Capacitor member for resonant power transfer, use of a capacitor member, and switched mode power supply having a capacitor member
By using multilayer capacitor components with low temperature coefficient of capacitance ceramic materials and copper electrode layers, the problems of low current and insufficient insulation in transformerless switching power supplies are solved, achieving high current carrying capacity and capacitance stability at high frequencies. This makes the power supply suitable for resonant power transmission, reduces equipment size, and increases power density.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- TDK ELECTRONICS AG
- Filing Date
- 2024-10-22
- Publication Date
- 2026-06-05
AI Technical Summary
Existing transformerless switching power supplies suffer from problems such as low current, lack of insulation from the power grid or other voltage sources, and insufficient current transmission by capacitors during resonant power transmission. Furthermore, existing capacitors are difficult to meet the complex technical and standard boundary conditions in high-frequency applications.
A multilayer capacitor component with ceramic materials and copper electrode layers with low capacitance temperature coefficient is used. By compensating for the positioning deviation of the electrode layers, the capacitor is ensured to provide high current carrying capacity and insulation performance at high frequencies, meeting the standard requirements of Y1 capacitors.
It achieves sufficiently large breakdown field strength and current capability with small component size, ensures capacitor stability, is suitable for resonant power transmission, reduces device size and increases power density.
Smart Images
Figure CN122162210A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a capacitor component for resonant power transfer. In particular, the capacitor component is configured for use in a switching power supply. The capacitor component can also be used, for example, in charging devices, especially in charging devices for wireless charging. Background Technology
[0002] Switching power supplies with magnetic cores are known, the simplest form of which is the linear converter. This structure is simple and reliable, but requires a large and expensive transformer. Furthermore, the relatively simple regulation introduces significant losses, necessitating the removal of power as heat. This leads to increased structural size and limited power density.
[0003] In clock-controlled switching-mode power supplies (SMPS), smaller transformers can be used, resulting in lower losses. The transformer ensures electrical isolation between the mains and the secondary side. For EMI filtering, X and Y capacitors can be used, for example. However, due to topology considerations, integration and power density, and thus overall size, remain significantly limited.
[0004] To reduce the size of switching power supplies or increase power density, transformerless topologies with fast-switching semiconductor switches can be used. Here, energy is transferred via a resonantly operating LC unit, rather than via the transformer core. The resonant section generates a square-wave sinusoidal signal with a frequency typically in the 1MHz range. This energy, pulsating with the grid frequency, is transferred to the secondary side via the LC unit. The fluctuations are then smoothed at a low voltage level on the secondary side by means of a power ripple buffer. For single-phase systems, the LC components are symmetrically implemented on the feed and return lines, necessitating capacitor pairs. However, complex technical and standard boundary conditions must be met in such capacitors.
[0005] The known disadvantages of transformerless switching power supplies include small transmittable current, especially small current that can be transmitted through capacitors, and a lack of insulation from the mains or other voltage sources requiring contact protection. For example, with such switching power supplies, currents typically less than 1 ampere can flow through capacitors.
[0006] A capacitor for use in an AC / DC or DC / DC converter is known from WO2014135340A1. The capacitor has a multilayer structure with a ceramic layer and an electrode layer located therebetween.
[0007] A ceramic material for capacitors is known from DE19749858C1, which can be used in LC filters for applications in the high-frequency range.
[0008] Ceramic multilayer devices are known from WO2020173727A1, TWM565389U, WO2020244972A1, and DE102006013227A1, in which the electrode layers have a geometric structure that compensates for misalignment of overlapping electrode layers and keeps the effective area of the component constant. Summary of the Invention
[0009] The object of this invention is to provide a capacitor component for resonant power transmission with improved characteristics.
[0010] According to a first aspect, a capacitor component for resonant power transmission has a substrate having dielectric layers disposed vertically stacked on top of each other and electrode layers disposed between the dielectric layers, wherein the electrode layers have first and second electrode layers extending to the edges of the substrate, and the electrode layers have a third electrode layer not extending to the edges of the substrate, wherein the electrode layers are configured to compensate for misalignment of the overlapping electrode layers, and wherein the dielectric layers have a ceramic material with a capacitance temperature coefficient of less than 20 ppm / K.
