CN112865538A - High-voltage-reduction-ratio dual-resonance three-level LLC resonant converter and control method thereof - Google Patents

High-voltage-reduction-ratio dual-resonance three-level LLC resonant converter and control method thereof Download PDF

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CN112865538A
CN112865538A CN202110058301.XA CN202110058301A CN112865538A CN 112865538 A CN112865538 A CN 112865538A CN 202110058301 A CN202110058301 A CN 202110058301A CN 112865538 A CN112865538 A CN 112865538A
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resonant
switching tube
source electrode
switch tube
converter
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马红波
卢松
徐帅东
易俊宏
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Southwest Jiaotong University
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Southwest Jiaotong University
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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
    • 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
    • H02M3/33569—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 having several active switching elements
    • 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
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • 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

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Dc-Dc Converters (AREA)

Abstract

The invention discloses a high step-down ratio double-resonance three-level LLC resonant converter and a control method thereof. The converter comprising a flying capacitor CFLYThree-level bridge arm and flying capacitor CMIDThe resonant circuit comprises a first resonant network, a first isolation transformer, a second resonant network, a second isolation transformer and a rectifying circuit. The three-level bridge arm is formed by sequentially connecting a first switching tube, a second switching tube, a third switching tube and a fourth switching tube in series and then connecting the first switching tube, the second switching tube, the third switching tube and the fourth switching tube to the positive end and the negative end of an input, and a flying capacitor CFLYA flying capacitor C connected between the source electrode of the first switching tube and the source electrode of the third switching tubeMIDAnd the source electrode of the second switching tube and the source electrode of the fourth switching tube are connected in a bridging mode. The invention has higher voltage reduction capability and is embodied in that the peak-to-peak value of the resonant cavity input voltage inverted by the three-level bridge arm is the input voltage VINThe number of turns of the transformer is reduced, so that the loss of a single transformer is reduced, and especially under the condition that the primary current of the transformer is large and the number of turns is large, the overall efficiency and power density of the converter can be greatly improved.

