CN111740622B - LLC circuit of single-stage PFC - Google Patents

LLC circuit of single-stage PFC Download PDF

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Publication number
CN111740622B
CN111740622B CN202010644407.3A CN202010644407A CN111740622B CN 111740622 B CN111740622 B CN 111740622B CN 202010644407 A CN202010644407 A CN 202010644407A CN 111740622 B CN111740622 B CN 111740622B
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inductor
primary winding
capacitor
circuit
resonant
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CN111740622A (en
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孙巨禄
徐�明
孙涓涓
张志成
刘建
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Chip Power Changzhou Co ltd
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Chip Power Changzhou Co ltd
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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
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
    • H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
    • H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/21—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/217—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M7/219—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only in a bridge configuration
    • 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
    • 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
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/33507—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters
    • H02M3/33523—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters with galvanic isolation between input and output of both the power stage and the feedback loop
    • 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 relates to an LLC circuit of a single-stage PFC.A loop for charging a capacitor in a Boost converter is formed by an input rectifier; the Boost converter further comprises a first inductor, a first switching element and a second switching element; the isolation DC-DC converter comprises a bridge arm structure, a resonant inductor, a resonant capacitor, a transformer and a rectification filter circuit; one end of a first inductor is connected with a first output end of the input rectifier, the other end of the first inductor is connected with a middle tap of the primary winding, and a connection point is connected with the middle point of the bridge arm structure through a branch comprising part of the primary winding, the resonant inductor and the resonant capacitor; or the other end of the first inductor is connected with one end of the primary winding, the connection point is connected with the midpoint of the bridge arm structure through a branch comprising a resonant inductor and a resonant capacitor, and the other end of the primary winding is connected with the first output end of the input rectifier. In the invention, the LLC working state of the circuit is not influenced, the bandwidth of the output voltage loop can be designed to be higher, and the secondary side output voltage power frequency ripple is small.

Description

LLC circuit of single-stage PFC
Technical Field
The invention relates to the technical field of power supply circuits, in particular to an LLC circuit of a single-stage PFC.
Background
The traditional rectifier bridge electrolytic capacitor circuit can cause the waveform of input current to be seriously distorted, the higher harmonic content is higher, the power factor is very low, and the load of a power grid is greatly increased. With the popularization of domestic 3C certification, more and more power supplies in the future need to meet certain harmonic wave requirements to pass the certification. To meet this requirement, a two-stage scheme, i.e., PFC + DCDC, is conventionally used, which can achieve relatively high power factor and low harmonic current, but at high cost. To reduce cost, single-stage PFC technology is gaining increasing attention.
In the prior art, a single-stage PFC is realized in a common manner as shown in fig. 1, and the basic idea is that a Boost converter and an isolated DC-DC converter share a switching tube. The isolation DC-DC converter is a hard switch topology such as a flyback converter or a forward converter, when a switch tube is switched on, the current of an inductor L rises, a capacitor C supplies energy to the isolation DC-DC converter, when the switch tube is switched off, the current of the inductor L falls, the inductor L charges the capacitor C, and the duty ratio is determined by the output of an error amplifier of an output voltage sampling Vo. The inductor L is generally small, so that the current in the inductor L works in an intermittent state, and the current peak value tracks the input voltage, thereby realizing the function of single-stage PFC.
In this way, the isolated DC-DC converters are all hard switching topologies, the switching loss is proportional to the switching frequency, the switching loss is large when the frequency is high, and the overall efficiency is low, so that the isolated DC-DC converters can only be used in occasions with low switching frequency, and the power density and the efficiency cannot be improved.
The prior art also has an embodiment as shown in fig. 2, in which there is no Boost inductance, there is no large Bus capacitance on the primary side, and the ripple is suppressed by means of the capacitance on the secondary side. The isolated DC-DC converter may be a flyback converter, a forward converter, an LLC, etc. The basic working principle is as follows: the product of the error amplifier output signal of the output voltage sampling signal Vo and the input voltage sampling signal Vac is used as the reference of the input current sampling signal Iac, so that the input current tracks Vac, and the single-stage PFC function is realized.