[0011] The electrode layer can be made of copper or composed of copper. This has the advantage of resulting in very high current carrying capacity.
[0012] This type of capacitor construction is particularly well-suited for resonant power transfer. A sufficiently large breakdown field strength can be achieved with a small component size through a third electrode layer, also known as a "floating" electrode. In particular, the capacitor is configured for a standard 8kV pulsed load. Thus, the capacitor meets the standard requirements of a Y1 capacitor.
[0013] Furthermore, using copper as the electrode material provides a sufficiently high current-carrying capacity for use in resonant power transmission. This is particularly important because the entire current flows through the capacitor.
[0014] Compensation for deviations in the electrode layer positioning can be achieved, stably maintaining the capacitance within the desired range. This is particularly important for resonant applications. In a pair of capacitors used in a switching power supply, the capacitance difference should be less than 1%.
[0015] Ceramic materials, for example, are COG ceramics based on the BaO-PbO-Nd2O3-TiO2 material system. For instance, a ceramic material disclosed in patent document DE19749858C1 is used. This relates to a reduction-stable COG ceramic material with a high dielectric constant.
[0016] For example, one or more electrode layers have a narrowing to compensate for misalignment. Here, overlapping electrode layers can be positioned such that their edges are located at the narrowing. In this manner, when the relative positioning of the electrodes changes, the effective total area changes slightly or not at all.
[0017] Relative to this alternative or additional location, the overlapping electrode layers in the top view can have different widths or lengths. This also ensures compensation for positioning deviations, since the overall overlap remains unchanged even with small deviations.
[0018] According to another aspect, the capacitor component has a substrate having dielectric layers disposed on top of each other and electrode layers disposed between the dielectric layers, wherein the electrode layers have first and second electrode layers that extend to the edge of the substrate, wherein at least one of the electrode layers has a narrowing portion, wherein the narrowing portion is configured as a contraction portion, such that the width of the electrode layer decreases from the outside of the substrate to the inside and then increases again.
[0019] This capacitor component can be configured for resonant power transmission. Alternatively, it can be configured for other applications. The capacitor component can also possess other functional and structural characteristics as described above.
[0020] According to another approach, the switching power supply has LC units, where the capacitance is formed by one of the capacitor components described above. The inductance is formed, for example, by a coil component. In particular, the switching power supply may have two such LC units.
[0021] Switching power supplies can be configured, for example, as devices for supplying power, charging devices, and / or charging adapters. In particular, switching power supplies can be configured for wirelessly charging devices, such as mobile phones.
[0022] This invention includes several aspects, particularly apparatus and methods. Features, characteristics, and embodiments described with respect to one aspect should also be applicable to the other aspect.
[0023] Furthermore, the description of the subject matter presented herein is not limited to a specific implementation. Rather, the features of the various implementations—provided they are technically meaningful—can be combined with each other. Attached Figure Description
[0024] The subject matter described herein is explained in detail below with reference to illustrative embodiments.
[0025] The attached diagram shows:
[0026] Figure 1A schematic circuit diagram illustrates one implementation of a switching power supply for resonant power transfer.
[0027] Figure 2 One embodiment of the capacitor component is shown in a perspective view.
[0028] Figure 3 One embodiment of the capacitor component is shown in longitudinal section.
[0029] Figure 4 One embodiment of the capacitor component is shown in cross-section.
[0030] Figure 5 Another embodiment of the capacitor component is shown in cross-section.
[0031] Figure 6 A graph showing the relationship between capacitance and the offset of the electrode layer along the width direction is presented.
[0032] Figure 7 A graph showing the relationship between capacitance and the offset of the electrode layer along the longitudinal direction is presented.
[0033] Figure 8 The breakdown voltage is shown in relation to the effective layer thickness of the capacitor.
[0034] In the following figures, the same reference numerals preferably refer to functionally or structurally corresponding parts in different embodiments. Detailed Implementation
[0035] Figure 1 The circuit diagram shows a switching power supply 1 used for resonant power transfer. This is a transformerless resonant topology.
