JP2502407B2 - Contactless information card - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-contact type information card that communicates with an external device by radio waves and processes data, and more particularly to a receiving circuit in the card.

[Prior Art] FIG. 4 is a block diagram showing a configuration of a contactless information card (IC card) of this type. CP that performs arithmetic and control for processing data (controls the entire IC card)
A U (Central Processing Unit) 41 is a ROM (Read Only Memory) 42 that stores a program via a bus 44, and a RAM (Random Access Memory) 4 that temporarily stores data.
3, and is connected to a UART (asynchronous serial transmission / reception circuit) 45 that serially transmits and receives data asynchronously. When transmitting data, the modulator circuit 4c modulates the serial data output from the UART45, and the transmitter circuit 4d uses the coil 4b.
Antenna (resonant circuit) 4ab consisting of and capacitor 4a
Drive and send out as radio waves. Also, when receiving data, the minute voltage received by the antenna 4ab is amplified by the receiving circuit 4f, converted to a logic level, and then demodulated by the demodulating circuit 4e.
The data is converted into parallel data by the UART 45 and is processed by the CPU 41. The oscillator 47 supplies the operating clock to the microcomputer 46, and the battery 48 is the microcomputer 46.
Supply power to. FIG. 5 (a) is a block diagram showing the configuration of a conventional receiving circuit 4f provided in the contactless information card, and FIG. 5 (b) is a circuit diagram of the constant voltage circuit 11 in FIG. 5 (a). is there. The output of the constant voltage circuit 11 that generates a constant voltage is given to the differential amplifier circuit 12 via the terminal 1s,
Bias current for operating 12 is generated. The differential amplifier circuit 12 amplifies the minute voltage received by the antenna (resonant circuit) 4ab, converts it to a logic level, and outputs it to the demodulation circuit 4e via the signal line 1t. n-channel transistors 1d and p
The channel transistor 1f functions to stop the constant voltage circuit 11, and the p-channel transistor 1e functions to inject a current into the constant voltage circuit 11 to start it. The D-type flip-flop 1a, the NAND gate 1b and the inverter 1c control on / off of these transistors 1d, 1f, 1e.

Next, the operation of the conventional receiving circuit 4f will be described with reference to FIG. 4 and FIG. First, when the receiving circuit 4f is in the non-operating state, the reception enable signal RXEN given from the CPU 41 via the bus 44 is set to the low level. Receiving enable signal RXEN
Is inverted by the inverter 1c and the n-channel transistor 1d
Is turned on to lower the potential of the terminal 1p of the constant voltage circuit 11 to the low level, and the reception enable signal RXEN is given to the p-channel transistor 1f, and the p-channel transistor 1f turns on and the potential of the terminal 1q is set to the high level. I have to. At this time, the p-channel transistors 51, 52 in the constant voltage circuit of FIG. 5 (b) are turned off, and the n-channel transistors 53, 54, 55 are also turned off. There is. In addition, since the bias current does not flow in the differential amplifier circuit 12, data cannot be received. Next, the activation and operation of the reception circuit 4f will be described.

When the CPU 41 raises the reception enable signal RXEN to high level to activate the reception circuit 4f, the output of the NAND gate 1b falls from high level to low level, the p-channel transistor 1e turns on, and the terminal 1p Increase the potential. At this time, the n-channel transistor 1d and the p-channel transistor 1f that have stopped the constant voltage circuit 11 are turned off. The current injection into the p-channel transistor 1e continues until the output Q of the D-type flip-flop 1a falls from the high level to the low level at the rising edge of the internal clock signal CLK. When the injected current causes a current to start flowing through the n-channel transistors 54 and 55 of the constant voltage circuit 11,
When the channel transistor 53 is turned on and the potential of the terminal 1s is lowered, the p-channel transistor 51 and the p-channel transistor 52 are turned on and a current starts to flow in the constant voltage circuit 11 and becomes stable at the bias point. Here, the operation of the constant voltage circuit 11 will be described. The p-channel transistors 51 and 52 are exactly the same transistor and form a current mirror circuit, and the same currents i1 and i2 are supplied to the n-channel transistor 5 respectively.
4,55 and n-channel transistor 53. Here, the gain constant β of the n-channel transistors 54 and 55 is sufficiently large,
Since the gain constant β of the n-channel transistor 53 is set to be sufficiently small, the terminal 1p (gate voltage of the transistor 53) hardly changes even if the current flowing into the p-channel transistors 51 and 52 changes due to the change of the power supply voltage. n
The current flowing through the channel transistor 53 does not fluctuate and the terminal
The potential of 1s increases and decreases, and the injection currents of the p-channel transistors 51 and 52 are restored. As described above, the currents i1 and i2 are equal and constant without being affected by the power supply voltage, so that the voltage between the output terminal 1s of the constant voltage circuit 11 and the power supply is constant. The output 1s of the constant voltage circuit 11 drives a p-channel transistor (not shown) included in the differential amplifier circuit 12 and supplies a bias current of the differential amplifier (not shown). As described above, since the voltage between the terminal 1s and the power supply is constant, the bias current is also constant without fluctuations in the power supply voltage, and the receiving circuit 4f can perform a stable receiving operation.

