JP2014050166A - Dc power supply - Google Patents

Abstract

A DC power supply device capable of protecting a high-speed diode in a circuit is provided.
A rectifier circuit (consisting of high-speed diodes 5 and 6 and general rectifier diodes 7a and 7b) for rectifying an AC voltage from an AC power source 1 and a reactor 2 connected between the AC power source 1 and the rectifier circuit. And switching elements 3 and 4 for short-circuiting / opening the AC voltage from the AC power source 1 through the reactor 2 and a smoothing capacitor 8, one end of which is connected to the connection point of the high-speed diode 5 and the high-speed diode 6. In addition, at the time of the on-control, the open / close means 10 is connected to the high-speed diodes 5 and 6 so that the general rectifier diodes 7c and 7d are connected in parallel, respectively. As a result, when the DC voltage of the smoothing capacitor 8 drops below a predetermined voltage value, the switching means 10 can be turned on to protect the high speed diode.
[Selection] Figure 1

Description

  The present invention relates to a DC power supply device that includes a rectifier circuit that rectifies an AC voltage from an AC power supply, and a switching unit that short-circuits / opens the AC voltage from the AC power supply via a reactor to obtain a DC output voltage. In particular, it relates to protection of a high-speed diode disposed between a reactor and a smoothing capacitor.

  Conventionally, a DC power supply device that converts an AC voltage from an AC power source into a desired DC voltage by using a switching element and short-circuiting / opening the AC voltage from the AC power source via a reactor is compared to a general rectifier diode. A fast recovery diode (hereinafter referred to as a fast diode) having a short reverse recovery time (trr) is used.

  That is, in this type of DC power supply device, when the number of times of switching per power supply cycle is relatively high, when turning on the switching element, through a diode in which a current flows in the forward direction immediately before turning on, In order to suppress an increase in switching loss that occurs when a reverse recovery current flowing in the reverse bias direction of the diode from the smoothing capacitor in which the DC voltage is stored flows through the switching element, a high-speed diode is used.

  High-speed diodes are made by performing processing such as lifetime killer irradiation in order to quickly eliminate carriers generated during forward bias during reverse bias. VF) is high, and further, the device tolerance (IFSM) against surge current is also low.

  Therefore, in a DC power supply with a high-speed diode in the main circuit, the inrush current (surge current) associated with charging the smoothing capacitor flows through the high-speed diode when the power is turned on or when power is restored from a power failure. In view of the above, design consideration is given to surge current (see, for example, Patent Document 1).

  FIG. 8 shows a DC power supply device described in Patent Document 1 that protects a high-speed diode by preventing a surge current from flowing through the high-speed diode during power recovery.

  The DC power supply device shown in FIG. 8 includes a series connection circuit in which a switching arm 201 and a diode 205 connected in antiparallel and a diode 207 are connected in series, a switching arm and a diode in which the switching element 202 and diode 206 are connected in antiparallel. A circuit in which a series connection circuit in which 208 is connected in series is connected in parallel, a reactor 209 connected between a connection point of the switching element 201 and the diode 207 and one end of the AC power supply 1, a switching element 202 and a diode 208, A reactor 210 connected between the connection point of the AC power supply 1 and the other end of the AC power supply 1; a smoothing capacitor 8 and a load 9 connected in parallel between the parallel connection points 213 and 214; The diodes connected between the positive electrode output terminals of 8 It is equipped with a 308 and 309.

  In FIG. 8, a diode 207 and a diode 208 are high-speed diodes, and bypass the reactor 209 and the diode 207, or the reactor 210 and the diode 208, respectively, when the power is turned on or when power is restored from an instantaneous power failure. By flowing the current through the connected bypass diode 308 or 309, the high-speed diodes (diode 207 and diode 208) having a small surge current resistance can be protected. (For details, see Patent Document 1).

