CN118659666A - A DC-DC power converter - Google Patents
A DC-DC power converter Download PDFInfo
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- CN118659666A CN118659666A CN202410858526.7A CN202410858526A CN118659666A CN 118659666 A CN118659666 A CN 118659666A CN 202410858526 A CN202410858526 A CN 202410858526A CN 118659666 A CN118659666 A CN 118659666A
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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
- H02M3/33571—Half-bridge at primary side of an isolation transformer
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F27/00—Details of transformers or inductances, in general
- H01F27/24—Magnetic cores
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F27/00—Details of transformers or inductances, in general
- H01F27/34—Special means for preventing or reducing unwanted electric or magnetic effects, e.g. no-load losses, reactive currents, harmonics, oscillations, leakage fields
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
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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
- H02M3/003—Constructional details, e.g. physical layout, assembly, wiring or busbar connections
-
- 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
- H02M3/01—Resonant DC/DC converters
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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
- H02M3/33576—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 having at least one active switching element at the secondary side of an isolation transformer
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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
- 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
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Dc-Dc Converters (AREA)
Abstract
The application discloses a DC-DC power converter, which comprises a front-stage three-level circuit module and a rear-stage LLC resonant circuit module; the two input ends of the front-stage three-level module are respectively connected with the positive electrode Vin+ and the negative electrode Vin-of the direct current bus, the two output ends of the front-stage three-level module are respectively connected with the two input ends of the rear-stage LLC resonant circuit module, the two output ends of the LLC resonant circuit module serve as direct current power output ends vo+ and Vo-of the DC-DC power converter, and the rear-stage LLC resonant circuit module comprises a first LLC resonant circuit and a second LLC resonant circuit. The application can meet the requirement of medium-high voltage input occasions, effectively reduces the stress of the primary side MOS tube, further improves the power switching frequency, further reduces the size of the magnetic core, further improves the power density of the whole power module, and is beneficial to realizing the high power density and light weight of the module power supply.
Description
Technical Field
The invention relates to the technical field of module power supplies, in particular to a DC-DC power supply converter.
Background
For equipment adopting direct current power supply, 50Hz alternating current provided by a power grid is usually firstly subjected to a Power Factor Correction (PFC) circuit, the alternating current is converted into high direct current (the direct current side output of the single-phase PFC circuit is usually about 380V, and the direct current side output of the three-phase PFC circuit is usually about 700V), and then the high direct current is converted into the required low-voltage direct current through a post-stage DC/DC converter. Because the output voltage of the front-stage PFC is higher (particularly a three-phase PFC circuit), the selection of the switching tube of the rear-stage DC/DC conversion circuit has high requirements, and for a DC/DC power supply module with a severe size requirement, the patch MOS tube meeting the voltage class requirement is difficult to match. Therefore, in order to meet the requirements of the market on a power module with small volume, light weight and high power density, increasing the switching frequency to reduce the volume and the weight of the magnetic component is an effective measure for realizing the light weight of the module, but high frequency has a great challenge on the mos tube, especially under the condition of medium-high voltage input, the mos tube with higher withstand voltage needs to be selected, however, the conduction and the switching loss of the mos tube are more outstanding as the withstand voltage is higher, and the improvement of the power of the module power supply is severely restricted.
Based on the above phenomena, it is necessary to provide a DC-DC power converter that can satisfy both medium-high voltage input occasions and small-size.
Disclosure of Invention
The technical problem to be solved by the invention is to provide the DC-DC power converter which can meet the requirement of a medium-high voltage input occasion, effectively reduce the stress of the primary side MOS tube, further improve the power switching frequency, further reduce the size of the magnetic core, further improve the power density of the whole power module and be beneficial to realizing the high power density and light weight of the module power supply.
