JP2002050953A - Semiconductor relay - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect an output MOSFET against overcurrent and make the output MOSFET to conduct without fail when an input signal is input. SOLUTION: This device has a light emitting element 1 which emits optical signal according to input signals, a light receiving element 2 which generates a photovoltaic force based on the optical signal from the light emitting element 1, an output MOSFET 3 which is energized by the application of the photovoltaic force, an output control circuit 30 which controls the gate charge of the output MOSFET 3, an overvoltage detecting MOSFET 7 in which a gate is connected to a drain of the output MOSFET 3, a weak electromotive force feeding means 50 which feeds a weak electromotive force weaker than that of the light receiving element 2 based on the optical signal from the light emitting element 1, a weak electromotive force drive MOSFET 7 which is connected along with the overvoltage detecting MOSFET 6 between the gate and the source of the output MOSFET 3 and is energized by the weak electromotive force of the weak electromotive force feeding means 50, and a weak electromotive force driving control circuit 40 which controls the gate charge of the drive MOSFET 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor relay having an overcurrent protection function.

[0002]

2. Description of the Related Art FIG. 7 shows a conventional semiconductor relay of this type. The light emitting diode 101 emits an optical signal in response to an input signal, the photodiode array 102 generates a photovoltaic power based on the optical signal of the light emitting diode 101, and the photovoltaic power is applied to a gate source. Output M that conducts between drain and source
An OSFET 103, a control circuit 104 whose impedance changes so as to control charging / discharging of the gate charge of the output MOSFET 103, a gate connected to the drain of the output MOSFET 103, and an output MOSFET between the drain and source.
The ET 103 includes an enhancement type overvoltage detection MOSFET 105 connected between the gate and the source of the ET 103.

The control circuit 104 includes a control resistor 104 connected in series with the photodiode array 102.
and a depletion-type control MOSFET 104b having a gate and a source connected to both ends of a and a control resistor 104a and a drain and a source connected to the photodiode array 102.

Next, the operation will be described. Light emitting diode 1
When 01 emits an optical signal according to the input signal, the photodiode array 102 receives the optical signal of the light emitting diode 101 and generates a photoelectromotive force. With this photovoltaic,
An electric charge is charged between the gate and source of the output MOSFET 103, and a current flows between the drain and source of the control MOSFET 104b through the control resistor 104a. Thus, when a current flows through the control resistor 104a,
A potential difference is generated between both ends of the control resistor 104a, and the potential difference changes the low impedance to the high impedance between the drain and the source of the control MOSFET 104b.

Thus, the control MOSFET 104b
When the impedance between the drain and the source changes from low impedance to high impedance, the output MOSFET 10
3, the charge is efficiently charged between the gate and the source, and the drain-source of the output MOSFET 103 conducts.

When the input signal is not input to the light emitting diode 101 and the light emitting diode 101 stops emitting light, the photodiode array 102 does not generate photovoltaic power. Then, no potential difference occurs between both ends of the control resistor 104a, and the control MOSFET 104b
Changes from high impedance to low impedance between the drain and the source of the control MOSFET 10.
4b, the current is quickly discharged through the control resistor 104a, and the drain-source of the output MOSFET 103 conducts.

When an overcurrent flows through the output MOSFET 103 while the output MOSFET 103 is in a conductive state, the drain potential of the output MOSFET 103 increases due to the overcurrent. Then, the output MOSFET
103 for overvoltage detection with a gate connected to the drain of 103
The gate potential of the OSFET 105 rises, the impedance between the drain and source of the overvoltage detection MOSFET 105 becomes low, and the charge charged between the gate and source of the output MOSFET 103 is discharged.
The connection between the drain and the source of the FET 103 is cut off.

[0008]

In the above-described conventional semiconductor relay, even if an overcurrent flows through the output MOSFET 103, the output MOSF caused by the overcurrent flows.
The rise in the drain potential of the ET 103 changes the impedance between the drain and the source of the overvoltage detection MOSFET 105 to a low impedance, and discharges the charge between the gate and the source of the output MOSFET 103 to discharge between the drain and the source of the output MOSFET 103. , The output MOSFET 103 can be protected from overcurrent.

