JP3163853B2 - noise filter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise filter inserted between an AC power supply and electronic equipment.

[0002]

2. Description of the Related Art FIG. 4 shows an example of a conventional noise filter 100. In the figure, input terminals 1, 2,
The capacitors C1, C2, and C3 are connected between each other. An AC power supply 16 is connected to this input terminal.
Capacitors C4, C are connected between the output terminals 4, 5, and 6.
5 and C6, and capacitors C7, C8 and C9 are connected between the ground terminal E and each output terminal. A common mode choke coil 11 composed of coils 7, 8, and 9 wound in the same direction on a magnetic core 10 made of a material such as ferrite is connected between the input terminal and the output terminal. Output terminals 4, 5, 6
Are connected to power terminals 13, 14, and 15 of the electronic device 12. The conventional noise filter 100 is configured as described above.

Next, the operation of the conventional noise filter 100 will be described. Common mode choke coil 11
Is a large common mode inductance of 1 mH or more between the input terminals 1, 2, 3 and the output terminals 4, 5, 6.
The common mode noises entering into the steps 2 and 3 are attenuated by the common mode choke coil 11 and the capacitors C7, C8 and C9 to prevent the noise from entering the electronic device 12. Also, since the coils 7, 8, 9 are partially wound, the coupling between them is not perfect and there is a leakage inductance. This leakage inductance and capacitors C1, C2, C3 connected between the input terminals 1, 2, 3 and capacitors C4, C connected between the output terminals 4, 5, 6
5, C6, the input terminals 1, 2, 3,
Normal mode noise entering the electronic device 12
To prevent intrusion of noise into the AC power supply 16 from the electronic device 12.

The electronic device 12 connected to the conventional noise filter 100 often uses a diode for its input terminal. Input terminals 13, 14, 1 of electronic device 12
5 generally includes diodes 74, 75, 76, 77, 7
There is a rectifier circuit to which a capacitor C16 is charged with a DC voltage. When the voltage of the RS phase of the three-phase AC voltage, that is, the voltage between the input terminals 13 and 14 increases, the current 80 flows in and the current 81 flows out. Next, when the voltage of the RS phase becomes lower than the voltage of the capacitor C16, the diode 74 is turned off. At this time, a recovery current flows through the diode 74 due to the reverse recovery characteristic of the diode, and the electronic device 1
2 generates higher voltage noise than the noise generated by the internal circuit 2 and contains a considerably high frequency component. FIG. 5A shows a voltage between the input terminals 13 and 14 of the electronic device 12.
(B) is a noise component included in the voltage of (a). At timing 90 when the diode 74 turns off, noise 91 occurs. Other noise is noise generated by other diodes. For example, at timing 92, the diode 7
7 turns off, and noise of 93 is generated. When this noise 91 is enlarged, it becomes as shown in (d), which contains high frequency components and generates high voltage noise.

[0005] A conventional method of manufacturing a noise filter is to form a common mode choke coil 11 by winding an electric wire to form coils 7, 8 and 9 on a core 10 and fixing the capacitor to a terminal insulated and attached to a metal case. It is manufactured by connecting the wires of the common mode choke coil 11 that are not performed, soldering, and then pouring and fixing a resin such as plastic.

[0006]

Since the conventional noise filter is configured as described above, there are the following problems. The electronic device 12 often uses a semiconductor, and the input is often constituted by a capacitor input type rectifier circuit including a diode and an electrolytic capacitor. In the case of such a rectifier circuit, the power factor of the input current is very poor, and the current is as shown in FIG. That is, the peak value is higher than the actual value of the current, that is, 1.5 to 2 times. In addition, an input current of the electronic device 12 such as an inverter often has an instantaneous large inrush current. For example, when a motor connected as a load such as an inverter is rapidly accelerated, or when a load is suddenly applied to the motor, a larger current flows than in a steady state. Therefore, when combined with the power factor of the rectifier circuit described above, the peak value of the current flowing through the common mode choke coil 11 of the noise filter becomes 2-3 times. When such a large current flows through the core 10 composed of a magnetic material such as a ferrite core as shown in FIG. 7 and the common mode choke coil 11 composed of the coils 7, 8 and 9, the leakage magnetic fluxes 20 and 21 increase. And coils 7, 8, 9-2
The magnetic flux density of the core 10 in the portions 2 and 23 increases and approaches the saturation magnetic flux density. As the core 10 approaches the saturation magnetic flux density, the magnetic permeability decreases and the inductance decreases. Therefore, the common mode inductance between the input terminals 1, 2, 3 and the output terminals 4, 5, 6 becomes small, and the attenuation performance of the common mode noise as a noise filter becomes low. Similarly, the attenuation performance of the normal mode noise is also reduced.

