JPH0445119B2 - - Google Patents

Description

[Detailed description of the invention] 〔Technical field〕 The present invention relates to improvements in hot wire detectors.

[Background technology]

Heat wire detectors are widely used to detect heat sources such as the human body, and include a pyroelectric element that detects the heat source as the sensor part, an amplifier circuit that amplifies the output signal from this pyroelectric element, and this amplifier circuit. The sensor is equipped with a window comparator that discriminates the signal, and switching means driven by the discrimination output of the window comparator, and is configured to supply a stabilized constant voltage power source to each circuit section of the detector. In order to improve reliability, such a hot wire type detector is configured to prohibit output when the power supply voltage drops or when the power is turned on. For example, FIG. 7 shows the basic configuration of a conventional hot wire type detector of this kind, in which the voltage monitoring section 12 monitors a drop in the power supply voltage supplied from the constant voltage circuit 11 to the sensor section 13. However, when the power supply voltage drops to a predetermined level, a prohibition signal is sent out to prohibit output. However, since the sensor section 13 of the heat ray detector handles weak signals, it responds sensitively to even slight voltage fluctuations. For this reason, in such voltage monitoring type hot wire detectors, output is often prohibited after the voltage supplied to the sensor unit 13 falls below the guaranteed operation level due to an operation delay, which may induce malfunction. It is the cause.

[Purpose of the invention]

The hot-wire type detector of the present invention was developed in view of the above-mentioned circumstances, and provides a highly reliable hot-wire type detector with a configuration that can inhibit output immediately before the power supply voltage drops to a guaranteed operation level. It is intended to.

[Disclosure of the invention]

The present invention proposed to achieve the above object,
A regulator circuit that constitutes a power supply circuit, a pyroelectric element that detects an object to be detected, an amplifier circuit that includes a gain control circuit and amplifies the output signal from the pyroelectric element to a predetermined level, and amplification from this amplifier circuit. The hot-wire type detector is equipped with a window comparator for discriminating signals and a switching means driven by the output of the window comparator, and is provided with a voltage discriminating circuit for detecting the voltage between the input and output of the regulator circuit. When it is determined that the voltage detected by the circuit has decreased to a level that guarantees the operation of the regulator circuit, the gain control circuit is activated to suppress the output of the amplifier circuit and prohibit driving of the switching means. It is characterized by what it did.

Example The invention will be explained below with reference to the accompanying drawings.

FIG. 1 is a diagram showing the basic configuration of the hot-wire type detector of the present invention. 1 is a regulator circuit that supplies stabilized power supply voltage to each part of the detector, and the input and output of this regulator circuit 1. A voltage discrimination circuit 2 is connected to the end. The voltage discrimination circuit 2 discriminates the voltage between the input and output of the regulator circuit 1, and this voltage Va-Vb is the operation guaranteed level of the regulator circuit 1 (the lowest level voltage at which the operation of the regulator circuit 1 is guaranteed). (the same applies hereafter), the gain control circuit 3 immediately activates the gain control circuit 3. The gain control circuit 3 controls the gain of the amplifier circuit 5 that amplifies the signal sent from the sensor section 4, and when activated, The output of the amplifier circuit 5 is forcibly reduced by suppressing the gain of the amplifier circuit 5 to approximately zero level. The window comparator 6 discriminates the output signal of the amplifier circuit 5, and when the sensor section 4 detects movement of a human body, it sets its output to "H" level and drives the switching means 7 to output a detection signal. When the gain control circuit 3 is activated and the output of the amplifier circuit 5 is reduced, the output becomes "L" level and the switching means 7 is not driven.

According to the hot wire type detector of the present invention, the power supply voltage of the sensor section 4 is determined by the input/output terminal voltage of the regulator circuit 1, so that the conventional method of monitoring the output voltage of the regulator circuit 1 is not required. Compared to this, output is not prohibited even after the operation guarantee level has already been lowered, and reliability can be significantly improved.

FIG. 2 shows a circuit configuration diagram of a more specific embodiment of the hot wire type detector of the present invention.

In the figure, parts corresponding to the configuration of each part shown in FIG. 1 are given the same reference numerals.

To explain the configuration of each circuit section along with its operation, a predetermined power supply voltage is rectified by a diode D1,
It is input to the regulator circuit 1. The input-output voltages Va, Vb of the regulator circuit 1 are guided to a voltage discrimination circuit 2 composed of a PNP transistor Q2, and the base-emitter voltage of the transistor Q2 is
Compared to VBE. Here, the regulator circuit 1 can be one with high operating accuracy, such as S81250HG, and in that case, the voltage Va between input and output
-Vb is the base-emitter voltage of transistor Q2
Operation is guaranteed if it is VBE or higher. Transistor Q2 turns ON when the voltage Vab between Va and Vb is higher than VBE, and turns OFF when Vab is lower than VBE.
becomes.

When the power is turned on, when the output becomes unstable, the capacitor C2 starts to be charged through the resistor R from a discharged state, and the transistor Q4 is turned on for a predetermined period of time (for example, about 15 to 20 seconds), so that the output of the amplifier circuit 5 Signals are prohibited. After that, when the unstable operation at power-on ends and Vab≧VBE becomes true, transistor Q2 turns on, transistor Q3 that constitutes gain control circuit 3 turns off, transistor Q4 also turns off, and amplifier circuit 5 output is acceptable. However, in such a stable state, if Vab<VBE,
Since transistor Q2 is turned off, transistor Q3 is turned on and discharges the charge accumulated in capacitor C2.