JP 2004-72846 A International Publication No. 2012/004927 JP 60-134782 A

  However, in the above-described conventional DC power supply device, the bypass diode that protects the high-speed diode by bypassing the reactor and the high-speed diode is in order when the instantaneous voltage (correctly the absolute value) of the AC voltage becomes higher than the DC voltage. Since it is biased to be in an on state, it cannot be stably operated with a DC voltage lower than the peak voltage of the AC voltage because of circuit characteristics.

  Therefore, a DC power supply device that realizes an operation of increasing the power conversion efficiency by stopping the switching operation of the switching means near the peak phase of the AC voltage and controlling the DC voltage to be lower than the peak voltage of the AC voltage (for example, There is a problem that it cannot be applied to Japanese Patent Application Laid-Open No. H10-228707.

  The present invention solves the above-described conventional problem, and can be controlled to be a DC voltage lower than the peak voltage of the AC voltage without affecting the normal switching operation, and To provide a DC power supply device capable of protecting a high-speed diode in a circuit even when there is a possibility that a large surge current flows through the high-speed diode at the time of the next power recovery due to an instantaneous power failure With the goal.

  In order to solve the above-described conventional problems, a DC power supply device according to the present invention includes a rectifier circuit that rectifies an AC voltage from an AC power supply, and an AC voltage from the AC power supply via a reactor using a single or a plurality of switching elements. Switching means for short-circuiting and opening, a smoothing capacitor provided on the output side of the rectifier circuit, and a switching element and a smoothing capacitor for suppressing a recovery current flowing from the smoothing capacitor to the switching element when the switching element is turned on. And a switching means for switching whether or not a general rectifier diode is connected in parallel to the high-speed diode. The switching means is controlled to be turned off during normal operation of the DC power supply device. The open / close means is controlled to be turned on when the DC voltage is lowered.

  By controlling this switching means, the normal rectifier diode is not connected in parallel to the high-speed diode during normal switching operation, so that the original switching characteristics are not affected. Since a general rectifier diode with a low voltage (VF) is connected in parallel with a high-speed diode, most of the inrush current to the smoothing capacitor is shunted to a general rectifier diode with a high surge current resistance, and an excessive surge current is generated in the high-speed diode. Prevent flow.

The DC power supply device of the present invention controls the forward drop voltage VF by controlling the switching means that is controlled to be turned off during normal operation when the DC voltage drops below a predetermined voltage due to an instantaneous power failure or the like. Low-current rectifier diodes are connected in parallel to high-speed diodes, and inrush current that flows through the smoothing capacitor when power is restored from a power failure can be passed to diodes with high surge current resistance such as general rectifier diodes. Is possible. Therefore, as a high-speed diode, a Si-based fast recovery diode that has a shorter reverse recovery time than a diode that can be used in the past, SiC, GaN, etc. that tend to have a low surge current resistance due to cost-related chip size constraints It is possible to use a wide band gap high breakdown voltage Schottky diode. As a result, it is possible to perform a high-efficiency operation for controlling the DC voltage to be equal to or lower than the peak voltage of the AC power supply, further reduce the switching loss, and configure a DC power supply device with low noise.

The figure which shows the structure of the direct-current power supply device which concerns on Embodiment 1 of this invention. The figure which shows the equivalent circuit when the opening / closing means of the direct-current power supply in Embodiment 1 is OFF The figure which shows the alternating current power supply voltage, direct current voltage, and input current waveform in the direct current power supply device which concerns on the same Embodiment 1. Timing chart showing behavior at momentary power failure in DC power supply according to Embodiment 1 The figure which shows the structure of the DC power supply device which concerns on Embodiment 2 of this invention. FIG. 7 is a diagram illustrating a configuration of a zero-cross detection circuit of the DC power supply circuit and a binary output thereof in the second embodiment, where (a) is a diagram illustrating a configuration example of a zero-cross detection circuit, and (b) is a configuration example of (a). The figure which shows the example of an output signal of a zero cross detection circuit, (c) is a figure which shows another example of a structure of a zero cross detection circuit, (d) is a figure which shows the example of another output signal of the zero cross detection circuit in the example of a structure of (c). The figure which shows another main circuit structure of the DC power supply device which concerns on Embodiment 2 of this invention. The figure which shows the structure of the conventional DC power supply device

