JP2003283177A - Radiation noise reduction apparatus for electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radiation noise reduction apparatus for an electronic device for effectively reducing the radiation noise produced at a resonant frequency of an FG system on a printed board. <P>SOLUTION: A noise current is shunted by separating the shield of a shield cable 101 through which a high frequency noise current flows and an FG pattern 121 from each other, and connecting a capacitor 9 between the FG pattern 122 where the noise current flowing through the shield is separated and a ground layer. Otherwise, the radiation noise is reduced by providing a plurality of lands 91 to 93 on the FDG pattern, and grounding them to the FG such as a heat sink 14 and the like through studs 131 to 133, and further shifting a resonant frequency of the FG system to a higher frequency band above 1 GHz or higher. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation noise reducing device for an electronic device including a printed circuit board, which reduces radiation noise generated from a cable connected to the printed circuit board.

[0002]

2. Description of the Related Art Conventionally, in the case of driving a motor, electronic devices of this type are connected as shown in FIGS. 5 to 7, for example. Was there.

FIG. 5 is a plan view showing wiring on a printed circuit board in a conventional electronic device, FIG. 6 is a front view thereof, and FIG. 7 is a connection diagram between electronic devices in the conventional electronic device.

In FIG. 7, 1 is a motor and 2 is a
Is an encoder, 3 is a servo amplifier, 4 is a controller,
Reference numeral 5 is an operator, 6 is an AC power supply, and P is a printed circuit board. In these electronic devices, the encoder 2 transfers the position information or the rotation direction of the motor to the servo amplifier 3 as a high frequency signal.

Further, the controller 4 and the operator 5
Sends a command signal or the like as a high frequency signal to the servo amplifier 3. Further, the AC power supply 6 supplies power to the servo amplifier 3. Each of the encoder 2, the servo amplifier 3, the controller 4, and the operator 5 is provided with a printed circuit board P, and a pattern of a normal frame ground (hereinafter referred to as FG) is provided.

As shown in the plan view of FIG. 5, the servo amplifier 3 is provided with an FG pattern 12 on its printed board, and lands 81, 82 on the FG pattern 12 are provided.
As shown in the front view of FIG. 6, the studs 71,
72 is screwed and grounded to the heat sink 14, which is an FG.

The servo amplifier 3 has a connector 11
1, 112, 113 and multi-core shielded cable 101,
The shield wire of each shield cable is connected to the FG pattern 12 of the servo amplifier 3 through the encoder 102, the controller 4, and the operator 5, respectively. And the FG of this electronic device
As shown in FIG. 7, the FG pattern, the shield of the shielded cable, and the heat sink are respectively connected, and these can be considered as an FG system as a whole.

By the way, the FG system has an inherent resonance frequency, and noise currents of various frequencies flow, but the radiation noise of these noise currents increases due to resonance depending on the frequency of this noise current. Will be done. For example, the encoder 2 and the servo amplifier 3 communicate with each other via the encoder cable 101,
Due to the stray capacitance between the high frequency signal line and the shield line in the encoder cable 101, a high frequency noise current flows in the encoder cable 101.

[0009]

However, in the above prior art, the impedance of the FG system of the electronic device is
Since it depends on the mounting condition of the electronic device and the cable length, the resonance frequency of the FG system also changes accordingly, and as a result, the frequency band cannot be grasped and it is impossible to prevent an increase in radiation noise due to the noise current flowing in the FG system. There was a problem.

Further, even when the high frequency noise current flowing in the FG pattern can be specified through the shielded cable, there is no method for easily reducing the noise current flowing in the FG system.

Therefore, the present invention has been made in order to solve the above-mentioned problems, and a radiation noise reducing apparatus for an electronic device, which effectively reduces radiation noise generated by a resonance frequency of an FG system on a printed circuit board. Is intended to provide.

[0012]

In order to achieve the above object, the present invention provides an FG pattern in addition to a power layer and a ground layer on a printed circuit board, and a shielded cable of the FG pattern via a connector. In an electronic device connecting a shield, a shield of a shielded cable through which a high frequency noise current flows is separated from the FG pattern, and a capacitor is connected between the FG pattern separating the noise current flowing through the shield and a ground layer. Yes,
It is characterized in that the noise current flowing in the FG system of the electronic device is shunted to suppress the radiation noise that increases due to the resonance frequency of the FG system.

Further, in an electronic device in which an FG pattern is provided on the printed circuit board in addition to the power source layer and the ground layer,
Provide a plurality of lands on the pattern and ground them to the FG such as a heat sink with a stud to set the resonance frequency of the FG system to 1 GHz.
It is characterized in that the frequency band is shifted to a high frequency band of z or more.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

1 and 2 show a first embodiment of the present invention. First, FIG. 1 shows a plan view of the printed circuit board and FIG. 2 shows a front view thereof.

In these figures, the same or similar parts as those described as the prior art in FIGS. 5 to 6 are designated by the same reference numerals and the description thereof will be omitted.

