JPS5881320A - Noise filter - Google Patents

Abstract

PURPOSE:To decrease the number of parts and to facilitate assembly by providing couples of windings having mutual inductance in parallel to core parts crossing inside legs through respective through holes, and then connecting two capacitors. CONSTITUTION:On a ferrite core 31, closed magnetic paths having inside legs are formed, and couples of windings 33 and 34, and 35 and 36 having mutual inductance are provided to core parts crossing the legs through respective through holes 48 and 49. Then, two capacitors 37 and 38 are provided in series between those parallel windings with earths between.

Description

[Detailed description of the invention] The present invention relates to improvements in noise filters.

Two types of circuit configurations are known as noise filters.

When configuring a noise filter using magnetic cores and capacitors (order 2).

Only a characteristic in which the rise curve of the attenuation characteristic is 12 dBloc can be obtained. Generally, if you want to obtain a noise filter with a 18 dBloct rise curve of the attenuation characteristic of order 3, you need to wind the two magnetic cores.

Two common motor chain coils are combined with two capacitors to form a noise filter circuit. 1st
The figure shows a configuration diagram of an example of a 9th order 3 noise filter. Figure 2 is.

This is an equivalent circuit of the noise filter in FIG. 1. In FIG. 1, the ferrite core 11 has a winding 16.degree. 17, and the ferrite core 12 has two windings 18.19.

Capacitors 13 and 14 are connected in series between the winding 16 and the winding 17 with the ground interposed therebetween.

The present invention aims at reducing the number of parts and simplifying assembly by integrating the two choke coils described above.

FIG. 3 is a plan view of the embodiment, and FIG. 4 is an equivalent circuit of the embodiment of FIG. Windings 33, 34 degrees 35, 36 are wound around a ferrite core 31 having through holes 48, 49.

FIG. 5 shows the frequency dependence of the amount of noise attenuation. In the figure, curve A is related to the noise filter of second order 2, curve B is related to the input coil shown in FIG. 1, and curve C is related to the embodiment shown in FIG. 3. Curves B and C show the case where magnetic core materials having the same characteristics are used and the total number of turns is the same. As shown in FIG. 5, the embodiment shown in FIG. 3 has substantially the same damping characteristics as the conventional example shown in FIG. 1, although the number of parts is small.

[Brief explanation of the drawing]

Figure 1 is a conventional noise filter configuration diagram, Figure 2 is an equivalent circuit, Figure 3 is a front view of the embodiment, Figure 4 is an equivalent circuit, and Figure 5 is the frequency dependence of noise attenuation. FIG. 31: Ferrite core, 32, 33, 34, 35: Winding wire, 37.38: Capacitor.

Claims (1)

[Claims] A closed magnetic path having a middle leg is formed by a soft magnetic core, and a pair of windings having mutual inductance is applied in parallel through each through hole in the core portion that intersects with the middle leg, and the parallel winding is A noise filter with two capacitors connected in series with a ground between the wires.