JP2003061338A - Switching power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a switching power supply which is simply constituted and yet produces sufficient effect of suppression of input current harmonic components or power factor improvement and also contributes to reduction in size and cost. SOLUTION: The switching power supply is provided with an active filter 24 which is connected to an alternating-current power supply 12 used for power factor improvement and harmonic current suppression, and designed substantially in correspondence with a rated load. To cope with input voltage drop at peak load exceeding the rated load, the switching power supply is provided with a DC-DC converter 26 whose holding voltage is set to a value significantly lower than the input voltage at rated load.

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 device which incorporates an active filter and a DC / DC converter and is capable of outputting peak power.

[0002]

2. Description of the Related Art Conventionally, a switching regulator power supply device having an active filter built therein is shown in FIG. 5 as a device capable of temporarily outputting peak power. In this switching power supply device 10, the AC power of the AC power supply 12 is input to the active filter 14, and the output of the active filter 14 is connected to the active filter boost voltage smoothing capacitor C1 and D
It is input to the C / DC converter 16. The capacitor C1 may be included as a component of the active filter 14.

The output of the DC / DC converter 16, which is the output of the switching power supply device 10, is connected to the rated load R1 and the peak load R2 via the switch 18.

In this switching power supply device 10, the active filter 14 and the DC / DC converter 16 each have a power supply capacity of, for example, 1 kW corresponding to the load of the peak load R2. Therefore, as shown in FIG. 6, even during the load period of the peak load R2, the capacitor C
There is almost no voltage drop of Vc1 which is the voltage across both ends of the DC / DC converter 26 and which is the input voltage of the DC / DC converter 26.
The holding voltage Vh of the converter 16 is set to a value slightly lower than Vc1.

[0005]

In the case of the above-mentioned conventional technique, as shown in FIGS. 5 and 6, the active filter 14 and the DC / DC converter 16 having a large capacity capable of handling a temporary peak power are used. The switching power supply device 10 is configured. Therefore, since the load factor in the rated load state is smaller than that in the peak load state, the effect of suppressing the input current harmonic component or improving the power factor is sufficiently obtained during the rated load period of the switching power supply device 10. There was a problem that I couldn't. Further, a large active filter 14 and a capacitor C1 are required to cope with the peak electric power which only needs to be dealt with for a short time, which causes a problem that the switching power supply device 10 as a whole becomes large and costly.

The present invention has been made in view of the above-mentioned prior art, and has a simple structure and can sufficiently suppress the input current harmonic component or improve the power factor, and can reduce the size and cost. Another object of the present invention is to provide a switching power supply device that also contributes.

[0007]

The present invention comprises an active filter connected to an AC power source and used for power factor improvement and harmonic current suppression, and a DC / DC converter connected to the active filter. It is a switching power supply device that can output peak power, and it has an active filter designed for almost rated load and a holding voltage for rated voltage that corresponds to the input voltage drop at peak load exceeding this rated load. And a DC / DC converter set to be significantly lower than the input voltage at the time.

Further, when the active filter is stopped or cannot perform a sufficient boosting operation due to the overcurrent operation at the time of outputting the peak power, the DC / DC converter can output the peak power by the input from the AC power supply. Is a switching power supply device having the circuit configuration described above.

The switching power supply device of the present invention is a combination of an active filter designed for a rated load and a DC / DC converter designed for a peak load and a low holding voltage, and is charged by the boosted voltage of the active filter. Of DC / DC by the electric charge of the input and the current supplied from the input through the active filter.
It is possible to output the peak power by the converter.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an active filter according to an embodiment of the present invention and a switching power supply device using the active filter.
0 indicates that the AC power of the AC power supply 12 is the active filter 2
4 and the output of the active filter 24 is connected to the active filter boosted voltage smoothing capacitor C1 and is also input to the DC / DC converter 26. The output of the DC / DC converter 26, which is the output of the switching power supply device 20, is the rated load R1.
And a peak load R2 via a switch 18. Here, the capacitor C1 may be included as one component of the active filter 24.

The active filter 24 of the switching power supply device 20 is designed to correspond to a rated load,
For example, the power of 200 W is used as the rated output. On the other hand, the DC / DC converter 26 has a power supply capacity of, for example, 1 kW in response to the load of the peak load R2. Then, as shown in FIG. 2, the DC / DC converter 26, during the load period of the peak load R2, corresponds to the input voltage of the peak load exceeding the rated load R1 and holds the holding voltage Vh at the rated load input voltage. The circuit configuration is set to be significantly lower than Vc1.

