JPH0392011A - Electric circuit - Google Patents

Abstract

PURPOSE: To reduce the effects of a spike by separating a 2nd capacitor from a resistor at the time of inputting a transient input pulse having short holding time and connecting 1st and 2nd capacitors to resistors at the time of inputting an input signal which has long holding time. CONSTITUTION: When voltage generated at the output terminal of an amplifier 1 based on a spike impressed to the positive polarity input terminal of the amplifier 1 is not a sufficient voltage for conducting a diode 15, a 2nd series circuit consisting of a capacitor 13 and a resistor 14 is separated from a 1st series circuit which consists of a capacitor 10 and a resistor 11 and a time constant is not unaffected. When an input is changed in a longer time, the diode 15 conducts, the resistor 14 is connected in parallel with the resistor 11, and the capacitor 10 is connected in parallel with the capacitor 13, so that the time constant of the circuit is changed. Consequently, a quick response to the normal change of input voltage can be generated, and the effect of the rise of a quick input voltage spike can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to electrical circuits of the type comprising an input circuit and an output circuit.

The present invention particularly relates to an electrical circuit which is capable of reducing the effects of electrical spikes.

BACKGROUND OF THE INVENTION Many analog electrical circuits need to be able to respond quickly to normal changes in input voltage while at the same time reducing the effects of short circuits, i.e. rapid input voltage spikes. . This is a particular problem in preamplifiers used in electrically noisy environments.

In pyrometry applications, the passage of incandescent particles across the field of view of the pyrometer causes a spike in the electrical sensing circuit.

Unless special care is taken to reduce the effects of these spikes, false results will be detected due to background radiation.

(Problem B to be Solved by the Invention) It is an object of the present invention to provide an electrical circuit that can be used to alleviate this problem.

SUMMARY OF THE INVENTION An example of the invention provides an electrical circuit of the type described above, wherein the output circuit is configured to reduce the slope of the output signal resulting from rapid changes in the transient input pulse. The output circuit includes a first capacitor and a resistor connected in series, and a second capacitor and a resistor connected in series, and a circuit element is connected between the series-connected circuits. the circuit element isolates the second capacitor and the resistor for short duration transient input pulses;
For long duration input signals, the first and second capacitors and the resistor are connected, and the time constant for the short duration pulse is determined by the first capacitor and the resistor;
The time constants for long duration input signals are set to the first and second time constants.
It is characterized by being determined by a combination of a capacitor and a resistor.

The circuit element is conductive when the voltage across it exceeds a predetermined value, and has a first connection point between the first capacitor and the resistor and a second connection point between the second capacitor and the resistor. can be connected between. Preferably, the circuit element is a diode, the anode and cathode of which can each be connected to a common point via a diode. The output circuit includes a second amplifier, and an input terminal of the amplifier is connected to the first capacitor and resistor and is connectable to the second capacitor and resistor via the circuit element. The input circuit may include a first amplifier, and an output terminal of the first amplifier may be connected to a first capacitor and a resistor and to a second capacitor and resistor via the circuit element. Preferably, the values of the first capacitor and resistor are selected such that when the second capacitor and resistor are separated, the rate of rise of the signal at the output terminal of the circuit is limited to approximately 10 mv/msec. The first and second capacitors and the resistor are arranged such that when the first and second capacitors and the resistor are connected, the rising speed of the signal at the output terminal of the circuit is limited to about 150 mv/msec. Preferably, a value of .

said input circuit comprises a pyrometer detector, and for a pulse equivalent to an incandescent particle passing through the field of view of said pyrometer detector;
The circuit element allows the capacitor and resistor to be separated.

(Example) The invention will now be described by way of example with reference to the drawings, in which the circuit takes the form of a preamplifier and comprises two integrated circuit amplifiers l and 2 connected in series. There is. The circuit has an input terminal 3 connected to the first amplifier l and an output terminal 4 connected to the output terminal of the second amplifier 2. A voltage is an input; for example, this voltage can be obtained from a pyrometer detector 30, such as a photodiode.

Capacitor 1 0 (0.47μF) and resistor 1 1
(3.3 MΩ) is connected between the O volt line and the 15 volt line, and the first amplifier l
The output terminal of the second amplifier 2 and the human power terminal of the second amplifier 2 are connected to the connection point l2 between this capacitor and the resistor.

Capacitor 1 3 (100 n F) and resistor 1 4
(1.2 MΩ) is connected in parallel with the first series circuit between the 0 volt line and the 15 volt line. Diode 15 has its anode connected to the second
It is connected to the connection point l6 between the capacitor 13 and the resistor 14, and its cathode is connected to the connection point 12 between the first capacitor 10 and the resistor 11.

The connection point 16 is connected to the output terminal of the amplifier l via a resistor l7 of 100 Ω and a series circuit of two diodes 18 and l9. Diodes 18 and 19 are connected for the same purpose. That is, the cathode of the diode l8 is connected to the resistor 17, and its anode is connected to the cathode of one diode.

Connect the anode of diode 19 to connection point 16. ，
A similar circuit from two diodes 21 and 22,
It is connected between the resistor 17 and the positive input terminal of the second amplifier 2. In this way, both the anode and cathode of diode 15 are connected to resistor 17 via diode pair l8 and 19 and diode pair 21 and 22, respectively.

In the absence of human power to the circuit, the zero human power voltage at each point in the circuit is as shown in FIG.

