JPS59160772A - Line abnormality detector - Google Patents

Abstract

PURPOSE:To correct change of power source voltage and enable stable abnormality detection by giving reference voltage to the first and second transistors (TRs) controlled by voltage that changes according to the state of a line, etc. from a common voltage dividing circuit. CONSTITUTION:When input resistance R is normal, a TR 11 becomes off state and TRs 12, 13 become off, and output is not generated in an output terminal C. When input resistance R becomes short-circuited state, a voltage of point A becomes 12V. The TR 11 becomes on and TRs 12, 13 become on, and output is generated in the output terminal C through a gate IC 14. When input resistance R is infinity (open state), if R2<<(R1+R3) the TR 11 becomes off and an emitter voltage of the TR 12 becoms about 8V. Because (R1+R2) R3, a base voltage of the TR 12 becomes about 6V. TRs 12, 13 become on and output is generated in the output terminal C. As reference voltage changes in the same rate when power source voltage changes, stable detection can be made.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a device for detecting line abnormalities in monitoring devices for various types of equipment.

1. Structure of a conventional example and its problems A conventional device of this kind is shown in FIG. This device has terminal A
, B, the state of the transistors TR, , TR2 is determined by the change in the input resistance R of the line between the lines, etc.
Depending on the state of 2, the transistor TR3 operates and the output generated at the terminal C changes. For example, when the input resistance R is normal (approximately 4000), the voltage at point A is approximately 4V when R=i=2R1. However, R2>>R1+ Ra>
>R1. Further, when the Zener voltage of the Zener diode z1 is 6V, the transistor x is in the OFF state, and when R4=2R5, the transistor TR2 is turned on and TR5 is turned off, so that no output is generated at the output terminal C.

Next, when the input resistance R becomes abnormal (short-circuited), if the Zener voltage of the voltage u12 at point A vs. the Zener diode Z is 5''I, R2: R3, the base voltage of the transistor TR1 will be about 3V, This transistor TR1 is ONl, transistor TR2 is OFF
It is. Note that when R6-1-R and six R8 are set, the transistor TR3 is turned on and an output is generated at the output terminal C via IC1. Also, input resistance R is 0 (open state)
In this case, an output is generated at the output terminal C via the P-gate IC, in which the transistor TR is turned on due to the voltage division ratio of the resistors R6, R7, and RB.

However, in such a circuit, when sensing the input state, the operating voltage of the transistor TR is determined by the voltage division ratio of the Zener diode Z1 and the resistors R2 and R5, so it is easily affected by fluctuations in the power supply voltage, and the input resistance The problem was that the sensing range was wide, making it difficult to distinguish between normal and abnormal conditions. For example, if the input resistance is R and R5, the power supply voltage (vl
) is 1ov, the base voltage of transistor TR1 is Ov, and this transistor TR1 is OFF.
However, when the power supply voltage becomes 13V, the base voltage becomes approximately 0.8V, and the transistor TR may be turned on, and an abnormal output is output even in a normal input state. Further, there is a problem that the Zener diode Z1 is susceptible to variations in characteristics and temperature changes.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a detection device that can eliminate the above-mentioned conventional drawbacks and accurately detect line abnormalities.

Structure of the Invention The inventive line abnormality detection device has the following features: 1. A means for controlling the first transistor by a voltage that changes depending on the state of a common resistive voltage divider circuit, a line, etc. that applies a reference voltage to the second transistor is provided, and the second transistor is controlled by the first transistor. This is used to determine the condition of the line, etc.

Explanation of an actual elliptical example In FIG. 2, 1 to 7 are resistors for setting the operating points of transistors 11 and 12, 8 is a compensation resistor for transistor 11, 9 and 1o are resistors for setting the operation of transistor 13, and 14
is an IC for matching logic.

18 is a delay capacitor. B [input resistance terminal, c, ni output terminal.

Next, the operation of this embodiment will be explained. Note that resistance 1-I-1
Each resistance value of 0 is R1, R2...R,. shall be. Now, when the input resistance R is normal (approximately 400Ω), the voltage at point A is approximately 4V, assuming that R is 2R. At this time 1
, the emitter voltage of the transistor 11 has a voltage division ratio of resistance 4° and 5.6, and if R4 is R5 and R6, it is about 4V. Therefore, the transistor 11[, is in the OFF state. However, it is assumed that resistors 1 and 3 have sufficiently high resistance. Next R1
If R3 is set, the base voltage of transistor 12 is approximately 8V.
The emitter voltage of one transistor 12 is Rs in R4: R6
When the voltage becomes about 8V, the transistor 12 is turned off, and the transistor 13 is also turned off. Therefore, no output is generated at output terminal C. Next, when the input resistance R becomes abnormal (short circuit state), the voltage at point A becomes 12V, the transistor 11 is turned on, the transistor 12.13 is turned on, and the output terminal is passed through IC1. An output occurs at C. Next, if the input resistance is W (open state), R
2<< (R4+Rs), transistor 11
is OFF, and the emitter voltage of transistor 12 is approximately 8V. Also, since (R+ +R2)jR, the base voltage of the transistor 12 is approximately 6V. Therefore, transistors 12+13 (each of which is turned on) produce an output at the output terminal C via IC1.

As is clear from the above embodiment, transistors 11 and 12
The operating state of is determined by the voltage at point A for each input resistance and the change in the base voltage of the transistor 12, with the voltage divided by the resistor 4°5.6 against the power supply voltage set as the reference voltage, so the power supply voltage changes. In this case, the reference voltage will also change at the same rate, and the state will be in such a state that the power supply voltage change will be corrected.
Operation is more stable than conventional methods. Additionally, since no Zener diode is used, there is no variation in reference voltage, and temperature stability is good.

Effects of the Invention As is clear from the above description, the present invention has great practical value because stable abnormality detection can be performed regardless of changes in power supply voltage.

[Brief explanation of drawings]

FIG. 1 is a wiring diagram of a conventional line abnormality detection device, and FIG. 2 is a wiring diagram of a line abnormality detection device according to an embodiment of the present invention. 1 to 8 ''''Resistors, 11, 12°°-°Shizu transistors. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
figure

Claims (1)

[Claims] In a line abnormality detection device that detects a change in input resistance of a line or the like of various equipment monitoring devices and generates an abnormal signal, the first. A common resistive voltage divider circuit that provides a reference voltage to the second transistor, and a voltage that changes depending on the state of the line, etc.
A line abnormality detecting device comprising means for controlling a transistor, the first transistor controlling the second transistor to determine the state of the line, etc.