CN113452260A - Hybrid LLC resonant converter topological structure based on working mode switching and control method - Google Patents
Hybrid LLC resonant converter topological structure based on working mode switching and control method Download PDFInfo
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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
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L53/00—Methods of charging batteries, specially adapted for electric vehicles; Charging stations or on-board charging equipment therefor; Exchange of energy storage elements in electric vehicles
- B60L53/20—Methods of charging batteries, specially adapted for electric vehicles; Charging stations or on-board charging equipment therefor; Exchange of energy storage elements in electric vehicles characterised by converters located in the vehicle
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- 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
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/60—Other road transportation technologies with climate change mitigation effect
- Y02T10/70—Energy storage systems for electromobility, e.g. batteries
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- 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
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/60—Other road transportation technologies with climate change mitigation effect
- Y02T10/7072—Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors
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- 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
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/60—Other road transportation technologies with climate change mitigation effect
- Y02T10/72—Electric energy management in electromobility
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- 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
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/80—Technologies aiming to reduce greenhouse gasses emissions common to all road transportation technologies
- Y02T10/92—Energy efficient charging or discharging systems for batteries, ultracapacitors, supercapacitors or double-layer capacitors specially adapted for vehicles
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- 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
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T90/00—Enabling technologies or technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02T90/10—Technologies relating to charging of electric vehicles
- Y02T90/14—Plug-in electric vehicles
Abstract
The invention discloses a hybrid LLC resonant converter topological structure based on working mode switching, belonging to the technical field of isolated switching power supplies1And T2The control circuit comprises an output current and voltage sampling circuit, a digital controller and a driving circuit; according to the invention, the PWM modulation signal is controlled to change the on and off of the four switching tubes of the hybrid LLC resonant converter, so that the topological structure conversion of the full-bridge LLC resonant converter and the half-bridge LLC resonant converter can be realized, no additional switching device is required, the loss of the LLC resonant converter under the light load condition is reduced through the switching of the working modes of the hybrid LLC resonant converter, the efficiency of the converter is improved, and the power is transmitted through a single transformer and two switching tubes at the later stage of the charging processThe electric energy is generated, and the problem of low efficiency under light load is solved.
Description
Technical Field
The invention relates to the technical field of isolated switching power supplies, in particular to a topological structure and a control method of a hybrid LLC resonant converter based on working mode switching.
Background
With the rapid development of power electronic technology, switching power supply power converters are widely used. The LLC resonant converter is simple in structure, high in conversion efficiency and has great advantages in the design aspect of a high-power charging circuit. However, the LLC resonant converter has the problems of low light-load efficiency, difficulty in designing a high-power transformer, and the like, so that the improved LLC resonant converter is more and more concerned.
Aiming at the problems of the LLC resonant converter, a published document Full-bridge LLC resonant converter with series-parallel connected transformers for an electric field on-board charger provides a Full-bridge LLC resonant converter which adopts a structure that a primary side of a transformer is connected in series and a secondary side of the transformer is directly connected in parallel after rectification. Under the same power level, compared with a single transformer structure of the traditional LLC resonant converter, the improved converter has the advantages that the current stress of a secondary winding can be reduced, the conduction loss of a rectifier diode is small, the loss of a transformer can be reduced through a low-profile iron core, the heat dissipation is improved, and the like. However, the document focuses on the improvement of the full-bridge LLC resonant converter topology, and the problem of low light-load efficiency is not well solved. For example, "A five-switch based reconfigurable LLC converter for deep simplified PEV changing applications" studies the reconfiguration of dual LLC resonant cavities by changing the switching mode. By adding an extra switch tube to the front bridge arm at the primary side of the transformer, various alternating input voltages can be generated or the structure of the resonant cavity can be changed, so that different voltage gains can be generated in a preset frequency span. Although the regulation range is improved, the current is unevenly distributed among the switches, and a switching tube is added, so that the switching loss is increased.
Therefore, it is desirable to design a hybrid LLC resonant converter topology and control method based on operating mode switching.
Disclosure of Invention
The present invention is directed to a hybrid LLC resonant converter topology and control method based on operation mode switching, so as to solve the problems in the background art mentioned above.
In order to achieve the purpose, the invention provides the following technical scheme: a hybrid LLC resonant converter topological structure based on working mode switching comprises a main circuit and a control circuit, and is characterized in that: the main circuit comprises an input side inverter network, an LLC resonant network and a high-frequency transformer T1And T2The secondary side rectifying and filtering network and the voltage division and sampling circuit, wherein the control circuit comprises an output current and voltage sampling circuit, a digital controller and a driving circuit.
