JPH0419867Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a signal isolating device for electrically insulating and coupling two electrical devices. For more details,
The present invention relates to a signal isolating device which insulates status signals, and which uses one pulse transformer to enable selection of the functions of both a status signal input circuit and a status signal output circuit. .

(Prior Art) Fig. 2 is a connection diagram of a conventional status signal input circuit, and Fig. 3 is a connection diagram of a conventional status signal output circuit, both of which are from Yokogawa Technical Report Vol. 1.25.
No.2 (1981). It is listed on page 22.

The input circuit shown in FIG. 2 reads the state of the non-voltage contact S1 or the voltage signal as a change in impedance via a pulse transformer PT whose center tap receives a clock signal, and is insulated from the field.

In the output circuit shown in Figure 3, the status signal to be output is isolated from the circuit side via a pulse transformer PT, and an open collector type transistor is used.
It is output by Q ₀ . Diode D ₀
is for circuit protection against reverse connection of external power supply.

(Problem to be solved by the invention) In a signal isolation circuit having such a configuration, in order to realize an input circuit and an output circuit, each circuit shown in Fig. 2 and Fig. 3 must be provided in advance. The problem was that two pulse transformers were required, making the configuration complicated.

The present invention was devised in view of these problems, and its purpose is to combine one pulse transformer and one pulse transformer.
The present invention aims to realize a signal isolating device with a simple configuration that uses two photocouplers and allows the functions of both the input circuit and the output circuit to be selected.

(Means for Solving the Problems) The present invention for solving the problems described above includes a pulse transformer having a primary coil and a secondary coil, and a clock for the pulse transformer provided on the primary side of the pulse transformer. circuit means driven by the pulse transformer; and a photovoltaic circuit driven by the voltage obtained by rectifying and smoothing the signal generated in the secondary coil of the pulse transformer, and turned on and off by the status signal to be output. It comprises a photocoupler having a transistor, a pair of terminals respectively connected to the collector and emitter of the phototransistor, and a flip-flop that reads and holds a signal generated at one end of the primary coil. setting the desired status signal to zero, placing the photocoupler in an OFF state, applying a clock to the primary coil of the pulse transformer, and applying an input status signal to the pair of terminals to obtain the input status signal from the flip-flop; In the output circuit mode, the signal isolating device is configured to apply a clock to the primary coil of the pulse transformer, apply a status signal to be output to the photocoupler, and obtain a status signal to be output from the pair of terminals. be.

(Example) FIG. 1 is a connection diagram showing an example of the device of the present invention. In the figure, PT is a pulse transformer having a primary coil n ₁ and a secondary coil n ₂ , and here, for convenience, the left side is the primary coil and the right side is the secondary coil. D _B is a diode connected between both ends of the primary coil n ₁ to absorb the backlash, DR1
is a driver connected to one end of the primary coil n ₁ via a resistor R ₁ , and the clock CLK is connected to its input end.
is applied. FF is a flip-flop that reads and holds the status signal generated at one end of the primary coil _n1 when working as an input circuit (input circuit mode).

_DR2 is a driver that inputs the status signal DODATA to be sent, and the PC is a photocoupler that has a light emitting diode PD that is turned on and off by this driver DR2.

On the secondary side of the pulse transformer PT, _D2 is a diode and _C1 is a capacitor, which are connected in series to both ends of the secondary coil _n2 . PTr is a phototransistor that operates by being supplied with the voltage obtained from the capacitor _C1 via the resistor _R3 , and forms a photocoupler PC together with the light emitting diode PD.
11 and 12 are a pair of terminals connected to the collector and emitter of this phototransistor PTr, respectively;
A diode connected to D ₀ between a pair of terminals 11 and 12, which is used to protect the circuit against reverse connection of the external power supply, and may be omitted.

Next, the operation of the device configured as described above will be explained separately in the input circuit mode and the output circuit mode.

(Input circuit mode) Apply the clock CLK to driver DR1 to drive the pulse transformer PT, and also output the status signal DODATA at the input terminal of driver DR2.
Let be 0. As a result, the photocoupler PC is turned off (the phototransistor PTr is turned off), and the load on the secondary coil _n2 of the pulse transformer PT becomes infinite (∞).

In this state, terminals 11 and 12 are input terminals, to which an input status signal such as a contact signal is applied, and the state of this status signal is determined by the resistance R ₃ , diode D ₂ and pulse transformer. Via PT, a change in impedance can be read at one end of the primary coil _n1 , and a status signal isolated from the terminals 11 and 12 can be obtained from the flip-flop FF.

(Output circuit mode) The clock CLK is applied to the driver DR1 to drive the pulse transformer PT, and the status signal DODATA to be output is applied to the input terminal of the driver DR2.

On the secondary side of the pulse transformer PT, the coil
The alternating current signal generated at _n2 is rectified by diode _D2 and appears as power supply voltage _EV across capacitor _C1 . The phototransistor PTr operates upon application of this power supply voltage _EV , and turns on and off in accordance with the status signal DODATA to be output.
Therefore, the status signal from terminals 11 and 12 is
It can be obtained by insulating it from the primary side of the pulse transformer PT.

(Effects of the invention) As explained above, the present invention realizes a signal isolation device with a simple configuration that allows selection of the functions of both the input circuit and the output circuit using one pulse transformer and one photocoupler. can.

[Brief explanation of drawings]

Figure 1 is a connection diagram showing an example of the device of the present invention;
3 and 3 are connection diagrams of conventional input circuits and output circuits. PT...Pulse transformer, n ₁ ...Primary coil,
n ₂ ... Secondary coil, PTr ... Phototransistor,
PC...Photocoupler, _D1 , _D2 ...Diode, 1
1, 12...terminal.

Claims (1)

[Claims for Utility Model Registration] A pulse transformer having a primary coil and a secondary coil; circuit means provided on the primary side of the pulse transformer for driving the pulse transformer with a clock; A photocoupler having a phototransistor that is operated by a voltage obtained by rectifying and smoothing a signal generated in a secondary coil and turned on and off according to a status signal to be output; and a collector and emitter of the phototransistor. and a flip-flop for reading and holding a signal generated at one end of the primary coil; in the input circuit mode, the status signal to be output is set to zero, and the photocoupler is turned off; A clock is applied to the primary coil of the pulse transformer, and an input status signal is applied to the pair of terminals to obtain the input status signal from the flip-flop, and in an output circuit mode, the input status signal is applied to the primary coil of the pulse transformer. A signal isolating device which provides a clock and applies a status signal to be output to the photocoupler to obtain a status signal to be output from the pair of terminals.