JP2961427B2 - High frequency winding component and switching power supply using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a high-frequency winding component such as a high-frequency transformer used in a DC-DC converter. As a result, a low-loss converter using this can be obtained. Furthermore, the present invention relates to a high-frequency winding component related to a winding of a choke coil, an inductor and the like, in addition to a high-frequency transformer.

(Prior art) Conventionally, as shown in technical data provided by a ferrite maker or the like, as a material characteristic used for a high-frequency transformer, only the skin effect of a single conductor placed in the air is used. Was not taken into account.

However, in reality, a high-frequency winding component is installed in a limited space of a winding frame while a plurality of windings interact with each other.

Therefore, a DC-DC converter incorporating a high-frequency transformer designed using the above data has a large loss far from reality.

As a conventional common sense, it is usual to use a copper wire having a low resistance value as the winding and to make ten or less parallel windings.

Here, the term "parallel winding" generally refers to a method in which a plurality of windings are bundled in parallel or twisted and wound around a bobbin as one collective wire. Conventionally, at most 10 or less were used because of the ease with which the winding frame could be attached to the pins.

(Problems to be Solved by the Invention) However, in the high-frequency region, the high-frequency resistance (related to loss) of the winding is determined not only by the resistivity and frequency of the conductor, but also by the AC magnetic flux at the place where the conductor exists. Depends on density. As a result, the increase in the high-frequency resistance became remarkable, and the object could not always be sufficiently achieved.

The high-frequency resistance increases significantly compared to the DC resistance. One of the causes is the skin effect, and the other is based on the proximity effect, which the present inventors have paid attention to.

The skin effect is known as a phenomenon in which when a high-frequency current flows through a conductor, current concentrates on the surface of the conductor due to lines of magnetic force inside and outside the conductor that are created by themselves in the axial direction of the conductor. In addition, the proximity effect is such that when a plurality of conductors exist close to each other, the current value increases in a plane perpendicular to the axial direction of the two conductors from a portion where the two conductors are close to each other outward. It is a phenomenon that changes.

The two causes of the increase in the high-frequency resistance can be considered as an interaction between the current and the magnetic field at each point in the conductor from the viewpoint of electromagnetism.

Therefore, the resistance ratio R as the sum of the skin effect and the proximity effect
The calculation formula of _AC / R _DC (R _AC is AC resistance value, R _DC is DC resistance value) was derived. As a result, they have found that a high-frequency winding component such as a high-frequency transformer and the like that is smaller, lighter, and more efficient with less loss can be obtained as follows.

That is, as a measure to reduce the loss, the number of parallel windings per turn (hereinafter referred to as the number of paras) is set to a predetermined range or more. A value of 50 or more is appropriate as this value. Conventionally, it was at most about 10 or less. Use a winding material with a resistivity 1.5 times or more higher than copper. Aluminum is suitable for this example. Increase the distance between the winding conductors to some extent. Specifically, the proximity effect is reduced, for example, by increasing the thickness of the insulating coating.

Therefore, an object of the present invention is to solve the conventional disadvantages in view of the above problems, and to solve high frequency winding components, for example, a high frequency winding component such as a high frequency transformer having a reduced high frequency resistance in consideration of the leakage magnetic flux inside the transformer, and And a switching power supply using the same.

B. Configuration of the Invention (Means for Solving the Problems) In order to achieve the above object, a high-frequency winding component of the present invention is a high-frequency winding component that passes a current of 100 KHz or more,
The conductor inside the bobbin of the high-frequency winding component is a coil wound around a magnetic core with 15 or more parallel conductors (para number) per turn of the bobbin, and has a resistivity of 2.5 × 10 ⁻⁸ at room temperature. Provided is a high-frequency winding component using a winding of Ωm or more and made of a nonmagnetic material.

Further, when the winding is made of a copper alloy having a copper content of 99% or less or an alloy containing aluminum as a main constituent element, further, when the magnetic permeability of the winding is 10 or less,
Still further, the present invention provides the high-frequency winding component having an insulating gap interposed between the winding conductors.

