CN113949255B - Passive clamping circuit suitable for switching tube serial auxiliary power supply - Google Patents

Passive clamping circuit suitable for switching tube serial auxiliary power supply Download PDF

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Publication number
CN113949255B
CN113949255B CN202111407121.4A CN202111407121A CN113949255B CN 113949255 B CN113949255 B CN 113949255B CN 202111407121 A CN202111407121 A CN 202111407121A CN 113949255 B CN113949255 B CN 113949255B
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diode
clamping
converter
switching
series
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CN113949255A (en
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孟涛
李春艳
王世刚
魏亮
常熠琛
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Heilongjiang University
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Heilongjiang 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
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • H02M1/34—Snubber circuits
    • 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

Abstract

The invention discloses a passive clamping circuit suitable for a switching tube series auxiliary power supply, belongs to the technical field of power electronics and switching power supplies, and aims to solve the problem that an auxiliary link of voltage equalization of a conventional series switching tube is applied to a switching tube series forward and flyback converter, and has a complex circuit structure. The invention comprises a clamping capacitor C 1 、C 2 The method comprises the steps of carrying out a first treatment on the surface of the Diode D 1 、D 2 、D L1 And D L2 The method comprises the steps of carrying out a first treatment on the surface of the Coupling inductance L 1 、L 2 The method comprises the steps of carrying out a first treatment on the surface of the Switch tube S 1 And S is 2 The maximum voltages during the switching operation of (2) are respectively C 1 And C 2 Clamped; the method comprises the following steps: when clamping capacitor C 1 And C 2 When a voltage difference occurs, the inductor L is coupled 1 、L 2 Realize the mutual energy transmission, when C 1 Is higher than C 2 At a voltage of (2), energy is represented by C 1 By coupling inductance L 1 、L 2 To C 2 Transferring; when C 2 Is higher than C 1 At a voltage of (2), energy is represented by C 2 By coupling inductance L 1 、L 2 To C 1 Transfer to clamp capacitor C 1 And C 2 Is equal to the voltage of the switch tube S 1 And S is 2 Is a voltage equalization of (a).

Description

Passive clamping circuit suitable for switching tube serial auxiliary power supply
Technical Field
The invention relates to a passive clamping circuit, and belongs to the technical fields of power electronics and switching power supplies.
Background
With the continuous and deep research of researchers at home and abroad in the technical field of power electronics, the direct current power supply technology has been developed from the traditional linear power supply to the high-frequency switching power supply. At present, research on high-frequency switching power supplies and related technologies thereof has been mature, and switching power supplies of various power classes have been widely used in various fields of industry and civilian use. Along with the development of national economy, various electric equipment are more and more, the input voltage levels of power supplies are different, and various high-voltage input occasions are gradually increased. For example, 1000V dc bus in future ships and unmanned aerial vehicles will become the mainstream; in an urban rail transit system, a power supply grid of a vehicle generally has two systems of direct current 750V and 1500V, wherein the maximum power supply voltage of the power supply grid can reach more than 1800V; in a high-speed railway electrical system, the voltage of an input direct current bus of various electrical equipment on a vehicle can reach 2000-4000V; in mining production, the DC bus voltage of the frequency converter of the high-voltage high-power coal mining machine can reach 2000-3000V, even higher; in modern energy internet, the voltage of medium voltage interconnection bus of flexible direct current distribution network can reach 10000V. How to effectively reduce the voltage stress of various devices is always a difficulty in the design process of the high-voltage converter due to the limitation of factors such as the voltage class of the power devices.
The mode of connecting a plurality of switching tubes in series is the most direct method for reducing the voltage stress of the switching devices of the high-voltage converter. The key of the series connection application of a plurality of switching tubes is to ensure the voltage balance, namely the dynamic and static voltage balance, of each switching tube at the moment of switching state transition and after entering a stable working state. Static balance of the voltages of the switching tubes in series can be achieved by connecting a resistor with a larger resistance value to each switching tube in parallel, but dynamic voltage balance is not easy to achieve generally. In general, two basic modes of power end control and drive end control can be adopted to realize dynamic voltage balance of each series switching tube. The power end control is adopted, and buffer circuits or clamping circuits and other auxiliary links are added at the two ends of each series switching tube to absorb the overvoltage at the moment of switching on and off each switching tube. The driving end control is usually used for realizing the on-off synchronization of each series switching tube, and common methods include synchronous control, master-slave control and the like. Various existing series switching tube voltage equalizing implementation methods can be classified into a passive method and an active method if they are classified according to whether or not active devices are used. The typical passive voltage equalizing mode is to add passive buffer circuits at two ends of each switching tube, which increases the loss of the circuit and limits the switching frequency of each switching tube.
When the auxiliary link for ensuring the voltage balance of the series switching tube is applied to the series forward and flyback converters of the switching tube, the forward converter is also added with the magnetic reset link of the transformer, and the flyback converter is also added with the leakage inductance energy absorption circuit of the transformer, so that the circuit structure becomes very complex.
Disclosure of Invention
The invention aims to solve the problem that the circuit structure is complex when the auxiliary link of the voltage equalization of the prior series switching tube is applied to the series forward and flyback converters of the switching tube, and provides a passive clamping circuit suitable for the series auxiliary power supply of the switching tube; when the passive clamping circuit is applied to the flyback converter, the flyback converter can omit a leakage inductance energy absorption circuit of the transformer, and the circuit structure is simplified.
