JP2008078844A - Noise filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a noise filter capable of enough raising power supply quality. <P>SOLUTION: The filter comprises: an X capacitor 110 connected between a pair of power supply lines; Y capacitors 121, 122 connected the pair of power supply lines and ground electric potential; a common mode choke coil 130 inserted between the pair of power supply lines; and a magnetic shield 140 for restricting magnetic interference among the common mode choke coil 130, X capacitor 110, and Y capacitors 121, 122. In accordance with the present invention, the magnetic shield 140 restricts the magnetic interference produced in the noise filter so that it is possible to raise power supply quality after filtering. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a noise filter, and more particularly to a noise filter for a power supply suitable for use in a power supply unit such as an electronic device.

  Electronic devices such as home appliances and computers are provided with a power supply unit called an inlet. The inlet is a connector for connecting to an outlet (outlet) of a commercial power supply. By connecting the inlet and the outlet, power is supplied to a power supply circuit provided in the electronic device, thereby operating the internal circuit. It becomes possible.

  However, various types of noise are superimposed on the power supplied from the outside, and the electronic device itself is a source of power noise, so a noise filter is often provided near the inlet. If a noise filter is provided in the vicinity of the inlet, the quality of the power supplied to the power supply circuit can be improved, so that malfunction of the internal circuit can be suppressed. In addition, malfunctions of other electronic devices can be suppressed.

  As this type of noise filter, the noise filters described in Patent Documents 1 to 3 are known. Each of the noise filters described in Patent Documents 1 to 3 includes an X capacitor, a Y capacitor, and a common mode choke coil. Here, the X capacitor is a capacitor connected between a pair of power supply lines, and the Y capacitor is a capacitor connected between the pair of power supply lines and the ground potential. The common mode choke coil is inserted into a predetermined position of the pair of power supply lines.

The noise filter having such a configuration may be affected by external noise generated by various electronic devices. Since the power quality after filtering may be deteriorated when affected by external noise, it is desirable to shield external noise by shielding the entire noise filter.
Japanese Utility Model Publication No. 5-53233 Japanese Patent Laid-Open No. 7-272942 Japanese Patent Laid-Open No. 10-41165

  However, there are cases in which the power quality after filtering cannot be sufficiently improved only by shielding the entire noise filter. The present invention has been made to solve such a problem, and an object thereof is to improve the performance of a noise filter for power supply.

  As a result of intensive studies on the reason why it is not sufficient to shield the entire noise filter, the present inventors have found that magnetic interference occurs between the electrical components constituting the noise filter.

  The present invention has been made based on such technical knowledge, and the noise filter according to the present invention includes a pair of power supply lines, an X capacitor connected between the pair of power supply lines, and the pair of power supplies. A Y capacitor connected between the line and the ground potential, a common mode choke coil inserted in the pair of power supply lines, and a magnetism between the common mode choke coil and at least one of the X capacitor and the Y capacitor. And a magnetic shield for suppressing interference.

  According to the present invention, since magnetic interference generated inside the noise filter is suppressed by the magnetic shield, the power quality after filtering can be improved.

  The magnetic shield is preferably a case-like member that accommodates the common mode choke coil without accommodating at least one of the X capacitor and the Y capacitor. Furthermore, the magnetic shield is more preferably a case-like member that accommodates only the common mode choke coil without accommodating either the X capacitor or the Y capacitor. According to this, it is possible to effectively reduce the influence of the X capacitor and the Y capacitor on the common mode choke coil.

  Moreover, it is preferable that a magnetic shield is comprised with resin containing a magnetic material. Such a material has a higher effect of blocking electromagnetic waves than metal, and is lighter than metal, so that magnetic interference generated inside the noise filter can be more effectively suppressed.

  The noise filter according to the present invention preferably further includes a metal case that houses the X capacitor, the Y capacitor, and the common mode choke coil. According to this, not only the magnetic interference generated inside the noise filter but also noise entering from the outside can be blocked.

  Thus, according to the present invention, since magnetic interference generated inside the noise filter is suppressed by the magnetic shield, the power quality after filtering can be improved. Therefore, if the noise filter according to the present invention is used for an inlet of an electronic device, it is possible to prevent malfunction of the electronic device.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  1 and 2 are a schematic plan view and a schematic perspective view, respectively, showing a configuration of a noise filter 100 according to a first preferred embodiment of the present invention. In both FIG. 1 and FIG. 2, (a) is a lid of a magnetic shield. (B) has shown the state which removed the lid | cover of the magnetic shield.

