JP3295929B2 - DC power supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC power supply having a power factor improving function, and more particularly, to a DC power supply capable of improving efficiency by reducing high-frequency current and high-frequency voltage generated on an AC input side with low loss. .

[0002]

2. Description of the Related Art In a case where DC power is obtained from 50 or 60 Hz commercial AC power, a sine wave AC input current is used in a capacitor input type rectifier circuit including a rectifying element such as a diode and a smoothing capacitor which has been widely used in the past. Since the charging current flows to the smoothing capacitor only in the vicinity of the maximum value, the conduction angle of the input current waveform is narrow and the input power factor is as low as about 0.6. Therefore, at least one M
It has a switching element such as an OS-FET, and controls the switching element on and off according to the output voltage and the input voltage and input current supplied from the commercial AC power supply, so that the commercial AC power from the commercial AC power supply is regulated. A DC power supply device that converts voltage to DC power and makes the input current proportional to the input voltage supplied from a commercial AC power supply and has an input power factor of 1.0 has been proposed and put into practical use.

[0005] FIG. 5 is a diagram showing a configuration in which commercial AC power supplied from an AC generator 3 connected to a power source 1 such as an engine or an electric motor via a joint 2 is converted into a constant-voltage DC power by the DC power supply 4. FIG. 2 shows a system for supplying the load 5 to the load 5. DC power source between the input terminal and the power source 1 of the apparatus 4 is provided with control means 6 for controlling the rotational speed of the power source 1 in accordance with the input voltage V _AC of the DC power supply 4, thereby alternator 3 input voltage V _AC power voltage of the DC power supply 4
It is controlled according to. In the system shown in FIG. 5, for example, when the input current I _AC supplied to the DC power supply 4 exceeds the normal value and the input voltage _VAC drops for some reason, the power is controlled by the control signal output from the control means 6. The number of revolutions of the power source 1 increases, and thereby the voltage generated by the alternator 3 increases. On the other hand, the output voltage _VDC of the DC power supply 4 is controlled at a constant voltage such that the output voltage _VDC decreases as the generated voltage of the AC generator 3 increases.

[0004]

By the way, when the DC power supply 4 is operated under the system shown in FIG. 5 when the power generation capacity of the AC generator 3 is small, the control system of the AC generator 3 and the DC power supply 4 is controlled. delay of signal transmission in the oscillation phenomenon at a frequency input current I _AC and the input voltage V _AC phases of the DC power supply device 4 is substantially in phase occurs. This allows
Direct-current power supply frequency current I _N flows shown in the AC input side of 4 in FIG. 6 (A), and at the same time since the high-frequency voltage V _N generated shown in FIG. 6 (B), when the DC power supply 4 is malfunctioning There is. Therefore, in the conventional connecting a damper circuit 9 consisting of a capacitor 7 and a resistor 8 connected in series as shown in FIG. 7 between the input terminal of the DC power supply 4, high frequency current I _N via a damper circuit 9 Thus, the high-frequency current _IN and the high-frequency voltage _VN are reduced, and malfunction of the DC power supply 4 is prevented. The disadvantage This method has the advantage of reducing the high-frequency current I _N and a high frequency voltage V _N by the damper circuit 9 having a simple circuit configuration, since the power loss occurs in the resistance 8, the efficiency of the DC power supply device 4 is lowered was there. Further, since a relatively large current flows through the damper circuit 9, it is necessary to use a large-capacity capacitor 7 and a resistor 8, which causes a problem that the DC power supply 4 becomes large.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a DC power supply capable of reducing high-frequency current and high-frequency voltage generated on an AC input side with low loss and improving efficiency.

