JP5640567B2 - Electronics - Google Patents

Description

  The present invention relates to an electronic device that operates with power extracted from received radio waves.

  Conventionally, there is an electronic device that operates with electric power extracted from received radio waves. An example of such an electronic device is an RFID (Radio Frequency Identification) tag.

  FIG. 17 is a block diagram showing a conventional RFID tag system. As shown in FIG. 17, in the RFID tag 1, power is extracted from the radio wave transmitted from the reader / writer 2 by the power regeneration circuit 3. The transmission / reception circuit 4, the tag controller 5, and the memory 6 when accessed by the tag controller 5 are driven by electric power supplied from the power supply reproduction circuit 3. The RFID tag 1 may include a sensor that detects information such as environmental temperature and humidity. In the RFID tag 1 having such a configuration, the sensor 7, the sensor controller 8, and the memory 6 when accessed by the sensor controller 8 are driven by electric power supplied from the battery 9.

  FIG. 18 is a timing chart showing the operation of the conventional RFID tag system. As shown in FIG. 18, the level of the reception signal 12 of the RFID tag 1 is lowered due to the influence of noise or the distance from the reader / writer 2 while the RFID tag 1 is receiving the transmission signal 11 of the reader / writer 2. Or reception interruption may occur temporarily. When the reception level is lowered or reception is interrupted, the transmission / reception operation voltage 14 supplied from the power regeneration circuit 3 may be lower than the level necessary for the operation of each unit. In this case, since the tag controller 5 is initialized, there is a problem that the response signal 13 of the RFID tag 1 is not transmitted to the reader / writer 2 and ends in the middle.

  In particular, when a large amount of data is transmitted from the RFID tag 1 to the reader / writer 2, the transmission time of the response signal 13 of the RFID tag 1 becomes long. For this reason, the reception level of the RFID tag 1 is likely to drop or the reception is cut off due to the RFID tag 1 moving away from the reader / writer 2 before the transmission is completed, and data is normally transferred from the RFID tag 1 to the reader / writer 2. The possibility of not being able to send increases.

  Thus, when receiving a signal, there is an electronic device such as a transponder that operates with power regenerated from the received signal and operates with battery power when transmitting a response signal.

JP 2000-307467 A JP 2002-31616 A

  However, the conventional electronic device has a problem that the battery is not good because the response signal is always transmitted using the power of the battery.

  It is an object of the present invention to provide an electronic device that can improve battery life.

  The electronic device includes a first power supply unit, a second power supply unit, a switching unit, a calculation unit, and a control unit. The first power supply unit extracts power from the radio wave transmitted from the transmission / reception device. The second power supply unit supplies power from the battery. The switching unit switches between the first power supply unit and the second power supply unit. The computing unit computes the amount of information received and responded to a command transmitted from the transmission / reception device. The control unit controls the switching unit according to the information amount.

  According to this electronic device, there is an effect that the battery can be held better.

1 is a block diagram illustrating a system using an electronic apparatus according to a first embodiment. FIG. 6 is a block diagram illustrating a system using an electronic apparatus according to a second embodiment. FIG. 9 is a schematic diagram illustrating an example of a frame format in a system using an electronic device according to a second embodiment. FIG. 6 is a block diagram illustrating a tag controller of an electronic device according to a second embodiment. 7 is a chart illustrating an example of a determination table for an electronic device according to a second embodiment; FIG. 6 is a block diagram illustrating a power supply coupling circuit of an electronic device according to a second embodiment. 12 is a chart illustrating an example of an output determination table of an electronic device according to a second embodiment. 12 is a flowchart illustrating a power supply switching procedure in the electronic apparatus according to the second embodiment. It is a flowchart which shows the continuation of FIG. FIG. 10 is a timing diagram illustrating an operation of a system using the electronic apparatus according to the second embodiment. FIG. 9 is a schematic diagram illustrating an example of a frame format in a system using an electronic device according to a third embodiment. FIG. 10 is a block diagram illustrating a tag controller of an electronic device according to a third embodiment. FIG. 9 is a block diagram illustrating a power supply coupling circuit of an electronic device according to a third embodiment. FIG. 10 is a schematic diagram illustrating an example of a frame format in a system using an electronic device according to a fourth embodiment. 14 is a flowchart illustrating a power supply switching procedure in the electronic apparatus according to the fourth embodiment. FIG. 10 is a timing diagram illustrating an operation of a system using the electronic apparatus according to the fourth embodiment. It is a block diagram which shows the conventional RFID tag system. It is a timing diagram which shows operation | movement of the conventional RFID tag system.

