JP2850701B2 - Connection method between electronic devices - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single grounding system in which a structural grounding system (FG) and a circuit grounding system (SG) are separated and provided with grounding terminals FG and SG and individually provided with noise shielding measures. The present invention relates to a method for connecting electronic devices, in which a plurality of operable electronic devices are connected by a cable, and the influence of electrostatic discharge noise and noise generated by the devices on other devices is suppressed.

[0002]

2. Description of the Related Art FIG. 4 shows an example of a conventional device connection.
(a) is a ground connection diagram of the individual devices, (b) is a connection diagram between the devices, FIG. 5 is a diagram showing the influence of internally generated noise in a conventional example of connection between devices, and FIG. FIG. 7 is a diagram showing the influence of internally generated noise in another conventional example of connection between devices.
FIG. 8 shows a connection diagram between other devices of the related art.

Conventional electronic devices individually take measures against electromagnetic noise, and are generally provided with a ground connection as shown in FIG. The basic configuration of the electronic device is composed of a main circuit component (CCT) 7, a power supply unit (PWR) 8, and a power input filter (FIL) that removes noise entering from a power supply 9. Also, some devices do not need power supply.) If you take measures against electromagnetic noise, the grounding system of the main circuit
(SG) is separated from the structural grounding system (FG) such as the housing and frame, and the two are connected at a location that is effective for countermeasures. Ground side power supply (CC
T7 is connected to the ground terminal FG with a low impedance, and is a wiring electrically floating from the input terminal G of the ground-side power supply through the FIL9 to the inside of the PWR8.

The input or output of the main circuit is a high-frequency, high-speed signal circuit when electromagnetic noise countermeasures are required.
An unbalanced shielded cable composed of an unbalanced circuit is used. A cable having a conductor 21 on the chip T side and an outer conductor 22 indicated by a dotted line in FIG. It is 29, and a coaxial cable is generally used. Here, the outer conductor 22 is not grounded at the input / output section of the device.

[0005] The dash-dot notation in the figure indicates the area of the device as well as the structural shielding enclosure. However, it is common practice to house a plurality of such individually noise-reduced devices in a housing and interconnect them to further configure a system. One example of this is shown in FIG.

In this case, the ground side SG of the circuit system is electrostatically connected to the ground terminal FG, so that capacitive coupling between the housing and the circuit is prevented. Does not affect other devices.

However, as shown in FIG. 5, noise generated inside the device indicated by oblique lines also flows to the circuit ground SG.
This flows into the structural ground FG connected internally, and also flows to the outer conductor 22 of the connecting cable 29, and eventually to the ground FG between other devices and the cable 29. A loop is formed on the R side of the main circuit via the external conductor 22, and the generated noise is shunted and flows also to the R side of the main circuit inside another device, affecting other devices. Will affect you. There is also a problem that the reverse case is the same, and that they affect each other.

Next, generally adopted countermeasures will be described in order, and problems will be listed. In order to eliminate the influence of the internally generated noise, the connection shown in FIG. 6 is performed, that is, one of the connection devices is used as a master unit 6 for distinction.
(a) is left as it is, and it is a slave unit 61 for distinction from other devices. In this slave unit 61, the ground side power supply (C
In the CT7, which is connected to the SG system) is grounded to the ground terminal FG, but is opened or connected with a high resistance. As a result, the loop on the R side of the main circuit is disconnected, and noise generated inside the master unit 6 does not affect the slave unit 61. However, on the contrary, the noise generated inside the slave unit 61 is internally
Due to the capacitive coupling between the circuits, the current flows from the SG side to the FG as well, and leads to the master unit 6 through the ground connection of the FG. It returns to the child device 61 via the outer conductor 22 of 29 to form a loop, and the child device 61 affects the parent device 6.

As a countermeasure, the connection method shown in FIG. 7 is used. This is because, in addition to the connection shown in FIG. 6, the magnetic body 3 of the annular ferrite core is loosely fitted to the cable 29 of the main circuit connection between the master unit 6 and the slave unit 61 near the entrance 62 of the device. I have.

In this example, the loop formed on the R side of the main circuit is cut with a high inductance by fitting the magnetic material 3, but as shown in FIG. As shown in FIG. 8, the noise generated on the slave unit 61 side has an influence directly or indirectly on the circuit on the master unit 6 side.