In order to realize the function of a single-stage PFC, the loop of output feedback needs to be far less than 2 times of power frequency, the bandwidth is very low, the loop is generally designed to be 10 Hz-20 Hz, and therefore the power frequency ripple on the output voltage is very large.
Disclosure of Invention
The invention provides an LLC circuit of a single-stage PFC, thereby effectively solving the problems in the background art.
In order to achieve the purpose, the invention adopts the technical scheme that:
an LLC circuit with a single stage PFC, comprising: an input rectifier, a Boost converter and an isolated DC-DC converter;
the input rectifier rectifies input voltage and forms a loop for charging a capacitor in the Boost converter; the Boost converter further comprises a first inductor, a first switching element and a second switching element; the isolation DC-DC converter comprises a bridge arm structure, a resonant inductor, a resonant capacitor, a transformer and a rectification filter circuit, wherein the bridge arm structure shares a first switching element and a second switching element with the Boost converter;
the primary winding of the transformer is driven by the bridge arm structure, and the secondary winding provides output to a load through the rectification filter circuit;
one end of the first inductor is connected with the first output end of the input rectifier, the other end of the first inductor is connected with a middle tap of the primary winding, and a connection point is connected with the middle point of the bridge arm structure through a branch comprising part of the primary winding, the resonant inductor and the resonant capacitor; or the other end of the first inductor is connected with one end of the primary winding, a connection point is connected with the midpoint of the bridge arm structure through a branch comprising the resonant inductor and the resonant capacitor, and the other end of the primary winding is connected with the first output end of the input rectifier.
Further, the input rectifier is a full-wave rectifier bridge circuit.
Further, in the Boost converter, a second capacitor is connected in parallel with the capacitor.
Further, the rectification filter circuit comprises a full-wave rectifier bridge circuit.
Furthermore, the rectification filter circuit comprises two rectification elements respectively connected with two ends of the secondary winding, one end of the load is connected with a middle tap of the secondary winding, the secondary winding is divided into two parts, and each part supplies energy to the load through the rectification elements.
Further, a diode is arranged between the input rectifier and the first inductor, and the diode is arranged on the direct current side or the alternating current side of the input rectifier.
Further, a diode is arranged on one side of the capacitor.
Furthermore, the other end of the first inductor is connected with a middle tap of the primary winding, so that the primary winding forms two parts in series, the two parts are respectively provided by two transformers, the secondary winding comprises two parts in parallel and is also respectively provided by the two transformers, and the two parts of the primary winding in series and the two parts of the secondary winding in parallel are respectively and correspondingly arranged.
Through the technical scheme of the invention, the following technical effects can be realized:
in the invention, the voltage at two ends of the first inductor is the difference value of the input voltage and the sum of the voltage of the primary winding, the resonant inductor and the resonant capacitor, the ripple current on the first inductor is small, the working state of LLC of the whole circuit is not influenced, the characteristic of LLC is reserved, ZVS can be realized by the first switching element and the second switching element, thereby high efficiency and high power density can be realized, the bandwidth of an output voltage ring can be designed to be higher, the power frequency ripple of secondary side output voltage is small, the use of power switching elements is saved by the sharing of the first switching element and the second switching element in a bridge arm structure and a Boost converter, thereby the cost is reduced, the product volume is reduced, and the soft switching mode is effectively realized.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments described in the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a first common single-stage PFC implementation in the background art;
fig. 2 is a second common single-stage PFC implementation of the prior art;
FIG. 3 is a topology of a first embodiment of the present invention;
FIG. 4 is a schematic diagram of a mode-operation of the topology of FIG. 3;
FIG. 5 is a schematic diagram of a mode two operation of the topology of FIG. 3;
fig. 6 is a Boost equivalent circuit when the second switching element is turned on;
fig. 7 is a Boost equivalent circuit when the second switching element is turned off;
fig. 8 is a topology structure in which the first inductor L1 branch is connected to one end of the primary winding of the transformer;
fig. 9 is a topology of the connection of the first inductor L1 branch to the center tap of the primary winding of the transformer;
FIG. 10 is a topology of a second embodiment of the present invention;
FIG. 11 is a schematic representation of a mode-operation of the topology of FIG. 10;
FIG. 12 is a schematic diagram of a mode two operation of the topology of FIG. 10;
FIG. 13 is a schematic diagram of the topology of FIG. 3 with the diodes disposed on the AC side;
FIG. 14 is a schematic diagram of an embodiment of the present invention in which two primary windings are provided by two transformers;
FIG. 15 is an equivalent circuit of FIG. 13;
FIG. 16 is another equivalent circuit of FIG. 13;
reference numerals: 31-input rectifier, 32-Boost converter, 33-isolated DC-DC converter.