  Exemplary embodiments of the electronic apparatus will be described below in detail with reference to the accompanying drawings. The electronic device calculates the amount of information to be transmitted in response to the received command, and switches between a power supply unit that extracts power from radio waves transmitted from the transmission / reception device and a power supply unit that supplies power from the battery according to the information amount Is. In the following description of each embodiment, the same components are denoted by the same reference numerals, and redundant descriptions are omitted.

Example 1
Description of Electronic Device FIG. 1 is a block diagram illustrating a system using the electronic device according to the first embodiment. As illustrated in FIG. 1, the electronic device 21 includes a first power supply unit 25, a second power supply unit 27, a switching unit 26, a calculation unit 23, and a control unit 24. The first power supply unit 25 extracts power from the radio wave transmitted from the transmission / reception device 22. The second power supply unit 27 supplies power from the battery. The switching unit 26 switches between the first power supply unit 25 and the second power supply unit 27. The computing unit 23 computes the amount of information received and responded to the command transmitted from the transmission / reception device 22. The control unit 24 controls the switching unit 26 according to the information amount obtained by the calculation unit 23. In addition, the electronic device 21 includes a transmission unit 28. The electronic device 21 transmits information to the transmission / reception device 22 via the antenna by the transmission unit 28 as a response to the command received from the transmission / reception device 22.

  According to the first embodiment, the first power supply unit 25 and the second power supply unit 27 are switched according to the amount of information transmitted to the transmission / reception device 22. There are a case where the power supplied from the power supply unit 25 is used and a case where the power supplied from the second power supply unit 27 is used. For example, the power supplied from the first power supply unit 25 is used when the amount of information to be transmitted is small, and the power supplied from the second power supply unit 27 is used when the amount of information to be transmitted is large. can do. Therefore, the battery can be held better than when information is always transmitted to the transmitting / receiving device 22 using the power of the battery.

(Example 2)
In the second embodiment, the electronic device according to the first embodiment is applied to an RFID tag system.

FIG. 2 is a block diagram of a system using the electronic apparatus according to the second embodiment. As shown in FIG. 2, the system using the electronic device includes an RFID tag 31 as an electronic device and a reader / writer 32 as a transmission / reception device.

Description of RFID Tag The RFID tag 31 includes a power regeneration circuit 33 as a first power source, a battery 39 as a second power source, and a power coupling circuit 40 as a switching unit. The power regeneration circuit 33 extracts power from the radio wave transmitted from the reader / writer 32. The power supply coupling circuit 40 switches between the power supplied from the power regeneration circuit 33 and the power supplied from the battery 39, and outputs one of them as supplied power to the transmission / reception circuit 34, tag controller 35, and memory 36. The power supply coupling circuit 40 switches power based on a switch signal from the tag controller 35. Details of the power supply coupling circuit 40 will be described later.

  In addition, power is supplied from the battery 39 to the memory 36, the sensor 37, and the sensor controller 38. At the time of access by the sensor controller 38, power is supplied from the battery 39 to the memory 36. At the time of access by the tag controller 35, power is supplied from the power supply coupling circuit 40 to the memory 36.

  The transmission / reception circuit 34 receives a command transmitted from the reader / writer 32. The transmission / reception circuit 34 transmits data in response to the received command to the reader / writer 32. The tag controller 35 writes the received command information into the memory 36 and reads out data to be transmitted to the reader / writer 32 from the memory 36. The tag controller 35 calculates the amount of data to be transmitted to the reader / writer 32 and outputs a switch signal based on the amount of data. Details of the tag controller 35 will be described later.

  The memory 36 includes a dual port memory accessible from both the tag controller 35 and the sensor controller 38, for example. The memory 36 may be a type of memory that consumes a large amount of power, such as a ferroelectric memory (FRAM: Ferroelectric Random Access Memory). Examples of the sensor 37 include a temperature sensor that detects the temperature of the environment, a humidity sensor that detects the humidity of the environment, and an acceleration sensor that detects vibration and impact.