Further, the present invention can be effectively provided by being used as a switching power supply having a DC power supply, a switching circuit, a transformer, a rectifier circuit, and a smoothing circuit, and using the high-frequency winding component as a winding component.

(Operation) According to the high-frequency winding component of the present invention, high-frequency, for example, 10
High-frequency resistance at 0 KHz or higher can be reduced. The reason is that high-frequency resistance due to the skin effect and the proximity effect between windings can be reduced. That is, when a portion of the conductor (copper wire) is viewed microscopically, the high frequency resistance of the minute portion is determined by the magnitude of the magnetic flux density in the minute portion. On the other hand, a remarkable effect was confirmed by taking the above-mentioned or the above-described measures for reducing the high-frequency resistance.

Further, the switching power supply functions as a highly efficient inverter despite its small size and light weight, and a remarkable reduction effect in terms of temperature rise was confirmed.

(Example) A high-frequency transformer will be described as an example of a high-frequency winding component of the present invention with reference to the drawings, but the present invention is not limited to these examples. In addition, as a high-frequency winding component, it was confirmed that any one of a high-frequency choke coil and an inductor could be implemented and exhibited the same level of effect. Therefore, an embodiment using a high-frequency transformer as a high-frequency winding component will be specifically described below. In addition, the choke coil, the inductor, and the like can be miniaturized with the increase in the frequency, and the present invention can exhibit excellent effects on the noise surface, the simplification of the circuit, the transient response, and the like.

Example 1 FIG. 1 shows a conductor wound into a bobbin 1 with a square cross section for analysis of high-frequency resistance according to the present invention. The winding frame cross section 2 is 4 × 4 mm, the average magnetic path length is 50 mm, the number of turns is 4 turns (T), and the conductors are uniformly distributed inside the winding frame 1. The change in the high-frequency resistance when the value was changed was confirmed.

When changing the number of parallel conductors, the thickness of the wire was selected so that the total cross-sectional area was substantially equal. The result is
This is shown in FIGS. The conductor material used for this was a copper wire, an aluminum wire, a copper alloy wire, and an aluminum alloy wire.

Here, the horizontal axis represents the number of parallel conductors (para number) per turn, and the vertical axis represents high-frequency resistance. FIG. 2 shows a relationship diagram between the high-frequency resistance and the para number, with the parameter being a frequency of 10 to 500 KHz.

Here, the relationship between the number of parallel conductors (para number) and the high-frequency resistance when the resistance value of the conductor is fixed is shown, and there is a maximum point of the resistance value at a specific para number for each frequency.
In particular, the tendency becomes remarkable at 100 KHz or more. It has been clarified that the conventional measures to reduce the loss by increasing the current value by connecting 5 to 10 conductors in parallel have an adverse effect.

FIG. 3 is a relational diagram of the conductor of FIG. 1 with the vertical axis representing high-frequency resistance and the horizontal axis representing para numbers. 200K frequency
When the frequency was fixed to Hz, the resistivity was expressed as a parameter in which the resistivity of copper was 1 and the resistivity of other conductors was a relative ratio.

Here, when the frequency is 200 KHz, in a region where the para number is 15 or more, the higher the resistivity, the lower the high-frequency resistance tends to be.

Further, in the region where the number of paras is 50 or more, it can be seen that the tendency of the decrease in the high-frequency resistance due to the magnitude of the resistivity is small and that it is significantly different from the resistivity of copper (1 in the figure). Also, the case where the frequency is set to 200 KHz is shown.
This tendency is observed above Hz. As a result, it is appropriate to design a conductor as a high-frequency winding component in a region where the number of paras is 50 or more.

FIG. 4 is a relationship diagram of the conductor of FIG. 1 in which the vertical axis represents the high-frequency resistance, the horizontal axis represents the resistivity of copper as 1, and the resistivity of the other conductors as a relative ratio.

When the number of paras was fixed at 40 and the frequency was fixed at 200 kHz, the resistivity was indicated by a parameter in which the resistivity of copper was 1 and the resistivity of other conductors was a relative ratio.

