JP2007335674A - Noise filter configuration - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid a deterioration of a noise filter characteristic caused by a case for housing equipment to satisfy a specification, and to avoid a problem of a footprint and handling of a device. <P>SOLUTION: Electronic equipment 3b and a noise filter 3a for remedying low-frequency region (mainly not more than 1 MHz) are arranged within a case 3, and only a noise filter 2 for remedying high-frequency region (mainly not less than 1 MHz) is arranged in the outside of the case 3. Basically, as the deterioration of the noise filter characteristic caused by the case 3 (espacially by the metal case) is prominent in the high-frequency region, arranging only the noise filter 2 for remedying high-frequency region in the outside of the case prevents the deterioration of the noise filter characteristic. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a noise filter configuration that is connected to a commercial power supply or a power line or a ground line inside a power supply apparatus and suppresses high-frequency pulsation components and noise flowing out from the power supply apparatus.

6 and 7 are configuration examples of noise filters shown in Patent Documents 1 and 2, for example. The noise filters of the electronic device are configured by, for example, arranging the former in the housing and the latter outside the housing, respectively. Yes.
FIG. 8 is a diagram showing the internal structure of a noise filter disclosed in Patent Document 1, and shows an example in which a noise filter for low frequency region countermeasures and a noise filter for high frequency region countermeasures are provided inside the noise filter.

  The noise filter is installed to satisfy the noise terminal voltage standard defined by CISPR (International Radio Interference Special Committee), etc., but the noise terminal voltage standard is mainly defined over a wide frequency range of 150 kHz to 30 MHz. Has been. However, since elements (reactors, capacitors) used for noise countermeasures cannot realize ideal elements, it is difficult to obtain attenuation characteristics effective for noise countermeasures in all regions.

  Therefore, for example, as shown in FIG. 8, it is easy to realize a filter that exhibits good attenuation characteristics over the entire frequency range of the standard by dividing the frequency region to which measures are taken. Generally, large elements (reactors, capacitors) with large inductance and capacitance but poor high-frequency characteristics are applied to noise filters for low-frequency region countermeasures, and inductances and capacitances are small for noise filters for high-frequency region countermeasures. However, small elements (reactors, capacitors) with good high frequency characteristics are applied.

JP 2003-338722 A JP 2000-244272 A

However, even if the attenuation characteristics of the noise filter alone are good over 150 kHz to 30 MHz, the noise filter characteristics may be greatly deteriorated due to the influence of the casing, particularly the casing made of sheet metal. In such a case, there is a problem that even if the filter configuration as shown in FIG. 8 is used, desired characteristics cannot be obtained and the standard is exceeded. Further, when the noise filter is arranged outside the housing as shown in FIG. 7, the above problem is eliminated, but the installation area of the apparatus is increased in size and the handling becomes troublesome because the noise filter is arranged outside the housing. A problem occurs.
Therefore, an object of the present invention is to avoid the deterioration of noise filter characteristics due to the housing and satisfy the standard, and to prevent problems with the installation area and handling of the apparatus.

In order to solve such a problem, the invention of claim 1 is a noise filter configuration of an electric device including a substrate on which an electronic component is mounted in a housing,
A low frequency countermeasure noise filter of 1 MHz or less is arranged in the housing, and a high frequency countermeasure noise filter of 1 MHz or more is dispersedly arranged outside the housing.
In the first aspect of the present invention, a choke coil using a core material having a relative permeability larger than 1 in a frequency band of 30 MHz or less can be applied to the noise filter for high frequency countermeasures of 1 MHz or more. (Invention of Claim 2).

  In the invention of claim 2, the choke coil is constituted by passing the electric wire through the core for one turn or winding several turns, and one end of the electric wire is drawn from the housing and fixed inside the housing, The other end can be fixed to a terminal block arranged outside the housing (invention of claim 3), and in the invention of claim 3, a cover covering the choke coil and the terminal block can be attached (invoice). Item 4).

  According to this invention, by devising the noise filter configuration, it is possible to satisfy the standard by avoiding the deterioration of the noise filter characteristics due to the housing, and it is possible to reduce the restrictions on the installation area and handling surface of the device It becomes.

FIG. 1 is a block diagram showing an embodiment of the present invention, in which an electronic device 3b and a noise filter 3a for low frequency region countermeasures (mainly 1 MHz or less) are arranged inside a housing 3 to prevent high frequency regions (mainly 1 MHz or more) ) Only the noise filter 2 is arranged outside the housing 3.
In general, the noise filter characteristics are deteriorated by the housing (particularly, the sheet metal housing) because the high-frequency region is significant. Therefore, only the high-frequency region countermeasure noise filter 2 is disposed outside the housing to prevent the deterioration of the noise filter properties. It is.

  FIG. 2 shows an example of the noise terminal voltage measurement result. FIG. 2A assumes a state where the standard is exceeded in a high frequency region of 5 MHz or higher, and assumes a state where measurement is performed using only the low frequency region countermeasure noise filter in the housing. On the other hand, FIG. 2B is an example in which a high frequency region countermeasure noise filter is added outside the housing, and a component of 5 MHz or more is attenuated.

  Comparing FIGS. 2 (a) and 2 (b), they are the same in the low frequency region of 1 MHz or less, and the effect of adding the noise filter for high frequency region is not seen. However, the attenuation effect by the noise filter for high frequency region countermeasure appears little by little from 1 MHz or more, and especially the attenuation effect at 5 MHz or more becomes large. That is, the noise filter for high frequency region countermeasures is designed to have such attenuation characteristics. Thus, a noise filter configuration having a good attenuation effect over a wide frequency range is realized.

