JP2000033855A - Anti-theft system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To permit judgment between whether the connection has failed or the battery has been removed by a thief, by detecting stoppage of power supply with a power supply stop detection means and inputting it to the CPU, starting operation of a timer means, giving an alarm when a reference time is due. SOLUTION: With a set switch 6 ON, anti-theft function of a CPU 14 starts operation. In the case that a battery 1 is removed after turning on the set switch 6, when the CPU 14 is reset, if voltage supplied to the CPU 14 gradually decreases to become smaller than the reference value of 4.5 V, a 5 V detection circuit (power supply stop detection means) 12 detects it and switches over to the high level for supplying the CPU 14. At this time, a 5 V charge/discharge circuit (timer means) 13 gives an alarm for removal of battery 1 if it judges that more than a reference time has lapsed since start of the discharging. On the other hand, when the CPU 14 is not reset, the system does not judge that the buttery is removed, thus evading an alarm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anti-theft device for generating an alarm when a vehicle is stolen.

[0002]

2. Description of the Related Art First, an outline of an antitheft device will be described with reference to FIG. The output from the battery 1 is supplied to the constant voltage circuit 3 via the first electrolytic capacitor 2. The constant voltage circuit 3 outputs the supply voltage from the battery 1 at a predetermined voltage, for example, 5 V, and when the output voltage is lower than the predetermined voltage, for example, 4.5 V, detects this and outputs a reset signal. Is supplied to the microcomputer 5 to stop the operation of the microcomputer 5. The microcomputer 5 has an anti-theft function,
The function starts when the set switch (theft alarm setting means) 6 is turned on, and while a door lock signal indicating that the door is locked is supplied from a door lock switch (not shown). For example, when a vibration signal is received from a vibration sensor (not shown), it is determined that the vehicle is stolen, and an alarm is generated from the speaker 8 via the alarm drive circuit 7, and a thief is generated. On the other hand, the microcomputer 5 turns off the relay 10 via the starter motor control circuit 9, stops the supply of power from the battery to the starter motor 11, and stops the start of the engine.

Here, for example, in an apparatus as described above,
When the battery 1 is removed after the occupant turns on the set switch 6 when the occupant gets off the vehicle and starts the anti-theft function of the microcomputer 5, FIG.
As shown in (A), the battery output becomes 0 V at the removed time t1. After that, the voltage supplied from the constant voltage circuit 3 to the microcomputer 5 gradually decreases as shown in FIG. 5B due to the decrease in the charging voltage of the second electrolytic capacitor 4. The output voltage is
The self-check is performed by the constant voltage circuit 3, and for example, when it is detected that the voltage has dropped below a threshold value of 4.5 V (minimum voltage for normal operation of the microcomputer 5), the reset terminal of the microcomputer 5 When a low-level reset signal (see FIG. 5C) is supplied, the microcomputer 5 stores "battery removed" in the built-in memory 5a and then stops the program operation (time t2). .

Thereafter, the charging voltage of the second electrolytic capacitor 4 continues to decrease to 0 V. However, when the battery 1 is connected at time t3, the first electrolytic capacitor 2 is charged by the battery output and the constant voltage circuit 3 Is also powered,
The second electrolytic capacitor 4 is charged, and a voltage equal to the charging voltage is supplied to the microcomputer 5, and the voltage rises at this time between the time t3 and the time t4 in FIG. It changes as follows. Since the voltage supplied to the microcomputer 5 at time t5 during the rise of the voltage exceeds the threshold value of 4.5 V, the microcomputer 5 starts operating. As a result, the anti-theft function is activated, the microcomputer 5 reads the stored content of the internal memory 5a, and indicates at time t that the stored content indicates that "battery has been removed".
4 to determine whether the time from time t2 to time t4 has exceeded the reference time. If it is determined that the time has exceeded the reference time, an alarm is generated from the speaker 8 via the alarm drive circuit 7 and the starter motor The drive control circuit 9 turns off the relay 10 to stop the power supply to the starter motor 11 and stop the engine start.

