JPH07115339A - Line filter and its impedance changing method - Google Patents

Abstract

PURPOSE:To provide a line filter and its impedance changing method to freely set a specific band width or attenuation quantity without using any ground. CONSTITUTION:A line filter 11 contained in a single-phase power cord 1 includes the 1st and 2nd transformers 13 and 15 which use the wires 7 and 9 connected to the plugs 3 and 5 that are inserted to a commercial power supply as the primary coils respectively, an amplifier part 17 which amplifies the noise current that is picked up by the secondary coil of the transformer 13, and a power supply part 19 which supplies the power to the part 17. The current amplified at the part 17 is sent to the secondary coil of the transformer 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a line filter and a method for changing the impedance of a line filter, and more particularly to an AC power supply line which attenuates noise or a specific frequency with a very large attenuation over a wide band frequency of 10 kHz to 100 MHz or more. To prevent malfunction of various electronic devices caused by high frequency noise transmitted to low frequency lines or DC lines, and to prevent normal operation of these devices from being disturbed, and to prevent harmful electromagnetic wave transmission or radiation to the lines. And a method of changing the impedance of a line filter, which can be applied as a band pass filter, a low-pass or high-pass filter, and a pass power adjustment filter for a specific band frequency, and can contribute to various electronics industry sectors. Regarding

[0002]

2. Description of the Related Art In recent years, digitalization of various electronic devices has progressed, and the number of noise sources that generate noise has increased in various fields including homes. For example, noise that enters various electronic devices from a line wire includes normal mode noise and common mode noise, and their generation mechanisms and transmission modes are different. When such noise enters, various electronic devices malfunction. Further, noise may also occur in various electronic devices. Therefore, if the noise is sent to the power supply, the various electronic devices that generate noise become a noise source for other various electronic devices.
Therefore, a line filter has been proposed as a device capable of absorbing the noise transmitted through the line wire.

A conventional line filter against common mode noise uses electromagnetic induction by, for example, penetrating a line wire in ferrite or a magnetic material similar thereto or winding the wire N times. That is, the square of the number of turns N is proportional to the impedance of the line filter, and the current blocking effect by the impedance is due to the counter electromotive force generated by the current flowing through the line wire. Therefore, the target frequency is blocked by the impedance determined by the number of turns N forming the line filter and the magnetic material.

[0004]

By the way, the International Commission on Radio Interference (CISPR) sets the conducted noise, that is, the noise transmitted through a line wire to 30 MHz or less. However, actually, the antenna effective length using the line through which noise is transmitted as an antenna may be ¼ or less of the electromagnetic wave length of 30 MHz. Further, even when the standing wave is an integral multiple of ¼ wavelength on the line wire, noise of 30 MHz or more is transmitted through the line wire. Therefore, it is currently desired that the line filter provided at the noise outlet is capable of extending the effective frequency to a frequency as high as possible.

However, the working energy that the conventional line filter absorbs noise mainly depends on the energy of the noise itself which acts on the inductance. Therefore, when the number of windings of the line wire wound around the toroidal core or the like is large, the straight capacity is increased and the high frequency is bypassed, so that the filter effect for the high frequency is weakened.

On the other hand, in order to further prevent noise, a power cord having a line filter may be provided with three plugs, one for grounding and one for AC voltage. However, most commercial power sources have two plugs inserted, and even a power cord having only two plugs needs to be equipped with a line filter capable of sufficiently absorbing noise from the line line. is there.

Therefore, the present invention solves the above problems, and is a power cord used in a commercial power source that sufficiently absorbs high-frequency noise transmitted through a line wire and only two plugs can be inserted. Another object of the present invention is to provide a line filter and a method of changing impedance of a line filter that can sufficiently absorb noise from a line line without requiring a ground line.

[0008]

According to a first aspect of the present invention, there is provided a method of changing impedance of a line filter, comprising: a first core; a second core; and a first core wound around the first and second cores. In a line filter including a first coil and a second coil electromagnetically coupled to the first coil, the current flowing through the first coil is detected and amplified, and the current amplified by the second coil is detected. By flowing, the impedance of the first coil is changed.