The technical scheme for solving the technical problems is as follows:
A DC-DC power converter comprises a front-stage three-level circuit module and a rear-stage LLC resonant circuit module; the two input ends of the front-stage three-level module are respectively connected with the positive electrode Vin+ and the negative electrode Vin-of the direct current bus, the two output ends of the front-stage three-level module are respectively connected with the two input ends of the rear-stage LLC resonant circuit module, the two output ends of the LLC resonant circuit module serve as direct current power supply output ends vo+ and Vo-of the DC-DC power converter, the rear-stage LLC resonant circuit module comprises a first LLC resonant circuit and a second LLC resonant circuit, the input ends of the first LLC resonant circuit and the input ends of the second LLC resonant circuit are connected in series, and the output ends of the first LLC resonant circuit and the output ends of the second LLC resonant circuit are connected in parallel.
Further, the front-stage three-level circuit module comprises at least one three-level circuit, and the three-level circuit comprises a first switching tube Q1, a second switching tube Q2, a third switching tube Q3 and a fourth switching tube Q4 which are connected in series; the first switching tube Q1, the second switching tube Q2, the third switching tube Q3 and the fourth switching tube Q4 are sequentially connected according to a source electrode and a drain electrode, the drain electrode of the first switching tube Q1 is connected with the positive electrode vin+ of the direct current bus to serve as a first input end of the front-stage three-level circuit module, the source electrode of the fourth switching tube Q4 is connected with the negative electrode Vin-of the direct current bus to serve as a second input end of the front-stage three-level circuit module, a node, connected with the first switching tube Q1 and the second switching tube Q2, of the three-level circuit is used as a first output end of the front-stage three-level circuit module, and meanwhile, the node, connected with the third switching tube Q3 and the fourth switching tube Q4, of the three-level circuit is used as a second output end of the front-stage three-level circuit module and simultaneously used as a second input end of the rear-stage LLC resonant circuit module.
The beneficial effects of the above-mentioned further scheme are: if the input voltage is higher, the front stage can adopt a plurality of three-level series connection, so that the voltage stress of the MOS tube is reduced; if the input current is larger, the front stage can adopt a plurality of three-level parallel connection, so that the current stress of the MOS is reduced, and meanwhile, the conduction loss of the MOS tube is reduced.
Furthermore, the two input ends of the front three-level circuit module are also connected with a voltage equalizing circuit in parallel, the voltage equalizing circuit comprises equivalent resistors R1 and R2 which are connected in series, and a middle node connected with the resistors R1 and R2 is connected to a middle node connected with the second switching tube Q2 and the third switching tube Q3.
The beneficial effects of the above-mentioned further scheme are: the voltage division on the equivalent resistors R1 and R2 is uniform, so that the voltage stress born by the first switching tube Q1, the second switching tube Q2, the third switching tube Q3 and the fourth switching tube Q4 in normal operation is halved.
Further, the front three-level circuit module comprises two identical three-level circuits, the two three-level circuits are connected in parallel or in series, and switching tubes at the same positions of the two three-level circuits can be out of phase by 90 degrees or other degrees.
The beneficial effects of the above-mentioned further scheme are: if the input voltage is higher, the front stage can adopt a plurality of three-level series connection, so that the voltage stress of the MOS tube is reduced; if the input current is larger, the front stage can adopt a plurality of three-level parallel connection, so that the current stress of the MOS is reduced, the conduction loss of the MOS tube is reduced, and the output ripple is reduced.
Furthermore, filter capacitors C1 and C2 are respectively connected in parallel to two ends of the resistors R1 and R2, and filter capacitors C5 and C6 are respectively connected in parallel to the output ends of the first LLC resonant circuit and the second LLC resonant circuit.
The beneficial effects of the above-mentioned further scheme are: the filter capacitors C1 and C2 are used in the input end of the direct current power supply to filter alternating current components, so that the input direct current is smoother, and the filter capacitors C5 and C6 are used in the output end of the direct current power supply to filter alternating current components, so that the output direct current is smoother.
