JP2002233151A - Switching power circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-efficiency switching power circuit by providing a snubber circuit which reduces its power loss to suppress an increase in the number of components, for a plurality of switching-type converters which are operated in parallel using interleave technique. SOLUTION: One-side ends of a first snubber capacitor 25 and a second snubber capacitor 35 are connected to a junction between a first primary coil 21 and a first switching means 23, and to a junction between a second primary coil 31 and a second switching means 33, respectively. From their other-side ends to a positive electrode of an input DC power source 1, a first diode 26 and a third diode 36 are connected, respectively. A second diode 27 and a fourth diode 37 form a series circuits together with an inductance means 6 respectively and the series circuits are connected between the other-side ends of individual snubber capacitors 25, 35 and a negative electrode of the power source 1. By adopting above configuration, it becomes possible to suppress surge voltage which are applied to the switching means by using a small number of components.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for various electronic devices, and is a switching type converter for supplying a controlled power to a load. In particular, the switching units are connected in parallel and each switch means is sequentially turned on and off with a predetermined time difference. The present invention relates to a switching power supply circuit including a plurality of switching converters.

[0002]

2. Description of the Related Art Conventionally, this type of switching power supply circuit has a configuration as shown in FIG. In FIG. 8, reference numeral 1 denotes an input DC power supply, 2 denotes a first switching type converter, and a first transformer 20 having a first primary winding 21 and a first secondary winding 22; It has a switch means 23 and a first output diode 24. Reference numeral 3 denotes a second switching type converter, which includes a second transformer 30 having a second primary winding 31 and a second secondary winding 32, second switching means 33, and a second output diode. 34. Reference numeral 7 denotes an output capacitor, which smoothes rectified voltages output from the first and second output diodes 24 and 34 and supplies an output DC voltage to the load 8. A control circuit 9 turns on and off the first and second switch means 23 and 33 so as to stabilize the output DC voltage.

First, when the first switch means 23 is turned on, a current flows from the input DC power supply 1 to the first primary winding 21 of the first transformer, the first switch means 23, and the input DC power supply 1. Flows, and magnetic energy is stored in the first transformer 20. When the first switch means 23 is turned off, the magnetic energy stored in the first transformer 20 becomes the first 2
The current is discharged from the next winding 22 as a current for charging the output capacitor 7 via the first output diode 24. The power is transmitted from the input DC power supply 1 to the output capacitor 7 by repeating the ON / OFF operation of the first switch means 23 as described above. Next, the operation of the second switching type converter 3 is the same as the operation of the first switching type converter 2, so that the description of the basic operation will be omitted.

[0004] The voltage of the output capacitor 7, that is, the output DC voltage, can be controlled by the ratio between the on-time and the off-time of the first and second switch means 23 and 33. The control circuit 9 detects the output DC voltage and determines the ON time and the OFF time so as to stabilize the output DC voltage.
3 and 33 are turned on and off. Further, the control circuit 9 includes a first switch 23 and a second switch 3
3 is set so as to have a time difference of a half switching cycle. Thereby, the period during which the operating current of each switching type converter flows is dispersed, the ripple frequency of the ripple current of the input DC power supply 1 and the output capacitor 7 is doubled, and the peak value and the effective value are reduced. That is, the input DC power supply 1, the output capacitor 7, and the input / output filters associated therewith can be made smaller than when the switching power supply circuit is constituted by a single switching type converter. Such a technique of operating a plurality of switching converters in parallel with a predetermined time difference is called an interleaving technique.

[0005]

However, in such a conventional switching power supply circuit, there is a problem that a surge voltage generated when the switch means is turned off is increased, which causes a deterioration in efficiency. The parallel operation of switching converters is limited when the shape, especially the height, of the components that make up the switching converter is limited and the purpose is to share the power handled to reduce the size and height of the components. Is big. However, the downsizing and low profile of the transformer which requires insulation properties cause loose coupling between the primary winding and the secondary winding, and increase the leakage inductance. As a result, a surge voltage generated at both ends of the switch means when the switch means is turned off increases switching loss, resulting in efficiency deterioration. Although a surge voltage absorbing circuit called a snubber circuit is installed as means for suppressing such a surge voltage, there is a problem that the number of parts increases if each surge converter is installed for each switching type converter.

