JPH01302180A - Disconnection detecting system - Google Patents

Abstract

PURPOSE:To detect even an instantaneous disconnection, by varying intensity of emission of an LED according to a binary signal to detect interception and variations in intensity of the emission of the LED from the output of a photo transistor. CONSTITUTION:When a disconnection occurs in transmission paths (a) and (b), an LED normally emitting light halts the emission with the disconnection. The continuity of a photo transistor of a photo coupler 4 is cut and a collector voltage value VA thereof rises to a power source voltage Vccz (>Vs) and an output of a comparator 12 moves to H detecting this condition. Thus, the disconnection is detected. In case of an instantaneous disconnection, an output of the comparator 12 goes to H momentarily. Thus, a circuit for holding this level is provided at the rear stage of the comparator 12 thereby facilitating the detection of even an instantaneous disconnection.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a disconnection detection system for electrically isolated transmission lines using photocouplers, and is particularly applicable to detecting instantaneous disconnections. The present invention relates to a disconnection detection system suitable for.

[Prior Art] FIG. 4 is a block diagram of a conventional disconnection detection system for a transmission line that is electrically isolated using a photocoupler. The transmitting section is provided with a pulse generator 101 that is a signal source, and a differential output driver 102 that receives a pulse signal from the pulse generator 101 and sends it to the receiving section via signals a and b. . The receiving section includes photocouplers 103.104 equipped with LEDs that emit light in response to a potential difference between signal lines a and b, and each photocoupler 103.1.
Resistors 105 and 106 with the same resistance value R that determine the threshold of 04, an exclusive Shibnor gate 109 that adopts exclusive Shibnor logic of the collector outputs of both photocouplers 103 and 104, and a high frequency output signal of the exclusive Shibnor gate 109. A filter 110 for removing components is provided, a signal output terminal 107 is connected to the collector of the photocoupler 103, and an alarm terminal 108 is connected to the collector of the photocoupler 103.
is connected to the output of filter 110.

Now, when a pulse signal as shown in FIG. 5 is outputted from the driver 102 to the signal line a, an inverted signal thereof is outputted to the signal line A. Transmission line (signal line a.

When b) is normal, the LEDs of the photocouplers 103 and 104 are turned on and off by the signals appearing on the signals 'NJAa and b, and a signal S having the same shape as the inverted signal of the signal appearing on the signal line a is output to the signal output terminal 107. The signal from the transmitter is detected as signal S by the receiver.

At this time, the collector of the photocoupler 104 outputs an inverted signal of the signal appearing at the signal output terminal 107, and the collector outputs of both photocouplers 103 and 104 are excluded.
A Shivnor logic is adopted at gate 109.

Therefore, the output signal of this gate device 09 becomes "L" level indicating that the transmission path is normal. However, the output signal of gate 109 itself has photocoupler 103.1.
Due to the difference in delay time of 0.04, an impulse signal is generated as shown in FIG. Therefore, in order to prevent the device from misrecognizing or malfunctioning due to this impulse signal, a signal from which the impulse signal has been removed by the filter 110 is output to the alarm terminal 108. When the transmission line is disconnected, the two signals input to the gate 109 are in phase and at the same level, and the output thereof, that is, the output of the filter 110 (output of the alarm terminal 107) becomes "H" level. This makes it possible to know if the transmission line is disconnected.

[Problem to be solved by the invention]

In the disconnection detection system according to the prior art described above, when the transmission line is instantaneously disconnected, the game HO9 detects this instantaneous disconnection and instantaneously sets its output to "H" level.
Outputs an impulse-like signal. However, since this impulse-like signal is removed by the filter 110,
A disconnection detection signal will not be output to the alarm terminal 107. In other words, the conventional wire breakage detection system has a problem in that it cannot detect instantaneous wire breaks. If the filter 110 is removed to solve this problem, the impulse signal caused by the difference in delay time occurring between the photocouplers 103 and 104 cannot be removed, and this impulse signal will be mistaken for a momentary disconnection.

An object of the present invention is to provide a disconnection detection system that can accurately detect instantaneous disconnections in transmission lines.

[Means to solve the problem]

The above purpose is to blink an LED of a photocoupler provided in a receiving unit using a binary signal sent from a transmitting unit, and to use the output of a phototransistor that changes according to the blinking to
In a system for detecting a value signal, a resistor is provided in the transmitting section to raise the L" level potential of the binary signal sent from the transmitting section to the receiving section above ground potential, and the LED of the photocoupler emits light in accordance with the binary signal. means for detecting the interruption of the light emission using the output of the phototransistor and detecting this as a disconnection, and means for detecting the transmitted binary signal based on the change in the output of the phototransistor according to the intensity of the light emission. This is achieved by providing it in the receiving section.

[Effect]

The potential indicating the "L" level of the binary signal is raised by the resistor provided in the transmitter. When this binary signal is sent to the receiving section through two transmission paths, and a photocoupler LED is connected between these two transmission paths at the receiving section, this LED has the following characteristics:
Of course, when the binary signal is at the “H” level, the binary signal is at the “L” level.
``Even when the LED is at the level, the current flows by the amount increased by the resistor.In other words, the LED does not blink according to the binary signal, but its light emission increases or decreases according to the binary signal.

