CN112398330A - Bridgeless PFC converter and control method thereof - Google Patents

Bridgeless PFC converter and control method thereof Download PDF

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Publication number
CN112398330A
CN112398330A CN202011561891.XA CN202011561891A CN112398330A CN 112398330 A CN112398330 A CN 112398330A CN 202011561891 A CN202011561891 A CN 202011561891A CN 112398330 A CN112398330 A CN 112398330A
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tube
switch tube
switching tube
main
current
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CN112398330B (en
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章治国
李世锋
章巧敏
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Chongqing Hongyi Electric Co ltd
Zhang Zhiguo
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Chongqing Hongyi Electric Co ltd
Chongqing University of Technology
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/42—Circuits or arrangements for compensating for or adjusting power factor in converters or inverters
    • H02M1/4208—Arrangements for improving power factor of AC input
    • H02M1/4241—Arrangements for improving power factor of AC input using a resonant converter
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
    • H02M1/083—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters for the ignition at the zero crossing of the voltage or the current
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
    • H02M1/088—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters for the simultaneous control of series or parallel connected semiconductor devices
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0048—Circuits or arrangements for reducing losses
    • H02M1/0054—Transistor switching losses
    • H02M1/0058—Transistor switching losses by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

The invention discloses a bridgeless PFC converter and a control method thereof, comprising an alternating voltage source VinThe power supply comprises a diode D1, a diode D2, a main switching tube Q1, a main switching tube Q2, a power inductor L, an output capacitor C0, an output capacitor C1, an output capacitor C2 and a resonant circuit, wherein two ends of the output capacitor C1 are connected with a source electrode and a drain electrode of the main switching tube Q1 in parallel, and two ends of the output capacitor C2 are connected with a source electrode and a drain electrode of the main switching tube Q2 in parallel; the resonant circuit comprises a resonant inductor Lr and a switching circuit, one end of the resonant inductor Lr is connected with the power inductor L, the other end of the resonant inductor Lr is connected with the switching circuit, and one side, far away from the side connected with the resonant inductor Lr, of the switching circuit is connected to two ends of the output capacitor C0 in parallel. The invention can effectively inhibit the reverse recovery characteristic of the parasitic body diode in the switch tube and realize zero voltage switching-on and zero current switching-off of each switch tube.

Description

Bridgeless PFC converter and control method thereof
Technical Field
The invention relates to the technical field of power supplies, in particular to a bridgeless PFC converter and a control method thereof.
Background
The wide application of power electronic technology brings the change of covering the ground for human life, but at the same timeAnd certain difficulty is caused to the harmonic treatment of the power grid. Harmonic standard IEC61000-3-2 pair specified by International electrotechnical CommissioninThe harmonic currents injected into the grid by the DC converter are severely limited and therefore are presentinIt becomes important to incorporate power factor correction techniques in the DC converter to reduce harmonic pollution to the grid.
In the past decades, various Boost bridgeless PFC converters have been proposed in succession, wherein a basic bridgeless PFC converter causes large common mode noise interference due to input voltage floating, while a dual Boost bridgeless PFC converter with a clamping diode can effectively overcome the common mode noise problem, but the number of excessive components limits further application and research.
Because the input end of the totem-pole bridgeless PFC converter is clamped to the output by the diode in each half period, the totem-pole bridgeless PFC converter has lower common-mode noise compared with other bridgeless topologies, and meanwhile, the totem-pole bridgeless PFC converter is widely concerned and researched due to the small number of components and high utilization rate of the components. The basic circuit diagram of a totem-pole bridgeless PFC converter is shown in figure 1 and comprises an alternating voltage source VinDiode D1, diode D2, main switch tube Q1, main switch tube Q2, power inductor L, output capacitor C0 and load resistor RL, wherein alternating voltage source VinThe positive pole of the diode is connected with one end of a power inductor L, the other end of the power inductor L is respectively connected with the source electrode of a main switching tube Q1 and the drain electrode of a main switching tube Q2, the drain electrode of the main switching tube Q1 is connected with the cathode of a diode D1, the source electrode of the main switching tube Q2 is connected with the anode of a diode D2, and the cathode of a diode D2 is respectively connected with the anode of a diode D1 and an alternating voltage source VinThe output capacitor C0 and the load resistor RL are connected in parallel, and then the two connection points are respectively connected to the drain of the main switch tube Q1 and the source of the main switch tube Q2.
When the totem-pole bridgeless PFC converter works, parasitic body diodes exist in Si-MOSFET (namely the main switch tube Q1 and the main switch tube Q2), because reverse recovery characteristics of most of Si-MOSFET parasitic body diodes are poor, the totem-pole bridgeless PFC converter can only work in a DCM (discontinuous conduction mode, wherein the inductive current in one switch period is not less than 0) or a BCM (critical conduction mode, wherein the CCM is switched to the mode that DCM experiences), if the totem-pole bridgeless PFC converter works in a CCM (continuous conduction mode, wherein the inductive current in one switch period is more than 0), because the reverse recovery characteristics of the Si-MOSFET parasitic body diodes are poor, for example, when a forward voltage is applied to the Si-MOSFET switch tube of an upper bridge arm, the Si-MOSFET switch tube of a lower bridge arm is under the action of a reverse voltage, and at the moment, the Si-MOSFET switch tube of the upper bridge arm has the current passing under the action of the forward voltage, and the parasitic body diode of the lower bridge arm Si-MOSFET switching tube can also have reverse current flowing under the action of reverse voltage, so that the upper bridge arm and the lower bridge arm can be directly connected, and the Si-MOSFET can be burnt. In recent years, some switching tubes with good reverse recovery characteristics appear, but the switching tubes generally have the problems of high price, low reliability and the like. Therefore, how to design a novel bridgeless PFC converter can effectively inhibit the reverse recovery characteristic of a parasitic body diode of a Si-MOSFET, and the realization of zero-voltage switching-on and zero-current switching-off of each switching tube also becomes a technical problem which needs to be solved urgently.
Disclosure of Invention
Aiming at the defects in the prior art, the technical problems to be solved by the invention are as follows: how to provide a bridgeless PFC converter which can effectively inhibit the reverse recovery characteristic of a parasitic body diode in a switch tube, realize zero-voltage switching-on and zero-current switching-off of each switch tube and further realize the operation in a CCM mode.
In addition, the invention also provides a control method of the bridgeless PFC converter, so as to effectively inhibit the reverse recovery characteristic of a parasitic body diode in the switch tube, realize zero voltage switching-on and zero current switching-off of each switch tube and further realize the purpose of working in a CCM mode.
In order to solve the technical problems, the invention adopts the following technical scheme:
a bridgeless PFC converter comprises a totem-pole bridgeless PFC converter circuit which comprises an alternating-current voltage source VinDiode D1, diode D2, main switch tube Q1, main switch tube Q2, power inductance L and output capacitor C0, the grid of main switch tube Q1 is connected with the secondThe driving circuit is used for providing a trigger signal to turn on the main switching tube Q1, the grid electrode of the main switching tube Q2 is connected with a second driving circuit, the second driving circuit is used for providing the trigger signal to turn on the main switching tube Q2, and the driving circuit is characterized by further comprising an output capacitor C1, an output capacitor C2 and a resonant circuit, two ends of the output capacitor C1 are connected to the source electrode and the drain electrode of the main switching tube Q1 in parallel, and two ends of the output capacitor C2 are connected to the source electrode and the drain electrode of the main switching tube Q2 in parallel;
the resonant circuit comprises a resonant inductor Lr and a switch circuit, one end of the resonant inductor Lr is connected with one end of the power inductor L, the source electrode of the main switch tube Q1 and the drain electrode of the main switch tube Q2, the other end of the resonant inductor Lr is connected with the switch circuit, and one side, far away from the switch circuit, of the switch circuit, which is connected with the resonant inductor Lr, is connected with two ends of the output capacitor C0 in parallel.