[0006] The present invention relates to a plurality of switching converters operated in parallel using interleaving technology.
An object of the present invention is to provide a high-efficiency switching power supply circuit by providing a snubber circuit in which the power loss is reduced while suppressing an increase in the number of parts by sharing constituent components.

[0007]

In order to solve this problem, a switching power supply circuit according to the present invention comprises an inductance unit and one end provided at a connection point between a primary winding of a transformer of each switching type converter and a switch unit. Are connected to each other, a diode is connected in a direction in which a current flows from the other end of each snubber capacitor to one end of the input DC power supply, and a series circuit is formed with the inductance means to connect the other end of each snubber capacitor to the input DC power supply. And a diode connected between the other ends of the power supply.

Further, a switching power supply circuit of the present invention
In a switching power supply circuit in which first and second switching type converters are connected in parallel to perform an interleaving operation, one end is connected to a connection point between a primary winding of a transformer of the first switching type converter and a switch means. One snubber capacitor, a second snubber capacitor having one end connected to a connection point between a primary winding of a transformer of the second switching type converter and the switch means, and a snubber capacitor connected between the other ends of the respective snubber capacitors. And a snubber circuit including a first diode and a second diode connected in a direction in which a charging current flows from both ends of the inductance means to the input DC power supply.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

(First Embodiment) FIG. 1 is a circuit diagram showing a configuration of a switching power supply circuit according to a first embodiment of the present invention. In FIG. 1, reference numeral 1 denotes an input DC power supply, 2 denotes a first switching type converter, and a first transformer 20 having a first primary winding 21 and a first secondary winding 22; It has a switch means 23 and a first output diode 24. 3 is a second switching type converter,
A second having a second primary winding 31 and a second secondary winding 32
, A second switch means 33, and a second output diode 34. Reference numeral 7 denotes an output capacitor, and the first and second switching type converters 2, 3
Rectified voltages output from the output diodes 24 and 34 are supplied, and an output DC voltage is supplied to the load 8. A control circuit 9 turns on and off the first and second switch means 23 and 33 so as to stabilize the output DC voltage. Further, the present switching power supply circuit includes an inductance unit 6.
And a first snubber capacitor 25 and a first diode 2
6, a second diode 27, a second snubber capacitor 35, a fourth diode 37, and a third diode 36. The first snubber capacitor 25 has one end connected to a connection point between the first primary winding 21 and the first switch means 23, and a first diode 26 connected from the other end to a positive electrode of the input DC power supply 1. Is done. The second diode 27 forms a series circuit with the inductance means 6 and is connected between the other end of the first snubber capacitor 25 and the negative electrode of the input DC power supply 1. Similarly, one end of the second snubber capacitor 35 is connected to a connection point between the second primary winding 31 and the second switch means 33, and a third diode 36 is connected from the other end to the positive electrode of the input DC power supply 1. Is connected. The fourth diode 37 forms a series circuit with the inductance means 6 and is connected between the other end of the second snubber capacitor 35 and the negative electrode of the input DC power supply 1.

FIG. 2 is an operation waveform diagram of each part of the switching power supply circuit according to the first embodiment. Hereinafter, the operation of the switching power supply circuit according to the first embodiment will be described with reference to FIG.

First, the basic operation of the first and second switching type converters 2 and 3 will be described. When the first switch means 23 is on, a current flows from the input DC power supply 1 to the first primary winding 21, the first switch means 23, and the input DC power supply 1 (FIG. 2 (i)). Magnetic energy is stored in the first transformer 20. When the first switch means 23 is turned off at time t0 (FIG. 2 (a)), each winding voltage of the first transformer 20 is inverted, and the first output diode 24 is turned on and stored in the first transformer 20. The obtained magnetic energy starts to be emitted from the first secondary winding 22 as a current (FIG. 2 (k)) for charging the output capacitor 7 via the first output diode 24. Time t
3, the second switch means 33 is turned on (FIG. 2 (b)), and current flows from the input DC power supply 1 to the second primary winding 31, the second switch means 33, and the input DC power supply 1. Flows (FIG. 2 (j)), and magnetic energy is stored in the second transformer 30. When the second switch means 33 is turned off at the time t5 (FIG. 2B), the respective winding voltages of the second transformer 30 are inverted, and the second output diode 34 is turned on and stored in the second transformer 30. The obtained magnetic energy starts to be emitted from the second secondary winding 32 via the second output diode 34 as a current (FIG. 2 (l)) for charging the output capacitor 7. When the first switch means 23 is turned on at time t6 (see FIG. 2).
(A)) The magnetic energy is stored in the first transformer 20 again.

