Noise filter

Abstract

To provide a technique capable of suppressing differential mode noise in addition to common mode noise in a noise filter connected to a pair of power lines.SOLUTION: A noise filter disclosed in the present specification is a noise filter connected to a pair of power lines, and includes a first bypass capacitor connected between one of the pair of power lines and a ground, a second bypass capacitor connected between the other of the pair of power lines and the ground, a first resistive element connected in series with the first bypass capacitor, and a second resistive element connected in series with the second bypass capacitor.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to a noise filter connected to a pair of power lines. [Background technology]

[0002] Patent Document 1 discloses a noise filter that is connected to a pair of power lines and includes a first bypass capacitor connected between one of the pair of power lines and ground, and a second bypass capacitor connected between the other of the pair of power lines and ground. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2016 / 027374 Summary of the Invention [Problem to be solved by the invention]

[0004] The noise filter described above is also called a Y capacitor, and is capable of returning common mode noise propagating through a pair of power lines to the noise source via the ground. However, it cannot function as a filter for differential mode noise.

[0005] In view of the above, this specification provides a technology that is capable of suppressing differential mode noise in addition to common mode noise in a noise filter connected to a pair of power lines. [Means for solving the problem]

[0006] The technology disclosed in this specification is embodied in a noise filter connected to a pair of power lines, and including a first bypass capacitor connected between one of the pair of power lines and ground, a second bypass capacitor connected between the other of the pair of power lines and ground, a first resistor element connected in series with the first bypass capacitor, and a second resistor element connected in series with the second bypass capacitor.

[0007] In the above configuration, the first and second resistor elements connected in series with each bypass capacitor damp the resonance of differential mode noise. This reduces the intensity of differential mode noise that resonates in a specific frequency band. Because only noise components of the current flowing through the pair of power lines flow through each resistor element, relatively small resistor elements can be used. This allows for a more compact noise filter. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a block diagram showing the configuration of a noise filter 10 according to an embodiment of the present invention. [Figure 2] 10A and 10B are schematic diagrams illustrating the operation of the noise filter 10 according to the embodiment. [Figure 3] 1 is a graph (A in the figure) showing the characteristics of the noise filter 10 of the embodiment, illustrating the frequency characteristics (intensity at each frequency) of differential mode noise occurring in the pair of power lines 6 and 8. Note that B in the figure is a comparative example, illustrating the frequency characteristics when the noise filter 10 does not include the resistive elements 22 and 24. DETAILED DESCRIPTION OF THE INVENTION

[0009] A noise filter 10 of this embodiment will be described with reference to the drawings. The noise filter 10 of this embodiment can be used in various types of power conversion devices 2. For example, the power conversion device 2 may be an on-board charger. The on-board charger is mounted on an electric vehicle such as a battery electric vehicle (BEV), and is configured to control charging power supplied from an external power source PS to charge an on-board battery pack (not shown).

[0010] Generally, a power conversion device 2 such as an on-board charger includes a switching circuit 4. The switching circuit 4 is, for example, a converter and / or an inverter, and includes one or more switching elements. Therefore, the power conversion device 2 may emit noise to the outside and may also be subject to noise interference from the outside. For this reason, the power conversion device 2 is provided with a noise filter 10 to meet requirements for electromagnetic compatibility (EMC). Note that the power conversion device 2 may be provided with other noise filters as appropriate in addition to the noise filter 10 of this embodiment.

[0011] As shown in FIG. 1, a noise filter 10 is connected to a pair of power lines 6, 8 in a power conversion device 2. The noise filter 10 includes a first bypass capacitor 12 and a second bypass capacitor 14. The first bypass capacitor 12 is connected between one power line 6 and ground G. The second bypass capacitor 14 is connected between the other power line 8 and ground G. This configuration is what is known as a Y capacitor, and functions mainly as a filter for common mode noise.

[0012] The noise filter 10 further includes a first resistor element 22 and a second resistor element 24. The first resistor element 22 is connected in series with the first bypass capacitor 12. The second resistor element 24 is connected in series with the second bypass capacitor 14. Although not particularly limited, the first resistor element 22 is connected to the first bypass capacitor 12 from the ground side. Similarly, the second resistor element 24 is connected to the second bypass capacitor 14 from the ground side.

[0013] In the above-described configuration, a first resistor element 22 and a second resistor element 24 are connected in series to two bypass capacitors 12 and 14, which constitute a so-called Y capacitor. As shown in FIG. 2, a noise component Y caused by differential mode noise, which is part of the current flowing through the power conversion device 2, flows through the noise filter 10. At this time, the presence of resistor elements 22 and 24 in the path through which noise component Y flows damps the resonance of the differential mode noise. As a result, the intensity of differential mode noise that resonates in a specific frequency band is suppressed, as shown in FIG. 3.

[0014] Of the currents flowing through the pair of power lines, only the noise component Y flows through each of the resistor elements 22, 24, and the main system current X does not flow through each of the resistor elements 22, 24. Therefore, relatively small resistor elements can be used for each of the resistor elements 22, 24, and the noise filter 10 can be made smaller. [Explanation of symbols]

[0015] 2: power conversion device, 4: switching circuit, 6, 8: power line, 10: noise filter, 12: first bypass capacitor, 14: second bypass capacitor, 22: first resistor element, 24: second resistor element, PS: external power supply, G: ground

Claims

[Claim 1] A noise filter connected to a pair of power lines, a first bypass capacitor connected between one of the pair of power lines and ground; a second bypass capacitor connected between the other of the pair of power lines and ground; a first resistor element connected in series with the first bypass capacitor; a second resistor element connected in series with the second bypass capacitor; A noise filter comprising:

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