JPH10327581A - Switching power unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the noise fed back to the AC input of a switching power unit and the ripple voltage component of the unit and improve the setting accuracy of the overcurrent limiting value of the output of the unit by connecting the third and fourth windings of the unit to the primary winding of the unit so that induced voltages may be generated in the opposite directions when a switching element is turned on. SOLUTION: In a switching power unit, a third winding 13 is connected to a primary winding 12 so that an induced voltage may be generated in the direction in which the both-terminal voltage of an input smoothing capacitor 17 increases when a switching element 18 is turned on. On the other hand, a fourth winding 14 is connected to the primary winding 12 so that an induced voltage may be generated in the direction in which the both-terminal voltage of the capacitor 17 decreases when the element 18 is turned on. These induced voltages are generated in the opposite directions when the element 18 is turned off. A controlled output winding 15 and a noncontrolled output winding 16 constitute the so-called secondary winding and the output from the winding 15 is utilized for controlling this switching power unit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching power supply for converting an AC input into a DC output and supplying the DC output to a load.

[0002]

2. Description of the Related Art A switching power supply converts an AC input from an AC power supply into a DC output and turns on a switch element.
By turning it off, the output voltage is controlled and supplied to the load. In such a switching power supply, generally,
It is required that the power factor of the AC input be increased, the harmonic components of the input current be suppressed, and the noise returned to the AC power supply and the ripple voltage component of the output voltage supplied to the load be sufficiently reduced. Furthermore, the limit value of the overcurrent at the output needs to be set with high accuracy in order to increase reliability.

In a conventional switching power supply device, there has been proposed, for example, Japanese Unexamined Patent Application Publication No. 7-15967, in which a conduction angle of an input current is widened to increase a power factor and a harmonic component is suppressed.
Is disclosed in Japanese Patent Application Laid-Open Publication No. HEI 9-203 (1995). The first conventional switching power supply device will be specifically described with reference to FIG. FIG. 13 is a block diagram showing a configuration of a first conventional switching power supply device. In FIG. 13, the switching power supply includes a commercial AC power supply 61,
Four diodes 6 connected to the commercial AC power supply 61
Full-wave rectifier 6 composed of 3, 64, 65, 66
2, and a transformer 68 connected to the full-wave rectifier 62 via an inductor 67. This transformer 68
Are the primary winding 69 and the third winding 7 provided on the power supply side.
0, and a control output winding 71 and a non-control output winding 72 provided on the load side. An input smoothing capacitor 73 is connected between the output terminals of the full-wave rectifier 62,
A primary winding 69, a switch element 74, and a resistor 75 connected in series are connected between the terminals of the input smoothing capacitor 73.
Is connected. Primary winding 69 is connected to inductor 67 via third winding 70. Third winding 70
Is connected to the primary winding 69 such that when the switch element 74 is turned on, an induced voltage is generated in a direction to reduce the voltage across the input smoothing capacitor 73.

[0004] A first rectifying / smoothing circuit 78 constituted by a diode 76 and a capacitor 77 is connected to both ends of the control output winding 71. First rectifying / smoothing circuit 7
A first load 79 is connected between the output terminals 8 to supply a DC output voltage. Similarly, the uncontrolled output winding 72
Are connected to a second rectifying / smoothing circuit 82 composed of a diode 80 and a capacitor 81. A second load 83 is connected between the output terminals of the second rectifying / smoothing circuit 82 to supply a DC output voltage. The control circuit 84 detects the output voltage to the first load 79,
The on / off ratio of the switch element 74 is changed so that the output voltage becomes a constant voltage. Further, the control circuit 84 detects an overcurrent state of each current to the first and second loads 79 and 83 by detecting the switching current flowing through the switch element 74 using the resistor 75. When the detected switching current value exceeds a preset limit value of the overcurrent, the control circuit 84 changes the on / off ratio of the switch element 74 to suppress and limit the overcurrent.

[0005] The operation of the first conventional switching power supply device is such that the AC input of the commercial AC power supply 61 is connected to the full-wave rectifier 6.
2 and the third of the inductor 67 and the transformer 68
And output to the input smoothing capacitor 73 through the winding 70 to smooth DC to a small ripple voltage component. Thereafter, by using a frequency higher than the commercial AC frequency of the AC input to turn on and off the switch element 74, the transformer 6
An AC voltage is applied to the primary winding 69 of FIG. Then, the induced voltage induced in the control output winding 71 and the non-control output winding 72 of the transformer 68 is applied to the first and second rectifying / smoothing circuits 78,
After performing rectification and smoothing on the respective outputs 82, a basic operation of supplying the DC output voltage to the first and second loads 79 and 83 is performed.

Next, FIG. 14 shows the voltage waveform and the current waveform of each part during the operation of the first conventional switching power supply device. In FIGS. 14A, 14B, 14C and 14D, the horizontal axis is the time axis. (A) of FIG.
V62 indicates a voltage waveform after the AC input of the commercial AC power supply 61 (FIG. 13) is rectified by the full-wave rectifier 62 (FIG. 13), and V68 is an induced voltage V70 of the third winding 70
13 shows a waveform obtained by adding (FIG. 13) and the voltage V73 across the input smoothing capacitor 73 (FIG. 13). I67 shown in FIG. 14B is the inductor 67 and the third winding 7.
2 shows a waveform of a current flowing through 0. I69 shown in FIG. 14C indicates the waveform of the current flowing through the primary winding 69 due to the current I67 flowing through the third winding 70.
(I71 + I72) shown in (d) of FIG. 14 corresponds to the result of the current I67 flowing through the third winding 70, and
1 (FIG. 13) and a composite waveform of the current flowing through the non-control output winding 72 (FIG. 13).

The operation of the switching power supply of the first conventional example shown in FIG. 13 for increasing the conduction angle of the input current and increasing the power factor will be specifically described. When the switching element 74 is turned on, the primary winding 6
An induced voltage V70 is generated by multiplying the turns ratio N between the number of turns N69 of Ninth 9 and the number of turns N70 of the third winding 70 by the voltage V73 across the input smoothing capacitor 73. The turns ratio N and the induced voltage V70 are calculated by the following equations (15) and (16), respectively.

N = N70 / N69 (15) V70 = V73 × N (16)

The induced voltage V 70 of the third winding 70 is generated in a direction in which the voltage V 73 across the input smoothing capacitor 73 is reduced as viewed from the inductor 67. In addition, the induced voltage V70
Is a voltage lower than the voltage V62 after the AC input of the commercial AC power supply 61 is rectified by the full-wave rectifier 62. Therefore, a current I67 shown in the following expression (17) flows through the inductor 67 in the direction of the third winding 70, and the commercial AC power 61
Energy is stored. Note that in equation (17),
L67 is the inductance value of the inductor 67, TON
Indicates an on-time during which the switch element 74 is turned on.

I67 = (V62−V73 + V70) × TON / L67 (17)

A current I67 flows from the inductor 67 to the third winding 70 through the switch element 74 and the resistor 75, and as a result, a current I69 flows through the primary winding 69 of the transformer 68. Flow in.

When the switch element 74 is turned off, the induced voltage V70 generated in the third winding 70 is inverted and added to the voltage V73 across the input smoothing capacitor 73, and the AC input of the commercial AC power supply 61 is converted to a full-wave rectifier. It becomes higher than the voltage V62 after rectification by 62. However, the inductor 67
(Hereinafter, referred to as the current of the inductor 67) continues to flow due to the energy stored in the capacitor, and the current of the inductor 67 flows into the input smoothing capacitor 73 via the third winding 70. Also, the current of the inductor 67 is
, And as a result, a current flows through the primary winding 69, the first and second rectifying / smoothing circuits 78, 78 via the control output winding 71 and the non-control output winding 72 of the transformer 68.
An output current flows from 82 to the first and second loads 79 and 83, respectively. At this time, as described above, the first load 79
Is detected by the control circuit 84 in order to control the switch element 74. Inductor 6
When all the energy stored in the capacitor 7 is released and the current in the inductor 67 becomes zero, the induced voltage V70 generated in the third winding 70 is added to the voltage V73 across the input smoothing capacitor 73. The voltage is higher than the voltage of the AC input at 61. However, commercial AC power supply 6
The current going back to 1 is blocked by the full-wave rectifier 62.

FIG. 15 is a waveform diagram showing current waveforms at various points during the operation of the first conventional switching power supply device shown in FIG. In addition, (a) of FIG. 15, (b), (c),
In (d), the horizontal axis is the time axis. FIG.
5 indicates a period in which the AC input of the commercial AC power supply 61 is near zero voltage, and a period indicated by "K" indicates a period in which the AC input is near the peak voltage. I have. I67 shown in FIG.
3 shows the current waveform. I74 shown in FIG.
Shows the waveform of the switching current flowing through the switch element 74. The hatched portion M indicates the switching current I
The current component of the current of the inductor 67 transmitted from the inductor 67 to the primary winding 69 and the switch element 74 by the energy stored in the inductor 67 is shown. L indicated by a two-dot chain line is the control circuit 8
4 shows a preset overcurrent limit value. FIG.
5C shows the waveform of the current flowing through the control output winding 71 of the transformer 68, and the hatched portion N indicates the inductor 6 due to the energy stored in the inductor 67.
7 shows the current component of the current of the inductor 67 transmitted to the control output winding 71 due to the current flowing from the seventh to the third winding 70. I72 shown in FIG. 15D indicates the waveform of the current flowing through the non-control output winding 72 of the transformer 68. As described above, in the switching power supply of the first conventional example, the energy from the commercial AC power supply 61 is stored by the inductor 67, and the current flowing by the stored energy is superimposed on the AC input, so that the input current is reduced. And the power factor was increased by widening the conduction angle.

Next, a conventional switching power supply device disclosed in Japanese Patent Application Laid-Open No. 7-298611 will be described with reference to FIG.
This will be described with reference to FIG. FIG. 16 is a block diagram showing the configuration of a second conventional switching power supply device. The switching power supply device of the second conventional example is adapted to cope with a case where the fluctuation range of the input voltage of the AC input is large. For the same switching power supply device as that of the first conventional example shown in FIG. , And the description thereof will be omitted. In FIG. 16, a fourth winding 85 connected in series to a primary winding 69 via a switch element 74 and a resistor 75 is provided on the power supply side of the transformer 68 '. 4th
The winding 85 is connected to the primary winding 69 such that when the switch element 74 is turned on, an induced voltage is generated in a direction to increase the voltage across the input smoothing capacitor 87. An inductor section 88 composed of two windings 89 and 90 is shown in FIG.
Is provided between the full-wave rectifier 62 and the transformer 68 'instead of the inductor 67 shown in FIG. These two windings 89, 90 are inductively coupled (coupling in polarities) so as to excite the inductor section 88 in the same direction by currents flowing to each other, and one of the windings 89 is a transformer 68 '. Is connected between one end of the third winding 70 and the positive output of the full-wave rectifier 62, and the other winding 90 is connected between one end of the fourth winding 85 and the negative output of the full-wave rectifier 62. It is connected. Between the other end of the third winding 70 and the other end of the fourth winding 85, instead of the input smoothing capacitor 73 shown in FIG. 87 are provided. Also, the switch element 91
Are connected between the connection point of the diodes 65 and 66 and the connection point of the input smoothing capacitors 86 and 87. The switch element 91 is used for switching between full-wave rectification and double voltage rectification of AC input. That is, when the input voltage of the AC input is low, in order to perform double voltage rectification of the AC input,
The switch element 91 is turned on. When the input voltage of the AC input is high, the switch element 91 is turned off in order to perform full-wave rectification of the AC input.

In the operation of the switching power supply of the second conventional example, when the input voltage from the commercial AC power supply 61 is high, the switch element 91 is turned off, and the AC input is full-wave rectified by the full-wave rectifier 62. . And the full-wave rectifier 6
2, the windings 89, 90 of the inductor section 88,
And via the third and fourth windings 70 and 85 of the transformer 68 ′, are supplied to two input smoothing capacitors 86 and 87 connected in series with each other.
Charge 6,87. Subsequently, the input smoothing capacitor 8
6, 87, by smoothing to a DC having a small ripple voltage component, using a frequency higher than the commercial AC frequency of the AC input to turn on and off the switch element 74,
An AC voltage is applied to the primary winding 69 of the transformer 68 '. Then, the induced voltages induced in the control output winding 71 and the non-control output winding 72 of the transformer 68 are respectively output to the first and second rectifying / smoothing circuits 78 and 82 for rectification and smoothing. The power is supplied to the first and second loads 79 and 83, respectively. When the input voltage from the commercial AC power supply 61 is low, the switch element 91 is turned on, and the AC input is applied to the input smoothing capacitor 8 every positive and negative half cycles of the voltage.
6, 87, and the input smoothing capacitors 86,
87 is charged. Specifically, in the positive half cycle of the commercial AC power supply 61, the current from the commercial AC power supply 61 is supplied to the diode 63 of the full-wave rectifier 62 and the winding 8 of the inductor unit 88.
9. The third winding 70 of the transformer 68 ', the input smoothing capacitor 86, and the switch element 91 flow in this order to charge the input smoothing capacitor 86. On the other hand, commercial AC power supply 6
In the negative half cycle of 1, the current from the commercial AC power supply 61 is
Switch element 91, input smoothing capacitor 87, fourth winding 85 of transformer 68 ', winding 9 of inductor section 88
Flowing in the order of 0 and the diode 64 of the full-wave rectifier 62, the input smoothing capacitor 87 is charged. As a result, the voltage between both ends of the input smoothing capacitors 86 and 87 can be twice the input voltage from the commercial AC power supply 61. After charging the input smoothing capacitors 86 and 87, the same operation as in the case where the above-described switch element 91 is turned off to perform full-wave rectification is performed, and the DC output voltage becomes first and second.
The first and second loads 7 from the second rectifying / smoothing circuits 78 and 82
9, 83, respectively.