Further, the first LLC resonant circuit and the second LLC resonant circuit have the same structure, the first LLC resonant circuit includes a first resonant transformer Tr1 and a first rectifying circuit, the second LLC resonant circuit includes a second resonant transformer Tr2 and a second rectifying circuit, a primary side end of the first resonant transformer Tr1 is connected to a first output end of the front three-level circuit module as a first input end of the rear LLC resonant circuit module, a primary side other end of the first resonant transformer Tr1 is connected to a primary side end of the second resonant transformer Tr2, a primary side other end of the second resonant transformer Tr2 is connected to a second output end of the front three-level circuit module as a second input end of the rear LLC resonant circuit module, each input end of the first rectifying circuit is connected to a secondary side corresponding end of the first resonant transformer Tr1, each input end of the second rectifying circuit is connected to a secondary side corresponding end of the second resonant transformer Tr2, and the first output end of the first rectifying circuit and the second rectifying circuit are connected to a corresponding DC-DC power supply end of the DC converter.
Further, the first LLC resonant circuit further includes a first series resonant circuit, one end of the first series resonant circuit is connected to the first input end of the rear-stage LLC resonant circuit module, and the other end of the first series resonant circuit is connected to the first output end of the front-stage three-level circuit module; the second LLC resonant circuit further comprises a second series resonant circuit, one end of the second series resonant circuit is connected with the second input end of the rear-stage LLC resonant circuit module, and the other end of the second series resonant circuit is connected with the second output end of the front-stage three-level circuit module.
Further, the first series resonant circuit comprises a first resonant inductor Lr1 and a first resonant capacitor C3 which are connected in series; the second series resonant circuit includes a second resonant inductance Lr2 and a second resonant capacitance C4 connected in series.
Further, the first resonant transformer Tr1 and the second resonant transformer Tr2 are transformers with center taps of secondary sidebands, and the center taps of the secondary edges of the first resonant transformer Tr1 and the second resonant transformer Tr2 are used as direct current power output ends vo+ of the DC-DC power converter; the first rectification circuit comprises a first rectification switch tube Q5 and a second rectification switch tube Q6, drains of the first rectification switch tube Q5 and the second rectification switch tube Q6 are respectively connected with two input ends of a secondary side of the first resonant transformer Tr1, the second rectification circuit comprises a third rectification switch tube Q7 and a fourth rectification switch tube Q8, drains of the third rectification switch tube Q7 and the fourth rectification switch tube Q8 are respectively connected with two input ends of a secondary side of the second resonant transformer Tr2, and sources of the first rectification switch tube Q5, the second rectification switch tube Q6, the third rectification switch tube Q7 and the fourth rectification switch tube Q8 are connected to serve as direct current power output ends Vo-of the DC-DC power converter.
Further, the first resonant transformer Tr1 and the second resonant transformer Tr2 have the same structure, and the transformer core may be a conventional U-shaped core, and the Base of the 2U-shaped cores may be combined to form a four-leg core, or a four-leg core may be used.
The beneficial effects of the above-mentioned further scheme are: the transformer adopts a parallel connection mode, and the magnetic core adopts a four-leg magnetic core, so that coil loss and magnetic core loss can be effectively reduced.
The application adopts the technical proposal and has at least the following beneficial effects:
The front-stage three-level circuit module adopts three-level LLC topology, the three-level topology can reduce the voltage stress at two ends of the switching tube to half of the traditional full-bridge or half-bridge circuit, the MOS tube selection is facilitated, and meanwhile, aiming at the DC/DC converter adopting LLC topology at the rear stage, the primary side can select a small-size MOS tube with lower withstand voltage.
According to the input voltage, the 4 switching tubes on the primary side of the transformer can be MOS tubes with different withstand voltage grades, and if the input current is larger, a plurality of MOS tubes can be connected in parallel.
Particularly, when the input voltage is lower than 400V, the MOS tube adopts a3 x 3 MOS tube with 150V, so that the switching frequency can be increased to 1MHz, and the power density of the module is greatly improved.
If the primary side of the transformer adopts 2 three-level cascading, the switching tubes at the same position of two three levels can be in error phase by software configuration, so that output ripple waves are reduced, and higher switching frequency can be realized by cascading a plurality of three-level circuits.