[0005]

However, the microcomputer 5 in the anti-theft device described above.
Is usually designed to periodically repeat the sleep mode and the wake-up mode to save the power of the battery 1 while the burglary alarm function is operating. Therefore, immediately after the battery 1 is removed, for example, from time t1 to time t2, the power consumption greatly differs depending on whether the microcomputer 5 is in the sleep mode or the wake-up mode. In other words, while in the sleep mode, the threshold value of 4.5 V is reached over a long time, whereas in the wake-up mode, the power consumption of the microcomputer 5 is large. .5
V when the microcomputer 5 determines when the battery 1 has been removed, it is necessary to use the time when the power supply voltage of the microcomputer 5 reaches the threshold value 4.5 V as a reference, so that the There has been a problem that the time t1 at which 1 has been removed cannot be detected. Although it is conceivable to estimate the time t1, the estimation cannot be performed because the output voltage of the constant voltage circuit 3 changes greatly depending on the load condition of the constant voltage circuit 3.

Therefore, the present invention can accurately grasp the time at which a battery is removed even if the load of a microcomputer or the like fluctuates, and can determine in a short time whether the battery is simply contact failure or the battery is removed by a thief. The purpose is to be able to.

[0007]

According to the present invention, there is provided an anti-theft apparatus comprising: a constant voltage circuit for stabilizing and outputting a voltage supplied from a DC power supply and outputting a reset signal when an output voltage is lower than a predetermined value; A microcomputer that is supplied with power from the constant voltage circuit to output a control signal to a load, receives a reset signal from the constant voltage circuit, and stops operating, and a burglar alarm setting unit. After the theft alarm setting means is set, when the power supply from the DC power supply is stopped for a predetermined time or more, in an anti-theft device that outputs an alarm signal to an alarm means, the DC power supply is connected to the constant voltage circuit. Power supply stop detecting means for detecting a stop of the power supply of the power supply and outputting a detection signal; and detecting the power supply stop detecting means to the microcomputer. Timer means for starting a timer operation by supplying a signal, and when the timer operation by the timer means is performed beyond a reference time, the microcomputer sends an alarm signal to the notification means. It is characterized by outputting.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 This embodiment will be described with reference to FIG. 1. Here, the same or equivalent components as those shown in FIG. 4 are denoted by the same reference numerals, and detailed description thereof will be omitted. That is, only the 5V detection circuit (power supply stop detection means) 12, the 5V charge / discharge circuit (timer means) 13, and the microcomputer 14 will be described below.

More specifically, the 5V detection circuit 12 has an input terminal connected to a power supply line between the battery 1 and the constant voltage circuit 3, a base connected to a zener diode 12a having a reference value of 5V, and a collector connected to the power supply line. (TV) and the emitter is grounded. When the power supply line is 5 V or more, the transistor 12b
Is turned on and a low level signal is sent to the microcomputer 14
To supply. At the moment when the voltage of the power supply line falls below 5 V, the transistor 12b is turned off, and a voltage equal to the voltage (tV) of the constant voltage power supply line is supplied to the microcomputer 14.

The 5V charging / discharging circuit 13 includes resistors 13a, 13
When the charge terminal of the microcomputer 14 is at a high level, it is charged to 5 V, and when the charge terminal is switched to a low level,
Start discharging and perform timer operation.

Next, the microcomputer 14 is constructed as shown in FIG.
Only the functions added to the functions of the microcomputer 5 will be described. That is, the microcomputer 14 normally supplies a high-level signal from the charge terminal to the 5V charging / discharging circuit 13 to always fully charge the capacitor 13c and keep the 5V detecting circuit 1
2 is supplied with a high-level signal, the charge terminal is switched to a low level, thereby switching the 5V charge / discharge circuit 1
The charge stored in the third capacitor 13c is discharged with a predetermined time constant, and the voltage at the time of the discharge is read by an A / D converter 14b built in the microcomputer 14.

Next, the operation of the above configuration will be described. Normally, the microcomputer 14 is supplied with power from the constant voltage circuit 3 and the charge terminal is at a high level (FIG. 2E).
Until time t1). Thus, the capacitor 13c of the 5V charge / discharge circuit 13 is fully charged, and a high level signal (until time t1 in FIG. 2F) is supplied from the 5V charge / discharge circuit 13 to the microcomputer 14. In such a state, when the occupant gets off the vehicle, the set switch 6 is turned on to start the anti-theft function of the microcomputer 5. After that, when the battery 1 is removed, (the microcomputer 14
(When reset is not performed) and (when not reset) are described below.

