JPH05243049A - Inductor - Google Patents

Abstract

PURPOSE:To avoid an increase in resistance due to a skin effect of a winding and to realize an inductor of which the loss is small, by using as the winding a conductor prepared by laminating an electric conductor and an insulator alternately in the shape of a concentric circle. CONSTITUTION:Flange-shaped parts are formed at the opposite ends of a drum core formed of ferrite and a winding 14 is formed on a columnar part of this drum core 12. As for the winding 14, a conductor prepared by laminating an electric conductor 16 and an insulator 18 alternately in the shape of a concentric circle is used. The electric conductor 16 is formed of an Ag layer, for instance, while the insulator 18 is formed of an SiO2 layer for instance. Since a current flows on the surface layer side of each electric conductor 16 when a skin effect of the winding acts, according to this constitution, the current is made to flow the whole of the electric conductor 16 substantially by laminating the electric conductor 16 and the insulator 18 in many layers. Accordingly, a part in the electric conductor 16 in which the current does not flow is diminished and the electric conductor 16 can be used effectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inductor, and more particularly to, for example, a wire-wound inductor used for an amplifier circuit, an oscillator circuit, etc. used in a high frequency region.

[0002]

2. Description of the Related Art As a conventional inductor, there is one in which a winding is wound around a drum core made of ferrite. As the winding wire, a conductor wire in which a conductor is covered with a resin insulator is used.

[0003]

In recent years, in the markets of video equipment, communication equipment, mobile communication, etc., electronic circuits have been made highly accurate and have high frequencies. Along with this, an inductor having a high Q in a high frequency region is required.

However, in the conventional wire-wound inductor, various losses depending on the structure occur, and a high Q cannot be obtained. Of these losses, the skin effect of the winding is particularly problematic in the high frequency region.

The skin effect of the winding will be described. Normal,
The current flowing through the conductor creates a magnetic field around the conductor. At this time, the outer peripheral portion of the conductor only interlinks with the magnetic force lines outside the outer peripheral portion of the conductor, but the central portion of the conductor also interlinks with the magnetic force lines generated inside the conductor. Therefore, the number of magnetic field lines interlinking with the conductor increases toward the central portion of the conductor. Inductance occurs due to the interlinking of the conductor and magnetic force lines, but the maximum number of magnetic flux lines interlinking with the central portion of the conductor maximizes the inductance in the central portion of the conductor. On the other hand, the surface area of the conductor has the smallest inductance. The higher the frequency of the current flowing through the conductor, the larger the difference in the inductance between the central portion and the surface portion of the conductor.
Therefore, in the high frequency region, the current density is maximum on the surface and sharply decreases toward the center. Therefore, the cross-sectional area of the conductor through which the current flows is substantially reduced and the resistance of the winding is increased. Therefore, the coil loss is significantly increased.

Generally, the skin thickness δ (m) is expressed by the equation (1). Here, ω is the angular frequency, μ is the magnetic permeability, and σ is the electrical conductivity (1 / Ωm). FIG. 5 is a graph showing the skin depth of the portion where the current flows when Ag is used for the conductor, using the formula of Formula 1. In this graph, the horizontal axis represents the logarithmic value of frequency (logF), and the vertical axis represents the logarithmic value of skin thickness (logδ). As can be seen from FIG. 5, the skin depth at a frequency of 100 MHz is 6.3 μm.
Is. That is, at this frequency, current flows only in the surface layer having a depth of 6.3 μm from the surface of the conductor.

[0007]

[Equation 1]

Therefore, the main object of the present invention is to avoid an increase in resistance due to the skin effect of the winding,
An object of the present invention is to provide an inductor with low loss even when used in a high frequency region of 100 MHz or higher.

[0009]

According to the present invention, in an inductor including a drum core made of ferrite and a winding formed around the drum core, conductors and insulators are alternately laminated in concentric circles as windings. It is an inductor using the conducting wire.

[0010]

When the skin effect works, a current flows in the surface layer portion of each of the plurality of concentric conductors divided by the insulator.

[0011]

According to the present invention, a current flows in the surface layer portion of each conductor divided by an insulator. Therefore, even if the skin effect is exerted, the current is applied to most of the cross-sectional area of the conductor as a whole. Flowing. Therefore, the increase in resistance due to the skin effect of the winding is small. Therefore, the loss of the inductor at high frequencies can be suppressed.

The above-mentioned objects, other objects, features and advantages of the present invention will become more apparent from the detailed description of the embodiments below with reference to the drawings.

[0013]

1 is a perspective view showing an embodiment of the present invention. The inductor 10 includes a drum core 12. The drum core 12 is made of ferrite. Drum core 12
Has a columnar portion formed in the central portion and collar portions formed at both ends thereof. The winding 14 is formed on the cylindrical portion of the drum core 12.

As shown in FIGS. 2 and 3, as the winding 14, a conductor wire 20 in which conductors 16 and insulators 18 are concentrically alternately laminated is used. The conductor 16 is, for example, A
formed by the g layer. The insulator 18 is formed of, for example, a SiO ₂ layer.

Since the inductor 10 has the structure as described above, when the skin effect is exerted, the current is transmitted to each conductor 1.
It flows on the surface side of No. 6. At this time, each conductor 16 and the insulator 1
If 8 and 8 are multi-layered, the current will flow through almost the entire conductor 16. Therefore, the portion of the conductor 16 where no current flows becomes small, and the conductor 16 can be used effectively. Therefore, even if it becomes a high frequency of 100 MHz or more,
The resistance of the winding 14, that is, the conductor wire does not increase so much, and the Q of the inductance can be improved.

FIG. 4 is a graph showing the relationship between the frequency and the Q of the inductor. In this graph, the horizontal axis shows the logarithmic value of frequency (logF) and the vertical axis shows the logarithmic value of Q (logF).
Q) is shown. In FIG. 4, the dotted line is the characteristic of the conventional inductor, and the solid line is the characteristic of the inductor of the present invention. As can be seen from FIG. 4, the conventional inductor has a low Q peak of 20, while the inductor of the present invention has a Q peak of more than 100. in this way,
It can be seen that the inductor of the present invention has a sufficient effect of avoiding the influence of the skin effect.

As described above, in the inductor of the present invention,
The increase in resistance due to the skin effect of the winding can be suppressed. From this, according to the present invention, it is possible to contribute to the performance improvement of the amplifier circuit and the inductor for the oscillation circuit.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention.

FIG. 2 is a perspective view showing a part of a conductor wire used as a winding wire of the inductor shown in FIG.

FIG. 3 is an enlarged sectional view showing a conductor wire used as a winding wire of the inductor shown in FIG.

FIG. 4 is a graph showing the characteristics of the inductor of the present invention and the conventional inductor.

FIG. 5 is a graph showing a skin thickness when Ag is used for a conductor, using the formula of Formula 1.

[Explanation of symbols]

 10 inductor 12 drum core 14 winding 16 conductor 18 insulation 20 conductor

Claims (1)

[Claims] 1. An inductor including a drum core made of ferrite and a winding formed around the drum core, wherein a conductor wire in which a conductor and an insulator are concentrically alternately laminated is used as the winding. An inductor.