A low inductance capacitor structure for use in a vehicle

Abstract

The application relates to a low-inductance capacitor structure for vehicles, comprising a shell and a capacitor element arranged in the shell, wherein the capacitor element comprises: a plurality of groups of copper bars, each group of the copper bars comprising input copper bars and output copper bars arranged in a stack, the plurality of groups of the copper bars are sequentially stacked, and an insulating diaphragm is arranged between each two adjacent copper bars; in the same group of the copper bars, the input copper bars and the output copper bars have a staggered structure, and the staggered structure can make the input copper bars and the output copper bars be arranged in a staggered mode in a thickness direction. The application can effectively reduce the working inductance of the capacitor, is suitable for high-frequency working conditions, and has higher stability and reliability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of capacitors, and particularly relates to a low-inductance vehicle capacitor structure. BACKGROUND

[0002] With the continuous progress of automobile technology, especially the development of electric vehicles (EV) and intelligent vehicles, the electronic system of the automobile becomes more and more complex. A large number of electronic components and electrical equipment (such as electric drive systems, vehicle communication systems, autonomous driving systems, infotainment systems, etc.) in modern vehicles also continuously increase the demand for capacitors. Capacitors are commonly used in automobiles for power filtering, signal coupling, noise elimination, and providing transient power, etc.

[0003] Among them, power filtering and high-frequency signal suppression are particularly important. In modern vehicles, electronic devices operate at higher and higher frequencies, especially in the complex electrical control systems of electric vehicles and intelligent vehicles, high-frequency noise and electromagnetic interference (EMI) have a huge impact on the stability and accuracy of the system. Therefore, capacitors with better performance that can work under high-frequency conditions are needed.

[0004] The capacitor structure in the prior art is shown in Figure 1 , Figure 2 The capacitor includes a shell and a capacitor assembly arranged inside the shell, and the capacitor assembly includes multiple layers of copper bars. The terminals of the copper bars are drawn out at a fixed interval. This structure will produce a superimposed inductance, greatly increasing the inductance generated when the capacitor works. In addition, the copper bars of the existing capacitor are connected to the circuit board by bolts, which has large contact resistance and unstable connection, and will generate large parasitic inductance under high-frequency working conditions. This will also increase the working inductance of the capacitor. High working inductance limits the performance of the film capacitor in high-frequency applications, increases energy loss, causes parasitic resonance, affects stability, and can cause electromagnetic interference and reliability to decrease.

[0005] In summary, the capacitor in the prior art has the problem of large working inductance, which needs to be improved. SUMMARY

[0006] In order to solve the problems existing in the prior art, the present application aims to provide a low-inductance vehicle capacitor structure. The present application can effectively reduce the working inductance of the capacitor, be suitable for high-frequency working conditions, and have higher stability and reliability.

[0007] The low-inductance vehicle capacitor structure described in the present application includes a shell and a capacitor element arranged in the shell, and the capacitor element includes:

[0008] A plurality of copper bars, each of the copper bars comprises an input copper bar and an output copper bar stacked together, the plurality of copper bars are stacked together, and an insulating diaphragm is arranged between each two adjacent copper bars; in the same group of copper bars, the input copper bar and the output copper bar have a staggered structure, and the staggered structure can make the input copper bar and the output copper bar staggered in the thickness direction.

[0009] Preferably, the staggered structure comprises a first comb tooth part formed on the input copper bar in the same group of copper bars, and a second comb tooth part formed on the output copper bar in the same group as the first comb tooth part, the first comb tooth part and the second comb tooth part are staggered to make the solid area of the first comb tooth part and the hollow area of the second comb tooth part at least partially overlap in the thickness direction, and the hollow area of the first comb tooth part and the solid area of the second comb tooth part at least partially overlap in the thickness direction.

[0010] Preferably, the staggered structure comprises a first wave part formed on the input copper bar in the same group of copper bars, and a second wave part formed on the output copper bar in the same group as the first wave part, the first wave part and the second wave part are staggered to make the solid area of the first wave part and the hollow area of the second wave part at least partially overlap in the thickness direction, and the hollow area of the first wave part and the solid area of the second wave part at least partially overlap in the thickness direction.

