JP2008204343A - Contactless communication device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a contactless communication device capable of improving reading performance of a non-contact data carrier, while reducing cost even when a device is miniaturized. <P>SOLUTION: Since the impedance of an RF part 30 is changed by approach of a contactless IC card 12, a signal level of a transmission signal from the RF part 30 is varied. A control part 29 outputs an interrupt signal to a main CPU 21, when data from an A/D conversion circuit 31 detecting the signal level of the transmission signal are changed. The main CPU 21 outputs a high-level power supply switching signal to a power supply switch circuit 18 so that the power supply switching circuit 18 connects an external power supply 23, connected to a switching power supply 19, to a dropper power supply 20. Thus, the RF part 30 can surely communicate with the non-contact IC card 12, since it is not affected by electromagnetic noise from the switching power supply 19. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a non-contact communication device that communicates with a non-contact data carrier in a power supply state from a switching power supply.

For example, in a security terminal device having a contactless IC card reader / writer for room entry management, the load current for executing screen display, LED lighting, or voice guidance is relatively large. For this reason, a highly efficient switching power supply is used.
In addition, since the patent document corresponding to the conventional example of this invention is not found, the disclosure is abbreviate | omitted.

  FIG. 5 is a schematic diagram showing a configuration of a security terminal apparatus having a non-contact IC card reader / writer. In FIG. 5, the security terminal device 1 includes a main circuit unit 2 and a non-contact IC card reader / writer unit 3. The main circuit unit 2 has a switching power supply 5 for supplying power to the entire apparatus in response to power supply from the external power supply 4. The non-contact IC card reader / writer unit 3 communicates with the non-contact IC card through the antenna 6 in response to a command from the main circuit unit 2. The non-contact IC card reader / writer unit 3 performs electromagnetic shielding by storing it in a sheet metal shield case 7 in order to avoid the influence of electromagnetic noise from the switching power supply 5 of the main circuit unit 2 during communication with the non-contact IC card. ing. Further, by interposing a noise absorbing sheet 8 that absorbs noise and converts it into heat between the main circuit unit 2 and the non-contact IC card reader / writer unit 3, electromagnetic noise from the main circuit unit 2 is reduced. As a result, the performance of the device is ensured. The main circuit unit 2 and the non-contact IC card reader / writer unit 3 are also designed to be kept away from each other.

  However, when the security terminal device 1 is downsized, that is, when the density is increased, the distance between the main circuit unit 2 and the non-contact IC card reader / writer unit 3 is shortened. It becomes easier to receive electromagnetic noise from the switching power supply 5. For this reason, the obstruction factor of the card reading distance becomes large, and it becomes difficult to improve the card reading performance. There is also a problem that the cost of the sheet metal shield case 7 or the noise absorbing sheet 8 is high.

  The present invention has been made in view of the above circumstances, and its purpose is non-contact that can improve the reading performance of a non-contact data carrier while reducing the cost even when the device is downsized. It is to provide a communication device.

  According to the invention of claim 1, the control means operates the power supply switching means when the detection means detects the non-contact data carrier. As a result, power is supplied from the dropper power supply instead of the switching power supply, so that it is possible to avoid the influence of electromagnetic noise from the switching power supply during communication with the non-contact data carrier. Therefore, even when the device is downsized, the communication distance with the non-contact data carrier can be improved. Further, since the dropper power supply is low in cost, the cost can be reduced as compared with the conventional sheet metal shield case or noise absorbing sheet.

  According to the second aspect of the present invention, when the non-contact data carrier approaches, the impedance of the transmission / reception circuit changes, and by detecting this, the non-contact data carrier can be detected without using any special means. .

According to the invention of claim 3, since the switching means can be constituted by a combination of transistors, it can be manufactured at low cost and the power source can be switched at high speed.
According to the invention of claim 4, since each circuit is mounted on the same printed circuit board, the cost can be further reduced and the size can be reduced.

