JPS5845270B2 - Optical coupling device control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control circuit for an optical coupling device that controls energization of an output circuit in response to changes in ambient temperature.

Conventionally, the output circuit has been used exclusively as a means to detect a temperature rise in the output circuit connected between the output side terminals of the control circuit of an optical coupler, or to detect a temperature rise in the optical coupler itself and cut off the current flowing through the output circuit. It has been attempted to provide a heat-sensitive element therein which responds to the temperature increase.

Specifically, for example, if it is desired to prevent the temperature of the load in the output circuit from rising, the load and the heat-sensitive element may be placed close to each other so as to be thermally coupled, and the heat-sensitive element may be connected in parallel with the load. good.

In this way, even if the temperature of the load rises due to some reason, such as an overcurrent, the heat-sensitive element senses this temperature rise, and by making the heat-sensitive element low impedance, current is transferred to the heat-sensitive element and the load The current is cut off and the load is protected.

However, in the conventional output circuit as described above, the main current flowing through the load in the output circuit is large, so in order to transfer this main current to the heat-sensitive element, a heat-sensitive element with a considerably large current capacity is required. becomes significantly more expensive.

The present invention relates to an output circuit connected to an output terminal of an optical coupler control circuit, and a heat sensitive element that responds to temperature changes of the casing or the optical coupler itself, connected to an input terminal of the optical coupler. And the price of the entire device including the output circuit is reduced.

FIG. 1 shows an embodiment of the present invention, in which 1 is a light emitting diode made of gallium-arsenic, 2 is a photothyristor which is turned on by the light emitted from the light emitting diode 1, and 1 is
0 is a photocoupler configured by holding a light emitting diode 1 and a photothyristor 2 facing each other in an electrically insulated state; 3 is a photocoupler thermally coupled to the photocoupler 10;
Thermal thyristor 4 is connected to the terminal of the thermal thyristor, and 4 is a resistor that determines the operation start temperature of the thermal thyristor 3.If this resistance value is increased, the injection current flowing between the gate and cathode of the thermal thyristor 3 becomes large, which is relatively low. Heat-sensitive rhinoceros 1 even at low temperatures
Nostar 3 is rendered conductive.

A and B are input terminals of the photocoupler 10, and a and b are output terminals of the photocoupler 10.

What is heat-sensitive thyristor 3 in the same housing as photocoupler 10?
When incorporating a light emitting diode 1, a means for blocking light between the two is required so that the heat sensitive zyristor 3 does not malfunction due to light emission from the light emitting diode 1.

The operation of the above embodiment will now be described.

Apply AC voltage to input terminals A and B and output terminal a.

When b is connected to an alternating current power source through a load, when the heat-sensitive thyristor 3 reaches a predetermined operating temperature determined by the resistor 4, the light-emitting diode 1 emits light and the photothyristor 2 is flushed and conductive.

However, if an overcurrent flows through the photothyristor 2 due to a short circuit in the load, and the temperature of the photocoupler 10 increases, or if the temperature of the photocoupler 10 itself increases due to a change in the surrounding state, the heat-sensitive thyristor 3 is thermally coupled to the photocoupler 10. Therefore, if the temperature rises above the operating temperature, it becomes conductive.

When the heat-sensitive thyristor 3 conducts, its on voltage (voltage drop in the on state) is smaller than the forward rising voltage (threshold voltage) of the light emitting diode 1, so the light emitting diode 1
Almost no current flows through the photothyristor 2, which stops emitting light, and the photothyristor 2 receives no light from the light emitting diode 1, turning off at the zero point of the applied voltage that occurs periodically, and the current flowing through the output circuit is cut off.

Therefore, the photocoupler 10 is maintained at a predetermined temperature or lower and is protected from destruction due to overheating, overcurrent, and the like.

When the temperature of the photocoupler 10 becomes lower than the operating temperature of the heat-sensitive thyristor 3, the heat-sensitive thyristor 3 turns off near the zero point of the input voltage, the light emitting diode 1 emits light again, and the photothyristor 2 is therefore tripped and current flows to the load. Return to normal state.

FIG. 2 shows another embodiment of the present invention, and the same reference numerals as in FIG. 1 represent corresponding parts, and the explanation thereof will be omitted.

C and d are power supply terminals of the output circuit, and 5 is a load connected in series with the photothyristor 2 between the power supply terminals of the output circuit, and this load and the heat-sensitive thyristor 3 are thermally coupled.