In order to facilitate the layout of a PCB and reduce the influence of parasitic parameters of the PCB as much as possible, the resonant capacitor and the resonant inductor are split into 2, and are symmetrically arranged on the primary side and the secondary side of the transformer, for the occasion of outputting large current, in order to reduce coil loss, LLC transformers Tr1 and Tr2 are connected in parallel, the magnetic cores can adopt two traditional U-shaped magnetic cores, the Base of the 2U-shaped magnetic cores can be combined by utilizing a magnetic integration technology, a four-leg magnetic core is formed, the coil loss and the magnetic core loss can be effectively reduced, the magnetic core size can be further reduced, the output ripple is reduced, and the power density of the module is improved.
Drawings
FIG. 1 is a circuit diagram of a DC-DC power converter of the present invention;
Fig. 2 is a schematic view of the magnetic flux direction of the four-leg core of the present invention.
Detailed Description
Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It is to be understood that the embodiments shown and described in the drawings are merely illustrative of the principles and spirit of the invention and are not intended to limit the scope of the invention.
The invention provides a DC-DC power converter, which relates to the technical field of DC-DC module power supplies, in particular to a high-voltage, high-frequency and high-power-density DC-DC converter, wherein the primary side of a resonant transformer adopts a three-level topology, so that the voltage stress of an MOS tube can be effectively reduced; aiming at LLC topology, the primary side of the transformer can use a small package MOS with lower withstand voltage to realize a plurality of three-level cascading, and the parasitic parameters of the MOS tube are small, so that the high frequency of a module power supply can be realized; the three-level rubbing of the primary side can effectively reduce output ripple through phase staggering; the resonant transformer adopts the four-leg magnetic core, and coil loss and magnetic core loss can be effectively reduced while the magnetic core size is reduced. The DC-DC converter is reliable and efficient, has high power density, realizes soft switching in a full range, has small output ripple, and can be widely applied to the field of DC/DC conversion of medium and high voltage input.
Examples:
As shown in fig. 1, the present embodiment provides a DC-DC power converter, which includes a front-stage three-level circuit module and a rear-stage LLC resonant circuit module; the two input ends of the front-stage three-level module are respectively connected with the positive electrode Vin+ and the negative electrode Vin-of the direct current bus, the two output ends of the front-stage three-level module are respectively connected with the two input ends of the rear-stage LLC resonant circuit module, the two output ends of the LLC resonant circuit module serve as direct current power supply output ends vo+ and Vo-of the DC-DC power converter, the rear-stage LLC resonant circuit module comprises a first LLC resonant circuit and a second LLC resonant circuit, the input ends of the first LLC resonant circuit and the input ends of the second LLC resonant circuit are connected in series, and the output ends of the first LLC resonant circuit and the output ends of the second LLC resonant circuit are connected in parallel.
The first LLC resonant circuit comprises a first resonant transformer Tr1 and a first rectifying circuit, the second LLC resonant circuit comprises a second resonant transformer Tr2 and a second rectifying circuit, one end of the primary side of the first resonant transformer Tr1 is connected with the first output end of the front-stage three-level circuit module to serve as the first input end of the rear-stage LLC resonant circuit module, the other end of the primary side of the first resonant transformer Tr1 is connected with one end of the primary side of the second resonant transformer Tr2, the other end of the primary side of the second resonant transformer Tr2 is connected with the second output end of the front-stage three-level circuit module to serve as the second input end of the rear-stage LLC resonant circuit module, each input end of the first rectifying circuit is connected with the corresponding end of the secondary side of the first resonant transformer Tr1, and each input end of the second rectifying circuit is connected with the corresponding end of the secondary side of the second resonant transformer Tr2, and the output end of the first rectifying circuit and the corresponding output end of the second rectifying circuit are connected in parallel to serve as the output end of the DC-DC power supply converter.
The first LLC resonant circuit and the second LLC resonant circuit have the same structure, the primary side of the first LLC resonant circuit and the primary side of the second LLC resonant circuit are in a series connection structure, the secondary side of the first LLC resonant circuit and the second resonant transformer of the second LLC resonant circuit are in a parallel connection structure, and the first resonant transformer and the second resonant transformer of the first LLC resonant circuit can adopt a magnetic integration mode, so that the size of the transformer can be greatly reduced, and meanwhile, the output ripple wave is reduced.