By repeating the above operation, the voltage of the output capacitor 7, that is, the output DC voltage is supplied to the load 8. This output DC voltage can be controlled by the ratio between the ON time and the OFF time of the first and second switch means 23 and 33. The control circuit 9 detects the output DC voltage, determines the ON time and the OFF time so as to be stabilized, and turns ON and OFF the first and second switch means 23 and 33. Further, the control circuit 9 sets the first switching means 23 and the second switching means 33 so as to have a half switching cycle time difference.

For the switching type converter to transmit power with high efficiency, it is desirable that the magnetic coupling between the primary winding and the secondary winding of the transformer be tightly coupled. However, in practice, a regulating inductor called a leakage inductance is interposed therebetween, and this causes a surge voltage to be generated across the switch means when the switch means is turned off. The operation of the switching power supply circuit according to the embodiment of the present invention for suppressing the surge voltage will be described below.

First, when the first switch means 23 is turned off at time t0 (FIG. 2A), the voltage applied to the first switch means 23 (FIG. 2C) rises sharply, but at time t1. The first diode 26 conducts and charges the first snubber capacitor 25 with the charging current (FIG. 2).
(G)) flows, the first switch means 23
Suppress surge voltage to. Next, at time t2, when the charging current of the first snubber capacitor 25 has finished flowing (FIG. 2 (g)), the voltage of the first switch means 23 is equal to the input DC voltage which is twice the turns ratio of the voltage of the output capacitor 7. It calms down to the sum of the voltages (FIG. 2 (c)). Eventually, at time t3, the second switch means 33 is turned on (FIG. 2).
(B)) At the same time as storing magnetic energy in the second transformer 30, the voltage of the second snubber capacitor 35 is applied to the inductance means 6 (FIG. 2 (e)). Therefore, the resonance current (FIG. 2 (f)) between the second snubber capacitor 35 and the inductance means 6 flows through the fourth diode 37 and the second switch means 33, and the second snubber capacitor 35 To discharge. At time t4, the resonance current disappears, and the voltage of the inductance means 6 converges to zero voltage while attenuating (FIG. 2 (e)).
At time t5, when the second switch means 33 is turned off (FIG. 2B), the voltage of the second switch means 33 rises sharply (FIG. 2D), and the second diode 36 is turned on. When a charging current flows through the second snubber capacitor 35 (FIG. 2 (h)), a surge voltage to the second switch means 33 is suppressed (FIG. 2).
(D)). When the first switch means 23 is turned on at time t6 (FIG. 2A), the magnetic energy is again stored in the first transformer 20 and at the same time, the voltage of the first snubber capacitor 25 is applied to the inductance means 6. 2 (e), and a resonance current (FIG. 2 (f)) between the first snubber capacitor 25 and the inductance means 6 flows through the second diode 27 and the first switch means 23. , The first snubber capacitor 25 is discharged.

As is apparent from the above operation, if the discharge period of the first snubber capacitor 25 and the discharge period of the second snubber capacitor 35 do not overlap, the switching type converters 2 and 3 share the inductance means 6. can do. This discharge period is half the resonance period of the inductance of the inductance means 6 and the capacitance of the first and second snubber capacitors 25 and 35.

As described above, the switching power supply circuit according to the present embodiment can suppress the surge voltage to the switching means while suppressing the increase in the number of parts by sharing the inductance means with each switching type converter.

Although the operation of this embodiment has been described with two switching converters, three or more switching converters are used if the discharge periods of the snubber capacitors of each switching converter do not overlap as described above. Even if the converters are connected in parallel and interleaved, the inductance means can be shared. FIG. 3 shows a circuit diagram of a switching power supply circuit according to the present invention constituted by three switching converters. In FIG. 3, circuits on the secondary side such as the secondary winding of each transformer, each output diode, and the output capacitor are omitted. Further, if the switching means which do not overlap the discharge periods of the snubber capacitors of the respective snubber circuits share the inductance means, any number of switching type converters may be connected in parallel to perform the interleaving operation.