Also, an amorphous core 1 is used as a magnetic material.
When a noise filter is formed using the common mode choke coil 11 in which the coils 7, 8, and 9 are wound using 0, the permeability of the amorphous core decreases as the frequency increases as shown in FIG. Coil 7, 8, 9
Also has a small inductance. For example, at 100 KHz, the inductance is reduced to a quarter of the inductance at 1 KHz, and there is a problem that the noise attenuation performance as a noise filter is low at a high frequency of 100 KHz or more.

In the conventional noise filter, capacitors C7, C8, and C9 having a large capacitance are used to attenuate low-frequency noise, but there is a problem that a leakage current increases.

Many electronic devices 12 connected to a conventional noise filter use diodes at their input terminals, and the noise voltage generated by the diodes of the electronic device 12 is high. To reduce this noise voltage, However, there is a problem that the noise attenuation performance of the noise filter must be increased.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and the noise attenuation performance is hardly reduced even when a current having a high peak value flows through a noise filter. It is an object of the present invention to obtain a noise filter that has high noise attenuation performance even at a low frequency and does not decrease noise attenuation performance even at a high frequency of 100 KHz or more.

[0011]

SUMMARY OF THE INVENTION A noise filter according to the present invention comprises a capacitor connected between lines of a common mode choke coil and a capacitor connected between each line and ground. In the noise filter inserted between the two, the core of the common mode choke coil is composed of a ferrite core and a core of an iron-based high permeability magnetic material such as permalloy, iron-based amorphous, silicon steel plate, etc. The coil is wound with the core of the high-permeability magnetic material outside and the same core.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a diagram showing a configuration of a noise filter according to Embodiment 1 of the present invention. In the figure, 1-6, 7-9,
C1 to C9 are the same as those in FIG. 4, and the description thereof is omitted. Reference numeral 17 denotes a core of an iron-based high magnetic permeability, 18 denotes a ferrite core, and 26a denotes a core 17 of an iron-based high magnetic permeability.
And the ferrite core 18 as the same core and the coil 7,
A common mode choke coil wound with 8, 9 is a noise filter 101.

The noise filter 101 has an input terminal 1,
Capacitors C1, C2, C connected between two or three
3, capacitors C4, C5, C6 connected between the output terminals 4, 5, 6; capacitors C7, C8, C9 connected between the ground terminal E and each output terminal; an input terminal and an output terminal And a common mode choke coil 26a connected therebetween. An AC power supply 16 is connected to the input terminals 1, 2, and 3.

As the iron-based high permeability magnetic material, permalloy,
There are iron-based amorphous and silicon steel plates. The iron-based high magnetic permeability core 17 has a high magnetic permeability and a high saturation magnetic flux density at a frequency of 10 KHz or less. For example, the permalloy has a saturation magnetic flux density of 1.5 T (tesla) and a magnetic permeability of 500.
00 to 200,000. The iron-based amorphous core has a saturation magnetic flux density of 1.5 T and a magnetic permeability of about 50,000. The silicon steel sheet has a saturation magnetic flux density of 2.0 T and a magnetic permeability of about 20,000. When the coil is wound 10 to 20 times around the single core 17 made of the iron-based high permeability magnetic material, 5
The inductance becomes as large as about mH. As shown at 24 in FIG. 8, when the frequency increases, the magnetic permeability decreases, and the inductance also decreases. For example, at 100 KHz, the inductance becomes 1/4 of the inductance at 1 KHz.

On the other hand, a ferrite core used for a noise filter is generally a Mn-Zn ferrite.
Saturation magnetic flux density is 0.5T, magnetic permeability is 2500-5000
It is about. This ferrite core is used for 18. When a coil is wound around the single ferrite core 18 for 10 to 20 times, the inductance becomes about 1 mH. The frequency characteristic of the inductance of the coil wound around the ferrite core 18 is substantially constant from a low frequency to a high frequency of 1 MHz or more as shown at 25 in FIG. Therefore, at a frequency of 100 KHz or less, the inductance of the iron-based high-permeability magnetic material is higher than the inductance of the ferrite core 18. Coil 7, 8, 9
Are the iron-based high-permeability magnetic core 17 and the ferrite core 1
Since 8 is wound as the same core, a combined inductance is obtained when the coil is wound around the single core. Accordingly, when the cores 18 and 17 having the characteristics shown in FIG. 8 are used, as shown at 27, 6 mH at 100 Hz, 1 KHz
5 mH at 10 KHz, 3.5 mH at 10 KHz, 2 at 100 KHz
A common mode choke coil 26a having a characteristic of 1 mH at 1 MHz is obtained.