  As shown in FIGS. 1 and 2, the noise filter 100 according to the present embodiment has an X capacitor 110, Y capacitors 121 and 122, and a common mode choke coil 130, and these are housed in a metal case 190. is doing. In the present embodiment, a case-like magnetic shield 140 is provided in the metal case 190, and only the common mode choke coil 130 is accommodated in the magnetic shield 140. That is, the magnetic shield 140 accommodates only the common mode choke coil 130 without accommodating the X capacitor 110 and the Y capacitors 121 and 122.

  The material of the magnetic shield 140 is not particularly limited as long as it has a shielding effect, but it is preferable to use a resin or metal containing a magnetic material such as ferrite. In order to obtain a high shielding effect, it is more preferable to use a resin containing a magnetic material such as ferrite. Further, since a resin containing a magnetic material such as ferrite has an insulating property, insulation between components is ensured, and it is possible to prevent occurrence of a short circuit defect.

  FIG. 3 is a circuit diagram of the noise filter 100 according to the present embodiment.

  As shown in FIG. 3, the noise filter 100 according to the present embodiment has three input terminals 151 to 153 and two output terminals 161 and 162. The pair of input terminals 151 and 152 are connected to an outlet, and the pair of output terminals 161 and 162 are connected to a power supply circuit or an internal circuit of an electronic device that uses the noise filter 100. That is, the noise filter 100 according to the present embodiment also serves as an inlet, and power can be supplied by inserting a power plug into the cavity 154 shown in FIG. Note that a ground potential is supplied to the third input terminal 153.

  Here, the wiring connecting the input terminal 151 and the output terminal 161 and the wiring connecting the input terminal 152 and the output terminal 162 constitute a pair of power supply lines. An X capacitor 110 is connected between the pair of power lines, and Y capacitors 121 and 122 are connected between the pair of power lines and the input terminal 153, respectively. The common mode choke coil 130 is inserted into a pair of power supply lines.

  As shown in FIGS. 1 and 2, the noise filter 100 having such a circuit configuration is entirely housed in a metal case 190, and only the common mode choke coil 130 is further housed in the magnetic shield 140. That is, the common mode choke coil 130 is in a state where a double magnetic shield is provided. As shown in FIGS. 1 and 2, the noise filter 100 according to the present embodiment uses the toroidal type common mode choke coil 130, but the structure of the common mode choke coil 130 is not limited to this. Absent.

  The above is the structure of the noise filter 100 according to the present embodiment. As described above, in the noise filter 100 according to the present embodiment, since the common mode choke coil 130 is accommodated in the magnetic shield 140, the magnetic field between the common mode choke coil 130 and the X capacitor 110 and the Y capacitors 121 and 122. Interference is suppressed. In other words, not only external noise but also interference between the electrical components constituting the noise filter 100 is suppressed, so that the power quality after filtering can be improved. Therefore, if the noise filter 100 according to the present embodiment is used for an inlet of an electronic device, it is possible to prevent malfunction of the electronic device.

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

  4A and 4B are schematic plan views showing the configuration of a noise filter 200 according to the second preferred embodiment of the present invention, in which FIG. 4A shows a state in which a magnetic shield lid is attached, and FIG. 4B shows a case in which the magnetic shield lid is removed. Shows the state. FIG. 5 is a circuit diagram of the noise filter 200 according to the present embodiment.

  The noise filter 200 according to the present embodiment is different from the noise filter 100 according to the above-described embodiment in that not only the common mode choke coil 130 but also the X capacitor 110 are collectively accommodated in the magnetic shield 240. Since the other points are the same as those of the noise filter 100 according to the above-described embodiment, the same elements are denoted by the same reference numerals, and redundant description is omitted.

  In the noise filter 200 according to the present embodiment, since the magnetic shield 240 accommodates both the X capacitor 110 and the common mode choke coil 130, an effect of suppressing magnetic interference between them cannot be obtained. As a result, the X capacitor 110 is double shielded, so that a high shielding effect against external noise can be obtained. The present embodiment is also effective when a magnetic shield that accommodates only the common mode choke coil 130 cannot be disposed due to space problems.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. Needless to say, it is included in the range.

