JPH02235420A - Noise filter - Google Patents

Abstract

PURPOSE:To reduce the number of components and to obtain a noise filter of small-sized, and low cost by containing a choke coil consisting of a rod core or a drum core whose spacer mounted to an intermediate part is provided with a winding at both sides to a middle part of a ring core with two troidal windings wound thereto. CONSTITUTION:A spacer 8 is provided in the middle of a rod core 10 or a drum core 7 of a noise filter and a winding terminal 14 of a normal mode choke coil having the winding to both sides of the spacer 8 is contained in the ring core of a winding terminal 13 of a common mode choke coil having two troidal windings 6. Then the magnetic path of the coil 14 is formed by connecting the ring core of the coil 13 or the core 10 with the air gap to decrease the magnetic reluctance and to increase the inductance so as to reduce number of components thereby obtaining a noise filter of small-sized, and low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a noise filter that is inserted into a power line of an electronic device to prevent noise from entering and leaking.

2. Description of the Related Art In general, a noise filter must prevent both components of normal mode noise occurring between a pair of reciprocating lines in a power supply line and common mode noise occurring between a pair of lines and ground. A circuit diagram of a conventional general noise filter is shown in FIG.

1 is a normal mode choke coil for preventing normal mode noise, one of which is inserted in each line, and 2 is a common mode choke coil for preventing common mode noise. The normal mode choke coil 1 is constructed by winding a rod-shaped core or a drum-shaped core with an open magnetic path to prevent magnetic saturation of the core due to the current flowing through each coil. The common mode choke coil 2 is made of ferrite. A ring-shaped core made of an amorphous metal or the like is constructed by winding a pair of wires around the core so that the magnetic flux (normal mode component) caused by the reciprocating current cancels out. Normally, the inductance of the normal mode choke coil 1 is 10 μH to several 100 μH, and the inductance of the common mode choke coil 2 is 1 mH to 20 mH.
It is. The two normal mode choke coils 1 combine with a capacitor 3 connected between the lines to form a filter circuit to reduce normal mode noise.

The common mode choke coil 2 constitutes a filter circuit with two capacitors 4 connected between each line and the ground,
Common mode noise is reduced. Conventional noise filters connect these components on a printed circuit board or by connecting the lead wires of each component in a straight line. It constituted a filter circuit.

Problems to be Solved by the Invention In the conventional configuration described above, there are many components, and the wiring assembly is complicated. In particular, the normal mode choke coil 1
Since it is difficult to magnetically saturate, an open magnetic path type core is used, and it is easy to increase the size of the core to obtain a predetermined inductance.

Therefore, a noise filter that combines these becomes large in size and is significantly disadvantageous in terms of cost.

As a solution to the above-mentioned problem, the present invention provides a noise filter that is small in size and low in cost by reducing the number of component parts.

Means for Solving the Problems In order to solve the above problems, the present invention provides a spacer attached to the center of a ring-shaped core around which two toroidal windings are wound, and a rod-shaped core with windings on both sides of the spacer. A noise filter is constructed by housing a choke coil consisting of a core or a drum-shaped core.

Function As mentioned above, a spacer is provided in the middle of a rod-shaped or drum-shaped core, and a normal mode choke coil with wires wound on both sides of this spacer is attached to a ring-shaped core of a common mode choke coil with two toroidal windings. By storing it, the magnetic path of the normal mode choke coil is constructed by connecting a rod-shaped or drum-shaped core and a ring-shaped core with an air gap, so it is different from the conventional open magnetic path consisting of a rod-shaped or drum-shaped core and a space. In comparison, the magnetic resistance is lower and the inductance is higher than before. This makes the normal mode choke coil smaller. Cost reduction becomes possible.

As for the common mode choke coil, a magnetic path is formed in the circumferential direction of the ring-shaped core, and since the magnetic path of the normal mode choke coil and the magnetic path of the normal mode choke coil intersect at right angles in the ring core, they do not affect each other and there is no deterioration of inductance.

In addition, by storing the normal mode choke coil inside the common mode choke coil and connecting it, 2 to 3
Each coil component can be handled as a single component, making wiring and assembly as a noise filter easier.

