JP3973489B2 - Switching power supply - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a switching power supply device that performs power factor improvement.
[0002]
[Prior art]
Switching power supply devices that provide an isolated DC output while improving the power factor of the input can be broadly divided into a 1-converter system and a 2-converter system.
The two-converter system is a system that combines a converter that improves power factor and a converter that provides an isolated DC output.
On the other hand, the single converter method is a method in which one converter has the two functions.
[0003]
An example of the two-converter system is shown in FIG. 80 is a converter that improves the power factor, and 81 is a converter that provides an isolated DC output.
Reference numeral 80 is a boost chopper type power factor correction converter that is generally used. Since the current of the choke 83 becomes equal to the input current due to the circuit configuration, the power factor is improved by controlling the current so as to be similar to the input voltage waveform.
81 is a commonly used forward converter. A pulse voltage generated by switching on and off the input voltage by the switch elements 87 and 88 is added to the primary winding of the transformer 89, and the pulse voltage that is converted in the turn ratio and appears in the secondary winding is passed through the rectifying and smoothing circuit 90 to generate a direct current. Get the output.
[0004]
The 2-converter method has the advantage of high reliability because it combines proven converters. However, since there are two converters, it is inevitable that the number of parts is inevitable.
[0005]
Since the 1-converter system has a single converter as the name suggests, it is possible to avoid an increase in the number of parts like the 2-converter system.
FIG. 15 shows an example of a single converter system, which is a boost type single converter. The operation is as follows.
[0006]
Although there are four operation modes, in mode 1, all the switch elements 101, 102, 103, and 104 are turned on. Since the input voltage is short-circuited by the choke 100, the voltage becomes Vi and the current increases linearly.
In mode 2, the switch elements 101 and 104 are turned off. A current flows through a route of 100 → 102 → 105 → 103, and the direction in which the current flows depends on the polarity of Vi at that time. Whichever the current flows, two of the diodes 106, 107, 108, 109 are turned on, and the secondary winding voltage of the transformer 105 becomes Vo. When the primary and secondary turns ratio is n: 1, the voltage of the primary winding is nVo. The voltage of the choke 100 becomes nVo-Vi, and the current decreases linearly.
In mode 3, as in mode 1, all the switch elements 101, 102, 103, 104 are turned on. The operation is the same as in mode 1.
In mode 4, the switch elements 102 and 103 are turned off. A current flows through a route of 100 → 101 → 105 → 104, and a current flows into the transformer 105 in the opposite direction. The voltage of the choke 100 becomes nVo-Vi, and the current decreases linearly.
[0007]
However, this circuit has a problem that a load short circuit cannot be performed.
As described above, the choke 100 is excited with Vin in modes 1 and 3, and the excitation is reset with nVo−Vin in modes 2 and 4. However, when the load is short-circuited, that is, when Vo = 0, excitation is performed with Vin, and excitation is reset with -Vin. -Reset with -Vin is equivalent to being excited with Vin, that is, the choke 100 is always excited with Vin. Therefore, the choke 100 will eventually be saturated, resulting in an input short circuit and damage.
[0008]
FIG. 16 shows another example of a single converter system, which is a step-down type single converter. The operation is as follows.
There are four operation modes. In mode 1, the switch elements 120 and 123 are turned on. Current flows along the route 120 → 124 → 123, but the direction of current flow depends on the polarity of Vi at that time. Whichever the current flows, two of the diodes 125, 126, 127, 128 are conducting. Since the secondary winding voltage of the transformer 124 becomes Vi / n, the voltage of the choke 129 becomes Vi / n−Vo, and the current increases linearly.
In mode 2, all switch elements are turned off. A current flows along a route of 129 → 130 → 128 → 127, the choke voltage becomes Vo, and the current decreases linearly.
In mode 3, the switch elements 121 and 122 are turned on. Current flows along a route of 121 → 124 → 122, and current flows into the transformer 124 in the opposite direction. The voltage of the choke 129 becomes Vi / n-Vo as in the mode 1, and the current increases linearly.
In mode 4, as in mode 2, all switch elements are turned off. The operation is the same as in mode 2.
[0009]
However, this circuit has a problem that the input current waveform is distorted. This is because the input current stops flowing when the input voltage is low.