  The sensor controller 38 reads the sensor ID (identifier) and parameter information from the memory 36 to activate and control the sensor 37. The ID (Identifier) and parameter information are included in the command received from the reader / writer 32 and are written in the memory 36 by the tag controller 35. The sensor controller 38 writes the data acquired by the sensor 37 into the memory 36.

FIG. 3 is a schematic diagram illustrating an example of a frame format in the system using the electronic device according to the second embodiment. FIG. 3 shows an example of the frame format of the log reading command. When the RFID tag 31 receives a log reading command from the reader / writer 32, the RFID tag 31 reads the log data stored in the memory 36 from the memory 36 and transmits it to the reader / writer 32.

  As shown in FIG. 3, for example, the frame format of the log read command has a log read command field 51, a head address field 52, and a read byte number field 53. The log read command field 51 stores a log read command. The start address field 52 stores the start address of the memory area where the log data to be read is stored. The read byte number field 53 stores the number of bytes when reading the log data to be read.

Description of Tag Controller FIG. 4 is a block diagram of a tag controller of the electronic device according to the second embodiment. As shown in FIG. 4, the tag controller 35 includes a command determination unit 61 as a calculation unit, a byte number determination unit 62, a determination table 63, and a switch signal generation unit 64 as a control unit.

  The command determination unit 61 decodes the command signal transmitted from the reader / writer 32 and extracts a command. In the case of a log read command, the command is obtained from the log read command field 51 in the frame format shown in FIG. The byte number determination unit 62 extracts the memory access byte number from the command signal transmitted from the reader / writer 32. The memory access byte number indicates the number of bytes when the RFID tag 31 accesses the memory 36. In the case of a log read command, the memory access byte number is obtained from the read byte number field of the frame format shown in FIG. The byte number determination unit 62 refers to the determination table 63 and determines whether to turn on or off the switch signal described above based on the type of command and the number of memory access bytes. The switch signal generation unit 64 outputs a switch signal based on the determination result of the byte number determination unit 62.

Description of Determination Table FIG. 5 is a table illustrating an example of the determination table for the electronic device according to the second embodiment. The determination table 63 is data that defines ON / OFF of a switch signal for a combination of a command type and the number of memory access bytes. For example, in the example shown in FIG. 5, the memory access byte number of the ID read command is 8 bytes, and the switch signal is OFF. When the number of memory access bytes of the log read command is small, for example, less than 24 bytes, the switch signal is off. When the number of memory access bytes of the log read command is large, for example, when it is 24 bytes or more, the switch signal is on.

  The number of bytes when the switch signal is switched on and off (24 bytes in this example) is the threshold value for the number of memory access bytes as the first threshold value. There are various commands other than the ID reading command and the log reading command. The threshold value for the number of memory access bytes is set as appropriate depending on the performance of the RFID tag 31 and the like.

FIG. 6 is a block diagram of a power supply coupling circuit of the electronic apparatus according to the second embodiment. As shown in FIG. 6, the power supply coupling circuit 40 includes a power supply switching unit 71, a voltage detection unit 72, a comparison determination unit 73, and a threshold storage memory 74.

  The voltage detection unit 72 detects the level of the voltage output from the power regeneration circuit 33. The voltage detection unit 72 includes, for example, an A / D (analog / digital) converter, and converts the detected voltage level (analog signal) into a digital signal for output. The threshold storage memory 74 stores the threshold of the output level of the power regeneration circuit 33 as the second threshold.

  Based on the output level of the power regeneration circuit 33, the threshold of the output level of the power regeneration circuit 33, and the switch signal output from the switch signal generator 64, the comparison determination unit 73 determines whether the power regeneration circuit 33 and the battery 39 It is determined from which power is supplied to the transmission / reception circuit 34, the tag controller 35, and the memory 36. The power supply switching unit 71 switches the power supplied to the transmission / reception circuit 34 and the like between the power supplied from the power regeneration circuit 33 and the power supplied from the battery 39 based on the determination result of the comparison determination unit 73.

