JP2003115755A - Drive circuit for semiconductor switch element and semiconductor relay using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drive circuit for a semiconductor switch element which can shorten the turn on time and turn off time of the semiconductor switch element. SOLUTION: This drive circuit is equipped with a light emitting element 11 which is lit and put out by a pulse power source 12, a solar cell 21 which is optically coupled with the light emitting element 11 and can supply control input to the section between the control input ends of the semiconductor switch element 22, and a photodiode 25 which is optically coupled with the light emitting element 11, with its cathode connected to the positive electrode terminal of the solar cell 21 via a resistor R3 and with its anode connected to the negative electrode terminal of the solar cell 21. An n-channel MOSFET 27a constituting the semiconductor switch connected between both ends of the solar cell 21 becomes off while the light emitting element 11 is lit and becomes on while the light emitting element 11 is put out, with its drain and source connected to the positive electrode terminal and negative electrode terminal, respectively, of the solar cell 21 and with its gate terminal connected to the cathode of the photodiode 25.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive circuit for a semiconductor switch element and a semiconductor relay using the drive circuit.

[0002]

2. Description of the Related Art In recent years, there is an increasing need for semiconductor switches as switching elements that can transmit high-frequency analog signals with high accuracy and can be turned on and off at high speed. Such a semiconductor switch includes a light emitting element such as a light emitting diode, a solar cell optically coupled to the light emitting element, and a pair of MOSFETs connected in anti-series, which is turned on / off by the output of the solar cell. A semiconductor relay including and is known.

A circuit diagram of this type of semiconductor relay is shown in FIG. 4 (see Japanese Patent Laid-Open No. 63-153916). The semiconductor relay shown in FIG. 4 is a light emitting device 1 including a light emitting diode.
1, a solar cell 21 that is optically coupled to the light emitting element 11 to generate a photoelectromotive force, and a gate terminal (hereinafter abbreviated as a gate).
And two source terminals (hereinafter abbreviated as sources) are commonly connected to each other in two n-channel MOSFEs.
The semiconductor switch element 22 composed of T22a and 22b is provided, and is configured to turn on / off the semiconductor switch element 22 in response to the electromotive force of the solar cell 21. It should be noted that the semiconductor switch element 22 is composed of n-channel MOSFs.
The drain terminals (hereinafter abbreviated as drains) of the ETs 22a and 22b respectively constitute main terminals and are connected to output terminals (relay output terminals) 26a and 26b.

Here, the light emitting element 11 is connected between both ends of a pulse power source 12 which is a driving power source via a resistor R1. The pulse power supply 12 is configured to output a pulse voltage. A normally-on type (depletion type) in which a bias resistor R2 is connected between the gate and the source between the connection point between the gates and the connection point between the sources (between the control input terminals) in the semiconductor switch element 22 described above. ) N-channel MOSFET 23 is connected. This normally-on type n-channel MOSFET 2
3 is each MOSFET 22 of the semiconductor switch element 22.
It is provided to pull out the gate charges of a and 22b. Furthermore, a normally-on type n-channel MOSFET
The gate-source of 23 is connected between the source and drain of an n-channel MOSFET 24 whose gate-drain is short-circuited. The n-channel MOS described above
The gates of the FETs 22a and 22b are connected to the positive terminal of the solar cell 21, and the sources are connected to the negative terminal of the solar cell 21 via the bias resistor R2.

In the semiconductor relay described above, the drive circuit for the semiconductor switch element 22 is constituted by the pulse power source 12, the resistor R1, the light emitting element 11, the solar cell 21, the normally-on type n-channel MOSFET 23, the bias resistor R2, and the n-channel MOSFET 24. The semiconductor switch element 22 is configured to be able to conduct and block AC power.

The operation of the above drive circuit will be described below.

First, the operation when the semiconductor switch element 22 shifts from the off state to the on state will be described.

