Power supply apparatus

Abstract

A POWER SUPPLY APPARATUS IS PROVIDED WITH A FIRST BRIDGE RECTIFIER CIRCUIT (5) CONNECTED TO A THREE-PHASE ALTERNATING CURRENT POWER SUPPLY (1) VIA FIRST REACTORS (2, 3, 4), AND A SMOOTHING CAPACITOR (13) THAT SMOOTHES A DIRECT CURRENT OUTPUT OF THE FIRST BRIDGE RECTIFIER CIRCUIT (5) . A SECOND BRIDGE RECTIFIER CIRCUIT (6) IS CONNECTED TO ALTERNATING CURRENT INPUT TERMINALS OF THE FIRST BRIDGE RECTIFIER CIRCUIT (5) VIA SECOND REACTORS (7, 8, 9), CAPACITORS (10, 11, AND 12) ARE PROVIDED RESPECTIVELY BETWEEN EACH TWO TERMINALS OF ALTERNATING CURRENT INPUT TERMINALS OF THE SECOND BRIDGE RECTIFIER CIRCUIT (6), AND DIRECT CURRENT OUTPUT TERMINALS OF THE SECOND BRIDGE RECTIFIER CIRCUIT (6) ARE RESPECTIVELY CONNECTED IN PARALLEL TO DIRECT CURRENT OUTPUT TERMINALS OF THE FIRST BRIDGE RECTIFIER CIRCUIT (5) . THUS, IT IS POSSIBLE TO REDUCE A HARMONIC CURRENT AND IMPROVE AN INPUT POWER FACTOR WITH A SIMPLE CONFIGURATION. THE MOST ILLUSTRATIVE DRAWING IS FIGURE 1