  According to a first aspect of the present invention, there is provided a rectifier circuit for rectifying an AC voltage from an AC power supply, a switching means for short-circuiting / opening an AC voltage from the AC power supply via a reactor using a single or a plurality of switching elements, and a rectifier circuit. And a reverse recovery current that flows from the smoothing capacitor to the switching element when the switching element is turned on, comprising a smoothing capacitor provided on the output side and controlling a DC voltage supplied to the load by turning on and off the switching element A high-speed diode connected between the switching element and the smoothing capacitor, and switching means for switching whether or not to connect a general rectifier diode in parallel to the high-speed diode. During operation, the switching means is controlled to be in an off state, and when the DC voltage is lowered Is obtained by a structure for controlling the switching means in the ON state.

  As a result, the DC power supply device of the present invention does not affect the original switching characteristics because the general rectifier diode is not connected in parallel to the high-speed diode during normal switching operation. Since a general rectifier diode with a low forward drop voltage VF is connected in parallel to the high-speed diode, most of the inrush current to the smoothing capacitor is passed through the general rectifier diode with a high surge current resistance, and an excessive surge is applied to the high-speed diode. It is possible to prevent a current from flowing.

  According to a second invention, in the first invention, the general rectifier diode connected in parallel to the high-speed diode is configured by a part or all of the diode elements of the diode bridge for general rectification. It is possible to adopt a package with low heat resistance and excellent heat dissipation that allows attachment of fins and the like, and can further withstand the surge current.

According to a third invention, in the first or second invention, there is provided a DC voltage detecting means for detecting the DC voltage, and the DC voltage obtained by the DC voltage detecting means is equal to or lower than a predetermined voltage value. The maximum current value of the inrush current to the smoothing capacitor that is assumed at the time of recovery from an instantaneous power failure by accurately detecting the DC voltage. Can be accurately controlled.

  According to a fourth invention, in any one of the first to third inventions, when the peak voltage of the AC power supply or the absolute value thereof is a specified voltage value or less for a predetermined time or more, the DC voltage Even if the detection accuracy of the DC voltage detection means is insufficient, such as when the DC voltage detection means is faulty, by detecting the power outage state of the AC power supply, Fast diodes can be reliably protected.

  A fifth invention is the invention according to any one of the first to third inventions, wherein the opening / closing means is constituted by a normally-on-type relay or a semiconductor switch. Even when the control unit or control power supply to be driven stops operating, it is possible to reliably prevent surge current from flowing through the high-speed diode, and a separate auxiliary power source is required to drive the control unit and switching means. The high-speed diode can be protected without any trouble.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a diagram showing a configuration of a DC power supply device according to the first embodiment of the present invention.

  As shown in FIG. 1, this DC power supply device is connected in series with a reactor 2 connected to one end of an AC power supply 1 in the same direction, and its series connection point is connected to the other end of the reactor 2. Switching elements 3 and 4, switching elements 3 and 4, high-speed diodes 5 and 6 connected in parallel in the direction in which current flows in the opposite direction, and one end of an AC input terminal connected to the other end of AC power supply 1 And a diode bridge 7 for general rectification connected to form a full-wave rectifier circuit together with the high-speed diodes 5 and 6 (rectification for realizing full-wave rectification with the high-speed diodes 5 and 6 and the diodes 7a and 7b). Circuit 13 (see FIG. 2) and a smoothing capacitor 8 for smoothing the voltage after full-wave rectification of the AC voltage from the AC power source 1 is provided. Supplying a DC voltage to the load 9.

