CN112636605B - Direct current conversion circuit and mode switching control method thereof under wide voltage range - Google Patents

Direct current conversion circuit and mode switching control method thereof under wide voltage range Download PDF

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CN112636605B
CN112636605B CN202011533662.7A CN202011533662A CN112636605B CN 112636605 B CN112636605 B CN 112636605B CN 202011533662 A CN202011533662 A CN 202011533662A CN 112636605 B CN112636605 B CN 112636605B
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direct current
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CN112636605A (en
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吴西奇
李睿
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Shanghai 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
    • 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
    • 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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Abstract

The invention provides a DC conversion circuit and a mode switching control method thereof under a wide voltage range, the DC conversion circuit comprises a DC input port, an inverter circuit, a resonance network, a rectification circuit and a DC output port, wherein, the inverter circuit can realize two inversion working modes, the rectifier circuit can realize two rectification working modes, the DC converter can realize four working modes by combining the two inversion modes of the inverter circuit and the two rectification modes of the rectifier circuit, the four working modes have different voltage gain characteristics, by controlling the converter to operate in different operating modes at different output voltages and input voltages, the wide voltage output and the wide voltage input of the direct current conversion circuit can be realized, and the frequency adjustment ranges of different modes are partially overlapped, so that the adjustment range of the whole wide output or input voltage range is reduced. The direct current conversion circuit has wide voltage output capability and smaller range of adjusting switching frequency.

Description

Direct current conversion circuit and mode switching control method thereof under wide voltage range
Technical Field
The invention relates to the technical field of direct current power conversion, in particular to a wide-output-voltage direct current converter, a rectifying circuit thereof and a mode switching control method.
Background
In recent years, the electric vehicle industry has continued to advance. Because different manufacturers and vehicle types use different battery specifications, the vehicle-mounted charger for the electric vehicle has the advantages of cost and benefit if the vehicle-mounted charger can meet the requirement of wide voltage range output. The vehicle-mounted charger generally adopts a two-stage conversion structure, and comprises a PFC (power factor correction) rectification part and a direct current conversion part, wherein the high-frequency isolation type DC-DC converter has the capabilities of electrical isolation, high efficiency, high power density and wide voltage gain range output, and is a research hotspot in academia and industry.
The LLC converter can realize zero-voltage switching (ZVS) switching-on of a primary side switch and zero-current switching (ZCS) switching-off of a secondary side switch in a full load range, and has the advantages of high efficiency, high power density and electrical isolation. But LLC converters face a wide voltage range of applications, the frequency range needed to adjust the voltage gain is wide. Too wide a frequency range of regulation leads to several disadvantages: 1) the efficiency is obviously reduced when the gain is less than 1; 2) designing a high frequency transformer according to the minimum switching frequency results in a large volume; 3) limited light load regulation capability, especially in view of secondary side equivalent parasitic capacitance. Therefore, conventional LLC converters are not suitable for applications where the voltage gain exceeds 2.
The LLC converter has higher transmission efficiency when the voltage gain is fixed, but when the LLC converter is applied in a wide voltage range, the value of the exciting inductance is reduced to realize a wider voltage gain range, and reducing the exciting inductance also causes an increase in the inductive exciting current at the input side of the LLC converter, and the switching on loss and the switching off loss at the input side are both correspondingly increased, resulting in a reduction in the transmission efficiency of the circuit. There are contradictions between wide voltage range and high efficiency in the parametric design of conventional LLC converters.
In the prior art, the following methods for improving the efficiency of a wide voltage range LLC converter have been proposed:
(1) chinese utility model patent with publication number CN210867516U proposes a switch wide voltage range LLC converter based on ac switch, constitutes a two-way switch through introducing two active switch tubes, and opens and shuts through the control and realizes the mode switching control of circuit, and then realizes the wide voltage range operation of LLC converter.
(2) The chinese patent application with publication number CN111030467A proposes an isolated LLC converter with an ultra-wide voltage range, which includes 2 high-voltage side H-bridge circuits, 2 LLC resonant circuits, 2 isolation transformers with the same transformation ratio and a three-phase bridge circuit, and has a complex circuit structure, more added elements, and is not favorable for cost reduction and power density improvement.
Disclosure of Invention
The invention provides a direct current converter, a rectifying circuit thereof and a mode switching control method aiming at the defects in the prior art.
The invention is realized by the following technical scheme.
According to an aspect of the present invention, there is provided a dc conversion circuit including: the device comprises a direct current input port, an inverter circuit, a resonant network, a rectifying circuit and a direct current output port; wherein:
the inverter circuit comprises a first capacitor, a first switch tube, a second capacitor, a second switch tube, a third switch tube and a fourth switch tube; the first capacitor, the first switch tube and the second switch tube are sequentially connected to form a loop; the second capacitor, the third switch tube and the fourth switch tube are sequentially connected to form a loop; the terminal of the first switch tube connected with the first capacitor is connected to the positive terminal of the direct current input port; the terminal of the first capacitor connected with the second switch tube is connected with the terminal of the second capacitor connected with the third switch tube; the terminal of the fourth switching tube connected with the second capacitor is connected to the negative terminal of the direct current input port;
the rectifying circuit comprises a first diode, a second diode, a third capacitor, a fourth capacitor, a fifth switching tube, a sixth switching tube and a blocking capacitor; the first diode, the fifth switch tube and the third capacitor are sequentially connected to form a loop; the sixth switching tube, the second diode and the fourth capacitor are sequentially connected to form a loop; the terminal of the first diode connected with the third capacitor is connected to the positive terminal of the direct current output port; the terminal of the third capacitor connected with the fifth switching tube is connected with the terminal of the fourth capacitor connected with the sixth switching tube; the terminal of the second diode connected with the fourth capacitor is connected to the negative terminal of the direct current output port; the terminal of the first diode connected with the fifth switching tube is connected to one end of the blocking capacitor;
the resonance network comprises a resonance inductor, a resonance capacitor, a parallel inductor and a transformer; one end of the resonant capacitor is connected to a terminal connected with the first switching tube and the second switching tube, and the other end of the resonant capacitor is connected to a terminal connected with the parallel inductor and one end of the primary side of the transformer; one end of the resonant inductor is connected to a terminal connected with the third switching tube and the fourth switching tube, and the other end of the resonant inductor is connected to a terminal connected with the parallel inductor and the other end of the primary side of the transformer; one end of the secondary side of the transformer is connected to one end of the blocking capacitor, and the other end of the secondary side of the transformer is connected to a terminal of the sixth switching tube connected with the second diode.
Preferably, the parallel inductor is an independently arranged inductor or an excitation inductor of the transformer.
Preferably, the inverter circuit operates in an inverter mode 1; the switching frequency of the first switching tube to the fourth switching tube in the inversion mode 1 is equal to the resonance frequency of the resonance network, and each switching period comprises the following processes:
in the first process, when a positive half period of an alternating current resonant current is carried out, the first switching tube and the fourth switching tube are conducted through a driving signal, and the current sequentially flows through one terminal of the direct current input port, the first switching tube, the resonant capacitor, the parallel inductor, the primary side of the transformer and the resonant inductor and flows into the other terminal of the direct current input port through the fourth switching tube;
in the second process, when the negative half period of the alternating-current resonant current is carried out, the second switching tube and the third switching tube are conducted through a driving signal, and the current sequentially flows through the resonant capacitor, the second switching tube, the third switching tube, the resonant inductor, the parallel inductor and the primary side of the transformer;
the input voltage of the resonant network is a square wave with a duty ratio of 0.5 and an amplitude equal to the voltage of the direct current input port and zero, and the direct current component of the voltage of the resonant capacitor is equal to one half of the voltage of the direct current input port;
the resonant capacitor stores energy during positive half-cycles of the ac resonant current and releases energy during negative half-cycles of the ac resonant current.
