JPH1126806A - Photo coupler type semiconductor relay - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photo coupler type semiconductor relay which never increases the output terminal capacitance at the time of the relay off. SOLUTION: A relay comprises a solar cell 1 to be a photo detector on a GND terminal frame 4 and LDMOSFETs 2, 3 each having an ISO structure on floating frames 5a, 5b electrically independent of the external potential in a resin package 8. The anodes 1a, 1b of the cell 1 are electrically connected to the gate electrodes 2a, 3a of the LDMOSFETs 2, 3 through bonding wires 6; a cathode 1c of the cell 1 and source electrodes 2b, 3b of the LDMOSFETs 2, 3 are electrically connected to the GND frame 4 through bonding wires 6, and the drain electrodes 2c, 3c of the LDMOSFETs 2, 3 are electrically connected to output terminal frames 7a, 7b through bonding wires 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting device and a light receiving device which are optically coupled to each other.
The present invention relates to an optically coupled semiconductor relay that causes a switching operation to be performed.

[0002]

2. Description of the Related Art As shown in FIG.
A photo-MOS relay using an ET as an output MOSFET is such that a solar cell 1 as a light receiving element is disposed on a GND terminal frame 4 and output terminal frames arranged side by side on both sides of the GND terminal frame 4. Vertical MOSF on the memory 7a, 7b
ETs 9 and 10 are provided.

[0003] As shown in FIG. 3, a light emitting diode 11 as a light emitting element is provided on an input terminal frame 12 arranged opposite to the GND terminal frame 4, and a solar cell is provided. 1 and the vertical MOSFETs 9, 1
The gate electrodes 9a and 10a of the solar cell 1 are electrically connected by bonding wires 6, respectively, and the cathode 1c of the solar cell 1 and the source electrodes 9 of the vertical MOSFETs 9 and 10 are connected.
b and 10b are electrically connected to the GND terminal frame 4 by bonding wires 6.

An opaque resin package 8 is formed as a whole.
To form a package, and optically couples the solar cell 1 and the light emitting diode 11 by a light guide path made of a transparent silicon resin 13, and receives light from the light emitting diode 11 as a light receiving element. The solar cell 1 can receive light.

[0005] The photo mosley relay constructed as described above.
The light emitting diode 11 emits light by an external drive signal, and the solar cell 1 receiving the light from the light emitting diode 11 generates a voltage. When the voltage reaches a certain level, the output vertical MOSFET 9 is turned on. , 10 are switched, and the photo MOS relay is turned on or off.

In the above-mentioned photo mosley relay, a load is applied between the output terminal frames 7a and 7b, and one of the output terminal frames 7a and 7b is connected to GND.
When a load is applied between the terminal frame 4 and the terminal frame 4, it can be selectively used for AC current application and DC current application.

Incidentally, in such a photomos relay, the capacitance between the output terminals of the relay is an important characteristic related to the insulation characteristics when the relay is off. The capacitance between output terminals is
Determined by the characteristics of the output MOSFET, the smaller the capacitance between the output terminals, the greater the high-frequency insulation of the relay.

In recent years, a vertical MOSFET has been used as an output MOSFET for the purpose of reducing the output capacitance at the time of relay-off.
Instead of 9 and 10, SOI (Silicon on Insulato)
r) Lateral double diffusion MOS field effect transistor having a structure, so-called LDMOSFET (Lateral Double D)
iffused MOSFET).

This is because the output capacitance of the MOSFET is a drain-source capacitance Cds, a gate-drain capacitance Cgd.
The LDMOSFET having the SOI structure is compared with the vertical MOSFET in that the drain-source capacitance Cds
Is significantly reduced.

As shown in FIG. 4, L having an SOI structure
In a photo-MOS relay using DMOSFETs 2 and 3 as output MOSFETs, a solar cell 1 which is a light receiving element is disposed on a GND terminal frame 4 in the same manner as when vertical MOSFETs 9 and 10 are used as output MOSFETs.
LDMOSFETs 2 and 3 are arranged on output terminal frames 7a and 7b arranged on both sides of the GND terminal frame 4, respectively. Then, the anodes 1a and 1b of the solar cell 1
And the gate electrodes 2a and 3a of the LDMOSFETs 2 and 3 are electrically connected by bonding wires 6, respectively.
A few source electrodes 2b and 3b are electrically connected to a GND terminal frame 4 by bonding wires 6,
The drain electrodes 2c and 3c of the DMOSFETs 2 and 3 are electrically connected to output terminal frames 7a and 7b by bonding wires 6.