[0036] In particular, the switching power supply 1 can be configured as a power supply, charging device, and / or charging adapter for supplying power to a device. For example, it relates to a charging device for wireless charging (Wireless Charging Applications).
[0037] Circuit 1 has a terminal 2 connected to the power grid, through which alternating current is supplied. Instead of a transformer, circuit 1 has a pair of LC components 3 and 4 for power transmission, which work in conjunction with converter 18. Converter 18 is used to convert the grid frequency into a resonant high frequency. In particular, converter 18 has fast-switching semiconductors.
[0038] Each of the LC components 3 and 4 has capacitors 5 and 6 and inductors 7 and 8. The LC components 3 and 4 are implemented in particular identically to ensure in-phase energy transfer on the feed and return lines, thereby ensuring the same energy transfer in both forward and return currents.
[0039] Capacitors 5 and 6 are configured to provide high insulation between the mains side and the secondary side. Specifically, the structure of capacitors 5 and 6 ensures safe electrical isolation between the primary and secondary sides. Furthermore, capacitors 5 and 6 should be implemented in a space-saving manner. Additionally, capacitors 5 and 6 must provide high current-carrying capacity, as all current flows through them.
[0040] The rapidly switching semiconductor switches of converter 18 generate a pulsating DC voltage from the input voltage. The semiconductor switches of converter 18 are configured, for example, as a "half-bridge" or "full-bridge" AC-AC modulator. The semiconductor switches have, for example, wide-bandgap semiconductors, such as SiC or GaN. Semiconductor switches 8 are configured for frequencies ranging from greater than 200 kHz to MHz, thereby causing rapid switching edges.
[0041] The switching power supply 1 has, for example, components 20, such as a rectifier and a current sensor, for improving power factor and energy transfer efficiency.
[0042] The switching power supply 1 also has a control and regulation system 19. In particular, the control and regulation system is used to control the converter 18 and other components 20.
[0043] An energy storage device 21 for buffering low-frequency power fluctuations is provided on the low-voltage side, for example, for buffering power fluctuations at 100Hz and 160V. Due to the smaller voltage level, for example, a capacitor with a smaller structural size can be used compared to a capacitor on the input side. This allows for higher capacitance density and simpler insulation, which enables a more compact overall implementation.
[0044] Figure 2 A capacitor 5 is shown that is suitable for resonant power transfer in a switching power supply. In particular, capacitor 5 can be used as… Figure 1 One of the capacitors 5 and 6 in the switching power supply 1. In particular, the two capacitors 5 and 6 can be constructed identically.
[0045] The capacitor 5 has a multilayer structure, which includes multiple dielectric layers 9 and electrode layers 10, 11, and 12 disposed between the dielectric layers. The dielectric layers 9 may in particular be ceramic layers.
[0046] For resonant power transfer, the capacitance of capacitor 5 should fluctuate as little as possible with changes in temperature or voltage. For this reason, the use of Class I ceramic is particularly advantageous.
[0047] For example, ceramic materials disclosed in patent document DE19749858C1 are used. This relates to reduction-stable C0G ceramic materials with high dielectric constants. C0G ceramics have a low (<20 ppm / K) temperature coefficient of capacitance.
[0048] Reduced and stable COG ceramic materials can be particularly based on the BaO-PbO-Nd2O3-TiO2 material system within the phase-forming range of orthorhombic bronze, with additives from glass melts of the following systems:
[0049] (A) ZnO-B2O3-SiO2,
[0050] (B) K2O-Na2O-BaO-Al2O3-ZrO2-ZnO-SiO2-B2O3, or
[0051] (G) Li2O-BaO-B2O3-SiO2.
[0052] This ceramic material is particularly advantageous in resonant power transmission, where capacitance deviation must be kept as low as possible.
[0053] Electrode layers 10, 11, and 12 are made of a metallic material, particularly copper. Using copper as the electrode material provides sufficient current-carrying capacity at high frequencies of resonant power transmission. For example, at frequencies from 1 MHz to 1.5 MHz, a current-carrying capacity of 1 A is required. RMS The current carrying capacity is within the range of [specific parameters]. Alternatively, electrode layers 10, 11, and 12 may also have nickel or be made of nickel, however, the current carrying capacity is reduced compared to copper.
