JPS62128207A - Line noise filter circuit - Google Patents

Abstract

PURPOSE:To attain sufficiently attenuation to both normal mode noise and common mode noise and to reduce the voltage loss of a line by connecting a capacitance between a common connection point of the 1st and the 4th winding common connecting point and a common connecting point of the 2nd and 3rd windings. CONSTITUTION:A capacitor Cn1 is connected between a common connection point of windings Lcn1a and Lcn2b and a common connection point of windings Lcn1b and Lcn2a, a capacitor Cn2 is connected between a common connection point of the winding Lcn1b and a load W and a common connecting point of the winding Lcn2b and the load W, a capacitor Cc1 is connected between a common connecting point of the winding Lcn1b and the load W and ground G, and a capacitor Cc2 is connected between the ground G and a common connecting point of the winding Lcn2b and the load W. In the circuit above, the combination of inductances Lcn1, Lcn2 and capacitors Cn1, Cn2 attenuates normal mode noise and the combination of inductances Lcn1, Lcn2 and capacitors Cc1, Cc2 attenuates common mode noise.

Description

[Detailed Description of the Invention] [Summary] In a line noise filter circuit, voltage loss in the line is reduced by expanding the use of inductance having a mutual inductance effect in the inductance inserted into the line loop.

[Industrial application field]

The present invention relates to improvements in line noise filter circuits.

A line noise filter circuit is inserted and connected between an electronic device and a power source to suppress noise that may cause malfunction of the electronic device from entering from the power source.

This noise includes normal mode noise (noise that exists between power lines connected to the load) and common mode noise (noise that exists between each power line and ground).
All of these frequencies are extremely high compared to the power supply frequency.

It is desired that the line noise filter circuit not only have excellent attenuation ability against both types of noise, but also have little voltage loss in the inserted line.

[Conventional technology]

FIG. 2 is a circuit diagram of an example of a conventional line noise filter circuit.

The line noise filter circuit shown in FIG.
and Lcb form an inductance Lc having a mutual inductance effect, and the line loop forms an inductance L
nl, the ridge Lcaz load W, the line Lcb, and the inductance Ln2 are connected in this order and in the direction of canceling mutual inductance between the windings Lca and LcbO,
There is a capacitance Cnl between the common connection point of the inductance Lnl and the winding Lca and the common connection point of the inductance Ln2 and the winding Lcb, and between the common connection point of the winding Lca and the load W and the common connection point of the winding Lcb and the load W. A capacitor Cn2 is connected between the common connection point of the winding Lca and the load W and the ground G, and a capacitor Cc2 is connected between the common connection point of the winding Lcb and the load W and the ground G. .

The inductance Lc is the winding 1. = Since the inductance values of c, a and Lcb are equal to each other, for example 2m11, there is almost no voltage loss due to line current, there is almost no damping effect on normal mode noise, and it is a common mode. It has the characteristic of having a noise damping effect.

Further, the inductance values of the inductances Lnl and Ln2 are smaller than the inductance values of the windings Lca and Lcb, for example, about 0.1 mtl each, for reasons described later.

Therefore, this circuit has inductances Lnl, Ln2 and 5
ItCnL Silk combination with Cn2 attenuates normal mode noise, and inductance Le and capacity tccl, Ca2
The combination with this attenuates common mode noise.

[Problem that the invention seeks to solve]

The inductance values of inductance Lnl and Ln2 are
Although it is desirable to make it large in order to attenuate normal mode noise, it causes voltage loss due to line current, so it should be set to about 0.1 mH, for example.

The voltage loss Vl due to line current in this circuit is the input voltage Vin and the output voltage V input to the load W.

Most of it is the difference between the inductances Lnl and L
It is occupied by the voltage loss of n2.

That is, Vo=Vin-VL VL #Vnl + Vn2 However, Vnl: Voltage loss due to Lnl Vn2: Voltage loss due to Ln2 and voltage loss VL are determined by the inductance Lnl and Ln2
Even if the inductance value of each is 0.1 mH,
When the power supply frequency is 50 Hz and the line current is 50 A, the inductance becomes a problematic value of about 3.2 V. If the inductance value is set to 1 mH, the inductance becomes about 32 V, which is a non-problematic value.

Also, as the line current increases, the inductance Lnl
, Ln2 cause magnetic saturation and the filter function deteriorates, and in order to prevent this magnetic saturation from occurring, there is a problem that the inductances Lnl and Ln2 must be made large.

[Means for solving problems]

The above problem is that the first and second windings have a first inductance that acts as a mutual inductance, and the third and fourth windings have a second inductance that acts as a mutual inductance, and the loop of the line is The first winding, the fourth winding,
The load, the second winding, and the third winding are connected in this order, and between the first and second windings and between the third and fourth windings, respectively, in a direction that cancels out the mutual inductance effect caused by the line current. The problem is solved by the line noise filter circuit of the present invention, in which a capacitor is connected between a common connection point of at least the first and fourth windings and a common connection point of the second and third windings.