[0006]

A DC power supply according to the present invention comprises a reactor (10) connected to an output line of an AC power supply (3), and at least one switching element (11, 12).
And a switching circuit (15) connected between output lines of the AC power supply (3), a smoothing capacitor (16) connected between output terminals of the switching circuit (15), and a smoothing capacitor (16). A control circuit (ON / OFF control of the switching elements (11, 12) of the switching circuit (15) according to the DC output voltage (V _DC ) and the AC input voltage (V _AC ) supplied from the AC generator (3) 17), and the control circuit (17) has an output voltage
An output voltage detecting means for detecting the level of (V _DC) (23), the detection signal of the AC input voltage (V _AC) and the output voltage detection means (23)
Multiplying means (24) for outputting a product signal (V _M ) with (V _D ), and on / off control of the switching elements (11, 12) by the product signal (V _M ) of the multiplying means (24). . The AC power source (3) is an AC generator having a small power generation capacity, and the multiplying means (24) is a filter circuit for extracting a fundamental frequency component of the _AC input voltage (VAC).
A product signal (V _M ) of the output signal (V _F ) of (21) and the detection signal (V _D ) of the output voltage detecting means (23) is output. The on / off control of the switching elements (11, 12) of the switching circuit (15) according to the product signal (V _M ) of the multiplying means (24) allows the AC power from the AC power supply (3) to have a constant voltage. AC input voltage converted from DC power and supplied from AC power supply (3)
(V _AC ) to make the AC input current (I _AC ) proportional.

The product signal (V) of the output signal (V _F ) of the filter circuit (21) for extracting the fundamental frequency component of the _AC input voltage (V _AC ) and the detection signal (V _D ) of the output voltage detecting means (23). _M )
(24), the switching elements (11, 12) of the switching circuit (15) are on / off controlled in accordance with the product signal (V _M ) of the multiplying means (24). The oscillation phenomenon of the input current (I _AC ) and the AC input voltage (V _AC ) can be reduced, and the high-frequency current and the high-frequency voltage generated on the AC input side can be reduced. This eliminates the need for a damper circuit or the like that generates power loss, so that high-frequency current and high-frequency voltage generated on the AC input side can be reduced with low loss and efficiency can be improved. Also, there is an advantage that the efficiency can be further improved by making the input power factor approximately 1.0 by making the _AC input current (I _AC ) proportional to the _AC input voltage (V _AC ).

In one embodiment of the present invention, the input current (I
_AC ), an input current detecting means (19) for detecting an input current (I _AC ) as a voltage corresponding to the product signal (V _M ) of the multiplying means (24), and a detection signal (V _M ) of the input current detecting means (19). ₂₎ comparing the by comparison output signal (V _P) comparator means for generating (25), comparing means
The switching element (1) according to the comparison output signal (V _P ) of (25)
ON / OFF control signal (V _G1 ,
V _G2 ) is provided.
By controlling on / off of the switching elements (11, 12) by the output signals of the control signal forming means (30, 31), the high-frequency current and the high-frequency voltage generated on the AC input side can be reduced with low loss.

In another embodiment of the present invention, when a DC power supply (4) is connected between each line of a polyphase AC power supply (32) having three or more phases, a high-frequency wave generated in each phase is connected. There is an advantage that the efficiency can be improved by reducing the current and the high-frequency voltage with low loss.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a DC power supply according to the present invention will be described below with reference to FIGS. However, in these drawings, substantially the same parts as those shown in FIGS. 5 and 6 are denoted by the same reference numerals, and description thereof will be omitted.

As shown in FIG. 1, a DC power supply 4 according to the present embodiment includes a reactor 10 connected to one output line of an AC generator 3 and a first power supply as a switching element.
A switching circuit 15 formed by bridge-connecting the second MOS-FETs 11 and 12 and the first and second diodes 13 and 14 and connected between the reactor 10 and the other output line of the AC generator 3; Circuit 1
A smoothing capacitor 16 connected between the output terminal of the 5, the first and in the switching circuit 15 in response to the ac input voltage V _AC and AC input current I _AC is supplied from the DC output voltage V _DC and the AC generator 3 Second MOS-FET 11, 1
And a control circuit 17 for controlling ON / OFF of the control circuit 2.
In the first and second MOS-FETs 11 and 12, first and second parasitic diodes 11 a and 12 are connected in parallel with each other.
a is formed. The AC input voltage V _AC supplied from the AC generator 3 is provided on the AC input side of the DC power supply 4.
And an input current detector as input current detecting means for detecting an _AC input current I _AC flowing from the AC generator 3 to the reactor 10 as a voltage signal V ₂ corresponding to the current I _AC . 19 are provided. Further, a DC-DC converter 20 that converts a DC output voltage V _DC generated at both ends of the smoothing capacitor 16 into a DC output voltage V _O having a different voltage level and supplies the DC output voltage V _O to the load 5 is connected to the output side of the DC power supply 4. Have been.

