CN108092515B - High-frequency soft-switching resonant direct-current converter and voltage gain calculation method - Google Patents

High-frequency soft-switching resonant direct-current converter and voltage gain calculation method Download PDF

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CN108092515B
CN108092515B CN201711289852.7A CN201711289852A CN108092515B CN 108092515 B CN108092515 B CN 108092515B CN 201711289852 A CN201711289852 A CN 201711289852A CN 108092515 B CN108092515 B CN 108092515B
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resonance
mode
capacitor
resonant
voltage
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CN108092515A (en
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顾玲
惠琦
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Nanjing University of Science and Technology
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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
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0048—Circuits or arrangements for reducing losses
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0048—Circuits or arrangements for reducing losses
    • H02M1/0054—Transistor switching losses
    • H02M1/0058—Transistor switching losses by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

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

Abstract

The invention discloses a high-frequency soft-switching resonant direct-current converter, which absorbs leakage inductance of a transformer as a part of resonant inductance, and absorbs junction capacitance of a switching tube and junction capacitance of a diode as a part of resonant capacitance. The converter can realize zero voltage switching of the switching tube and the diode and zero current turn-off of the diode at the same time, the switching loss of the converter is almost zero, the efficiency of the converter is improved, the voltage stress of the diode is guaranteed to be clamped to twice of the output voltage, and the voltage stress is reduced.

Description

High-frequency soft-switching resonant direct-current converter and voltage gain calculation method
Technical Field
The invention relates to a technology of a resonant converter, in particular to a high-frequency soft-switching resonant direct-current converter and a voltage gain calculation method.
Background
Increasing the switching frequency of a converter is an effective means to increase its power density. For hard switching circuits, however, increasing the switching frequency means an increase in switching losses, which can significantly reduce the overall efficiency of the converter. Therefore, it is important to research soft switching technology to increase the switching frequency of the converter without increasing the switching loss.
The resonance technique is an important means to realize soft switching. At present, most of commonly used switching tubes adopt MOSFET, and the method for realizing zero-voltage switching by using the body diode is a commonly used method, such as LLC resonant converter, phase-shifted full-bridge converter and the like. However, most of these converters are multi-tube converters, and in some occasions with lower power, a single-tube soft switching converter needs to be researched to reduce the cost and the complexity of a control and driving circuit, and in the process of increasing the switching frequency, the multi-tube converter cannot avoid floating driving, and the converter can be unreliable in operation. The diode voltage stress of the existing single-tube zero-voltage switch quasi-resonance or multi-resonance converter is large at present, and the converter is not suitable for the application of a Schottky diode, so that the conduction voltage drop of the selected diode is large, the conduction loss is increased, and the conversion efficiency is influenced.
Disclosure of Invention
The invention aims to provide a high-frequency soft-switching resonant direct-current converter and a voltage gain calculation method, which realize zero-voltage switching of a switching tube and a diode and zero-current turn-off of the diode, the switching loss of the converter is almost zero, the efficiency of the converter is improved, and the technical problems that the zero-voltage switching quasi-resonant converter can only improve the switching condition of one device in the switching tube and the diode and the voltage stress of the zero-voltage switching multi-resonant converter diode is overlarge are solved.
A high-frequency soft-switching resonant direct-current converter comprises a direct-current power supply, an input side inductor, a switching tube, a first resonant capacitor, a blocking capacitor, a resonant inductor, an isolation transformer, a first diode, a second resonant capacitor, a third resonant capacitor and an output filter capacitor; the isolation transformer comprises a primary winding, a first secondary winding and a second secondary winding; the first pin of the input side inductor is connected with the positive end of a direct current power supply, the second pin of the input side inductor is respectively connected with the drain electrode of a switching tube, the first pin of a first resonant capacitor and the first pin of a blocking capacitor, the second pin of the blocking capacitor is connected with the first pin of the resonant inductor, the second pin of the resonant inductor is connected with the dotted terminal of a primary winding of an isolation transformer, the negative end of the direct current power supply, the source electrode of the switching tube, the second pin of the first resonant capacitor and the dotted terminal of the primary winding of the isolation transformer are grounded, the anode of a first diode is respectively connected with the first pin of a second resonant capacitor and the dotted terminal of a first secondary winding of the isolation transformer, the anode of a second diode is respectively connected with the first pin of a third resonant capacitor and the dotted terminal of the second secondary winding of the isolation transformer, the cathode of a first diode, the second pin of the second resonant capacitor, the cathode of the second diode, the second pin of the third resonant capacitor and the, and the second pin of the output filter capacitor, the different-name end of the first secondary winding of the isolation transformer and the same-name end of the second secondary winding of the isolation transformer are grounded.