Detailed Description
The invention is further described below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.
As shown in fig. 3, an LLC circuit of a single-stage PFC includes: an input rectifier 31, a Boost converter 32 and an isolated DC-DC converter 33; the input rectifier 31 rectifies the input voltage and forms a loop that charges a capacitor C1 in the Boost converter; boost converter 32 further includes a first inductor L1, a first switching element Q1, and a second switching element Q2; the isolated DC-DC converter 33 includes a bridge arm structure sharing the first switching element Q1 and the second switching element Q2 with the Boost converter 32, a resonant inductor Lr, a resonant capacitor Cr, a first transformer T1, and a rectifying filter circuit; the primary winding of the first transformer T1 is driven by a bridge arm structure, and the secondary winding provides output to a load through a rectifier filter circuit.
In this embodiment, one end of the first inductor L1 is connected to the first output end of the input rectifier 31, the other end of the first inductor L1 is connected to a center tap of the primary winding, so that the primary winding forms a first primary winding P1 and a second primary winding P2, a connection point is connected to a midpoint of the bridge arm structure through a branch including the second primary winding P2, the resonant inductor Lr, and the resonant capacitor Cr, and the other end of the first primary winding P1 is connected to the first output end of the input rectifier 31.
The working method of the circuit comprises the following steps:
modality one as shown in fig. 4: when the first switching element Q1 is turned off and the second switching element Q2 is turned on, the input rectifier 31 stores energy for the first inductor L1, and the current of the first inductor L1 rises; the capacitor C1 provides energy to the first transformer T1 and the voltage drops.
Modality two as shown in fig. 5: when the first switching element Q1 is turned on and the second switching element Q2 is turned off, the first inductor L1 charges the capacitor C1, and the voltage of the capacitor C1 rises; the current of the first inductor L1 is reduced, and the stored energy is reduced; the resonant inductor Lr and the resonant capacitor Cr provide energy to the first transformer T1.
In the invention, the voltage at two ends of the first inductor L1 is the difference value of the sum of the input voltage Vin and the voltages of the primary winding, the resonant inductor Lr and the resonant capacitor Cr, the ripple current on the first inductor L1 is small, and meanwhile, ZVS can be realized by the first switching element Q1 and the second switching element Q2, so that high efficiency and high power density can be realized, the bandwidth of the output voltage ring can be designed to be higher, and the power frequency ripple of the secondary output voltage is small. The first switching element Q1 and the second switching element Q2 are shared in the bridge arm structure and the Boost converter 32, so that the use of power switching elements is saved, the cost is reduced, the product volume is reduced, and the soft switching mode is effectively realized.
When the second switching element Q2 is turned on, the Boost equivalent circuit is as shown in fig. 6, and the voltage VL = Vin-P2/S1 × Vout of the first inductor L1 is compared with that of the conventional Boost circuit, VL = Vin, so that the voltage of the first inductor L1 is relatively small and the ripple current is small. When the second switching element Q2 is turned off, the Boost equivalent circuit is as shown in fig. 7, and the voltage of the first inductor L1 is
VL = Vin-Vbus-P1/S1 × Vout, compared to the Boost circuit, VL = Vin-Vbus, so the first inductor L1 has a relatively small voltage and a small ripple current.