[0054] The substrate 17, which consists of stacked dielectric layers 9 and electrode layers 10, 11, and 12, is manufactured, in particular, by common sintering of dielectric layers 9 and electrode layers 10, 11, and 12.
[0055] The capacitor 5 can be surface-mounted. Therefore, a particularly space-saving installation is possible. A minimum creepage distance is preset by using standard boundary conditions when the capacitor is used for resonant power transmission. Specifically, the minimum creepage distance can be 10 mm. This yields a minimum length and correspondingly a minimum spacing between the external electrodes. In this way, the capacitor meets the requirements of the standard Y1 classification.
[0056] For example, the capacitor has a length l between 5 mm and 10 mm, a width b between 5 mm and 10 mm, and a height between 1.5 mm and 2.5 mm. In particular, the capacitor can have dimensions in the range of approximately 11.5 mm × 8.0 mm × 1.5 mm.
[0057] The size of capacitor 5 can be achieved, enabling the manufacture of power supplies, charging devices, and / or charging adapters with very small structural dimensions and very high energy density. For example, for 65W, the energy density is at least 30W / cubic inch, and more particularly at least 35W / cubic inch. This allows for a 40%-60% reduction in device size compared to commonly available devices on the market. In the case of charging devices used for wireless charging, a flat structural space is also advantageous, as the structural space surrounding the transmitting and / or receiving coils is limited. Here, the operating frequency is, for example, in the range of 100kHz to 1MHz, and communication occurs in the single-digit MHz range.
[0058] Figure 3 A longitudinal section is shown in one embodiment of capacitor component 5. This is particularly relevant to... Figure 2 The capacitor component 5 is shown in the figure. The capacitor component 5 has a first electrode layer 10 and a second electrode layer 11, which are respectively led to the edge of the capacitor 5 and connected there to external electrodes (not shown) of different polarities. The first electrode layer 10 and the second electrode layer 11 are respectively provided at the same height.
[0059] A third electrode layer 12 is disposed between the first electrode layers 10 and 11, and the third electrode layer is not connected to the external electrode. This electrode layer 12 is also called a "floating" electrode.
[0060] External electrodes are applied, for example, as end caps, to opposite sides of the substrate. The end caps can extend from the sides to which the electrode layers 10, 11 extend, through the edges of the substrate to adjacent sides.
[0061] In particular, capacitor component 5 can therefore be configured for surface mounting. The end cap can be configured as a weldable end cap. For example, the end cap has copper as the material. The end cap can be coated, for example, with a Ni / Sn surface to improve weldability.
[0062] Alternatively, external contacts can be made in the form of a thin sheet (so-called a leadframe). The leadframe may be made of materials such as copper, nickel, or Invar, or may have a multi-layered material combination, such as Cu-Invar-Cu. The external contacts may be soldered to the substrate or sintered, for example, with silver sintering.
[0063] This structure is particularly advantageous for resonant power transfer because it provides sufficient breakdown strength, allowing for a small dielectric layer thickness even under a standard pulsed load of 8 kV. Voltage strength is technically defined by the ripple generated, for example, in the range of 100 V at a maximum of 1.5 MHz with an AC current of 1 A. Because capacitor 5 also provides electrical isolation between the mains side and the low-voltage side, it must meet reinforced insulation requirements. For example, current flow during contact (“Touch Currents”) must be suppressed as much as possible. Capacitor 5, in particular, meets the requirements of standard Y1 classification.
[0064] Figure 4 The electrode layers 10, 11, and 12 are shown from a top view, representing one embodiment of capacitor component 5. Capacitor component 5 can be implemented as shown in the previous figures, however... Figure 2 Unlike other electrode layers, the first and second electrode layers 10 and 11 have narrowed portions 13 and 14, respectively.
