JP2011228339A - Optical coupler - Google Patents

Abstract

An optical coupling device in which malfunction due to electromagnetic noise is suppressed is provided.
An optical coupling device 1 is held in a first frame 11 having a signal input terminal 11t to which a first electric signal s1 is input, and a light emitting element that converts the first electric signal s1 into an optical signal. 21 and a second frame 12 having a signal output terminal 12t from which a second electric signal s2 is output are held in opposition to the light emitting element 21 and are connected to the light receiving element and the light receiving element. Including a light receiving IC 22 that receives an optical signal output from the light emitting element 21, converts the optical signal into a second electrical signal s 2, and outputs the second electric signal s 2, and the frames 11 and 12 between the light emitting element 21 and the light receiving IC 22. The light-transmitting film 50 includes at least one light-transmitting conductive layer 51 that is provided independently and is disposed so as to block between the light receiving IC 22 and the light emitting element 21.
[Selection] Figure 1

Description

  The present invention relates to an optical coupling device such as a photocoupler.

  A photocoupler is an optical coupling device that once converts an electrical signal input from a primary circuit into an optical signal, converts the optical signal into an electrical signal again, and outputs the electrical signal to a secondary circuit.

  FIG. 3 shows a configuration example of a conventional photocoupler having a basic configuration of the photocoupler described in FIG. FIG. 3 is a cross-sectional view.

The photocoupler 101 shown is
The first electric signal s1 is input from the primary side (a side), and the light emitting element 121 such as a light emitting diode (LED) that converts the input first electric signal s1 into an optical signal is separated from the light emitting element 121. A light receiving element such as a photodiode (PD) which is disposed oppositely and receives an optical signal output from the light emitting element 121, converts it into a second electric signal s2, and outputs it to the secondary side (b side). And a light receiving IC 122 mounted thereon.

  The light emitting element 121 is held by the first lead frame 111 having a signal input terminal 111t to which the first electric signal s1 is input from the primary side (a). The light receiving IC 122 is held by a second lead frame 112 having a signal output terminal 112t that outputs a second electric signal s2 on the secondary side (b side).

The light emitting element 121 and the light receiving IC 122 are electrically connected to the lead frames 111 and 112 via bonding wires 131 and 132, respectively.
A light-transmitting resin 161 is filled between the light-emitting element 121 and the light-receiving IC 122, and the outside thereof is sealed with a light-shielding resin 162. A light-transmitting insulating film 150 having a single layer structure is provided between the light emitting element 121 and the light receiving IC 122 in order to ensure insulation between the first and second orders. With such a configuration, transmission and reception of signals are realized in a state where the input side and the output side are electrically cut off and electrically insulated.

  When the input signal s1 is input from the primary side (a side), the light emitting element 121 is driven and turned on, signal transmission to the light receiving IC 122 is performed, and the output from the photocoupler 101 is inverted. When the light emitting element 121 is OFF, there is no signal transmission to the light receiving IC 122, so the output from the photocoupler 101 is not inverted.

  The photocoupler having the above configuration is an electrical isolator that transmits an electrical signal between the first and second order by optical coupling, but is an element having a stray capacitance between the first and second order. If an electrical noise is applied from the outside between the first and second order, a displacement current flows through the stray capacitance, and an output malfunction occurs.

As malfunction due to electrical noise,
Case (1) in which electrical noise is mixed from the primary side even when the light emitting element is OFF, so that the displacement current flowing from the primary side to the secondary side flows into the light receiving IC and the photocoupler output is inverted. ,as well as,
Even when the light-emitting element is ON, electrical noise is mixed from the secondary side. This causes the displacement current flowing from the secondary side to the primary side to cancel the input current to the light-receiving IC and invert the photocoupler output. There is a case (2) that does not.