[0011]

However, the LDMOSFETs 2 and 3 having the SOI structure are replaced with output MOSFETs.
When the output MOSFET is provided on the output terminal frames 7a and 7b, there arises a problem that the capacitance between the output terminals at the time of relay-off is increased.

That is, in the LDMOSFETs 2 and 3, the capacitance between the output terminals when the relay is turned off is usually the sum of the capacitance Cds between the drain and the source and the capacitance Cgd between the gate and the drain, as shown in FIG. When the potential of the output terminal frames 7a, 7b rises in such a mounting state, as shown in FIG.
Rises to the potential of the drain, the buried oxide film 14b
A capacitance Cgsub between the gate and the supporting substrate and a capacitance Cssub between the source and the supporting substrate are generated through the gate.

As a result, as shown in FIG. 6, a normal drain-source capacitance Cds and a gate-drain capacitance Cgd are obtained.
In addition, since the capacitance Cgsub between the gate and the supporting substrate and the capacitance Cssub between the source and the supporting substrate are superposed in parallel, the capacitance between the output terminals is increased.

The present invention has been made in view of the above points, and an object of the present invention is to provide an optically coupled semiconductor relay which does not cause an increase in capacitance between output terminals when the relay is turned off. To provide.

[0015]

According to the first aspect of the present invention,
A light-emitting element that emits light in response to a signal on the input side, a light-receiving element that generates a photovoltaic power by receiving an optical signal from the light-emitting element, and an output that is turned on / off in response to the photovoltaic power of the light-receiving element In an optical coupling type semiconductor relay comprising a switching element,
LDMOS having SOI structure as output switching element
Using an FET, the light receiving element is disposed on a GND terminal frame, the LDMOSFET is disposed in an electrically floating state on a floating frame that does not depend on an external potential, and the light receiving element is anodized. And the LDMOSFET
Are electrically connected to each other, and the cathode of the light receiving element and the source electrode of the LDMOSFET are connected to the G electrode.
The LDMOS is electrically connected to an ND terminal frame.
The drain electrode of the FET is electrically connected to the output terminal frame.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic plan view showing a mounted state of a photo MOSFET using LDMOSFETs 2 and 3 having an SOI structure as output MOSFETs according to an embodiment of the present invention. In the photo-MOS relay according to the present embodiment, a solar cell 1 as a light receiving element is disposed on a GND terminal frame 4 and housed in a resin package 8 so that the solar cell 1 is in a floating state that does not depend on an external potential electrically. L having an SOI structure is provided on the floating frames 5a and 5b.
DMOSFETs 2 and 3 are provided.

The anodes 1a and 1b of the solar cell 1 are electrically connected to the gate electrodes 2a and 3a of the LDMOSFETs 2 and 3 by bonding wires 6, and the cathode 1c and the LDMOSFET 2 of the solar cell 1 are connected. 3 is connected to the source electrode 2b, 3b by the bonding wire 6.
LDMOSFET electrically connected to terminal frame 4
A few drain electrodes 2c and 3c are output terminal frames 7
a and 7b are electrically connected by bonding wires 6, respectively.

Therefore, in this embodiment, the LDMO
The source electrodes 2b, 3b of the SFETs 2, 3 are connected to the GND terminal frame 4 without passing through the floating frames 5a, 5b.
Connected to the floating frame 5a,
5b does not depend on the external potential or the potentials of the source electrodes 2b and 3b of the LDMOSFETs 2 and 3. For this reason, LD
No parasitic capacitance component is generated due to the support substrates of the MOSFETs 2 and 3, and the capacitance between the output terminals is reduced.

In this embodiment, since the source electrodes 2b and 3b of the LDMOSFETs 2 and 3 and the cathode 1c of the solar cell 1 are connected via the GND terminal frame 4, the output is In addition to the use of alternating current for applying a load between the terminal frames 7a and 7b, the output terminal frame 7
It can also be used for direct current application in which a load is applied between a, 7b and the GND terminal frame 4.

