JP2003244962A - Switching power source - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a switching power source capable of reducing loss, improving control and a power factor and controlling the stabilization of an output voltage using a single control system. <P>SOLUTION: A switching element SW is controlled on and off at a frequency higher than the frequency of an AC power source AC. The element SW supplies a rectified output to an inductor L during the on-period of the element SW to store energy, discharges a capacitor C to supply power to an input winding T1, and discharges the energy stored in the inductor L during the off-period of the element SW to charge the capacitor C. An output circuit 3 converts a voltage induced to an output winding T2 into a DC and outputs the DC. A control circuit 4 is electrically insulated from an input side, and disposed at an output side to synchronous-control both a power factor improving type power converter 2 circuit and a synchronous rectifier circuit 31. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synchronous rectification type switching power supply device equipped with a power factor correction type power conversion circuit to which a dither circuit is applied.

[0002]

2. Description of the Related Art A switching power supply device rectifies and smoothes an AC power supply by an input rectifying and smoothing circuit to convert it into a DC voltage, which is intermittently switched by a switching element.
Supply the switching output to the output rectification smoothing circuit,
It is smoothed to obtain an arbitrary DC output voltage.
In such a switching power supply device, if the smoothing circuit on the input side is a capacitor input type, the input current flows only during a period when the rectified voltage is higher than the charging voltage of the input smoothing capacitor, which causes a reduction in power factor. was there. To solve this problem, DC-
A switching power supply device including a step-up power factor correction circuit is used in front of a DC converter.

The booster type power factor correction circuit includes a choke coil, a switching element, a rectifying / smoothing circuit, and a control circuit. A voltage obtained by rectifying an AC power supply is supplied to the choke coil. The switching element switches the rectified voltage supplied through the choke coil at a frequency higher than the frequency of the AC power source, boosts the voltage, and outputs the boosted voltage. The rectifying and smoothing circuit rectifies and smoothes the switched output,
Converted to a DC voltage higher than the input rectified voltage and output.
The control circuit controls switching of the switching element.

Since the switching element switches the rectified voltage of the input at a frequency higher than the frequency of the AC power source, boosts and outputs the rectified voltage, the input current can be distributed and flowed throughout the entire period of one AC cycle. If the current flowing through the switching element is controlled so as to be proportional to the voltage waveform of the AC power supply, the power factor of the switching power supply device can be improved.

In addition, in recent years, switching power supplies have been required to have improved conversion efficiency in addition to the above-mentioned improvement in power factor. In order to cope with this demand, instead of the rectifying diode forming the output rectifying circuit of the DC-DC converter, a field effect transistor or the like having a lower voltage drop is used to form the synchronous rectifying circuit, resulting in loss of the output rectifying circuit. Means have been proposed.

However, when the step-up type power factor improving circuit as described above is provided in the preceding stage of the DC-DC converter provided with such a synchronous rectifying circuit to constitute the switching power supply device, the power factor improving circuit and the DC-DC are provided. A control circuit is required for each of the power conversion circuit and the synchronous rectification circuit of the converter, and the circuit configuration becomes extremely complicated.

On the other hand, as one form of the power factor correction circuit, a dither circuit or a circuit to which the dither circuit is applied is known (for example, Japanese Patent No. 2808190, JP-A-8-29).
4279, JP-A-8-172774, JP-A-9-2
15332, JP-A-11-191960, etc.). Such a dither circuit or a power factor correction type power conversion circuit to which the dither circuit is applied has an advantage that power factor correction and output voltage stabilization control can be performed by a single control system. However, when the output rectifier circuit is a synchronous rectifier circuit, the control target exists on the input side and the output side. Therefore, simply replacing the conventional output rectifier circuit using the rectifier diode with the synchronous rectifier circuit results in two systems. A control system is required, and the circuit configuration is still complicated.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a switching power supply device capable of reducing loss and improving power factor by a synchronous rectification circuit.

Another object of the present invention is to provide a switching power supply device which can be controlled by a single control system.

Yet another object of the present invention is to provide a switching power supply device which can be driven at a single switching frequency.

Yet another object of the present invention is to provide a switching power supply device having a simple circuit configuration and capable of stable operation.

[0012]

In order to solve the above problems, a switching power supply device according to the present invention includes a rectifier circuit, a power factor correction type power conversion circuit, an output circuit, and a control circuit.

