CN219875692U - Combined filter and switching power supply - Google Patents
Combined filter and switching power supply Download PDFInfo
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- CN219875692U CN219875692U CN202320311788.2U CN202320311788U CN219875692U CN 219875692 U CN219875692 U CN 219875692U CN 202320311788 U CN202320311788 U CN 202320311788U CN 219875692 U CN219875692 U CN 219875692U
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- switching power
- ceramic capacitor
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- 239000003985 ceramic capacitor Substances 0.000 claims abstract description 85
- 239000003990 capacitor Substances 0.000 claims abstract description 80
- -1 inductor Substances 0.000 claims 1
- RVCKCEDKBVEEHL-UHFFFAOYSA-N 2,3,4,5,6-pentachlorobenzyl alcohol Chemical compound OCC1=C(Cl)C(Cl)=C(Cl)C(Cl)=C1Cl RVCKCEDKBVEEHL-UHFFFAOYSA-N 0.000 abstract description 14
- 238000010586 diagram Methods 0.000 description 5
- 238000004146 energy storage Methods 0.000 description 5
- 238000001914 filtration Methods 0.000 description 4
- 238000000034 method Methods 0.000 description 4
- 238000002791 soaking Methods 0.000 description 4
- 239000000463 material Substances 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000012938 design process Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000004992 fission Effects 0.000 description 1
- 230000017525 heat dissipation Effects 0.000 description 1
- 230000020169 heat generation Effects 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
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Abstract
The utility model relates to the field of filter design, in particular to a combined filter and a switching power supply, wherein the combined filter comprises an electrolytic capacitor PCBA and a ceramic capacitor PCBA welded on the electrolytic capacitor PCBA; the electrolytic capacitor PCBA comprises an electrolytic capacitor, a first PCB and an inductor, wherein the first PCB is used as a main PCB of the switching power supply, and the electrolytic capacitor and the inductor are welded on the first PCB; the ceramic capacitor PCBA comprises a ceramic capacitor and a second PCB, and the ceramic capacitor is welded on the second PCB.
Description
Technical Field
The present utility model relates to the field of filter design, and in particular, to a combined filter and a switching power supply.
Background
In Printed Circuit Boards (PCBs) of electronic products, the use of chip ceramic capacitors (ceramic capacitors may be divided into chip ceramic capacitors and card ceramic capacitors according to the package form, the chip ceramic capacitors are also referred to as MLCCs, and for convenience of description, the chip ceramic capacitors are collectively and simply referred to as ceramic capacitors herein), and the use of chip ceramic capacitors has its own limitations, and in terms of physical characteristics, the chip ceramic capacitors are easily broken materials, and are easily deformed by external mechanical stress to fail. Therefore, the ceramic capacitor has higher requirements in the PCB layout, for example, the length direction of the ceramic capacitor body is parallel to the bending deformation direction of the PCB as much as possible in the PCB layout, so as to reduce the influence of mechanical stress on the performance of the ceramic capacitor body; as such, ceramic capacitors are susceptible to damage during product manufacture and transportation and require additional attention. However, as the requirements of miniaturization, high power density and the like of products are higher and higher, the layout requirements of ceramic capacitors are difficult to meet in the process of designing the products, and therefore, another searching method is needed to solve the problems of cracking and space layout of the ceramic capacitors.
In addition, during the PCB design process of the switching power supply (also referred to as a switching converter), the output end uses a capacitor to store energy and filter, but with the extremely pursuit of small volume, high power density and high cost performance in the power industry, it is difficult to meet the requirements of performance, volume and cost when actually performing the PCB layout. When the output end is rectified and then is used for low-voltage high-current output, if the power output end uses a conventional electrolytic capacitor to store energy and filter, in order to meet the ripple current requirement, a plurality of electrolytic capacitors with low Equivalent Series Resistance (ESR) are required to be used in parallel, and the following problems are brought: (1) The output capacitor is difficult to completely average ripple current (i.e. current sharing requirement) and completely balance temperature rise (i.e. soaking requirement), and especially when the output capacitor is applied to occasions with higher cost requirements and is designed and laid out by using a single-sided PCB, the ripple current and the temperature rise of the output capacitor are extremely unbalanced due to limited PCB wiring and layout space, and the output capacitor is usually the capacitor which flows into current first after rectification, and the temperature rise and the current are highest; (2) The tiled layout of the electrolytic capacitors occupies a large space of the PCB, which is extremely disadvantageous for miniaturization of the power supply.