The operation of the other embodiments described above will be explained below.

When an AC power source is connected between input terminals A and B and between output terminals e and d, the temperature of load 5 is
If the temperature exceeds the operating temperature of 1, the power to load 5 is cut off.
Further, when the temperature of the load 5 becomes lower than the operating temperature of the heat-sensitive iris register 3, power supply to the load 5 is resumed.

In the other embodiments as well, the load 5 is maintained at a predetermined temperature or lower and is protected from destruction due to overheating, overcurrent, etc.

Although the power supplies in the above two embodiments have been described using alternating current for both input and output, the input may be direct current or pulsating current, and the output may be pulsating current.

Note that when the human power is direct current, the thermal zyristor 3 becomes conductive at a temperature higher than the operating temperature and will not turn off even if the temperature drops below the operating temperature. Therefore, in such a case, the thermal zyristor 3 is A switch such as a transistor is provided in series with 3, and when the switch is turned off to cut off the current to the heat-sensitive thyristor 6, the light emitting diode 1 emits light and the energization of the output circuit is resumed.

FIG. 3 shows still another embodiment of the present invention, in which a zero voltage switch circuit is connected to the output side of the photocoupler, and a reverse blocking three-terminal thyristor or a bidirectional three-terminal thyristor is further connected to this zero voltage switch circuit. , so-called SS
This figure shows a circuit in which the present invention is applied to a zero-voltage non-contact switch called a relay (solid-state relay).

E. F is the DC input terminal of the SS relay, 7 is the DC input circuit that receives this DC input, and its output terminal is connected to the photocoupler 1.
Connected to the 00 input terminal.

. 8 is a zero voltage switch circuit connected to the output side terminal of the photocoupler 10, and 9 is a bidirectional three terminal whose gate and one of the main electrodes are connected to the output terminals of each of the photocoupler 10 and the zero voltage switch circuit 8. With a thyristor,
It performs on/off control of alternating current to the load 5 and is thermally coupled to the heat-sensitive thyristor 3.

In such an SS relay, even if the temperature of the expensive bidirectional three-terminal thyristor 9 rises above a predetermined temperature due to an overcurrent or the like, the heat-sensitive thyristor 3 is quickly activated and the light emitting diode 1 stops emitting light. The terminal thyristor 9 is turned off and kept below a predetermined temperature to prevent overheating.
Protected from overcurrent.

Although the present invention has been described above with reference to several examples, the present invention is not limited thereto.

For example, the light emitting element of the photocoupler is not limited to a light emitting diode, but may be a light emitting element other than a semiconductor such as a discharge lamp (neon lamp).

The light receiving element may be a photodiode or a phototransistor in addition to a photothyristor.

Furthermore, when an amplifier circuit is connected to the output side of the photocoupler, it can be thermally coupled to the transistor or IC to keep them at a predetermined temperature or lower and protect them from overheating.

Furthermore, instead of a heat-sensitive thyristor, a heat-sensitive switch element with a semiconductor PiN structure, or an nP equivalent to a heat-sensitive thyristor is used.
A heat-sensitive switching element consisting of a combination of an n) transistor and a pnp transistor may also be used.

As explained above, this invention has the advantage of connecting the heat-sensitive element, which was conventionally connected to the output side of the optical coupling device, to the input side, which makes it possible to reduce the current capacity of the heat-sensitive element, and therefore allows for inexpensive construction. can do.

[Brief explanation of drawings]

FIGS. 1, 2, and 3 are circuit diagrams showing embodiments of the present invention. 1... Light emitting diode, 2... Photothyristor, 3... Heat sensitive thyristor, 5...
...Load, 7...Bidirectional three-terminal thyristor, 1
0...Hoto coupler. The same reference numerals in the figures represent the same or corresponding parts.

Claims (1)

[Claims] 1. An optical coupling device and an 8g connector connected to the output terminal of the optical coupling device.
an output circuit, which is connected to an input terminal of the optical coupling device, is thermally coupled to the optical coupling device or the output circuit, and controls light emission of the optical coupling device in response to the temperature of the optical coupling device or the output circuit. 1. A control circuit for an optical coupling device, characterized in that it is equipped with a heat-sensitive element. 2. A control circuit for an optical coupling device according to claim 1, wherein the output circuit includes a high-power semiconductor element to which the heat-sensitive element is thermally coupled.