However, the output MOSFET 103
Output MO when the drain-source connection is cut off
The drain potential of the SFET 103 is high,
Therefore, since the impedance between the drain and the source of the overvoltage detecting MOSFET 105, that is, between the gate and the source of the output MOSFET 103 is low, an input signal is input between the input terminals and the photodiode generates electromotive force in this state. However, due to this electromotive force, the output MO
Electric charges may not be sufficiently charged between the gate and the source of the SFET 103, and the output MOSFET 103 may not easily change to the conductive state.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object thereof is to protect an output MOSFET from an overcurrent and to surely output an output signal when an input signal is input. It is an object of the present invention to provide a semiconductor relay in which a power MOSFET conducts.

[0011]

According to a first aspect of the present invention, there is provided a semiconductor relay which emits an optical signal in response to an input signal, and a light emitting element which emits an optical signal based on the optical signal of the light emitting element. A light-receiving element that generates an electromotive force, an output MOSFET that conducts between the drain and source when the photoelectromotive force is applied to the gate and source, and an output control circuit that controls charging and discharging of the gate charge of the output MOSFET. An enhancement type overvoltage detection MOSFET having a gate connected to the drain of the output MOSFET, weak electromotive force supply means for supplying a weak electromotive force weaker than the light receiving element based on an optical signal of the light emitting element, and an overvoltage detection MOSFET And a series circuit connected between the gate and the source of the output MOSFET to form a circuit by applying the weak electromotive force of the weak electromotive force supply means. And upbeat power driving MOSFET to,
And a weak electromotive force drive control circuit that controls charging and discharging of the gate charge of the weak electromotive force drive MOSFET.

[0012] The semiconductor relay according to the second aspect is the first aspect.
In the semiconductor relay described above, the weak electromotive force supply means is configured to include a photodiode array that generates a weak electromotive force as the weak electromotive force than the light receiving element.

According to a third aspect of the present invention, there is provided a semiconductor relay.
In the semiconductor relay described above, the photodiode array is configured to be arranged farther from the light emitting element than the light receiving element.

According to a fourth aspect of the present invention, there is provided a semiconductor relay according to the second aspect.
In the semiconductor relay described above, the photodiode array has a configuration in which a light receiving portion of the optical signal is smaller than the light receiving element.

According to a fifth aspect of the present invention, there is provided a semiconductor relay.
In the semiconductor relay described above, the photodiode array has a configuration in which an impurity concentration of a semiconductor diffusion region forming a light receiving portion of the optical signal is lower than that of the light receiving element.

According to a sixth aspect of the present invention, there is provided a semiconductor relay.
In the semiconductor relay described above, the photodiode array has a configuration in which the depth of a silicon single crystal having a semiconductor diffusion region forming a light receiving portion of the optical signal is smaller than that of the light receiving element.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A semiconductor relay according to a first embodiment of the present invention will be described below with reference to FIG.

Reference numeral 1 denotes a light emitting diode (light emitting element) which emits an optical signal according to an input signal inputted between the input terminals 20a and 20b. Reference numeral 2 denotes a photodiode array (light receiving element), which includes a plurality of photodiodes 2a connected in series, receives an optical signal from the light emitting diode 1, and generates a photoelectromotive force.

Reference numeral 3 denotes an output MOSFET 3 in an enhancement mode, the gate of which is connected to the anode of the photodiode array 2 and the drain of which is the output terminal 2.
0c, and the source is connected to the cathode of the photodiode array 2 via an output control resistor 4 described later, and to the output terminal 20d.

An output control resistor 4 has one end connected to the cathode of the photodiode array 2 and the output control MOSF.
The other end is connected to the gate of ET5, and the other end is MOSF for output control.
Source of ET5, MOSFET 6 for overvoltage detection described later
And the source of the output MOSFET 3.