Patent Document 2 discloses a light-receiving IC (28) having a grounded metal layer (22) on the main surface as a light-transmitting conductive layer (as a countermeasure against electrical noise transmitted between primary and secondary in a photocoupler. 21) is proposed (claims, FIG. 1). In such a configuration, since external electrical noise flows to the ground (GND) through the translucent conductive layer (21) and is removed, it is possible to prevent electrical noise from being input to the light receiving IC.
FIG. 3 illustrates a noise countermeasure example in which the light receiving IC 122 having the grounded metal layer 141 is covered with the light-transmitting conductive layer 142.

JP 2002-353495 A Japanese Unexamined Patent Publication No. 01-241872

However, photocouplers are affected by various noises from the environment in which they are used. For example, when exposed to electromagnetic wave noise from surrounding electronic devices, the electromagnetic wave noise is taken in through the lead and re-emitted in the photocoupler.
In the configuration of Patent Document 2, there is a certain reduction effect against electromagnetic noise. However, as a countermeasure against noise, only the grounded metal layer (22) and translucent conductive layer (21) are provided on the main surface of the light receiving IC. Therefore, electromagnetic noise is transmitted. Particularly in recent years, with the increase in the speed of photocouplers, the influence of this electromagnetic noise has become ignorable, and further reduction is required.

The optical coupling device of the present invention is
A light-emitting element that is held in a first frame having a signal input terminal to which a first electric signal is input and that converts the first electric signal into an optical signal;
A second frame having a signal output terminal from which a second electrical signal is output; and a light receiving element and an electric circuit connected to the light receiving element. A light receiving IC (integrated circuit) that receives the output optical signal, converts the optical signal into the second electrical signal, and outputs the second electrical signal;
At least one layer provided between the light emitting element and the light receiving IC independently from the first frame and the second frame, and arranged to block between the light receiving element and the light emitting element. And a translucent film having a translucent conductive layer.

  In the optical coupling device of the present invention configured as described above, electromagnetic wave noise can be effectively removed by the light-transmitting conductive layer in the light-transmitting film provided between the light emitting element and the light receiving IC, and malfunction caused by electromagnetic wave noise Can be suppressed.

  According to the present invention, it is possible to provide an optical coupling device that can remove electromagnetic wave noise at a higher level than before, suppress malfunction due to electromagnetic wave noise, and is excellent in signal transmission reliability.

1 is an overall cross-sectional view of a photocoupler (optical coupling device) according to an embodiment of the present invention. It is sectional drawing and a top view of the translucent film (noise removal film) with which the photocoupler of FIG. 1 was equipped. It is a whole sectional view of the conventional photocoupler.

  A configuration of a photocoupler (optical coupling device) according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an overall cross-sectional view of the photocoupler of this embodiment. FIG. 2 is a cross-sectional view and a plan view of a translucent film (noise removal film) provided in the photocoupler of this embodiment. In order to facilitate visual recognition on the drawings, the scale and position of each member are appropriately different from the actual ones. In the cross-sectional view, hatching is omitted as appropriate.

As shown in FIG.
The photocoupler 1 of this embodiment is
A light-emitting element 21 such as a light-emitting diode (LED) that receives the first electric signal s1 from the primary side (a-side) and converts the input first electric signal s1 into an optical signal;
It includes a light receiving element such as a photodiode (PD) and an electric circuit connected to the light receiving element, receives an optical signal output from the light emitting element 21, converts it into a second electric signal s2, and converts it into a secondary circuit side ( a light receiving IC 22 for outputting to the b side). The light receiving IC 22 is mounted with an electric circuit for amplifying an electric signal from the light receiving element.

The light emitting element 21 is held on the holding surface 11a of the first lead frame 11 including the signal input terminal 11t to which the first electric signal s1 is input from the primary side (a side). The light receiving IC 22 is held on the holding surface 12a of the second lead frame 12 having a signal output terminal 12t for outputting the second electric signal s2 on the secondary side (b side).
The holding surface 11a of the first lead frame 11 and the holding surface 12a of the second lead frame 12 are spaced apart from each other. As a result, the light emitting element 21 and the light receiving IC 22 are spaced apart from each other.
The light emitting element 21 and the light receiving IC 22 are electrically connected to the lead frames 11 and 12 via bonding wires 31 and 32, respectively.