Preferably, the inverter circuit operates in an inverter mode 2; the switching frequency of the first switching tube to the fourth switching tube in the inversion mode 2 is equal to half of the alternating-current resonance frequency of the resonance network, and each switching period comprises the following processes:
in the first process, when a positive half period of a first alternating current resonant current period is formed, the first switching tube and the third switching tube are conducted through a driving signal, and current flows through a positive terminal of the first capacitor, the first switching tube, the resonant capacitor, the parallel inductor, a primary side of the transformer and the resonant inductor in sequence and flows into a negative terminal of the first capacitor through the third switching tube;
in the second process and in the negative half period of the first alternating current resonant current period, the first switching tube is turned off by a driving signal, the second switching tube is turned on by a driving signal, and the current sequentially flows through the resonant capacitor, the second switching tube, the third switching tube, the resonant inductor, the parallel inductor and the primary side of the transformer;
in the third process and in the positive half period of the second alternating current resonant current period, the third switching tube is turned off by a driving signal, the fourth switching tube is turned on by the driving signal, and the current sequentially flows through the positive terminal of the second capacitor, the second switching tube, the resonant capacitor, the parallel inductor, the primary side of the transformer and the resonant inductor and flows into the negative terminal of the second capacitor through the fourth switching tube;
in the fourth process and in the negative half period of the second alternating current resonant current period, the fourth switching tube is turned off by a driving signal, the third switching tube is turned on by the driving signal, and the current sequentially flows through the resonant capacitor, the second switching tube, the third switching tube, the resonant inductor, the parallel inductor and the primary side of the transformer;
the input voltage of the resonant network is a square wave with a duty ratio of 0.5 and an amplitude equal to one half and zero of the voltage of the direct current input port, and the direct current component of the voltage of the resonant capacitor is equal to one quarter of the voltage of the direct current input port;
the first capacitor stores energy during positive half cycles of the ac resonant current and the first capacitor discharges energy during negative half cycles of the ac resonant current.
Preferably, the rectifier circuit operates in a rectification mode a; the switching frequency of the fifth switching tube and the sixth switching tube in the rectification mode a is equal to the resonance frequency of the resonance network, and each switching cycle comprises the following processes:
in the first process, during a positive half cycle of the alternating-current resonant current, the fifth switching tube and the sixth switching tube are turned off by a driving signal, and the current sequentially flows through one terminal of the secondary side of the transformer, the blocking capacitor, the first diode and the direct-current output port and flows into the other terminal of the secondary side of the transformer through the second diode;
in the second process, during a negative half cycle of the alternating-current resonant current, the fifth switching tube and the sixth switching tube are conducted through a driving signal, and the current sequentially flows through one terminal of the secondary side of the transformer, the sixth switching tube and the fifth switching tube and flows into the other terminal of the secondary side of the transformer through the blocking capacitor;
the output voltage of the resonant network is a square wave with the duty ratio of 0.5 and the amplitude equal to one half of the voltage of the positive direct current output port and one half of the voltage of the negative direct current output port, and the direct current component of the voltage of the blocking capacitor is equal to one half of the voltage of the direct current output port;
the blocking capacitor stores energy during a positive half cycle of the ac resonant current and releases energy during a negative half cycle of the ac resonant current.
Preferably, the rectifier circuit operates in a rectification mode b; the switching frequency of the fifth switching tube and the sixth switching tube in the rectification mode b is equal to half of the alternating-current resonance frequency of the resonance network, and each switching period comprises the following processes:
in the first process, when the positive half period of the first alternating current resonant current period is carried out, the fifth switching tube is conducted through a driving signal, and current flows through one terminal of the secondary side of the transformer, the blocking capacitor, the fifth switching tube and the fourth capacitor in sequence and flows into the other terminal of the secondary side of the transformer through the second diode;
in the second process, when the negative half period of the first alternating current resonant current period is carried out, the sixth switching tube is switched on through a driving signal, and the current flows through one terminal of the secondary side of the transformer, the sixth switching tube and the fifth switching tube in sequence and flows into the other terminal of the secondary side of the transformer through the DC blocking capacitor;
in the third process and in the positive half period of the second alternating-current resonant current period, the fifth switching tube is turned off by a driving signal, and current flows through one terminal of the secondary side of the transformer, the blocking capacitor, the first diode and the third capacitor in sequence and flows into the other terminal of the secondary side of the transformer through the sixth switching tube;
in the fourth process and in the negative half period of the second alternating-current resonant current period, the fifth switching tube is switched on by a driving signal, and current flows through one terminal of the secondary side of the transformer, the sixth switching tube and the fifth switching tube in sequence and flows into the other terminal of the secondary side of the transformer through the blocking capacitor;
the output voltage of the resonant network is a square wave with the duty ratio of 0.5 and the amplitude equal to one fourth of the voltage of the positive direct current output port and one fourth of the voltage of the negative direct current output port, and the direct current component of the voltage of the blocking capacitor is equal to one fourth of the voltage of the direct current output port;
the blocking capacitor stores energy during a positive half cycle of the ac resonant current and releases energy during a negative half cycle of the ac resonant current.
Preferably, the dc conversion circuit implements four operation modes by combining an inverter mode of the inverter circuit and a rectification mode of the rectifier circuit:
mode I: the inverter circuit works in an inverter mode 1, the rectifier circuit works in a rectifier mode a, and a complex frequency domain circuit model of the resonant network is obtained by using a phasor method;
calculating the voltage gain expression G of the resonant network in the mode I by using a fundamental equivalent methodI(fn) Comprises the following steps:
Figure BDA0002852659630000051
mode II: the inverter circuit works in an inverter mode 1, the rectifier circuit works in a rectifier mode b, and the voltage gain expression G of the resonant network in the mode II is calculated by using a fundamental equivalent methodII(fn) Comprises the following steps:
Figure BDA0002852659630000052
mode III: the inverter circuit works in an inverter mode 2, the rectifier circuit works in a rectifier mode a, and the voltage gain expression G of the resonant network in the mode III is calculated by using a fundamental equivalent methodIII(fn) Comprises the following steps:
Figure BDA0002852659630000053
mode IV: the inverter circuit works in an inverter mode 2, the rectifier circuit works in a rectifier mode b, and the harmonic network voltage gain expression G in the mode IV is calculated by using a fundamental equivalent methodIV(fn) Comprises the following steps:
Figure BDA0002852659630000061
wherein, V1For input voltage, V2To output voltage, fnTo normalize frequency, fn＝fS/fr，fsTo the operating frequency, frIs the resonance inductance LrAnd said resonant capacitor CrThe frequency of the series resonance is such that,
Figure BDA0002852659630000062
Figure BDA0002852659630000063
k＝Lm/Lr，R1to output the load, LmThe inductance is the parallel inductance or the excitation inductance of the transformer, and n is the turn ratio of the transformer.