The invention relates to a passive clamping circuit suitable for a switching tube serial auxiliary power supply, which adopts two switching tubes S 1 、S 2 The converters are connected in series, and are forward converters or flyback converters;
The passive clamp circuit comprises a clamp capacitor C 1 、C 2 The method comprises the steps of carrying out a first treatment on the surface of the Diode D 1 、D 2 、D L1 And D L2 The method comprises the steps of carrying out a first treatment on the surface of the Coupling inductance L 1 、L 2 The method comprises the steps of carrying out a first treatment on the surface of the Coupling inductance L 1 、L 2 The number of turns of the windings is the same;
clamping capacitor C 2 Diode D 2 Diode D 1 Clamping capacitor C 1 The clamping capacitors C of the serial branches are serially connected in sequence 2 The positive electrode end is simultaneously connected with a switch tube S 2 Drain of (D) and diode D L1 A cathode of the series branch, a clamping capacitor C 1 Switch tube S with simultaneous connection of negative electrode end 1 Source of (D) and diode D L2 Anode of diode D 2 Cathode and diode D of (D) 1 Is connected with the switch tube S at the same time with the anode of 1 Drain electrode of (d) and switching tube S 2 A source of (a);
coupling inductance L 2 And diode D L2 In series, the coupling inductance L of the series branch 2 One end is connected with the clamping capacitor C 2 Is a negative electrode of (a);
coupling inductance L 1 And diode D L1 In series, the coupling inductance L of the series branch 1 One end is connected with the clamping capacitor C 1 Is a positive electrode of (a);
switch tube S 1 And S is 2 The maximum voltages during the switching operation of (2) are respectively C 1 And C 2 Clamped; the method comprises the following steps:
when clamping capacitor C 1 And C 2 When a voltage difference occurs, the inductor L is coupled 1 、L 2 Realize the mutual energy transmission, when C 1 Is higher than C 2 At a voltage of (2), energy is represented by C 1 By coupling inductance L 1 、L 2 To C 2 Transferring; when C 2 Is higher than C 1 At a voltage of (2), energy is represented by C 2 By coupling inductance L 1 、L 2 To C 1 Transfer to clamp capacitor C 1 And C 2 Is equal to the voltage of the switch tube S 1 And S is 2 Is a voltage equalization of (a).
Further, it also includes a diode D L Diode D L Is connected with the anode of the coupling inductance L 1 And diode D L1 Is a common node of diode D L The cathode of the converter is connected with the primary side of the converter; switch tube S 1 And S is 2 When turned off, the coupling inductance L 1 、L 2 The energy absorbed in each switching cycle passes through diode D L Feedback to the input side of the converter.
Further, the coupling inductance L of the clamping circuit in the flyback converter 1 、L 2 The equivalent inductance value is:
simultaneously satisfies the conditions:
wherein: l (L) p Primary winding inductance L of transformer which is flyback converter lk Transformer equivalent leakage inductance of flyback converter, V C1 For clamping capacitor C 1 Voltage at two ends, and V C1 ＝V C2 ，V C2 For clamping capacitor C 2 Voltage at two ends, V i For the converter input side voltage, D is the switching tube S in each switching cycle 1 And S is 2 Is a duty cycle of (c).
Further, the coupling inductance L of the clamping circuit in the forward converter 1 、L 2 The equivalent inductance value is:
simultaneously satisfies the conditions:
L m is a forward transformer T F Equivalent excitation inductance of V C1 For clamping capacitor C 1 Voltage at two ends, and V C1 ＝V C2 ，V C2 For clamping capacitor C 2 Voltage at two ends, V i For the converter input side voltage, D is the switching tube S in each switching cycle 1 And S is 2 Is a duty cycle of (c).
Further, the winding also comprises a flyback winding L f And diode D f Flyback winding L f And diode D f The series branch is connected in parallel with the output side of the converter, and the flyback winding L f And coupling inductance L 1 、L 2 Jointly wound on the same magnetic core, and coupled with the inductor L 1 、L 2 The energy absorbed in each switching cycle passes through the flyback winding L f And diode D f The series branch is fed back to the output side of the converter.
Further, the coupling inductance L of the clamping circuit in the flyback converter 1 、L 2 The equivalent inductance value is:
simultaneously satisfies the conditions:
wherein: l (L) p Primary winding inductance L of transformer which is flyback converter lk Transformer equivalent leakage inductance of flyback converter, V C1 For clamping capacitor C 1 Voltage at two ends, and V C1 ＝V C2 ，V C2 For clamping capacitor C 2 Voltage at two ends, V i For the voltage at the input side of the converter, V o For the output side voltage of the converter, n f For coupling inductance L 1 Winding turns of (2) and flyback winding L thereof f Is provided for the ratio of the number of winding turns,d is a switching tube S in each switching period 1 And S is 2 Is a duty cycle of (c).
Further, the coupling inductance L of the clamping circuit in the forward converter 1 、L 2 The equivalent inductance value is:
Simultaneously satisfies the conditions:
L m is a forward transformer T F Equivalent excitation inductance of V C1 For clamping capacitor C 1 Voltage at two ends, and V C1 ＝V C2 ，V C2 For clamping capacitor C 2 Voltage at two ends, V i For the voltage at the input side of the converter, V o For the output side voltage of the converter, n f For coupling inductance L 1 Winding turns of (2) and flyback winding L thereof f Is provided for the ratio of the number of winding turns,d is a switching tube S in each switching period 1 And S is 2 Is a duty cycle of (c).
The invention also provides a technical scheme that: the passive clamping circuit is suitable for a switching tube serial auxiliary power supply, the switching tube serial auxiliary power supply adopts 2K converters with switching tubes connected in series, and the converters are forward converters or flyback converters; the passive clamping circuit comprises K clamping units and a diode D L ；
2K series switching tubes in the converter are divided into K pairs, two adjacent switching tubes are 1 pair, each pair of series switching tubes is provided with 1 clamping unit, and the clamping unit comprises a clamping capacitor C 1 、C 2 The method comprises the steps of carrying out a first treatment on the surface of the Diode D 1 、D 2 、D L1 And D L2 The method comprises the steps of carrying out a first treatment on the surface of the Coupling inductance L 1 、L 2 The method comprises the steps of carrying out a first treatment on the surface of the Coupling inductance L 1 、L 2 The number of turns of the windings is the same;
clamping capacitor C 2 Diode D 2 Diode D 1 Clamping capacitor C 1 The clamping capacitors C of the serial branches are serially connected in sequence 2 The positive electrode end is simultaneously connected with a switch tube S 2 Drain of (D) and diode D L1 A cathode of the series branch, a clamping capacitor C 1 Switch tube S with simultaneous connection of negative electrode end 1 Source of (D) and diode D L2 Anode of diode D 2 Cathode and diode D of (D) 1 Is connected with the switch tube S at the same time with the anode of 1 Drain electrode of (d) and switching tube S 2 A source of (a);
coupling inductance L 2 And diode D L2 In series, the coupling inductance L of the series branch 2 One end is connected with the clamping capacitor C 2 Is a negative electrode of (a);
coupling inductance L 1 And diode D L1 In series, the coupling inductance L of the series branch 1 One end is connected with the clamping capacitor C 1 Is a positive electrode of (a);
the coupling inductors of the K clamping units are wound on the same magnetic core together;
diode D L Coupled inductance L in the anode-connected topmost clamping unit 1 And diode D L1 Is a common node of diode D L The cathode of the converter is connected with the primary side of the converter; switch tube S 1 And S is 2 When turned off, the coupling inductance L 1 、L 2 The energy absorbed in each switching cycle passes through diode D L Feedback to the input side of the converter.