[0011] Preferably, the staggered structure comprises a first sawtooth part formed on the input copper bar in the same group of copper bars, and a second sawtooth part formed on the output copper bar in the same group as the first sawtooth part, the first sawtooth part and the second sawtooth part are staggered to make the solid area of the first sawtooth part and the hollow area of the second sawtooth part at least partially overlap in the thickness direction, and the hollow area of the first sawtooth part and the solid area of the second sawtooth part at least partially overlap in the thickness direction.

[0012] Preferably, if the application current of the vehicle capacitor is 100A to 200A, the thickness of the copper bar is 0.8mm to 1.2mm, and if the application current of the vehicle capacitor is 200A to 400A, the thickness of the copper bar is 1.2mm to 2.5mm.

[0013] Preferably, the insulating diaphragm uses at least one of polypropylene, polyimide or polytetrafluoroethylene.

[0014] Preferably, the capacitor assembly further comprises a circuit board, and the circuit board is laser welded with the copper bar.

[0015] Preferably, the capacitor assembly further comprises a connecting lead, and the connecting lead is electrically connected with the circuit board.

[0016] Preferably, the length of the connecting lead satisfies an inductance calculation formula:

[0017]

[0018] wherein L represents inductance, μ0 represents vacuum permeability, l represents the length of the connecting lead, and d represents the diameter of the connecting lead.

[0019] Preferably, the connecting lead is determined according to the following steps:

[0020] According to the parameter requirements of the vehicle capacitor, a simulation model of the vehicle capacitor is established, and the parameter requirements include rated voltage, capacity and working frequency;

[0021] The working condition parameters of the vehicle capacitor are input into the simulation model, and the working condition parameters include input current and frequency;

[0022] Through iterative calculation, the shortest lead length that meets the electrical performance is obtained as the length of the connecting lead;

[0023] The iterative calculation is specifically:

[0024] According to the size of the circuit board pad and the current carrying requirement, the diameter d of the connecting lead is determined;

[0025] According to the capacitor design requirement, the maximum target inductance L max is set;

[0026] The inductance constraint condition is set as:

[0027] L≤L max ,

[0028] A plurality of values of the length l of the connecting lead are preset, the plurality of values are sequentially substituted into the inductance calculation formula in order from small to large, and inductance calculation results are obtained, and when the inductance constraint condition is met, the corresponding connecting lead length is selected as the shortest lead length;

[0029] The optional length is verified and corrected, and the verification and correction includes: judging whether the optional length meets the wiring space and welding process requirements, if yes, the optional length is taken as the shortest lead length, otherwise the next value is substituted into the inductance calculation formula until the verification and correction is passed.

[0030] The low-inductance capacitor structure for vehicles has the advantages that the input copper bars and the output copper bars are arranged in a laminated manner, and a partial overlap misalignment structure is arranged between adjacent input copper bars and output copper bars, the electric field coupling effect between the copper bar layers is used to compensate the capacitance and the parasitic inductance generated by the copper bars in different layers, so as to reduce the working inductance of the capacitor, and the capacitor can be applied to high-frequency working conditions, and has higher stability and reliability.

[0031] In addition, the laser welding is adopted, the problems of large contact resistance, unstable connection, and large parasitic inductance under high-frequency working conditions are effectively avoided, and the working inductance of the capacitor is further reduced.

[0032] Furthermore, the length of the connecting lead is reasonably designed through the simulation model, so that the connecting lead can realize the shortest length under the working condition, and the problem of extra inductance caused by the too long length of the lead is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 is a schematic diagram of the external structure of the capacitor structure for vehicles in the prior art;

[0034] Figure 2 is a schematic diagram of the internal structure of the capacitor structure for vehicles in the prior art;

[0035] Figure 3 is a schematic diagram of the external structure of the capacitor structure for vehicles in the prior art;

[0036] Figure 4 is a schematic diagram of the internal structure of the capacitor structure for vehicles in the prior art;

[0037] Figure 5 is a schematic diagram of the cooperation structure of the input copper bar and the output copper bar in embodiment 1;

[0038] Figure 6 is a schematic diagram of the cooperation structure of the input copper bar and the output copper bar in embodiment 2;

[0039] Figure 7 is a schematic diagram of the cooperation structure of the input copper bar and the output copper bar in embodiment 3.