When the battery 1 is removed (when the microcomputer 14 is reset), FIG.
As shown in (A), at time t1, the battery output becomes 0V. Accordingly, the voltage supplied from the constant voltage circuit 3 to the microcomputer 14 gradually decreases as shown in FIG. 2B due to the power consumption of the microcomputer 14 and falls below the reference value of 4.5 V. Then, the 5V detection circuit 12 detects this, instantaneously switches the output to the high level, and supplies it to the microcomputer 14 (time t1 in FIG. 2D). The microcomputer 14
The 5V detection circuit 12 determines that the high level output is supplied when the ignition switch 1a is turned on, and switches the charge output terminal from the high level to the low level. As a result, the 5V charge / discharge circuit 13 starts discharging, and the voltage of the input to the A / D converter 14b of the microcomputer 14 decreases.

Next, when the microcomputer 14 detects that the output voltage of the constant voltage circuit 3 has dropped below the threshold value of 4.5 V (time t2 in FIG. 2B), the microcomputer 14 supplies the reset terminal of the microcomputer 5 with A low-level reset signal (see FIG. 2C) is supplied to stop the program operation (time t2).

Thereafter, when the battery 1 is connected at the time t3, the first electrolytic capacitor 2 is charged by the battery output, the power is also supplied to the constant voltage circuit 3, the second electrolytic capacitor 4 is charged, and the charging is performed. A voltage equal to the voltage is supplied to the microcomputer 14, and the voltage rise at this time is as shown from time t3 to time t4 in FIG. 5B. At time t5 during the rise of the voltage, the voltage supplied to the microcomputer 14 exceeds the threshold value of 4.5 V, and the microcomputer 14 starts operating, and the anti-theft function operates. At this time, the microcomputer 14 reads the output voltage of the 5 V charging / discharging circuit 13 by the A / D converter 14b, and when the voltage value is equal to or less than a predetermined value, that is, the time t from the time t1 has passed the reference time t0 or more. If it is determined that the battery 1 has been removed, an alarm is issued from the speaker 8 via the alarm drive circuit 7 and the relay 10 is turned off by the starter motor drive control circuit 9 to control the starter motor 11. Stop power supply and stop engine start.

If the battery 1 is momentarily removed at time t1 (when the microcomputer 14 is not reset), the output voltage of the constant voltage circuit 3 becomes low as shown in FIG. If the battery 1 is reconnected while the voltage does not drop below the threshold value 4.5V, the microcomputer 14 is not reset by the constant voltage circuit 3,
Since the charge terminal switches to the high level state before the output of the 5V charge / discharge circuit 13 falls below the reference voltage value, the microcomputer 14 does not judge that the battery has been removed, and no alarm is issued. Further, even if the output voltage of the constant voltage circuit 3 becomes equal to or lower than the threshold value 4.5V, if the output of the 5V charge / discharge circuit 13 does not decrease below the reference voltage value, no alarm is issued.

[0017]

According to the present invention, the time at which the battery was removed can be accurately grasped even when the load of the microcomputer or the like fluctuates. The effect of being able to judge is exhibited.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram of an anti-theft device according to the present invention.

FIG. 2 is a timing chart for explaining the operation of the microcomputer 14 in FIG. 1 when the microcomputer 13 is reset.

FIG. 3 is a timing chart for explaining an operation of the microcomputer 14 in FIG. 1 when the microcomputer 13 is not reset.

FIG. 4 is a circuit block diagram of a conventional anti-theft device.

FIG. 5 is a timing chart for explaining the operation of the microcomputer 14 in FIG. 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Battery 2, 4 Electrolytic capacitor 3 Constant voltage circuit 5, 14 Microcomputer 6 Set switch (theft alarm setting means) 7 Alarm drive circuit 8 Speaker 9 Starter motor control circuit 10 Relay 11 Starter motor 12 5 V detection circuit (power supply stop detection Means) 135V charge / discharge circuit (timer means)

Claims (1)

[Claims] 1. A constant voltage circuit for stabilizing and outputting a voltage supplied from a DC power supply and outputting a reset signal when an output voltage becomes equal to or less than a predetermined value, and a control signal supplied from the constant voltage circuit to a load. And a microcomputer that receives a reset signal from the constant voltage circuit and stops operating, and a burglar alarm setting unit. An anti-theft device that outputs an alarm signal to a notification unit when power supply from a power supply continues for a predetermined time or more, and outputs a detection signal by detecting a stop of power supply from the DC power supply to the constant voltage circuit. Power supply stop detecting means,
Timer means for starting a timer operation by supplying a detection signal from the power supply stop detection means to the microcomputer, wherein when the timer operation by the timer means exceeds a reference time, the microcomputer The anti-theft device, wherein the computer outputs an alarm signal to the notifying means.