Noise filter

Abstract

This invention provides a technique for suppressing differential-mode noise in addition to common-mode noise in a noise filter connected to a pair of power lines. The noise filter disclosed in this specification is a noise filter connected to a pair of power lines, comprising: a first bypass capacitor connected between one of the power lines and ground; a second bypass capacitor connected between the other of the power lines and 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.

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. This noise filter is 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 wire; and a second bypass capacitor connected between the other of the pair of power lines and a ground wire.

[0003] Patent Document 1: International Publication No. 2016 / 027374

[0004] The noise filter described above, also known as a Y capacitor, allows common-mode noise propagating in a pair of power lines to be fed back to the noise source via the ground wire. On the other hand, it cannot function as a filter for differential-mode noise. Utility Model Content

[0005] In view of the above, this specification provides a technique for suppressing differential-mode noise in addition to common-mode noise in a noise filter connected to a pair of power lines.

[0006] The technology disclosed in this specification is specifically embodied in a noise filter. This noise filter is connected to a pair of electric field lines and includes: a first bypass capacitor connected between one of the pair of electric field lines and ground; a second bypass capacitor connected between the other of the pair of electric field lines and 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.

[0007] In the above structure, the resonance of differential-mode noise is passivated by the first and second resistive elements connected in series with each bypass capacitor. This suppresses the intensity of differential-mode noise resonating in a specific frequency band. Since only the noise component flows through each resistive element in the current flowing in the pair of electric field lines, relatively small resistive elements can be used. Therefore, miniaturization of the noise filter is possible. Attached Figure Description

[0008] Figure 1 This is a block diagram illustrating the configuration of the noise filter 10 in the embodiment.

[0009] Figure 2 The operation of the noise filter 10 in the embodiment is illustrated schematically.

[0010] Figure 3The graph shown (A) represents the characteristics of the noise filter 10 in the embodiment, illustrating the frequency characteristics (intensity of each frequency) of the differential-mode noise generated by the pair of power lines 6 and 8. Furthermore, B in the graph is a comparative example, showing the frequency characteristics of the noise filter 10 without the resistive elements 22 and 24.

[0011] Explanation of reference numerals in the attached figures

[0012] 2…Power conversion device; 4…Switching circuit; 6, 8…Power lines; 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 wire. Detailed Implementation

[0013] The noise filter 10 of this embodiment will be described with reference to the accompanying drawings. The noise filter 10 of this embodiment can be used in various power conversion devices 2. For example, the power conversion device 2 can also be an on-board charger. The on-board charger is configured to be installed in an electric vehicle such as a battery electric vehicle (BEV), and controls the charging power supplied from an external power source PS to charge the on-board battery pack (not shown).

[0014] Typically, power conversion devices 2, such as vehicle chargers, include a switching circuit 4. The switching circuit 4, for example, is a converter and / or inverter, and includes one or more switching elements. Therefore, in the power conversion device 2, noise may be emitted to the outside, and interference from external noise is also possible. Therefore, in the power conversion device 2, a noise filter 10 is provided to meet electromagnetic compatibility (EMC) requirements. In addition, besides the noise filter 10 of this embodiment, other noise filters may be appropriately provided in the power conversion device 2.

[0015] like Figure 1 As shown, the noise filter 10 is connected to a pair of power lines 6 and 8 in the 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 the ground line G. The second bypass capacitor 14 is connected between the other power line 8 and the ground line G. This configuration up to this point is called a so-called Y capacitor, which mainly functions as a filter for common-mode noise.

[0016] The noise filter 10 also includes a first resistive element 22 and a second resistive element 24. The first resistive element 22 is connected in series with the first bypass capacitor 12. The second resistive element 24 is connected in series with the second bypass capacitor 14. Although not specifically limited, the first resistive element 22 is connected to the first bypass capacitor 12 from the ground side. Similarly, the second resistive element 24 is connected to the second bypass capacitor 14 from the ground side.

[0017] In the above structure, the first resistive element 22 and the second resistive element 24 are connected in series with two bypass capacitors 12 and 14 that constitute the so-called Y capacitor. Figure 2 As shown, the noise component Y caused by differential-mode noise in the current flowing to the power conversion device 2 flows through the noise filter 10. At this time, by sandwiching the resistors 22 and 24 in the path of the noise component Y, the resonance of the differential-mode noise is passively neutralized. Thus, as... Figure 3 As shown, this represents the intensity of differential-mode noise suppressed at specific frequency band resonances.

[0018] In the current flowing through a pair of electric field lines, only the noise component Y flows through each resistive element 22, 24, and not the mainstream system current X. Therefore, each resistive element 22, 24 can be made of relatively small resistive elements, enabling miniaturization of the noise filter 10.

Claims

1. A noise filter connected to a pair of electric field lines, characterized in that, The noise filter has the following features: A first bypass capacitor is connected between one of the pair of power lines and the ground line; A second bypass capacitor is connected between the other of the pair of power lines and the ground line; The first resistive element is connected in series with the first bypass capacitor; as well as The second resistive element is connected in series with the second bypass capacitor.

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