Description

The present invention relates to a power supply apparatus that converts a three-phase AC power supply to a DC power supply, reduces harmonic currents flowing in the three-phase AC power supply, and improves an input power factor. Conventionally, the most basic power supply that converts three-phase AC to DC is a power supply that performs so-called three-phase full-wave rectification, which combines a bridge rectifier circuit consisting of six diodes and a DC reactor attached to the DC output. widely used as a standard. However, such a simple type of power supply cannot improve the power factor above a certain level, and the adverse effect of the generated harmonic current on the power system has been a problem. Therefore, in recent years, for the purpose of improving the power factor and reducing the harmonic current, a power supply apparatus has been developed that converts the current of a three-phase AC power supply into a DC current by approximating it to a sine wave. Such a power supply device generally employs a method in which the switching element is driven at several kHz to ten and several kHz, and the current flowing through the switching element is controlled at high speed to follow a target reference sinusoidal waveform. However, such a method has problems such as a large number of parts, complicated control means, noise generation, and high cost. On the other hand, in a power supply device that does not use a switching element, an AC reactor is inserted on the AC input side as a commonly used means for improving the power factor and reducing harmonics. However, in order to comply with overseas harmonic current regulations, it is necessary to set the inductance of the AC reactor to several tens of milliseconds. In this case, there is a problem that the DC voltage drops significantly as the load increases, and the input power factor deteriorates as a lagging power factor, so the scope of application was limited. Therefore, in recent years, in addition to realizing circuit simplification and low cost for power supply devices having switching elements, it is possible to prevent DC voltage drop and power factor deterioration at high load compared to simple AC reactor application, and harmonics A power supply device capable of reducing current (hereinafter referred to as a high power factor power supply device) has been proposed. For example, as a high power factor power supply device that combines conventional passive components to improve the power factor and reduce harmonic currents, a bridge rectifier circuit consisting of six diodes connected to a three-phase AC power supply and this bridge rectifier Between the three capacitors connected in parallel to the three diodes on the positive output side of the circuit, and the three capacitors connected between the AC input terminals of the diode bridge and the three-phase AC power supply. A power supply device has been proposed that includes three reactors that form a resonant circuit with a frequency equal to the frequency of a three-phase AC power supply (see, for example, Japanese Patent Application Laid-Open No. 2002-369530). A conventional high power factor power supply will be described below with reference to the drawings. FIG. 22 is a diagram showing the configuration of a conventional high power factor power supply apparatus that obtains DC power from a three-phase AC power supply disclosed in Japanese Unexamined Patent Application Publication No. 2002-369530. The diode bridge 50 of this high power factor power supply device consists of three diodes D1, D2 and D3 on the positive output side and three diodes D4, D5 and D6 on the negative output side. Capacitors C1, C2 and C3 are connected in parallel to the diodes D1, D2 and D3 on the positive output side, respectively. Between U-phase power supply Ug of three-phase AC power supply 1 consisting of U-phase, V-phase and W-phase and first power supply input terminal u of diode bridge 50 (connection point between anode of diode D1 and cathode of diode D4) A first reactor L1 is inserted in series. Similarly, a second reactor L2 is inserted between the V-phase power supply Vg and the second power supply input terminal v (connection point between the anode of the diode D2 and the cathode of the diode D5). Furthermore, a third reactor L3 is inserted between the W-phase power supply Wg and the third power supply input terminal w (connection point between the anode of the diode D3 and the cathode of the diode D6). The diode bridge 50 has a positive output side connected to the output terminal OUT1 and a negative output side connected to the output terminal OUT2. When the output terminal OUT2 is grounded, the DC voltage of the power supply becomes a positive voltage. The DC voltage is smoothed by a smoothing circuit including, for example, a reactor Lf and a capacitor Cf, and supplied to the load resistor RL. In the conventional high power factor power supply device configured as described above, the phase currents iu, iv, and iw flowing through the power supply input terminals u, v, and w by the phase power supplies Ug, Vg, and Wg of the three-phase AC power supply 1 are , the current becomes a sinusoidal wave despite the rectification by the diodes D1 to D6. This sinusoidal current will be described using the U-phase as an example. FIG. 23 shows waveforms for explaining the current flowing through the u-phase first power input terminal u of the diode bridge 50, the diodes D1 and D4, and the capacitor C1 and the power waveform of the three-phase AC power supply 1 by the U-phase power supply Ug. It is a diagram. Also, FIG. 24 is a current path diagram for explaining the U-phase current iu by the U-phase power supply Ug. Here, each output voltage of each phase power supply Ug, Vg, Wg (hereinafter referred to as "U phase voltage, V phase voltage, W phase voltage") eu, vu, wu It is shown like Formula (3). eu=Em×sinωt (1) ev=Em×sin(ωt-2π / 3) (2) ew=Em×sin(ωt-4π / 3) (3) In equations (1), (2) and (3), Em is the maximum value of each phase voltage, the unit of angle is radian, ω is each frequency of the three-phase AC power supply 1, t is the time. As shown in FIG. 23, when the U-phase voltage eu is negative, the V-phase voltage ev is positive and the W-phase voltage ew is positive. and Therefore, as shown in FIG. 24(a), at time t0, the diode D4 becomes conductive and the current id4 flows from the negative output side. The forward voltage drop Vf of diode D4 is assumed to be approximately 0 volts. On the other hand, the diode D1 is blocked, and the absolute value current Ic of the current ic (hereafter, the current Ic represents the absolute value of the current ic) flows from the positive electrode output side to the capacitor C1 as a charging current. C1 is charged with the terminal connected to the positive output side as a positive potential. Therefore, the current id4 and the current ic form the U-phase current iu that flows from the power supply input terminal u to the U-phase power supply Ug via the reactor L1, and the absolute value Iu of the U-phase current iu (hereafter, the U-phase current Iu is represents the absolute value of the U-phase current iu), resulting in the following equation (4). Iu=id4+Ic (4) In equation (4), the U-phase current iu and the current ic of the capacitor C1 are indicated by absolute values ​​(Iu, Ic) in order to clarify the direction of current flow. Also, the absolute value voltage of the U-phase voltage eu is defined as voltage Eu. In the following description, absolute values ​​of current and the like are used to clarify the direction of current flow and the like. Also, let the charging voltage of the capacitor C1 be voltage Vc. Before time t0, the capacitor C1 is already charged, as will be described later. After time t0, capacitor C1 is further charged by current Ic and voltage Vc rises to its maximum value. After that, when the U-phase voltage eu becomes positive, the current Ic changes from the charging current of the capacitor C1 to the discharging current as shown in FIG. 24(b). At this time, the U-phase current Iu is given by the following formula (5). Iu=Ic-id4 (5) Let time tc be the time when the current Ic changes from the charging current to the discharging current. At this time tc, as shown in FIG. 23, the V-phase voltage ev is lower than the U-phase voltage eu. As a result, the diode D5 to which the V-phase voltage ev is applied soon becomes conductive, and the current id4 flowing through the diode D4 begins to flow through the diode D5, and the diode D4 cuts off. Thus, the time at which diode D4 cuts off is t1. At this time t1, the anode-cathode voltage of the diode D4 becomes a reverse voltage. If this reverse voltage is Vr, Vr is negative. In this manner, during the period from time t0 to time t1, a resonance current resonating with the power supply frequency flows through the resonance circuit composed of the reactor L1 and the capacitor C1. Hereinafter, a resonant circuit that resonates at the power supply frequency will be described as a "resonant circuit". After the time t1, the diode D4 is cut off and the current Ic of the capacitor C1 has already become the discharge current of the voltage Vc, as described above. Here, as shown in FIG. 24(c), the diode D1 connected in parallel with the capacitor C1 has a positive voltage on the cathode side and cuts off the voltage until the capacitor C1 is completely discharged. Therefore, in this period, the U-phase current Iu and the current Ic are equal to each other, resulting in the state shown in the following formula (6). Iu=Ic (6) When capacitor C1 eventually finishes discharging, diode D1 conducts and current id1 flows. The time at which the diode D1 conducts in this way is t2. On the other hand, in the period from time t1 to time t2, the reverse voltage Vr of the diode D4 gradually rises from 0V as the voltage Vc decreases due to the discharge of the capacitor C1. In this manner, a resonant current flows through the resonant circuit of reactor L1 and capacitor C1 during the period from time t1 to time t2. As described above, when the capacitor C1 finishes discharging and the current id1 flows through the diode D1 (after the time t2), the voltage Vc (the same voltage as the forward voltage drop Vf of the diode D1) becomes almost 0 volts. Become. At this time, the U-phase current Iu and the current absolute value Id1 are equal (hereinafter, the current Id1 represents the absolute value of the U-phase current id1), and the state is expressed by the following formula (7). Then, the U-phase current iu (current id1) is supplied from the output terminal OUT1 to the load. Iu=Id1 (7) Eventually, the polarity of U-phase current iu is reversed. Let t3 be the time at which the polarity of the U-phase current iu reverses. 