JPS5821183Y2 - Photocoupler - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an improvement of a photocoupler using a photothyristor as a light receiving element.

A photocoupler is a device in which a light emitting element and a light receiving element are placed in a single container and electrically separated from each other. It is mainly used when joining.

Conventionally, a photocoupler shown in FIG. 1 has been proposed.

This photocoupler 1 is composed of a first light emitting element 2, a second light emitting element 3, a photothyristor 4, and a solar cell 5 that reverse biases the photothyristor 4 between its gate and cathode. When the photothyristor 4 receives the light emitted from the first light emitting element 2, it is turned on, and conversely, when the solar cell 5 receives the light emitted from the second light emitting element 3, a voltage is generated between the cathode SK and the anode terminal of the solar cell 5. A voltage is generated, which reverse biases the photothyrist 4, drawing current from its gate region and turning it off.

However, there are two light-emitting elements in the diagonal photocoupler 1.
Therefore, there is a drawback that the number of parts is large and the cost increases.

This invention was made in view of this point, and one embodiment will be explained below.

In FIG. 2, 6 is a light emitting element, such as a GaAs light emitting diode.

7 is an anode terminal A, a cathode terminal K and a gate terminal G
The photoresist is turned on by receiving the light emitted from the light emitting element 6.

Reference numeral 8 denotes a solar cell which receives the light emitted from the light emitting element 6 and generates a voltage, and has its cathode SK connected to the gate terminal G and its anode SA connected sideways to the cathode terminal.

A resistor 9 is connected in series with the solar cell 8, and functions to limit the current flowing through the series circuit 10 of the resistor 9 and the solar cell 8.

A series circuit 10 of a resistor 9 and a solar cell 8 is connected between the gate and cathode of the photothyristor 8.

Generally, the photothyristor 7 is turned on by weak light emission of a small current of about several tens of milliamps.

On the other hand, in the solar cell 8, a desired voltage is generated by strong light emission with a large current of about several amperes.

As shown above, there is a large difference between the light emitting element current value when the photothyristor 7 is turned on and the light emitting element current value when the solar cell 8 generates a desired voltage.

Taking advantage of such a current difference, the photothyristor 7
Turn on and turn off.

When turning on the photothyristor 7, a small signal of about 3QmA is supplied to the light emitting diode 6 to cause it to emit weak light.

Then, the photothyristor 7 is turned on by the optical signal from the light emitting diode 6.

At this time, the solar cell 8 also receives light, but since the current flowing out from the solar cell 8 is small and the resistor 9 is connected in series with the solar cell 8, the current in the series circuit 10 is limited to a small value, so that the photothyristor of the solar cell 8 7 No effect on operation.

Once turned on, the photothyristor 7 continues to be on even when the light emitting diode 6 is turned off.

Next, when turning off the photothyristor 7, the light emitting diode 6 is supplied with a pulsed large current on the order of LA to cause it to emit strong light.

Then, due to the large pulsed current, the light emitting diode 6 emits strong light, and this strong light enters the solar cell 8.
A large voltage is developed between the cathode SK and the anode SA of the photothyristor 7 and the photothyristor 7 is biased in the opposite direction between its gate terminal G and cathode terminal, so that a current is drawn from its gate region and the photothyristor 7 is turned off.

At this time, the photothyristor 7 also receives the light emitted from the light emitting diode 6, so the photothyristor 7 tends to continue in the on state, but the tendency to turn off by the solar cell 8 is stronger than the tendency to continue in the on state. acts more strongly, so the photothyristor 7 is turned off.

Since this device is constructed as described above, the weak light emission of the light emitting element turns on the photothyristor, and the strong light emission of the light emitting element induces a desired voltage in the solar cell, turning off the photothyristor, thereby reducing the light emission intensity of the light emitting element. The photothyristor can be turned on and off by simply switching it, and therefore the photothyristor can be turned on and off by simply controlling the current of the light emitting element.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a conventional example, and FIG. 2 is an electric circuit diagram of an embodiment of this invention. 6...Light emitting element, 7...Photothyristor, 8...Solar cell.

Claims (1)

[Scope of utility model registration request] In a device comprising a light emitting element whose light emission intensity can be controlled by current, and a photothyristor which turns on by receiving the weak light emission of the light emitting element, the strong light emission of the light emitting element is connected between the gate and cathode of the photothyristor. A photocoupler characterized by having a solar cell that receives light and generates an operating voltage connected with reverse bias polarity.