Reference numeral 5 denotes an output control MOSFET which is in a depletion mode. The source of the MOSFET 5 is connected to the other end of the output control resistor 4 as described above, and is connected to the sources of the output MOSFET 3 and the overvoltage detection MOSFET 6. The drain is connected to the anode of the photodiode array 2, the drain of a weak electromotive force driving MOSFET 7 described later, and the gate of the output MOSFET 3. The output control MOSFET 5, together with the output control resistor 4, constitutes an output control circuit 30 that controls charging and discharging of a charge (gate charge) between the gate and the source of the output MOSFET 3.

Reference numeral 6 denotes an overvoltage detection MOSFET, which is an enhancement mode, the source of which is connected to the other end of the output control resistor 4 as described above, and the source of the output MOSFET 3 and the output control MOSFET 5. Connected, drain is weak electromotive force drive MOSFET
7 is connected to the source and the gate is the output MOSFET 3
Connected to the drain of

Reference numeral 7 denotes a weak electromotive force driving MOSFET in an enhancement mode, the source of which is connected to a power source 10 to be described later via a weak electromotive force driving control resistor 8 to be described later, and the drain of which is a photodiode array. 2, the drain of the output control MOSFET 5, and the gate of the output MOSFET 3, and the gate is connected to a photoconductive element 10 and a weak electromotive force drive control MOSFET described later.
9 is connected to the drain. This weak electromotive force drive MO
The threshold value of the SFET 7 is set to be equal to or higher than the threshold value of the output MOSFET 3.

Reference numeral 8 denotes a weak electromotive force drive control resistor, one end of which is connected to the power supply 11 and the gate of the weak electromotive force drive MOSFET 9 which will be described later, and the other end of which is the weak electromotive force drive MOSFET 7.
And the drain of the MOSFET 6 for overvoltage detection.

Reference numeral 9 denotes a weak electromotive force drive control MOSFET.
In the depletion mode, the source is connected to the other end of the weak electromotive force drive control resistor 8 and the connection point between the source of the weak electromotive force drive MOSFET 7 and the drain of the overvoltage detection MOSFET 6 as described above. The drain is connected to the photoconductive element 10 and the gate of the weak electromotive force drive control MOSFET 9. The weak electromotive force drive control MOSFET 9 includes a weak electromotive force drive control resistor 8 and a weak electromotive force drive control circuit that controls charging / discharging of a charge (gate charge) between the gate and the source of the weak electromotive force drive control MOSFET 9. 40.

Reference numeral 10 denotes a photoconductive element, which is formed of, for example, a phototransistor, which receives an optical signal from the light emitting diode 1 and conducts.

Reference numeral 11 denotes a power supply, which is a photodiode array 2
And a weak electromotive force that is weaker than that of the photoconductive element 10.

Next, the operation will be described. Light emitting diode 1
Emits an optical signal according to the input signal, the photodiode array 2 receives the optical signal of the light emitting diode 1 and generates a photovoltaic voltage. With this photovoltaic power, the output MOS
An electric charge is charged between the gate and the source of the FET 3 and the output control MOSFET 4 passes through the output control resistor 4.
5, a current flows between the drain and the source. When a current flows through the output control resistor 4 in this manner, a potential difference is generated between both ends of the output control resistor 4, and the potential difference causes the output control M
The impedance between the drain and the source of the OSFET 5 changes from low impedance to high impedance.

As described above, when the impedance between the drain and the source of the output control MOSFET 5 changes from low impedance to high impedance, the charge is efficiently charged between the gate and source of the output MOSFET 3,
The conduction between the drain and the source of the output MOSFET 3 is conducted.

On the other hand, the photoconductive element 10 conducts when the light emitting diode 1 receives an optical signal emitted according to an input signal, and a weak electromotive force weaker than the electromotive force of the photodiode array 2 is generated from the power supply 11. Supplied. With this weak electromotive force, electric charges are charged between the gate and source of the weak electromotive force drive MOSFET 7, and a current flows between the drain and source of the weak electromotive force drive control MOSFET 9 through the weak electromotive force drive control resistor 8. When a current flows through the weak electromotive force drive control resistor 8 in this manner, a potential difference is generated at both ends of the weak electromotive force drive control resistor 8, and the potential difference causes
The impedance between the drain and the source of the weak electromotive force drive control MOSFET 9 changes from low impedance to high impedance.