According to a second aspect of the present invention, a mode switching control method for a dc conversion circuit in a wide voltage range is provided, wherein a frequency conversion modulation strategy is combined with a mode switching strategy to adjust a wide output voltage of the dc conversion circuit; wherein:
the direct current conversion circuit works in a wide output voltage mode, and the principle of adopting the mode switching strategy is as follows:
when the output voltage of the direct current conversion circuit is greater than or equal to the minimum output voltage and less than or equal to the first output critical switching voltage, the control signal enables the direct current conversion circuit to work in a mode III of the direct current conversion circuit;
when the output voltage of the direct current conversion circuit is greater than the first output critical switching voltage and less than or equal to the second output critical switching voltage, the control signal enables the direct current conversion circuit to work in a mode I or IV of the direct current conversion circuit;
when the output voltage of the direct current conversion circuit is greater than the second output critical switching voltage and less than or equal to the maximum output voltage, the control signal enables the direct current conversion circuit to work in a mode II of the direct current conversion circuit;
the direct current conversion circuit works in each mode, and the voltage gain of the output side and the voltage gain of the input side of the resonant network are changed by changing the working frequency of the direct current conversion circuit by adopting the variable frequency modulation strategy; the voltage gain of the primary side and the secondary side of the transformer is equal to the turn ratio of the transformer; the voltage amplitude of the alternating current port of the inverter circuit and the rectifying circuit is in a proportional relation with the voltage value of the direct current port, and the output voltage is adjusted by adjusting the switching frequency of the direct current conversion circuit.
By combining the variable frequency modulation strategy with the mode switching strategy, the output voltage of the direct current conversion circuit is greater than or equal to the minimum output voltage and less than or equal to the first output critical switching voltage, the output voltage of the direct current conversion circuit is greater than the first output critical switching voltage and less than or equal to the second output critical switching voltage, and the output voltage of the direct current conversion circuit is greater than the second output critical switching voltage and less than or equal to the maximum output voltage, the output of the resonant network and the voltage gain of the input side partially coincide, and further the range of required frequency adjustment partially coincides, so that the range of required adjustment of the whole wide output voltage range is reduced.
According to a third aspect of the present invention, there is provided a mode switching control method for a dc converter circuit in a wide voltage range, wherein a frequency conversion modulation strategy is combined with a mode switching strategy to stabilize the output voltage of the converter circuit in a wide input voltage range; wherein:
the direct current conversion circuit works in a wide input voltage mode, and the principle of adopting the mode switching strategy is as follows:
when the input voltage of the direct current conversion circuit is greater than or equal to the minimum input voltage and less than or equal to the first input critical switching voltage, the control signal enables the direct current conversion circuit to work in a mode II of the direct current conversion circuit;
when the input voltage of the direct current conversion circuit is greater than the first input critical switching voltage and less than or equal to the second input critical switching voltage, the control signal enables the direct current conversion circuit to work in a mode I or IV of the direct current conversion circuit;
when the input voltage of the direct current conversion circuit is greater than the second input critical switching voltage and less than or equal to the maximum input voltage, the control signal enables the direct current conversion circuit to work in a mode III of the direct current conversion circuit;
the direct current conversion circuit works in each mode, and the voltage gain of the output side and the voltage gain of the input side of the resonant network are changed by changing the working frequency of the direct current conversion circuit by adopting the variable frequency modulation strategy; the voltage gain of the primary side and the secondary side of the transformer is equal to the turn ratio of the transformer; the voltage amplitude of the alternating current port of the inverter circuit and the voltage amplitude of the direct current port of the rectifier circuit have a proportional relation with the voltage value of the direct current port, and the output voltage of the inverter circuit is stabilized in a wide input voltage range by adjusting the switching frequency of the direct current conversion circuit.
By combining the variable frequency modulation strategy with the mode switching strategy, the output of the resonant network and the voltage gain of the input side partially coincide under three conditions that the input voltage of the direct current conversion circuit is greater than or equal to the minimum input voltage and less than or equal to the first input critical switching voltage, the input voltage of the direct current conversion circuit is greater than the first input critical switching voltage and less than or equal to the second input critical switching voltage, and the input voltage of the direct current conversion circuit is greater than the second input critical switching voltage and less than or equal to the maximum input voltage, and further the range of required frequency adjustment partially coincides, so that the range of required adjustment of the whole wide input voltage range is reduced.
Due to the adoption of the technical scheme, compared with the prior art, the invention has the following beneficial effects:
the direct current conversion circuit provided by the invention can work in four working modes, corresponding to three voltage gain modes, when the direct current converter works in a wide output voltage range, the direct current converter works in different voltage gain modes under different voltages, the gain parts of resonant cavities coincide under the three voltage gain modes, the frequency ranges of the voltage gain regulated by the circuit partially coincide, and the frequency range needing to be regulated under the wide output voltage range is reduced; when the direct current converter works in a wide input voltage range and works in different voltage gain modes under different voltages, the gain parts of the resonant cavities are overlapped under the three voltage gain modes, the frequency range of the voltage gain regulated by the circuit is partially overlapped, and the frequency range needing to be regulated under the wide input voltage range is reduced.
According to the mode switching control method of the direct current conversion circuit in the wide voltage range, the converter can work in three different gain modes under three sections of different output voltages by selecting two proper output critical switching voltages, the frequency range needing to be adjusted in the wide output voltage range is reduced, the output working voltage range of the converter is widened, and the efficiency of the converter is improved.
According to the mode switching control method of the direct current conversion circuit under the wide voltage range, the converter under three sections of different input voltages can work in three different gain modes by selecting the two proper input critical switching voltages, the frequency range needing to be adjusted under the wide input voltage range is reduced, the input working voltage range of the converter is widened, and the efficiency of the converter is improved.
Of course, it is not necessary for any product in which the invention is practiced to achieve all of the above-described advantages at the same time.
Drawings
Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:
FIG. 1 is a circuit diagram of a DC converter circuit in accordance with a preferred embodiment of the present invention;
fig. 2 is a steady-state waveform diagram of an inverter mode 1 of an inverter circuit of a dc converter circuit according to a preferred embodiment of the present invention;
fig. 3 is a steady-state waveform diagram of an inverter mode 2 of an inverter circuit of a dc converter circuit according to a preferred embodiment of the present invention;
FIG. 4 is a steady state waveform diagram of rectification mode 1 of the rectification circuit of the DC converter circuit in accordance with a preferred embodiment of the present invention;
FIG. 5 is a steady state waveform diagram of rectification mode 2 of the rectification circuit of the DC converter circuit in accordance with a preferred embodiment of the present invention;
FIG. 6 is a graph showing the gain curves of the DC converter circuit in different modes according to a preferred embodiment of the present invention;
fig. 7 is a gain curve diagram of the resonant network corresponding to different output voltages in the application of the wide output voltage of the dc-dc conversion circuit in the preferred embodiment of the present invention;
fig. 8 is a gain curve diagram of the resonant network under different input voltages in the application of the dc conversion circuit with wide input voltage according to a preferred embodiment of the present invention.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications can be made by persons skilled in the art without departing from the spirit of the invention. All falling within the scope of the present invention.
