TWI493857B - Power conversion device - Google Patents

Description

Power conversion device

The present invention relates to a conversion device, and more particularly to a power conversion device.

Light Emitting Diodes (LEDs) are widely used in road lighting and related lighting industries due to their high power, long life and small size.

Referring to FIG. 1 , a conventional power conversion device is electrically connected between an AC power source and a LED module as a load, and converts an input voltage VAC from the AC power source to generate The output voltage Vo, dc is used to drive the LED module LED, and the power conversion device comprises: a filter circuit 10, a full bridge rectifier circuit 11, a power factor correction circuit 12, a buck conversion circuit 13, A first control circuit 14, and a second control circuit 15.

The filter circuit 10 is electrically connected to the AC power source to receive the input voltage VAC, and is used for filtering electromagnetic interference (EMI) and high frequency noise in the input voltage VAC to generate a filtered voltage.

The full bridge rectifier circuit 11 is electrically connected to the filter circuit 10 to receive the filter voltage and an input current Iin, and to perform the whole Stream to output a DC voltage.

The power factor correction circuit 12 is electrically connected to the rectifier circuit 11 to receive the DC voltage, and the power factor correction circuit 12 is a boost converter, and includes: a first capacitor C1, a second capacitor C2, and a capacitor The first diode D1, the second diode D2, a first inductor L1, a second inductor L2, a first switch S1, a second switch S2, and a third capacitor C3. The first switch S1 and the second switch S2 are controlled to switch between a conducting state and a non-conducting state, so that the first inductor L1 and the second inductor L2 perform energy storage or release, thereby correcting the power factor. Circuit 12 boosts the DC voltage to produce a boost voltage.

The step-down conversion circuit 13 is electrically connected to the power factor correction circuit 12 and includes a third switch S3 and a fourth switch S4. The third and fourth switches S3, S4 are controlled to switch between the conducting and non-conducting states, and the buck converting circuit 13 steps down the boosting voltage from the power factor correcting circuit 12 to the DC output. Voltage Vo, dc.

The first control circuit 14 is electrically connected to the power factor correction circuit 12, and provides two control signals Vgs1 and Vgs2 to the first and second switches S1 and S2, respectively, to control the first and second switches S1 and S2. Switching.

The second control circuit 15 is electrically connected to the buck conversion circuit 13 and provides two control signals Vgs3 and Vgs4 to the third and fourth switches S3 and S4, respectively, to control the third and fourth switches S3 and S4. Switching.

Conventional power conversion devices have the following disadvantages:

Disadvantage 1 , the power factor correction circuit 12 needs the first capacitor C1, the second capacitor C2, and the second inductor L2 to perform power factor correction, and the full bridge rectifier circuit 11 requires four poles. Rectification of the body results in increased component cost of the circuit.

Disadvantage 2, two control circuits 14, 15 are required, resulting in a complicated control method and architecture of the circuit.

Disadvantage 3, the power factor correction circuit 12 and the buck conversion circuit 13 use a total of four switches, and the number is large.

The fourth disadvantage is that the four circuits of the filter circuit 10, the full bridge rectifier circuit 11, the power factor correction circuit 12, and the buck converter circuit 13 perform conversion power, thereby reducing the performance of the conversion power.

Accordingly, it is an object of the present invention to provide a power conversion device that can reduce the cost of a circuit.

Therefore, the power conversion device of the present invention comprises a filter circuit, a power factor correction circuit, and a buck conversion circuit.

The filter circuit receives an input voltage and an input current, and filters the input voltage and high frequency noise in the input current to generate a filtered voltage.

The power factor correction circuit is electrically connected to the filter circuit to receive the filter voltage, and boost the filter voltage to generate a boost voltage, and the power factor correction circuit comprises: a DC link capacitor; a first inductor a first end and a second end electrically connected to the filter circuit; a first diode and a second diode connected in series are connected in parallel to the DC link capacitor, and a common contact of the first diode and the second diode is electrically connected to the second end of the first inductor; and a first switch and a second switch connected in series are connected to the DC link capacitor. Each of the switches is operable in a conducting state and a non-conducting state, wherein the first and second switches are respectively controlled by two control signals to alternately switch between the conducting and the non-conducting states, and to cross the second A voltage of the switch acts as the boost voltage.