If the output end of the switching converter uses a ceramic capacitor for filtering, the following problems still exist: (1) The ceramic capacitor is extremely easy to be deformed and lose efficacy due to mechanical stress, especially when the ceramic capacitor is used in occasions where a single-sided PCB (printed Circuit Board) has to be used due to higher cost requirements, the ceramic capacitor is easy to lose efficacy due to deformation caused by the conventional single-sided PCB materials in the market, and the reliability of the product is greatly reduced; if a better material or a PCB with more layers is used, the cost is obviously increased; (2) The ceramic capacitor has small capacity, and the capacity of the ceramic capacitor is obviously reduced after a certain voltage is applied to the ceramic capacitor due to the DC bias characteristic, so that the ceramic capacitor is difficult to meet the energy storage and filtering requirements of the converter.
Disclosure of Invention
The utility model aims to overcome the defects in the prior art, and provides a combined filter and a switching power supply, wherein the combined filter comprises a ceramic capacitor PCBA and an electrolytic capacitor, so that the problems of uneven flow and uneven heat generated by the output capacitor due to larger ripple current flowing through the output capacitor are solved, the layout space of a PCB (printed circuit board) is reduced, and the power density of a product is improved; meanwhile, the ceramic capacitor is not easy to lose efficacy due to deformation, and the reliability of the ceramic capacitor in the production, transportation and use processes is improved.
In order to achieve the above purpose, the present utility model adopts the following technical scheme:
the combined filter comprises a first circuit board, an electrolytic capacitor, an inductor, a ceramic capacitor and a second circuit board, wherein the first circuit board is used as a main circuit board of the switch power supply, the electrolytic capacitor and the inductor are respectively welded on the first circuit board, the ceramic capacitor is welded on the second circuit board, and the second circuit board is welded on the first circuit board.
Preferably, the combined filter is connected with a rectifying circuit at the output end of the switching power supply, wherein one end of the ceramic capacitor is respectively connected with the output positive electrode of the rectifying circuit and one end of the inductor, the positive electrode of the electrolytic capacitor is connected with the other end of the inductor, the other end of the ceramic capacitor and the negative electrode of the electrolytic capacitor are respectively connected with the output negative electrode of the rectifying circuit, the positive electrode of the electrolytic capacitor is used as the output positive electrode of the switching power supply, and the negative electrode of the electrolytic capacitor is used as the output negative electrode of the switching power supply.
Preferably, the second circuit board is perpendicular to the first circuit board, and the second circuit board is a two-layer circuit board.
Preferably, the area of the second circuit board is smaller than the area of the first circuit board.
Preferably, the ceramic capacitor is a chip ceramic capacitor.
Preferably, the first circuit board is a single panel.
In terms of the circuit connection mode of the combined filter, the combined filter circuit provided by the utility model can obviously reduce the ripple current of the electrolytic capacitor, can realize complete current sharing of the filter capacitor and prolongs the service life of the switching power supply. The specific principle is described in detail below. Let the total capacity of the ceramic capacitor be Co1, the inductance of the inductor be Lo, the total capacity of the electrolytic capacitor be Co2, the switching frequency of the switching power supply be fs, and setI.e. < ->Is the resonant frequency of the inductor Lo and the electrolytic capacitor Co 2. After the output end of the switching power supply is rectified, as the impedance of the inductor at the rear end of the ceramic capacitor and the impedance of the electrolytic capacitor are far greater than the capacitance of the ceramic capacitor, the ceramic capacitor absorbs most of ripple current, and the service life of the electrolytic capacitor is ensured because the current flowing into the electrolytic capacitor is very small; the ceramic capacitor has strong capability of tolerating high-frequency ripple current, and the temperature rise of the ceramic capacitor is slow along with the change of the current, so that even if the ceramic capacitor absorbs most of the high-frequency current, the ceramic capacitor can ensure that the temperature rise and the service life of the ceramic capacitor can easily meet the requirements. In addition, the total capacity Co2 of the electrolytic capacitor ensures a larger capacity required for the load of the switching power supply to ensure that the output ripple of the switching power supply is small and within an acceptable range.
According to the utility model, the ceramic capacitor and the electrolytic capacitor are used for combined energy storage filtering, so that most ripple current flows through the ceramic capacitor in the aspect of optimization of ripple current, and the service life of the capacitor is prolonged; in the aspect of energy storage filtering, a plurality of electrolytic capacitors can be connected in parallel to form a larger capacity so as to provide the energy required by the output end of the switching power supply; in the aspects of technology and structural design, the ceramic capacitor PCBA is formed by the ceramic capacitor and the second circuit board, and the second circuit board in the ceramic capacitor PCBA is vertically welded on the first circuit board and is not easy to deform because of small area or volume, so that the ceramic capacitor is not easy to be impacted by mechanical stress to generate fission failure, and meanwhile, the layout space of the main circuit board of the switching power supply is reduced.