The line filter according to the invention of claim 2 is
A line filter for absorbing a noise current, the first transformer including a primary side coil and a secondary side coil, a second transformer including a primary side coil and a secondary side coil, and a first transformer. An amplifying unit that amplifies the noise current electromagnetically induced in the secondary coil of the first transformer by the noise current flowing in the primary coil is provided, and the noise current amplified by the amplifying unit is supplied to the second transformer. It is supplied to the secondary coil to change the impedance of the primary coil of the second transformer.

In the third aspect, the primary side coil of the first transformer of the second aspect and the primary side coil of the second transformer are connected to each other, and are wound over the first core and the second core.

In claim 4, the first and second aspects of claim 3
Cores include a plurality of cores having different natural electric vibration frequency bands.

According to a fifth aspect of the present invention, the amplifying means of the second aspect includes an amplifier, and the power supply voltage, the bias voltage, the output phase and the amplification degree for the amplifier are adjusted to change the impedance of the primary side coil of the second transformer. .

[0013]

A line filter and a method of changing impedance of a line filter according to the present invention use two transformers, pick up a noise current from a primary side coil of a first transformer to a secondary side coil, and pick up the picked up noise current. The impedance of the primary side coil of the second transformer connected in series to the primary side coil of the first transformer can be changed by amplifying and flowing the amplified secondary side coil of the second transformer.

[0014]

1 is a perspective view of a single-phase power cord incorporating a line filter according to an embodiment of the present invention. Figure 1
The outline of the configuration of the line filter will be described with reference to FIG.

The single-phase power cord 1 does not have a grounding plug, but has plugs 3 and 5 that are input to a commercial power source.
The line filter 11 is incorporated. Line filter 11
Is a first transformer (denoted as T _{1 in the} drawing) 13, a second transformer
Transformer (denoted as T _{2 in the} drawing) 15, first transformer 1
An amplifier 17 for amplifying noise picked up by the amplifier 3 and a power supply 19 for supplying electric power to the amplifier 17 are included. The plugs 3 and 5 are connected to the line wires 7 and 9 via the first transformer 13 and the second transformer 15, respectively.

FIG. 2 is a diagram for explaining the principle of a method of absorbing common mode noise by a line filter according to an embodiment of the present invention, and FIG. 3 is an equivalent circuit of a main part of the line filter shown in FIG. It is a figure.

The line filter incorporated in the single-phase power cord shown in FIG. 1 will be described in detail with reference to FIGS. 2 and 3. A line filter for three-phase, direct current, low frequency signals, etc. may use the following principle.

First, referring to FIG. 2, the line ends of the line lines 7 and 9 connected to the plug side are line ends A and B.
And the line ends connected to the various electronic device sides are line ends C and D. The line wires 7 and 9 are also the first winding wire 27 wound around the core of the first transformer 13 and the primary winding wire 29 wound around the core of the second transformer 15, and the magnetic flux generated by the power supply current is The second transformers 13 and 15 are wired in parallel so as not to affect them. Although not shown, the line end C
And the line end D are connected in series via various electronic devices. The secondary winding 23 is wound around the core of the first transformer 13, and the secondary winding 25 is wound around the core of the second transformer 15. However, the primary windings 27 and 29 have a small number of turns, and the secondary windings 23 and 25 are wound to such an extent that the phase is delayed. One of the secondary windings 23 of the first transformer 13 has the amplifying unit 1
7 large slew rate phase inversion amplifier (A in the drawing
Represented by NP. ) 21 and the other end is connected to the phase inverting amplifier 21 at the connection point E, and is further connected to one end of the secondary winding 25 of the second transformer 15 through the grounded connection point F. The other side of the secondary winding 25 of the second transformer 15 is connected to the phase inverting amplifier 21. The current flowing through the secondary winding 23 of the first transformer 13 is inverted in phase and amplified by the phase inverting amplifier 21, and the secondary winding 2 of the second transformer 15 is amplified.
Flowing through 5.