[Problems to be Solved by the Invention]

As described above, the conventional non-contact type information card is configured to apply the pulse voltage to the terminal 1p of the constant voltage circuit 11 to activate it when the receiving circuit 4f is activated. If the constant voltage circuit 11 stops abnormally due to disturbances such as power supply noise or noise from internal circuits after the start of the receiving circuit 4f, there is no means for confirming that the problem cannot be detected and a receiving error occurs. However, if the constant voltage circuit 11 stops during reception, there is no means to restart it, so the receiving circuit 4f
There was also a problem that stable operation of could not be secured.

The present invention has been made to solve the above-described problems, and when the constant voltage circuit stops abnormally, it can be detected and a reception error can be prevented, and the constant voltage circuit can be restarted to receive the reception circuit. It is an object of the present invention to provide a non-contact type information card that can ensure stable operation of the.

[Means for solving the problem]

The non-contact type information card according to the first aspect of the present invention is a voltage detection circuit (Schmitt trigger circuit 14) for detecting the voltage at a predetermined terminal 1p of a constant voltage circuit 11 which is a feedback type bias voltage generation circuit provided in a reception circuit 4f. Then, when the voltage at this predetermined terminal 1p becomes lower than the predetermined voltage, the output of the voltage detection circuit that detects the operation stop of the feedback type bias voltage generation circuit is received, and the starting current is injected to generate the feedback type bias voltage. A starting element for restarting the circuit is provided.

In the contactless information card according to the second aspect of the present invention, the feedback-type bias voltage generating circuit is configured such that the feedback-type bias voltage generating circuit has the voltage at the predetermined terminal 1p of the feedback-type bias voltage generating circuit equal to or higher than the predetermined voltage. A voltage detection circuit for detecting the start-up of the generation circuit and a starter element for receiving the output of the voltage detection circuit and stopping the injection of the start-up current are provided.

The non-contact type information card according to the third aspect of the present invention is provided with storage means (register 13) for storing the content detected by the voltage detection means and reading the stored content by the central processing unit (CPU 41). is there.

[Action]

The voltage detection circuit (simulation trigger circuit 14) detects the voltage of a predetermined terminal 1p of the constant voltage circuit 11 which is a feedback type bias voltage generation circuit. The register 13 stores the output of the voltage detection circuit. The central processing unit 41 reads the contents of the register 13 and detects the operating state of the receiving circuit 4f. In addition, the output of the voltage detection circuit is the starting element (p-channel transistor 1
When applied to e), the starting current again flows through the stop voltage circuit 11 which is the feedback type bias voltage generating circuit, and the constant voltage circuit (feedback type bias voltage generating circuit) 11 is restarted.

〔Example〕

The overall structure of the non-contact type information card according to the embodiment of the present invention is the same as the structure shown in FIG. FIG. 1 (a) is a block diagram showing the configuration of the receiving circuit according to this embodiment, and FIG. 1 (b) is a block diagram showing the configuration of the register in FIG. 1 (a). In FIG. 1 (a), 14
Is a Schmitt trigger circuit (voltage detection circuit) that detects the voltage of the terminal (predetermined terminal) 1p of the stop voltage circuit 11 that is a feedback type bias voltage generation circuit and consists of inverters 1g, 1h, 1k, and outputs it at a logic level, 13 The CPU 41 stores the output of the Schmitt trigger circuit 14 and detects the operating state of the receiving circuit 4f.
Is a register from which the stored contents are read. The other components are the same as in the conventional example.