The buck converter circuit is electrically connected to the power factor correction circuit to receive the boost voltage, and step down the boost voltage to a DC output voltage.

2‧‧‧Filter circuit

Lf‧‧‧Input Inductance

Cf‧‧‧ input capacitor

3‧‧‧Power correction circuit

Lpfc1‧‧‧first inductor

Lpfc2‧‧‧second inductance

D1‧‧‧First Diode

D2‧‧‧ second diode

S1‧‧‧ first switch

S2‧‧‧ second switch

CB‧‧‧DC link capacitor

4‧‧‧Control circuit

5‧‧‧Buck conversion circuit

51‧‧‧Transformers

N1‧‧‧ primary winding

N2‧‧‧secondary winding

Cr‧‧‧Resonance Capacitor

Lr‧‧‧Resonant Inductance

Lm‧‧‧Magnetic Inductance

D3‧‧‧ third diode

D4‧‧‧ fourth diode

Co‧‧‧ output capacitor

LED‧‧‧Light Diode Module

Other features and effects of the present invention will be apparent from the following description of the drawings, wherein: FIG. 1 is a circuit diagram of a conventional power conversion device; and FIG. 2 is a first preferred embodiment of the power conversion device of the present invention. FIG. 3 is a timing diagram of the first preferred embodiment; FIG. 4 is a circuit diagram of the first preferred embodiment operating in mode one; FIG. 5 is a first preferred embodiment operating in mode two Figure 6 is a circuit diagram of the first preferred embodiment operating in mode three; Figure 7 is a circuit diagram of the first preferred embodiment operating in mode four; Figure 8 is a first preferred embodiment operating in mode five Figure 9 is a circuit diagram of the first preferred embodiment operating in mode six; Figure 10 is a circuit diagram of the first preferred embodiment operating in mode seven; Figure 11 is a first preferred embodiment operating in mode 8 is a circuit diagram; FIG. 12 is a circuit diagram of the first preferred embodiment operating in mode IX; Figure 13 is a circuit diagram of the first preferred embodiment operating in mode ten; Figure 14 is a circuit diagram of the first preferred embodiment operating in mode eleven; Figure 15 is a first preferred embodiment of the invention from an alternating current source FIG. 16 is a waveform diagram of an output voltage and an output current of the step-down conversion circuit of the first preferred embodiment; FIG. 17 is a waveform diagram of the first preferred embodiment. A waveform diagram of a voltage across a first switch and a current through the first switch illustrates the use of a zero voltage switching technique to control the first switch; FIG. 18 is one of the first preferred embodiment spanning one The waveform of the second switch and the waveform of the current through the second switch indicate that the second switch is controlled by a zero voltage switching technique; FIG. 19 is the first preferred embodiment of the first switch. The waveform of the voltage and the current through the third diode indicates that the first switch reaches the zero current switching; FIG. 20 is the voltage across the second switch and the first-class one through the first preferred embodiment. The waveform of the current of the fourth diode, indicating that The second switch is switched to zero current; Figure 21 is a circuit diagram of a second preferred embodiment of the power conversion device of the present invention; and Figure 22 is a circuit diagram of a variation of the second preferred embodiment.

Before the present invention is described in detail, it should be noted that in the following description, similar elements are denoted by the same reference numerals.

<First Preferred Embodiment>

Referring to FIG. 2, a first preferred embodiment of the power conversion device of the present invention is adapted to be electrically connected between an AC power source and a LED module as a load, and an input voltage from the AC power source. The VAC performs conversion to generate a DC output voltage Vo, dc to drive the LED module LED, and the power conversion device includes: a filter circuit 2, a power factor correction circuit 3, a control circuit 4, and a Buck conversion circuit 5.