The working principle of the invention is as follows: the invention is applied to an alternating voltage source VinBefore the main switch tube Q2 is turned on, the power inductor L will freewheel through the parasitic body diode of the main switch tube Q1, at this time, the switch circuit is turned on, so that the resonant current flowing through the resonant inductor Lr increases, the freewheel current of the parasitic body diode of the main switch tube Q1 decreases, and when the current of the power inductor L is equal to the resonant current of the resonant inductor Lr, the freewheel current of the parasitic body diode of the main switch tube Q1 is zero; when the resonant current of the resonant inductor Lr continues to increase to a current greater than that of the power inductor L, the output capacitor C2 connected in parallel with the drain and source of the main switching transistor Q2 discharges, so that the voltage Vds2 between the drain and source of the main switching transistor Q2 decreases while the output capacitor C1 connected in parallel with the source and drain of the main switching transistor Q1 charges; when the output capacitor C2 discharges to enable the voltage Vds2 between the drain and the source of the main switching tube Q2 to be reduced to zero, the switching circuit is turned off, the second driving circuit provides a trigger signal to turn on the main switching tube Q2, at the moment, the main switching tube Q2 realizes zero-voltage turn-on and the parasitic body diode of the main switching tube Q1 realizes zero-current turn-off;
at an AC voltage source VinIs on in the main switching tube Q1Before the power is turned on, the power inductor L continues to flow current through the parasitic body diode of the main switching tube Q2, at the moment, the switching circuit is turned on, so that the resonant current flowing through the resonant inductor Lr is increased, the follow current of the parasitic body diode of the main switching tube Q2 is reduced, when the current of the power inductor L is equal to the resonant current of the resonant inductor Lr, the follow current of the parasitic body diode of the main switching tube Q2 is zero, and as the resonant current of the resonant inductor Lr continues to be increased to be larger than the current of the power inductor L, the output capacitor C1 connected with the drain and the source of the main switching tube Q1 in parallel is discharged, so that the voltage Vds1 between the drain and the source of the main switching tube Q1 is reduced, and the output capacitor C2 connected with the source and the drain of the main switching tube Q2 in parallel is; when the output capacitor C1 discharges to make the voltage Vds1 between the drain and the source of the main switching tube Q1 drop to zero, the switching circuit is turned off, the first driving circuit provides a trigger signal to turn on the main switching tube Q1, at this time, the main switching tube Q1 realizes zero-voltage turn-on and the parasitic body diode of the main switching tube Q2 realizes zero-current turn-off.
The invention has the beneficial effects that: 1. when the main switch tube Q1 and the main switch tube Q2 are turned on, voltages Vds1 and Vds2 at two ends of the main switch tube Q1 and the main switch tube Q2 are zero, and meanwhile, when the main switch tube Q1 and the main switch tube Q2 are turned off, currents of a parasitic body diode of the Q1 and a parasitic body diode of the Q2 are zero, so that zero current turn-off of the main switch tube Q1 and the main switch tube Q2 is realized, reverse currents cannot pass through the parasitic body diodes of the main switch tube Q1 and the main switch tube Q2 under the action of reverse voltages, reverse recovery characteristics of the parasitic body diodes in the switch tubes are effectively inhibited, through of upper and lower bridge arms is avoided, and therefore the bridgeless PFC converter can work in a CCM (continuous working) mode.
2. According to the bridgeless PFC converter, the PFC function is realized through the connection of the resonant circuit and the traditional totem-pole PFC circuit, and by controlling the on-off of the resonant circuit, the resonant current is linearly increased, and the current in the power inductor L is linearly reduced, so that the current flowing through a parasitic body diode in a main switching tube is naturally zero, and the problem of reverse recovery is suppressed; and meanwhile, the resonant current is utilized to discharge the output capacitor connected in parallel with the main switching tube, and each main switching tube realizes zero voltage switching-on, so that the efficiency of the converter is improved.
Preferably, the switching circuit includes a switching tube Q3, a switching tube Q4 and a switching tube Q5, one end of the resonant inductor Lr remote from the end connected with the power inductor L is connected with the drain of the switching tube Q5, the source of the switching tube Q5 is simultaneously connected with the source of the switching tube Q3 and the drain of the switching tube Q4, the drain of the switching tube Q3 is simultaneously connected with the drain of the main switching tube Q1 and one end of the output capacitor C0, and the source of the switching tube Q4 is simultaneously connected with the source of the main switching tube Q2 and the other end of the output capacitor C0;
the gate of the switching tube Q3 is connected to a third driving circuit, the third driving circuit is used for providing a trigger signal to turn on the switching tube Q3, the gate of the switching tube Q4 is connected to a fourth driving circuit, the fourth driving circuit is used for providing a trigger signal to turn on the switching tube Q4, the gate of the switching tube Q5 is connected to a fifth driving circuit, and the fifth driving circuit is used for providing a trigger signal to turn on the switching tube Q5.
Preferably, the switch circuit further includes a switch tube Q6, the source of the switch tube Q6 is connected to the source of the switch tube Q5, the drain of the switch tube Q6 is connected to both the source of the switch tube Q3 and the drain of the switch tube Q4, the gate of the switch tube Q6 is connected to a sixth driving circuit, and the sixth driving circuit is configured to provide a trigger signal to turn on the switch tube Q6.
By providing the switching tube Q6 in this way, when the energy of the resonant inductor Lr is discharged to the output side, the one-way conduction characteristic of the parasitic body diode of the switching tube Q6 is utilized to prevent the occurrence of secondary resonance from being blocked in the reverse direction.
