Emc filter and power conversion device

Abstract

An EMC filter of the present application and a power conversion device provided with the filter are provided with a capacitor element having a lead conductor for connection with a bus bar that supplies direct current to the capacitor element, and the area of the connection portion of the lead conductor with the bus bar is smaller than the cross-sectional area of the lead conductor.

Description

Technical Field

[0001] This invention relates to an EMC filter and a power converter. Background Technology

[0002] EMC filters are designed to absorb noise using capacitors. However, if capacitors are added to the inverter circuit, noise peaks are generated due to circuit resonance, so it is necessary to reduce these peaks. Techniques for reducing these peaks are being improved daily.

[0003] As background technology for the present application, the following patent document 1 is known. Patent document 1 discloses a configuration in which a pair of parallel buses are grounded via a pair of capacitors, wherein the capacitors are connected to the bus and the grounding terminal at positions symmetrical with respect to the pair of buses, and their length direction is arranged near the bus along the extension direction of the bus. Existing technical documents Patent documents

[0004] Patent Document 1: Japanese Patent Application Publication No. 2005-12908. Summary of the Invention The problem the invention aims to solve

[0005] In the configuration of Patent Document 1, for example, a damping resistor is provided in addition to the capacitor to reduce the peak value caused by circuit resonance. As a result, the number of components such as the substrate other than the capacitor and resistor increases in order to connect these components, which leads to an increase in cost. Therefore, it is necessary to remove the components other than the capacitor that absorbs noise.

[0006] Therefore, the object of the present invention is to provide an EMC filter and a power conversion device that generate the effect of damping resistance in the circuit without using additional components. Technical means to solve the problem

[0007] The EMC filter and power conversion device of the present invention include a capacitor element and a busbar supplying DC power to the capacitor element. The capacitor element has a lead conductor for connection to the busbar, and the area of ​​the connection portion of the lead conductor to the busbar is smaller than the cross-sectional area of ​​the lead conductor. The effects of the invention

[0008] According to the present invention, an EMC filter and a power conversion device that generate a damping resistance in the circuit without using additional components can be provided. Attached Figure Description

[0009] Figure 1 This is a circuit diagram of a power conversion device. Figure 2 This is an unfolded view of a power conversion device according to one embodiment of the present invention. Figure 3 This is a magnified view of the EMC filter. Figure 4 for Figure 3 The unfolded diagram. Figure 5 This is a diagram showing the welded portion of the capacitor terminal and busbar before and after welding, according to one embodiment of the present invention. Figure 6 for Figure 5 A variation of the above. Figure 7 for Figure 4 A variation of the above. Figure 8 This is a diagram of the housing section of an EMC filter. Figure 9 To observe from another perspective Figure 8 The image. Detailed Implementation

[0010] (An embodiment and the configuration of the EMC filter and power converter) The following description, with reference to the accompanying drawings, illustrates the methods for implementing the present invention. Figure 1 This is a circuit diagram of a power conversion device.

[0011] In the circuit diagram 101 of the power conversion device 100, the power conversion device 100 converts DC power from the battery 102 into AC power. In this embodiment, the power conversion device 100 is a high-power power conversion device that supplies AC power to the vehicle drive motor 103.

[0012] The power conversion device 100 comprises a power semiconductor circuit section 202, a smoothing capacitor 203, an EMC filter 204, etc., and is connected to a battery 102 and a vehicle drive motor 103. The power semiconductor circuit section 202 has a pair of switching elements, one upper arm and one lower arm. The EMC filter 204 includes a capacitor 107 and a damping resistor 108. The capacitor 107 absorbs noise generated by the switching of the power semiconductor circuit section 202.

[0013] The smoothing capacitor 203 absorbs current changes caused by the switching of the power semiconductor circuit section 202, thereby stabilizing the output.

[0014] For capacitor 107, the capacitor connected between the positive (P) side 109 and the negative (N) side 110 is designated as the X capacitor, and the capacitor connected between the positive (P) side 109 or the negative (N) side 110 and ground is designated as the Y capacitor.