A voltage gain calculation method of a high-frequency soft switching resonant direct-current converter comprises the following steps:
step 1, setting a first mode as a first resonance capacitor (C)s) Resonant inductor (L)s) A second resonant capacitor (C)d1) A third resonant capacitor (C)d2) The four participate in resonance;
with input side inductance (L)f) Current rises to IoIs the starting time t0Setting the initial conditions as follows: iL (t)0)＝Io，vs(t0)＝Vs0，vd1(t0)＝2Vo，vd2(t0)＝0；
Setting the output voltage (V)o) And a first resonance capacitor (C)s) Voltage across (v)s) Initial value as iterative variationAmount, Vs0、VoRespectively presetting initial values of iteration variables;
at t1At time, the first resonance capacitance (C)s) Voltage across (v)s) Resonating to 0, calculating the duration t of the first mode01While calculating the initial condition i of the second modeL(t1)＝iL(t01)，vs(t1)＝0，vd1(t1)＝vd1(t01)，vd2(t1)＝vd2(t01)；
Step 2, the converter enters a second mode, wherein the second mode is a resonance inductor (L)s) A second resonant capacitor (C)d1) A third resonant capacitor (C)d2) The three parts participate in resonance;
at t2Time of day, second resonant capacitance (C)d1) Voltage across (v)d1) Down to 0, third resonant capacitance (C)d2) Voltage v acrossd2Rise to 2VoCalculating the duration t of the second mode12(ii) a The initial conditions for the third modality are also calculated: i.e. iL(t2)＝iL(t12)，vs(t2)＝0，vd1＝0，vd2＝2Vo；
Step 3, the converter enters a third mode, the third mode is that no resonance exists, and the inductance current is linearly reduced;
at t3At that moment, the inductor current drops to IoFrom this, the duration t of the third modality can be calculated23(ii) a The initial conditions for the fourth modality are also calculated: i.e. iL(t3)＝Io，vs(t3)＝0，vd1(t3)＝0，vd2(t3)＝2Vo；
Step 4, the fourth mode is resonance inductance (L)s) A second resonant capacitor (C)d1) A third resonant capacitor (C)d2) The three parts participate in resonance;
if at t4Time of day, third resonant capacitance (C)d2) Two endsVoltage (v)d2) Firstly, the temperature is decreased to 0, and then the step S401 is executed; if at t4At the moment, the switching tube (S) is turned off first, and then the step S411 is executed;
step S401, calculating the duration t of the fourth mode34(ii) a The initial conditions for the fifth modality are also calculated: i.e. iL(t4)＝iL(t34)，vs(t4)＝0，vd1(t4)＝2Vo，vd2(t4) 0; turning to step S501;
step S501, resonance does not exist in the fifth mode, and the inductive current linearly rises or falls;
at t5At the moment, the switching tube (S) is turned off, and the duration of the fifth mode is assumed to be txAnd calculating the initial condition of the sixth mode: i.e. iL(t5)＝iL(tx)，vs(t5)＝0，vd1(t5)＝2Vo，vd2(t5) 0; turning to step S601;
step S601, the sixth mode is resonance inductance (L)s) And a first resonance capacitor (C)s) Resonating;
at t6At that moment, the inductor current rises to IoThe first mode will be returned to, from which the duration t of the sixth mode can be calculated56(ii) a Final value for the sixth modality: i.e. iL(t6)＝Io，vs(t6)＝vs(t56)，vd1(t6)＝2Vo，vd2(t6)＝0；
In step S701, the duration of the whole switching cycle may be calculated as: t iss＝t01+t12+t23+t34+tx+t56(ii) a By the voltage v across the dioded1Or vd2The average value of the output voltage V in a switching period is calculatedof。
Step S411, the first resonant capacitor (C)s) Begins to participate in resonance, assuming the duration of the fourth mode is txCan calculate the firstInitial conditions for five modalities: i.e. iL(t4)＝iL(tx)，vs(t4)＝vs(tx)，vd1(t4)＝vd1(tx)，vd2(t4)＝vd2(tx) (ii) a Go to step S511;
in step S511, the fifth mode is set to participate in resonance and has a first resonance capacitor (C)s) Resonant inductor (L)s) A second resonant capacitor (C)d1) A third resonant capacitor (C)d2) (ii) a At t5Time of day, third resonant capacitance (C)d2) Voltage across (v)d2) Decreases to 0, thereby calculating the duration of the fifth mode as t45And simultaneously calculating the initial conditions of the sixth mode: i.e. iL(t5)＝iL(t45)，vs(t5)＝vs(t45)，vd1(t5)＝2Vo，vd2(t5) 0; turning to the step S611,
step S611, setting the sixth mode as resonance inductance (L)s) And a first resonance capacitor (C)s) Resonating;
at t6At that moment, the inductor current rises to IoThe first mode will be returned to, from which the duration t of the sixth mode can be calculated56(ii) a Final value for the sixth modality: i.e. iL(t6)＝Io，vs(t6)＝vs(t56)，vd1(t6)＝2Vo，vd2(t6)＝0；
In step S711, the duration of the whole switching cycle can be calculated as: t iss＝t01+t12+t23+tx+t45+t56(ii) a By the voltage v across the dioded1Or vd2The average value of the output voltage V in a switching period is calculatedof。
If the first resonance capacitance (C)s) Voltage across (v)s) Cannot resonate to 0 or when the switching tube S is switched off, a small input current occursAt the inductive current Iin<iLOr the sixth mode inductor current cannot rise to IoOr respectively output the final value V of the voltageofAnd a first resonant capacitor (C)s) Final value v of voltage across terminalss(t56) Respectively with preset iteration variable initial values VoAnd Vs0Comparing, if any one of the two is not in the error allowable range, the iteration is considered to fail, and the initial value V of the preset iteration variable needs to be changedoAnd Vs0And carrying out calculation again. If none of the above occurs, the iteration is considered successful and T is recordedsAnd VoAnd obtaining a curve of the voltage gain changing along with the switching frequency (switching period) through multiple iterations.