The control circuit 17 includes a low-pass filter circuit 21 for extracting a fundamental frequency (50 or 60 Hz) component of the _AC input voltage VAC detected by the input voltage detecting transformer 18, and a DC output voltage _VDC . reference power source 2 which generates a reference voltage V _R as a constant voltage level defining a reference value
2, DC output voltage _VDC and reference voltage V _R of reference power supply 22
Output voltage error amplifier 23 as detecting means, multiplying means for outputting a product signal V _M of the output signal V _D of the output signal V _F and the error amplifier 23 of the low-pass filter circuit 21 for detecting a level difference between the Multiplying circuit 24 as
, And a comparator 25 as comparing means for comparing the product signal V _M of the input current detector 19 with the detection signal V ₂ of the input current detector 19, and the switching frequency (20) of the first and second MOS-FETs 11 and 12.
a triangular wave oscillation circuit 26 for generating a triangular wave signal V _T which defines the kHz), PWM outputs PWM modulation signal V _PWM compares the triangular wave signal V _T of the comparison output signal V _P and triangular wave oscillation circuit 26 of the comparator 25 a comparator 27, the detection signal low when the polarity of V ₁ is an output to and negative high (H) level signal V ₃ of when a positive (L) level signal V ₃ of the input voltage detecting transformer 18 , An inverter 29 that outputs an inverted signal −V ₃ of the output signal V ₃ of the positive / negative judgment circuit 28, the PWM modulation signal V _PWM of the PWM comparator 27, and the output signal V of the positive / negative judgment circuit 28. of the inverted signal of the logical product of the ₃ in the switching circuit 15 as the first on-off control signal V _G1 first MOS
A second on / off control of an inverted signal of a logical product of the first NAND gate 30 output to the gate terminal of the FET 11 and the PWM signal V _PWM of the PWM comparator 27 and the inverted signal −V ₃ of the inverter 29; and a second NAND gate 31 for outputting a signal V _G2 to the gate terminal of the second MOS-FET 12 in the switching circuit 15. Triangular wave oscillation circuit 26, PWM comparator 27, positive / negative determination circuit 28, inverter 29, first and second NAND
The gate 30 and 31 are first and second on-off control signal V to be applied to the gate terminals of the first and second MOS-FETs 11 and 12 in response to the comparison output signal V _P of the comparator 25
_It constitutes control signal forming means for forming _G1 and _VG2 .

Next, the operation of the DC power supply 4 shown in FIG. 1 when the AC generator 3 having a small power generation capacity is used will be described. Figure 2 when the polarity of the AC input voltage V _AC from the AC generator 3 shown in (A) is positive, the control circuit 1
7 outputs a high-level signal V ₃ from the positive / negative determination circuit 28. At this time, the first on / off control signal V _G1 output from the first NAND gate 30 to the gate terminal of the first MOS-FET 11 in the switching circuit 15 has a low level as shown in FIG. It will be constant. For this reason,
The first MOS-FET in the switching circuit 15 during the positive half cycle of the _AC input voltage VAC from the AC generator 3
11 turns off. At the same time, the second NAND
From the gate 31 to the second MOS in the switching circuit 15
A second on / off control signal V _G2 shown in FIG. 2C is output to the gate terminal of the FET 12 and the second MOS-FE
T12 is turned on / off. On the contrary, FIG.
When the polarity of the ac input voltage V _AC from the AC generator 3 shown in (A) is negative, positive or negative judgment circuit in the control circuit 17 2
8 signal V ₃ of the low level is outputted from. In this case, the first on-off control signal V _G1 indicating the first NAND gate 30 to the gate terminal of the first MOS-FET 11 in the switching circuit 15 in FIG. 2 (B) is output. Therefore, alternator in the switching circuit 15 in the AC input voltage V _AC negative half cycle from 3 first MOS-
The FET 11 is turned on / off. At the same time, the second on / off control signal V _G2 output from the second NAND gate 31 to the gate terminal of the second MOS-FET 12 in the switching circuit 15 becomes low as shown in FIG. Since the level is constant, the second MOS-FET 12 is turned off.