The filter circuit 2 is electrically connected to the AC power source to receive the input voltage VAC and an input current Iin, and is used for filtering electromagnetic interference (EMI) and the high frequency miscellaneous in the input voltage VAC and the input current Iin. The signal is generated to generate a filtered voltage, and the filter circuit 2 includes an input inductor Lf and an input capacitor Cf. The input inductor Lf and the input capacitor Cf connected in series are connected in parallel to the AC power source to receive the input voltage VAC and the input current Iin, and a voltage across the input capacitor Cf is used as the filtered voltage.

The power factor correction circuit 3 is electrically connected to the filter circuit 2 to receive the filter voltage, and boost the filter voltage to generate a boost voltage, and adjust the phase of the input voltage VAC and the input current Iin to Reducing the total harmonic distortion of the current and correcting the power factor, thereby achieving the purpose of high power to meet the standard of the harmonics of the input current of the IEC 61000-3-2 Class C lighting device, and the power correction circuit 3 includes : a continuous flow chain capacitor CB, a first inductor Lpfc1, a first diode D1, a second diode D2, a first switch S1, and a second switch S2 .

The DC link capacitor CB is used to store the boost voltage.

The first inductor Lpfc1 has a first end and a second end electrically connected to a common contact of the input inductor Lf and the input capacitor Cf. The first diode D1 is connected in series to the second diode D2, and the common contact is electrically connected to the second end of the first inductor Lpfc1. The first diode D1 has an anode and a cathode electrically connected to the second end of the first inductor Lpfc1. The second diode D2 has a cathode electrically connected to the anode of the first diode D1 and an anode.

The first switch S1 and the second switch S2 are electrically connected between the cathode of the first diode D1 and the anode of the second diode D2, and a common contact is electrically connected to the input capacitor a common contact between the Cf and the AC power source, and each switch is operable in an on state and a non-conduction state, and the first and second switches S1 and S2 are respectively controlled by two control signals to be alternately turned on. And switching between the non-conduction states, and a voltage across the second switch S2 is used as the boosting voltage.

In this embodiment, when the first switch S1 is in the conducting state, the second switch S2 is in the non-conducting state, and when the second switch S2 is in the conducting state, the first switch S1 is in the non-conducting state. The period in which the first switch S1 adjacent to the timing is in the on state and the period in which the second switch S2 is in the on state are separated by a predetermined time (see FIG. 3). In addition, when the first and second switches S1 and S2 are switched, interference (for example, EMI) is generated on the input current Iin, and the interference can be filtered by the filter circuit 2. The first and second switches S1 S2 is implemented as a metal oxide semiconductor field effect transistor (MOSFET).

The control circuit 4 is electrically connected to the power factor correction circuit 3, and provides the two control signals to the respective first and second switches S1 and S2, and the two control signals are respectively a first control signal Vgs1 and A second control signal Vgs2, the first and second control signals Vgs1, Vgs2 are two square waves complementary to each other.

The step-down conversion circuit 5 adopts a resonant architecture, and is electrically connected to the power factor correction circuit 3 to receive the boosted voltage, and steps down the boosted voltage to the DC output voltage Vo, dc, and the step-down conversion circuit 5 includes: a resonant capacitor Cr, a resonant inductor Lr, a magnetizing inductor Lm, a transformer 51, a third diode D3, a fourth diode D4, and an output capacitor Co.

The resonant capacitor Cr, the resonant inductor Lr and the magnetizing inductance Lm connected in series are electrically connected between the common contact of the input capacitor Cf and the alternating current power source and the ground.

The transformer 51 has a primary side winding n1 and a secondary side winding n2 connected in parallel to the exciting inductance Lm. The primary side winding n1 has a first end and a second end. The secondary winding n2 has a first end, a second end and a center tap between the first and second ends. The number of turns of the secondary side winding n2 between the first end and the intermediate tap is smaller than the number of turns of the primary side winding n1, and the secondary side winding n2 is between the intermediate tap and the second end The number is smaller than the number of turns of the primary side winding n1. The first and second ends of the primary and secondary windings n1 and n2 are a polarity point end and a non-polar point end, respectively.