[0015] A damping resistor 108 is needed to suppress circuit resonance caused by the introduction of capacitor 107. The damping resistor 108 is connected in series with capacitor 107. The damping resistor 108 connected in series with capacitor X uses a resistance of, for example, 0.11Ω or higher. The damping resistor connected in series with capacitor Y uses a resistance of, for example, 1.5Ω or higher.

[0016] Figure 2 This is an unfolded view of a power conversion device used in one embodiment of the present invention.

[0017] The power conversion device 100 has a metal frame, namely the housing 201, made of aluminum alloy or the like, which is a box-shaped cuboid with a pair of short side walls and a pair of long side walls. The housing 201 houses the power semiconductor circuit section 202, the smoothing capacitor 203, the EMC filter 204, the AC side bus 205, the DC side bus 206, etc.

[0018] As described above, the EMC filter 204 is composed of a module of noise-absorbing capacitor 107 and resistor 108, and is connected to the EMC filter bus. The capacitor 107 in the EMC filter 204 absorbs EMC noise generated by the switching of the power semiconductor circuit section 202.

[0019] AC side bus 205 is the output side terminal, and... Figure 1 The motor 103 shown is connected. The DC side bus 206 is connected to the EMC filter 204 and the AC side bus 205, and is connected from the input to the output. In addition, the DC side bus 206 is also electrically connected to the smoothing capacitor 203.

[0020] Figure 3 This is a magnified view of the EMC filter.

[0021] The EMC filter 204 consists of a positive (P) side bus 211 and a negative (N) side bus 212 that supply DC power to the capacitor 107.

[0022] In existing technologies, to achieve the effect of damping resistance, when capacitors and resistors are required as circuit elements, the various components, such as fixed resistors or film capacitors, are typically assembled and connected on a substrate. However, if a substrate is used to combine or separately configure other components, the footprint increases and the component cost rises.

[0023] Figure 4 To unfold Figure 3 A diagram of an EMC filter.

[0024] Lead conductors 214 for connection to busbars 211 (212) are drawn from capacitor 107. Lead conductors 214 are welded together via protrusions 216 on the positive (P) side busbar 211 and the negative (N) side busbar 212. Welding is performed using, for example, projection welding or ultrasonic welding. After the lead conductors 214 and the busbar protrusions 216 are welded together, capacitor 107 is supported by support portions 215 on the positive (P) side busbar 211 and the negative (N) side busbar 212.

[0025] Figure 5 This diagram shows the welded parts before and after welding the capacitor terminals and busbars.

[0026] The protrusion 216 is triangular in shape with an acute angle on the side connected to the lead conductor 214. The protrusion 216 and the lead conductor 214 are connected (welded) to form a weld portion 219. Using this connection method, the connection portion (welded portion) 219 between the protrusion 216 and the lead conductor 214 can be formed to be smaller than the cross-sectional area of ​​the lead conductor 214. Consequently, contact resistance is generated at this connection portion (welded portion) 219. The following experimental results were obtained regarding this contact resistance.

[0027] Given a fixed inherent resistance of busbar 211 (212) and lead conductor 214, assuming a lead conductor 214 with a radius of 0.4 mm contacts busbar 211 (212) at a circular contact point 11 with a radius of 0.4 mm, the contact resistance is 50 mΩ. Here, by setting this circular contact point as one point and reducing its radius to 0.15 mm, the resistance becomes approximately 1.5 Ω, increasing the contact resistance. Therefore, the more contact points are added or the contact surface diameter is increased, the lower the damping resistance becomes. That is, the contact resistance is proportional to the inherent resistance and inversely proportional to the radius of the contact surface and the number of contact points.

[0028] According to another experimental result, the area of ​​the connection part 219 is preferably the area that achieves damping resistance, which is required to be from 0.1 mm to 0.8 mm in diameter when the diameter of the lead conductor 214 is 0.8 mm.

[0029] Furthermore, the damping resistor of this invention may exhibit slight deviations in resistance value depending on the connection conditions of the busbar and capacitor terminals. Based on other experimental results, such as those applied to the damping resistor of an EMC filter structure, the following impact evaluation was conducted.