Description of Output Determination Table FIG. 7 is a table illustrating an example of the output determination table of the electronic device according to the second embodiment. The comparison determination unit 73 is provided with an output determination table 75 serving as a determination reference. For example, in the example shown in FIG. 7, when the level A of the output voltage of the power regeneration circuit 33 is equal to or higher than the threshold value, the output voltage C to the transmission / reception circuit 34 and the like is not limited to ON / OFF of the switch signal. The voltage A is supplied from. This is because the output level of the power regeneration circuit 33 is sufficiently high so that log data can be normally transmitted to the reader / writer 32 with the power supplied from the power regeneration circuit 33.

  When the level A of the output voltage of the power regeneration circuit 33 is less than the threshold value and the switch signal is on, the output voltage C to the transmission / reception circuit 34 and the like becomes the voltage B supplied from the battery 39. This is because the output level of the power regeneration circuit 33 is not sufficient and the number of memory access bytes, that is, the amount of log data to be returned to the reader / writer 32 is large. This is because the log data may not be transmitted normally. Therefore, log data can be normally transmitted to the reader / writer 32 by supplying power from the battery 39.

  When the level A of the output voltage of the power regeneration circuit 33 is less than the threshold value and the switch signal is OFF, the output voltage C to the transmission / reception circuit 34 and the like is the voltage A supplied from the power regeneration circuit 33. This is because the output level of the power regeneration circuit 33 is not sufficient, but since the number of memory access bytes is small, log data can be normally transmitted to the reader / writer 32 with the power supplied from the power regeneration circuit 33. Because it is expected.

FIG. 8 is a flowchart of a power switching procedure in the electronic apparatus according to the second embodiment. FIG. 9 is a flowchart showing a continuation of FIG. As shown in FIG. 8, when the process is started, the voltage detection unit 72 first detects the level A of the output voltage of the power regeneration circuit 33. Then, the comparison / determination unit 73 determines whether or not the level A of the output voltage of the power regeneration circuit 33 is equal to or greater than a threshold (step S1). When the level A of the output voltage of the power regeneration circuit 33 is not equal to or higher than the threshold (step S1: No), it is assumed that the RFID tag 31 is not receiving radio waves from the reader / writer 32, and the level A of the output voltage of the power regeneration circuit 33 is Wait for it to finish.

  When the level A of the output voltage of the power regeneration circuit 33 is equal to or higher than the threshold, or when it is equal to or higher than the threshold (step S1: Yes), the output voltage A of the power regeneration circuit 33 is supplied to the transmission / reception circuit 34 and the tag controller 35. (Step S2). As a result, the transmission / reception circuit 34 and the tag controller 35 are activated. Next, the command determination unit 61 determines whether a command is received from the reader / writer 32 (step S3). If no command has been received (step S3: No), the RFID tag 31 waits to receive a command from the reader / writer 32.

  When a command is received from the reader / writer 32 (step S3: Yes), a command determination process is executed (step S4). In the command determination process, the command determination unit 61 decodes the command signal and extracts the command. Further, the number of memory access bytes is extracted by the byte number determination unit 62. Then, the byte number determination unit 62 determines whether or not the memory access byte number is equal to or larger than the threshold value of the memory access byte number (step S5).

  If the memory access byte count is not equal to or greater than the threshold value of the memory access byte count (step S5: No), the switch signal generating unit 64 turns off the switch signal (step S7) and returns to step S1. When the memory access byte number is equal to or greater than the threshold value of the memory access byte number (step S5: Yes), the switch signal generating unit 64 turns on the switch signal (step S6).

  Next, as shown in FIG. 9, it is determined whether or not a response (command response) to the received command has been completed (step S8). When the command response is completed (step S8: Yes), the switch signal generator 64 turns off the switch signal (step S7), and the process returns to step S1. When the command response is not completed (step S8: No), the comparison / determination unit 73 determines whether or not the level A of the output voltage of the power regeneration circuit 33 is less than the threshold (step S9). When the level A of the output voltage of the power regeneration circuit 33 is not less than the threshold value (step S9: No), the process returns to step S8.