Hereinafter, an embodiment in which the present invention is applied to a security terminal apparatus having a non-contact IC card reader / writer will be described with reference to FIGS.
FIG. 2 is a schematic diagram showing a configuration of a security terminal apparatus having a non-contact IC card reader / writer. In FIG. 2, a security terminal device (corresponding to a non-contact communication device) 11 is installed on the wall next to the entrance / exit of a room where general employees are restricted from entering, and a specific employee who is permitted to enter the room. The card data is read from a non-contact IC card (corresponding to a non-contact data carrier) 12 (refer to FIG. 1) carried by N. When the card data is authenticated, the door is unlocked. Further, an alarm is issued by outputting an operation guidance as a voice message, displaying a text message on a display, or turning on an alarm lamp. The security terminal device 11 is configured by housing a printed wiring board 14 and an antenna 15 in a resin case 13. A main circuit unit 16 and a non-contact IC card reader / writer unit 17 are mounted on the printed wiring board 14.

  FIG. 1 is a functional block diagram showing an electrical configuration of the security terminal device 11. In FIG. 1, the main circuit section 16 is composed of a power supply switching circuit (corresponding to switching means) 18, a switching power supply 19, a dropper power supply 20, a main CPU (corresponding to control means) 21, a dropper power supply monitoring circuit 22, and the like. Yes. The power supply switching circuit 18 selectively switches the connection between the external power supply 23 that supplies DC voltage and the switching power supply 19 or the dropper power supply 20 in accordance with a command from the main CPU 21.

  The switching power supply 19 generates a pulse signal by performing high-frequency switching of a DC voltage with a switching regulator, and rectifies the pulse signal with an output smoothing circuit (inductor, capacitor, etc.), thereby supplying a power supply voltage (for example, 5 V) of the main circuit. ) Is generated. The switching power supply 19 is characterized by high electromagnetic noise due to switching, although it has high efficiency because it generates less heat.

  The dropper power supply 20 generates a power supply voltage for the main circuit by stepping down the DC voltage with a series regulator (3-terminal regulator). The feature of the dropper power supply 20 is that the electromagnetic noise is small, but the efficiency is poor because the voltage is adjusted using a voltage drop. However, the dropper power supply 20 is generally low in cost.

  Input terminals of the switching power supply 19 and the dropper power supply 20 are connected to the ground line through capacitors (corresponding to power storage means) 24 and 25, respectively. Output terminals of the switching power supply 19 and the dropper power supply 20 are connected to a power supply line 28 that is a power supply line through diodes 26 and 27. The power supply line 28 is a line for supplying power to each electronic circuit mounted on the printed wiring board 14.

The dropper power supply monitoring circuit 22 monitors the output voltage of the dropper power supply 20, and notifies the main CPU 21 when the output voltage reaches a certain level.
The non-contact IC card reader / writer unit 17 includes a control unit (corresponding to detection means) 29, an RF unit (corresponding to transmission / reception circuit) 30, and an A / D conversion circuit (corresponding to impedance change detection means) 31 constituted by a microcomputer. It is composed of The control unit 29 amplifies the high-frequency transmission signal modulated by multiplying the carrier wave (13.56 MHz) and the encoded digital data, and outputs the amplified signal to the RF unit 30. The RF unit 30 constitutes a resonance circuit together with the antenna 15, and outputs a transmission signal from the control unit 29 to the antenna 15. The antenna 15 outputs a transmission signal from the RF unit 30 by radio waves, supplies power to the non-contact IC card 12, and receives card data by radio waves. The RF unit 30 outputs the card data signal from the non-contact IC card 12 received by the antenna 15 to the control unit 29. The A / D conversion circuit 31 detects the signal level of the transmission signal from the RF unit 30 and notifies the control unit 29 of the signal level. When the control unit 29 determines that the non-contact IC card 12 is detected based on the signal level detected by the A / D conversion circuit 31, it outputs an interrupt signal to the main CPU 21.

  When the main CPU 21 receives an interrupt signal from the control unit 29, the main CPU 21 outputs a power switching signal to the power switching circuit 18, and when the dropper power monitoring circuit 22 is notified that the dropper power 20 has started up. The control unit 29 is permitted to communicate with the non-contact IC card 12.

