Capacitor component for resonant power transmission, use of the capacitor component and switched-mode power supply having the capacitor component

Abstract

The invention relates to a capacitor component (5, 6) for resonant power transmission, having a main body (17) with dielectric layers (9) arranged one above the other and electrode layers (10, 11, 12) arranged therebetween, wherein the electrode layers (10, 11, 12) have first and second electrode layers (10, 11) which in each case reach to the edge of the main body (17) and third electrode layers (12) which do not reach to the edge of the main body (17), wherein the electrode layers (10, 11, 12) are configured to compensate for variance in the positioning of overlapping electrode layers (10, 11, 12), wherein the dielectric layers (9) comprise a ceramic material having a temperature coefficient of capacitance of less than 20 ppm / K.

Description

[0001] Description

[0002] Capacitor component for resonant power transmission, use of the capacitor component and switching power supply with the capacitor component

[0003] The present invention relates to a capacitor component for resonant power transmission. In particular, the capacitor component is designed for use in a switching power supply. The capacitor component can also be used, for example, in a charger, in particular a charger for wireless charging.

[0004] Switching power supplies with a magnetic core are well known, the simplest form being a linear converter. Such designs are simple and reliable, but require a large and expensive transformer. Furthermore, the relatively simple control system produces significant losses, so that power losses must be dissipated in the form of heat. This leads to increased size and a limitation of power density.

[0005] With a switched-mode power supply (SMPS), a smaller transformer can be used, resulting in lower losses. The transformer ensures galvanic isolation between the mains and the secondary side. X and Y capacitors, for example, can be used for EMI filtering. However, even here, topology-related limitations still place significant limits on integration and power density, and thus on the overall size.

[0006] In order to reduce the size of switched-mode power supplies or increase the power density, transformerless topologies with fast-switching semiconductor switches can be used. In this case, the energy is transferred through a resonantly operated LC element instead of through a magnetic core of a transformer. The resonant part generates a square sine wave with frequencies typically in the range of 1 MHz. This energy, which pulsates at the mains frequency, is transferred via the LC element to the secondary side. On the secondary side, the fluctuation is then smoothed at the low voltage level using a power pulsation buffer. For a single-phase system, the LC components are designed symmetrically on the forward and return lines, so that a pair of capacitors is required. However, complex technical and normative boundary conditions must be met for capacitors of this type.

[0007] Disadvantages of conventional transformerless switching power supplies are the low currents that can be transmitted, especially via the capacitor, as well as the lack of insulation from the mains or other voltage sources, which requires contact protection. For example, with such switching power supplies, currents of less than 1 ampere can generally flow through the capacitor.

[0008] WO2014135340A1 discloses a capacitor for use in an AC / DC or DC / DC converter. The capacitor has a multilayer structure with ceramic layers and electrode layers between them.

[0009] DE19749858C1 discloses a ceramic material for a capacitor that can be used in an LC filter for applications in the high-frequency range. WO2020173727A1, TWM565389U, WO2020244972A1, and DE102006013227A1 disclose ceramic multilayer components in which electrode layers have a geometry such that variations in the positioning of overlapping electrode layers are compensated and the active area of ​​the component is kept constant.

[0010] The object of the present invention is to provide a capacitor component for resonant power transmission with improved properties.

[0011] According to a first aspect, a capacitor component for resonant power transmission has a base body with dielectric layers arranged one above the other and electrode layers arranged therebetween, wherein the electrode layers have first and second electrode layers which each extend to the edge of the base body and have third electrode layers which do not extend to the edge of the base body, wherein the electrode layers are designed such that variances in the positioning of overlapping electrode layers are compensated, wherein the dielectric layers have a ceramic material with a temperature coefficient of capacitance of less than 20 ppm / K.

[0012] The electrode layers can be made of copper or copper. This has the advantage of providing a very high current-carrying capacity.

