JPH08167822A - Harmonic current suppressor - Google Patents

Abstract

PURPOSE: To simultaneously suppress a harmonic current and electromagnetic interference(EMI) by a miniaturized device and the small number of parts. CONSTITUTION: A choke coil 5 for suppressing a harmonic current and a noise filter 6 for EMI countermeasure are integrated with a case body 7. Consequently a harmonic current in a switching power supply device 2 can be suppressed only by one choke coil 5. Since the coil 5 itself is not a noise source, the noise filter 6 itself can be miniaturized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a harmonic current suppressor intended to suppress harmonic current generated from various electronic devices, and more particularly to a harmonic current suppressor suitable for suppressing harmonic current generated from a switching power supply device. Wave current suppressor.

[0002]

2. Description of the Related Art Generally, in the case of various electronic devices equipped with a capacitor input type rectifier circuit, the input current flows only during a period when the AC input voltage is higher than the voltage between the terminals of the capacitor. Becomes extremely large near the maximum value of the AC input voltage and contains harmonic current exceeding the standard. To avoid this situation,
For example, Japanese Patent Laid-Open No. 2-84069 discloses a power supply device in which an active filter circuit is incorporated on the output side of a rectifier circuit. This active filter circuit is composed of a step-up converter having a so-called switching element. By switching the switching element, the input current is approximated to a sine wave waveform that is substantially the same as the input voltage, thereby suppressing the harmonic current. .

[0003]

In the above-mentioned prior art, the active filter circuit used as a means for suppressing the harmonic current requires complicated control for switching at least the switching element, which increases the number of parts. Cause a cost increase. Moreover, since the switching element switches the input voltage line, the switching element is used as a noise source for EMI (Electro Magnetic Interference).
ference: Electromagnetic interference generated from electronic equipment) is larger than that of a normal power supply unit, and is the same level as that of a power supply unit that does not incorporate an active filter circuit.
To limit I, E in front of the active filter circuit
A large noise filter for MI countermeasure is required.

In view of the above problems, it is an object of the present invention to provide a harmonic current suppressor that is small in size and has a small number of parts, and can simultaneously suppress not only harmonic current but also EMI. To do.

[0005]

In the harmonic current suppressor of the present invention, a choke coil for suppressing the harmonic current and a noise filter for preventing electromagnetic interference are integrally provided on the case body.

[0006]

With the above structure, the harmonic current from the electronic device can be suppressed by only one choke coil. Moreover, since the choke coil itself does not become a noise source, it does not cause electromagnetic interference. Therefore, the noise filter provided integrally with the choke coil can also be downsized.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention in which a harmonic current suppressor 1 is connected to a front stage of a switching power supply device 2 which is an electronic device will be described below with reference to FIGS. Reference numeral 3 denotes a commercial power supply for supplying an AC input voltage to the switching power supply device 2. Both ends of the commercial power supply 3 are connected to the input terminals 4 and 4A of the harmonic current suppressor 1, respectively. The switching power supply device 2 converts an AC input voltage into a DC input voltage by a capacitor input type rectifier circuit (not shown), and intermittently applies this DC input voltage to the primary winding of the main transformer by switching the main switching element. In this way, a predetermined DC output voltage is obtained.

The harmonic current suppressor 1 is one in which a choke coil 5 for suppressing the harmonic current and a noise filter 6 for preventing EMI are integrally provided inside a box-shaped case body 7. In addition to the input terminals 4 and 4A, the output terminals 8 and 8A connected to the switching power supply device 2 and the ground terminal 9 that is grounded together with the case body 7 provide electrical connection to the outside.

The choke coil 5 is inserted and connected to one of the input voltage lines from the input terminal 4 to the output terminal 8, which is connected to the frequency of the commercial power source 3 (50 to 60).
It has a pass band that extends the pass period of the input current taken into the switching power supply device 2 in the low frequency region of about (Hz). Further, the noise filter 6 is provided mainly as an EMI countermeasure for attenuating and blocking noise in a high frequency region of the switching power supply device 2 at a switching frequency (several tens to several hundreds of kHz). A line-across capacitor 11 connected to the common mode choke 12 and a line bypass capacitors 13 and 14 provided as a common mode noise elimination circuit. The common mode choke 12 is, for example, a toroidal core having an annular shape, in which wire rods are wound with the same number of turns in a direction in which mutual magnetic fluxes are canceled, and each wire rod has a line-across capacitor 11 and a line bypass capacitor 13. , 14 are inserted and connected to each input voltage line. The connection point of the line bypass capacitors 13 and 14 is connected to the ground terminal 9.