The third diode D3 has an anode and a cathode electrically connected to the first end of the secondary winding n2.

The fourth diode D4 has an anode electrically connected to the second end of the secondary winding n2 and a cathode electrically connected to the cathode of the third diode D3.

The output capacitor Co is electrically connected between the cathode of the third diode D3 and the center tap of the secondary winding n2, and the DC output voltage Vo, dc is supplied to the two ends of the output capacitor Co to the LED Body module LED.

Referring to FIG. 2 and FIG. 3, the parameters Vgs1 and Vgs2 respectively represent the first control signal and the second control signal, and the parameters Vds1 and Vds2 respectively represent the voltage across the first and second switches S1 and S2, and the parameter VLpfc1 indicates the The voltage of the first inductor Lpfc1, the parameters iLpfc1, iLr, iLm, iD3, iD4 respectively represent the current flowing through the first inductor Lpfc1, the current flowing through the resonant inductor Lr, and the current flowing through the magnetizing inductor Lm, flowing through the current Currents of the third and fourth diodes D3, D4.

Hereinafter, the filtered operation of the input voltage VAC is discussed in 11 modes, and for convenience of explanation, in FIG. 4 to FIG. 14, the filter circuit 2 and the control circuit 4 are omitted, and the turned-on components are implemented. The lines are drawn, the non-conducting elements are drawn in dashed lines, and the intrinsic diodes DS1, DS2 and parasitic capacitances CS1, VS2 of the first and second switches S1, S2 are shown in more detail than in FIG.

Mode one (t0~t1):

Referring to FIG. 3 and FIG. 4, when the voltage across the first switch S1 drops to zero, the first switch S1 is turned on to have zero voltage switching, and the input voltage VAC is passed through the first diode D1 and The first switch S1 stores the first inductor Lpfc1 to linearly increase the first inductor current iLpfc1.

At this time, the polarity of the primary side winding n1 of the transformer 51 is upper and lower, and the exciting inductance Lm supplies part of the energy to the LED module LED via the transformer 51 and the third diode D3.

Since the resonant inductor current iLr is negative, the resonant inductor current iLr discharges the resonant capacitor Cr and transfers energy to the DC link capacitor CB via the intrinsic diode DS1 of the first switch S1. When the resonant inductor current iLr rises to zero, it enters mode two.

Mode 2 (t1~t2):

Referring to FIG. 3 and FIG. 5, the first switch S1 is continuously turned on, and the input voltage VAC continuously supplies energy, so that the first inductor Lpfc1 continues to store energy, and the first inductor current iLpfc1 continues to rise linearly.

The DC link capacitor CB releases energy to the resonant capacitor Cr, the resonant inductor Lr, and the primary winding n1 of the transformer 51, and then is discharged to the light emitting diode via the secondary winding n2 and the third diode D3 that is turned on. Polar body module LED.

At the same time, the magnetizing inductance Lm continuously supplies energy to the LED module LED via the transformer 51 and the third diode D3. When the magnetizing inductor current iLm rises to zero, it enters mode three.

Mode three (t2~t3):

Referring to FIG. 3 and FIG. 6, the input voltage VAC continuously supplies energy to continuously store the first inductor Lpfc1. The difference between mode three and mode two is that the magnetizing inductance Lm is no longer released.

The DC link capacitor CB and the resonant inductor Lr release energy to the magnetizing inductance Lm, and are simultaneously discharged to the LED module LED via the transformer 51 and the third diode D3. When the resonant inductor current iLr falls to be equal to the magnetizing inductor current iLm, it enters mode four.

Mode 4 (t3~t4):

Referring to FIG. 3 and FIG. 7, the difference from mode three is that the input voltage VAC continuously supplies energy such that the first inductor current iLpfc1 linearly rises to a maximum value.

Since the resonant inductor current iLr is equal to the magnetizing inductor current iLm at this time, no current flows to the transformer 51, so the third and fourth diodes D3 and D4 are not turned on, and the output capacitor Co is released to the output capacitor Co. The LED module LED. Mode 4 ends when the first switch S1 is non-conducting.

