JP2000299615A - Low frequency power supply noise protector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact and lightweight low frequency power supply noise protector capable of reducing the common mode noise and normal mode noise in a low frequency band from several dozens of kHz to several hundreds of kHz propagated from a commercial power source. SOLUTION: A common mode choke coil (CL) 11 and a normal mode choke coil (NL) 13 are serially connected between input terminals 1 and 3 to connect the commercial power source and output terminals 5 and 7 to connect equipment 9. Further, first and second capacitors (C1 and C2) 15 and 17 are connected on the input/output terminal side of the normal mode choke coil (NL) 13 and further, a resistor (R) 19 is connected parallel to the first capacitor (C1) 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-frequency power supply noise protection device inserted between a commercial power supply and a power supply line of the equipment to reduce conducted noise from the commercial power supply and protect the equipment. The present invention relates to a low-frequency power supply noise protection device for protecting devices such as communication devices and electronic devices from conduction noise in a low-frequency band.

[0002]

2. Description of the Related Art In recent years, with the spread of electric appliances using inverters, such as air conditioners and lighting fixtures, noise in a low frequency band of several tens of kHz to several hundreds of kHz has leaked to a commercial power supply. The number of cases where equipment breaks down is increasing year by year.

As a countermeasure against a failure, there is a method of implementing a noise countermeasure in a power supply circuit unit or a failed circuit unit in a device.
There were problems such as the mounting space of countermeasure parts and circuit remodeling. Therefore, conventionally, a method has been adopted in which a power supply noise protection transformer is inserted between a commercial power supply outlet and a device power supply line as shown in FIG. 5 to reduce electromagnetic noise in the low frequency band as described above.

[0004]

The above-described conventional method using the power supply noise protection transformer has a disadvantage that the protection transformer is large and heavy since the power supply required by the equipment must be borne by itself. For this reason, there is a problem that as the power capacity increases, the mounting location of the protective transformer is restricted, and the mounting becomes difficult.

[0005] In addition, there are two types of conducted noise: those conducted in the common mode and those conducted in the normal mode. If the protective transformer is not grounded, the conducted noise is not sufficient for the conducted noise in the common mode. Although there is a problem that the blocking effect cannot be expected, there is a problem that it is often difficult to ground the ground due to recent housing circumstances.

[0006] The present invention has been made in view of the above,
Its purpose is to dozens of kilograms conducted from commercial power.
An object of the present invention is to provide a small and lightweight low-frequency power supply noise protection device that can reduce common mode noise and normal mode noise in a low frequency band of Hz to several hundred kHz.

[0007]

In order to achieve the above object, the present invention according to claim 1 is inserted between a commercial power supply and a power supply line of the equipment, and operates the equipment against conduction noise from the commercial power supply. A low-frequency power supply noise protection device for protecting, connected to an input terminal of a commercial power supply, a common mode choke coil for preventing common mode conducted noise in a low frequency band, and between the common mode choke coil and the device. A normal mode choke coil connected to prevent normal mode conducted noise in a low frequency band, a first capacitor connected between lines on an input side of the normal mode choke coil, and an output side of the normal mode choke coil. A second capacitor connected between the lines;
And a resistor connected in parallel to both ends of the capacitor.

According to the first aspect of the present invention, the common mode choke coil connected to the input terminal of the commercial power supply effectively attenuates the common mode conducted noise in the low frequency band, and also includes the normal mode choke coil and the common mode choke coil. The combination with the first and second capacitors connected in parallel to the input / output terminals effectively attenuates the normal mode conduction noise while making them both compact and economical.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing a configuration of a low-frequency power supply noise protection device according to one embodiment of the present invention.
In the low frequency power supply noise protection device shown in FIG. 1, a common mode choke coil (CL) 11 and a normal mode choke coil 11 are provided between input terminals 1 and 3 to which commercial power is supplied and output terminals 5 and 7 to which equipment 9 is connected. Mode choke coil (N
L) 13 are connected in series, and a first capacitor (C1) 1 is connected between both ends of the normal mode choke coil (NL) 13.
5 and a second capacitor (C2) 17 are connected in parallel, and a resistor (R) 19 is connected in parallel to both ends of the first capacitor (C1) 15.