As described above, the weak electromotive force drive control MOSF
When the impedance between the drain and the source of ET9 changes from low impedance to high impedance, the weak electromotive force driving MO
The electric charge is efficiently charged between the gate and the source of the SFET 7, and the conduction between the drain and the source of the weak electromotive force driving MOSFET 7 is achieved.

However, since the aforementioned weak electromotive force is weaker than the electromotive force generated by the photodiode array 2, the output M is applied between the drain and source of the weak electromotive force driving MOSFET 7.
The conduction will be delayed later than the OSFET 3. Therefore, the overvoltage detection MOSFET 6 and the weak electromotive force drive MO
The flow of current through the series circuit composed of the SFET 7 is delayed.

When no input signal is input to the light emitting diode 1 and the light emitting diode 1 stops emitting light, the photodiode array 2 stops generating photovoltaic power. Then, no potential difference is generated between both ends of the output control resistor 4, the potential between the drain and the source of the output control MOSFET 5 changes from a high impedance to a low impedance, and the charge charged between the gate and the source of the output MOSFET 3 is output. The discharge is quickly performed between the drain and source of the control MOSFET 5 and through the output control resistor 4, and the drain and source of the output MOSFET 3 are cut off.

On the other hand, the photoconductive element 10 is cut off when the input signal is not input to the light emitting diode 1 and the light emitting diode 1 stops emitting light, so that the weak electromotive force is not supplied from the power supply 11. Then, no potential difference occurs between both ends of the weak electromotive force drive control resistor 8, the drain-source of the weak electromotive force drive control MOSFET 9 changes from high impedance to low impedance, and the gate-source of the weak electromotive force drive MOSFET 7 changes. Is discharged quickly through the drain-source of the weak electromotive force drive control MOSFET 9 and through the weak electromotive force drive control resistor 8, and the drain-source of the weak electromotive force drive MOSFET 7 is cut off.

When an overcurrent flows through the output MOSFET 3 when the output MOSFET 3 is conducting,
The drain potential of the output MOSFET 3 rises due to the overcurrent. Then, the gate potential of the overvoltage detection MOSFET whose gate is connected to the drain of the output MOSFET 3 rises, the impedance between the drain and the source of the overvoltage detection MOSFET 6 becomes low, and the low impedance overvoltage detection MOSFET 6 becomes low. Then, the electric charge charged between the gate and the source of the output MOSFET 3 is discharged through the series circuit of the weak electromotive force driving MOSFET 7 already conducting with the output MOSFET 3 with a delay. Become blocked.

In such a semiconductor relay, the output M
If an overcurrent flows while the OSFET 3 is conducting, the output M
Since the drain potential of the OSFET 3 increases, the output M
The overvoltage detection MOSFET 6 whose gate is connected to the drain of the OSFET 3 conducts, and the output MOSFET 3
Is discharged through a series circuit composed of the MOSFET 6 for overvoltage detection and the MOSFET 7 for weak electromotive force, so that the output MOSFET 3 does not conduct,
The output MOSFET 3 can be protected from overcurrent.

In addition, at the time of input of an input signal, even if the drain potential of the output MOSFET 3 which has not been turned on is high, a weak electromotive force weaker than the photoelectromotive force of the photodiode array 2 is applied. For this reason, the weak electromotive force drive MOSFET 7 conducts later than the output MOSFET 3, so that current flows through a series circuit composed of the overvoltage detection MOSFET 6 and the weak electromotive force MOSFET 7, so that the overvoltage detection MOSFET 6 and the weak By the time the current flows through the series circuit composed of the electromotive force driving MOSFET 7, the gate charge is reliably charged in the output MOSFET 3, and the output MOSFET 3 can be reliably turned on.