[0013] A capacitor component designed in this way is particularly well suited for resonant power transmission. The third electrode layers, also known as "floating" electrodes, allow a sufficiently high breakdown field strength to be achieved with a small component size. In particular, the capacitor component is designed for a standard pulse load of 8 kV. The capacitor thus meets the standard requirements of a Yl capacitor.

[0014] In addition, copper as the electrode material provides a sufficiently high current-carrying capacity for use in resonant power transmission. The requirements here are particularly high, since the full current flows through the capacitor.

[0015] Compensation for variations in the positioning of the electrode layers makes it possible to keep the capacitance stable within the desired range. This is particularly important for resonant applications. For a pair of capacitor components used in a switching power supply, the capacitance difference should be less than 1%.

[0016] The ceramic material is, for example, a COG ceramic based on the material system BaO-PbO-NdO2O5-TiO2. For example, a ceramic material disclosed in patent DE19749858C1 is used. This is a reduction-stable COG ceramic mass with a high dielectric constant.

[0017] For example, one or more of the electrode layers have a constriction to compensate for variances. An overlapping electrode layer can be positioned such that the edge of this electrode layer is positioned at the constriction. In this way, the total active area changes little or not at all when the relative positioning of the electrodes changes.

[0018] Alternatively or additionally, electrode layers that overlap in plan view can have different widths or lengths. This also ensures compensation for positioning variances, since the overall overlap remains unchanged even with small deviations.

[0019] According to a further aspect, a capacitor component has a base body with dielectric layers arranged one above the other and electrode layers arranged therebetween, wherein the electrode layers have first and second electrode layers, which each extend to the edge of the base body, in which at least one of the electrode layers has a constriction, in which the constriction is designed as a constriction, so that the width of the electrode layer first decreases from an outside of the base body to the inside and then increases again.

[0020] Such a capacitor component can be designed for resonant power transmission. It is also possible for the capacitor component to be designed for other applications. The capacitor component can have the additional functional and structural properties as the previously described capacitor component.

[0021] According to a further aspect, a switching power supply comprises an LC element, in which the capacitance is formed by one of the previously described capacitor components. The inductance is formed, for example, by a coil component. In particular, the switching power supply can comprise two such LC elements.

[0022] The switching power supply is designed, for example, as a power supply device, as a charger, and / or as a charging adapter. In particular, the switching power supply can be designed for wireless charging of a device, such as a cell phone.

[0023] The present invention comprises several aspects , in particular devices and methods . The features , properties and

[0024] The same implementation forms should also apply to the other aspect.

[0025] Furthermore, the description of the objects specified here is not limited to the specific embodiments.

[0026] Rather, the features of the individual designs can be combined with one another – as far as technically feasible.

[0027] In the following, the objects described here are explained in more detail using schematic examples.

[0028] It shows :

[0029] Figure 1 shows an embodiment of a switching power supply for resonant power transmission in a schematic circuit view,

[0030] Figure 2 shows an embodiment of a capacitor component in perspective view,

[0031] Figure 3 shows an embodiment of a capacitor component in longitudinal section,

[0032] Figure 4 shows an embodiment of a capacitor component in a cross section,

[0033] Figure 5 shows a further embodiment of a capacitor component in a cross section,

[0034] Figure 6 is a diagram of a capacitance as a function of an offset of the electrode layers along a width direction,

[0035] Figure 7 is a diagram of a capacity as a function of an offset of the electrode layers along a longitudinal direction,

[0036] Figure 8 shows a breakdown voltage as a function of an effective layer thickness of a capacitor.

[0037] Preferably, in the following figures, the same reference numerals refer to functionally or structurally corresponding parts of the various embodiments.

[0038] Figure 1 shows a circuit diagram of a switching power supply 1 for resonant power transmission. It is a transformerless resonant topology.

