JPH0227534Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a high-frequency coil, and is particularly designed to effectively block high-frequency noise components.

[Background technology and its problems]

Conventional power supplies with a switching regulator configuration have come to be used in large numbers as power supplies for electronic devices because they are small and lightweight. Analog electronic equipment, such as the

Furthermore, in a system in which analog electronic equipment and digital electronic equipment are connected to the same signal line, there is a problem in that high frequency noise components generated from the digital electronic equipment adversely affect the analog electronic equipment through the commonly connected signal line.

In order to solve such problems, conventional measures have been taken to block high frequency noise by providing a high frequency coil at the output end of a power supply or at the input/output end of each electronic device. For example, as shown in FIG. 2, a power output line 3 is connected to the output end of a power supply 1 having a switching regulator configuration through a high frequency coil 2, and an analog electronic device 4 and a digital Similarly, high frequency coils 6 and 7 are inserted at the connection points of the electronic device 5.

If these high-frequency coils 2, 6, and 7 have good high-frequency noise blocking characteristics, the high-frequency noise generated in the power supply 1 will be blocked in the high-frequency coil 2, and will not be sent to the power supply output line 3. Furthermore, the high frequency noise generated inside the digital electronic device 5 by the high frequency coil 7 of the digital electronic device 5 can be blocked by the high frequency coil 7 and cannot be sent to the power output line 3. In addition to this effect, the high frequency coil 6 can prevent high frequency noise from flowing into the analog electronic device 4 by blocking high frequency noise leaked into the power supply output line 3.

As this type of high-frequency coil, a multilayer winding coil 11 as shown in FIG. 3 has conventionally been used. The chi-yoke coil 11 is constructed by simply winding a single wire in multiple layers to form an inductance large enough to block high frequency noise.

However, as shown in FIG. 4, the equivalent circuit of a chiyoke coil with this configuration has a configuration in which a stray capacitance CSO formed between each winding is connected in parallel with an inductance L0 obtained by each winding.

As shown in FIG. 5, the high-frequency noise blocking characteristic of the chi-yoke coil 11 is, for example, approximately
If the inductance L is selected to have a cut-off frequency near 40 [MHz], this cut-off frequency is 40 [MHz].
Hz] can block almost all high-frequency noise in the vicinity. However, when the frequency becomes higher than this cut-off frequency, high-frequency noise components higher than the cut-off frequency are transmitted to the chiyoke coil 11 through the stray capacitance CSO.
A phenomenon of leakage occurred through the filter, and it was still insufficient as a means for shielding high frequency components.

[Purpose of invention]

This idea was created taking the above points into consideration.
The present invention aims to obtain a high-frequency coil that further improves the cut-off characteristics of conventional high-frequency coils.

[Summary of the idea]

In order to achieve this purpose, in this invention,
A multi-layer coil section and a single-layer coil section connected in series to the multi-layer coil section are provided, one lead wire is drawn out from the multi-layer coil section, and the other lead wire is drawn out from the single-layer coil section. By doing so, the value of the stray capacitance that occurs equivalently in parallel with the inductance is determined by the sufficiently small stray capacitance that occurs in the single-layer coil portion.

〔Example〕

An embodiment of the present invention will be described in detail below with reference to the drawings. As shown in FIG. 1, the high-frequency coil 15 according to the present invention has a multilayer coil portion 17 and a single layer coil portion 18 wound on an H-type ferrite core 16 so as to be sequentially adjacent to each other. One lead wire 19 is drawn out from the single-layer coil portion 18, and the other lead wire 20 is drawn out from the single-layer coil portion 18.

The equivalent circuit of the high frequency coil 15 having such a configuration is as follows:
As shown in FIG. 6, it has an inductance formed by connecting in series an inductance L1 formed by the multilayer coil section 17 and an inductance L2 formed by the single layer coil section 18. . However, in this case as well, the multilayer coil part 1
Stray capacitances CS1 and CS2 are formed in parallel in 7 and the single-layer coil portion 18, respectively, but the stray capacitance formed in the single-layer coil portion 17
The capacitance value of CS1 is actually extremely larger than the value of stray capacitance CS2 formed by the single-layer coil portion 18. For example, when trying to obtain an overall inductance of 100 (μH), if a stray capacitance CS1 of the multilayer coil portion 17 is approximately 100 [pF], then the stray capacitance CS2 of the single layer coil portion 18 is Capacity of about 1/100, that is, 1 [pF]
A certain amount of capacity is generated.

Since these stray capacitances CS1 and CS2 are connected in series with each other, their combined capacitance value is determined by the small capacitance, that is, the value of the stray capacitance CS2, which in this example is close to 1 [pF]. Becomes a value. Thus, the influence of stray capacitance on the high frequency coil 15 as a whole becomes a sufficiently small value determined mainly by the stray capacitance CS2 occurring in the single-layer coil portion 18. As a result, high frequency coil 1
As shown in FIG. 7, the high-frequency noise cut-off characteristics of No. 5 are such that the leakage amount is sufficiently suppressed against high-frequency noise having a high frequency exceeding, for example, 40 [MHz], which is determined by the inductance of the high-frequency coil 15. can be kept to a low value.