When a forward current flows from the pulse power source 12 to the light emitting element 11 via the resistor R1, the light emitting element 11 is turned on (emits light), and the solar cell 21 generates a photoelectromotive force. The current due to this photovoltaic power is initially the positive terminal of the solar cell 21
It flows in the path of the drain of the normally-on type n-channel MOSFET 23-the source of the normally-on type n-channel MOSFET 23-the bias resistance R2-the negative terminal of the solar cell 21. This current causes a voltage drop across the bias resistor R2 in the direction of reverse biasing between the gate and the source of the n-channel MOSFET 23, and when the voltage across the bias resistor R2 exceeds the threshold voltage of the n-channel MOSFET 23, the n-channel MOSFET 23 is turned on. High impedance. After this, most of the photovoltaic current of the solar cell 21 is the positive terminal of the solar cell 21-the gates of the n-channel MOSFETs 22a and 22b-the source of the n-channel MOSFETs 22a and 22b-the bias resistance R2-the negative electrode of the solar cell 21. The n-channel MOSFETs 22a and 22b are charged in the direction of forward bias between the gates and sources by flowing through the path of the terminals. When this charging voltage exceeds the threshold voltage of each n-channel MOSFET 22a, 22b, each n-channel MOSFET 22a, 22b
Turns on. Furthermore, each n-channel MOSFET
After the gate-sources of 22a and 22b are completely charged, the current due to the photovoltaic power is passed through the normally-on type n-channel MOSFET 23 having high impedance,
The current continues to flow in the path of the positive electrode terminal of the solar cell 21, the drain of the normally-on type n-channel MOSFET 23, the source of the normally-on type n-channel MOSFET 23, and the bias resistor R2-the negative terminal of the solar cell 21. This is because the normally-on type n-channel MOSFET 23 reaches the equilibrium state with a certain impedance because the current flowing therethrough maintains the high impedance state due to the voltage drop in the bias resistor R2. In this state, most of the current flowing through the bias resistor R2 comes to flow through the n-channel MOSFET 24 that is connected in parallel and adjusted to a medium impedance, and the voltage drop of the bias resistor R2 causes the n-channel M to flow.
The bias voltage between the gate and the source of the OSFETs 22a and 22b is lowered to decrease the n-channel MOSFETs 22a and 22b.
The on-resistance of b is prevented from increasing.

In this state, the primary side circuit 10 including the light emitting element 11 and the secondary side circuit 2 including the solar cell 21.
Since it is electrically well isolated from 0 through a very small electrostatic capacity, the output terminal 26a to which each main terminal of the semiconductor switch element 22 of the secondary side circuit 20 is connected,
Also when a high frequency power supply is connected between 26b,
The high frequency impedance with the primary side circuit 10 having a large capacitance to ground (capacitance between a fixed potential) is very large. Therefore, the semiconductor relay having the configuration shown in FIG. 4 has excellent high-frequency characteristics (conduction characteristics of high-frequency signals between the output terminals 26a and 26b) when the semiconductor switch element 22 is conductive, and the output of the high-frequency power source is the inductance of the circuit. It has a feature that the amount of dip drop caused by interference with the component and the capacitance to ground is very small. In short, it is possible to suppress the occurrence of a dip that maximizes the conduction loss at a specific frequency.

Next, the operation when the semiconductor switch element 22 shifts from the on state to the off state will be described.

The output voltage of the pulse power source 12 becomes 0V,
When the light emitting element 11 is turned off, the output current of the solar cell 21 decreases. Therefore, the voltage drop of the bias resistor R2 is reduced, and the normally-on type n-channel MOSFET 23 is in a low impedance state. Then, n channel MO
The electric charge accumulated between the gate and the source of the SFETs 22a and 22b and the electric charge accumulated between the positive electrode terminal and the negative electrode terminal of the solar cell 21 are the n-channel MOSFET 2
3 through the n-channel MOSFET 22a,
When the gate-source voltage of 22b falls below the threshold voltage, each n-channel MOSFET 22a, 22b is turned off.

The semiconductor relay configured as described above is
Each n-channel MOSFET 2 of the semiconductor switch element 22
N-channel MSOFT when 2a and 22b are turned on
The gate-sources of T22a and 22b operate so as to be charged in a relatively short time and turned on at high speed, and most of the output voltage of the solar cell 21 after the completion of charging is the gate-source of the n-channel MOSFETs 22a and 22b. It is applied between the n-channel MOSFETs 22a and 22b so that the n-channel MOSFETs 22a and 22b are maintained at low on-resistance. On the other hand, even when turned off, the n-channel MOSFETs 22a, 2
The charge accumulated between the gate and the source of 2b is discharged in a relatively short time and turned off at a high speed. Furthermore, since the electrostatic capacitance between the primary side circuit 10 and the secondary side circuit 20 is extremely small when the semiconductor switching element 22 is conducting, high frequency characteristics (output terminal 26a,
There is also an advantage that the conduction characteristic of the high frequency signal between 26b) is excellent.

