JPS59139493A - Analog output type smoke detection circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Technical Field] This invention relates to an analog output type smoke detection circuit used in an analog output type scattering type smoke detector, etc. Background Art] Conventional analog output type smoke detection circuit The smoke detection output was maintained by biasing the gate of the FET (?h, field effect transistor) used for peak hold as a double source to a negative voltage. However, in this configuration, positive and negative power supplies are required, and the ground line cannot be shared between the power input and analog output.
The composition of one river route is extremely complicated.

10,000, f'1 with a single power supply to simplify the circuit configuration.
If you try to make l-vJ, P-chan will not be able to do it/＼
It is possible to use an analog output type FET or an analog output circuit formed by combining these elements into an integrated circuit, but these devices have drawbacks such as difficulty in obtaining the elements and high cost.

[Purpose of the invention]

An object of the present invention is to provide an analog output type smoke detection circuit that can perform intermittent peak hold of the light reception output using a simple circuit structure 63ET using easily available and inexpensive elements.

[Disclosure of the invention]

The analog output smoke detection circuit of the present invention includes a pulse oscillator that periodically generates pulses, a light emitting element that lights up in response to the output of the pulse oscillator, and light emitted from the light emitting element. a light-receiving element that receives light; a light-receiving amplifier that amplifies the output of the light-receiving element; and an output pulse from the pulse oscillation unit that quickly charges a charging/discharging capacitor and slowly discharges the charging/discharging capacitor during a pulse pause period. a charging/discharging section that generates a peak-hold capacitor that is charged by the output of the light-receiving amplifier section, and a peak-hold capacitor that is inserted in series between the front-distribution light-receiving amplifier section and the peak-hold capacitor to generate the output pulse of the pulse oscillating section. The present invention is characterized in that it is configured to include a symmetrical FET which is forward biased via the charging/discharging capacitor and reverse biased by the voltage of the charging/discharging capacitor during the pulse pause period.

With this configuration, it is possible to perform intermittent peak hold of the received light output using a single power supply and using a cheap and easily available dissension type t;Er.

An analog smoke detection circuit according to an embodiment of the present invention will be explained with reference to FIGS. 1 and 2. In FIG. 1, TIN,
DIN is a power input terminal to which a DC voltage of 5 to 24 V is applied. 1 is added to IM, # input terminal 5-2
A constant voltage section that stabilizes the 1-page current voltage of 4V, a bipolar transistor Q1. Resistor R, Zener diode Z [
) and a capacitor C1, and outputs a constant voltage of 3 to 12V. 2 is a pulse oscillation section that oscillates pulses at a constant cycle when pressure is applied to the output cuff of the constant voltage section 1, and includes bipolar transistors 7r to Tr3 and resistors R2 to R9.
, diode D and capacitors C2 and C3, the pulse period is 100 to 200, and the pulse width is 100.
A light-emitting diode (LEI) is periodically lit intermittently with a large current of about IA by outputting a pulse of light. SPD Vi,
A silicon photodiode whose optical axis is arranged in a direction other than a straight line (for example, at 90 degrees) with respect to the light emitting diode LE+ receives scattered light due to the smoke of light from the light emitting diode LED. The light receiving amplification section amplifies and converts the light receiving current output of the three silicon photodiodes SPD into voltage, and includes bipolar transistors 'l''r, ~Tr, , resistors R, Lo -R1.
, , and capacitors C4 to C6. 4ke,
A charging/discharging section synchronized with the L oscillation pulses, which is rapidly charged by the output pulse of the pulse oscillation section 2 and slowly discharged during the pulse rest period, includes a capacitor C7 and a discharging resistor R1B.

Charging resistor R work9. It consists of a resistor R20 and a diode D2. Reference numeral 5 designates a peak hold unit for peak-holding the output of the light receiving amplifying unit 3, which is inserted in series between a capacitor C8 charged by the output of the light receiving amplifying unit 3, and the output end of the light receiving amplifying unit 3 and the capacitor C8. When the charge/discharge unit 4 is charged, the FkT Tr8 turns on and responds to the output convenience of the light receiving amplification unit 3. When the charging/discharging section 4 is discharging, the N-channel junction QFE'rTr8 is turned off and the voltage of the capacitor C8 changes.
8 retains the state it was in 100 years ago. 6
The impedance conversion section converts the impedance voltage into a low impedance voltage.
It is composed of a source follower circuit consisting of an N-type non-junction type FET Tr9 and a resistor R21.
Reference numeral 7 denotes an arithmetic unit which converts the output of the impedance converter 6 into a necessary voltage and changes the 0 point by f, and is composed of an operational amplifier OP and resistors 1<22 to R25.

TOUT and Tout-14 analog output terminals.

Next, the operation of this analog output smoke increase detection circuit will be explained with reference to FIG. 2 IAI to +El.