[0010] Common mode choke coil (CL) 11
Is designed to have a large inductance composed of self-inductance and mutual inductance, thereby effectively attenuating common mode conduction noise in a low frequency band.

Also, a normal mode choke coil (N
L) 13 and first and second capacitors (C1, C2) 15, 17 connected in parallel to both ends thereof attenuate the normal mode conducted noise, and the normal mode choke coil (NL) 13 Only or the first or second capacitor (C1, C2) 15 or 1
7, it is difficult to effectively attenuate noise in the low frequency band, so that the normal mode choke coil (N
L) 13 and first and second capacitors (C1, C2)
15 and 17 are combined.

Note that a normal mode choke coil (N
The reason why the first and second capacitors (C1, C2) 15, 17 are connected in parallel to both ends of the L) 13 is to effectively attenuate noise flowing out from the device 9 side.

Normal mode choke coil (NL) 1
No. 3 does not have the effect of mutual inductance unlike the common mode choke coil (CL) 11, so that low-frequency noise must be attenuated only by the self-inductance. To increase the self-inductance, the number of windings of the coil may be increased. However, if the number of windings of the coil is increased, the winding resistance increases.
, The number of windings is restricted, and a sufficient noise suppression effect in a low frequency band cannot be expected. For example, the winding resistance of the normal mode choke coil (NL) 13 is 1
If the output terminals 5 and 7 are connected to a device having a current consumption of 5 A, the commercial power supply voltage is reduced by 5 V by the normal mode choke coil (NL) 13. Therefore, the number of windings of the normal mode choke coil (NL) 13 cannot be increased much.

Therefore, in order to increase the self-inductance of the normal mode choke coil (NL) 13 with a limited number of windings, a method of increasing the size of the core or a method of using a core material having a high magnetic permeability is used. However, the former is not suitable for miniaturizing the coil, and the latter is expensive,
There is a problem that it is not suitable for economy.

Therefore, by combining the normal mode choke coil (NL) 13 with the first and second capacitors (C1, C2) 15, 17 as in the present embodiment, the noise suppression effect in the low frequency band is enhanced. At the same time, the size and cost of the coil can be reduced.

On the other hand, in order to attenuate the noise in the low frequency band only by the capacitor, it is sufficient to increase the capacitance of the capacitor.
Even at 60 Hz), a current flows into the capacitor, and there is a problem that extra power is consumed in the capacitor. For example, in order to attenuate a noise having a frequency of 20 kHz by 20 dB or more, a capacitor having a capacitance of about 12 μF is required. As a result, power consumption of about 45 VA (60 Hz) is caused in the capacitor. In order to avoid such a problem, the capacity of the capacitor is restricted, and a sufficient noise suppression effect in a low frequency band cannot be expected.

Therefore, in the present embodiment, by combining the normal mode choke coil (NL) 13 with the first and second capacitors (C1, C2) 15, 17, both the size and economy of both can be reduced. The common mode choke coil (CL) 11, the normal mode choke coil (NL) 13, and the filter circuit including the first and second capacitors (C1, C2) 15 and 17 conduct common mode conduction in a low frequency band from a commercial power supply. The noise and the normal mode conduction noise can be effectively attenuated.

The resistor (R) 19 connected in parallel to the first capacitor (C1) 15 is connected to the first and second terminals when the input terminals 1 and 3 including, for example, a power plug are pulled out from the commercial power supply. Capacitors (C1, C2) 1
The voltage charged to the terminals 5 and 17 is discharged, thereby preventing an electric shock due to contact with the terminal of the power plug.

FIG. 2 is an exploded perspective view showing the structure of the low frequency power supply noise protection device shown in FIG. As shown in the figure, the common mode choke coil (CL) 11, the first capacitor (C1) 15 and the resistor (R) 19 are mounted on a printed circuit board 25 to improve the efficiency of wiring work. . The input side of the common mode choke coil (CL) 11 mounted on the printed board 25 is connected to the input terminals 1 and 3 of the power plug 27 via the power cord 31, and the commercial side is connected via the power plug 27. It is designed to be connected to a power supply. Further, a second capacitor (C
2) The output side of 17 is connected to the output terminals 5 and 7 of the outlet 26, and is connected to the device 9 via the outlet 26. The electric component thus configured is housed between the upper case 23 and the lower case 24.