Description

High-voltage-reduction-ratio dual-resonance three-level LLC resonant converter and control method thereof
Technical Field
The invention relates to the technical field of double-resonance converters, in particular to a high-voltage-reduction-ratio double-resonance three-level LLC resonance converter and a control method thereof.
Background
LLC resonant converters have received extensive attention in academia and industry due to advantages such as simple topology and superior soft switching characteristics. The double-resonance LLC converter is provided with two resonant cavities and an isolation transformer, so that the double-resonance LLC converter is high in efficiency, good in heat dissipation characteristic, easy to realize double-path output and the like, and is widely applied.
A widely used half-bridge dual-resonant LLC resonant converter in industry and industry is shown in fig. 1a, 1 b. The structure shown in fig. 1a is a structure in a two-path output scene, and the structure shown in fig. 1b is a structure in a one-path output scene. Each of the half-bridge dual-resonant LLC resonant converters shown in fig. 1a and 1b is composed of a switching inverter bridge arm circuit, a resonant circuit, a transformer, a rectifier circuit, and the like, where the switching inverter bridge arm circuit is composed of two switching tubes Q1、Q2The series connection is used for inverting the direct current voltage into a square wave; the resonant circuit helps to realize the soft switching characteristic of the switching tube; the transformer and the rectifying circuit are used for transmitting energy to a load end. The control strategy of the half-bridge double-resonant LLC resonant converter shown in FIG. 1a and FIG. 1b is shown in FIG. 2, and the switching tube Q in the topology1Driven by a 50% duty cycle control signal, and switching transistor Q2Driven by another complementary 50% duty ratio control signal, so that the peak-to-peak value of the input voltage of the two resonant cavities inverted by the bridge arms is equal to the input voltage VIN. In practical application, dead time is required between the driving signals of the two tubes for preventing the tubes from being connected in a straight-through manner and realizing zero-voltage conduction of the switching tubes.
With the development of modern industrial systems, the disadvantages of the two half-bridge LLC dual-resonant converter topologies shown in fig. 1a and 1b are gradually revealed. Under high-voltage input occasion or high-voltage reduction ratio scene, the problem of insufficient voltage reduction capability exists in the existing double-resonance half-bridge LLC converter, the number of turns of the primary side of the transformer is increased, extra loss and volume of the two transformers are increased, and the efficiency and the power density of the converter are not improved favorably.
Disclosure of Invention
The invention aims to provide a high step-down ratio dual-resonance three-level LLC resonant converter and a control method thereof.
The technical scheme for realizing the purpose of the invention is as follows:
a high voltage reduction ratio double-resonance three-level LLC resonance converter comprises a three-level bridge arm; the three-level bridge arm comprises a first switch tube, a second switch tube, a third switch tube and a fourth switch tube which are sequentially connected in series, and further comprises a first flying capacitor bridged between the source electrode of the first switch tube and the source electrode of the third switch tube and a second flying capacitor bridged between the source electrode of the second switch tube and the source electrode of the fourth switch tube, wherein the drain electrode of the first switch tube is connected to the positive electrode of a power supply, and the source electrode of the fourth switch tube is connected to the negative electrode of the power supply; the first resonant network, the first isolation transformer and the first rectifying circuit are sequentially connected; the positive input end of the first resonant network is connected to the drain electrode of the first switch tube, and the negative input end of the first resonant network is connected to the source electrode of the first switch tube; the second resonant network, the second isolation transformer and the second rectifying circuit are sequentially connected; and the positive input end of the second resonant network is connected to the source electrode of the third switching tube, and the negative input end of the second resonant network is connected to the source electrode of the fourth switching tube.
The further technical scheme is as follows: the output end of the first rectifying circuit is used for being connected with a first load, and the output end of the second rectifying circuit is used for being connected with a second load. Or the number of turns of the first isolation transformer is equal to that of the second isolation transformer, and the output end of the first rectifying circuit is connected with the output end of the second rectifying circuit in parallel and then used for connecting a load.
According to the control method of the high step-down ratio double-resonance three-level LLC resonant converter, a first group of driving signals with 50% duty ratio are simultaneously applied to a first switching tube and a third switching tube, and a second group of driving signals with 50% duty ratio are simultaneously applied to a second switching tube and a fourth switching tube; the first set of drive signals and the second set of drive signals are complementary; a dead time is provided between the first set of drive signals and the second set of drive signals.
Compared with the prior art, the invention has the advantages that,
1. the converter has higher voltage reduction capability, and is embodied in that the peak-to-peak value of the resonant cavity input voltage inverted by the three-level bridge arm is the input voltage VINAnd half of the high buck ratio characteristics make the converter more suitable for high voltage input or high buck ratio applications.
