JPH0143757Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an electronic buzzer in which the buzzer notifies the user for a certain period of time when the power is turned off.

Conventionally, there has been a need in various fields for a power outage alarm, a warning buzzer to notify when the power of a device is accidentally turned off, or a notification buzzer after the switch is turned off, and various types of buzzers have been proposed accordingly. has been done. However, all of the conventional devices are relatively large in size, have complicated circuit configurations, and are expensive.

For example, in a notification buzzer that notifies the end of a timer attached to a household electrical appliance, the movable contact piece of the main switch that turns the load on and off is in sliding contact with the outer periphery of a cam that rotates at a constant speed.
A concave groove is formed on the outer periphery of the cam, and when the movable contact piece falls into the concave groove, the main switch is turned off. The movable contact piece for the buzzer switch that slides on the outer circumference of the cam contacts the movable contact piece of the main switch to turn on the buzzer switch, and after a certain period of time, the movable contact piece for the buzzer switch is inserted into the groove formed in the second cam. It has been proposed to switch off the buzzer by dropping the contact piece. However, with this type of notification buzzer, if the timer is set for a long time, such as 12 hours, for example, if the timer is set at 270 degrees and the timer is set for 12 hours, one minute is 0.375 degrees, and there are 10 ~
It is extremely difficult to create a short buzzer time period such as 20 seconds, resulting in an extremely long buzzer time.

The present invention eliminates the above-mentioned drawbacks of the conventional technology, and provides an electronic buzzer that uses a simple electronic circuit to make an alarm for a predetermined period of time after the power is turned off.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is an electrical circuit diagram showing a first embodiment of the present invention. E is an AC power supply, and a voltage drop resistor R
1. A DC power supply circuit consisting of a rectifying diode D1 and a smoothing capacitor C1 is connected in series with a switch SW1 for turning on and off the power, and a backflow prevention diode D2 and a power supply capacitor C2 are connected. series circuit, and resistance R
Time constant circuits each comprising a capacitor C3 and a capacitor C3 are connected to the DC power supply circuit. TR1 is the first
The time constant circuit switching transistor constitutes the switching circuit, the base is connected to the anode side of the diode D1 via the bias resistor R2, and the collector is connected to the diode D3 at the connection point with the resistor R3 and capacitor C3 of the time constant circuit. The emitter is connected to the negative side of the power supply. TR2 and TR3 are transistors that turn on and off according to the time constants of the time constant circuits R3 and C3, and TR2 has its base connected to a voltage dividing circuit of resistors R4 and R5, and its emitter connected to the time constant circuits R3 and C3. The collector is connected to the connection point of the transistor TR3, and the collector is connected to the base of the transistor TR3. The collector of the transistor TR3 is connected to the base of a transistor TR4, which will be described later, and the emitter is grounded to the negative side of the power supply. Also, transistor
The collector of TR3 and the collector of the transistor TR1 are connected via a diode D4.
TR4 is a transistor that keeps the voltage applied to the oscillation circuit (described later) constant, prevents changes in sound pressure, and turns the oscillation circuit on and off.A bias resistor R6 is connected to the base, and a Zener diode ZD is connected to the base for a voltage cutoff effect. are connected. Also,
The transistors TR2, TR3, and TR4 constitute a second switching circuit. TR5 is a transistor for piezoelectric buzzer oscillation, and resistor R6,
R7, R8, R9, capacitor C4 and diode D5 constitute an oscillation circuit, and piezoelectric buzzer BZ
It causes self-oscillation.

For example, when SW1 is turned on and a commercial AC power source is turned on, a DC power source is created by the voltage drop resistor R1, the rectifying diode D1, and the smoothing capacitor _C1 . is charged. Furthermore, a base current flows through the resistor R2 to the base of the transistor TR1, turning on the transistor TR1, but when the transistor TR1 turns on, the capacitor C3 is short-circuited through the diode D3, so the emitter voltage of the transistor TR2 is The transistor TR2 is in an off state. Further, since the transistor TR2 is off, no base current flows to the transistor TR3, and both the transistors TR3 are in the off state. Furthermore, since the transistor TR1 is turned on, the transistor TR4 becomes a diode D4.
The collector current of the transistor TR1 flows through the transistor TR1, and the base potential of the transistor TR4 is close to OV and is in an off state. Therefore, no voltage is applied to the oscillation circuit constituted by resistors R7, R8, R9, diode D5, capacitor C4, and transistor TR5, and piezoelectric buzzer BZ cannot oscillate.

Next, when the switch SW1 is turned off to stop the power supply, the current to the transistor TR1 is stopped and turned off, and the capacitor C2
The charging current charged to transistor TR4 and
It is discharged through TR5, thereby operating the oscillation circuit including the transistor TR5 and the like, causing the piezoelectric buzzer BZ to self-oscillate. Further, the power supply to the transistor TR1 is stopped and the piezoelectric buzzer BZ starts oscillating, and the capacitor C3 and the resistor R3
The voltage across capacitor C3 gradually rises with a time constant determined by , and when the voltage across capacitor C3 rises to a value determined by resistors R4 and R5, transistor TR2 is turned on, and at the same time, transistor TR2 is turned on. Output is transistor
Transistor TR3 flows to the base of TR3 and TR2
It turns on with this. As a result, the current discharged from the capacitor C2 flows through the resistor 6 to the collector of the transistor TR3, so that the base potential of the transistor TR4 decreases, turning off the transistor TR4, cutting off current to the oscillation circuit and Stops buzzer BZ oscillation. still,
The transistor TR4, together with the Zener diode ZD, keeps the voltage applied to the oscillation circuit of the piezoelectric buzzer BZ constant, thereby preventing the sound pressure of the piezoelectric buzzer BZ from changing.

