Ultra-low inductance feed-through capacitor

Abstract

The invention discloses a feed-through capacitor with ultralow inductance, which relates to the technical field of capacitors, and comprises a capacitor core, a positive bus, a negative bus, a shell and a filler, the capacitor core is formed by continuously winding the same metallized film, and comprises a plurality of groups of positive annular belt layers and reverse annular belt layers which are coaxially and alternately distributed; insulating sleeves are arranged between the adjacent forward annular belt layers and the reverse annular belt layers, axial openings are formed in the pipe walls of the insulating sleeves, a through copper pipe is arranged in the center of the capacitor core, insulating coatings are arranged on the inner wall and the outer wall of the through copper pipe, and the positive bus and the negative bus are arranged in the through copper pipe in parallel in a penetrating mode and are separated through an insulating plate. The positive bus is conducted with all the forward annular belt layers at one end of the capacitor core, the negative bus is conducted with all the reverse annular belt layers at the other end of the capacitor core, the outer side of the capacitor core is sleeved with the shell, and the filler is poured between the capacitor core and the shell. According to the invention, the inductance of the capacitor is effectively reduced, and a more reliable solution with better performance is provided.

Description

Technical Field

[0001] This invention relates to the field of capacitor technology, and more specifically, to a feedthrough capacitor with ultra-low inductance. Background Technology

[0002] Capacitors are indispensable electronic components in electronic devices. Their core function is to store charge. They can play key roles in circuits such as DC blocking and AC passing, coupling, bypassing, filtering, tuning circuits, energy conversion, and control. They are widely used in power electronics, industrial control, new energy, communications, and many other fields. Their performance directly determines the operational reliability of the entire equipment.

[0003] As electronic devices rapidly evolve towards higher frequencies and higher power densities, more stringent requirements are being placed on the performance of capacitors. In particular, low inductance has become a key factor limiting their suitability for high-frequency, high-power applications. Under high-frequency, high-power operating conditions, the stray inductance of capacitors becomes increasingly prominent: excessive stray inductance can easily lead to significant switching losses and voltage overshoot, causing voltage fluctuations across the capacitor and interfering with normal circuit operation. It also prolongs the capacitor's response time to circuit changes, slows down the charging and discharging process, and may interact with other inductive components in the circuit, causing resonance or oscillation, further affecting the stability and safety of circuit operation.

[0004] Therefore, we propose an ultra-low inductance feedthrough capacitor to solve the above-mentioned technical problems. Summary of the Invention

[0005] To address the technical problems existing in the prior art, this invention proposes an ultra-low inductance feedthrough capacitor to meet the development needs of high-frequency and high-power-density electronic devices and effectively reduce the stray inductance of the capacitor.

[0006] This invention is achieved through the following technical solution: An ultra-low inductance feedthrough capacitor includes a capacitor core, a positive busbar, a negative busbar, a shell, and a filler. The capacitor core is a ring electrode core formed by continuous winding of the same metallized film, comprising multiple sets of coaxially alternating positive and negative ring layers. An insulating sleeve is provided between adjacent positive and negative ring layers. The wall of the insulating sleeve has an axial opening for the metallized film to be led out and the winding direction to be switched. A feedthrough copper tube is located at the center of the capacitor core. Both the inner and outer walls of the feedthrough copper tube are provided with an insulating coating. The positive and negative busbars are parallel to each other inside the feedthrough copper tube and are separated by an insulating plate. The positive busbar is conductive to all positive ring layers at one end of the capacitor core, and the negative busbar is conductive to all negative ring layers at the other end of the capacitor core. The shell is fitted over the outside of the capacitor core, and the filler is cast between the capacitor core and the shell.

[0007] In a further technical solution, both the positive and negative busbars are composed of fixed posts and conductive posts. The fixed posts are inserted into a through copper tube, and the conductive posts are slidably mounted on the fixed posts along the axial direction. A locking component is provided between the fixed posts and the conductive posts to lock their relative axial positions.