The rectifier circuit rectifies an AC power source to generate a rectified output, and supplies the generated rectified output to the power factor improving power conversion circuit.

The power factor improving power conversion circuit includes a conversion transformer, a switching element, an inductor, a capacitor, and a diode.

The conversion transformer includes an input winding and an output winding, and induces a voltage in the output winding.

The diode is connected to block a reverse voltage applied to the inductor.

The switching element is ON / OFF controlled at a frequency higher than the frequency of the AC power supply, and supplies the rectified output to the inductor to store energy and discharge the capacitor during the ON period of the switching element. Then, power is supplied to the input winding, and the energy stored in the inductor is released during the off period of the switching element to charge the capacitor.

The output circuit includes a synchronous rectification circuit and an output smoothing circuit, is connected to the output winding, rectifies and smoothes the voltage induced in the output winding, converts the voltage into DC, and outputs the DC.

The control circuit is electrically insulated from the input side and arranged on the output side, and synchronously controls both the power factor correction type power conversion circuit and the synchronous rectification circuit.

The present invention focuses on the fact that a single control system can perform power factor correction and output voltage stabilization control in a dither circuit or a power factor correction type power conversion circuit applying the dither circuit. When a synchronous rectification circuit is combined with a power factor correction type power conversion circuit applying a dither circuit, it is possible to control the dither circuit or the power factor correction type power conversion circuit applying the dither circuit from the output side. The idea is that the circuit configuration can be simplified compared to the case where the control is performed from the input side.

That is, in the above-described switching power supply device, the rectifier circuit rectifies an AC power source to generate a rectified output, and supplies the generated rectified output to the power factor correction type power conversion circuit. The power factor correction type power conversion circuit includes a conversion transformer, a switching element, an inductor, a capacitor, and a diode. The diode is connected to block the reverse voltage applied to the inductor.

The switching element is ON / OFF controlled at a frequency higher than the frequency of the AC power supply, and supplies the rectified output to the inductor to store energy and discharges the capacitor during the ON period of the switching element. Then, the power is supplied to the input winding, the energy stored in the inductor is released during the OFF period of the switching element, and the capacitor is connected so as to charge the capacitor. The input current can be turned on and off via the, and the input current can be distributed and passed.

The output circuit includes a synchronous rectification circuit and an output smoothing circuit, is connected to the output winding, rectifies and smoothes the electric power supplied to the input winding, converts the electric power into a direct current, and outputs the direct current.

The control circuit is electrically insulated from the input side and arranged on the output side, and synchronously controls both the power factor correction type power conversion circuit and the synchronous rectification circuit. It is possible to improve the power factor and stabilize the output voltage.

As described above, in the switching power supply device of the present invention, the loss can be reduced by the synchronous rectification circuit, and the control of the synchronous rectification circuit, the improvement of the power factor and the stabilization control of the output voltage can be performed by a single control system. In addition, since it can be driven at a single switching frequency, the circuit configuration is simple and stable operation can be obtained.

Other objects, configurations and advantages of the present invention will be described in more detail with reference to the accompanying drawings. However, the attached drawings are merely examples.

[0027]

1 is an electric circuit diagram showing an embodiment of a switching power supply device according to the present invention. The illustrated switching power supply device includes a rectifier circuit 1, a power factor correction type power conversion circuit 2, an output circuit 3, and a control circuit 4. AC is an AC power supply, and 5 is an insulation coupling circuit that electrically insulates the input side and the output side and transmits a control signal.

The rectifier circuit 1 is a circuit that rectifies an AC power supply AC to generate a rectified output, and is composed of a diode bridge or the like. The AC power supply AC may be any other AC power supply other than the commercial AC.

The power factor correction type power conversion circuit 2 is a power factor correction type power conversion circuit to which a dither circuit is applied, and includes a conversion transformer T, a switching element SW, an inductor L, and
It includes a capacitor C and first and second diodes D1 and D2. The conversion transformer T includes an input winding T1 and an output winding T2.

The first and second diodes D1 and D2 are oriented and connected to block the reverse voltage applied to the inductor L.

The inductor L has one end connected to the positive output end of the rectifier circuit 1 and the other end connected to the negative output end b of the rectifier circuit 1 via the first diode D1 and the capacitor C. The other end is similarly connected to the negative side output end of the rectifier circuit 1 via the second diode D2 and the switching element SW.