  For example, in the above-described embodiment, an example in which the noise filter according to the present invention is applied to a power supply unit such as an electronic device has been described. However, the application range of the noise filter according to the present invention is not limited thereto. Therefore, for example, the noise filter according to the present invention can be used on the outlet side of the commercial power supply.

  Moreover, in the said embodiment, although a case-shaped member is used as a magnetic shield, this invention is not limited to this, For example, you may use the mold resin containing a magnetic material as a magnetic shield.

  Hereinafter, although the Example of this invention is described, this invention is not limited to this Example at all.

  First, the noise filter of Example 1 having the same configuration as the noise filter 100 shown in FIGS. The capacity of the X capacitor was set to 0.47 μF, and the capacity of the two Y capacitors was set to 470 pF. The inductance of the common mode choke coil was set to 3 mH. As a material for the magnetic shield, a resin containing ferrite was used.

  Moreover, the noise filter of Example 2 which has the same structure as the noise filter 200 shown in FIG.4 and FIG.5 was produced. The capacitances of the X capacitor and the Y capacitor and the inductance of the common mode choke coil were set to the same values as in the first embodiment. As for the material of the magnetic shield, as in Example 1, a resin containing ferrite was used.

  Further, a noise filter of Example 3 having the same configuration as that of Example 2 was produced except that metal was used as a material for the magnetic shield.

  Furthermore, the noise filter of the comparative example which has the same structure as Examples 1-3 except having deleted the magnetic shield was produced.

  Next, the noise filters of Examples 1 to 3 and the comparative example were connected between the outlet of the commercial power source and the electronic device, and power noise in the 150 KHz to 30 MHz band was measured in an anechoic chamber. A plasma display was used as the electronic device. The measurement result about Examples 1-3 and a comparative example is shown in FIGS. 6-9, respectively.

  As shown in FIGS. 6 to 9, it was confirmed that the noise level of the power supply was lower when the noise filters of Examples 1 to 3 were used than when the noise filter of the comparative example was used. The effect is most noticeable in the noise filter of Example 1, and the improvement of the noise level in the low frequency band is particularly remarkable.

1A and 1B are schematic plan views showing a configuration of a noise filter 100 according to a first preferred embodiment of the present invention, in which FIG. 1A shows a state where a magnetic shield cover is attached, and FIG. 2B shows a state where a magnetic shield cover is removed; ing. It is a schematic perspective view which shows the structure of the noise filter 100 by preferable 1st Embodiment of this invention, (a) is the state which attached the lid | cover of the magnetic shield, (b) shows the state which removed the lid | cover of the magnetic shield. ing. 2 is a circuit diagram of the noise filter 100. FIG. It is a schematic plan view which shows the structure of the noise filter 200 by preferable 2nd Embodiment of this invention, (a) shows the state which mounted | wore with the cover of a magnetic shield, (b) shows the state which removed the cover of the magnetic shield. ing. 2 is a circuit diagram of a noise filter 200. FIG. It is a graph which shows the measurement result of the power supply noise about the noise filter of Example 1. FIG. It is a graph which shows the measurement result of the power supply noise about the noise filter of Example 2. It is a graph which shows the measurement result of the power supply noise about the noise filter of Example 3. It is a graph which shows the measurement result of the power supply noise about the noise filter of a comparative example.

Explanation of symbols

100, 200 Noise filter 110 X capacitor 121, 122 Y capacitor 130 Common mode choke coils 140, 240 Magnetic shield 151-153 Input terminal 154 Cavity 161, 162 Output terminal 190 Metal case

Claims (5)

  A pair of power supply lines, an X capacitor connected between the pair of power supply lines, a Y capacitor connected between the pair of power supply lines and the ground potential, and a common mode choke inserted into the pair of power supply lines A noise filter comprising: a coil; and a magnetic shield that suppresses magnetic interference between the common mode choke coil and at least one of the X capacitor and the Y capacitor.   The noise filter according to claim 1, wherein the magnetic shield is a case-like member that accommodates the common mode choke coil without accommodating at least one of the X capacitor and the Y capacitor.   The noise filter according to claim 2, wherein the magnetic shield is a case-like member that accommodates only the common mode choke coil without accommodating both the X capacitor and the Y capacitor.   The noise filter according to any one of claims 1 to 3, wherein the magnetic shield is made of a resin containing a magnetic material.   The noise filter according to any one of claims 1 to 4, further comprising a metal case that accommodates the X capacitor, the Y capacitor, and the common mode choke coil.

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