Either method can be said to be defenseless against radiation due to noise flowing through the outer conductor 22 of the cable 29.

[0012]

As described above, as enumerated in the above-mentioned conventional example, the electrostatic noise caused by external induction and the radiated noise generated by one device affect other devices. This has no effect on noise flowing around the outer conductor 22 of the interconnecting cable 29.

The present invention has been made in view of the above problems, and has as its object to provide a method of connecting devices that can suppress the effects of noise caused by external induction and radiation noise generated inside other devices.

[0014]

Means for Solving the Problems As shown in FIG. 1, the object is to separate the ground terminals FG and SG by separating a structural ground system (FG) and a circuit ground system (SG). Connect a plurality of individually operable electronic devices with noise shielding measures individually,
A connection method between electronic devices for suppressing the influence of electrostatic discharge noise and noise generated by a device on other devices, wherein the ground terminal FG, SG of one of a group of electronic devices to be connected and a base unit 1
Are connected to each other, and further grounded, and the connection between the ground terminals FG and SG of the other device and the slave unit 11 and the ground connection are not performed, and the T-side conductor 21 is connected to the R-side external conductor 22 for the connection. The cable 2 is an unbalanced type that is enclosed and the outer conductor 22 is covered with a shielded conductor 23.
In the vicinity, the outer conductor 22 and the shielded conductor 23 are connected, and the outer conductor 22 is surrounded by the magnetic body 3 on the inner side of the connection position between the outer conductor 22 and the shielded conductor 23 in the master unit 1, Outer conductor 22
This is achieved by the method for connecting electronic devices according to the present invention, which increases the inductance of the electronic device to a predetermined value. [2] In the cable 2, the outer conductor 22 and the shield conductor 23 are insulated by the insulating layer 4 having a high dielectric constant.
It is also suitable according to the connection method between the electronic devices described above.

[0015]

In other words, the connection is made as shown in FIG. 1 (a), and when the slave unit 11 receives an induced noise from the outside, it flows as shown by the arrow,
It flows to the main unit 1 through the connected cable 2 and reaches the ground through the FG grounding.
It flows through 23 and hardly penetrates into the outer conductor 22 of the inner layer, and therefore has no effect.

Conversely, when the base unit 1 receives the induction noise, although not shown, the base unit 1 is directly grounded from the FG ground, and
Has no effect. Also, noise generated inside the slave unit 11 indicated by oblique lines causes noise current to flow to the R side of the main circuit as shown by the arrow in FIG. After flowing through the outer conductor 22 and arriving at the master unit 1, the magnetic material 3 provided inside the entrance 12 of the master unit 1 causes CC to function.
It cannot reach T7, and is grounded via FG grounding,
Alternatively, a path is formed to pass through the shielded conductor 23 outside the cable 2 and return to the slave unit 11.
It flows outside the shielding conductor 23 and inside the shielding conductor 23 and hardly affects the conductor 21.

Conversely, the noise generated inside the main unit 1
The effect on the cable 11 is to flow on the R side of the main circuit and try to communicate with the outer conductor 22 on the cable 2 side.
And flows to the housing or the like by connection with the FG ground at the output end of the PWR 8 and flows to the shield conductor 23 outside the cable 2 at the entrance 12. This flows into the slave unit 11, but flows to the FG grounding side of the housing and the like, and the C side flows to the R side of the main circuit.
Since the connection to the FG ground is cut off at the output terminal of the PWR 8 through the CT 7, the PWR 8 does not flow and does not affect the main circuit section CCT 7 of the slave unit 11. However, the flow to the FG ground at the entrance / exit 12 is transmitted via the outer conductor 22 inside the cable 2 to the master unit 1.
Back to the entrance 12 of the
Flows outside the shield conductor 23 and has little effect on the conductor 21.

Thus, according to the present invention, it is possible to provide a method of connecting devices that can suppress the effects of noise caused by external induction and radiation noise generated inside other devices.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the embodiments shown in the drawings. The same reference numerals indicate the same objects throughout the drawings. 2A and 2B show an embodiment of the present invention. FIG. 2A is a diagram showing the configuration of the device, FIG. 2B is a diagram showing an enlarged configuration of the entrance and exit of the device, and FIG.

This embodiment is applied to a multiplex conversion unit in an optical transmission system. As shown in FIG. 2, a plurality of shelves 51 are overlapped on an apparatus housing 5, and each shelf 51 has a plurality of shelves. The plurality of printed boards 52 are plug-in connected by a connector 53 and mounted side by side.