Next, a semiconductor relay according to a second embodiment of the present invention will be described below with reference to FIGS. Elements that are substantially the same as those of the semiconductor relay of the first embodiment are denoted by the same reference numerals, and only those parts that differ from the semiconductor relay of the first embodiment are described. In the semiconductor relay of the first embodiment, the weak electromotive force supply means 50 includes the photoconductive element 10 and the power supply 11 connected in series to the photoconductive element 10. In the semiconductor relay of the present embodiment, the photodiode 12a is Photoelectrode array 1 for weak electromotive force connected in series
2 is constituted.

This weak electromotive force photodiode array 1
As shown in FIG. 3, the semiconductor relay chip 60 is disposed diagonally opposite to the light emitting diode 1 as compared with the photodiode array 2 disposed opposite to the light emitting diode 1 in the semiconductor relay chip 60. As a result, the photodiode array 2 Than the light emitting diode 1, so that
A photoelectromotive force weaker than the photoelectromotive force of the photodiode array 2 is generated and supplied as a weak electromotive force.

In such a semiconductor relay, the weak electromotive force supply means 50 including the weak electromotive force photodiode array 12 for generating a weak electromotive force as compared with the photodiode array 2 is based on an optical signal. The required number of elements can be reduced as compared with the semiconductor relay according to the first embodiment, which includes the photoconductive element 10 that conducts and the power supply 11 connected in series to the photoconductive element 10.

Further, since the photodiode array 12 for weak electromotive force is disposed farther from the light emitting diode 1 than the photodiode array 2, the photoelectromotive force generated by the photodiode array 12 for weak electromotive force can be easily reduced. , A weak electromotive force weaker than the photoelectromotive force of the photodiode array 2.

Next, a semiconductor relay according to a third embodiment of the present invention will be described below with reference to FIG. Elements that are substantially the same as those of the semiconductor relay of the second embodiment are denoted by the same reference numerals, and only those parts that differ from the semiconductor relay of the second embodiment will be described. In the semiconductor relay according to the second embodiment, the weak electromotive force supply means 50 includes the weak electromotive force photodiode array 12.
Is arranged farther away from the light emitting diode 1 than the photodiode array 2, whereas in the semiconductor relay of the present embodiment, the weak electromotive force supply means 50 is a photodiode array for weak electromotive force. Reference numeral 12 is configured by making the light receiving portion of the optical signal smaller than the photodiode array 2.

The semiconductor diffusion region (first conductivity type semiconductor region) 2c provided on the silicon single crystal 2b so as to form the light receiving portion of the photodiode array 2 forms the light receiving portion of the photodiode array 12 for weak electromotive force. The semiconductor diffusion region (first region) provided in the silicon single crystal 12b
It is smaller than the conductive semiconductor region 12c. In FIG. 4, reference numerals 2d and 12d denote second conductivity type semiconductor regions. In FIG. 4, 2e and 12e are aluminum wiring portions.

In such a semiconductor relay, similarly to the semiconductor relay of the second embodiment, the number of necessary elements can be reduced as compared with the semiconductor relay of the first embodiment.

Further, by making the light receiving portion of the light signal in the photodiode array 12 for weak electromotive force smaller than the light receiving portion of the light signal in the photodiode array 2, the photodiode array 12 for weak electromotive force is generated. The photoelectromotive force is easily set to a weak electromotive force weaker than the photoelectromotive force of the photodiode array 2.

Next, a semiconductor relay according to a fourth embodiment of the present invention will be described below with reference to FIG. Elements that are substantially the same as those of the semiconductor relay of the second embodiment are denoted by the same reference numerals, and only those parts that differ from the semiconductor relay of the second embodiment will be described. In the semiconductor relay according to the second embodiment, the weak electromotive force supply means 50 includes the weak electromotive force photodiode array 12.
Is arranged farther away from the light emitting diode 1 than the photodiode array 2, whereas in the semiconductor relay of the present embodiment, the weak electromotive force supply means 50 is a photodiode array for weak electromotive force. Twelve semiconductor diffusion regions 12c are formed by lowering the impurity concentration than the semiconductor diffusion regions 2c of the photodiode array 2.

In such a semiconductor relay, similarly to the semiconductor relay of the second embodiment, the number of necessary elements can be reduced as compared with the semiconductor relay of the first embodiment.

