JP3815252B2 - Communication equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a communication device such as a portable device for a keyless entry system of a vehicle, for example, and prevents a control circuit from running out of control due to a power supply voltage drop (including a power failure, the same applies hereinafter), and consumes less power. About.
[0002]
[Prior art]
Generally, in a vehicle keyless entry system, a main unit mounted on a vehicle performs wireless communication (one-way communication or two-way communication) with a portable device carried by a user, and verification of a predetermined authentication code is confirmed. Then, the vehicle door lock mechanism is controlled.
For example, when the main unit receives a radio signal (a signal including an authentication code) transmitted from the portable device in response to a user operating an operation switch provided on the portable device while the vehicle door is locked. After confirming that the authentication code included in the received signal corresponds to the authentication code set in the main body in advance, the main body performs vehicle door unlock control.
Further, in a smart entry system (also called a hands-free entry system or the like), which is an advanced type of a keyless entry system, the vehicle door is automatically locked and unlocked based on bidirectional communication between the main unit and the portable device. For example, when a portable device that has entered a communicable range for the main unit receives a request signal (or activation signal) periodically output from the main unit, a signal including an authentication code is automatically transmitted to the main unit, The main body that has received this signal performs the above-mentioned verification verification of the authentication code, and then performs unlocking control of the vehicle door in the locked state.
[0003]
By the way, a communication device such as a portable device in the keyless entry system (including the smart entry system) described above includes a control circuit 1 (normally one) including a microcomputer (hereinafter referred to as a microcomputer) as shown in a circuit diagram of FIG. The control circuit 1 controls the communication circuit 2 to perform wireless communication with the main unit (not shown). Further, the internal control circuit 1 and the communication circuit 2 are driven by the built-in battery 3 so that the user can carry them, and the control circuit 1 stops operating except during the communication operation in order to reduce power consumption. In addition, the battery 3 is configured to be supplied with a voltage by the contact of the battery terminals 3a and 3b so that the battery 3 can be easily replaced when the battery is consumed, and the structure for holding the battery 3 is too strong. It is not.
However, since such a communication device is used as a key holder suspended from a vehicle key or placed in a user's pocket, the communication device is subject to vibrations and shocks when the vehicle is running and when the user is operating. In particular, when the battery is dropped on the ground, the built-in battery 3 may be displaced from an appropriate position due to a strong impact.
For this reason, it is difficult to avoid the possibility of occurrence of a problem that the contact state of the battery terminals 3a, 3b becomes defective for a period of time or the contact is momentarily separated, and the control circuit 1 is caused by a voltage drop (including power interruption) due to such a problem. Needs to be dealt with so as not to run away. If the control circuit 1 runs out of control, the data (for example, the data of the above-mentioned authentication code) registered in the nonvolatile memory (for example, EEPROM) in the control circuit 1 is rewritten with an incorrect content, and then normal This is because the operation may be disabled.
[0004]
Therefore, conventionally, as shown in FIG. 3, a large-capacitance capacitor 4 for power backup (for example, 220 μF or more) is connected in parallel to the battery 3, or a reset circuit 5 based on low voltage detection is connected. I have to. Here, the capacitor 4 supplies power for a predetermined time instead of the battery 3 when the contact between the battery terminals 3a and 3b is temporarily separated, and also functions as a noise absorbing capacitor. In addition, the reset circuit 5 sets in advance a potential difference (that is, a power supply voltage) between the positive power supply line L1 connected to the positive electrode of the battery 3 and the negative power supply line L2 connected to the negative electrode of the battery 3. This is a circuit that outputs a reset signal to the CPU that constitutes the microcomputer of the control circuit 1 when it falls below a set threshold value (for example, the minimum value of the voltage at which the control circuit 1 is not likely to run away).
In addition, what is shown with the code | symbol 6 in FIG. 3 is an antenna for communication. Reference numeral 7 denotes an operation switch. When the operation switch 7 is operated, for example, the keyless entry radio signal (signal for locking and unlocking) is transmitted from the antenna 6.
[0005]
[Problems to be solved by the invention]
The capacitor 4 described above can supply power for a certain period of time instead of the battery 3 when the contact between the battery terminals 3a and 3b is temporarily separated, thereby avoiding the runaway of the control circuit 1. However, since the capacity is large, there is a problem that the communication device becomes large. Further, when the contact failure between the battery terminals 3a and 3b continues for a long time or when a voltage drop occurs due to the life of the battery 3 itself, the runaway of the control circuit 1 cannot be prevented. That is, when the power supply due to the discharge of the capacitor 4 is exhausted, the control circuit 1 may run away.
On the other hand, if there is a reset circuit 5 based on low voltage detection, a reset signal is always input to the CPU of the control circuit 1 when a voltage drop exceeding the threshold occurs due to poor contact of the battery terminals 3a and 3b. Therefore, the operation of the control circuit 1 is stopped and the runaway is surely avoided.