The voltage stress of the first switching tube Q1, the second switching tube Q2 and the third switching tube Q3 and the fourth switching tube Q4 on the primary side of the first resonant transformer Tr1 is half of the input voltage; therefore, a small-package MOS (metal oxide semiconductor) tube (such as 3x3 MOS) can be used on the primary side of the transformer, high frequency (such as 1 MHz) of the power supply module can be realized, the resonance network is connected to the midpoints of the first switching tube Q1 and the second switching tube Q2 and the midpoints of the third switching tube Q3 and the fourth switching tube Q4, in order to ensure the voltage equalizing effect, voltage equalizing circuits are further connected in parallel to the two input ends of the front-stage three-level circuit module, each voltage equalizing circuit comprises equivalent resistors R1 and R2 connected in series, the middle node of the connection of the resistors R1 and R2 is connected to the middle node of the connection of the second switching tube Q2 and the third switching tube Q3, and the secondary side of the first resonant transformer Tr1 and the second resonant transformer Tr2 adopts a synchronous rectification scheme.
The first resonant transformer Tr1 and the second resonant transformer Tr2 are transformers with secondary side band center taps, and the secondary side center taps of the first resonant transformer Tr1 and the second resonant transformer Tr2 are used as direct current power supply output ends vo+ of the DC-DC power supply converter; the first rectification circuit comprises a first rectification switch tube Q5 and a second rectification switch tube Q6, drains of the first rectification switch tube Q5 and the second rectification switch tube Q6 are respectively connected with two input ends of a secondary side of the first resonant transformer Tr1, the second rectification circuit comprises a third rectification switch tube Q7 and a fourth rectification switch tube Q8, drains of the third rectification switch tube Q7 and the fourth rectification switch tube Q8 are respectively connected with two input ends of a secondary side of the second resonant transformer Tr2, and sources of the first rectification switch tube Q5, the second rectification switch tube Q6, the third rectification switch tube Q7 and the fourth rectification switch tube Q8 are connected to serve as direct current power output ends Vo-of the DC-DC power converter.
In this embodiment, the first LLC resonant circuit further includes a first series resonant circuit, where the first series resonant circuit is connected to the first input end of the later-stage LLC resonant circuit module, and the other end of the first series resonant circuit is connected to the first output end of the earlier-stage three-level circuit module; the first series resonant circuit comprises a first resonant inductor Lr1 and a first resonant capacitor C3 which are connected in series; specifically, the first resonance capacitor C3 is connected to the intermediate node of the first switching tube Q1 and the second switching tube Q2, and the first resonance inductor Lr1 is connected to one end of the primary side of the first resonance transformer Tr 1. The second LLC resonant circuit further comprises a second series resonant circuit, the second series resonant circuit is connected with a second input end of the rear-stage LLC resonant circuit module, and the other end of the second series resonant circuit is connected with a second output end of the front-stage three-level circuit module; the second series resonant circuit includes a second resonant inductance Lr2 and a second resonant capacitance C4 connected in series. Specifically, the second resonance capacitor C4 is connected to the intermediate node of the third switching tube Q3 and the fourth switching tube Q4, and the second resonance inductor Lr2 is connected to one end of the primary side of the second resonance transformer Tr 2.
In order to make the input direct-current voltage signal smoother and more stable, the input end of the front-stage three-level circuit module is also respectively connected with filter capacitors C1 and C2 in parallel, and specifically, the filter capacitors C1 and C2 are respectively connected with two ends of the resistors R1 and R2 in parallel.
In order to effectively reduce output ripple, the front-stage three-level circuit module can adopt two identical three-level circuits, and if the input voltage is higher, the two three levels are connected in series, so that the voltage stress of the MOS tube is reduced; if the input current is larger, the two three-level circuits are connected in parallel, so that the current stress of the MOS is reduced, and when software configuration is carried out, the switching tubes at the same positions of the two three-level circuits can be out of phase by 90 degrees or other degrees, so that the conduction loss of the MOS tube can be reduced, and the ripple wave is reduced.
