JP2003333848A - Switching power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a switching power supply in which harmonics are suppressed without requiring an expensive extra countermeasure circuit. <P>SOLUTION: The switching power supply comprises a diode stack 1, a main converter 15 and a backup circuit 14 wherein the diode stack 1 rectifies AC power, the main converter 15 is connected with the diode stack 1 and transmits power to the backup circuit 14 in the post-stage by a switching operation, and the backup circuit 14 is connected in parallel with the main converter 15. The backup circuit 14 corrects ripples in an output from the main converter 15 thus suppressing the generation of harmonic currents. The inventive arrangement can contribute greatly to the cost reduction of a system by eliminating the problem of a one-converter system by discharge power from a battery in a backup power supply without requiring an extra component. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching power supply, and more particularly to a switching power supply in which generation of harmonic current is suppressed.

[0002]

2. Description of the Related Art Conventionally, a switching power supply is generally provided with a high frequency suppressing circuit. The choke input method and the active filter method are mainly used for the harmonic suppression circuit in this switching power supply due to the power consumption.

FIG. 2 is a circuit diagram showing a configuration example of a conventional switching power supply. Referring to FIG. 2, in a conventional switching power supply, an AC power supply is rectified by a diode stack 1 and smoothed by a capacitor 2, and thereafter is composed of a switching element 4, a power transformer 3, diodes 5 and 6, a choke coil 7, and a capacitor 11. Is stabilized to DC by the main converter 15.
Outputs Vo1, Vo2, Von by 2 and 13 respectively
And the generated outputs Vo1, Vo2, Von are supplied to the respective loads L1, L2, Ln.

Prior invention example 1 similar in technical field to the present invention
As an example, there is "Uninterruptible power supply" of Japanese Patent Laid-Open No. 9-56085. In the invention example 1 of the prior application, a capacitor for energy storage provided in order to increase the power factor of the input and reduce the AC frequency ripple of the output is used, and a backup element such as a battery is connected to this capacitor through a charging circuit. It is said that the AC input power supply device having a relatively simple structure and a high power factor can be provided with a backup function by connecting them.

According to FIG. 1 of the invention 1 of the prior application, a commercial storage battery is connected to the output side instead of the smoothing capacitor on the input side to reduce the commercial ripple and enhance the instantaneous proof strength. It is presumed to be something. Also,
It seems that it will also contribute to cost reduction.

Further, as a combination of a harmonic suppression circuit and a backup circuit, Japanese Unexamined Patent Application Publication No. H11-11 of the invention 2 of the prior application.
-136942 is available.

[0007]

However, as described above, the harmonic suppression circuit in the conventional switching power supply mainly employs the choke input method and the active filter method, but the cost due to the addition of the countermeasure circuit is high. Up is a challenge.

The above-mentioned invention 1 of the prior application has many technical problems. For example, there are restrictions on switching operation and whether or not stabilization control of the output voltage is possible by deleting the input capacitor. Further, connecting the battery to the output side is a commonly used floating system. It is estimated that batteries are generally more expensive than capacitors.

Japanese Unexamined Patent Application Publication No. 11-136942 of the prior invention example 2
In No. 6, the problem still remains in terms of cost because it is combined with the active filter method.

The capacitor-less system, which is the base of the present invention, can suppress harmonics only by reducing the input capacitor, but it is a secondary countermeasure circuit due to the problems of increase of commercial ripple and deterioration of momentary interruption resistance. Must be added,
Not adopted very often.

An object of the present invention is to provide a switching power supply that can suppress harmonics without adding an expensive countermeasure circuit. More specifically, the present invention provides
In the backup power source, the discharge power of the storage battery solves the problem of the one-converter method without additional parts, and contributes greatly to the cost reduction of the system.

[0012]

In order to achieve such an object, a switching power supply of the present invention has a diode stack, a main converter and a backup circuit, the diode stack rectifies an AC power supply, and the main converter is a diode stack. Is connected to the main circuit by the switching operation to transfer power to the backup circuit in the subsequent stage, and the backup circuit is connected in parallel with the main converter.The backup circuit corrects the ripple of the output power from the main converter and It is characterized by suppressing the occurrence.

Further, the backup circuit has a charging resistor, a discharging diode and a storage battery, the charging resistor and the discharging diode are connected in parallel, and the parallel connection portion and the storage battery are connected in series to form a main converter. It is preferable to be connected to the output side of.

Further, the main converter includes a power transformer, a switching element connected in series with a primary winding of the power transformer, and two diodes connected in series with a secondary winding of the power transformer. And a choke coil 7 connected to the connection point of the two diodes,
It is preferable to further include a capacitor connected in parallel between the output terminal of the choke coil and the secondary winding of the power transformer.

The backup circuit is configured to be capable of supplying power, and the commercial ripple generated by the one-converter method is compensated by using the backup circuit so that the backup circuit can be constantly supplied with power, and is deteriorated by the one-converter method. The instantaneous power interruption resistance of the power supply is supplemented by using the backup circuit of the constant power supply system.
It is advisable to configure a bridge circuit with individual diodes to perform full-wave rectification of the AC power supply.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of a switching power supply according to the present invention will be described in detail with reference to the accompanying drawings. Referring to FIG. 1, there is shown one embodiment of the switching power supply of the present invention.

The present invention provides an inexpensive backup type switching power supply having a harmonic suppression function and composed of a simple circuit. By removing the smoothing capacitor 2 on the primary side, harmonic current is suppressed, and the secondary side storage battery 10
By constantly supplying power to the power supply, the commercial ripple noise, which is a harmful effect of the above harmonic suppression method, is reduced and the instantaneous interruption resistance is secured.

