JP2000058344A - Choke coil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable miniaturization and reducing cost of a choke coil by arranging a first core and a second core in parallel providing a coil thereon. SOLUTION: A choke coil is formed by providing a ferrite based core 1 and a core 2 magnetically in parallel, the core 1 which is formed of a material difficult to be saturated magnetically due to the high magnetic saturation level, and the core 2 which is formed of a material with low magnetic saturation level but high permeability. The core 1 is formed as an open magnetic circuit and the core 2 is formed as a closed magnetic circuit. A coil 3 is wound across the core 1 and the core 2, and the terminal of the coil 3 is connected to the terminal 4. Inductance of the core 2 is set larger than the inductance of the core 2. As a result, while high impedance and high rated current is satisfied, the choke coil can be obtained with miniaturization and at low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a choke coil, and more particularly, to a choke coil used in a DC chopper circuit for driving a DC motor.

[0002]

2. Description of the Related Art A DC chopper circuit for driving a DC motor turns on / off a power supply voltage by a power transistor and changes a conduction period of the power transistor.
A variable voltage is supplied to the DC motor to control the rotation speed of the DC motor. FIG. 2 shows the basic circuit, and FIG. 3 shows the current waveform of each part. In FIG. 2, E is a DC power supply, Tr is a power transistor, D is a flywheel diode,
C is a choke coil, M is a DC motor, TG is a tacho generator, 11 is a speed detection circuit, 12 is a speed setting circuit, 1
3 is a current detection circuit, 14 is a chopper control circuit, 15 is a base amplifier, and 16 is a speed setting device.

A speed detecting circuit 11 detects a speed from an output of the tach generator TG, and a speed setting circuit 12 outputs a control signal to a chopper control circuit 14 based on a comparison between the output of the speed detecting circuit 11 and a set value of a speed setting device 16. . On the other hand, the current detection circuit 13 detects the current load current Im and sends a control signal to the chopper control circuit 14. When it is desired to increase the load current Im, the chopper control circuit 14 increases the on-time of the base signal current IB of the power transistor Tr so as to increase the time of turning on the power transistor Tr.
To reduce the load current Im, the base signal current I
Shorten the on time of B.

[0004] While the base signal current IB is being applied to the power transistor Tr, the power transistor Tr is turned on, and the power supply voltage V0 appears in the output voltage. The load current Im flowing through the DC motor increases at a value determined by the coil inductance and the characteristics of the DC motor. On the other hand, while the base signal current IB is turned off and the power transistor Tr is turned off, the energy stored in the choke coil and the inductance of the DC motor is returned through the flywheel diode D.

FIG. 3A shows a current Ic flowing through the power transistor Tr, and FIG. 3B shows a current Id flowing back through the flywheel diode D. The current flowing through the DC motor has a waveform as shown in FIG. 3C in which the current Ic flowing through the power transistor Tr and the current Id flowing back through the flywheel diode are combined.

The rating of the choke coil used in such a DC chopper system for driving a DC motor is determined from a maximum drive current, a voltage applied between coil terminals which varies according to load conditions, and a minimum inductance determined by the drive current. In the DC chopper system for driving a DC motor, the maximum drive current flows through the choke coil when the load of the DC motor is high, but at this time, the applied voltage between the coil terminals is low. No large inductance is required). A large inductance is required when the voltage applied between the coil terminals is large. In this case, the driving current is small because the DC motor has a low load.

Since only one kind of choke coil inductance and rated current can be selected, both the inductance (maximum value) and the rated current (maximum value) are not required at the same time, but a choke coil that satisfies both standards is selected. There is a need to. In order to satisfy such a condition, a choke coil having a large size and a high cost must be selected. In a normal choke coil, if the winding is made thick to obtain the rated current, the number of turns cannot be obtained, and it is difficult to obtain an inductance. Also, because the core dimensions are such that magnetic saturation does not occur even when the flowing current increases,
There is a problem that it is difficult to configure the choke coil in a small size.

[0008]

As described above, a choke coil used in a conventional DC chopper circuit for driving a DC motor requires a high inductance and a high rated current, and the winding is inevitably thick. , Many turns,
As a result, it was expensive and large in size.

An object of the present invention is to solve this problem by a relatively simple method and to realize a small and inexpensive choke coil while satisfying a high inductance and a high rated current.

