JP4623285B2 - Light-emitting diode flashing drive circuit - Google Patents

Description

  The present invention relates to a blinking drive circuit for a light emitting diode that causes a light emitting diode to blink at a constant cycle by a small battery as a power source.

  In recent years, various crime prevention devices have been developed as crimes worsen, but it is possible to discourage the intrusion by informing the person who is about to intrude that the intrusion is being monitored. It is said to be an extremely effective means.

  Examples of crime prevention means threatening with such prior notice include, for example, a “sticker stating that a security device is installed” or flashing to inform an intruder that the security device is in operation. It is possible to install a device equipped with a light emitting diode, but the former is the most effective to install the latter because the sticker is difficult to see or cannot be seen at night when monitoring is most necessary. It is thought that.

  Here, the security device provided with the light emitting diode is often installed on a window or the like where a suspicious person often intrudes (for example, installed on the inner surface of the outer glass in such a manner that the window can be opened and closed). Therefore, there is no choice but to use a small battery with a small capacity as a power source despite continuous use for a long time. Therefore, in this type of security device, a CMOS element with low current consumption is generally used.

  In addition, as a blinking drive circuit of the light emitting diode in such a crime prevention device, the blinking cycle is 0.1 to 0.2 Hz from the purpose of suppressing battery consumption as much as possible and the condition that the blinking state can be visually recognized. It is appropriate that the duty factor (duty factor) for driving the light emitting diode is about 1/1000.

  As a method for realizing such a light-emitting diode blinking drive circuit by using the prior art, for example, a blinking drive circuit 2 ′ shown in FIG. 5 using an astable multivibrator constituted by a CMOS gate is used. Conceivable.

  However, in this LED flashing drive circuit 2 ', CMOS-structured P-channel and N-channel transistors (the output of the leftmost NAND gate in FIG. 5) that are generated each time the output of the unstable multivibrator is inverted. Are turned on at the same time, so-called through current becomes so large that it cannot be ignored. For this reason, in the security device using the light emitting diode blinking drive circuit 2 ′ as shown in FIG. 5, the consumption of the battery increases, and the battery needs to be replaced in a short period of time.

  Note that this phenomenon occurs when the oscillation period is long, the voltage between the terminals of the capacitor supplied to the input gate changes very slowly, and thus the time during which the through current generated in the output transistor flows increases. Because.

In recent years, in the industry that handles this type of product, there is a long-awaited development of a light-emitting diode blinking drive circuit that can be used for a long time even if the power source is a small battery with a small capacity.
EK JAPAN Development Department "Basics of Digital Circuit Basics Understandable" EK Japan Co., Ltd. April 1, 2001 P28-29

  Therefore, an object of the present invention is to provide a blinking drive circuit for a light emitting diode that can be used reliably for a long time even if the power source is a small battery with a small capacity.

(Invention of Claim 1)
A light-emitting diode blinking drive circuit according to the present invention includes a light-emitting diode, a capacitor connected in parallel to the light-emitting diode, an open-drain output voltage detector for monitoring a voltage between terminals of the capacitor, and an output of the voltage detector And a switching element that controls the current supplied to the light-emitting diode by the output of the mono-stable multi-vibrator, and the lighting time of the light-emitting diode is a monostable multi-vibrator. Depending on the output pulse width of the vibrator, the turn-off time is defined by the time until the voltage between the terminals of the capacitor decreases to the detection voltage of the voltage detector.

  The light-emitting diode blinking drive circuit according to the present invention can be used reliably for a long time even if the power source is a small battery with a small capacity.

  Embodiments as the best mode for carrying out the blinking drive circuit for light emitting diodes of the present invention will be described in detail below.

1 is a perspective view of a security device B using a light emitting diode flashing drive circuit 2 according to an embodiment of the present invention, FIG. 2 is a diagram of the light emitting diode flashing drive circuit 2, and FIG. 3 is an aluminum sash for the security device B. FIG. 4 is a plan view showing a state in which the security device B is attached to the aluminum sash window 9.
(About this security device B)
As shown in FIG. 1, the security device B is composed of a thin and small resin case 1 having a vertical dimension of 120 mm, a horizontal dimension of 35 mm, and a thickness dimension of 8 mm, and the resin case 1 has an upper end. A transparent case 10 on the part side and an opaque case 11 in the range from the middle part to the lower end part are formed.

  As shown in FIG. 1, the opaque case 11 houses a printed circuit board 29 on which an intrusion detection circuit, a buzzer driving circuit, and a light emitting diode blinking driving circuit 2 are arranged. A buzzer (not shown) that emits an alarm sound by output is provided.

  As shown in FIG. 1, the transparent case 10 is configured to face a light emitting diode that penetrates and projects from the upper end of the opaque case 11.

In the crime prevention device B, as shown in FIG. 1, a small-capacity small battery (for example, a circular thin battery) as a power source is exchangeably accommodated in the opaque case 11.
(About this LED flashing drive circuit K)
As shown in FIG. 2, the light-emitting diode blinking drive circuit 2 includes a light-emitting diode 20, a capacitor 21 connected in parallel to the light-emitting diode 20, and an open drain output voltage for monitoring a voltage between terminals of the capacitor 21. The detector 22 is triggered by the output of the voltage detector 22 and is configured by a CMOS gate 23a, and controls the current supplied to the light emitting diode 20 by the output of the monostable multivibrator 23. The switching element 24 is provided. In the circuit, what is indicated by a symbol R is a resistor.