Compared with the prior art, the invention has the following advantages:
(1) the high-frequency soft-switching resonant direct-current converter can realize zero-voltage switching of a switching tube and a diode and zero-current turn-off of the diode at the same time, and has the advantage of lower voltage stress of the diode compared with the conventional zero-voltage switching multi-resonant converter;
(2) the high-frequency soft-switching resonant direct-current converter absorbs the leakage inductance of the transformer as a part of the resonant inductance, and absorbs the junction capacitance of the switching tube and the junction capacitance of the diode as a part of the resonant capacitance, so that the problem that the influence of parasitic parameters under high-frequency work is obvious is solved, and the efficiency of the converter is improved.
The invention is further described below with reference to the accompanying drawings.
Drawings
Fig. 1 is a schematic diagram of a circuit structure of a high-frequency soft-switching resonant direct-current converter.
Fig. 2 is a schematic diagram of an equivalent circuit structure of a high-frequency soft-switching resonant dc converter.
Fig. 3 is a schematic diagram of the main waveforms of the operating mode a of the high-frequency soft-switching resonant dc-dc converter.
Fig. 4 is a schematic diagram of the main waveforms of the operating mode B of the high-frequency soft-switching resonant dc-dc converter.
Fig. 5 is an equivalent circuit structure diagram of the mode 1 of operation mode a switch and the mode 2 of operation mode B switch.
Fig. 6 is an equivalent circuit structure diagram of the switching mode 2 in the operating mode a and the switching modes 1 and 3 in the operating mode B.
Fig. 7 is an equivalent circuit configuration schematic diagram of the operating mode a switching modes 3, 5 and the operating mode B switching modes 4, 6.
Fig. 8 is an equivalent circuit structure diagram of the operating mode a switching mode 4 and the operating mode B switching mode 5.
Fig. 9 is an equivalent circuit structure diagram of the operating mode a switching mode 6.
Fig. 10 is a voltage gain calculation method and a mode switching flowchart of the high frequency soft switching resonant dc-dc converter.
Detailed Description
The invention provides a high-frequency soft-switching resonant direct-current converter suitable for occasions needing electrical isolation, and aims to solve the technical problems that a zero-voltage switching quasi-resonant converter can only improve the switching condition of one device in a switching tube and a diode, and the voltage stress of the diode of a zero-voltage switching multi-resonant converter is overlarge.
FIG. 1 is a schematic diagram of a basic circuit structure of a high-frequency soft-switching resonant DC converter, which is composed of a DC power supply VinInput side inductor LfSwitch tube S and parasitic body diode D of switch tubesA first resonant capacitor CsDC blocking capacitor CbResonant inductor LsIsolation transformer TrA first diode D1A second diode D2A second resonant capacitor Cd1A third resonant capacitor Cd2An output filter capacitor CoAnd (4) forming. The isolation transformer comprises a primary winding npA first secondary winding ns1A second secondary winding ns2. Input side inductance LfThe first pin is connected with a direct current power supply VinPositive side, input side inductance LfThe second pin, the drain electrode of the switch tube S and the first resonant capacitor CsFirst pin and blocking capacitor CbIs connected with a DC blocking capacitor CbThe second pin is connected with a resonant inductor LsFirst pin, resonant inductor LsThe second pin is connected with a primary winding n of the isolation transformerpEnd of same name, DC power supply VinNegative terminal of (1), source electrode of switching tube S, and first resonant capacitor CsSecond pin and primary winding n of isolation transformerpThe different name ends of the first diode D are all grounded1Anode and second resonant capacitor Cd1First pin of and a first secondary winding n of an isolation transformers1Are connected with the same name end of the first diode D2Anode and third resonant capacitor Cd2First pin and second secondary winding n of isolation transformers2Are connected with each other, a first diode D1Cathode and second resonant capacitor Cd1Second pin and second diode D2Cathode and third resonant capacitor Cd2Second pin and output filter capacitor CoThe first pins are connected with each other and output a filter capacitor CoSecond pin of the isolation transformer and a first secondary winding n of the isolation transformers1Different name end of the isolating transformer and a second secondary winding n of the isolating transformers2The homonymous terminals of the two terminals are all grounded. The switch tube S comprises a switch tube parasitic body diode D connected in parallel between the drain electrode and the source electrode of the switch tube Ss. First resonant capacitor CsThe capacitor comprises a junction capacitor of a switching tube S and a capacitor additionally connected in parallel at two ends of the switching tube S; second resonant capacitor Cd1Comprising a first diode D1The junction capacitance of the diode and the capacitance additionally connected in parallel at two ends of the diode; third resonant capacitor Cd2Comprising a second diode D2The junction capacitance of the diode and the capacitance additionally connected in parallel at two ends of the diode; resonant inductor LsIncluding the leakage inductance of the transformer and the additional series resonance inductance. The high-frequency soft switching resonant direct-current converter absorbs the leakage inductance of the isolation transformer as a part of the resonant inductance, and absorbs the junction capacitance of the switching tube and the junction capacitance of the diode as a part of the resonant capacitance, so that the problem that the influence of parasitic parameters under high-frequency work is obvious can be solved.