[0040] Explanation of reference signs: 1 - shell, 2 - copper bar, 21 - input copper bar, 21a - first comb tooth part, 21b - first wave part, 21c - first sawtooth part, 22 - output copper bar, 22a - second comb tooth part, 22b - second wave part, 22c - second sawtooth part. DETAILED DESCRIPTION

[0041] As Figure 3 , Figure 4As shown, the low inductance capacitor structure for vehicle described in the present application comprises a shell 1 and a capacitor element arranged in the shell 1. In a specific embodiment, the shell 1 is a square shell structure made of plastic material and has an internal hollow for accommodating the capacitor element.

[0042] The capacitor element comprises a plurality of groups of copper bars 2, each group of copper bars 2 comprises an input copper bar 21 and an output copper bar 22 arranged in a stack, and the plurality of groups of copper bars 2 are arranged in a stack in sequence to form an input copper bar 21-output copper bar 22-input copper bar 21-output copper bar 22 stack structure. In the same group of copper bars 2, the input copper bar 21 and the output copper bar 22 have a staggered structure, which can make the input copper bar 21 and the output copper bar 22 staggered in the thickness direction.

[0043] The present application adopts a multi-layer electrode copper bar 2 stack layout to optimize the total capacitance and inductance performance of the capacitor without increasing the size of the device. The electrode copper bar 2 structure is staggered, and the copper bars 2 of adjacent layers bear the current input and output functions, respectively. The copper bars 2 are complementary in shape and partially overlap to form an interlayer coupling region. The capacitors and parasitic inductances generated by different layers of copper bars 2 are compensated for each other by using the electric field coupling effect between the layers of copper bars 2 to reduce the working inductance of the capacitor.

[0044] Specifically, the copper bars 2 with a staggered structure are formed by laser cutting, stamping and other processes, and the layers are insulated and isolated by an insulating film. After stacking, pressing and packaging, the interlayer capacitance and parasitic inductance form a kind of resonant circuit, which can offset part of the inductance in the capacitor working frequency range to reduce the overall inductance. Compared with the single-layer or simply stacked copper bar 2 structure in the prior art, the inductance can be reduced by 20% to 40% under high-frequency working conditions such as 10kHZ and above.

[0045] There are at least three implementation methods for the staggered structure.

[0046] Embodiment 1

[0047] As shown in Figure 5 The staggered structure comprises a first comb tooth part 21a formed on the input copper bar 21 in the same group of copper bars 2 and a second comb tooth part 22a formed on the output copper bar 22 in the same group as the first comb tooth part 21a. The first comb tooth part 21a and the second comb tooth part 22a are arranged in a staggered manner, so that the solid area of the first comb tooth part 21a and the hollow area of the second comb tooth part 22a at least partially overlap in the thickness direction, and the hollow area of the first comb tooth part 21a and the solid area of the second comb tooth part 22a at least partially overlap in the thickness direction.

[0048] Specifically, for the two copper busbars 2 in the same group, namely the input copper busbar 21 and the output copper busbar 22, a first comb tooth portion 21a is formed on one side edge of the input copper busbar 21. The first comb tooth portion 21a includes square protrusions and square recesses that are alternately arranged along the length direction of the copper busbar 2. The output copper busbar 22 is provided with a second comb tooth portion 22a at the position corresponding to the first comb tooth portion 21a. The second comb tooth portion 22a also includes square protrusions and square recesses that are alternately arranged. In a preferred embodiment, the square protrusions and square recesses have the same width. Each square protrusion of the first comb tooth portion 21a corresponds to each square recess of the second comb tooth portion 22a, thereby forming a structure in which the first comb tooth portion 21a and the second comb tooth portion 22a are staggered.

[0049] Example 2

[0050] like Figure 6 As shown, the misaligned structure includes a first wave portion 21b formed on the input copper busbar 21 in the same group of copper busbars 2, and a second wave portion 22b formed on the output copper busbar 22 in the same group as the first wave portion 21b. The first wave portion 21b and the second wave portion 22b are misaligned so that the solid area of ​​the first wave portion 21b and the hollow area of ​​the second wave portion 22b at least partially overlap in the thickness direction, and the hollow area of ​​the first wave portion 21b and the solid area of ​​the second wave portion 22b at least partially overlap in the thickness direction.