The invention also provides a technical scheme that: the passive clamping circuit is suitable for a switching tube serial auxiliary power supply, the switching tube serial auxiliary power supply adopts 2K converters with switching tubes connected in series, and the converters are forward converters or flyback converters; the passive clamping circuit comprises K clamping units and a flyback winding L f And diode D f ；
2K series switching tubes in the converter are divided into K pairs, two adjacent switching tubes are 1 pair, each pair of series switching tubes is provided with 1 clamping unit, and the clamping unit comprises a clamping capacitor C 1 、C 2 The method comprises the steps of carrying out a first treatment on the surface of the Diode D 1 、D 2 、D L1 And D L2 The method comprises the steps of carrying out a first treatment on the surface of the Coupling inductance L 1 、L 2 The method comprises the steps of carrying out a first treatment on the surface of the Coupling inductance L 1 、L 2 The number of turns of the windings is the same;
clamping capacitor C 2 Diode D 2 Diode D 1 Clamping capacitor C 1 The clamping capacitors C of the serial branches are serially connected in sequence 2 The positive electrode end is simultaneously connected with a switch tube S 2 Drain of (D) and diode D L1 A cathode of the series branch, a clamping capacitor C 1 Switch tube S with simultaneous connection of negative electrode end 1 Source of (D) and diode D L2 Anode of diode D 2 Cathode and diode D of (D) 1 Is connected with the switch tube S at the same time with the anode of 1 Drain electrode of (d) and switching tube S 2 A source of (a);
coupling inductance L 2 And diode D L2 In series, the coupling inductance L of the series branch 2 One end is connected with the clamping capacitor C 2 Is a negative electrode of (a);
coupling inductance L 1 And diode D L1 In series, the coupling inductance L of the series branch 1 One end is connected with the clamping capacitor C 1 Is a positive electrode of (a);
the coupling inductors of the K clamping units are wound on the same magnetic core together;
flyback winding L f And diode D f The series branch is connected in parallel with the output side of the converter, and the flyback winding L f Coupling inductance L with K clamping units 1 、L 2 Jointly wound on the same magnetic core, and coupled with the inductor L 1 、L 2 The energy absorbed in each switching cycle passes through the flyback winding L f And diode D f The series branch is fed back to the output side of the converter.
The invention has the beneficial effects that: the invention is directed to high-voltage input, medium and small power occasions, and discloses a passive clamping circuit suitable for a series flyback type auxiliary power supply converter and a forward type auxiliary power supply converter of a switching tube. The passive clamping circuit is composed of a clamping capacitor, a coupling inductor and a diode, and has the advantages of simple structure and high reliability. In the operation process of the related converter, the adoption of the passive clamp circuit can effectively ensure the voltage balance of each series switching tube. In addition, when the passive clamping circuit is applied to the flyback converter, the passive clamping circuit can also absorb leakage inductance energy of the transformer and feed the absorbed energy back to the input side or the output side of the converter, so that the flyback converter does not need to adopt various traditional leakage inductance energy absorbing circuits of the transformer; when the passive clamp circuit is applied to a forward converter, the passive clamp circuit can also complete magnetic reset of the transformer and feed back the absorbed excitation inductance energy of the transformer to the input side or the output side of the converter, so that the forward converter does not need to adopt various traditional magnetic reset links of the transformer. The structure of the switching tube series type flyback and forward auxiliary power converters is greatly simplified.
Drawings
FIG. 1 is a schematic diagram of a passive clamp circuit for a switching tube series auxiliary power supply, a two-switch series flyback converter, a first type of structure clamp circuit;
FIG. 2 is a schematic diagram of a passive clamp circuit for a switching tube series auxiliary power supply, a two-switch series flyback converter, and a second type of clamp circuit according to the present invention;
FIG. 3 is a schematic diagram of a passive clamp circuit for a switching tube series auxiliary power supply, a two-switch series forward converter, a first type of clamp circuit;
FIG. 4 is a schematic diagram of a passive clamp circuit for a switching tube series auxiliary power supply, a two-switch series forward converter, and a second type of clamp circuit according to the present invention;
FIGS. 5 (a) - (d) are equivalent circuits of stages of a two-switching tube series flyback converter employing the passive clamp circuit of FIG. 1;
fig. 6 (a) - (d) are equivalent circuits of the stages of a two-switching tube series flyback converter employing the passive clamp circuit of fig. 2;
fig. 7 (a) - (c) are equivalent circuits of each stage of a two-switching-tube series forward converter using the passive clamp circuit shown in fig. 3;
Fig. 8 shows equivalent circuits of stages of a two-switching-tube series forward converter using the passive clamp circuit shown in fig. 4;
FIG. 9 is a schematic diagram of a passive clamp circuit for a switching tube series auxiliary power supply, a four-switch series flyback converter, a first type of structure clamp circuit according to the present invention;
FIG. 10 is a schematic diagram of a passive clamp circuit for a switching tube series auxiliary power supply, a four-switch series flyback converter, and a second type of clamp circuit according to the present invention;
fig. 11 is a schematic diagram of a passive clamping circuit suitable for a switching tube serial auxiliary power supply according to the present invention, wherein the first type of the passive clamping circuit is a four-switch Guan Chuanlian forward converter;
fig. 12 is a schematic diagram of a passive clamp circuit for a switching tube serial auxiliary power supply according to the present invention, a four-switch Guan Chuanlian forward converter, and a second type of structure clamp circuit;
Detailed Description
In the middle and small power occasions, the auxiliary power supply generally adopts flyback type or other typeForward topology. The flyback converter comprises a flyback transformer T f Flyback transformer T f Is equivalent to leakage inductance L lk Dc input voltage V i Dc output voltage V o Output rectifier diode D o And output filter capacitor C o ，L p And L s Respectively flyback transformers T f Primary winding and secondary winding, output filter capacitor C o The two ends of the load are connected in parallel, and the voltage of the two ends of the load is the direct current output voltage V o 。
The forward converter comprises a forward transformer T F Dc input voltage V i Dc output voltage V o Output rectifier diode D o1 Freewheel diode D o2 Output filter inductance L o And output filter capacitor C o ，L m Is a forward transformer T F Equivalent excitation inductance of (2), output filter capacitance C o The two ends of the load are connected in parallel, and the voltage of the two ends of the load is the direct current output voltage V o 。
The first embodiment is as follows: next, a passive clamp circuit applied to a switching tube series type auxiliary power supply according to the present embodiment will be described with reference to fig. 1 to 4, which are two switching tube series type flyback and forward type (fig. 1 and 2 are flyback and fig. 3 and 4 are forward type) auxiliary power converters (mainly described herein by taking a two switching tube series type converter as an example). S is S 1 And S is 2 Is a series of 2 Power switching transistors (typically Power MOSFET switching transistors).