Embodiment 2 FIG. 2 is a diagram showing a configuration of a common mode choke coil according to Embodiment 2 of the present invention. In the figure,
6, 7 to 9 are the same as those in FIG. 4, and the description thereof is omitted. Reference numeral 17 denotes a core of an iron-based high permeability magnetic material, 18 denotes a ferrite core, and 26b denotes a core 17 of an iron-based high permeability magnetic material.
And the ferrite core 18 as the same core and the coil 7,
A common mode choke coil wound with 8, 9 is a noise filter 101. 28, 29 are current, 3
0 and 31 are magnetic fluxes. In the first embodiment, an example in which the iron-based high-permeability magnetic material core 17 and the ferrite core 18 are overlapped and used as the same core has been described, but in the second embodiment, the ferrite core 18 is disposed inside, The core 17 made of an iron-based high permeability magnetic material is disposed outside and used as the same core.

The common mode choke coil 26b is formed by winding the coils 7, 8, and 9 with the same core having the ferrite core 18 on the inside and the core 17 of the iron-based high magnetic permeability on the outside. Since the ferrite core 18 is manufactured by baking ferrite at a high temperature, a large core is difficult to manufacture and is expensive. Therefore, the inner small side is the ferrite core 18
Is good. The outer core 17 made of an iron-based high-permeability magnetic material is often manufactured by winding a ribbon-shaped magnetic material. Therefore, the core 17 on the outer large side is preferably made of an iron-based high-permeability magnetic material.

Considering a case where a current 28 flowing from the AC power supply 16 to the electronic device 12 flows through the coil 7 and a current 29 simultaneously flows through the coil 8, the frequency of this current is 1
Since the frequency is lower than KHz, the iron-based high-permeability magnetic material core 17 has a higher magnetic permeability than the ferrite core 18, and the magnetic flux is almost completely reduced.
Go through 7. Since the magnetic permeability is much higher than the magnetic permeability of air, the leakage magnetic flux is very small. Therefore coil 8
The magnetic flux 30 caused by the current 29 flowing through the coil 7 is almost the same in intensity and opposite to each other as the magnetic flux 31 caused by the current 28 flowing through the coil 7, and cancels out each other. Is unlikely to occur. In addition, the iron-based high permeability magnetic material has a saturation magnetic flux density of 3% of the ferrite core.
Because the ferrite core 18 is not yet saturated, even if a large current near the saturation flows through the coils 7, 8, and 9, the frequency is higher than 100 KHz. In this case, the inductance does not decrease and the noise attenuation performance does not decrease.

Further, the frequency characteristic of the inductance of the common mode choke coil 26 shown in FIG.
The noise filter 1 is higher than 00 kHz.
01 noise reduction performance of 100 kHz or less can be improved. For example, at 10 KHz, the inductance becomes 3.5 times that of the ferrite core alone, so that the noise filter 101 of the present invention has a noise attenuation performance of 3.
The performance is improved five times, that is, 10 db (decibel) or more. In particular, the electronic device 12 is an IGBT or a MOSFE
Frequency 1 above audio frequency with switching element such as T
Since the frequency of switching at 6 to 20 KHz is increasing, 100 KH is required for such an electronic device 12.
The noise filter according to the present invention, which has a high noise attenuation performance of z or less, exhibits an excellent effect.

In general, the inner side is close to the winding, so that the leakage flux is small, and the outside is large in the open portion of the winding, so the leakage flux is large. However, if there is an iron-based high-permeability magnetic material core with high magnetic permeability outside, the iron-based high-permeability magnetic material core absorbs the leakage flux from the ferrite core,
Since the core itself of iron-based high permeability magnetic material has low leakage flux,
The leakage flux of the whole core can be reduced, and a common mode choke coil in which the ferrite core is not saturated even with a large current can be obtained.

Embodiment 3 FIG. 3 is a diagram showing a configuration of a common mode choke coil according to Embodiment 3 of the present invention. In the figure,
6, 7 to 9 are the same as those in FIG. 4, and the description thereof is omitted. Further, 32 and 33 are ferrite cores, 34 and 35 are iron-based high-permeability magnetic cores, and 36 is a bobbin around which coils 7, 8, and 9 are wound.