[0010]

In order to achieve the above-mentioned object, a choke coil according to the present invention comprises a first core made of a material having a high magnetic saturation region and hardly magnetically saturated, and a low magnetic saturation region. It is characterized by comprising a second core made of a material having a high magnetic permeability, and a coil wound on and arranged in parallel with the magnetic paths of the first core and the second core. And

Further, a third core forming a spatially open magnetic path, a fourth core forming a closed magnetic path, and a magnetic path of the third core and the fourth core are arranged in parallel and placed thereon. And a wound coil.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a choke coil according to the present invention will be described in detail with reference to the accompanying drawings. FIG.
It is a side view of a model of one embodiment of a choke coil of the present invention used in a DC chopper system for DC motor drive. In FIG. 1, reference numeral 1 denotes a core 1 as a first core, reference numeral 2 denotes a core 2 as a second core, reference numerals 3 and 2 denote cores 1, coils wound on the core 2, and reference numeral 4 denotes terminals. This choke coil is configured by providing two cores, a generally used ferrite core 1 and a core 2 having a large magnetic permeability, in parallel magnetically.

The core 1 has an open magnetic circuit, and the core 2 has a closed magnetic circuit. The coil 3 is wound over the core 1 and the core 2, and the end of the coil 3 is connected to the terminal 4. The inductance of core 2 is core 1
Is larger than the inductance due to When the current flowing through the coil 3 of the choke coil is small, the core 1
Of course, since the core 2 does not cause magnetic saturation, a large value is obtained for the combined inductance of the choke coil.

On the other hand, when the load on the DC motor is increased and the current flowing through the choke coil is increased, the core 1 which is an open magnetic circuit (has a large reluctance) and is made of a material having a high magnetic saturation capability causes magnetic saturation. However, magnetic saturation occurs in the core 2 of the closed magnetic circuit. For this reason, the inductance of the core 2 is equivalent to the inductance of the air-core coil, and is sufficiently smaller than the value before saturation. Therefore, at this time, the combined inductance of the choke coil is smaller than the value before saturation. Therefore, from this result, when the current flowing through the choke coil increases,
Although the inductance value becomes small, it is possible to realize a choke coil having a large inductance value when the current flowing through the choke coil is small. As a result, a choke coil having a sufficiently small size and a low cost can be obtained as compared with a general choke coil having the same rated current and the same inductance as that at a light load.

[0015]

As described above, according to the first aspect of the present invention,
According to the invention, a first core made of a material having a high magnetic saturation region and hardly magnetically saturated, a second core made of a material having a low magnetic saturation region but having a high magnetic permeability, and the first core And a coil wound on the magnetic path of the second core arranged in parallel. Thus, when the current flowing through the choke coil increases, the second core is magnetically saturated, and the combined inductance of the choke coil becomes a small value. When the current flowing through the choke coil is small, the saturation of the second core is released, and The combined inductance of the coil becomes a large value, and it is possible to realize a small and inexpensive choke coil while satisfying high inductance and high rated current.

According to a second aspect of the present invention, there is provided a third core forming a spatially open magnetic circuit, a fourth core forming a closed magnetic circuit, a magnetic path of the third core and the fourth core. And a coil wound thereon. Accordingly, when the current flowing through the choke coil increases, the fourth core is magnetically saturated, and the combined inductance of the choke coil becomes a small value. When the current flowing through the choke coil is small, the saturation of the fourth core is released, and The combined inductance of the coil becomes a large value, and it is possible to realize a small and inexpensive choke coil while satisfying high inductance and high rated current.

The invention according to claim 3 of the present invention is characterized in that the first core forms a spatially open magnetic circuit and the second core forms a closed magnetic circuit. Accordingly, when the current flowing through the choke coil increases, the second core is magnetically saturated, and the combined inductance of the choke coil becomes a small value.
When the current flowing through the choke coil is small, the saturation of the second core is released and the combined inductance of the choke coil becomes a large value, and the saturation phenomenon appears more remarkably. And a low-cost choke coil can be realized.

[Brief description of the drawings]

FIG. 1 is a side view of a model of an embodiment of a choke coil of the present invention.

FIG. 2 is a basic circuit diagram of a DC chopper circuit for driving a DC motor.

3 is a current waveform of each part of the DC chopper circuit for driving the DC motor shown in FIG.

[Explanation of symbols]

1 ... Core 1, 2 ... Core 2, 3 ... Coil, 4 ... Terminal, C ...
Choke coil, D… Fly wheel diode,
11: speed detection circuit, 12: speed setting circuit, 13: current detection circuit, 14: chopper control circuit, 15: base amplifier, 16: speed setting device, E: DC power supply, M: DC motor, TG: tacho generator, Tr ... power transistors.

Claims (3)

[Claims] A first core made of a material having a high magnetic saturation region and being hardly magnetically saturated; a second core made of a material having a low magnetic saturation region but having a high magnetic permeability; A choke coil comprising: a core; and a coil wound on the core in parallel with the magnetic path of the second core. 2. A third core forming a spatially open magnetic path, a fourth core forming a closed magnetic path, and magnetic paths of the third core and the fourth core are arranged in parallel and placed thereon. A choke coil comprising: a wound coil. 3. The first core forms a spatially open magnetic circuit,
The choke coil according to claim 1, wherein the second core forms a closed magnetic circuit.