In this embodiment, the LDMOS
N-type MOSFET as shown in FIG.
However, the present invention is not limited to this.
An FET may be used.

Further, in this embodiment, the LDMOSFETs 2 and 3 having the SOI structure are used as the output switching elements. However, the present invention is not limited to this, and JFETs, IGBTs, UMOSFETs, and bipolars having the SOI structure are used.
Transistor, or an LDMOSFET, JFET, IGBT, UMOSF formed on an epi-substrate.
ET may be used, and LDM formed on bulk substrate
OSFET, JFET, IGBT, UMOSFET may be used.

[0022]

According to the first aspect of the present invention, there is provided a light emitting element which emits light in response to a signal on the input side, a light receiving element which generates a photoelectromotive force by receiving an optical signal from the light emitting element, and a light receiving element for receiving light. In an optically coupled semiconductor relay comprising an output switching element which is turned on / off in response to an electromotive force, S
An LDMOSFET having an OI structure is used. The light receiving element is disposed on a GND terminal frame. The LDMOSFET is disposed in an electrically floating state on a floating frame which does not depend on an external potential. Anode and LDM
The gate electrode of the OSFET is electrically connected, and the cathode of the light receiving element and the source electrode of the LDMOSFET are GN.
LDMOSFET electrically connected to the D terminal frame
Since the drain electrode is electrically connected to the output terminal frame, no parasitic capacitance component due to the supporting substrate of the LDMOSFET is generated, and the capacitance between the output terminals at the time of relay off does not increase. An optically coupled semiconductor relay can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic plan view showing a mounted state of a photo MOSFET using an LDMOSFET having an SOI structure according to an embodiment of the present invention as an output MOSFET.

FIG. 2 shows a conventional vertical MOSFET connected to an output MOS.
FIG. 5 is a schematic plan view showing a mounted state of a photomoss relay used as an FET.

FIG. 3 is a schematic configuration diagram of a photo mosley relay according to a conventional example.

FIG. 4 shows a conventional LDMOSF having an SOI structure.
FIG. 11 is a schematic plan view showing a mounting state of a photo-mosley relay using ET as an output MOSFET.

FIG. 5 shows a conventional photo MOS relay LDMOSF.
It is a schematic sectional drawing of ET.

FIG. 6 is a photoMOS relay LDMOSF according to a conventional example.
It is an equivalent circuit diagram of the capacitance between output terminals of ET.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Solar cell 1a, 1b Anode 1c Cathode 2, 3 LDMOSFET 2a, 3a Gate electrode 2b, 3b Source electrode 2c, 3c Drain electrode 4 GND terminal frame 5a, 5b Floating frame 6 Bonding wire 7a, 7b Output terminal frame 8 Resin package 9, 10 Vertical MOSFET 9a, 10a Gate electrode 9b, 10b Source electrode 11 Light emitting diode 12 Input terminal frame 13 Silicon Resin 14a Support substrate 14b Buried oxide film 14c SOI layer 15 p-type well region 16 n + -type drain region 17 n + -type source region

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshiki Hayasaki 1048 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Works, Ltd. (72) Inventor Takashi Kishida 1048 Kazuma Kadoma, Kadoma City, Osaka Prefecture Inside Matsushita Electric Works Co., Ltd. (72) Inventor Takeshi Yoshida 1048 Kadoma Kadoma, Kadoma City, Osaka Prefecture Inside Matsushita Electric Works, Ltd.

Claims (1)

[Claims] 1. A light-emitting element that emits light in response to a signal on an input side, a light-receiving element that generates a photoelectromotive force by receiving an optical signal from the light-emitting element, and In an optically coupled semiconductor relay comprising an ON / OFF switching element, an LDMOSFET having an SOI structure is used as the output switching element, and the light receiving element is disposed on a GND terminal frame, and the LDMOSFET is electrically operated. A floating state, which is disposed on a floating frame which does not depend on an external potential, and is connected to the anode of the light receiving element and the LD.
The gate electrode of the MOSFET is electrically connected, the cathode of the light receiving element and the source electrode of the LDMOSFET are electrically connected to the GND terminal frame, and the drain electrode of the LDMOSFET is output. An optically coupled semiconductor relay, which is electrically connected to a terminal frame.