In this embodiment, according to the magnitude of the input dc voltage, the first switching tube Q1, the second switching tube Q2, the third switching tube Q3 and the fourth switching tube Q4 may be MOS tubes with different withstand voltage levels, and if the input current is larger, a plurality of MOS tubes may be connected in parallel. Particularly, when the input voltage is lower than 400V, two three-level cascading is adopted, and the MOS tube adopts 3 x 3 MOS of 150V, so that the switching frequency can be increased to 1MHz, and the power density of the module is greatly improved.
In this embodiment, the first resonant transformer Tr1 and the second resonant transformer Tr2 have the same structure, the primary side of the first transformer Tr1 includes a first coil, the secondary side includes a second coil, and one end of the first coil is connected to the first resonant inductor Lr1; two ends of the second coil are respectively connected with drains of the first rectifying switch tube Q5 and the second rectifying switch tube Q6; the primary side of the second transformer Tr2 comprises a third coil, the secondary side comprises a fourth coil, one end of the third coil is connected with the other end of the first coil, the other end of the third coil is connected with the second resonant inductor Lr2, and two ends of the fourth coil are respectively connected with drains of the third rectifying switch tube Q7 and the fourth rectifying switch tube Q8.
In addition, in order to facilitate the layout of the PCB and reduce the influence of parasitic parameters of the PCB as much as possible, the resonant capacitor and the resonant inductor are split into 2, and are symmetrically arranged on the primary side and the secondary side of the transformer, and the first resonant inductor Lr1 and the second resonant inductor Lr2 can adopt U-shaped magnetic cores. For the occasion of outputting large current, in order to reduce coil loss, the first resonant transformer Tr1 and the second resonant transformer Tr2 are connected in parallel, the magnetic cores can adopt two traditional U-shaped magnetic cores, and the Base of 2U-shaped magnetic cores can be combined by utilizing a magnetic integration technology to form a four-leg magnetic core, so that the size of the magnetic core can be further reduced, and the power density of the module is improved.
The four-leg magnetic core comprises a first leg 1, a second leg 2, a third leg 3 and a fourth leg 4, the first switching tube Q and the second switching tube Q2 are in a group, the third switching tube Q3 and the fourth switching tube Q4 are in a group and are respectively arranged on one side of the four-leg magnetic core, the first coil and the second coil are respectively wound on the first leg 1 and the second leg 2 to form a first primary winding and a second primary winding, each power tube of the first rectifying circuit and the second rectifying circuit is arranged on the other side of the four-leg magnetic core, and the third coil and the fourth coil are respectively wound on the third leg 3 and the fourth leg 4 to form a first secondary winding and a second secondary winding.
As shown in fig. 2, in this embodiment, the first leg 1 and the second leg 2 form a reverse magnetic flux, the third leg 3 and the fourth leg 4 also form a reverse magnetic flux, and the opposite angles of the first leg 1, the second leg 2, the third leg 3 and the fourth leg 4 form a same-directional magnetic flux, and the adjacent two legs form a reverse magnetic flux. Because the switch tube is arranged close to the magnetic core and is arranged on the coil outlet end, the alternating current impedance of the coil can be effectively reduced, the alternating current loss of the coil is further reduced, and meanwhile, the space of the PCB is also saved. Because the alternating magnetic flux on the two adjacent legs has opposite directions, the alternating magnetic flux density on the Base is more uniform, and the magnetic core loss is reduced.
The output ends of the first LLC resonant circuit and the second LLC resonant circuit provided by the embodiment of the application are respectively connected with filter capacitors C5 and C6 in parallel, so that the output of the post-stage LLC resonant circuit module after filtering is realized. The filter capacitor is used in the power rectifying circuit to filter AC component and make the output DC smoother.