The input winding T1 of the conversion transformer T has one end connected to the positive end of the capacitor C and the other end connected to the negative end of the capacitor C via the switching element SW.

The switching element SW is ON / OFF controlled at a frequency higher than the frequency of the AC power supply AC.

The switching element SW has only to be capable of switching the supplied electric power at a frequency higher than the frequency of the AC power source AC, and typically a semiconductor element such as a bipolar transistor or a field effect transistor is used. This embodiment uses a field effect transistor.

In the above-described structure, during the ON period of the switching element SW, the rectified output is supplied to the inductor L via the second diode D2 and the switching element SW to store energy, and at the same time, the input winding T1 and the switching element are switched. The capacitor C is discharged via SW and the input winding T1 is supplied with power.

During the OFF period of the switching element SW, the energy stored in the inductor L is released through the first diode D1 to charge the capacitor C. This configuration is the basis for improving the power factor of the switching power supply device.

The output circuit 3 includes a synchronous rectification circuit 31 and an output smoothing circuit 32, and is connected to the output winding T2 of the conversion transformer T. The synchronous rectification circuit 31 includes a synchronous rectification element 311 and
312 is included. The synchronous rectifying elements 311, 312 are
A semiconductor element having a lower voltage drop than a rectifier diode is used and has a control electrode. This embodiment uses a field effect transistor.

The output smoothing circuit 32 is a choke coil 32.
1 and an output smoothing capacitor 322, which is a choke input type. One end of the synchronous rectification element 311 is connected to one end of the output winding T2, the other end is connected to one end of the output smoothing capacitor 322 via the choke coil 321, and is also connected to one output terminal of the switching power supply device. It The synchronous rectifying element 312 has one end connected to a connection point between the synchronous rectifying element 311 and the choke coil 321, the other end connected to the other end of the output winding T2, and the other end of the output smoothing capacitor 322. , Is connected to the other output terminal of the switching power supply device.

The control circuit 4 detects the output voltage as an output voltage signal, generates a pulse width control signal according to the detected output, and outputs the switching element SW and the synchronous rectifying element 31.
Drive signals S1 and S311 and S312 for controlling ON / OFF of 1 and 312 are output.

The control circuit 4 is generally constituted by including a control IC. The switching power supply device of the present embodiment is
The control circuit 4 is electrically insulated from the input side and arranged on the output side, and the switching element SW of the power factor correction type power conversion circuit 2 arranged on the input side and the synchronous rectifying elements 311 and 312 arranged on the output side. Both of the above are synchronously controlled by one control circuit 4. Therefore, the drive signal S1 of the switching element SW is transmitted to the input side via the insulating coupling circuit 5. The insulating coupling circuit 5 uses a pulse transformer in this embodiment, but an insulating coupling circuit such as a photocoupler can also be used.

The switching power supply unit of the present embodiment having such a configuration can improve the power factor and stabilize the output voltage with a single control system. This point will be described below.

FIG. 2 is a diagram showing on / off timings of the switching power supply device shown in FIG. In the figure, a switching element SW and a synchronous rectifying element 31
The ON period of each of 1 and 312 is shown as a high level, and the OFF period is shown as a low level. As shown in FIG. 2, the switching element SW and the synchronous rectifying element 311 have basically the same on-off timing (see FIGS. 2A and 2B), and the synchronous rectifying element 312 has the opposite phase (see FIG. a), (c)
Control). More practically, the ON / OFF timing of each element is set via a delay circuit or the like in consideration of prevention of simultaneous ON of the synchronous rectification elements 311 and 312 due to variations in turn-ON / OFF times unique to each element. Stabilization of the output voltage is performed by pulse width control that moves the OFF timing of the switching element SW and the synchronous rectifying element 311 and the ON timing of the synchronous rectifying element 312 back and forth according to the output voltage as indicated by the arrow. The off timing of the switching element SW is controlled so that the off timing of the synchronous rectifying element 311 and the on timing of the synchronous rectifying element 312 are synchronized.

In the switching power supply device shown in FIG. 1, the control circuit 4 detects the output voltage as an output voltage signal, generates a pulse width control signal according to the detected output, and outputs the switching element SW and the synchronous rectifying element. 311
The drive signals S1 and S311, S312 for controlling the ON / OFF of the 312 are output.