Between the second transformer 15 of the line lines 7 and 9 and the line ends C and D, a connection point G is provided for the line line 7 and a connection point H is provided for the line line 9. . Line line 7 is connected to a second bypass capacitor (denoted as C _{2 in the} drawing) 33 at connection point G, and line line 9 is connected to a first bypass capacitor (denoted as C _{1 in the} drawing) 31 at connection point H. Connected to. The first and second bypass capacitors 31 and 33 are connected to a rectifier (denoted by D in the drawing) 35 which is grounded together, whereby the rectifier 35 receives electric power, and the output thereof is amplified by the amplifier 1.
7 to the phase inversion amplifier 21. If the line is a DC line or a signal line, the phase inverting amplifier 2
When one needs a relatively large DC power supply, another method must be used.

Next, the operation including the principle will be described with reference to FIG. 3 which is an equivalent circuit diagram of the first transformer 13, the second transformer 15 and the amplifying section 17 of FIG. The noise is absorbed even if the noise enters from either side of the line ends A and B or the line ends C and D of the line lines 7 and 9, but from the line ends A and B for simplification of description. It is assumed that noise has entered. Further, as shown in FIG. 3, the primary winding 27 of the first transformer 13 in FIG. 2 is connected to the first resistor 45 having a resistance value R ₁ and the first coil 3 having a self-inductance L ₁ .
7, the secondary winding 23 is a second resistor 47 having a resistance value R _{2 and} a second coil 39 having a self-inductance L ₂ , and the primary winding 29 of the second transformer 15 is a third resistor 49 having a resistance value R ₃ The third coil 41 having an inductance L ₃ and the secondary winding 25 are converted into a fourth resistor having a resistance value R _{4 and} a fourth coil 43 having a self-inductance L ₄ . Furthermore, the first transformer 13
The mutual inductance for the coil 37 and the second coil 39 is M ₁ , and the third coil 4 in the second transformer 15
The mutual inductance for the first and fourth coils 43 is M ₂
Is.

Based on these assumptions, the impedance Z _{1 of} the primary winding 27 in the first transformer 13 and the secondary winding 2
3 of the impedance Z _2, the impedance Z ₄ of the impedance Z ₃ and the secondary winding 25 of the second transformer 15 in the primary winding 29 is expressed by the equation (1).
Next, if the current I ₁ flows through the primary winding 27 of the first transformer 13 and the current I ₃ flows through the primary winding 15 of the second transformer 15, the secondary winding 23 of the first transformer 13 is assumed. And the secondary winding 25 of the second transformer 15 has induced electromotive force e ₂ ,
e ₄ occurs. If the resistance of the ferrite core itself is neglected, the induced electromotive forces e ₂ and e ₄ are respectively (2)
This is represented by the equation and the equation (3). Similarly, the first
If the current I ₂ flows through the secondary winding 29 of the transformer 13 and the current I ₄ flows through the secondary winding 43 of the second transformer 15, the primary winding 27 and the second transformer 13 of the first transformer 13 Induced electromotive forces e ₁ and e ₃ generated in the primary winding 29 of the container 15 are expressed by equations (4) and (5), respectively.

Further, assuming that the potential difference in the primary winding 27 of the first transformer 13 is E ₁ , the Kirchhoff's law is applied to the first transformer 13, and the relationship is expressed by the equation (6). It is expressed as follows. When the equation (6) is calculated and the currents I ₁ and I ₂ are derived, it can be expressed as the equation (7). The current I ₂ flows through the second coil 39, so that the current I ₂ is different from the current I _1. It can be seen that the phase is delayed by 90 °. When the current I ₂ passes through the phase inversion amplifier 21, it is amplified to 27 with respect to the current I ₁ as shown in the equation (8).
The current I ₅ is delayed by 0 °. The current I ₅ is the fourth coil 4
When flowing through 3, the current I ₄ becomes in-phase with the current I ₁ as shown in the equation (9). However, this is the impedance Z ₁ , Z of the primary and secondary windings 23, 25, 27, 29 of the first and second transformers 13, 15.
_This is the case where the reactance components of ₂ , Z ₃ , and Z ₄ are about the same.