As explained earlier, in mode 1 and mode 3, the choke is excited with Vi / n-Vo. Therefore, when Vi / n falls below Vo, the current of the choke 129 cannot be increased, and the current becomes zero. For this reason, input current does not flow.
When viewed at a commercial frequency, the waveform is such that the input current partially becomes zero as shown in FIG.
[0010]
As described above, since the input current does not flow when the input voltage is low in the step-down type, there is a problem that the input current waveform is distorted. In the step-up type, when the load is short-circuited, the excitation of the choke becomes saturated and breaks. There was a problem.
[0011]
[Problems to be solved by the invention]
The present invention provides means for solving the problems in the single converter.
[0012]
[Means for Solving the Problems]
Full-wave rectifier circuit for full-wave rectification of the AC input, a series circuit of an inductor connected to the output of the full-wave rectifier circuit and the first switch element, and a second switch connected in parallel to the first switch element A series circuit of an element, a primary winding of the first transformer and a third switch element, a fourth switch element connected in parallel to the first switch element, a primary winding of the second transformer, and a fifth A series circuit of switch elements; a first rectifier element connected in parallel to a series circuit of a primary winding of an inductor, a second switch element, and a first transformer; an inductor, a fourth switch element, and a second A second rectifying element connected in parallel to the series circuit of the primary winding of the transformer; a third rectifying element and capacitor series circuit connected in parallel to the secondary winding of the first transformer; Transformer secondary winding and capacitor directly SUMMARY by the circuit and a fourth rectifier element connected in parallel with the circuit.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an embodiment of the present invention.
FIG. 1 shows an isolated converter having three operation modes: a boost mode, a step-down mode, and a step-up / step-down mode. Therefore, by combining these operation modes, it is possible to avoid the problems of the step-up type 1 converter and the step-down type 1 converter described above.
[0014]
As indicated by arrows in FIG. 1, the input voltage is Vi and the output voltage is Vo.
Further, the turns ratio of the primary winding and the secondary winding of the transformers 10 and 11 is n: 1.
First, the role of each switch will be described.
[0015]
The switch element 5 is a boost control switch.
In the boost mode, the operation is the same as that of the boost chopper, but the switch element 5 plays the same role as the switch element in the boost chopper.
[0016]
The switch elements 6 and 8 are current changeover switches.
In the case of FIG. 1, when the switch element 5 is turned off, the current of the choke 2 flows either through the switch element 6 to the transformer 10 or through the switch element 8 to the transformer 11. It is the role of the switch elements 6 and 8 to select one of them.
The necessity of the switch elements 6 and 8 is due to the limitation on the excitation period of the transformer. In the case of a choke, there is no problem even if excitation is performed for a period close to 100% of one cycle. On the other hand, in the case of a transformer, considering that there is a danger of saturation and that a high voltage is applied to the switch element due to a high flyback voltage, the excitation period is practically limited to 50 to 60%. .
However, if the input current is to be a sine wave, it is necessary to change the excitation period of the choke from 0% to 100%. Therefore, the maximum excitation period of 50-60% is a major limitation.
In the present invention, this problem is solved by preparing a plurality of transformers and switching between these transformers. In the case of FIG. 1, even if the excitation period of each transformer is 50%, it is possible to ensure a total excitation period of 100%. Accordingly, the switch elements 6 and 8 are alternately turned on and off in one cycle.
[0017]
The switch elements 7 and 9 are step-down control switches.
In the step-down mode, the operation is the same as that of the step-down chopper, but the switch elements 7 and 9 play the same role as the switch element in the step-down chopper.
[0018]
Each operation mode will now be described.
The boost mode will be described first, but before that, the operation of the boost chopper will be described. FIG. 2 is a circuit diagram of the boost chopper.
When the switch element 22 is turned on, the input voltage Vi is applied to the choke 21, and the choke 21 is excited to increase its current linearly. When the switch element 22 is turned off, a current flows through a route of 20 → 21 → 23 → 24 → 20. The voltage of the choke 21 is inverted to become Vo-Vin, and the current decreases linearly.
The voltage and current waveforms of the choke 21 are shown in FIG.
The step-up mode operation of FIG. 1 is basically the same as this, only including an insulating transformer.
[0019]
An on / off pattern of each switch in the boost mode of FIG. 1 will be described.
The step-up control switch 5 serves as a switch in the step-up chopper, and the control is performed by turning it on and off.