[0039] In particular, the switched-mode power supply 1 can be designed as a power supply for supplying power to a device, as a charger and / or charging adapter. For example, it is a charger for wireless charging ("wireless charging applications"). The circuit 1 has a connection 2 to a power grid, through which an alternating current is provided. Instead of a transformer, the circuit 1 for power transmission has a pair of LC components 3, 4 in interaction with a converter 18. The converter 18 serves to convert the grid frequency to a resonant high frequency. In particular, the converter 18 has fast-switching semiconductors.

[0040] Each of the LC components 3, 4 has a capacitor 5, 6 and an inductor 7, 8. The LC components 3, 4 are, in particular, identically designed to ensure in-phase energy distribution on the forward and return lines and thus identical energy transport in the forward and return flow.

[0041] The capacitor 5, 6 is designed to meet the high insulation properties between the mains and secondary sides. In particular, the design of the capacitor 5, 6 ensures reliable galvanic isolation between the primary and secondary sides. Furthermore, the capacitor 5, 6 should be designed to save space. Furthermore, the capacitors 5, 6 must provide a high current-carrying capacity, since the full current flows through the capacitors 5, 6.

[0042] Fast-switching semiconductor switches of the converter 18 generate a pulsating direct voltage from the input voltage. The semiconductor switches of the converter 18 are designed, for example, as "half-bridge" or "full-bridge" AC-AC modulators. The semiconductor switches comprise, for example, wide-bandgap semiconductors such as SiC or GaN. The semiconductor switches 8 are designed for frequencies in the range from greater than 200 kHz up to the MHz range, which results in fast switching edges.

[0043] The switching power supply 1 has, for example, components 20 such as a rectifier and a current sensor to improve the power factor and the efficiency of the energy transmission.

[0044] The switching power supply 1 also has a control and monitoring system 19. In particular, the control and monitoring system serves to control the converter 18 and the other components 20.

[0045] On the low-voltage side, an energy storage device 21 is provided to absorb low-frequency power fluctuations, for example, at 100 Hz, 160 V. Due to the lower voltage level, a capacitor with a smaller size can be used, for example, compared to a capacitor on the input side. This enables a higher capacitance density and easier insulation, which allows for an overall more compact design.

[0046] Figure 2 shows a suitable capacitor 5 for resonant power transmission in a switched-mode power supply. In particular, the capacitor 5 can be used as one of the capacitors 5, 6 from the switched-mode power supply 1 in Figure 1. In particular, both capacitors 5, 6 can be designed identically.

[0047] The capacitor 5 has a multilayer structure with a

[0048] A plurality of dielectric layers 9 and electrode layers 10, 11, 12 arranged therebetween. The dielectric layers 9 can in particular be ceramic

[0049] layers may be formed.

[0050] For resonant power transmission, the capacitance of capacitor 5 should fluctuate as little as possible with changes in temperature or voltage. For this reason, the use of a Class I ceramic is particularly advantageous.

[0051] For example, a ceramic material disclosed in patent DE19749858C1 is used. This is a reduction-stable COG ceramic mass with a high dielectric constant. COG ceramic exhibits a low (<20 ppm / K) temperature coefficient of capacitance.

[0052] A reduction-stable COG ceramic mass can be prepared, in particular, based on the material system BaO-PbO-Nd2O3-TiO2 in the area of ​​phase formation of rhombic bronzes with additions of a glass frit from the systems

[0053] (A) ZnO - B2O3 - SiO2,

[0054] (B) K2O - Na2O - BaO - A12O3- ZrO2- ZnO - SiO2- B2O3 or (G) Li2O - BaO - B2O3- SiO2.

[0055] Such a ceramic mass is particularly advantageous in resonant power transmission, since capacitance deviations must be kept as low as possible.

[0056] The electrode layers 10, 11, 12 comprise a metallic material, in particular copper. Using copper as the electrode material can provide sufficient current-carrying capacity at the high frequencies of resonant power transmission. For example, a current-carrying capacity in the range of 1Ajyfg is required at 1 to 1.5 MHz. Alternatively, the electrode layers 10, 11, 12 can also comprise nickel, for example, or consist of nickel; however, the current-carrying capacity is reduced compared to copper.