  Further, the DC power supply device of the present embodiment is provided between the connection point of the two high-speed diodes 5 and 6 (same as the connection point of the switching elements 3 and 4) and the other AC input terminal of the diode bridge 7. In addition to the opening / closing means 10 constituted by a relay or the like, the DC voltage detecting means 11 for detecting the DC voltage of the smoothing capacitor 8, and the opening / closing means 10 are turned on or off according to the DC voltage detected by the DC voltage detecting means 11. The control part 12 controlled to a state is provided.

  In the DC power supply device of the present embodiment, the switching element 4 is connected to the AC power supply 1 during a power supply half cycle in which the instantaneous voltage of the AC power supply 1 is positive so that the DC voltage of the smoothing capacitor 8 becomes a desired target voltage. The switching element 3 is turned on and off during the half cycle of the power supply in which the instantaneous voltage is negative.

  As a specific method for controlling the switching elements 3 and 4, a conventionally known method may be used.

For example, in a configuration generally referred to as an active filter, an input current detection means (not shown) is provided, and a switching operation is performed at a relatively high frequency of 20 kHz to 50 kHz or more, so that the input current from the AC power supply 1 is approximately sinusoidal. A method may be used in which the DC output voltage of the smoothing capacitor 8 is controlled to a desired voltage by adjusting the amplitude of the input current while controlling the waveform to be a wavy waveform.

  In addition, the current feedback control of the input current itself is not performed, and the switching elements 3 and 4 are short-circuited / opened several times to several tens of times every half cycle of the AC power supply 1. A method of performing only the voltage feedback control for the DC output voltage of the smoothing capacitor 8 by adjusting the short-circuit width (ON width) may be used.

  Any of the control methods is known and well known, and the presence or absence of DC voltage feedback or input current feedback is not directly related to the present invention, so description of the details of the control method is omitted.

  FIG. 3 is a diagram showing AC voltage, input current, and DC voltage waveforms of the AC power supply 1 in the DC power supply device of the present embodiment.

  As shown in FIG. 3, the DC power supply device of the present invention sets the target value of the DC voltage to a voltage value lower than the peak voltage of the AC power supply 1, thereby switching elements 3 and 4 near the peak voltage of the AC power supply 1. The switching loss is reduced by stopping the switching operation and suppressing the switching frequency per power cycle.

At that time, if the switching stop period is provided in a state where the DC voltage is controlled to be higher than the peak voltage of the AC voltage of the AC power supply 1, the input current is likely to rapidly decrease to zero during the switching stop period. Since the harmonic component in the input current increases, in this DC power supply device, the DC voltage is higher than the peak voltage of the AC voltage of the AC power supply 1 so that the input current flows smoothly and continuously during the switching stop period. Is also controlled to be low. (Since this control is not directly related to the operation of the present invention, detailed description is omitted. For details, see Reference 3.)
FIG. 2 is a diagram showing an equivalent circuit of the main circuit configuration during normal operation in the DC power supply device of the present embodiment. That is, the control unit 12 has a circuit configuration as shown in FIG. 2 by turning off the switching means 10 during normal operation and disconnecting the diodes 7c and 7d from the power supply circuit.

  During the positive power supply half cycle of the AC power supply 1, a current flows alternately to the switching element 4 or the high-speed diode 5 by turning the switching element 4 on and off. Therefore, when the switching element 4 is turned on by the recovery characteristic of the high-speed diode 5 The reverse recovery current is suppressed.

  During the negative power supply half cycle of the AC power supply 1, current flows alternately to the switching element 3 or the high-speed diode 6 by turning on / off the switching element 3, so that when the switching element 3 is turned on by the recovery characteristic of the high-speed diode 6 The reverse recovery current is suppressed.

  Next, a method for controlling the opening / closing means 10 in the DC power supply according to the present embodiment will be described.

  FIG. 4 is a diagram showing the behavior at the time of an instantaneous power failure in the DC power supply device of the present embodiment.

