JPS5934609A - Core for small sized reactor - Google Patents

Abstract

PURPOSE:To prevent the fluctuation of output voltage when a small current is applied without increasing the voltage regulation at large current by a method wherein a non-magnetic gap material, which occupies a part of core cross section, is inserted in a part of the magnetic path for core. CONSTITUTION:A notch is provided at a part of the magnetic path of the core 11 consisting of the magnetic material having an excellent squareness ratio such as thin silicon steel, PE parmalloy and the like, and a non-magnetic gap material 12 is inserted in said notch in such a manner that it will occupy a part of the core cross section, thereby enabling to maintain an inductance L when a rated current is applied and also to have a large inductance when a small current is applied.

Description

[Detailed description of the invention] The present invention relates to an iron core used in a small reactor.

A small reactor is a device with an inductance wound around an iron core, and is used in switching power supplies, computer power supplies, etc. This small reactor also includes what are called choke coils and inductors.

As shown in FIG. 1, a conventional iron core used in a small reactor has a non-magnetic gap material 2 sandwiched between a part of a thin silicon steel core 1 so as to occupy the entire cross section of the core. This iron core has a DC hysteresis curve as shown in Figure 2,
Furthermore, the current-inductance characteristic when winding is applied to form a small reactor is such that the inductance remains almost constant even when the current is small, as shown in FIG.

Incidentally, a switching power supply incorporating this small reactor is required to have little variation in output voltage even when the load current changes. However, in the choke input type rectifier circuit of a switching power supply, as shown in Fig. 4, the current flowing through the small reactor becomes discontinuous in the shaded area where the load current IL is small, and as a result, it does not operate as a normal choke input type.
Output voltage fluctuates.

To solve this problem using a conventional small reactor, the inductance L can be increased. This allows the shaded area in FIG. 4 to be narrowed. However, if the inductance L is made large, the DC resistance increases and there is a problem that the voltage fluctuation rate at large currents becomes low.

The present invention has been made in view of the above circumstances, and its purpose is to maintain the inductance L at the rated current and to have a large inductance at the small current, thereby reducing the voltage fluctuation rate at the large current. The advantage of this iron core for a small reactor is that it can prevent fluctuations in the output voltage at low currents without increasing the current.

The present invention will be explained below with reference to the drawings.

FIG. 5 is a perspective view of the iron core for a small reactor. This iron core is made of a magnetic material with a good squareness ratio such as thin silicon steel or PE permalloy, and a notch is provided in a part of the magnetic path of the iron core.
It is sandwiched between. A small reactor is manufactured by placing this iron core in a suitable case and winding it.

This iron core has a DC hysteresis curve as shown in curve n in FIG. 6, and a small reactor with wire windings has current-inductance characteristics as shown in FIG. In this case, the three points in Figure 6 are at point a' in Figure 7, point b is at point b',
0 points correspond to 07 points.

The reason why the small reactor core according to the present invention has such characteristics is as follows. The DC hysteresis curve of the gapless core is as shown by curve mI in FIG. 6, and the DC hysteresis curve of the gapped core is as shown by curve m2 in FIG. Therefore, the iron core for a small reactor according to the present invention has characteristics that are a combination of curved and C.

In this case, by changing the ratio α/h of the non-magnetic gap material 12 to the core cross section, "Oa" in FIG. 6 can be changed, and by changing the gap length 1g, (the slope of the straight line I-a b J) can be changed. can.

In other words, when a gap is inserted in a part of the core cross section (α
β), the following approximate formula holds.

α/β= B r' /B r Hm: B=B when gap is zero, I becomes be able to.

In the above embodiment, a notch is provided in a part of the outer periphery of the core to insert the non-magnetic gap material, but the present invention is not limited to this, and as shown in FIG. A type with a notch and a non-magnetic gap material inserted, or a type 9
As shown in the figure, a notch may be provided in a part of the inner periphery of the core and a nonmagnetic gap material may be inserted therein. Further, the iron core for a small reactor according to the present invention may be manufactured by combining the gapless iron core 11a and the gear lug iron core 11b as shown in FIG. 10.

Next, specific examples of the present invention will be described.

Inner diameter 20JILh as a thin silicon steel core! , outer diameter 30U
, quotient 1QIItJIl, non-magnetic gear gap length Q, 51111N, α/β-0,9, α/β=
0.60) Prepare two types of wires and wire them with 30 wires.
A small reactor was fabricated by turning.

The current-inductance characteristics of this small reactor are
Shown in Figure 1. In this case, the curve n1 shows α/β-0.9, and the curve n2 shows α/β=0.6. For comparison, the current-inductance characteristic of a conventional small reactor (α/β=1) is shown by curve n. Shown below.

As is clear from the above results, according to the present invention, it is possible to have a large inductance when the current is small and a constant inductance when the current is large, so it is suitable for smoothing inductors used in rectifier circuits of switching power supplies. Moreover, by changing the proportion of the non-magnetic gap material in the cross section and the gap length, it is possible to easily adjust the characteristics, which is a remarkable effect.

[Brief explanation of drawings]

Figure 1 is a plan view of a conventional iron core for a small reactor, Figure 2 is a diagram showing a DC hysteresis curve of the iron core, and Figure 3 is a diagram showing the relationship between current and inductance in a small reactor using the iron core. Fig. 4 is a diagram showing the relationship between load current and output voltage of a choke input rectifier circuit using a small reactor, Figs. 5 to 11 are explanatory diagrams of the present invention, and Fig. 5 is an iron core for a small reactor. FIG. 6 is a diagram showing the DC hysteresis curve of the same core, FIG. 7 is a diagram showing the current-inductance characteristics of a small reactor using the same core, and FIGS. 8 to 10 are diagrams showing the DC hysteresis curve of the core. FIG. 11 is a perspective view of an iron core for a small reactor showing an embodiment of the present invention, and is a diagram showing the relationship between current and inductance in a specific embodiment of the present invention in comparison with a conventional one. 11... Iron core, 12... Nonmagnetic gap material. Applicant's agent Patent attorney Suzu Seinarihiko0 Current (A
) 0 Hayabusa conversion Figure 8 Figure 9 Figure 101

Claims (1)

[Claims] An iron core for a small reactor that is made by inserting a non-magnetic gap material that occupies a part of the cross section of the iron core into a part of the iron core magnetic path.