  Next, the power supply switching circuit 18 will be described. FIG. 3 is an electric circuit diagram showing the power supply switching circuit 18, and only main components will be described for the sake of simplicity. In FIG. 3, the external power source 23 is connected to the switching power source 19 via a transistor (corresponding to a first transistor) 32. The collector of the transistor 32 is connected to the ground line via the capacitor 24 and to the 24V line 33. The 24V line 33 is a line for supplying power to the switching power supply 19 and the dropper power supply 20 and supplying power to an electronic circuit for executing screen display, LED lighting, or voice guidance. The base of the transistor 32 is connected to the ground line via the transistor 34. The base of the transistor 34 is connected to the ground line via the transistor 35. The collector of the transistor 35 is connected to the 24V line 33. The base of the transistor 35 is connected to the output terminal of the main CPU 21.

  The external power supply 23 is connected to the dropper power supply 20 via a transistor (corresponding to a second transistor) 36. The collector of the transistor 36 is connected to the ground line through the capacitor 25 and to the 24V line 33. The base of the transistor 36 is connected to the ground line via the transistor 37. The base of the transistor 37 is connected to the output terminal of the main CPU 21.

  The main CPU 21 outputs a power switching signal from the output terminal to the power switching circuit 18. The main CPU 21 normally does not output a power supply switching signal, and outputs a high-level power supply switching signal when performing power supply switching, as will be described later. In a state where no power source switching signal is output from the main CPU 21, the transistor 35 is turned on because the transistor 35 is turned off and the transistor 34 is turned on. At this time, the transistor 36 is turned off because the transistor 37 is turned off. Therefore, the external power supply 23 is connected to the switching power supply 19 through the transistor 32, and is in a power supply state from the switching power supply 19 to the power supply line.

On the other hand, the contactless IC card 12 demodulates the reception signal received from the RF unit 30 to decode the reception data and process it as digital data.
FIG. 4 shows the electrical configuration of the non-contact IC card 12. When the non-contact IC card 12 receives the transmission signal transmitted from the security terminal device 11 by the antenna 38, the operation power supply circuit 39 rectifies the transmission signal to generate the operation power, and the processing circuit 40 configured by a microcomputer. And other components. The communication speed extraction circuit 41 extracts the communication speed of data superimposed on the transmission signal. The clock generation circuit 42 generates a clock signal having a frequency corresponding to the extracted communication speed and outputs the clock signal to the processing circuit 40 and the encoding / decoding circuit 43.

The demodulation circuit 44 demodulates the transmission data superimposed on the transmission signal. The encoding / decoding circuit 43 decodes the transmission data demodulated by the demodulation circuit 44 and outputs the decoded data to the processing circuit 40. When the operation power is supplied from the operation power supply circuit 39 and activated, the processing circuit 40 reads the card data stored in the internal memory 45 in response to the transmission data, or writes the reception data in response to the write command. To do. The card data includes ID data for identifying a carrying employee and a card expiration date.
The encoding / decoding circuit 43 encodes the transmission data from the processing circuit 40 and outputs it to the modulation circuit 46. The modulation circuit 46 outputs a modulated signal obtained by load-modulating the carrier with the encoded data to the antenna 38.

Next, the operation of the above configuration will be described.
In a state where power is supplied from the external power source 23, the power switch signal is not output from the main CPU 21, so that the transistor 32 is on and the transistor 36 is off. As a result, the DC voltage from the external power supply 23 is supplied to the switching power supply 19 through the transistor 32, so that the power supply stabilized by the switching power supply 19 is supplied to the printed wiring board 14 as a power supply voltage and mounted on the printed wiring board 14. Each electronic circuit thus operated is operated. At the same time, 24V is supplied as a power source for the entire security terminal device 11. In this case, since the switching power supply 19 controls the output voltage (power supply voltage) by switching control of the transistor, electromagnetic noise is generated, but at the time of non-communication with the non-contact IC card 12. Each electronic circuit mounted on the printed wiring board 14 operates without being affected by electromagnetic noise.

In a state where power is supplied from the switching power supply 19 as described above, the RF unit 30 outputs a transmission signal having a predetermined frequency. When the non-contact IC card 12 is not located in the communication area, the output level of the transmission signal is constant. In this case, even if the transmission signal from the RF unit 30 is affected by the electromagnetic noise from the switching power supply 19, such electromagnetic noise is spike noise, so the output level of the transmission signal can be regarded as almost constant. This does not hinder the detection of the output level of the transmission signal.
Here, the A / D conversion circuit 31 digitally converts the signal level of the transmission signal of the RF unit 30 and outputs the signal level to the control unit 29. The control unit 29 receives the signal level given from the A / D conversion circuit 31. Is constant, it is determined that the non-contact IC card 12 does not exist in the communication area.