The following describes a specific operation principle of the high frequency soft switching resonant dc converter with reference to fig. 2 to 9 by taking the converter in fig. 1 as an example. Prior to analysis, the following assumptions were made: (1) all inductors, capacitors and transformers are ideal elements; (2) input deviceThe inductance is large enough to be approximately regarded as a current source Iin，IinIs the input current; (3) the output filter capacitor is large enough to be approximately considered as a voltage source Vo，VoIs the output voltage; (4) the blocking capacitance is large enough to be approximately considered as a voltage source Vin，VinIs the input voltage. The converter equivalent circuit shown in fig. 2 can thus be obtained. The operation principle of the converter is described by performing modal analysis on the converter.
According to different working conditions, the converter has two working modes, and the main waveforms are respectively shown in fig. 3 and fig. 4.
Firstly, an operating mode A:
1. switched mode 1[ t ]0，t1]
At t0At the moment, the switch tube S is turned off and the second diode D is turned off2In the on state, the first resonant capacitor CsAnd a resonant inductor LsThe equivalent circuit of the switched mode is shown in fig. 5 at resonance.
2. Switched mode 2[ t ]1，t2]
At t1Time of day, resonant inductor current iLIs raised to IoThen flows through the second diode D2Is naturally turned off when the current of the second resonant capacitor C is reduced to 0d1And a third resonant capacitor Cd2Also participating in resonance, the element participating in resonance having a first resonance capacitance CsResonant inductor LsA second resonant capacitor Cd1A third resonant capacitor Cd2Second resonant capacitor Cd1Voltage v acrossd1Resonance down, third resonance capacitance Cd2Voltage v acrossd2The resonance rises and the equivalent circuit of this switching mode is shown in figure 6.
3. Switching mode 3[ t ]2，t3]
At t2At the moment, the first resonant capacitor CsVoltage v acrosssThe resonance is exited after the resonance reaches 0, and the switching tube S is turned on after that moment, so that zero-voltage switching can be realized. The equivalent circuit of the switching mode is shown in FIG. 7, where the elements participating in resonance have harmonicsVibration inductance LsA second resonant capacitor Cd1A third resonant capacitor Cd2Second resonant capacitor Cd1Voltage v acrossd1Continuing to decrease the resonance, and a third resonance capacitor Cd2Voltage v acrossd2The resonance rises continuously.
4. Switch mode 4[ t ]3，t4]
At t3Time of day, third resonant capacitor Cd2Voltage v acrossd2Rise to 2VoSecond resonant capacitor Cd1Voltage v acrossd1Down to 0, the first diode D1Realizing zero voltage turn-on and a third resonant capacitor Cd2Voltage v acrossd2Is clamped to 2VoThe equivalent circuit of the switching mode is shown in fig. 8. The mode does not have any resonance process, and the inductive current iLThe linearity decreases.
5. Switching mode 5[ t ]4，t5]
At t4Time of day, resonant inductor current iLDown to IoWhile flowing through the first diode D1Is naturally turned off when the current of the second resonant capacitor C is reduced to 0d1And a third resonant capacitor Cd2Also participating in resonance, the element participating in resonance having a resonant inductance LsA second resonant capacitor Cd1A third resonant capacitor Cd2Second resonant capacitor Cd1Voltage v acrossd1Resonant rise, third resonant capacitance Cd2Voltage v acrossd2The resonance drops and the equivalent circuit of the switching mode is shown in figure 7.
6. Switched mode 6[ t ]5，t6]
At t5Time of day, second resonant capacitor Cd1Voltage v acrossd1Rise to 2VoThird resonant capacitor Cd2Voltage v acrossd2Down to 0, second diode D2Realize zero voltage turn-on and the second resonant capacitor Cd1Voltage v acrossd1Is clamped to 2VoThe equivalent circuit of the switching mode is shown in fig. 9. The mode does not have any resonance process, and the inductive current iLOn the linear directionAscending or descending.