2. The high step-down ratio characteristic of the converter is beneficial to reducing the turns of the transformer, thereby reducing the loss of a single transformer, and particularly greatly improving the overall efficiency and power density of the converter under the condition that the primary current of the transformer is large and the number of turns is large.
3. The four switching tubes on the primary side of the converter are driven by two pairs of control signals with 50% duty ratio, and the control strategy is simple and easy to implement.
Drawings
Fig. 1a is a diagram of a conventional half-bridge dual-resonant LLC resonant converter in a two-way output scenario.
Fig. 1b shows a conventional half-bridge dual-resonant LLC resonant converter in a single-output scenario.
Fig. 2 is a schematic diagram of a control strategy of a conventional half-bridge dual-resonant LLC resonant converter.
Fig. 3a is a double-resonance half-bridge three-level LLC topology under a two-way output scenario of the present invention.
Fig. 3b is a double-resonant half-bridge three-level LLC topology under the single-output scenario of the present invention.
Fig. 4 is a waveform diagram of steady-state operation of the dual-resonant half-bridge three-level LLC at single-path output of the present invention.
FIG. 5a is the equivalent circuit diagram of the single output operating mode I of the present invention.
Fig. 5b is an equivalent circuit diagram of the present invention in the operating state II when outputting one-way.
Fig. 5c is an equivalent circuit diagram of the working state III when the single output is performed according to the present invention.
Fig. 5d is an equivalent circuit diagram of the present invention in a single output operating state IV.
Fig. 6a and 6b are operation waveform diagrams of actual measurement key signals of a single-path output prototype.
The labels in the figure are: vINThe power supply voltage is input. Q1、Q2、Q3、Q4And a switch tube. CQ1、CQ2、CQ3、CQ4And the parasitic capacitance of the switching tube. DQ1、DQ2、DQ3、DQ4A switching body diode. CFLY、CMIDA flying capacitor. L isr1A resonant inductance in the first resonant network. L ism1And exciting an inductor in the first resonant network. Cr1A resonant capacitor in the first resonant network. TR1, first isolation transformer. L isr2And a resonant inductance in the second resonant network. L ism2And exciting an inductance in the second resonant network. Cr2A resonant capacitor in the first resonant network. TR2, second isolation transformer. D1、D2、D3、D4And a secondary side rectifying diode. C0And outputting a filter capacitor. RLAnd a single output load. RL1And the first path of load is output by two paths. RL2And the second load is loaded when the two paths output. V0And outputting the voltage in a single way. V01And the first path outputs voltage when the two paths output. V02And the second path outputs voltage when the two paths output. VABAnd the voltage between the point A and the point B is the input voltage of the first resonant network. VCDAnd the voltage between the point C and the point D is the input voltage of the second resonant network. VCFLYFlying capacitor CFLYA steady state operating voltage. VCMIDFlying capacitor CMIDA steady state operating voltage. Vgs_Q1、Vgs_Q2、Vgs_Q3、Vgs_Q4And four switching tube driving waveforms. Vds_Q1、Vds_Q2、Vds_Q3、Vds_Q4And the voltage waveform between the drain electrode and the source electrode when the four switching tubes work. i.e. iLr1The resonant current waveform in the first resonant network. i.e. iLr2The resonant current waveform in the second resonant network. i.e. iD1、iD2、iD3、iD4And a secondary side rectifying diode current waveform. n, the number of turns of the isolation transformers TR1 and TR2 when the single output is obtained. n is1Isolation in two-way outputTransformer TR1 turns. n is2And the number of turns of the isolation transformer TR2 is two-way output.
Detailed Description
The invention provides a novel double-resonance half-bridge three-level LLC resonance converter with a high step-down ratio and a control method thereof. The main advantages of this topology are: compared with a traditional half-bridge three-double resonance LLC converter, the input voltage of the two resonant cavities is reduced by half, namely the square wave inverter bridge arm has higher voltage reduction capability, which means that the number of turns of the primary sides of the two transformers can be reduced by half, and the transformer loss and the size of the converter are reduced.
The high step-down ratio double-resonance three-level LLC resonance converter is characterized by comprising a flying capacitor CFLYThree-level bridge arm and flying capacitor CMIDThe resonant circuit comprises a first resonant network (first resonant cavity), a first isolation transformer, a second resonant network (second resonant cavity), a second isolation transformer and a rectifying and filtering circuit.
The three-level bridge arm is composed of a first switching tube, a second switching tube, a third switching tube and a fourth switching tube which are sequentially connected in series and then connected to the positive end and the negative end of an input, wherein the four switching tubes respectively comprise parasitic body diodes and parasitic capacitors of the four switching tubes. Flying capacitor CFLYA flying capacitor C connected between the source electrode of the first switching tube and the source electrode of the third switching tubeMIDAnd the source electrode of the second switching tube is connected with the source electrode of the fourth switching tube in a bridging mode.
For a single-path output scene and a two-path scene, the dual-resonance three-level LLC resonant converter of the present invention has two application structure forms, as shown in fig. 3a and fig. 3b, respectively. It is noted that, in the scenario of dual output application, the number of turns n of the isolation transformers TR1 and TR21、n2The voltages of the two paths of outputs can be equal or unequal, depending on whether the voltages of the two paths of outputs are required to be equal, but when the actual closed loop carries out output control, only one path of outputs is selected as the main control, and the other path of outputs works in an open loop state; in the single-output application scenario, the numbers of turns of the isolation transformers TR1 and TR2 must be equal, and are both n.
