JPH0629689A - Printed circuit board - Google Patents

Abstract

PURPOSE:To prevent that a noise which creeps into a photocoupler and which causes its malfunction is added to the photocoupler when the photocoupler is mounted on a printed circuit board. CONSTITUTION:A printed pattern 5f is formed as a shielding plane near a position in which a photocoupler is mounted on a printed-circuit board 4; a printer pattern 5e which surrounds the circumference of a printer pattern 5c connected to a base terminal 11 which is not resistant to the noise of an output transistor inside the photocoupler 1 is formed as a shielding plane; both shielding planes are connected. Thereby, a noise which creeps from the outside is shielded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed circuit board on which electronic parts are mounted.

[0002]

2. Description of the Related Art A conventional technique will be described with reference to the drawings. 4 and 5
Based on Figures 2-7 and 19 on page 99 of the data book “Photocoupler” published by Toshiba Corporation, Semiconductor Business Division, Semiconductor Sales Division, the characteristic structure of the conventional technology is described below. It is a representation.

In the figure, 1 is a photocoupler, 2 is a package of the photocoupler 1, 3 is an input / output terminal of the photocoupler 1, 4 is a printed circuit board on which the photocoupler 1 is mounted, 5
Is a printed pattern wired on the printed circuit board 4, 6
Is a capacitor of an electric component mounted on the printed circuit board 4.

FIG. 6 is a diagram in which the configuration of FIG. 5 is represented by an electric circuit. In the figure, 7 is a light emitting diode on the input side of the photocoupler, 8 is an anode terminal of the light emitting diode 7, 9 is a cathode terminal of the light emitting diode 7, 10 is an output transistor of the photocoupler 1, and 11 is a base terminal of the output transistor 10. , 12 is an emitter terminal of the output transistor 10, 13 is a collector terminal of the output transistor 10, 14 is a load driven by the output transistor 10, 15
Is a power supply for supplying power to the load, and 16 is the ground of the power supply 15.

Next, the operation will be described. In FIG. 5, the signal applied to the photocoupler 1 is supplied from the anode terminal 8 to the cathode terminal 9 of the light emitting diode 7. At this time, the light emitting diode 7 emits light and the emitted light reaches the output transistor 10. A load 14 supplied with power from a power supply 15 is connected to the collector terminal 13 of the output transistor 10. Normally, when there is no light from the light emitting diode 7, the output transistor 10 is in the off state and the collector terminal 13 The potential of the power source 15
It is at the potential of. On the other hand, when the output transistor 10 is in a conductive state by receiving the light emitted from the light emitting diode 7, a current flows from the collector terminal 13 of the output transistor 10 to the emitter terminal 12, and a signal is sent to the load 14.

At this time, if noise is mixed in the base terminal 11 of the output transistor 10, a noise current flows from the base terminal 11 to the emitter terminal 12, and the output transistor 10 is temporarily turned on. At this time, this noise current is shunted to the capacitor 6 having good frequency characteristics provided between the base terminal 11 and the emitter terminal 12, and the noise current flowing from the base terminal 11 to the emitter terminal 12 is reduced to make the output transistor 10 conductive. Control.

[0007]

Output transistor 10
Noise current mixed in the base terminal 11 of the base terminal 1
When the output transistor 10 is turned on / off,
Since the rise / fall time of the current increases due to the influence of the capacitor 6, there is a drawback that the repetition frequency that can be turned on / off becomes slow. Further, the heat generated in the photocoupler 1 increases in proportion to the on / off rising / falling time, and thus there is a drawback that the reliability decreases.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a printed circuit board that shields noise from a noise source to prevent noise.

[0009]

In the printed circuit board according to the present invention, a shield plane is provided on the printed circuit board in the vicinity of the mounting position of the photo coupler by using a printed pattern. In addition, in a printed circuit board that mounts a photocoupler with a built-in output transistor, a shield plane is provided near the photocoupler mounting position on this printed circuit board using a printed pattern, and the printed pattern and shield connected to the emitter of the output transistor are shielded. Connected to the plane.

