JPH0584969B2 - - Google Patents

Description

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

(Prior art) Fig. 5 is a connection diagram of a conventional status signal input circuit, and Fig. 5 is a connection diagram of a conventional status signal output circuit.
(1981) described on p.22.

The input circuit shown in FIG. 5 reads the state of the non-voltage contact S1 or the voltage signal as a change in impedance via a pulse transformer PT to which a clock signal is applied to the center tap, and is insulated from the field.

In the output circuit shown in Figure 6, 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.

(Problems 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 of the circuits shown in FIGS. 5 and 6 must be provided in advance. The problem was that two pulse transformers were required, making the configuration complicated.

The present invention was made in view of these problems, and its purpose is to provide a signal isolating device with a simple configuration that uses one pulse transformer and allows selection of both the input circuit and output circuit functions. This is what we are trying to achieve.

(Means for Solving the Problems) The present invention solves the above-mentioned problems by providing a pulse transformer having a primary coil with a center tap and a secondary coil with a center tap, and a pulse transformer having a primary coil with a center tap and a center tap between one end of the primary coil and the center tap. a switch element connected between the other end of the primary coil of the pulse transformer and the center tap and turned on when the input circuit is selected and turned on when the output circuit is selected; A rectifier diode and a capacitor are connected between one end of the secondary coil and the center tap of the pulse transformer, an open collector type transistor is turned on and off by the voltage obtained from this capacitor, and the transistor is connected to the collector and emitter of this transistor, respectively. a pair of terminals, a diode and a capacitor connected between the other end of the secondary coil of the pulse transformer and a center tap, and a resistor connecting a common connection point of the diode and the capacitor to one of the pair of terminals; When selecting a circuit, an input status signal is applied to the pair of terminals, and a drive signal is applied to the other end of the primary coil of the pulse transformer, and changes in the current flowing through the primary coil are extracted as an isolated status signal, and output circuit selection is performed. The present invention is characterized in that a status signal to be output is sometimes applied to one end of the primary coil of the pulse transformer, and an isolated status signal is obtained from the pair of terminals.

(Example) FIG. 1 is a connection diagram showing an example of a device according to the present invention. In the figure, PT is a pulse transformer,
Both have a primary coil _n1 and a secondary coil _n2 with a center tap. Note that, for convenience, in the pulse transformer PT, the left side shown in the figure is the primary coil n ₁ and the right side is the secondary coil n ₂ .

G ₁ and G ₂ are gate circuits connected to both ends of the primary coil n ₁ via a resistor R ₁ , and Q ₁ is a gate circuit connected between one end of the primary coil n ₁ and the center tap, and the collector and emitter via a diode D ₁ . A transistor Q ₂ is connected between the other end of the primary coil n ₁ and the center tap, through a diode D ₂ to the collector,
This is a transistor whose emitters are connected. These diodes D ₁ , D ₂ , transistors Q ₁ , Q ₂
Both constitute switch elements that turn on/off depending on the selection of the input circuit and output circuit. A selection signal SEL for selecting an input circuit and an output circuit is applied to the base of the transistor _Q1 via an inverter IV1, and the transistor _Q1
serves to absorb the backlash of the transformer when in output circuit mode (mode that functions as an output circuit). At the base of transistor Q ₂ ,
A selection signal SEL is applied via inverters IV2 and IV3, and when transistor _Q2 is in input circuit mode (mode functioning as an input circuit),
It plays the role of absorbing the stress of trance. Here, the primary coil of the pulse transformer PT
A voltage of 5V is applied to the center tap of _n1 .
FF is a flip-flop circuit in which the signal generated at the other end of the primary coil is applied to the D terminal.

D ₃ and D ₄ are diodes connected to both ends of the secondary coil n ₂ , and C ₁ and C ₂ are diodes D ₃ and D ₄ respectively.
A capacitor is connected between one end of the secondary coil and the center tap via a capacitor, R ₂ and R ₃ are resistors that divide the voltage obtained at the capacitor C ₁ , and Q ₀ is a voltage divided by resistors R ₂ and R ₃ at the base. It is an open collector type transistor to which a voltage is applied, and a pair of terminals 11 and 12 are connected to the collector and emitter. R ₄ is a resistor that connects the common connection point of diode D ₄ and capacitor C ₂ and terminal 11. D ₀ is a diode connected between 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) When the circuit shown in FIG. 1 is desired to function as an input circuit, the selection signal SEL is set to low ("L") level. This turns on transistor _Q1 ,
Transistor Q ₂ is turned off, and as a result, transistor Q ₀ is turned off (not turned on), and the circuit of FIG. 1 in this state can be represented by the circuit of FIG. 2.