A control method of a bridgeless PFC converter adopts the bridgeless PFC converter and comprises a control method of a main switching tube Q2 and a control method of a main switching tube Q1;
the control method for the main switching tube Q2 comprises the following steps:
at an AC voltage source VinIn the positive half-cycle of the main switchBefore the transistor Q2 is turned on, the power inductor L will freewheel through the parasitic body diode of the main switching transistor Q1, at this time, the switching circuit is turned on, so that the resonant current flowing through the resonant inductor Lr increases, the freewheel current of the parasitic body diode of the main switching transistor Q1 decreases, and when the current of the power inductor L is equal to the resonant current of the resonant inductor Lr, the freewheel current of the parasitic body diode of the main switching transistor Q1 is zero;
when the resonant current of the resonant inductor Lr continues to increase to a current greater than that of the power inductor L, the output capacitor C2 connected in parallel with the drain and source of the main switching transistor Q2 discharges, so that the voltage Vds2 between the drain and source of the main switching transistor Q2 decreases while the output capacitor C1 connected in parallel with the source and drain of the main switching transistor Q1 charges;
when the output capacitor C2 discharges to enable the voltage Vds2 between the drain and the source of the main switching tube Q2 to be reduced to zero, the switching circuit is turned off, the second driving circuit provides a trigger signal to turn on the main switching tube Q2, at the moment, the main switching tube Q2 realizes zero-voltage turn-on and the parasitic body diode of the main switching tube Q1 realizes zero-current turn-off;
the control method for the main switching tube Q1 comprises the following steps:
at an AC voltage source VinBefore the main switching tube Q1 is turned on, the power inductor L freewheels through the parasitic body diode of the main switching tube Q2, at this time, the switching circuit is turned on, so that the resonant current flowing through the resonant inductor Lr increases, the freewheeling current of the parasitic body diode of the main switching tube Q2 decreases, when the current of the power inductor L is equal to the resonant current of the resonant inductor Lr, the freewheeling current of the parasitic body diode of the main switching tube Q2 is zero, and as the resonant current of the resonant inductor Lr continues to increase to be greater than the current of the power inductor L, the output capacitor C1 connected in parallel with the drain and the source of the main switching tube Q1 discharges, so that the voltage Vds1 between the drain and the source of the main switching tube Q1 decreases, and the output capacitor C2 connected in parallel with the source and the drain of the main switching tube Q2 charges;
when the output capacitor C1 discharges to make the voltage Vds1 between the drain and the source of the main switching tube Q1 drop to zero, the switching circuit is turned off, the first driving circuit provides a trigger signal to turn on the main switching tube Q1, at this time, the main switching tube Q1 realizes zero-voltage turn-on and the parasitic body diode of the main switching tube Q2 realizes zero-current turn-off.
The control method of the invention adds a resonance circuit on the basis of the traditional totem-pole bridgeless PFC, creates a resonance inductor, a main switch tube Q1, a main switch tube Q2, a connecting circuit between the traditional totem-pole bridgeless PFC circuit and a control method, reduces the voltage and current stress of the main switch tube Q1 and the main switch tube Q2 by controlling the on-off of the switch circuit in a staged mode in corresponding positive and negative half periods of input, inhibits the reverse recovery characteristic of a parasitic diode in the main switch tube Q1 and the main switch tube Q2, enables the main switch tube Q1 and the main switch tube Q2 to realize zero-voltage on, improves the efficiency of the converter, and ensures that the efficiency of the converter is improved, thereby ensuring that the converter has zero-voltage onSiApplications of MOSFETs in this field are possible.
Preferably, the switching circuit includes a switching tube Q3, a switching tube Q4 and a switching tube Q5, one end of the resonant inductor Lr remote from the end connected with the power inductor L is connected with the drain of the switching tube Q5, the source of the switching tube Q5 is simultaneously connected with the source of the switching tube Q3 and the drain of the switching tube Q4, the drain of the switching tube Q3 is simultaneously connected with the drain of the main switching tube Q1 and one end of the output capacitor C0, and the source of the switching tube Q4 is simultaneously connected with the source of the main switching tube Q2 and the other end of the output capacitor C0;
the gate of the switching tube Q3 is connected to a third driving circuit, the third driving circuit is used for providing a trigger signal to turn on the switching tube Q3, the gate of the switching tube Q4 is connected to a fourth driving circuit, the fourth driving circuit is used for providing a trigger signal to turn on the switching tube Q4, the gate of the switching tube Q5 is connected to a fifth driving circuit, and the fifth driving circuit is used for providing a trigger signal to turn on the switching tube Q5;
the switch circuit further comprises a switch tube Q6, the source of the switch tube Q6 is connected with the source of the switch tube Q5, the drain of the switch tube Q6 is simultaneously connected with the source of the switch tube Q3 and the drain of the switch tube Q4, the gate of the switch tube Q6 is connected with a sixth drive circuit, and the sixth drive circuit is used for providing a trigger signal to turn on the switch tube Q6;
in the control method for the main switching tube Q2:
at an AC voltage source VinBefore the main switching tube Q2 is turned on, the power inductor L freewheels through a parasitic body diode of the main switching tube Q1, the fourth driving circuit, the fifth driving circuit and the sixth driving circuit respectively provide trigger signals to turn on the switching tube Q4, the switching tube Q5 and the switching tube Q6, the resonant inductor Lr, the switching tube Q5, the switching tube Q6, the switching tube Q4, the parasitic body diode of the main switching tube Q1 and the output capacitor C0 form a current loop, the voltage at two ends of the resonant inductor Lr is equal to the voltage at two ends of the output capacitor C0, the resonant current of the resonant inductor Lr increases linearly, the freewheel current of the parasitic body diode of the main switching tube Q1 decreases linearly, and when the current of the power inductor L is equal to the resonant current of the resonant inductor Lr, the freewheel current of the parasitic body diode of the main switching tube Q1 is zero, so that zero current turn-off of the parasitic body diode of the main switching tube Q1 is realized;
when the resonant current of the resonant inductor Lr continues to increase to be larger than the current of the power inductor L, the output capacitor C2 connected in parallel with the drain and the source of the main switching tube Q2 discharges to reduce the voltage Vds2 between the drain and the source of the main switching tube Q2, meanwhile, the output capacitor C2 also generates series resonance with the resonant inductor Lr to continuously reduce the voltage across the resonant inductor Lr, and the output capacitor C1 connected in parallel with the source and the drain of the main switching tube Q1 charges;
when the output capacitor C2 discharges to enable the voltage Vds2 between the drain and the source of the main switch tube Q2 to be reduced to zero, the resonant current of the resonant inductor Lr is maximum, at this time, the switch tube Q4 and the switch tube Q6 are disconnected, the switch tube Q5 is kept to be connected, the second driving circuit provides a trigger signal to connect the main switch tube Q2, at this time, the main switch tube Q2 realizes zero-voltage connection and the parasitic diode of the main switch tube Q1 realizes zero-current connection, meanwhile, energy in the resonant inductor Lr is output through the switch tube Q5, the switch tube Q3 and the parasitic diode of the switch tube Q6, the voltage at two ends of the resonant inductor Lr is the voltage of the reversed output capacitor C0, the resonant current of the resonant inductor Lr linearly decreases, and the switch tube Q5 is closed when the resonant current of the resonant inductor Lr is zero.
Therefore, through reasonable connection, connection and disconnection control of the switching tube Q6, the switching tube Q4 and the switching tube Q5 in the switching circuit, the resonant current in the resonant inductor Lr can change according to a preset trend, zero voltage connection of the main switching tube Q2 and zero current disconnection of the main switching tube Q1 are guaranteed, and meanwhile, the resonant current in the resonant inductor Lr can effectively release energy to an output end after resonance is finished, so that the next operation is facilitated.