The embodiment of the invention provides a wide-output-voltage direct-current conversion circuit and a mode switching control method thereof, which weaken the contradiction between the wide voltage range and the high efficiency of an LLC resonant network while adding no extra element to the circuit under the condition of not increasing the complexity of the circuit as much as possible.
The technical solutions provided by the embodiments of the present invention are described in detail below with reference to the accompanying drawings.
Fig. 1 is a schematic circuit diagram of a dc converter circuit according to an embodiment of the present invention.
Referring to fig. 1, the dc conversion circuit provided in this embodiment includes: the device comprises a direct current input port, an inverter circuit, a resonant network, a rectifying circuit and a direct current output port; wherein:
the inverter circuit part comprises a first capacitor C1A first switch tube S1A second capacitor C2A second switch tube S2A third switch tube S3And a fourth switching tube S4(ii) a Wherein the first capacitor C1A first switch tube S1And a second switching tube S2Are sequentially connected to form a loop; second capacitor C2A third switch tube S3And a fourth switching tube S4Are sequentially connected to form a loop; first switch tube S1And a first capacitor C1The connected terminal is connected to the positive terminal of the direct current input port; a first capacitor C1And a second switch tube S2The connected terminals being connected to a second capacitor C2And a third switch tube S3A terminal connected; fourth switch tube S4And a second capacitor C2The connected terminal is connected to the negative terminal of the direct current input port;
the rectifying circuit part comprises a blocking capacitor CDA first diode D1A second diode D2A third capacitor C3A fourth capacitor C4The fifth switch tube S5And a sixth switching tube S6(ii) a First diode D1The fifth switch tube S5And a third capacitor C3Are sequentially connected to form a loop; sixth switching tube S6A second diode D2And a fourth capacitance C4Are sequentially connected to form a loop; first diode D1And a third capacitor C3The connected terminal is connected to the positive terminal of the DC output port; third capacitor C3And a fifth switching tube S5The connected terminals are connected to a fourth capacitor C4And a sixth switching tube S6A terminal connected; second diode D2And a fourth capacitor C4The connected terminal is connected to the negative terminal of the direct current output port; first diode D1In the fifth switch tube S5The connected terminals being connected to a dc blocking capacitance CDOne end of (a);
the resonant network part comprises a resonant inductance LrResonant capacitor CrParallel inductor LmAnd a high frequency transformer T; resonant capacitor CrIs connected to the first switching tube S1And a second switching tube S2Connected terminals, resonant capacitors CrIs connected at the other end to a parallel inductance LmA terminal connected to one end of the primary side of the transformer T; resonant inductor LrIs connected to the third switching tube S3And a fourth switching tube S4Connected terminals, resonant inductance LrIs connected at the other end to a parallel inductance LmA terminal connected with the other end of the primary side T of the transformer; one end of the secondary side of the transformer T is connected to a DC blocking capacitor CDAnd the other end of the secondary side of the transformer T is connected to a sixth switching tube S6And a second diode D2And an associated terminal.
The inverting part of the dc-to-dc converter circuit can operate in two modes, as shown in fig. 2, which is a steady-state waveform diagram of the inverting mode 1 of the inverting circuit of the dc-to-dc converter circuit provided in a preferred embodiment of the present invention.
Referring to fig. 2, when operating in the inverter mode 1, the switching frequency of the first to fourth switching tubes is equal to the ac resonant frequency of the resonant network, and each switching cycle includes the following two processes:
in the first process, when the positive half period of the alternating current resonant current is carried out, the driving signals of the first switching tube and the fourth switching tube are conducted, and the current sequentially flows through one terminal of the direct current input port, the first switching tube, the resonant capacitor, the parallel inductor, the primary side of the transformer and the resonant inductor and flows into the other terminal of the direct current input port through the fourth switching tube;
in the second process, when the negative half period of the alternating current resonant current is carried out, the driving signals of the second switching tube and the third switching tube are conducted, and the current sequentially flows through the resonant capacitor, the second switching tube, the third switching tube, the resonant inductor, the parallel inductor and the primary side of the transformer.
In some embodiments of the present invention, the input voltage of the resonant network is a square wave with a duty cycle of 0.5 and an amplitude equal to the dc input port voltage and zero, and the dc component of the resonant capacitor voltage is equal to half of the dc input port voltage.
In some embodiments of the invention, the resonant capacitor stores energy during positive half cycles of the ac resonant current and releases energy during negative half cycles of the ac resonant current.
Fig. 3 is a steady-state waveform diagram of an inverter mode 2 of an inverter circuit of a dc converter circuit according to a preferred embodiment of the present invention.
Referring to fig. 3, the inverter circuit may further operate in the inverter mode 2, and when operating in the inverter mode 2, the switching frequency of the first to fourth switching tubes is equal to half of the ac resonant frequency of the resonant network, and each switching cycle includes the following four processes:
in the first process, when the positive half period of the first alternating current resonant current period is started, the driving signals of the first switching tube and the third switching tube are conducted, and current flows through the positive terminal of the first capacitor, the first switching tube, the resonant capacitor, the parallel inductor, the primary side of the transformer and the resonant inductor in sequence and flows into the negative terminal of the first capacitor through the third switching tube;
in the second process and in the negative half period of the first alternating current resonant current period, the driving signal of the first switching tube turns off the first switching tube, the driving signal of the second switching tube turns on the second switching tube, and the current sequentially flows through the resonant capacitor, the second switching tube, the third switching tube, the resonant inductor, the parallel inductor and the primary side of the transformer;
in the third process and in the positive half period of the second alternating current resonant current period, the third switching tube is turned off by a driving signal, the fourth switching tube is turned on by a driving signal, and current flows through the positive terminal of the second capacitor, the second switching tube, the resonant capacitor, the parallel inductor, the primary side of the transformer and the resonant inductor in sequence and flows into the negative terminal of the second capacitor through the fourth switching tube;
in the fourth process and in the negative half period of the second alternating current resonant current period, the driving signal of the fourth switching tube turns off the fourth switching tube, the driving signal of the third switching tube turns on the third switching tube, and the current sequentially flows through the resonant capacitor, the second switching tube, the third switching tube, the resonant inductor, the parallel inductor and the primary side of the transformer.
In some embodiments of the present invention, the input voltage of the resonant network is a square wave with a duty cycle of 0.5 and an amplitude equal to one-half and zero of the voltage of the dc input port, and the dc component of the voltage of the resonant capacitor is equal to one-fourth of the voltage of the dc input port.
In some embodiments of the invention, the first capacitor stores energy during positive half cycles of the ac resonant current and the first capacitor discharges energy during negative half cycles of the ac resonant current.
Similarly, the rectifying part of the dc converter circuit can also operate in two modes, as shown in fig. 4, which is a steady-state waveform diagram of the rectifying mode 1 of the rectifying circuit of the dc converter circuit provided in a preferred embodiment of the present invention.