However, in the conventional communication device, since the reset circuit 5 is always connected to the power supply lines L1 and L2, the battery 3 must have a very large capacity due to the dark current of the reset circuit 5. In addition, there was a disadvantage that the communication device was increased in size and cost.
[0006]
Incidentally, in the case of a portable device for keyless entry, the power required during communication operation is about 5 mA / hr, and the actual communication operation is completed in about 0.5 seconds, and the control circuit 1 stops operating. Return to state immediately. And since such a communication operation is only performed several times to 10 times a day, the power required for the communication operation itself is very small.
On the other hand, the dark current of the reset circuit 5 is, for example, 2.4 μA / hr. However, since it always flows continuously, it becomes very large as a whole. According to a trial calculation by the inventors, if the reset circuit 5 is not provided, even if the battery 3 has 10 years or more, the provision of the reset circuit 5 results in a life of 2 to 3 years. For this reason, in order to provide the reset circuit 5, it is necessary to attach a battery 3 having a capacity three times or more.
Accordingly, an object of the present invention is to provide a communication device that operates while being supplied with power from a battery, and prevents a control circuit from running away due to a decrease in power supply voltage and consumes less power.
[0007]
[Means for Solving the Problems]
A communication device according to the present invention is a communication device powered by a battery,
An operation switch;
A control circuit that controls a communication operation of transmitting a radio signal in response to a signal interruption caused by the operation of the operation switch ;
A reset circuit that detects a voltage drop in a power supply line connected to a terminal of the battery and outputs a reset signal to the control circuit;
A switching element for opening and closing the energization line of the reset circuit;
When the control circuit starts operating upon receiving the signal interrupt , the switching element is controlled to be closed to enable the reset circuit, and when the control circuit stops operating after transmitting the radio signal , the switching circuit Reset circuit control means for disabling the reset circuit by controlling the element in an open state .
[0008]
According to this communication device, the reset circuit is valid only during the period when the control circuit is operating, and the control circuit is prevented from being runaway, and the reset circuit dark current flows only for the minimum necessary period. The power consumption of the circuit is greatly reduced. For this reason, the runaway of the control circuit can be avoided, and a battery having a small capacity can be used, and the reliability of the communication device can be improved while avoiding the enlargement of the communication device.
In addition, the preferable aspect of this invention is a communication apparatus which a battery is built in and a user can carry. This is because, if the communication device has a built-in battery and is carried by the user, the power supply voltage is likely to decrease due to poor contact of the battery terminal as described above, and the necessity of avoiding the runaway of the control circuit due to this is particularly high. . Further, in the case of a portable communication device, since the small size is particularly strongly required, the practicality of the present invention becomes more remarkable.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a circuit configuration of a portable device of a vehicle keyless entry system. It should be noted that the same elements as those in FIG.
The portable device (communication device) of this example includes a control circuit 11 including a reset circuit 11a based on low voltage detection. Further, a noise absorbing capacitor 12 (for example, a capacitor having a small capacity of about 0.1 μF) is connected between the power supply lines L1 and L2, and a resistor 13 and a capacitor 14 for generating a reset signal when the power is turned on, It is also connected in series between the power supply lines L1 and L2.
The control circuit 11 is a circuit including a microcomputer composed of a CPU, a ROM, a RAM, and the like, a reset circuit 11a, and a nonvolatile memory (for example, EEPROM) that stores program data, authentication code data, and the like. It consists of a microcomputer chip.
[0010]
When the power supply voltage (VDD) supplied from the power supply line L1 to the control circuit 11 falls below a threshold value, the reset circuit 11a in the control circuit 11 resets a reset signal (in this case, to the microcomputer CPU). Is an active low signal that is effective when the signal voltage is lower than the threshold value, and basically performs the same function as the reset circuit 5 shown in FIG. . However, in this case, the energization line of the reset circuit 11a is provided with a switching element (not shown) (for example, a transistor such as an FET), and this switching element is controlled by the processing described later of the microcomputer, so that the reset circuit 11a The microcomputer is disconnected from the power supply line L1 or L2 when the operation of the microcomputer is stopped. The switching element and the control function of the microcomputer constitute the reset circuit control means of the present invention.
[0011]
In addition, a signal line L3 for extracting a reset signal when the power is turned on is connected to a connection portion between the resistor 13 and the capacitor 14, and the signal line L3 is connected to a reset signal input unit in the control circuit 11. . The potential of the signal line L3 depends on a time constant determined by the resistor 13 and the capacitor 14 for a certain time immediately after the battery 3 is turned on (for example, when the battery 3 is newly attached and the voltage of the power line L1 exceeds a predetermined value). The signal is maintained in a state below a predetermined signal voltage threshold (that is, an active state as a reset signal) for a certain period of time from the time of rising, and thus the reset signal is input to the CPU of the control circuit 11 when the power is turned on. As a result, the control circuit 11 normally starts from the initial state when the power is turned on. FIG. 1 shows a state in which the reset signal output line of the reset circuit 11a and the signal line L3 are connected. However, actual circuit patterns constituting each line are not connected. This means that the reset signal is actually input to the CPU when the signal of one or both lines becomes active.
