JPH11186076A - Transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize reduction in size and cost of a transformer, the leakage inductance of a primary winding of which is large. SOLUTION: A secondary winding 2 is wound on a primary winding 1 of a transformer via a magnetic material 4 for enlarging leak inductance. When a current flows to the primary winding 1, magnetic fluxes ϕ1 , ϕ2 passing through outer legs 6, 7 are generated as shown by a dotted line, and a leakage magnetic flux ϕ3 passing through the magnetic material 4 is also generated. The leak magnetic flux ϕ3 is one which is not interlinked with the secondary wiring 2 and provides the leakage inductance of the primary winding 1. Furthermore, the magnetic material 4 can be partially inserted without being wound all over the primary winding 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a transformer suitable for suppressing harmonic current in a power supply device.

[0002]

2. Description of the Related Art DC power supplies such as switching regulators and inverters are composed of a diode rectifier circuit and a smoothing capacitor. By the way, since the charging current of the smoothing capacitor flows at or near the peak of the sine wave AC voltage, the current on the input side of the rectifier circuit contains harmonic components.

[0003]

In order to reduce the above-mentioned harmonic components, a reactor (choke coil) is connected in series with the power supply line. However, the provision of the reactor inevitably increases the size of the power supply device. Further, in the resonance type switching power supply device, an inductance is required to form a resonance circuit together with the resonance capacitor. In order to obtain this resonance inductance, the inductance of the primary winding of the output transformer may be used instead of using an independent resonance inductance. But,
In order to obtain the required inductance with the primary winding of the transformer, it is necessary to increase the number of turns of the primary winding.

Accordingly, an object of the present invention is to reduce the size and cost of a transformer having a large leakage inductance of a primary winding.

[0005]

SUMMARY OF THE INVENTION In order to solve the above problems and achieve the above object, the present invention provides a magnetic core, a primary winding wound around the magnetic core, and The present invention relates to a transformer having a wound secondary winding, wherein a magnetic material is disposed between the primary winding and the secondary winding.

[0006]

According to the present invention, the magnetic material on the primary winding functions as a path for the leakage magnetic flux, so that the leakage magnetic flux can be increased, and the leakage inductance of the primary winding can be increased. it can. In the present invention, the leakage inductance is not increased by increasing the number of turns, but the leakage inductance is increased by a very simple configuration in which a magnetic material is arranged between the primary winding and the secondary winding. ,
It is possible to provide a transformer having a large leakage inductance while suppressing an increase in the size and cost of the transformer.

[0007]

Embodiments and Examples Next, embodiments and examples of the present invention will be described with reference to FIGS. The core-type power transformer according to the embodiment of the present invention shown in FIGS. 1 and 2 includes a primary winding 1, a secondary winding 2, a core 3 as an iron core, that is, a magnetic core, and a magnetic material 4 according to the present invention. The core 3 is composed of an E-shaped core 3a and I
It consists of a combination with a mold core 3b and has a central leg 5 and first and second outer legs 6,7. The primary winding 1 is wound around the center leg 5, and the secondary winding 2 is wound on the primary winding 1 via the magnetic material 4. Note that the core 3 may be configured by a combination of two E-shaped cores. It can also be a two-legged core.

The magnetic material 4 is made of a flexible silicon steel strip and wound on the primary winding 1. In addition,
The magnetic material 4 is arranged so as to have a gap with respect to the core 3.

When a current flows through the primary winding 1, magnetic fluxes φ1 and φ2 passing through the outer legs 6 and 7 are generated as shown by dotted lines, and a leakage magnetic flux φ3 passing through the magnetic material 4 is generated. This leakage flux φ3 does not link with the secondary winding 2 and provides the leakage inductance of the primary winding 1.

FIG. 3 shows a switching power supply using the transformer of FIG. The transformer of FIG. 1 is used as a power transformer 10 of FIG. 3, and the primary winding 1 is connected to commercial AC power terminals 11 and 12. The primary winding 1
Is connected in series to the primary winding 1
3 shows the leakage inductance of the circuit. 4 for the secondary winding 2
A smoothing capacitor 17 is connected via a rectifier circuit composed of the diodes 13, 14, 15, and 16. An output transformer 18 is connected between both terminals of the smoothing capacitor 17.
The transistor 19 is connected via the primary winding 17a. A smoothing capacitor 22 is connected to the secondary winding 20 via a diode 21. The control circuit 23 controls on / off of the transistor 19 so as to make the voltage of the output stage of the capacitor 22 constant.

If the leakage inductance L of the primary winding 1 of the transformer 10 of FIG. 3 is large, the effect of suppressing the inrush current of the smoothing capacitor 17 and the effect of reducing the harmonic component of the charging current of the capacitor 17 are generated. A switching power supply device with suppressed wave components can be provided. When the harmonic component and the noise cannot be sufficiently suppressed only by the inductance L of FIG. 3, a well-known input filter, that is, a noise filter is connected to the AC power supply line. Even in this case, the input filter is connected to the primary winding 1 of the transformer.
The input filter can be downsized by the inductance L.

[0012]

Next, another embodiment of the present invention will be described with reference to FIG. However, in FIG. 4, substantially the same parts as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. In the transformer shown in FIG. 4, a magnetic material layer 4a made of a resin containing ferrite particles (magnetic particles) is provided on the primary winding 1, and the secondary winding 2 is disposed on the magnetic material layer 4a. Since the ferrite of the magnetic material layer 4a is a magnetic material having electrical insulation properties, it contributes to an increase in leakage inductance similarly to the magnetic material 4 of FIG. It contributes to the improvement of the breakdown voltage.

[0013]

[Modifications] The present invention is not limited to the above-described embodiment, and for example, the following modifications are possible. (1) The magnetic material 4 in FIG. 1 can be replaced with another magnetic material such as a ferrite plate. (2) A transformer having the same configuration as that of FIG. 1 or FIG. 4 can be used as the output transformer 30 of the resonance type switching power supply device shown in FIG. In FIG. 5, the first and second switches 3 composed of FETs are connected to the DC power supply capacitor 31.
2 and 33 are connected, and the primary winding 1 of the transformer 30 and the resonance capacitor 3 are connected in parallel with the second switch 33.
4 and the auxiliary capacitor 35 is connected in parallel. The secondary winding 2 of the transformer 30 has a center tap, is divided into first and second portions 2a and 2b, and is connected to a smoothing capacitor 37 via diodes 35 and 36. When the transformer 30 is configured in the same manner as in FIG. 1 or FIG. Becomes unnecessary. Thus, the size of the resonance switching power supply device can be reduced. (3) The magnetic material 4 can be partially inserted without being wound all over the primary winding 1.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a transformer according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of the transformer of FIG.

FIG. 3 is a circuit diagram showing a switching power supply device using the transformer of FIG. 1;

FIG. 4 is a longitudinal sectional view showing a part of a transformer according to a modification.

FIG. 5 is a circuit diagram showing a resonance-type switching power supply device using a transformer according to a modified example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Primary winding 2 Secondary winding 3 Core 4 Magnetic material

Claims (1)

[Claims] A transformer having a magnetic core, a primary winding wound on the magnetic core, and a secondary winding wound on the primary winding; A transformer, wherein a magnetic material is disposed between the secondary winding and the secondary winding.