[0030] The damping resistor is 0.33Ω. Due to welding variations, the resistance value changes by approximately ±10%. However, within the effective range of 0.1–10MHz for the 0.33Ω damping resistor, there is almost no deviation in noise level caused by the resistance change. That is, even with variations in the contact resistance at the weld point, a damping resistor suitable for EMC noise can be reproduced.

[0031] Furthermore, in other experimental results verifying the effectiveness of the noise filter when implementing the present invention, conventional noise filters, due to EMC specifications around 1MHz, also incorporate capacitors and require additional damping resistors. However, with the structure of the present invention, it achieves the effect of not conflicting with EMC standards around 1MHz without requiring additional resistors.

[0032] Furthermore, in the high-frequency region of 10MHz, if the structure of the present invention is used, there is a tendency for the noise level to be slightly higher than before, but it can still function as a filter capacitor within the noise range that meets the required specifications.

[0033] Based on the above experimental results, by making the area of ​​the connection between the lead conductor 214 and the busbar 211 (212) smaller than the cross-sectional area of ​​the lead conductor 214, the resistance of the connection is inversely proportional to the radius of the connection surface, and the resistance value of the connection increases. The contact resistance of this connection (welding part) 219 is greater than the parasitic resistance of the lead conductor 214, and it can function as a damping resistor.

[0034] Therefore, by providing a solder joint 219 on the lead conductor 214, which serves as a capacitor terminal, to connect to the busbar 211 (212), a damping resistor effect is achieved. The resistance value of the connection 219 is greater than the ESR (Electron Spin Resonance) of the terminal itself, simulating the situation where a resistor component is installed. As a result, since a damping resistor component is no longer required, compared to the past, a resistor component is not needed as an additional component, and consequently, a connection substrate is not required, thereby reducing costs, decreasing the number of components, and simplifying the process.

[0035] Furthermore, it has the effect of simply forming the resistive components and improving the accuracy of the resistance value. The area of ​​the connection portion can be reduced by the protrusion 216 formed on the busbar 211 (212), thereby increasing the resistance value. Since the protrusion 216 is a linear protrusion, when connected to the lead conductor 214, the deviation of the connection portion area can be suppressed by connecting it approximately orthogonally to the extension direction of the lead conductor 214.

[0036] In this embodiment, the application of the invention is illustrated for the damping resistor connected in series with the X capacitor, but the same configuration can be used in the Y capacitor.

[0037] Figure 6 for Figure 5 Another embodiment of the welded connection (welded part).

[0038] The protrusion 217 of the busbar is rectangular. The shape of the connection part (welding part) 219A is not limited to the above example; it can be any shape as long as the required damping resistance effect can be achieved.

[0039] Figure 7 for Figure 4 Another embodiment of the protrusion.

[0040] The busbar-side protrusion 218 connected to the lead conductor 214 may be formed at two points to adjust the damping resistance value, and furthermore, more than two protrusions 218 may be formed for adjustment.

[0041] Figure 8 This is a diagram of the EMC filter housing 301.

[0042] The capacitor 107 of the EMC filter 204 is supported by a support portion 215 of the positive (P) side bus 211 and the negative (N) side bus 212. The capacitor 107 is soldered to the contact portion of the lead conductor 214 and the protrusion 216 of the positive (P) side bus 211 and the negative (N) side bus 212. The positive (P) side bus 211 and the negative (N) side bus 212 extend along the bottom surface of the housing portion 301, and... Figure 2 The DC side bus 206 shown is connected.

[0043] Figure 9 A diagram showing the sealed state of the capacitor used in the filter.

[0044] During the assembly of the components, resin 302, which is an electrically insulating fixing component, flows into the receiving part 301, thereby covering and sealing the connection part 219 of the busbar 211 (212) and the lead conductor 214.

[0045] Because capacitor 107 is sealed with resin 302, the vibration resistance of EMC filter 204 is improved. Since the small connection area is covered by resin 302 as a sealing material, the covered connection area is fixed and less susceptible to vibration.