Here, a printed circuit board 52 constitutes a small circuit, a plurality of such circuits are combined to constitute a circuit device for each shelf 51, and a plurality of circuit devices are interconnected to constitute a system device. ing.

The printed board 52 constitutes a circuit by mounting circuit components on a printed wiring board, the input / output main circuit is an unbalanced circuit of 75Ω, and the SG ground circuit on the R side is insulated from the structural ground FG. is there. The two side edges are slid into the guide rails of the shelf 51 and inserted, and the external connection is made by the connector 53 provided at the rear.
Accordingly, the connector is plugged in and mounted on the connector 54 provided on the shelf 51.

The shelf 51 is in the form of a metal box with an open front, and guide rails for inserting and guiding the printed board 52 are arranged on the upper and lower surfaces so as to face each other at predetermined intervals, and further provided with ventilation holes for air cooling. On the rear surface, a connector 54 is provided corresponding to the mounting position of the printed board 52.

The connection between the plurality of printed boards 52 mounted in the shelf 51 is made by wiring and connecting the terminals of the connector 54 at the corresponding positions of the shelf 51. In this case, coaxial lines are used for interconnection of the main circuit, and the outer conductor on the R side is insulated from the structural ground FG of the shelf 51. Further, the shelf 51 itself is electrically insulated and fixed from the apparatus housing 5, and the shelves 51 are naturally insulated from each other.

A plurality of shelves 51 constituting a circuit device are connected in a star or tandem main circuit in the device housing 5 to constitute a system device. When connecting the devices, it is necessary to connect the shelves 51 as shown in FIG. 1A so as not to affect each other.

FIG. 2 (a) shows an example in which three units are connected in tandem. The uppermost shelf 51 is the master unit 1, the other shelves 51 are all slave units 11, and the coaxial cable 2 is used. Connect the main circuit.

The power supply to each of the shelves 51 is not connected to the ground, but is connected to the power supply of the apparatus housing 5 without being grounded. For grounding, a structural ground FG such as a housing or a frame is connected to the outside with the device housing 5, and the internal shelf 51 is individually designated for FG.
The ground connection is made to the device housing 5. In this case, only the shelf 51 of the master unit 1 is connected to the device housing 5 by the grounding metal 55.
It is fixed between 51 and connected to low impedance. Furthermore,
Inside the printed board 52 at the connection end of the base unit 1, the connector 53
The wiring on the ground potential side at the output terminal of the power supply circuit drawn out from the connector is connected to the structure of the shelf 51 from the terminal on the connector 54 side to the FG ground connection. In the other slave units 11, the above FG
No ground connection is made.

The connection of the main circuit uses a coaxial cable 2 shown in FIG. In this cable 2, the conductor 21 on the center side of 0.2 mmφ is coaxially insulated with Teflon resin (trade name), and the outer conductor 22 is formed with a copper thin wire braid that wraps coaxially to obtain a characteristic impedance of 75Ω. The insulating layer 4 is formed by thinly insulating coating with a nylon resin, and is further surrounded by a shielding conductor 23 made of a braided copper wire, and the upper portion is again covered with a nylon resin to form a protective insulating jacket 41.

At the entrance and exit 12 of the cable 2 of each shelf 51, it is necessary to connect the outer conductor 22 and the shielded conductor 23 of this cable 2 together to the structural part of the shelf 51 by FG grounding. An example of this connection is shown in an enlarged view of FIG.

That is, a flat fixing metal member 58 is conductively fixed at the position of the entrance 12 at the rear edge of the shelf 51, and both sides are screwed and fixed thereto. The protective insulation jacket 41 of the cable 2 and the shield conductor 23 thereunder are cut off from the tip to this position, and the shield conductor 23 is exposed to a length exceeding the length of the clamp 59. Then, the portion of the insulating layer 4 thereunder that overlaps the exposed shielding conductor 23 is peeled off, the exposed shielding conductor 23 is placed on a fixing bracket 58, and a curved portion is put thereon, and a fastening bracket 59 is screwed. Then, the cable 2 is pressed and fixed to the fixing bracket 58. Thereby, the outer conductor 22 and the shielding conductor 23
And the fixing bracket 58 are electrically connected to establish FG ground connection.