Further, in the topology structure of the hybrid LLC resonant converter based on the switching of the working modes, the high-frequency transformer T is arranged in the resonant tank1And T2The primary side is connected in series, the midpoint is connected with the negative end of the power supply, and the secondary side is connected in parallel with the load through the rectifying circuit.
A control method of a topological structure of a hybrid LLC resonant converter based on working mode switching is characterized in that load partition control is implemented by detecting load current judgment, and a PWM modulation signal is output to control a switching device Q in an input side inverter network1、Q2、Q3、Q4The switching on and off of the full bridge and the half bridge can be realized.
Further, in the control method of the topology structure of the hybrid LLC resonant converter based on the switching of the working modes, Q is controlled1、Q4And Q2、Q3When alternately switched on and off, the high-frequency transformer T is used1And T2Transformer T in1And T2Working in full-bridge mode, controlling the switch tube Q1And Q2Alternately on and off, Q3And Q4When the power is always turned off, the power passes through a high-frequency transformer T1And T2Transformer T in1Operating in half bridge mode.
Further, in the control method of the topology structure of the hybrid LLC resonant converter based on the working mode switching, in the constant-voltage charging process, the output current I is selectedO＝I2As the switching point of the working mode, the full-bridge working mode is switched to the switching point b of the half-bridge working mode, and the output current at this time is:
IO＝I3
switching the half-bridge working mode to the full-bridge working mode at a point a, wherein the output current:
IO＝I1
when the output current is larger than I1At the same time, the half-bridge working mode is switched to the full-bridge working mode, and the voltage is transmitted through the transformer T1And T2The batteries are provided with larger charging current together; when the output current is less than I3At the same time, the full-bridge working mode is switched to the half-bridge working mode through the transformer T1And the converter works in a light load state, so that the circuit loss of the converter in the light load state is reduced.
Further, the control method of the hybrid LLC resonant converter topology based on the operation mode switching includes the following steps:
s1: in a full-bridge working mode, an input side direct current power supply is connected to the LLC resonant network through an input side inverter network and then passes through a high-frequency transformer T1And T2Transformer T in1、T2Then the output is carried out after the secondary side rectification filter network;
s2: in a half-bridge working mode, an input side direct current power supply is connected to the LLC resonant network through an input side inverter network and then passes through a high-frequency transformer T1And T2Transformer T in1Then the output is output through a secondary side rectification filter network;
s3: the current and voltage sampling circuit samples the output voltage and the output current of the main circuit and performs analog-to-digital conversion to the digital controller;
s4: the digital controller takes the feedback voltage and the feedback current as input signals of an internal digital closed-loop control program, compares the input signals with a set value, and judges whether the digital controller is in a constant-current charging mode or a constant-voltage charging mode;
s5: when in the constant voltage charging mode, the output current is further compared with the working switching point.
Further, the above-mentioned is based on the mode of operation is cutIn the method for controlling the topology of the hybrid LLC resonant converter, in the above S4, if the converter is in the constant current charging mode, the controller outputs the PWM modulation signal to control the Q by using the output current and the reference current to form a closed loop negative feedback system1、Q4And Q2、Q3And conducting alternately to enable the whole to work in a full-bridge working mode, and executing the next step if the whole works in a constant-voltage charging mode.
Further, in the method for controlling the topology of the hybrid LLC resonant converter based on the switching of the operation modes, in S5, if the output current is greater than the predetermined value, I is1Still operating in a full-bridge operating mode; if the output current is less than I3And the controller outputs PWM modulation signals, and the PWM modulation signals are controlled and alternately conducted through the driving circuit and work in a half-bridge working mode until the charging of the battery of the electric automobile is finished.
Compared with the prior art, the invention has the beneficial effects that:
1. according to the invention, the PWM modulation signal is controlled to change the on and off of the four switching tubes of the hybrid LLC resonant converter, so that the topological structure conversion of the full-bridge LLC resonant converter and the half-bridge LLC resonant converter can be realized, and no additional switching device is required.
2. According to the hybrid LLC resonant converter topology structure and the control method for realizing switching of the full-bridge working mode and the half-bridge working mode, the loss of the LLC resonant converter under the condition of light load is reduced and the efficiency of the converter is improved through switching of the working modes of the hybrid LLC resonant converter.