According to the different energy feedback directions, the passive clamping circuit has 2 basic structures. Wherein: passive clamp (configuration 1) as shown in fig. 1 and 3, the passive clamp feeding back the absorbed energy to the input side of the converter during each switching cycle; passive clamp (configuration 2) as shown in fig. 2 and 4, the passive clamp feeds back the absorbed energy to the output side of the converter during each switching cycle. The passive clamp circuit of 2 structures mainly consists of a clamp capacitor (C 1 ＝C 2 ) Coupling inductance (L) 1 ＝L 2 ) Diode (D) 1 、D 2 、D L1 、D L2 ) Composition is prepared. On the basis, a diode D is added in the structure 1 L The power supply circuit is used for feeding back the energy absorbed by the passive clamping circuit to the input side of the converter; in the structure 2, the flyback winding L is added on the coupling inductance f And is connected with a diode D f For feeding back the energy absorbed by the passive clamp to the output side of the converter.
The second embodiment is as follows: next, an embodiment one will be further described with reference to fig. 1 and 2, in which the operation of a two-switching-tube series flyback converter using a passive clamp circuit is analyzed. For ease of analysis, the following assumptions are made: flyback converters operate in a current discontinuous mode (discontinuous current mode, DCM); all devices in the circuit are ideal devices; clamping capacitor C 1 、C 2 Output filter capacitor C o Is sufficiently large to be considered a constant voltage source during analysis.
FIG. 1 shows a passive clamp circuit with a diode D L Will couple inductance L 1 、L 2 The energy absorbed during each switching cycle is fed back to the input side of the converter. FIG. 2 shows a passive clamp circuit passing through a flyback winding L f And diode D f The series branch being formed to couple the inductance L 1 、L 2 The energy absorbed during each switching cycle is fed back to the output side of the converter. The clamping circuit of the flyback converter not only realizes the voltage clamping function of the series switching tube, but also realizes the energy recovery function, and a separate energy absorption circuit is not needed to be additionally arranged, so that the whole circuit structure is simplified.
The passive clamp circuit shown in FIG. 1 includes a clamp capacitor C 1 、C 2 The method comprises the steps of carrying out a first treatment on the surface of the Diode D 1 、D 2 、D L1 And D L2 The method comprises the steps of carrying out a first treatment on the surface of the Coupling inductance L 1 、L 2 The method comprises the steps of carrying out a first treatment on the surface of the Coupling inductance L 1 、L 2 The number of turns of the windings is the same;
clamping capacitor C 2 Diode D 2 Diode D 1 Clamping capacitor C 1 The clamping capacitors C of the serial branches are serially connected in sequence 2 Positive electrode terminalSimultaneously connected with a switch tube S 2 Drain of (D) and diode D L1 A cathode of the series branch, a clamping capacitor C 1 Switch tube S with simultaneous connection of negative electrode end 1 Source of (D) and diode D L2 Anode of diode D 2 Cathode and diode D of (D) 1 Is connected with the switch tube S at the same time with the anode of 1 Drain electrode of (d) and switching tube S 2 A source of (a);
coupling inductance L 2 And diode D L2 In series, the coupling inductance L of the series branch 2 One end is connected with the clamping capacitor C 2 Is a negative electrode of (a);
coupling inductance L 1 And diode D L1 In series, the coupling inductance L of the series branch 1 One end is connected with the clamping capacitor C 1 Is a positive electrode of (a);
switch tube S 1 And S is 2 The maximum voltages during the switching operation of (2) are respectively C 1 And C 2 Clamped; the method comprises the following steps:
when clamping capacitor C 1 And C 2 When a voltage difference occurs, the inductor L is coupled 1 、L 2 Realize the mutual energy transmission, when C 1 Is higher than C 2 At a voltage of (2), energy is represented by C 1 By coupling inductance L 1 、L 2 To C 2 Transferring; when C 2 Is higher than C 1 At a voltage of (2), energy is represented by C 2 By coupling inductance L 1 、L 2 To C 1 Transfer to clamp capacitor C 1 And C 2 Is equal to the voltage of the switch tube S 1 And S is 2 Is a voltage equalization of (a).
Further, diode D L Is connected with the anode of the coupling inductance L 1 And diode D L1 Is a common node of diode D L The cathode of the converter is connected with the primary side of the converter; switch tube S 1 And S is 2 When turned off, the coupling inductance L 1 、L 2 The energy absorbed in each switching cycle passes through diode D L Feedback to the input side of the converter.
C of clamp circuit 2 The positive electrode is connected with the primary winding of the transformer and the diode D L Is connected with the DC input voltage V i And the primary side of the transformer.
The passive clamp circuit shown in fig. 1 operates as follows:
in 1 switching cycle, the two-switching-tube series flyback converter shown in fig. 1 has the following 4 main operation phases, and the equivalent circuit of each phase is shown in fig. 5.
Working phase 1 (t) f0 ～t f1 )：t f0 At the moment, switch tube S 1 And S is 2 Conducting. At this stage, input voltage V i Reverse flyback transformer T f Primary inductance L of (2) p Charging, the inductor current rising from zero, the output current of the converter being only output filter capacitor C o The discharge is provided. In the clamp circuit, a clamp capacitor C 1 Through S 1 、S 2 And D L1 To L 1 Discharging C 2 Through S 1 、S 2 And D L2 To L 2 And discharging, wherein the coupling inductance current starts to rise from zero. To t f1 At the end of this stage, L 1 、L 2 And L p To a maximum value of 1 switching cycle.