Next, the operation of this embodiment will be described with reference to FIGS. 1, 3, and 4. Since the starting and stopping operations of the receiving circuit 4f are the same as those of the conventional example, a method of detecting whether the constant voltage circuit 11 is operating or stopped will be described. The voltage of the terminal 1p is constant at a predetermined voltage (bias point) during the operation of the constant voltage circuit 11, and becomes OV when stopped. Therefore, the Schmitt trigger circuit 14 converts the potential of the terminal 1p into high-level and low-level signals and supplies them to the register 13, and the CPU 41 reads the contents of the register 13 to read the operation state of the constant voltage circuit 11, that is, the receiving circuit 4f. The operating state, that is, the operating state of the receiving circuit 4f can be detected. The operation of the Schmitt trigger circuit 14 will be described with reference to FIG. Characteristic line 31 indicates the characteristic for the change in the power supply voltage V _DD of the input voltage VTH to the circuit 14 (+) when the output of the Schmitt trigger circuit 14 is inverted from the low level to the high level, the characteristic line 33 is a Schmitt trigger The characteristic of the input voltage VTH (-) to the circuit 14 when the output of the circuit 14 changes from the high level to the low level with respect to the change of the power supply voltage V _DD is shown. The characteristic line 32 is the characteristic of the voltage of the terminal 1p during the operation of the constant voltage circuit 11 with respect to the change of the power supply voltage V _DD . The input voltage VTH (+), VTH (-) decreases with the decrease of the power supply voltage V _DD , but the operating terminal 1p is
It is constant regardless of _DD .

When the reception circuit 4f is inactive, the reception enable signal RXEN is at low level, the potential of the terminal 1p is set to OV by the n-channel transistor 1d, and the Schmitt trigger circuit
The output of 14 is low level. That is, the state is point A in FIG. Next, when the reception circuit 4f is activated, the CPU 41 raises the reception enable signal RXEN to the high level, and p
The injection current of the channel transistor 1e raises the potential of the terminal 1p to reach point B. At this time, the potential of the terminal 1p exceeds the input voltage VTH (+) and the output of the Schmitt trigger circuit 14 becomes high level. Next, when the p-channel transistor 1e stops current injection at the rise of the internal clock CLK, the potential of the terminal 1p shifts to the bias point of the point C, and the constant voltage circuit 11
Starts stable operation. At this time, the Schmitt trigger circuit 14
The output of is still outputting the high level signal. Also,
When the constant voltage circuit 11 is cut off due to disturbance during operation, the potential of the terminal 1p shifts to the point A again, and the output of the Schmitt trigger circuit 14 becomes low level. Therefore, when the constant voltage circuit 11 starts up normally and starts to operate, the output of the Schmitt trigger circuit 14 becomes high level.

On the other hand, when the receiving circuit 4f is inactive, and when the current injection into the p-channel transistor 1e is insufficient and the bias point is not exceeded and the constant voltage circuit 11 is not normally started,
Further, during operation, when the constant voltage circuit 11 is stopped due to power source noise or the like, the output of the Schmitt trigger circuit 14 becomes low level. The output of the Schmitt trigger circuit 14 is given to the register 13. When the CPU 41 outputs the address of the register 13 to the address bus included in the bus 44, the address decoder 15 in FIG. 1 (b) raises the signal line 1Z to the high level, opens the gate of the clocked inverter 1l, and outputs the Schmitt signal. The output of the trigger circuit 14 is sent to the data bus included in the bus 44. That is, the CPU 41 can access the contents of the register 13 to read the output of the Schmitt trigger circuit 14 and detect the operating state of the receiving circuit 4f (constant voltage circuit 11).