Next, the operation of increasing the conduction angle of the input current of the commercial AC power supply 61 to increase the power factor in the second conventional switching power supply device shown in FIG. 16 will be described.
First, an operation when the input voltage of the AC input is high and the switch element 91 is turned off to perform full-wave rectification on the AC input will be described. When the switch element 74 is turned on, an induced voltage is generated in the fourth winding 85 of the transformer 68 ′ in a direction that becomes a positive voltage when viewed from the winding 90 of the inductor unit 88,
The current due to the induced voltage flows through the winding 90 and the full-wave rectifier 62 to the third winding 70 of the transformer 68 '. At the same time, similarly to the switching power supply device of the first conventional example shown in FIG.
A current flows from the winding 89 of the inductor section 88 to the third winding 70. As a result, current flows from the commercial AC power supply 61 through the full-wave rectifier 62, the winding 89, the third winding 70, the input smoothing capacitors 86 and 87, the fourth winding 85, and the winding 90. The windings 89, 90 of the inductor section 88 are inductively coupled so as to excite the inductor section 88 in the same direction by currents flowing through each other. 90
Stores the energy of the commercial AC power supply 61. Further, the current flows through the third and fourth windings 70 and 85 into the switch element 74 and the resistor 75, and as a result, the current flows through the primary winding 69 of the transformer 68 '.

When the switching element 74 is turned off, the induced voltage generated in the fourth winding 85 is inverted, and the inductor 88
, And becomes lower than the voltage after the AC input of the commercial AC power supply 61 is rectified by the full-wave rectifier 62. However, the current continues to flow due to the energy stored in the winding 90, and the current flows through the fourth winding 85 to the input smoothing capacitor 87. Similarly, current continues to flow from the winding 89 of the inductor section 88 to the input smoothing capacitor 86 via the third winding 70. Also, current flows from the windings 89 and 90 to the third and fourth windings 70 and 85,
As a result, the first and second rectifying / smoothing circuits 78 and 82 pass through the control winding 71 and the non-control output winding 72 of the transformer 68 ′. Output currents flow through the second loads 79 and 83, respectively. When all the energy stored in the windings 89 and 90 of the inductor unit 88 is released and the current of the windings 89 and 90 becomes zero, the input smoothing capacitors 86 and 8 connected in series
7, the third and fourth windings 7 of the transformer 68 '
Since the induced voltages at 0 and 85 are added, the voltage becomes higher than the input voltage of the commercial AC power supply 61. However, the current that is going to return to the commercial AC power supply 61 is blocked by the full-wave rectifier 62.

Next, the operation in the case where the switch element 91 is turned on to perform double voltage rectification on the AC input will be described. When the switch element 74 is turned on, the third and fourth windings 70, 8 of the transformer 68 'are turned on in the same manner as in the above-described full-wave rectification.
5 generates an induced voltage. As a result, the current flows from the commercial AC power supply 61 to the diode 63 of the full-wave rectifier 62,
A state in which the winding 89 of the inductor section 88, the third winding 70, the input smoothing capacitor 86, and the switch element 91 flow in this order, and a current is supplied from the commercial AC power supply 61 to the switch element 9
1. The state of flowing in the order of the input smoothing capacitor 87, the fourth winding 85, the winding 90 of the inductor unit 88, and the diode 64 of the full-wave rectifier 62 changes every positive and negative half cycle of the voltage of the commercial AC power supply 61. Appear alternately. As a result, the winding 8
The energy of the commercial AC power supply 61 is stored in 9, 90. Further, similarly to the case where the switch element 91 is turned off, the current flows through the third and fourth windings 70 and 85 through the switch element 74 and the resistor 75. ′ Flows through the primary winding 69.

When the switching element 74 is turned off, the currents in the windings 89 and 90 of the inductor section 88 continue to flow in the same current path as when the switching element 74 is turned on due to the stored energy, and all the energy is released. When the current becomes zero, the induced voltage in the third and fourth windings 70 and 85 of the transformer 68 'is added to the voltage across the input smoothing capacitors 86 and 87, respectively. The voltage becomes higher than the input voltage. However,
The current to be fed back to the commercial AC power supply 61 depends on the positive / negative half cycle of the voltage and the diode 63 of the full-wave rectifier 62.
And 64 are alternately blocked. The current is the winding 89, 9
From zero to the third and fourth windings 70 and 85 and consequently to the primary winding 69, the transformer 68 '
Through the control output winding 71 and the non-control output winding 72, output currents flow from the first and second rectifying / smoothing circuits 78 and 82 to the first and second loads 79 and 83, respectively. Thus, in the switching power supply device of the second conventional example, the windings 89,
The energy of the commercial AC power supply 61 is stored in 90, and the current flowing due to the stored energy is superimposed on the AC input, thereby increasing the conduction angle of the input current and increasing the power factor. The reason why the current of the windings 89 and 90 of the inductor section 88 flows only alternately every positive and negative half cycle of the voltage of the commercial AC power supply 61 is that the third and fourth windings 70 and 8
This is because the input voltage is alternately applied from the commercial AC power supply 61 to the windings 89 and 90 even if an induced voltage is constantly generated in the winding 5.

When the input voltage of the AC input is low and voltage doubler rectification is performed, as described above, the input voltage is
Are applied to the windings 89 and 90 alternately, so that the current value IL flowing alternately through the windings 89 and 90 of the inductor unit 88 is changed.
Is obtained by the following equation (18). In the expression (18), VT is the third and fourth windings 7 of the transformer 68 '.
The induced voltage values at 0 and 85 (the same voltage as during full-wave rectification) are shown, and V62 indicates the voltage value after the AC input of the commercial AC power supply 61 is rectified by the full-wave rectifier 62. Further, L indicates the inductance value of one of the windings 89 and 90 of the inductor section 88, and VC indicates the input smoothing capacitor 8
6 and 87 are shown. Also, TON
Indicates an on-time during which the switch element 74 is turned on.

IL = (V62−VC + VT) × TON / L (18)

On the other hand, when the input voltage of the AC input is high and full-wave rectification is performed, the current value IL 'flowing simultaneously through the windings 89 and 90 of the inductor section 88 is obtained by the following equation (19). In Expression (19), 2VT represents a voltage value of the sum of the induced voltage values VT at the third and fourth windings 70 and 85, and 4L represents a winding value of the windings 89 and 90 of the inductor unit 88. An inductance value determined by the sum of the numbers (the windings 89 and 90 are coupled to each other with additional polarities and becomes four times as large as the voltage doubled rectification). Further, V62 'is a commercial AC power supply 61.
, And 2VC indicates the sum of the voltage values VC across the input smoothing capacitors 86 and 87.

IL ′ = (V62′−2VC + 2VT) × TON / 4L— (19)

In the equation (19), when the input voltage of the commercial AC power supply 61 is set to twice the voltage at the time of voltage doubler rectification, the winding 89,
The current value IL ′ flowing simultaneously through 90 becomes half of the current value IL flowing alternately through the windings 89 and 90 during voltage doubler rectification. That is, the above-mentioned current value IL ′ is obtained by the following equation (21) by substituting V62 ′ shown in the following equation (20) into the equation (19) and deforming it.

V62 ′ = 2V62− (20) IL ′ = (V62−VC + VT) × TON / 2L = IL / 2− (21)

Taking into account the above assumption that the input voltage at the time of full-wave rectification is twice the input voltage at the time of voltage doubler rectification, it is clear from equation (21) that the input voltage during full-wave rectification and the voltage doubler rectification are different. It can be seen that the same power is supplied from the AC input and the operating conditions in the switching power supply are the same.

As described above, in the switching power supply of the second conventional example, the AC input of the commercial AC power supply 61 is double-voltage rectified or full-wave rectified by turning on and off the switch element 91. As a result, in the switching power supply device of the second conventional example, even when the fluctuation range of the input voltage of the AC input is large, the passing current and the breakdown voltage of the switch element 74 and the diodes 76 and 80 have substantially the same value. Therefore, it is not necessary to use a switch element 74 and diodes 76 and 80 that have a large current and a high breakdown voltage.

[0028]

In the first conventional switching power supply shown in FIG. 13, the current flowing from the inductor 67 to the primary winding 69 of the transformer 68 is as shown in FIG.
15 (b) and FIG. 15 (b), the peak value was large in a triangular wave shape. For this reason, a high-frequency ripple current component fed back to the input current becomes large, and the noise filter disposed between the commercial AC power supply 61 and the full-wave rectifier 62 for suppressing normal noise becomes large. there were. Further, as shown in FIG. 15B, the switching current I74 flowing through the switch element 74 is not limited to the current determined by the output currents to the first and second loads 79 and 83, and is a constantly changing commercial AC power supply. The current component of the input current from the inductor 61, that is, the current of the inductor 67 flowing due to the energy stored in the inductor 67 is superimposed. For this reason, since the control circuit 84 detects the output current and the current of the inductor 67 from the resistor 75, it is necessary to set the overcurrent limit value L (FIG. 15B) to an unnecessarily large value. Was. as a result,
The setting accuracy of the overcurrent limit value L and the stability of the overcurrent control are greatly impaired, causing a problem that the circuit scale of the switching power supply becomes large. Further, FIG.
As shown in (1), the current component of the current of the inductor 67 is also superimposed on the current flowing through the control output winding 71 of the transformer 68. Therefore, in the output voltage supplied to the first rectifying / smoothing circuit 78, the ripple voltage component of the commercial alternating current has increased. When the gain of the control circuit 84 for controlling the output from the first rectifying / smoothing circuit 78 is increased to suppress the ripple voltage component, the second rectifying / smoothing circuit 82
In the output voltage supplied to the power supply, there is a problem that a ripple voltage component is increased. The current waveforms shown in FIGS. 15C and 15D correspond to the transformer 68.
Of the control output winding 71 is compared with the non-control output winding 72.
This figure shows a case where the current flows well before the uncontrolled output winding 72 due to good coupling with the primary winding 69. That is, since the current of the inductor 67 becomes zero in the first half of the off period,
Almost all of the current component of the current of the inductor 67 is superimposed on the current ((c) in FIG. 15) flowing through the control output winding 71 with good coupling. Further, when the input voltage fluctuation range of the AC input is large, the switch element 74 and the diodes 76 and 80 need to withstand the applied voltage at the maximum input voltage and withstand the passing current at the minimum input voltage.
Inevitably, it was required to use a device with a high breakdown voltage and a large current.

Also in the switching power supply of the second conventional example shown in FIG. 16, the circuit size is increased due to the increase of the limit value of the overcurrent, the ripple voltage component of the commercial AC at the output voltage is increased, and When the gain of the control circuit 84 for controlling the output from the first rectifying / smoothing circuit 78 is increased, the ripple voltage component in the output voltage supplied to the second rectifying / smoothing circuit 82 increases, as shown in FIG. The same problems as those of the first conventional switching power supply shown above have not been solved.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and is intended to suppress noise feedback to an AC input and a ripple voltage component at an output, and to set a limit value of an output overcurrent. It is an object of the present invention to provide a switching power supply that can improve accuracy.

[0031]

A switching power supply according to the present invention comprises a primary winding connected to a power supply, a secondary winding connected to a load, and third and fourth power supplies connected to the power supply. A first diode, a first inductor, and a third winding provided between the output terminal of the full-wave rectifier connected to an AC power supply, the output terminal of the full-wave rectifier, and the third winding. And a second series connected body in which a first series connected body is connected in series with a second diode, a second inductor, and the fourth winding are connected in series. A smoothing capacitor having one end connected to one output terminal of the full-wave rectifier via the parallel circuit and the other end connected to the other output terminal of the full-wave rectifier;
A switching element connected in series with the next winding, provided at both ends of the smoothing capacitor together with the primary winding, and a control circuit for controlling on / off operation of the switching element; A line is connected to the primary winding such that the induced voltages are generated in opposite directions when the switch element is turned on. With this configuration, the current of the first inductor and the current of the second inductor increase and decrease in the on and off periods of the switch element, and as a result, the peak value of the input current of the AC power supply decreases. As a result, the high-frequency ripple current component that returns to the input is reduced, and normal noise is also suppressed. Further, the current of each inductor is reduced, and the setting accuracy of the overcurrent limit value and the stability of the overcurrent control can be improved. Further, during the off period of the switch element, the current flowing through one of the inductors continues to flow through the primary winding during the off period of the switch element. For this reason, the current component of the current of one inductor transmitted to the secondary winding of the transformer affects the entire OFF period, and the ripple voltage component of the output voltage due to the different coupling of each winding in the transformer is reduced. be able to.