In addition, as described above, the noise filter for countermeasures against the high frequency region can be configured with smaller elements than the noise filter for countermeasures against the low frequency region, so that the problem in terms of installation area and handling can be reduced even if it is arranged outside the housing. become.
As described above, it is possible to avoid the deterioration of the noise filter characteristics due to the casing, to realize a noise filter that satisfies the standard, and to realize a noise filter configuration of an electronic device that has no problem in terms of installation area and handling of the apparatus.

It is conceivable to use a choke coil as the high frequency region countermeasure noise filter of FIG. At this time, as a core material for the choke coil, a magnetic material having a high frequency characteristic that can obtain a value of zero or more is applied in a frequency band of at least 30 MHz. FIG. 3 shows an example of the characteristics of the core material for the high frequency countermeasure choke coil. This shows the relative permeability (μ _r ) on the vertical axis with respect to the horizontal frequency, and the relative permeability is greater than 1 in the region of 30 MHz or lower.

  By using the core material having the above characteristics, it is possible to realize a reactor having good high frequency characteristics that behaves as a reactor in a region of 30 MHz or less. In general, there is a trade-off relationship between the magnitude of the relative permeability and the high-frequency characteristics, and the core material for the choke coil included in the noise filter for low-frequency region countermeasures arranged in the housing has a relative permeability of A large magnetic material having a relatively low frequency characteristic is applied, and a magnetic material having a small relative permeability but a good frequency characteristic is applied to the magnetic material disposed outside the housing.

Since the choke coil for high frequency countermeasures has a small inductance but an impedance in the high frequency region, the noise in the high frequency region can be suppressed. Further, since the inductance may be small, the applied core is very small as compared with the choke coil for low frequency region countermeasures, and there is no possibility of increasing the size of the device even if it is disposed outside the housing.
As described above, it is possible to avoid the deterioration of the noise filter characteristics due to the housing, to realize a noise filter that satisfies the standard, and to realize a noise filter for electronic equipment that has no problem in terms of installation area and handling of the apparatus.

In the above, the choke coil for countermeasures against the high frequency region is arranged outside the housing, but it is desirable for the manufacturer to avoid leaving the choke coil to the user as much as possible considering the control of filter characteristics and safety. Therefore, the following is performed.
FIG. 4 shows another embodiment of the present invention and shows a method of attaching a choke coil arranged outside the housing.

  A low frequency region countermeasure noise filter is arranged inside the housing. One end of the wiring that is not connected to the main circuit is pulled out of the housing, and the drawn wire (wiring cable) 11 is turned to the core material 12 for one turn or several turns. After winding, the terminal block 13 is connected. Since the user only needs to wire from the other end of the terminal block 13, it is not necessary for the user to attach a choke coil to be arranged outside the housing, and the problem of safety can be solved. In addition, since the choke coil is attached by the manufacturer, the filter characteristics can be managed.

In FIG. 4, one of the electric wires 11 is directly connected to the terminal block 13 without being wound around the core material 12, and a common mode choke coil and a ground wire are assumed. Can be considered. Specific examples thereof are omitted here.
By doing as described above, it is possible to avoid the deterioration of noise filter characteristics due to the housing, to realize a noise filter that satisfies the standard, and to realize a noise filter for electronic equipment that has no problem in terms of installation area and handling of the device. .

  In FIG. 4, since the terminal block and the choke coil are exposed, there is a problem that safety during use cannot be managed. FIG. 5 copes with this problem by adding a terminal block 13 and a cover 14 covering the choke coil. Here, the cover 14 is shown in a state shifted from its original position. By providing a cover that covers all the parts arranged outside the housing, safety during use can be ensured.

Further, the material of the cover 14 is preferably different from that of the housing 3, but the same material may be used. This is because even if the housing material and the cover material that degrade the noise filter characteristics in the high frequency region are the same, they are separated from the main circuit board. Because it is.
By doing as described above, it is possible to avoid the deterioration of noise filter characteristics due to the housing, to realize a noise filter that satisfies the standard, and to realize a noise filter for electronic equipment that has no problem in terms of installation area and handling of the device. .

Schematic diagram showing an embodiment of the present invention Characteristic diagram showing examples of noise terminal voltage measurement results Characteristic diagram showing the relationship between frequency and relative permeability The perspective view which shows other embodiment of this invention The perspective view which shows other embodiment of this invention. Schematic diagram showing the first conventional example Schematic diagram showing a second conventional example Schematic diagram showing the internal configuration of the first conventional example

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Commercial power source, 2 ... Noise filter for high frequency area countermeasures, 3 ... Housing, 3a ... Noise filter for low frequency area countermeasures, 3b ... Electronic equipment, 11 ... Electric wire (wiring cable), 12 ... Core material, 13 ... Terminal block , 14 ... Cover.

Claims (4)

A noise filter configuration of an electric device including a board on which electronic components are mounted in a housing,
A noise filter configuration characterized in that a low frequency countermeasure noise filter of 1 MHz or less is arranged inside a housing, and a high frequency countermeasure noise filter of 1 MHz or more is dispersedly arranged outside the housing.   2. The noise according to claim 1, wherein a choke coil using a core material having a relative permeability larger than 1 is applied to the noise filter for high frequency countermeasures of 1 MHz or higher at least in a frequency band of 30 MHz or lower. Filter configuration.   The choke coil is configured by passing the electric wire through the core for one turn or winding several turns, and one end of the electric wire is drawn from the housing and fixed inside the housing, and the other end of the winding is arranged outside the housing. The noise filter configuration according to claim 2, wherein the noise filter configuration is fixed to a terminal block.   The noise filter configuration according to claim 3, wherein a cover that covers the choke coil and the terminal block is attached.

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