Further, in the printed board on which the photocoupler is mounted, a shield plane is provided by using the print pattern so as to surround the print pattern connected to the terminal of the photocoupler susceptible to noise. In addition, on the printed circuit board on which the photocoupler is mounted, provide a shield plane near the photocoupler mounting position on this printed circuit board using a printed pattern, and place it around the printed pattern connected to the terminals of the photocoupler susceptible to noise. A shield plane was provided using a printed pattern so as to surround it.

[0011]

[Function] The shield plane shields noise coming from the outside, and prevents noise that is mixed into terminals that are vulnerable to noise.

[0012]

EXAMPLES Example 1. FIG. 1 shows an embodiment of the present invention.
1A shows the front surface side of the printed board, FIG. 1B shows the side surface side of the printed board, and FIG. 1C shows the back surface side of the printed board. In the figure, 1 to 4 and 6 to 13 are equivalent to the conventional ones. 5a, 5b, 5c, 5d, 5e are printed patterns to be wired on the printed board 4, 17 is opened on the printed board 4, and the input / output terminal 3 of the photocoupler is inserted,
It is a through hole for soldering.

The portion to be shielded from the noise source is the base and the base terminal 11 of the output transistor 10 inside the package 2 of the photocoupler 1 and the printed pattern 5c wired from the base terminal 11. On the other hand, as a noise source, a signal from a printed wiring other than the printed pattern 5c on the printed circuit board 4, a signal input to the photocoupler 1 from the anode terminal 8 and the cathode terminal 9, and a print connected to the collector terminal 13 of the output transistor 10 There are patterns 5d and the like.

In order to shield from these noise sources, the surface of the printed board 4 on which the photocoupler 1 is mounted is opposed to the package 2 of the photocoupler 1 and is connected to the emitter terminal 12 of the output transistor 10 in the photocoupler 1. Shielding is performed by providing the printed pattern 5f that constitutes the shield plane. Further, a printed pattern 5e forming a shield plane is provided on the back surface of the printed circuit board 4 facing the photocoupler 1 so as to surround the printed pattern 5c connecting the base terminal 11 and the capacitor 6 as shown in FIG. That is, in this embodiment, the print pattern 5e and the print pattern 5f form a shield plane.

With such a configuration, the printed circuit board 4
If moisture in the air adheres to the surface of the
3 and the leak current flowing from the print pattern 5d connected to the print pattern 5c to the print pattern 5c is blocked by the print pattern 5e, and the malfunction of the output transistor 10 can be prevented.

Particularly, even when noise is introduced from the print pattern 5e connected to the emitter terminal 12 or the print pattern 5d connected to the collector terminal 13, a difference can be generated between the base potential and the emitter potential of the output transistor 10. Since it does not exist, the output transistor 10 is not accidentally turned on by noise. In the above example, the print patterns 5f and 5e are shield planes, but only the print pattern 5f may be a shield plane, or only the print pattern 5e may be a shield plane. As the shield planes 5f and 5e, either the surface on the side where the photo coupler is attached or the surface on the back side may be used.

Example 2. The second embodiment is similar to the first embodiment in that the printed pattern 5f constituting the shield plane is formed.
2 is not connected at the emitter terminal 12 of the photocoupler 1, but is connected to the ground as shown in FIGS. 2 (a) (b) (c). That is, in this embodiment, the shield plane is composed of the print pattern 5g and the print pattern 5f, and the shield plane is formed through the through hole 17
Connect with.

In this case as well, the same noise shielding effect as that of the first embodiment can be obtained, but in particular, the noise penetrating from the print pattern 5a connected to the anode terminal 8 and the print pattern 5b connected to the cathode terminal 9 of the light emitting diode 7 is obtained. , And the printed pattern 5d of the printed circuit board 4
Even if there is noise that comes in from another printed pattern (not shown) of the printed circuit board 4, it is transferred to the shield plane of the printed patterns 5g and 5f connected to the ground, so that the effect of suppressing the noise is high.