Assuming operation in CCM mode, it can be calculated
Vbus=(Vin - D*P2/S1*Vout - (1-D)*P1*S1*Vout)/(1-D)
Vbus = Vin/(1-D), compared to Boost circuits, so the capacitance C1 voltage is small;
the meaning in the above formula is as follows:
VL is the voltage across the first inductor L1;
vin is the input voltage;
P2/S1 is the turn ratio of the second section of the primary winding P2 to the first section of the secondary winding S1;
vout is the output voltage;
vbus is the voltage across the electrolytic capacitor, i.e. across capacitor C1;
d is the duty cycle;
wherein, P2/S1 and D are constants, and other parameters are voltage values, so that the unit consistency is ensured.
The input rectifier 31 is a full-wave bridge circuit, and as shown in mode one in fig. 4, the ac input current passes through the first diode D1 and the fourth diode D4 in the full-wave bridge circuit to store energy for the first inductor L1. In mode two as shown in fig. 5, the first inductor L1 charges the capacitor C1 through the first diode D1 and the fourth diode D4.
As another embodiment, as shown in fig. 8, the other end of the first inductor L1 is connected to one end of the primary winding, and the connection point is connected to the midpoint of the bridge arm structure through a branch including the resonant inductor Lr and the resonant capacitor Cr, that is, in the figure, one pin a of the first transformer T1 is directly connected to the positive electrode of the capacitor C1, and the other pin C is connected to the negative electrode of the capacitor C1, so that the primary winding only includes the first section of the primary winding P1; the resonance inductor Lr and the resonance capacitor Cr are connected between the midpoint of the bridge arm structure and the pin C. This embodiment and the way in which the first inductor L1 is connected to the center tap of the primary winding are both effective to achieve the objects of the present invention.
When the primary winding is divided into the first-stage primary winding P1 and the second-stage primary winding P2, the turn ratio of the first-stage primary winding P1 and the second-stage primary winding P2 is arbitrary.
As a preferred example of the above embodiment, as shown in fig. 9, in the Boost converter 32, a second capacitor C2 is connected in parallel with the capacitor C1, so as to improve the reliability of the circuit and increase the service life of the capacitor.
In the present invention, the rectifying-smoothing circuit includes a full-wave rectifying bridge circuit, and in mode one shown in fig. 4, the electrode of the first secondary winding S1 of the first transformer T1 is positive and negative, and the fifth diode D5 and the eighth diode D8 are turned on to supply power to the load. In mode two shown in fig. 5, the electrode of the secondary winding S1 of the first segment of the first transformer T1 is positive, negative, and the sixth diode D6 and the seventh diode D7 are turned on to supply energy to the load.
As another embodiment of the rectifying and smoothing circuit, as shown in fig. 10, the rectifying and smoothing circuit includes two rectifying elements respectively connected to two ends of the secondary winding, one end of the load is connected to a center tap of the secondary winding, and the secondary winding is divided into two parts, namely a first secondary winding S1 and a second secondary winding S2, wherein each part supplies energy to the load through the rectifying elements. Specifically, as shown in fig. 11, the mode one in the above embodiment is shown, in which the electrode of the first secondary winding S1 of the first transformer T1 is positive, negative, and the rectifying element connected to one end of the first secondary winding S1 is turned on to provide energy to the load; as shown in fig. 12, the second mode in the above embodiment is shown, in which the electrode of the second secondary winding S2 of the first transformer T1 is positive, and the rectifying element connected to one end of the second secondary winding S2 is turned on to provide energy to the load. Wherein, the rectifier element only needs to adopt the diode.
As a preference of the above embodiment, a diode is disposed between the DC side or ac side of the input rectifier 31 and the first inductor L1, and as shown in fig. 3, 8 to 10, a ninth diode D9 is disposed on the DC side of the input rectifier 31 and connected in series with the first inductor L1; alternatively, as shown in fig. 13, an eleventh diode D11 and a twelfth diode D12 are provided on the AC side of the input rectifier 31. With continued reference to fig. 13, the rectifier filter circuit may further include a capacitor C0. In order to reduce the voltage fluctuation of the capacitor C1, a twelfth diode D10 is provided on the capacitor C1 side.
