JPH03214714A - Choke coil - Google Patents

Abstract

PURPOSE:To reduce cost and achieve compactness by providing a winding at the drum part having different thickness between flanges of a multiple-type drum core. CONSTITUTION:A coil 11 is wound around a series of drum cores 30 comprising drum parts having different diameters between flanges, in series, two or more drum parts 31 having different diameters are provided as a magnetic body, and a flange 32 is provided at the opposite ends and the intermediate part. As a result, a non-linear DC superposition characteristic can be obtained and a large inductance can be obtained for a light-load current, thus reducing the number of circuit parts and achieving compactness and reduced cost.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a secondary smooth choke coil used in a feedforward switching power supply.

BACKGROUND ART A conventional choke coil has a configuration as shown in FIGS. 15 and 16. A conventional choke coil will be explained below with reference to the drawings.

FIG. 16 shows a circuit example of a switching power supply using the same choke coil. The first choke coil
As shown in FIG. 5, a coil 3 was wound around a bobbin 2, and a magnetic material 1 was incorporated into the bobbin 2. Such a choke coil is connected to two parts of the transformer as shown in Figure 16.
The output current of the next winding 4 is rectified by a choke coil 5 and a smoothing capacitor 6, and used in the circuit configuration of a switching power supply that stabilizes the output.

Problems to be Solved by the Invention In such a conventional configuration, when the load current becomes small and the mode becomes discontinuous, the output voltage increases, and in order to stabilize the output voltage, the voltage divider circuit 7 and the error amplifier circuit 8 are required. The pulse width was narrowed in the control circuit 9 via the. To this end, increase the capacity of the smoothing capacitor 6, increase the dummy current of the dummy resistor 10, or connect choke coils with different DC superposition characteristics in series as shown in FIGS. 17 and 18.
The inductance was set high when the load current was small to prevent discontinuous mode, which not only increased costs and reduced efficiency, but also complicated mounting on a printed circuit board and made it difficult to miniaturize the switching power supply. The problem was that there was no.

The present invention is intended to solve these problems, and aims to reduce the cost of choke coils and downsize switching power supplies.

Means for Solving the Problems In order to solve the problems, the present invention provides windings on the body parts of a multi-type drum core provided with flanges with different thicknesses, and winding a plurality of drum cores with an insulator. A winding is applied to the wires connected through the wire, and a magnetic material is arranged on the winding surface with an insulator interposed therebetween.

Effect: With the above configuration, a nonlinear direct current superimposition characteristic can be obtained, and a large inductance can be obtained at a light load current.

Example The present invention will be explained in detail below based on examples.

FIG. 1 shows a choke coil according to an embodiment of the present invention, which is constructed by winding a coil 11 in series around a multiple drum core 30 having body parts with different thicknesses between the flanges.

In addition, as shown in FIGS. 3 and 4, the structure of the magnetic body is composed of two or more bodies 31 of different thicknesses, with flanges 32 provided at both ends and in the middle.
As shown in FIGS. 5 and 6, the direct current superposition characteristic can be a step-like characteristic proportional to the number of body parts 31.

A choke coil having such a configuration is used in a switching power supply for secondary side control, as shown in FIG. In FIG. 2, 12 is an input terminal, and this input terminal 12 is connected to the primary winding 15 of the converter transformer via a rectifying diode 13 and a smoothing capacitor 14, and is also connected to one end of a feedback winding 16. The other end of the feedback winding 16 is grounded via a diode 17. The other end of the primary winding 15 is connected to the collector of a switching transistor 18. The emitter of this switching transistor 18 is grounded, and the base is connected to a control circuit 19. One end of the drive winding 20 is connected to the control circuit 19 via a diode 21. The other end of the drive winding 120 is grounded.

Further, the choke coil 11 is connected to the secondary winding 29 of the converter transformer via a rectifier diode 22, and a commutation diode 23 is also connected thereto. The other end of the choke coil 11 is a smoothing capacitor 24 and a dummy resistor 2.
5. Connected to output terminals 27 and 27' via voltage dividing circuit 26.

Further, the voltage dividing circuit 26 is connected to the control circuit 19 via an error amplifying circuit 28. The other end of the error amplification circuit 28 is grounded.