[0013]

However, in the above-mentioned conventional drive circuit, at the time of turn-on, two n-channel MOSFETs forming the semiconductor switch element 22 are formed.
The normally-on type n-channel MOSFET 2 is provided before the forward bias between the gate and source of 22a and 22b.
Since the time for turning off 3 is required, there is a problem that the high speed of turn-on is not sufficiently satisfied.

Further, even at the time of turn-off, the two n-channel MOSFEs constituting the semiconductor switch element 22 are formed.
In addition to the gate-source capacitance of T22a and 22b, it is necessary to discharge the accumulated charge of each large terminal capacitance of the solar cell 21, and it takes time for the accumulated charge of the terminal capacitance of the solar cell 21 to disappear. That, solar cell 2
Since the discharge current of the electric charge accumulated in the inter-terminal capacitance of 1 operates the normally-on type n-channel MOSFET 23 to have a high impedance, the turn-off speed is not satisfactory, and further speed-up can be achieved. Is required.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a drive circuit for a semiconductor switch element, which can shorten the turn-on time and turn-off time of the semiconductor switch element.

[0016]

In order to achieve the above-mentioned object, the invention of claim 1 is a drive circuit for a semiconductor switch element which is turned on / off according to a control input provided between control input terminals. An element, a solar cell optically coupled to the light emitting element and capable of providing a control input for turning on the semiconductor switch element between the control input terminals, and a photocell optically inserted into both ends of the solar cell and optically coupled to the light emitting element. A diode and a semiconductor switch that is connected between both ends of the solar cell and is turned on / off by conduction / non-conduction of the photodiode and turned off while the light emitting element is on and turned on while the light emitting element is off. It is characterized by the fact that a photodiode is inserted between both ends of the solar cell and optically coupled to the light emitting element common to the solar cell, by the conduction / non-conduction of the semiconductor. Control input to between the control input of switch elements will be change, n-channel M of normally-as in the prior art when turning on the semiconductor switching element
It does not require time to turn off the OSFET, it can be turned on at high speed, and when the semiconductor switch element is turned off, the accumulated charge of the solar cell is discharged without passing through elements other than the semiconductor switch connected between both ends of the solar cell. Therefore, as compared with the conventional case where a bias resistor and a normally-on type n-channel MOSFET in which the bias resistor is connected between the gate and the source are inserted in the discharge path from the solar cell, the semiconductor switch element is Can be turned off at high speed. Therefore, the turn-on time and turn-off time of the semiconductor switch element can be shortened as compared with the conventional case.

According to a second aspect of the invention, in the first aspect of the invention, the photodiode has a cathode connected to a positive electrode terminal of the solar cell through a resistor and an anode connected to a negative electrode terminal of the solar cell. The semiconductor switch is an n-channel MOSFET having a drain terminal and a source terminal connected to the positive electrode terminal and the negative electrode terminal of the solar cell, respectively, and a gate terminal connected to the cathode of the photodiode. The semiconductor switch is a p-channel MOSFET because it is composed of a MOSFET.
The ON resistance of the semiconductor switch can be reduced without increasing the element area of the semiconductor switch occupying the semiconductor chip, as compared with the configuration described above, which is advantageous in shortening the turn-off time.

According to a third aspect of the invention, in the first aspect of the invention, the photodiode has a cathode connected to a positive electrode terminal of the solar cell and an anode connected to a negative electrode terminal of the solar cell through a resistor, Since the semiconductor switch is a p-channel MOSFET in which a source terminal and a drain terminal are connected to the positive electrode terminal and the negative electrode terminal of the solar cell, respectively, and a gate terminal is connected to the anode of the photodiode, the semiconductor switch is a p-channel MOSFET. When the solar cell is constituted by a MOSFET, and the surface of the p-type diffusion region formed on the main surface side of the n-type semiconductor substrate constitutes a light receiving surface, the solar cell and the solar cell are used. It is possible to simplify the process of integrating the semiconductor switch and the same semiconductor chip, and to reduce the cost. It attained the reduction.