FIG. 2 is a block diagram showing the structure of a receiving circuit according to another embodiment. In FIG. 2, components corresponding to those shown in FIG. 1 are designated by the same reference numerals, and their description will be omitted. In FIG. 2, 21 is a D-type flip-flop, 2a
Is a NOR gate and 2b is an inverter. In the embodiment of FIG. 2, the operation state detecting means of the constant voltage circuit 11 and its operation are the same as those of the embodiment of FIG. 1, but the CPU 41 outputs the output of the Schmitt trigger circuit 14 in the embodiment of FIG. By reading the contents of register 13 connected to
2 is detected, the output of the Schmitt trigger circuit 14 is fed back to the p-channel transistor 1e as a starting element via the NOR gate 2a and the inverter 2b in addition to the above. Since the configuration is such that on / off control is performed, the constant voltage circuit 11 can be surely activated, and even if the constant voltage circuit 11 is stopped during operation due to power supply noise or the like, the p-channel transistor 1e is automatically turned on. The voltage circuit 11 is restarted. This operation will be described with reference to FIG. When the receiving circuit 4f is stopped, the voltage at the terminal 1p is at point A '. Next, when the CPU 41 activates the reception circuit 4f to raise the reception enable signal RXEN to high level, the p-channel transistor 1e turns on, the potential of the terminal 1p rises, and when it rises to point B ', the Schmitt Trigger circuit 14
Output is inverted from low level to high level to turn off the p-channel transistor 1e. When the p-channel transistor 1e stops current injection, the potential of the terminal 1p shifts to the bias point C ', and the constant voltage circuit 11 starts stable operation. That is, the reception circuit 4f starts the determined operation. At this time, the output of the Schmitt trigger circuit 14 remains high level. When the constant voltage circuit 11 stops due to power source noise or the like, the voltage at the terminal 1p decreases but drops to the point D ', the output of the Schmitt trigger circuit 14 falls from the high level to the low level, and the p-channel transistor Since 1e is turned on, the potential of the terminal 1p rises again to reach the point B ', the output of the Schmitt trigger circuit 14 rises from low level to high level, the p-channel transistor 1e stops current injection, and the voltage of the terminal 1p voltage rises. Shifts to point C'and the constant voltage circuit 11 starts stable operation again. That is, CPU41
When the reception enable signal RXEN rises in order to activate the reception circuit 4f, the terminal 1p is surely charged up to the operating point (C 'point) or more, the constant voltage circuit 11 is activated, and the power supply noise etc. Thus, even when the constant voltage circuit 11 is cut off, it has a function of returning to the operating point again, and the receiving circuit 4f reliably continues to operate.

Further, in the embodiment of FIG. 2, when the CPU 41 reads the contents of the register 13, the history of whether or not the receiving circuit 4f (constant voltage circuit 11) has been restarted can be known. If there is a restart, the output of the Schmitt trigger circuit 14 falls at least once, so D
The output of the flip-flop 21 becomes high level, this high level signal is stored in the register 13, and the CPU 41
Read by. In the case of no restart, the output of the D-type flip-flop 21 remains at low level, so a low level signal is read out.

As described above, in the embodiment of FIG. 1, as the operation detecting means of the constant voltage circuit 11, the voltage of the predetermined terminal 1P of the constant voltage circuit 11 is detected and a high level or low level signal is output according to the detected voltage. Schmitt trigger circuit 14 to
A register 13 that can be read by the CPU 41 is provided, and the output of the Schmitt trigger circuit 14 is connected to the register 13
Since the contents of the register 13 are read according to the operating state, it is possible to easily detect whether the constant voltage circuit 11 is operating or stopped. Further, in the case of this embodiment, the constant voltage circuit 11 can be restarted by software. In addition, in the other embodiment of FIG. 2, in addition to the basic configuration of one embodiment, the output of the Schmitt trigger circuit 14 controls the on / off of the p-channel transistor 1e as the starting element. In addition to the effects of the embodiment, when the constant voltage circuit 11 is stopped, current is injected into the constant voltage circuit 11 until it is activated again, and the receiving circuit
You can also keep 4f operating reliably.

Although the Schmitt trigger circuit is used as the voltage detection circuit of the constant voltage circuit in each of the above embodiments, the same effect can be obtained by using the differential amplifier circuit. Further, although the above-mentioned embodiment shows the non-contact type information card having the built-in battery, the present invention is also effective for the non-contact type information card which does not have the built-in battery and can obtain power from an external electromagnetic field or light. Further, the non-contact transmission medium is not limited to radio waves and may be light or the like.