When the second MOS-FET 12 in the switching circuit 15 is on during the positive half cycle of the _AC input voltage VAC from the AC generator 3 shown in FIG. -Reactor 10-Second MOSFE
An AC input current I _AC flows from the AC generator 3 to the reactor 10 through a path from T12 to the second diode 14, and energy is stored in the reactor 10. Second MOS-FET
When the state of the reactor 12 changes from the on state to the off state, the reactor 10
Most of the energy stored in the reactor 10-1
Of the parasitic diode 11a, the smoothing capacitor 16 and the second diode 14,
Are boosted and charged with the polarity shown. Further, the first MOS-F in the switching circuit 15 during the negative half cycle of the _AC input voltage VAC from the AC generator 3 shown in FIG.
When the ET 11 is in the ON state, an AC input current I _AC flows from the AC generator 3 to the reactor 10 through the path of the AC generator 3-the first diode 13-the first MOS-FET 11-the reactor 10, and the reactor 10 Energy is stored. When the first MOS-FET 11 changes from the on state to the off state, most of the energy stored in the reactor 10 is discharged through the path of the first diode 13 -the smoothing capacitor 16 -the second parasitic diode 12a -the reactor 10. Then, the smoothing capacitor 16 is boosted and charged with the polarity shown. As described above, the DC output voltage _VDC is output from both ends of the smoothing capacitor 16, and the DC-DC converter 2
The voltage is converted into a DC output voltage V _O having a different voltage level by 0 and supplied to the load 5.

The DC output voltage _VDC output from both ends of the smoothing capacitor 16 is input to the inverting input (-) terminal of the error amplifier 23 in the control circuit 17, where the DC output voltage _VDC and the non-inverting input (+) level difference between the reference voltage V _R of the reference power source 22 which is input to the terminal is detected. On the other hand, the high frequency voltage V _N supplied from the alternator 3
AC input voltage, including the V _AC input voltage detecting transformer 18
Is detected by, the detection signal V ₁ was fundamental frequency (50 or 60Hz) component of the AC input voltage V _AC high-frequency voltage V _N is blocked by the low-pass filter circuit 21 is extracted. The output signal V _F of the low-pass filter circuit 21 is input to the multiplier circuit 24 together with the output signal V _D of the error amplifier 23, the output signal V _D of the output signal V _F and the error amplifier 23 of the low-pass filter circuit 21 product signal V _M and is outputted from the multiplier circuit 24. Product signal V _M of the multiplier circuit 24 is compared with the input current detector 19 detects the signal V ₂ of the detected AC input current I _AC by the comparator 25, product signal V _M and the comparison output signal of the detection signal V ₂ V _P is output from the comparator 25. Comparison output signal V _P of the comparator 25 is a triangular wave signal V triangular wave oscillation circuit 26 in a PWM comparator 27
Is compared by _T, becomes low level when the relationship between the comparison output signal V _P and the triangular wave signal V _T is V _P> V _T, a high level when the V _P <V _T PWM modulation signal V _PWM is PWM The signal is output from the comparator 27 and input to one input terminal of the first and second NAND gates 30 and 31. At the same time, the output signal V ₃ of the positive / negative judgment circuit 28 is directly input to the other input terminal of the first NAND gate 30,
The output signal V ₃ of the positive / negative determination circuit 28 is input to the other input terminal of the NAND gate 31 through the inverter 29. Therefore, the AC input voltage V _AC from the AC generator 3
Since the polarity of the positive matrix half period the output signal V ₃ of negative determination circuit 28 becomes a high level, the first on-off control signal V _G1 output from the first NAND gate 30
Becomes a low level constant. On the other hand, the second NAND gate 3
From 1 the PWM modulation signal V of the PWM comparator 27
_PWM is output as the second on / off control signal _VG2 . Further, since the polarity of the AC input voltage V _AC from the AC generator 3 is in the negative in a half period an output signal V ₃ of negative determination circuit 28 becomes a low level, the first NAND gate 3
0 to the PWM modulation signal V _PWM of the PWM comparator 27
There is output as the first on-off control signal V _G1. On the other hand, the second on / off control signal _VG2 output from the second NAND gate 31 is kept at a low level. The first and second on / off control signals V _G1 and V _G2 output from the first and second NAND gates 30 and 31, respectively, are the first and second on / off control signals.
Of the first MOS-FET 11 and the second MOS-FET 12 respectively.
11 and the second MOS-FET 12 is the AC input voltage V _AC
ON / OFF control is performed alternately every half cycle. As described above, the DC output voltage _VDC output from both ends of the smoothing capacitor 16 is maintained at a constant level, and the AC generator 3
The AC input current I _AC flowing from the to the reactor 10 is controlled in proportion to the _AC input voltage VAC. Alternator 3
Ac input voltage V _AC, including a high-frequency voltage V _N is supplied from
To the AC input voltage V _AC by the low-pass filter circuit 21.
By inputting the fundamental frequency component multiplying circuit 24 extracts a high-frequency current I _N and a high frequency voltage V _N generated in the AC input side is reduced.