  When the level A of the output voltage of the power regeneration circuit 33 is less than the threshold or when it is less than the threshold (step S9: Yes), the supply voltage to the transmission / reception circuit 34 and the tag controller 35 by the power switching unit 71 is The output voltage A of the regeneration circuit 33 is switched to the output voltage B of the battery 39 (step S10). Then, it is determined whether or not the command response is completed (step S11). If the command response has not been completed (step S11: No), it waits for the command response to be completed.

  When the command response is completed (step S11: Yes), the power supply switching unit 71 switches the supply voltage to the transmission / reception circuit 34 and the tag controller 35 from the output voltage B of the battery 39 to the output voltage A of the power regeneration circuit 33 ( Step S12). Then, the switch signal is turned off by the switch signal generation unit 64 (step S7), and the process returns to step S1.

FIG. 10 is a timing chart illustrating the operation of the system using the electronic apparatus according to the second embodiment. As an example, a case where the log read command has a memory access byte count of 100 bytes will be described. As shown in FIG. 10, when the RFID tag 31 receives the transmission signal 81 of the reader / writer 32, decodes the command, and starts transmitting log data as the response signal 85, the switch signal 83 is switched from OFF to ON. Then, the output voltage level 82 of the power regeneration circuit 33 gradually decreases.

  Until the level 82 of the output voltage of the power regeneration circuit 33 reaches the threshold value, the output voltage of the power regeneration circuit 33 is applied to the transmission / reception circuit 34 and the tag controller 35 as the transmission / reception operation voltage 84 of the RFID tag 31. When the output voltage level 82 of the power regeneration circuit 33 reaches the threshold value and becomes lower than the threshold value, the output voltage of the battery 39 is applied to the transmission / reception circuit 34 and the tag controller 35 as the transmission / reception operation voltage 84 of the RFID tag 31. As a result, the transmission / reception operating voltage 84 is stabilized at a sufficient voltage. Accordingly, since all the response signals 85 of the RFID tag 31 are transmitted to the reader / writer 32, the transmission of the log data ends normally. The switch signal 83 is switched from on to off at the end of transmission of log data.

  According to the second embodiment, when the level of the output voltage of the power regeneration circuit 33 becomes low and the log data amount (number of memory access bytes) to be transmitted to the reader / writer 32 is small, the transmission / reception circuit 34 and the tag controller 35 are used. Electric power is supplied from the power regeneration circuit 33. When the amount of log data to be transmitted to the reader / writer 32 is large, power is supplied from the battery 39 to the transmission / reception circuit 34 and the tag controller 35. Therefore, the battery 39 can be held better than when log data is always transmitted to the reader / writer 32 using the power of the battery 39.

  Further, the power supply source to the transmission / reception circuit 34 and the tag controller 35 is switched based on the level of the output voltage of the power regeneration circuit 33 and the amount of log data transmitted to the reader / writer 32. Therefore, for example, even when a noise signal is mixed into the antenna of the RFID tag 31 and the level of the output voltage of the power regeneration circuit 33 rises to a level that does not reach the threshold value, a command is not received from the reader / writer 32. It is possible to prevent power from being supplied from the battery 39 to the circuit 34 and the tag controller 35. Therefore, the battery 39 can be held better than when the power supply source to the transmission / reception circuit 34 and the tag controller 35 is switched without considering the amount of log data to be transmitted to the reader / writer 32.

Example 3
In the third embodiment, the threshold value of the output level of the power regeneration circuit 33 can be changed from the reader / writer 32 side in the second embodiment. For example, the threshold of the output level of the power regeneration circuit 33 is specified as a parameter in the log read command.

Description of Frame Format FIG. 11 is a schematic diagram illustrating an example of a frame format of a log read command in a system using the electronic apparatus according to the third embodiment. As shown in FIG. 11, for example, the frame format of the log read command has a log read command field 51, a head address field 52, and a read byte number field 53, as in the second embodiment. Further, the frame format of the log read command has a threshold field 54. The threshold field 54 stores the threshold of the output level of the power regeneration circuit.

Description of Tag Controller FIG. 12 is a block diagram of a tag controller of the electronic device according to the third embodiment. As shown in FIG. 12, the tag controller 35 includes a command determination unit 61, a byte number determination unit 62, a determination table 63, and a switch signal generation unit 64 as in the second embodiment. The tag controller 35 further includes a threshold setting unit 65.