Mode 5 (t4~t5):

Referring to FIG. 3 and FIG. 8 , the parasitic capacitance CS2 of the second switch S2 begins to release energy, so that the first switch S1 is non-conducting, and the first inductor Lpfc1 is turned to release energy to the parasitic capacitance CS1 of the first switch S1. The first inductor current iLpfc1 is linearly decreased.

When the first switch S1 is turned off, the DC link capacitor CB starts to supply energy to the parasitic capacitance CS1 of the first switch S1 and The resonant capacitor Cr.

At the same time, the parasitic capacitance CS2 of the second switch S2 is discharged, causing the terminal voltage Vds2 of the second switch S2 to drop. When the voltage Vds2 drops to zero, it enters mode six.

Mode six (t5~t6):

Referring to FIG. 3 and FIG. 9 , since the voltage Vds2 drops to zero, the second switch S2 is turned on to have zero voltage switching. At this time, the first inductor Lpfc1 is connected to the first diode D1 and the second switch S2. The DC link capacitor CB performs energy storage, so that the first inductor current iLpfc1 continues to decrease linearly, and the polarity of the primary side winding n1 of the transformer 51 is turned upside down, and the magnetizing inductance Lm passes through the transformer 51 and the fourth The diode D4 supplies a portion of the energy to the LED module LED such that the magnetizing inductor current iLm begins to decrease.

At the same time, the resonant inductor Lr releases the resonant inductor current iLr to the resonant capacitor Cr via the intrinsic diode DS2 of the second switch S2. When the resonant inductor current iLr drops to zero, it enters mode seven.

Mode seven (t6~t7):

Referring to FIG. 3 and FIG. 10, the second switch S2 is continuously turned on, and the first inductor Lpfc1 continuously stores the DC link capacitor CB, so that the first inductor current iLpfc1 continues to decrease linearly.

At this time, the resonant capacitor Cr starts to release energy to the LED module LED via the transformer 51 and the fourth diode D4, and provides partial energy to the resonant inductor Lr, and the magnetizing inductance Lm continues through the The transformer 51 and the fourth diode D4 provide partial energy to the light emitting diode The polar body module LED causes the exciting inductor current iLm to continuously decrease linearly.

Since the first inductor Lpfc1 continues to release energy, when the first inductor current iLpfc1 falls to zero, mode eight is entered.

Mode eight (t7~t8):

Referring to FIG. 3 and FIG. 11, the resonant capacitor Cr and the exciting inductor Lm respectively release energy, and when the exciting inductor current iLm falls to zero, it enters mode IX.

Mode nine (t8~t9):

Referring to FIG. 3 and FIG. 12, the resonant capacitor Cr releases energy to the exciting inductor Lm, the resonant inductor Lr, and the LED module LED. When the resonant inductor current iLr falls to be equal to the magnetizing inductor current iLm, it enters mode ten.

Mode ten (t9~t10):

Referring to FIG. 3 and FIG. 13, since the resonant inductor current iLr falls to be equal to the magnetizing inductor current iLm, no current flows to the transformer 51, causing the third and fourth diodes D3 and D4 to be turned off. The output capacitor Co is discharged to the LED of the LED module. When the second switch S2 is non-conducting, mode 11 is entered.

Mode 11 (t10~t11):

Referring to FIG. 3 and FIG. 14, when the second switch S2 is turned off and the first switch S1 is not turned on, the resonant capacitor Cr releases energy to the parasitic capacitance CS2 of the second switch S2.

At the same time, the parasitic capacitance CS1 of the first switch S1 releases energy to the resonant inductor Lr, the resonant capacitor Cr, and the DC link capacitor CB. . When the parasitic capacitance CS1 of the first switch S1 continues to discharge, causing the terminal voltage Vds1 of the first switch S1 to drop to zero, the mode XI ends. At this time, the first switch S1 is turned on to have a zero voltage switching, and returns to the mode one to restart a new cycle.