[0008] In a further technical solution, the locking component includes an external thread on the outer side wall of the fixed post and an internal thread on the inner side wall of the conductive post. The external thread and the internal thread are matched. The external thread is distributed in segments at uniform intervals along the circumference of the fixed post, and the circumferential arc length between adjacent external threads is greater than the circumferential arc length of a single external thread segment. The circumferential arc length of the internal thread is not greater than the circumferential arc length of the external thread.

[0009] In a further technical solution, the number of turns of the forward and reverse annular layers varies in a gradient along the radial direction of the capacitor core: from the outer ring to the inner ring of the capacitor core, the number of turns of the forward and reverse annular layers are opposite to each other, the number of turns of the forward annular layer first increases and then decreases, and the number of turns of the reverse annular layer first decreases and then increases.

[0010] In a further technical solution, the number of turns of the middle set of forward annular layers does not exceed twice that of the outermost forward annular layer, and the number of turns of the middle set of reverse annular layers does not exceed twice that of the outermost reverse annular layer.

[0011] In a further technical solution, the surface of the forward annular layer at one end of the capacitor core is coated with a gold layer for conduction with the positive busbar, and the reverse annular layer is coated with an insulating layer. The surface of the reverse annular layer at the other end of the capacitor core is coated with a gold layer for conduction with the negative busbar, and the forward annular layer is coated with an insulating layer.

[0012] In a further technical solution, the outer shell is made of oxygen-free copper, the inner wall is in contact with the outer side of the capacitor core through conductive adhesive, and the outer side of the outer shell is provided with a grounding plate.

[0013] In a further technical solution, the insulating sleeve is made of alumina ceramic, aluminum nitride ceramic or beryllium oxide ceramic.

[0014] In a further technical solution, the insulating coating is a polyimide coating or an epoxy resin coating.

[0015] In a further technical solution, the filler is made by epoxy resin casting.

[0016] The technical solution of the present invention has at least the following beneficial effects: 1. This invention achieves efficient magnetic field cancellation through the alternating distribution of forward and reverse ring layers on the same side, effectively reducing the stray inductance of the capacitor core itself. It overcomes problems such as high switching losses, voltage overshoot, response hysteresis, and resonance risk caused by excessively high inductance parameters under high-frequency and high-power operating conditions, thus providing a more reliable and superior solution for high-frequency power electronic equipment.

[0017] 2. In this invention, the positive and negative busbars are parallel to each other inside the copper tube and are respectively connected to all the positive ring layers at one end of the capacitor core and all the reverse ring layers at the other end, forming a symmetrical low-inductance current path. The current directions are opposite, and the magnetic fields generated cancel each other out, restricting the flow loop of high-frequency current to a very small space and reducing the loop inductance introduced by the external leads.

[0018] 3. The positive and negative busbars of this invention are both designed as separate units, consisting of two main parts: fixed posts and conductive posts. The length of the conductive posts can be adjusted independently to make the lengths of the conductive posts inside the copper tube different, thereby changing the range of mutual cancellation of the magnetic field generated by the reverse current. This ultimately achieves precise fine-tuning in the low-inductance range, which not only meets the needs of different high-frequency equipment, but also takes into account the controllability and stability of the inductance.

[0019] 4. The gradient design of the number of turns of the forward and reverse annular layers in this invention achieves efficient superposition and cancellation of the axial global magnetic field of the capacitor core, effectively avoiding the phenomenon of local magnetic field concentration or insufficient cancellation. Attached Figure Description

[0020] The present invention will be described by way of example and with reference to the accompanying drawings, wherein: Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 for Figure 1 A magnified view of a portion of point A in the middle; Figure 3 for Figure 1 A cross-sectional view along the direction of the cutting symbol BB; Figure 4 This is a schematic diagram of the structure of the insulating sleeve of the present invention; Figure 5 This is a cross-sectional schematic diagram of the fixed column and the conductive column of the present invention.