Preferably, in the method for controlling the main switching tube Q1:
at an AC voltage source VinBefore the main switching tube Q1 is turned on, the power inductor L continues current through the parasitic body diode of the main switching tube Q2, the third driving circuit, the fifth driving circuit and the sixth driving circuit respectively provide trigger signals to turn on the switching tube Q3, the switching tube Q5 and the switching tube Q6, the resonant inductor Lr, the switching tube Q3, the switching tube Q5, the switching tube Q6, the parasitic body diode of the main switching tube Q2 and the output capacitor C0 form a current loop, the voltage at two ends of the resonant inductor Lr is equal to the voltage at two ends of the output capacitor C0, the resonant current of the resonant inductor Lr increases linearly, the follow current of the parasitic body diode of the main switching tube Q2 decreases linearly, and when the current of the power inductor L is equal to the resonant current of the resonant inductor Lr, the follow current of the parasitic body diode of the main switching tube Q2 is zero, so that zero current turn-off of the parasitic body diode of the main switching tube Q2 is realized;
when the resonant current of the resonant inductor Lr continues to increase to be larger than the current of the power inductor L, the output capacitor C1 connected in parallel with the drain and the source of the main switching tube Q1 discharges to reduce the voltage Vds1 between the drain and the source of the main switching tube Q1, meanwhile, the output capacitor C1 also generates series resonance with the resonant inductor Lr to continuously reduce the voltage across the resonant inductor Lr, and the output capacitor C2 connected in parallel with the source and the drain of the main switching tube Q2 charges;
when the output capacitor C1 discharges to enable the voltage Vds1 between the drain and the source of the main switch tube Q1 to be reduced to zero, the resonant current of the resonant inductor Lr is maximum, at this time, the switch tube Q3 and the switch tube Q5 are disconnected, the switch tube Q6 is kept to be connected, the first driving circuit provides a trigger signal to connect the main switch tube Q1, at this time, the main switch tube Q1 realizes zero-voltage connection and the parasitic diode of the main switch tube Q2 realizes zero-current connection, meanwhile, energy in the resonant inductor Lr is output through the switch tube Q6, the switch tube Q4 and the parasitic diode of the switch tube Q5, the voltage at two ends of the resonant inductor Lr is the voltage of the reversed output capacitor C0, the resonant current of the resonant inductor Lr linearly decreases, and the switch tube Q6 is closed when the resonant current of the resonant inductor Lr is zero.
Therefore, through reasonable connection, connection and disconnection control of the switching tube Q3, the switching tube Q6 and the switching tube Q5 in the switching circuit, the resonant current in the resonant inductor Lr can change according to a preset trend, zero voltage connection of the main switching tube Q1 and zero current disconnection of the main switching tube Q2 are guaranteed, and meanwhile, the resonant current in the resonant inductor Lr can effectively release energy to an output end after resonance is finished, so that the next operation is facilitated.
Preferably, in the method for controlling the main switching tube Q2: and when the resonant current of the resonant inductor Lr is zero, delaying for a set time, and then closing the switching tube Q5.
Preferably, in the method for controlling the main switching tube Q1: and when the resonant current of the resonant inductor Lr is zero, delaying for a set time, and then closing the switching tube Q6.
In this way, after the resonant current in the resonant inductor Lr is zero, the switching tube Q5 or the switching tube Q6 is turned off after delaying for the set time, and the resonant current in the resonant inductor Lr is ensured to be completely reduced to zero by delaying for the set time.
Drawings
Fig. 1 is a basic circuit diagram of a typical totem-pole bridgeless PFC converter in a prior art solution;
fig. 2 is a circuit diagram of a bridgeless PFC converter according to an embodiment of the present invention;
FIG. 3 shows an AC voltage source V according to an embodiment of the present inventioninA flow chart of a control method for the main switching tube Q2 in the positive half period;
FIG. 4 shows an AC voltage source V according to an embodiment of the present inventioninIs a timing diagram of the working voltage and current of each device in the positive half period.
Detailed Description
The invention will be further explained with reference to the drawings and the embodiments.
As shown in fig. 2, a bridgeless PFC converter includes a totem-pole bridgeless PFC converter circuit including an ac voltage source VinThe high-power-factor switching circuit comprises a diode D1, a diode D2, a main switching tube Q1, a main switching tube Q2, a power inductor L and an output capacitor C0, wherein the grid electrode of the main switching tube Q1 is connected with a first driving circuit, the first driving circuit is used for providing a trigger signal to turn on the main switching tube Q1, the grid electrode of the main switching tube Q2 is connected with a second driving circuit, and the second driving circuit is used for providing a trigger signal to turn on the main switching tube Q2;
the resonant circuit comprises a resonant inductor Lr and a switching circuit, one end of the resonant inductor Lr is connected with one end of the power inductor L, the source electrode of the main switching tube Q1 and the drain electrode of the main switching tube Q2, the other end of the resonant inductor Lr is connected with the switching circuit, and one side, far away from the side, connected with the resonant inductor Lr, of the switching circuit is connected with the two ends of the output capacitor C0 in parallel.
The working principle of the invention is as follows: the invention is applied to an alternating voltage source VinBefore the main switch tube Q2 is turned on, the power inductor L will freewheel through the parasitic body diode of the main switch tube Q1, at this time, the switch circuit is turned on, so that the resonant current flowing through the resonant inductor Lr increases, the freewheel current of the parasitic body diode of the main switch tube Q1 decreases, and when the current of the power inductor L is equal to the resonant current of the resonant inductor Lr, the freewheel current of the parasitic body diode of the main switch tube Q1 is zero; when the resonant current of the resonant inductor Lr continues to increase to a current greater than that of the power inductor L, the output capacitor C2 connected in parallel with the drain and source of the main switching transistor Q2 discharges, so that the voltage Vds2 between the drain and source of the main switching transistor Q2 decreases while the output capacitor C1 connected in parallel with the source and drain of the main switching transistor Q1 charges; when the output capacitor C2 discharges, the drain and the source of the main switch tube Q2 are enabledWhen the voltage Vds2 between the poles is reduced to zero, the switching circuit is disconnected, the second driving circuit provides a trigger signal to turn on the main switching tube Q2, at the moment, the main switching tube Q2 realizes zero-voltage turn-on, and the parasitic body diode of the main switching tube Q1 realizes zero-current turn-off;
at an AC voltage source VinBefore the main switching tube Q1 is turned on, the power inductor L freewheels through the parasitic body diode of the main switching tube Q2, at this time, the switching circuit is turned on, so that the resonant current flowing through the resonant inductor Lr increases, the freewheeling current of the parasitic body diode of the main switching tube Q2 decreases, when the current of the power inductor L is equal to the resonant current of the resonant inductor Lr, the freewheeling current of the parasitic body diode of the main switching tube Q2 is zero, and as the resonant current of the resonant inductor Lr continues to increase to be greater than the current of the power inductor L, the output capacitor C1 connected in parallel with the drain and the source of the main switching tube Q1 discharges, so that the voltage Vds1 between the drain and the source of the main switching tube Q1 decreases, and the output capacitor C2 connected in parallel with the source and the drain of the main switching tube Q2 charges; when the output capacitor C1 discharges to make the voltage Vds1 between the drain and the source of the main switching tube Q1 drop to zero, the switching circuit is turned off, the first driving circuit provides a trigger signal to turn on the main switching tube Q1, at this time, the main switching tube Q1 realizes zero-voltage turn-on and the parasitic body diode of the main switching tube Q2 realizes zero-current turn-off.
The invention has the beneficial effects that: 1. when the main switch tube Q1 and the main switch tube Q2 are turned on, voltages Vds1 and Vds2 at two ends of the main switch tube Q1 and the main switch tube Q2 are zero, and meanwhile, when the main switch tube Q1 and the main switch tube Q2 are turned off, currents of a parasitic body diode of the Q1 and a parasitic body diode of the Q2 are zero, so that zero current turn-off of the main switch tube Q1 and the main switch tube Q2 is realized, reverse currents cannot pass through the parasitic body diodes of the main switch tube Q1 and the main switch tube Q2 under the action of reverse voltages, reverse recovery characteristics of the parasitic body diodes in the switch tubes are effectively inhibited, through of upper and lower bridge arms is avoided, and therefore the bridgeless PFC converter can work in a CCM (continuous working) mode.