The converter regulates output power by changing the frequency of the control signal of the switching tubeAnd (6) pressing. Moreover, the converter proposed by the present invention can adopt the same control strategy as the existing half-bridge dual-resonant LLC converter, namely: for the first switch tube Q1And a third switching tube Q3Applying a set of driving signals with 50% duty ratio to the second switching tube Q2And a fourth switching tube Q4Another set of complementary 50% duty cycle drive signals is applied, but with a dead band between the two sets of drive signals. The closed-loop control of the topology provided by the invention is simple to operate and easy to realize.
Fig. 3a and 3b are schematic diagrams of the basic structure of the present invention. Fig. 3a shows a structure in a double-resonance half-bridge three-level LLC topology two-way output application scenario, and fig. 3b shows a structure in a double-resonance half-bridge three-level LLC topology one-way output application scenario. The specific circuit is composed of a flying capacitor CFLYThree-level bridge arm and flying capacitor CMIDThe first resonant network, the first isolation transformer, the second resonant network, the second isolation transformer and the rectifying and filtering circuit. The secondary side of the two isolation transformers can adopt a full-wave rectification mode or a full-bridge rectification mode, wherein the full-wave rectification mode is taken as an example, D1、D2、D3、D4Are four rectifying diodes. The two resonant networks are used for realizing zero-voltage switching of the switching tube and zero-current switching of the rectifier diode.
The specific control mode of the converter provided by the invention is as follows: for the first switch tube Q1And a third switching tube Q3Applying a set of driving signals with 50% duty ratio to the second switching tube Q2And a fourth switching tube Q4Another set of complementary 50% duty cycle drive signals is applied with a dead band between the two sets of drive signals. The converter for single-path and double-path output application can adjust output voltage by changing the switching frequency of a driving signal of a switching tube, wherein one path of output is selected to be used as a main control under the application of double-path output, and the other path of output works in an open-loop mode. Since the two topology principles shown in fig. 3a and fig. 3b are similar, the analysis is performed by taking the single-output application scenario shown in fig. 3b as an example. Before performing a detailed modal analysis, the following assumptions are made:
1. the output filter capacitor is large enough to make the output voltage as a constant value in one switching period;
2. the resonant parameters in the two resonant cavities being identical, i.e. resonant capacitance Cr1、Cr2Are all equal to CrResonant inductance Lr1、Lr2Are all equal to LrExcitation inductance Lm1、Lm2Are all equal to Lm；
3. Flying capacitor CFLYAnd CMIDThe resonance capacitance is large enough not to affect the resonance frequency of the resonance network.
So that f can be usedrRepresenting the resonant capacitance CrAnd a resonant inductor LrResonant frequency of both, by fmRepresenting the resonant capacitance CrResonant inductor LrAnd an excitation inductance LmResonant frequency of the three, andr>fm. Due to the magnitude relationship between the switching frequency fs and the resonant frequency fr, the operating mode of the converter is divided into three modes, namely, the under-resonant mode (fs)<fr), quasi-resonant mode (fs ═ fr), and over-resonant mode (fs)>fr). The operation principle of the converter in different modes is slightly different, but the LLC converter has the highest efficiency when operating in a quasi-resonant mode (fs ═ fr). Therefore, the present description only deals with the case of fs ═ fr to analyze the working principle, and the other two analysis methods are similar. In the quasi-resonant mode (fs ═ fr) mode, one switching period of the converter can be divided into 4 working modes, and in the steady-state operation, the waveforms of each key voltage and current are as shown in fig. 4.
The specific working principle is as follows:
(1) operating state I, as shown in fig. 5 a: t is t0<t<t1And (5) stage. At t0Time, Q1And Q3Zero voltage conduction, input voltage V of the first resonant cavity and the second resonant cavityABAnd VCD0 and 0.5V respectivelyIN. In the first resonant network, Lr1And Cr1Series resonance, reverse resonance of resonant current, secondary side rectifier diode D1On, the primary side voltage of the first isolation transformer is clamped to-nV0With excitation current starting from a maximum value at-nV0/LmIs linearly decreased and stored in the resonant capacitor Cr1The energy in (b) is transferred to the load through the first isolation transformer as a difference between the resonant current and the excitation current. In the second resonant network, Lr2And Cr2Series resonance, forward resonance of resonant current, secondary side rectifier diode D4On, the primary side voltage of the second isolation transformer is clamped to nV0With excitation current starting from a minimum value at nV0/LmThe slope of the resonant current and the excitation current are linearly increased, and the difference between the resonant current and the excitation current transfers energy to the load through the second isolation transformer. In this stage, the source of the resonant current in the second resonant network is divided into two parts, half of the resonant current is from the input and flows through the flying capacitor CFLYAnd to flying capacitor CFLYCharging, the other half of resonant current is driven by flying capacitor CMIDProviding, i.e. flying capacitors CMIDAnd (4) discharging.