Referring to fig. 4, when operating in the rectification mode 1, the switching frequency of the fifth switching tube and the sixth switching tube is equal to the ac resonant frequency of the resonant network, and each switching cycle includes the following processes:
in the first process, when the positive half period of the alternating-current resonant current is carried out, the driving signals of the fifth switching tube and the sixth switching tube are turned off, and the current sequentially flows through one terminal of the secondary side of the transformer, the blocking capacitor, the first diode and the direct-current output port and flows into the other terminal of the secondary side of the transformer through the second diode;
in the second process, when the negative half period of the alternating-current resonant current is carried out, the driving signals of the fifth switching tube and the sixth switching tube are conducted, and the current sequentially flows through one terminal of the secondary side of the transformer, the sixth switching tube and the fifth switching tube and flows into the other terminal of the secondary side of the transformer through the blocking capacitor.
In some embodiments of the present invention, the output voltage of the resonant network is a square wave having a duty cycle of 0.5 and an amplitude equal to one half of the voltage of the positive dc output port and one half of the voltage of the negative dc output port, and the dc component of the voltage of the dc blocking capacitor is equal to one half of the voltage of the dc output port.
In some embodiments of the invention, the blocking capacitor stores energy during positive half cycles of the ac resonant current and the blocking capacitor releases energy during negative half cycles of the ac resonant current.
Fig. 5 is a steady-state waveform diagram of a rectification mode 2 of a rectification circuit of a dc converter circuit according to a preferred embodiment of the present invention.
Referring to fig. 5, when operating in the rectification mode 2, the switching frequency of the fifth switching tube and the sixth switching tube is equal to half of the ac resonant frequency of the resonant network, and each switching cycle includes the following processes:
in the first process, when the positive half period of the first alternating current resonant current period is carried out, the driving signal of the fifth switching tube enables the fifth switching tube to be conducted, and the current flows through one terminal of the secondary side of the transformer, the blocking capacitor, the fifth switching tube and the fourth capacitor in sequence and flows into the other terminal of the secondary side of the transformer through the second diode;
in the second process, when the negative half period of the first alternating current resonant current period is carried out, the driving signal of the sixth switching tube enables the sixth switching tube to be switched on, and the current flows through one terminal of the secondary side of the transformer, the sixth switching tube and the fifth switching tube in sequence and flows into the other terminal of the secondary side of the transformer through the blocking capacitor;
in the third process and in the positive half period of the second alternating current resonant current period, the driving signal of the fifth switching tube turns off, and the current flows through one terminal of the secondary side of the transformer, the blocking capacitor, the first diode and the third capacitor in sequence and flows into the other terminal of the secondary side of the transformer through the sixth switching tube;
in the fourth and second half periods of the alternating current resonant current cycle, the driving signal of the fifth switching tube turns on the fifth switching tube, and the current flows through one terminal of the secondary side of the transformer, the sixth switching tube and the fifth switching tube in sequence and flows into the other terminal of the secondary side of the transformer through the blocking capacitor.
In some embodiments of the present invention, the output voltage of the resonant network is a square wave having a duty cycle of 0.5 and an amplitude equal to one fourth of the voltage of the positive dc output port and one fourth of the voltage of the negative dc output port, and the dc component of the voltage of the dc blocking capacitor is equal to one fourth of the voltage of the dc output port.
In some embodiments of the invention, the blocking capacitor stores energy during positive half cycles of the ac resonant current and the blocking capacitor releases energy during negative half cycles of the ac resonant current.
As shown in fig. 6, a gain curve diagram of the dc converter circuit according to the preferred embodiment of the present invention is shown in different modes.
Referring to fig. 6, the dc converter can realize four operation modes by combining two inversion modes of the inverter circuit and two rectification modes of the rectifier circuit:
mode I: the inverter circuit works in an inverter mode 1, the rectifier circuit works in a rectifier mode 1, and a complex frequency domain circuit model of the resonant network is obtained by utilizing a phasor method;
calculating a resonant network voltage gain expression G in a mode I by using a fundamental equivalent methodI(fn) Comprises the following steps:
Figure BDA0002852659630000121
mode II: the inverter circuit works in an inverter mode 1, the rectifier circuit works in a rectifier mode 2, and a resonant network voltage gain expression G in a calculation mode II is calculated by applying a fundamental wave equivalent methodII(fn) Comprises the following steps:
Figure BDA0002852659630000122
mode III: the inverter circuit works in an inverter mode 2, the rectifier circuit works in a rectifier mode 1, and a resonant network voltage gain expression G in a calculation mode III is calculated by applying a fundamental equivalent methodIII(fn) Comprises the following steps:
Figure BDA0002852659630000123
mode IV: the inverter circuit works in an inverter mode 2, the rectifier circuit works in a rectifier mode 2, and a resonant network voltage gain expression G in a calculation mode IV is calculated by applying a fundamental equivalent methodIV(fn) Comprises the following steps:
Figure BDA0002852659630000124
wherein, V1For input voltage, V2To output voltage, fnTo normalize frequency, fn＝fS/fr，fSTo the operating frequency, frIs a resonant inductor LrAnd a resonance capacitor CrThe frequency of the series resonance is such that,
Figure BDA0002852659630000125
k＝Lm/Lr，R1to output the load, LmThe inductance is parallel inductance or excitation inductance of the transformer, and n is the turn ratio of the transformer.
The direct current converter circuit provided by the invention has four working modes corresponding to three voltage gain modes, so that the direct current converter can be suitable for application of wide output voltage and wide input voltage.
In some embodiments of the present invention, the parallel inductor may be an inductor separately disposed, or may be an excitation inductor of a transformer.
Another embodiment of the present invention provides a mode switching control method for a dc conversion circuit in a wide voltage range, the method using a variable frequency modulation strategy in combination with a mode switching strategy to regulate a wide output voltage of the dc conversion circuit; wherein:
the direct current conversion circuit works in a wide output voltage mode, and the principle of adopting the mode switching strategy is as follows:
when the output voltage of the direct current conversion circuit is greater than or equal to the minimum output voltage and less than or equal to the first output critical switching voltage, the control signal enables the direct current conversion circuit to work in a mode III of the direct current conversion circuit;
when the output voltage of the direct current conversion circuit is greater than the first output critical switching voltage and less than or equal to the second output critical switching voltage, the control signal enables the direct current conversion circuit to work in a mode I or IV of the direct current conversion circuit;
when the output voltage of the direct current conversion circuit is greater than the second output critical switching voltage and less than or equal to the maximum output voltage, the control signal enables the direct current conversion circuit to work in a mode II of the direct current conversion circuit;
the direct current conversion circuit works in each mode, and the voltage gain of the output side and the voltage gain of the input side of the resonant network are changed by changing the working frequency of the direct current conversion circuit by adopting the variable frequency modulation strategy; the voltage gain of the primary side and the secondary side of the transformer is equal to the turn ratio of the transformer; the voltage amplitude of the alternating current port of the inverter circuit and the rectifying circuit is in a proportional relation with the voltage value of the direct current port, and the output voltage is adjusted by adjusting the switching frequency of the direct current conversion circuit.
As shown in fig. 7, a gain curve diagram of the resonant network corresponding to different output voltages in the application of the wide output voltage of the dc converter circuit according to a preferred embodiment of the present invention is provided.
