the first state or the second state, the resonance frequency of the IC card model 3s changes, and the voltage across the load model 22s becomes about 2.3V to 2.5V ( Assume that the voltage value in the second state has fallen and returned (within the range of voltage values in the first state).

  Under such assumption, the modulation rate in each state is calculated using the model circuit 1s shown in FIG. Note that the modulation factor is the voltage of the AC voltage source 31 of the reader / writer model 2s (corresponding to 12V in the first state, 30V in the second and third states, hereinafter referred to as “state setting voltage” as appropriate). Calculation is based on the change in the 0-peak value of the voltage across the load model 22s when the load model 22s is reduced by 7%. Specifically, when the AC voltage source 31 is set to a state setting voltage under each state, the voltage across the load model 22s is V1, and the AC voltage source 31 is 16 state setting voltage under each state. When the voltage across the load model 22s when the voltage is set to a voltage reduced by 7% (hereinafter referred to as “comparison target voltage”) is V2, the modulation factor R is calculated by the following equation (1).

(Equation 1)
R = (V1-V2) / (V1 + V2)

  Under such settings, if the capacitance value of the capacitor C1 constituting the capacitive element model 13s in the first state is 100 pF (at this time, the resonance frequency of the IC card model 3s is 15.9 MHz), In the first state, the voltage V1 across the load model 22s when the AC voltage source 31 is set to the state setting voltage (12V) is calculated as 2.5V, and the AC voltage source 31 is compared with the comparison target voltage (from 12V to 16.7). The voltage V2 across the load model 22s when the voltage is set to a voltage reduced by 10% (10V) is calculated as 2.1V. Then, by substituting this calculation result into Equation 1, the modulation rate R in the first state is calculated to be 8.7%.

  Similarly, in the second state, the voltage V1 across the load model 22s when the AC voltage source 31 is set to the state setting voltage (30V) is calculated as 5.8V, and the AC voltage source is compared with the comparison target voltage (from 30V). Since the voltage V2 across the load model 22s when the voltage is set to 16.7% reduced voltage (25V) is calculated as 5.1 V, the modulation rate R in the second state is 6.4% from Equation 1. Is calculated.

Similarly, the modulation rate R in the third state is calculated. At this time, the voltage across the load model 22s when the AC voltage source 31 is set to the state setting voltage (30V) by changing the capacitance value of the capacitor C1 from 100 pF to a predetermined value due to the temperature rise. It is necessary to select the capacitance value of the capacitor C1 so that V1 is substantially equal to the voltage V1 in the first state. As a result of the simulation, when the capacitance value changes from 100 pF to 47 pF due to the temperature rise (thereby changing the resonance frequency of the IC card model 3s from 15.9 MHz to 23.2 MHz), the AC voltage source 31 is set in the state. Since the voltage V1 across the load model 22s when the voltage (30V) is set is calculated as 2.3V, a desired result can be obtained by employing the capacitor C1 indicating the capacitance value. At this time, the voltage V2 across the load model 22s is calculated to be 1.9V when the AC voltage source 31 is set to the comparison target voltage (voltage (25V) reduced by 16.7% from 30V). From Equation 1, the modulation factor R in the third state is calculated as 9.5%.

  As a result, the change rate of the modulation rate R between the states can be calculated. That is, the change rate of the modulation factor R when the transition from the first state to the second state is −26.4% (decrease of 26.4%), and the modulation factor R when the transition from the first state to the third state is performed. The change rate is calculated to be 9.2% (9.2% increase).

  That is, in the first embodiment, if the voltage across the load model 22s is adjusted to a desired value in order to suppress the temperature rise inside the IC card 3s due to excessive power supply, the capacitance value of the capacitive element model C1. Is uniquely determined (47 pF in the above example), and there is no room for selection in determining the modulation rate.

  On the other hand, in the second embodiment described above, the parameters that change depending on the ambient temperature are the maximum two types of impedance values of the impedance elements Z1 and Z2. There are multiple combinations of Z1 and Z2 that can be suppressed. Therefore, by selecting a combination having a relatively small change in the modulation rate from among them, it is possible to suppress the temperature rise inside the IC card 3a while minimizing the influence on the communication characteristics.

  Similar to the first embodiment, modeling is also performed in the second embodiment, and numerical calculation results using this model are shown below.

