JPH0420010A - Optical coupling type relay circuit - Google Patents

Abstract

PURPOSE:To easily realize BBM(Break Before Make) in a semiconductor relay of a C contact type by connecting a control transistor(TR) between a gate and a source of a 2nd output MOSFET and switching the control TR with a voltage generated across a bias resistor to which a load current flows from a 1st output MOSFET. CONSTITUTION:A control TR 7 is connected between a gate and a source of a 2nd output MOSFET 5 and switched by a voltage generated across a bias resistor 6 resulting from a load current flowing to a 1st output MOSFET 4. Thus the 1st output MOSFET 4 is nonconductive and a photoelectromotive force generated from a 2nd photo diode array 3 is fed to the 2nd output MOSFET 5 which is conductive after a bias voltage of the resistor 6 is lost. Thus, the BBM is realized for a semiconductor relay of a C contact type without a change in the capability of the photodiode array or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optically coupled relay circuit that uses an optical coupling method to insulate input and output.

[Prior Art] FIG. 3 is a circuit diagram showing a conventional C-contact type optically coupled relay circuit. In this circuit, input terminals 16a, 1
The first and second photodiode arrays 2.3 receive the optical signal generated by the light emitting diode l connected between the light emitting diodes 6b and 6b to generate a photovoltaic force.
and is applied between the gate and source of the second output MOSFET 4.5. Note that the first output MOSF
ET4 is normally on type, and the second output MOSFE
T5 is a normally off type.

The gate and source of the output MOSFET 4.5 are connected to the sources and drains, or the drains and sources, of normally-on control transistors 8 and 9 constituting the discharge circuit, respectively.
．． Resistors 10 and 11 are connected between the gate and source of each transistor 9.

When an input signal is applied to the light emitting diode 1 and a photovoltaic force is generated in the photodiode arrays 2 and 3, a photocurrent is generated between the drain and source of the normally-on control transistor 89 and through the resistor 10.11. Flow, each resistance 10
．． A voltage is generated across 11. This voltage biases the control transistor 8.9 to a high resistance state, so that the photovoltaic forces of the photodiode arrays 2 and 3 are applied between the gate and source of the output MOSFET 4.5, and the first The output MOSFET 4 is turned off, and the second output MOSFET 5 is turned on.

When the input signal to the light emitting diode 1 is cut off, the photovoltaic force of the photodiode array 2.3 disappears, and the resistor 10.
11 disappears, the normally-on control transistor 89 returns to the on state, and the output MOS
Since the accumulated charge between the gate and source of the FET 4.5 is discharged, the first output MOSFET 4 is turned on and the second output MOSFET 5 is turned off.

[The problem that the invention tries to solve! ! ] By the way, in a C contact type semiconductor relay, the B contact side is in a non-conducting state B (Break) before the A contact side is in a conducting state (Make), that is, B B M
(Break Before Make) may be required.

However, in the above-mentioned conventional circuit, when the first and second photodiode arrays 2 and 3 have the same ability, the mirror effect of the drain-gate capacitance of the output MOSFET 45 causes the normal Since the switching speed of the first output MOSFET 4, which is on-type, is slow, there is a problem in that it is difficult to realize BBM.

The present invention has been made in view of these points, and its purpose is to provide an optically coupled relay that can realize BBM in a C-contact type semiconductor relay without changing the capabilities of the photodiode array, etc. The purpose is to provide circuits.

[Means for Solving the Problems] In order to solve the above problems, the optically coupled relay circuit according to the present invention generates an optical signal in response to a human input signal, as shown in FIG. Light-emitting diode 1, first and second photodiode arrays 2, 3 arranged to receive optical signals from light-emitting diode 1, and respective lights of first and second photodiode arrays 2.3. A normally-on type first output MOSFET 4 and a normally-off type second output MOSFET 5 in which an electromotive force is applied between the gate and source to switch between a conductive state and a non-conductive state between the respective drains and sources. , a bias resistor 6 connected to the source of the first output MOSFET 4 and generating a bias voltage by the load current flowing through the first output MOSFET 4, and a second output MOSFET 4.
A bias resistor 6 is connected between the gate and source of ET5.
The control transistor 7 becomes conductive due to the voltage generated by the control transistor 7, and the first and second output MOSFETs 4.
discharge circuits 18 and 19 for discharging the accumulated charge between the gate and source of each of the first and second output M
Each drain of OSFET4.5 is connected to its respective output terminal +
7a and 17b, and the first output MOSFET 4
The source of is connected to the common output terminal 1 via the bias resistor 6.
7c and the source of the second output MOSFET 5.

[Function] In the present invention, as described above, the second output MOSF
A control transistor 7 is connected between the gate and source of the ET 5, and it is switched between conduction and non-conduction by the voltage generated in the bias resistor 6 due to the load current flowing through the first output MOSFET 4, so that the first output The second output MOSFET 5 is turned off only after the second output MOSFET 4 becomes non-conductive and the bias voltage of the resistor 6 disappears.
A photovoltaic force emitted by the second photodiode array 3 is applied to the second photodiode array 3, resulting in a conductive state, and BBM is realized.

[Embodiment] FIG. 1 is a circuit diagram showing an embodiment of the present invention. In this embodiment, the discharge circuits 18 and 19 each include a normally-on control transistor 8.9 and a resistor 10.1.
It consists of 1.

