JPS6036096B2 - Electrolytic capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrolytic capacitor, and more particularly, to a low impedance electrolytic capacitor with a four-terminal structure suitable for power sources such as switching regulators.

Generally, a stabilized DC power source is essential for driving electrical and electronic equipment, and a stabilized power source (dropper type) that uses rectified commercial alternating current has been used for this power source for a long time. Since this type of power supply has drawbacks such as large size, weight, and low efficiency, small, lightweight, and highly efficient switching regulators (switching DC stabilized power supplies) have been put into practical use in place of such stabilized power supplies. In this switching regulator, an electrolytic capacitor is an important element in determining its performance.

In particular, switching power supplies handle frequencies of 100K to 200K, which are much higher than commercial frequencies, so the impedance characteristics of electrolytic capacitors become a problem, and it is also important to reduce size and weight, that is, to improve volumetric efficiency.
This is one issue. For this reason, an electrolytic capacitor with a four-terminal structure was proposed, and FIG. 1 shows a switching regulator using this electrolytic capacitor. As shown in Figure 1,
The electrolytic capacitors 2 and 4 have anodes 2A and 4A and a cathode 2B.
, 4B are provided with two terminals T, , L, T3, respectively.
, T4 and has a four-terminal structure. In such a switching regulator, a direct current obtained by rectifying a commercial power source is applied between the input terminals 6A and 6B, and a ripple current and a direct current flow inside the electrolytic capacitor 2.

The DC current flows from the terminal T, through the anode 2A side, and from the terminal T2 into the switching circuit 8, and the DC current flowing out from the switching circuit 8 flows from the terminal T4 through the cathode 2B side, and then from the terminal L to the input terminal 6B. However, the high frequency intermittent current obtained by the switching circuit 8 is supplied to a rectifier circuit 10' via a transformer 9, and its rectified output is supplied to terminals T, L of the electrolytic capacitor 4. As a result, similar to the electrolytic capacitor 2, DC output is taken out from the terminals T2 and T4 and output from the output terminals 12A and 12B.
In particular, an excessive inrush current flows through the electrolytic capacitor 2 when the input is turned on, and a high-frequency ripple current flows through the electrolytic capacitor 4, so each electrolytic capacitor 2,
4 requires low impedance characteristics. Figure 2 shows
A vertical cross section of electrolytic capacitors 2 and 4, Fig. 3 shows the blood in Fig. 2.
A cross section along the m-line is shown.

This electrolytic capacitor uses a flat-wound aluminum electrolytic capacitor element 20 (hereinafter referred to as capacitor element 20), and the terminals T, T2, T8, and T4 are connected to the pedestal on the green floor of the case 22. 24A, 24B, 24
It is formed of metal rods erected at C and 24D. These terminals T, -T4 and the capacitor element are electrically connected using an anode foil 26 and a cathode foil 28 drawn out from the end face of the capacitor element 20. That is, the pedestal 24A,
The anode foil 26 is placed in a laminated state on the upper surface of the pedestal 24B, and the washer 30 is placed on top of the anode foil 26, and the anode foil 28 is laminated and placed on the upper surface of the pedestals 24C and 24D, and the washer 3 is placed on top of the anode foil 26.
The anode foil 26, the terminals T, .
8 and the terminals L, L are mechanically fixed and electrically connected by ohmic contact. However, the current path formed in this way is formed by laminating the foils with etched surfaces and mechanical contact, and there is a large contact resistance, so when current flows, the anode foil 26 and the cathode There is a risk that the foil 28 will generate heat and generate vibrations. Therefore, with such a terminal structure, a sufficient current capacity cannot be obtained, and there is even a risk of damage or characteristic deterioration due to inrush current when input is applied. Also,
The anode foil 26 and cathode foil 28 that are pulled out for electrical connection must have the same number and thickness, but it is extremely difficult to handle foils whose mechanical strength has been reduced by etching. Moreover, it is impossible to manufacture large quantities of products with uniform characteristics. Moreover, in order to draw out the anode foil 26 and the cathode foil 28, it is necessary to provide sufficient electrical insulation at both ends of the capacitor element 20. It is necessary to extend the separator with a greater width.

As a result, the length that can contribute to the formation of capacitance with respect to the length of the capacitor element 20 becomes shorter as shown in the figure. Further, at the end of the electrically succeeding upper capacitor element 20,
Due to the presence of the anode foil 26 and the cathode foil 28, the volumetric efficiency of the case 22 is extremely poor, which prevents the case from being made into a four-type case, and furthermore, the area occupied by the circuit board becomes large.