In the DC power supply device 4 according to the embodiment shown in FIG. 1, the AC input voltage V
Extracting the fundamental frequency component of the _AC, by input to the multiplier circuit 24 with the difference signal between the reference voltage V _R of the level and the reference power supply 22 of the DC output voltage V _DC, which is detected by the error amplifier 23, the control system It is reduced oscillation phenomenon of the ac input current I _AC and AC input voltage V _AC generated by the delay of the signal transmission, high-frequency current I _N and a high frequency voltage V _N is reduced which occurs to the AC input side. Therefore, it is possible to improve the efficiency by reducing unnecessary damper circuit for generating a power loss, a high-frequency current I _N and a high frequency voltage V _N generated at the alternating-current input side with low loss. Also, the AC input current I _AC is detected as a voltage corresponding to the current I _AC by the input current detector 19, compares the detected signal V ₂ of the product signal V _M and the input current detector 19 of the multiplier circuit 24 25 compared with to form a PWM modulation signal V _PWM by the PWM comparator 27 in response to the comparison output signal V _P of the comparator 25, a PWM modulation signal V _PWM output from the PWM comparator 27 of the first or second on- off control signal V _G1, V _G2 first or second MOS-FE every half cycle of the ac input voltage V _AC as
The first or second M is given to the gate terminals of T11 and T12.
By on-off controlling the OS-FETs 11 and 12, and controlled in proportion to the AC input current I _AC to the AC input voltage V _AC, it is possible to input power factor to approximately 1.0.

The embodiments of the present invention are not limited to the above embodiments, and various modifications are possible. For example, in the above embodiment, a MOS-FET having a parasitic diode as a switching element constituting the switching circuit 15
(MOS type field effect transistor) is shown, but if a diode is connected in parallel with the switching element, a bipolar type transistor, a J-FET (junction type field effect transistor) or an IGBT (insulated gate type transistor) can be used. Can be used. In the above embodiment, the present invention is applied to the DC power supply 4 for converting the _AC input voltage VAC from the single-phase AC generator 3 to the DC output voltage _VDC. The present invention can also be applied to a DC power supply device that converts each line voltage from a polyphase AC generator having the following phases into a DC output voltage. FIG. 3 shows that the DC power supplies 4A, 4B, and 4C are connected between each line of the three-phase AC generator 32, and the output terminals of the DC power supplies 4A, 4B, and 4C are connected in parallel.
1 shows a DC power supply that supplies a DC output voltage V _O to a load 5 via a C converter 20. In FIG. 3, reference numerals 18A, 18B, and 18C denote U-phase, V-phase, and W-phase, respectively.
Transformers for phase voltage detection of phases 19A, 19B and 19C are U-phase, V-phase and W-phase line current detectors, respectively. The internal configuration of each of the DC power supplies 4A, 4B, 4C connected between the U-V phase, the V-W phase, and the W-U phase is substantially the same as the DC power supply 4 shown in FIG. Illustration is omitted. Also, in the DC power supply device shown in FIG. 3, the first and second MOSs in the DC power supply devices 4A, 4B, and 4C between the respective phase voltages V _U , V _V , and V _W of the three-phase AC generator 32 and the respective lines.
-FET11A-12A, 11B-12B, 11C-1
First-second, third-fourth, fifth-sixth on / off control signals V _G1 -V _G2 , V _{G3 applied to} each gate terminal of 2C
The timings of -V _G4 , V _G5 -V _G6 are shown in FIGS.
As shown in FIG.

