JPH0681490B2 - Smoothing circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a smoothing circuit for converting an output of a pulsating power source such as a pulsed current into a flat direct current.

(Prior Art) Conventionally, a circuit as shown in FIG. 2 has been used as a smoothing circuit for converting a pulsed current into a flat DC current.

In FIG. 2, 1 is a pulsating power source that generates a pulsed current, 2 is a capacitor, and 3 is a load. Here, the AC component i _AC of the output current from the pulsating power supply 1 flows through the capacitor 2, and the load 3 is supplied with the DC component I _O smoothed by the capacitor 2.

(Problems to be Solved by the Invention) In the smoothing circuit configured as described above, in order to sufficiently exert the smoothing effect, (1) the capacitance of the capacitor 2 is sufficiently large.

(2) The high-frequency impedance of the capacitor 2 is sufficiently low so that the AC component can flow sufficiently.

is necessary.

Conventionally, an aluminum electrolytic capacitor has been used as a capacitor satisfying this condition, but the aluminum electrolytic capacitor usually has a so-called dry-up phenomenon in which the electrolytic solution inside evaporates in about 5 to 7 years. , Because the function as a capacitor disappears,
When it is applied to a communication device that has a short service life and is used for a long period of time, there are operational problems such as periodical replacement.

Therefore, there are multilayer ceramic capacitors and tantalum electrolytic capacitors as alternatives to aluminum electrolytic capacitors, and the dry-up phenomenon does not occur in either of them, but it is difficult to manufacture a small and large-capacity multilayer ceramic capacitor. The tantalum electrolytic capacitor has a drawback that it cannot pass a large amount of the alternating current component i _{AC, and} thus cannot be simply used in place of the aluminum electrolytic capacitor.

An object of the present invention is to eliminate these problems and to provide a smoothing circuit having smoothing characteristics equivalent to those of an aluminum electrolytic capacitor and having a long life.

(Means for Solving Problems) In order to solve the above problems, the present invention provides a non-polar capacitor such as a laminated ceramic capacitor or a film capacitor connected in parallel to a pulsating power source in a smoothing circuit, and the non-polar capacitor. A choke coil connected in parallel to the capacitor and a series circuit of a polar capacitor such as a tantalum electrolytic capacitor are provided, and an output is taken out from both ends of the polar capacitor.

(Operation) According to the present invention, since the smoothing circuit is configured as described above, most of the AC component of the output current of the pulsating power supply flows through the nonpolar capacitor. Further, the ripple voltage generated between the terminals of the nonpolar capacitor is attenuated by the filter circuit formed by the choke coil and the polar capacitor, and a flat DC output is obtained from the polar capacitor.

Therefore, it is possible to use a multilayer ceramic capacitor having a small capacity and a high ripple resistance as the non-polar capacitor, and since an AC component is hardly applied to the polar capacitor, it is possible to make it small and have a large capacity. However, polar capacitors such as low ripple tolerant tantalum electrolytic capacitors can be used.

(Example) Hereinafter, the Example of this invention is described in detail, referring drawings.

FIG. 1 is a smoothing circuit diagram showing a first embodiment of the present invention.

In FIG. 1, 1 is a pulsating power source, 3 is a load, 4 is a non-polarized capacitor having a high ripple withstanding capability (hereinafter referred to as a first capacitor), 5 is a choke coil, 6 is a polar capacitor having a low ripple withstanding capability ( Hereinafter referred to as a second capacitor).

Here, most of the AC component i _AC of the output current of the pulsating power supply 1 flows through the first capacitor 4. Therefore, as the first capacitor 4, a monolithic ceramic capacitor or a film capacitor having a high ripple resistance is used.
It is not necessary to increase the capacity of this first capacitor 4. The ripple voltage generated between the terminals due to the small capacitance is attenuated by the filter circuit formed by the choke coil 5 and the second capacitor 6, and the load 3 is supplied with smoothed direct current.

Further, since the current flowing through the choke coil 5 is substantially constant, it is not necessary to flow an AC component so much in the second capacitor 6. Therefore, as the second capacitor 6, it is possible to use a tantalum electrolytic capacitor having a low ripple withstanding capacity although it is possible to make it small and have a large capacity.

In FIG. 1, each of the first capacitor 4 and the second capacitor 6 is represented by one capacitor symbol, but a parallel circuit using a plurality of capacitors may be used if necessary. Needless to say.

FIG. 3 is a smoothing circuit diagram showing a second embodiment of the present invention.

In this embodiment, reference numerals 1, 3 to 6 are the same as those in FIG. That is, the pulsating power supply 1 is connected to the first capacitor 4, the choke coil 5, the second capacitor 6, and the load 3.

The pulsating power supply 1 is a DC power supply 10 and a second capacitor 1
2, the choke coil 13 and the first capacitor 14 are connected. A transformer is connected across the first capacitor 14.
The primary coil of 15 and the switching element 16 are connected in series, and the diode 17 is connected to the secondary coil of the transformer 15. A so-called known switching regulator is configured.

Here, most of the AC component flowing from the pulsating power supply 1 flows to the first capacitor 4, and it is not necessary to flow much AC component to the second capacitor 6, which is the case in the first embodiment. It is similar to FIG.

The present invention is not limited to the above embodiment,
Various modifications are possible based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

(Effect of the Invention) As described in detail above, according to the present invention, a non-polarized capacitor such as a multilayer ceramic capacitor or a film capacitor is mainly supplied with an AC component, and a DC current taken out through a choke coil is supplied. Since a pulsating current is smoothed by using a polar capacitor such as a tantalum electrolytic capacitor, the circuit operation failure due to the dry-up phenomenon of the aluminum electrolytic capacitor is eliminated, and it is made compact and for a long period of time. A smoothing circuit that can be used can be obtained.

[Brief description of drawings]

FIG. 1 is a smoothing circuit diagram showing the first embodiment of the present invention, and FIG.
FIG. 3 is a conventional smoothing circuit diagram, and FIG. 3 is a smoothing circuit diagram showing a second embodiment of the present invention. 1 ... Pulsating power supply, 3 ... Load, 4,14 ... Nonpolar capacitor (first capacitor), 5,13 ... Choke coil, 6,
12 …… Polarized capacitor (second capacitor), 10 ……
DC power supply, 15 …… transformer, 16 …… switching element,
17 …… Diode.

Claims (3)

[Claims] 1. A non-polar capacitor connected in parallel to a pulsating power source, a series circuit of a choke coil and a polar capacitor connected in parallel to the non-polar capacitor, and an output is taken out from both ends of the polar capacitor. A smoothing circuit characterized by the above. 2. The smoothing circuit according to claim 1, wherein the non-polar capacitor is a laminated ceramic capacitor or a film capacitor. 3. The smoothing circuit according to claim 1 or 2, wherein the polar capacitor is a tantalum electrolytic capacitor.