[0021] Reference numerals in the attached diagram: 1-Capacitor core, 101-Forward ring layer, 102-Reverse ring layer, 2-Positive busbar, 3-Negative busbar, 4-Shell, 5-Filling material, 6-Insulating sleeve, 7-Axial opening, 8-Through copper tube, 9-Fixing post, 10-Conductive post, 11-External thread, 12-Internal thread, 13-Gold plating layer, 14-Insulating layer, 15-Ground plate, 16-Insulating board. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Example: See Figures 1-5 This invention provides a feedthrough capacitor with ultra-low inductance, comprising a capacitor core 1, a positive busbar 2, a negative busbar 3, a shell 4, and a filler 5. The capacitor core 1 is a ring-shaped electrode core formed by continuous winding of the same metallized thin film, including multiple sets of coaxially alternating forward ring layers 101 and reverse ring layers 102. An insulating sleeve 6 is provided between adjacent forward ring layers 101 and reverse ring layers 102. The wall of the insulating sleeve 6 is provided with a method for leading out the metallized thin film and switching the winding direction. The capacitor core 1 has an axial opening 7. A copper tube 8 is provided in the center of the capacitor core 1. The inner and outer walls of the copper tube 8 are provided with an insulating coating. The positive busbar 2 and the negative busbar 3 are parallel to each other in the copper tube 8 and are separated by an insulating plate 16. The positive busbar 2 is connected to all the positive ring layers 101 at one end of the capacitor core 1, and the negative busbar 3 is connected to all the reverse ring layers 102 at the other end of the capacitor core 1. The outer shell 4 is fitted on the outside of the capacitor core 1, and the filler 5 is poured between the capacitor core 1 and the outer shell 4.

[0024] Specifically, the capacitor core 1 is continuously wound from the same metallized film. The winding direction is switched using the axial opening 7 on the wall of the insulating sleeve 6, thereby forming multiple sets of coaxially alternating forward annular layers 101 and reverse annular layers 102. The insulating sleeve 6 not only serves to switch the winding direction between the forward and reverse annular layers 101 and 102, but also strengthens the electrical isolation between them, effectively preventing short circuits. Simultaneously, the rigid support of the insulating sleeve 6 prevents stress-release deformation of the metallized film after winding, ensuring the uniformity of the metallized film spacing and coaxial accuracy between the forward and reverse annular layers 101 and 102, thus laying the structural foundation for magnetic field cancellation and inductance reduction. The through-tube copper tube 8, as the core support structure of the capacitor core 1, serves multiple functions including mechanical positioning, electrical isolation, and thermal management. By providing a central reference for the winding of the metallized film, it ensures that the forward annular layer 101 and the reverse annular layer 102 are distributed around the same axis, thereby improving the magnetic field overlap. The insulating coating on its outer wall provides electrical isolation to prevent short circuits. The through-tube copper tube 8 has good thermal conductivity, enabling it to quickly dissipate heat from inside the capacitor core 1, achieving efficient heat dissipation. The positive busbar 2 and the negative busbar 3 are parallel to each other inside the through-tube copper tube 8 and are respectively connected to all the forward annular layers 101 at one end of the capacitor core 1 and all the reverse annular layers 102 at the other end, forming a symmetrical low-inductance current path. The currents are in opposite directions, and the magnetic fields generated cancel each other out, confining the high-frequency current flow loop to a very small space and reducing the loop inductance introduced by the external leads. When the capacitor operates, current flows through these adjacent ring layers with opposite winding directions. The current flows in opposite directions in the forward ring layer 101 and the reverse ring layer 102. According to the principle of electromagnetic induction, the magnetic fields generated by the opposite currents will weaken and cancel each other out. In addition, the high coaxiality of the forward ring layer 101 and the reverse ring layer 102 ensures efficient cancellation of the two magnetic fields, effectively reducing the stray inductance of the capacitor core 1 itself. Compared with capacitors in the prior art, this feedthrough capacitor, through the above design, effectively suppresses stray inductance and overcomes the problems of high switching losses, voltage overshoot, response hysteresis, and resonance risk caused by excessively high inductance parameters under high-frequency and high-power conditions. Thus, it provides a more reliable and higher-performance solution for high-frequency power electronic equipment.