2. According to the bridgeless PFC converter, the PFC function is realized through the connection of the resonant circuit and the traditional totem-pole PFC circuit, and by controlling the on-off of the resonant circuit, the resonant current is linearly increased, and the current in the power inductor L is linearly reduced, so that the current flowing through a parasitic body diode in a main switching tube is naturally zero, and the problem of reverse recovery is suppressed; and meanwhile, the resonant current is utilized to discharge the output capacitor connected in parallel with the main switching tube, and each main switching tube realizes zero voltage switching-on, so that the efficiency of the converter is improved.
In this embodiment, the switching circuit includes a switching tube Q3, a switching tube Q4 and a switching tube Q5, one end of the resonant inductor Lr far from the end connected with the power inductor L is connected with the drain of the switching tube Q5, the source of the switching tube Q5 is connected with the source of the switching tube Q3 and the drain of the switching tube Q4 at the same time, the drain of the switching tube Q3 is connected with the drain of the main switching tube Q1 and one end of the output capacitor C0 at the same time, and the source of the switching tube Q4 is connected with the source of the main switching tube Q2 and the other end of the output capacitor C0 at the same time;
the gate of the switching tube Q3 is connected to the third driving circuit, the third driving circuit is used for providing a trigger signal to turn on the switching tube Q3, the gate of the switching tube Q4 is connected to the fourth driving circuit, the fourth driving circuit is used for providing a trigger signal to turn on the switching tube Q4, the gate of the switching tube Q5 is connected to the fifth driving circuit, and the fifth driving circuit is used for providing a trigger signal to turn on the switching tube Q5.
In this embodiment, the switch circuit further includes a switch Q6, the source of the switch Q6 is connected to the source of the switch Q5, the drain of the switch Q6 is connected to both the source of the switch Q3 and the drain of the switch Q4, the gate of the switch Q6 is connected to a sixth driving circuit, and the sixth driving circuit is configured to provide a trigger signal to turn on the switch Q6.
By providing the switching tube Q6 in this way, when the energy of the resonant inductor Lr is discharged to the output side, the one-way conduction characteristic of the parasitic body diode of the switching tube Q6 is utilized to prevent the occurrence of secondary resonance from being blocked in the reverse direction.
In this embodiment, the driving circuit for providing the trigger signal to the gate of each switching tube to make it conductive may adopt a driving circuit mature in the prior art, and therefore, a specific circuit structure of the driving circuit of each switching tube is not described in the present invention.
As shown in fig. 3, a control method of a bridgeless PFC converter, which includes a control method for a main switching transistor Q2 and a control method for a main switching transistor Q1, is adopted;
the control method of the main switching tube Q2 is as follows:
at an AC voltage source VinBefore the main switch tube Q2 is turned on, the power inductor L will freewheel through the parasitic body diode of the main switch tube Q1, at this time, the switch circuit is turned on, so that the resonant current flowing through the resonant inductor Lr increases, the freewheel current of the parasitic body diode of the main switch tube Q1 decreases, and when the current of the power inductor L is equal to the resonant current of the resonant inductor Lr, the freewheel current of the parasitic body diode of the main switch tube Q1 is zero;
when the resonant current of the resonant inductor Lr continues to increase to a current greater than that of the power inductor L, the output capacitor C2 connected in parallel with the drain and source of the main switching transistor Q2 discharges, so that the voltage Vds2 between the drain and source of the main switching transistor Q2 decreases while the output capacitor C1 connected in parallel with the source and drain of the main switching transistor Q1 charges;
when the output capacitor C2 discharges to enable the voltage Vds2 between the drain and the source of the main switching tube Q2 to be reduced to zero, the switching circuit is turned off, the second driving circuit provides a trigger signal to turn on the main switching tube Q2, at the moment, the main switching tube Q2 realizes zero-voltage turn-on and the parasitic body diode of the main switching tube Q1 realizes zero-current turn-off;
the control method of the main switching tube Q1 is as follows:
at an AC voltage source VinBefore the main switch Q1 is turned on, the power inductor L will freewheel through the parasitic body diode of the main switch Q2, at this time, the switch circuit is turned on, so that the resonant current flowing through the resonant inductor Lr increases, the freewheel current of the parasitic body diode of the main switch Q2 decreases, when the current of the power inductor L is equal to the resonant current of the resonant inductor Lr, the freewheel current of the parasitic body diode of the main switch Q2 is zero, and when the resonant current of the resonant inductor Lr continues to increase to a current greater than the current of the power inductor L, the freewheel current of the parasitic body diode of the main switch Q2 is zero, and when the resonant current of the resonant inductor Lr continues to increase toThe output capacitor C1 connected in parallel with the drain and the source of the switch tube Q1 discharges, so that the voltage Vds1 between the drain and the source of the main switch tube Q1 decreases, and the output capacitor C2 connected in parallel with the source and the drain of the main switch tube Q2 charges;
when the output capacitor C1 discharges to make the voltage Vds1 between the drain and the source of the main switching tube Q1 drop to zero, the switching circuit is turned off, the first driving circuit provides a trigger signal to turn on the main switching tube Q1, at this time, the main switching tube Q1 realizes zero-voltage turn-on and the parasitic body diode of the main switching tube Q2 realizes zero-current turn-off.
The control method of the invention adds a resonance circuit on the basis of the traditional totem-pole bridgeless PFC, creates a resonance inductor, a main switch tube Q1, a main switch tube Q2, a connecting circuit between the traditional totem-pole bridgeless PFC circuit and a control method, reduces the voltage and current stress of the main switch tube Q1 and the main switch tube Q2 by controlling the on-off of the switch circuit in a staged mode in corresponding positive and negative half periods of input, inhibits the reverse recovery characteristic of a parasitic diode in the main switch tube Q1 and the main switch tube Q2, enables the main switch tube Q1 and the main switch tube Q2 to realize zero-voltage on, improves the efficiency of the converter, and ensures that the efficiency of the converter is improved, thereby ensuring that the converter has zero-voltage onSiApplications of MOSFETs in this field are possible.