The current change-over switches 6 and 8 are always turned on and off alternately with a duty of 50%.
The step-down control switches 7 and 9 are alternately turned on when the step-up control switch is off, and the phase thereof is synchronized with the current selector switches 6 and 8.
FIG. 4 shows an on / off pattern of each switch in the boost mode. FIG. 4 shows two cycles.
[0020]
When the boost control switch 5 is turned on, the input is short-circuited by the choke 2.
Therefore, at this time, if the voltage drop of the bridge diode 1 is ignored, the input voltage Vi is applied to the choke 2.
[0021]
When the step-up control switch 5 is turned off, the current of the choke 2 flows through either the route of the current selector switch 6 → the transformer 10 → the step-down control switch 7 or the route of the current selector switch 8 → the transformer 11 → the step-down control switch 9. . In any case, when a current flows through the primary winding of the transformer, the rectifier diode 12 or 13 on the secondary side becomes conductive.
If the voltage drop of the rectifier diodes 12 and 13 is ignored, the secondary winding voltage of the transformer 10 or the transformer 11 at this time becomes Vo. Therefore, the primary winding voltage of the transformers 10 and 11 is nVo. Therefore, if the voltage drop of the switch elements 6, 7, 8, 9 is ignored, the voltage of the choke 2 becomes nVo-Vi.
[0022]
When the above is shown in the figure, the voltage and current waveforms of the choke 2 shown in FIG. 4 are obtained.
This is only the output voltage Vo converted to the turn ratio by the transformer to become nVo, which is essentially the same operation as the step-up chopper described above.
[0023]
Next, the step-down mode will be described, but before that, the operation of the step-down chopper will be described. FIG. 5 is a circuit diagram of the step-down chopper.
When the switch element 31 is turned on, Vi-Vo is applied to the choke 31, the choke 33 is excited, and its current increases linearly. When the switch element 31 is turned off, a current flows through a route 33 → 34 → 32 → 33. The voltage of the choke 33 is inverted and becomes Vo, and the current decreases linearly.
The voltage and current waveforms of the choke 33 are shown in FIG.
The step-down mode operation of FIG. 1 is basically the same operation as this, only including an insulating transformer.
[0024]
An on / off pattern of each switch in the step-down mode of FIG. 1 will be described.
The step-up control switch 5 is not used in this mode. Always off.
The current change-over switches 6 and 8 are always turned on and off alternately with a duty of 50%.
The step-down control switches 7 and 9 serve as switches in the step-down chopper, and control is performed by turning them on and off. The phase is synchronized with the current selector switches 6 and 8.
FIG. 7 shows an on / off pattern of each switch in the step-down mode. FIG. 7 shows two cycles.
[0025]
First, the operation when the step-down control switches 7 and 9 are turned on will be described.
When the step-down control switch is turned on, the corresponding current changeover switch is turned on as described above. Therefore, the current of the choke 2 flows through either the route of the current changeover switch 6 → the transformer 10 → the step-down control switch 7 or the route of the current changeover switch 8 → the transformer 11 → the step-down control switch 9. Therefore, as described in the step-up mode, the voltage of the choke 2 is nVo-Vi. However, since the step-down mode is used when the input voltage is higher than the output voltage, it is correct to write Vi-nVo.
[0026]
When the step-down control switches 7 and 9 are turned off, the current of the choke 2 flows through either the route of the current changeover switch 6 → the transformer 10 → the diode 3 or the route of the current changeover switch 8 → the transformer 11 → the diode 4. At this time, since the secondary side rectifier diode becomes conductive, the primary winding voltage of the transformer becomes nVo as described in the step-up mode. Therefore, if the voltage drop of the diodes 3 and 4 is ignored, the voltage of the choke 2 is nVo.
[0027]
When the above is shown in the figure, the voltage and current waveforms of the choke 2 shown in FIG. 7 are obtained.
This is just the output voltage Vo converted to a turn ratio by the transformer to become nVo, which is essentially the same operation as the step-down chopper described above.
[0028]
Next, the step-up / step-down mode will be described, but before that, the operation of the step-up / step-down chopper will be described. FIG. 8 is a circuit diagram of the step-up / down chopper.