Referring to fig. 7, the principle of the mode switching strategy adopted when the dc conversion circuit operates in the wide output voltage mode is as follows:
when the output voltage of the DC conversion circuit is greater than or equal to the minimum output voltage V2minAnd is less than or equal to the first output threshold switching voltage V2switch1The control signal makes the DC conversion circuit work in the mode III of the DC conversion circuit, the inverter circuit of the DC conversion circuit works in the inverter mode 2, the equivalent input AC voltage of the resonance network is the difference between the input voltage of the resonance network and the DC component of the voltage of the resonance capacitor, namely the square wave with the duty ratio of 0.5 and the amplitude equal to one fourth of the voltage of the positive DC input port and one fourth of the voltage of the negative DC input port, and the voltage gain ranges of the output side and the input side of the resonance network are
Figure BDA0002852659630000131
When the output voltage of the DC conversion circuit is greater than the first output critical switching voltage V2switch1And is less than or equal to the second output critical switching voltage V2switch2The control signal makes the DC conversion circuit work in a mode I or IV of the DC conversion circuit; when the DC conversion circuit works in the mode I of the DC conversion circuit, the inverter circuit of the DC conversion circuit works in the inverter mode 1, and the equivalent input AC voltage of the resonant network is the DC components of the input voltage of the resonant network and the voltage of the resonant capacitorA square wave having a duty cycle of 0.5 and an amplitude equal to one half of the voltage at the positive dc input port and one half of the voltage at the negative dc input port, the voltage gain at the output and input sides of the resonant network ranging from
Figure BDA0002852659630000141
Figure BDA0002852659630000142
When the DC conversion circuit works in the mode IV of the DC conversion circuit, the inverter circuit of the DC conversion circuit works in the inverter mode 2, and the voltage gain ranges of the output side and the input side of the resonant network are
Figure BDA0002852659630000143
Figure BDA0002852659630000144
Therefore, the voltage gain ranges of the output and the input sides of the resonant networks corresponding to the modes I and IV of the direct current conversion circuit are the same;
when the output voltage of the DC conversion circuit is greater than the second output critical switching voltage V2switch2And is less than or equal to the maximum output voltage V2maxThe control signal makes the direct current conversion circuit work in a mode II of the direct current conversion circuit; the inverter circuit of the DC conversion circuit works in an inverter mode 1, and the voltage gain ranges of the output side and the input side of the resonant network are
Figure BDA0002852659630000145
The direct current conversion circuit works in each mode, and the output of the resonant network and the voltage gain of the input side are changed by changing the working frequency of the direct current conversion circuit by adopting a frequency conversion modulation strategy; the voltage gain of the primary side and the secondary side of the transformer is equal to the turn ratio of the transformer; the voltage amplitude of the alternating current port of the inverter circuit and the rectifying circuit has a proportional relation with the voltage value of the direct current port, and the output voltage is adjusted by adjusting the switching frequency of the direct current conversion circuit;
the frequency conversion modulation strategy is combined with the mode switching strategy, the output voltage of the direct current conversion circuit is larger than or equal to the minimum output voltage and smaller than or equal to the first output critical switching voltage, the output voltage of the direct current conversion circuit is larger than the first output critical switching voltage and smaller than or equal to the second output critical switching voltage, and the output voltage of the direct current conversion circuit is larger than the second output critical switching voltage and smaller than or equal to the maximum output voltage, the output of the resonant network and the voltage gain range of the input side are partially overlapped, further the frequency regulation range is partially overlapped, and therefore the regulation range of the whole wide output voltage range is reduced.
In a third embodiment of the present invention, another mode switching control method for a dc converter circuit in a wide voltage range is provided, in which a frequency conversion modulation strategy is combined with a mode switching strategy to stabilize the output voltage of the converter circuit in a wide input voltage range; wherein:
the direct current conversion circuit works in a wide input voltage mode, and the principle of adopting the mode switching strategy is as follows:
when the input voltage of the direct current conversion circuit is greater than or equal to the minimum input voltage and less than or equal to the first input critical switching voltage, the control signal enables the direct current conversion circuit to work in a mode II of the direct current conversion circuit;
when the input voltage of the direct current conversion circuit is greater than the first input critical switching voltage and less than or equal to the second input critical switching voltage, the control signal enables the direct current conversion circuit to work in a mode I or IV of the direct current conversion circuit;
when the input voltage of the direct current conversion circuit is greater than the second input critical switching voltage and less than or equal to the maximum input voltage, the control signal enables the direct current conversion circuit to work in a mode III of the direct current conversion circuit;
the direct current conversion circuit works in each mode, and the voltage gain of the output side and the voltage gain of the input side of the resonant network are changed by changing the working frequency of the direct current conversion circuit by adopting the variable frequency modulation strategy; the voltage gain of the primary side and the secondary side of the transformer is equal to the turn ratio of the transformer; the voltage amplitude of the alternating current port of the inverter circuit and the voltage amplitude of the direct current port of the rectifier circuit have a proportional relation with the voltage value of the direct current port, and the output voltage of the inverter circuit is stabilized in a wide input voltage range by adjusting the switching frequency of the direct current conversion circuit.
As shown in fig. 8, a gain curve diagram of the resonant network corresponding to different input voltages in the application of the wide input voltage of the dc conversion circuit according to a preferred embodiment of the present invention is provided.
Referring to fig. 8, the dc conversion circuit operates in the wide input voltage mode, and the principle of the mode switching strategy is as follows:
when the input voltage of the DC conversion circuit is greater than or equal to the minimum input voltage V1minAnd is less than or equal to the first input critical switching voltage V1switch1The control signal makes the DC conversion circuit work in the mode II of the DC conversion circuit, the inverter circuit of the DC conversion circuit works in the inverter mode 1, and the voltage gain range of the output side and the input side of the resonant network is
Figure BDA0002852659630000151
When the input voltage of the DC conversion circuit is greater than the first input critical switching voltage V1switch1And is less than or equal to the second input critical switching voltage V1switch2The control signal makes the DC conversion circuit work in a mode I or IV of the DC conversion circuit; when the DC conversion circuit works in the mode I of the DC conversion circuit, the inverter circuit of the DC conversion circuit works in the inverter mode 1, and the voltage gain ranges of the output side and the input side of the resonant network are
Figure BDA0002852659630000152
When the DC conversion circuit operates in the mode IV of the DC conversion circuit, the voltage gain range of the output side and the input side of the resonant network is
Figure BDA0002852659630000153
Therefore, the voltage gain ranges of the output and the input sides of the resonant networks corresponding to the modes I and IV of the direct current conversion circuit are the same;
when the input voltage of the DC conversion circuit is greater than the second input critical switching voltage V1switch2And is less than or equal to the maximum input voltage V2minThe control signal makes the DC conversion circuit work in the mode III of the DC conversion circuit, the inverter circuit of the DC conversion circuit works in the inverter mode 1, and the voltage gain ranges of the output side and the input side of the resonant network are
Figure BDA0002852659630000154
Figure BDA0002852659630000161
The direct current conversion circuit works in each mode, and the output of the resonant network and the voltage gain of the input side are changed by changing the working frequency of the direct current conversion circuit by adopting a frequency conversion modulation strategy; the voltage gain of the primary side and the secondary side of the transformer is equal to the turn ratio of the transformer; the voltage amplitude of the alternating current port of the inverter circuit and the voltage amplitude of the direct current port of the rectifier circuit have a proportional relation with the voltage value of the direct current port, and the output voltage of the inverter circuit is stabilized in a wide input voltage range by adjusting the switching frequency of the direct current inverter circuit;
the frequency conversion modulation strategy is combined with the mode switching strategy, the output of the resonant network and the voltage gain of the input side partially coincide under the three conditions that the input voltage of the direct current conversion circuit is greater than or equal to the minimum input voltage and less than or equal to the first input critical switching voltage, the input voltage of the direct current conversion circuit is greater than the first input critical switching voltage and less than or equal to the second input critical switching voltage and less than or equal to the maximum input voltage, and further the required frequency adjustment range partially coincides, so that the required adjustment range of the whole wide input voltage range is reduced.