In the harmonic current suppressor 1 configured as described above, the choke coil 5 lengthens the passage period of the input current mainly from the commercial power source 3 taken into the switching power supply device 2 in the low frequency region. The peak value of the input current becomes small and the harmonic component thereof is suppressed. Further, the normal mode noise generated between the switching power supply device 2 and the input voltage line is absorbed by the line across capacitor 11, and the common mode noise generated between each input voltage line and the ground is the noise component in the input voltage line. Is cut off by the common mode choke 12 and flows out to the ground via the ground terminal 9 by the line bypass capacitors 13 and 14. Thus, the commercial power supply 3 and the switching power supply 2
The harmonic current from the switching power supply device 2 can be suppressed by the choke coil 5 only by connecting the harmonic current suppressor 1 between the switching power supply device 2 and
The noise filter 6 can also remove noise components such as normal mode noise and common mode noise generated from the above.

Next, the effect of the harmonic current suppressor 1 in this embodiment will be described from the measured data shown in FIGS. 2 and 3 show 10 kHz to 30 MHz performed based on the class B standard of VDE-0871.
2 is an actual measurement value of the noise terminal voltage, and FIG. 2 shows a case where the commercial power supply 3 is directly connected to the switching power supply device 2 to which a load is connected without connecting the harmonic current suppressor 1, and FIG. The actual measurement value when the harmonic current suppressor 1 is connected to the switching power supply device 2 to which a load is connected and the commercial power supply 3 is connected is shown. As is clear from this figure, when the harmonic current suppressor 1 is connected, especially 10 kHz to 30 M
EMI of 20 to 30 dBμ in the frequency band of Hz
It is attenuated by about V.

On the other hand, FIGS. 4 and 5 show IEC555-
2 is an actual measurement value of the harmonic current made based on the 2 standards, and FIG.
When the commercial power supply 3 is directly connected without connecting the harmonic current suppressor 1, in FIG. 3, the harmonic current suppressor 1 is connected to the switching power supply device 2 to which the same load is connected and the commercial power supply 3 is connected. The actual measurement value when connected is shown. Also in this case, if the harmonic current suppressor 1 is connected, the third to 39th
It can be seen that the next harmonic current is improved.

Since the harmonic current suppressor 1 of the present invention suppresses the harmonic current from the switching power supply device 2 by using only one choke coil 5, like the conventional active filter circuit, It is not necessary to control the switching element, and the number of parts can be significantly reduced. Moreover, since the choke coil 5 does not include an active element such as a switching element unlike an active filter circuit, it does not itself become a noise source and there is no risk of electromagnetic interference. This is
The noise filter 6 provided integrally with the choke coil 5 can be downsized, and as a result, the overall shape of the harmonic current suppressor 1 can be reduced. That is, the choke coil 5 having a pass band in the low frequency region is used to suppress the harmonic current.
And the noise filter 6 for EMI measures, the case body 7
It is possible to suppress not only the harmonic current but also the EMI at the same time by being integrally provided in the above, because of the small size and the small number of parts.

The harmonic current suppressor 1 of the present invention is applicable not only to the switching power supply device 2 having an inverter, but also to various electronic devices. However, in the case of the switching power supply device 2, noise in a high frequency region is generated due to switching of the main switching elements and the like, so that the noise filter 6 of the present embodiment is particularly effective as a countermeasure against noise from the switching power supply device 2. Becomes Further, the noise filter 6 can be applied with various circuit configurations other than those shown in the embodiments. For example, as a normal mode noise elimination circuit, an inductor is inserted and connected to each input voltage line. Good.

The present invention is not limited to the above embodiment, but various modifications can be made within the scope of the present invention.

[0016]

According to the present invention, a choke coil for suppressing a harmonic current and a noise filter for preventing electromagnetic interference are integrally provided in a case body, and a harmonic wave can be obtained by a small size and a small number of parts. It is possible to provide a harmonic current suppressor capable of suppressing not only current but also EMI at the same time.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention.

FIG. 2 is a graph showing an actual measurement value of a noise terminal voltage when the harmonic current suppressor is not connected.

FIG. 3 is a graph showing an actual measurement value of a noise terminal voltage when the harmonic current suppressor is connected.

FIG. 4 is a graph showing measured values of harmonic currents when the harmonic current suppressor is not connected.

FIG. 5 is a graph showing an actually measured value of a harmonic current when the same harmonic current suppressor is connected.

[Explanation of symbols]

 5 Choke coil 6 Noise filter 7 Case body

Claims (1)

[Claims] 1. A choke coil for suppressing harmonic current,
A harmonic current suppressor characterized in that a noise filter for preventing electromagnetic interference is provided integrally with the case body.