  FIG. 7 is a circuit diagram for numerical calculation in which the information communication system 1a in the second embodiment shown in FIG. 5 is modeled for numerical calculation. An information communication system model circuit (hereinafter abbreviated as “model circuit” as appropriate) 1as is an impedance element model Z1s constituted by a capacitor C2 instead of the capacitive element model 13s as compared with the model circuit 1s in FIG. And an impedance control unit model 21s having an impedance element model Z2s composed of an inductor L2, and the other parts are the same as the model circuit 1s, and thus the description thereof is omitted.

  The results of numerical calculation using the model circuit 1as illustrated in FIG. 7 are shown below. For comparison, various conditions are the same as those in the case where numerical calculation is performed using the model circuit 1s in FIG.

  That is, when the voltage of 12V is supplied from the AC voltage source 31 to model the first state, the voltage across the card-side load model 22s at the time of non-modulation becomes about 2.3V to 2.5V. In order to model the second state, a voltage of 30 V (excess voltage compared with the first state) is supplied from the AC voltage source 31 to thereby provide both ends of the card-side load model 22s at the time of no modulation. Is assumed to be 5.8V (a value larger than the voltage across the load model 22s in the first state), and in order to model the third state, a voltage of 30V from the AC voltage source 31 (first state) IC card by changing the capacitance of the capacitor C2 and the inductance of the inductor L2 as compared with the first state or the second state. When the impedance of the Dell 3as changes and the voltage across the load model 22s returns to about 2.3V to 2.5V (decreases from the voltage value in the second state and falls within the voltage value range in the first state) Is assumed.

  Under such a condition, the voltage V1 across the load model 22s when the AC voltage source 31 is set to the state setting voltage (12V) in the first state is within a range of about 2.3V to 2.5V. As a combination of the capacitance value of C2 and the inductance value of the inductor L2, the first combination in which the capacitance value of the capacitor C2 is 110 pF and the inductance value of the inductor L2 is 10 μH, and the capacitance value of the capacitor C2 is 150 pF and the inductance value of the inductor L2 Suppose that the second combination with 10 μH is calculated. In the first combination, V1 = 2.4V, and in the second combination, V1 = 2.5V (both voltage values in the range of about 2.3V to 2.5V).

  For each of the first combination and the second combination, when the modulation rate under each state is calculated by the same method as the numerical calculation when the first embodiment is modeled, The voltage V1 in the first state is 2.4V, the voltage V2 is 2.0V, the modulation factor R is 9.1%, the voltage V1 in the second state is 5.8V, the voltage V2 is 4.7V, and the modulation factor R Is 10.5%, the voltage V1 in the third state is 2.4V, the voltage V2 is 2.1V, and the modulation factor R is 6.7%. Similarly, in the second combination, the voltage V1 in the first state is 2.5V, the voltage V2 is 2.1V, the modulation factor R is 8.7%, the voltage V1 in the second state is 5.8V, and the voltage V2 Is 4.9 V, the modulation rate R is 8.4%, the voltage V1 in the third state is 2.5 V, the voltage V2 is 2.1 V, and the modulation rate R is 8.7%.

  Therefore, the change rate of the modulation rate R in each combination is 15.4% (15.4% increase) in the first combination when the change rate of the modulation rate R shifts from the first state to the second state. , The change rate of the modulation rate R when the state transitions from the second state to the third state is calculated to be −26.4% (decrease of 26.4%), and in the second combination, The change rate of the modulation factor R when the transition to the second state is -3.4% (3.4% decrease), and the change rate of the modulation factor R when the transition from the first state to the third state is approximately 0% ( No increase / decrease).

  That is, when both the first combination and the second combination are compared, the rate of change of the modulation factor R when shifting from the first state to the second state or the third state is smaller in the second combination. By adopting the capacitor C2 and the inductor L2 defined by the second combination, it is possible to suppress the temperature rise inside the IC card while suppressing the change in the modulation factor. In addition, according to the said 2nd combination, it turns out that it has fallen rather than the change rate of the modulation factor in 1st Embodiment.

  As described above, in the second embodiment, even when the temperature inside the IC card rises, the change in the modulation factor is the smallest among the combinations of capacitors and inductors that can maintain the voltage across the load model 22s. Since one combination can be selected, it is possible to suppress an increase in temperature inside the IC card while suppressing a decrease in communication characteristics as much as possible as compared with the first embodiment.