A light-transmitting resin 61 such as an epoxy resin having a predetermined dielectric constant is filled between the light emitting element 21 and the light receiving IC 22, and the outside thereof is sealed with a light shielding resin 62 such as an epoxy resin. With such a configuration, transmission and reception of signals are realized in a state where the input side and the output side are electrically cut off and electrically insulated.
The translucent resin 61 only needs to have a light transmittance necessary for transmitting an optical signal from the light emitting element 21 to the light receiving IC 22.

In the present embodiment, a noise removal film 40 that covers the main surface of the light receiving IC 22 is provided for the purpose of removing electrical noise from the outside. The noise removal film 40 is formed of a laminated body in which a metal layer 41 and a translucent conductive layer 42 that are grounded from the light receiving IC 22 side are sequentially laminated. A plurality of metal layers 41 and / or translucent conductive layers 42 forming the noise removal film 40 may be provided.
The composition of the metal layer 41 is not particularly limited, and examples thereof include Al.
The composition of the translucent conductive layer 42 is not particularly limited, and polysilicon or the like is preferable in consideration of conductivity and translucency.
The translucent conductive layer 42 needs to have a light transmittance necessary for transmitting an optical signal from the light emitting element 21 to the light receiving IC 22.

In the present embodiment, a translucent film (noise removal film) 50 is further provided between the light emitting element 21 and the light receiving IC 22 in order to increase noise resistance. The translucent film 50 is provided independently of these members at positions separated from the lead frames 11 and 12 and the light emitting element 21 and the light receiving IC 22.
The translucent film 50 is provided so as to be electrically insulated from the lead frame 11 on the primary side and the lead frame 12 on the secondary side, and is in an electrically floating state. The translucent film 50 is disposed so as to block between the light emitting element 21 and the light receiving IC 22.
As shown in the drawing, the translucent film 50 preferably projects so as to block between the holding surface 11a of the primary lead frame and the holding surface 12a of the secondary lead frame. That is, it is preferable that the translucent film 50 is disposed so as to block an area where the primary-side lead frame 11 and the secondary-side lead frame 12 face each other.

In the present embodiment, the translucent film 50 is a three-layer laminated film including a single translucent conductive layer 51 and a pair of insulating layers 52 sandwiching the translucent conductive layer 51 as shown in FIG.
Although the said aspect is preferable, the translucent film 50 should just contain the at least 1 layer of translucent conductive layer 51, and the at least 1 layer of translucent conductive layer 51, the at least 1 layer of insulating layer 52, and A laminated film of at least one light-transmitting conductive layer 51 and a pair of insulating layers 52 sandwiching at least one light-transmitting conductive layer 51 is particularly preferable.

  In the translucent film 50 made of a laminated film with a pair of insulating layers 52 sandwiching at least one translucent conductive layer 51, the outermost layer is made of an insulating layer. High insulation is secured between the secondary side and this is preferable. Note that in a laminated film of a plurality of light-transmitting conductive layers 51 and a pair of insulating layers 52 sandwiching the plurality of light-transmitting conductive layers 51, an insulating layer is interposed between the plurality of light-transmitting conductive layers 51. 52 may be provided.

  Further, as shown in FIG. 2, the area of the light-transmitting conductive layer 51 is preferably smaller than the area of the insulating layer 52. In such a configuration, since the translucent conductive layer 51 is not exposed at the side end face of the translucent film 50, the translucent film 50 ensures high insulation between the primary side and the secondary side, which is preferable. .

The composition of the translucent conductive layer 51 is not particularly limited, and ITO (indium tin oxide), ZnO, and the like are preferable in order to effectively remove electromagnetic wave noise and ensure sufficient translucency.
The composition of the insulating layer 52 is not particularly limited, and a polyimide resin or the like is preferable in order to have high insulating properties and ensure sufficient translucency.
The composition and thickness of each layer are designed so that the translucent film 50 as a whole has a light transmittance necessary for transmitting an optical signal from the light emitting element 21 to the light receiving IC 22.