3. The invention is used in the stage charging process of the electric automobile, the primary sides of the double transformers are connected in series when high power is output, the secondary sides are directly connected in parallel after rectification, the power of the transformers is uniform, and the problem of difficult design of the transformers under the conditions of high power and high frequency is solved; and in the later stage of the charging process, electric energy is output through a single transformer and two switching tubes, so that the problem of low efficiency under light load is solved.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a topological structure diagram of the present invention;
FIG. 2 is an AC equivalent circuit diagram of a full-bridge operating mode according to the present invention using fundamental analysis;
FIG. 3 is an AC equivalent circuit diagram of a half-bridge operating mode of the present invention using fundamental analysis;
FIG. 4 shows PWM waveforms for the full-bridge mode and half-bridge mode of operation of the present invention;
FIG. 5 is a charging characteristic curve of the charging power supply according to the present invention;
FIG. 6 is a logic flow diagram of a control method for switching the full-bridge operation mode and the half-bridge operation mode according to the present invention;
FIG. 7 is a control block diagram of the closed loop control circuit of the present invention;
in the drawings, the components represented by the respective reference numerals are listed below:
1-main circuit, 2-input side inverter network, 3-LLC resonant network, 4-high frequency transformer T1And T25-secondary side rectifying and filtering network, 6-voltage division sampling circuit, 7-control circuit, 8-output current and voltage sampling circuit, 9-digital controller and 10-drive circuit.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
A hybrid LLC resonant converter topology based on working mode switching comprises a main circuit 1 and a control circuit 7, and is characterized in that: the main circuit 1 comprises an input side inverter network 2,LLC resonant network 3, high frequency transformer T1And T24. A secondary side rectifying and filtering network 5 and a voltage division sampling circuit 6, and a control circuit 7 comprises an output current and voltage sampling circuit 8, a digital controller 9 and a drive circuit 10. High-frequency transformer T1And T24, the primary side is connected in series, the middle point is connected with the negative end of the power supply, and the secondary side is connected with the load in parallel through the rectifying circuit, so that the design difficulty of the transformer in the high-power LLC resonant conversion circuit is reduced by adopting a series-parallel structure on the basis of meeting the basic gain of the LLC resonant converter.
A control method of a topological structure of a hybrid LLC resonant converter based on working mode switching is characterized in that load partition control is implemented by detecting load current judgment, and a PWM modulation signal is output to control a switching device Q in an input side inverter network 21、Q2、Q3、Q4The switching on and off of the full bridge and the half bridge can be realized. Control Q1、Q4And Q2、Q3When alternately switched on and off, the high-frequency transformer T is used1And T24 transformer T1And T2Working in full-bridge mode, controlling the switch tube Q1And Q2Alternately on and off, Q3And Q4When the power is always turned off, the power passes through a high-frequency transformer T1And T24 transformer T1Operating in half bridge mode. In the full-bridge working mode, the resonant converter passes through the transformer T1And T2Meanwhile, energy is provided for the load, the two transformers are connected in parallel for output, the power is evenly distributed, heat dissipation and parameter design are facilitated, and the current stress of the secondary side diode is greatly reduced; in a half-bridge working mode, the converter only needs one transformer and two switching tubes, and the loss is effectively reduced.
During constant voltage charging, the output current I is selectedO＝I2As the switching point of the working mode, the full-bridge working mode is switched to the switching point b of the half-bridge working mode, and the output current at this time is:
IO＝I3
switching the half-bridge working mode to the full-bridge working mode at a point a, wherein the output current:
IO＝I1
when the output current is larger than I1At the same time, the half-bridge working mode is switched to the full-bridge working mode, and the voltage is transmitted through the transformer T1And T2The batteries are provided with larger charging current together; when the output current is less than I3At the same time, the full-bridge working mode is switched to the half-bridge working mode through the transformer T1The converter works in a light load state, so that the circuit loss of the converter in the light load state is reduced, and the conversion efficiency is improved.