[0046] In this way, by sealing the capacitor 107 with resin 302, the capacitor 107 can be integrally supported and fixed with the housing that forms the outer frame of the EMC filter 204. In addition, since the contact area of ​​the solder joints between the lead conductor 214 and the protrusions 216 of the positive (P) side busbar 211 and the negative (N) side busbar 212 is reduced, the connection of the solder joints can be strengthened by sealing with resin 302.

[0047] According to one embodiment of the present invention described above, the following effects are achieved.

[0048] (1) The EMC filter 204 includes a capacitor element 107 and a bus 211 (212) supplying DC power to the capacitor element 107. The capacitor element 107 has a lead conductor 214 for connecting to the bus 211 (212). The area of ​​the connection portion 219 between the lead conductor 214 and the bus 211 (212) is smaller than the cross-sectional area of ​​the lead conductor 214. In this way, an EMC filter and a power conversion device that generate a damping resistance effect in the circuit without the use of additional components can be provided.

[0049] (2) The busbar 211 (212) of the EMC filter 204 has a protrusion 216, and the lead conductor 214 is connected to the protrusion 216. In this way, a damping resistor can be realized.

[0050] (3) The protrusion 216 of the EMC filter 204 is a linear protrusion that is approximately orthogonal to the extension direction of the lead conductor 214. In this way, for multiple capacitor elements 107, the area of ​​the solder part 219 can be smaller than the cross-sectional area of ​​the lead conductor 214.

[0051] (4) It also has a fixing member 302 that covers the connection portion 219 of the busbar 211 (212) and the lead conductor 214 of the EMC filter 204. In this way, the stability of the EMC filter 204 implementing the present invention can be maintained.

[0052] (5) The fixing component 302 of the EMC filter 204 is a resin sealing material with electrical insulation properties. In this way, the safety of the EMC filter 204 implemented according to the present invention can be ensured.

[0053] (6) It also includes a housing filled with resin sealing material 302 of EMC filter 204, and the housing has a support portion 215 that supports the main body of capacitor element 107. In this way, together with resin 302, the fixation of EMC filter 204 on the housing is improved.

[0054] (7) A power conversion device 100 having the EMC filter 204 described in (1) to (6) is provided. Thus, a power conversion device 100 implementing the present invention can be provided.

[0055] The above-mentioned methods of deletion, substitution of other structures, and addition of other structures are all included within the scope of this invention, without departing from the technical concept of the invention. Symbol Explanation

[0056] 100 power conversion device 101 Circuit Diagram 102 battery 103 Electric motors for vehicle drive 107 capacitor 108 damping resistor 109 capacitor positive (P) side 110 capacitor negative (P) side 201 housing 202 Power Semiconductor Circuits Division 203 Smoothing Capacitor 204EMC filter 205 AC side busbar 206 DC side bus 211EMC filter positive (P) side bus The negative (N) side bus of the 212EMC filter 214 lead conductor 215 Support section 216 busbar protrusion 217 Busbar protrusion (deformation example) 218 Busbar protrusion (Deformation Example 2) 219 Connection (Welding) 301 Storage Department 302 resin.

Claims

1. An EMC filter, characterized in that, have: Capacitor elements; and The bus that supplies DC power to the capacitor element. The capacitor element has lead conductors for connection to the busbar. The area of ​​the connection between the lead conductor and the busbar is smaller than the cross-sectional area of ​​the lead conductor, resulting in a contact resistance at the connection that is greater than the parasitic resistance of the lead conductor.

2. The EMC filter according to claim 1, characterized in that, The busbar has a protrusion. The lead conductor is connected to the protrusion.

3. The EMC filter according to claim 2, characterized in that, The protrusion is a linear protrusion that is approximately orthogonal to the extension direction of the lead conductor.

4. The EMC filter according to claim 1, characterized in that, It also includes a fixing component that covers the connection between the busbar and the lead conductor.

5. The EMC filter according to claim 4, characterized in that, The fixing component is a resin sealing material with electrical insulation.

6. The EMC filter according to claim 5, characterized in that, It also includes a housing for filling the resin sealing material. The housing has a support portion that supports the capacitor element.

7. A power conversion device, characterized in that, It has an EMC filter according to any one of claims 1 to 6.

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