Therefore, the primary winding 2 of the first transformer 13
If the number of turns of the primary winding 29 of 7 and the second transformer 15 is small and the phase shift is small, the current I ₁ and the current I ₃ are substantially in phase, so that the current I ₃ and the current I ₄ are also in phase. Become. Further, the third coil 41 and the fourth coil 43 are
It is wound concentrically on the ferrite core of the transformer 15,
Since the amplified current I ₄ is larger than the current I ₃ , the induction current as shown in the formula (5) is generated in the third coil 41 when the current I ₄ flows in the fourth coil 43. The electric power e ₃ is larger than the counter electromotive force generated by the current I ₃ flowing through the third coil 41.

Therefore, as if the first transformer 15 of the second transformer 15
3 coil 41 self-inductance L₃Seems to have increased
Looks like. That is, if the equivalent back electromotive force is applied to the third coil 41,
Force eL₃If it happens, the self-inductance L_3e
And the relation as shown in the equation (10) is established.
One. Note that i₃Is a deviation current flowing in the third coil 41.
I_FourIs the excursion current flowing in the fourth coil. Furthermore
And the self-inductance L _3eIs shown in the equation (11).
And the effective resistance value of the third resistor 49 is R_3e
Then, the effective impedance Z_3eIs R_3e+ JωL_3eso
Represented, i₃≪ i _FourTherefore, Z_3e≫ Z₃Seki
The relationship is established. Therefore, extremely large impedance
Equal to being pushed into line 7 or 9
The result is that if you adjust its impedance,
The target frequency is blocked. The rectifier 3 shown in FIG.
5 acts as a power source for the phase inversion amplifier 21, but a rectifier
The impedance of 35 is equal to that of the first and second bypass capacitors.
Extremely small compared to the impedance of capacitors 31 and 33
I'm sorry. As a result, the noise transmitted to the line wires 7 and 9
-Mal mode noise will be bypassed.

[0025]

[Equation 1]

FIG. 4 shows a first and a second transformer of a line filter according to an embodiment of the present invention, a line line, a pickup line for picking up noise from the line line, and an output for outputting amplified noise to the line line. It is a figure which shows the state of a line. FIG. 5 is an actual circuit diagram of a line filter according to an embodiment of the present invention, and FIG. 6 is an equivalent circuit diagram of FIG. 7 is an actual circuit diagram of a line filter according to another embodiment of the present invention, and FIG. 8 is an equivalent circuit diagram of FIG.

Referring to FIG. 4, the line wire 53 is wound through a core formed of two ferrite cores of different materials, that is, the first transformer 13 and the second transformer 15. The part wound around the transformer 13 is the primary winding 27, and the part wound around the second transformer 15 is the secondary winding 29. On the other hand, the secondary winding 23 of the first transformer 13 is also the pickup wire 55 for picking up the noise current transmitted through the line 53, and the secondary winding 25 of the second transformer 15
Is also the output line 57 that outputs the amplified noise current to the line line 53. By combining a plurality of cores made of different materials in this way, the relationship between the noise sample picked up by the pickup line 55 and the amplified noise sample output from the output line 57 becomes various, and the broadband effect as a filter effect is obtained. Appears. The combination of the transformer cores is not limited to two. further,
In order to amplify the noise sample picked up by the pickup line 55 and pass it to the output line 57, a circuit as shown in FIG. 5 or 7 may be used.

Referring to FIG. 5, FIG. 5 is a more detailed version of the circuit shown in FIG. 2. The part particularly different from FIG. 2 is that a transistor 59 is used as an amplifier. Accordingly, the secondary winding 23 of the first transformer 13
Is the base of transistor 59 (denoted by B in the drawing).
One terminal is connected to the terminal, the other is connected to + BIAS, and is grounded via the capacitor 64. The secondary winding 25 of the second transformer 15 is connected to the collector (indicated by C in the drawing) terminal of the transistor 59, and the other is + E.
Connected to CC. Further, the emitter (denoted by E in the drawing) terminal of the transistor 59 is grounded via a resistor 61 and a capacitor 63 which are connected in parallel.