A control method of a hybrid LLC resonant converter topological structure based on work mode switching comprises the following steps:
s1: in the full-bridge working mode, an input side direct current power supply passes through an input side inverter network 2 to an LLC resonant network 3 and then passes through a high-frequency transformer T1And T24 transformer T1、T2Then the output is carried out after passing through a secondary side rectification filter network 5;
s2: in a half-bridge working mode, an input side direct current power supply passes through an input side inverter network 2 to an LLC resonance network 3 and then passes through a high-frequency transformer T1And T24 transformer T1Then the output is output through a secondary side rectification filter network 5;
s3: the current and voltage sampling circuit 8 outputs a voltage V to the main circuit 1oOutput current IoSampling, and performing analog-to-digital conversion to a digital controller 9;
s4: the digital controller 9 feeds back the voltage vfCurrent ifThe input signal as an internal digital closed-loop control program is compared with a set value, and whether the charging mode is a constant-current charging mode or a constant-voltage charging mode is judged; if the charging device is in a constant current charging mode, a closed loop negative feedback system is formed by the output current and the reference current, and the controller outputs a PWM (pulse width modulation) signal to control Q1、Q4And Q2、Q3And conducting alternately to enable the whole to work in a full-bridge working mode, and executing the next step if the whole works in a constant-voltage charging mode.
S5: when the constant voltage charging mode is adopted, the output current is further compared with the working switching point; if it isWhen the output current is greater than time I1Still operating in a full-bridge operating mode; if the output current is less than I3The controller outputs PWM modulation signals, and the PWM modulation signals are controlled and alternately conducted through the driving circuit 10 and work in a half-bridge working mode until the charging of the battery of the electric automobile is finished.
Fig. 1 is a block diagram of a main circuit and a control circuit of a hybrid LLC resonant converter for switching full-bridge and half-bridge operating modes according to the present invention.
FIG. 2 and FIG. 3 are the AC equivalent circuit obtained by the fundamental analysis method in the full-bridge mode and the half-bridge mode, respectively, and the resonant inductor L in the full-bridge moder1、Lr2Resonant capacitor Cr1、Cr2And an excitation inductance Lm1、Lm2Form a resonant network, Rac1And Rac2Equivalent to the primary side equivalent resistance. Resonant inductor L in half-bridge mode of operationr1Resonant capacitor Cr1And an excitation inductance Lm1Form a resonant network, RacEquivalent to the primary side equivalent resistance. The LLC normalized direct-current voltage gain formula obtained by the alternating-current equivalent circuit is as follows:
where k is the ratio of excitation inductance to resonance inductance, Q is the quality factor, and fnIs a normalized frequency.
Fig. 4 shows a driving waveform with dead time outputted from the driving circuit (10). When operating in the full-bridge operating mode, the drive circuit (10) outputs four drive waveforms of PWM1, PWM2, PWM3 and PWM4 with dead time. When the full-bridge working mode is switched to the half-bridge working mode, the driving circuit (10) outputs driving waveforms with dead time of two paths of PWM1 and PWM2, and driving signals of two paths of PWM3 and PWM4 are 0.
Fig. 5 is a designed charging characteristic curve of the charging power supply, which is divided into two stages. At the beginning of charging, at a constant current INThe battery is charged quickly and the voltage rises continuously during this process. To t0At time, voltage risesSet value V to constant voltage charging modeNThen charging at constant voltage with the voltage value, and the current continuously drops to t due to the internal resistance of the battery3At the moment, the full-bridge operating mode is switched to the half-bridge operating mode at the switching point, and at the moment, the operating mode can be switched from the full-bridge operating mode to the half-bridge operating mode.
Fig. 6 is a logic flow chart of the control method for switching the working modes, the input voltage and the current obtained by sampling are firstly used for judging whether the charging stage is a constant current charging stage or a constant voltage charging stage, and when the charging stage is the constant current charging stage, the constant current charging is continued. When the charging stage is the constant voltage charging stage, whether the working mode needs to be switched or not is judged according to the magnitude of the output current. When the output current value is less than I3When the output current is larger than I, the full-bridge working mode is switched to the half-bridge working mode1The half-bridge mode of operation is switched to the full-bridge mode of operation.
Fig. 7 is a control block diagram of a closed-loop control circuit, which adopts a control mode of current single-loop control in a constant-current stage, current-voltage double closed-loop control in a constant-voltage stage, and switching of working modes. And according to different working modes, PWM driving waves with fixed duty ratio and variable frequency are output in a closed loop mode, and then the corresponding switching tubes are controlled to be switched on and off through a driving circuit, so that the purposes of stable output and mode switching are achieved.
In the description herein, references to the description of "one embodiment," "an example," "a specific example" or the like are intended to mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
The preferred embodiments of the invention disclosed above are intended to be illustrative only. The preferred embodiments are not intended to be exhaustive or to limit the invention to the precise embodiments disclosed. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention. The invention is limited only by the claims and their full scope and equivalents.