K source input terminal 1,000 TIN, between 'r'IN': 5 to 24
When a current voltage of V is applied, the constant voltage section 1 generates VJ and outputs a stable constant voltage of 3 to 12V. The output of the constant voltage section 2 activates the pulse@wall section 2, which periodically oscillates pulses, causing the light-emitting diode LED 171m Fig. 2 (A
A pulse current of approximately IA with a pulse period of 100 to 200 m5ec and a pulse width of 100 μm as shown in FIG.

The light from the light-emitting diode LED is received by a silicon photodiode SPυ, and the light receiving amplification unit (3) is shown in Figure 2 (
As shown in Bl, when the light emitting diode LED is turned on and there is no smoke, it outputs a voltage of, for example, somv, and as the smoke concentration increases, it outputs a voltage of about 100mV, 15
It outputs a voltage that increases sequentially from 0 mV to 200 mV. Note that the minute waves that exist during the light-off period (pulse rest period) of the light emitting diode (LEI) are due to noise.

゛ On the other hand, for example, 8V output from the pulse oscillating section 2
The pulse of capacitor C7, diode D2 and charging resistor +<, g7? - quickly charges the capacitor C7 through the pulse rest period, and slowly discharges the capacitor C7 through the discharge resistor R8 during the pulse rest period. The resistance value of the resistor R9 is approximately several Ω, and the capacitor C7 is fully charged in a short period of time between the 100 μ% pulse width, and when the charging is completed and the pulse becomes Ov (at the beginning of the buffless rest period). capacitor C7
(e.g. -8V) reverse biases the gate of the N-thylene non-junction type FET Tr8 as shown in FIG. 2, 1cI.
Tr8 is put into a pinch-off state, and the light receiving intensifier unit 3 and the capacitor C8 are disconnected from each other.

The resistance value of resistor R18 is several MΩ, and the capacitor 0.7 is 10
Slowly discharge to, for example, about -4V in a cycle period of 0 to 2QQm, and connect the N-channel junction g FETTr.
8 remains in the pinch-off state during this period.

When an 8V pulse is generated again from the pulse oscillation circuit 2,
The voltage at the gate of the N-channel junction Q FET TrB instantaneously rises to +4V as shown in Figure 2 tcI, resulting in a forward bias state, and the N-channel junction type FET TrB becomes an on-state section, which connects the light receiving and amplifying section 3. The capacitor C8 becomes conductive, and the capacitor CB is charged with the output of the light receiving amplification section 3.

In this way, the charge/discharge unit 4 periodically turns on and off the N-channel junction FET Tr8, so that
The voltage of capacitor C8 is @2 as shown in Figure 2 1cI.
(The peak of the output voltage of the light receiving and amplifying section 3 of Bl is maintained.

The voltage of this capacitor C8 is applied to the calculation unit 7 via the impedance conversion unit 6, and from the calculation unit 7, as shown in FIG. Voltage according to 1. OV, 1.5V, 2.
It will be output as OV.

Note that the calculation unit 7 of this embodiment sets the voltage output from the light receiving amplification unit to, for example, 70 mV as a threshold;
, the output is set to 1-tov in the following cases, and the amplification degree is 10 times higher if it is further north.

In this way, in this embodiment, the capacitor C7 of the charging/discharging section 4 is rapidly charged by the output pulse of the pulse oscillating section 2 that causes the light emitting diode (LEI) to be lit intermittently, and the capacitor C7 of the charging/discharging section 4 is charged during the pulse rest period. When the charging/discharging section 4'' is charging, a forward bias is applied to the N-channel junction type FET TTB through the capacitor C7 due to the output voltage of the pulse oscillating section 2, and when the charging/discharging section 4 is discharging, the capacitor C7 is Since reverse bias is applied to the N-channel junction type FET Tr8 by the voltage of It is possible to hold the peak of the received light output.Also, the impedance conversion section 6 can also hold the peak of the received light output.
Since this circuit is implemented using a channelless registration type FET Trg, this circuit can also be realized at low cost.

[Young fruit of invention]

The analog output type smoke detection circuit of the present invention is capable of peak-holding the light receiving output that occurs intermittently with a simple circuit configuration using a single power supply using a junction type FET that is easy to handle and inexpensive.

[Brief explanation of drawings]

@Figure 1 is a circuit diagram of an embodiment of this invention, Figure 2 +Al~
tEl is a waveform diagram of each part.

Claims (1)

[Claims] A pulse oscillation section that periodically generates pulses, a light emitting element that lights up in response to the output pulse of this pulse oscillation section, a light receiving element that receives light emitted from this light emitting element, and amplifying the output of this light receiving element. a charging/discharging unit that rapidly charges a charging/discharging capacitor with the output pulse of the pulse oscillation unit and slowly discharging the charging/discharging capacitor during a pulse pause period; and an output of the light receiving/amplifying unit. A peak hold capacitor charged by a peak hold capacitor is inserted in series between the light reception amplification section and the peak hold capacitor, and is forward biased by the output pulse of the pulse oscillation section via the charge/discharge capacitor. and a junction field effect transistor that is reverse biased by the voltage of the charging/discharging capacitor during the pulse pause period.