Working phase 2 (t) f1 ～t f2 )：t f1 At the moment, switch tube S 1 And S is 2 And (5) switching off. t is t f1 After the moment, flyback transformer T f Primary inductance L of (2) p Energy transfer to secondary inductance L s And pass through output rectifying diode D o To the load. In this process, L p Is clamped at nV o (in the figure, the positive and negative polarities are that of upper negative and lower positive; n is that of flyback transformer T) f The turns ratio of the primary winding and the secondary winding, where n 2 ＝L p /L s ) Leakage inductance L lk Energy clamped capacitor C of (2) 1 、C 2 Absorption (clamp capacitor voltage V) C1 ＝V C2 >V i /2+nV o /2). In the clamp circuit, D 1 、D 2 、D L And D L2 Conduction, D L1 Cut off, at this time, L 1 And L 2 In series and through D L 、D 1 And D 2 The energy is fed back to the input side of the converter. To t f2 At the moment, leakage inductance L lk The current of (c) decreases to zero and this phase ends.
Working phase 3 (t) f2 ～t f4 )：t f2 After the moment L s Continuing to transfer energy to the load, L 1 And L 2 Energy continues to be fed back to the input side of the converter. To t f3 Time, L 1 And L 2 The current of (2) decreases to zero to t f4 Time, L s The current of (c) decreases to zero and this phase ends. In this stage, the sequence of decreasing the inductor current to zero does not need to be strictly fixed.
Working phase 4 (t) f4 ～t f5 ): to t f4 After the moment, the primary and secondary side currents of the transformer are kept to be zero, and the output current of the converter is only obtained by an output filter capacitor C o The discharge is provided. To t f5 At the moment, switch tube S 1 And S is 2 And conducting again, and enabling the converter to enter the operation of the next switching cycle.
The passive clamp circuit of FIG. 2 includes a clamp capacitor C 1 、C 2 The method comprises the steps of carrying out a first treatment on the surface of the Diode D 1 、D 2 、D L1 And D L2 The method comprises the steps of carrying out a first treatment on the surface of the Coupling inductance L 1 、L 2 The method comprises the steps of carrying out a first treatment on the surface of the Coupling inductance L 1 、L 2 The number of turns of the windings is the same;
clamping capacitor C 2 Diode D 2 Diode D 1 Clamping capacitor C 1 The clamping capacitors C of the serial branches are serially connected in sequence 2 The positive electrode end is simultaneously connected with a switch tube S 2 Drain of (D) and diode D L1 A cathode of the series branch, a clamping capacitor C 1 Switch tube S with simultaneous connection of negative electrode end 1 Source of (D) and diode D L2 Anode of diode D 2 Cathode and diode D of (D) 1 Is connected with the switch tube S at the same time with the anode of 1 Drain electrode of (d) and switching tube S 2 A source of (a);
coupling inductance L 2 And diode D L2 In series, the coupling inductance L of the series branch 2 One end is connected with the clamping capacitor C 2 Is a negative electrode of (a);
coupling inductance L 1 And diode D L1 In series, the coupling inductance L of the series branch 1 One end is connected with the clamping capacitor C 1 Is a positive electrode of (a);
switch tube S 1 And S is 2 The maximum voltages during the switching operation of (2) are respectively C 1 And C 2 Clamped; the method comprises the following steps:
when clamping capacitor C 1 And C 2 When a voltage difference occurs, the inductor L is coupled 1 、L 2 Realize the mutual energy transmission, when C 1 Is higher than C 2 At a voltage of (2), energy is represented by C 1 By coupling inductance L 1 、L 2 To C 2 Transferring; when C 2 Is higher than C 1 At a voltage of (2), energy is represented by C 2 By coupling inductance L 1 、L 2 To C 1 Transfer to clamp capacitor C 1 And C 2 Is equal to the voltage of the switch tube S 1 And S is 2 Is a voltage equalization of (a).
Further, includes flyback winding L f And diode D f Flyback winding L f And diode D f The series branch is connected in parallel with the output side of the converter, and the flyback winding L f And coupling inductance L 1 、L 2 Jointly wound on the same magnetic core, and coupled with the inductor L 1 、L 2 The energy absorbed in each switching cycle passes through the flyback winding L f And diode D f The series branch is fed back to the output side of the converter.
Diode D of series branch in clamping circuit f Cathode connection rectifier diode D o Cathode, flyback winding L of series branch f The end is connected with an output filter capacitor C o And a load negative terminal.
The passive clamp circuit shown in fig. 2 operates as follows:
in 1 switching cycle, the two-switching-tube series flyback converter shown in fig. 2 has the following 4 main operating phases, and the equivalent circuit of each phase is shown in fig. 6.
Working phase 1 (t) f0 ～t f1 )：t f0 At the moment, switch tube S 1 And S is 2 Conducting. At this stage, input voltage V i Reverse flyback transformer T f Primary inductance L of (2) p Charging, the inductor current rising from zero, the output current of the converter being only output filter capacitor C o The discharge is provided. In the clamp circuit, a clamp capacitor C 1 Through S 1 、S 2 And D L1 To L 1 Discharging C 2 Through S 1 、S 2 And D L2 To L 2 And discharging, wherein the coupling inductance current starts to rise from zero. To t f1 At the end of this stage, L 1 、L 2 And L p To a maximum value of 1 switching cycle.
Working phase 2 (t) f1 ～t f2 )：t f1 At the moment, switch tube S 1 And S is 2 And (5) switching off. t is t f1 After the moment, flyback transformer T f Primary inductance L of (2) p Energy transfer to secondary inductance L s And pass through output rectifying diode D o To the load. In this process, L p Is clamped at nV o (in the figure, the positive and negative polarities are that of upper negative and lower positive; n is that of flyback transformer T) f The turns ratio of the primary winding and the secondary winding, where n 2 ＝L p /L s ) Leakage inductance L lk Energy clamped capacitor C of (2) 1 、C 2 Absorption (clamp capacitor voltage V) C1 ＝V C2 >V i /2+nV o /2). In the clamp circuit, D 1 、D 2 And D f Conduction, D L1 And D L2 Cut-off, transfer of energy of coupled inductor to flyback winding L f On L 1 And L 2 The current becomes zero, L f Energy of (2) passes through D f To the load. To t f2 At the moment, leakage inductance L lk The current of (c) decreases to zero and this phase ends.