Therefore, by detecting the interruption of the light emission of the LED and its intensity from the output of the phototransistor, it is possible to detect the disconnection and the transmitted binary signal.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

FIG. 1 is a configuration diagram of a disconnection detection system according to an embodiment of the present invention. The transmitter includes a pulse generator 1 as a signal source, a driver 2, and a resistor 9. The driver 2 is composed of a transistor and a resistor, for example, as shown in FIG. is inserted. Therefore, the signal output from the driver 2 to the signal line a is transmitted to this resistor 9.
The level of the signal is raised by the voltage drop, and the °L" level of the signal becomes higher than the ground potential G1 by the voltage drop.

The transmission line includes a signal line a connected to the output of the driver 2,
It consists of a signal line connected to the ground of the transmitter.

The receiving section includes a photocoupler 3 for signal reception, a photocoupler 4 dedicated to disconnection detection, a resistor 5 with a resistance value R1 that limits the current flowing to the phototransistor of the photocoupler 3, and a resistor 5 that limits the current flowing to the phototransistor of the photocoupler 4. It includes a resistor 6 with a resistance value R2 and a resistor 10 that limits the current flowing to the LED of each photocoupler 3.4. Comparator 1
1 compares the reference voltage value ■, and the collector voltage value v3 of the photocoupler 3, and outputs an ``H level signal'' when ≧V, and an ``L'' level signal when Vs<Vm, to the signal output terminal. 7. The comparator 12 compares the reference voltage value ■, and the collector voltage value vA of the photocoupler 4, and determines that ■, ≧
(2) Outputs an "L" level signal to the alarm output terminal 8 when 3, and an "H" level signal (alarm signal) when V<V. In addition, 13 is a reference voltage source, and by setting R2>R1 so that the reference voltage value V is an intermediate value of the change in ■, and a value smaller than the lowest level of ■^, Set.

As described above, due to the action of the resistor 9, the signal sent to the signal line a is raised by a predetermined voltage 2 with respect to the ground voltage G1 of the signal line 3, as shown in FIG.

As a result, if transmission lines a and b are normal, current always flows to the LED of photocoupler 3.4 in a fixed direction and emits light, and the strength of the light emission changes depending on the binary signal. It is in a state of being. Therefore, both couplers 3
, 4 are always in a conductive state.

The photocoupler 4 and the comparator 12 are connected to the transmission path a.

This is specially provided to detect the disconnection of the wire b. When the transmission lines a and b are disconnected, the LED that has always been emitting light stops emitting light at the time of the disconnection. As a result, photocoupler 4
The conduction of the phototransistor is cut off, and its collector voltage value vA rises to the power supply voltage ■ccχ (>Vs), and the comparator 12 detects this and sets its output to "H". Thereby, a disconnection is detected. In the case of a momentary disconnection, the output of the comparator 12 becomes "Hn" momentarily, and in the illustrated configuration becomes "Lo" the next moment.

However, by providing a circuit subsequent to the comparator 12 that holds "H" when the comparator 12 outputs "H", instantaneous disconnections can be easily detected.

On the other hand, the detection of the binary signal sent from the transmitter is performed by the photocoupler 3 and the comparator 11. In other words,
Collector potential v3 that changes according to the intensity of light emission of the LED
is performed by comparing it with a reference voltage V, and when the emission intensity is large, that is, v, <■, the comparator 11 outputs "L" to the signal terminal 7, and when ■, ≧V, "
This causes the signal terminal 7 to output an inverted signal of the binary signal from the transmitter.

In this embodiment, the reference voltage (2) used for the comparators 11 and 12 is the same, but it goes without saying that they may be different. Although the photocoupler 4 is provided separately, it is also possible to detect disconnection using the output of the photocoupler 3 without providing the photocoupler 4.

〔Effect of the invention〕

According to the present invention, it is possible to detect the normal state and the disconnection state of the transmission line as in the past, and also to detect instantaneous disconnections, so there is an effect that more reliable signal transmission can be performed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a disconnection detection system according to an embodiment of the present invention, FIG. 2 is a detailed configuration diagram of the driver shown in FIG. 1, and FIG. 3 is a diagram showing the operation of the disconnection detection system shown in FIG. The signal waveform diagram to be explained, Figure 4 is a configuration diagram of a conventional disconnection system,
FIG. 5 is a signal waveform diagram illustrating the operation of a conventional disconnection detection system. 1- Pulse generator, 2- Driver, 3-
Photocoupler for signal reception, 4 - Photocoupler for disconnection detection, 5, 6.9.10 - Resistor, 7 - Signal detection terminal, 8 -
Alarm output terminal, 11.12-・Comparator, a,
b...Signal line. Patent applicant Hitachi Seiko Co., Ltd. Agent Patent attorney Tadashi Akimoto 1 other person Figure 1 Figure 2 ``Icc 3!

Claims (1)

[Claims] 1. In a system in which an LED of a photocoupler provided in a receiving section is blinked in response to a binary signal sent from a transmitting section, and the binary signal is detected by the output of a phototransistor that changes according to the blinking, from the transmitting section. A resistor is provided in the transmitting section to raise the "L" level potential of the binary signal sent to the receiving section from the ground potential, and when the LED of the photocoupler is emitting light according to the binary signal, the light emission is blocked by a photocoupler. A disconnection characterized in that the receiver is provided with means for detecting this as a disconnection by detecting the output of the transistor, and means for detecting a binary signal transmitted by a change in the output of the phototransistor according to the intensity of the light emission. detection system.