For the above reasons, the noise filter can be made smaller and lower in cost.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

Figure 1. FIG. 2 is a plan view and a front sectional view of a noise filter in an embodiment of the present invention. 3 and 4 are a plan view and a front sectional view of a noise filter in another embodiment of the present invention. A pair of toroidal windings 6 are applied to a ring-shaped core 5 made by winding a magnetic metal foil such as a ferrite core or amorphous metal foil, and a pair of toroidal windings 6 are applied to the copper wire in a direction that cancels out the magnetic flux due to the reciprocating current, forming a common mode choke coil. do.

Next, the diameter of the brim is slightly smaller than the inner diameter of the ring-shaped core 5;
Two semicircular spacers 8 made of resin molding are attached from both sides to the center of the drum-shaped core 7, the distance between the flanges of which is approximately equal to the height of the ring-shaped core 5, and fixed to the drum-shaped core 7. A pair of drum-shaped cores 7 are wound with windings 9 on both sides of the spacer 8 so that the magnetic flux caused by the reciprocating current points in the same direction.
Forms a normal mode choke coil.

As another example, as shown in FIGS. 3 and 4, a resin-molded coil bobbin 12 having flanges 11 on both sides and a spacer 8 in the center is attached to a rod-shaped core 10, and the spacer 8
A normal mode choke coil may be formed by providing a pair of windings 9 on both sides of the coil so that the magnetic flux due to the reciprocating current is directed in the same direction.

This normal mode choke coil is inserted into the center of the ring-shaped core 5 of the common mode choke coil, and fixed at a position where the spacer 8 becomes 1/2 the height of the ring-shaped core 5. At this time, the gap between the collar portion 8 of the ring-shaped core 5 and the drum-shaped core 7 or the collar portion l1 of the resin-molded coil bobbin 12 attached to the rod-shaped core 10 is set to be uniform over the entire circumference. The method of fixing the common mode choke coil and the normal mode choke coil is to temporarily fix the spacer 8 of the normal mode choke coil to the ring-shaped core 5 by the spring pressure of the copper wire wound toroidally.
After that, adhesive is poured into the ring-shaped core 5 to fix both choke coils. After integrating both choke coils, a pair of winding terminals 13 in the same direction of the common mode choke coil and a pair of winding terminals 14 of the normal mode choke coil are connected to connect the normal mode choke coil and the common mode choke coil. It is an integrated structure. By connecting a line, an inter-line capacitor, and a line-to-ground capacitor to this integrated choke coil, a noise filter circuit configuration as shown in FIG. 5 can be obtained.

Effects of the Invention The present invention as described above is configured by storing and fixing a normal mode choke coil wound around a rod-shaped or drum-shaped core in the center of a ring-shaped core of a common mode choke coil wound in a toroidal manner. Therefore, the inductance of the normal mode choke coil increases by 1.5 to 2 times compared to when it is not housed in a ring-shaped core, so the rod-shaped core or drum-shaped core for the normal mode choke coil can be configured smaller than before. This reduces the cost of the noise filter, and since the normal mode choke coil is housed and integrated with the common mode choke coil, both choke coils can be constructed with approximately the same volume as a conventional common mode choke coil, reducing noise. It is possible to significantly reduce the size of the filter, and since both jog coils are integrated, wiring can be done in the shortest possible distance, improving the noise reduction effect in the high frequency range. Furthermore, the leakage flux of the normal mode choke coil is reduced compared to the conventional choke coil, and the influence on peripheral components is reduced.This has many advantages and is of great industrial value.

[Brief explanation of the drawing]

1 and 2 are a plan view and a front sectional view of a noise filter according to one embodiment of the present invention, and FIGS. 3 and 4 are a plan view and a front sectional view of a noise filter according to another embodiment of the present invention. , FIG. 5 is an electrical circuit diagram of the noise filter. 5...Ring-shaped core, 6...Troidal winding, 7...Drum-shaped core, 8'-...
・Subasa, 9...Winding, 10...Rod-shaped core, 11...Brim part, 12...Coil bobbin, l3... Winding Wire terminal (common mode choke coil), 14... Winding terminal (normal mode choke coil). Name of agent: Patent attorney Shigetaka Awano and one other person
Evil second ward! E5F: 1li

Claims (1)

[Claims] A noise generated by installing a spacer in the middle of a ring-shaped core wound with two toroidal windings, and housing choke coils consisting of rod-shaped cores or drum-shaped cores with respective windings on both sides of this spacer. filter.