FIGS. 3A and 3B show the low frequency power supply noise protection device shown in FIGS. 1 and 2 in the upper case 2 shown in FIG.
FIG. 3A is a view showing the internal structure when the lower case 24 is housed between the lower case 24 and the lower case 24, and FIG. 3
(B) is a diagram showing an internal structure in a state where electric components are stored between the upper case 23 and the lower case 24 and the two cases 23 and 24 are fixed together.

In such a structure, the normal mode choke coil (NL) 13 is provided in both cases 23, 2
The ribs provided at 4 omit mounting hardware and the like, and are directly fixed.

The low-frequency power supply noise protection device configured as shown in FIG. 3 has an outer shape of 55 mm × 157 mm × 40 m.
m can be realized with a size and weight of 450 g, and the size and weight can be reduced to 1/10 or less, and the size and weight can be reduced as compared with the conventional power supply noise protection transformer.

FIG. 4 is a characteristic diagram showing the noise attenuation with respect to the frequency of the low frequency power supply noise protection device shown in FIG. In the noise attenuation characteristic diagram shown in FIG.
It can be seen that the common mode noise can be attenuated by 30 dB or more and the normal mode noise can be attenuated by 20 dB or more with respect to the low frequency noise of 000 kHz, and excellent noise suppression characteristics can be obtained. This is because a common mode choke coil (CL) 11 designed to effectively attenuate low frequency band common mode noise and a normal mode choke coil (NL) to effectively attenuate low frequency band normal mode noise are used. ) 13 and first and second capacitors (C1, C2) 15, 17 in combination.

[0024]

As described above, according to the present invention,
Since the common mode choke coil and the normal mode choke coil are connected in series between the commercial power supply and the device, and the first and second capacitors are connected in parallel to the input / output terminals of the normal mode choke coil,
The common mode choke coil effectively attenuates the common mode conducted noise in the low frequency band, and the combination of the normal mode choke coil and the first and second capacitors connected in parallel to the input / output terminals makes them both compact. It can effectively attenuate normal mode conduction noise while being economical, and achieves excellent noise suppression characteristics without being limited by installation location, by reducing size, weight, and economy. I have.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a low-frequency power supply noise protection device according to an embodiment of the present invention.

FIG. 2 is an exploded perspective view showing the structure of the low frequency power supply noise protection device shown in FIG.

FIG. 3 is a diagram showing an internal structure when the low frequency power supply noise protection device shown in FIGS. 1 and 2 is housed between an upper case and a lower case.

FIG. 4 is a characteristic diagram showing noise attenuation with respect to frequency of the low-frequency power supply noise protection device shown in FIG. 1;

FIG. 5 is a circuit diagram showing a configuration of a low-frequency power supply noise protection device using a conventional power supply noise protection transformer.

[Explanation of symbols]

 11 Common mode choke coil (CL) 13 Normal mode choke coil (NL) 15 First capacitor (C1) 17 Second capacitor (C2) 19 Resistance (R)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazumi Sakurai 3-19-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Within Japan Telegraph and Telephone Corporation (72) Mitsuo Hattori 3-19, Nishi-Shinjuku, Shinjuku-ku, Tokyo No. 2 Nippon Telegraph and Telephone Corporation F term (reference) 5J024 AA01 BA14 BA18 DA01 DA26 DA27 DA32 EA09

Claims (1)

[Claims] 1. A low-frequency power supply noise protection device inserted between a commercial power supply and a power supply line of the equipment to protect the equipment against conducted noise from the commercial power supply, and connected to an input terminal of the commercial power supply. A common mode choke coil that blocks common mode conducted noise in a low frequency band, a normal mode choke coil that is connected between the common mode choke coil and the device, and blocks normal mode conducted noise in a low frequency band; A first capacitor connected between input-side lines of the normal mode choke coil, a second capacitor connected between output-side lines of the normal mode choke coil, and both ends of the first capacitor. A low frequency power supply noise protection device comprising: a resistor connected in parallel.