According to a fourth aspect of the present invention, there is provided a semiconductor switch element drive circuit according to any one of the first to third aspects and the semiconductor switch element, wherein the semiconductor switch element has two electric fields. Between the control input terminals between the connection points of the gate terminals and the connection points of the source terminals of the effect transistor, and the drain terminals are respectively configured as main terminals, and the solar cell is connected between the control input terminals. It is possible to use, for example, a series circuit of a load and an AC power source connected between the main terminals of the semiconductor switch element, and to turn the semiconductor switch element on and off at high speed. You can

[0020]

(First Embodiment) In the present embodiment,
As shown in FIG. 1, a drive circuit for the semiconductor switch element 22 composed of an n-channel MOSFET is illustrated. In the present embodiment, the gate terminal (hereinafter abbreviated as a gate) -source terminal (hereinafter abbreviated as a source) of the n-channel MOSFET that is the semiconductor switching element 22 serves as the control input terminal, and the drain terminal (hereinafter , Abbreviated as drain) and a source respectively constitute a main terminal,
A gate voltage (gate-source voltage) applied between the gate and the source serves as a control input. Here, each main terminal is connected to the output terminals 26a and 26b, respectively.

The drive circuit in this embodiment includes a light emitting element 11 formed of a light emitting diode, a solar cell 21 optically coupled to the light emitting element 11, and a photodiode 25 optically coupled to the light emitting element 11. That is, the solar cell 21 and the photodiode 25 are the same as the light emitting element 1.
Optically coupled to 1. The solar cell 21 is capable of supplying a gate voltage (gate-source voltage) for turning on an n-channel MOSFET that constitutes the semiconductor switch element 22.

Here, the light emitting element 11 is connected through a resistor R1 between both ends of a pulse power source 12 which is a driving power source. The pulse power supply 12 is a unipolar pulse power supply that outputs a pulse voltage, and the output voltage is a light emitting element 11
It is possible to take a binary value of a first specified voltage for turning on the light emitting element and a second specified voltage (0V) for turning off the light emitting element 11, so that the light emitting element 11 can be turned on and off. .

A series circuit of a resistor R3 and the above-mentioned photodiode 25 is connected between both ends of the solar cell 21. Here, in the photodiode 25, the cathode is connected to the positive electrode terminal of the solar cell 21 via the resistor R3, and the anode is connected to the negative electrode terminal of the solar cell 21. Furthermore, a semiconductor switch n is provided between both ends of the solar cell 21.
The channel MOSFET 27a is connected. The n-channel MOSFET 27 a has a drain and a source connected to the positive electrode terminal and the negative electrode terminal of the solar cell 21, respectively, and a gate terminal connected to the cathode of the photodiode 25. That is, an n-channel M which is connected between both ends of the solar cell 21 and constitutes a semiconductor switch which is turned on / off by conduction / non-conduction of the photodiode 25.
The OSFET 27a is connected so as to be off while the light emitting element 11 is on and on when the light emitting element 11 is off. Further, the n-channel MOSFET 27a that constitutes the semiconductor switch is an n-channel MO that constitutes the semiconductor switch element 22 between the source and the drain.
The gate and source of the SFET are connected.

The operation of the drive circuit of this embodiment will be described below.

First, the operation when the semiconductor switch element 22 shifts from the off state to the on state will be described.

In the drive circuit of this embodiment, the pulse power source 1
When the pulse voltage is output from 2 (when the output voltage of the pulse power supply 12 becomes the first specified voltage), the light emitting element 11
Is turned on, the solar cell 21 generates a photovoltaic power by photoelectric conversion, and an n-channel M that constitutes the semiconductor switch element 22.
Gate-source capacitance of OSFET and solar cell 21
Charge the inter-terminal capacitance of. When the light emitting element 11 is turned on, the photodiode 25 is turned on, the gate-source voltage of the n-channel MOSFET 27a forming the semiconductor switch becomes lower than the threshold voltage, and the n-channel MOSFET 27a is turned off. No current flows through the MOSFET 27a, and all the electromotive force generated in the solar cell 21 is generated by the semiconductor switch element 2.
Since it is used to charge the gate-source capacitance of the n-channel MOSFET and the inter-terminal capacitance of the solar cell 21 that form the element 2, the semiconductor switch element 22 turns on at high speed.