When the switching element SW is turned on, the inductor L, the second diode D2 and the switching element S
The rectified output is supplied to the inductor L via W and stores energy. On the other hand, the capacitor C discharges the electric charge charged during the OFF period of the previous switching element SW through the input winding T1 and the switching element SW during the ON period of the switching element SW to supply power to the input winding T1. Supply and induce a voltage in the output winding T2.

At this time, in the output circuit 3, the synchronous rectifying element 31
1 is on, the voltage induced in the output winding T2 causes a current to flow through the output smoothing capacitor 322, the choke coil 321 and the synchronous rectifying element 311 to charge the output smoothing capacitor 322, and at the same time, the choke coil 321.
Store energy in. The charging voltage of the output smoothing capacitor 322 is supplied to the output terminal of the switching power supply device and is also supplied to the control circuit 4 as an output voltage signal.

When the switching element SW is turned off, the energy stored in the inductor L is released through the first diode D1 to charge the capacitor C. At this time, in the output circuit 3, the synchronous rectifying element 312 is turned on, the energy stored in the choke coil 321 is released, and a current flows through the synchronous rectifying element 312.
The output smoothing capacitor 322 is charged.

In the switching power supply device of this embodiment constructed as described above, the switching element SW is the AC power supply AC.
The power factor can be improved because the on / off control is performed at a frequency higher than the frequency, and the input current can be turned on / off and the input current can be dispersed and flowed throughout the entire period of one AC cycle.
Further, the switching element SW and the synchronous rectifying element 311,
Since 312 is driven based on the pulse width control signal corresponding to the output voltage, the output voltage can be stabilized. Furthermore, the above-mentioned control is performed by a single control system, and since the switching frequency can be driven at a single switching frequency without mixing various frequencies, the control system is simple and the operation is stable.

As described above, in the switching power supply device of the present embodiment, the loss can be reduced by the synchronous rectification circuit, and the control of the synchronous rectification circuit, the improvement of the power factor and the stabilization control of the output voltage are controlled by a single control system. Since it is possible and can be driven at a single switching frequency, the circuit configuration is simple and stable operation can be obtained.

FIG. 3 is an electric circuit diagram showing another embodiment of the switching power supply device according to the present invention. The illustrated switching power supply device is similar to the embodiment shown in FIG.
Although the rectifier circuit 1, the power factor correction type power conversion circuit 2, the output circuit 3, and the control circuit 4 are included, the configuration of the power factor correction type power conversion circuit 2 is different. This point will be mainly described below.

The power factor correction type power conversion circuit 2 includes a conversion transformer T and first and second switching elements SW1 and SW2.
And an inductor L, a capacitor C, and a diode D. The conversion transformer T includes an input winding T1 and an output winding T2.

Diode D is oriented and connected to block the reverse voltage on inductor L.

One end of the inductor L is connected to the positive output end of the rectifier circuit 1, and the other end is connected to the diode D and the capacitor C.
Is connected to the negative side output terminal of the rectifier circuit 1 through, and the other end is similarly connected to the negative side output terminal b of the rectifier circuit 1 through the second switching element SW2.

The input winding T1 of the conversion transformer T has one end connected to the positive side end of the capacitor C and the other end connected to the negative side end of the capacitor C via the first switching element SW1.

First and second switching elements SW1 and S
W2 is ON / OFF controlled in synchronization with a frequency higher than the frequency of the AC power supply AC.

In the above-described structure, the first and second switching elements SW1 and SW2 are controlled to be turned on and off in synchronization, and the second switching element SW is turned on during the on period.
The rectified output is supplied to the inductor L via 2 to store energy, and the capacitor C is discharged via the input winding T1 and the first switching element SW1 to supply power to the input winding T1.

First and second switching elements SW1 and S
During the off period of W2, the energy stored in the inductor L is released through the diode D and the capacitor C
To charge.

The configurations of the output circuit 3 and the control circuit 4 are similar to those of the embodiment shown in FIG. 1, and the first and second switching elements SW1 and SW2 and the synchronous rectifying elements 311 and 312 are turned on and off. The relationship is the switching elements SW1, SW
Since ON and OFF of 2 are synchronized, they are equivalent to FIG.

Also in the switching power supply device of this embodiment, the loss can be reduced by the synchronous rectification circuit, and the control of the synchronous rectification circuit, the improvement of the power factor and the stabilization control of the output voltage can be performed by a single control system. Moreover, since it can be driven at a single switching frequency, the circuit configuration is simple and stable operation can be obtained. Further, since the power factor improving switching element SW2 and the power converting switching element SW1 are individually provided, the currents flowing through the respective switching elements SW1 and SW2 are dispersed, and switching is performed by an appropriate element having a small current capacity. A power supply device can be configured.