[0057] The base body 17 made of stacked dielectric layers 9 and electrode layers 10, 11, 12 is produced in particular by joint sintering of the dielectric layers 9 and electrode layers 10, 11, 12.

[0058] The capacitor 5 is designed to be surface-mounted.

[0059] This allows for particularly space-saving installation. Normative boundary conditions for the use of the capacitor for resonant power transmission stipulate a minimum creepage distance. In particular, this can be 10 mm. This results in a minimum length and, accordingly, a minimum distance between the outer electrodes. The capacitor thus meets the requirements of a normative Yl classification.

[0060] For example, a capacitor has a length l between 5 and 10 mm, a width b between 5 and 10 mm, and a height of 1.5 to 2.5 mm. In particular, a capacitor can have dimensions in the range of approximately 11.5 mm x 8.0 mm x 1.5 mm.

[0061] The dimensions of capacitor 5 allow the production of a power supply, charger, and / or charging adapter with a very small footprint and very high energy density. For example, the energy density is at least 30 W / inch. 3, in particular at least 35 W / inch 3 for 65 W. This makes it possible to reduce the size of the device by 40-60% compared to conventional devices. A flat design is also advantageous for wireless chargers, as the space around the transmitter and / or receiver coil is limited. The operating frequency here, for example, is in the range of 100 kHz to 1 MHz, and communication takes place in the single-digit MHz range.

[0062] Figure 3 shows a longitudinal section through an embodiment of a capacitor component 5. In particular, it can be the capacitor component 5 shown in Figure 2. The capacitor component 5 has first electrode layers 10 and second electrode layers 11, each of which is led to the edge of the capacitor 5 and connected there to external electrodes (not shown) of different polarity. A first electrode layer 10 and a second electrode layer 11 are provided at the same height.

[0063] Between levels in which first electrode layers 10, 11 are arranged, third electrode layers 12 are arranged, which are not connected to external electrodes. Such electrode layers 12 are also referred to as "floating" electrodes.

[0064] The outer electrodes are applied, for example, as caps to opposite sides of the base body. The caps can extend from one side surface, to which the electrode layers 10, 11 extend, over the edges of the base body to the adjacent side surfaces.

[0065] In particular, the capacitor component 5 can thus be designed for surface mounting. The caps can be designed as solder caps. For example, the caps are made of copper. The caps can be coated, for example, with a Ni / Sn surface to improve the soldering properties.

[0066] Alternatively, external contact can be made in the form of thin sheets (so-called leadframes). The leadframes can be made of copper, nickel, or Invar, for example, or can be a multilayer combination of materials, such as Cu-Invar-Cu. The external contact can be soldered to the base body or attached by sintering, for example, silver sintering.

[0067] This design is particularly advantageous for use in resonant power transmission, as it can provide sufficient breakdown strength so that the thickness of the dielectric layers can be small at a normative pulse load of 8 kV. The dielectric strength is technically defined by the ripple that occurs at an AC current of 1 A at a maximum of 1.5 MHz, for example in the range of 100 V. Since capacitor 5 also represents the galvanic isolation between the mains and low-voltage sides, it must satisfy reinforced insulation conditions. For example, current flows upon contact ("touch currents") must be prevented as far as possible. Capacitor 5 meets the requirements of a normative Yl classification in particular.