The semiconductor diffusion region 1 serving as a light receiving portion of an optical signal in the photodiode array 12 for weak electromotive force.
By making the impurity concentration of 2c smaller than the impurity concentration of the semiconductor diffusion region 2c forming the light receiving portion of the optical signal in the photodiode array 2, the photovoltaic power generated by the photodiode array 12 for weak electromotive force can be easily reduced. , A weak electromotive force weaker than the photoelectromotive force of the photodiode array 2.

Next, a semiconductor relay according to a fifth embodiment of the present invention will be described below with reference to FIG. Elements that are substantially the same as those of the semiconductor relay of the second embodiment are denoted by the same reference numerals, and only those parts that differ from the semiconductor relay of the second embodiment will be described. In the semiconductor relay according to the second embodiment, the weak electromotive force supply means 50 includes the weak electromotive force photodiode array 12.
Is arranged farther away from the light emitting diode 1 than the photodiode array 2, whereas in the semiconductor relay of the present embodiment, the weak electromotive force supply means 50 is a photodiode array for weak electromotive force. 12 is a silicon single crystal 12 having a semiconductor diffusion region 12c forming a light receiving portion 12b of an optical signal more than the photodiode array 2.
It is constituted by making the depth of d shallow.

In such a semiconductor relay, similarly to the semiconductor relay of the second embodiment, the number of necessary elements can be reduced as compared with the semiconductor relay of the first embodiment.

The semiconductor diffusion region 1 serving as a light receiving portion of the optical signal in the photodiode array 12 for weak electromotive force.
By making the depth of the silicon single crystal 12b having 2c smaller than the depth of the silicon single crystal 2b having the semiconductor diffusion region 2c forming the light receiving portion of the optical signal in the photodiode array 2, the photo for weak electromotive force is obtained. The photoelectromotive force generated by the diode array 12 can be easily set to a weak electromotive force weaker than that of the photodiode array 2.

In the first to fourth embodiments, the output control circuit 30 includes the output control MOSFET 5 and the output control resistor 4, but the present invention is not limited to this.

In the first to fourth embodiments, the weak electromotive force drive control circuit 40 includes the weak electromotive force drive control MOSFET 9 and the weak electromotive force drive control resistor 8, but is not limited thereto. Absent.

[0054]

According to the first aspect of the present invention, when an overcurrent flows during conduction of the output MOSFET, the output M
Since the drain potential of the OSFET increases, the output MO
The MOSFET for overvoltage detection whose gate is connected to the drain of the SFET conducts, and the gate charge of the MOSFET for output is reduced by the MOSFET for overvoltage detection and the weak electromotive force drive M.
Since it is discharged through a series circuit composed of OSFET,
The output MOSFET stops conducting and the output MOSF
ET can be protected from overcurrent. In addition, when input signals are input, the output MOSFET is not yet conductive.
Even if the drain potential of the light-emitting element is high, since the weak electromotive force weaker than the photoelectromotive force of the light receiving element is applied, the conduction occurs later than the output MOSFET. Since the flow of the current in the series circuit composed of the power drive MOSFET is delayed, the gate charge is reliably charged in the output MOSFET until the current flows in the series circuit, and the output MOSFET can be reliably made conductive.

The semiconductor relay according to the second aspect is the first aspect.
In addition to the effects of the semiconductor relay described above, the weak electromotive force supply means, which is a photodiode that generates a weak electromotive force as a weak electromotive force than the light receiving element, includes a photoconductive element that conducts based on an optical signal, and the photoconductive element. The number of necessary elements can be reduced as compared with the case where the power supply is connected in series to the power supply.

The semiconductor relay according to the third aspect is the second aspect.
In addition to the effect of the semiconductor relay described above, the photodiode array is disposed farther from the light emitting element than the light receiving element. Weak electromotive force can be obtained.

The semiconductor relay according to the fourth aspect is the second aspect.
In addition to the effect of the semiconductor relay described, by making the light receiving portion of the optical signal in the photodiode array smaller than the light receiving portion of the optical signal in the light receiving element, the photovoltaic power generated by the photodiode array can be easily reduced. The weak electromotive force can be made weaker than the photoelectromotive force of the light receiving element.