25 is an equivalent circuit diagram showing the configuration of the resonance circuit in the state of (d) of FIG. 24. FIG. As described above, from time t2 to time t3, reactor L1 does not form a resonant circuit with capacitor C1. However, in diode bridge 50, as shown in FIG. 25, reactor L2 and capacitor C2 act as resonant circuits in the V phase, and reactor L3 and capacitor C3 act as resonant circuits in the W phase. Therefore, V-phase and W-phase resonant currents (currents from the input power supply terminals v and w), which are currents flowing out from the power supply input terminals v and w, flow to the power supply input terminal u via the reactor L1. . In this manner, a resonant current flows through reactor L1 during the period from time t2 to time t3. In FIG. 25, blocking diodes are omitted, and only conductive diodes are shown. Also, since the diode D1 is conducting, the capacitor C1 does not act as a capacitor, so it is omitted from the drawing. Also at time t3, the polarity of the U-phase current iu is reversed and the diode D1 is cut off. Furthermore, even after the time t3, the diode D4 is still not conducting, so the (charging) current ic flows in the capacitor C1 toward the power supply input terminal u, and the voltage Vc rises. This current becomes the U-phase current iu. Therefore, in this period, the U-phase current Iu and the current Ic are equal to the following formula (8). Iu=Ic (8) On the other hand, the reverse voltage Vr is applied to the diode D4 after the time t1. Assuming that the DC voltage generated at the output terminals OUT1 and OUT2 is V10, the DC voltage V10 is given by the following equation (9). V10=Vc+Vr (9) Here, the DC voltage V10 is obtained by outputting the voltage having the highest absolute value among the instantaneous voltages generated at the power supply input terminals u, v, and w by the U-phase voltage eu, V-phase voltage ev, and W-phase voltage ew. Therefore, the DC voltage V10 becomes a voltage linked not only to the U-phase voltage eu but also to the V-phase voltage ev and the W-phase voltage ew. Therefore, the reverse voltage Vr blocking the diode D4 also temporarily rises in association with the V-phase voltage ev and the W-phase voltage ew. However, as the voltage Vc increases and the DC voltage V10 decreases, the reverse voltage Vr of the diode D4 decreases to 0 volts. Then, the polarity of the voltage between the anode and cathode of diode D4 is reversed and diode D4 becomes conductive. Let t4 be the time at which the diode D4 conducts. At time t4, capacitor C1 continues to be charged by current ic. As described above, during the period from time t3 to time t4, a resonant current flows through the resonant circuit of reactor L1 and capacitor C1. Here, the operating state of diode bridge 50 at time t4 is the same as the operating state of diode bridge 50 at time t0, and capacitor C1 is already in a charged state at time t0 as described above. In this manner, the diode bridge 50 repeats the operation during the period from time t0 to time t4. As described above, in the conventional power supply, the U-phase current iu becomes a sinusoidal wave due to the resonance circuit, and similarly, the V-phase current iv and the W-phase current iw also become sinusoidal currents. As a result, it is possible to reduce the generation of harmonic currents. By appropriately selecting the inductances of reactors L1, L2, and L3 and the constants of capacitors C1, C2, and C3 according to the load capacity, it is possible to make the input power factor nearly 1 at rated load. JP-A-2002-369530 However, in the configuration of the conventional power supply device described above, the capacitor connected in parallel with the reactor and the diode is used to clear the IEC (International Electrotechnical Commission) harmonic regulation and to achieve an input power factor of 99% or more at rated load. Selecting constants, the inductance of the reactor should be 30~40mH. For this reason, the conventional power supply has the problem that the parts are large and the cost is high. The present invention solves the problems of conventional power supply devices. An object of the present invention is to provide a power supply device that can avoid an increase in the size of a reactor. To achieve the above object, a power supply device according to the present invention includes a three-phase AC power supply, a first bridge rectifier circuit connected to the three-phase AC power supply via a first reactor, and a first bridge rectifier. Simple configuration by providing a second bridge rectifier circuit connected from the AC input end of the circuit via a second reactor, and a capacitor between each terminal of the AC input end of the second bridge rectifier circuit can reduce the harmonic current and improve the input power factor. A power supply device according to a first aspect of the present invention comprises a three-phase AC power supply, a first reactor provided for each phase of the three-phase AC power supply, and a power supply via the three-phase AC power supply and the first reactor. a first bridge rectifier circuit having a plurality of diodes connected together; a second reactor provided for each phase of an AC input terminal of the first bridge rectifier circuit; A second bridge rectifier circuit connected from an input terminal via the second reactor is provided, and the DC output terminals of the first bridge rectifier circuit and the second bridge rectifier circuit are connected in parallel and smoothed. A capacitor and a load are connected in parallel, and the capacitor is connected between terminals of the AC input terminal of the second bridge rectifier circuit. The power supply device of the first aspect configured in this manner can reduce harmonic current and improve the input power factor. Further, the power supply device of the first aspect can obtain the same harmonic suppression effect even if the inductance value is small, so that the drop in the DC output voltage is small. A power supply device according to a second aspect of the present invention is particularly provided with an opening / closing section between the first bridge rectifier circuit and the second reactor according to the first aspect. The power supply device of the second aspect configured in this manner can switch between the operation of a three-phase full-wave rectification power supply device and the operation of a high power factor power supply device. A power supply device according to a third aspect of the present invention is particularly provided with an input current detection unit in the power supply device according to the second aspect, and the opening / closing unit is controlled according to the input current detected by the input current detection unit. Configure. The power supply device of the third aspect configured in this manner can reduce harmonic current and improve the input power factor in normal operation, and can prevent DC voltage rise at light load and It is possible to prevent an accompanying decrease in input power factor and an increase in harmonic current. A power supply device according to a fourth aspect of the present invention is particularly provided with an output power detection unit in the power supply device according to the second aspect, and the opening / closing unit is controlled according to the output power detected by the output power detection unit. Configure. The power supply device of the fourth aspect configured in this manner can reduce harmonic current and improve the input power factor in normal operating conditions, and can prevent a DC voltage rise at light load and It is possible to prevent an accompanying decrease in input power factor and an increase in harmonic current. A power supply device according to a fifth aspect of the present invention, particularly the power supply device according to the second aspect, is provided with a DC current detection section for detecting a current flowing through a load, and according to the DC current detected by the DC current detection section, is configured to control the opening / closing portion. The power supply device of the fifth aspect configured as described above opens the opening and closing portion when, for example, the detected DC current falls below a predetermined value, thereby reducing the harmonic current in the normal operating state and reducing the input power factor. can be improved, and it is also possible to prevent a rise in the DC voltage at a light load, a decrease in the input power factor associated therewith, and an increase in harmonic current. A power supply device according to a sixth aspect of the present invention is particularly characterized in that the power supply device according to the second aspect is provided with a pre-charging control section, and the pre-charging is performed in order to suppress the current flowing through the capacitor when the opening / closing section is turned on. The opening / closing unit is configured to be controlled by a control unit. The power supply device of the sixth aspect configured in this manner can prevent generation of an excessive current flowing through the capacitor when the opening / closing portion is turned on. A power supply device according to a seventh aspect of the present invention is particularly characterized in that a series circuit of an extension capacitor and an extension capacitor opening / closing section is provided between each terminal of the AC input terminals of the second diode bridge in the second aspect, and the series A circuit is connected in parallel with each of said capacitors connected to the AC input of said second diode bridge. The power supply device of the seventh aspect configured as described above can prevent a DC voltage drop by switching the capacitor capacity according to the load, and can select appropriate constants for improving the input power factor and reducing the harmonic current. becomes. The power supply device according to the eighth aspect of the present invention is particularly the power supply device according to the seventh aspect, provided with a DC voltage detection section for detecting the voltage across the load, and detecting the DC voltage detected by the DC voltage detection section. is configured to control the opening / closing portion of the extension capacitor. The power supply device of the eighth aspect configured in this way can prevent a drop in the DC voltage and a drop in the input power factor under heavy load. A power supply device according to a ninth aspect of the present invention is particularly provided with an input current detection unit in