The constitution of the present invention will be described with reference to FIG. The switching power supply of the embodiment shown in FIG. 1 includes a diode stack 1 for rectifying an AC power supply and a main converter 1
5, the backup circuit 14, the converters 16 and 1
2 and 13, and the stabilized power supply is load L
1, L2, Ln.

The main converter 15 comprises a power transformer 3, a switching element (for example, transistor, p-type or n-type MOSFET) 4, two diodes 5 and 6, a choke coil 7, and a capacitor 11. To be done. Further, the backup circuit 14 uses the storage battery 1
0, a charging resistor 8 and a discharging diode 9 are provided.

The switching power supply of the present invention shown in FIG. 1 configured as described above is different from the conventional switching power supply shown in FIG. 2 in that it does not have the input smoothing capacitor 2 and has a secondary side of the main converter 15. Storage battery 10 and charging resistor 8
And a backup circuit 14 which is newly provided with a discharge diode 9 and which can always supply power.

In the above switching power supply, the diode stack 1 full-wave rectifies the AC power supply. The switching element 4 includes a diode stack 1 and a power transformer 2.
The switching operation is performed with the primary winding. The backup circuit 14 is connected in parallel with the main converter 15 and corrects ripples by discharging.

(Operation Example) Next, the operation of the circuit of FIG. 1 will be described with reference to the drawings. The AC power source Ein is full-wave rectified by the diode stack 1 and
In the normal switching power supply such as the conventional example, which is supplied to the primary winding of the above, the current flows only during the period when the AC power supply Ein becomes higher than the terminal voltage of the capacitor 2.
Therefore, the input current becomes a peak current, which becomes a harmonic current. In the present invention, since there is no conventionally used capacitor 2, no harmonic current is generated.

Next, the full-wave rectified AC power source is directly stabilized by the main converter 15 to the charging voltage of the storage battery 10, and the commercial ripple noise increases due to the absence of the smoothing capacitor 2. But the main converter 1
The ripple is corrected by the discharge from the backup circuit 14 connected in parallel with 5. Since the capacitor 2 is not connected as in the conventional example, there is a concern that the output voltage will drop during an instantaneous power failure. However, since the backup circuit 14 is constantly charged by the charging resistor 8 and can be constantly discharged through the diode 9, the output is guaranteed by the power supply from the storage battery 10.

(Effect of the Embodiment) The addition of the harmonic countermeasure circuit in the switching power supply has been a serious problem in that the circuit is complicated and the cost is increased accordingly. In addition, in systems that require highly reliable power supply, a power supply with a backup function using a storage battery has been standardly adopted.
The present invention is realized by eliminating the harmonic components of the switching power supply having the backup function by removing the conventional circuit components instead of adding the countermeasure circuit. Therefore, the cost of the switching power supply is greatly reduced.

The above-mentioned embodiment is an example of a preferred embodiment of the present invention. However, the present invention is not limited to this, and various modifications can be made without departing from the scope of the present invention.

[0026]

As is apparent from the above description, in the switching power supply of the present invention, the backup circuit corrects the ripple of the output from the main converter and suppresses the generation of harmonic current. Therefore, harmonics can be suppressed without adding an expensive countermeasure circuit, and in the backup type power supply, the problem of the one-converter method can be solved by the discharge power of the storage battery without any additional parts, greatly contributing to the system cost reduction. You can

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration example of an embodiment of a switching power supply of the present invention.

FIG. 2 is a circuit diagram showing a configuration example of a conventional switching power supply.

[Explanation of symbols]

1 diode stack 3 power transformer 4 switching elements 5, 6 diode 7 choke coil 8 charging resistors 9 Discharge diode 10 storage battery 11 capacitors 12, 13, 16 converter 14 Backup circuit 15 Main converter L1, L2, Ln load

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Claims (6)

[Claims] 1. A diode stack, a main converter, and a backup circuit, wherein the diode stack rectifies an AC power supply, and the main converter is connected to the diode stack to transfer power to a backup circuit in a subsequent stage by a switching operation. A switching power supply characterized in that the backup circuit is connected in parallel with the main converter, and the backup circuit corrects the ripple of the output power supply from the main converter to suppress the generation of harmonic current. . 2. The backup circuit includes a charging resistor, a discharging diode, and a storage battery, the charging resistor and the discharging diode are connected in parallel, and the parallel connection portion and the storage battery are connected in series. The switching power supply according to claim 1, wherein the switching power supply is configured to be connected to an output side of the main converter. 3. The main converter comprises a power transformer, a switching element connected in series with a primary winding of the power transformer, and a switching element connected in series with a secondary winding of the power transformer.
A diode, a choke coil 7 connected to the connection point of the two diodes, and a capacitor connected in parallel between the output terminal of the choke coil and the secondary winding of the power transformer. The switching power supply according to claim 1 or 2, further comprising: 4. The backup circuit is configured to be capable of supplying power, and commercial ripple generated by a one-converter method is compensated for by using the backup circuit. Switching power supply. 5. The backup circuit is configured to be capable of supplying power at all times, and the instantaneous power interruption resistance of the power supply which is deteriorated by the one-converter method is supplemented by using the backup circuit of the always supplying method. The switching power supply according to any one of 3 above. 6. The switching power supply according to claim 1, wherein the diode stack is composed of four diodes in a bridge circuit and full-wave rectifies the AC power supply.