[Effect]

In the above configuration, the first and second inductances are
Since it functions in the same manner as the conventional inductance Lc shown in FIG. 2, there is almost no voltage loss due to line current, and it has a damping effect against common mode noise.

Furthermore, when normal mode noise passes through the above capacitance, a difference occurs in the flow rate between the first and second windings and between the third and fourth windings, and the normal mode noise is also reduced. Exhibits a damping effect.

In this way, in this line noise filter circuit, the first and second inductances are sufficient to attenuate both noises, and it is possible to have almost no voltage loss due to line current.

〔Example〕

Embodiments of the line noise filter circuit according to the present invention will be described below with reference to the circuit diagram of FIG.

The same reference numerals refer to the same objects throughout the design.

The circuit shown in FIG.
winding) and winding Lcnlb (the second winding) have a mutual inductance effect Lcnl (
the first inductance), and the winding L cn2a
(the third winding) and the winding Lcn2b (the fourth winding) have a mutual inductance effect.
cn2 (the second inductance), and the line loops are winding Lcnla and winding Lcn2b.
, load W, 1'4 & line Lcnlb, T'S line Lcn2
a, and between the ridges Lcnla and Lcnlb and between the windings Lcn2a and Lcn2b, respectively, in the direction of canceling the mutual inductance effect due to the line current, and the common connection point of the windings Lcnla and Lcn2b. There is a capacitance Cnl between the common connection point of the windings Lcnlb and Lcn2a, a capacitance 1Cn2 between the common connection point of the II4 wire Lcnlb and the load W and a common connection point of the winding Lcn2b and the load W, and a capacitance 1Cn1 between the common connection point of the II4 wire Lcnlb and the load W.
There is a capacitance Cc between the common connection point of B and load W and ground G.
1, a capacitor Cc2 is connected between the common connection point of the winding L cn2b and the load W and the ground G.

The inductances Lcnl and Lcn2 are the winding Lc
nla and Lcnlb and winding L cn2a and L cn
Since the inductance values of 2b are equal, for example, 1 mH, they function similarly to the inductance Lc shown in Figure 2, with almost no voltage loss due to line current and attenuation against common mode noise. It has an effect.

Furthermore, as normal mode noise passes through the capacitor Cnla, the winding L between the windings Lcnla and Lcnlb is
A difference occurs in the flow rate between cn2a and Lcn2b, and a damping effect is also exerted on normal mode noise.

Therefore, this circuit has an inductance Lcnl, L c
The combination of n2 and capacitances Cnl and Cn2 attenuates normal mode noise, and inductances Lcnl and L cn
The combination of CC2 and capacitance CC1% CC2 attenuates common mode noise.

The voltage loss VL due to the line current is minute because it consists only of the voltage loss caused by the inductances Lcnl and Lcn2, and the inductance values of the windings Lcnla and Lcnlb and the windings Lcn2a and Lcn2b are sufficient to attenuate normal mode noise. Even if the magnitude value (for example, the above 1 mH) is much larger than the inductance value (for example, the above 0.1 mH) of the conventional inductance Lnl or Ln2,
The value is not a problem.

That is, this circuit is Vo#Vin becomes.

Further, the inductances Lcnl and Lcn2 do not need to be made large because their configuration makes it difficult to cause magnetic saturation even when the line current increases.

Note that the inductances Lcnl and Lcn2 may be of a toroidal type or a solenoid type.

〔Effect of the invention〕

As explained above, the configuration of the present invention has the effect of making it possible to provide a line noise filter circuit that secures sufficient attenuation for both normal mode noise and common mode noise and has low line voltage loss. be.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention, and FIG. 2 is a circuit diagram of an example of a conventional line noise filter circuit. In the figure, Lnl, Ln2, LC% Lcnl, Lcn2 are inductances, L caS
L cb-L cnlas Lcnlb, Ucn2a, Lcn2b is winding, Cn
l, Cn2, Ccl, and Cc2 are capacitances, W is load, G is ground, Vtn is input voltage, Vo is output voltage, and Vnl and Vn2 are voltage losses.

Claims (1)

[Claims] The first and second windings have a first inductance with mutual inductance, and the third and fourth wires have a second inductance with mutual inductance, and the loop of the line is connected to the first winding. , the fourth winding, the load, the second winding, the third winding in this order, and the mutual inductance effect due to the line current between the first and second windings and between the third and fourth windings, respectively. Line noise formed by connecting in a canceling direction, and characterized in that a capacitor is connected between at least a common connection point of the first and fourth windings and a common connection point of the second and third windings. filter circuit.