JPS5838471Y2 - Kodenshikikemurikanchiki - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a photoelectric smoke detector, and particularly provides a photoelectric smoke detector that can prevent alarms in non-fire situations, that is, false alarms.

Conventionally, as shown in FIG. 1, there has been a photoelectric type in which smoke flowing into a measurement chamber changes the amount of light 3 from a light emitting element 1 to a light receiving element 2, and the change in light amount is detected by the light receiving element 2. Smoke detectors are known.

This device includes a light emitting circuit 5 having the light emitting element 1 and the oscillation circuit 4, a light receiving amplifying circuit 8 having the light receiving element 2, the amplifier 6 and the switching transistor 7, and A constant voltage power supply circuit 9 supplies a voltageized power supply current, and the amount of light 3 reaching the light receiving element 2 from the light emitting element 1, which is intermittently driven by the oscillation circuit 4, reaches a predetermined level due to the intrusion of smoke. When the transistor 7 is attenuated by the value 1, the amplifier 6 turns on the transistor 7, and this turns on the gate voltage of the SCR and turns on the SCR.
0a and 10b are short-circuited to issue an alarm.

By the way, in the above-mentioned device shown in FIG. 1, the current consumption of the light emitting circuit 5 is extremely large compared to other circuits, and this causes voltage fluctuations, which may result in the generation of false alarms.

As an example of this, if the ambient temperature is low and the constant voltage power supply circuit 9
When the hPE of the transistor 11 becomes \\, the charging of the capacitor 12 is delayed, and when the voltage is low, the voltage fluctuation described above becomes similar to driving the light receiving amplifier circuit 8 in pulses, and the characteristics of the differential amplifier change. The inventor of the present invention has confirmed that one of the transistors in the amplifier 6 operates first and outputs an output, causing the transistor 7 to turn on, causing a false alarm to be generated when the power is turned on.

The present invention eliminates the occurrence of the above-mentioned false alarms, and is configured so that the light emitting circuit 5 does not affect the power supply voltage supplied from the constant voltage power supply circuit 9 to the light receiving and amplifying circuit 8.

That is, the photoelectric smoke detector according to the present invention is a photoelectric smoke detector in which the amount of light reaching the light receiving element from the light emitting element is changed by smoke flowing into the measurement chamber, and the change in the amount of light is detected by the light receiving element. A light emitting circuit having the above light emitting element and an oscillation circuit for intermittently driving the light emitting element, and a light receiving amplification circuit having the above light receiving element are provided on the smoke detector; the light emitting circuit and the light receiving amplification circuit are provided. A smoothing capacitor for supplying a constant voltage power supply current to the light receiving amplification circuit is connected in parallel to the light receiving amplifying circuit.

An embodiment of the present invention will be described in detail below with reference to FIG.

In Fig. 2, buttons with the same reference numerals as in Fig. 1 indicate those with the same effect.

In FIG. 2, 13 is a diode and 14 is a capacitor, and the diode 13 and capacitor 14 are configured so that the power supply voltage of the light receiving and amplifying circuit 8 is not affected by fluctuations in the power supply voltage of the light emitting circuit 5. .

FIG. 3 shows another embodiment, and the same reference numerals as in FIG. 1 indicate the same effects.

In FIG. 3, reference numeral 15 denotes a transistor, and constant voltage power supply current is supplied from the constant voltage power supply circuit 9 to the light emitting circuit 5 and the light receiving and amplifying circuit 8 through the transistor 11 and the transistor 15, respectively. circuit 5
Also, fluctuations in the power supply voltage applied to the light receiving and amplifying circuit 8 are not affected by other circuits.

As described above, the present invention is constructed so that the power supply voltage supplied from the constant voltage power supply circuit to the light receiving and amplifying circuit is not influenced by the light emitting circuit, so that malfunctions when the power is turned on can be effectively prevented.

Although it is conceivable to provide separate constant voltage power supply circuits to prevent fluctuations in the power supply voltage of the light receiving and amplifying circuit 8 due to fluctuations in the power supply voltage of the light emitting circuit 5, this would increase the cost of the constant voltage power supply circuit. .

In this respect, the present invention can achieve the same effect without providing separate constant voltage power supply circuits.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a conventional example, FIG. 2 is a circuit diagram showing one embodiment of the present invention, and FIG. 3 is a circuit diagram showing another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Light emitting element, 2... Light receiving element, 5... Light emitting circuit, 8... Light receiving amplifier circuit, 9... Constant voltage power supply circuit,
13...Diode, 14...Capacitor, 15.
...Transistor.

Claims (1)

[Claims for Utility Model Registration] A photoelectric smoke detector in which the amount of light from the light emitting element to the light receiving element is changed by smoke flowing into the measurement chamber, and the change in the light amount is detected by the light receiving element, A light emitting circuit having the above light emitting element and an oscillation circuit for intermittently driving the light emitting element, and a light receiving amplifying circuit having the above light receiving element; and a smoothing capacitor for supplying a constant voltage power supply current to the light receiving amplification circuit is connected in parallel to the light receiving amplifying circuit.