the power supply device according to the seventh aspect, and controls the expansion capacitor opening / closing unit according to the input current detected by the input current detection unit. It is configured to The power supply device of the ninth aspect configured in this way makes it possible to prevent a drop in the DC voltage and a drop in the input power factor during a heavy load. A power supply device according to a tenth aspect of the present invention is particularly provided with an output power detection unit in the power supply device according to the seventh aspect, and controls the expansion capacitor opening / closing unit according to the output power detected by the output power detection unit. It is configured to The power supply device of the tenth aspect configured in this manner can prevent a drop in the DC voltage and a drop in the input power factor during a heavy load. The power supply device according to the eleventh aspect of the present invention is particularly provided with a DC current detection unit in the power supply device according to the seventh aspect, and controls the expansion capacitor opening / closing unit according to the DC current detected by the DC current detection unit. It is configured to The power supply device of the eleventh aspect configured in this manner can prevent a drop in the DC voltage and a drop in the input power factor during a heavy load. A power supply device according to a twelfth aspect of the present invention is particularly provided in the power supply device according to the seventh aspect with an additional capacitor precharging control unit to suppress the current flowing through the additional capacitor when the additional capacitor opening / closing unit is turned on. For this reason, the expansion capacitor switching section is controlled by the expansion capacitor precharging control section. The power supply device of the twelfth aspect configured in this manner can prevent the generation of an excessive current flowing through the extension capacitor when the extension capacitor opening / closing portion is turned on. A power supply device according to a thirteenth aspect of the present invention is particularly the power supply device according to the first aspect, wherein when the current flowing through the reactor reaches a predetermined value or more, the inductance of the reactor changes according to the current flowing through the reactor. A reactor having a saturation characteristic such that the is lowered is used as the first reactor. The power supply device of the thirteenth aspect configured in this manner can prevent DC voltage drop during heavy load. A power supply device according to a fourteenth aspect of the present invention, particularly in the power supply device according to the first aspect, uses a three-phase reactor in which windings are applied to three legs of one iron core as the reactor. The power supply device of the fourteenth aspect configured in this manner allows the reactor to be made smaller and lighter. The power supply device of the present invention is a simple three-phase full-wave rectifier circuit using three reactors and one bridge rectifier circuit, with three reactors, one bridge rectifier circuit and three capacitors added. The input current can be made sinusoidal by the configuration to reduce harmonic currents, and the input power factor can be improved, making it possible to reduce the size of the reactor compared to conventional high power factor power supply devices. Moreover, the power supply device of the present invention can obtain the same harmonic suppression effect as the conventional power supply device even if the inductance value is small, so that the drop in the DC output voltage is small. While the novel features of the invention are as particularly pointed out in the appended claims, the invention, both as to organization and content, together with other objects and features, will be appreciated by reading the following detailed description in conjunction with the drawings. , will be better understood and appreciated. Circuit diagram showing the configuration of the power supply device of Embodiment 1 according to the present invention Waveform diagram of each part in the power supply device of Embodiment 1 according to the present invention Waveforms of other parts of the power supply device of Embodiment 1 according to the present invention Waveform diagram of each part in the power supply device of Embodiment 1 according to the present invention Explanatory diagram of current paths at time t0 in the power supply device of Embodiment 1 according to the present invention Power supply device of Embodiment 1 according to the present invention Explanatory diagram of current paths at time t1 to t2 in the power supply device according to the first embodiment of the present invention Explanatory diagram of current paths at time t2 in the power supply device according to the first embodiment of the present invention Explanatory diagram of current paths at time t3 in the power supply device according to the first embodiment of the present invention Current path explanatory diagram at time t4 of the power supply device of Embodiment 1 according to the present invention Current path explanatory diagram at time t5 of the power supply device of Embodiment 1 according to the present invention Input power in the power supply device of Embodiment 1 according to the present invention A characteristic diagram showing the input power factor of the power supply device according to the first embodiment of the present invention A characteristic diagram showing a harmonic current with respect to the input power in the power supply device according to the first embodiment of the present invention Input voltage and input at rated load in the power supply device according to the first embodiment of the present invention Waveform diagram of current Circuit diagram showing the configuration of the power supply device according to Embodiment 2 of the present invention Diagram showing changes in input power factor with respect to operation of the opening / closing part and input power in the power supply device according to Embodiment 2 of the present invention A circuit diagram showing the configuration of a power supply device according to Embodiment 3 of the present invention A characteristic diagram showing input current versus input power in the power supply device according to Embodiment 1 of the present invention Configuration of a power supply device according to Embodiment 4 of the present invention A circuit diagram showing a configuration of a power supply device according to a fifth embodiment of the present invention A circuit diagram showing a configuration of a power supply device according to a sixth embodiment of the present invention A circuit diagram showing a configuration of a power supply device according to a seventh embodiment of the present invention Circuit diagram showing the configuration Circuit diagram showing the configuration of the conventional power supply Waveform diagram of each part of the conventional power supply Explanatory diagram of the current path of the conventional power supply Equivalent circuit diagram omitting the blocking diode of the conventional power supply Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. The present invention is not limited to the configurations described in the following embodiments, but includes configurations based on similar technical ideas. Embodiment 1 Hereinafter, a power supply device according to Embodiment 1 of the present invention will be described with reference to FIGS. 1 to 13. FIG. FIG. 1 is a circuit diagram showing the configuration of a power supply device according to Embodiment 1 of the present invention. In FIG. 1, a three-phase AC power supply 1 is a commercial power supply, and the output terminals of the U-phase, V-phase, and W-phase are connected to reactors 2, 3, and 4, respectively. Hereinafter, the U-phase, V-phase, and W-phase refer to the output terminals of this three-phase AC power supply 1, and the voltage between UV, the voltage between VW, and the voltage between UW are also the lines between the output terminals of the three-phase AC power supply 1. shall refer to the voltage between As shown in Figure 1, the reactors 2, 3, 4 are the AC input of the first diode bridge 5, which is the first bridge rectifier circuit composed of six diodes 5a, 5b, 5c, 5d, 5e, 5f Connected to ends u1, v1, w1. Further, the power supply device of Embodiment 1 is provided with a second diode bridge 6 which is a second bridge rectifier circuit connected in parallel with the first diode bridge 5 . The second diode bridge 6 consists of six diodes 6a, 6b, 6c, 6d, 6e, 6f. Reactors 7 , 8 , 9 are connected between AC input terminals u 1 , v 1 , w 1 of the first diode bridge 5 and AC input terminals u 2 , v 2 , w 2 of the second diode bridge 6 . Capacitors 10, 11 and 12 are connected between the AC input terminals u2, v2 and w2 of the second diode bridge 6, respectively. The DC output terminal of the first diode bridge 5 and the DC output terminal of the second diode bridge 6 are connected in parallel. The first diode bridge 5 and the second diode bridge 6 are connected in parallel with an electrolytic capacitor 13, which is a smoothing capacitor, and configured to supply a load 14 with a DC voltage. The operation of the power supply device according to the first embodiment configured as described above will be described using FIG. 2 to FIG. 10, taking the U phase as a representative example. 2, 3, and 4 show operation waveforms of respective parts in the power supply device of the first embodiment. 2, 3 and 4, the voltage between UV, the voltage between VW and the voltage between UW are the line voltages at the output end of the three-phase AC power supply 1, respectively, and the voltage between UV and the voltage between UW are the U phase side. is positive, and the V-phase side of the V-W voltage is shown as positive. In FIG. 2, Vc10, Vc11, and Vc12 represent voltages between terminals of capacitors 10, 11, and 12, respectively, and the same polarity as the above-mentioned line voltage is indicated as positive. In FIGS. 2, 3 and 4, Ic10, Ic11 and Ic12 indicate currents flowing through the capacitors 10, 11 and 12, respectively. The currents flowing through the respective capacitors 10, 11, 12 are indicated as being positive when flowing into the respective capacitors 10, 11, 12 from the positive direction of the above-mentioned line voltage. 