FIG. 4 is an electric circuit diagram showing still another embodiment of the switching power supply device according to the present invention. The illustrated switching power supply device is obtained by adding a duty setting circuit 6 to the embodiment shown in FIG. The duty setting circuit 6 is a circuit for fixing the on-duty of the first switching element SW1 to a predetermined value, and is added to the drive signal path of the first switching element SW1 in this embodiment. In the illustrated switching power supply device, a duty setting circuit 6 is used to fix the on-duty of the first switching element SW1 to, for example, 50%, and control the on-periods of the synchronous rectifying elements 311 and 312 according to the output voltage. By this, the output voltage can be stabilized.

Next, this point will be described with reference to FIG. FIG. 5 is a diagram showing another on / off timing of the switching power supply device shown in FIG. 4, showing a case where the synchronous rectifying elements 311 and 312 are controlled to stabilize the output voltage. In the figure, first and second switching elements SW1 and SW2, and synchronous rectifying elements 311 and 3
Each of the 12 ON periods is shown as a high level and the OFF period is shown as a low level.

As shown in FIG. 5, the first switching element SW1 has a fixed on-duty and is controlled at 50%, for example. The synchronous rectifying element 311 is turned on at the same time when the first switching element SW1 is turned on, and the timing of turning off according to the output voltage is moved forward and backward as shown by the arrow, and is controlled at an on-duty of less than 50% to stabilize the output voltage. Turn into. Second switching element SW2
Are controlled at the same timing when the synchronous rectifying element 311 is turned on and off. The synchronous rectifying element 312 is basically on,
The off timing is controlled so as to be in the opposite phase to the synchronous rectifying element 311.

Also in the present embodiment, more practically, the on / off timing of each element is set through a delay circuit or the like in consideration of variations in turn-on and turn-off times unique to each element.

In the switching power supply device of the present embodiment, since the output voltage stabilization control can be performed by the synchronous rectification circuit 31, the conversion transformer T is provided with a plurality of output windings T2, and the output provided with the synchronous rectification circuit 31 for each. When the circuit 3 is connected to configure a multi-output switching power supply device, each synchronous rectification circuit 31 can be controlled according to each output voltage, and thus a multi-output switching power supply device with high stability accuracy can be configured.

FIG. 6 is an electric circuit diagram showing still another embodiment of the switching power supply device according to the present invention. The power factor correction type power conversion circuit 2 of the embodiment shown in FIG. 3 has a peak current limiting circuit. An example in which 20 is added is shown. Other configurations are similar to those of the embodiment shown in FIG. FIG. 7 is a diagram showing on / off timings of the switching power supply device shown in FIG. 6, showing on / off timings of the first and second switching elements SW1 and SW2. In FIG. 6, first and second switching elements SW
1, the ON period of SW2 is shown at a high level, and the OFF period is shown at a low level.

The peak current limiting circuit 20 will be mainly described below with reference to FIGS. 6 and 7. The peak current limiting circuit 20 is a circuit that detects the current flowing through the second switching element SW2 and limits it to a predetermined value or less. The peak current limiting circuit 20 is supplied with the drive signal S1 for driving the first switching element SW1 and outputs the drive signal S2 for driving the second switching element SW2. The drive signal S2 is a signal that can control the off timing of the second switching element SW2 as indicated by the arrow in FIG. 6 according to the peak current flowing through the second switching element SW2 to limit the on period.

In the switching power supply device of this embodiment, since the current supplied to the inductor L can be limited, the power factor can be improved appropriately, and further, even when the load of the switching power supply device is light, the capacitor C The charging voltage can be limited to a predetermined value, and the first and second switching elements SW1 and SW2
Further, there is an advantage that a capacitor having a low breakdown voltage can be used as the capacitor C.

The stabilization of the output voltage in this embodiment is performed by the first switching element SW1, the synchronous rectifying elements 311, 3
A method of controlling the pulse width of 12 or fixing the on-duty of the first switching element SW1 to 50%,
Any of the methods of controlling the ON periods of the synchronous rectifying elements 311 and 312 may be used. Synchronous rectifying elements 311 and 3
When controlling 12 to stabilize the output voltage, the second switching element SW2 is controlled to be turned on at the same time as the synchronous rectifying element 311 and turned off before the synchronous rectifying element 311 is turned off.