The light emitting diode 1 is connected between the input terminals 16a and 16b, and the light emitting diode 1 is optically coupled to the first and second photodiode arrays 2 and 3, and the positive electrode of the first photodiode array 2 is connected to the The negative electrode is connected to the source of the normally-on first output MOSFET 4 through the third bias resistor 6 for the third control transistor 7, and the negative electrode is connected to the first bias resistor 6 for the first control transistor 8. They are connected to the gates of the first output MOSFETs 4 via resistors 10, respectively. The positive electrode of the second photodiode array 3 is connected to the gate of the normally-off second output MOSFET 5, and the negative electrode is connected to the gate of the second output MOSFET 5 through the second bias resistor 11 for the second control transistor 9. The gates of the first output MOSFETs 4 connected to the sources of the second output MOSFETs 5,
The source of a normally-on first control transistor 8 is connected, and the drain of this control transistor 8 is connected to the positive electrode of the first photodiode array 2 . The drain of a normally-on second control transistor 9 is connected to the gate of the second output MOSFET 5, and the source of the control transistor 9 is connected to the source of the second output MOSFET 5.

The drain of the first output MOSFET 4 is connected to the negative output terminal 17a, and the source is connected to the common output terminal 17c via the third bias resistor 6. M for second output
The drain of the OSFET 5 is connected to the other output terminal 17b, and the source is connected to the common output terminal 17c. The normally-off type third control transistor 7 has its drain connected to the gate of the second output MOSFET 5, its source connected to the source of the second output MOSFET 5, and its gate connected to the first output MOSFET 5.
are connected to the sources of the output MOSFETs 4, respectively. A first DC power supply 1 is connected between the output terminals 17a and 17c.
2 and the first load 14 are connected, and the output terminal 1
A second DC power supply 13 and a second load 1 are connected between 7b and 17c.
5 series circuits are connected.

Next, the operation of the above embodiment will be explained.

The first output MOSFET 4 is normally on type, and a load current flows through it. Therefore, a bias voltage is generated in the third resistor 6, making the third control transistor 7 conductive. In this state, input terminals 16a and 16b
When an input signal is applied during this period, the light emitting diode 1 generates an optical signal, and upon receiving this optical signal, the second photodiode array 3 generates a photovoltaic force. One of these days it will be light
The current flows to the second resistor 11 via the second and third control transistors 9.7. Therefore, the second resistor 11 generates a bias voltage and biases the second control transistor 9 to a high resistance state. However, since the third control transistor 7 is in the conductive state as described above, the photovoltaic force generated in the second photodiode array 3 is not applied to the second output MOSFET 5.

On the other hand, a photocurrent is also generated in the first photodiode array 2 due to the optical signal generated by the light emitting diode l, and the photocurrent flows through the first control transistor 8 and the first resistor lO. The voltage generated in the resistor 10 biases the first control transistor 8 to a high resistance state, and the photovoltaic force generated in the first photodiode array 2 is applied to the first output MOSFET 4, and the first control transistor 8 is applied to the first output MOSFET 4. MOSFET 4 is made non-conductive.

When the first output MOSFET 4 becomes non-conductive, the load current flowing through the first DC power supply I2 and the first load 14 is cut off, and the voltage generated at the third resistor 6 disappears. As a result, the third control transistor 7 becomes non-conductive, and the photovoltaic force generated in the second photodiode array 3 is applied to the second output MOSFET 5.
5 becomes conductive.

As described above, the B contact side becomes non-conductive before the A contact side becomes conductive, and BBM is realized.

In the above embodiment, the first and second output M
A discharge circuit 18.19 for discharging the accumulated charge between the gate and source of each OSFET 4.5 is connected to a normally-on control transistor 8.9 and a resistor 10.19, respectively.
11, but it goes without saying that the present invention is not limited to this.

[Effect 1 of the Invention In the present invention, as described above, the second output MOS
A normally-on control transistor is connected between the gate and source of the FET, and this is connected to the first output MOSFE.
Since conduction and non-conduction are switched by the voltage generated in the bias resistor due to the load current flowing through T, the first output MOS FET becomes non-conductive and the load current is cut off, thereby reducing the voltage generated in the bias resistor. Only after the bias voltage that had been applied disappears does the second output MO
The photovoltaic force generated by the second photodiode array is applied to the SFET, and the SFET becomes conductive. Therefore, according to the present invention, it is possible to provide an optically coupled relay circuit that can realize BBM in a C-contact type semiconductor relay without changing the capabilities of the photodiode array or the like.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a circuit diagram showing a conventional example. DESCRIPTION OF SYMBOLS 1... Light emitting diode, 2... Photodiode array, 3... Second photodiode array, 4...
...First output MOSFET, 5...Second output MOSFET, 6...Bias resistor, 7...Control transistor, 17a, 17b...Output terminal, 17c
...Common output terminal, 18.19...Discharge circuit.

Claims (1)

[Claims] (1) A light emitting diode that generates an optical signal in response to an input signal; first and second photodiode arrays respectively arranged to receive the optical signal of the light emitting diode; and first and second photodiode arrays. A normally-on type first output MOSFET and a normally-off type first output MOSFET, in which the photovoltaic force of each of the diode arrays is applied between the gate and source to switch between a conductive state and a non-conductive state between the respective drains and sources. a bias resistor that is connected to the source of the first output MOSFET and generates a bias voltage by a load current flowing through the first output MOSFET; and a second output MOSFET.
a control transistor connected between the gate and source of the ET and turned on by a voltage generated by a bias resistor; and a discharge circuit that discharges accumulated charges between the gates and sources of each of the first and second output MOSFETs. The drains of the first and second output MOSFETs are connected to their respective output terminals, and the first output MOSFET
The source of is connected to the common output terminal via the bias resistor,
An optically coupled relay circuit characterized in that it is connected together with a source of a second output MOSFET.