(Embodiment 2) FIG. 4 is a circuit diagram showing a configuration of a switching power supply circuit according to Embodiment 2 of the present invention. Components similar to those of the circuit of FIG. The description is omitted. 4 differs from FIG. 1 in that the inductance means 6 has a transformer configuration having a primary winding 61 and a secondary winding 62, and a secondary winding 62 of the inductance means 6 is connected to the transformer via a diode 64. This is a point connected to the output capacitor 7.

Hereinafter, the operation of the inductance means 6 of the switching power supply circuit according to this embodiment will be mainly described. First
Since the operations of the switching type converter 2 and the second switching type converter 3 are the same, only the operation of the first switching type converter 2 will be described.
First, when the first switch means 23 is turned off, a charging current flows through the first snubber capacitor 25, thereby suppressing a surge voltage to the first switch means 23. Next, when the first switch means 23 is turned on, the voltage of the first snubber capacitor 25 is applied to the inductance means 6, and the first snubber capacitor 25 is passed through the second diode 27 and the first switch means 23. The resonance current between the capacitor 25 and the inductance means 6 flows to discharge the first snubber capacitor 25. The operation up to this point is the same as in the first embodiment. When the discharge of the first snubber capacitor 25 proceeds and the voltage is inverted, the voltage generated in the secondary winding 62 of the inductance means 6 reaches the voltage of the output capacitor 7 and the diode 64 is turned on. When the diode 64 conducts, the voltage of the first snubber capacitor 25 is clamped, and this state continues until the current of the diode 64 stops. When the current of the diode 64 disappears, each winding voltage of the inductance means 6 converges to zero voltage while attenuating. The electric charge of the snubber capacitor stored for suppressing the surge voltage is discharged by resonance with the inductance means during the ON period of the switch means, and a part of this energy is discharged to the output capacitor 7.

As described above, the switching power supply circuit according to the present embodiment can suppress the surge voltage to the switch means while suppressing an increase in the number of parts by sharing the inductance means with each switching type converter. By supplying a part of the electric charge of the snubber capacitor stored for suppressing the surge voltage to the output, the efficiency can be further improved.

(Embodiment 3) FIG. 5 is a circuit diagram showing a configuration of a switching power supply circuit according to Embodiment 3 of the present invention. Components similar to those of the circuit of FIG. The description is omitted. 5 is different from FIG. 1 in that the inductance means 6 includes a primary winding 61 and two
A series circuit of a transformer 60 having secondary windings 62 and 63 and a choke coil 66 is connected to the secondary winding 62 of the transformer 60 via the diode 64 to the output capacitor 7, and the secondary winding of the transformer 60 is formed. Diode 65 on line 63
Is connected to the output capacitor 7 via the

Hereinafter, the operation of the inductance means 6 of the switching power supply circuit according to the present embodiment will be mainly described. First
Since the operations of the switching type converter 2 and the second switching type converter 3 are the same, only the operation of the first switching type converter 2 will be described.
First, when the first switch means 23 is turned off, a charging current flows through the first snubber capacitor 25, thereby suppressing a surge voltage to the first switch means 23. Next, when the first switch means 23 is turned on, the voltage of the first snubber capacitor 25 is applied to the inductance means 6. At this time, the primary winding 61 of the transformer 60 has
Assuming that the turns ratio between the primary winding 61 and the secondary winding 63 of the transformer 60 is N3 and the voltage of the output capacitor 7 is Eo,
A voltage of about N3 · Eo is generated. Therefore, the second diode
The resonance current of the first snubber capacitor 25 and the choke coil 66 flows through the capacitor 27, the first switch means 23, and the primary winding 61 of the transformer 60, and discharges the first snubber capacitor 25. At the same time, two
The current induced in the next winding 63 flows through the diode 65 to charge the output capacitor 7. When this current ends, the diode 65 is turned off, and the primary side is connected to the first snubber capacitor 25, the choke coil 66 and the transformer 60.
Resonance with the next winding 61 occurs. First snubber capacitor 2
When the discharge of 5 advances and the voltage is inverted, the voltage generated in the secondary winding 62 of the transformer 60 eventually reaches the voltage of the output capacitor 7, and the diode 64 becomes conductive. When the current of the diode 64 disappears, each winding voltage of the inductance means 6 converges to zero voltage while attenuating. The electric charge of the snubber capacitor stored for suppressing the surge voltage is discharged by resonance with the inductance means during the ON period of the switch means, and a part of this energy is discharged to the output capacitor 7. Since the discharge amount is performed twice at the initial stage and the final stage of the resonance, the discharge amount is larger than that in the second embodiment.