  Further, in each of the above-described embodiments, the non-contact type reader / writer is described as the external device, and the non-contact type IC card is described as the semiconductor device, but the antenna coil is provided inside. A reader / writer and an IC card if power is supplied from an external device to the semiconductor device by electromagnetic coupling and information can be exchanged between the external device and the semiconductor device (a configuration in which RFID technology can be used). It is not limited to.

1 is a block diagram showing a schematic configuration of an information communication system including a semiconductor device according to a first embodiment of the present invention. As an example of a capacitive element, a graph showing the relationship between the ambient temperature of the element and the capacitance value when a multilayer ceramic capacitor having F characteristics is employed The graph which shows the relationship between the electric power supplied with respect to an IC card, and the temperature which concerns on the inside of an IC card A graph illustrating the relationship between the power supplied from the reader / writer and the power received by the IC card The block diagram which shows schematic structure of the information communication system containing the semiconductor device which concerns on 2nd Embodiment of this invention. 1 is a circuit diagram for numerical calculation of an information communication system including a semiconductor device according to a first embodiment of the present invention; Circuit diagram for numerical calculation of an information communication system including a semiconductor device according to a second embodiment of the present invention

Explanation of symbols

1, 1a: Information communication system 1s, 1as: Information communication system model circuit 2: Reader / writer (one embodiment of external device)
2s: Reader / Writer Model 3, 3a: IC Card (One Embodiment of Semiconductor Device According to the Present Invention)
3s, 3as: IC card model 4: oscillator 4s: oscillator model 5: matching circuit 5s: matching circuit model 6: antenna coil for power transmission 6s: antenna coil model for power transmission 11: antenna coil for power reception 11s: antenna coil model for power reception 12 : Rectifier circuit 13: Capacitive element 13s: Capacitive element model 14: Constant voltage circuit 15: Internal logic circuit 21: Impedance controller 22s: Load model 31: AC voltage source 32: Resistor 33: Capacitor 34: Capacitor 35: Resistor 36: Inductor 37: Inductor 38: Inductor 39: Resistor C1, C2: Capacitor L2: Inductor EMC: Electromagnetic coupling EMCs: Electromagnetic coupling model Z1: Impedance element (element having capacitance component)
Z1s: Impedance element (element having a capacitance component) model Z2: Impedance element (element having an inductance component)
Z2s: Impedance element (element having inductance component) model

Claims (7)

A semiconductor device that is supplied with electric power by forming electromagnetic coupling with an external device, and that can exchange information with the external device,
A power transmission antenna coil included in the external device and a power reception antenna coil for forming the electromagnetic coupling, and a resonance circuit configured by an impedance control unit including at least a capacitive element;
The semiconductor device, wherein the impedance control unit includes a temperature-dependent impedance element whose impedance value changes according to a change in ambient temperature. A constant voltage circuit for obtaining a predetermined voltage from the power supplied from the external device;
The temperature-dependent impedance element is installed in the vicinity of the constant voltage circuit, and has a characteristic of changing an impedance value due to an increase in ambient temperature due to heat radiation from the constant voltage circuit. The semiconductor device according to claim 1. The resonant circuit is
The impedance value of the temperature-dependent impedance element changes due to an increase in ambient temperature accompanying heat dissipation from the constant voltage circuit, so that the value of the resonance frequency in the resonance circuit is the frequency of the carrier wave transmitted by the external device The semiconductor device according to claim 2, wherein the semiconductor device is changed in a direction away from the value of.   4. The temperature-dependent impedance element includes a temperature-dependent capacitive element having a characteristic in which a capacitance value changes in accordance with a change in ambient temperature. 5. Semiconductor device.   5. The temperature-dependent capacitive element includes an F-characteristic capacitor having a characteristic that a capacitance value decreases with an increase in ambient temperature within a range higher than a predetermined temperature. Semiconductor device.   The temperature-dependent impedance element includes a temperature-dependent inductive element having a characteristic in which an inductance value changes in accordance with a change in ambient temperature. Semiconductor device.   The semiconductor device according to claim 1, wherein the semiconductor device is an IC card or an IC tag.