At t6At this moment, the switching tube S is turned off, and returns to the switching mode 1, until the one switching cycle is completed.
II, working mode B:
1. switched mode 1[ t ]0，t1]
At t0At the moment, the switch tube S is turned off, and the first resonant capacitor CsThe element which starts to participate in resonance has a first resonance capacitance CsResonant inductor LsA second resonant capacitor Cd1A third resonant capacitor Cd2The equivalent circuit of the switching mode is shown in fig. 6.
2. Switched mode 2[ t ]1，t2]
At t1Time of day, third resonant capacitor Cd2Voltage v acrossd2Down to 0, second resonant capacitor Cd1Voltage v acrossd1Rise to 2VoA second diode D2Realize zero voltage turn-on and the second resonant capacitor Cd1Voltage v acrossd1Is clamped to 2VoThe element participating in resonance having a resonant inductance LsA first resonant capacitor CsThe equivalent circuit of the switching mode is shown in fig. 5.
3. Switching mode 3[ t ]2，t3]
At t2Time of day, resonant inductor current iLIs raised to IoThen flows through the second diode D2Is naturally turned off when the current of the second resonant capacitor C is reduced to 0d1And a third resonant capacitor Cd2Also participating in resonance, the element participating in resonance having a first resonance capacitance CsResonant inductor LsA second resonant capacitor Cd1A third resonant capacitor Cd2Second resonant capacitor Cd1Voltage v acrossd1Resonance down, third resonance capacitance Cd2Voltage v acrossd2The resonance rises and the equivalent circuit of this switching mode is shown in figure 6.
4. Switch mode 4[ t ]3，t4]
At t3At the moment, the first resonant capacitor CsVoltage v acrosssThe resonance is exited after the resonance reaches 0, and the switching tube S is turned on after that moment, so that zero-voltage switching can be realized. The equivalent circuit of the switching mode is shown in FIG. 7, and the element participating in resonance has a resonance inductance LsA second resonant capacitor Cd1A third resonant capacitor Cd2Second resonant capacitor Cd1Voltage v acrossd1Continuing to decrease the resonance, and a third resonance capacitor Cd2Voltage v acrossd2The resonance rises continuously.
5. Switching mode 5[ t ]4，t5]
At t4Time of day, second resonant capacitor Cd1Voltage v acrossd1Down to 0, third resonant capacitance Cd2Voltage v acrossd2Rise to 2VoFirst diode D1Realizing zero voltage turn-on and a third resonant capacitor Cd2Voltage v acrossd2Is clamped to 2VoThe equivalent circuit of the switching mode is shown in fig. 8. The mode does not have any resonance process, and the inductive current iLThe linearity decreases.
6. Switched mode 6[ t ]5，t6]
At t5Time of day, resonant inductor current iLDown to IoWhile flowing through the first diode D1Is naturally turned off when the current of the second resonant capacitor C is reduced to 0d1And a third resonant capacitor Cd2Also participating in resonance, the element participating in resonance having a resonant inductance LsA second resonant capacitor Cd1A third resonant capacitor Cd2Second resonant capacitor Cd1Voltage v acrossd1Resonant rise, third resonant capacitance Cd2Voltage v acrossd2The resonance drops and the equivalent circuit of the switching mode is shown in figure 7.
At t6At this moment, the switching tube S is turned off, and returns to the switching mode 1, until the one switching cycle is completed.
From the above analysis, it can be known that the high-frequency soft-switching resonant dc converter can realize the switch tube S and the diode D in both the operating mode a and the operating mode B1、D2Zero voltage turn-on, and diode D1、D2The zero current of (c) is turned off.
The high-frequency soft-switching resonant direct-current converter can convert a diode D1、D2To a voltage stress clamp of 2V twice the output voltageoTherefore, the voltage stress is lower.
To calculate the gain of the converter, the present invention provides a gain calculation method that combines two modes of operation, as shown in fig. 10.