In this embodiment, the switching circuit includes a switching tube Q3, a switching tube Q4 and a switching tube Q5, one end of the resonant inductor Lr far from the end connected with the power inductor L is connected with the drain of the switching tube Q5, the source of the switching tube Q5 is connected with the source of the switching tube Q3 and the drain of the switching tube Q4 at the same time, the drain of the switching tube Q3 is connected with the drain of the main switching tube Q1 and one end of the output capacitor C0 at the same time, and the source of the switching tube Q4 is connected with the source of the main switching tube Q2 and the other end of the output capacitor C0 at the same time;
the grid electrode of the switching tube Q3 is connected with a third driving circuit, the third driving circuit is used for providing a trigger signal to turn on the switching tube Q3, the grid electrode of the switching tube Q4 is connected with a fourth driving circuit, the fourth driving circuit is used for providing a trigger signal to turn on the switching tube Q4, the grid electrode of the switching tube Q5 is connected with a fifth driving circuit, and the fifth driving circuit is used for providing a trigger signal to turn on the switching tube Q5;
the switching circuit further comprises a switching tube Q6, the source electrode of the switching tube Q6 is connected with the source electrode of the switching tube Q5, the drain electrode of the switching tube Q6 is simultaneously connected with the source electrode of the switching tube Q3 and the drain electrode of the switching tube Q4, the grid electrode of the switching tube Q6 is connected with a sixth driving circuit, and the sixth driving circuit is used for providing a trigger signal to turn on the switching tube Q6;
the control method for the main switching tube Q2 comprises the following steps:
at an AC voltage source VinBefore the main switching tube Q2 is turned on, the power inductor L freewheels through a parasitic body diode of the main switching tube Q1, the fourth driving circuit, the fifth driving circuit and the sixth driving circuit respectively provide trigger signals to turn on the switching tube Q4, the switching tube Q5 and the switching tube Q6, the resonant inductor Lr, the switching tube Q5, the switching tube Q6, the switching tube Q4, the parasitic body diode of the main switching tube Q1 and the output capacitor C0 form a current loop, the voltage at two ends of the resonant inductor Lr is equal to the voltage at two ends of the output capacitor C0, the resonant current of the resonant inductor Lr increases linearly, the freewheel current of the parasitic body diode of the main switching tube Q1 decreases linearly, and when the current of the power inductor L is equal to the resonant current of the resonant inductor Lr, the freewheel current of the parasitic body diode of the main switching tube Q1 is zero, so that zero current turn-off of the parasitic body diode of the main switching tube Q1 is realized;
when the resonant current of the resonant inductor Lr continues to increase to be larger than the current of the power inductor L, the output capacitor C2 connected in parallel with the drain and the source of the main switching tube Q2 discharges to reduce the voltage Vds2 between the drain and the source of the main switching tube Q2, meanwhile, the output capacitor C2 also generates series resonance with the resonant inductor Lr to continuously reduce the voltage across the resonant inductor Lr, and the output capacitor C1 connected in parallel with the source and the drain of the main switching tube Q1 charges;
when the output capacitor C2 discharges to enable the voltage Vds2 between the drain and the source of the main switch tube Q2 to be reduced to zero, the resonant current of the resonant inductor Lr is maximum, at this time, the switch tube Q4 and the switch tube Q6 are disconnected, the switch tube Q5 is kept to be connected, the second driving circuit provides a trigger signal to connect the main switch tube Q2, at this time, the main switch tube Q2 realizes zero-voltage connection and the parasitic diode of the main switch tube Q1 realizes zero-current connection, meanwhile, energy in the resonant inductor Lr is output through the switch tube Q5, the switch tube Q3 and the parasitic diode of the switch tube Q6, the voltage at two ends of the resonant inductor Lr is the voltage of the reversed output capacitor C0, the resonant current of the resonant inductor Lr linearly decreases, and the switch tube Q5 is closed when the resonant current of the resonant inductor Lr is zero.
Therefore, through reasonable connection, connection and disconnection control of the switching tube Q6, the switching tube Q4 and the switching tube Q5 in the switching circuit, the resonant current in the resonant inductor Lr can change according to a preset trend, zero voltage connection of the main switching tube Q2 and zero current disconnection of the main switching tube Q1 are guaranteed, and meanwhile, the resonant current in the resonant inductor Lr can effectively release energy to an output end after resonance is finished, so that the next operation is facilitated.
In this embodiment, in the control method for the main switching tube Q1:
at an AC voltage source VinBefore the main switching tube Q1 is turned on, the power inductor L continues current through the parasitic body diode of the main switching tube Q2, the third driving circuit, the fifth driving circuit and the sixth driving circuit respectively provide trigger signals to turn on the switching tube Q3, the switching tube Q5 and the switching tube Q6, the resonant inductor Lr, the switching tube Q3, the switching tube Q5, the switching tube Q6, the parasitic body diode of the main switching tube Q2 and the output capacitor C0 form a current loop, the voltage at two ends of the resonant inductor Lr is equal to the voltage at two ends of the output capacitor C0, the resonant current of the resonant inductor Lr increases linearly, the follow current of the parasitic body diode of the main switching tube Q2 decreases linearly, and when the current of the power inductor L is equal to the resonant current of the resonant inductor Lr, the follow current of the parasitic body diode of the main switching tube Q2 is zero, so that zero current turn-off of the parasitic body diode of the main switching tube Q2 is realized;
when the resonant current of the resonant inductor Lr continues to increase to be larger than the current of the power inductor L, the output capacitor C1 connected in parallel with the drain and the source of the main switching tube Q1 discharges to reduce the voltage Vds1 between the drain and the source of the main switching tube Q1, meanwhile, the output capacitor C1 also generates series resonance with the resonant inductor Lr to continuously reduce the voltage across the resonant inductor Lr, and the output capacitor C2 connected in parallel with the source and the drain of the main switching tube Q2 charges;
when the output capacitor C1 discharges to enable the voltage Vds1 between the drain and the source of the main switch tube Q1 to be reduced to zero, the resonant current of the resonant inductor Lr is maximum, at this time, the switch tube Q3 and the switch tube Q5 are disconnected, the switch tube Q6 is kept to be connected, the first driving circuit provides a trigger signal to connect the main switch tube Q1, at this time, the main switch tube Q1 realizes zero-voltage connection and the parasitic diode of the main switch tube Q2 realizes zero-current connection, meanwhile, energy in the resonant inductor Lr is output through the switch tube Q6, the switch tube Q4 and the parasitic diode of the switch tube Q5, the voltage at two ends of the resonant inductor Lr is the voltage of the reversed output capacitor C0, the resonant current of the resonant inductor Lr linearly decreases, and the switch tube Q6 is closed when the resonant current of the resonant inductor Lr is zero.
Therefore, through reasonable connection, connection and disconnection control of the switching tube Q3, the switching tube Q6 and the switching tube Q5 in the switching circuit, the resonant current in the resonant inductor Lr can change according to a preset trend, zero voltage connection of the main switching tube Q1 and zero current disconnection of the main switching tube Q2 are guaranteed, and meanwhile, the resonant current in the resonant inductor Lr can effectively release energy to an output end after resonance is finished, so that the next operation is facilitated.
In this embodiment, in the control method for the main switching tube Q2: and when the resonant current of the resonant inductor Lr is zero, delaying for a set time, and then closing the switching tube Q5.
In this embodiment, in the control method for the main switching tube Q1: and when the resonant current of the resonant inductor Lr is zero, delaying for a set time, and then closing the switching tube Q6.
In this way, after the resonant current in the resonant inductor Lr is zero, the switching tube Q5 or the switching tube Q6 is turned off after delaying for the set time, and the resonant current in the resonant inductor Lr is ensured to be completely reduced to zero by delaying for the set time.
Due to the positive and negative half-cycle symmetry, only AC voltage source V is used for simplifying analysisinThe positive half cycle is exemplified by the case where the AC voltage source V is usedinIn the positive half cycle, a Boost circuit is formed by the diode D2, the main switching tube Q1, the main switching tube Q2 and the power inductor L, and a voltage-current timing diagram of each main device in the circuit is shown in fig. 4.
In thatt 0Time, main switch tube Q2During the off period, the energy stored in the power inductor L flows to the output side through the parasitic diode of the main switching transistor Q1, which is the same as the freewheeling process of the conventional totem-pole bridgeless PFC, and the current of the power inductor L decreases linearly.