〔The invention's effect〕

As described above, according to the first aspect of the invention, the voltage detecting circuit for detecting the voltage at the predetermined terminal of the feedback bias voltage generating circuit provided in the receiving circuit and the voltage at the predetermined terminal are equal to or lower than the predetermined voltage. In this case, since the output of the voltage detection circuit that detects the operation stop of the feedback type bias voltage generation circuit is received and the starting element for injecting the starting current and restarting the feedback type bias voltage generation circuit is provided, the feedback type bias voltage is generated. Even if the voltage generating circuit is stopped, it is automatically started again. Therefore, once the receiving circuit is started, the feedback bias voltage generating circuit is surely started, and stable operation of the receiving circuit can be secured.

According to the second aspect of the present invention, the feedback bias voltage generation circuit detects the start-up of the feedback bias voltage generation circuit when the voltage at the predetermined terminal of the feedback bias voltage generation circuit becomes equal to or higher than the predetermined voltage. Since a voltage detection circuit that operates and a starting element that receives the output of this voltage detection circuit and stops the injection of the starting current are provided, even if the feedback-type bias voltage generation circuit is stopped, it is automatically started again, and therefore the reception Once the circuit is started up, the feedback bias voltage generating circuit is surely started up, and stable operation of the receiving circuit can be secured.

According to the third aspect of the present invention, since the content detected by the voltage detection means is stored and the storage content is read out by the central processing unit, it is possible to confirm that the receiving circuit is activated, and It is possible to detect that the feedback type bias voltage generating circuit has stopped abnormally, so that the abnormality of the received data can be easily recognized and the reception error can be prevented.
Even if the constant voltage circuit is stopped, the constant voltage circuit is automatically started again. Therefore, once the receiving circuit is started, the constant voltage circuit is surely activated, and the stable operation of the receiving circuit can be secured. .

[Brief description of drawings]

FIG. 1 (a) is a block diagram showing the structure of a receiving circuit according to an embodiment of the present invention, FIG. 1 (b) is a block diagram of the register in FIG. 1 (a), and FIG. 2 is another embodiment. 3 is a block diagram showing a configuration of a receiving circuit according to an example, FIGS. 3 (a) and 3 (b) are characteristic diagrams for explaining the operation of each of the above embodiments, and FIG. 4 is a non-contact type information of the embodiment and the conventional example. FIG. 5 (a) is a block diagram showing the overall configuration of the card, FIG. 5 (a) is a block diagram showing the configuration of a conventional receiving circuit, and FIG. 5 (b) is a circuit diagram of the constant voltage circuit of the embodiment and the conventional example. 41 ... Central processing unit, 4f ... Reception circuit, 11 ... Constant voltage circuit (feedback bias voltage generation circuit), 13 ... Register,
14 …… Schmidt trigger circuit (voltage detection circuit), 1e ……
P-channel transistor (starting element).

Claims (3)

(57) [Claims] 1. A non-contact transmission medium such as a radio wave, which has a central processing unit for performing arithmetic and control for processing data and a receiving circuit for receiving data from an external device and giving it to the central processing unit. In a non-contact type information card which communicates with an external device by using the data processing device, a voltage detection circuit for detecting a voltage at a predetermined terminal of a feedback bias voltage generation circuit provided in the receiving circuit, and a voltage at the predetermined terminal. Is less than or equal to a predetermined voltage, the start element that receives the output of the voltage detection circuit that has detected the operation stop of the feedback bias voltage generation circuit and injects the startup current to restart the feedback bias voltage generation circuit A non-contact type information card characterized by having and. 2. A voltage detection circuit for detecting the activation of the feedback bias voltage generation circuit when the voltage at a predetermined terminal of the feedback bias voltage generation circuit is equal to or higher than a predetermined voltage. The non-contact type information card according to claim 1, further comprising a circuit and a starting element that receives the output of the voltage detection circuit and stops the injection of the starting current. 3. The non-contact type information card according to claim 1, further comprising storage means for storing the content detected by the voltage detecting means and for reading the stored content by the central processing unit. .