Step 1, setting a first mode as a first resonance capacitor (C)s) Resonant inductor (L)s) A second resonant capacitor (C)d1) A third resonant capacitor (C)d2) The four participate in resonance;
with input side inductance (L)f) Current rises to IoIs the starting time t0Setting the initial conditions as follows: i.e. iL(t0)＝Io，vs(t0)＝Vs0，vd1(t0)＝2Vo，vd2(t0)＝0；
Setting the output voltage (V)o) And a first resonance capacitor (C)s) Voltage across (v)s) Initial value as an iteration variable, Vs0、VoRespectively presetting initial values of iteration variables;
at t1At time, the first resonance capacitance (C)s) Voltage across (v)s) Resonating to 0, calculating the duration t of the first mode01While calculating the initial condition i of the second modeL(t1)＝iL(t01)，vs(t1)＝0，vd1(t1)＝vd1(t01)，vd2(t1)＝vd2(t01)；
Step 2, the converter enters a second mode, wherein the second mode is a resonance inductor (L)s) A second resonant capacitor (C)d1) A third resonant capacitor (C)d2) The three parts participate in resonance;
at t2At a time of dayTwo resonance capacitors (C)d1) Voltage across (v)d1) Down to 0, third resonant capacitance (C)d2) Voltage v acrossd2Rise to 2VoCalculating the duration t of the second mode12(ii) a The initial conditions for the third modality are also calculated: i.e. iL(t2)＝iL(t12)，vs(t2)＝0，vd1＝0，vd2＝2Vo；
Step 3, the converter enters a third mode, the third mode is that no resonance exists, and the inductance current is linearly reduced;
at t3At that moment, the inductor current drops to IoFrom this, the duration t of the third modality can be calculated23(ii) a The initial conditions for the fourth modality are also calculated: i.e. iL(t3)＝Io，vs(t3)＝0，vd1(t3)＝0，vd2(t3)＝2Vo；
Step 4, the fourth mode is resonance inductance (L)s) A second resonant capacitor (C)d1) A third resonant capacitor (C)d2) The three parts participate in resonance;
if at t4Time of day, third resonant capacitance (C)d2) Voltage across (v)d2) Firstly, the temperature is decreased to 0, and then the step S401 is executed; if at t4At the moment, the switching tube (S) is turned off first, and then the step S411 is executed;
step S401, calculating the duration t of the fourth mode34(ii) a The initial conditions for the fifth modality are also calculated: i.e. iL(t4)＝iL(t34)，vs(t4)＝0，vd1(t4)＝2Vo，vd2(t4) 0; turning to step S501;
step S501, resonance does not exist in the fifth mode, and the inductive current linearly rises or falls;
at t5At the moment, the switching tube (S) is turned off, and the duration of the fifth mode is assumed to be txAnd calculating the initial condition of the sixth mode: i.e. iL(t5)＝iL(tx)，vs(t5)＝0，vd1(t5)＝2Vo，vd2(t5) 0; turning to step S601;
step S601, the sixth mode is resonance inductance (L)s) And a first resonance capacitor (C)s) Resonating;
at t6At that moment, the inductor current rises to IoThe first mode will be returned to, from which the duration t of the sixth mode can be calculated56(ii) a Final value for the sixth modality: i.e. iL(t6)＝Io，vs(t6)＝vs(t56)，vd1(t6)＝2Vo，vd2(t6)＝0；
In step S701, the duration of the whole switching cycle may be calculated as: t iss＝t01+t12+t23+t34+tx+t56(ii) a By the voltage v across the dioded1Or vd2The average value of the output voltage V in a switching period is calculatedof。
Step S411, the first resonant capacitor (C)s) Begins to participate in resonance, assuming the duration of the fourth mode is txThe initial conditions for the fifth modality can be calculated: i.e. iL(t4)＝iL(tx)，vs(t4)＝vs(tx)，vd1(t4)＝vd1(tx)，vd2(t4)＝vd2(tx) (ii) a Go to step S511;
in step S511, the fifth mode is set to participate in resonance and has a first resonance capacitor (C)s) Resonant inductor (L)s) A second resonant capacitor (C)d1) A third resonant capacitor (C)d2) (ii) a At t5Time of day, third resonant capacitance (C)d2) Voltage across (v)d2) Decreases to 0, thereby calculating the duration of the fifth mode as t45And simultaneously calculating the initial conditions of the sixth mode: i.e. iL(t5)＝iL(t45)，vs(t5)＝vs(t45)，vd1(t5)＝2Vo，vd2(t5) 0; turning to the step S611,
step S611, setting the sixth mode as resonance inductance (L)s) And a first resonance capacitor (C)s) Resonating;
at t6At that moment, the inductor current rises to IoThe first mode will be returned to, from which the duration t of the sixth mode can be calculated56(ii) a Final value for the sixth modality: i.e. iL(t6)＝Io，vs(t6)＝vs(t56)，vd1(t6)＝2Vo，vd2(t6)＝0；
In step S711, the duration of the whole switching cycle can be calculated as: t iss＝t01+t12+t23+tx+t45+t56(ii) a By the voltage v across the dioded1Or vd2The average value of the output voltage V in a switching period is calculatedof。
If the first resonance capacitance (C)s) Voltage across (v)s) Can not resonate to 0 or when the switch tube S is turned off, the input current is smaller than the inductive current, i.e. Iin<iLOr the sixth mode inductor current cannot rise to IoOr respectively output the final value V of the voltageofAnd a first resonant capacitor (C)s) Final value v of voltage across terminalss(t56) Respectively with preset iteration variable initial values VoAnd Vs0Comparing, if any one of the two is not in the error allowable range, the iteration is considered to fail, and the initial value V of the preset iteration variable needs to be changedoAnd Vs0And carrying out calculation again. If none of the above occurs, the iteration is considered successful and T is recordedsAnd VoAnd obtaining a curve of the voltage gain changing along with the switching frequency (switching period) through multiple iterations.