Figure 2 shows the second embodiment, in which the logic IC
An electrical circuit diagram constructed using the following is shown. E is an AC power supply, and a DC power supply circuit consisting of a voltage drop resistor R11, a rectifying diode D6, and a smoothing capacitor C5 is turned on. switch to turn off
A series circuit with SW2 is connected, and a reverse current prevention diode D7 and a power supply capacitor C6 are connected.
A series circuit is connected in parallel to the DC circuit, and a time constant circuit consisting of a resistor R14 and a capacitor C7 is further connected in parallel. INT1 is an inverter constituting the first switching circuit, whose input side is connected to the power supply circuit via a resistor R12, and whose output side is connected via a diode D8 to the connection point between the resistor R14 and capacitor C7 of the time constant circuit. is connected to the inverter via resistor R15.
Connected to INT2. INT3 and INT4 are inverters that constitute an intermittent oscillation circuit, and resistor R1
6, R17 and capacitor C8 are connected.
INT5 and INT6 are inverters forming a continuous oscillation circuit, to which resistors R19 and R20 and a capacitor C9 are connected, and a piezoelectric buzzer BZ is connected to the output side of the inverter INT6. In addition, D9 connects the output side of the inverter INT2 and the inverter
Diode that connects the input side of INT3, D11
is a diode connected to the input side of the inverter INT3 and the output side of the inverter INT1,
Further, R18 and D10 are a resistor and a diode connected between the output side of the inverter INT4 and the inverter INT5.

For example, when switch SW2 is turned on and commercial AC power is turned on, a DC power is created by voltage drop resistor R11, rectifier diode D6, and smoothing capacitor C5, and then DC power is generated by voltage drop resistor R11, rectifier diode D6, and smoothing capacitor C5. is charged. In addition, the input side of the inverter INT1 has a high potential and becomes "HIGH", and the output side is inverted and becomes "LOW", so the current flowing through the resistor R14 is passed through the diode D8 to the inverter with a low potential.
The current flows to the output side of INT1, and the capacitor C7 is in a short-circuited state. Furthermore, the current on the input side of the inverter INT3 constituting the intermittent oscillation circuit is passed through the diode D11 to the inverter with a low potential.
The inverter flows into the output side of INT1.
The potential on the input side of INT3 becomes "LOW" and the oscillation circuit does not operate, so the piezoelectric buzzer BZ does not oscillate.

Next, when the switch SW2 is turned off to stop the power supply, the capacitor C, which is in a charging state,
Due to the discharge current of 6, the input side potential of the inverter INT3 forming the intermittent oscillation circuit becomes "HIGH", and each oscillation circuit operates and the piezoelectric buzzer BZ oscillates. Additionally, capacitor C7 and resistor R1
capacitor C7 with a time constant determined by 4
When the voltage of the capacitor C7 rises to a certain value, the input side potential of the inverter INT2 becomes "HIGH" and the output side becomes "LOW", so that the inverter forming the intermittent oscillation circuit
The input side potential of INT3 also goes to the "LOW" state, stopping the oscillation circuit and the piezoelectric buzzer BZ stopping sounding.

In the present embodiment, a DC power supply circuit is provided since both AC power sources are used, but this circuit is not necessary if a DC power supply such as a battery is used as the power source. In particular, the logic shown in the second embodiment
Electrical circuit diagrams using ICs consume very little current, so they can be operated using dry batteries.

As described above, the present invention consists of a power switch, a capacitor that is charged when the power is turned on, an oscillation circuit that uses the capacitor as a power source when the power is turned off, and drives a buzzer, and a CR that generates an output when a predetermined voltage is reached.
a time constant circuit; a first circuit that turns off the CR time constant circuit and turns off the oscillation circuit when the power is turned on;
and a second switching circuit that turns off the oscillation circuit according to the output of the CR time constant circuit.
Since the buzzer is made to sound for an arbitrary period of time determined by the time constant of There is an effect that can be done. In addition, since it is composed of electronic circuits, power consumption is extremely low, and in particular, C-
MOSIC can also be used, and it has the excellent effect of being able to operate for a long time with dry batteries.
In addition, the number of parts is extremely small and the size can be reduced, resulting in cost reduction.

[Brief explanation of the drawing]

FIG. 1 is an electrical circuit diagram showing an embodiment of the present invention;
FIG. 2 is an electrical circuit diagram showing another embodiment of the present invention. E...AC power supply, SW1, SW2...Power switch, R...Resistor, C...Capacitor, TR...
Transistor, INT...inverter, BZ...piezoelectric buzzer.

Claims (1)

[Scope of utility model registration request] a power switch; a capacitor that is charged when the power switch is held in the on state; and a first switching circuit that is turned on when the power switch is in the on state and turned off when the power switch is turned off. , when the first switching circuit is turned off, the capacitor is used as a power source,
The CR time constant circuit, which produces an output after a time determined by the CR time constant, and the first switching circuit are in the off state while they are on, and when they are turned off, they switch to the on state, and the first switching circuit is in the off state.
It consists of a second switching circuit that is turned off again by the output of the CR time constant circuit, and an oscillation circuit that uses a capacitor as a power source to drive the buzzer while the second switching circuit is on. The electronic buzzer is characterized in that the buzzer is made to sound only for a time determined by the time constant of the first CR.