In particular, as the current capacity increases, the areas of the anode foil 26 and the cathode foil 28 need to be increased, so this drawback becomes even more noticeable. Further, since flattening of the capacitor element 20 causes deterioration of characteristics, it is not suitable as a component of a highly efficient switching regulator.

The purpose of this invention is to improve the volumetric efficiency of the case to reduce the area occupied by the circuit board, improve the reliability of the terminal structure, and increase the allowable current.
The present invention aims to provide a low-impedance electrolytic capacitor that has a filter function by adding an inductance component. That is, the present invention includes a plurality of electrolytic capacitor elements arranged in parallel inside a sealed case, and a plurality of electrolytic capacitor elements arranged in an end face portion of the electrolytic capacitor elements, a part of which is embedded in a substrate forming a part of the case. , and a terminal board that connects each electrolytic capacitor element in parallel through its own inductance, and a terminal board that is attached with the inductance interposed therebetween, and whose ends protrude outside the case. It is made up of a main body and a card part.

Hereinafter, the present invention will be explained in detail based on embodiments shown in the drawings. 4 and 5 show an embodiment of the electrolytic capacitor of the present invention, FIG. 4 is a longitudinal sectional view thereof, and FIG.
The figure is a sectional view taken along line V-V in FIG. 4.

As shown in FIGS. 4 and 5, a rectangular case 40 molded from an insulating synthetic resin is composed of a substrate 42 constituting a floor plate, and a cover 44 covered with the substrate 42. The substrate 42 and the cover 44 are integrally fixed together by a joining means such as ultrasonic welding, and are maintained in an airtight state. Two circularly wound aluminum electrolytic capacitor elements 46 and 48 (hereinafter referred to as capacitor element 4) are mounted on the upper surface of the substrate 42.
6,48) are layered in parallel.

The number of capacitor elements 46, 48 arranged in parallel is two in this embodiment, but it may be two or more. As is well known, these capacitor elements 46 and 48 are made by winding an aluminum foil for a cathode and an aluminum foil for an anode having a compound oxide film formed on the surface into a circular cross-section with a separator interposed therebetween. It is impregnated with electrolyte.
At the ends of each capacitor element 46, 48, there are anode tabs 50, 52 connected to the anode aluminum foil and cathode tabs 54, 56 connected to the cathode aluminum foil.
are pulled out, and the anode tabs 50 and 52 are electrically fixed at a constant interval to one terminal plate 58 erected on the substrate 42, and the cathode tabs 54 and 56 are similarly provided. It is similarly fixed to the other terminal plate 60.

That is, each capacitor element 46, 48 is connected to a terminal plate 58, 60.
The terminal boards 58 and 60 are connected in parallel with the inductance interposed therebetween. The inductance of the terminal plates 68, 60 is formed by the planar portion of the terminal plates 58, 60 interposed within the spacing between the tabs 50, 52 or 54, 56. As shown in FIG. 6, the terminal plate 58 is integrally molded from an aluminum plate, and is connected to the substrate 42.
A U-shaped vertical wall 66 is integrally erected at the ends of the supporting parts 62 and 64, which are partially embedded in the plane of the vertical wall 6.
Connecting pieces 68 and 70, to which the tabs 50 and 52 are fixed by aluminum welding and are electrically connected, are integrally provided at the upper ends of the connectors 6 at regular intervals. In addition, the support part 6
Connecting lead parts 72 and 74 formed of solderable metal wire are protrudingly provided on the back surfaces of the walls 2 and 64 at positions away from the standing position of the standing wall 66, that is, near the ends.
2 and 74 protrude from the back surface of the substrate 42 of the case 40.

Further, the terminal board 60 is similarly configured, and the supporting parts 62, 64
The shield portions 76 and 78 protrude from the back surface of the substrate 42, as shown in FIG. And terminal board 5
8 and the anode tabs 50, 52 are fixed by welding without bending the connecting pieces 68, 70.
is bent and faces the inner surface of the vertical wall 66 together with the tabs 50 and 52.

Therefore, the tabs 50 and 52 are fixed to the connection pieces 68 and 70, and the unfixed portions of the tabs 50 and 52 are held by the fixed portions and the inner surface of the vertical wall 66.
As a result, the electrical connection area is increased, the capacitor elements 46 and 48 are connected in parallel over a short distance, and vibration resistance is improved. In this case, the terminal plate 58
The inductance possessed by the tabs 50 and 52 is mainly formed by the vertical wall 66 between the tabs 50 and 52. In addition, the terminal board 60
The terminal board 58 is also configured in the same manner as the terminal board 58. With the above configuration, the capacitor element 46 can be placed inside the case 40.
, 48 are connected in parallel by the terminal plates 58, 60' through the inductance of the standing wall 66, and as a result, the equivalent circuit between the four-terminal lead sections 72, 74, 76, and 78 is shown in FIG. It is given by the circuit shown in .