[0025] In one specific implementation, see Figure 1 and Figure 2 Both the positive busbar 2 and the negative busbar 3 are composed of a fixed post 9 and a conductive post 10. The fixed post 9 is inserted into the through copper tube 8, and the conductive post 10 is slidably installed on the fixed post 9 along the axial direction. A locking component is provided between the fixed post 9 and the conductive post 10 to lock their relative axial positions.

[0026] Both the positive busbar 2 and the negative busbar 3 adopt a split design, consisting of two main parts: a fixed post 9 and a conductive post 10. The fixed post 9 is inserted inside the copper tube 8 and mainly serves as an electrical connection. The conductive post 10 is mounted on the fixed post 9 by axial sliding, and the axial relative position of the two is fixed by a locking component, allowing for flexible adjustment of the extension length of the conductive post 10. Specifically, by independently adjusting the extension length of the conductive post 10 of the positive busbar 2 and the negative busbar 3, a suitable length configuration can be formed between the positive busbar 2 and the negative busbar 3 without compromising the core structure of the capacitor. The different lengths of the conductive post 10 inside the copper tube 8 of the two buses change the range of mutual cancellation of the magnetic field generated by the reverse current, ultimately achieving precise fine-tuning in the low-inductance range. This adapts to the needs of different high-frequency devices while also ensuring inductance controllability and stability.

[0027] In one specific implementation, see Figure 5 The locking assembly includes an external thread 11 on the outer side wall of the fixed post 9 and an internal thread 12 on the inner side wall of the conductive post 10. The external thread 11 and the internal thread 12 are matched. The external thread 11 is distributed in segments at uniform intervals along the circumference of the fixed post 9, and the circumferential arc length between adjacent external threads 11 is greater than the circumferential arc length of a single segment of external thread 11. The circumferential arc length of the internal thread 12 is not greater than the circumferential arc length of the external thread 11.

[0028] The external threads 11 on the outer wall of the fixed post 9 are designed with circumferentially segmented and evenly spaced distribution, and the circumferential arc length between adjacent external threads 11 is greater than the arc length of a single external thread 11 segment. The circumferential arc length of the internal threads 12 on the inner wall of the conductive post 10 is not greater than the circumferential arc length of the external threads 11, so that the internal threads 12 can form both non-engaged and engaged states with the external threads 11. The two are firmly fixed in their axial relative positions through thread engagement. When adjustment is required, simply rotate the conductive post 10 to disengage the internal threads 12 from the external threads 11 of the fixed post 9, and the adjustment state can be entered. The extension length of the conductive post 10 can be freely and flexibly adjusted along the axial direction of the fixed post 9.

[0029] In one specific embodiment, the number of turns of the forward annular layer 101 and the reverse annular layer 102 varies in a gradient along the radial direction of the capacitor core 1: from the outer ring to the inner ring of the capacitor core 1, the number of turns of the forward annular layer 101 and the reverse annular layer 102 are opposite to each other, the number of turns of the forward annular layer 101 first increases and then decreases, and the number of turns of the reverse annular layer 102 first decreases and then increases.

[0030] The gradient variation is reflected in the following: in the outer and inner regions of capacitor core 1, the number of turns in the forward ring layer 101 is less, while the number of turns in the reverse ring layer 102 is more; in the central region of capacitor core 1, the number of turns in the forward ring layer 101 reaches its maximum, while the number of turns in the reverse ring layer 102 reaches its minimum. This opposite gradient distribution design results in a radial magnetic field gradient of "strong at the center and weak at the edge" for the forward ring layer 101 and "weak at the center and strong at the edge" for the reverse ring layer 102, forming a complementary magnetic field distribution. Specifically, the strong positive magnetic field in the middle is radially and bidirectionally canceled by the reverse magnetic fields on both the inner and outer sides, while the weak positive magnetic field in the edge region is directly covered and canceled by the adjacent reverse magnetic fields, effectively reducing magnetic field leakage caused by edge effects, improving the overall magnetic field cancellation efficiency, and thus significantly reducing the overall inductance of capacitor core 1.