Through the technical scheme provided by the embodiment of the invention, the designed direct current converter has wide voltage output capability, the range of adjusting the switching frequency is smaller, and the design of a transformer is facilitated.
The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes and modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention.

Claims (5)

1. A dc conversion circuit, comprising: the device comprises a direct current input port, an inverter circuit, a resonant network, a rectifying circuit and a direct current output port; wherein:
the inverter circuit comprises a first capacitor, a first switch tube, a second capacitor, a second switch tube, a third switch tube and a fourth switch tube; the first capacitor, the first switch tube and the second switch tube are sequentially connected to form a loop; the second capacitor, the third switch tube and the fourth switch tube are sequentially connected to form a loop; the terminal of the first switch tube connected with the first capacitor is connected to the positive terminal of the direct current input port; the terminal of the first capacitor connected with the second switch tube is connected with the terminal of the second capacitor connected with the third switch tube; the terminal of the fourth switching tube connected with the second capacitor is connected to the negative terminal of the direct current input port;
the rectifying circuit comprises a first diode, a second diode, a third capacitor, a fourth capacitor, a fifth switching tube, a sixth switching tube and a blocking capacitor; the first diode, the fifth switch tube and the third capacitor are sequentially connected to form a loop; the sixth switching tube, the second diode and the fourth capacitor are sequentially connected to form a loop; the terminal of the first diode connected with the third capacitor is connected to the positive terminal of the direct current output port; the terminal of the third capacitor connected with the fifth switching tube is connected with the terminal of the fourth capacitor connected with the sixth switching tube; the terminal of the second diode connected with the fourth capacitor is connected to the negative terminal of the direct current output port; the terminal of the first diode connected with the fifth switching tube is connected to one end of the blocking capacitor;
the resonance network comprises a resonance inductor, a resonance capacitor, a parallel inductor and a transformer; one end of the resonant capacitor is connected to a terminal connected with the first switching tube and the second switching tube, and the other end of the resonant capacitor is connected to a terminal connected with the parallel inductor and one end of the primary side of the transformer; one end of the resonant inductor is connected to a terminal connected with the third switching tube and the fourth switching tube, and the other end of the resonant inductor is connected to a terminal connected with the parallel inductor and the other end of the primary side of the transformer; one end of the secondary side of the transformer is connected to one end of the blocking capacitor, and the other end of the secondary side of the transformer is connected to a terminal of the sixth switching tube connected with the second diode;
the inverter circuit works in an inverter mode 1 or an inverter mode 2:
the inverter circuit works in an inverter mode 1, wherein the switching frequency of a first switching tube to a fourth switching tube in the inverter mode 1 is equal to the resonance frequency of the resonance network, and each switching period comprises the following processes:
in the first process, when a positive half period of an alternating current resonant current is carried out, the first switching tube and the fourth switching tube are conducted through a driving signal, and the current sequentially flows through one terminal of the direct current input port, the first switching tube, the resonant capacitor, the parallel inductor, the primary side of the transformer and the resonant inductor and flows into the other terminal of the direct current input port through the fourth switching tube;
in the second process, when the negative half period of the alternating-current resonant current is carried out, the second switching tube and the third switching tube are conducted through a driving signal, and the current sequentially flows through the resonant capacitor, the second switching tube, the third switching tube, the resonant inductor, the parallel inductor and the primary side of the transformer;
the input voltage of the resonant network is a square wave with a duty ratio of 0.5 and an amplitude equal to the voltage of the direct current input port and zero, and the direct current component of the voltage of the resonant capacitor is equal to one half of the voltage of the direct current input port;
the resonant capacitor stores energy during a positive half cycle of the alternating resonant current, and the resonant capacitor releases energy during a negative half cycle of the alternating resonant current;
the inverter circuit works in an inverter mode 2, wherein the switching frequency of the first switching tube to the fourth switching tube in the inverter mode 2 is equal to half of the alternating-current resonance frequency of the resonance network, and each switching period comprises the following processes:
in the first process, when a positive half period of a first alternating current resonant current period is formed, the first switching tube and the third switching tube are conducted through a driving signal, and current flows through a positive terminal of the first capacitor, the first switching tube, the resonant capacitor, the parallel inductor, a primary side of the transformer and the resonant inductor in sequence and flows into a negative terminal of the first capacitor through the third switching tube;
in the second process and in the negative half period of the first alternating current resonant current period, the first switching tube is turned off by a driving signal, the second switching tube is turned on by a driving signal, and the current sequentially flows through the resonant capacitor, the second switching tube, the third switching tube, the resonant inductor, the parallel inductor and the primary side of the transformer;
in the third process and in the positive half period of the second alternating current resonant current period, the third switching tube is turned off by a driving signal, the fourth switching tube is turned on by the driving signal, and the current sequentially flows through the positive terminal of the second capacitor, the second switching tube, the resonant capacitor, the parallel inductor, the primary side of the transformer and the resonant inductor and flows into the negative terminal of the second capacitor through the fourth switching tube;
in the fourth process and in the negative half period of the second alternating current resonant current period, the fourth switching tube is turned off by a driving signal, the third switching tube is turned on by the driving signal, and the current sequentially flows through the resonant capacitor, the second switching tube, the third switching tube, the resonant inductor, the parallel inductor and the primary side of the transformer;
the input voltage of the resonant network is a square wave with a duty ratio of 0.5 and an amplitude equal to one half and zero of the voltage of the direct current input port, and the direct current component of the voltage of the resonant capacitor is equal to one quarter of the voltage of the direct current input port;
the first capacitor stores energy during a positive half cycle of the alternating resonant current and releases energy during a negative half cycle of the alternating resonant current;
the rectification circuit works in a rectification mode a or a rectification mode b;
the rectification circuit works in a rectification mode a, wherein the switching frequency of a fifth switching tube and a sixth switching tube in the rectification mode a is equal to the resonance frequency of the resonance network, and each switching period comprises the following processes:
in the first process, during a positive half cycle of the alternating-current resonant current, the fifth switching tube and the sixth switching tube are turned off by a driving signal, and the current sequentially flows through one terminal of the secondary side of the transformer, the blocking capacitor, the first diode and the direct-current output port and flows into the other terminal of the secondary side of the transformer through the second diode;
in the second process, during a negative half cycle of the alternating-current resonant current, the fifth switching tube and the sixth switching tube are conducted through a driving signal, and the current sequentially flows through one terminal of the secondary side of the transformer, the sixth switching tube and the fifth switching tube and flows into the other terminal of the secondary side of the transformer through the blocking capacitor;
the output voltage of the resonant network is a square wave with the duty ratio of 0.5 and the amplitude equal to one half of the voltage of the positive direct current output port and one half of the voltage of the negative direct current output port, and the direct current component of the voltage of the blocking capacitor is equal to one half of the voltage of the direct current output port;