Therefore, the high-frequency coil 15 having the configuration shown in FIG. 1 has significantly better blocking characteristics against high-frequency noise than conventional characteristics.

When attaching the high frequency coil 15 having the configuration shown in FIG. 1 to a substrate, attaching it in the manner shown in FIG. 8 is a good method to prevent deterioration of the high frequency noise blocking characteristics.

That is, in FIG. 8, the ferrite core 16 is mounted on the substrate 21 so that the single-layer coil portion 18 and the multi-layer coil portion 17 are stacked in sequence. The lead wire 2 drawn out from the single-layer coil portion 18
0 directly through the substrate 21, and the lead wire 19 drawn out from the multilayer coil section 17 is led out to the substrate 21 side through the outside of the single layer coil section 18.

In this way, the lead wire 19 led out from the multi-layer coil section 17 can be configured to pass through a position quite far away from the single-layer coil section 18. In this way, by utilizing the small winding diameter of the single-layer coil portion 18, the lead wire 19 is connected to the single-layer coil portion 1.
8, thereby further reducing the electrostatic coupling between the lead wire and the coil portion.

According to experiments, for example, in a high-frequency coil with an inductance of about 20 to 470 [μH],
The capacitance value of the stray capacitance between the single-layer coil portion 18 and the lead wire could be reduced to about 0.1 [pF].

Therefore, according to this configuration, the single-layer coil portion 18
By being able to reduce the high frequency noise escaping from the lead wire 19 to the lead wire 19, the stray capacitance between the windings of the single-layer coil portion 18 can be maintained small as described above with reference to FIG. Therefore, it is possible to prevent the lead wire from deteriorating the high frequency noise blocking characteristic described above with reference to FIG.

As a configuration for suppressing the adverse effects of such lead wires, parts corresponding to those in FIG.
As shown in the figure, the ferrite core 16 of the high-frequency coil 15 is fitted into a cylindrical ferrite case 25, and the lead wire 19 is extended to the outside thereof.

In this way, since the influence of the lead wire 19 on the single-layer coil portion 18 can be shielded by the case 25, it is possible to obtain a high-frequency coil that can prevent the high-frequency noise blocking characteristics described above with reference to FIG. 7 from deteriorating. Can be done. In fact, this high frequency coil 15 is suitable for use when obtaining an inductance of about 100 [μH] to 2.2 [mH].

Further, as a method for leading out the lead wires, as shown in FIG.
Even if the lead wires 19 and 20 are configured to be led out to the substrate 21 in a state where the lead wires 20 and 19 are laid down, it is possible to avoid the possibility that the high frequency noise blocking characteristics will be deteriorated by the lead wires 20 and 19. Incidentally, in this case, since the lead wire 20 does not extend along each wire ring of the single-layer coil portion 18, the lead wire 20 does not extend along each wire ring of the single-layer coil portion 18.
This can eliminate the risk of unnecessary increase in stray capacitance.

[Effect of idea]

As described above, according to the present invention, by configuring the high-frequency coil so that the multi-layer coil part and the single-layer winding coil part are connected in series, the combined stray capacitance of the high-frequency coil 15 as a whole is mainly reduced by the simple By making it determined by the small stray capacitance generated in the layer-wound coil portion 18, it is possible to realize a high-frequency coil with excellent blocking characteristics against high-frequency noise.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing an embodiment of the high-frequency coil according to the present invention, Fig. 2 is a system diagram of a system showing how to use the high-frequency coil, Fig. 3 is an end view showing the configuration of a conventional chiyoke coil, and Fig. 4 is a cross-sectional view showing an embodiment of the high-frequency coil according to the present invention. 5 and 5 are respectively an equivalent circuit diagram and a noise isolation characteristic curve diagram, FIGS. 6 and 7 are an equivalent circuit diagram and a high frequency noise isolation characteristic curve diagram of the high frequency coil in FIG. 1, respectively, and FIGS. FIG. 10 is an end view showing another embodiment of the high frequency coil according to the present invention. 11...Chiyoke coil, 15...High frequency coil, 16...H type ferrite core, 17...Multilayer winding coil section, 18...Single layer winding coil section, 19,2
0... Lead wire, 21... Board.

Claims (1)

[Scope of utility model registration request] It comprises a multi-layer coil part and a single-layer coil part connected in series to the multi-layer coil part, one lead wire is drawn out from the multi-layer coil part and the other lead wire is drawn out from the single-layer coil part. A high-frequency coil that is characterized by drawing out.