Next, the operation when the n-channel MOSFET forming the semiconductor switch element 22 shifts from the on state to the off state will be described.

When the output voltage of the pulse power source 12 becomes 0V (when the output voltage of the pulse power source 12 becomes the second specified voltage), the light emitting element 11 is turned off, the photoelectric conversion of the solar cell 21 and the photoelectric conversion of the photodiode 25 are performed. Since the conversion is completed, the gate potential of the n-channel MOSFET 27a is raised to the potential of the positive terminal of the solar cell 21, the n-channel MOSFET 27a is turned on, and the n-channel MOSFET between the both ends of the solar cell 21 and the semiconductor switching element 22 is formed. N-channel MOSFET in which the charge accumulated between the gate and the source constitutes a semiconductor switch
It is rapidly discharged through the drain-source of 27a,
The semiconductor switch element 22 is turned off. At the time of this discharge, the gate voltage of the n-channel MOSFET 27a is biased by the voltage due to the accumulated charges of the solar cell 21, so that the phenomenon that the on-resistance increases due to the large discharge current does not occur (the voltage of the solar cell 21). Is larger, the on-resistance tends to be lower). Also,
A bias resistor R of the conventional type is used in the discharge path during this discharge.
Since 2 is not inserted, the semiconductor switch element 22 can be turned off at high speed.

In this embodiment, however, the solar cell 21
The light emitting element 11 that is inserted between both ends of the
When the semiconductor switch element 22 is turned on, the control input between the control input terminals of the semiconductor switch element 22 is changed depending on the conduction / non-conduction of the photodiode 25 optically coupled to the semiconductor switch element 22, as shown in FIG. It does not require time to turn off the normally-on type n-channel MOSFET 23 and can be turned on at high speed. Further, when the semiconductor switch element 22 is turned off, the accumulated charge of the solar cell 21 is connected between both ends of the solar cell 21. Since it is discharged without passing through elements other than the n-channel MOSFET 27a which is a semiconductor switch, the bias resistor R2 and the bias resistor R2 are connected normally between the gate and the source in the discharge path from the solar cell 21 as in the conventional configuration. Type n-channel MOSFET 23, compared to the case of inserting a semiconductor The switch element 22 can be turned off at high speed. In short, the turn-on time and turn-off time of the semiconductor switch element 22 can be shortened as compared with the conventional configuration.

Since the semiconductor switch connected between both ends of the solar cell 21 is composed of the n-channel MOSFET 27a, the semiconductor switch element occupies the semiconductor chip as compared with the case where the semiconductor switch is composed of the p-channel MOSFET. The ON resistance of the semiconductor switch can be reduced without increasing the area, which is advantageous for shortening the turn-off time.

(Embodiment 2) The basic structure of the drive circuit in this embodiment is substantially the same as that in Embodiment 1, and the cathode of the photodiode 25 is connected to the positive terminal of the solar cell 21 as shown in FIG. Moreover, the anode is connected to the negative electrode terminal of the solar cell 21 via the resistor R3, and the semiconductor switch connected between both ends of the solar cell 21 is configured by a p-channel MOSFET 27b. Here, the p-channel MOSFET 27b
Has a source and a drain connected to the positive terminal and the negative terminal of the solar cell 21, respectively, and a gate connected to the anode of the photodiode 25. Since other configurations are similar to those of the first embodiment, the same components as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

In the drive circuit of the present embodiment, however, as in the first embodiment, the photodiode 25 inserted between both ends of the solar cell 21 and optically coupled to the light emitting element 11 common to the solar cell 21 is electrically connected. The non-conduction changes the control input between the control input terminals of the semiconductor switch element 22, and when the semiconductor switch element 22 is turned on, the normally-on type n-channel MOSFET 23 is turned off as in the conventional configuration shown in FIG. It is a semiconductor switch in which the semiconductor switch element 22 can be turned on at high speed without requiring time for storing, and the accumulated charge of the solar cell 21 is connected between both ends of the solar cell 21 when the semiconductor switch element 22 is turned off.
Since it is discharged without passing through elements other than the channel MOSFET 27a, a normally-on type n-channel MOSFET 23 in which the bias resistor R2 and the bias resistor R2 are connected between the gate and the source in the discharge path from the solar cell 21 as in the conventional configuration. The semiconductor switch element 22 can be turned off at a higher speed than in the case where is inserted. In short, the turn-on time and turn-off time of the semiconductor switch element 22 can be shortened as compared with the conventional configuration.