In another switching power supply of the present invention, the bias voltage for operating the control circuit reduces the voltage across the smoothing capacitor when the switch element of the third and fourth windings is turned off. The induced voltage is supplied from one of the windings in which the induced voltage is generated. With this configuration, it is not necessary to provide a bias winding for supplying a bias voltage to the control circuit, and the switching power supply device can be downsized.

In another switching power supply of the present invention, at least one of the third and fourth windings and at least a part of the other windings of the transformer are common.
With this configuration, the size of the switching power supply device can be reduced.

Another switching power supply of the present invention comprises a primary winding connected to the power supply, a secondary winding connected to the load, and third, fourth, and fifth connected to the power supply. , A transformer having at least a sixth winding, an output terminal of a full-wave rectifier connected to an AC power supply, first and second inductors coupled to each other in polarities, and third and third inductors coupled to each other in polarities. A first series connected body, which is connected to the first inductor, the first inductor, and the third winding, which are connected in series to the first inductor, one output terminal of the full-wave rectifier, and the second series. A diode of the third inductor,
A first parallel circuit in which a second series connected body in which the fourth winding is sequentially connected in series is connected to the other output terminal of the full-wave rectifier; a third diode;
A third series connected body in which the fourth inductor and the fifth winding are sequentially connected in series, a fourth diode, the second inductor, and the sixth winding are sequentially connected in series. A second parallel circuit connected in parallel with a fourth series connection body, connected in series, one end connected to one output terminal of the full-wave rectifier via the first parallel circuit, and the other end connected First and second smoothing capacitors connected to the other output terminal of the full-wave rectifier via the second parallel circuit, the first and second smoothing capacitors are connected in series to the primary winding, and the first and second smoothing capacitors are connected together with the primary winding. A second switch element connected between a connection point between the first and second smoothing capacitors and one end of the AC power supply;
And a control circuit for controlling the on and off operations of the first switch element, wherein the third and fourth windings generate induced voltages in opposite directions when the first switch element is turned on. The fifth and sixth windings are connected to the primary winding such that induced voltages are generated in opposite directions when the first switch element is turned on. With this configuration, the currents of the first and second inductors or the third and fourth inductors increase and decrease in the on and off periods of the switch element, respectively.
As a result, the peak value of the input current of the AC power supply decreases. As a result, the high-frequency ripple current component that returns to the input is reduced, and normal noise is also suppressed. Further, the current of each inductor is also reduced, and is occupied by the current component of the current to be detected which is determined by the output current of the transformer, so that the setting accuracy of the overcurrent limit value and the stability of the overcurrent control can be improved. Further, during the off period of the first switch element, the current flowing through one of the inductors continues to flow through the primary winding during the off period of the first switch element. For this reason, the current component of the current of each inductor transmitted to the secondary winding of the transformer affects the entire OFF period, and the ripple voltage component of the output voltage due to the different coupling of each winding in the transformer is reduced. can do.

According to another switching power supply of the present invention, the bias voltage for operating the control circuit is the first or fourth winding or the fifth or sixth winding.
When the switch element is turned off, the induced voltage is supplied from one of the windings in a direction to reduce the voltage across the first and second smoothing capacitors. With this configuration, it is not necessary to provide a bias winding for supplying a bias voltage to the control circuit, and the switching power supply device can be downsized.

In another switching power supply of the present invention, at least one of the third to sixth windings and at least a part of the other windings of the transformer are common. With this configuration, the size of the switching power supply device can be reduced.

Another switching power supply of the present invention has at least a primary winding connected to the power supply, a secondary winding connected to the load, and a third winding connected to the power supply. A transformer, an output terminal of the full-wave rectifier connected to the AC power supply, one end connected to one output terminal of the full-wave rectifier, and the other end connected to one end of the third winding;
A smoothing capacitor having one end connected to one output terminal of the full-wave rectifier via the third winding and the inductor, and the other end connected to the other output terminal of the full-wave rectifier, in series with the primary winding; A switching element provided at both ends of the smoothing capacitor together with the primary winding, and a control circuit for controlling on / off operation of the switching element, wherein the third winding has the switching element turned off. Is connected to the primary winding so that the induced voltage is generated in a direction to reduce the voltage across the smoothing capacitor. With this configuration, the current of the inductor flowing from the inductor decreases due to the energy stored in the inductor and becomes zero during the ON period of the switch element, and the current of the inductor flowing through the switch element decreases. Can be reduced. As a result, the majority of the switching current flowing through the switch element is occupied by the current component of the current to be detected determined by the output current of the transformer, thereby improving the setting accuracy of the overcurrent limit value and the stability of the overcurrent control. Can be. Further, during the off period of the switch element, the current flowing through the inductor continues to flow through the winding to the primary winding during the off period of the switch element. For this reason, the current component of the inductor current transmitted to the secondary winding of the transformer affects the entire OFF period, and the ripple voltage component of the output voltage due to the different coupling of each winding in the transformer can be reduced. it can.

According to another switching power supply of the present invention, the bias voltage for operating the control circuit is equal to the third voltage.
Are supplied from the windings of. With this configuration, it is not necessary to provide a bias winding for supplying a bias voltage to the control circuit, and the switching power supply device can be downsized.

In another switching power supply of the present invention, the third winding and at least a part of the other windings of the transformer are common. With this configuration, the size of the switching power supply device can be reduced.

Another switching power supply of the present invention comprises a primary winding connected to the power supply, a secondary winding connected to the load, and third and fourth windings connected to the power supply. A transformer having at least an output terminal of a full-wave rectifier connected to an AC power supply, one end connected to one output terminal of the full-wave rectifier, and the other end connected to one end of a third winding. An inductor, one end connected to the other output terminal of the full-wave rectifier, the other end connected to one end of a fourth winding, connected in series, one end of the third winding, A first terminal connected to one output terminal of the full-wave rectifier via the first inductor and the other end connected to the other output terminal of the full-wave rectifier via the fourth winding and the second inductor. , A second smoothing capacitor, a primary winding connected in series with the primary winding. A first switch element provided at both ends of the first and second smoothing capacitors, and a second switch connected between a connection point of the first and second smoothing capacitors and one end of the AC power supply. And a control circuit for controlling the on / off operation of the first switch element, wherein the third and fourth windings are configured such that when the first switch element is turned off, an induced voltage is a voltage across the smoothing capacitor. Is connected to the primary winding so as to occur in the direction to reduce
With this configuration, the current of each inductor flowing from each inductor due to the energy stored in each inductor decreases during the ON period of the first switch element and becomes zero during the ON period, Current component of each inductor flowing through the switch element can be reduced. As a result, most of the switching current flowing through the first switch element is occupied by the current component of the current to be detected, which is determined by the output current of the transformer, and the setting accuracy of the overcurrent limit value and the stability of the overcurrent control are reduced. Can be improved. Further, during the off-period of the first switch element, the current flowing through each inductor continues to flow through the winding to the primary winding during the off-period of the first switch element. For this reason, the current component of the current of each inductor transmitted to the secondary winding of the transformer affects the entire OFF period, and the ripple voltage component of the output voltage due to the different coupling of each winding in the transformer is reduced. Can be.

In another switching power supply of the present invention, a bias voltage for operating the control circuit is supplied from one of the third and fourth windings. With this configuration, it is not necessary to provide a bias winding for supplying a bias voltage to the control circuit, and the switching power supply device can be downsized.

In another switching power supply of the present invention, at least one of the third and fourth windings and at least a part of the other windings of the transformer are common.
With this configuration, the size of the switching power supply device can be reduced.

[0043]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the switching power supply according to the present invention will be described below with reference to the drawings.

<< First Embodiment >> FIG. 1 is a block diagram showing a configuration of a switching power supply device according to a first embodiment of the present invention. In FIG. 1, the switching power supply device includes:
A commercial AC power supply 1, a full-wave rectifier 2 connected to the commercial AC power supply 1, and composed of four diodes 3, 4, 5, and 6, a primary winding 12 provided on the power supply side, and a third winding 1
Control output winding 1 provided on the load side with third and fourth windings 14
5 and a transformer 11 having an uncontrolled output winding 16. Between the output terminals of the full-wave rectifier 2, a parallel circuit pcc in which the following two series-connected bodies are connected in parallel, and an input smoothing capacitor 1 connected in series to the parallel circuit pcc
7 is connected. Specifically, the positive output of the full-wave rectifier 2 includes a series connection body in which a first diode 7, a first inductor 8, and a third winding 13 are sequentially connected in series, and a second diode One end of a parallel circuit pcc with a series-connected body in which the 9, the second inductor 10 and the fourth winding 14 are sequentially connected in series is connected. Parallel circuit pc
The other end of c is connected to one end of an input smoothing capacitor 17,
The other end of the input smoothing capacitor 17 is connected to the negative output of the full-wave rectifier 2. Between the terminals of the input smoothing capacitor 17, the primary winding 12 and the switch element 1 connected in series are connected.
8 and a resistor 19 are connected. That is, the parallel circuit pcc is connected between the output terminals of the full-wave rectifier 2. The first and second inductors 8 and 10 finely adjust the inductance value on the power supply side in the switching power supply device, and are configured by windings that are wound separately from the windings of the transformer 11. Further, the third and fourth windings 1
3 and 14 are connected to the primary winding 12 so as to generate induced voltages which are induced in opposite directions when a current flows through the windings 13 and 14 by the on / off operation of the switch element 18. ing. Specifically, the third winding 13
Is connected to the primary winding 12 such that when the switch element 18 is turned on, an induced voltage is generated in a direction to increase the voltage across the input smoothing capacitor 17. On the other hand, the fourth winding 14 is connected to the primary winding 12 so that when the switch element 18 is turned on, an induced voltage is generated in a direction to reduce the voltage across the input smoothing capacitor 17. These induced voltages are generated in opposite directions when the switch element 18 is turned off. The control output winding 15 and the non-control output winding 16 constitute a so-called secondary winding, and the output from the control output winding 15 is used for controlling the switching power supply. The switch element 18 controls an output output from a secondary winding (output winding) of the transformer 11 to a load (details will be described later).

A first rectifying / smoothing circuit 22 composed of a diode 20 and a capacitor 21 is connected to both ends of the control output winding 15. First rectifying and smoothing circuit 2
A first load 23 is connected between the two output terminals, and a DC output voltage is supplied. Similarly, the uncontrolled output winding 16
Is connected to a second rectifying / smoothing circuit 26 composed of a diode 24 and a capacitor 25. A second load 27 is connected between the output terminals of the second rectifying / smoothing circuit 26 to supply a DC output voltage. The control circuit 28 detects an output voltage to the first load 23,
The on / off ratio of the switch element 18 is changed so that the output voltage becomes a constant voltage. Further, the control circuit 28 detects an overcurrent state of each current to the first and second loads 23 and 27 by detecting the switching current flowing through the switch element 18 using the resistor 19. When the detected switching current value exceeds a preset limit value of the overcurrent, the control circuit 28 changes the on / off ratio of the switch element 18 to suppress and limit the overcurrent.

The operation of the switching power supply of this embodiment is as follows. The AC input from the commercial AC power supply 1 is rectified by the full-wave rectifier 2, and the first and second diodes 7, 9 and the first and second diodes are used.
Inductors 8 and 10 and third and fourth transformers 11
Is output to an input smoothing capacitor 17 through a parallel circuit constituted by the windings 13 and 14, and is smoothed to a DC having a small ripple voltage component. Thereafter, the switching element 18 is turned on and off using a frequency higher than the commercial AC frequency of the AC input, thereby applying an AC voltage to the primary winding 12 of the transformer 11. Then, the induced voltages induced in the control output winding 15 and the non-control output winding 16 of the transformer 11 are output to the first and second rectifying / smoothing circuits 22 and 26, respectively, and rectified and smoothed. The basic operation for supplying the first and second loads 23 and 27 is performed.

Next, FIG. 2 shows the voltage waveform and the current waveform of each part during the operation of the switching power supply of this embodiment.
In FIGS. 2A, 2B, 2C, 2D, and 2E, the horizontal axis is the time axis. In FIG. 2A, V2 indicates a voltage waveform after the AC input of the commercial AC power supply 1 (FIG. 1) is rectified by the full-wave rectifier 2 (FIG. 1). The waveform shows the sum of the induced voltage V14 (FIG. 1) and the voltage V17 across the input smoothing capacitor 17 (FIG. 1). V8 indicated by a dotted line indicates a waveform obtained by adding the induced voltage V13 of the third winding 13 (FIG. 1) and the voltage V17 across the input smoothing capacitor 17. I2 shown in FIG. 2B indicates the waveform of the current output from the full-wave rectifier 2. This current I2 is generated by the second inductor 10 and the fourth winding 14 connected in series.
And a current I10 flowing through the line (shown by a solid line in FIG.
First inductor 8 and third winding 13 connected in series
2 (shown by a dotted line in FIG. 2C). Id shown in FIG. 2D is the current I8, I10
Shows the waveform of the current flowing through the primary winding 12 due to the fact that the current flows through the third and fourth windings 13 and 14, respectively.
(E15 + I16) shown in FIG.
Shows the composite waveform of the current flowing through the control output winding 15 (FIG. 1) and the non-control output winding 16 (FIG. 1), corresponding to the results flowing through the third and fourth windings 13 and 14, respectively. ing.