In comparison with the above-mentioned prior art, this embodiment is
A different point is that the capacitor 9 which is a feature of this embodiment is provided and the FG pattern between the connector 112 and the connector 111 is separated. That is, in this embodiment, the FG pattern connected to the shield of the encoder cable 101 is separated from the FG pattern 121, and the capacitor 9 is provided between the separated FG pattern 122 and the ground layer.

The high frequency noise current is generated by the stray capacitance between the high frequency signal line and the shield line in the encoder cable 101.
FG pattern 1 of servo amplifier 3 via the shield of 1
22 and a part will flow to the ground layer through the capacitor 9.

That is, in this embodiment, since the noise current itself directly flowing in the FG system can be reduced by shunting the noise current, it is possible to suppress an increase in radiation noise due to the resonance frequency of the FG system. .

Next, a second embodiment of the present invention will be described.

3 to 4 show a second embodiment of the present invention. First, FIG. 3 shows a plan view of the printed circuit board and FIG. 4 shows a front view thereof.

The second embodiment is different from the prior art shown in FIGS. 5 to 6 in that countermeasure lands 91, 92, 93 and mounting studs 131, 132, 133 are provided. . In other words, the resonance frequency of the FG system can be shifted to a higher frequency band by increasing the number of grounds, but in the second embodiment, F
Since the structure is such that multiple points can be grounded on the G pattern, the resonance frequency of the FG system can be shifted to a high frequency band of 1 GHz or higher, and the frequency of the noise current can be set to a frequency band outside this resonance frequency. It is possible to prevent the radiation noise of the noise current from increasing due to the frequency.

As the number of studs increases, the resonance frequency can be shifted to a high frequency band, but this resonance frequency is FG.
Since it depends on the impedance of the system, radiation noise may be measured after the electronic device is actually installed, and the number of studs may be appropriately increased when the frequency band in question becomes clear.

[0024]

As described above, the present invention has the following effects.

(1) In an electronic device in which an FG pattern is provided on the printed circuit board in addition to the power supply layer and the ground layer, and the shield of the shielded cable is connected to the FG pattern via a connector, a high frequency noise current flows. A shield of the shielded cable is separated from the FG pattern, and a capacitor is connected between the FG pattern separating the noise current flowing in the shield and the ground layer,
Since the noise current flowing in the FG system of the electronic device is shunted, the radiation noise generated by the resonance frequency of the FG system on the printed circuit board can be effectively reduced.

(2) In an electronic device in which an FG pattern is provided on the printed circuit board in addition to the power supply layer and the ground layer,
Provide a plurality of lands on the pattern and ground them to the FG such as a heat sink with a stud to set the resonance frequency of the FG system to 1 GHz.
Since it is configured to shift to a high frequency band of z or more, it is possible to effectively reduce the radiation noise generated by the resonance frequency of the FG system on the printed circuit board.

(3) The cost can be reduced as compared with the case where a countermeasure component such as a ferrite core is used.

[Brief description of drawings]

FIG. 1 is a plan view showing a first embodiment of the present invention.

FIG. 2 is a front view showing a first embodiment of the present invention.

FIG. 3 is a plan view showing a second embodiment of the present invention.

FIG. 4 is a front view showing a second embodiment of the present invention.

FIG. 5 is a plan view showing wiring on a printed circuit board in a conventional electronic device.

FIG. 6 is a front view showing wiring on a printed circuit board in a conventional electronic device.

FIG. 7 is a connection diagram between electronic devices in a conventional electronic device.

[Explanation of symbols]

1: Motor, 2: Encoder, 3: Servo amplifier, 4:
Controller, 5: operator, 6: AC power supply, 71,
72: stud, 81, 82: land, 9: capacitor, 91, 92, 92: countermeasure land, 101: encoder cable, 102: controller cable, 1
03: operator cable, 111: encoder connector, 112: controller connector, 113: operator connector, 12: FG pattern, 121, 1
22: FG pattern, 131, 132, 133: mounting studs, 14: heat sink

Claims (2)

[Claims] 1. An electronic device in which a FG pattern is provided on a printed circuit board in addition to a power supply layer and a ground layer, and a shield of a shielded cable is connected to the FG pattern via a connector, in which a high-frequency noise current flows. A cable shield is separated from the FG pattern, and a capacitor is connected between the FG pattern separating the noise current flowing in the shield and the ground layer;
A radiated noise reduction apparatus for an electronic device, characterized in that a radiated noise that flows due to a resonance frequency of the FG system is suppressed by shunting a noise current that flows through the FG system of the electronic device. 2. An electronic device in which an FG pattern is provided on a printed circuit board in addition to a power supply layer and a ground layer, a plurality of lands are provided on the FG pattern, and an FG such as a heat sink is provided.
A radiated noise reduction device for an electronic device, characterized in that the FG resonance frequency is shifted to a high frequency band of 1 GHz or higher by grounding with a stud.