In this embodiment, the semiconductor switch connected between both ends of the solar cell 21 is a p-channel MOSF.
Since it is composed of ET27b, p formed on the main surface side of the n-type semiconductor substrate as the solar cell 21.
When a solar cell in which the surface of the shape diffusion region constitutes the light receiving surface is adopted, it is possible to simplify the process of integrating the solar cell 21 and the semiconductor switch in the same chip. P channel MOSF on main surface
Since the step of introducing the p-type impurity for forming the drain region and the source region of ET and the step of introducing the p-type impurity for forming the p-type marked region of solar cell 21 can be made common. Therefore, the number of steps can be reduced and the cost can be reduced.

(Third Embodiment) In this embodiment, a semiconductor relay having the drive circuit of the first embodiment and having the structure shown in FIG. 3 is exemplified. In the present embodiment, the semiconductor switch element 22 configured by one n-channel MOSFET in the first embodiment has two n-channel MOSFEs whose gates and sources are commonly connected.
It is composed of T22a and T22b. In the present embodiment, the drains of the n-channel MOSFETs 22a and 22b form main terminals and are connected to the output terminals (relay output terminals) 26a and 26b, respectively. The n-channel MOS of each n-channel MOS
A gate voltage (gate-source voltage) applied between the gates and sources of the FETs 22a and 22b serves as a control input.

Therefore, in the semiconductor relay of this embodiment, for example, a series circuit of a load and an AC power source can be connected between the output terminals 26a and 26b connected to the main terminal of the semiconductor switch element 22 for use. The semiconductor switch element 22 can be turned on and off faster than in the conventional configuration.

In the present embodiment, the case where the drive circuit of the first embodiment is used as the drive circuit has been exemplified.
Of course, the drive circuit of the second embodiment may be used.

By the way, in each of the above-mentioned embodiments, one or two n-channel MOSF semiconductor switch elements 22 are provided.
Although the example configured by the ET has been described, it is not limited to the n-channel MOSFET, but the p-channel MOSFET, the IG
You may comprise by other semiconductor elements, such as BT.

[0038]

According to a first aspect of the present invention, there is provided a drive circuit for a semiconductor switch element which is turned on / off according to a control input provided between control input terminals, wherein the light emitting element and the control input are optically coupled to the light emitting element. A solar cell that can provide a control input to turn on the semiconductor switch element between the ends, a photodiode that is inserted between both ends of the solar cell and optically coupled to the light emitting element, and connected between both ends of the solar cell. It is equipped with a semiconductor switch that is turned on and off by conduction / non-conduction of the photodiode and turned off while the light emitting element is lit and turned on while the light emitting element is off. The control input between the control input terminals of the semiconductor switch element will change due to conduction / non-conduction of the photodiode optically coupled to the light emitting element common to the solar cell. , The normally-as in the prior art when turning on the semiconductor switching element n-channel MOS
It does not require time to turn off the FET, it can be turned on at high speed, and when the semiconductor switch element is turned off, the accumulated charge of the solar cell is discharged without passing through elements other than the semiconductor switch connected between both ends of the solar cell. Therefore, as compared with the conventional case where a bias resistor and a normally-on type n-channel MOSFET in which the bias resistor is connected between the gate and the source are inserted in the discharge path from the solar cell, the semiconductor switch element is Can be turned off at high speed. Therefore, there is an effect that the turn-on time and the turn-off time of the semiconductor switch element can be shortened as compared with the conventional case.

According to a second aspect of the invention, in the first aspect of the invention, the photodiode has a cathode connected to a positive electrode terminal of the solar cell through a resistor and an anode connected to a negative electrode terminal of the solar cell. The semiconductor switch is an n-channel MOSFET having a drain terminal and a source terminal connected to the positive electrode terminal and the negative electrode terminal of the solar cell, respectively, and a gate terminal connected to the cathode of the photodiode. The semiconductor switch is a p-channel MOSFET because it is composed of a MOSFET.
As compared with the configuration described above, the on-resistance of the semiconductor switch can be reduced without increasing the element area of the semiconductor switch in the semiconductor chip, which is advantageous in shortening the turn-off time.

