JPS59119280A - Detecting circuit for breaking of wire - Google Patents

Abstract

PURPOSE:To detect the breaking of a cable immediately even in an operation state by comparing the detection voltage of a resistance for detection between the output terminal of a transmission part and a power source with a reference voltage. CONSTITUTION:The resistance value of the detecting resistance 4 is set to about 10kOMEGA although the resistance value of a terminating resistance Rphi is generally about 100OMEGA; transistors (TR) Q1 and Q2 and diodes D1 and D2, and D4 and D5 are provided with the identical characteristics respectively, and the resistances R1 and R4, and R2 and R5 have the same values. Further, the voltages VBE of the TRs Q1 and Q2 and the forward voltages of the D1-D3 are equalized to a value Vd. If the cable 3 is broken, the voltage at a point A rises almost to the value VCC and the base voltage of a Q3 is rised by VdXR2/(R1+R2) higher than the base voltage of the Q4; and the Q8 of an output circuit 7 turns on, and while an LED turns on, a logical output B is 0, so detecting the breaking of the cable easily.

Description

DETAILED DESCRIPTION OF THE INVENTION (4) Technical Field of the Invention The present invention relates to a circuit for detecting a break in a cable connecting a transmitter and a receiver.

03) Background of the technology Relatively many failures in electronic equipment are caused by disconnections or incorrect connections in cables. Therefore, it is necessary to confirm disconnections or incorrect connections in cables when testing electronic equipment or investigating faults. Although the amount of time required to confirm this is increasing significantly, it is extremely difficult to confirm this, especially when the part to be confirmed is located in an airtight area, such as a magnetic disk drive, and countermeasures are required. .

(C) Prior Art and Problems Conventional disconnection detection circuits are commonly provided for a plurality of cables and are displayed on a control panel or the like separate from the disconnection detection section.

Therefore, in order to identify a disconnected cable, it is necessary to directly check the presence or absence of a disconnection for each cable using a measuring device, which poses a problem in that it takes a lot of time. Furthermore, in the magnetic disk drives and the like, it is almost impossible to check whether there is a disconnection during operation.

(2) Object of the Invention An object of the present invention is to provide a disconnection detection circuit that can immediately identify a cable disconnection even in an operating state.

(G) Structure of the Invention The disconnection detection circuit according to the present invention is a circuit for detecting disconnection of a cable connecting a transmitting section and a receiving section, and is a circuit provided between an output end of the transmitting section and a power source. a disconnection detection circuit that detects a disconnection of the cable by comparing a detection voltage obtained by the detection resistor with a reference voltage; and a disconnection detection circuit that displays a disconnection detection signal generated by the disconnection detection circuit by emitting light. The present invention includes one output circuit and a second output circuit that outputs the disconnection detection signal as a logic signal.

(G) Embodiment of the Invention FIG. 1 shows a first embodiment of the invention, in which a cable driver 1 using a TTL logic circuit is used as a transmitting section, the cable driver 1 and a receiving section 2 are connected, and a terminating resistor RO is provided. This is a WrM detection circuit for cable 3. Reference numeral 4 indicates a detection resistor provided between the output end A of the cable driver 1 and the power supply VCC, and 5 and 6 detect a disconnection of the cable 3 by comparing the detection voltage obtained by the detection resistor 4 with a reference voltage. A disconnection detection circuit 5 converts the level of the detection voltage obtained by the detection resistor 4 using a transistor o1, a diode DI, a resistor R1, a diode D2, and a resistor R2, and converts the reference voltage obtained by a diode D3 and a resistor R3. A level converter that converts levels using transistor Q2, diode D4, resistor R4, diode D5, and resistor R5, 6 is differential amplification transistors Q3 and Q4, load resistor R6, constant current transistors Q5, Q6, Q7, and resistor R7. , R8 and R9, and a comparator for comparing the detected voltage obtained through the level converter 5 with a reference voltage; 7 is a level converting diode D6;
and D7, a resistor RIO for discharging accumulated charge, a transistor Q8 for driving a light emitting diode, a light emitting diode LED, a pull-up resistor R11, and a resistor R12 for current limiting. A first output circuit that displays by emitting light from a diode LED, 8 is a transistor Q9, QIO, Qll, and Q12.
and 013, diode D8, resistor R13, R14, and R1
A second output circuit is a TTL AND circuit consisting of 5 and 5, and outputs a disconnection detection signal obtained when the collector voltage i of the transistor Q8 of the first output circuit 7 becomes a low level as a logic signal from the transistor Q13. It is.

In the above configuration, the resistance value of the termination resistor RO is generally about 1000, but in contrast, the resistance value of the detection resistor 4 is set to about 10Ω, and the resistance value of the detection resistor 4 is set to about 10Ω.
The diodes D1, D2, D4, and D5 have the same characteristics, and the resistors R1 and R4 and the resistors R2 and R5 have the same resistance value.

Furthermore, the voltages between the bases and emitters of transistors Q1 and Q2 and the forward voltages of diodes DI-02 and D3 are set to the same value, which is assumed to be Vd.

When a break occurs in the cable 3, the voltage at the output terminal A of the cable driver 1 rises to a value close to the power supply voltage Vcc, and the base potential of the transistor Q3 of the comparator 6 becomes Vd XR2/ compared to the base potential of the transistor Q4. (R1+R2
), the transistor Q4 remains nearly off, and the transistor Q8 of the first output circuit 7 is turned on via the load resistor R6, causing the light emitting diode LED to emit light.