(2) Operating state II, as shown in fig. 5 b: t is t1<t<t2And (5) stage. At t1Time, Q1And Q3Simultaneously turn off and flow through the secondary side rectifier diode D1、D4The current just resonates to 0, the primary side resonant current in the first resonant network and the secondary side resonant current in the second resonant network are respectively equal to the minimum value and the maximum value of the excitation current, the input voltage of the first resonant network is reversed from 0, and the input voltage of the second resonant network is reversed from 0.5VINThe commutation is started. In the first resonant network, Lr1、Lm1、Cr1The three elements resonate together and, because of the long resonant period of the three elements, the resonant current in the first resonant cavity, which may remain approximately within the dead time, is approximately constant, equal to its excitation current. Similarly, in the second resonant network, Lr2、Lm2、Cr2The three elements resonate together in this phase, the resonant current being approximately equal to the excitation current. In this stage, the exciting currents of the two resonant networks are commonly supplied to the switching tube Q1、Q3Output capacitor CQ1、CQ3Charging while supplying Q to the switch tube2、Q4Output capacitor CQ2、CQ4Discharge of Q2、Q4The zero voltage conduction creates conditions.
(3) Operating state III, as shown in fig. 5 c: t is t2<t<t3And (5) stage. At t2Time of day, Vds_Q1And Vds_Q3Has been charged to 0.5VIN，Vds_Q2And Vds_Q4Is discharged to 0, at which time Q2And Q4Zero voltage conduction, the first resonant network input voltage has been commutated to 0.5VIN，Lr1And Cr1Starting series resonance, the input voltage of the second resonance network has been commutated to 0, Lr2And Cr2The series resonance is started. Similar to the operating state I, since the secondary side rectifier diode D is in this stage2And D3Is turned on, so that the primary side voltage of the first isolation transformer is clamped to nV0With excitation current starting from a minimum value at nV0/LmThe slope of the second isolation transformer is linearly increased, and the primary side voltage of the second isolation transformer is clamped to-nV0With excitation current starting from a maximum value at-nV0/LmThe slope of (a) decreases linearly and the resonant current in the two resonant networks is always greater than the excitation current, the difference between the two transferring energy to the load through the two transformers.
(4) Operating state IV, as shown in fig. 5 d: t is t3<t<t4And (5) stage. At t3Time, Q2And Q4Is turned off simultaneously and flows through a secondary side rectifier diode D similar to the working state II2、D3The current just resonates to 0, the primary side resonant current in the first resonant network and the secondary side resonant current in the second resonant network are respectively equal to the maximum value and the minimum value of the exciting current, and the input voltage of the first resonant network is controlled to be 0.5VINThe commutation is started and the input voltage of the second resonant network commutates from 0. Similarly, in both resonant networks, the resonant inductor, the excitation inductor and the resonant capacitor resonate together, so that both resonant currents can be considered to be approximately constant and equal to the excitation currents. In this stage, the exciting currents of the two resonant networks are commonly supplied to the switching tube Q2、Q4Output capacitor CQ2、CQ4Charging while supplying Q to the switch tube1、Q3Output capacitor CQ1、CQ3Discharge of electricityIs Q1、Q3The zero voltage conduction creates conditions.
In order to verify the correctness of the theoretical analysis of the circuit, a 48V input and 6V output double-resonance half-bridge three-level LLC two-way output prototype is set up in a laboratory, and the maximum output current is 40A. When the output current of the prototype is 40A, the steady-state operating voltage waveform of the prototype is shown in fig. 6a and 6b, wherein each channel in fig. 6a sequentially comprises: fourth switch tube Q4Driving voltage, fourth switching tube Q4The resonant current in the first resonant network and the resonant current in the second resonant network. The first and second channel waveforms in FIG. 6b are changed to the first flying capacitor CFLYAnd a second flying capacitor CMIDThe other two channels still have two resonant current waveforms. According to experimental results and actually measured waveforms, after circuit parameters are reasonably designed, zero voltage conduction can be realized by four main switches in the topology, and the steady-state voltage and the resonant cavity input voltage of the two flying capacitors are half of the input voltage, so that the correctness of theoretical analysis is proved.
In conclusion, the two-way output and one-way output application topologies of the novel double-resonance half-bridge three-level LLC resonant converter with the high voltage reduction ratio provided by the invention keep the zero-voltage conduction and zero-current turn-off characteristics of the LLC resonant converter, but have the high voltage reduction ratio characteristic, so that the novel double-resonance half-bridge three-level LLC resonant converter with the high voltage reduction ratio is more suitable for high-voltage input or high voltage reduction ratio application occasions. The high voltage reduction ratio characteristic relieves the requirement on the number of turns of the transformer, can reduce the number of turns of the transformer, effectively reduces the loss of a single transformer, and can greatly improve the integral efficiency and power density of the converter particularly under the condition that the primary side current of the transformer is large and the number of turns is large. In addition, the four switching tubes on the primary side are driven by two pairs of control signals with 50% duty ratio, and the four switching tubes on the primary side have the characteristics of simple control strategy and easiness in implementation.