In the following, when noises omitted for explaining the principle of the line filter shown in FIG. 2 are introduced from the side of various electronic devices by using FIG. 6 which is an equivalent circuit diagram of the circuit shown in FIG. The operation will be described briefly, including.

First, for example, on the power source side of the line wire 53.
Current from above to the first coil 37 ₁= 10 μA input
Suppose As the current flows through the first coil 37,
A current flows from the + BIAS to the second coil 39, and the current
Is multiplied by, for example, 1000 in the phase inverting amplifier 21,
Flow I_Five= 10,000 μA. Current I_FiveIs the fourth coil
43 and current I_FourBecomes the third coil 41
Current I₃Will be narrowed down to 10/10010.
Therefore, the current I₃Is output from the third coil 41 as
The resulting current is 0.01 μA.
The current I flowing through the first coil 37₁Also 0.01 μA
Become. Therefore, at the next moment, the current I _FiveIs 0.01 ×
Since only 1000 = 10 μA flows, the current I₃
Seems to be narrowed down to 0.01 / 10.01, but
Current I flowing in coil 43_FourIs as small as 10 μA
In this case, the current I flowing through the first coil 37 cannot be narrowed down.₁Is
It suddenly increases. This kind of repetition
And the current I flowing through the third coil 41 is₃Deviation current i₃When
Current I flowing through the fourth coil 43_FourDeviation current i_FourIn the ratio of
I_Four/ I₃Settles down to a certain value and satisfies Equation (11).
Will be added.

On the other hand, for example, various electronic machines of line line 53
Current I from the lower side of the device side to the third coil 41.₃Is 10μ
It is assumed that A is input. This current I₃Is the current I as it is₁
Therefore, the first coil 37 also flows. The first coil 37 is charged
The current flows from + BIAS to the second coil 39 due to the flow of current.
I₁Flow, and the current is 1000 times multiplied by the phase inversion amplifier.
Current I_Five= 10,000 μA. This current I_FiveBut
Flowing through the third coil 41 by flowing through the fourth coil 43
Current I₃Is still reduced by 10/10010 times, and the current I
₃Is 0.01 μA. Thereby, the first coil 37
Current I flowing through ₁Also becomes 0.01 μA, and at the next moment
Current I_FiveIs 0.01 × 1000 = 10 μA. Third
A current of 10 μA will flow into the coil 41 from below.
Therefore, the current I₃Is reduced to 10/20 = 1/2
Is 0.5 μA. This 0.5 μA current I₃Is
Current I₁As it flows through the first coil 37,
And a large diaphragm. Repetition like this
Therefore, also in this case, the deviation current flowing through the third coil 41
i₃And the current I flowing through the fourth coil 43_FourDeviation current i_Four
I is the ratio of_Four/ I₃Settles down to a certain value, number (11)
The formula will be satisfied.

If the current I ₁ flowing into the first coil 37 from above becomes 0 ampere due to the narrowing down to 100%, the current I ₂ also becomes 0 ampere. The shown i ₄ / i ₃ should not set to infinity and settle to a constant value, and similarly when the current flowing from below into the third coil 41 is narrowed down and the current I ₁ becomes 0 amperes. i ₄ / i ₃ should not set to infinity but settle to a constant value.

By the way, in the embodiment shown in FIG.
Since only one phase inversion amplifier is used, the space-saving line filter can be operated with low power consumption, but a part of the high frequency of the sample noise induced in the second coil 39 is dropped to the ground. However, there is a drawback in that the blocking ability when the noise comes from the various electronic devices side of the line 53 is smaller than the blocking ability when the noise comes from the power source side as described above. To compensate for these drawbacks, a line filter having a circuit as shown in FIG. 7 may be used.