[0018]

According to the present invention, there is no need for a damper circuit or the like for generating power loss, so that the high-frequency current and the high-frequency voltage generated on the AC input side are reduced with low loss and the efficiency of the DC power supply device is improved. can do. Further, since the above-described effect can be obtained only by changing the circuit configuration in the control circuit, it is not necessary to provide a large-sized and large-capacity damper circuit on the AC input side, and the DC power supply device can be downsized. There are advantages.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram showing an embodiment of a DC power supply device according to the present invention.

[2] AC input voltage V _AC of the DC power supply device shown in FIG. 1
And time chart of each ON / OFF control signal V _G1 , V _G2

FIG. 3 is an electric circuit diagram showing another embodiment of the DC power supply device according to the present invention.

FIG. 4 shows the phase voltages V _U ,
Time chart V _V, V _W and the on-off control signal V _G1 ~V _G6

FIG. 5 is an electric circuit diagram showing a DC power supply system using a conventional DC power supply device.

Figure 6 is a waveform diagram showing a high-frequency voltage V _N and a high-frequency current I _N generated at the input side of the DC power supply device in FIG. 5

FIG. 7 is an electric circuit diagram showing an example of a conventional high-frequency countermeasure;

[Explanation of symbols]

1. Drive source, 2. Joint, 3. AC generator (AC power supply), 4. DC power supply, 5. Load, 6.
..Control means, 7..capacitor, 8..resistance,
9 ・ Damper circuit, 10 ・ Reactor, 11 ・ ・
1st MOS-FET (switching element), 11a
..First parasitic diode, 12 second MOS-
FET (switching element), 12a ... second parasitic diode, 13 ... first diode, 14 ...
2nd diode, 15 ... switching circuit, 1
6. Smoothing capacitor, 17. Control circuit, 18.
・ Transformer for input voltage detection, 19 ・ ・ Input current detector (input current detection means), 20 ・ ・ DC-DC converter, 21 ・ ・ Low-pass filter circuit (filter circuit), 22 ・ ・ Reference power supply, 23 ..Error amplifier (output voltage detection means), 24.Multiplication circuit (multiplication means)
25 ··· Comparator (comparing means), 26 ·· Triangle wave oscillation circuit, 27 ··· PWM comparator, 28 ··· Positive / negative judgment circuit, 29 ··· Inverter, 30 ··· First NAN
D gate, 31 second NAND gate, 32
・ Three-phase AC generator (multi-phase AC power supply)

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-10-304669 (JP, A) JP-A-10-191641 (JP, A) JP-A-9-252578 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H02M 7/12 H02M 7/219

Claims (3)

(57) [Claims] 1. A reactor connected to an output line of an AC power supply, a switching circuit including at least one switching element, connected between output lines of the AC power supply, and connected between output terminals of the switching circuit. A smoothing capacitor, and a control circuit that controls ON / OFF of a switching element of the switching circuit according to a DC output voltage between the smoothing capacitors and an AC input voltage supplied from the AC power supply, wherein the control circuit includes: Output voltage detecting means for detecting the level of the output voltage; and multiplying means for outputting a product signal of the AC input voltage and a detection signal of the output voltage detecting means. In a DC power supply device that performs on / off control, the AC power supply is an AC generator having a small power generation capacity; The means outputs a product signal of an output signal of a filter circuit for extracting a fundamental frequency component of the AC input voltage and a detection signal of the output voltage detection means, and the switching of the switching circuit according to the product signal of the multiplication means. By controlling on / off of the element, the AC power from the AC power is converted into DC power of a constant voltage, and the AC input current is proportional to the AC input voltage supplied from the AC power. DC power supply. 2. An input current detection means for detecting the input current as a voltage corresponding to the input current, and a comparison output signal generated by comparing a product signal of the multiplication means with a detection signal of the input current detection means. And a control signal forming means for forming an on / off control signal to be applied to the control terminal of the switching element in accordance with a comparison output signal of the comparing means. The DC power supply device according to claim 1, wherein on / off control of the switching element is performed. 3. A DC power supply device, wherein the DC power supply device according to claim 1 or 2 is connected for each line of a polyphase AC power supply having three or more phases.