With this configuration, it is possible to operate the switching circuit in continuous mode over a wide load range, so there is no need to carelessly add the choke coil 11 or increase the capacitance of the smoothing capacitor 24. , there is no need to increase the dummy current of the dummy resistor 25, and the circuit configuration can be simplified.

Other embodiments of the present invention are shown in FIGS. 7 to 10.

In FIG. 7, numeral 30 is a drum core provided with flanges 32 at both ends, and an insulator 33 is provided at the joint portion of the drum core 30 between the flanges 32, where the winding body 31 has an even thickness. FIG. 8 shows a structure in which the thickness of the winding body 31 is different.

9 and 10 show the effect of changing the thickness of the insulator 33 in this example as a rate of change in inductance with respect to direct current. As shown in the figure, the insulator 33 is thin
By doing so, the initial value of inductance can be increased and the rate of change can also be increased. From the above, by changing the thickness of the insulator 3, the rate of change in inductance can be finely adjusted.

As a result, for the required inductance change rate,
If the coils are prepared at regular intervals, it is only necessary to change the thickness of the insulator 33, which enables standardization and reduces manufacturing costs.

In addition, as examples having the same effect, Figures 11 to 14 show examples.
As shown in the figure.

In FIG. 11, reference numeral 30 denotes a multiple type drum core with flanges 32 provided at both ends and the middle part, and the winding body 31 between the flanges 32 has an equal thickness. A magnetic body 35 is placed close to the magnetic body 34 via the magnetic body 34 .

FIG. 12 shows a configuration in which the winding body portions 31 of the multiple drum cores have different thicknesses.

As is clear from the rate of change in inductance due to changes in the thickness of the insulator 34 in this embodiment shown in Figures 13 and 14, the rate of change in inductance can be finely adjusted by changing the thickness of the insulator 34. It is.

Although the present invention has been described above based on the examples, the present invention is not limited to the above-mentioned examples. Can be used in combination.

Further, a material with low magnetic permeability may be used for the insulator, or a resin molded material made of magnetic powder may be used. Furthermore, an insulated copper foil tape may be used for the coil portion.

Effects of the Invention As described above, the choke coiley according to the present invention has a structure in which the coil is directly wound around the drum core, thereby making it possible to reduce the size and cost. Furthermore, by combining drum cores with different body thicknesses, nonlinear inductance can be obtained, making it possible to reduce the number of circuit components, resulting in smaller size and lower costs. Furthermore, by changing the thickness of the insulator, the inductance can be adjusted (coarse adjustment and fine adjustment), the manufacturing yield is high, and choke coils of several ranks can be obtained with the same coil specifications, so manufacturing costs can be reduced.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing one embodiment of the choke coil of the present invention, Fig. 2 is a circuit diagram of a switching power supply using the choke coil, and Figs. A perspective view of the continuous drum core, Figures 5 and 6 are DC superimposition characteristic diagrams of the same choke coil, Figures 7 and 8,
Figures 11 and 12 are perspective views of drum cores and multiple drum cores in other examples, and Figures 9, 10, 13, and 14 are perspective views of drum cores and multiple drum cores using the same drum cores and multiple drum cores. DC superposition characteristic diagram of choke coil, No. 15
The figure is a perspective view of a conventional choke coil, Figure 16 is a circuit diagram of a switching power supply using the same choke coil, and Figure 1
7 and 18 are DC superimposition characteristics diagrams of the same choke coil. 11... Coil, 30... Multiple drum core, 31... Winding body, 32...
Tsuba, 33.34...9 Insulator, 35...Magnetic material.

Claims (3)

[Claims] (1) Equipped with a multiple drum core with flanges at both ends and the middle part, the thickness of the winding body between the flanges of this drum core is different, and each winding body is wound on the winding body between the flanges. A choke coil made of wire. (2) The thickness of the winding body of a drum core provided with flanges at both ends may be equal or different, an insulator is provided at the joint of the drum core, and windings are respectively applied to the winding body of the drum core. choke coil. (3) The thickness of the winding body of a drum core having flanges at least on both ends is made equal or different, winding is applied to each of the winding bodies of this drum core, and an insulator is interposed between the winding surfaces. A choke coil made by arranging magnetic material.