When the switch element 41 is turned on, Vi is applied to the choke 42, the choke 42 is excited, and its current increases linearly. When the switch element 41 is turned off, a current flows through a route of 42 → 44 → 43 → 42. The voltage of the choke 42 is inverted and becomes Vo, and the current decreases linearly.
The voltage and current waveforms of the choke 42 are shown in FIG.
The step-up / step-down mode operation of FIG. 1 is basically the same operation as this, only including an insulating transformer.
[0029]
An on / off pattern of each switch in the step-up / step-down mode of FIG. 1 will be described. The step-up control switch 5 serves as a switch in the step-up / step-down chopper, and the control is performed by turning it on and off.
The current change-over switches 6 and 8 are always turned on and off alternately with a duty of 50%.
The step-down control switches 7 and 9 are not used in this mode. Always off.
FIG. 10 shows an on / off pattern of each switch in the step-up / step-down mode. FIG. 10 displays two cycles.
[0030]
When the boost control switch 5 is turned on, the input is short-circuited by the choke 2.
Therefore, at this time, if the voltage drop of the bridge diode 1 is ignored, the input voltage Vi is applied to the choke 2.
[0031]
When the boost control switches 7 and 9 are turned off, the current of the choke 2 flows through either the route of the current changeover switch 6 → the transformer 10 → the diode 3 or the route of the current changeover switch 8 → the transformer 11 → the diode 4. At this time, since the secondary side rectifier diode becomes conductive, the primary winding voltage of the transformer becomes nVo. Therefore, if the voltage drop of the diodes 3 and 4 is ignored, the voltage of the choke 2 is nVo.
[0032]
When the above is shown in the figure, the voltage and current waveforms of the choke 2 shown in FIG. 10 are obtained.
This is merely an output voltage Vo converted to a turn ratio by the transformer to become nVo, which is essentially the same operation as the step-up / step-down chopper described above.
[0033]
As described above, the converter of FIG. 1 operates in the same manner as the step-up chopper in the step-up mode, operates in the same manner as the step-down chopper in the step-down mode, and operates in the same manner as the step-up / step-down chopper in the step-up / step-down mode. By simply changing the on / off pattern of each switch element, it is possible to freely select the operation of step-up, step-down and step-up / step-down.
Therefore, it is easy to avoid the step-up type problem that the load cannot be short-circuited. When the load is short-circuited, the choke will not saturate if it is shifted to the step-down mode. Furthermore, the step-down type problem that the input current waveform is distorted can be avoided. When the input voltage is low, the input current can be flowed by operating in the boost mode. Therefore, the waveform is not distorted.
With the present invention, the problem of one converter has been overcome.
[0034]
FIG. 11 shows another embodiment of the present invention.
The only difference from FIG. 1 is the position of the current selector switches 56 and 58, and there is no difference in their functions. Therefore, if it is alternately turned on and off as described above, the operation is exactly the same.
Since the current selector switches 56 and 58 and the diodes 53 and 54 are connected in series, the diodes 53 and 54 may be short-circuited and deleted when the switches 56 and 58 are capable of blocking current in both directions. Is possible. A circuit diagram when the diodes 53 and 54 are deleted is shown in FIG.
[0035]
FIG. 13 shows another embodiment of the present invention.
In FIG. 1, two transformers are used to prevent the transformer excitation period from becoming too long. However, the number of transformers is not limited to two. FIG. 13 shows an expansion so that an arbitrary number of transformers can be used.
By adding circuit blocks 74 and 75, the number of transformers can be increased. Increasing the transformer has the advantage of reducing output ripple. This is because when the number of transformers is two, the voltage of the choke 72 is reversed twice plus or minus in one cycle. However, for example, when the number of transformers is three, the voltage is reversed three times. Accordingly, the ripple current of the choke 72 is reduced, so that the ripple voltage generated when the ripple current flows into the output capacitor 76 is reduced.
This is the same operation and feature as a so-called multi-phase converter.
[0036]
【The invention's effect】
As described above, according to the present invention, it is possible to realize a converter that solves the problem of the conventional single converter system.
First, compared with a conventional step-down type 1 converter, the input current waveform is not distorted, so that the characteristics are improved. Even a large-capacity converter that cannot be applied to the conventional step-down type 1 converter due to a large waveform distortion can be handled by the technique of the present invention.
Compared with the conventional boost type 1 converter, there is an advantage that a special countermeasure circuit for a load short circuit is unnecessary.