  If an instantaneous power failure occurs in the AC power supply 1 during the operation of the load 9, no power is supplied from the AC power supply 1 to the smoothing capacitor 8, while the load 9 has a DC voltage higher than the voltage necessary for the operation of the load 9. In order to continue to operate as long as possible, the voltage of the smoothing capacitor 8, that is, the DC voltage, decreases according to the size of the load 9.

  The control unit 12 constantly monitors the DC voltage by the DC voltage detecting means 11, and turns on the switching means 10 when the DC voltage reaches a predetermined lower limit voltage level (V1 level in FIG. 4) or less, and the forward voltage drop. By connecting the general rectifier diodes 7c and 7d having a low (VF) in parallel with the high-speed diodes 5 and 6, respectively, current is prevented from flowing through the high-speed diodes 5 and 6, and the high-speed diodes 5 and 6 are substantially almost ineffective. Turn into.

  The lower limit voltage level V1 is determined in advance so that the maximum inrush current that can flow to the smoothing capacitor 8 when the AC power supply 1 is restored does not exceed the surge withstand capability of the high-speed diodes 5 and 6.

  Thereby, at the power recovery timing of the AC power supply 1, when the DC voltage is equal to or higher than the lower limit voltage level V1, only the inrush current less than the surge current resistance flows through the high speed diodes 5 and 6, and the DC voltage is lower than the lower limit voltage level. When the level is less than V1, most of the inrush current flows through the general rectifier diodes 7a and 7b having a surge current resistance larger than that of the high-speed diodes 5 and 6, so It is possible to prevent the high-speed diodes 5 and 6 from being broken due to current flowing.

  Furthermore, if the general rectifying diode bridge 7 is connected to a heat sink or the like, the heat dissipation capability is improved, so that the surge current tolerance of the diode bridge 7 against the inrush current to the smoothing capacitor 8 can be further improved.

  Further, the control unit 12 prevents the chattering of the opening / closing means 10 at the timing when the DC voltage rises above the return voltage level (V2 level in FIG. 4) set to a voltage higher than the lower limit voltage level V1. Return to the off state.

  When the DC voltage is reduced, the operation of the diode having poor recovery characteristics continues until the DC voltage recovers to the recovery voltage level or higher, so that the capacity of the smoothing capacitor 8 is large and the DC voltage is increased. It is assumed that the period until the return voltage level is reached becomes longer. In such a case, the frequency and amount of switching noise may be reduced by limiting the number of times of switching or temporarily stopping the switching operation compared to during normal operation until the DC voltage reaches the return voltage level. It is even better to suppress.

  Further, when the switching means 10 is configured with a 1b contact relay or the like and has normally-on characteristics, the voltage of the control unit 12 and a control power source (not shown) for driving the switching means 10 is insufficient. In this case, since the opening / closing means 10 can be kept on, the control power source for driving the opening / closing means 10 can be constituted by the DC voltage of the smoothing capacitor 8.

  When the opening / closing means 10 has a normally-off characteristic, the controller 12 and the opening / closing means 10 are driven using an external auxiliary power supply or the like, and the opening / closing means 10 is preceded when the DC power supply is turned on. Can be controlled to ON.

  As described above, the DC power supply according to Embodiment 1 controls the switching means 10 to be turned on when the DC voltage drops due to an instantaneous power failure or the like, and the forward voltage drop voltage is applied to the high-speed diodes 5 and 6. Since the general rectifier diodes 7c and 7d having a low VF are connected in parallel, most of the inrush current associated with the charging of the smoothing capacitor 8 can be shunted to the general rectifier diodes 7c and 7d when power is restored. In addition to the protection of 6, the surge current flowing through the high-speed diodes 5 and 6 can be limited to a low level.

Therefore, it is possible to employ a high-speed diode having a smaller surge current resistance than that of the prior art and a shorter reverse recovery time (trr), and the switching loss and switching noise of the DC power supply device can be further reduced.