  In the third embodiment, the command determination unit 61 decodes the command signal transmitted from the reader / writer 32 and extracts the threshold of the command and the output level of the power regeneration circuit. In the case of a log read command, the threshold of the output level of the power regeneration circuit is obtained from the frame format threshold field 54 shown in FIG. The threshold setting unit 65 outputs the threshold of the output level of the power regeneration circuit extracted by the command determination unit 61 to the threshold storage memory 74 of the power coupling circuit 40.

FIG. 13 is a block diagram of a power supply coupling circuit of the electronic apparatus according to the third embodiment. As shown in FIG. 13, the power supply coupling circuit 40 includes a power supply switching unit 71, a voltage detection unit 72, a comparison determination unit 73, and a threshold storage memory 74, as in the second embodiment. In the threshold storage memory 74, the threshold setting unit 65 of the tag controller 35 stores the threshold of the output level of the power regeneration circuit.

  Since the other configuration of the RFID tag 31 and the power supply switching procedure are the same as those in the second embodiment, a duplicate description is omitted. However, in the power supply switching procedure, in the command determination process in step S4 of the flowchart shown in FIG. In step S9, the threshold of the output level of the power regeneration circuit extracted in step S4 is used. In step S1, an initial value set in advance in the RFID tag 31 may be used as a threshold of the output level of the power regeneration circuit.

  According to the third embodiment, the same effect as in the second embodiment can be obtained. In addition, since the threshold value of the output level of the power regeneration circuit can be set in the threshold value field 54 in the log reading command according to the data amount of the log data read from the RFID tag 31, the battery 39 can be held better. Can do.

Example 4
In the fourth embodiment, the threshold value 1 (corresponding to the output level threshold value of the power regeneration circuit of the third embodiment) and the threshold value 2 are provided as the output level threshold value of the power regeneration circuit 33 in the second embodiment. 2 can be changed from the reader / writer 32 side. For example, threshold 1 and threshold 2 are specified as parameters in the log read command. When the output level of the power regeneration circuit 33 is less than the threshold value 1, the output voltage C to the transmission / reception circuit 34 and the like is switched from the voltage A supplied from the power regeneration circuit 33 to the voltage B supplied from the battery 39. When the output level of the power regeneration circuit 33 becomes equal to or higher than the threshold value 2, the output voltage C to the transmission / reception circuit 34 and the like returns from the voltage B supplied from the battery 39 to the voltage A supplied from the power regeneration circuit 33. The threshold level 2 may be higher than the threshold level 1. For example, threshold 1 may be 2.5V and threshold 2 may be 2.8V.

FIG. 14 is a schematic diagram illustrating an example of a frame format of a log read command in a system using the electronic device according to the fourth embodiment. As shown in FIG. 14, for example, the frame format of the log read command has a log read command field 51, a head address field 52, and a read byte number field 53 as in the second embodiment. Further, the frame format of the log read command has a threshold value 1 field 55 and a threshold value 2 field 56. The threshold 1 field 55 stores the threshold 1. The threshold 2 field 56 stores the threshold 2.

Description of Tag Controller and Power Supply Coupling Circuit The configurations of the tag controller 35 and the power supply coupling circuit 40 in the fourth embodiment are the same as those in the third embodiment. However, in the fourth embodiment, the command determination unit 61 extracts the threshold value 1 and the threshold value 2 as the output level threshold value of the power regeneration circuit. In the case of the log reading command, the threshold value 1 and the threshold value 2 are obtained from the threshold value 1 field 55 and the threshold value 2 field 56 of the frame format shown in FIG. The extracted threshold 1 and threshold 2 are stored in the threshold storage memory 74 by the threshold setting unit 65. Since the other configuration of the RFID tag 31 is the same as that of the second embodiment, a duplicate description is omitted.

FIG. 15 is a flowchart of a power switching procedure in the electronic apparatus according to the fourth embodiment. FIG. 15 shows step S8 and subsequent steps, but step S1 to step S7 are as described with reference to FIG. 8 in the second embodiment. However, in the command determination process in step S4 of the flowchart shown in FIG. 8, the threshold value 1 and the threshold value 2 are also extracted as the output level threshold value of the power regeneration circuit. In step S1, an initial value set in advance in the RFID tag 31 may be used as a threshold of the output level of the power regeneration circuit.