[0012]
Next, main processing contents of the microcomputer in the control circuit 11 will be described. When the reset signal is canceled while a predetermined power supply voltage is supplied, the microcomputer starts from the initial state, performs memory initialization processing, etc., and then repeats the following processing shown in FIG. . At the time of this startup, the reset circuit 11a is in an invalid state disconnected from the power supply line L1 or L2.
First, in step S1, the CPU is stopped by executing a STOP instruction, for example, in a stop state (a state in which the CPU operation and the microcomputer clock operation are stopped). Here, not the stop state but a simple wait state (a state where only the operation of the CPU is stopped and the clock is operating) may be employed.
Next, in step S2, whether or not there is an interruption due to switch input (that is, signal interruption due to operation of the operation switch 7) is monitored periodically, for example, and if there is an interruption, the process proceeds to step S3, and if there is no interruption, the process proceeds to step S1. It returns and maintains the operation stop state of the control circuit 11 (CPU).
On the other hand, when the process proceeds to step S3, the reset circuit 11a is connected to the power supply lines L1 and L2, and the reset circuit 11a is validated.
In step S4, a remote control signal (that is, a radio signal including an authentication code for locking and unlocking the vehicle door) is transmitted.
Next, in step S5, after resetting the reset circuit 11a from the power supply line L1 or L2 and invalidating it, the process returns to step S1 to return to the operation stop state.
[0013]
According to the above control processing, the reset circuit 11a is always connected to the power supply lines L1 and L2 when the operation of the control circuit 11 is started, and is valid. When the control circuit 11 stops operating, the reset circuit 11a is activated. Is always disconnected from the power supply line L1 or L2 and invalidated.
For this reason, according to the communication device (keyless entry portable device) described above, the reset circuit 11a is enabled only during the period in which the control circuit 11 is operating, and the control circuit 11 runs out of control (i.e. Runaway) is reliably avoided, and the dark current of the reset circuit 11a flows only for the minimum necessary period, and the power consumption of the reset circuit 11a is greatly reduced. For this reason, the runaway of the control circuit 11 can be avoided, and the battery 3 having a small capacity can be used, and the reliability of the communication device can be improved while avoiding the enlargement of the communication device.
[0014]
The present invention is not limited to the above-described embodiments, and various modifications and applications are possible.
For example, the reset circuit based on low voltage detection may be provided outside the control circuit 11 and separately from the control circuit 11. However, if the configuration is built in the control circuit 11 as in the above embodiment, the circuit is simplified and more advantageous in terms of cost.
Moreover, although the example which applied this invention to the portable machine for keyless entry of a vehicle was shown in the said example, it is not limited to this, For example, this invention can also be applied to the portable machine for smart entry mentioned above, for example. . Further, the present invention can be applied to a communication device of another remote control device in a vehicle (for example, a device that remotely controls opening / closing of a trunk, operation of a window, etc.). Further, the present invention is not limited to a communication device of a remote control device in a vehicle, and the same effect can be achieved by applying the present invention as long as the communication device is powered by a battery and may cause a control circuit runaway due to a power supply voltage drop. it can.
The battery of the present invention is not limited to a battery that cannot be recharged, and may be a rechargeable battery.
[0015]
【The invention's effect】
As described above, according to the communication device of the present invention, the reset circuit is enabled only during the period in which the control circuit is operating, the control circuit is prevented from runaway, and the dark current of the reset circuit is minimized. The power consumption of the reset circuit is greatly reduced by flowing for a limited period. For this reason, the runaway of the control circuit can be avoided, and a battery having a small capacity can be used, and the reliability of the communication device can be improved while avoiding the enlargement of the communication device.
[Brief description of the drawings]
FIG. 1 is a circuit diagram of a communication device (portable device).
FIG. 2 is a flowchart showing control processing of a communication device.
FIG. 3 is a circuit diagram of a conventional communication device.
[Explanation of symbols]
2 Communication circuit 3 Battery 11 Control circuit (reset circuit control means)
11a Reset circuit L1 Power line (Positive power line)
L2 power line (negative power line)

Claims (2)

A communication device powered by a battery,
An operation switch;
A control circuit that controls a communication operation of transmitting a radio signal in response to a signal interruption caused by the operation of the operation switch ;
A reset circuit that detects a voltage drop in a power supply line connected to a terminal of the battery and outputs a reset signal to the control circuit;
A switching element for opening and closing the energization line of the reset circuit;
When the control circuit starts operating upon receiving the signal interrupt , the switching element is controlled to be closed to enable the reset circuit, and when the control circuit stops operating after transmitting the radio signal , the switching circuit And a reset circuit control means for invalidating the reset circuit by controlling the element to an open state .   The communication apparatus according to claim 1, wherein the battery is built in and can be carried by a user.

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