JPH09283345A - Winding having noise killing effect - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a winding having noise killing effect capable of reducing the circuit required of killing noise especially the part numbers and packaging area of power supply part, even in an inductor or transformer unit body. SOLUTION: This winding having noise killing effect is provided with electrostatic shields S1, S2 arranged on the outer periphery of windings P, S, the first shields 3, 5 and the second shields 4, 6 positioned on the windings P, S sides than the electrostatic shields S1, S2 and generating the capacities between the windings P, S and the electrostatic shields S1, S2. In such a constitution, the first shields 3, 4 and the second shield 4, 6 are respectively connected to one end and the other end of the windings P, S while the electrostatic shields S1, S2 are constituted to be grounded, and the windings P, S and a line filter are integrated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply transformer used mainly for CRTs, power supply circuits for audio equipment, circuits for consumer electronic appliances, home electronics, etc., which require noise suppression. Inductors, etc.

[0002]

2. Description of the Related Art Conventionally, a circuit as shown in FIG. 10 is known as a noise prevention circuit provided in a power supply section of an electronic device. In the figure, CX is an X capacitor, L1 is a coil, and CY is a Y capacitor.

This circuit is a so-called AC line filter, and both the external noise and the noise generated by itself are attenuated by the capacitors CX and CY and the coil L1. By the way, noise includes normal mode noise in which a noise source exists between two lines and common mode noise in which a noise source exists between a line and ground. The operation for each noise of the above circuit will be described below. Will be described.

FIG. 11 shows the flow of normal mode noise current in the circuit of FIG. As can be seen, the normal mode noise current from the noise source on the AC line side and the load side is absorbed by the X capacitor CX. Further, FIG. 12 shows the flow of the common mode noise current in the circuit of FIG. In this figure,
The common mode noise current from the noise source on the AC line side is absorbed by each Y capacitor CY after being attenuated by the coil, and the common mode noise current from the load side is directly absorbed by each Y capacitor CY. . In this way, both normal mode and common mode noise currents are reduced.

[0005]

However, the conventional AC line filter requires the plurality of capacitors CX, CY and the coil L1 as described above, which increases the cost due to the increase in the number of parts, the work process, and the mounting area. There was an adverse effect of increasing the size of the product due to the increase.

The present invention has been made in view of the above points, and an object thereof is to reduce the number of parts and the mounting area of a circuit, especially the power supply section, which needs to suppress noise, and to reduce noise even in an inductor or a transformer alone. It is to provide a winding with a noise prevention effect that can reduce the noise.

[0007]

In order to solve the above problems, the present invention is directed to electrostatic shields S1 and S2 arranged on the outer periphery of windings P and S, and winding P from electrostatic shields S1 and S2. , S side, windings P, S and electrostatic shield S1,
The first shields 3 and 5 and the second shield 3
And the first shields 3, 5
The second shields 4 and 6 are connected to one end and the other end of the windings P and S, respectively, and the electrostatic shields S1 and S2 are grounded.

Alternatively, the transformer for a power supply has the above-mentioned noise-preventing winding.

[0009]

Next, an embodiment of the present invention will be described. FIG. 1 is a structural view conceptually showing a power transformer having a winding with a noise prevention effect according to the present invention. In the figure, P is the primary winding of the transformer, S is the secondary winding of the transformer, 1 is the electrostatic shield of the primary winding, and 2 is 2
Electrostatic shield of secondary winding, 3 is primary shield of primary winding, 4 is secondary shield of primary winding, 5 is primary shield of secondary winding, 6 is secondary winding The second shield 13 is a core.

CX1 is the capacitance between the primary winding P and the first and second shields 3, 4 and CY1 is the capacitance between the first and second shields 3, 4 and the electrostatic shield 1. capacity,
CX2 is a secondary winding S and first and second shields 5, 6
, CY2 is a capacitance between the first and second shields 5,
It is the capacitance between 6 and the electrostatic shield 2.

However, in this example, the primary winding and the secondary winding are coaxially overlapped with each other, and the primary winding and the secondary winding are wound around the primary winding and the secondary winding, for example, in the upper and lower portions, that is, on the outer peripheral portion. By providing the electric shields 1 and 2 and grounding the terminals S1 and S2 of the electrostatic shields 1 and 2, it is possible to electrostatically shield (Faraday shield) between the primary and secondary windings.

A first shield S is provided inside the electrostatic shields S1 and S2 and around the windings P and S.
3, S5 and the second shields S4, S6 are arranged, for example, on the lower side and the upper side of the winding (planes parallel to the central axis of the winding) so as not to overlap each other. Further, although omitted in this figure, the electrostatic shields S1, S
2, the first shield S3, S5, the second shield S
An insulating material made of paper, synthetic resin, air or the like is provided between 4, S6 and the windings P, S so as to be electrically insulated from each other.