According to a third aspect of the present invention, in the first aspect of the invention, the photodiode has a cathode connected to a positive electrode terminal of the solar cell and an anode connected to a negative electrode terminal of the solar cell through a resistor, Since the semiconductor switch is a p-channel MOSFET in which a source terminal and a drain terminal are connected to the positive electrode terminal and the negative electrode terminal of the solar cell, respectively, and a gate terminal is connected to the anode of the photodiode, the semiconductor switch is a p-channel MOSFET. When the solar cell is constituted by a MOSFET, and the surface of the p-type diffusion region formed on the main surface side of the n-type semiconductor substrate constitutes a light receiving surface, the solar cell and the solar cell are used. It is possible to simplify the process of integrating the semiconductor switch and the same semiconductor chip, and to reduce the cost. There is an effect that attained the reduction.

According to a fourth aspect of the present invention, there is provided a semiconductor switch element drive circuit according to any one of the first to third aspects, and the semiconductor switch element, wherein the semiconductor switch element has two electric fields. Between the control input terminals between the connection points of the gate terminals and the connection points of the source terminals of the effect transistor, and the drain terminals are respectively configured as main terminals, and the solar cell is connected between the control input terminals. It is possible to use, for example, a series circuit of a load and an AC power source connected between the main terminals of the semiconductor switch element, and to turn the semiconductor switch element on and off at high speed. There is an effect that can be.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment.

FIG. 2 is a circuit diagram showing a second embodiment.

FIG. 3 is a circuit diagram showing a third embodiment.

FIG. 4 is a circuit diagram showing a conventional example.

[Explanation of symbols]

11 Light emitting element 12 pulse power supply 21 solar cells 22 Semiconductor switch element 25 photodiode 26a, 26b output terminals 27a n-channel MOSFET R3 resistance

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 5J050 AA02 BB16 BB21 CC00 DD03                       EE02 EE17 EE34 FF04 FF10                 5J055 AX02 BX16 BX48 CX24 DX09                       DX22 DX61 DX72 EX07 EX30                       EY01 EY12 EY14 EY21 EY28                       EZ28 EZ51 GX01

Claims (4)

[Claims] 1. A drive circuit for a semiconductor switch element, which is turned on / off according to a control input applied between control input terminals, wherein a semiconductor switch element is optically coupled to the light emitting element and the light emitting element. A solar cell that can provide a control input to turn it on, a photodiode that is inserted between both ends of the solar cell and optically coupled to the light emitting element, and a photodiode that is connected between both ends of the solar cell
A semiconductor switch element drive circuit, comprising: a semiconductor switch which is turned on and off by non-conduction and turned off while the light emitting element is on and turned on while the light emitting element is off. 2. The photodiode has a cathode connected to a positive electrode terminal of the solar cell through a resistor and an anode connected to a negative electrode terminal of the solar cell, and the semiconductor switch includes a positive electrode terminal of the solar cell and 2. The drive circuit for a semiconductor switch element according to claim 1, comprising an n-channel MOSFET in which a drain terminal and a source terminal are respectively connected to a negative electrode terminal and a gate terminal is connected to a cathode of the photodiode. 3. The photodiode has a cathode connected to a positive electrode terminal of the solar cell and an anode connected to a negative electrode terminal of the solar cell through a resistor, and the semiconductor switch includes a positive electrode terminal of the solar cell and 2. The drive circuit for a semiconductor switch element according to claim 1, comprising a p-channel MOSFET in which a source terminal and a drain terminal are respectively connected to a negative electrode terminal and a gate terminal is connected to an anode of the photodiode. 4. A semiconductor switch element drive circuit according to claim 1, and the semiconductor switch element, wherein the semiconductor switch element is 2
Between the connection points of the gate terminals and the connection points of the source terminals of the two field effect transistors are the control input terminals and each drain terminal is configured as a main terminal,
A semiconductor relay, wherein the solar cell is connected between the control input terminals.