[0051] Specifically, for the two copper busbars 2 in the same group, namely the input copper busbar 21 and the output copper busbar 22, a first wave portion 21b is formed on one side edge of the input copper busbar 21. The first wave portion 21b includes arc-shaped protrusions and arc-shaped concave portions alternately arranged along the length direction of the copper busbar 2. The output copper busbar 22 is provided with a second wave portion 22b at the position corresponding to the first wave portion 21b. The second wave portion 22b also includes arc-shaped protrusions and arc-shaped concave portions alternately arranged. In a preferred embodiment, the diameters of the arc-shaped protrusions and arc-shaped concave portions are equal. Each arc-shaped protrusion of the first wave portion 21b corresponds to each arc-shaped concave portion of the second wave portion 22b, thereby forming a structure in which the first wave portion 21b and the second wave portion 22b are staggered.

[0052] Example 3

[0053] like Figure 7 As shown, the misaligned structure includes a first serrated portion 21c formed on the input copper busbar 21 in the same group of copper busbars 2, and a second serrated portion 22c formed on the output copper busbar 22 in the same group as the first serrated portion 21c. The first serrated portion 21c and the second serrated portion 22c are misaligned so that the solid area of ​​the first serrated portion 21c and the hollow area of ​​the second serrated portion 22c at least partially overlap in the thickness direction, and the hollow area of ​​the first serrated portion 21c and the solid area of ​​the second serrated portion 22c at least partially overlap in the thickness direction.

[0054] Specifically, for two copper bars 2 of the same group, respectively, the input copper bar 21 and the output copper bar 22, the first sawtooth part 21c is formed at one side edge of the input copper bar 21, the first sawtooth part 21c includes alternatingly arranged angular protrusions and angular recesses along the length direction of the copper bar 2, the output copper bar 22 is provided with a second sawtooth part 22c at the corresponding position of the first sawtooth part 21c, the second sawtooth part 22c also includes alternatingly arranged angular protrusions and angular recesses, in a preferred embodiment, the size of the angular protrusion is equal to that of the angular recess, each angular protrusion of the first sawtooth part 21c corresponds to each angular recess of the second sawtooth part 22c, thereby forming a structure in which the first sawtooth part 21c and the second sawtooth part 22c are arranged in a staggered manner.

[0055] Through the above three different embodiments, the two copper bars 2 of the same group can have a structure arranged in a staggered manner in the thickness direction, so as to reduce the overall working inductance of the capacitor. It is easily conceivable that those skilled in the art can set the specific shape of the staggered structure according to the processing requirements and material properties, and the present application does not limit the specific shape of the staggered structure. Other conventional shapes designed based on the concept of the present application should fall within the protection scope of the present application.

[0056] Further, in the present embodiment, if the application current of the vehicle capacitor is 100A to 200A, the thickness of the copper bar 2 is 0.8mm to 1.2mm, and if the application current of the vehicle capacitor is 200A to 400A, the thickness of the copper bar 2 is 1.2mm to 2.5mm. The thickness of the copper bar 2 is designed according to the size of the application current, so that the size of the copper bar 2 can be suitable for the working scene.

[0057] Further, in the present embodiment, the insulating diaphragm adopts at least one of polypropylene, polyimide or polytetrafluoroethylene, and the above-mentioned insulating material has the characteristics of high insulation and low dielectric loss, and is suitable as an insulating diaphragm material.

[0058] Further, in the present embodiment, the capacitor assembly further comprises a circuit board, and the circuit board is laser welded with the copper bar 2. Laser welding can realize high-quality metallurgical bonding of the copper bar 2 and the circuit welding point, eliminate the influence of contact gap and oxidation layer in the traditional connection mode, greatly reduce the contact resistance by 70%-90%, significantly reduce the loss in the current transmission process, thereby effectively reducing the parasitic inductance. Compared with the traditional connection mode, the inductance can be reduced to 1 / 5-1 / 3 of the original.