[0031] In one specific embodiment, the number of turns of the middle set of forward annular layers 101 does not exceed twice that of the outermost forward annular layers 101, and the number of turns of the middle set of reverse annular layers 102 does not exceed twice that of the outermost reverse annular layers 102.

[0032] This multiple constraint avoids excessive differences in the number of turns of the forward annular layer 101 and the reverse annular layer 102 between the middle region and the two end regions, ensuring that the enhancement of the forward magnetic field from the two end regions to the middle and the weakening of the reverse magnetic field from the two end regions to the middle are within a reasonable range. At the same time, it can prevent excessive thickness due to too many turns, thereby avoiding the problem of longer heat dissipation paths and reduced heat dissipation efficiency, and ensuring the stability of the capacitor's heat dissipation performance under high frequency and high power conditions.

[0033] In one specific implementation, see Figure 1 and Figure 2 The surface of the forward annular layer 101 at one end of the capacitor core 1 is coated with a gold-plated layer 13 for conduction with the positive busbar 2, and the reverse annular layer 102 is coated with an insulating layer 14. The surface of the reverse annular layer 102 at the other end of the capacitor core 1 is coated with a gold-plated layer 13 for conduction with the negative busbar 3, and the forward annular layer 101 is coated with an insulating layer 14.

[0034] The capacitor core 1 employs a differentiated treatment scheme at its ends, using a gold-plated layer 13 for conduction and an insulating layer 14 for isolation. This scheme achieves conduction between the electrodes and the corresponding ring layers while effectively blocking the current exchange between the forward ring layer 101 and the reverse ring layer 102 at the same end of the capacitor core 1, thereby avoiding potential cross-short circuit problems caused by interlayer electrical contact.

[0035] In one specific implementation, see Figure 1 and Figure 3 The outer casing 4 is made of oxygen-free copper. The inner wall of the casing is in contact with the outer side of the capacitor core 1 through conductive adhesive. The outer side of the casing 4 is provided with a grounding plate 15.

[0036] The oxygen-free copper casing 4 is in close contact with the capacitor core 1 through conductive adhesive, achieving both electrical connection and heat dissipation. A grounding plate 15 is provided on the outside of the casing 4, which provides a low-impedance grounding path for internal high-frequency current, effectively suppressing electromagnetic interference and quickly discharging stray current and static electricity, significantly improving electrical safety.

[0037] In one specific embodiment, the insulating sleeve 6 is made of alumina ceramic, aluminum nitride ceramic or beryllium oxide ceramic.

[0038] Alumina ceramics offer both good thermal conductivity and affordability; aluminum nitride ceramics provide near-metallic thermal conductivity, meeting the needs of high-performance applications; and beryllium oxide ceramics are suitable for specialized fields requiring extreme heat dissipation. Flexible selection based on product performance requirements and cost budgets achieves the optimal balance between heat dissipation performance and cost control.

[0039] In one specific embodiment, the insulating coating is a polyimide coating or an epoxy resin coating.

[0040] The polyimide coating and epoxy resin have excellent insulation properties, and are resistant to high temperature and aging. They can resist the heat erosion of the capacitor core 1 during operation, and have stable performance over a long period of use, thus extending the product's service life.

[0041] In one specific embodiment, the filler 5 is made by epoxy resin casting.

[0042] After curing, epoxy resin has excellent structural strength and adhesion, which can fix the relative positions of various components and prevent displacement or loosening; at the same time, it has good insulation properties, which can improve electrical safety under high frequency and high power conditions and eliminate the risk of short circuit.