As described above, the switching power supply circuit according to the present embodiment can suppress the surge voltage to the switch means while suppressing the increase in the number of parts by sharing the inductance means with each switching type converter. By supplying a part of the electric charge of the snubber capacitor stored for suppressing the surge voltage to the output, the efficiency can be further improved.

(Embodiment 4) FIG. 6 is a circuit diagram showing a configuration of a switching power supply circuit according to Embodiment 4 of the present invention. In FIG. 6, 1 is an input DC power supply, 2 is a first switching type converter,
And the first switch means 23 is the same as in the first embodiment. Reference numeral 3 denotes a second switching type converter.
Of the transformer 30 and the second switch means 33 are the same as in the first embodiment. The first primary winding 21 of the first switching type converter 2 and the first switch means 2
3 is connected to one end of a first snubber capacitor 25, and the second switching type converter 3 is connected to a primary winding 31 of a transformer 30 and a second switching means 33 at a second connection point. One end of the snubber capacitor 35 is connected, and the inductance means 6 is connected between the other ends of the snubber capacitors. 36 is connected. As described above, the snubber circuit 5 is constituted by the first snubber capacitor 25, the second snubber capacitor 35, the inductance means 6, the first diode 26, and the second diode 36. It should be noted that secondary-side circuits such as a secondary winding of each transformer, each output diode, and an output capacitor are omitted.

As described above, in the switching power supply circuit according to the present embodiment in which the first and second switching type converters 2 and 3 are connected in parallel and perform an interleaving operation, the basic operation of each switching type converter 2 and 3 is as follows. The description is omitted because it is the same as that of the first embodiment, and the operation of the snubber circuit 5 will be mainly described below. First, the first snubber capacitor 25 is charged when the first switch means 23 is turned off, thereby suppressing a surge voltage to the first switch means 23. Similarly, the second snubber capacitor 35 is charged when the second switch means 33 is turned off, thereby suppressing a surge voltage to the second switch means 33. When the first switch means 23 is turned on, the second snubber capacitor 35 is further charged by series resonance of the first snubber capacitor 25, the inductance means 6, and the second snubber capacitor 35, and the first snubber capacitor 25 is turned on. Is discharged. When the first switch means 23 is turned off, the series resonance of the first snubber capacitor 25, the inductance means 6, and the second snubber capacitor 35 causes the second snubber capacitor 35
Is discharged, the first snubber capacitor 25 is charged, and the surge # voltage of the first switch means 23 is absorbed. Eventually, the first diode 26 and the second diode 36 become conductive, and the potentials of the second snubber capacitor 35, the inductance unit 6, and the first snubber capacitor 25 return to the state before the first switch unit 23 was turned on. . Next, when the second switch means 33 is turned on, the series resonance of the first snubber capacitor 25, the inductance means 6, and the second snubber capacitor 36 causes the second snubber capacitor 35 to be further charged and the first snubber capacitor 35 to be charged. Discharge 25. When the second switch means 33 is turned off,
The series resonance of the first snubber capacitor 25, the inductance means 6 and the second snubber capacitor 35 charges the second snubber capacitor 35, discharges the first snubber capacitor 25, and sets the surge voltage of the second switch means 33. Absorb. Eventually, the first diode 26 and the second diode 36 become conductive, and the potentials of the first snubber capacitor 25, the inductance unit 6, and the second snubber capacitor 36 return to the state before the second switch unit 33 was turned on. .

As described above, the switching power supply circuit according to the present embodiment can suppress the surge voltage to the first and second switch means with a small number of parts.