In FIG. 2, terminals 11 and 12 are input terminals to which an input status signal is applied. A clock CLK is applied to the gate circuit _G2 to drive the pulse transformer PT. This drive consists of a pulse transformer PT primary coil n ₁
This is done by a coil on one side centered on the center tap.

The state of the status signal, such as a contact signal, applied to the terminals 11 and 12 is determined by the pulse transformer PT.
This appears on the primary coil _n1 side as a change in impedance through the flip-flop circuit FF, and the status signal is held in the flip-flop circuit FF. That is _, when a voltage of 5V is applied to the primary coil n ₁ of the pulse transformer PT by the clock as shown in FIG. Depending on the state (impedance change), a current flows as shown by the solid line (contact on state) or the broken line (contact off state) in Figure 3B, and this change in impedance is held in the flip-flop circuit FF as a status signal. The Rukoto. This status signal is taken out from the Q terminal of flip-flop circuit FF.

(Output circuit mode) When the circuit shown in FIG. 1 is desired to function as an output circuit, the selection signal SEL is set to a high (“H”) level. This turns off transistor _Q1 ,
Transistor Q ₂ turns on. The circuit of FIG. 1 in this state can be represented by the circuit of FIG. 4, where signal isolation is performed by a coil on one side centered on the center tap of the pulse transformer PT.

In FIG. 4, a status signal to be output is applied to the gate circuit _G1 , and terminals 11 and 12 serve as output terminals, to which an insulated status signal is output. i.e. pulse transformer PT
When a 5V voltage is applied to the primary coil n ₁ in accordance with the status signal to be output, the secondary coil n ₂
A voltage corresponding to the status signal is induced, and this is half-wave rectified by diode _D3 . The transistor Q ₀ is turned on and off by a signal obtained by dividing the voltage obtained at the capacitor C ₁ , and status signals are obtained from terminals 11 and 12 .

(Effects of the Invention) As described above, according to the present invention, it is possible to realize a signal isolation device that can be configured with one pulse transformer and can select the functions of both the input circuit and the output circuit.

[Brief explanation of the drawing]

1 is a connection diagram showing an example of a device according to the present invention, FIG. 2 is an equivalent circuit of the circuit in FIG. 1 in input circuit mode, and FIG. 3 is an operating waveform diagram of the circuit in FIG. 2.
FIG. 4 is an equivalent circuit diagram of the circuit of FIG. 1 in output circuit mode, and FIGS. 5 and 6 are connection diagrams of conventional input circuits and output circuits. PT...Pulse transformer, n ₁ ...Primary coil,
n ₂ ... Secondary coil, Q ₁ , Q ₂ , Q ₀ ... Transistor, D ₀ , D ₁ to _{D 4} ... Diode, C ₁ , C ₂ ... Capacitor, 11, 12 ... Terminal.

Claims (1)

[Claims] 1. A pulse transformer having a primary coil with a center tap and a secondary coil with a center tap, which is connected between one end of the primary coil of this pulse transformer and the center tap, and is turned on when an input circuit is selected and turned off when an output circuit is selected. a switch element connected between the other end of the primary coil of the pulse transformer and the center tap, which turns off when an input circuit is selected and turns on when an output circuit is selected; a switch element connected between one end of the secondary coil of the pulse transformer and the center tap; a rectifier diode and a capacitor, an open collector transistor that is turned on and off by the voltage obtained across this capacitor, a pair of terminals connected to the collector and emitter of this transistor, respectively, a secondary coil of the pulse transformer, etc. A diode and a capacitor are connected between the end and the center tap, and a resistor connects the common connection point of the diode and the capacitor to one of the pair of terminals, and when an input circuit is selected, an input status signal is given to the pair of terminals. A drive signal is applied to the other end of the primary coil of the pulse transformer, and changes in the current flowing through the primary coil are extracted as an isolated status signal, and when an output circuit is selected, the status to be output to one end of the primary coil of the pulse transformer. A signal isolating device characterized in that a signal is applied and an isolated status signal is obtained from the pair of terminals.