2, 3 and 4, I5a, I5b, I5c, I5d, I5e, I5f, I6a, I6b, I6c, I6d, I6e and I6f are the diodes 5a and 5b in the first diode bridge 5, respectively. , 5c, 5d, 5e, 5f and the currents through the diodes 6a, 6b, 6c, 6d, 6e, 6f in the second diode bridge 6. FIG. In the voltage between UV, voltage between VW, and voltage between UW shown in Fig. 2, Fig. 3 and Fig. 4, time is the zero point where the U-phase voltage changes from negative to positive, that is, when the voltage between VW shows the maximum value on the positive side. The time t0 is defined as t0, and the time up to the point where the VW voltage becomes zero is divided into times t1 to t5, and each state transition will be described. 5 to 10 are equivalent circuit diagrams showing a simplified circuit configuration of the power supply device from time t0 to time t5. 5 to 10, diodes that are not conducting are omitted. Also, the direction of the current flowing through the first diode bridge 5 to the electrolytic capacitor 13 and the load 14 is indicated by a solid arrow, and the current flows through the second diode bridge 6 to the electrolytic capacitor 13 and the load 14. The direction of the flowing current is indicated by a dotted arrow. In the following description, the path through which the current is supplied to the electrolytic capacitor 13 and the load 14 via the first diode bridge 5 is defined as the "main current path", and the current is supplied through the second diode bridge 6 to the electrolytic capacitor 13 and the load The path for supplying current to 14 is called the "auxiliary current path". The state of the power supply device of the first embodiment at time t0 will be described below using the equivalent circuit diagram of FIG. At time t0, the voltage across VW is the maximum, so it exceeds Vdc, which is the voltage across the terminals of electrolytic capacitor . In the first diode bridge 5, the diodes 5b and 5f are conductive to form a main current path. On the other hand, as will be described later, at time t0, the capacitor 11 has already been charged to a voltage of approximately Vdc, and the diodes 6b and 6f in the second diode bridge 6 are conducting. Also, at 60° before time t0, that is, at the time when the UV-to-UV voltage reaches its maximum value on the negative side, the capacitor 10 is similarly charged to a voltage of approximately V dc on the negative side, and the reactor 8, the diode 6b, the electrolytic Since the current was flowing through the auxiliary current path via the capacitor 13, the diode 6d and the reactor 7, the current continues to flow due to the energy storage effect of the reactor 7 and the reactor 8, and the diode 6d is in a conductive state at time t0. ing. Therefore, the voltage across capacitors 10, 11, and 12 is in a state where any of the diodes connected to them are conducting. is charged to the negative side with a voltage of approximately Vdc, and the capacitor 11 is charged to the positive side with a voltage of approximately Vdc. Also, the capacitor 12 is in a state where the voltages across it are substantially equal, that is, substantially 0 volts. The current flowing through the auxiliary current path from reactor 8 to diode 6b, electrolytic capacitor 13, diode 6d and reactor 7 decreases and eventually becomes zero. When the current flowing through this auxiliary current path becomes zero, the diode 6d becomes non-conductive, and the power supply device of the first embodiment assumes the state of the equivalent circuit shown in FIG. This state is assumed to be time t1. Focusing on the voltages of the capacitors 10 and 12, changes in the current flowing through the second diode bridge 6 will now be described. As described above, since the diode 6d stops conducting at time t1, the U-phase AC input terminal u2 connected to the diode 6d becomes unstable. is charged to a voltage of approximately Vdc. In addition, since the voltage across UW is positive, it exceeds Vdc between the V-phase AC input terminal v2 and the W-phase AC input terminal w2 (W-phase power supply), and the voltage from reactor 2 to reactor 7, capacitor 10, diode Current flows through 6b, electrolytic capacitor 13, diode 5f, and reactor 4, causing capacitor 10 to discharge. In this case, the slope of the current flowing through the capacitor 10 depends on the resonance frequency due to the capacity of the reactors 2 and 7 and the capacitor 10 because the terminal voltage Vdc of the electrolytic capacitor 13 is substantially constant. A current obtained by adding a substantially constant current flowing through the reactor 8 to the discharging current of the capacitor 10 flows through the diode 6b. The discharge of capacitor 10 causes the voltage across capacitor 10 to go to 0 volts. That is, the voltages of the U-phase AC input terminal u2 and the V-phase AC input terminal v2 become equal. As a result, the capacitor 12, which was in a state of approximately 0 volts, is charged to the same voltage as the capacitor 11, namely approximately Vdc. At this time, the path of the charging current is reactor 2, reactor 7, capacitor 12, reactor 9, and reactor 4. The slope of the charging current in this case depends on the resonance frequency due to the capacity of the reactor 2, the reactor 7, and the capacitor 12, because the current flowing through the reactor 9 operates at a substantially constant current for the reason described later. This charging current does not pass through the second diode bridge 6, but is included in the substantially constant current flowing through the reactor 9, so that the current flowing through the diode 6f changes from the substantially constant current state to the capacitor 12 shows a waveform as if the charging current of Then, when the capacitor 12 is charged to a voltage of approximately Vdc, the diode 6a becomes conductive, resulting in the equivalent circuit shown in FIG. This time is assumed to be time t2. Since the voltage Vdc across electrolytic capacitor 13 decreases due to load 14, current flows from conductive diode 6a to electrolytic capacitor 13 simultaneously with charging capacitor 12, and the voltage across capacitor 12 and electrolytic capacitor 13 drops below Vdc. A current flows through the reactor 7 so that the voltage is the same. The current waveform until the capacitor 12 is charged has a slope that depends on the resonance frequency due to the capacity of the reactor 7 and the capacitor 10 . At this point, a constant current is flowing through the reactor 8 . Here, in the auxiliary current path, the fact that the current flowing through the reactor 8 becomes a substantially constant current operation will be described. At this point, the diodes 5b and 6b connected to the V-phase AC input terminals v1 and v2, which are both ends of the reactor 8, are both conducting, and the voltage drop caused by the diode 5b and the voltage drop caused by the diode 6b are almost equal, the voltage across the reactor 8 will be equal and the voltage drop across the reactor 8 can be viewed as 0 volts. It is known that the voltage across the reactor is given by the following equation (10). VL=L×di / dt (10) In equation (10), VL is the voltage across the reactor, L is the inductance of the reactor, and i is the current flowing through the reactor. Therefore, it can be seen that di / dt=0 at this point, ie constant current operation. On the other hand, in the charging operation of the capacitor 11, the same operation as the charging operation of the capacitor 12 described above is performed, and current flows through the reactor 8. This operation is performed. Therefore, when the charging operation of the capacitor 11 is completed, that is, when the diode 6b becomes conductive, the current flowing through the reactor 8 becomes the current value of the constant current operation. As described above, the current modes that flow through the reactor in the auxiliary current path include a current mode that depends on the resonance frequency of the reactor and capacitor capacitance when charging and discharging the capacitor (hereafter referred to as a charge / discharge mode), and a three-phase mode that uses a diode. There are two current modes: a constant current mode (hereinafter referred to as constant current mode) that utilizes the conduction of any two phases. In the constant current mode, the condition is that the diodes in the second diode bridge 6 are conductive, so the condition is that the power supply voltage exceeds the terminal voltage Vdc of the smoothing capacitor 13. is required to flow. Therefore, when there is no load, that is, when the terminal voltage Vdc of the electrolytic capacitor 13, which is a smoothing capacitor, is equal to the maximum value of the power supply voltage, the constant current mode does not exist. It can be seen that a resonance current flows. Next, when the UW voltage exceeds Vdc, the diode 5a conducts with a delay caused by the reactor 2, and current flows through the main current path composed of the electrolytic capacitor 13 and the diode 5f. This time is assumed to be time t3. FIG. 8 is an equivalent circuit of the power supply device of Embodiment 1 at time t3. As shown in FIG. 8, at time t3, diodes 5a, 5b, 6a, and 6b across reactors 7 and 8 are all conducting, so the currents flowing through reactors 7 and 8 are both constant currents. mode. Then, although the voltage across VW becomes lower than Vdc, current continues to flow due to the energy storage effect of reactor 3 . When the current eventually becomes zero with a delay, the diode 5b cuts off. After that, due to the energy storage effect of the reactor 8, the current flowing through the diode 6b gradually decreases with a delay, and eventually becomes zero. This time is assumed to be time t4. FIG. 9 is an equivalent circuit of the power supply device of Embodiment 1 at time t4. As in the case described with reference to FIG. 6, the current in the charge / discharge mode starts to flow through the reactor 8 so that the capacitor 10 is charged and the capacitor 11 is discharged for the V-phase AC input terminal v2. As a result, capacitor 10 is charged to a voltage of Vdc and diode 6e conducts. This time is assumed to be time t5. FIG. 10 is an equivalent circuit of the power supply device of Embodiment 1 at time t5. The equivalent circuit shown in FIG. 10 is the same as the state of the equivalent circuit at time t0 described with reference to FIG. 5 with the U phase and V phase interchanged. Therefore, after the state shown in FIG. 10, the transition is made with the U-phase and the V-phase being exchanged, and hence the subsequent description will be omitted. As described above, in the power supply device according to the first embodiment of the present invention, the auxiliary current path composed of the reactor, the capacitor, and the diode bridge is used to perform the charging operation in the