In thatt 1The time switch tube Q4, the switch tube Q5 and the switch tube Q6 are respectively conducted under the triggering action of the fourth driving circuit, the fifth driving circuit and the sixth driving circuit, in this period, the voltage borne at the two ends of the resonant inductor Lr is the output voltage Vo, the resonant current is linearly increased, and the follow current of the parasitic body diode of the main switch tube Q1 is linearly decreased.
In thatt 2At the moment, the current of the power inductor L is exactly equal to the resonance current of the resonance inductor Lr, so that the current of a parasitic body diode of the main switching tube Q1 is reduced to zero, the controllable di/dt eliminates the influence of reverse recovery, and the zero current turn-off of the main switching tube Q1 is realized; at the same time due to the fact thatt 2At the moment, the parasitic body diode current of the main switch tube Q1 is reduced to zero, the output capacitor C1 of the main switch tube Q1 in the circuit starts to charge, the output capacitor C2 of the main switch tube Q2 starts to discharge, the voltage Vds2 between the drain and the source of the main switch tube Q2 is reduced, meanwhile, the output capacitor C2 and the resonant inductor generate series resonance, and in the period, the voltage across the resonant inductor Lr is gradually reduced.
Tot 3At the moment, the voltage drop across the resonant inductor Lr is zero, the resonant current reaches the maximum value, at this moment, the resonance is finished, the voltage Vds2 between the drain and the source of the main switching tube Q2 is reduced to zero, and in this time period, a circulating current flows through the parasitic body diode of the main switching tube Q2, the resonant inductor Lr and the switching tube Q4, and the circulating current can reduce the efficiency of the whole system, so that a better design is required.
In thatt 4At the moment, the second driving circuit provides a trigger signal to the main switching tube Q2 and enables the main switching tube Q2 to be switched on, ZVS is further realized because the voltage at two ends of the main switching tube Q2 is reduced to zero, the switching tube Q4 and the switching tube Q6 are switched off at the moment, the switching tube Q5 keeps on, and the energy stored in the resonant inductor Lr passes through the switching tube Q6The parasitic body diode and the parasitic body diode of the switching tube Q3 flow to the output side, and the two ends of the resonant inductor Lr bear the reverse output voltage-V oThe resonant current decreases linearly.
In thatt 5The resonant current of the resonant inductor Lr is reduced to zero at the moment, and is delayed for a little timet 6The drive signal to the opening light pipe Q5 is turned off at a time.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the technical solutions, and those skilled in the art should understand that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions, and all that should be covered by the claims of the present invention.

Claims (8)

1. A bridgeless PFC converter comprises a totem-pole bridgeless PFC converter circuit which comprises an alternating-current voltage source VinThe high-power switch comprises a diode D1, a diode D2, a main switch tube Q1, a main switch tube Q2, a power inductor L and an output capacitor C0, wherein the grid electrode of the main switch tube Q1 is connected with a first driving circuit, the first driving circuit is used for providing a trigger signal to turn on the main switch tube Q1, the grid electrode of the main switch tube Q2 is connected with a second driving circuit, the second driving circuit is used for providing a trigger signal to turn on the main switch tube Q2, the high-power switch is characterized by further comprising an output capacitor C1, an output capacitor C2 and a resonant circuit, two ends of the output capacitor C1 are connected with the source electrode and the drain electrode of the main switch tube Q1 in parallel, and two ends of the output capacitor C2 are connected with the source electrode and the drain electrode of the main switch tube Q2 in parallel;
the resonant circuit comprises a resonant inductor Lr and a switch circuit, one end of the resonant inductor Lr is connected with one end of the power inductor L, the source electrode of the main switch tube Q1 and the drain electrode of the main switch tube Q2, the other end of the resonant inductor Lr is connected with the switch circuit, and one side, far away from the switch circuit, of the switch circuit, which is connected with the resonant inductor Lr, is connected with two ends of the output capacitor C0 in parallel.
2. The bridgeless PFC converter according to claim 1, wherein the switching circuit comprises a switching tube Q3, a switching tube Q4 and a switching tube Q5, one end of the resonant inductor Lr, which is far away from the end connected with the power inductor L, is connected with the drain of the switching tube Q5, the source of the switching tube Q5 is simultaneously connected with the source of the switching tube Q3 and the drain of the switching tube Q4, the drain of the switching tube Q3 is simultaneously connected with the drain of the main switching tube Q1 and one end of the output capacitor C0, and the source of the switching tube Q4 is simultaneously connected with the source of the main switching tube Q2 and the other end of the output capacitor C0;
the gate of the switching tube Q3 is connected to a third driving circuit, the third driving circuit is used for providing a trigger signal to turn on the switching tube Q3, the gate of the switching tube Q4 is connected to a fourth driving circuit, the fourth driving circuit is used for providing a trigger signal to turn on the switching tube Q4, the gate of the switching tube Q5 is connected to a fifth driving circuit, and the fifth driving circuit is used for providing a trigger signal to turn on the switching tube Q5.
3. The bridgeless PFC converter according to claim 2, wherein the switch circuit further comprises a switch tube Q6, the source of the switch tube Q6 is connected with the source of the switch tube Q5, the drain of the switch tube Q6 is connected with the source of the switch tube Q3 and the drain of the switch tube Q4, the gate of the switch tube Q6 is connected with a sixth driving circuit, and the sixth driving circuit is used for providing a trigger signal to turn on the switch tube Q6.
4. A control method of a bridgeless PFC converter is characterized in that the bridgeless PFC converter of claim 1 is adopted, and the control method comprises a control method of a main switching tube Q2 and a control method of a main switching tube Q1;
the control method for the main switching tube Q2 comprises the following steps:
at an AC voltage source VinBefore the main switch Q2 turns on, the power inductor L will freewheel through the parasitic body diode of the main switch Q1, which turns on the switching circuit to flow through resonanceThe resonant current of the inductor Lr is increased, the freewheeling current of the parasitic body diode of the main switching tube Q1 is decreased, and when the current of the power inductor L is equal to the resonant current of the resonant inductor Lr, the freewheeling current of the parasitic body diode of the main switching tube Q1 is zero;
when the resonant current of the resonant inductor Lr continues to increase to a current greater than that of the power inductor L, the output capacitor C2 connected in parallel with the drain and source of the main switching transistor Q2 discharges, so that the voltage Vds2 between the drain and source of the main switching transistor Q2 decreases while the output capacitor C1 connected in parallel with the source and drain of the main switching transistor Q1 charges;
when the output capacitor C2 discharges to enable the voltage Vds2 between the drain and the source of the main switching tube Q2 to be reduced to zero, the switching circuit is turned off, the second driving circuit provides a trigger signal to turn on the main switching tube Q2, at the moment, the main switching tube Q2 realizes zero-voltage turn-on and the parasitic body diode of the main switching tube Q1 realizes zero-current turn-off;
the control method for the main switching tube Q1 comprises the following steps:
at an AC voltage source VinBefore the main switching tube Q1 is turned on, the power inductor L freewheels through the parasitic body diode of the main switching tube Q2, at this time, the switching circuit is turned on, so that the resonant current flowing through the resonant inductor Lr increases, the freewheeling current of the parasitic body diode of the main switching tube Q2 decreases, when the current of the power inductor L is equal to the resonant current of the resonant inductor Lr, the freewheeling current of the parasitic body diode of the main switching tube Q2 is zero, and as the resonant current of the resonant inductor Lr continues to increase to be greater than the current of the power inductor L, the output capacitor C1 connected in parallel with the drain and the source of the main switching tube Q1 discharges, so that the voltage Vds1 between the drain and the source of the main switching tube Q1 decreases, and the output capacitor C2 connected in parallel with the source and the drain of the main switching tube Q2 charges;
when the output capacitor C1 discharges to make the voltage Vds1 between the drain and the source of the main switching tube Q1 drop to zero, the switching circuit is turned off, the first driving circuit provides a trigger signal to turn on the main switching tube Q1, at this time, the main switching tube Q1 realizes zero-voltage turn-on and the parasitic body diode of the main switching tube Q2 realizes zero-current turn-off.