Referring to FIG. 7, two transistors are used as an amplifier in this embodiment. Along with this, one side of the secondary winding 23 of the first transformer 13 is connected to the base terminal of the transistor 65, the other side is connected to the base terminal of the transistor 66, and is connected to + BIAS midway. One side of the secondary winding 25 of the second transformer 15 is a transistor 6
5 is connected to the collector terminal and the other is connected to the transistor 66.
Is connected to the collector terminal of and is connected to + ECC in the middle. The emitter terminals of the transistors 66 and 65 are connected to a grounded resistor 68 for a simple constant current source. A constant current source may be used instead of the resistor 68. Referring to FIG. 8 which is an equivalent circuit diagram of the circuit configured as described above, the phase inverting amplifier 2 represented by the transistors 65 and 66 is shown.
It can be seen that there is symmetry about 1, 22. Therefore, even if the noise current flows from the power supply side to the first coil 37 or from various electronic device sides to the third coil 41, the same amplification is performed and the target frequency is blocked.

To summarize the above, the reason why the current can be narrowed down is that although the noise waveform sharply changes in a very short time, for example, the phase and the waveform in the range of several 1,000,000th of a hertz at 1 MHz. Depend on the same phase and same waveform. But,
It is not possible to narrow down only by this, and as a further condition, the currents flowing through the first transformer 13 and the second transformer 15 are currents with different amounts of current, and the currents of the first transformer 13 and the second transformer 15 are different. It must resonate with the intrinsic electrical vibration of each core. This means that if the first transformer 13 and the second transformer 15 are combined into one, the current I ₄ affects one transformer, and the phase inverting amplifier 21 becomes 100%. This is to give a near negative feedback, and the filter effect of the line filter is not performed by this. Therefore, the windings for the first transformer 13 and the second transformer 15 must be partially penetrated as shown in FIG. 4 or wound separately.

The impedance of the second transformer can be changed by adjusting the power supply voltage, the bias voltage, the output phase and the amplification degree for the transistor used as the amplifier, so that the target frequency can be blocked easily. .

FIG. 9 is a diagram for explaining the structure of a specific example of the line filter used in the experiment, and FIG. 10 shows a common mode between AC line grounds using the line filter as shown in FIG. It is the figure which showed the outline of the apparatus which experimented the attenuation characteristic with respect to noise, and FIG. 11 is the graph which showed the experimental result. In particular, in FIG. 11, when the winding of the line wire is changed, the vertical axis represents the attenuation characteristic decibel, and the horizontal axis represents the frequency which is a semilogarithm thereof.

Referring to FIG. 9, the inner diameter is 8 mm and the outer diameter is 14 m.
m and height 6.5 mm, two cores 70 with the same inner diameter,
Two cores 71 having an outer diameter and a height of 4.5 mm are prepared and arranged in series to form a complex core. Then, the line wires 7 and 9 having a diameter of 1.0 mm are wound 5 times through the complex core as a pair, and the winding wire having a diameter of 0.3 mm is wound 7 times around the two cores 70 to form the pickup wire 55. A wire having a diameter of 0.3 mm is wound around the two cores 71 five times to form the output wire 57. The output of the pickup line 55 is input to the amplifier (AMP) 21, and the output of the amplifier 21 is input to the output line 57. Pickup line 55 and output line 5
The number of windings of 7 is correlated, and when increasing the number of windings on one side, decrease the number on the other side. The total number of turns is determined by the toroidal core and is almost constant. In the experiment, the number of turns of the line wire was changed to 3, 5, 9, 13, 17 times, but the diameter of the line wire when the number of turns was 3, 9, 13 was:
It was performed at 0.6 mm.