Claims (8)
1. A hybrid LLC resonant converter topology based on operating mode switching, comprising a main circuit (1) and a control circuit (7), characterized by: the main circuit (1) comprises an input side inverter network (2), an LLC resonant network (3) and a high-frequency transformer T1And T2(4) The secondary side rectifying and filtering network (5) and the voltage division sampling circuit (6), wherein the control circuit (7) comprises an output current and voltage sampling circuit (8), a digital controller (9) and a driving circuit (10).
2. A hybrid LLC resonant converter topology based on operating mode switching, according to claim 1, characterized in that: the high-frequency transformer T1And T2(4) The primary side is connected in series, the midpoint is connected with the negative end of the power supply, and the secondary side is connected in parallel with the load through the rectifying circuit.
3. The method according to claim 1, wherein the method comprises: load zone control is implemented by detecting load current and judging, and a PWM modulation signal is output to control a switching device Q in an input side inverter network (2)1、Q2、Q3、Q4The switching on and off of the full bridge and the half bridge can be realized.
4. A control method for a hybrid LLC resonant converter topology based on operation mode switching according to claim 3, characterized by: control Q1、Q4And Q2、Q3When alternately switched on and off, the high-frequency transformer T is used1And T2(4) Transformer T in1And T2Working in full-bridge mode, controlling the switch tube Q1And Q2Alternately on and off, Q3And Q4When the power is always turned off, the power passes through a high-frequency transformer T1And T2(4) Transformer T in1Operating in half bridge mode.
5. A control method for a hybrid LLC resonant converter topology based on operation mode switching according to claim 4, characterized by: during constant voltage charging, the output current I is selectedO＝I2As the operating mode switching point, the full-bridge operating mode is set to be switched to the half-bridge operating mode switching point (point b), and the output current at this time is:
IO＝I3
switching the half-bridge operation mode to the full-bridge operation mode at a switching point (point a), wherein the output current:
IO＝I1
when the output current is larger than I1At the same time, the half-bridge working mode is switched to the full-bridge working mode, and the voltage is transmitted through the transformer T1And T2The batteries are provided with larger charging current together; when the output current is less than I3At the same time, the full-bridge working mode is switched to the half-bridge working mode through the transformer T1And the converter works in a light load state, so that the circuit loss of the converter in the light load state is reduced.
6. A control method for a hybrid LLC resonant converter topology based on operation mode switching according to claims 1-5, characterized by the steps of:
s1: in a full-bridge working mode, an input side direct current power supply passes through an input side inverter network (2) to an LLC resonance network (3) and then passes through a high-frequency transformer T1And T2(4) Transformer T in1、T2Then the output is carried out after passing through a secondary side rectification filter network (5);
s2: in a half-bridge working mode, an input side direct current power supply passes through an input side inverter network (2) to an LLC resonance network (3) and then passes through a high-frequency transformer T1And T2(4) In the transformerDevice T1Then the output is output through a secondary side rectification filter network (5);
s3: the current and voltage sampling circuit (8) outputs a voltage V to the main circuit (1)oOutput current IoSampling, and carrying out analog-to-digital conversion to a digital controller (9);
s4: the digital controller (9) feeds back the voltage vfCurrent ifThe input signal as an internal digital closed-loop control program is compared with a set value, and whether the charging mode is a constant-current charging mode or a constant-voltage charging mode is judged;
s5: when in the constant voltage charging mode, the output current is further compared with the working switching point.
7. The control method of the operation mode switching based hybrid LLC resonant converter topology according to claim 6, characterized by: in S4, if the charging mode is the constant current charging mode, the output current and the reference current form a closed loop negative feedback system, and the controller outputs the PWM modulation signal to control the Q1、Q4And Q2、Q3And conducting alternately to enable the whole to work in a full-bridge working mode, and executing the next step if the whole works in a constant-voltage charging mode.
8. The control method of the operation mode switching based hybrid LLC resonant converter topology according to claim 6, characterized by: in S5, if the output current is larger than the predetermined value I1Still operating in a full-bridge operating mode; if the output current is less than I3The controller outputs PWM modulation signals, and the PWM modulation signals are controlled and alternately conducted through the driving circuit (10) and work in a half-bridge working mode until the charging of the battery of the electric automobile is finished.
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