In a specific implementation, as shown in fig. 14, as another embodiment of the connection between the other end of the first inductor L1 and the center tap of the primary winding, the center tap is used as a boundary, the first primary winding P1 is provided by a first transformer T1, and the second primary winding P2 is provided by a second transformer T2, so that the primary windings form two parts connected in series, and the secondary winding includes two first secondary windings S1 arranged in parallel and also provided by a first transformer T1 and a second transformer T2, respectively, so that the two first secondary windings S1 arranged in parallel respectively correspond to the first primary winding P1 and the second primary winding. The above topology also achieves the technical objects of the present invention. The various topologies provided in the above embodiments of the present invention can be implemented in the present invention, and do not cover all embodiments, and the topologies shown in fig. 15 and 16 are all within the scope of the present invention.
The foregoing illustrates and describes the principles, general features, and advantages of the present invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims (8)

1. An LLC circuit with a single stage PFC, comprising: an input rectifier, a Boost converter and an isolated DC-DC converter;
the input rectifier rectifies input voltage and participates in a loop for charging a capacitor in the Boost converter; the Boost converter further comprises a first inductor, a first switching element and a second switching element, and a capacitor in the Boost converter is connected in parallel with a bridge arm structure formed by connecting the first switching element and the second switching element in the Boost converter in series; the isolation DC-DC converter comprises a bridge arm structure, a resonant inductor, a resonant capacitor, a transformer and a rectification filter circuit, wherein the bridge arm structure shares a first switching element and a second switching element with the Boost converter;
one end of the primary winding of the transformer is connected with one end of a first switch element, the other end of the primary winding of the transformer is connected with the other end of the first switch element and one end of a second switch element through a resonant inductor and a resonant capacitor, the other end of the second switch element is connected with a second output end of the input rectifier, the primary winding of the transformer is driven by the bridge arm structure, and the secondary winding provides output to a load through the rectifier filter circuit;
the input rectifier is a full-wave rectifier bridge circuit and is provided with two input ends and two output ends, the two input ends are respectively connected with two ends of an alternating current input power supply, a first output end is connected with one end of a first inductor, a second output end is connected with the other end of a second switch element, one end of the first inductor is connected with the first output end of the input rectifier, the other end of the first inductor is connected with a middle tap of the primary winding, and a connection point is connected with the middle point of the bridge arm structure through a branch consisting of part of the primary winding, the resonant inductor and the resonant capacitor; or the other end of the first inductor is connected with one end of the primary winding, and a connection point is connected with the midpoint of the bridge arm structure through a branch consisting of the resonant inductor and the resonant capacitor; the other end of the primary winding is connected with the first output end of the input rectifier.
2. The LLC circuit of claim 1, wherein said input rectifier is a full wave rectifier bridge circuit.
3. The LLC circuit of claim 1, wherein a second capacitor is connected in parallel with the capacitor in the Boost converter.
4. The LLC circuit of a single stage PFC according to any one of claims 1 to 3, wherein said rectifying and filtering circuit comprises a full wave rectifier bridge circuit.
5. The LLC circuit of one-stage PFC according to any one of claims 1 to 3, wherein said rectifying and filtering circuit comprises two rectifying elements connected to two ends of said secondary winding respectively, one end of a load being connected to a center tap of said secondary winding to divide said secondary winding into two parts, wherein each part supplies energy to said load through a rectifying element respectively.
6. The LLC circuit of claim 1, wherein a diode is disposed between said input rectifier and said first inductor, said diode being disposed on the DC side of said input rectifier.
7. The LLC circuit of claim 1 wherein a diode is provided between said capacitor and said first output of said input rectifier.
8. The LLC circuit of a single-stage PFC according to any one of claims 1 to 3, 6 and 7, wherein the other end of said first inductor is connected to a center tap of said primary winding, such that said primary winding forms two parts in series, and said two parts are respectively provided by two transformers, and said secondary winding comprises two parts in parallel, and is also respectively provided by two said transformers, wherein said two parts of primary winding in series and said two parts of secondary winding in parallel are respectively provided correspondingly.
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CN108471232A (en) * 2018-04-24 2018-08-31 上海推拓科技有限公司 Double rectifier bridge formula single stage power factor correction power circuit

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