Radiant energy – Photocells; circuits and apparatus – Signal isolator
Reexamination Certificate
2001-04-19
2004-07-06
Luu, Thanh X. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Signal isolator
C257S082000
Reexamination Certificate
active
06759667
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a photocoupling device which comprises an input section having a plurality of light emitting elements and lead terminals for supplying a drive current to these light emitting elements and an output section having a light receiving element opposed to light emitting faces of the light emitting elements and lead terminals for supplying a drive current to the light receiving element, and relates to a method of manufacturing the same.
2. Description of the Related Art
In recent years, it has become important to make equipment energy-saving. With regard to photocoupling devices, a photocoupling device of low input current driving type which can be directly driven by a microcomputer is expected to be mainstream as a photocoupling device from now. For example, in the case where it becomes possible to directly drive a photocoupling device by a microcomputer, the need for a transistor of a drive stage is eliminated. Especially, a plurality of photocoupling devices are needed in an interface section of FA (factory automation) equipment since a plurality of signals are inputted and outputted therein. Therefore, by using a low-input-driving photocoupler, effects of energy saving are increased. Moreover, it is also possible to downsize a current limiting resistor of a light emitting element, so that costs can be reduced.
Consequently, as equipment with a microcomputer becomes widespread, such equipment has been advanced, and a market of photocoupling devices has expanded. Therefore, a demand of developing a photocoupling device of low input current driving type which meets an energy-saving design has grown.
For example, in a microcomputer drive circuit such as a programming console, a conventional general-purpose photocoupling device (for example, a photocoupling device driven at a forward current IF (referred to as IF hereinafter) of 5 mA) is controlled by a microcomputer via a transistor of a drive stage. By using a photocoupling device of low input current driving type (for example, a photocoupling device driven at IF of 0.5 mA) instead of the general-purpose photocoupling device, the circuit can be directly driven by the microcomputer, the current can be reduced to one tenth, and the need of the transistor for the drive stage is eliminated. As a result, costs can be reduced.
In addition, in general household electrical appliances (for example, motor-controlled household electrical appliances such as an air conditioner, a microwave oven and a washer), a photocoupling device is used as an AC (alternating current) line zero cross point detecting device. The device is used for judgment whether frequency is 50 Hz or 60 Hz, detection of an instantaneous shutdown, detection of an AC zero cross point, timer count and so on. A current limiting resistor is inserted to directly drive a light emitting element of a photocoupling device with an AC power source. In this case, in a conventional general-purpose photocoupling device, a voltage of the AC power source is high when an input current is set to IF=5 mArms, so that a current limiting resistor of 20 k&OHgr;/2W (which costs approximately 3 yen) is needed and power consumption reaches 500 mW. In the case where a photocoupling device of low input current driving type is used instead of the general-purpose photocoupling device, an input current can be limited to IF=0.5 mArms, so that it is enough to apply a current limiting resistor of 200 k&OHgr;/0.25W (which is 1 yen or less), and power consumption is lowered to 50 mW. Accordingly, it is possible to achieve both cost reduction and energy saving.
As mentioned above, a variety of advantages can be obtained by making a photocoupling device drive at a low input current.
Next, a structure of a conventional photocoupling device of low input current driving type will be described referring to drawings.
FIG. 10
is a longitudinal sectional view showing an example of a conventional photocoupling device of low input current driving type,
FIG. 11
is a transverse sectional view showing an example of the conventional photocoupling device of low input current driving type, and
FIG. 12
is an explanatory view showing an example of a connection of the photocoupling device shown in
FIGS. 10 and 11
. Here,
FIG. 11
mainly shows an input section.
The photocoupling device comprises an input section having a light emitting element
101
and an output section having a light receiving element
102
opposed to a light emitting face of the light emitting element
101
.
The light emitting element
101
is die-bonded on a header
109
a
which is connected to one lead terminal
103
a
for the light emitting element, and further wire-bonded via a wire
105
on a header
109
b
which is connected to the other lead terminal
103
b
for the light emitting element. An exposed face of the light emitting element
101
is covered with a protecting resin layer
104
(shown in
FIG. 10
only) which is formed by pre-coating with a transparent silicone resin.
On the other hand, the light receiving element
102
is die-bonded on a header
119
a
which is connected to one lead terminal
113
a
for the light receiving element, and further wire-bonded via a wire
115
on a header
119
b
which is connected to the other lead terminal
113
b
for the light receiving element.
Furthermore, the light emitting element
101
and the light receiving element
102
are covered with a first epoxy resin member
107
which is formed by primary molding with a light-transmitting epoxy resin, in a state where the light emitting face and the light receiving face are opposed to each other. This first epoxy resin member
107
is covered with a second epoxy resin member
106
which is formed by secondary molding with a light proof resin.
This photocoupling device has a 4-pin package (two pins on the input section side and two pins on the output section side).
In this example, a phototransistor is used as the light receiving element
102
. As the light emitting element
101
, a high-intensity light emitting element of GaAlAs or the like is used so as to drive with a low input current using a single light emitting element. By using the high-intensity light emitting element, not only the amount of light at a low current range is ensured but also sensitivity of the light receiving element is increased, thereby realizing a drive at a low input current. However, a high-intensity light emitting element of GaAlAs or the like is expensive, which costs at least three times more than a general-purpose light emitting element of GaAs or the like.
Next, a photocoupling device equipped with a plurality of elements will be explained referring to drawings.
FIG. 13
is a transverse sectional view showing another example of a structure of a conventional photocoupling device of low input current driving type. Here,
FIG. 13
mainly shows an input section.
In general, as the number of elements increases, the number of headers
109
c
for mounting the elements and headers
109
d
for wire-bonding increases. In addition, along with the lead terminals
103
a
,
103
b
,
113
a
and
113
b
, lead terminals
103
c
,
103
d
,
113
c
and
113
d
are disposed. As compared with a 4-pin photocoupling device as shown in
FIGS. 10 and 11
, the above photocoupling device has a large package of 6-pin or 8-pin.
This photocoupling device is manufactured, in the same manner as a 4-pin photocoupling device as shown in
FIGS. 10 and 11
, through the steps of: mounting a light receiving element (not shown), a light emitting element
101
and another element
111
on specified headers
109
a
and
109
c
and connecting to lead terminals
103
a
,
103
c
and
113
a
; wire-bonding the light receiving element, the light emitting element
101
and the other element
111
on specified headers
109
b
,
109
d
and so on with wires
125
a
,
125
b
and so on and connecting to lead terminals
103
b
,
103
d
and
113
b
; and if necessary, pre-coating and so on. After that, lead frames on the input sectio
Birch & Stewart Kolasch & Birch, LLP
Luu Thanh X.
Sharp Kabushiki Kaisha
Sohn Seung C
LandOfFree
Photocoupling device and method of manufacturing the same does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Photocoupling device and method of manufacturing the same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Photocoupling device and method of manufacturing the same will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3241039