Working phase 3 (t) f2 ～t f4 )：t f2 After the moment L s And L f Energy continues to be transferred to the load. To the point oft f3 Time, L f The current of (2) decreases to zero to t f4 Time, L s The current of (c) decreases to zero and this phase ends. In this stage, the sequence of decreasing the inductor current to zero does not need to be strictly fixed.
Working phase 4 (t) f4 ～t f5 ): to t f4 After the moment, the primary and secondary side currents of the transformer are kept to be zero, and the output current of the converter is only obtained by an output filter capacitor C o The discharge is provided. To t f5 At the moment, switch tube S 1 And S is 2 And conducting again, and enabling the converter to enter the operation of the next switching cycle.
During the operation of the passive clamp (structure 1), 2 equivalent inductances L of the coupling inductance 1 And L 2 The coupling action of (2) occurs in the working stage 1-3; during the operation of the passive clamp (structure 2), 2 equivalent inductances L of the coupling inductance 1 And L 2 The coupling action of (2) occurs in the working phase 1. In the process, if the clamp capacitor C 1 And C 2 Are differentiated by the voltage of (c) which will be transferred through the coupling inductance (L 1 And L 2 ) The mutual energy transmission is realized: when C 1 Is higher than C 2 At a voltage of (2), energy is represented by C 1 Through coupling inductance to C 2 Transferring; when C 2 Is higher than C 1 At a voltage of (2), energy is represented by C 2 Through coupling inductance to C 1 And (5) transmitting. Thus, during operation of the converter, the clamp capacitance C is ensured in each switching cycle due to the presence of the coupling inductance 1 And C 2 Is a voltage equalization of (a). In the switching tube S 1 And S is 2 During the switching operation of (2), the maximum voltages are respectively C 1 And C 2 The adoption of the proposed passive clamping circuit (structure 1 or structure 2) thus achieves voltage equalization of each series switching tube of the switching tube series flyback converter.
During operation of the passive clamp circuits (Structure 1 and Structure 2), the clamp capacitance C 1 And C 2 The capacitance of (2) should be large enough to ensure C 1 And C 2 Voltage approximation during charge and discharge of each switching cycleConstant.
Coupling inductance L of clamping circuits (structure 1 and structure 2) in flyback converter 1 、L 2 The equivalent inductance value is:
simultaneously satisfies the conditions:to ensure that the coupling inductor current can be reduced to zero during switching off of the switching tube;
Wherein: v (V) C1 For clamping capacitor C 1 Voltage at two ends, and V C1 ＝V C2 ，V C2 For clamping capacitor C 2 The voltage at two ends, D is the switching tube S in each switching period 1 And S is 2 Duty cycle of d= (t f1 -t f0 ) T, T is the switching period.
For the passive clamp circuit (structure 2), in order to ensure that the energy of the coupling inductor can be transferred to the flyback winding L after the switching tube is turned off f On top of this, further assurance is needed:
wherein n is f For coupling inductance L 1 Winding turns of (2) and flyback winding L thereof f Is provided for the ratio of the number of winding turns,
and a third specific embodiment: next, a first embodiment will be further described with reference to fig. 3 and 4, in which the operation of the two-switching-tube series forward converter using the passive clamp circuit is analyzed. For ease of analysis, the following assumptions are made: the forward converter operates in an output filter inductor current continuous mode (continuous current mode, CCM); all devices in the circuit are ideal devices; clamping capacitor C 1 、C 2 Output filter capacitor C o Is sufficiently large to be considered a constant voltage source during analysis.
FIG. 3 shows a passive clamp circuit passing through diode D L Will couple inductance L 1 、L 2 The energy absorbed in each switching cycle is fed back to the input side of the forward converter. FIG. 4 shows a passive clamp circuit passing through a flyback winding L f And diode D f The series branch being formed to couple the inductance L 1 、L 2 The energy absorbed in each switching cycle is fed back to the output side of the forward converter. The clamping circuit of the forward converter not only realizes the clamping function of the series switching tube, but also completely absorbs the excitation inductance energy of the transformer in the switching tube switching-off period, thereby realizing the magnetic reset function of the forward converter, and therefore, a separate magnetic reset circuit is not required to be additionally arranged, and the whole circuit structure is simplified.
FIG. 3 shows a passive clamp circuit clamp capacitor C 1 、C 2 The method comprises the steps of carrying out a first treatment on the surface of the Diode D 1 、D 2 、D L1 And D L2 The method comprises the steps of carrying out a first treatment on the surface of the Coupling inductance L 1 、L 2 The method comprises the steps of carrying out a first treatment on the surface of the Coupling inductance L 1 、L 2 The number of turns of the windings is the same;
clamping capacitor C 2 Diode D 2 Diode D 1 Clamping capacitor C 1 The clamping capacitors C of the serial branches are serially connected in sequence 2 The positive electrode end is simultaneously connected with a switch tube S 2 Drain of (D) and diode D L1 A cathode of the series branch, a clamping capacitor C 1 Switch tube S with simultaneous connection of negative electrode end 1 Source of (D) and diode D L2 Anode of diode D 2 Cathode and diode D of (D) 1 Is connected with the switch tube S at the same time with the anode of 1 Drain electrode of (d) and switching tube S 2 A source of (a);
coupling inductance L 2 And diode D L2 In series, the coupling inductance L of the series branch 2 One end is connected with the clamping capacitor C 2 Is a negative electrode of (a);
coupling inductance L 1 And diode D L1 In series, the coupling inductance L of the series branch 1 One end is connected with the clamping capacitor C 1 Is a positive electrode of (a);
switch tube S 1 And S is 2 The maximum voltages during the switching operation of (2) are respectively C 1 And C 2 Clamped; the method comprises the following steps:
when clamping capacitor C 1 And C 2 When a voltage difference occurs, the inductor L is coupled 1 、L 2 Realize the mutual energy transmission, when C 1 Is higher than C 2 At a voltage of (2), energy is represented by C 1 By coupling inductance L 1 、L 2 To C 2 Transferring; when C 2 Is higher than C 1 At a voltage of (2), energy is represented by C 2 By coupling inductance L 1 、L 2 To C 1 Transfer to clamp capacitor C 1 And C 2 Is equal to the voltage of the switch tube S 1 And S is 2 Is a voltage equalization of (a).