Drawings
FIG. 1 is a schematic diagram of a combined filter applied to a flyback switching power supply;
FIG. 2 is a schematic diagram of a combined filter (with a first circuit board cut away) according to the present utility model;
fig. 3 is a schematic diagram of the circuit connections of electrolytic capacitors, ceramic capacitors and inductors in the combined filter of the present utility model.
Detailed Description
The present utility model will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present utility model more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the utility model.
Referring to fig. 1 to 2, fig. 1 is a schematic structural diagram of a combined filter applied to a flyback switching power supply according to the present utility model, and fig. 2 is a schematic diagram of a combined filter according to the present utility model; the flyback switching power supply 100 has an output voltage of 24VDC, an output power of 350W, and a switching frequency of 65kHz, and the combined filter includes an electrolytic capacitor PCBA and a ceramic capacitor PCBA soldered to the electrolytic capacitor PCBA.
The electrolytic capacitor PCBA is provided with a first circuit board 11, an electrolytic capacitor 12 and an inductor 13, wherein the first circuit board 11 is used as a main circuit board of a switching power supply, and the electrolytic capacitor 12 and the inductor 13 are respectively welded on the first circuit board 11; the ceramic capacitor PCBA is provided with a chip ceramic capacitor 21 (hereinafter referred to as ceramic capacitor) and a second circuit board 22, the ceramic capacitor 21 is soldered to the second circuit board 22, the second circuit board 22 is soldered to the first circuit board 11, and the second circuit board 22 is perpendicular to the first circuit board 11.
Referring to fig. 3, the combined filter is connected to a rectifying circuit connected to an output terminal of the switching power supply, wherein one end of a ceramic capacitor 21 is connected to an output positive electrode of the rectifying circuit and one end of an inductor 13, respectively, the positive electrode of an electrolytic capacitor 12 is connected to the other end of the inductor 13, the other end of the ceramic capacitor 21 and a negative electrode of the electrolytic capacitor 12 are connected to an output negative electrode of the rectifying circuit, the positive electrode of the electrolytic capacitor 12 is used as an output positive electrode of the switching power supply, and the negative electrode of the electrolytic capacitor 12 is used as an output negative electrode of the switching power supply.
In this embodiment, the ceramic capacitor 21 is composed of 32 ceramic capacitors of 4.7uF/50V/1206 (i.e., the capacity of a single ceramic capacitor is 4.7uF, the withstand voltage is 50V, and the package size is 1206) connected in parallel; the electrolytic capacitors 12 are formed by connecting 4 electrolytic capacitors 12 with 470uF/35V in parallel; the inductance Lo of the inductor 13 is 0.15uH, whereby the resonance frequency fr of the inductor 13 and the electrolytic capacitor 12 is obtained as:that is, the inductor 13 and the electrolytic capacitor 12 form an LC low-pass filter with the cut-off frequency fr, and the switching frequency fs=65khz≡6.9fr is far greater than the resonant frequency fr, so that the ripple current carrying the switching frequency fs is very difficult to flow into the LC low-pass filter due to being greatly blocked, and most of the ripple current after the switching power supply is rectified flows through the ceramic capacitor 21.
On the other hand, the impedance Z1 of the ceramic capacitor 21 at the switching frequency is While the LC circuit formed by the inductor 13 and the electrolytic capacitor 12 has an impedance Z at the switching frequency 2 Is->Visible Z 2 Is Z 1 This means that the ripple current flowing into the ceramic capacitor 21 is 3.83 times the ripple current flowing into the electrolytic capacitor 12, and the total ripple current effective value of the output capacitor in the flyback switching power supply of the present embodiment is about 15A, and the ripple current effective value flowing through each electrolytic capacitor is about 0.77A.
For the traditional scheme that only electrolytic capacitors are used as energy storage filter elements, if the ripple current which can be tolerated by each electrolytic capacitor is 2A, 8 electrolytic capacitors are needed to meet the requirements, and because the ripple current flowing into each electrolytic capacitor is larger (the average current which is born by each capacitor is 1.875A), the number of electrolytic capacitors is large, the occupied area of a circuit board is large, the current which is born is large, and the parallel connection of a plurality of electrolytic capacitors is difficult to realize complete current sharing and soaking; in addition, if a single-sided circuit board is used, the first electrolytic capacitor closest to the rectifying tube must bear the largest current, the heating of the first electrolytic capacitor is the most serious, and the smaller the current born by the electrolytic capacitor further away from the rectifying tube, the smaller the heating of the first electrolytic capacitor is, which inevitably leads to the serious reduction of the service life of the electrolytic capacitor, and the remarkable reduction of the service life and reliability of the switching power supply.