  Now, when a specific employee enters the room, the impedance of the RF unit 30 changes when the portable non-contact IC card 12 approaches the security terminal device 11 installed at the entrance, that is, the RF unit 30. Therefore, the signal level of the transmission output of the RF unit 30 changes. As a result, the data transmitted from the A / D conversion circuit 31 to the control unit 29 changes greatly, so that the control unit 29 determines that the non-contact IC card 12 is located in the communication area and sends an interrupt signal to the main CPU 21. Output.

When the main CPU 21 receives the interrupt signal, it outputs a high-level power switching signal to the power switching circuit 18. As a result, the transistor 32 that has been turned on until then is turned off, the connection between the external power supply 23 and the switching power supply 19 is disconnected, and the transistor 36 that has been turned on until then is turned on, so that the external power supply 23 and the dropper power supply 20 Are connected through the transistor 36, so that power is supplied from the external power source 23 to the dropper power source 20.
When power is supplied from the external power supply 23, the dropper power supply 20 is controlled by voltage drop control so that the output voltage becomes constant. In this case, since the voltage control by the dropper power supply 20 is analog continuous control, the electromagnetic noise is small.

  Here, if the connection between the external power supply 23 and the switching power supply 19 is cut as described above, the power supply from the switching power supply 19 is cut off, but the power supply voltage from the dropper power supply 20 rises to a certain level. Takes time. In this case, power is supplied to the switching power supply 19 from the capacitor 24 that has been in a charged state until then, and the output state of the power supply voltage is short even after the switching power supply 19 is disconnected from the external power supply 23. The power supply voltage from the dropper power supply 20 rises to a certain level during that time.

The dropper power supply monitoring circuit 22 monitors the power supply voltage from the dropper power supply 20, and notifies the main CPU 21 when the voltage reaches a certain level.
The main CPU 21 transmits a card reading permission signal to the control unit 29 when detecting that switching to the dropper power supply 20 is made by a notification from the dropper power supply monitoring circuit 22. When receiving a card reading permission signal from the main CPU 21, the control unit 29 transmits a request command to the non-contact IC card 12. The non-contact IC card 12 returns ID data assigned to itself to the reader / writer side (ID response). When the security terminal device 11 transmits a Read command to the non-contact IC card 12, the non-contact IC card 12 returns predetermined card data to the security terminal device 11 side (data response).

  Here, in the operating state of the dropper power supply 20, the electromagnetic noise from the dropper power supply 20 is significantly reduced as compared with the switching power supply 19, so that the transmission signal from the RF unit 30 is affected by the electromagnetic noise. There is nothing. Therefore, the data superimposed on the transmission signal from the control unit 29 can be accurately transmitted to the non-contact IC card 12.

When the main CPU 21 receives the card data from the non-contact IC card 12 as described above, the main CPU 21 determines that the communication with the non-contact IC card 12 is finished, and switches the power switch signal to the low level. As a result, the external power source 23 is connected from the dropper power source 20 to the switching power source 19, so that power is supplied from the switching power source 19. Also in this case, since the power supply state from the dropper power supply 20 is continued by the power supply from the capacitor 25, even if the connection between the external power supply 23 and the dropper power supply 20 is cut off, the power supply state of the power supply is cut off. There is no end.
Since the rise time of the switching power supply 19 is faster than that of the dropper power supply 20, the output voltage from the switching power supply 19 is not monitored, but may be monitored.

  Next, the main CPU 21 executes an authentication operation based on the received card data, and outputs an unlock signal to the door lock device when the authentication result is “true”. Thereby, since the door is unlocked, the employee can open the door and enter the room.

According to such an embodiment, the security terminal device 11 is normally operated by power feeding from the switching power supply 19. When the non-contact IC card 12 is detected, the security terminal device 11 is switched from the switching power supply 19 to the dropper power supply 20. Since communication with the non-contact IC card 12 is performed, even if electromagnetic noise is large as a characteristic of the switching power supply 19, it is possible to reliably communicate with the non-contact IC card 12 without being affected by the electromagnetic noise from the switching power supply 19. it can. Accordingly, when the security terminal device is downsized, the security terminal device 11 is not affected by the switching power supply 19 as compared with the conventional example that is further affected by the electromagnetic noise from the switching power supply. Can be miniaturized.
Moreover, since the dropper power supply 20 is low in cost, it can be implemented at a low cost as compared with a configuration using a sheet metal shield case or a noise absorbing sheet as a countermeasure against electromagnetic noise from the switching power supply 19.