Furthermore, when the light emitting diode LED emits light, the collector voltage of the transistor Q8 becomes a low level, and the transistor Q13 of the second output 1 channel 8 is turned on, and the logic output 10 is turned on.
” occurs.

Under normal conditions, the voltage between the base and emitter of the output transistor QO of cable driver l is Vbe.
Then, the maximum value of the base voltage of the transistor Q1 of the level converter 5 is (Vcc-2Vbe), and Vb
The value of e is the above-mentioned Vd.

If it is equal to the value, the transistor Q4 of the comparator 6 will be lower by va The light emitting diode LED of circuit 7 does not emit light. Also, the transistor Q13 of the second output circuit 8 is cut off and generates a logic output "1#".

FIG. 2 shows a second embodiment of the present invention, in which an ECL logic circuit (
This is a disconnection detection circuit for two cables 23A and 23B, which connect a transmitting section 21 and a receiving section 22 using an emitter force (noble logic control) and respectively have terminating resistors RA and RB. 24A is a detection resistor provided between the output terminal A of the transmitting section 21 and the power supply Vcc, 24B is a detection resistor provided between the output terminal B of the transmitting section 21 and the power supply Vcc, 2
5 and 26 are @ wire detection circuits that detect disconnection of the cable 23A or 23B by comparing the detection voltage obtained by the detection resistor 24A or 24B with the reference voltage, and 25 is the @ line detection circuit obtained by the detection resistor 24A or 24B. The detected voltage is level-converted by transistors Q21 and Q22, diode D21, and resistor R21, and also by diode D22 and dividing resistors R23 and R2.
4 and the bias resistor R25, the reference voltage obtained by the transistor Q23, the diode D23, and the resistor R22
a level converter 26 for converting the level by differential amplification transistors Q24 and Q25 and a current source resistor R26; a comparator 27 for comparing the detected voltage obtained via the level converter 25 with a reference voltage; are clamping resistors R27 and R28, transistor Q26, and current source resistor R
A first output circuit includes 29, a transistor Q27, and a light emitting diode LED, and displays a disconnection detection signal obtained by the collector of the transistor Q24 of the comparator 26 by light emission from the light emitting diode LED; 28 is an output voltage determining resistor R30 and R31; , a transistor Q28, and a logic output emitter follower transistor Q29, the second output circuit outputs a disconnection detection signal obtained from the collector of the transistor Q25 of the comparator 26 as a logic signal from the emitter follower transistor Q29.

In the above configuration, the terminating resistor RA is 1! :R
The resistance value of B is generally about 1000, whereas the resistance value of the detection resistors 24A and 24B is IOKΩ, and the transistors Q21 and Q that constitute the level converter 25 are
22 and Q23 and diodes D21 and D23 have the same characteristics, and resistors R21 and R22 and resistors R23 and R24 have the same resistance value.

Further, the voltages between the bases and emitters of the transistors Q21, Q22, and Q23 and the forward direction of the diodes D21, D22, and D23 are set to the same value, and this is set as vd.

When a break occurs in the cable 23A or 23B, the voltage at the output terminal A or B of the transmitter 21 increases to a value close to VCC, and the base potential of the transistor Q24 of the comparator 26 becomes Vd higher than the base potential of the transistor Q25. /2
becomes a high potential, transistor Q24 turns on, transistor Q25 turns off, and the base potential of transistor Q27 of the second output circuit 27 decreases, transistor Q27 turns on, causing the light emitting diode LED to emit light. do.

Also, since the transistor Q25 of the comparator 26 is in an off state, the logic signal "1'" is output to the output C of the second output circuit 28.
occurs.

In a normal state, the Q of the transistor in the transmitter 21 is
The voltage between the base and emitter of OA/QOB is Vbe
Then, the maximum value of the input voltage of the level converter 25, that is, the base voltage of transistors Q21 and Q22 is (V
cc-Vbe), and if the Vbe0 value is equal to the value of ■d, then one input of the comparator 26, that is, Q
The base potential of Q24 is lower by Vd/2 than the base potential of the other input, ie, Q25. That is, this is opposite to the case where the cable 23A or 23B is broken, and the light emitting diode LED of the first output circuit 27 does not emit light. Further, the second output circuit 28 has a logic output '0'.
occurs.

Although the second embodiment shows an example of balanced transmission,
In the case of unbalanced transmission, the detection resistor 24 is
A and the transistor Q21 or the detection resistor 24B and the transistor Q22 may be removed.

The above-mentioned first embodiment (Fig. 1) and second embodiment (Fig. 2)
Figure 1) shows a cable disconnection detection circuit for one channel, and displays a light emitting diode (LED) and outputs a logic signal for each channel.

Alternatively, one set of the first detection circuit and the second detection circuit can be provided for each disconnection detection circuit for a plurality of channels, for example, four channels, and packaged as an integrated circuit.

As described in detail, according to the present invention, cable breakage is output not only by a logic signal but also by a light emitting diode, so that, for example, in a magnetic disk device, etc., it can be detected even during operation. wire breakage can also be immediately identified.

[Brief explanation of drawings]

Claims (1)

[Claims] A circuit for detecting a disconnection of a cable connecting a transmitter and a receiver, the circuit having a detection resistor provided between the output end of the transmitter and a power supply, and a detection voltage obtained by the detection resistor as a reference. a disconnection detection circuit that detects a disconnection of the cable by comparing it with a voltage; a first output circuit that displays a disconnection detection signal generated by the disconnection detection circuit by emitting light; and outputs the # line detection signal as a logic signal. A disconnection detection circuit comprising: a second output circuit for detecting a disconnection;