charging / discharging mode from the state where the U-phase voltage is zero. Since the current flows, it is possible to extend the period during which the current flows in the power supply, and the effect of improving the power factor can be obtained. Further, the power supply device of Embodiment 1 according to the present invention is configured to keep the current flowing through the auxiliary current path constant in the constant current mode, and allow the remaining current to flow through the main current path. Therefore, the reactor provided in the auxiliary current path can have a lower rated current than the reactor in the main current path. can be made smaller. FIG. 11 shows the inductance of reactors 2, 3, and 4 in the main current path in the power supply device of Embodiment 1 when the input frequency of the three-phase AC power supply 1 is 50 Hz, the input line voltage is 398 V, and the rated power is 6.5 kW. is 15mH, the inductance of reactors 7, 8, and 9 in the auxiliary current path is 20mH, the capacity of capacitors 10, 11, and 12 is 5uF, and the capacity of electrolytic capacitor 13 is 840uF, input power [W] and input power factor [% ] is a characteristic diagram showing the relationship of As can be understood from FIG. 11, in the power supply device of Embodiment 1, the input power factor near the rated power is set to 99% or more, and an input power factor of 95% or more is secured even at a load factor of 1 / 2. I know it's done. The rated input power used as the basis for calculating the load factor is 6500W. The circuit operation in the power supply device of Embodiment 1 has been described above from the viewpoint of the input power factor. Next, the effect of reducing the harmonic current will be described. FIG. 12 is a characteristic showing the relationship between the input power [W] in the power supply device of Embodiment 1 and the ratio of the harmonic current to the IEC harmonic current regulation value (the ratio of the harmonic current to the standard [%]). It is a diagram. Regarding the characteristics shown in FIG. 12, the conditions such as the constants of each part in the power supply device are the same as in the case of FIG. 11 described above. FIG. 12 shows the harmonic currents of the four orders that have the highest ratios to the regulation values ​​of the harmonic currents. Harmonic currents other than the four-order harmonic currents shown in FIG. 12 are smaller than the harmonic currents shown in FIG. According to the characteristic diagram in Fig. 12, even the 5th harmonic, which has the largest ratio to the regulation value, is 80% at maximum, and has a margin of 20% against the regulation value. FIG. 13 shows waveforms of the U-phase voltage eu and the U-phase current Iu at an input of 6.5 kW at the constants set as described above in the power supply device of the first embodiment. As can be understood from Fig. 13, in the power supply device of Embodiment 1, the phases of the current and voltage are almost the same, and the current waveform is sinusoidal. is possible. The effect of improving the input power factor and downsizing of the reactor will be described below by comparing the power supply device of Embodiment 1 and the conventional power supply device. In the conventional power supply, as in the power supply of Embodiment 1, the constant setting at the input voltage of 398 V and the rated power of 6.5 kW is set to an input power factor of 99% or more at the rated load, and the margin for harmonic regulation is 10%. To ensure the above, the inductance of the reactor needs to be about 30mH. On the other hand, in the power supply device of Embodiment 1, since the inductance of the reactors 2, 3, and 4 of the main current path is 15 mH, it is possible to halve the inductance. In addition, in the power supply device of Embodiment 1, the inductance of the auxiliary current path is 35 mH, which is increased. Since a rated current lower than that of the current path is sufficient, the wire diameter of the winding wire can be reduced, and the component dimensions can be reduced. In addition, with conventional power supplies, the input power factor drops to about 90% at a load factor of 1 / 2 under the influence of the phase-leading current of the capacitor when the load is light. Become. As described above, in the power supply device of the first embodiment, it is possible to improve the input power factor and reduce the harmonic current with a smaller reactor than in the conventional power supply device. It is also possible to improve the decrease in the input power factor of In the power supply device of Embodiment 1, the inductance characteristics of the reactors 2, 3, and 4 in the main current path are not particularly defined, but when these reactors 2, 3, and 4 exceed a predetermined current value, The reactors 2, 3 and 4 may be used as so-called supersaturated reactors by setting the inductance to drop from the point. In this case, when the voltage of the three-phase AC power supply 1 drops under heavy load, the DC voltage drop caused by the voltage drop caused by the reactors 2, 3, and 4 is prevented. It is also possible to prevent a decrease in the input power factor due to a phase shift between the input current and the power supply voltage. Furthermore, in the power supply device of Embodiment 1, the reactor is divided into three parts for each of the main current path and the auxiliary current path, and each of the reactors is divided into one iron core and its three legs are wound. It can also be used as a three-phase reactor in configuration. It is widely known that a three-phase reactor takes advantage of the fact that the sum of the currents in each phase is zero, and that less iron core is required to obtain the same inductance than three single-phase reactors. It has advantages and is effective in reducing the size and weight of the entire device. Embodiment 2 A power supply device according to Embodiment 2 of the present invention will be described below with reference to FIGS. 14 and 15. FIG. FIG. 14 is a circuit diagram showing the configuration of the power supply device according to the second embodiment. As shown in FIG. 14, the power supply device of the second embodiment has AC input terminals u1, v1, w1 of a diode bridge 5 and reactors 7, 8 in contrast to the circuit configuration of the power supply device of the first embodiment. , 9 is provided with an opening / closing portion 15 as an opening / closing means. The power supply device of the second embodiment has the same basic circuit operation as the power supply device of the first embodiment, but performs different operations in a light load operation state with a low load factor. The power supply device of the second embodiment is designed to cope with a light load state in which the load factor is low, and is intended to improve the input power factor at the time of the light load. In the power supply device of the second embodiment, if the basic circuit operation is continued with the switching unit 15 closed, the energy supplied by the constant current mode in the reactors 7, 8, and 9 will increase as the load becomes lighter. outweighs the energy consumed by 14. As a result, the current from the main current path through the diode bridge 5 is reduced. That is, since the state is the same as the state in which the diode bridge 5 is not conducting, the proportion of the lead current due to the capacitors 10, 11, and 12 increases with respect to the conduction period of the current flowing through the reactors 2, 3, and 4. It will be. This is clear from the fact that the current flowing through reactors 2, 3, and 4 is only the reactive current of reactors 7, 8, 9 and capacitors 10, 11, and 12 when no load is considered. be. Therefore, in the power supply device of the second embodiment, the reactors 7, 8, 9, the capacitors 10, 11, 12, and the diode bridge 6 are separated by opening the switching unit 15 in the case of operation under light load, and the light load is It is configured to prevent the power factor from deteriorating at times. FIG. 15 is a characteristic diagram showing the relationship between the input power [W] and the power factor [%] when the switching unit 15 is opened and when the switching unit 15 is not opened when operating at an input power of 3 kW or less. be. In FIG. 15, the measurement points when the opening / closing part 15 is opened are indicated by squares (□), and the measurement points when the opening / closing part 15 is not opened are indicated by crosses (X). As shown in FIG. 15, the deterioration of the power factor is prevented by opening the opening / closing unit 15 when the input power is 3 kW or less and the load is light. As described above, in the power supply device of the second embodiment, provision of the opening / closing unit 15 makes it possible to prevent deterioration of the input power factor during light load. (Embodiment 3) Hereinafter, a power supply device according to Embodiment 3 of the present invention will be described with reference to FIGS. 16 and 17. FIG. FIG. 16 is a circuit diagram showing the configuration of the power supply device according to the third embodiment. As shown in FIG. 16, in the power supply device of the third embodiment, an input current detection section 16, which is an input current detection means, is added to the circuit configuration of the power supply device of the second embodiment. In the power supply device of the third embodiment, the basic circuit operation is the same as that of the power supply device of the first embodiment, and the input power factor at light load is improved by opening the switching unit 15. is the same as in the second embodiment. A feature of the power supply device of Embodiment 3 is that the timing to open the opening / closing unit 15 is determined based on the input current. In the explanation of the power supply device according to the second embodiment, the improvement of the input power factor when the switching unit 15 is opened when the input power is around 3 kW under light load has been explained with reference to FIG. 17 is a characteristic diagram showing the relationship between the input power [W] and the input current [A] in the configuration of the power supply device of Embodiment 1. FIG. As shown in Fig. 17, the input current is around 4.5A when the input power is around 3kW at light load. For this reason, in the power supply device of the third embodiment, if the conditions such as the constants of each part are set to be the same as those of the power supply device of the first embodiment, the opening / closing portion 15 is configured to be opened near the input current of 4.5 A. , the same effect