Although the present invention has been described in detail with reference to the preferred embodiments, the present invention is not limited to these, and those skilled in the art can make various modifications based on the basic technical idea and teaching. It is self-evident that the modified example can be conceived.

[0069]

As described above, according to the present invention, the following effects can be obtained. (A) It is possible to provide a switching power supply device capable of reducing the loss and improving the power factor by the synchronous rectification circuit. (B) It is possible to provide a switching power supply device that can be controlled by a single control system. (C) It is possible to provide a switching power supply device that can be driven at a single switching frequency. (D) It is possible to provide a switching power supply device having a simple circuit configuration and capable of obtaining stable operation.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram showing an embodiment of a switching power supply device according to the present invention.

FIG. 2 is a circuit diagram showing that the switching power supply device shown in FIG.
It is a figure which shows an off timing.

FIG. 3 is an electric circuit diagram showing another embodiment of the switching power supply device according to the present invention.

FIG. 4 is an electric circuit diagram showing still another embodiment of the switching power supply device according to the present invention.

FIG. 5 is a circuit diagram illustrating that the switching power supply device illustrated in FIG.
It is a figure which shows an off timing.

FIG. 6 is an electric circuit diagram showing still another embodiment of the switching power supply device according to the present invention.

FIG. 7 is a circuit diagram illustrating that the switching power supply device illustrated in FIG.
It is a figure which shows an off timing.

[Explanation of symbols]

1 rectifier circuit 2 Power factor improvement type power conversion circuit 3 output circuits 31 Synchronous rectification circuit 32 output smoothing circuit 4 control circuit T conversion transformer T1 input winding T2 output winding SW switching element L inductor C capacitor D diode

Claims (5)

[Claims] 1. A switching power supply device including a rectifier circuit, a power factor improving power conversion circuit, an output circuit, and a control circuit, wherein the rectifier circuit rectifies an AC power source to generate a rectified output. The generated rectified output is supplied to the power factor correction type power conversion circuit, and the power factor correction type power conversion circuit includes a conversion transformer, a switching element, an inductor, a capacitor, and a diode. Includes an input winding and an output winding, induces a voltage in the output winding, the diode is connected so as to block a reverse voltage applied to the inductor, the switching element is connected to the AC power supply. ON / OFF control is performed at a frequency higher than the frequency, and during the ON period of the switching element, the rectified output is supplied to the inductor to store energy, and The capacitor is discharged to supply power to the input winding, and the energy stored in the inductor is discharged during the OFF period of the switching element to connect the capacitor to charge the output circuit. The control circuit includes a synchronous rectification circuit and an output smoothing circuit, is connected to the output winding, rectifies and smoothes a voltage induced in the output winding, converts the voltage into a direct current, and outputs the direct current. A switching power supply device that is electrically isolated and disposed on the output side to synchronously control both the power factor correction type power conversion circuit and the synchronous rectification circuit. 2. The switching power supply device according to claim 1, wherein the diode includes a first diode and a second diode, and one end of the inductor has one output of the rectification circuit. The other end of the rectifier circuit via the first diode and the capacitor, and the other end of the rectifier circuit via the second diode and the switching element. And the other end of the rectifier circuit, the input winding is connected to one end of the capacitor, the other end is connected to the other end of the capacitor through the switching element, switching Power supply. 3. The switching power supply device according to claim 1, wherein the switching element is a first switching element,
A second switching element, wherein the inductor has one end connected to one output end of the rectifier circuit and the other end connected to the other output end of the rectifier circuit via the diode and the capacitor. In addition, the other end is connected to the other output end of the rectifier circuit via a second switching element, the input winding has one end connected to one end of the capacitor, and the other end connected to the first output terminal. A switching power supply device, which is connected to the other end of the capacitor through the switching element. 4. The switching power supply device according to claim 3, wherein the power factor correction type power conversion circuit includes a peak current limiting circuit, and the peak current limiting is a current flowing through the second switching element. A switching power supply device that detects a current and limits it to a predetermined value or less. 5. The switching power supply device according to claim 1, wherein the switching voltage stabilizes an output voltage by controlling an on / off time ratio of a synchronous rectification element of the synchronous rectification circuit. Power supply.