That is, the voltage at the junction of diodes 18 and 21 with resistor l7 is -1 volt;
The voltage at the connection point between diodes 21 and 22 and the voltage at the connection point between diodes 21 and 22 are both 10. 5 volts, and the voltage at the anode of diode 15 is 0 volts.

The operation of the circuit is described in relation to its response to input voltage spikes or similar short duration transient pulses. As a result of the incandescent particle passing through the viewing angle of the pyrometer detector 30, the duration of the spike shown in FIG. This spike causes a fast rising pulse as shown in FIG. 3 at the output terminal of amplifier l, ie between resistor 17 and diodes 18 and 2l.

The time constant of the first series circuit from the capacitor 10 and the resistor 11 is such that the signal supplied to the input terminal of the second amplifier 2 and the signal thereby produced at the fourth output terminal has a gentler slope. In addition, as shown in FIG. 4, it is 10 mv/msec.

During this short 1msec input cycle, diode 15 develops a slight forward voltage that increases from 0 to 140 mV at the end of this 1msec period. This voltage is not high enough to make the diode 15 conductive, and the capacitor 13 and resistor 14
The second series circuit consisting of is effectively isolated from the first series circuit and does not affect the time constant.

Alternatively, if the input to this circuit changes over a longer period of time, usually in relation to the change in the human voltage being amplified, i.e. if it changes so that an output voltage of +10 volts is produced, then this circuit operate with different time constants. During the first 4 msec of this new input, diode 15 is still ? It remains conductive, but then becomes conductive, and a resistor 14 is connected in parallel with the resistor 11, and a capacitor 13 is connected in parallel with the capacitor 10. This changes the time constant of this circuit, which causes 150
There is a steep slope of mV/ms e c, and the output voltage is 1
The time it takes to reach 0 volts is approximately 55Qmse.
It is lowered to c. If the second series circuit consisting of the capacitor 13 and resistor 14 is not provided, it will take about 1800 msec for the output voltage to reach 10 volts. Once this circuit is set to a new output voltage, the voltage across diode 15 drops to O and capacitor 13
and 14 are effectively separated again. This means that 10 mv/m detected by capacitor 10 and resistor 11
sec speed means that any sequentially received spikes cannot be filtered out. A circuit according to the invention allows the effects of transient input currents to be effectively reduced while still providing a relatively fast response to longer-existing signals.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing the electric circuit of the present invention, and FIGS. 2 to 4 are waveform diagrams showing the response of the electric circuit at various points. l...First amplifier 2...Second amplifier 10...First capacitor 13...Second capacitor l2...First connection point l6...Second connection point 10.11... 1st series circuit 13.14... 2nd series circuit

Claims (1)

[Claims] 1. An electric circuit comprising an input circuit and an output circuit,
The output circuit includes a first circuit connected to reduce the slope of the output signal resulting from rapid changes in the transient input pulse.
The output circuit includes a first capacitor (10) and a resistor (11) connected in series, and a second capacitor (13) and a resistor (14) connected in series. and a circuit element (
15), and this circuit element (15) allows a second capacitor (13) to be connected for short duration transient input pulses.
and a resistor (14), as well as first and second capacitors (10 and 1) for long duration input signals.
3) and resistors (11 and 14), the time constant for short duration pulses is determined by the first capacitor (10) and resistor (11), while the time constant for long duration input signals is determined by the first capacitor (10) and resistor (11). An electric circuit characterized in that the electric circuit is determined by a combination of first and second capacitors (10 and 13) and resistors (11 and 14). 2. The electric circuit according to claim 1, wherein the circuit element (15) is made conductive when the voltage across it exceeds a predetermined value. 3. The circuit element (15) is connected to the first capacitor (1
0) and the resistor (11) and a second connecting point (16) between the second capacitor (13) and the resistor (14). The electric circuit according to item 1 or 2. 4. The electric circuit according to any one of claims 1 to 3, wherein the circuit element is a diode (15). 5. Electrical circuit according to claim 4, characterized in that the anode and cathode of the diode (15) are connected to a common point via diodes (18, 19 and 21, 22), respectively. 6. The output circuit includes a second amplifier (2), the input terminal of the amplifier (2) is connected to the first capacitor (10) and the resistor (11), and the circuit element (15)
through the second capacitor (13) and the resistor (14)
The electric circuit according to any one of claims 1 to 5, characterized in that the electric circuit is connected to. 7. The input circuit comprises a first amplifier (1);
The output terminal of the amplifier (1) is connected to the first capacitor (10) and the resistor (11) via the circuit element (15), and also to the second capacitor (13) and the resistor (14). An electric circuit according to any one of claims 1 to 6. 8. A first capacitor ( 10) and the resistance (11) can be selected. 9. When the first and second capacitors (10 and 13) and the resistors (11 and 14) are connected, the rising speed of the signal at the output terminal of the circuit is about 150 m.
Any one of claims 1 to 8, characterized in that the values of the first and second capacitors (10 and 13) and the resistors (11 and 14) can be selected so as to be limited to v/msec. The electric circuit according to item 1. 10. The input circuit comprises a pyrometer detector (30), and for a pulse equivalent to an incandescent particle passing through the field of view of the pyrometer detector (30), the circuit element (15)
Electric circuit according to any one of claims 1 to 9, characterized in that the capacitor (13) and the resistor (14) are insulated.