(Embodiment 5) FIG. 7 is a circuit diagram showing a configuration of a switching power supply circuit according to Embodiment 5 of the present invention. Components similar to those in the circuit of FIG. The description is omitted. 7 is different from FIG. 6 in that the inductance means 6 is a series circuit of a transformer 60 having a primary winding 61 and a secondary winding 62 and a choke coil 66. A point 62 is connected to the output capacitor 7 via a full-wave rectifier circuit 67.

Hereinafter, the operation of the inductance means 6 of the switching power supply circuit according to the present embodiment will be mainly described. First
Is turned on, the series resonance of the first snubber capacitor 25, the inductance means 6, and the second snubber capacitor 36 further charges the first snubber capacitor 25 and discharges the second snubber capacitor 35. . At this time, the primary winding 61 of the transformer 60 has N
2. A voltage of Eo is generated. The resonance current is transmitted to the secondary winding 62 by the transformer 60, and the current flows to the output capacitor 7 via the full-wave rectifier circuit 67. When the first switch means 23 is turned off, the series resonance of the first snubber capacitor 25, the inductance means 6, and the second snubber capacitor 35 charges the first snubber capacitor 25,
The second snubber capacitor 35 is discharged, and the surge voltage of the first switch means 23 is absorbed. Eventually, the first diode 26 and the second diode 36 become conductive, and the first snubber capacitor 25, the inductance means 6, and the second
Of the snubber capacitor 36 of the first switch means 2
Return to the state before 3 was turned on.

When the second switch means 33 is turned on, the first
Snubber capacitor 31 and inductance means 6 and the second
Due to the series resonance of the snubber capacitor 35, the first snubber capacitor 25 is further charged and the second snubber capacitor 35 is discharged. Transformer 60-1
Assuming that the turns ratio between the secondary winding 61 and the secondary winding 62 is N2 and the voltage of the output capacitor 7 is Eo, the transformer 6
A voltage of −N2 · Eo is generated in the 0 primary winding 61. The resonance current is transmitted to the secondary winding 62 by the transformer 60, and the current flows to the output capacitor 7 via the full-wave rectifier circuit 67. Next, when the second switch means 33 is turned off, the series resonance of the first snubber capacitor 25, the inductance means 6, and the second snubber capacitor 35 discharges the first snubber capacitor 25 and charges the second snubber capacitor 35. And the surge of the second switch means 33
Absorbs voltage. Eventually, the first diode 26 and the second
Of the first snubber capacitor 2
5, inductance means 6 and second snubber capacitor 3
The potential of 5 returns to the state before the second switch means 33 was turned on. The electric charge of the snubber capacitor stored for suppressing the surge voltage is discharged by resonance with the inductance means during the ON period of the switch means, and a part of this energy is discharged to the output capacitor 7.

As described above, the switching power supply circuit according to the present embodiment can suppress the surge voltage to the switch means with a small number of parts, and can reduce the charge of the snubber capacitor stored for suppressing the surge voltage. By supplying a part to the output, the efficiency can be further improved.

[0032]

As described above, the switching power supply circuit of the present invention comprises an inductance means, a snubber capacitor having one end connected to a connection point between a primary winding of a transformer and a switch means of each switching type converter. A diode connected in the direction in which current flows from the other end of each snubber capacitor to one end of the input DC power supply, and a series circuit with inductance means to form a series circuit between the other end of each snubber capacitor and the other end of the input DC power supply By having a diode to be connected, the switching means can share the inductance means and suppress the increase in the number of parts, suppress the surge voltage to the switching means, and achieve a highly efficient switching power supply circuit. it can.

Also, the switching power supply circuit of the present invention
In a switching power supply circuit in which first and second switching type converters are connected in parallel to perform an interleaving operation, one end is connected to a connection point between a primary winding of a transformer of the first switching type converter and a switch means. One snubber capacitor, a second snubber capacitor having one end connected to a connection point between a primary winding of a transformer of the second switching type converter and the switch means, and a snubber capacitor connected between the other ends of the respective snubber capacitors. Each switching type converter has an inductance means connected to the input DC power supply in a direction in which a charging current flows from both ends of the inductance means. To switch means while suppressing the increase in the number of parts by sharing It is possible to suppress a surge voltage, can achieve high-efficiency switching power supply circuit.