In addition, compared with the 2-converter method, there is an advantage that the smoothing filter which is a large component can be reduced. In the 2-converter method, each converter required one set of smoothing filters, for a total of two sets. In the present invention, only one set is sufficient. For this reason, it contributes to size reduction and weight reduction of a product.
[Brief description of the drawings]
FIG. 1 is a circuit diagram of an embodiment of the present invention.
FIG. 2 is a circuit diagram of a boost chopper.
FIG. 3 is a graph of an operation waveform of a boost chopper.
4 is a graph of operation waveforms in the boost mode of FIG. 1. FIG.
FIG. 5 is a circuit diagram of a step-down chopper.
FIG. 6 is a graph of an operation waveform of a step-down chopper.
7 is a graph of operation waveforms in the step-down mode of FIG. 1;
FIG. 8 is a circuit diagram of a buck-boost chopper.
FIG. 9 is a graph of operation waveforms of the step-up / down chopper.
10 is a graph of operation waveforms in the step-up / step-down mode of FIG. 1. FIG.
FIG. 11 is a circuit diagram of another embodiment of the present invention.
FIG. 12 is a circuit diagram of another embodiment of the present invention.
FIG. 13 is a circuit diagram of another embodiment of the present invention.
FIG. 14 is a circuit diagram of a conventional example of a two-converter.
FIG. 15 is a circuit diagram of a conventional example (step-up type) of one converter.
FIG. 16 is a circuit diagram of a conventional example (step-down type) of one converter.
17 is a graph of the input voltage and input current waveforms of FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Full wave rectifier circuit 2 Inductor 3, 4 Rectifier 5-9 Switch element 10, 11 Transformer 12, 13 Rectifier 14 Capacitor 20, 30, 40 Capacitor 21, 33, 42 Inductor 22, 31, 41 Switch element 23, 32 43 Rectifier elements 24, 34, 44 Capacitor 51 Full wave rectifier circuit 52 Inductors 53, 54 Rectifier elements 55-59 Switch elements 60, 61 Transformer 62, 63 Rectifier element 64 Capacitor 71 Full wave rectifier circuit 72 Inductor 73 Switch element 74, 75 circuit block 76 capacitor 80 step-up chopper type power factor correction circuit 81 forward converter 82 full-wave rectifier circuit 83, 93 inductor 84, 87, 88 switch element 85, 91, 92 rectifier element 86, 94 capacitor 89 transformer 90 rectifier smoothing circuit 100 Indak 101 to 104 Switch element 105 Transformer 106 to 109 Rectifier element 110 Capacitor 120 to 123 Switch element 124 Transformer 125 to 128 Rectifier element 129 Inductor 130 Capacitor

Claims (6)

A full-wave rectification circuit that full-wave rectifies the AC input;
An inductor connected to the output of the full-wave rectifier circuit ;
A first switch element connected in series to the inductor;
A second switch element connected to one end of the first switch element and a series circuit of a primary winding of the first transformer ;
A third switch element connected between the series circuit and the other end of the first switch element;
A series circuit of a fourth switch element connected to one end of the first switch element and a primary winding of a second transformer ;
A fifth switch element connected between the series circuit and the other end of the first switch element;
A first rectifier element connected in parallel to a series circuit of a primary winding of the inductor, the second switch element, and the first transformer;
A second rectifying element connected in parallel to a series circuit of a primary winding of the inductor, the fourth switch element, and the second transformer;
A series circuit of a third rectifying element and a capacitor connected in parallel to the secondary winding of the first transformer;
A switching power supply device comprising: a secondary winding of the second transformer; and a fourth rectifying element connected in parallel to a series circuit of the capacitors. A full-wave rectifier circuit for full-wave rectification of an AC input, an inductor connected to the output of the full-wave rectifier circuit, and a first switch element connected in series to the inductor ,
A series circuit of the second switch element and the primary winding of the transformer, a third switch element connected in series to the series circuit, a series circuit of the secondary winding of the transformer and the first rectifier element, and one end of the series circuit Consists of a second rectifying element connected to the connection point of the primary winding and the third switch element, both ends of the series circuit of the second switch element, the primary winding of the transformer and the third switch element A first input terminal pair, the other end of the second rectifier element as a second input terminal, and a circuit having both ends of a series circuit of the secondary winding of the transformer and the first rectifier element as an output terminal pair Provide any number of blocks equal to or greater than 2,
Each circuit block has the output terminal pair connected to both ends of a capacitor, the first input terminal pair connected to both ends of the first switch element, and the second input terminal connected to the full-wave rectifier circuit. And a switching power supply device connected to a connection point of the inductor. A full-wave rectification circuit that full-wave rectifies the AC input;
An inductor connected to the output of the full-wave rectifier circuit ;
A first switch element connected in series to the inductor;