[0065] In particular, the widths of the first and second electrode layers 10 and 11 in the regions of the lateral edges 15 and 16 of the capacitor member 5 are smaller than their widths in the more inner regions of the capacitor member. In this manner, fluctuations caused by manufacturing processes in the stacked structure can be compensated. Through the narrowing portions 13 and 14, when the longitudinal positioning of the electrode layers 10 and 11 differs slightly, the total overlap with the adjacent third electrode layer 13 remains approximately the same, ensuring that the effective area remains constant even with lateral deviations during the stacking process.
[0066] Here, the third electrode layer 13 is sized such that its lateral edge is positioned within the region of the narrow portions 13 and 14. Furthermore, the width of the third electrode layer 13 is slightly smaller than that of the first and second electrode layers, so that even if there are deviations in the positioning of the electrode layers 10, 11, and 12 in the width direction, the effective area remains constant.
[0067] Figure 5 Another embodiment of capacitor component 5 is shown from a viewpoint observing the electrode layer from above. This embodiment is similar to... Figure 4 The difference between the embodiments shown is in the position of the narrowing portions 13 and 14.
[0068] Therefore, in the embodiment described above, the narrowing portions 13 and 14 are configured as contraction portions, such that the width of the first and second electrode layers 10 and 11 decreases from the inside to the outside in the narrowing portions 13 and 14 and then increases again.
[0069] At the edges of the first and second electrode layers 13 and 14 of the capacitor component 5 where they contact the external electrode, the width is the same as in the more inner effective region. In the described embodiment, with Figure 4Compared to the previous implementation, the contact with the external electrodes is improved. Overall, the increased width of the electrode layers 13 and 14, which extend outwards, improves the robustness and reliability of further contact.
[0070] For example, the widths of electrode layers 10 and 11 within the narrowed portions 13 and 14 are each 1 / 3 of the width outside the narrowed portion.
[0071] Here, the third electrode layer 12 also extends longitudinally into the region of the narrowed portions 13 and 14. Furthermore, the width of the third electrode layer 12 is smaller than the width of the first and second electrode layers 10 and 11.
[0072] In principle, it is also feasible for the third electrode layer 12 to have a wider width than the first and second electrode layers 10 and 11. It is also feasible for the third electrode layer 12 to have a narrowing portion, for example, a narrowing portion in the middle region along half the length of the third electrode layer 12.
[0073] For according to Figure 4 or Figure 5 Capacitor component 5, Figure 6 The relative capacitance value C is shown as a result of the offset x of the pair consisting of the first and second electrode layers 10 and 11 relative to the third electrode layer 12 in the width direction.
[0074] Due to the difference in width between the first and second electrode layers 10, 11 and the third electrode layer 12, the capacitance C remains constant when the offset x reaches 200µm, because the overlapping area of the electrode layers 10, 11, 12 remains constant. Only with a larger offset does the capacitance C decrease.
[0075] The absolute value of capacitor C is approximately in the range of 1nF.
[0076] For according to Figure 5 The capacitor component without the narrowing section (curve A) and the capacitor component with the narrowing section (curve B). Figure 7 The relative capacitance value C is shown as a result of the longitudinal offset x of the pair consisting of the first and second electrode layers 10 and 11 relative to the third electrode layer 12.
[0077] For capacitor component 5 without a narrowing section (curve A), the capacitance changes significantly with increasing offset. For capacitor component 5 with a narrowing section (curve B), the capacitance change is significantly smaller.
[0078] Figure 8 Shown and according to Figure 3 , Figure 4 , Figure 5The effective layer thickness d of the capacitors (“MLSCs”) with first, second, and third electrode layers 10, 11, 12 and the capacitors (“MLCCs”) with electrode layers comb-bonded to each other but without so-called “floating” electrodes, and the associated breakdown voltage U. BD (“Breakdown Voltage”). Additionally, the volumetric capacitance density C / V of the effective volume is shown in relation to the effective layer thickness d.
[0079] The dielectric breakdown strength and dielectric thickness are crucial factors in the withstand voltage of a capacitor. In MLSC capacitors, the effective layer thickness d is only half that of MLCC capacitors. Because the maximum electric field strength increases with a smaller effective dielectric thickness, a higher breakdown field strength can be achieved in the case of MLSC capacitors. This allows for a smaller capacitor component 5 and increases capacitance density. In particular, a small component height can be achieved while adhering to creepage distance requirements, for example, a component height of less than 4 mm in a small footprint.