Inductances 80 and 82 interposed between the capacitor elements 46 and 48 are inductances that the vertical wall 66 has. In this way, the equivalent circuit constitutes a filter circuit consisting of capacitor elements 46, 48 and inductances 80, 82, and is suitable for smoothing rectified output including ripple current. That is, the inductances 80 and 82 function as impedances proportional to the frequency for high-frequency ripple currents, and the inductances 80 and 82 function as impedances proportional to the frequency for high-frequency ripple currents.
, 82 are provided by the vertical walls 66 having a wide area, so that they function as low resistance, so that a large current capacity can be obtained. In addition, since the capacitor elements 46 and 48 are connected in parallel, the resistance and inductance that exist in the series state of each capacitor element 46 and 481 are reduced by parallel connection, and the capacitance is increased. The equivalent series resistance (ESR) and equivalent series inductance (ESL) are extremely small compared to a configuration made of one capacitor element, and low impedance characteristics can be obtained.

As a result, it is possible to prevent the deterioration of characteristics caused by heat generation due to the flow of ripple current, increasing the service life.Since the equivalent series inductance is small, the operating frequency can be increased, and the impedance is low even at high frequencies. Therefore, it is suitable for switching regulators that handle high-frequency ripple current. Further, the terminal plates 58 and 60 in the case 40 can be formed of aluminum plates with a thickness of about 0.5 to 1, and the anode and cathode tabs 50, 52, 54, 50 necessary for connection Because of their short lengths, they occupy an extremely small proportion of the interior of the case 40, and the volumetric efficiency within the case 40 is improved compared to conventional products, making it possible to reduce the area occupied on the circuit board. In particular, the width of the isolator for insulation at both ends of the capacitor elements 46 and 48 can be reduced compared to conventional products.
The length of the capacitor elements 46 and 48 functioning as capacitors can be increased, the volumetric efficiency is increased, and the capacitance can be increased as well as the size. Furthermore, the supporting parts 62 and 64 of the terminal plates 58 and 60 are molded into the plane of the substrate 42 of the case 40 and are integrated with the case 40, so that the support parts 62 and 64 of the terminal plates 58 and 60 are firmly attached to the case 40. 40 and has a large area.
2 ensures an adhesive area with the substrate 42, and the support part 6
2, 64 protruding from the guard portion 72, 74 or 76,
78, the airtightness inside the case 40 is not reduced at all.

Moreover, since it has such a structure, mechanical strength is sufficiently maintained, there is no failure due to vibration, and it can be constructed as a highly reliable and stable capacitor.

In particular, the lead portions 72, 74 or 76, 78 are connected to the support portion 62.
, 64, the standing wall 66
Since the parts of the leads 72, 74 or 76, 78 exposed by the lower surface of the board 42 are separated from each other by the lower surface of the board 42, the risk of airtight leakage between them is also reduced.
Further, as shown in FIG.
4 is indicated by a broken line, the terminal plate 5 is maintained while maintaining elasticity between the inner wall surface of the cover 44 and the end surfaces of the capacitor elements 46 and 48.
Since the capacitor elements 46 and 48 are held in the case 40 via the terminal plates 58 and 60, the mounting state of the capacitor elements 46 and 48 in the case 40 is stable and reliable. Improves sex. In addition, the terminal board 5
Alternatively, as shown in FIG. 8, the connecting piece may be removed and the anode tabs 50, 52 or the cathode tabs 54, 56 may be fixed to the inner surface of the vertical wall 66.

According to the terminal board configured in this way, the number of steps required to bend and form the connection piece is reduced, and the space corresponding to the thickness of the connection piece can be used for the capacitor element, making it particularly suitable for small electrolytic capacitors. In addition, when increasing the inductance of the terminal plates 58 and 60, the vertical wall 66 is formed with uneven notches 84 shown in FIG. It is also possible to increase the inductance.

In the case of the above embodiment, two capacitor elements 46 and 48 were housed in the case 40, but as shown in FIG.
The capacitor elements 92, 94, 96 may be housed and connected in parallel using a wide terminal plate 580.