The operation of the switching power supply device of the present embodiment for increasing the conduction angle of the input current flowing from the commercial AC power supply 1 to the full-wave rectifier 2 and increasing the power factor is described below with reference to the first diode 7, the first inductor 8, And the operation of a series-connected body composed of the second diode 9, the second inductor 10, and the fourth winding 14 will be specifically described. I do. First, the operation of the series-connected body including the second diode 9, the second inductor 10, and the fourth winding 14 will be described. When the switch element 18 is turned on, the fourth winding 14 of the transformer 11 has an input smoothing ratio N1 between the number of turns N12 of the primary winding 12 and the number of turns N14 of the fourth winding 14. An induced voltage V14 multiplied by the voltage V17 across the capacitor 17 is generated. These turns ratio N1 and induced voltage V14 are calculated by the following equation (1).
And (2).

N1 = N14 / N12 (1) V14 = V17 × N1 (2)

The induced voltage V 14 of the fourth winding 14 is generated in a direction in which the voltage V 17 across the input smoothing capacitor 17 is reduced as viewed from the second inductor 10. The induced voltage V13 is a voltage lower than the voltage V2 after the AC input of the commercial AC power supply 1 is rectified by the full-wave rectifier 2. Therefore, the current I10 shown in the following equation (3) flows in the direction of the fourth winding 14 in the second inductor 10, and the energy of the commercial AC power supply 1 is accumulated. Note that in equation (3),
L10 is the inductance value of the second inductor 10, and TON indicates the on-time during which the switch element 18 is turned on.

I10 = (V2−V17 + V14) × TON / L10 (3)

The switch element 18 and the resistor 19 supply a current I10 from the second inductor 10 to the fourth winding 1.
As a result, the current flows through the primary winding 12 of the transformer 11.

When the switch element 18 is turned off, the induced voltage V14 generated in the fourth winding 14 is inverted and added to the voltage V17 across the input smoothing capacitor 17, and the AC input of the commercial AC power supply 1 is connected to a full-wave rectifier. 2 after rectification by V
Higher than 2. However, the second inductor 1
A current (hereinafter, referred to as a current of the second inductor 10) continues to flow due to the energy stored in 0, and a current of the second inductor 10 flows into the input smoothing capacitor 17 via the fourth winding 14. Also, the current of the second inductor 10 flows through the fourth winding 14, and as a result, the current flows through the primary winding 12, so that the control output winding 15 and the non-control output winding 16 Through the first and second
From the rectifying and smoothing circuits 22, 26 of the first and second loads 23,
Output currents respectively flow through 27. At this time, as described above, the output voltage applied to the first load 23 is detected by the control circuit 28 in order to control the switch element 18. When all the energy stored in the second inductor 10 is released and the current of the second inductor 10 becomes zero, the voltage V17 across the input smoothing capacitor 17 becomes the fourth voltage V17.
Since the induced voltage V14 generated in the winding 14 is added, the voltage becomes higher than the AC input voltage of the commercial AC power supply 1. However, the current that is going to return to the commercial AC power supply 1 is blocked by the second diode 9.

Next, the operation of the series connection composed of the first diode 7, the first inductor 8, and the third winding 13 will be described. When the switch element 18 is turned off, the third winding 13 of the transformer 11 has a turn ratio N15 between the number N15 of the control output winding 15 and the number N13 of the third winding 13.
2 is multiplied by the output voltage V22 to the first rectifying / smoothing circuit 22 to generate an induced voltage V13. These turns ratio N2 and induced voltage V13 are calculated by the following equations (4) and (5), respectively.

N2 = N13 / N15 (4) V13 = V22 × N2 (5)

The induced voltage V13 of the third winding 13 is generated in such a direction as to reduce the voltage V17 across the input smoothing capacitor 17 as viewed from the first inductor 8. Also, the induced voltage V
Reference numeral 13 denotes a voltage lower than the voltage V2 after the AC input of the commercial AC power supply 1 is rectified by the full-wave rectifier 2. Therefore, a current I8 expressed by the following equation (6) flows through the first inductor 8 in the direction of the third winding 13 so that the commercial AC power supply 1
Energy is stored. Note that, in equation (6), L
8 is the inductance value of the first inductor 8, and TO
FF indicates an off time during which the switch element 18 is turned off.

I8 = (V2−V17 + V13) × TOFF / L8 (6)

Further, the current I8 flows from the first inductor 8 to the third winding 13, and as a result,
The first from the control output winding 15 and the non-control output winding 16
The currents supplied to the first and second loads 23 and 27 via the rectifying and smoothing circuits 22 and 26, respectively, decrease. However, the output voltage to the first load 23 is
The ON / OFF operation of the switch element 18 by the control circuit 28 is controlled to a constant voltage.

When the switching element 18 is turned on, the induced voltage V13 generated in the third winding 13 is inverted and added to the voltage V17 across the input smoothing capacitor 17, so that the AC input of the commercial AC power supply 1 is full-wave rectified. 2 after rectification by V
Higher than 2. However, the first inductor 8
(Hereinafter, referred to as the current of the first inductor 8) continues to flow due to the energy stored in the first inductor 8, and the current of the first inductor 8 flows into the input smoothing capacitor 17 via the third winding 13. Also, the current I8 is the first inductor 8
To the third winding 13, and as a result, the switching element 18 and the resistor 1 via the primary winding 12.
The current flowing through 9 decreases. All the energy stored in the first inductor 8 is released, and the first inductor 8
Is zero, the induced voltage V13 generated in the third winding 13 is added to the voltage V17 across the input smoothing capacitor 17, so that the voltage becomes higher than the AC input voltage of the commercial AC power supply 1. However, the current that is going to return to the commercial AC power supply 1 is blocked by the first diode 7.

As described above, the currents flowing through the first and second inductors 8 and 10 increase and decrease in opposite directions due to the ON and OFF operations of the switch element 18, and the commercial AC power supply 1
The input current flowing through the full-wave rectifier 2 is a continuous current having a small peak current as shown by the waveform of the current I2 shown in FIG.

FIG. 3 is a waveform diagram showing current waveforms at various parts during operation of the switching power supply of the first embodiment shown in FIG. In FIGS. 3A, 3B, 3C, and 3D, the horizontal axis is the time axis. In addition, FIG.
A period indicated by “F” indicates a period in which the AC input of the commercial AC power supply 1 is near zero voltage, and a period indicated by “G” indicates a period in which the AC input is near the peak voltage.
In FIG. 3A, I10 indicated by a solid line indicates a current waveform of the second inductor 10, and I8 indicated by a dotted line indicates a current waveform of the first inductor 8. FIG. 3 (b)
I18 shown in FIG. 9 indicates the waveform of the switching current flowing through the switch element 18. A shown by a two-dot chain line
Indicates a limit value of the overcurrent set in the control circuit 28 in advance. When the switching current I18 exceeds the overcurrent limit value A, the control circuit 28 determines that the output current supplied to the first load 23 is an overcurrent, and
Turn 8 off. Further, the hatched portion B indicates the second inductor 10 transmitted from the second inductor 10 to the primary winding 12 and the switch element 18 by the energy stored in the second inductor 10 of the switching current I18.
Shows the current component of the current. The hatched portion C indicates the current of the first inductor 8 which is transmitted from the first inductor 8 to the primary winding 12 and the switch element 18 by the energy stored in the first inductor 8 in the switching current I18. Of the current component of FIG. FIG. 3 (c)
I15 shown in FIG. 9 indicates a waveform of a current flowing through the control output winding 15 of the transformer 11. Further, the hatched portion D is caused by the energy stored in the second inductor 10,
The current component of the current of the second inductor 10 transmitted to the control output winding 15 due to the current flowing from the inductor 10 to the primary winding 12 indicates the current component of the second inductor 10. A current flows from the first inductor 8 to the primary winding 12 by the stored energy, so that the first inductor 8 is transmitted to the control output winding 15.
Shows the current component of the current. I shown in FIG.
16 shows a waveform of a current flowing through the non-control output winding 16 of the transformer 11, and a hatched portion E ′ is generated from the first inductor 8 to the primary winding 12 by the energy stored in the first inductor 8. The current component of the current of the first inductor 8 transmitted to the non-control output winding 16 due to the flow of the current is shown.

As described above, in the switching power supply of this embodiment, the energy from the commercial AC power
The current stored in the second inductors 8, 10 and flowing by the stored energy is superimposed on the AC input.
As a result, the conduction angle of the input current of the commercial AC power supply 1 can be widened and the power factor can be increased. Further, the current of the second inductor 10 increases while the switch element 18 is on and decreases during the off period, and conversely, the current of the first inductor 8 decreases while the switch element 18 is on and the off period To increase. Therefore, as shown by the current waveform I2 in FIG. 2, the input current from the commercial AC power supply 1 flows continuously as a result, and the peak current value is greatly reduced. As a result, the commercial AC power supply 1
The noise filter disposed between the power supply and the full-wave rectifier 2 can be downsized. In addition, since the input current flows separately to the first and second inductors 8 and 10, the current value shared by the inductors 8 and 10 is reduced. For this reason, each inductance value of the first and second inductors 8 and 10 can be set large, and large output can be easily performed. Further, due to the decrease in the current of the second inductor 10, as shown in FIG. 3B, the second current superimposed on the current flowing through the primary winding 12 during the ON period of the switch element 18. The current component B of the current of the inductor 10 also decreases. As a result, most of the switching current detected by the resistor 19 is occupied by the current component of the current to be detected, which is determined by the output current to the first and second loads 23 and 27, and the overcurrent limit value A The setting accuracy and the stability of the overcurrent control can be improved. Further, the switch element 18
During the off period of the first and second inductors 8, 1
Since the increase and decrease of the current flowing through 0 are opposite to each other, the current components transmitted to the control output winding 15 and the non-control output winding 16 are canceled out and reduced. As a result, the ripple voltage component of the commercial AC at the output voltage can be reduced. Further, the current of the first inductor 8 continues to flow through the third winding 13 to the control output winding 15 and the non-control output winding 16 while the switch element 18 is off. Therefore, the current component of the current of the first inductor 8 transmitted to the control output winding 15 and the non-control output winding 16 of the transformer 11 affects the entire off period, and the output voltage to the first load 23 is reduced. And the ripple voltage of the commercial AC generated in the output voltage to the second load 27 is also generated in both, and even if the gain of the control circuit 28 is increased to suppress the ripple voltage of the commercial AC, The AC ripple voltage can be reduced at the same time.

<< Second Embodiment >> FIG. 4 is a block diagram showing a configuration of a switching power supply device according to a second embodiment of the present invention. In this embodiment, in the configuration of the switching power supply device, an input smoothing capacitor for applying an input voltage to the primary winding is constituted by two capacitors connected in series, and a connection point of these capacitors and a series connection of a full-wave rectifier are provided. A switch element for switching the rectifier circuit of the AC input is provided between the connection point of the two diodes connected to the switch. Further, a fifth winding and a sixth winding are provided on the power supply side of the transformer, and the fifth and sixth windings are connected in series with two series-connected bodies in which a winding of an inductor part and a diode are connected in series. pcc 'was formed, and the parallel circuit pcc' was connected to the negative output of the full-wave rectifier. The other parts are the same as those of the first embodiment, and the duplicated description thereof will be omitted. As shown in FIG. 4, on the power supply side of the transformer 29,
A fifth winding 30 and a sixth winding 31 are provided. These fifth and sixth windings 30 and 31 are turned on and off by the switching element 18, respectively.
It is connected to the primary winding 12 so as to generate induced voltages that are induced in opposite directions when a current flows through 31.
Specifically, when the switch element 18 is turned on, the fifth winding 30 causes the induced voltage to change to an input smoothing capacitor 41 described later.
Of the primary winding 12 so as to be generated in a direction to increase the voltage between both ends.
It is connected to the. On the other hand, the sixth winding 31 is connected to the primary winding 12 such that when the switch element 18 is turned on, an induced voltage is generated in a direction to reduce the voltage across the input smoothing capacitor 41. These induced voltages are generated in opposite directions when the switch element 18 is turned off.
Instead of the first and second inductors 8 and 10 shown in FIG. 1, first and second inductor units 32 and 35 are provided, respectively. The first inductor section 32 includes two windings 3
3, 34. These windings 33, 3
4 is a first inductor unit 3 which is driven by currents flowing through each other.
2 are inductively coupled (coupled to polarities) so as to excite them in the same direction. Similarly, the second inductor section 35
It is constituted by two windings 36 and 37. These windings 36 and 37 are inductively coupled (coupled to polarities) so as to excite the second inductor section 35 in the same direction by currents flowing through each other. The windings 34 and 37 are
It has the same function as the first and second inductors 8 and 10 shown in FIG.

The positive output of the full-wave rectifier 2 includes the first diode 7, the winding 34 of the first inductor 32, and the third
A series connection body in which windings 13 of
, The winding 37 of the second inductor part 35,
One end of a parallel circuit pcc is connected to a series connection body in which the fourth winding 14 is sequentially connected in series. Similarly,
The negative output of the full-wave rectifier 2 includes a third diode 38, a winding 33 of the first inductor 32, and a fifth winding 30.
Are serially connected in series, the fourth diode 39, the winding 36 of the second inductor unit 35, and the sixth
Is connected to one end of a parallel circuit pcc 'with a serially connected body in which the windings 31 are sequentially connected in series. Between the other ends of these two parallel circuits pcc and pcc ', instead of the input smoothing capacitor 17 shown in FIG.
Two input smoothing capacitors 40 and 41 are connected.
A switch element 42 is connected between a connection point between the diodes 5 and 6 and a connection point between the input smoothing capacitors 40 and 41. The switch element 42 is used for switching between full-wave rectification and double voltage rectification of AC input. That is, when the input voltage of the AC input is low, the switch element 42 is turned on to perform voltage doubler rectification of the AC input. When the input voltage of the AC input is high, the switch element 42 is turned off to perform full-wave rectification of the AC input.

In the operation of the switching power supply of this embodiment, when the input voltage from the commercial AC power supply 1 is high, the switch element 42 is turned off and the AC input is full-wave rectified by the full-wave rectifier 2. The current from the full-wave rectifier 2 is divided into the first and second diodes 7 and 9, the winding 34 of the first inductor 32 and the winding 3 of the second inductor 35.
7 and two input smoothing capacitors 4 connected in series via the third and fourth windings 13 and 14 of the transformer 29.
0, 41 and their input smoothing capacitors 4
Charge 0,41. Subsequently, the input smoothing capacitor 4
After smoothing to a DC having a small ripple voltage component by 0, 41, the switching element 18 is turned on and off using a frequency higher than the commercial AC frequency of the AC input,
An AC voltage is applied to the primary winding 12 of the transformer 29. Then, the induced voltages induced in the control output winding 15 and the non-control output winding 16 of the transformer 29 are output to the first and second rectifying and smoothing circuits 22 and 26, respectively, and rectified and smoothed. The power is supplied to the first and second loads 23 and 27, respectively. When the input voltage from the commercial AC power supply 1 is low, the switch element 42 is turned on, and the AC input is supplied to the input smoothing capacitors 40 and 41 every positive and negative half cycle of the voltage.
And the input smoothing capacitors 40 and 41 are charged. Specifically, in the positive half cycle of the commercial AC power supply 1, the current from the commercial AC power supply 1 is supplied to the diode 3, the first and second diodes 7, 9 of the full-wave rectifier 2, and the first inductor 32. , The winding 37 of the second inductor part 35, the third and fourth windings 13, 14 of the transformer 29,
The current flows in the order of the input smoothing capacitor 40 and the switch element 42 to charge the input smoothing capacitor 40. on the other hand,
In the negative half cycle of the commercial AC power supply 1, the current from the commercial AC power supply 1
1, the fifth and sixth windings 30, 31 of the transformer 29, the first
Of the inductor part 32 and the second inductor part 3
5 flows in the order of the winding 36, the third and fourth diodes 38 and 39, and the diode 4 of the full-wave rectifier 2, and charges the input smoothing capacitor 41. As a result, the voltage across the input smoothing capacitors 40 and 41 is
Can be twice as high as the input voltage. After charging the input smoothing capacitors 40 and 41, the same operation as in the case where the above-described switch element 42 is turned off to perform full-wave rectification is performed, and the DC output voltage is reduced to the first and second rectifications. The smoothing circuits 22 and 26 supply the first and second loads 23 and 27, respectively.

Next, an operation of increasing the conduction angle of the input current flowing from the commercial AC power supply 1 to the full-wave rectifier 2 to increase the power factor in the switching power supply of the second embodiment shown in FIG. 4 will be described. First, the operation when the input voltage of the AC input is high and the switch element 42 is turned off to perform full-wave rectification on the AC input will be described. When the switch element 18 is turned on, an induced voltage is generated in the sixth winding 31 of the transformer 29 in a direction that becomes a positive voltage when viewed from the winding 36 of the second inductor section 35, and a current due to the induced voltage is generated. The current flows through the winding 36, the fourth diode 39, and the full-wave rectifier 2 toward the fourth winding 14 of the transformer 29. At the same time, similarly to the switching power supply of the first embodiment shown in FIG.
A current flows from the winding 37 of the inductor section 35 to the fourth winding 14. As a result, the full-wave rectifier 2, the second diode 9, the winding 37, the fourth winding 14,
A current flows through the input smoothing capacitors 40 and 41, the sixth winding 31, the winding 36, and the fourth diode 39. Since the windings 36 and 37 of the second inductor unit 35 are inductively coupled to each other to excite the second inductor unit 35 in the same direction by the current flowing through each other, the second current is caused to flow by the second current. The energy of the commercial AC power supply 1 is stored in the windings 36 and 37 of the inductor section 35. In addition, the switch element 18 and the resistor 19 have a fourth,
As a result of the current flowing through the sixth windings 14 and 31, as a result, the current flows through the primary winding 12 of the transformer 29.

When the switch element 18 is turned on,
An induced voltage is generated in the fifth winding 30 of the transformer 29 in a direction that becomes a negative voltage when viewed from the winding 33 of the first inductor unit 32. This induced voltage is lower than the voltage after the AC input of the commercial AC power supply 1 is rectified by the full-wave rectifier 2. However, the energy stored in the winding 33 of the first inductor portion 32 causes the fifth
The current continues to flow to the input smoothing capacitor 41 via the winding 30 of FIG. At the same time, as in the switching power supply of the first embodiment shown in FIG.
Due to the energy stored in 4, a current flows from the winding 34 of the first inductor section 32 to the input smoothing capacitor 40 via the third winding 13. As a result, the full-wave rectifier 2, the first diode 7, the winding 34,
The third winding 13, the input smoothing capacitors 40 and 41, the fifth
A current flows through the winding 30, the winding 33, and the third diode 38, and the input smoothing capacitors 40 and 41 are charged. Further, since the current flows through the third and fifth windings 13 and 30 of the transformer 29, as a result, 1
The current flowing through the switch element 18 and the resistor 19 via the secondary winding 12 decreases. Winding 3 of first inductor section 32
When all the energy stored in the windings 33 and 34 is released and the current from the windings 33 and 34 becomes zero, the voltage across the input smoothing capacitors 40 and 41 is applied to the third and fifth windings 13 and 3.
0, the commercial AC power supply 1
Is higher than the AC input voltage. However,
The currents to be returned to the commercial AC power supply 1 are the first and third currents.
Are blocked by the diodes 7 and 38 of FIG.

When the switch element 18 is turned off, the induced voltage generated in the sixth winding 31 is inverted and becomes a negative voltage when viewed from the winding 36 of the second inductor section 35, so that the AC input of the commercial AC power supply 1 is completely reduced. It becomes lower than the voltage after being rectified by the wave rectifier 2. However, the current continues to flow due to the energy stored in the winding 36, and the current flows to the input smoothing capacitor 41 via the sixth winding 31. At the same time, FIG.
Similarly to the switching power supply of the first embodiment shown in FIG.
The current continues to flow from the winding 37 to the input smoothing capacitor 40 via the fourth winding 14 due to the energy stored in the winding 37 of the second inductor section 35. Further, the current flows through the fourth and sixth windings 14 and 31 and, as a result, flows through the primary winding 12, so that the current flows through the control output winding 15 and the non-control output winding 16 of the transformer 29. , First and second loads 23 and 2 from first and second rectifying and smoothing circuits 22 and 26.
7, the output currents respectively flow. Second inductor section 3
When all the energy accumulated in the windings 36 and 37 is released and the current in the windings 36 and 37 becomes zero, the voltage across the input smoothing capacitors 40 and 41 is applied to the fourth and sixth windings 1.
Since the induced voltages at 4 and 31 are added, the voltage becomes higher than the input voltage of the commercial AC power supply 1. However,
The currents to be returned to the commercial AC power supply 1 are the second and fourth currents.
Are blocked by the diodes 9 and 39.

When the switch element 18 is turned off,
The induced voltage generated in the fifth winding 30 is also inverted, and becomes a positive voltage when viewed from the winding 33 of the first inductor 32. Then, a current caused by the induced voltage flows toward the third winding 13 via the winding 33, the third diode 38, and the full-wave rectifier 2. At the same time, similarly to the switching power supply of the first embodiment shown in FIG. 1, the induced voltage generated in the third winding 13 causes the third winding 13 of the first inductor 32 to
Current flows through the winding 13. As a result, the commercial AC power supply 1
Through the full-wave rectifier 2, the first diode 7, the winding 34, the third winding 13, the input smoothing capacitors 40 and 41, the fifth winding 30, the winding 33, and the third diode 38. Electric current flows. The winding 33 of the first inductor part 32,
34 are inductively coupled to excite the first inductor 32 in the same direction by currents flowing through each other, so that the current flows to the windings 33 and 34 of the first inductor 32. Stores the energy of the commercial AC power supply 1. Further, since the current flows from the windings 33 and 34 to the third and fifth windings 13 and 30, as a result, the control output winding 15 and the non-control output winding 16
, The current supplied to the first and second loads 23 and 27 via the first and second rectifying / smoothing circuits 22 and 26 respectively decreases. However, the output voltage to the first load 23 is controlled to be a constant voltage by the control circuit 28 turning on and off the switch element 18.

Next, the operation in the case where the switching element 42 is turned on and the AC input is subjected to voltage doubler rectification will be described. When the switch element 18 is turned on, the fourth and sixth windings 14 and 31 of the transformer 29 are turned on, as in the above-described full-wave rectification.
Generates an induced voltage. As a result, the current flows from the commercial AC power supply 1 to the diode 3, the second diode 9, the winding 37 of the second inductor unit 35, the fourth
And the current flows from the commercial AC power supply 1 to the switch element 42, the input smoothing capacitor 41, the sixth winding 31, and the second inductor 35. The winding 36, the fourth diode 39, and the diode 4 of the full-wave rectifier 2 appear alternately in every positive and negative half cycle of the voltage of the commercial AC power supply 1. Thereby, the windings 36, 37
Stores the energy of the commercial AC power supply 1. Further, when an induced voltage is generated in the third and fifth windings 13 and 30, each of the windings 33 and 30 is turned off when the switch element 18 is turned off.
Until all the energy stored in 34 is released, the current of each winding 33, 34 due to the energy flows alternately through the third and fifth windings 13, 30 for each of the positive and negative half cycles. That is, the current of the winding 34 is changed from the commercial AC power supply 1 to the diode 3 of the full-wave rectifier 2, the first diode 9,
The winding 34 of the first inductor part 32, the third winding 13,
The state in which the input smoothing capacitor 40 and the switch element 42 flow in this order, and the current of the winding 33 flows from the commercial AC power supply 1 to the switch element 42, the input smoothing capacitor 41, the fifth winding 30, and the first inductor 32 The state in which the winding 33, the third diode 38, and the diode 4 of the full-wave rectifier 2 flow in this order appears alternately in each of the positive and negative half cycles described above. When all the energy stored in each of the windings 33 and 34 is released and the current in each of the windings 33 and 34 becomes zero, the current to be returned to the commercial AC power supply 1 becomes the first and third currents as described above. Blocked by diodes 7,38. Further, the current is applied to the fourth and sixth windings 1 of the transformer 29.
4 and 31, the current flowing through the switching element 18 and the resistor 19 via the primary winding 12 increases, and furthermore, the current flowing through the third and fifth windings 13 and 30 increases
The current flowing through the switch element 18 and the resistor 19 via the secondary winding 12 decreases.

When the switch element 18 is turned off, an induced voltage is generated in the fourth and sixth windings 14 and 31 in a direction opposite to that when the switch element 18 is turned on. This allows
Until all of the energy stored in the windings 36 and 37 is released when the switch element 18 is turned on, the current of each of the windings 36 and 37 due to the energy is supplied through the same current path as when the switch element 18 is turned on. It flows alternately every positive and negative half cycle of the voltage of the AC power supply 1. Each winding 36, 37
All the energy stored in the windings is released, and each winding 36,
When the current at 37 becomes zero, the current that is going to return to the commercial AC power supply 1 is blocked by the second and fourth diodes 9 and 39 as described above. Similarly, an induced voltage is generated in the third and fifth windings 13 and 30 in a direction opposite to that when the switch element 18 is turned on. As a result, current flows from the commercial AC power supply 1 to the diode 3 of the full-wave rectifier 2, the first diode 7, and the winding 3 of the first inductor unit 32.
4, a state in which the third winding 13, the input smoothing capacitor 40, and the switch element 42 flow in this order, and a current flows from the commercial AC power supply 1 to the switch element 42, the input smoothing capacitor 4
1, fifth winding 30, winding 3 of first inductor section 32
The state of flowing in the order of 3, the third diode 38, and the diode 4 of the full-wave rectifier 2 appears alternately in each of the positive and negative half cycles described above. As a result, the windings 33 and 34 have
The energy of the commercial AC power supply 1 is stored. Also, current flows through the fourth and sixth windings 14 and 31 of the transformer 29,
As a result, a current flows through the primary winding 12, and the control output winding 15 and the non-control output winding 16
Output currents flow from the first and second rectifying and smoothing circuits 22 and 26 to the first and second loads 23 and 27, respectively. further,
Since the current flows through the third and fifth windings 13 and 30, and as a result, the current flows through the primary winding 12, the output current to the first and second loads 23 and 27 decreases. . still,
The reason that the currents of the windings 36 and 37 of the second inductor part 35 and the windings 33 and 34 of the first inductor part 32 flow only alternately every positive and negative half cycle of the voltage of the commercial AC power supply 1 is as follows. Even if an induced voltage is constantly generated in the third to sixth windings 13, 14, 30, 31, the input voltage is changed from the commercial AC power supply 1 to the winding 33 or the winding 34 and the winding 36 or the winding 3.
7 is applied alternately.

When the input voltage of the AC input is low and voltage doubler rectification is performed, the input voltage is alternately applied from the commercial AC power supply 1 to the windings 36 and 37 of the second inductor section 35, so that the respective windings 36 and 37 are applied. The current value IL2 that flows alternately is determined by the following equation (7). Incidentally, in equation (7), VT2
Indicates the induced voltage values at the fourth and sixth windings 14 and 31 of the transformer 29 (the same voltage as during full-wave rectification), and V2
Indicates a voltage value after the AC input of the commercial AC power supply 1 is rectified by the full-wave rectifier 2. Further, L2 indicates the inductance value of one of the windings 36, 37 of the second inductor section 35, and VC indicates the voltage value across one of the input smoothing capacitors 40, 41. Further, TON indicates an on-time during which the switch element 18 is turned on.

IL2 = (V2−VC + VT2) × TON / L2 (7)

On the other hand, when the input voltage of the AC input is high and full-wave rectification is performed, the windings 36 and 37 of the second inductor section 35 are used.
Is obtained by the following equation (8). In equation (8), 2VT2 indicates the voltage value of the sum of the induced voltage values VT2 in the fourth and sixth windings 14 and 31, and 4L2 indicates the winding 3 of the second inductor 35.
6 shows an inductance value determined by the sum of the numbers of windings of the windings 6 and 37 (the windings 36 and 37 are coupled to each other with additional polarities, which is four times that of the voltage doubled rectification). Further, V2 'indicates a voltage value after the AC input of the commercial AC power supply 1 is rectified by the full-wave rectifier 2, and 2VC indicates an input smoothing capacitor 40,
41 shows the voltage value of the sum of the voltage values VC at both ends.

IL 2 ′ = (V 2 ′ −2 VC + 2 VT 2) × TON / 4L 2-(8)

In the equation (8), when the input voltage of the commercial AC power supply 1 is twice as large as that during the double voltage rectification, the windings 36 and 37
Of the current IL2 'flowing simultaneously through the windings 36 and 37 during the voltage doubling rectification is half of the current IL2' flowing through the windings 36 and 37. That is, the above-mentioned current value IL2 'is obtained by the following equation (10) by substituting V2' shown in the following equation (9) into the equation (8) and deforming it.

V2 '= 2V2 --- (9) IL2' = (V2-VC + VT2) .times.TON / 2L2 = IL2 / 2 / --- (10)

Considering the above assumption that the input voltage at the time of full-wave rectification is twice the input voltage at the time of voltage doubler rectification, it is clear from the equation (10) that the input voltage during full-wave rectification and the voltage doubler rectification are different. It can be seen that the same power is supplied from the AC input and the operating conditions in the switching power supply are the same.

Similarly, in the first inductor section 32, when the input voltage of the AC input is low and voltage doubler rectification is performed,
The input voltage is changed from the commercial AC power supply 1 to the first inductor section 32.
Are applied alternately to the windings 33 and 34 of each winding.
The current value IL1 flowing alternately to the third and the third 34 is represented by the following (1)
1) It is obtained by the equation. Incidentally, in equation (11), VT1
Indicates the induced voltage values at the third and fifth windings 13 and 30 of the transformer 29 (the same voltage as in full-wave rectification), and V2
Indicates a voltage value after the AC input of the commercial AC power supply 1 is rectified by the full-wave rectifier 2. Further, L1 indicates the inductance value of one of the windings 33, 34 of the first inductor section 32, and VC indicates the voltage value across one of the input smoothing capacitors 40, 41. Further, TON indicates an on-time during which the switch element 18 is turned on.

IL1 = (V2−VC + VT1) × TON / L1 (11)

On the other hand, when the input voltage of the AC input is high and full-wave rectification is performed, the windings 33 and 34 of the first inductor portion 32 are used.
Is obtained by the following equation (12). In the equation (12), 2VT1 represents a voltage value of the sum of the induced voltage values VT1 in the third and fifth windings 13 and 30, and 4L1 represents the windings 33 and 34 of the first inductor section 32. (The windings 33 and 34 are coupled to each other by polarities and become four times as large as the voltage doubled rectification). Furthermore, V
1 'denotes a voltage value after the AC input of the commercial AC power supply 1 is rectified by the full-wave rectifier 2, and 2VC denotes a voltage value of the sum of the voltage values VC across the input smoothing capacitors 40 and 41.

IL1 '= (V2'-2VC + 2VT1) .times.TON / 4L1 --- (12)

In the equation (12), when the input voltage of the commercial AC power supply 1 is twice as large as that during the voltage doubler rectification, the windings 33 and 3
The current value IL1 'flowing simultaneously to 4 is half of the current value IL1 flowing alternately through the windings 33 and 34 during voltage doubling rectification. That is, the above-mentioned current value IL1 'is calculated by the following (13)
By substituting V2 'shown in the equation into the equation (12) and transforming it, it is obtained by the following equation (14).

V2 ′ = 2V2− (13) IL1 ′ = (V2−VC + VT1) × TON / 2L1 = IL1 / 2 −− (14)

Considering the above assumption that the input voltage at the time of full-wave rectification is twice the input voltage at the time of voltage doubler rectification, as is apparent from the equation (14), the input voltage at the time of full-wave rectification and that at the time of voltage doubler rectification are different. It can be seen that the same power is supplied from the AC input and the operating conditions in the switching power supply are the same.

As described above, in the switching power supply of this embodiment, the AC input of the commercial AC power supply 1 is double-voltage rectified or full-wave rectified by turning on and off the switch element 42. As a result, the switching power supply of the present embodiment has, in addition to the effects of the above-described first embodiment, the passage of the switching element 18 and the diodes 20, 24 even when the input voltage of the AC input has a large fluctuation range. The current and the breakdown voltage have almost the same value. Therefore, it is possible to configure a switching power supply device that is compatible with commercial AC used worldwide, without using a large current and a high withstand voltage for the switch element 18 and the diodes 20 and 24.

<< Third Embodiment >> FIG. 5 is a block diagram showing a configuration of a switching power supply device according to a third embodiment of the present invention. In this embodiment, in the configuration of the switching power supply, a primary winding and a third winding connected to the primary winding are provided on the power supply side of the transformer, and the first inductor and the third winding are connected to each other. The series-connected body connected in series was connected to a full-wave rectifier. The other parts are the same as those of the first embodiment, and the duplicated description thereof will be omitted. As shown in FIG. 5, in the transformer 43, a primary winding 12 and a third winding 13 are provided as windings on the power supply side. The positive output of the full-wave rectifier 2 is connected to a series connection body in which the first inductor 8 and the third winding 13 are sequentially connected in series. When the switch element 18 is turned on and off, the induced voltage of the third winding 13 increases the voltage across the input smoothing capacitor 17, as in the first embodiment shown in FIG. And to the primary winding 12 so as to occur in the decreasing direction. With this configuration, in the switching power supply of the present embodiment, the full-wave rectifier 2 functions in the same manner as the first diode 7 shown in FIG. The second inductor 10 and the fourth winding 14 can be omitted.

Next, FIG. 6 shows the voltage waveform and the current waveform of each part during the operation of the switching power supply of this embodiment.
In FIGS. 6A, 6B, 6C, and 6D, the horizontal axis is the time axis. In FIG. 6A, V2
Is the AC input of the commercial AC power supply 1 (FIG. 5)
FIG. 5 shows the waveform of the voltage after rectification, and V8 shows the waveform obtained by adding the induced voltage V13 of the third winding 13 (FIG. 5) and the voltage V17 across the input smoothing capacitor 17. . I8 shown in FIG. 6B is the first inductor 8
5 shows the waveform of the current flowing through the third winding 13. Ic shown in FIG. 6C indicates the waveform of the current flowing through the primary winding 12 due to the current I8 flowing through the third winding 13. (I15 + I16) shown in FIG. 6D corresponds to the result of the current I8 flowing through the third winding 13 and the control output winding 15 (FIG. 5) and the non-control output winding 16 (FIG. 5). )
3 shows a composite waveform of a current flowing through the rectifier.

The operation of the switching power supply of this embodiment for increasing the conduction angle of the input current flowing from the commercial AC power supply 1 to the full-wave rectifier 2 and increasing the power factor will be specifically described.
When the switch element 18 is turned off, an induced voltage V13 is generated in the third winding 13 of the transformer 43 in such a direction as to reduce the voltage V17 across the input smoothing capacitor 17 as viewed from the first inductor 8. The induced voltage V13 can be obtained by the above equation (5), and is lower than the voltage V2 after the AC input of the commercial AC power supply 1 is rectified by the full-wave rectifier 2. Therefore, the current I8 flows through the first inductor 8 in the direction of the third winding 13, and the energy of the commercial AC power supply 1 is accumulated. In addition, the current I8 flows from the first inductor 8 to the third winding 13, and as a result, the first and second rectification smoothes from the control output winding 15 and the non-control output winding 16. Circuit 22, 2
6, the current supplied to the first and second loads 23, 27 respectively decreases. However, the output voltage to the first load 23 is controlled to be a constant voltage by the control circuit 28 turning on and off the switch element 18.

When the switch element 18 is turned on, the induced voltage V13 generated in the third winding 13 is inverted and added to the voltage V17 across the input smoothing capacitor 17, and the AC input of the commercial AC power supply 1 is converted to a full-wave rectifier. 2 after rectification by V
Higher than 2. However, the first inductor 8
, The current of the first inductor 8 continues to flow, and the current of the first inductor 8 flows into the input smoothing capacitor 17 via the third winding 13. Further, the current I8 is supplied from the first inductor 8 to the third winding 13
As a result, the current flowing through the switch element 18 and the resistor 19 via the primary winding 12 decreases. When all the energy stored in the first inductor 8 is released and the current in the first inductor 8 becomes zero, the induced voltage V13 generated in the third winding 13 is added to the voltage V17 across the input smoothing capacitor 17. Therefore, the voltage becomes higher than the AC input voltage of the commercial AC power supply 1. However, the current that is going to return to the commercial AC power supply 1 is blocked by the full-wave rectifier 2.

FIG. 7 is a waveform diagram showing current waveforms at various parts during the operation of the switching power supply of the first embodiment shown in FIG. In FIGS. 7A, 7B, 7C, and 7D, the horizontal axis is the time axis. FIG.
The period indicated by “F” indicates a period during which the AC input of the commercial AC power supply 1 is near zero voltage, and the period indicated by “G” indicates a period during which the AC input is near the peak voltage. . In FIG. 7A, I8 indicates the waveform of the current of the first inductor 8. I18 shown in FIG.
Shows the waveform of the switching current flowing through the switch element 18. A indicated by a two-dot chain line indicates an overcurrent limit value preset in the control circuit 28. When the switching current I18 exceeds the overcurrent limit value A, the control circuit 28 determines that the output current supplied to the first load 23 is an overcurrent and turns off the switch element 18. Further, the hatched portion H indicates the current of the first inductor 8 which is transmitted from the first inductor 8 to the primary winding 12 and the switch element 18 by the energy stored in the first inductor 8 in the switching current I18. Of the current component of FIG. I15 shown in FIG. 7C indicates the waveform of the current flowing through the control output winding 15 of the transformer 43. The hatched portion I indicates that a current flows from the first inductor 8 to the third winding 13 due to the energy stored in the first inductor 8, and the control output winding 15
3 shows the current component of the current of the first inductor 8 transmitted to the first inductor 8. I16 shown in FIG. 7D indicates the waveform of the current flowing through the non-control output winding 16 of the transformer 43, and the hatched portion I 'indicates the first inductor 8 8 shows the current component of the current of the first inductor 8 that is transmitted to the non-control output winding 16 due to the current flowing from 8 to the third winding 13.

As described above, in the switching power supply of the present embodiment, the energy from the commercial AC power supply 1 is stored in the first inductor 8, and the current flowing by the stored energy is superimposed on the AC input. Thus, the conduction angle of the input current flowing from the commercial AC power supply 1 to the full-wave rectifier 2 can be widened and the power factor can be increased. Further, since the current of the first inductor 8 decreases during the ON period of the switch element 18 and becomes zero during the ON period, the influence of the current component of the current of the first inductor 8 flowing through the switch element 18 also occurs. It disappears by the peak of the switching current. That is, due to the decrease in the current of the first inductor 8, as shown in FIG. 7B, the current component H of the current of the first inductor 8 superimposed on the current flowing through the primary winding 12 is also small. Become. As a result, most of the switching current detected by the resistor 19 is transferred to the first and second loads 2.
It is occupied by the current component of the current to be detected, which is determined by the output currents to the output currents 3 and 27, so that the setting accuracy of the overcurrent limit value A and the stability of the overcurrent control can be improved. Further, during the off period of the switch element 18, the current flowing through the first inductor 8 flows through the third winding 13 to the control output winding 15 and the non-control output winding 16 during the off period of the switch element 18. to continue. Therefore, the current component of the current of the first inductor 8 transmitted to the control output winding 15 and the non-control output winding 16 of the transformer 43 affects the entire off period, and the first The ripple voltage of the commercial AC generated in the output voltage to the load 23 and the output voltage to the second load 27 also occurs in both, and the gain of the control circuit 28 is increased to suppress the ripple voltage of the commercial AC. The ripple voltage of the commercial AC of both output voltages can be reduced at the same time.

<< Fourth Embodiment >> FIG. 8 is a block diagram showing a configuration of a switching power supply device according to a fourth embodiment of the present invention. In this embodiment, in the configuration of the switching power supply, a primary winding and third and fifth windings connected to the primary winding are provided on the power supply side of the transformer, and one of the windings of the inductor unit is connected to the primary winding. 3 and a series-connected body in which the other winding of the inductor section and the fifth winding are connected in series were connected to the positive output and the negative output of the full-wave rectifier, respectively. . The other parts are the same as those of the second embodiment, and the duplicated description thereof will be omitted. As shown in FIG. 8, on the power supply side of the transformer 44,
Primary winding 12, third and fifth windings 1 as power supply-side windings
3, 30 are provided. The positive output of the full-wave rectifier 2 includes the winding 34 of the first inductor 32 and the third winding 1
3 are connected in series. When the switch element 18 is turned on and off, the induced voltage of the third winding 13 increases the voltage across the input smoothing capacitor 40, as in the second embodiment shown in FIG. And one that occurs in the decreasing direction respectively
It is connected to the next winding 12. The negative output of the full-wave rectifier 2 includes the winding 33 of the first inductor 32 and the fifth winding 3
0 is connected in series. As in the fourth embodiment shown in FIG. 4, when the switch element 18 is turned on and off, the fifth winding 30 increases the voltage across the input smoothing capacitor 41 when the switch element 18 is turned on and off. And one that occurs in the decreasing direction respectively
It is connected to the next winding 12. With this configuration, in the switching power supply device of the present embodiment, the full-wave rectifier 2 includes the first and third diodes 7, 38 shown in FIG.
And the first to fourth diodes 7, 9,.
38, 39, the second inductor section 35, and the fourth and sixth
Can be omitted.

The operation of the switching power supply of this embodiment for widening the conduction angle of the input current flowing from the commercial AC power supply 1 to the full-wave rectifier 2 and increasing the power factor will be specifically described.
First, the operation when the input voltage of the AC input is high and the switch element 42 is turned off to perform full-wave rectification on the AC input will be described. When the switch element 18 is turned off, an induced voltage is generated in the third and fifth windings 13 and 30 of the transformer 44 in a direction to reduce the voltage across the input smoothing capacitors 40 and 41, respectively. Therefore, each of the windings 33,
A current flows through 34, and the input smoothing capacitors 40 and 41 are charged and energy is stored in the windings 33 and 34. Also,
As a result of the current flowing through the third and fifth windings 13 and 30, the control output winding 15
The current supplied from the non-control output winding 16 to the first and second loads 23 and 27 via the first and second rectifying / smoothing circuits 22 and 26 respectively decreases. However, the output voltage to the first load 23 is controlled to be a constant voltage by the control circuit 28 turning on and off the switch element 18.

When the switch element 18 is turned on, the third,
The induced voltages generated in the fifth windings 13 and 30 are inverted, and the induced voltages are added to the voltages across the input smoothing capacitors 40 and 41, respectively, but all the energy stored in the windings 33 and 34 is discharged. Until each winding 33,3
4 continues to flow through the input smoothing capacitors 40 and 41. Further, the current flowing through the third and fifth windings 13 and 30 through the windings 33 and 34 reduces the current flowing through the primary winding 12 to the switching element 18 and the resistor 19.
When all the energy stored in each of the windings 33 and 34 is released and the current in each of the windings 33 and 34 becomes zero, the current that is going to be fed back to the commercial AC power supply 1 is blocked by the full-wave rectifier 2. By the operation described above, the first inductor unit 3
2 becomes an input current from the commercial AC power supply 1 via the full-wave rectifier 2, and widens the conduction angle of the input current.

Next, the operation in the case where the input voltage of the AC input is low and the switch element 32 is turned on to perform the voltage doubler rectification of the AC input will be described. When the switch element 17 is turned off, an induced voltage is generated in the third winding 13 of the transformer 44 in a direction to reduce the voltage between both ends of the input smoothing capacitor 40, and an input smoothing capacitor 41 is applied to the fifth winding 30. An induced voltage is generated in a direction to decrease the voltage between both ends. As a result, a current flows through the winding 34 of the first inductor section 32 by a voltage lower than the voltage obtained by rectifying the AC input of the commercial AC power supply 1 by the full-wave rectifier 2, and the input smoothing capacitor 40 is charged. The state in which the energy is stored in the windings 34 and the state in which a current flows through the windings 33 of the first inductor section 32 to charge the input smoothing capacitor 41 and store the energy in the windings 33 are different from each other. It is alternately repeated every positive and negative half cycle of one voltage. In addition, since the current flows through the third and fifth windings 13 and 30, as a result, the first and second rectifying / smoothing circuits are output from the control output winding 15 and the non-control output winding 16 of the transformer 44. 22, 26
, The current supplied to the first and second loads 23 and 27 respectively decreases. However, the output voltage to the first load 23 is controlled to be a constant voltage by the control circuit 28 turning on and off the switch element 18.

When the switch element 18 is turned on, the third,
The induced voltages generated in the fifth windings 13 and 30 are inverted, and the induced voltages are added to the voltages across the input smoothing capacitors 40 and 41, respectively. However, until all the energy stored in the winding 33 of the first inductor section 32 is released, the current of the winding 33
1 and the state where the current of the winding 34 continues to flow through the input smoothing capacitor 40 until all the energy stored in the winding 34 of the first inductor 32 is released. Are alternately repeated for every positive and negative half cycle of the voltage. In addition, when current flows through the third and fifth windings 13 and 30 of the transformer 44, the primary winding 12
, The current flowing through the switch element 18 and the resistor 19 decreases. When all the energy stored in each of the windings 33 and 34 is released and the current in each of the windings 33 and 34 becomes zero,
The current that is going to return to the commercial AC power supply 1 is blocked by the full-wave rectifier 2. By the above-described operation, the current flowing through the windings 33 and 34 of the first inductor unit 32 passes through the diodes 3 and 4 of the full-wave rectifier 2 every positive and negative half cycles of the voltage of the commercial AC power supply 1. As a result, the input current from the commercial AC power supply 1 is generated, and the conduction angle of the input current is increased. still,
The reason that the currents of the windings 33 and 34 of the first inductor section 32 flow only alternately every positive and negative half cycles of the voltage of the commercial AC power supply 1 is that the currents are constantly induced in the third and fifth windings 13 and 30. Even if a voltage is generated, the input voltage is
3 or the winding 34.

As described above, in the switching power supply of this embodiment, the AC input of the commercial AC power supply 1 is double-voltage rectified or full-wave rectified by turning on and off the switch element 42. As a result, the switching power supply device of the present embodiment, even in the case where the fluctuation range of the AC input voltage is large, is
The passing current and the breakdown voltage of the switch element 18 and the diodes 20 and 24 have substantially the same value. Therefore, it is possible to configure a switching power supply device that is compatible with commercial AC used worldwide, without using a large current and a high withstand voltage for the switch element 18 and the diodes 20 and 24. Further, during the OFF period of the switch element 18, the current flowing through the windings 33 and 34 of the first inductor section 32 passes through the third winding 13 and the fifth winding 30, and the control output winding 15 and the uncontrolled Switch element 1 in output winding 16
8 keeps flowing during off period. Therefore, the transformer 44
The current components of the currents of the windings 33 and 34 transmitted to the control output winding 15 and the non-control output winding 16 affect the entire off period, and the output voltage to the first load 23 and the second load 27
The ripple voltage of the commercial AC generated in the output voltage to both the AC voltage and the AC voltage ripple is suppressed. Can be smaller.

<< Fifth Embodiment >> FIG. 9 is a block diagram showing a configuration of a switching power supply device according to a fifth embodiment of the present invention. In this embodiment, in the configuration of the switching power supply device, a bias voltage is supplied from the fifth winding 30 of the transformer to the control circuit 28. The other parts are the same as those of the first embodiment, and the duplicated description thereof will be omitted. As shown in FIG. 9, a primary winding 12 and fifth and sixth windings 30 and 31 connected to the primary winding 12 are provided on the power supply side of the transformer 45. The fifth winding 30 is connected to the primary winding 12 so that when the switch element 18 is turned off, an induced voltage is generated in a direction to reduce the voltage across the input smoothing capacitor 17. On the other hand, the sixth winding 31 is connected to the primary winding 12 so that when the switch element 18 is turned off, an induced voltage is generated in a direction to increase the voltage across the input smoothing capacitor 17. The negative output of the full-wave rectifier 2 includes a series connection body in which a third diode 38, a third inductor 46, and a fifth winding 30 are connected in series, a fourth diode 39, a fourth One end of a parallel circuit pcc ′ is connected to the inductor 47 and a series connection body in which the sixth winding 31 is sequentially connected in series. Fifth winding 30 of transformer 45
Is connected to a rectifying / smoothing circuit composed of a diode 48 and a capacitor 49. To operate the control circuit 28, the voltage across the capacitor 49 is supplied to the control circuit 28 as a bias voltage. With this configuration, in the switching power supply of the present embodiment, the transformer 45 generated when the switch element 18 is turned off is provided.
Can be rectified and smoothed by the diode 48 and the capacitor 49 and supplied to the control circuit 28 as a bias voltage. Therefore, a configuration for supplying the bias voltage, for example, a bias winding provided on the power supply side of the transformer can be omitted. Since the induced voltage of the fifth winding 30 of the transformer 45 is proportional to the output voltage of the control output winding 15 of the transformer 45, a substantially constant voltage can be supplied to the control circuit 28 as the bias voltage.

<< Sixth Embodiment >> FIG. 10 shows a sixth embodiment of the present invention.
FIG. 2 is a block diagram illustrating a configuration of a switching power supply device according to an embodiment of the present invention. In this embodiment, in the configuration of the switching power supply device, a configuration is adopted in which a bias voltage is supplied from the fifth winding 30 of the transformer to the control circuit. The other parts are the same as those of the second embodiment, and the duplicated description thereof will be omitted. As shown in FIG. 10, a rectifying / smoothing circuit including a diode 48 and a capacitor 49 is connected to both ends of the fifth winding 30 of the transformer 29. To operate the control circuit 28, the voltage across the capacitor 49 is supplied to the control circuit 28 as a bias voltage. With this configuration, in the switching power supply of the present embodiment, the induced voltage of the fifth winding 30 of the transformer 29 generated when the switch element 18 is turned off is rectified and smoothed by the diode 48 and the capacitor 49,
It can be supplied to the control circuit 28 as a bias voltage. Therefore, a configuration for supplying the bias voltage, for example, a bias winding provided on the power supply side of the transformer can be omitted. Fifth winding 3 of transformer 29
Since the induced voltage of 0 is proportional to the output voltage of the control output winding 15 of the transformer 29, a substantially constant voltage can be supplied to the control circuit 28 as the bias voltage.

<< Seventh Embodiment >> FIG. 11 shows a seventh embodiment of the present invention.
FIG. 2 is a block diagram illustrating a configuration of a switching power supply device according to an embodiment of the present invention. In this embodiment, in the configuration of the switching power supply device, a bias voltage is supplied from the fifth winding 30 of the transformer to the control circuit 28. The other parts are the same as those of the third embodiment, and the duplicated description thereof will be omitted. As shown in FIG. 11, on the power supply side of the transformer 50, a primary winding 12 and a fifth winding 30 connected to the primary winding 12 are provided. The fifth winding 30 is connected to the primary winding 12 so that when the switch element 18 is turned off, an induced voltage is generated in a direction to reduce the voltage across the input smoothing capacitor 17. A diode 48 and a capacitor 49 are provided at both ends of the fifth winding 30.
And a bias voltage is supplied from the capacitor 49 to the control circuit 28. A third inductor 46 and a fifth winding 30 are sequentially connected in series to the negative output of the full-wave rectifier 2. With such a configuration, in the switching power supply of the present embodiment,
The induced voltage of the fifth winding 30 of the transformer 50 generated when the switch element 18 is turned off can be rectified and smoothed by the diode 48 and the capacitor 49 and supplied to the control circuit 28 as a bias voltage. Therefore, a configuration for supplying the bias voltage, for example, a bias winding provided on the power supply side of the transformer can be omitted.
Since the induced voltage of the fifth winding 30 of the transformer 50 is proportional to the output voltage of the control output winding 15 of the transformer 50, a substantially constant voltage can be supplied to the control circuit 28 as the bias voltage.

<< Eighth Embodiment >> FIG. 12 shows an eighth embodiment of the present invention.
FIG. 2 is a block diagram illustrating a configuration of a switching power supply device according to an embodiment of the present invention. In this embodiment, in the configuration of the switching power supply device, a bias voltage is supplied from the fifth winding 30 of the transformer to the control circuit 28. The other parts are the same as those of the fourth embodiment, and the duplicated description thereof will be omitted. As shown in FIG. 12, a diode 4 is connected to both ends of the fifth winding 30 of the transformer 44.
8, and a rectifying / smoothing circuit composed of a capacitor 49 are connected. To operate the control circuit 28, the voltage across the capacitor 49 is supplied to the control circuit 28 as a bias voltage. With this configuration, in the switching power supply device of the present embodiment, the induced voltage of the fifth winding 30 of the transformer 44 generated when the switch element 18 is turned off is rectified and smoothed by the diode 48 and the capacitor 49, It can be supplied to the control circuit 28 as a bias voltage. Therefore, a configuration for supplying the bias voltage, for example, a bias winding provided on the power supply side of the transformer can be omitted. The induced voltage of the fifth winding 30 of the transformer 44 is controlled by the control output winding 15 of the transformer 44.
, It is possible to supply a substantially constant voltage to the control circuit 28 as the bias voltage.

In the first to eighth embodiments, the so-called one-piece configuration using one switch element 18 has been described. However, the first switch element, the primary winding 12, and the second switch A series circuit in which elements are sequentially connected in series is connected to both ends of the input smoothing capacitor 17 or two input smoothing capacitors 40 and 41 connected in series, and a connection point between the first switch element and the primary winding 12. And the input smoothing capacitor 17 or two input smoothing capacitors 40 and 41
Is connected between the primary winding 12 and the connection point between the second switch element and the input smoothing capacitor 17 or the positive terminals of the two input smoothing capacitors 40 and 41. The same effect can be obtained in a configuration in which the above-mentioned diodes are connected, that is, in a so-called multi-stone configuration. In addition, the first
In the eighth to eighth embodiments, the configuration in which the third to sixth windings are connected to the primary winding 12 has been described. However, the winding is drawn to another winding of the transformer, for example, in the middle or one end of the primary winding 12. By providing the terminal, at least one of the third to sixth windings and at least a part of the other windings of the transformer may be configured to be common. Furthermore, the first and second rectifying / smoothing circuits 22 and 26 are of the capacitor input type, and the output is transmitted when the switch element 18 is turned off. , A choke input system, and the transmission of the output
Each of the rectifying and smoothing circuits 22 and 26 may be configured by a so-called forward method performed when the switch is turned on. Further, the configuration has been described in which the control circuit 28 detects the output voltage to the first load 23 and turns on and off the switch element 18 so as to have a constant voltage. The same effect can be obtained by a separately-excited type in which the ON / OFF ratio is changed, or a self-excited type in which the ON / OFF ratio of the switch element 18 is changed by detecting the timing of resetting the excitation of the primary winding 12. Furthermore, the configuration in which the secondary winding (output winding) provided on the load side of the transformer is configured by the control output winding 15 and the non-control output winding 16 to enable multiple outputs has been described. However, the same effect can be obtained with a single output configuration.

[0104]

As described above, in the switching power supply according to the present invention, the primary winding of the transformer and the switch element for controlling the output of the transformer, which are connected in series to the primary winding, include a smoothing capacitor. It is provided at both ends. Furthermore, when the smoothing capacitor is turned off, a winding in which an induced voltage is generated in a direction to reduce the voltage between both ends of the smoothing capacitor is connected to the primary winding, and a full-wave rectifier connected to an AC power supply is connected via an inductor. The above windings are connected. As a result, the energy from the AC power supply is stored in the inductor, the current flowing from the stored energy is superimposed on the AC input, the conduction angle of the input current flowing from the AC power supply into the full-wave rectifier is increased, and the power factor is increased. can do. Furthermore, the current of the inductor flowing from the inductor due to the energy stored in the inductor decreases during the ON period of the switch element and becomes zero during the ON period. Also disappears by the peak of the switching current. As a result, the current component of the inductor current superimposed on the current flowing through the primary winding also decreases due to the decrease in the inductor current. Therefore, most of the switching current flowing through the switching element is occupied by the current component of the current to be detected, which is determined by the output current of the transformer, thereby improving the setting accuracy of the overcurrent limit value and the stability of the overcurrent control. Can be. Furthermore, during the off period of the switch element, the current flowing through the inductor continues to flow through the transformer winding to the control output winding and the non-control output winding during the off period of the switch element. For this reason, the current component of the inductor current transmitted to the secondary winding of the transformer affects the entire OFF period, and the ripple voltage component of the output voltage due to the different coupling of each winding in the transformer can be reduced. it can.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a switching power supply device according to a first embodiment of the present invention.

FIG. 2 is a graph showing a voltage waveform and a current waveform of each part during operation of the switching power supply device of the first embodiment.

FIG. 3 is a graph showing current waveforms at various points during operation of the switching power supply device according to the first embodiment.

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

FIG. 5 is a block diagram showing a configuration of a switching power supply device according to a third embodiment of the present invention.

FIG. 6 is a graph showing a voltage waveform and a current waveform of each part when the switching power supply device of the third embodiment operates.

FIG. 7 is a graph showing current waveforms at various points during operation of the switching power supply device according to the third embodiment.

FIG. 8 is a block diagram showing a configuration of a switching power supply device according to a fourth embodiment of the present invention.

FIG. 9 is a block diagram showing a configuration of a switching power supply device according to a fifth embodiment of the present invention.

FIG. 10 is a block diagram showing a configuration of a switching power supply device according to a sixth embodiment of the present invention.

FIG. 11 is a block diagram showing a configuration of a switching power supply device according to a seventh embodiment of the present invention.

FIG. 12 is a block diagram showing a configuration of a switching power supply device according to an eighth embodiment of the present invention.

FIG. 13 is a block diagram showing the configuration of a first conventional switching power supply device.

FIG. 14 is a graph showing a voltage waveform and a current waveform of each unit when the switching power supply device of the first conventional example operates.

FIG. 15 is a graph showing current waveforms at various points during operation of the first conventional switching power supply device.

FIG. 16 is a block diagram showing a configuration of a second conventional switching power supply device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Commercial AC power supply 2 Full-wave rectifier 7, 9, 38, 39 Diode 8, 10, 33, 34, 36, 37 Inductor 11, 29, 43, 44, 45, 50 Transformer 12 Primary winding 13 Third winding Line 14 fourth winding 17, 40, 41 smoothing capacitor 18 first switch element 28 control circuit 30 fifth winding 31 sixth winding 42 second switching element

Claims (12)

[Claims] A transformer having at least a primary winding connected to a power supply, a secondary winding connected to a load, and third and fourth windings connected to the power supply; An output terminal of the connected full-wave rectifier, a first series connection provided between the output terminals of the full-wave rectifier and sequentially connecting a first diode, a first inductor, and the third winding in series A parallel circuit in which a body, a second diode, a second inductor, and a second series connection body in which the fourth winding is sequentially connected in series are connected in parallel. A smoothing capacitor connected to one output terminal of the wave rectifier and the other end connected to the other output terminal of the full-wave rectifier, connected in series to the primary winding and connected to both ends of the smoothing capacitor together with the primary winding Provided switch element, and the switch element A control circuit for controlling on / off operation, wherein the third and fourth windings are connected to the primary winding such that induced voltages are generated in opposite directions when the switch element is turned on. A switching power supply device characterized by the above-mentioned. 2. A bias voltage for operating the control circuit is such that an induced voltage is generated in such a direction as to reduce a voltage across a smoothing capacitor when a switch element of the third and fourth windings is turned off. The switching power supply according to claim 1, wherein the switching power supply is supplied from the winding of (1). 3. The switching device according to claim 1, wherein at least one of the third and fourth windings and at least a part of other windings of the transformer are common. Power supply. 4. At least a primary winding connected to a power supply side, a secondary winding connected to a load side, and third, fourth, fifth, and sixth windings connected to a power supply side. An output terminal of a full-wave rectifier connected to an AC power supply; first and second inductors coupled to each other in polarities; third and fourth inductors coupled to each other in polarities; A first series connected body, a second diode, and a third inductor, which are connected to one output terminal of the first series, and sequentially connect a first diode, the first inductor, and the third winding in series. A first parallel circuit in which the fourth winding is connected in series with a second series connection body in which the fourth winding is connected in series; a third diode connected to the other output terminal of the full-wave rectifier; , The fourth inductor, and the fifth winding in series A second parallel connection in which a connected third series connection is connected in parallel with a fourth diode, the second inductor, and a fourth series connection in which the sixth winding is sequentially connected in series. A circuit, one end of which is connected to one output terminal of the full-wave rectifier via the first parallel circuit, and the other end of which is connected to the second
A first and a second smoothing capacitor connected to the other output terminal of the full-wave rectifier via a parallel circuit of the first and second primary windings; a first and a second smoothing capacitor connected in series with the primary winding; A first switch element provided at both ends of the capacitor, a second switch element connected between a connection point of the first and second smoothing capacitors and one end of the AC power supply, and the first switch A control circuit for controlling on / off operations of the elements, wherein the third and fourth windings are connected to the primary winding such that induced voltages are generated in opposite directions when the first switch element is turned on. And a fifth and a sixth winding connected to the primary winding so that induced voltages are generated in opposite directions when the first switch element is turned on. apparatus. 5. A bias voltage for operating the control circuit is set to a first voltage when a first switch element of the third and fourth windings or the fifth and sixth windings is turned off. 5. The switching power supply device according to claim 4, wherein the induced voltage is supplied from one of the windings in which the induced voltage is generated in a direction to reduce the voltage between both ends of the second smoothing capacitor. 6. The switching according to claim 4, wherein at least one of the third to sixth windings and at least a part of other windings of the transformer are common. Power supply. 7. A transformer having at least a primary winding connected to the power supply side, a secondary winding connected to the load side, and a third winding connected to the power supply side, connected to an AC power supply. An output terminal of the full-wave rectifier, one end of which is connected to one output terminal of the full-wave rectifier, the other end of which is connected to one end of a third winding, and one end of which is connected to the third winding and the inductor. A smoothing capacitor connected to one output terminal of the full-wave rectifier and the other end connected to the other output terminal of the full-wave rectifier; a smoothing capacitor connected in series with the primary winding, A switch element provided at both ends, and a control circuit for controlling on / off operations of the switch element, wherein the third winding is configured such that, when the switch element is turned off, an induced voltage reduces a voltage across the smoothing capacitor. As occurs in The switching power supply apparatus characterized by being connected to the primary winding. 8. The switching power supply according to claim 7, wherein a bias voltage for operating the control circuit is supplied from the third winding. 9. The switching power supply device according to claim 7, wherein the third winding and at least a part of other windings of the transformer are common. 10. A primary winding connected to the power supply side, a secondary winding connected to the load side, and a third winding connected to the power supply side.
A transformer having at least a fourth winding, an output terminal of a full-wave rectifier connected to an AC power supply, one end connected to one output terminal of the full-wave rectifier, and the other end connected to one end of a third winding; A first inductor, one end of which is connected to the other output terminal of the full-wave rectifier, and the other end of which is connected to one end of a fourth winding. 3 and one output terminal of the full-wave rectifier via the first inductor, and the other end is connected to the other output terminal of the full-wave rectifier via the fourth winding and the second inductor. Connected first and second
A first switch element connected in series with the primary winding and provided at both ends of the first and second smoothing capacitors together with the primary winding; and a first switching element of the first and second smoothing capacitors. A second switch element connected between a connection point and one end of the AC power supply; and a control circuit for controlling on / off operation of the first switch element, wherein the third and fourth windings are provided. However, the switching power supply device is connected to the primary winding such that the induced voltage is generated in a direction to reduce the voltage across the smoothing capacitor when the first switch element is turned off. 11. The switching power supply device according to claim 10, wherein a bias voltage for operating said control circuit is supplied from one of said third and fourth windings. 12. The switching device according to claim 10, wherein at least one of the third and fourth windings and at least a part of other windings of the transformer are common. Power supply.