Here, when the resistivity of copper is 1 and the resistivity of the other conductor is 1.5 times as a relative ratio, the high-frequency resistance is about 80%, 2
In the case of twice, it is recognized that the high frequency resistance is reduced to about 55%. As a result, by applying the present invention to a high-frequency winding component, the loss can be significantly reduced.

Generally, the resistivity of copper at room temperature (20 ° C) is 1.72 × 10 ^-8 Ωm
As the conductor, a nonmagnetic material having a resistivity of 2.5 × 10 ⁻⁸ Ωm or more at room temperature is suitable.

It was also confirmed that high-frequency resistance can be reduced when a copper alloy having a copper content of 99% or less is used as a winding when the above resistivity condition is met.

Similarly, the effect was confirmed in the case of an alloy containing aluminum as a main constituent element and in the case of a copper alloy being aluminum bronze.

Furthermore, it has been confirmed that the conductor may be any material as long as it is substantially a non-magnetic material, for example, if the magnetic permeability is 10 or less, preferably 5 or less.

Embodiment 2 FIG. 5 is a schematic diagram of a main part of a series resonance type converter using a high-frequency transformer as an example of a high-frequency winding component with reduced high-frequency resistance according to the present invention.

This is an example of a DC-DC converter that uses the DC power supply 11 again as a DC power supply via a high-frequency transformer 16, and includes switching elements 12, 13, a high-frequency choke 14, a capacitor 15, rectifying diodes 17, 18, and a smoothing capacitor 19. A resonant converter was constructed.

In the high-frequency transformer of the present invention, the harmonic noise from the converter output was at a very low level.

(Effect of the Invention) According to the high-frequency winding component of the present invention, there is an effect that the high-frequency resistance can be reduced as compared with the conventional example, and the skin effect and the proximity effect, which have been the conventional problems, can be significantly reduced. it can.

In addition, a converter that can be used in a high-frequency region using the same reduced size, reduced weight, reduced harmonic noise, and functioned as a high-efficiency converter, confirming a remarkable reduction in temperature rise.

According to the first aspect of the present invention, the high-frequency winding component is 100K.
At a frequency of more than Hz, the reduction rate of the high-frequency resistance can be increased by selecting a predetermined resistivity and a non-magnetic material, and the leakage magnetic flux inside the transformer can be reduced. According to the second and third aspects of the present invention, this reduction effect can be further expected.

[Brief description of the drawings]

FIG. 1 is a partial configuration diagram of a conductor (copper wire) for a high-frequency transformer showing one embodiment of the present invention, FIG. 2 is a diagram showing the relationship between high-frequency resistance and the number of paras, and FIG. FIG. 4 is a graph showing the relationship between resistivity and high-frequency resistance of copper and other conductors, and FIG. 5 is a series resonance type using a high-frequency transformer having a reduced high-frequency resistance according to the present invention.
It is a schematic diagram of the main part of a DC-DC converter. 1: Reel, 2: Reel cross section 11: DC power supply 12, 13: Switching element 14: Choke, 15, 19: Capacitor 15, 19: Capacitor 16: High frequency transformer 17, 18: Diode

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-254714 (JP, A) JP-A-62-126814 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01F 27/28 H01F 31/00 H01F 17/00

Claims (5)

(57) [Claims] 1. A high-frequency winding component for passing a current of 100 KHz or more, wherein a conductor inside a winding frame of the high-frequency winding component is connected to one of the winding frames.
It is characterized by using a winding wound around a magnetic core with more than 15 parallel conductors (para number) per turn, and using a winding made of non-magnetic material with a resistivity of 2.5 × 10 ^-8 Ωm or more at room temperature. High frequency winding parts. 2. The high-frequency winding component according to claim 1, wherein the winding is made of a copper alloy having a copper content of 99% or less or an alloy mainly containing aluminum. 3. The winding according to claim 1, wherein the permeability of the winding is 10 or less.
Or the high frequency winding component according to claim 2. 4. The high-frequency winding component according to claim 1, wherein an insulating gap is interposed between the winding conductors. 5. A DC power supply, a switching circuit, a transformer,
A switching power supply comprising a rectifier circuit and a smoothing circuit, wherein the high-frequency winding component according to claim 1 is used as a winding component.