The first switching tube Q1, the second switching tube Q2, the third switching tube Q3, the fourth switching tube Q4, the first rectifying switching tube Q5, the second rectifying switching tube Q6, the third rectifying switching tube Q7 and the fourth rectifying switching tube Q8 may be of various kinds, for example, may include a metal oxide semiconductor field effect transistor (metal oxide semiconductor, MOS) or an insulated gate bipolar transistor (Insulated GateBipolar Transistor, IGBT). It should be understood that, although the technical solution provided by the embodiment of the present application is described by taking the NMOS transistor as an example in the drawing of fig. 1, the present application is not limited to the type of the switching transistor, and may be implemented by other corresponding electronic components, and these simple substitutions do not deviate from the protection scope of the present application.
In addition, in the embodiment of the present application, if the rectifying element is a switching transistor, the switching on and switching off of the rectifying element may be triggered by an external circuit, and the specific structure of the external circuit may include a controller, or may include other hardware circuits, etc., which will not be described herein.
In the technical scheme provided by the embodiment, the three-level topology can reduce the voltage stress at two ends of the switching tube to half of the traditional full-bridge or half-bridge circuit, thereby being beneficial to the selection of MOS tubes, meanwhile, aiming at the DC/DC converter adopting LLC topology at the later stage, the primary side can select a small-size MOS tube with lower withstand voltage, and higher switching frequency can be realized through cascading a plurality of three-level circuits; the transformer adopts a parallel connection mode, so that the coil loss can be effectively reduced, and the power density of the power supply module is further improved. Particularly, when two three-level circuits are cascaded, the primary side switching tube can be in phase staggering, and meanwhile, the transformer adopts a four-leg magnetic core, so that the size of the transformer can be greatly reduced, and meanwhile, the output ripple wave is reduced. In addition, because the primary side is input in series, the voltage division and the secondary side is output in parallel, and the current increase can be realized, the scheme can be better suitable for the technical scenes of medium-high voltage input and larger current output.
The foregoing is only illustrative of the present invention and is not to be construed as limiting thereof, but rather as various modifications, equivalent arrangements, improvements, etc., within the spirit and principles of the present invention.
Claims (10)
1. The DC-DC power converter is characterized by comprising a front-stage three-level circuit module and a rear-stage LLC resonant circuit module; the two input ends of the front-stage three-level module are respectively connected with the positive electrode Vin+ and the negative electrode Vin-of the direct current bus, the two output ends of the front-stage three-level module are respectively connected with the two input ends of the rear-stage LLC resonant circuit module, the two output ends of the LLC resonant circuit module serve as direct current power supply output ends vo+ and Vo-of the DC-DC power converter, the rear-stage LLC resonant circuit module comprises a first LLC resonant circuit and a second LLC resonant circuit, the input ends of the first LLC resonant circuit and the input ends of the second LLC resonant circuit are connected in series, and the output ends of the first LLC resonant circuit and the output ends of the second LLC resonant circuit are connected in parallel.
2. A DC-DC power converter according to claim 1, wherein the pre-stage three-level circuit module comprises at least one three-level circuit including a first switching tube Q1, a second switching tube Q2, a third switching tube Q3 and a fourth switching tube Q4 connected in series; the first switching tube Q1, the second switching tube Q2, the third switching tube Q3 and the fourth switching tube Q4 are sequentially connected according to a source electrode and a drain electrode, the drain electrode of the first switching tube Q1 is connected with the positive electrode vin+ of the direct current bus to serve as a first input end of the front-stage three-level circuit module, the source electrode of the fourth switching tube Q4 is connected with the negative electrode Vin-of the direct current bus to serve as a second input end of the front-stage three-level circuit module, a node, connected with the first switching tube Q1 and the second switching tube Q2, of the three-level circuit is used as a first output end of the front-stage three-level circuit module, and meanwhile, the node, connected with the third switching tube Q3 and the fourth switching tube Q4, of the three-level circuit is used as a second output end of the front-stage three-level circuit module and simultaneously used as a second input end of the rear-stage LLC resonant circuit module.
3. A DC-DC power converter according to claim 2, wherein the pre-stage three-level circuit module comprises two identical three-level circuits, two of the three-level circuits are connected in parallel or in series, and switching transistors at the same position of the two three-level circuits can be phase-shifted by 90 degrees.
