JPS6249746B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a photosensitive switching element, and an object thereof is to switch a large DC current using a small input optical signal.

Conventionally, thyristors and transistors have been used as switching elements, but thyristors cannot switch on and off direct current (only alternating current), and transistors require a large input signal to switch on and off their output current.

Furthermore, there is a phototransistor that switches direct current using an optical signal, but this also requires a large optical signal.

The present invention was invented in view of these problems, and embodiments thereof will be specifically described below with reference to the drawings.

FIG. 1 is a block diagram of the present invention, where 9 is a silicon semiconductor element of the present invention, in which p5-n1-p2-n3 form a horizontal thyristor, n1-p2-n3 form a transistor, and p5-n3 form a transistor. n1 forms a solar cell. Electrodes 6, 7, and 8 are provided on n3, n1, and p5, respectively, and electrode 7 applies a positive voltage Va and electrode 6 applies a negative polarity voltage Va. R _L is the load resistance,
A resistor R ₁ is connected between electrodes 7 and 8, and light L is irradiated from the upper surface of element 9.

FIG. 2 is an example in which a solar cell SC is connected between the electrodes 7 and 8 instead of the high resistance R ₁ in FIG. 1 to operate with a smaller light signal.

Next, the operating state of the present invention will be described.

When the element 9 is irradiated with light L in the configuration shown in FIG. 1, holes are accumulated in p5 and electrons are accumulated in n1 in the p5-n1 solar cell configuration, and an electromotive force is generated in which p5 is positive and n1 is negative. On the other hand, excessive holes, which are majority carriers, are accumulated in the p2 layer due to light irradiation, increasing the potential of the p2 layer, biasing the p2-n3 junction in the forward direction, and causing a large photocurrent to flow. This photocurrent is p5
-n1-p2-n3 becomes a trigger current for the thyristor configuration and makes this thyristor conductive. At this time, p2-n1 junction J ₁ is completely opened, and n1-p2-n
Transistor 3 becomes conductive, and a large current flows through the load R _L . When the thyristor is conducting, double injection of electrons and holes occurs, but electrons are supplied from n3 and holes are supplied from _R1.
The holes that entered p5 through the solar cell, the holes stored in p5 due to light irradiation due to the effect of the solar cell, and the holes generated by light irradiation in the n1 and p2 layers are supplied to p5, resulting in a double injection are connected. During this period of light irradiation, the transistor is in a conductive state and continues to flow a large current to the load.

When the light irradiation is removed, the photovoltaic force of the solar cell composed of p5-n1 disappears, so that p5
The potential difference between p5 and n1 due to light disappears, and p5
The generation of holes due to light irradiation also disappears. Also, n
1, p2 and no holes are generated by light. However, although holes are injected into p5 through _R1 , the potential of p5 becomes more negative than n1 by the voltage drop of _R1 due to the current passing through _R1 , so p5-n
1 junction is reverse biased. Therefore, p5-n1
Since there is no hole injection in the -p2-n3 thyristor structure, this thyristor immediately becomes non-conducting and the junction _J1 is closed.

Then, the transistors n1-p2-n3 also become non-conductive, and no current flows to the load R _L.

When a solar cell SC is connected in place of the resistor _R1 in Figure 2, a photovoltaic voltage is generated in the solar cell SC due to light irradiation, biasing the p5 layer more positively and increasing the number of holes injected into the p5 layer. to make conduction of the thyristor easier.

When there is no light irradiation, the solar cell SC is completely in a current blocking state, and no holes are injected into p5.
Further, since no holes are generated in the p5 layer, the thyristor immediately becomes non-conductive, and the transistor structure also becomes non-conductive.

As described above, the present invention allows a large current to flow through the element when there is light irradiation, and allows the element to be completely non-conductive when there is no light irradiation.
That is, a large current can be switched on and off using an optical signal, and since the element is switched using a thyristor structure, the element can be made conductive with a very small optical signal. Moreover, since the load current is passed through the transistor structure, a large load current can be taken regardless of the current in the thyristor structure, making the load current irrelevant to making the thyristor non-conductive.

Furthermore, since the element can be made conductive or non-conductive depending on the presence or absence of an optical signal, not only alternating current but also direct current can be switched on and off.

Moreover, since the input signal is provided as light, the input and output can be completely isolated, the signal is unidirectional, and the output signal does not bounce back to the input side.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a photosensitive switching element according to the present invention, and FIG. 2 is a block diagram of a case where a solar cell is used in place of the high resistance in the block diagram of FIG. 1. n1 is an n-type substrate, n3 is an n-type layer, p5 is a p-type layer, 6, 7, 8 are electrodes, _R1 is a resistance, R _L is a load,
SC is the solar cell, Va is the power supply.

Claims (1)

[Claims] 1. A P-type layer P2 is formed partially on one surface of the n-type substrate n1, and an n-type layer n3 is formed on P2, and a P-type layer P5 is formed on the other surface of n1. , this n
3. Provide electrodes on P5 and on the opposite side of n1, apply a positive voltage to the n1 layer electrode and negative voltage to the n3 layer electrode, and create a resistance between the n1 layer electrode and the P5 layer electrode.
Connect R ₁ and make the element conductive by light irradiation.
A photosensitive switching element characterized in that the element becomes non-conductive when no light is irradiated. 2 Connect a solar cell instead of resistor _R1 between the n1 and P5 layers so that when light is irradiated to this element and the solar cell, the element becomes conductive, and when no light is irradiated, the element becomes non-conductive. Characteristic claim 1
The photosensitive switching element described in .