A primary winding of a first transformer connected to one end of the first switch element ;
A second switch element connected between the primary winding of the first transformer and the other end of the first switch element;
A primary winding of a second transformer connected to one end of the first switch element ;
A third switch element connected between the primary winding of the second transformer and the other end of the first switch element;
A series circuit of a first rectifier element and a fourth switch element connected in parallel to a series circuit of the primary winding of the inductor and the first transformer;
A series circuit of a second rectifier element and a fifth switch element connected in parallel to a series circuit of the primary winding of the inductor and the second transformer;
A series circuit of a third rectifying element and a capacitor connected in parallel to the secondary winding of the first transformer;
A switching power supply device comprising: a secondary winding of the second transformer; and a fourth rectifying element connected in parallel to a series circuit of the capacitors. A full-wave rectifier circuit for full-wave rectification of an AC input, an inductor connected to the output of the full-wave rectifier circuit, and a first switch element connected in series to the inductor ,
The primary winding of the transformer, the second switching element the primary winding and one end of which is connected a series circuit of the transformer secondary winding and the first rectifier element, and one end of the primary winding of said transformer said A series circuit of a second rectifier element and a third switch element connected to a connection point of the second switch element, and both ends of the primary circuit of the transformer and the series circuit of the second switch element are connected to the first circuit The other end of the series circuit of the input terminal pair, the second rectifier element and the third switch element is the second input terminal, and the both ends of the series circuit of the secondary winding of the transformer and the first rectifier element. Provide any number of circuit blocks as output terminal pairs of 2 or more,
In each circuit block, the output terminal pair is connected to both ends of a capacitor, the first input terminal pair is connected to both ends of the first switch element, and the second input terminal is connected to the inductor and all the terminals. A switching power supply device connected to a connection point of a wave rectifier circuit. A full-wave rectification circuit that full-wave rectifies the AC input;
An inductor connected to the output of the full-wave rectifier circuit ;
A first switch element connected in series to the inductor;
A primary winding of a first transformer connected to one end of the first switch element ;
A second switch element connected between the primary winding of the first transformer and the other end of the first switch element;
A primary winding of a second transformer connected to one end of the first switch element ;
A third switch element connected between the primary winding of the second transformer and the other end of the first switch element;
A fourth switch element connected in parallel to a series circuit of the inductor and the primary winding of the first transformer;
A fifth switch element connected in parallel to a series circuit of the primary winding of the inductor and the second transformer;
A series circuit of a third rectifying element and a capacitor connected in parallel to the secondary winding of the first transformer;
A fourth winding rectifier connected in parallel with the secondary winding of the second transformer and the series circuit of the capacitor;
A switching power supply device characterized in that the fourth switch element and the fifth switch element are switch elements having bidirectional current interruption capability. A full-wave rectifier circuit for full-wave rectification of an AC input, an inductor connected to the output of the full-wave rectifier circuit, and a first switch element connected in series to the inductor ,
The primary winding of the transformer, the second switching element the primary winding and one end of which is connected a series circuit of the transformer secondary winding and the first rectifier element, and one end of the primary winding of said transformer said The third switch element is connected to the connection point of the second switch element, and the first input terminal pair is connected to both ends of the series circuit of the transformer primary winding and the second switch element, and the third switch An arbitrary number of two or more circuit blocks having the other end of the element as a second input terminal, and the secondary winding of the transformer and the both ends of the series circuit of the first rectifying element as output terminal pairs are provided
In each circuit block, the output terminal pair is connected to both ends of a capacitor, the first input terminal pair is connected to both ends of the first switch element, and the second input terminal is connected to the inductor and all the terminals. Connected to the connection point of the wave rectifier circuit,
A switching power supply device characterized in that the third switch element is a switch element having a bidirectional current interruption capability.

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