15 to 20 are simulation experiment diagrams corresponding to the above embodiments: Referring to FIG. 15, a waveform diagram of the input voltage VAC and the input current Iin from the AC power source of the first preferred embodiment, and the input voltage VAC And the waveform of the input current Iin is in phase.

Referring to Figure 16, there is shown a waveform diagram of the DC output voltage Vo, dc and its output current Io of the buck converter circuit 5 of the first preferred embodiment.

Referring to FIG. 17 and FIG. 18, the voltage Vds1 across the first switch S1 and the current Ids1 flowing through the first switch S1 and the voltage Vds2 across the second switch S2 are respectively used in the first preferred embodiment. The waveform diagram of the current Ids2 flowing through the second switch S2 illustrates the switching of the first and second switches S1, S2 by a zero voltage switching (ZVS) technique.

Referring to FIG. 19 and FIG. 20, the voltage Vds1 across the first switch S1 and the current iD3 flowing through the third diode D3, and the voltage across the second switch S2 are the first preferred embodiment. A waveform diagram of Vds2 and current iD4 flowing through the fourth diode D4 illustrates that the switching of the first and second switches S1, S2 reaches a zero current switching (ZCS) technique.

<Second preferred embodiment>

Referring to FIG. 21, a second preferred embodiment of the power conversion device of the present invention is different from the first preferred embodiment in that the first inductor Lpfc1 is electrically connected to the cathode of the first diode D1 and the first switch. Between S1, the power factor correction circuit 3 further includes a second inductor Lpfc2.

The second inductor Lpfc2 is electrically connected between the anode of the second diode D2 and the second switch S2.

The operation procedure and the operation principle of the second preferred embodiment are respectively approximated to the first preferred embodiment, and therefore are not described again.

Referring to FIG. 22, a modification of the second preferred embodiment is different from the second preferred embodiment in that the first and second inductors Lpfc1 and Lpfc2 are integrated into a single coupled inductor to enable magnetic The number of components (i.e., inductance) is halved to achieve a simplified number of components, and the operational procedure of the deformation is the same as that of the second preferred embodiment, and therefore will not be repeated.

In summary, the above embodiment has the following advantages:

1. The power conversion device has a low circuit cost. Since the power factor correction circuit 3 has fewer electronic components such as the first capacitor C1, the second capacitor C2, and the second inductor L2 (see FIG. 1) than the prior art power factor correction circuit 12, and the power source The conversion device does not need to additionally use a rectifying circuit for rectification, so that the number of electronic components of the power conversion device is small, so that the component cost can be reduced.

2. The control method and architecture of the power conversion device are relatively simple. Since the power conversion device requires only one control circuit 4 compared to the prior art power conversion device, the circuit architecture can be simplified and the control is simpler. The method realizes the operation of power conversion.

3. The number of switches of the power conversion device is small. Since the power factor correction circuit 3 uses only two switches S1 and S2, and the step-down conversion circuit 5 does not need to additionally use a switch, the number of switches of the power conversion device can be reduced.

4. Improve the performance of conversion power. Since the power conversion device only needs one control circuit 4, and the three-stage circuit such as the filter circuit 2, the power factor correction circuit 3, and the step-down conversion circuit 13 can be used to convert power, compared with the prior art. The power conversion device (see FIG. 1) does not need to additionally pass through the full bridge rectifier circuit 11, and the third and fourth switches S3 and S4 of the buck conversion circuit 13 are simplified, and the power loss of the two switches is reduced. The performance of the conversion power can be improved by substantially changing the respective switching of the secondary circuit of the power correction circuit 12 and the buck conversion circuit 13 (see FIG. 1).

The above is only the preferred embodiment of the present invention, and the scope of the present invention is not limited thereto, that is, the simple equivalent changes and modifications made by the patent application scope and patent specification content of the present invention, All remain within the scope of the invention patent.