  In addition, wide-gap SiC and GaN high-voltage Schottky diodes with excellent recovery characteristics tend to be smaller in chip size and lower in surge current resistance due to price constraints, etc. Even when a diode is used, the present invention is very effective.

  In the DC power supply according to the first embodiment, the type of diode connected in parallel to the high-speed diodes 5 and 6 has been described as a general rectifier diode. However, if the assumed surge current withstand is small, the protection target It goes without saying that the same effect can be obtained if the forward drop voltage VF is smaller than that of the high-speed diodes 5 and 6 and the surge current withstand capability is large.

(Embodiment 2)
FIG. 5 is a diagram showing a configuration of a DC power supply device according to the second embodiment of the present invention.

  As shown in FIG. 5, this DC power supply device includes a rectifier circuit 13 composed of a general rectifier diode connected to the AC power supply 1 so as to full-wave rectify the AC voltage from the AC power supply 1, and the rectifier circuit 13. And the other end of the reactor 2, the switching element 3 connected between the other end of the reactor 2 and the DC output terminal (-) of the rectifier circuit 13, and the other end of the reactor 2. In the one-step boost type circuit composed of the high-speed diode 5 connected between the smoothing capacitors 8, one of the general rectification diode bridge 14 and the general rectification diode bridge 14 connected in parallel to both ends of the smoothing capacitor 8 or Opening / closing means 10 connected between both AC input terminals and the anode of the high-speed diode 5 (in FIG. 5, the opening / closing means 10 is connected to both AC input terminals) It described the case).

  Since the on / off control timing of the opening / closing means 10 is the same as that of the first embodiment, the detailed description thereof is omitted, but the DC power supply device of the present embodiment is a direct current according to the first embodiment. Similar to the power supply device, the high-speed diode 5 can be prevented from being destroyed by flowing the inrush current that flows when charging the smoothing capacitor 8 at the time of recovery to the side of the general rectifier diodes 14a and 14b having a large surge current withstand capability.

  Also, if the inrush current at power-on cannot be ignored, such as when the AC voltage of the AC power source 1 is assumed to be high due to power supply circumstances, or when the capacity of the smoothing capacitor 8 is large, the following is performed. That's fine. That is, as shown in FIG. 5, an inrush current prevention circuit 15 including an inrush current prevention resistor 15a such as PTC and a relay 15b connected in parallel to the inrush current prevention resistor 15a is separately connected to the AC power source 1 and smoothed. Provided between the capacitors 8, when the power is turned on, the current peak of the inrush current to the smoothing capacitor 8 is suppressed via the inrush current prevention resistor 15a, and then the relay 15b is turned on several seconds later to invalidate the inrush current prevention resistor 15a. do it.

  Since this content is well known, a detailed description is omitted (see Reference 3 for details).

  Further, as another determination method for determining the timing for controlling the opening / closing means 10 to be on, the DC voltage drop is estimated by the time during which the AC voltage of the AC power source 1 is low (power failure state) and the opening / closing means 10 is It is also possible to turn it on, and the method is described below.

  FIG. 6 is a diagram showing the configuration of the zero-cross detection circuit 16 that recognizes whether or not the AC voltage of the AC power supply 1 is lower than a predetermined voltage threshold value and outputs a binary signal, and the binary signal output.

  The zero cross detection circuit 16 shown in FIG. 6A includes a resistor 16a for adjusting a voltage threshold in a binary output AC voltage, a photocoupler 16b for insulation with the control unit 12, and the like. As shown in FIG. 6 (b), a zero cross detection signal is output that outputs H when the voltage of the AC power supply 1 is lower than the predetermined voltage Vth, and outputs L when the voltage is equal to or higher than the predetermined voltage Vth.

  As another circuit example, in the zero cross detection circuit 16 shown in FIG. 6 (c), as shown in FIG. 6 (d), when the absolute value of the voltage of the AC power supply 1 becomes less than a predetermined voltage Vth, H output, When the voltage becomes equal to or higher than the predetermined voltage Vth, a zero cross detection signal that outputs L is output.