Embodiment 3 FIGS. 3 (a), (b) and (c) show an embodiment in which the photocoupler 1 has a surface mounting specification, and the print patterns 5a, 5b, 5c, 5d, 5e are printed on the surface. And the print pattern 5f is provided on the back side of the printed circuit board 4. In the case of this example, the emitter terminal 1 of the photocoupler 1 is included in the print pattern 5e that forms the shield plane.
The portion of the photocoupler 1 facing the package 2 from the connection portion with 2 prevents noise, and the base terminal 11
5e surrounding the print pattern 5c connected to
Prevents the surface leak current from entering the print pattern 5c. In addition, the print pattern 5f shields noise that enters the base terminal 11 and the print pattern 5c connected to the base terminal 11 from other portions of the printed circuit board 4.

Example 4. In Examples 1 to 3, the printed pattern of the printed circuit board 4 has two layers, the front and the back, but the printed circuit board 4 may have a multilayer structure. In this case, if the shield planes such as the print patterns 5f, 5e, and 5g are located at positions facing the photocoupler 1,
The same effect can be obtained on any surface of the multilayer substrate. For example, when the printed pattern 5f is on the surface of the printed board 4, the printed pattern 5e may be on any surface in the multilayer board.

Example 5. In this embodiment, the photo coupler 1
In the above, the output transistor 10 is used, but the same effect can be obtained by using a Darlington transistor, a MOS.FET, a thyristor, a triac, a photobolt, and an IC circuit instead of the output transistor. Also, in a photocoupler using an output transistor, the base of the output transistor is a terminal that is weak against noise, and this terminal is surrounded by a shield.However, when using an element other than the output transistor as described above,
The terminal, which is weak against noise, may be surrounded by a shield. When there are a plurality of terminals vulnerable to noise, the plurality of terminals may be surrounded by shields, or the plurality of terminals may be collectively surrounded.

Embodiment 6. In this embodiment, the photo coupler 1
Although the case where the capacitor 6 is inserted between the base terminal 11 and the emitter terminal 12 of the output transistor 10 has been described, the capacitor 6 can be changed to a small value or can be omitted by the effect of the present invention. .

[0023]

According to the present invention, since the shield plane is formed by using the print pattern of the printed circuit board,
The shield plane shields noise to prevent malfunction of the photocoupler due to noise. Also, if this printed board is used, the capacitor for noise prevention should be made smaller, or
Alternatively, since it can be omitted, the heat generated when the photocoupler is turned on and off is reduced, and the reliability is improved.

[Brief description of drawings]

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

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

FIG. 3 is a configuration diagram showing a third embodiment of the present invention.

FIG. 4 is a configuration diagram of a photocoupler.

FIG. 5 is a conventional configuration diagram.

FIG. 6 is a circuit diagram of a photo coupler.

[Explanation of symbols]

1 Photocoupler 2 Package of Photocoupler 1 3 Input / output terminal of Photocoupler 4 Printed circuit board 5a, 5b, 5c, 5d, 5e, 5f, 5g Print pattern 6 Capacitor 7 Light emitting diode 10 Output transistor 11 Base terminal 12 Emitter terminal 13 Collector terminal 17 Through hole

Claims (4)

[Claims] 1. A printed circuit board on which a photocoupler is mounted, characterized in that a shield plane is provided in the vicinity of the mounting position of the photocoupler on the printed circuit board by using a printed pattern. 2. A printed circuit board on which a photocoupler having a built-in output transistor is mounted, a shield plane is provided using a printed pattern in the vicinity of the mounting position of the photocoupler on the printed circuit board, and the shield plane is connected to the emitter of the output transistor. A printed circuit board having a printed pattern and a shield plane connected to each other. 3. A printed circuit board on which a photocoupler is mounted, wherein a shield plane is provided by using the printed pattern so as to surround the printed pattern connected to a terminal susceptible to noise of the photocoupler. Printed board. 4. In a printed circuit board on which a photo coupler is mounted, a shield plane is provided using a printed pattern in the vicinity of the mounting position of the photo coupler on the printed circuit board, and the shield plane is connected to a terminal susceptible to noise of the photo coupler. A printed circuit board, wherein another shield plane is provided by using the print pattern so as to surround the print pattern.