Further, since the presence of the non-contact IC card 12 is detected by detecting that the signal level of the transmission signal from the RF unit 30 changes, the non-contact IC card 12 can be installed without using any special means. This can be detected and the cost can be reduced.
Further, since the power source switching circuit 18 is configured by combining transistors, it can be manufactured at low cost and the power source can be switched at high speed.
Furthermore, since the non-contact IC card reader / writer unit 17 is not affected by the influence of the switching power source 19 of the main circuit unit 16 as described above, the main circuit unit 16 and the non-contact IC are provided on one printed wiring board 14. The card reader / writer unit 17 can be mounted, so that the cost can be further reduced and the size can be reduced.

The present invention is not limited to the above embodiment, and can be modified or expanded as follows.
Instead of communication with a non-contact IC card, the present invention may be applied to a non-contact communication device that communicates with an ID tag.
Switching between the switching power supply 19 and the dropper power supply 20 may be performed by a relay.
Instead of changing the impedance of the transmission output, for example, a non-contact IC card may be detected by transmitting a preamble signal and receiving a response signal.
Instead of the capacitors 24 and 25, a secondary battery that is charged by receiving power from the 24V line 33 or the power supply line 28 of the main circuit may be provided.
The present invention may be applied to devices other than the security terminal device.

1 is a functional block diagram showing the configuration of a security terminal device according to an embodiment of the present invention. Schematic diagram showing the configuration of the security terminal Electrical circuit diagram showing the power switching circuit Functional block diagram showing the configuration of a non-contact IC card FIG. 2 equivalent diagram showing a conventional example

Explanation of symbols

  In the drawing, 11 is a security terminal device (non-contact communication device), 12 is a non-contact IC card (non-contact data carrier), 14 is a printed wiring board, 15 is an antenna, 18 is a power supply switching circuit (switching means), 19 is Switching power supply, 20 is a dropper power supply, 21 is a main CPU (control means), 23 is an external power supply, 24 and 25 are capacitors (power storage means), 29 is a control section (detection means), 30 is an RF section (transmission / reception circuit), 31 is an A / D conversion circuit (impedance change detecting means), 32 is a transistor (first transistor), and 36 is a transistor (second transistor).

Claims (5)

A non-contact data carrier including a switching power supply that performs power feeding operation in a connected state with an external power source, and a transmission / reception circuit that transmits a transmission signal from the antenna to the contactless data carrier and receives a reception signal from the contactless data carrier through the antenna. In contact communication devices,
A dropper power supply that feeds power in a connected state with the external power supply;
Detecting means for detecting the non-contact data carrier;
Switching means for switching from feeding by the switching power supply to feeding by the dropper power supply;
Control means for activating the switching means when the detecting means detects the non-contact data carrier, and ending the operation of the switching means when communication with the non-contact data carrier by the transmission / reception circuit is completed; A non-contact communication device comprising: An impedance change detecting means for detecting a change in impedance of a transmission output of the transmission / reception circuit;
2. The non-contact communication apparatus according to claim 1, wherein the detection unit determines that the non-contact data carrier is detected when the impedance change detection unit detects a change in impedance. The control means outputs a power supply switching signal to the switching means when operating the switching means,
The switching means is
A first transistor that is turned on in a non-input state of the power supply switching signal and connects the external power supply and the switching power supply;
3. The non-contact communication apparatus according to claim 1, further comprising a second transistor that is turned on in an input state of the power switching signal and connects the external power source and the dropper power source.   Power storage provided to store power in a connected state with the external power source, and maintaining a power feeding state to the switching power source or the dropper power source in a state in which the connection between the external power source and the switching power source or the dropper power source is released 4. The non-contact communication apparatus according to claim 1, further comprising means.   The contactless communication apparatus according to claim 1, wherein the transmission / reception circuit, the switching power supply, and the dropper power supply are mounted on the same printed circuit board.

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