Further, one ends of the windings P and S are connected to one ends of the first shields 3 and 5, and the other ends of the windings P and S are connected to one ends of the second shields 4 and 6. The other ends of the first shields 3 and 5 and the other ends of the second shields 4 and 6 are connected to one terminals S3 and S5 of the windings P and S, respectively.
It is connected to the other terminals S4 and S6 of the windings P and S. As a result, each winding P, S has a first shield 3, 5
And the terminals S3, S via the second shields 4, 6
5, S4, S6 will be connected.

That is, the electrostatic shields 1 and 2 and the winding P,
The first shields 3 and 5 and the second shields 4 and 6 arranged between the S and the S shields respectively have a capacitance component (capacitor) CX1 between the windings P and S and the electrostatic shields 1 and 2. CX
2, CY1 and CY2.

The capacitance CX between the windings P and S and the first shields 3 and 5 and the second shields 4 and 6 corresponds to the X capacitor because it is the capacitance between the lines. The capacitance CY between the shields 3 and 5, the second shields 4 and 6, and the electrostatic shields 1 and 2 becomes the capacitance between the line and the ground, and corresponds to the Y capacitor.

FIG. 2 shows an equivalent circuit of the transformer shown in FIG. 1. The capacitors CX on the primary side and the secondary side of the transformer are combined with the inductance components of the windings P and S. , CY, a noise filter that acts on both the normal mode and the common mode is formed. In the figure, AC is an AC power source input to the primary side, R
L is the load on the secondary side.

As described above, since the inductor or the transformer itself has the function of the noise filter, it is not necessary to provide a special noise filter circuit, and the number of parts and the number of assembling steps can be reduced. Also, by adjusting the values of the capacitors CX and CY to appropriate values, a filter of several MHz to several 100 MHz can be obtained.

[0018]

EXAMPLE FIG. 3 shows a concrete example of the case where the noise-preventing winding according to the present invention is used in a transformer, and the characteristics in comparison with the control example are shown in FIGS. Show and explain.

FIG. 3 is a partial sectional view of a transformer having a winding with a noise prevention effect. In the figure, 1 is an electrostatic shield, 3 is a first shield, 4 is a second shield, and 7-1.
1 is an insulating material, 12 is a coil bobbin, 13 is a core, P is 1
The secondary winding, S is a secondary winding.

The core 13 is made of a magnetic material such as iron, cobalt or ferrite, and is appropriately selected and used depending on the magnetic saturation characteristics required for the transformer. Coil bobbin 1 made of resin or the like formed around this core 13
Although not shown in the figure, 2 also appears on the lower part of the U-shaped bobbin so that the windings P and S can be wound inside the bobbin.

Further, the electrostatic shield 1, the first shield 3 and the second shield 4 are formed of a copper plate or copper foil which is a conductive material having a low electric resistance in this example, but other materials such as aluminum are used. It may be a conductive material. The materials of the insulating materials 7 to 11 are not particularly specified as long as they are electrically non-conducting insulating materials. However, when the breakdown voltage is taken into consideration, a material having a high insulating property is used and the capacitance of each of the capacitors CX and CY. When it is desired to increase the amount, it is preferable to use a dielectric material.

Inside the coil bobbin 12, the electrostatic shield 1, the insulating material 7, the first shield 3, the insulating material 8, the primary winding P, the insulating material 9 and the second shield are arranged in this order from the core 13 side. , Insulating material 10, electrostatic shield 1, insulating material 11, 2
The secondary winding S is arranged concentrically. Further, the electrostatic shield 1 on the core 13 side and the electrostatic shield 1 on the secondary winding S side are electrically connected in an actual use and work together. In this example, only the primary winding P side is provided with a noise prevention effect, and the secondary winding S side is omitted.

In the transformer having such a structure, the connection between the electrostatic shield 1, the first shield 3, the primary winding P, and the second shield 4 is changed to transmit from the primary P side to the secondary S side. The measured noise level is shown in FIGS.

In FIG. 4, the terminals of the primary winding P and the secondary winding S are taken out of the winding as they are, normal mode noise is applied to the primary side, and the noise level generated on the secondary side is measured. It is shown in the graph. The vertical axis of the graph represents the secondary side level in decibels (dB) when the noise level applied to the primary side is 0 dB, and the horizontal axis of the graph represents the noise frequency in the range of 10K to 10M (Hz). Shows.