[0068] Figure 4 shows a view from above of electrode layers 10, 11, 12 of an embodiment of a capacitor component 5. The capacitor component 5 can be designed as in the preceding figures, but in contrast to Figure 2, the first and second electrode layers 10, 11 each have a constriction 13, 14. In particular, the width of the first and second electrode layers 10, 11 in the region of the lateral edges 15, 16 of the capacitor component 5 is smaller than further inside the capacitor component. In this way, production-related fluctuations in the stack structure can be compensated for. As a result of the constriction 13, 14, the total overlap with the adjacent third electrode layer 13 remains approximately the same if the electrode layers 10, 11 are positioned slightly differently in the longitudinal direction, so that the active area remains constant despite lateral deviations in the stacking process.

[0069] The third electrode layer 13 is dimensioned such that the lateral edges are positioned in the region of the constriction 13, 14. Furthermore, the third electrode layer 13 is somewhat narrower than the first and second electrode layers, so that even with a variance in the positioning of the electrode layers 10, 11, 12 in the width direction, the active area remains constant.

[0070] Figure 5 shows a further embodiment of a capacitor component 5 with a top view of the electrode layers. This embodiment differs from the embodiment shown in Figure 4 in the position of the constrictions 13, 14.

[0071] Thus, in this embodiment, the constrictions 13, 14 are designed as constrictions, so that the width of the first and second electrode layers 10, 11 decreases in the constrictions 13, 14 from the inside to the outside and then increases again. At the edge of the capacitor component 5, at which the first and second electrode layers 13, 14 are contacted with external electrodes, the width is the same as in the active region further inside. In this embodiment, the contact with the external electrodes is improved compared to the embodiment from Figure 4. Overall, the greater width with which the electrode layers 13, 14 are led outwards can improve the robustness and reliability of the further contact.

[0072] For example, the width of the electrode layers 10, 11 in the constriction 13, 14 is each 1 / 3 of the width outside the constriction.

[0073] Here, too, the third electrode layer 12 extends longitudinally into the region of the constriction 13, 14. Furthermore, the width of the third electrode layer 12 is smaller than the width of the first and second electrode layers 10, 11.

[0074] In principle, it is also possible for the third electrode layer 12 to have a greater width than the first and second electrode layers 10, 11. It is also possible for the third electrode layer 12 to have a narrowing, for example, in a central region halfway along the length of the third electrode layer 12.

[0075] Figure 6 shows the change of a relative capacitance value C as a function of an offset x in the width direction of a pair of first and second electrode layers 10, 11 to the third electrode layer 12 for a

[0076] Capacitor component 5 according to Figure 4 or 5. Due to the difference in the width of the first and second electrode layers 10, 11 compared to the third electrode layer 12, the capacitance C remains constant for an offset x of up to 200 pm, since the overlap area of ​​the electrode layers 10, 11, 12 remains constant. Only with a larger offset does the capacitance C decrease.

[0077] The absolute value of the capacitance C is somewhat in the range of InF .

[0078] Figure 7 shows the change in a relative capacitance value C as a function of an offset x in the longitudinal direction of a pair of first and second electrode layers 10, 11 to the third electrode layer 12 for a capacitor component without constriction (curve A) and a capacitor component 5 with constriction (curve B) according to Figure 5.

[0079] For the capacitor component without constriction (curve A), the capacitance changes significantly with increasing offset. For the capacitor component 5 with constriction (curve B), the capacitance change is significantly smaller.

[0080] Figure 8 shows a breakdown voltage Ußp (“Breakdown Voltage”) as a function of an effective layer thickness d of a capacitor with first, second and third electrode layers 10, 11, 12 according to Figures 3, 4, 5 (“MLSC”) and of a capacitor with comb-like interlocking electrode layers (“MLCC”), without so-called “floating” electrodes. In addition, the volumetric capacitance density C / V of an active volume is shown as a function of the effective layer thickness d. The electrical breakdown strength of the dielectric material and the thickness of the dielectric are the decisive factors for the dielectric strength of the capacitor. The effective layer thickness d of an MLSC capacitor is only half that of an MLCC capacitor. Since the maximum field strength increases with decreasing effective thickness of the dielectric, a higher breakdown field strength can be achieved in an MLSC capacitor.This allows the capacitor component 5 to be made smaller and the capacitance density to be increased. In particular, a low component height, for example, less than 4 mm, can be achieved with a small footprint while maintaining the creepage distance requirement.