A line filter having such a configuration is shown in FIG.
Attach it to the network analyzer used as the experimental device as shown in. The network analyzer connects each line of the line filter between terminals L and N.
A mounting portion 74 connected between the mounting portion 74 and an output portion 75 including an oscillator having an internal resistance of 50Ω that oscillates an output of 4 dBM in the mounting portion 74.
And an input unit 76 having an internal resistance of 50Ω to which the output from the mounting unit 74 is input. The terminal of the mounting portion 74 is provided with a terminal E in addition to the terminals L and N between which the line wire is connected, and one of the terminals L and one of the terminals N are connected together, and the output portion 75, and one terminal E is grounded. The other of the terminals L is connected to the input section 76, the other of the terminals N is connected to a resistance of 50Ω and is grounded, and the other of the terminals E is also grounded. From the line wire mounted on the mounting portion 73 to the pickup wire 5
When the noise picked up via 5 was input to the amplifier 21 for amplification and output to the output line 57, the result as shown in FIG. 11 was obtained.

Referring to FIG. 11, when the concept of the attenuation bandwidth product is applied to the attenuator so that the operational amplifier has the gain bandwidth product (GBW), the total surrounded by the line of 0 dB and each line is applied. It can be considered that the width of the area represents the damping characteristic. Therefore, even if the attenuator is not turned on, the number of turns is 3, 9, and 13 with the same line diameter of 0.6 mm.
It can be seen from the broken lines that the damping effect is improved as the number of turns is increased in the low frequency band in this figure when the number of turns is changed to 17 times. However, in the high frequency band, the larger the number of turns, the worse the damping effect. Therefore, with respect to a line wire having a diameter of 1.0 mm and 5 turns, the amplifier is turned on or off to compare the attenuation characteristics. Since the solid line showing that the amplifier is in the ON state shows the attenuation characteristic remarkably in most frequency regions as compared with the broken line showing the OFF state, it can be seen how great the effect of the present invention is.

As described above, how large the damping effect on the common mode noise is according to the present invention has been shown. Next, the damping effect on the normal mode noise will be described.

FIG. 12 is a diagram showing the outline of an apparatus in which the attenuation characteristics for normal mode noise between AC line grounds are tested by using the line filter as shown in FIG. 9, and FIG. It is a figure for demonstrating the power supply for 12 amplifiers, and FIG. 14 is a graph which showed the experimental result.

Differences from FIGS. 9 to 11 showing experiments on common mode noise will be described with reference to FIGS. 12 to 14.

In FIG. 12, what is different is an experiment on normal mode noise. Therefore, one of the terminals N of the mounting portion 74 is not connected to the output of the output portion 75 but connected to a resistance of 50Ω. It is grounded.

Further, as shown in FIG. 13, AC lines 78 and 79 corresponding to line lines are connected to 1.2 μF bypass capacitors 31 and 33, respectively, and the bypass capacitors 31 and 33 include a rectifier 35 including a Zener diode. It is connected to the. One of the rectifiers 35 is connected to the capacitor 80 and the diodes 81 and 82. The other side of the Zener diode 82 is connected to the other side of the rectifier 35 via the resistors 84 and 83, the other side of the Zener diode 81 is connected to the other side of the rectifier 35 via the resistance 83, and the other side of the capacitor 84 is the other side of the rectifier 35. Connected to.
The power supply voltage VCC is input to the amplifier 21 from the connection point between the Zener diode 81 and the resistors 83 and 84, and the substrate voltage VBB is input from the connection point between the Zener diode 82 and the resistor 84.
Is input to the amplifier 21.

In this way, the power source for the amplifier 21 under the same condition as the actual use is used, the line filter is attached to the network analyzer 73 shown in FIG. 12, and the experimental result as shown in FIG. 14 is obtained. It was

Referring to FIG. 14, similar to the common-mode noise attenuation characteristics shown in FIG. 11, the amplifier is not in the ON state, and the number of turns of the line wire is changed to 3, 9, 13, and 17 times. As a result, as shown by each broken line, the attenuation characteristic is improved as the number of turns is increased in the relatively low frequency band in the figure.

However, above about 1 MHz, the attenuation characteristic does not change even if the number of turns is changed. Therefore,
For a line wire with 1.0mm and 5 turns,
Let's compare the attenuation characteristics with N state or OFF state. The solid line indicating that the amplifier has turned on is off
It can be seen that the attenuation characteristic is more prominently represented than the broken line showing the state.