Further, by supplying power to the output at the time of resonance with the snubber capacitor by forming the inductance means as a transformer, the energy stored in the snubber capacitor can be effectively used for suppressing the surge voltage. The effect is obtained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a switching power supply circuit according to Embodiment 1 of the present invention.

FIG. 2 is an operation waveform diagram of each part of the switching power supply circuit according to Embodiment 1 of the present invention.

FIG. 3 is a circuit diagram showing another configuration of the switching power supply circuit according to the first embodiment of the present invention.

FIG. 4 is a circuit diagram showing a configuration of a switching power supply circuit according to a second embodiment of the present invention.

FIG. 5 is a circuit diagram showing a configuration of a switching power supply device according to Embodiment 3 of the present invention.

FIG. 6 is a circuit diagram showing a configuration of a switching power supply device according to Embodiment 4 of the present invention.

FIG. 7 is a circuit diagram showing a configuration of a switching power supply device according to Embodiment 5 of the present invention.

FIG. 8 is a circuit diagram showing a waveform of an input current of a conventional switching power supply circuit.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 input DC power supply 2 first switching type converter 3 second switching type converter 6 inductance means 5 first diode 6 second diode 7 output capacitor 8 load 9 control circuit 20 first transformer 21 first primary Winding 22 First secondary winding 23 First switching means 24 First output diode 25 First snubber capacitor 26 First diode 27 Second diode 30 Second transformer 31 Second primary winding Line 32 second secondary winding 33 second switch means 34 second output diode 35 second snubber capacitor 36 third diode 37 fourth diode

Claims (5)

[Claims] 1. A plurality of switching converters having an input DC power supply and having at least a series circuit including a primary winding of a transformer and switch means are connected in parallel with the input DC power supply, and each of the switching converters is connected to the input DC power supply. The switching means is a switching power supply circuit which is sequentially turned on and off with a predetermined time difference, comprising: an inductance means; an n-th primary winding of an n-th transformer of an n-th (n is a natural number) switching type converter; an n-th snubber capacitor having one end connected to a connection point with the n-th switch means, and a (2n-)-th snubber capacitor connected in a direction in which current flows from the other end of the n-th snubber capacitor to one end of the input DC power supply. 1) forming a series circuit with the diode and the inductance means to form a series circuit with the other end of the n-th snubber capacitor and the input; Switching power supply circuit having a first 2n diode connected between the other end of the flow source. 2. The method according to claim 1, wherein said inductance means includes a primary winding and a secondary winding.
A transformer having a secondary winding, wherein the primary winding of the inductance means forms a series circuit with the (2n-1) th diode, and the voltage generated in the secondary winding of the inductance means is rectified. The switching power supply circuit according to claim 1, wherein the output is output. 3. The method according to claim 2, wherein said inductance means includes a primary winding and a secondary winding.
A transformer having two secondary windings and a choke coil in series.
2. The voltage generator according to claim 1, wherein the secondary winding and the choke coil form a series circuit with the (2n-1) th diode, and a voltage generated in each secondary winding of the transformer of the inductance means is rectified and output. Switching power supply circuit. 4. A first switching type converter in which a series circuit comprising an input DC power supply, a primary winding of a first transformer, and first switch means is connected in parallel with the input DC power supply; A series circuit comprising a primary winding of a transformer and a second switch means has a second switching type converter connected in parallel with the input DC power supply, and the first and second switch means have a predetermined switching function. A switching power supply circuit that performs an on / off operation with a time difference, wherein a first snubber capacitor having one end connected to a connection point between a primary winding of the first transformer and first switch means; A second snubber capacitor having one end connected to a connection point between the primary winding of the transformer and the second switch means; an inductance means connected between the other ends of the snubber capacitors; First diode and the second diode and the switching power supply circuit having a composed snubber circuit from the charging current to the input DC power source from both ends are connected in the direction of flow of the inductance means. 5. The method according to claim 1, wherein said inductance means includes a primary winding and a secondary winding.
A third transformer having a secondary winding and a choke coil, wherein the primary winding and the choke coil of the third transformer form a series circuit and are connected between the other ends of the respective snubber capacitors; 5. The switching power supply circuit according to claim 4, wherein the voltage generated in the secondary winding of the third transformer is full-wave rectified and output.