  The control unit 12 always detects the time during which the L output of the zero cross detection signal continues, and when the L output continues for a predetermined period or longer, a level at which a large surge current may flow when the voltage of the AC power supply 1 is restored. It is determined that the DC voltage has decreased until the switching means 10 is turned on.

  In the DC power supply device according to the present embodiment, a general single-step boost type circuit has been described as the main circuit configuration. However, the same reactor, switching element, and high-speed diode as the single-step boost type are described. The present invention can be similarly applied to an interleave type circuit in which a set is provided and driven with a phase difference.

FIG. 7 is a diagram showing a configuration when the DC power supply device of the present invention is applied to another main circuit configuration (interleave method). (The control unit 12 is not shown)
As shown in FIG. 7, the switching means 10a, 10b are connected to the two high-speed diodes 5a, 5b in such a manner that the general rectifier diodes 14a, 14b each composed of a general rectifier diode bridge 14 are connected in parallel. Provided.

  As is apparent from FIG. 7, the opening / closing means 10a and 10b are turned on / off at the same timing as the opening / closing means 10 of the DC power supply device of the first embodiment, so that the smoothing capacitor from the AC power supply 1 is used. Since the inrush current to 8 flows separately into the reactor 2a-general rectifier diode 14a and the reactor 2b-general rectifier diode 14b, it goes without saying that the same effect as that of the DC power supply device of the first embodiment is obtained.

  As described above, the DC power supply according to the present invention safely protects a high-speed diode that is vulnerable to surge current by connecting a general rectifier diode in parallel with a high-speed diode when the DC voltage drops due to an instantaneous power failure or the like. Air conditioners, refrigerators, washing machines, heat pump water heaters, etc. that convert AC voltage from an AC power source to DC voltage by short-circuiting / opening with a switching element via a reactor and supplying power to the load It can be widely applied to various uses.

DESCRIPTION OF SYMBOLS 1 AC power supply 2 Reactor 2a Reactor 2b Reactor 3 Switching element 3a Switching element 3b Switching element 4 Switching element 5 High speed diode 6 High speed diode 7 Diode bridge 7a, 7b General rectifier diode 7c, 7d General rectifier diode 8 Smoothing capacitor 9 Load 10 10a Open / close means 10b Open / close means 11 DC voltage detection means 12 Control unit 13 Rectifier circuit 14 Diode bridge 14a General rectifier diode 14b General rectifier diode

Claims (5)

Provided on the output side of the rectifier circuit, the rectifier circuit that rectifies the AC voltage from the AC power source, the switching means that short-circuits / opens the AC voltage from the AC power source via the reactor using a single or multiple switching elements In a DC power supply device comprising a smoothing capacitor and controlling a DC voltage supplied to a load by turning on and off the switching element, the switching element for suppressing a reverse recovery current flowing from the smoothing capacitor to the switching element when the switching element is turned on A high-speed diode connected between a smoothing capacitor and a single or a plurality of switching means for switching whether or not a general rectifier diode is connected in parallel to the high-speed diode. During operation, the switching means is controlled to be in an off state, and the DC voltage is lowered. DC power supply unit and controls the switching means to the ON state to. 2. The DC power supply device according to claim 1, wherein the general rectifier diode is configured by a part or all of a diode element of a general rectifier diode bridge connected in parallel to a high-speed diode. DC voltage detection means for detecting the DC voltage is provided, and when the DC voltage obtained by the DC voltage detection means falls below a predetermined voltage value, it is determined that the DC voltage is in a lowered state. The DC power supply device according to claim 1 or 2, wherein 4. The DC voltage is judged to be in a lowered state when the peak voltage of the AC power supply or the absolute value thereof falls below a specified voltage value for a predetermined time or more. The direct-current power supply device according to item 1. 5. The DC power supply device according to claim 1, wherein the opening / closing means has a normally-on characteristic.

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