5. The control method of the bridgeless PFC converter according to claim 4, wherein the switch circuit comprises a switch tube Q3, a switch tube Q4 and a switch tube Q5, one end of the resonance inductor Lr, which is far away from the end connected with the power inductor L, is connected with the drain of the switch tube Q5, the source of the switch tube Q5 is simultaneously connected with the source of the switch tube Q3 and the drain of the switch tube Q4, the drain of the switch tube Q3 is simultaneously connected with the drain of the main switch tube Q1 and one end of the output capacitor C0, and the source of the switch tube Q4 is simultaneously connected with the source of the main switch tube Q2 and the other end of the output capacitor C0;
the gate of the switching tube Q3 is connected to a third driving circuit, the third driving circuit is used for providing a trigger signal to turn on the switching tube Q3, the gate of the switching tube Q4 is connected to a fourth driving circuit, the fourth driving circuit is used for providing a trigger signal to turn on the switching tube Q4, the gate of the switching tube Q5 is connected to a fifth driving circuit, and the fifth driving circuit is used for providing a trigger signal to turn on the switching tube Q5;
the switch circuit further comprises a switch tube Q6, the source of the switch tube Q6 is connected with the source of the switch tube Q5, the drain of the switch tube Q6 is simultaneously connected with the source of the switch tube Q3 and the drain of the switch tube Q4, the gate of the switch tube Q6 is connected with a sixth drive circuit, and the sixth drive circuit is used for providing a trigger signal to turn on the switch tube Q6;
in the control method for the main switching tube Q2:
at an AC voltage source VinBefore the main switch tube Q2 is turned on, the power inductor L will follow current through the parasitic body diode of the main switch tube Q1, the fourth driving circuit, the fifth driving circuit and the sixth driving circuit respectively provide trigger signals to turn on the switch tube Q4, the switch tube Q5 and the switch tube Q6, the resonant inductor Lr, the switch tube Q5, the switch tube Q6, the switch tube Q4, the parasitic body diode of the main switch tube Q1 and the output capacitor C0 form a current loop, the voltage at two ends of the resonant inductor Lr is equal to the voltage at two ends of the output capacitor C0, the resonant current of the resonant inductor Lr increases linearly, and the parasitic body two of the main switch tube Q1The follow current of the pole tube is linearly reduced, when the current of the power inductor L is equal to the resonance current of the resonance inductor Lr, the follow current of the parasitic body diode of the main switch tube Q1 is zero, and zero current turn-off of the parasitic body diode of the main switch tube Q1 is realized;
when the resonant current of the resonant inductor Lr continues to increase to be larger than the current of the power inductor L, the output capacitor C2 connected in parallel with the drain and the source of the main switching tube Q2 discharges to reduce the voltage Vds2 between the drain and the source of the main switching tube Q2, meanwhile, the output capacitor C2 also generates series resonance with the resonant inductor Lr to continuously reduce the voltage across the resonant inductor Lr, and the output capacitor C1 connected in parallel with the source and the drain of the main switching tube Q1 charges;
when the output capacitor C2 discharges to enable the voltage Vds2 between the drain and the source of the main switch tube Q2 to be reduced to zero, the resonant current of the resonant inductor Lr is maximum, at this time, the switch tube Q4 and the switch tube Q6 are disconnected, the switch tube Q5 is kept to be connected, the second driving circuit provides a trigger signal to connect the main switch tube Q2, at this time, the main switch tube Q2 realizes zero-voltage connection and the parasitic diode of the main switch tube Q1 realizes zero-current connection, meanwhile, energy in the resonant inductor Lr is output through the switch tube Q5, the switch tube Q3 and the parasitic diode of the switch tube Q6, the voltage at two ends of the resonant inductor Lr is the voltage of the reversed output capacitor C0, the resonant current of the resonant inductor Lr linearly decreases, and the switch tube Q5 is closed when the resonant current of the resonant inductor Lr is zero.
6. The method of claim 5, wherein the method of controlling the main switching transistor Q1 comprises:
at an AC voltage source VinBefore the main switch tube Q1 is turned on, the power inductor L will follow current through the parasitic body diode of the main switch tube Q2, the third driving circuit, the fifth driving circuit and the sixth driving circuit respectively provide trigger signals to turn on the switch tube Q3, the switch tube Q5 and the switch tube Q6, the resonant inductor Lr, the switch tube Q3, the switch tube Q5, the switch tube Q6, the parasitic body diode of the main switch tube Q2 and the output capacitor C0 form a current loop, the voltage at two ends of the resonant inductor Lr is equal to the voltage at two ends of the output capacitor C0,the resonant current of the resonant inductor Lr increases linearly, the freewheeling current of the parasitic body diode of the main switching tube Q2 decreases linearly, and when the current of the power inductor L is equal to the resonant current of the resonant inductor Lr, the freewheeling current of the parasitic body diode of the main switching tube Q2 is zero, so that zero current turn-off of the parasitic body diode of the main switching tube Q2 is realized;
when the resonant current of the resonant inductor Lr continues to increase to be larger than the current of the power inductor L, the output capacitor C1 connected in parallel with the drain and the source of the main switching tube Q1 discharges to reduce the voltage Vds1 between the drain and the source of the main switching tube Q1, meanwhile, the output capacitor C1 also generates series resonance with the resonant inductor Lr to continuously reduce the voltage across the resonant inductor Lr, and the output capacitor C2 connected in parallel with the source and the drain of the main switching tube Q2 charges;
when the output capacitor C1 discharges to enable the voltage Vds1 between the drain and the source of the main switch tube Q1 to be reduced to zero, the resonant current of the resonant inductor Lr is maximum, at this time, the switch tube Q3 and the switch tube Q5 are disconnected, the switch tube Q6 is kept to be connected, the first driving circuit provides a trigger signal to connect the main switch tube Q1, at this time, the main switch tube Q1 realizes zero-voltage connection and the parasitic diode of the main switch tube Q2 realizes zero-current connection, meanwhile, energy in the resonant inductor Lr is output through the switch tube Q6, the switch tube Q4 and the parasitic diode of the switch tube Q5, the voltage at two ends of the resonant inductor Lr is the voltage of the reversed output capacitor C0, the resonant current of the resonant inductor Lr linearly decreases, and the switch tube Q6 is closed when the resonant current of the resonant inductor Lr is zero.
7. The method of claim 5, wherein the method of controlling the main switching transistor Q2 comprises: and when the resonant current of the resonant inductor Lr is zero, delaying for a set time, and then closing the switching tube Q5.
8. The method of claim 6, wherein the method of controlling the main switching transistor Q1 comprises: and when the resonant current of the resonant inductor Lr is zero, delaying for a set time, and then closing the switching tube Q6.
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