In the filter structure of the present utility model, most of the current flows into the ceramic capacitor 21, and in this embodiment, the average current received by each electrolytic capacitor 12 is 0.77A, which is only 38.5% of the rated value, and the current received by the electrolytic capacitor is small, and the heat generated by the electrolytic capacitor is low, so that the current sharing and soaking are easy to achieve. In the case of the ceramic capacitor 21, the ESR is small (about 1-10 mΩ), and the circuit board is largely copper-clad to easily realize the current sharing, the average current to each ceramic capacitor is about 15A/4.83×3.83/32=0.37A, and the rated current of the ceramic capacitor 21 is 2-5A, so the heat generation of the ceramic capacitor 21 is not serious.
From the above, the following beneficial effects can be achieved by using the scheme of the combined filter of the utility model:
(1) The second circuit board for welding the ceramic capacitor is perpendicular to the first circuit board (main circuit board), and the second circuit board is a two-layer circuit board, so that the second circuit board can be coated with copper in a large area, and the ceramic capacitor has good heat dissipation and current sharing effects; in addition, because the second circuit board is small in area and vertical to the first circuit board, the ceramic capacitor is not easy to deform, and the reliability of the ceramic capacitor is improved.
(2) The ceramic capacitor is arranged on the combined filter, most ripple current flows into the ceramic capacitor when the combined filter is electrified, the ripple current actually born by the electrolytic capacitor is small, current sharing and soaking are easy to realize, and the reliability and the service life of the switching power supply are greatly improved;
(3) Compared with the traditional method that only an electrolytic capacitor is used as a main energy storage filter element, the number of the electrolytic capacitors is greatly reduced, and the ceramic capacitor PCBA is laterally erected on a main circuit board, so that the layout space of the switching power supply is greatly reduced, and the power density is improved.
Variations and modifications of the above embodiments will occur to those skilled in the art to which the utility model pertains from the foregoing disclosure and teachings. Therefore, the present utility model is not limited to the above-described embodiments, but is intended to be capable of modification, substitution or variation in light thereof, which will be apparent to those skilled in the art in light of the present teachings. In addition, although specific terms are used in the present specification, these terms are for convenience of description only and do not limit the present utility model in any way.
Claims (8)
1. The utility model provides a combination formula wave filter for among the switching power supply, its characterized in that, combination formula wave filter includes first circuit board, electrolytic capacitor, inductor, ceramic capacitor and second circuit board, wherein, first circuit board is as switching power supply's main circuit board, electrolytic capacitor with the inductor welds respectively on the first circuit board, ceramic capacitor welds on the second circuit board, the second circuit board welds on the first circuit board.
2. The combined filter according to claim 1, wherein the combined filter is connected to a rectifying circuit connected to an output terminal of the switching power supply, one end of the ceramic capacitor is connected to an output positive electrode of the rectifying circuit and one end of an inductor, the positive electrode of the electrolytic capacitor is connected to the other end of the inductor, the other end of the ceramic capacitor and a negative electrode of the electrolytic capacitor are connected to an output negative electrode of the rectifying circuit, the positive electrode of the electrolytic capacitor serves as the output positive electrode of the switching power supply, and the negative electrode of the electrolytic capacitor serves as the output negative electrode of the switching power supply.
3. The combination filter of claim 1, wherein the second circuit board is perpendicular to the first circuit board and the second circuit board is a two-layer circuit board.
4. The combination filter of claim 1, wherein the second circuit board has an area smaller than an area of the first circuit board.
5. The combination filter of claim 1, wherein the ceramic capacitor is a chip ceramic capacitor.
6. The combination filter of claim 1, wherein the first circuit board is a single panel.
7. A switching power supply comprising the combination filter of claim 1.
8. The switching power supply according to claim 7, wherein the combined filter is connected to a rectifying circuit connected to an output terminal of the switching power supply, wherein one end of the ceramic capacitor is connected to an output positive electrode of the rectifying circuit and one end of the inductor, respectively, the positive electrode of the electrolytic capacitor is connected to the other end of the inductor, the other end of the ceramic capacitor and a negative electrode of the electrolytic capacitor are connected to an output negative electrode of the rectifying circuit, respectively, the positive electrode of the electrolytic capacitor is used as the output positive electrode of the switching power supply, and the negative electrode of the electrolytic capacitor is used as the output negative electrode of the switching power supply.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202320311788.2U CN219875692U (en) | 2023-02-24 | 2023-02-24 | Combined filter and switching power supply |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202320311788.2U CN219875692U (en) | 2023-02-24 | 2023-02-24 | Combined filter and switching power supply |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN219875692U true CN219875692U (en) | 2023-10-20 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202320311788.2U Active CN219875692U (en) | 2023-02-24 | 2023-02-24 | Combined filter and switching power supply |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN219875692U (en) |
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2023
- 2023-02-24 CN CN202320311788.2U patent/CN219875692U/en active Active
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