The semiconductor relay according to the fifth aspect is the second aspect.
In addition to the effect of the semiconductor relay described above, the impurity concentration of the semiconductor diffusion region forming the light receiving portion of the optical signal of the photodiode array is made lower than the impurity concentration of the semiconductor diffusion region forming the light receiving portion of the optical signal of the light receiving element. Accordingly, the photoelectromotive force generated by the photodiode can be easily set to a weak electromotive force weaker than that of the light receiving element.

The semiconductor relay according to the sixth aspect is the second aspect.
In addition to the effect of the semiconductor relay described, the depth of the silicon single crystal having the semiconductor diffusion region forming the light receiving portion of the optical signal in the photodiode array is increased by the semiconductor diffusion region forming the light receiving portion of the optical signal in the light receiving element. By making the depth smaller than the depth of the silicon single crystal, the photoelectromotive force generated by the photodiode can be easily set to a weak electromotive force weaker than that of the light receiving element.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a first embodiment of the present invention.

FIG. 2 is a circuit diagram of a second embodiment of the present invention.

FIG. 3 is a perspective view showing a photodiode for weak electromotive force and a positional relationship between the photodiode and a light emitting diode according to the first embodiment;

FIG. 4 is a plan view showing a photodiode for weak electromotive force and a light receiving portion of the photodiode according to a third embodiment of the present invention.

FIG. 5 is a cross-sectional view showing a photodiode for weak electromotive force according to a fourth embodiment of the present invention and an impurity concentration of a semiconductor region forming a light receiving portion of the photodiode.

FIG. 6 is a cross-sectional view showing the depth of a silicon single crystal region having a photodiode for weak electromotive force and a semiconductor region forming a light receiving portion of the photodiode according to a fifth embodiment of the present invention.

FIG. 7 is a circuit diagram of a conventional example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 light emitting diode (light emitting element) 2 photodiode array (light receiving element) 3 output MOSFET 6 overvoltage detection MOSFET 7 weak electromotive force drive MOSFET 12 weak electromotive force photodiode array 12 b silicon single crystal 12 c semiconductor diffusion region 30 output control Circuit 40 Weak electromotive force drive control circuit 50 Weak electromotive force supply means

Claims (6)

[Claims] 1. A light emitting element that emits an optical signal in response to an input signal, a light receiving element that generates a photovoltaic power based on an optical signal of the light emitting element, and a drain when the photovoltaic power is applied to a gate source. Output MOSFE that conducts between sources
T, an output control circuit for controlling charging and discharging of the gate charge of the output MOSFET, an enhancement type overvoltage detection MOSFET having a gate connected to the drain of the output MOSFET, and light receiving based on a light signal of the light emitting element. Weak electromotive force supply means for supplying a weak electromotive force weaker than the element,
Output MOSFET together with overvoltage detection MOSFET
A weak electromotive force drive MOSFET that forms a series circuit connected between the gate and the source of the weak electromotive force and that conducts when the weak electromotive force of the weak electromotive force supply means is applied;
A weak electromotive force driving control circuit for controlling charging and discharging of the gate charge of the semiconductor relay. 2. The semiconductor relay according to claim 1, wherein said weak electromotive force supply means comprises a photodiode array that generates an electromotive force weaker than said light receiving element as said weak electromotive force. 3. The semiconductor relay according to claim 2, wherein said photodiode array is disposed farther from said light emitting element than said light receiving element. 4. The semiconductor relay according to claim 2, wherein said photodiode array has a light receiving portion of said optical signal smaller than said light receiving element. 5. The semiconductor relay according to claim 2, wherein said photodiode array has a lower impurity concentration in a semiconductor diffusion region forming a light receiving portion of said optical signal than said light receiving element. 6. The semiconductor relay according to claim 2, wherein said photodiode array is formed such that a silicon single crystal having a semiconductor diffusion region forming a light receiving portion of said optical signal is made shallower than said light receiving element.