Further, diode D L Is connected with the anode of the coupling inductance L 1 And diode D L1 Is a common node of diode D L The cathode of the converter is connected with the primary side of the converter; switch tube S 1 And S is 2 When turned off, the coupling inductance L 1 、L 2 The energy absorbed in each switching cycle passes through diode D L Feedback to the input side of the converter.
C of clamp circuit 2 The positive pole is connected with the different name end of the primary winding of the transformer, and the diode D L Is connected with the DC input voltage V i And the same name end of the positive pole and the primary winding.
The passive clamp circuit shown in fig. 3 operates as follows:
in 1 switching cycle, the two-switching-tube series forward converter shown in fig. 3 has the following 3 main operation phases, and the equivalent circuit of each phase is shown in fig. 7.
Working phase 1 (t) F0 ～t F1 )：t F0 At the moment, switch tube S 1 And S is 2 Conducting. At this stage, output rectifier diode D o1 Conduction, freewheel diode D o2 Cut-off, input voltage V i Through forward transformer T F Supplying power to load, exciting inductance L of transformer m Electric currentOutput filter inductance L o The current rises linearly. In the clamp circuit, a clamp capacitor C 1 Through S 1 、S 2 And D L1 To L 1 Discharging C 2 Through S 1 、S 2 And D L2 To L 2 And discharging, wherein the coupling inductance current starts to rise from zero. To t F1 At the end of this stage, L 1 、L 2 、L m And L o To a maximum value of 1 switching cycle.
Working phase 2 (t) F1 ～t F3 )：t F1 At the moment, switch tube S 1 And S is 2 And (5) switching off. t is t F1 After the moment, output rectifying diode D o1 Cut-off, freewheel diode D o2 Conduction and output filter inductance L o Through D o2 Freewheel and provide energy to the load. In this process, the excitation inductance L m Energy steering clamp capacitor C of (2) 1 、C 2 Releasing. In the clamp circuit, D 1 、D 2 、D L And D L2 Conduction, D L1 Cut off, at this time, L 1 And L 2 In series and through D L 、D 1 And D 2 The energy is fed back to the input side of the converter. To t F2 Time, L 1 And L 2 The current of (2) decreases to zero to t F3 At the moment, excitation inductance L m The current of (c) decreases to zero and this phase ends. In this stage, the sequence of decreasing the inductor current to zero does not need to be strictly fixed.
Working phase 3 (t) F3 ～t F4 ): to t F3 After the moment, the primary side current and the secondary side current of the transformer are kept to be zero, and a filter inductance L is output o The energy continues to be supplied to the load. To t F4 At the moment, switch tube S 1 And S is 2 And conducting again, and enabling the converter to enter the operation of the next switching cycle.
The passive clamp circuit shown in FIG. 4 includes a clamp capacitor C 1 、C 2 The method comprises the steps of carrying out a first treatment on the surface of the Diode D 1 、D 2 、D L1 And D L2 The method comprises the steps of carrying out a first treatment on the surface of the Coupling inductance L 1 、L 2 The method comprises the steps of carrying out a first treatment on the surface of the Coupling inductance L 1 、L 2 The number of turns of the windings is the same;
clamping capacitor C 2 Diode D 2 Diode D 1 Clamping capacitor C 1 The clamping capacitors C of the serial branches are serially connected in sequence 2 The positive electrode end is simultaneously connected with a switch tube S 2 Drain of (D) and diode D L1 A cathode of the series branch, a clamping capacitor C 1 Switch tube S with simultaneous connection of negative electrode end 1 Source of (D) and diode D L2 Anode of diode D 2 Cathode and diode D of (D) 1 Is connected with the switch tube S at the same time with the anode of 1 Drain electrode of (d) and switching tube S 2 A source of (a);
coupling inductance L 2 And diode D L2 In series, the coupling inductance L of the series branch 2 One end is connected with the clamping capacitor C 2 Is a negative electrode of (a);
coupling inductance L 1 And diode D L1 In series, the coupling inductance L of the series branch 1 One end is connected with the clamping capacitor C 1 Is a positive electrode of (a);
switch tube S 1 And S is 2 The maximum voltages during the switching operation of (2) are respectively C 1 And C 2 Clamped; the method comprises the following steps:
When clamping capacitor C 1 And C 2 When a voltage difference occurs, the inductor L is coupled 1 、L 2 Realize the mutual energy transmission, when C 1 Is higher than C 2 At a voltage of (2), energy is represented by C 1 By coupling inductance L 1 、L 2 To C 2 Transferring; when C 2 Is higher than C 1 At a voltage of (2), energy is represented by C 2 By coupling inductance L 1 、L 2 To C 1 Transfer to clamp capacitor C 1 And C 2 Is equal to the voltage of the switch tube S 1 And S is 2 Is a voltage equalization of (a).
Further, includes flyback winding L f And diode D f Flyback winding L f And diode D f The series branch is connected in parallel with the output side of the converter, and the flyback winding L f And coupling inductance L 1 、L 2 Jointly wound on the same magnetic core, and coupled with the inductor L 1 、L 2 The energy absorbed in each switching cycle passes through the flyback winding L f And diode D f The series branch is fed back to the output side of the converter.
Diode D of series branch in clamping circuit f Cathode connection output filter inductance L o And output filter capacitor C o Common node, flyback winding L of series branch f The end is connected with an output filter capacitor C o And a load negative terminal.
The passive clamp circuit shown in fig. 4 operates as follows:
in 1 switching cycle, the two-switching-tube series forward converter shown in fig. 4 has the following 3 main operation phases, and the equivalent circuit of each phase is shown in fig. 8.
Working phase 1 (t) F0 ～t F1 )：t F0 At the moment, switch tube S 1 And S is 2 Conducting. At this stage, output rectifier diode D o1 Conduction, freewheel diode D o2 Cut-off, input voltage V i Through forward transformer T F Supplying power to load, exciting inductance L of transformer m Current and output filter inductance L o The current rises linearly. In the clamp circuit, a clamp capacitor C 1 Through S 1 、S 2 And D L1 To L 1 Discharging C 2 Through S 1 、S 2 And D L2 To L 2 And discharging, wherein the coupling inductance current starts to rise from zero. To t F1 At the end of this stage, L 1 、L 2 、L m And L o To a maximum value of 1 switching cycle.