[0043] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A feedthrough capacitor with ultra-low inductance, characterized in that, The capacitor core (1) comprises a capacitor core (1), a positive electrode busbar (2), a negative electrode busbar (3), a shell (4), and a filler (5). The capacitor core (1) is a ring electrode core formed by continuous winding of the same metallized thin film, including multiple sets of coaxially alternating forward ring layers (101) and reverse ring layers (102). An insulating sleeve (6) is provided between adjacent forward ring layers (101) and reverse ring layers (102). The wall of the insulating sleeve (6) is provided with an axial opening (7) for the metallized thin film to be led out and the winding direction to be switched. The center of the capacitor core (1) A through-core copper tube (8) is provided, and the inner and outer walls of the through-core copper tube (8) are provided with an insulating coating. The positive busbar (2) and the negative busbar (3) are parallel to each other inside the through-core copper tube (8) and are separated by an insulating plate (16). The positive busbar (2) is connected to all the positive ring layers (101) at one end of the capacitor core (1), and the negative busbar (3) is connected to all the reverse ring layers (102) at the other end of the capacitor core (1). The outer shell (4) is fitted on the outside of the capacitor core (1), and the filler (5) is poured between the capacitor core (1) and the outer shell (4).

2. The ultra-low inductance feedthrough capacitor according to claim 1, characterized in that, The positive busbar (2) and the negative busbar (3) are both composed of a fixed post (9) and a conductive post (10). The fixed post (9) is inserted into the through copper tube (8), and the conductive post (10) is slidably installed on the fixed post (9) along the axial direction. A locking component is provided between the fixed post (9) and the conductive post (10) to lock their axial relative positions.

3. A feedthrough capacitor with ultra-low inductance according to claim 2, characterized in that, The locking assembly includes an external thread (11) on the outer side wall of the fixed post (9) and an internal thread (12) on the inner side wall of the conductive post (10). The external thread (11) and the internal thread (12) are matched. The external thread (11) is evenly distributed in segments along the circumference of the fixed post (9), and the circumferential arc length between adjacent external threads (11) is greater than the circumferential arc length of a single external thread (11). The circumferential arc length of the internal thread (12) is not greater than the circumferential arc length of the external thread (11).

4. A feedthrough capacitor with ultra-low inductance according to claim 1, characterized in that, The number of turns of the forward annular layer (101) and the reverse annular layer (102) varies in a gradient along the radial direction of the capacitor core (1): from the outer ring to the inner ring of the capacitor core (1), the number of turns of the forward annular layer (101) and the reverse annular layer (102) are opposite to each other. The number of turns of the forward annular layer (101) first increases and then decreases, while the number of turns of the reverse annular layer (102) first decreases and then increases.

5. A feedthrough capacitor with ultra-low inductance according to claim 4, characterized in that, The number of turns of the middle set of positive annular layers (101) does not exceed twice that of the outermost positive annular layer (101), and the number of turns of the middle set of negative annular layers (102) does not exceed twice that of the outermost negative annular layer (102).

6. A feedthrough capacitor with ultra-low inductance according to claim 1, characterized in that, The surface of the forward ring layer (101) at one end of the capacitor core (1) is coated with a gold layer (13) for conduction with the positive busbar (2), and the reverse ring layer (102) is coated with an insulating layer (14). The surface of the reverse ring layer (102) at the other end of the capacitor core (1) is coated with a gold layer (13) for conduction with the negative busbar (3), and the forward ring layer (101) is coated with an insulating layer (14).

7. A feedthrough capacitor with ultra-low inductance according to claim 1, characterized in that, The outer shell (4) is made of oxygen-free copper. The inner wall is in contact with the outer side of the capacitor core (1) through conductive adhesive. The outer side of the outer shell (4) is provided with a grounding plate (15).

8. A feedthrough capacitor with ultra-low inductance according to claim 1, characterized in that, The insulating sleeve (6) is made of alumina ceramic, aluminum nitride ceramic or beryllium oxide ceramic.

9. A feedthrough capacitor with ultra-low inductance according to claim 1, characterized in that, The insulating coating is a polyimide coating or an epoxy resin coating.

10. A feedthrough capacitor with ultra-low inductance according to claim 1, characterized in that, The filler (5) is made by epoxy resin casting.

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