In the present embodiment, the electromagnetic wave noise that enters from the outside via the lead frame can be effectively removed by the translucent film (noise removal film) 50. With reference to FIG.1 and FIG.2, the noise removal mechanism by the noise removal film 50 is demonstrated.
When electromagnetic wave noise N is mixed from the primary side (a side), the electromagnetic wave N passes through the insulating layer 52 of the translucent film 50 and enters the translucent conductive layer 51 and is trapped. When the electromagnetic wave noise N enters the translucent conductive layer 51, a magnetic field is generated in the translucent conductive layer 51 in a direction to cancel the electromagnetic wave noise N by electromagnetic induction, thereby canceling the electromagnetic wave noise N. Further, a counterclockwise eddy current I is generated in the translucent conductive layer 51 by electromagnetic induction. Since the translucent conductive layer 51 itself has a resistance value, the generated eddy current I is released to the outside as heat. By this mechanism, the electromagnetic wave noise N does not propagate to the light receiving IC 22, and malfunction of the light receiving IC 22 is suppressed. The normal operation of the photocoupler 1 becomes possible.
The electromagnetic noise N mixed from the secondary side (b side) can also be removed by the same mechanism.

In the present embodiment, the translucent film 50 is provided at a position separated from the light emitting element 21 and the light receiving IC 22 so as to block between the light emitting element 21 and the light receiving IC 22. Electromagnetic wave noise is prevented from being transmitted through.
In the present embodiment, since the holding surface 11a of the lead frame 11 on the primary side and the holding surface 12a of the lead frame 12 on the secondary side can be arranged so as to block each other, electromagnetic waves can be compared with the conventional case. The shielding effect is high against noise.
Further, as in the present embodiment, a noise removal film 40 that covers the main surface of the light receiving IC 22 that removes electrical noise can be used in combination, which has an effect of reducing various noises.

  As described above, according to the present embodiment, the photocoupler 1 (optical coupling device) that can remove the electromagnetic noise that enters the photocoupler from the environment at a higher level than the prior art and has excellent signal transmission reliability is provided. can do.

1 Photocoupler (Optical coupling device)
11 First lead frame (first frame)
11t signal input terminal 12 second lead frame (second frame)
12t signal output terminal 21 light emitting element 22 light receiving IC
40 Noise removal film 41 Metal layer 42 Translucent conductive layer 50 Translucent film (noise removal film)
51 translucent conductive layer 52 insulating layer N electromagnetic wave noise s1 first electric signal s2 second electric signal

Claims (6)

A light-emitting element that is held in a first frame having a signal input terminal to which a first electric signal is input and that converts the first electric signal into an optical signal;
A second frame having a signal output terminal from which a second electrical signal is output; and a light receiving element and an electric circuit connected to the light receiving element. A light receiving IC (integrated circuit) that receives the output optical signal, converts the optical signal into the second electrical signal, and outputs the second electrical signal;
At least one layer provided between the light emitting element and the light receiving IC independently from the first frame and the second frame, and arranged to block between the light receiving element and the light emitting element. An optical coupling device comprising: a translucent film having a translucent conductive layer.   2. The translucent film is disposed so as to block between a holding surface of the first frame that holds the light emitting element and a holding surface of the second frame that holds the light receiving element. The optical coupling device according to 1.   The optical coupling device according to claim 1, wherein the translucent film is a laminated film of at least one translucent conductive layer and at least one insulating layer.   4. The optical coupling according to claim 3, wherein the translucent film is a laminated film of at least one translucent conductive layer and a pair of insulating layers sandwiching the at least one translucent conductive layer. apparatus.   The translucent film has a structure in which an area of the translucent conductive layer is smaller than an area of the insulating layer, and the translucent conductive layer is not exposed on a side end surface of the translucent film. The optical coupling device as described.   The optical coupling device according to claim 1, wherein a main surface of the light receiving IC is covered with at least one grounded metal layer.

Images