FIG. 5 shows the noise level when the electrostatic shields 1 on the core 13 side and the secondary winding S side are connected to each other, and the other conditions are the same as in the case of FIG. Under the conditions of this figure, it can be seen that no special effect is produced on the noise in the normal mode as compared with the case of FIG.
FIG. 6 shows a capacitor (0.1 μF) in parallel with the primary winding P.
Shows the noise level when connecting the so-called X
This corresponds to the case where a capacitor is provided. In this case, it can be seen that the noise of high frequency centered on 1 MHz is significantly reduced as compared with the graph of FIG.

FIG. 7 shows noise levels when the first shield 3 and the second shield 4 are connected to one end and the other end of the primary winding, respectively, and other conditions are shown in FIG.
Is the same as Under this condition, although the noise level is slightly higher than that in FIG. 6, the noise in the normal mode is remarkably reduced (about 20 dB).

In FIG. 8, the terminals of the primary winding P and the secondary winding S are taken out from the winding as they are, and common-mode noise is applied between the primary winding P and the ground to generate secondary current. This is a graph showing the measured noise level. The vertical axis and the horizontal axis of the graph are the same as in the case of FIG.

In FIG. 9, the electrostatic shields 1 on the core 13 side and the secondary winding S side are connected to each other and grounded, and the first shield 3 and the second shield 4 are connected to the primary winding. 2 shows the noise level when connected to one end and the other end, respectively. Under this condition, it can be seen that the common mode noise is reduced by about 20 to 30 dB or more on average as compared with the case of FIG.

As described above, the transformer using the winding with the noise prevention effect according to the present invention has the effect of reducing the noise in both the normal mode and the common mode.
In the above example, the noise-preventing winding is applied only to the primary winding P side. However, if the manufacturing cost, the size of the transformer, or the like may be increased to some extent, the primary and secondary windings may be used. If the windings with a noise prevention effect are applied to both of them, a further noise reduction effect can be obtained. Further, by using such a transformer as a power transformer of a power source section for which there is a great demand for measures against harmonics, it can be utilized more effectively.

[0030]

As described above, according to the present invention, noise can be reduced even with an inductor or a transformer alone, the number of circuit components and the mounting area can be reduced, and the electronic device can be reduced in size and weight.

Further, by applying it to the power transformer, it is possible to effectively prevent the noise from leaking to the power line with a small number of parts.

[Brief description of drawings]

FIG. 1 is a structural diagram conceptually showing a power transformer having a winding with a noise prevention effect according to the present invention.

FIG. 2 is a circuit diagram showing an equivalent circuit of the transformer of FIG.

FIG. 3 is a partial cross-sectional view of a transformer having a winding with a noise prevention effect, which is an embodiment of the present invention.

FIG. 4 shows the results of measuring the noise level generated on the secondary side by extracting the terminals of the primary winding and the secondary winding of FIG. 3 as they are from the winding and applying normal mode noise to the primary side. It is the graph shown.

5 is a graph showing a noise level in a normal mode when the electrostatic shields on the core side and the secondary winding side of FIG. 3 are mutually connected.

6 is a graph showing a noise level in a normal mode when a capacitor is connected in parallel with the primary winding of FIG.

FIG. 7 shows the first shield and the second shield of FIG.
6 is a graph showing a normal mode noise level when connected to one end and the other end of the primary winding, respectively.

FIG. 8: The terminals of the primary winding and the secondary winding of FIG. 3 are taken out from the winding as they are, common mode noise is applied between the primary winding and ground, and the noise level generated on the secondary side is detected. It is the measured graph.

9 is a cross-sectional view of the core side and the secondary winding side of FIG. 3 in which the electrostatic shields are connected to each other and grounded, and the first shield and the second shield are respectively connected to one end of the primary winding and the other. It is the graph which showed the common mode noise level when connecting at the end.

FIG. 10 is a circuit diagram showing a basic configuration of a conventional AC line filter.

11 is a diagram showing a flow of a normal mode noise current in the circuit of FIG.

12 is a diagram showing the flow of common mode noise current in the circuit of FIG.

[Explanation of symbols]

 S primary winding P secondary winding 1,2 electrostatic shield 3,5 first shield 4,6 second shield 7-11 insulating material 12 coil bobbin 13 core CX X capacitor CY Y capacitor

Claims (2)

[Claims] 1. An electrostatic shield arranged on an outer peripheral portion of a winding, and a first shield and a second shield which are located closer to the winding than the electrostatic shield and generate a capacitance between the winding and the electrostatic shield.
And a shield for preventing noise, wherein the first shield and the second shield are respectively connected to one end and the other end of the winding, and the electrostatic shield is grounded. line. 2. A transformer having a winding with a noise prevention effect according to claim 1.