[0081] Due to its small size, the capacitor component 1 can be easily overmolded and / or encapsulated. Furthermore, heating occurs primarily via the electrical connections, thus simplifying encapsulation.

[0082] In summary, the capacitor component 5 ensures a combination of high-frequency current carrying capacity, insulation capacity, capacitance value and capacitance matching and also meets the requirements of a Yl classification, so that it can be used in a resonantly operated transformerless switching power supply with high power density.

[0083] Reference sign

[0084] 1 switching power supply

[0085] 2 Input supply

[0086] 3 LC component

[0087] 4 LC component

[0088] 5 Capacitor component

[0089] 6 Capacitor component

[0090] 7 Inductance

[0091] 8 Inductance

[0092] 9 dielectric layer

[0093] 10 first electrode layer

[0094] 11 second electrode layer

[0095] 12 third electrode layer

[0096] 13 Constriction

[0097] 14 Constriction

[0098] 15 lateral margin

[0099] 16 lateral margin

[0100] 17 basic bodies

[0101] 18 inverters

[0102] 19 Tax system

[0103] 20 components

[0104] 21 Energy storage b Width base body

[0105] 1 Length of base body h Height of base body

[0106] C Capacity x Offset

[0107] A Condenser with constriction

[0108] B Condenser without constriction

[0109] Ußp breakdown voltage effective layer thickness

Claims

Patent claims 1. Capacitor component (5, 6) for resonant power transmission, comprising a base body (17) with dielectric layers (9) arranged one above the other and electrode layers (10, 11, 12) arranged therebetween, wherein the electrode layers (10, 11, 12) have first and second electrode layers (10, 11), each of which extends to the edge of the base body (17) and third electrode layers (12) which do not extend to the edge of the base body (17), wherein the electrode layers (10, 11, 12) are designed to compensate for variances in the positioning of overlapping electrode layers (10, 11, 12), wherein the dielectric layers (9) comprise a ceramic material with a temperature coefficient of capacitance of less than 20 ppm / K.

2. Capacitor component (5, 6) according to claim 1, wherein the electrode layers (10, 11, 12) comprise copper.

3. Capacitor component (5, 6) according to one of the preceding claims, wherein the ceramic material comprises a COG ceramic based on the material system BaO-PbO-NdgOS-TiOg.

4. Capacitor component (5, 6) according to one of the preceding claims, in which at least one of the electrode layers (10, 11, 12) has a constriction (13, 14).

5. Capacitor component (5, 6) according to claim 4, wherein the constriction (13, 14) is designed as a constriction, so that the width of the electrode layer (10, 11, 12) from the outside of the base body (17) to the inside first decreases and then increases again.

6. Capacitor component (5, 6), comprising a base body (17) with dielectric layers (9) arranged one above the other and electrode layers (10, 11, 12) arranged therebetween, wherein the electrode layers (10, 11, 12) have first and second electrode layers (10, 11), which each extend to the edge of the base body (17), in which at least one of the electrode layers (10, 11, 12) has a constriction (13, 14), in which the constriction (13, 14) is designed as a constriction, so that the width of the electrode layer (10, 11, 12) first decreases from an outside of the base body (17) to the inside and then increases again.

7. Switching power supply (1) comprising an LC component (3, 4), in which the capacitance is formed by the capacitor component according to one of the preceding claims.

8. Switching power supply (1) according to claim 7, which is designed as a power supply device, as a charger and / or charging adapter.

9. Switching power supply (1) according to one of claims 7 or 8, which is designed for wireless charging of a device.

10. Use of the capacitor component (5) according to one of claims 1 to 6 for resonant power transmission in an LC component (3, 4) of a switched-mode power supply (1).

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