JPS639138Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a noise filter element used in computers and digital equipment.

Conventional Structure and Problems Switching noise generally exhibits a waveform similar to the clock frequency (several MHz) of a microcomputer, which is a pulse waveform with steep rises and falls. This steep waveform may generate harmonics in a wide range up to the VHF band, causing radio wave damage prevention.

In addition, there are many problems in which computers, digital devices, etc. malfunction due to reception of external noise. Therefore, in order to improve the electromagnetic environment and improve noise resistance, noise filters are generally installed on power lines, signal lines, etc. to take noise countermeasures.

First, a conventional noise filter element will be explained with reference to the drawings.

FIG. 1 is a circuit diagram of an inductor, 1 and 2 are terminals, and 3 is an inductance element. Its structure is as shown in FIG. 2, in which a ferrite bead core 4 is inserted into a lead wire 5.

Figure 3 is a circuit diagram of a T-type LC filter.
3 is an input/output terminal, 3 is an inductance element, 6 is a ground terminal, and 7 is a capacitance element.

The structure is as shown in FIG.
0, and two ferrite bee cores 4 are inserted into this lead wire 10. these are,
A low-cost noise filter that can be attached to a printed circuit board.

By the way, LC filters and inductors use inductance elements with high Q in order to increase the filter effect, especially the steepness of the attenuation characteristics.Also, when the applied frequency is high, core loss (mainly hysteresis loss) is used. Use a core with low eddy current loss, etc.). When a pulse voltage waveform with steep rises and falls similar to switching noise is applied to noise filter elements such as LC filters and inductors, the waveform resonates due to electrostatic capacitance and stray capacitance. There are also phenomena in which the vibrations become louder, or the vibrations persist for a certain period of time. These phenomena occur when a noise filter element that uses an inductance element with high Q and low core loss is connected to the noise source side, and there is a problem in that it protects other equipment from damage due to, for example, electrostatic coupling. .

In other words, when noise filter elements such as the above-mentioned LC filter and inductor are used to eliminate switching noise, contrary to the original filter effect, the noise can be prevented at a certain frequency (frequency where resonance or vibration persists). There were serious shortcomings such as causing harm.

Purpose of the Invention In view of the above drawbacks, the present invention provides a noise filter element that can be attached to a substrate and has an excellent noise removal effect without causing interference at a specific frequency.

Structure of the invention In order to achieve the above object, the invention divides the inductor into a plurality of parts, and divides the inductor into multiple parts from the noise source side terminal to one terminal, starting from the one with the lowest Q of the inductor or the one with the highest core loss. It has a structure in which they are arranged side by side, and is characterized by having both a noise absorption effect and a filter effect.

DESCRIPTION OF EMBODIMENTS A noise filter element according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 5 shows an inductor which is a noise filter element in an embodiment of the present invention, 1 and 2 are input/output terminals, 11a, 11b, and 11c are ferrite bead cores divided into a plurality of sections, 12a and 12b are air gaps, and 5 indicates a lead wire.

Here, if the terminal connected to the noise source side is terminal 1, the ferrite bee cores 11a, 11b,
The order of magnitude of Q of the noise inductor 11c is 11
so that a<11b<11c, or,
The order of the core loss of the ferrite bead cores 11a, 11b, and 11c is 11a>11b>11
They are arranged side by side so that c. Here, the first core 11a and the second core 11a arranged on the noise source side
It is desirable that the difference in Q or loss between the core 11b and the core 11b is about 10 times or more.

Next, FIGS. 6b to 6c show the results of applying a pulse voltage between the terminals of individual inductors having different Qs, that is, between the input and output terminals 1 and 2 of FIG. 2, and measuring the waveform of the rebound voltage.

FIG. 6a shows the applied pulse voltage waveform.

Figure 6b shows the terminal voltage waveform of the inductor, and the Q of the inductor is about 10. Figure 6c shows the terminal voltage waveform of the inductor, and the Q of the inductor is about 10.
is about 1. It can be seen that inductors with a small Q or a large core loss have a low rebound voltage A and do not sustain vibration. This is because the energy stored in the inductor is dissipated as heat due to core losses, ie there is an absorbing effect.

Therefore, by arranging the cores like an inductor, which is a noise filter element in an embodiment of the present invention shown in FIG. 5, the energy component of switching noise with steep rise and fall can be reduced to The arranged core 11a consumes it as heat, the remaining relatively low energy component is consumed in the second core 11b, and then the waveform becomes dull due to the action of inductance by an ordinary inductor 11c with a high Q. In other words, it is possible to increase the steepness of the attenuation characteristic by reflecting the noise toward the noise source side using a filter effect. As a result, resonance between the inductor and stray capacitance and persistence of vibration can be eliminated, and the effects of capacitive coupling can be eliminated, as well as harmful noise components.

As for the material of the inductor, it is also effective to use a Mn-Zn ferrite bead core for the first arrangement core, and a Ni-Zn ferrite bead core for the second and subsequent cores.

Effects of the invention As described above, the present invention uses an inductance element array configured to absorb high energy components on the noise source side, ie, to consume them as heat, and to remove dull waveforms through a filter effect. High energy components on the noise source side are not directly applied to the high Q inductance element. Therefore, the persistence of resonance and vibration as in the past is eliminated, and the effects of electrostatic coupling are no longer generated, so there is no interference at specific frequencies, no harmful noise is passed through, and an excellent noise removal effect is achieved. shows. Therefore, noise resistance can be improved.

Furthermore, the gap between the cores has the effect of preventing the above-mentioned switching noise from passing through on the inductor surface.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a conventional inductor, Figure 2 is a perspective view of the same inductor, and Figure 3 is a conventional T-type inductor.
A circuit diagram of the LC filter, FIG. 4 is a perspective view of the same filter, FIG. 5 is a perspective view of a noise filter element in an embodiment of the present invention, FIG. 6a is an applied voltage waveform diagram, FIG. 6b, c is the Q of the inductor, respectively.
10 and 1 are terminal voltage waveform diagrams. 1, 2...terminal, 6...earth terminal, 11a,
11b, 11c... core, 12a, 12b... void.

Claims (1)

[Scope of utility model registration request] It has an input/output terminal at both ends, and is divided into a plurality of sections, and is connected to the noise source side including the frequency band to be eliminated. 1. A noise filtering element, characterized in that inductors are connected in series in descending order of magnitude, and the inductors are selected so that the inductor on the other input/output terminal side performs a filtering operation for the frequency band to be excluded.