as that of the power supply device of the second embodiment can be obtained. Therefore, in the power supply device of the third embodiment, the input current detection section 16 detects the input current, and when the detected current exceeds a predetermined current value, the switching section 15 is automatically opened. be. In the power supply device of Embodiment 3, an example using the input current detection section 16 has been described, but instead of the input current detection section 16, an output power detection section for detecting output power may be provided. In this case, the opening / closing unit 15 is controlled to be opened when the output power detection unit detects output power equal to or lower than a predetermined power value. Further, instead of the input current detection section 16, a DC current detection section for detecting a DC current after rectification may be provided. In this case, control is performed so that the opening / closing unit 15 is opened when the DC current detection unit detects that the DC current is equal to or less than a predetermined DC current. (Embodiment 4) Hereinafter, a power supply device according to Embodiment 4 of the present invention will be described with reference to FIG. FIG. 18 is a circuit diagram showing the configuration of the power supply device according to the fourth embodiment. As shown in FIG. 18, the power supply device of the fourth embodiment is provided with a preliminary charging control section 17, which is preliminary charging control means for controlling the opening / closing section 15, in the circuit configuration of the power supply device of the second embodiment. is. In the power supply device of the fourth embodiment, the operation and effect of improving the input power factor in the normal operating state are the same as those of the power supply device of the first embodiment. Further, in the power supply device of the fourth embodiment, the switching unit 15 is changed from the closed state, which is the conductive state, to the open state for the purpose of preventing the deterioration of the input power factor at the time of light load. performs the same operation and has the same effect. A characteristic feature of the power supply device of Embodiment 4 is the operation of switching the opening / closing unit 15 from the open state to the closed state when the operation state under light load is shifted to the normal operation state. If the switching unit 15 is simply closed, an inrush current from the three-phase AC power supply 1 flows through the capacitors 10, 11, and 12, and there is a risk of deterioration of parts having contacts and blowing of the fuse. The power supply device according to the fourth embodiment solves such problems. That is, in the power supply device of Embodiment 4, when switching unit 15 from the open state to the closed state, preliminary charging control unit 17 gradually increases the period during which the switch is closed (the period during which the conductive state is established). It is controlled so that By controlling in this way, the power supply device of the fourth embodiment prevents rush current. In addition, in order to prevent the rush current, it is also possible to deal with various kinds of control such as gradually changing the resistance value of the connection point in the opening / closing section 15 . (Embodiment 5) Hereinafter, a power supply device according to Embodiment 5 of the present invention will be described with reference to FIG. FIG. 19 is a circuit diagram showing the configuration of the power supply device of Embodiment 5. FIG. As shown in FIG. 19, the power supply device of the fifth embodiment is provided with additional capacitors 18, 19, 20 and additional capacitor opening / closing units 21, 22, 23 in addition to the circuit configuration of the power supply device of the first embodiment. It is a thing. In the power supply device of the fifth embodiment, the operation and effects of improving the input power factor and reducing the harmonic current in the normal operating state are the same as those of the power supply device of the first embodiment. What is characteristic of the power supply device of Embodiment 5 is the effect of preventing the DC voltage from dropping when the input voltage drops or when the load is heavy, and the effect of preventing the input power factor from dropping due to the phase lag of the input current. have. Furthermore, the characteristic feature of the power supply device of Embodiment 5 is that it has the effects of preventing DC overvoltage at light load and preventing input power factor reduction due to advance of the input current phase. In the circuit configuration of the power supply device of Embodiment 1 described above, if the constants of capacitors 10, 11, and 12 are increased in order to prevent a drop in DC voltage, a drop in DC voltage can be prevented by the boosting effect. , there is a problem that the operation of the capacitors 10, 11 and 12 causes the DC voltage to rise when the load is light. Further, increasing the constants of the capacitors 10, 11, 12 increases the proportion of the leading phase current of the capacitors in the input current, resulting in a decrease in the input power factor. Conversely, if the constants of capacitors 10, 11, and 12 are reduced in the circuit configuration of the power supply device of Embodiment 1, the input power factor can be improved and the DC voltage can be prevented from rising during light load. There is a problem that the current phase is shifted and the input power factor deteriorates. In the power supply device of Embodiment 5, the above problem is solved. , 11 and 12 in parallel to prevent a DC voltage drop and compensate for the phase lag of the input current to improve the input power factor. When the constants of capacitors 10, 11, and 12 are set to maximize the input power factor near the rated power, DC voltage drop prevention during input voltage drop or heavy load and input current phase delay It is possible to obtain the effect of preventing a decrease in the input power factor. Further, when the constants of the capacitors 10, 11 and 12 are set to maximize the input power factor at light load, it is possible to obtain the effect of improving the input power factor at light load. (Embodiment 6) Hereinafter, a power supply device according to Embodiment 6 of the present invention will be described with reference to FIG. FIG. 20 is a circuit diagram showing the configuration of the power supply device of Embodiment 6. FIG. As shown in FIG. 20, the power supply device of the sixth embodiment has a DC voltage detector 24 in addition to the circuit configuration of the power supply device of the fifth embodiment. Basic operation of the power supply device of the sixth embodiment is the same as that of the power supply device of the fifth embodiment. Also in the power supply device of the sixth embodiment, by controlling the expansion capacitors 18, 19 and 20 by opening and closing the expansion capacitor opening / closing sections 21, 22 and 23, the same effects as those of the power supply device of the fifth embodiment can be obtained. is obtained. A feature of the power supply device of Embodiment 6 is that the timing of opening the additional capacitors 18, 21, 20 is automatically controlled by the DC voltage across the electrolytic capacitor 13, which is a smoothing capacitor. It should be noted that the control of the timing of opening the extension capacitors 18, 21, and 20 may be performed based on the input current instead of the DC voltage, or may be performed based on the DC current. Alternatively, the same effect can be obtained by controlling the timing of opening the additional capacitors 18, 21, and 20 according to the output power. (Embodiment 7) Hereinafter, a power supply device according to Embodiment 7 of the present invention will be described with reference to FIG. FIG. 21 is a circuit diagram showing the configuration of the power supply device of Embodiment 7. FIG. As shown in FIG. 21, the power supply device of the seventh embodiment includes an additional capacitor preliminary charging control unit 25 for controlling the additional capacitor opening / closing units 21, 22, and 23 in the circuit configuration of the power supply device of the fifth embodiment. is provided. In the power supply device of the seventh embodiment, the operation and effects related to input power factor improvement and DC overvoltage prevention are the same as those of the power supply device of the fifth embodiment. What is characteristic of the power supply device of Embodiment 7 is the operation when the additional capacitor opening / closing sections 21, 22, and 23 are changed from the open state to the closed state. If the expansion capacitor switching parts 21, 22, and 23 are simply closed, the inrush current from the three-phase AC power supply 1 will flow through the expansion capacitors 21, 22, and 23, causing deterioration of parts with contacts, Fuse may blow. The power supply device of Embodiment 7 prevents rush current from flowing into the extension capacitors 21, 22, and 23 from the three-phase AC power supply 1 when the extension capacitor opening / closing sections 21, 22, and 23 are closed. . In the power supply device of Embodiment 7, when the extension capacitor switching units 21, 22, and 23 are switched from the open state to the closed state, the extension capacitor precharging control unit 25 controls the extension capacitor switching units 21, 22, and 23. The inrush current is prevented by gradually lengthening the closing period, which is the period during which the is conducting. In addition, in order to prevent the rush current, it is also possible to deal with various kinds of control such as gradually changing the resistance value of the connection point in the additional capacitor opening / closing units 21, 22, and 23. FIG. Although the preferred form of the invention has been described with a certain degree of detail, the present disclosure of the preferred form is subject to variations in details of construction, and variations in the combination and order of elements are within the scope of the claimed invention. It can be implemented without departing from the scope and spirit. By using the power supply device of the present invention as a DC power supply device or as a power supply device in the preceding stage of a compressor drive device, it is possible to reduce harmonic currents and improve the input power factor, so that the power supply equipment can be effectively utilized. It becomes a useful device that does not adversely affect other load facilities.