[0059] For example, the laser welding step is as follows:

[0060] Surface treatment and positioning: Use a special cleaner to thoroughly clean the welding area of the circuit bus, load end and capacitor copper bar 2, remove oxidation layer, oil stains and other impurities, and ensure the surface is clean and free of foreign matter. Use high-precision positioning tool to accurately align the input and output copper bars 22 of the multilayer electrode copper bar 2 capacitor with the circuit welding points, and fix them with clamps to ensure that the copper bar 2 is tightly attached to the welding points with a positioning error of less than ±0.05 mm.

[0061] Laser welding process implementation: Select a high-power pulsed fiber laser and set the laser parameters accurately according to the thickness and material of the copper bar 2 (such as pure copper, copper alloy) and welding requirements. Generally, the laser power is set to 1-3 kW, the pulse width is adjusted to 1-5 ms, the frequency is controlled to 10-50 Hz, and the defocusing amount is kept at ±0.2 mm. Use continuous or lap welding method to scan along the edge of the copper bar 2 and circuit welding point to make the copper bar 2 and circuit achieve firm metallurgical bonding and form a low-resistance, high-reliability connection path.

[0062] Welding quality detection and debugging: After welding, use laser ultrasonic detection technology to detect the welding site for non-destructive testing to check for defects such as pores and cracks; at the same time, measure the contact resistance of the welding point with a micro-ohmmeter to ensure it is at a very low level. If the working frequency, load and other conditions of the circuit system change, the copper bar 2 stack module with different interlayer coupling parameters (such as copper bar shape, overlap area, insulating medium thickness) can be replaced according to actual needs to optimize the capacitor's capacitance-inductance compensation effect, thus meeting the performance requirements of the circuit system.

[0063] Further, in the embodiment, the capacitor assembly further comprises a connecting lead, the connecting lead being electrically connected with the circuit board, and a length of the connecting lead satisfies an inductance calculation formula:

[0064]

[0065] wherein L represents inductance, μ0 represents vacuum permeability, 1 represents the length of the connecting lead, and d represents the diameter of the connecting lead.

[0066] The connecting lead is determined according to the following steps:

[0067] According to the parameter requirements of the vehicle capacitor, a simulation model of the vehicle capacitor is established by using an electromagnetic simulation software, such as ANSYS, and the parameter requirements include rated voltage, capacity and working frequency;

[0068] The working condition parameters of the vehicle capacitor are input into the simulation model, and the working condition parameters include input current and frequency;

[0069] Through iterative calculation, the shortest lead length satisfying the electrical performance is obtained as the length of the connecting lead;

[0070] The iterative calculation is specifically:

[0071] According to the circuit board pad size and current carrying requirement, the diameter d of the connecting lead is determined;

[0072] According to the capacitor design requirement, the target inductance maximum value L is set max ;

[0073] The inductance constraint condition is set as:

[0074] L≤L max ,

[0075] A plurality of values of the length l of the connecting lead are preset, the plurality of values are sequentially substituted into the inductance calculation formula in order from small to large in value and inductance calculation results are obtained, and when the inductance constraint condition is satisfied, the corresponding connecting lead length is selected as the optional length;

[0076] The optional length is verified and corrected, and the verification and correction includes: judging whether the optional length satisfies the wiring space and welding process requirement, if yes, the optional length is selected as the shortest lead length, otherwise the next value is substituted into the inductance calculation formula until the verification and correction is passed.

[0077] In the embodiment, the electric field simulation analysis is used, the electrode layout is optimized based on the current uniform distribution and the minimum loop area principle, and the problem of excessive inductance caused by too long lead length is reduced.

[0078] In the description of the present application, it should be understood that the orientation words such as "front, back, up, down, left, right", "transverse, vertical, horizontal" and "top, bottom" and the like indicate the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, without the opposite description, these orientation words do not indicate and imply that the indicated device or element must have a specific orientation or be constructed and operated in a specific orientation, therefore it cannot be understood as a limitation on the protection scope of the present application.

[0079] For those skilled in the art, other various corresponding changes and deformations can be made according to the above described technical solutions and concepts, and all these changes and deformations should belong to the protection scope of the claims of the present application.