2‧‧‧Filter circuit

Lf‧‧‧Input Inductance

Cf‧‧‧ input capacitor

3‧‧‧Power correction circuit

Lpfc1‧‧‧first inductor

D1‧‧‧First Diode

D2‧‧‧ second diode

S1‧‧‧ first switch

S2‧‧‧ second switch

CB‧‧‧DC link capacitor

4‧‧‧Control circuit

5‧‧‧Buck conversion circuit

51‧‧‧Transformers

N1‧‧‧ primary winding

N2‧‧‧secondary winding

Cr‧‧‧Resonance Capacitor

Lr‧‧‧Resonant Inductance

Lm‧‧‧Magnetic Inductance

D3‧‧‧ third diode

D4‧‧‧ fourth diode

Co‧‧‧ output capacitor

LED‧‧‧Light Diode Module

Claims (6)

A power conversion device is electrically connected to an AC power supply that provides an input voltage and an input current, and includes: a filter circuit that receives the input voltage and the input current, and filters out the input voltage and the input current Frequency noise to generate a filtered voltage, the filter circuit comprising a series input inductor and an input capacitor connected in parallel to the AC power source to receive the input voltage and the input current, and to cross the input capacitor a voltage is used as the filter voltage; a power factor correction circuit is electrically connected to the filter circuit to receive the filter voltage, and the filter voltage is boosted to generate a boost voltage, and the power factor correction circuit comprises: a continuous current a first capacitor having a first end and a second end electrically connected to the filter circuit; a first diode and a second diode connected in series are connected in parallel to the DC link capacitor, and a common contact of the first diode and the second diode is electrically connected to the second end of the first inductor; and a first switch and a second switch connected in series are connected to the DC link capacitor Each of the switches is operable in a conducting state and a non-conducting state, wherein the first and second switches are respectively controlled by two control signals to alternately switch between the conducting and the non-conducting states, and to cross the second a voltage of the switch is used as the boost voltage; and a step-down conversion circuit is electrically connected to the power factor correction circuit to receive The boosting voltage is stepped down to a DC output voltage; wherein the first end of the first inductor is electrically connected to a common contact of the input inductor and the input capacitor, the first diode An anode and a cathode electrically connected to the second end of the first inductor, the second diode has a cathode electrically connected to the anode of the first diode and an anode, and the DC link capacitor is electrically connected to Between the cathode of the first diode and the anode of the second diode, the boost voltage is stored, and a common contact of the first switch and the second switch is electrically connected to the input capacitor A common contact of the AC power source. The power conversion device of claim 1, further comprising: a control circuit electrically connected to the power factor correction circuit, and providing the two control signals to the corresponding first and second switches, and the two controls The signal is a square wave with two complementary phases. The power conversion device of claim 1, wherein the second switch is in the non-conducting state when the first switch is in the conducting state, and the first switch is in the conducting state when the second switch is in the conducting state In the non-conduction state, a period in which the first switch adjacent to the timing is in the on state and a period in which the second switch is in the on state are separated by a predetermined time. The power conversion device of claim 3, wherein the step-down conversion circuit comprises: a resonant capacitor connected in series, a resonant inductor and a magnetizing inductor electrically connected to the common contact of the input capacitor and the alternating current power source Between one place; a transformer having a primary winding and a secondary winding connected in parallel with the exciting inductor, the primary winding having a first end and a second end, the secondary winding having a first end and a second end And a middle tap between the first end and the second end, the number of turns of the secondary side winding between the first end and the intermediate tap is smaller than the number of turns of the primary side winding, and the secondary side The number of turns of the winding between the intermediate tap and the second end is smaller than the number of turns of the primary side winding; a third diode having an anode electrically connected to the first end of the secondary winding and a cathode a fourth diode having an anode electrically connected to the second end of the secondary winding and a cathode electrically connected to the cathode of the third diode; and an output capacitor electrically connected to the third The cathode of the diode and the center tap of the secondary winding, and the DC output voltage is provided at both ends of the output capacitor. The power conversion device of claim 1, wherein the first inductor is electrically connected between the cathode of the first diode and the first switch, and the power correction circuit further comprises: a second inductor, Electrically connected between the anode of the second diode and the second switch. The power conversion device of claim 5, wherein the first inductor and the second inductor are coupled inductors that are integrated.