Claims (1)

1. AA voltage gain calculation method of a high-frequency soft-switching resonant DC converter adopts the following high-frequency soft-switching resonant DC converter comprising a DC power supply (V)in) Input side inductance (L)f) A switch tube (S), a first resonance capacitor (C)s) A DC blocking capacitor (C)b) Resonant inductor (L)s) Isolation transformer (T)r) A first diode (D)1) A second diode (D)2) A second resonant capacitor (C)d1) A third resonant capacitor (C)d2) An output filter capacitor (C)o)；
Isolation transformer (T) shownr) Comprising a primary winding (n)p) A first secondary winding (n)s1) And a second secondary winding (n)s2)；
Input side inductance (L)f) The first pin is connected with a direct current power supply (V)in) The positive end of the air conditioner is provided with a fan,
input side inductance (L)f) The second pin is respectively connected with the drain electrode of the switch tube (S) and the first resonance capacitor (C)s) First pin and blocking capacitor (C)b) The first lead of (a) the first lead,
blocking capacitor (C)b) The second pin of the inductor is connected with a resonance inductor (L)s) A first lead-out pin is provided,
resonance inductance (L)s) The second pin is connected with an isolation transformer (T)r) Primary winding (n)p) The end of the same name of (c) is,
DC power supply (V)in) Negative terminal, source of switching tube (S), first resonant capacitor (C)s) Second pin of (2) and isolation transformer (T)r) Primary winding (n)p) The end of the different name of the network is grounded,
a first diode (D)1) The anodes are respectively connected with second resonance capacitors (C)d1) First pin of (2), isolation transformer (T)r) First secondary winding (n)s1) The end of the same name of (c) is,
second diode (D)2) The anodes are respectively connected with a third resonance capacitor (C)d2) First pin of (2), isolation transformer (T)r) Second secondary winding (n)s2) The end of the synonym of (c) is,
a first diode (D)1) Cathode, second resonant capacitor (C)d1) Second pin, firstTwo diodes (D)2) Cathode, third resonant capacitor (C)d2) Second pin, output filter capacitor (C)o) The first pin is connected with the second pin,
output filter capacitor (C)o) Second pin, isolation transformer (T)r) First secondary winding (n)s1) Different name terminal, isolation transformer (T)r) Second secondary winding (n)s2) The homonymous terminal is grounded;
the first resonance capacitor (C)s) The capacity is equivalent to the sum of the capacity of the junction capacitor of the switching tube (S) and the capacity of a resonance capacitor connected between the source electrode and the drain electrode of the switching tube (S) in parallel;
the second resonance capacitor (C)d1) Capacity equivalent to a first diode (D)1) The junction capacitance is connected in parallel with the first diode (D)1) The sum of the capacities of the resonance capacitors at both ends;
the third resonance capacitor (C)d2) Capacity is equivalent to a second diode (D)2) The junction capacitance is connected in parallel with the second diode (D)2) The sum of the capacities of the resonance capacitors at both ends;
the resonance inductance (L)s) Is equivalent to an isolation transformer (T)r) Leakage inductance and series connection to a DC blocking capacitor (C)b) Isolation transformer (T)r) Primary winding (n)p) The sum of the inductance values of the resonant inductors in between;
the switch tube (S) also comprises a switch tube parasitic body diode (D)s) Parasitic body diode of switch tube (D)s) The anode is connected with the source of the switch tube (S), and the parasitic body diode (D)s) The cathode is connected with the drain electrode of the switching tube (S);
the method is characterized by comprising the following steps:
step 1, setting a first mode as a first resonance capacitor (C)s) Resonant inductor (L)s) A second resonant capacitor (C)d1) A third resonant capacitor (C)d2) The four participate in resonance;
with input side inductance (L)f) Current rises to IoIs the starting time t0Setting the initial conditions as follows: i.e. iL(t0)＝Io，vs(t0)＝Vs0，vd1(t0)＝2Vo，vd2(t0)＝0；
Setting the output voltage (V)o) And a first resonance capacitor (C)s) Voltage across (v)s) Initial value as an iteration variable, Vs0、VoRespectively presetting initial values of iteration variables;
at t1At time, the first resonance capacitance (C)s) Voltage across (v)s) Resonating to 0, calculating the duration t of the first mode01While calculating the initial condition i of the second modeL(t1)＝iL(t01)，vs(t1)＝0，vd1(t1)＝vd1(t01)，vd2(t1)＝vd2(t01)；
