JPS6035313Y2 - data transmission equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a data transmission device provided with a path for dissipating charges accumulated in stray capacitance generated in a connection line between a data signal applying element and a photocoupler.

An example of a conventional device of this type is shown in FIG.

When transmitting a signal from point A to point B, the grounding point GND
-A (!: If there is a potential difference between GND-8 and the common point is grounded, ground current will flow and signal transmission will be affected by noise. Therefore, use a photocoupler PC as an insulating element to connect GND-A and Each is individually grounded to GND-B.

The transistor TrA is used as a signal applying element, and when applying a pulse signal, a connection line LL is connected between the element and the photocoupler PC.
The stray capacitance Cs that occurs in this case becomes a problem.

For example, when TrA is in the off state without applying a signal, Cs
Induced charges are accumulated by the power supply VBA voltage for T and A operations.

At time T1 shown in FIG. 2, a pulse signal is applied and T
When rA is turned on, the discharge current from Cs flows through TrA in a superimposed manner with the current from power supply BA, which may exceed the allowable current of TrA and eventually destroy it.

This is because the vertical axis in FIG. 2 indicates the collector current of TrA, which has a value of (vBA/ON resistance of TrA) at time T1.

After that, in a steady state, the value becomes ①BA/R, where R is the resistance of the collector circuit.

SUMMARY OF THE INVENTION An object of the present invention is to improve the above-mentioned drawbacks and to provide a transmission device that has a simple configuration and can prevent damage to the signal applying element by forming a path for discharging the charges accumulated in the stray capacitance.

An embodiment of the present invention shown in FIG. 3 and below will be described.

FIG. 3 shows a first embodiment of the present invention in which a path for discharging charges is attached to a connecting line between a signal applying element and a photocoupler c, and in particular, a pair of shielded cables are connected to the connecting line. Use SLL.

A resistor RsL is connected between the shield covering and the ground GND-A.

Since the shield coating is one terminal of the stray capacitance Cs, the charged charge passes through the shield coating and is discharged to R3L.

In this case, in addition to the shielding sheath, a conductor other than the signal transmission conductor attached to the same cable can be used as the discharge path, and in place of the shielding sheath/resistor R8L, resistive conductive paint or the like can be applied to the cable. One end of the smeared surface may be grounded.

FIG. 4 shows a resistor R similar to that in FIG. 3 as a second embodiment of the present invention.
This shows the case where the SC is connected to the photocoupler PC side.

The operation is similar to that shown in FIG. FIG. 5 is an operation explanatory diagram corresponding to FIG. 2, and the collector current of the transistor TrA at time T2 is the value of (■BA/T, on-resistance Rs t of A), smaller than the case.

In other words, resistor R8L is adjusted so that this value is within the allowable value of the element.
Select the value of

In this way, according to the present invention, the path for discharging the charge charged in the stray capacitance is formed or the discharge current is suppressed by extremely simple means, so that even if the stray capacitance is charged by the operating power source of the signal applying element, Even if the signal applying element is used, the current passing through the signal applying element does not become excessive and the element is not destroyed, which has the effect of improving the reliability of the device.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of a conventional data transmission device, FIG. 2 is a diagram showing the time course of the transistor current in FIG. 1, and FIG.
The figure shows the first embodiment of the invention, FIG. 4 shows the second embodiment of the invention, and FIG. 5 shows the operation of FIGS. 3 and 4 in correspondence with FIG. 2. be. TrA...Transistor (signal application element), P
C: Photocoupler, LL: Connection line,
C1... Stray capacitance, GND-A, GND-B-
-----Ground, R, R8L. 'Rsc... Resistor, SLL... Shielded pair cable.

Claims (1)

[Claims for Utility Model Registration] 1. In a data transmission device that drives a photocoupler by a signal application element to which a data signal is applied and transmits the data to the next stage, the data transmission device is provided along with a connection line between the signal application element and the photocoupler, and the connection A data transmission device characterized in that a discharge path is provided to discharge charges accumulated in stray capacitance generated in a line. 2 The discharge path for discharging the charge stored in the stray capacitance is
The data transmission device according to claim 1, which is a shielding coating for shielding a connection line between a signal applying element and a photocoupler.