Claims (4)

1. A high voltage reduction ratio double-resonance three-level LLC resonant converter is characterized by comprising a three-level bridge arm; the three-level bridge arm comprises a first switch tube, a second switch tube, a third switch tube and a fourth switch tube which are sequentially connected in series, and further comprises a first flying capacitor bridged between the source electrode of the first switch tube and the source electrode of the third switch tube and a second flying capacitor bridged between the source electrode of the second switch tube and the source electrode of the fourth switch tube, wherein the drain electrode of the first switch tube is connected to the positive electrode of a power supply, and the source electrode of the fourth switch tube is connected to the negative electrode of the power supply; the first resonant network, the first isolation transformer and the first rectifying circuit are sequentially connected; the positive input end of the first resonant network is connected to the drain electrode of the first switch tube, and the negative input end of the first resonant network is connected to the source electrode of the first switch tube; the second resonant network, the second isolation transformer and the second rectifying circuit are sequentially connected; and the positive input end of the second resonant network is connected to the source electrode of the third switching tube, and the negative input end of the second resonant network is connected to the source electrode of the fourth switching tube.
2. A high step-down ratio dual-resonant three-level LLC resonant converter as claimed in claim 1, wherein the output of the first rectifying circuit is adapted to be connected to a first load, and the output of the second rectifying circuit is adapted to be connected to a second load.
3. The dual-resonant three-level LLC resonant converter with the high step-down ratio as claimed in claim 1, wherein the first isolation transformer and the second isolation transformer have the same number of turns, and the output end of the first rectifying circuit is connected in parallel with the output end of the second rectifying circuit for connecting a load.
4. A control method for a high step-down ratio dual resonant three level LLC resonant converter as claimed in claim 1, 2 or 3, wherein a first set of 50% duty cycle drive signals is applied simultaneously to the first switching tube and the third switching tube, and a second set of 50% duty cycle drive signals is applied simultaneously to the second switching tube and the fourth switching tube; the first set of drive signals and the second set of drive signals are complementary; a dead time is provided between the first set of drive signals and the second set of drive signals.
CN202110058301.XA 2021-01-15 2021-01-15 High-voltage-reduction-ratio dual-resonance three-level LLC resonant converter and control method thereof Pending CN112865538A (en)

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CN115296540A (en) * 2022-03-15 2022-11-04 电子科技大学 Novel mix and fall isolated form and press converter

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CN101047337A (en) * 2007-04-12 2007-10-03 艾默生网络能源有限公司 Three-level LLC resonance inverter
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Publication number Priority date Publication date Assignee Title
CN115296540A (en) * 2022-03-15 2022-11-04 电子科技大学 Novel mix and fall isolated form and press converter
CN115296540B (en) * 2022-03-15 2024-04-12 电子科技大学 Isolation type hybrid buck converter

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Application publication date: 20210528