4. A DC-DC power converter according to claim 2, wherein the two input terminals of the preceding three-level circuit module are further connected in parallel with a voltage equalizing circuit, the voltage equalizing circuit comprises equivalent resistors R1 and R2 connected in series, and an intermediate node of the resistors R1 and R2 is connected to an intermediate node of the second switching tube Q2 and the third switching tube Q3.
5. The DC-DC power converter according to claim 4, wherein filter capacitors C1 and C2 are connected in parallel across the resistors R1 and R2, respectively; and the output ends of the first LLC resonant circuit and the second LLC resonant circuit are respectively connected with filter capacitors C5 and C6 in parallel.
6. A DC-DC power converter according to claim 1, characterized in that the first LLC resonant circuit and the second LLC resonant circuit have the same structure, the first LLC resonant circuit includes a first resonant transformer Tr1 and a first rectifying circuit, the second LLC resonant circuit includes a second resonant transformer Tr2 and a second rectifying circuit, a primary side end of the first resonant transformer Tr1 is connected to a first output end of the front three-level circuit module as a first input end of the rear LLC resonant circuit module, a primary side other end of the first resonant transformer Tr1 is connected to a primary side end of the second resonant transformer Tr2, a primary side other end of the second resonant transformer Tr2 is connected to a second output end of the front three-level circuit module as a second input end of the rear resonant circuit module, each input end of the first rectifying circuit is connected to a secondary side corresponding end of the first resonant transformer Tr1, each input end of the second rectifying circuit is connected to a corresponding end of the second secondary resonant transformer Tr2, and the first rectifying circuit is connected to a DC power supply end of the DC-DC converter.
7. A DC-DC power converter according to claim 6, wherein the first LLC resonant circuit further comprises a first series resonant circuit having one end connected to the first input of the succeeding LLC resonant circuit module and the other end connected to the first output of the preceding three-level circuit module; the second LLC resonant circuit further comprises a second series resonant circuit, one end of the second series resonant circuit is connected with the second input end of the rear-stage LLC resonant circuit module, and the other end of the second series resonant circuit is connected with the second output end of the front-stage three-level circuit module.
8. A DC-DC power converter according to claim 7, characterized in that the first series resonant circuit comprises a first resonant inductance Lr1 and a first resonant capacitance C3 connected in series; the second series resonant circuit includes a second resonant inductance Lr2 and a second resonant capacitance C4 connected in series.
9. The DC-DC power converter according to claim 6, wherein the first resonant transformer Tr1 and the second resonant transformer Tr2 are transformers with secondary side band center taps, and the secondary side center taps of the first resonant transformer Tr1 and the second resonant transformer Tr2 are used as the DC power output terminal vo+ of the DC-DC power converter; the first rectification circuit comprises a first rectification switch tube Q5 and a second rectification switch tube Q6, drains of the first rectification switch tube Q5 and the second rectification switch tube Q6 are respectively connected with two input ends of a secondary side of the first resonant transformer Tr1, the second rectification circuit comprises a third rectification switch tube Q7 and a fourth rectification switch tube Q8, drains of the third rectification switch tube Q7 and the fourth rectification switch tube Q8 are respectively connected with two input ends of a secondary side of the second resonant transformer Tr2, and sources of the first rectification switch tube Q5, the second rectification switch tube Q6, the third rectification switch tube Q7 and the fourth rectification switch tube Q8 are connected to serve as direct current power output ends Vo-of the DC-DC power converter.
10. The DC-DC power converter according to claim 9, wherein the first resonant transformer Tr1 and the second resonant transformer Tr2 have the same structure, and the transformer core may be a conventional U-shaped core, a four-leg core formed by combining Base of 2U-shaped cores, or a four-leg core.
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| CN120934358A (en) * | 2025-10-16 | 2025-11-11 | 南京航空航天大学 | Three-level capacitive-sensing hybrid isolation type direct-current transformer and control method thereof |
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