[0080] Due to its small size, capacitor component 1 can be easily encapsulated and / or potted. Furthermore, heat generation is primarily achieved through the electrical terminals, simplifying the packaging process.
[0081] In summary, capacitor component 5 ensures a combination of high-frequency current carrying capacity, insulation capability, capacitance value, and capacitance matching, and also meets the requirements of Y1 classification, enabling its use in transformerless switching power supplies with high power density resonant operation.
[0082] List of reference numerals
[0083] 1 Switching power supply
[0084] 2 Input Power Supply
[0085] 3LC parts
[0086] 4LC parts
[0087] 5 Capacitor Components
[0088] 6 Capacitor Components
[0089] 7 Inductors
[0090] 8 inductors
[0091] 9 dielectric layers
[0092] 10 First Electrode Layer
[0093] 11 Second electrode layer
[0094] 12 Third electrode layer
[0095] 13 narrowing section
[0096] 14 Narrowing section
[0097] 15 Horizontal Edges
[0098] 16 Horizontal Edges
[0099] 17 matrix
[0100] 18 converters
[0101] 19 control systems
[0102] 20 parts
[0103] 21 Energy Storage
[0104] b matrix width
[0105] Length of the matrix
[0106] h matrix height
[0107] C capacitor
[0108] x offset
[0109] A capacitor with a narrow section
[0110] B. Capacitors without a narrow section
[0111] U BD Breakdown voltage
[0112] d Effective layer thickness
Claims
1. A capacitor component (5, 6) for resonant power transfer. The capacitor component has a substrate (17) having dielectric layers (9) stacked on top of each other and electrode layers (10, 11, 12) disposed between the dielectric layers. The electrode layers (10, 11, 12) have first and second electrode layers (10, 11) extending to the edge of the substrate (17), respectively, and a third electrode layer (12) not extending to the edge of the substrate (17). The electrode layers (10, 11, 12) are configured to compensate for positioning misalignments of the overlapping electrode layers (10, 11, 12). The dielectric layer (9) therein has a ceramic material with a capacitance temperature coefficient of less than 20 ppm / K.
2. The capacitor component (5, 6) according to claim 1, wherein the electrode layers (10, 11, 12) are made of copper.
3. The capacitor component (5, 6) according to any one of the preceding claims, wherein the ceramic material has a COG ceramic based on the BaO-PbO-Nd2O3-TiO2 material system.
4. The capacitor component (5, 6) according to any one of the preceding claims, wherein at least one of the electrode layers (10, 11, 12) has a narrowing portion (13, 14).
5. The capacitor components (5, 6) according to claim 4. The narrowing portions (13, 14) are configured as contractions, such that the width of the electrode layers (10, 11, 12) decreases from the outside of the substrate (17) to the inside and then increases again.
6. A capacitor component (5, 6). The capacitor component has a substrate (17) having dielectric layers (9) stacked on top of each other and electrode layers (10, 11, 12) disposed between the dielectric layers. The electrode layers (10, 11, 12) have first and second electrode layers (10, 11), which extend to the edges of the substrate (17), respectively. At least one of the electrode layers (10, 11, 12) has a narrowed portion (13, 14). The narrowing portions (13, 14) are configured as contractions, such that the width of the electrode layers (10, 11, 12) decreases from the outside of the substrate (17) to the inside and then increases again.
7. A switching power supply (1) having LC components (3, 4), wherein the capacitor is formed by a capacitor member according to any one of the preceding claims.
8. The switching power supply (1) according to claim 7, wherein the switching power supply is configured as a device for supplying power, a charging device and / or a charging adapter.
9. The switching power supply (1) according to any one of claims 7 or 8, wherein the switching power supply is configured for wireless charging of a device.
10. An application of a capacitor component (5) according to any one of claims 1 to 6 for resonant power transfer in the LC components (3, 4) of a switching power supply (1).