Claims

1. A low inductance capacitor structure for use in an automobile, comprising a case and a capacitor element disposed in said case, characterized by, The capacitor element comprises: A plurality of groups of copper bars, each group of the copper bars comprising an input copper bar and an output copper bar stacked, the plurality of groups of the copper bars being stacked in sequence, and an insulating diaphragm being arranged between each two adjacent copper bars; in the same group of the copper bars, the input copper bar and the output copper bar have a staggered structure, which can make the input copper bar and the output copper bar staggered in the thickness direction; The staggered structure comprises a first comb tooth part formed on the input copper bar in the same group of copper bars, and a second comb tooth part formed on the output copper bar in the same group as the first comb tooth part, the first comb tooth part and the second comb tooth part being staggered to make the solid area of the first comb tooth part and the hollow area of the second comb tooth part at least partially overlap in the thickness direction, and the hollow area of the first comb tooth part and the solid area of the second comb tooth part at least partially overlap in the thickness direction; Alternatively, the staggered structure comprises a first wave part formed on the input copper bar in the same group of copper bars, and a second wave part formed on the output copper bar in the same group as the first wave part, the first wave part and the second wave part being staggered to make the solid area of the first wave part and the hollow area of the second wave part at least partially overlap in the thickness direction, and the hollow area of the first wave part and the solid area of the second wave part at least partially overlap in the thickness direction; Alternatively, the staggered structure comprises a first sawtooth part formed on the input copper bar in the same group of copper bars, and a second sawtooth part formed on the output copper bar in the same group as the first sawtooth part, the first sawtooth part and the second sawtooth part being staggered to make the solid area of the first sawtooth part and the hollow area of the second sawtooth part at least partially overlap in the thickness direction, and the hollow area of the first sawtooth part and the solid area of the second sawtooth part at least partially overlap in the thickness direction.

2. The low inductance capacitor structure for a vehicle according to claim 1, wherein If the application current of the vehicle capacitor is 100A to 200A, the thickness of the copper bar is 0.8mm to 1.2mm, and if the application current of the vehicle capacitor is 200A to 400A, the thickness of the copper bar is 1.2mm to 2.5mm.

3. The low inductance capacitor structure for a vehicle according to claim 1, wherein The insulating diaphragm is made of at least one of polypropylene, polyimide or polytetrafluoroethylene.

4. The low inductance capacitor structure for a vehicle according to claim 1, wherein The capacitor element further comprises a circuit board, which is laser welded with the copper bar.

5. The low inductance capacitor structure for a vehicle according to claim 4, wherein The capacitor element further comprises a connecting lead, which is electrically connected with the circuit board.

6. The low inductance capacitor structure for a vehicle according to claim 5, wherein The length of the connecting lead satisfies the inductance calculation formula: ， wherein L represents an inductance, represents a vacuum permeability, represents a length of a connecting lead wire, represents a diameter of a connecting lead wire.

7. The low inductance capacitor structure for a vehicle according to claim 6, wherein The connecting lead is determined by the following steps: According to the parameter requirements of the vehicle capacitor, a simulation model of the vehicle capacitor is established, the parameter requirements including rated voltage, capacity and working frequency; The working condition parameters of the vehicle capacitor are input into the simulation model, the working condition parameters including input current and frequency; Through iterative calculation, the shortest lead length that meets the electrical performance is obtained as the length of the connecting lead; Wherein, the iterative calculation is specifically: According to the circuit board pad size and current carrying requirement, the diameter of the connecting lead is determined ; Setting a target inductance maximum value according to capacitor design requirements ; Set the inductance constraint condition: ， Pre-set several values of the length of the connecting lead , and the inductance calculation results are obtained by substituting the several values into the inductance calculation formula in order from small to large in value. When the inductance constraint condition is met, the corresponding connecting lead length is selected as the optional length. The optional length is verified and corrected, the verification and correction including: judging whether the optional length meets the wiring space and welding process requirements, if yes, taking the optional length as the shortest lead length, otherwise, continuing to substitute the next value into the inductance calculation formula until passing the verification and correction.

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