the blocking capacitor stores energy in the positive half period of the alternating current resonant current, and releases energy in the negative half period of the alternating current resonant current;
the rectification circuit works in a rectification mode b, wherein the switching frequency of a fifth switching tube and a sixth switching tube in the rectification mode b is equal to half of the alternating-current resonance frequency of the resonance network, and each switching period comprises the following processes:
in the first process, when the positive half period of the first alternating current resonant current period is carried out, the fifth switching tube is conducted through a driving signal, and current flows through one terminal of the secondary side of the transformer, the blocking capacitor, the fifth switching tube and the fourth capacitor in sequence and flows into the other terminal of the secondary side of the transformer through the second diode;
in the second process, when the negative half period of the first alternating current resonant current period is carried out, the sixth switching tube is switched on through a driving signal, and the current flows through one terminal of the secondary side of the transformer, the sixth switching tube and the fifth switching tube in sequence and flows into the other terminal of the secondary side of the transformer through the DC blocking capacitor;
in the third process and in the positive half period of the second alternating-current resonant current period, the fifth switching tube is turned off by a driving signal, and current flows through one terminal of the secondary side of the transformer, the blocking capacitor, the first diode and the third capacitor in sequence and flows into the other terminal of the secondary side of the transformer through the sixth switching tube;
in the fourth process and in the negative half period of the second alternating-current resonant current period, the fifth switching tube is switched on by a driving signal, and current flows through one terminal of the secondary side of the transformer, the sixth switching tube and the fifth switching tube in sequence and flows into the other terminal of the secondary side of the transformer through the blocking capacitor;
the output voltage of the resonant network is a square wave with the duty ratio of 0.5 and the amplitude equal to one fourth of the voltage of the positive direct current output port and one fourth of the voltage of the negative direct current output port, and the direct current component of the voltage of the blocking capacitor is equal to one fourth of the voltage of the direct current output port;
the blocking capacitor stores energy in the positive half period of the alternating current resonant current, and releases energy in the negative half period of the alternating current resonant current;
any one of four working modes I-IV is realized by combining an inversion mode of an inverter circuit and a rectification mode of a rectification circuit:
mode I: the inverter circuit works in an inverter mode 1, the rectifier circuit works in a rectifier mode a, and a complex frequency domain circuit model of the resonant network is obtained by using a phasor method;
calculating the voltage gain expression G of the resonant network in the mode I by using a fundamental equivalent methodI(fn) Comprises the following steps:
Figure FDA0003499037050000041
mode II: the inverter circuit works in an inverter mode 1, the rectifier circuit works in a rectifier mode b, and the voltage gain expression G of the resonant network in the mode II is calculated by using a fundamental equivalent methodII(fn) Comprises the following steps:
Figure FDA0003499037050000042
mode III: the inverter circuit works in an inverter mode 2, the rectifier circuit works in a rectifier mode a, and the voltage gain expression G of the resonant network in the mode III is calculated by using a fundamental equivalent methodIII(fn) Comprises the following steps:
Figure FDA0003499037050000043
mode IV: the inverter circuit works in an inverter mode 2, the rectifier circuit works in a rectifier mode b, and the harmonic network voltage gain expression G in the mode IV is calculated by using a fundamental equivalent methodIV(fn) Comprises the following steps:
Figure FDA0003499037050000044
wherein, V1For input voltage, V2To output voltage, fnTo normalize frequency, fn＝fS/fr，fSTo the operating frequency, frIs the resonance inductance LrAnd said resonant capacitor CrThe frequency of the series resonance is such that,
Figure FDA0003499037050000045
Figure FDA0003499037050000046
k＝Lm/Lr，R1to output the load, LmThe inductance is the parallel inductance or the excitation inductance of the transformer, and n is the turn ratio of the transformer.
2. The dc conversion circuit of claim 1, wherein the parallel inductor is an independently arranged inductor.
3. The dc conversion circuit according to claim 1, wherein the shunt inductor is an excitation inductor of the transformer.
4. A mode switching control method under a wide voltage range of the dc conversion circuit according to any one of claims 1 to 3, wherein a variable frequency modulation strategy is adopted in combination with a mode switching strategy to adjust the wide output voltage of the dc conversion circuit; wherein:
the direct current conversion circuit works in a wide output voltage mode, and the principle of adopting the mode switching strategy is as follows:
when the output voltage of the direct current conversion circuit is greater than or equal to the minimum output voltage and less than or equal to the first output critical switching voltage, the control signal enables the direct current conversion circuit to work in a mode III of the direct current conversion circuit;
when the output voltage of the direct current conversion circuit is greater than the first output critical switching voltage and less than or equal to the second output critical switching voltage, the control signal enables the direct current conversion circuit to work in a mode I or IV of the direct current conversion circuit;
when the output voltage of the direct current conversion circuit is greater than the second output critical switching voltage and less than or equal to the maximum output voltage, the control signal enables the direct current conversion circuit to work in a mode II of the direct current conversion circuit;
the direct current conversion circuit works in each mode, and the voltage gain of the output side and the voltage gain of the input side of the resonant network are changed by changing the working frequency of the direct current conversion circuit by adopting the variable frequency modulation strategy; the voltage gain of the primary side and the secondary side of the transformer is equal to the turn ratio of the transformer; the voltage amplitude of the alternating current port of the inverter circuit and the rectifying circuit is in a proportional relation with the voltage value of the direct current port, and the output voltage is adjusted by adjusting the switching frequency of the direct current conversion circuit.
5. A mode switching control method in a wide voltage range of a dc converter circuit according to any one of claims 1 to 3, characterized in that a variable frequency modulation strategy is used in combination with a mode switching strategy to stabilize the converter circuit output voltage in the wide input voltage range; wherein:
the direct current conversion circuit works in a wide input voltage mode, and the principle of adopting the mode switching strategy is as follows:
when the input voltage of the direct current conversion circuit is greater than or equal to the minimum input voltage and less than or equal to the first input critical switching voltage, the control signal enables the direct current conversion circuit to work in a mode II of the direct current conversion circuit;
when the input voltage of the direct current conversion circuit is greater than the first input critical switching voltage and less than or equal to the second input critical switching voltage, the control signal enables the direct current conversion circuit to work in a mode I or IV of the direct current conversion circuit;
when the input voltage of the direct current conversion circuit is greater than the second input critical switching voltage and less than or equal to the maximum input voltage, the control signal enables the direct current conversion circuit to work in a mode III of the direct current conversion circuit;
the direct current conversion circuit works in each mode, and the voltage gain of the output side and the voltage gain of the input side of the resonant network are changed by changing the working frequency of the direct current conversion circuit by adopting the variable frequency modulation strategy; the voltage gain of the primary side and the secondary side of the transformer is equal to the turn ratio of the transformer; the voltage amplitude of the alternating current port of the inverter circuit and the voltage amplitude of the direct current port of the rectifier circuit have a proportional relation with the voltage value of the direct current port, and the output voltage of the inverter circuit is stabilized in a wide input voltage range by adjusting the switching frequency of the direct current conversion circuit.
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