The common mode choke coil 26c has coils 7, 8, and 9 wound around a bobbin 36, and includes a U-shaped ferrite core 32, 33 and a U-shaped core 34, 35 of an iron-based high magnetic permeability magnetic material. Are the same core. Since the bobbin 36 is used, automatic winding is possible, and the cores 32, 33, 3
Since the common mode choke coil 26c can be assembled by inserting the components 4 and 35 later, the assembly is easy and an inexpensive noise filter can be provided.

When the common mode choke coil shown in FIG. 3 is constituted only by the ferrite cores 32 and 33 as in the conventional noise filter, the magnetic path length of the portion where the coils 7, 8, and 9 are not wound is long, and the leakage magnetic flux is reduced. As a result, the ferrite core was immediately saturated and the noise attenuation performance was likely to be reduced at a large current. However, as in the noise filter 101 of the present invention, the core 34, made of an iron-based high permeability magnetic material, was used.
Since the coils 7, 8, and 9 are wound using the same core as the core 35 and the ferrite cores 32 and 33, even if the magnetic path length becomes long, the magnetic permeability of the iron-based high magnetic permeability cores 34 and 35 is high, and the leakage occurs. Since the magnetic flux is small and the core is unlikely to be saturated, there is an effect that a noise filter in which the noise attenuating performance is hardly reduced even with a large current can be provided.

In the above description, a three-phase AC noise filter has been described. However, a noise filter for a single-phase AC or a single-phase three-wire AC has the same effect.

[0025]

Since the present invention is configured as described above, it has the following effects.

The noise filter, which is composed of a capacitor connected between the lines of the common mode choke coil and a capacitor connected between each line and the ground, is inserted between the AC power supply and the electronic equipment, is used for the common mode choke coil. The core is composed of a ferrite core and an iron-based high-permeability magnetic material core such as permalloy, iron-based amorphous, and silicon steel plate.The ferrite core is on the inside and the iron-based high-permeability magnet is on the outside. And the same core, the coil is wound, so that even if a current having a high peak value flows, the noise attenuating performance is hardly reduced and 10K
It is possible to obtain a noise filter that has high noise attenuation performance even at a low frequency between 100 Hz and 100 KHz, and does not deteriorate even at a high frequency of 100 KHz or more. Further, since the coil is wound with the ferrite core inside and the iron-based high-permeability magnetic material core outside, and both are the same core, the leakage flux of the whole core can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a noise filter according to Embodiment 1 of the present invention.

FIG. 2 is a diagram showing a configuration of a common mode choke coil of a noise filter according to Embodiment 2 of the present invention.

FIG. 3 is a diagram showing a configuration of a common mode choke coil of a noise filter according to Embodiment 3 of the present invention.

FIG. 4 shows an example of a conventional noise filter 100.

FIG. 5 is a waveform chart for explaining the operation of a conventional noise filter.

FIG. 6 is a diagram illustrating a waveform of an input current of the electronic device 12 whose input is configured by a capacitor input type rectifier circuit including a diode and an electrolytic capacitor.

FIG. 7 is a configuration diagram for explaining the operation of a conventional noise filter.

FIG. 8 is a waveform diagram for explaining the operation of a conventional noise filter.

[Explanation of symbols]

1,2,3 input terminal, 4,5,6 output terminal,
7, 8, 9 coil, 10 magnetic core, 11 common mode choke coil, 12 electronic equipment, 13, 1
4, 15 power supply terminal, 16 AC power supply, 17 iron-based high magnetic permeability core, 18 ferrite core, 2
6a, 26b, 26c common mode choke coil,
28,29 current, 30,31 magnetic flux, 32,3
3 Ferrite core, 34, 35 Iron-based high magnetic permeability core, 36 bobbin, 74, 75, 76 diode, 77, 78, 79 diode, 100 noise filter, 101 noise filter, C1,
C2, C3 capacitor, C4, C5, C6 capacitor, C7, C8, C9 capacitor, C16 capacitor, E Ground terminal.

Claims (1)

(57) [Claims] 1. A noise filter comprising a capacitor connected between lines of a common mode choke coil and a capacitor connected between each line and ground, and inserted between an AC power supply and an electronic device. The core of the choke coil is composed of a ferrite core, a core of a permalloy, an iron-based amorphous, a core of an iron-based high permeability magnetic material such as a silicon steel plate, and a core of the iron-based high permeability magnetic material inside the ferrite core. A noise filter characterized in that a coil is wound around the outside with the same core.