As described above, it can be seen that the line filter according to the present invention has an attenuating effect over a wide frequency band even with respect to normal mode noise and common mode noise, and particularly with respect to the high frequency band, it is particularly effective against normal mode noise. It was found that there was a large damping effect.

[0050]

As described above, according to the present invention, the noise current is picked up from the primary coil of the first transformer to the secondary coil, amplified, and connected in series to the primary coil of the first transformer. The amount of attenuation and the bandwidth as a filter effect can be changed by flowing the secondary coil of the second transformer including the primary coil. Furthermore, by combining the cores of the transformer with different intrinsic electrical vibration characteristics, a very wideband or bandwidth filtering effect can be created. Furthermore, since the number of turns of the primary side coils of the first and second transformers can be reduced, the straight capacity can be suppressed and the damping effect in the high frequency range can be increased. Further, by adjusting the self-inductance of the coils forming the first and second transformers, the mutual inductance, and the amplification degree of the amplifier, the bandwidth and the amount of attenuation as the filter effect can be freely selected.

[Brief description of drawings]

FIG. 1 is a perspective view of a single-phase power cord incorporating a line filter according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining the principle of a method of absorbing common mode noise by a line filter according to an embodiment of the present invention.

FIG. 3 is an equivalent circuit diagram of a main part of the line filter shown in FIG.

FIG. 4 shows states of first and second transformers of a line filter, a line line, a pickup line for picking up noise from the line line and an output line for outputting amplified noise to the line line according to an embodiment of the present invention. FIG.

FIG. 5 is a specific circuit diagram of a line filter according to an embodiment of the present invention.

FIG. 6 is an equivalent circuit diagram of FIG.

FIG. 7 is a specific circuit diagram of a line filter according to another embodiment of the present invention.

FIG. 8 is an equivalent circuit diagram of FIG. 7.

FIG. 9 is a diagram for explaining the configuration of a specific example of the line filter used in the experiment.

FIG. 10 is a diagram showing an outline of an apparatus in which an attenuation characteristic for common mode noise between AC line grounds has been tested.

FIG. 11 is a graph of experimental results obtained by the experimental apparatus shown in FIG.

FIG. 12 is a diagram showing an outline of an apparatus in which an attenuation characteristic for normal mode noise between AC line grounds was tested.

13 is a diagram for explaining the amplifier power supply of FIG.

FIG. 14 is a graph of experimental results obtained by the experimental apparatus shown in FIG.

[Explanation of symbols]

 7,9,53 Line wire 13 1st transformer 15 2nd transformer 23,25 Secondary winding 27,29 Primary winding 37 1st coil 39 2nd coil 41 3rd coil 43 4th coil 55 Pickup wire 57 Output line 70,71 core

Claims (5)

[Claims] 1. A first core, a second core, and the first core.
And a line filter including a first coil wound over a second core and a second coil electromagnetically coupled to the first coil, detecting a current flowing through the first coil. A method of changing the impedance of a line filter, in which the impedance of the first coil is changed by causing the amplified current to flow through the second coil. 2. A line filter for absorbing noise current, comprising: a first transformer including a primary side coil and a secondary side coil; a second transformer including a primary side coil and a secondary side coil; An amplifying unit that amplifies a noise current electromagnetically induced in the secondary coil of the first transformer by causing a noise current to flow in the primary coil of the first transformer; A line filter, wherein the line filter is caused to flow in a secondary coil of the second transformer to change impedance of a primary coil of the second transformer. 3. The primary side coil of the first transformer and the primary side coil of the second transformer are connected to each other, and are wound over the first core and the second core. The line filter according to claim 2. 4. The line filter according to claim 3, wherein the first and second cores include a plurality of cores having different natural electric vibration frequency bands. 5. The amplifying means includes an amplifier, and adjusts a power supply voltage, a bias voltage, an output phase and an amplification degree for the amplifier to change the impedance of the primary side coil of the second transformer. The line filter according to claim 2.