Claims

A first bridge having a three-phase AC power supply, a first reactor provided for each phase of the three-phase AC power supply, and a plurality of diodes connected to the three-phase AC power supply via the first reactor. a rectifier circuit, a second reactor provided for each phase of the AC input terminal of the first bridge rectifier circuit, and a circuit connected from the AC input terminal of the first bridge rectifier circuit via the second reactor. has a second bridge rectifier circuit with The DC output terminals of the first bridge rectifier circuit and the second bridge rectifier circuit are connected in parallel, and the smoothing capacitor and the load are connected in parallel. A power supply with a capacitor connected to 2. The power supply device according to claim 1, further comprising an opening / closing section provided between said first bridge rectifier circuit and said second reactor.

3. The power supply device according to claim 2, further comprising an input current detection section, and configured to control the switching section according to the input current detected by the input current detection section.

3. The power supply device according to claim 2, further comprising an output power detection section, and configured to control the switching section according to the output power detected by the output power detection section.

3. The power supply device according to claim 2, further comprising a DC current detection section for detecting current flowing through a load, and configured to control the switching section according to the DC current detected by the DC current detection section.

3. The power supply device according to claim 2, further comprising a preliminary charging control section, wherein the opening and closing section is controlled by the preliminary charging control section in order to suppress current flowing through the capacitor when the opening and closing section is turned on. A series circuit of an extension capacitor and an extension capacitor switch is provided between each terminal of the AC input terminal of the second diode bridge, and the series circuit is connected to the AC input terminal of the second diode bridge.

3. The power supply according to claim 2, connected in parallel with each other.

8. The power supply device according to claim 7, further comprising a DC voltage detection section for detecting voltage across a load, and configured to control the extension capacitor opening / closing section according to the DC voltage detected by the DC voltage detection section.

8. The power supply device according to claim 7, further comprising an input current detection section, and configured to control the extension capacitor opening / closing section according to the input current detected by the input current detection section.

8. The power supply device according to claim 7, further comprising an output power detection section, and configured to control the extension capacitor opening / closing section according to the output power detected by the output power detection section.

8. The power supply device according to claim 7, further comprising a direct current detection section, and configured to control the extension capacitor opening / closing section according to the direct current detected by the direct current detection section. An extension capacitor pre-charging control unit is provided, and the extension capacitor switching unit is controlled by the extension capacitor pre-charging control unit in order to suppress current flowing through the extension capacitor when the extension capacitor switching unit is turned on.

8. The power supply device according to item 7.

2. The reactor according to claim 1, wherein a reactor having saturation characteristics such that the inductance of the reactor decreases according to the current flowing through the reactor when the current flowing through the reactor reaches or exceeds a predetermined value, is used as the first reactor. power supply.

2. The power supply device according to claim 1, wherein a three-phase reactor in which three legs of one iron core are respectively wound is used as the reactor.