  Further, as shown in FIG. 15, steps S9 to S12 are the same as those described in the second embodiment with reference to FIG. However, in Example 4, the threshold value 1 is used as the threshold value of the output level of the power regeneration circuit in step S9. That is, the comparison / determination unit 73 determines whether or not the output voltage level A of the power regeneration circuit 33 is less than the threshold value 1.

  In the fourth embodiment, when the command response is not completed in step S11 (step S11: No), the comparison determination unit 73 determines whether the level A of the output voltage of the power regeneration circuit 33 is equal to or higher than the threshold value 2. Is determined (step S13). When the level A of the output voltage of the power regeneration circuit 33 is not equal to or higher than the threshold 2 (step S13: No), the process returns to step S11 and waits for the completion of the command response. When the level A of the output voltage of the power regeneration circuit 33 is equal to or higher than the threshold 2 (step S13: Yes), the supply voltage to the transmission / reception circuit 34 and the tag controller 35 is supplied from the output voltage B of the battery 39 by the power switching unit 71. The output voltage A is switched to the reproduction circuit 33 (step S14). Then, the process returns to step S8. Since the rest of the power supply switching procedure is the same as that of the second embodiment, a duplicate description is omitted.

Description of Operation Timing FIG. 16 is a timing diagram illustrating the operation of the system using the electronic apparatus according to the fourth embodiment. As shown in FIG. 16, when the RFID tag 31 starts transmitting log data as a response signal 95 to the reader / writer 32, the level 92 of the output voltage of the power regeneration circuit 33 gradually decreases.

  Until the level 92 of the output voltage of the power regeneration circuit 33 reaches the threshold value 1, the output voltage of the power regeneration circuit 33 is applied to the transmission / reception circuit 34 and the tag controller 35 as the transmission / reception operation voltage 94 of the RFID tag 31. When the level 92 of the output voltage of the power regeneration circuit 33 reaches the threshold value 1 and becomes lower than the threshold value 1, the output voltage of the battery 39 is given to the transmission / reception circuit 34 and the tag controller 35 as the transmission / reception operation voltage 94 of the RFID tag 31. Thereafter, when the level 92 of the output voltage of the power regeneration circuit 33 rises and reaches the threshold value 2 due to, for example, the RFID tag 31 approaching the reader / writer 32, the power regeneration circuit 33 is used as the transmission / reception operation voltage 94 of the RFID tag 31. Output voltage.

  According to the fourth embodiment, the same effects as the second and third embodiments can be obtained. Further, when the output voltage A of the power regeneration circuit 33 rises while the output voltage B of the battery 39 is applied to the transmission / reception circuit 34 and the tag controller 35, the output voltage of the power regeneration circuit 33 is transmitted to the transmission / reception circuit 34 and the tag controller 35. Since A is supplied, the battery 39 can be held better.

DESCRIPTION OF SYMBOLS 21 Electronic device 22 Transmission / reception apparatus 23 Calculation part 24 Control part 25 1st power supply part 26 Switching part 27 2nd power supply part

Claims (5)

A first power supply unit that extracts power from radio waves transmitted from the transmission / reception device;
A second power supply for supplying power from the battery;
A switching unit that switches between the first power supply unit and the second power supply unit;
A calculator for calculating the amount of information of the response signal in response to receiving a command transmitted from the transceiver device,
Together when starting the transmission of the response signal controls the front Symbol switching unit according to the amount of the information, the output level of the first power supply section while the transmitting the response signal to the transmitting and receiving device based to have a, and a controller for controlling the switching unit,
An electronic device characterized by that.   The electronic device according to claim 1, wherein the control unit controls the switching unit to switch to the second power supply unit side when the information amount is larger than a first threshold.   The electronic device according to claim 2, wherein the switching unit switches to the second power supply unit side when an output level of the first power supply unit is lower than a second threshold value. The second threshold value, the electronic device according to claim 3, characterized in that it is set by a command transmitted from the transceiver.   5. The electronic device according to claim 3, wherein the switching unit switches to the first power supply unit side when an output level of the first power supply unit becomes higher than a third threshold value.

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