Further, the figure shows the case of the entrance 12 of the master unit 1. A magnetic material 3 of a two-part annular ferrite core of 25 mm × 30 mm is loosely fitted to the insulating layer 4 inside the entrance 12, and the cable 2 The tip is connected to the coaxial terminal 57 of the connector 54.

Of course, there is no loose fitting of the magnetic body 3 in the other slaves 11. The above embodiment shows an example of the connection, and the specific structure, shape, size, and material of each part are not limited to those described above.

[0033]

As described above, according to the embodiment of the present invention, all the connected devices affect the static noise and the noise generated from inside the device to the circuit in the housing of another device. And the double braid of the outer conductor and the shielded conductor of the cable complement each other with the opening of the stitch, so that the radiation noise caused by the cable can be suppressed.

In addition, the existing frame balanced type cable is not simply double-covered with a shielded conductor, but is provided with an insulating layer made of an insulating material having a high dielectric constant, thereby assisting the return of noise and further improving the effect. It is possible to demonstrate.

Thus, the connection method between the devices according to the present invention provides a connection method capable of suppressing the effects of noise caused by external induction and radiation noise generated inside other devices.

[Brief description of the drawings]

FIG. 1 illustrates the principle of the present invention. (A) Connection diagram between devices. (B) Effect diagram of internally generated noise.

FIG. 2 shows an embodiment of the present invention. (A) Configuration diagram of device (b) Enlarged configuration diagram of doorway of device

FIG. 3 shows a coaxial cable according to an embodiment of the present invention.

FIG. 4 shows an example of conventional device connection (a) Ground connection diagram of individual device (b) Connection diagram between devices

FIG. 5 is a diagram showing the influence of internally generated noise in a conventional example of connection between devices.

FIG. 6 is a connection diagram between devices of another example of the related art.

FIG. 7 is a diagram showing the influence of internally generated noise in a connection between devices according to another conventional example.

FIG. 8 is a connection diagram between devices of another conventional example.

[Explanation of symbols]

1,6 Base unit 2,29 Cable 3
Magnetic material 4 Insulating layer 5 Device housing 7
Main circuit configuration part CCT 8 Power supply part PWR 9 Power input filter FIL 11,61 Slave unit 12,62 Doorway 21
Conductor 22 Outer conductor 23 Shield conductor 41
Protective insulation jacket 51 Shelf 52 Printed board 5
3,54 Connector 55 Grounding bracket 57 Coaxial terminal 58
Fixing bracket 59 Tightening bracket

Continued on the front page (72) Inventor Maki Kitajima 1015 Uedanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Inside Fujitsu Co., Ltd. Document JP-A-53-107216 (JP, A) JP-A-57-95700 (JP, A) JP-A-58-89899 (JP, A) JP-A-2-183599 (JP, A) 96893 (JP, U) JP2-24593 (JP, U) JP2, 76890 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) H05K 9/00

Claims (2)

(57) [Claims] 1. A structural grounding system (FG) and a circuit grounding system (S)
G) and separate grounding terminals (FG, SG) and individually operable electronic devices with noise shielding measures are connected with a cable, so that electrostatic discharge noise and noise generated by the device can be A method of connecting electronic devices that suppresses the effect on the device, comprising connecting the ground terminals (FG, SG) of one device (hereinafter referred to as a master unit (1)) in the group of electronic devices to be connected, and The ground connection is made, the connection between the ground terminals (FG, SG) of other devices (hereinafter referred to as the slave unit (11)) and the ground connection are not performed. For the connection, the conductor (21) on the T side is connected to the R side. Unbalanced type surrounded by an outer conductor (22), and furthermore, the outer conductor (22) is a shielded conductor.
Using the cable (2) covered by (23), the outer conductor (22) and shielded conductor (23) near the entrance (12) of the cable (2) for both the master unit (1) and the slave unit (11). The parent machine (1) surrounds the outer conductor (22) with a magnetic body (3) on the inner side of the connection position between the outer conductor (22) and the shield conductor (23) with the magnetic body (3), A method for connecting electronic devices, wherein the inductance of the outer conductor (22) is increased to a predetermined value. 2. The cable (2) according to claim 1, wherein
A method for connecting electronic devices, characterized in that the outer conductor (22) and the shielding conductor (23) are insulated by an insulating layer (4) having a high dielectric constant.