Here, in the blinking drive circuit 2 of the light emitting diode, the light emitting diode 20 blinks when each component constituting the circuit 2 functions as shown in the following (1) to (4).
(1) When the light-emitting diode 20 is turned on The light-emitting diode 20 is turned on only for the output time of the monostable multivibrator 23 (time when a pulse with a small pulse width is generated).
(2) When the light emitting diode 20 is extinguished When the generation time of the above pulse ends, the terminal voltage of the capacitor 21 connected in parallel to the light emitting diode 20 is also equal to the forward voltage of the light emitting diode 20 and is supplied from the switching element 24. The current to the light emitting diode 20 is stopped. At this time, a part of the electric charge accumulated in the capacitor 21 is supplied to the light emitting diode 20 for a very short period of time. However, when the voltage between the terminals of the capacitor 21 becomes lower than the forward voltage of the light emitting die auto 20, the capacitor 21 The accumulated charge is gradually discharged as a leak current at the input terminal of the voltage detector 22.
(3) When the light emitting diode 20 is turned on Here, when the voltage between the terminals of the capacitor 21 reaches the detection voltage of the voltage detector 22, the voltage detector 22 inverts its output, and the monostable multi-stage of the next stage Trigger the vibrator 23. By this trigger, the monostable multivibrator 23 generates a pulse having a small pulse width, controls the switching element 24, and turns on the light emitting diode 20 again.
(4) The above operations (1) to (3) are repeated, and the light emitting diode 20 blinks. That is, in the light emitting diode blinking drive circuit 2, the lighting time of the light emitting diode 20 is defined by “the output pulse width of the monostable multivibrator 23”, and the lighting time of the light emitting diode 20 is “the voltage between terminals of the capacitor 21 is a voltage. The time until the voltage decreases to the detection voltage of the detector 22 ”.
(About usage of this security device B)
As shown in FIGS. 3 and 4, the security device B is attached to the inside of the glass surface of the aluminum sash window 9 so that the light emitting diode 20 can be seen from the outside.

  In the security device B, when a switch (not shown) is turned on, the light-emitting diode blinking drive circuit 2 is activated, and the blinking of the light-emitting diode 20 can be visually recognized from the outside. Especially at night when you cannot see the sticker stating that security equipment is installed, the psychological effect on suspicious intruders is great (by making you think you are monitoring the intrusion), so that you can stop intrusion Can be very effective. Also, when the intruder detection circuit is activated due to the intruder opening the window or breaking the glass, the flashing cycle of the light emitting diode 20 is accelerated to about 4 Hz simultaneously with the generation of the buzzer sound. On the other hand, the threatening effect can be enhanced both visually and auditorily.

The crime prevention device B having the light-emitting diode blinking drive circuit 2 is thin and small with a vertical dimension of 120 mm, a horizontal dimension of 35 mm, and a thickness dimension of 8 mm, and the power source is a small battery. It can be used even in a confined place where the power supply cannot be drawn.
(About the excellent point of this LED flashing drive circuit 2)
In the prior art light-emitting diode flashing drive circuit, if the oscillation frequency is set to about 0.1 to 0.2 Hz so as to minimize battery consumption, a P-channel having a CMOS structure is generated each time the output is inverted as described above. As a result, the through current of the N-channel transistor (the output of the leftmost NAND gate in FIG. 5) becomes so large that it cannot be ignored. In other words, the light emission diode blinking drive circuit consumes a large amount of current, and therefore cannot be used in a short period of time when the power source is a small battery.

  On the other hand, in the flashing drive circuit 2 of the light emitting diode, the “lighting time is the output pulse width of the monostable multivibrator 23” in the light emitting diode 20, and “the voltage between the terminals of the capacitor 21 is the voltage detector during the turn-off time”. Since the output of the voltage detector 22 does not have a CMOS structure, no through current flows at the time of output inversion. In order to reduce the current consumption and reduce the average current consumption by the light emitting diode 20, the duty factor is reduced. Therefore, even when the power source is a small battery, it can be used reliably for a long time.

  The light-emitting diode blinking drive circuit 2 ′ shown in FIG. 5 and the light-emitting diode blinking drive circuit 2 of this embodiment, which are actually the prior arts, have the current consumption in the drive circuit excluding the current supplied to the light-emitting diode 20. When the ratio was examined, the result was about 20: 1.

  In this embodiment, the light-emitting diode blinking drive circuit 2 is used for the crime prevention device B. However, the present invention is not limited to this and can be used for other devices.

The perspective view of the security device using the blinking drive circuit of the light emitting diode of the Example of this invention. The figure of the blinking drive circuit of the said light emitting diode. The perspective view which shows the state which mounted | wore the aluminum sash window with the said security device. The top view which shows the state which mounted | wore the aluminum sash window with the said security device. FIG. 3 is a diagram of a prior art light emitting diode flashing drive circuit.

Explanation of symbols

B Security device 1 Resin case 10 Transparent case 11 Opaque case 2 Light-emitting diode blinking drive circuit 20 Light-emitting diode 21 Capacitor 22 Voltage detector 23 Monostable multivibrator 23a CMOS gate 29 Substrate 9 Aluminum sash window

Claims (1)

A light-emitting diode, a capacitor connected in parallel to the light-emitting diode, an open-drain output voltage detector for monitoring a voltage across the capacitor, and a single gate configured by a CMOS gate triggered by the output of the voltage detector. A stable multivibrator and a switching element for controlling the current supplied to the light emitting diode by the output of the monostable multivibrator. The lighting time of the light emitting diode is based on the output pulse width of the monostable multivibrator, and the turn-off time is a capacitor. A light-emitting diode flashing drive circuit, characterized in that the voltage between the terminals of each is defined by the time until the voltage of the voltage detector decreases to the detection voltage of the voltage detector.

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