The switching power supply device 20 of this embodiment
As shown in FIG. 2, when the output changes from the rated load state to the peak power output state, the output of power decreases the terminal voltage Vc1 of the capacitor C1.
The active filter 24 has a terminal voltage V of the capacitor C1.
Control is performed to increase c1.

At this time, the current Iin for charging the capacitor C1 is the overcurrent operating point Ih of the active filter 24.
Up to are charged by the output from the active filter 24 and the input current from the AC power supply 12. Therefore,
The lower limit of the input voltage range in which the DC / DC converter 26 designed according to the peak power output can output the power is the holding voltage Vh which is the rectified voltage at the lower limit of the input voltage range in which the peak power output of the switching power supply device 20 is possible. Is set to.

The switching power supply device 20 of this embodiment
According to the above, the active filter 24 designed in the rated load state and the DC / D designed in accordance with the peak power output are provided.
By the C converter 26, it is possible to suppress the input current harmonic component in the rated load state or improve the power factor improving effect, and it is possible to downsize the entire device and reduce the cost.

Next, a second embodiment of the present invention will be described with reference to FIGS. Here, the same members as those in the above-described embodiment are designated by the same reference numerals and the description thereof will be omitted. The switching power supply device 30 of this embodiment has the same configuration as that of the above-described embodiment, and the holding voltage Vh of the DC / DC converter 36 is set to be lower than that of the above-described embodiment, and the capacitance of the capacitor C1 is reduced. is there.

In this case, the current Ic1 that charges the capacitor C1 is the overcurrent operating point Ih of the active filter 24.
Up to, the capacitor C1 is charged by the active filter 24 and the input current from the AC power supply 12. Then, at or near the point where the current Iin exceeds the overcurrent operating point Ih of the active filter 24, the active filter 24 does not stop its operation or does not perform a sufficient boosting operation, and power is supplied only by the current from the AC power supply 12. Be seen. Therefore, also in this case, the lower limit of the input voltage range in which the DC / DC converter 26 designed according to the peak power output can output power is the lower limit of the input voltage range in which the peak power output as the switching power supply device 30 is possible. Is set to the holding voltage Vh.

The switching power supply device 30 of this embodiment
According to the above, in addition to the effects of the above embodiment, the capacitor C1
Can be further miniaturized.

The active filter and the switching power supply device of the present invention are not limited to the above embodiment,
The combination of the active filter and the DC / DC converter can be appropriately set, and in the DC / DC converter designed according to the peak power output, the active filter corresponding to the rated load is connected to the input capable of outputting the output power. The lower limit of the voltage range may be set low.

[0019]

The switching power supply device of the present invention is capable of dealing with peak power output after designing the active filter with the rated load power, suppressing the input current harmonic component in the rated load state, or reducing the power factor. It is possible to improve the improvement effect, and it is possible to reduce the size of the entire apparatus and reduce the cost.

[Brief description of drawings]

FIG. 1 is a schematic circuit diagram of a switching power supply device according to a first embodiment of the present invention.

FIG. 2 is a graph showing the operation of each part of the switching power supply device of this embodiment.

FIG. 3 is a schematic circuit diagram of a switching power supply device according to a second embodiment of the present invention.

FIG. 4 is a graph showing the operation of each part of the switching power supply device of this embodiment.

FIG. 5 is a schematic circuit diagram of a conventional switching power supply device.

FIG. 6 is a graph showing the operation of each part of the conventional switching power supply device.

[Explanation of symbols]

10, 20, 30 Switching power supply 12 AC power supply 14, 24, 34 Active filters 16, 26, 36 DC / DC converter 18 switch R1 rated load R2 peak load

Claims (2)

[Claims] 1. An active filter connected to an AC power supply, and a DC / DC connected to this active filter.
In a switching power supply device that is equipped with a converter and is capable of outputting peak power due to a peak load exceeding the rated load, an active filter designed almost corresponding to the rated load and a drop in the input voltage at the peak load exceeding this rated load The switching power supply device is provided with a DC / DC converter whose holding voltage is set to be significantly lower than the input voltage at the rated load. 2. The DC / DC converter is capable of outputting peak power by inputting from an AC power supply when the active filter cannot stop or perform a sufficient boosting operation due to an overcurrent operation during peak power output. The switching power supply device according to claim 1, wherein