When transistor Q3 turns on, amplifier circuit 5
The gate voltage of the transistor (FET) Q4 connected to the inverting input terminal and the output terminal of the transistor increases, turning on the transistor Q4, suppressing the gain of the amplifier circuit 5 to approximately zero level, and inhibiting the output again.

The amplifier circuit 5 amplifies the output signal from the pyroelectric element 4, which is configured by forming an impedance conversion circuit using FETs, to a predetermined level and sends it to the window comparator 6. When a heat source is detected by the pyroelectric element 4, the filter capacitor C1 detects a frequency component (for example,
A signal of 0.1 Hz to 10 Hz) is taken out, inputted to the amplifier circuit 5, amplified to a predetermined level, and then inputted to the window comparator 6. Here, the window comparator 6 has a configuration that combines one operational amplifier, two diodes D2 and D3 with the same characteristics, and an external resistor, and a resistive voltage divider circuit is connected to the inverting and non-inverting input terminals of the operational amplifier. diodes D2 and D3 are connected between the inverting and non-inverting input terminals as shown in the figure. Therefore, when a predetermined "H" level output (higher level due to the voltage drop of diode D3) is sent from the amplifier circuit 5, the diode D3 becomes conductive, pulling the non-inverting input voltage to a high level, and the amplifier circuit When a predetermined "L" level output (a level lower than the voltage drop of diode D2) is sent from 5, diode D2 becomes conductive and pulls down the inverting input voltage.
In either case, the output is inverted to "H" level. When the window comparator 6 outputs the "H" level signal in this way, the transistor Q1 constituting the switching means 7 is turned on,
Outputs a detection signal. In the case of the embodiment, the output of the window comparator 6 generates a drive pulse for the transistor Q1 by a differentiating circuit using a capacitor C3, thereby turning on the transistor Q1.
It stipulates the time. During this ON time, the circuit including transistor Q1 and diode D4 is closed, and the voltage at terminals E1 and E2 drops from about 12V to about 4V. This charge is used to maintain the driving state of each circuit section. Note that the diode circuit 8 connected to the terminals E1 and E2 is provided to make the power supply voltage non-polar.

According to the above configuration, when the power supply voltage is turned on or when the power supply voltage drops to the level at which the operation of the regulator circuit 1 is guaranteed due to some reason, driving of the switching means 7 is immediately prohibited, so that the operation is not guaranteed. There is no risk of malfunction under certain conditions. In Figure 3, A, B in Figure 2,
Change in potential at point C and transistor Q
The operating status time charts of 2, Q3, and Q4 are shown below.

4 to 6 are other examples of the regulator circuit according to the present invention, and FIG. 4 shows that the input-output voltage that guarantees the operation of the regulator circuit 1 is the base of the transistor Q2 of the voltage discrimination circuit 2.・Example diagrams in which the discrimination level can be adjusted by the zener voltage VZD of the zener diode ZD when the emitter voltage is larger than VBE, FIGS.
Another example of the terminal type regulator is shown. In the figure, TR1 to TR4 are transistors, R1 to TR4 are transistors, and R1 to TR4 are transistors.
R3 is a resistor, C1 and C2 are capacitors, ZD1,
ZD2 indicates a Zener diode.

〔Effect of the invention〕

According to the hot wire type detector of the present invention, when the input/output voltage of the regulator circuit drops to a guaranteed operation level, the output is immediately inhibited, so the operation of the regulator circuit is better than that of the conventional voltage monitoring type. Since output can be inhibited under guaranteed conditions, there is no malfunction due to operation delay, and reliability is significantly improved.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the basic configuration of the hot wire type detector of the present invention, FIG. 2 is a circuit configuration diagram of a specific embodiment of the present invention, and FIG. 3 is a diagram showing the circuit configuration of a specific embodiment of the present invention. A time chart explaining the change in potential and the operation of transistors Q2 to Q3, Figures 4 to 6 are other examples of the regulator circuit, and Figure 7 is the basic configuration of a conventional voltage monitoring type hot wire detector. FIG. (Explanation of symbols), 1...Regulator circuit, 2
...Voltage discrimination circuit, 3...Gain control circuit, 4...Sensor section, 5...Amplification circuit, 6...
Window comparator, 7...Switching means.

Claims (1)

[Claims] 1. An amplifier circuit that includes a regulator circuit constituting a power supply circuit, a pyroelectric element that detects an object to be detected, and a gain control circuit that amplifies the output signal from the pyroelectric element to a predetermined level. , a hot wire type detector comprising a window comparator for determining the amplified signal from the amplification circuit, and a switching means driven by the output of the window comparator, the voltage for detecting the voltage between the input and output of the regulator circuit. A discrimination circuit is provided, and when the voltage detected by the discrimination circuit drops to a level that guarantees the operation of the regulator circuit, the gain control circuit is activated to suppress the output of the amplifier circuit and prohibit the driving of the switching means. A hot wire type detector characterized by having a configuration in which: