JP3400160B2 - Switching power supply - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching type DC stabilized power supply device which inputs AC.

[0002]

2. Description of the Related Art FIG. 23 shows a first structure of a conventional AC input switching power supply. This conventional AC input switching power supply has a configuration including a commercial AC power supply 10 and a diode 2.
Full-wave rectifier 20 composed of 1, 22, 23, and 24,
A smoothing capacitor 30, a transformer 40 having a primary winding 41 and a secondary winding 42, a switch element 50, a rectifying / smoothing circuit 60, a load 70, and a control circuit 80. The operation of the first configuration of the conventional AC input switching power supply is as follows. The input of the commercial AC power supply 10 is rectified by the full-wave rectifier 20 and smoothed by the smoothing capacitor 30 to a direct current with less ripple, and then the switch element 50 is input. The primary winding 4 of the transformer 40 is turned on and off at a frequency higher than the commercial AC frequency.
An AC voltage is applied to the output terminal 1, and its output is applied from the secondary winding 42 of the transformer 40 to the rectifying and smoothing circuit 60 to be rectified and smoothed, and applied to the load 70 as a DC output voltage. Here, the control circuit 80 detects the output voltage of the rectifying / smoothing circuit 60 and turns on / off the switch element 50 so that the output voltage becomes a predetermined voltage. As described above, this configuration has a function of converting the input of the commercial AC power supply 10 into a stable DC voltage and outputting the DC voltage. FIG. 24 shows operation waveforms of the conventional AC input switching power supply shown in FIG. V _in (1) of the same figure (a) shows the output voltage of the full wave rectifier 20 with respect to the voltage of the commercial alternating current power supply 1, and I of the same figure (b).
_in (1) shows the waveform of the input current from the commercial AC power supply 1. As can be seen from the figure, in this conventional example, there is a problem that the input current becomes a surge and the power factor is extremely low. Therefore, the inventors of the present application invented the switching power supply shown in FIG. 25 and applied for a patent as Japanese Patent Application No. 5-177379 (hereinafter referred to as prior invention). The circuit of the switching power supply according to the invention of the prior application in FIG. 25 includes an inductor 3 between the full-wave rectifier 20 and the smoothing capacitor 30.
1 and a control winding 45 of the transformer 40 are provided in series, and the switching power supply has a high power factor, as is apparent from the waveform diagram of the input voltage and current shown in FIG.

[0003]

However, as shown in FIG.
In the conventional AC input switching power supply and the circuit of the prior invention of FIG. 25, a voltage about twice the voltage of the smoothing capacitor 30 is applied between the terminals of the switch element 50 while the switch element 50 is off. A switch element having a high withstand voltage must be used, which increases the ON resistance of the switch element and increases the conduction loss of the switch element, which makes it difficult to increase the efficiency of the switching power supply. The present invention has been made in view of the above points,
The power factor is set to be high as in the prior invention, and a switch element having a lower breakdown voltage and a smaller on-resistance can be used as a switch element to increase efficiency as a switching power supply. .

[0004]

Means for Solving the Problems According to the first invention of the present application
The switching power supply includes a full-wave rectifier connected to an AC power supply, a smoothing capacitor connected between output terminals of the full-wave rectifier, and a transformer having a primary winding and a control winding on the primary side.
And between the full-wave rectifier and the smoothing capacitor
Series winding of the controlled inductor and the control winding of the transformer
Path, both ends of the smoothing capacitor and the primary of the transformer
Consists of an even number of switch elements connected between windings
A bridge circuit, a rectifying / smoothing circuit connected to the secondary winding of the transformer and a load connected to the output side thereof, and an output voltage of the rectifying / smoothing circuit is detected to set the output voltage to a predetermined voltage. Switch to the bridge circuit
And a control circuit for controlling the element.

Switching according to the first invention of the present application
The bridge circuit consisting of an even number of switch elements of the power supply,
Consists of a first switch element to a fourth switch element
And the first switch element and the second switch
The connection point with the element, the third switch element and the fourth switch
The primary winding of the transformer is connected to the connection point with the H element.
It is configured to be connected.

Switching according to the first invention of the present application
The bridge circuit consisting of an even number of switch elements of the power supply,
It is composed of a first switch element and a second switch element.
To connect the first switch element and the second switch element.
The connection point and the smoothing capacitor are connected to the first smoothing capacitor and the
Between the smoothing capacitor and the connection point
Is configured so that the primary winding of the transformer is connected to
It is a thing.

A switching power supply according to a second invention of the present application
Is a full-wave rectifier connected to an AC power source, and the full- wave rectifier
The first smoothing capacitor and the second smoothing capacitor connected between the output terminals of
Series circuit with the smoothing capacitor and primary winding on the primary side
Transformer having first control winding and second control winding
And one end of the full-wave rectifier and the first smoothing capacitor
And one end of the series circuit of the second smoothing capacitor
First inductor connected and first control of the transformer
A series circuit with a winding, the other end of the full-wave rectifier and the first
Series circuit of the second smoothing capacitor and the second smoothing capacitor
A second inductor connected between the other end of the
A series circuit with a second control winding of the
The connection point between the capacitor and the second smoothing capacitor
Switch installed between one terminal of the
Direct connection between the first smoothing capacitor and the second smoothing capacitor
The first switching element and the second switching element connected to both ends of the column circuit
A series circuit with a switch element, and the first switch element
The connection point with the second switch element and the first smoothing capacitor
Between the sensor and one end of the series circuit of the second smoothing capacitor
To the condenser connected through the primary winding of the transformer
And a rectifying / smoothing circuit connected to the secondary winding of the transformer and having a load connected to the output side thereof, and the output voltage of the rectifying / smoothing circuit is detected and the output voltage becomes a predetermined voltage. The first switch element and the second switch
And a control circuit for controlling the switch element .

A switching power supply according to a third invention of the present application
Is a full-wave rectifier connected to an AC power source, a smoothing capacitor connected between the output terminals of the full-wave rectifier, and a primary side
Having a first primary winding, a second primary winding and a control winding
Of the transformer, the full-wave rectifier and the smoothing capacitor
An inductor connected between and a control winding of the transformer
Connected between the series circuit and the smoothing capacitor terminal.
And a first primary winding and a first switch element of the transformer
A series circuit with the second primary winding of the transformer and the second
, A rectifying / smoothing circuit connected to the secondary winding of the transformer and a load connected to the output side of the transformer, and the output voltage of the rectifying / smoothing circuit detected by the rectifying / smoothing circuit. said first Sui but to a predetermined voltage
Switch element and a control circuit for controlling the second switch element .

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a first embodiment of the present invention. The configuration of this embodiment includes a commercial AC power supply 10, a diode 21,
Full-wave rectifier 20 composed of 22, 23, 24, smoothing capacitor 30, inductor 31, primary winding 41, first
Secondary winding 42, second secondary winding 44 and control winding 4
5, the transformer 40, the first switch element 51, the second switch element 52, the third switch element 53, the fourth
Switch element 54 and diodes 55, 56, 57, 5 connected in parallel to the first to fourth switch elements , respectively.
8, a diode 61, 62, an inductor 63, and a capacitor 64, a rectifying / smoothing circuit 60, a load 70, and a control circuit 80. Next, the operation of this embodiment will be described.

First, the number of turns of each winding of the transformer 40 is N1 for the primary winding 41 and N2- for the first secondary winding 42.
1, the second secondary winding 44 is N2-2, the control winding 45 is N
4 and then, a point in FIG. 1, the potential of the point b respectively V _a,
Let V _b . Here, when N1 = N4 is set, when the switch elements 51 and 54 are turned on and the switch elements 52 and 53 are turned off by the control circuit 80, the voltage of the smoothing capacitor 30 is applied to the primary winding 41 of the transformer 40. That is, V _b is applied. At this time, V is applied to the control winding 45 of the transformer 40.
_Although a voltage of _b × N4 / N1 is generated, it is a voltage equal to V _b because N1 = N4 is set. Therefore, the voltage V _a of a point, the voltage V _b of the smoothing capacitor 30
When the generated voltage _Vb of the control winding 45 of the transformer 40 is subtracted from this, the voltage becomes zero volts. That is, the switch elements 51 and 54
Is on and the switch elements 52 and 53 are off, the potential at the point a is always 0 volt.

The current flow in the circuit at this time is
First, the smoothing capacitor 30 to the first switch element 5
1, primary winding 41 of transformer 40, first secondary winding 4
2. Returning to the primary winding 41 of the transformer 40 via the rectifier circuit 60 and the load 70, the current flows through the fourth switch element 54, and thereby the energy of the smoothing capacitor 30 is sent to the load 70. Further, at this time, the voltage V a at the point _a is always zero volt, so that the input voltage V _in (3) is applied to the inductor 31, the inductance of the inductor 31 is L ₃₁ , and the current flowing through the inductor 31 is I _{L. -1,} and the time after the switch elements 51 and 54 are turned on is t
Then,

[Equation 1] The current determined by is flowing through the inductor 31. This current first flows through the control winding 45 of the transformer 40, passes through the smoothing capacitor 30, the commercial AC power supply 10 and the full-wave rectifier 20, and then returns to the inductor 31. During this period, the commercial AC power supply 10 Energy is stored in the inductor 31.

Next, when the control circuit 80 turns off the first switch element 51 and the fourth switch element 54, the exciting current of the transformer 40 is smoothed from the primary winding 41 of the transformer 40 to the third diode 57. It flows through the capacitor 30 and the second diode 56 in the course of returning to the primary winding 41. Therefore, the potential at the point c becomes substantially the same as the potential on the negative side of the smoothing capacitor 30, while the potential at the point d becomes substantially the same as the potential on the positive side of the smoothing capacitor 30. for that reason,
The voltage applied to the first switch element 51 and the fourth switch element 54 is the voltage V _b between the terminals of the smoothing capacitor 30.
Is almost the same as. Also, during this period, one of the transformers 40
A voltage of −V _b is applied to the secondary winding 41, and the transformer 4
A voltage of −V _b × N4 / N1 is generated in the control winding 45 of 0.

Next, when the control circuit 80 turns on the second switch element 52 and the third switch element 53 while keeping the first switch element 51 and the fourth switch element 54 off, the transformer 40 is turned on. The voltage of −V _b is continuously applied to the primary winding 41 of the
, A voltage of −V _b × N4 / N1 is generated. Also,
The flow of current in the circuit at this time is as follows: firstly, the smoothing capacitor 30 to the third switch element 53 and the transformer 40
Secondary winding 41, second secondary winding 44, rectifying / smoothing circuit 60
Then, it returns to the primary winding 41 of the transformer 40 via the load and flows through the second switch element 52, whereby the energy of the smoothing capacitor 30 is sent to the load 70. Further, a voltage of −V _b is applied to the primary winding 41 of the transformer 40, and −V _b × N is also applied to the control winding 45 of the transformer 40.
A voltage of 4 / N1 is generated. Therefore, during this period, a voltage that is a difference from the input voltage V _in (3), that is, a voltage of V _in (3) −V _b × N4 / N1 is applied to the inductor 31, and the current flowing through the inductor 31 is Decrease. At this time, the current flowing through the inductor 31 is

[Equation 2] The current determined by is from the inductor 31 to the transformer 40.
Through the smoothing capacitor 30, the commercial AC power source 10, the full-wave rectifier 20, and the inductor 31. During this period, the energy stored in the inductor 31 is sent to the smoothing 30. To be

Next, when the control circuit 80 turns off the second switch element 52 and the third switch element 53,
The exciting current of the transformer 40 is the primary winding 41 of the transformer 40.
To the first diode 55, the smoothing capacitor 30, the fourth
It flows through the diode 58 of the above and returns to the primary winding 41. Therefore, the potential at the point c becomes substantially the same as the potential on the positive side of the smoothing capacitor 30, while the potential at the point d becomes substantially the same as the potential on the negative side of the smoothing capacitor 30. Therefore, the second switch element 52 and the third switch element 53
Voltage applied becomes almost like the terminal voltage V _b of the smoothing capacitor 30 to. Also, during this period, transformer 40
The primary winding 41 of is a voltage of V _b is applied to the control winding 45 of the transformer 40, V _b × N4 / N1 becomes a voltage is generated.

At the same time when the above operation is repeated, the control circuit 80 controls the first to fourth switch elements 51 to 54 so that the output voltage of the rectifying / smoothing circuit 60 becomes a predetermined voltage.
Control is performed by changing the ON / OFF periods of the first to fourth switch elements 51 to 54 of the full bridge circuit configured by the following circuits. FIG. 21 is a waveform chart showing the operation timing of the first embodiment shown in FIG. 1 of the present invention. FIG. 10A shows the on / off timings of the first switch element 51 and the fourth switch element 54, which are on for the period of T ₂ . FIG. 2B shows the second switch element 5
2 and 3 show the on / off timings of the third switch element 53, which is on for the period of T ₄ . The figure (c) is c
The potential of the point is shown, (d) of the figure shows the potential of the d point, and (e) of the figure shows the potential difference between the c point and the d point. The same figure (f)
Is a voltage generated in the control winding 45 of the transformer 40, that is, V
_b- V _a is shown, and FIG. 9 (g) shows the current flowing through the inductor 31. FIG. 22 is an operation waveform diagram of the first embodiment of the present invention. The figure (a) is a waveform diagram of the output voltage V _in (3) of the full-wave rectifier 20, and the figure (b) is a waveform diagram of the output current V _in (3) of the full-wave rectifier 20. FIG. 7C is a partially enlarged waveform diagram of the output current I _in (3) shown in FIG. Here, in the figure, the inductor 3 during the period t _l
Since the current flowing through 1 increases according to the above-mentioned equation 1, the current flowing through the inductor 31 during the one cycle in which the first to fourth switch elements 51 to 54 are turned on and off at a high frequency is always returned to zero amperes. When the constant of each part is set to, the peak value I _L (perk) of the current of the inductor 31 in each one cycle that turns on and off at high frequency is

[Equation 3] Becomes

Since V _in (3) is a sine wave, the peak value I _L (p of the current of the inductor 31 is calculated from the above equation.
The line connecting (erk) also becomes a sine wave, the current flowing through the inductor 31 becomes as shown in FIG. 22 (b), and the average value I _L (ave) in one cycle of the high frequency switching also becomes a sine wave. . That is, by using a low-pass filter for removing high-frequency ripple immediately before or after the full-wave rectifier 20 with respect to the current of the inductor 31 that increases or decreases at high frequencies, the commercial input current waveform is approximately converted to a sine wave. The power factor can be increased. As described above, the first embodiment shown in FIG. 1 is a power source with a high power factor as in the circuit of the prior invention of the present inventors, but the voltage applied to the switch element is In the circuit of the prior invention, about twice the voltage of the smoothing capacitor 30 is applied, whereas in the first embodiment shown in FIG. 1 of the present invention, the same voltage as the voltage of the smoothing capacitor 30 is applied. So
A switch element having a low withstand voltage and a low on-resistance can be used, and the efficiency as a switching power supply can be increased.

FIG. 2 shows a second embodiment of the present invention. Figure 2
1 is different from the embodiment of FIG. 1 in that instead of the third switch element 53 and the third diode 57 of FIG.
Smoothing capacitor 33 of the fourth switch element 54
The second smoothing capacitor 34 is used instead of the fourth diode 58 and the smoothing capacitor 30 of FIG. 1 is not used. The operation of the embodiment of FIG. 2 is substantially the same as the operation of the embodiment of FIG. 1, except that the first capacitor 33 and the second capacitor 33
If the capacitance value of the capacitor 34 of is the same,
The potential at the point e in FIG. 2 is fixed to 1/2 of the potential V _{b at} the point _b . Therefore, the voltage applied between the terminals of the primary winding 41 of the transformer 40 is the same as that shown in FIG. In the example, the applied voltage between the terminals is ½. Therefore, if the number of turns N4 of the control winding 45 of the transformer 40 is set to be twice the number of turns N1 of the primary winding 41, the voltage generated in the control winding 45 can be the same as that in the embodiment of FIG. it can.

Further, the role of the smoothing capacitor 30 of FIG. 1 is fulfilled by the series circuit of the second smoothing capacitor 33 and the second smoothing capacitor 34 of FIG. 2, and the third switch element 53 of FIG. Alternatively, the current flowing through the third diode 57 is the first smoothing capacitor 3 in FIG.
3 through the fourth switch element 54 or the fourth switch element 54 in FIG.
2 flows through the second smoothing capacitor 34 in FIG. At the same time as repeating the above-mentioned operation, the control circuit 80 causes the output voltage of the rectifying / smoothing circuit 60 to be a predetermined voltage by the half bridge including the circuits after the first and second switch elements 51 and 52. The circuit is controlled by changing the on / off period of the first and second switch elements 51 and 52.

As described above, the second embodiment shown in FIG.
Similar to the first embodiment shown in FIG. 1, the power source has a high power factor and, at the same time, the first and second switch elements 5 are provided.
The voltage applied to the first and second capacitors 52 is the same as that of the first smoothing capacitor 3
3 and the voltage V _{b of the} input smoothing circuit composed of the series circuit of the second smoothing capacitor 34,
A switch element having a low withstand voltage and a low on-resistance can be used, and the efficiency as a switching power supply can be increased.

FIG. 3 shows a third embodiment of the present invention. Figure 3
2 is different from the embodiment of FIG. 2 in that the smoothing capacitor 30 is used instead of the series circuit of the first smoothing capacitor 33 and the second smoothing capacitor 34 of FIG. It is connected between the primary winding 41 of the transformer 40 and the smoothing capacitor 30.
This operation is the same as the basic operation of the circuit of FIG. 2, except that the leakage inductor of the transformer 40 and the capacitor 59 are different.
Are connected in series, the current flowing therethrough becomes a resonance current and has a sinusoidal waveform. Therefore, the first and second switching elements 5
This has the effect of reducing the switching loss at 1,52. As for the other operations, as in the second embodiment of FIG. 2, the power supply has a high power factor, and at the same time, a switching element having a low withstand voltage and a low on-resistance can be used. As a result, the efficiency can be increased.

FIG. 4 shows a fourth embodiment of the present invention. Figure 4
2 is different from the embodiment of FIG. 2 in that the smoothing capacitor 30 is used instead of the series circuit of the first and second smoothing capacitors 33 and 34 of FIG.
The primary winding of the first primary winding 41 and the second primary winding 46
And a series circuit of the first primary winding 41 and the first switching element 51, and the second primary winding and the second switching element 52.
Is connected between both terminals of the smoothing capacitor 30. The operation of the embodiment shown in FIG. 4 is substantially the same as the operation of the second embodiment shown in FIG. 2, except that the second embodiment differs from the first switch element 51 or the second switch element 52 in the second embodiment. First capacitor 33 when the power turns on
And a voltage of 1/2 of the voltage V _b of the smoothing capacitor constituted by the series connection of the second smoothing capacitor 34, the transformer 4
0 is applied to the primary winding 41, while the fourth winding of FIG.
In this embodiment, when the first switch element 51 or the second switch element 52 is turned on, the first switch element of the transformer 40 is turned on.
That is, the voltage V _b of the smoothing capacitor 30 is directly applied to the secondary winding 41 or the second primary winding 46.

At the same time when the above operation is repeated, the control circuit 80 is constituted by the circuits after the first and second switch elements 51 and 52 so that the output voltage of the rectifying / smoothing circuit 60 becomes a predetermined voltage. The first and second push-pull circuits
The switching elements 51 and 52 are controlled by changing the on / off period. In the fourth embodiment of FIG. 4,
The number of turns N1-1 of the first primary winding 41 and the second primary winding 4
The number of turns N of the control winding 45 is the same as the number of turns N1-2 of 6
If 4 is the same as the number of turns of the first and second primary windings,
The voltage generated in the control winding 45 is the same as in the embodiment of FIG. Therefore, the fourth embodiment shown in FIG. 4 is also a power source with a high power factor as in the embodiment of FIG.
Since the voltage applied to the second switch elements 51 and 52 is only the same voltage as the voltage Vb of the smoothing capacitor 30, it is possible to use a switch element having a low withstand voltage and a low on-resistance. As a result, the efficiency can be increased.

FIG. 5 shows a fifth embodiment of the present invention. Figure 5
3 differs from the embodiment of FIG. 3 in that the smoothing capacitor 30 is used in FIG.
A smoothing capacitor 35 and a second smoothing capacitor 36 in a series circuit are used, and the connection point between the first smoothing capacitor 35 and the second capacitor 36 and the AC power supply 10 are used.
A switch 37 is connected between the inductor 31 and the control winding 45 of the transformer 40 between the full-wave rectifier 20 and the smoothing capacitor 30 in FIG. 5, the series circuit of the first inductor 31 and the first control winding 45 of the transformer 40 is connected between the full-wave rectifier 20 and the first smoothing capacitor 35, and the full-wave rectifier 20 and the second smoothing circuit are connected. The point is that the second inductor 38 and the second control winding 47 of the transformer 40 are connected between the capacitors 36.

The operation of FIG. 5 is generally the same as that of FIG. 3, except that in FIG. 5, the switch 37 is turned off when the effective voltage of the AC power supply 10 is high, and turned on when the effective voltage is low. That is. If you do this, first
When the effective voltage of the AC power supply 10 is high and the switch 37 is off, the inductances of the first inductor 31 and the second inductor 38 of FIG. 5 are set to 1/2 of the inductor 31 of FIG. 3, respectively, and The number of turns of the first control winding 45 and the second control winding 47 of the transformer 40 is shown in FIG.
If it is set to 1/2 of the control winding 45 of FIG.
Inductor 31 and the second inductor 38 of the transformer 40, and the first control winding 45 and the second control winding 47 of the transformer 40.
3 has a form in which the inductor 31 and the control winding 45 in FIG. 3 are vertically distributed between the full-wave rectifier 20 and the smoothing capacitor 30, respectively, but the circuit operation is the same.

On the other hand, when the effective voltage of the AC power supply 10 is low and the switch 37 is turned on, the full-wave rectifier 2 operates from the AC power supply 10 during the period when the polarity of the AC power supply 10 is shown in FIG.
0 diode 21, first inductor 31, first control winding 45, first smoothing capacitor 35, switch 37.
There is a first path through which returns to the AC power supply 10. Further, during a period in which the polarity of the AC power supply 10 is opposite to that shown in FIG. 5, the switch 37, the second smoothing capacitor 36, the second control winding 47, the second inductor 3 are switched from the AC power supply 10.
8. There is a second path back to the AC power supply 10 through the diode 22 of the full wave rectifier 20. These first path and second path perform the same operation as the path returning from the AC power supply 10 to the full-wave rectifier 20, the inductor 31, the control winding 45, and the smoothing capacitor 30 to the AC power supply 10 in FIG.

Therefore, when the switch 37 is turned on when the effective voltage of the AC power supply 10 is low, the terminals of the series circuit of the first smoothing capacitor 35 and the second smoothing capacitor 36 when the switch 37 is off. A voltage approximately the same as the voltage generated between can be generated between the terminals of the first smoothing capacitor 35 and the second smoothing capacitor 36, and as a result, when the effective voltage of the AC power supply 10 is low. Also, the inter-terminal voltage of the series circuit of the first smoothing capacitor 35 and the second smoothing capacitor 36 can be approximately doubled.

Therefore, in general, when the input voltage is low,
The voltage of the smoothing capacitor also becomes low, and a large current is required to obtain the same electric power, but the embodiment of FIG. 5 has a lower voltage of the input power supply 10 than the embodiment of FIG. Since the voltage of the smoothing capacitors 35 and 36 is kept high, it has a feature that a large current does not flow. on the other hand,
The configuration of the DC / DC converter unit of the fifth embodiment of FIG. 5 is the same as that of the third embodiment of FIG.
The power source has a high power factor as in the third embodiment. At the same time, the voltage applied to the first switch element 51 and the second switch element 52 is the same voltage as the terminal voltage of the series circuit of the first smoothing capacitor 35 and the second smoothing capacitor 36. Therefore, since a switch element having a low breakdown voltage and a low on-resistance can be used, the efficiency of the switching power supply can be increased.

FIG. 6 shows a sixth embodiment of the present invention. This embodiment has the same basic circuit configuration as that of the embodiment shown in FIG. 1. In the configuration of FIG. 6 different from the configuration of FIG. 1, a capacitor 91 is connected in series with the control winding 45, and the control winding is further connected. The point is that the diode 92 is connected in parallel with the series circuit of the line 45 and the capacitor 91. The operation of the embodiment shown in FIG.
The first switch element 51 and the fourth switch element 54 are turned on, and the second switch element 52 and the third switch element 5 are turned on.
When 3 is off, the current in inductor 31 is
1 flows through the control winding 45 of the transformer 40 and the smoothing capacitor 30, so that when the capacitor 91 is charged by the current and its voltage becomes higher than the voltage of the smoothing capacitor 30, the current of the inductor 31 is changed to the diode 72. Through to the smoothing capacitor 30. That is, the first switch element 51 and the fourth switch element 54
Despite being turned on, the boosting time of the inductor 31 becomes shorter, and the boosting time becomes shorter as the input voltage V _in (3) becomes higher.

During the period in which the first switch element 51 and the fourth switch element 54 are off and the second switch element 52 and the third switch element 53 are on, the current in the inductor 31 is the diode 92. Flow into the smoothing capacitor 30 via the
5, the capacitor 91 is charged in the opposite direction, and the voltage drops. That is, in the configuration of FIG. 6, the boosting time of the inductor 31 becomes shorter as the input voltage V _in (3) becomes higher.
Even in the current continuous mode of the inductor 31 where the current of the inductor 31 does not return to zero ampere in one cycle in which the first to fourth switching elements 51 to 54 are on / off-operated, the input current I _in (3) has a waveform substantially corresponding to a sine wave, and the power factor can be increased. Further, in the configuration of FIG. 6, the voltage applied to the first to fourth switch elements 51 to 54 is the same as the voltage of the smoothing capacitor 30 as in the embodiment of FIG. , A low on-resistance can be used, and the efficiency as a switching power supply can be increased.

FIG. 7 shows a seventh embodiment of the present invention. This embodiment has the same basic circuit configuration as that of the embodiment shown in FIG. 2, and the configuration of FIG. 7 different from the configuration of FIG. The point is that the diode 92 is connected in parallel with the series circuit of the line 45 and the capacitor 91. The operation of the circuit in which the capacitor 91 and the diode 92 are added in FIG. 7 is the same as the operation of the capacitor 91 and the diode 92 in FIG. 6, and the current of the inductor 31 becomes the continuous mode,
The input current I _in (3) has a waveform substantially corresponding to a sine wave, and the power factor can be increased. In addition, the configuration of FIG. 7 is similar to that of the embodiment of FIG.
The voltage applied to the first and second capacitors 52 is
Since the voltage of the third smoothing capacitor 34 and the second smoothing capacitor 34 are the same as the voltage of the smoothing capacitor connected in series, it is possible to use a switch element with low withstand voltage and low on-resistance, and to improve efficiency as a switching power supply. You can

FIG. 8 shows an eighth embodiment of the present invention. This embodiment has the same basic circuit configuration as that of the embodiment shown in FIG. 3, and the configuration of FIG. 8 different from the configuration of FIG. 3 has a capacitor 91 connected in series with the control winding 45, and a control winding. The point is that the diode 92 is connected in parallel with the series circuit of the line 45 and the capacitor 91. The operation of the circuit in which the capacitor 91 and the diode 92 are added in FIG. 8 is the same as the operation of the capacitor 91 and the diode 92 in FIG. 6, and the current of the inductor 31 becomes the continuous mode.
The input current I _in (3) has a waveform substantially corresponding to a sine wave, and the power factor can be increased. Further, the configuration of FIG. 8 is similar to that of the embodiment of FIG.
Since the voltage applied to 1, 52 is the same as the voltage of the smoothing capacitor 30, it is possible to use a switch element having a low withstand voltage and a low on-resistance, and it is possible to increase the efficiency of the switching power supply. .

FIG. 9 shows a ninth embodiment of the present invention. This embodiment has the same basic circuit configuration as that of the embodiment shown in FIG. 4, and the configuration of FIG. 9 different from the configuration of FIG. 4 is such that a capacitor 91 is connected in series with the control winding 45, and The point is that the diode 92 is connected in parallel with the series circuit of the line 45 and the capacitor 91. The operation of the circuit in which the capacitor 91 and the diode 92 are added in FIG. 9 is the same as the operation of the capacitor 91 and the diode 92 in FIG. 6, and the current of the inductor 31 becomes the continuous mode,
The input current I _in (3) has a waveform substantially corresponding to a sine wave, and the power factor can be increased. In addition, the configuration of FIG. 9 is similar to that of the embodiment of FIG.
Since the voltage applied to 1, 52 is the same as the voltage of the smoothing capacitor 30, it is possible to use a switch element having a low withstand voltage and a low on-resistance, and it is possible to increase the efficiency of the switching power supply. .

FIG. 10 shows a tenth embodiment of the present invention.
This embodiment has the same basic circuit configuration as the embodiment shown in FIG. 5, and the configuration of FIG. 10 different from the configuration of FIG.
A second capacitor 91 is connected in series with the first control winding 45, a third diode 92 is connected in parallel with the series circuit of the first control winding 45 and the second capacitor 91, and The third capacitor 93 is connected in series with the control winding 47, and the fourth diode 94 is connected in parallel with the series circuit of the second control winding 47 and the third capacitor 93.

The operation of the circuit in which the second capacitor 91 and the third diode 92 in FIG. 10 and the third capacitor 93 and the fourth diode 94 are added is the same as the operation of the capacitor 91 and the diode 92 in FIG. That is, the currents of the first inductor 31 and the second inductor 38 are in the continuous mode, the input current I _in (3) has a waveform substantially corresponding to the sine wave, and the power factor can be increased. The configuration of FIG. 10 is similar to that of the embodiment of FIG.
Since the voltage applied to the switch element 51 and the second switch element 52 is the same as the terminal voltage of the series circuit of the first smoothing capacitor 35 and the second smoothing capacitor 36, the switch element has low breakdown voltage. , A low on-resistance can be used, and the efficiency as a switching power supply can be increased.

FIG. 11 shows an eleventh embodiment of the present invention.
This embodiment has the same basic circuit configuration as that of the embodiment shown in FIG. 1. The configuration of FIG. 11 different from the configuration of FIG.
A first capacitor 95 is provided in parallel with the first switch element 51.
, The second capacitor 96 is connected in parallel with the second switch element 52, the third capacitor 97 is connected in parallel with the third switch element 53, and the fourth switch element 5 is connected.
The fourth capacitor 98 is connected in parallel with the fourth capacitor 98. With this configuration, the first to fourth capacitors 95 to 98 form a series resonance circuit together with the leakage inductance of the transformer 40, and the capacitors 95 to 98 are connected in parallel. While the switch elements 51 to 54 are off, the voltage across the terminals of the switch elements can be reduced to zero volt by resonance. Therefore, if the switch elements 51 to 54 are turned on after the voltage across the terminals of each of the switch elements 51 to 54 has dropped to zero volts, the switching loss at turn-on of the switch elements can be reduced. The efficiency of the switching power supply can be increased. In addition, since the other components of FIG. 11 are the same as the configuration of FIG. 1, the same effects as the embodiment of FIG. 1 can be obtained in addition to the above effects. That is, like the embodiment of FIG. 1, the configuration of FIG. 11 is a switching power supply with a high power factor, and at the same time, the voltage applied to the switch elements 51 to 54 is the same as the voltage of the smoothing capacitor 30, so the switch A device having a low breakdown voltage and a low on-resistance can be used as an element, and efficiency as a switching power supply can be increased.

FIG. 12 shows a twelfth embodiment of the present invention.
This embodiment has the same basic circuit configuration as the embodiment shown in FIG. 2, and the configuration of FIG. 12 different from the configuration of FIG.
A first capacitor 95 is provided in parallel with the first switch element 51.
Is connected, and the second capacitor 96 is connected in parallel with the second switch element 52. With such a configuration, the first and second capacitors 95, 96
Respectively form a series resonance circuit together with the leakage inductance of the transformer 40, and the capacitors 95 and 96 respectively change the voltage across the terminals of the switch elements 51 and 52 to which they are connected in parallel during the OFF period. Resonance can reduce it to zero volts. Therefore, if the switch elements 51 and 52 are turned on after the voltage between the terminals of the respective switch elements 51 and 52 has dropped to zero volts, the switching loss at the time of turn-on of the switch elements can be reduced. The efficiency of the switching power supply can be increased. Also, FIG.
Since the other components of 2 are the same as the configuration of FIG. 2, the same effects as the embodiment of FIG. 2 can be obtained in addition to the above-mentioned effects. That is, similarly to the embodiment of FIG. 2, the configuration of FIG. 12 is a switching power supply having a high power factor, and at the same time, the voltage applied to the switch elements 51 and 52 is the same as that of the first smoothing capacitor 33 and the second smoothing capacitor. Since it is the same as the voltage across the terminals of the smoothing capacitor configured by the series circuit of the capacitor 34, it is possible to use a switch element having a low breakdown voltage and a low on-resistance, and it is possible to increase the efficiency as a switching power supply.

FIG. 13 shows a thirteenth embodiment of the present invention.
This embodiment has the same basic circuit configuration as the embodiment shown in FIG. 3, and the configuration of FIG. 13 different from the configuration of FIG.
A first capacitor 95 is provided in parallel with the first switch element 51.
Is connected, and the second capacitor 96 is connected in parallel with the second switch element 52. With such a configuration, the first and second capacitors 95, 96
Respectively form a series resonance circuit together with the leakage inductance of the transformer 40, and the capacitors 95 and 96 respectively change the voltage across the terminals of the switch elements 51 and 52 to which they are connected in parallel during the OFF period. Resonance can reduce it to zero volts. Therefore, if the switch elements 51 and 52 are turned on after the voltage between the terminals of the respective switch elements 51 and 52 has dropped to zero volts, the switching loss at the time of turn-on of the switch elements can be reduced. The efficiency of the switching power supply can be increased. Also, FIG.
Since the other components of 3 are the same as the configuration of FIG. 3, the same effects as the embodiment of FIG. 3 can be obtained in addition to the above-described effects. That is, similarly to the embodiment of FIG. 3, the configuration of FIG. 13 is a switching power supply with a high power factor, and at the same time, the voltage applied to the switch elements 51 and 52 is the same as the terminal voltage of the smoothing capacitor 30. Therefore, a switch element with low withstand voltage and low on-resistance can be used,
The efficiency of the switching power supply can be increased.

FIG. 14 shows a fourteenth embodiment of the present invention.
This embodiment has the same basic circuit configuration as the embodiment shown in FIG. 4, and the configuration of FIG. 14 different from the configuration of FIG.
A first capacitor 95 is provided in parallel with the first switch element 51.
Is connected, and the second capacitor 96 is connected in parallel with the second switch element 52. With such a configuration, the first and second capacitors 95, 96
Respectively form a series resonance circuit together with the leakage inductance of the transformer 40, and the capacitors 95 and 96 respectively change the voltage across the terminals of the switch elements 51 and 52 to which they are connected in parallel during the OFF period. Resonance can reduce it to zero volts. Therefore, if the voltage between the terminals of the respective switch elements 51, 52 is reduced to zero volt and then the switch elements are turned on, the switching loss at the time of turning on the switch elements 51, 52 can be reduced. The efficiency of the switching power supply can be increased. Also, FIG.
Since the other components of 4 are the same as the configuration of FIG. 4, the same effects as the embodiment of FIG. 4 can be obtained in addition to the above-mentioned effects. That is, similarly to the embodiment of FIG. 4, the configuration of FIG. 14 is a switching power supply having a high power factor, and at the same time, the voltage applied to the switch elements 51 and 52 is the same as the terminal voltage of the smoothing capacitor 30. Therefore, a switch element with low withstand voltage and low on-resistance can be used,
The efficiency of the switching power supply can be increased.

FIG. 15 shows a fifteenth embodiment of the present invention.
This embodiment has the same basic circuit configuration as that of the embodiment shown in FIG. 5, and the configuration of FIG. 15 different from the configuration of FIG.
A first capacitor 95 is provided in parallel with the first switch element 51.
Is connected, and the second capacitor 96 is connected in parallel with the second switch element 52. With such a configuration, the first and second capacitors 95, 96
Respectively form a series resonance circuit together with the leakage inductance of the transformer 40, and the capacitors 95 and 96 respectively change the voltage across the terminals of the switch elements 51 and 52 to which they are connected in parallel during the OFF period. Resonance can reduce it to zero volts. Therefore, if the switch elements 51 and 52 are turned on after the voltage between the terminals of the respective switch elements 51 and 52 has dropped to zero volts, the switching loss at the time of turn-on of the switch elements can be reduced. The efficiency of the switching power supply can be increased. Also, FIG.
Since the other components of 5 are the same as the configuration of FIG. 5, the same effects as the embodiment of FIG. 5 can be obtained in addition to the above effects. That is, similarly to the embodiment of FIG. 5, the configuration of FIG. 15 is a switching power supply with a high power factor, and at the same time, the voltage applied to the switch elements 51 and 52 is the same as that of the first smoothing capacitor 35 and the second smoothing capacitor. Since the voltage is the same as the voltage across the terminals of the smoothing capacitor formed by the series circuit of the capacitors 36, it is possible to use a low withstand voltage and low on-resistance as the switch element, and it is possible to increase the efficiency of the switching power supply.

FIG. 16 shows a sixteenth embodiment of the present invention.
This embodiment has the same basic circuit configuration as the embodiment shown in FIG. 6, and the configuration of FIG. 16 different from the configuration of FIG.
A first capacitor 95 is provided in parallel with the first switch element 51.
, The second capacitor 96 is connected in parallel with the second switch element 52, the third capacitor 97 is connected in parallel with the third switch element 53, and the fourth switch element 5 is connected.
The fourth capacitor 98 is connected in parallel with the fourth capacitor 98. With this configuration, the first to fourth capacitors 95 to 98 form a series resonance circuit together with the leakage inductance of the transformer 40, and the capacitors 95 to 98 are connected in parallel. While the switch elements 51 to 54 are off, the voltage across the terminals of the switch elements can be reduced to zero volt by resonance. Therefore, if the switch elements 51 to 54 are turned on after the voltage across the terminals of each of the switch elements 51 to 54 has dropped to zero volts, the switching loss at turn-on of the switch elements can be reduced. The efficiency of the switching power supply can be increased. Further, since the other components of FIG. 16 are the same as the configuration of FIG. 6, the same effects as those of the embodiment of FIG. 6 can be obtained in addition to the above effects. That is, as in the embodiment of FIG. 6, the configuration of FIG. 16 is a switching power supply with a high power factor, and at the same time, the voltage applied to the switch elements 51 to 54 is the same as the terminal voltage of the smoothing capacitor 30. Therefore, a switch element having a low breakdown voltage and a low on-resistance can be used, and the efficiency as a switching power supply can be increased.

FIG. 17 shows a seventeenth embodiment of the present invention.
This embodiment has the same basic circuit configuration as the embodiment shown in FIG. 7, and the configuration of FIG. 17 different from the configuration of FIG.
A first capacitor 95 is provided in parallel with the first switch element 51.
Is connected, and the second capacitor 96 is connected in parallel with the second switch element 52. With such a configuration, the first and second capacitors 95, 96
Respectively form a series resonance circuit together with the leakage inductance of the transformer 40, and the capacitors 95 and 96 respectively change the voltage across the terminals of the switch elements 51 and 52 to which they are connected in parallel during the OFF period. Resonance can reduce it to zero volts. Therefore, if the switch elements 51 and 52 are turned on after the voltage between the terminals of the respective switch elements 51 and 52 has dropped to zero volts, the switching loss at the time of turn-on of the switch elements can be reduced. The efficiency of the switching power supply can be increased. Also, FIG.
Since the other components of 7 are the same as those of the configuration of FIG. 7, the same effects as the embodiment of FIG. 7 can be obtained in addition to the above-described effects. That is, similarly to the embodiment of FIG. 7, the configuration of FIG. 17 is a switching power supply with a high power factor, and at the same time, the voltage applied to the switch elements 51 and 52 is the same as that of the first smoothing capacitor 33 and the second smoothing capacitor. Since it is the same as the voltage across the terminals of the smoothing capacitor configured by the series circuit of the capacitor 34, it is possible to use a switch element having a low breakdown voltage and a low on-resistance, and it is possible to increase the efficiency as a switching power supply.

FIG. 18 shows the 18th embodiment of the present invention.
This embodiment has the same basic circuit configuration as the embodiment shown in FIG. 8, and the configuration of FIG. 18 different from the configuration of FIG.
A first capacitor 95 is provided in parallel with the first switch element 51.
Is connected, and the second capacitor 96 is connected in parallel with the second switch element 52. With such a configuration, the first and second capacitors 95, 96
Respectively form a series resonance circuit together with the leakage inductance of the transformer 40, and the capacitors 95 and 96 respectively change the voltage across the terminals of the switch elements 51 and 52 to which they are connected in parallel during the OFF period. Resonance can reduce it to zero volts. Therefore, if the switch elements 51 and 52 are turned on after the voltage between the terminals of the respective switch elements 51 and 52 has dropped to zero volts, the switching loss at the time of turn-on of the switch elements can be reduced. The efficiency of the switching power supply can be increased. Also, FIG.
Since the other components of 8 are the same as the configuration of FIG. 8, the same effects as the embodiment of FIG. 8 can be obtained in addition to the above-described effects. That is, similarly to the embodiment of FIG. 8, the configuration of FIG. 18 is a switching power supply having a high power factor, and at the same time, the voltage applied to the switch elements 51 and 52 is the same as the terminal voltage of the smoothing capacitor 30. Therefore, a switch element with low withstand voltage and low on-resistance can be used,
The efficiency of the switching power supply can be increased.

FIG. 19 shows a nineteenth embodiment of the present invention.
This embodiment has the same basic circuit configuration as the embodiment shown in FIG. 9, and the configuration of FIG. 19 different from the configuration of FIG.
A first capacitor 95 is provided in parallel with the first switch element 51.
Is connected, and the second capacitor 96 is connected in parallel with the second switch element 52. With such a configuration, the first and second capacitors 95, 96
Respectively form a series resonance circuit together with the leakage inductance of the transformer 40, and the capacitors 95 and 96 respectively change the voltage across the terminals of the switch elements 51 and 52 to which they are connected in parallel during the OFF period. Resonance can reduce it to zero volts. Therefore, if the switch elements 51 and 52 are turned on after the voltage between the terminals of the respective switch elements 51 and 52 has dropped to zero volts, the switching loss at the time of turn-on of the switch elements can be reduced. The efficiency of the switching power supply can be increased. Also, FIG.
Since the other components of 9 are the same as the configuration of FIG. 9, the same effects as the embodiment of FIG. 9 can be obtained in addition to the above-described effects. That is, similarly to the embodiment of FIG. 9, the configuration of FIG. 19 is a switching power supply with a high power factor, and at the same time, the voltage applied to the switch elements 51 and 52 is the same as the terminal voltage of the smoothing capacitor 30. Therefore, a switch element with low withstand voltage and low on-resistance can be used,
The efficiency of the switching power supply can be increased.

FIG. 20 shows a twentieth embodiment of the present invention.
This embodiment has the same basic circuit configuration as that of the embodiment shown in FIG. 10. In the configuration of FIG. 20, which is different from the configuration of FIG. 10, a first capacitor 95 is connected in parallel with a first switch element 51. , The second capacitor 96 is connected in parallel with the second switch element 52. With such a configuration, the first and second capacitors 95, 9
6 constitutes a series resonance circuit together with the leakage inductance of the transformer 40, and the respective capacitors 95 and 96.
Is a switching element 51, 52 to which it is connected in parallel
The voltage between the terminals of the switch element can be reduced to zero volt by resonance during the off period of. Therefore, if the switch elements 51 and 52 are turned on after the voltage between the terminals of the respective switch elements 51 and 52 has dropped to zero volts, the switching loss at the time of turn-on of the switch elements can be reduced. The efficiency of the switching power supply can be increased.

The other components of FIG. 20 are the same as those of FIG.
Since the configuration is the same as that of 0, the same effect as the embodiment of FIG. 10 can be obtained in addition to the above-mentioned effect. That is, similarly to the embodiment of FIG. 10, the configuration of FIG. 20 is a switching power supply having a high power factor, and at the same time, the voltage applied to the switch elements 51 and 52 is the same as that of the first smoothing capacitor 33 and the second smoothing capacitor. Since it is the same as the voltage across the terminals of the smoothing capacitor configured by the series circuit of the capacitor 34, it is possible to use a switch element having a low breakdown voltage and a low on-resistance, and it is possible to increase the efficiency as a switching power supply.

[0046]

As described above, according to the present invention, the circuit is the same as the circuit of the prior invention (Japanese Patent Application No. 5-177379) previously invented by the present inventors with respect to the conventional AC input switching power supply. In addition, the power factor can be increased and the voltage applied to the switch element in the circuit of the invention of the earlier application is about twice that of the smoothing capacitor, whereas in the circuit of the present invention, the voltage is applied to the switch element. since the voltage is the same voltage as the voltage of the smoothing capacitor, as a switching element, it is possible to use a low on-resistance at low withstand voltage, as a result, decreases the power loss in the switching element, a high efficiency of the switching power supply Can be realized.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a first embodiment of the present invention.

FIG. 2 is a circuit diagram of a second embodiment of the present invention.

FIG. 3 is a circuit diagram of a third embodiment of the present invention.

FIG. 4 is a circuit diagram of a fourth embodiment of the present invention.

FIG. 5 is a circuit diagram of a fifth embodiment of the present invention.

FIG. 6 is a circuit diagram of a sixth embodiment of the present invention.

FIG. 7 is a circuit diagram of a seventh embodiment of the present invention.

FIG. 8 is a circuit diagram of an eighth embodiment of the present invention.

FIG. 9 is a circuit diagram of a ninth embodiment of the present invention.

FIG. 10 is a circuit diagram of a tenth embodiment of the present invention.

FIG. 11 is a circuit diagram of an eleventh embodiment of the present invention.

FIG. 12 is a circuit diagram of a twelfth embodiment of the present invention.

FIG. 13 is a circuit diagram of a thirteenth embodiment of the present invention.

FIG. 14 is a circuit diagram of a fourteenth embodiment of the present invention.

FIG. 15 is a circuit diagram of a fifteenth embodiment of the present invention.

FIG. 16 is a circuit diagram of a sixteenth embodiment of the present invention.

FIG. 17 is a circuit diagram of a seventeenth embodiment of the present invention.

FIG. 18 is a circuit diagram of an eighteenth embodiment of the present invention.

FIG. 19 is a circuit diagram of a nineteenth embodiment of the present invention.

FIG. 20 is a circuit diagram of a twentieth embodiment of the present invention.

FIG. 21 is a waveform chart showing the operation timing of the first embodiment of the present invention.

FIG. 22 is an operation waveform diagram of the first embodiment of the present invention.

FIG. 23 is a circuit diagram of a conventional AC input switching power supply.

FIG. 24 is a waveform diagram of input voltage / current of a conventional AC input switching power supply.

FIG. 25 is a circuit diagram of a prior application of the present inventors' invention.

FIG. 26 is an operation waveform diagram of the prior invention of the present inventors.

[Explanation of symbols]

10 Commercial power source 20 Full-wave rectifiers 21-24, 32, 55-58, 61, 62, 92, 9
4 Diodes 30, 35, 36, 64 Smoothing capacitors 31, 63 Inductor 37 Switch 40 Transformer 41, 46 Transformer primary winding 42, 44 Transformer secondary winding 43 Transformer tertiary winding 45 , 4 7 Control winding Lines 50 to 54 Switch elements 59, 91, 93, 95 to 98 Capacitor 60 Rectifying and smoothing circuit 70 Load 80 Control circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-128669 (JP, A) JP-A-6-217537 (JP, A) JP-A-4-42779 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H02M 7/217 H02M 3/335 H02M 3/337

Claims (9)

(57) [Claims] And 1. A full-wave rectifier connected to an AC power source, and connected to a smoothing capacitor between the output terminals of該全wave rectifier, a transformer having a control winding with the primary winding on the primary side, the Connected between the full wave rectifier and the smoothing capacitor
Circuit of the inductor and the control winding of the transformer
And both ends of the smoothing capacitor and the primary winding of the transformer
A bridge consisting of an even number of switch elements connected between
Di circuit, a rectifying smoothing circuit load on the output side is connected is connected to the secondary winding of the transformer, the output voltage by detecting the output voltage of the rectifying smoothing circuit to a predetermined voltage So that the switching element of the bridge circuit
A switching power supply having a control circuit for controlling the . 2. The bridge circuit is a first switch element.
To a fourth switch element, and
A connection point between the first switch element and the second switch element,
A connection point between the third switch element and the fourth switch element,
The primary winding of the transformer is connected between
The switching power supply according to claim 1, made a. 3. The bridge circuit comprises a first switch element.
And a second switch element, the first switch
Connection point between the switch element and the second switch element and the smoothing contact
The capacitor is a first smoothing capacitor and a second smoothing capacitor.
It is divided into two parts, and one of the transformers between the connection point and
The switching power supply according to claim 1, wherein the switching power supply is configured to be connected to a secondary winding . 4. The bridge circuit is a first switch element.
And a second switch element, and
A connection point between the switch element and the second switch element, and
With the other end of the capacitor connected to one end of the smoothing capacitor
The primary winding of the transformer is connected between
The switching power supply according to claim 1 . 5. A full-wave rectifier connected to an AC power supply, and a first smoothing capacitor connected between output terminals of the full-wave rectifier.
A series circuit of a capacitor and a second smoothing capacitor, a primary winding on the primary side, a first control winding and a second control winding
A transformer , an end of the full-wave rectifier, and the first smoothing capacitor
Connect between the second smoothing capacitor and one end of the series circuit
First inductor and first control winding of the transformer
A series circuit with a wire , the other end of the full-wave rectifier, and the first smoothing capacitor
Connected to the other end of the series circuit with the second smoothing capacitor
Second inductor and second control winding of the transformer
Of a series circuit with a line, the first smoothing capacitor and the second smoothing capacitor
Provided between the connection point and one terminal of the AC power supply
A switch, and the first smoothing capacitor and the second smoothing capacitor
A first switch element and a second switch element connected to both ends of the series circuit.
Series circuit with the switch element and the connection point between the first switch element and the second switch element
And the first smoothing capacitor and the second smoothing capacitor
And the primary winding of the transformer between one end of the series circuit and
A capacitor connected through a rectifier smoothing circuit for the transformer load on the output side is connected to the secondary winding is connected, is detected to the output voltage an output voltage of the rectifying smoothing circuit The first switch element and the first switch element are controlled so that a predetermined voltage is obtained .
A switching power supply having a control circuit for controlling the second switching element . 6. A full-wave rectifier connected to an AC power source, a smoothing capacitor connected between output terminals of the full-wave rectifier, a first primary winding and a second primary winding on the primary side. Wire and control winding
And a transformer connected between the full-wave rectifier and the smoothing capacitor.
Circuit of the inductor and the control winding of the transformer
And the transformer connected between the terminals of the smoothing capacitor
A series circuit of the first primary winding and the first switching element of
And a second primary winding of the transformer and a second switch element
A series circuit with a child, a rectifying / smoothing circuit connected to the secondary winding of the transformer and having a load connected to the output side thereof, and detecting the output voltage of the rectifying / smoothing circuit to determine a predetermined output voltage. The first switching element and the first switching element
A switching power supply having a control circuit for controlling the second switching element . 7. A control winding for the inductor and the transformer.
A capacitor connected between the wire and the capacitor
A diode connected in parallel to the series circuit with the control winding
The switching power supply according to claim 1, 2, 3, 4, 5 or 6, further comprising: 8. The first to fourth switch elements.
A diode connected in parallel with the switch element.
The switching power supply according to 1, 2, 3, 4, 5, 6 or 7 . 9. The first switch element through the fourth switch element.
A capacitor connected in parallel with the switch element.
The switching power supply according to 1, 2, 3, 4, 5, 6, 7 or 8 .