In this case, the terminal board 580 has three connection pieces 98, 100.
, 102 are provided protrudingly. With this configuration, three capacitor elements 92,
Since 94 and 96 are connected in parallel, an electrolytic capacitor with extremely low impedance characteristics and improved filtering effect can be provided. Note that polarity can be determined by changing the spacing between the terminal boards 58, 6 protruding lead portions 72, 74, 76, and 78, thereby preventing problems caused by misidentification of polarity. can.

Further, the capacitor elements 46 and 48 of this embodiment may be foil-type tantalum electrolytic capacitor elements, and are not limited to aluminum electrolytic capacitor elements.

Next, experimental results of this invention will be explained with reference to FIG.

Figure 11 shows impedance characteristics versus frequency,
A is the characteristic of an electrolytic capacitor according to the present invention using an electrolytic capacitor element with a height of 2 mm x width of 35 mm x length of 5 mm and a volume of 35 mm. A kite has a volume of 3
5.3 Characteristics of conventional electrolytic capacitors using ground-wound electrolytic capacitor elements, and C is 35 cm in diameter x 5 cm in length.
These are the characteristics of a conventional electrolytic capacitor that uses a wound type electrolytic capacitor element with a volume of 48.1 mm.Each electrolytic capacitor has a rated voltage of 16WV with different etching magnification.
, Sadahiragi capacitance is set to 1000 F.

As is clear from the comparison of these characteristics, the characteristic A of the electrolytic capacitor according to the present invention is from 1 Hz to 200 KHz.
It exhibits a constant impedance until then, and has a low impedance, and it can be seen that the impedance characteristics are improved compared to conventional products.

This means that as a result of varying the etching magnification, the impedance characteristics change depending on the magnification. Furthermore, when comparing the volumes of the electrolytic capacitors used in this experiment, the electrolytic capacitor according to the present invention had improved volumetric efficiency and was smaller.

As explained above, according to the present invention, the area occupied by the circuit board is reduced by improving volumetric efficiency, and low impedance characteristics are achieved by connecting multiple capacitor elements in parallel with inductance interposed. At the same time,
The reliability of the electrical connection between the terminal board, capacitor, and child is improved, allowing for a larger allowable current.Furthermore, the filter function can be achieved by the inductance and capacitor element, and high-frequency ripple current can be smoothed with high efficiency. It can be done with

[Brief explanation of the drawing]

Figure 1 is a block diagram showing a switching regulator.
FIG. 2 is a longitudinal cross-sectional view showing a conventional electrolytic capacitor, FIG. 3 is a cross-sectional view taken along line mm in FIG. 2, and FIG. Figure 5 is the fourth
6 is a perspective view showing the terminal board, FIG. 7 is a circuit diagram showing an equivalent circuit of an electrolytic capacitor,
Figure 8 is a sectional view showing a modified example of the terminal plate, Figure 9 is a front view showing a modified example of the terminal plate, Figure 10 is a sectional view showing another example of the electrolytic capacitor, and Figure 11 is the experimental result. FIG. 40... Case, 46, 48, 92, 94, 96. ．． ．．
．． ．． ．． Electrolytic capacitor element, 58, 60, 580...
・Terminal board, 62, 64...Support part, 66...
...Buddhist wall, 68,70... Connection piece, 80,82.
...Inductance, 84...Notch. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11

Claims (1)

[Claims] 1. A plurality of electrolytic capacitor elements 46, 48, 92, 94, 96 arranged in parallel inside a sealed case 40, and a part inside a substrate 42 forming a part of the case 40. The electrolytic capacitor elements 46, 48, 92, 94,
Each electrolytic capacitor element 46, 48, 9
Terminal board 58, 60, 5 connecting 2, 94, 96 in parallel
80, and lead portions 72, 74, 76, 7 attached to the terminal plates 58, 60, 580 with the inductances interposed therebetween, and whose ends protrude outside the case.
An electrolytic capacitor characterized by comprising: 8. 2 The terminal plates 58, 60, 580 are connected to the substrate surface 42
The lead portions 72, 74, 7
6.78 are provided on the supporting parts 62, 64, and the electrolytic capacitor elements 46, 64 are provided on the supporting parts 62, 64.
Standing wall 66 arranged at the end face part of 48, 92, 94, 96
Connection pieces 68 and 7 are provided protruding from the upper end of the vertical wall 66 to which the electrode tabs of the electrolytic capacitor element are fixed, and are bent to face the wall surface of the vertical wall 66.
0. The electrolytic capacitor according to claim 1, further comprising: 0. 3. The electrolytic capacitor according to claim 2, wherein the vertical wall 66 has an uneven cutout to set a specific inductance value.