Step 2, the converter enters a second mode, wherein the second mode is a resonance inductor (L)s) A second resonant capacitor (C)d1) A third resonant capacitor (C)d2) The three parts participate in resonance;
at t2Time of day, second resonant capacitance (C)d1) Voltage across (v)d1) Down to 0, third resonant capacitance (C)d2) Voltage v acrossd2Rise to 2VoCalculating the duration t of the second mode12(ii) a The initial conditions for the third modality are also calculated: i.e. iL(t2)＝iL(t12)，vs(t2)＝0，vd1＝0，vd2＝2Vo；
Step 3, the converter enters a third mode, the third mode is that no resonance exists, and the inductance current is linearly reduced;
at t3At that moment, the inductor current drops to IoFrom this, the duration t of the third modality can be calculated23(ii) a The initial conditions for the fourth modality are also calculated: i.e. iL(t3)＝Io，vs(t3)＝0，vd1(t3)＝0，vd2(t3)＝2Vo；
Step 4, the fourth mode is resonance inductance (L)s) A second resonant capacitor (C)d1) A third resonant capacitor (C)d2) The three parts participate in resonance;
if at t4Time of day, third resonant capacitance (C)d2) Voltage across (v)d2) Firstly, the temperature is decreased to 0, and then the step S401 is executed; if at t4At the moment, the switching tube (S) is turned off first, and then the step S411 is executed;
step S401, calculating the duration t of the fourth mode34(ii) a The initial conditions for the fifth modality are also calculated: i.e. iL(t4)＝iL(t34)，vs(t4)＝0，vd1(t4)＝2Vo，vd2(t4) 0; turning to step S501;
step S501, resonance does not exist in the fifth mode, and the inductive current linearly rises or falls;
at t5At the moment, the switching tube (S) is turned off, and the duration of the fifth mode is assumed to be txAnd calculating the initial condition of the sixth mode: i.e. iL(t5)＝iL(tx)，vs(t5)＝0，vd1(t5)＝2Vo，vd2(t5) 0; turning to step S601;
step S601, the sixth mode is resonance inductance (L)s) And a first resonance capacitor (C)s) Resonating;
at t6At that moment, the inductor current rises to IoThe first mode will be returned to, from which the duration t of the sixth mode can be calculated56(ii) a Final value for the sixth modality: i.e. iL(t6)＝Io，vs(t6)＝vs(t56)，vd1(t6)＝2Vo，vd2(t6)＝0；
In step S701, the duration of the whole switching cycle may be calculated as: t iss＝t01+t12+t23+t34+tx+t56(ii) a By the voltage v across the dioded1Or vd2The average value of the output voltage V in a switching period is calculatedof；
Step S411, the first resonant capacitor (C)s) Begins to participate in resonance, assuming the duration of the fourth mode is txThe initial conditions for the fifth modality can be calculated: i.e. iL(t4)＝iL(tx)，vs(t4)＝vs(tx)，vd1(t4)＝vd1(tx)，vd2(t4)＝vd2(tx) (ii) a Go to step S511;
in step S511, the fifth mode is set to participate in resonance and has a first resonance capacitor (C)s) Resonant inductor (L)s) A second resonant capacitor (C)d1) A third resonant capacitor (C)d2) (ii) a At t5Time of day, third resonant capacitance (C)d2) Voltage across (v)d2) Decreases to 0, thereby calculating the duration of the fifth mode as t45And simultaneously calculating the initial conditions of the sixth mode: i.e. iL(t5)＝iL(t45)，vs(t5)＝vs(t45)，vd1(t5)＝2Vo，vd2(t5) 0; turning to the step S611,
step S611, setting the sixth mode as resonance inductance (L)s) And a first resonance capacitor (C)s) Resonating;
at t6At that moment, the inductor current rises to IoThe first mode will be returned to, from which the duration t of the sixth mode can be calculated56(ii) a Final value for the sixth modality: i.e. iL(t6)＝Io，vs(t6)＝vs(t56)，vd1(t6)＝2Vo，vd2(t6)＝0；
In step S711, the duration of the whole switching cycle can be calculated as: t iss＝t01+t12+t23+tx+t45+t56(ii) a By the voltage v across the dioded1Or vd2The average value of the output voltage V in a switching period is calculatedof；
If the first resonance capacitance (C)s) Voltage across (v)s) Can not resonate to 0 or when the switch tube S is turned off, the input current is smaller than the inductive current, i.e. Iin<iLOr the sixth mode inductor current cannot rise to IoOr respectively output the final value V of the voltageofAnd a first resonant capacitor (C)s) Final value v of voltage across terminalss(t56) Respectively with preset iteration variable initial values VoAnd Vs0Comparing, if any one of the two is not in the error allowable range, the iteration is considered to fail, and the initial value V of the preset iteration variable needs to be changedoAnd Vs0Carrying out calculation again; if none of the above occurs, the iteration is considered successful and T is recordedsAnd VoAnd obtaining a curve of the voltage gain changing along with the switching frequency/switching period through multiple iterations.
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