Working phase 2 (t) F1 ～t F3 )：t F1 At the moment, switch tube S 1 And S is 2 And (5) switching off. t is t F1 After the moment, output rectifying diode D o1 Cut-off, freewheel diode D o2 Conduction and output filter inductance L o Through D o2 Freewheel and provide energy to the load. In this process, the excitation inductance L m Energy direction clamp of (a)Bit capacitor C 1 、C 2 Releasing. In the clamp circuit, D 1 、D 2 And D f Conduction, D L1 And D L2 Cut-off, transfer of energy of coupled inductor to flyback winding L f On L 1 And L 2 The current becomes zero, L f Energy of (2) passes through D f To the load. To t F2 Time, L f The current of (2) decreases to zero to t F3 At the moment, excitation inductance L m The current of (c) decreases to zero and this phase ends. In this stage, the sequence of decreasing the inductor current to zero does not need to be strictly fixed.
Working phase 3 (t) F3 ～t F4 ): to t F3 After the moment, the primary side current and the secondary side current of the transformer are kept to be zero, and a filter inductance L is output o The energy continues to be supplied to the load. To t F4 At the moment, switch tube S 1 And S is 2 And conducting again, and enabling the converter to enter the operation of the next switching cycle.
During the operation of the passive clamp (structure 1), 2 equivalent inductances L of the coupling inductance 1 And L 2 The coupling action of (2) occurs in working phases 1 and 2; during the operation of the passive clamp (structure 2), 2 equivalent inductances L of the coupling inductance 1 And L 2 The coupling action of (2) occurs in the working phase 1. In the process, if the clamp capacitor C 1 And C 2 Are differentiated by the voltage of (c) which will be transferred through the coupling inductance (L 1 And L 2 ) The mutual energy transmission is realized: when C 1 Is higher than C 2 At a voltage of (2), energy is represented by C 1 Through coupling inductance to C 2 Transferring; when C 2 Is higher than C 1 At a voltage of (2), energy is represented by C 2 Through coupling inductance to C 1 And (5) transmitting. Thus, during operation of the converter, the clamp capacitance C is ensured in each switching cycle due to the presence of the coupling inductance 1 And C 2 Is a voltage equalization of (a). In the switching tube S 1 And S is 2 During the switching operation of (2), the maximum voltages are respectively C 1 And C 2 Clamped, therefore, the adoption of the proposed passive clamping circuit (structure 1 or structure 2) The voltage balance of each series switching tube of the switching tube series forward converter is realized.
During operation of the passive clamp circuits (Structure 1 and Structure 2), the clamp capacitance C 1 And C 2 The capacitance of (2) should be large enough to ensure C 1 And C 2 The voltage is approximately constant during the charge and discharge of each switching cycle.
Coupling inductance L of clamping circuit in forward converter 1 、L 2 The equivalent inductance value is:
simultaneously satisfies the conditions:
wherein: l (L) m Is a forward transformer T F Equivalent excitation inductance of V C1 For clamping capacitor C 1 Voltage at two ends, and V C1 ＝V C2 ，V C2 For clamping capacitor C 2 Voltage at two ends, V i For the voltage at the input side of the converter, V o For the output side voltage of the converter, n f For coupling inductance L 1 Winding turns of (2) and flyback winding L thereof f Is provided for the ratio of the number of winding turns,d is a switching tube S in each switching period 1 And S is 2 Is a duty cycle of (c).
Condition 1 is to ensure that the exciting inductance energy of the forward transformer is fully absorbed during the switching off of the switching tube, i.e. the forward transformer achieves magnetic reset, condition 1 applies to both structure 1 and structure 2.
Condition 2 is to ensure that the coupling inductor current in the passive clamp (applicable to configuration 1) can be reduced to zero during switching off of the switching tube.
Condition 3 is to ensure that the energy of the coupling inductance in the passive clamp (applied to structure 2) can be transferred to the flyback winding Lf after the switching tube is turned off.
The specific embodiment IV is as follows: next, referring to fig. 9 and 10, this embodiment is an extension of the two-switching-tube serial flyback converter in the second embodiment, in which the switching-tube serial auxiliary power supply adopts 2K switching-tube serial converters, and when k=2, the switching-tube serial flyback converter is a four-switching serial flyback converter, and the passive clamp circuit of fig. 9 feeds back the absorbed energy to the input side of the converter in each switching period; the passive clamp circuit of fig. 10 feeds back the absorbed energy to the output side of the converter during each switching cycle; the clamp circuit is mainly composed of a clamp capacitor (C 1 ＝C 2 ＝C 3 ＝C 4 ) Coupling inductance (L) 1 ＝L 2 ＝L 3 ＝L 4 ) Diode (D) 1 、D 2 、D 3 、D 4 、D L1 、D L2 、D L3 、D L4 ) Composition is prepared.
On the basis of this, a diode D is added in FIG. 9 (Structure 1) L The power supply circuit is used for feeding back the energy absorbed by the passive clamping circuit to the input side of the converter; the method comprises the following steps:
the passive clamping circuit comprises 4 clamping units and a diode D L ；
The 4 series switching tubes in the converter are divided into 2 pairs, two adjacent switching tubes are 1 pair, each pair of series switching tubes is provided with 1 clamping unit, and the switching tubes S 1 、S 2 The clamping unit of (1) comprises a clamping capacitor C 1 、C 2 The method comprises the steps of carrying out a first treatment on the surface of the Diode D 1 、D 2 、D L1 And D L2 The method comprises the steps of carrying out a first treatment on the surface of the Coupling inductance L 1 、L 2 The method comprises the steps of carrying out a first treatment on the surface of the Switch tube S 3 、S 4 The clamping unit of (1) comprises a clamping capacitor C 3 、C 4 The method comprises the steps of carrying out a first treatment on the surface of the Diode D 3 、D 4 、D L3 And D L4 The method comprises the steps of carrying out a first treatment on the surface of the Coupling inductance L 3 、L 4 The method comprises the steps of carrying out a first treatment on the surface of the Coupling inductance L 1 、L 2 、L 3 、L 4 The number of turns of the windings is the same and the windings are wound on the same magnetic core together;
clamping capacitor C 2 Diode D 2 Diode D 1 Clamping capacitor C 1 Sequentially stringingA clamp capacitor C of the series branch 2 The positive electrode end is simultaneously connected with a switch tube S 2 Drain of (D) and diode D L1 A cathode of the series branch, a clamping capacitor C 1 Switch tube S with simultaneous connection of negative electrode end 1 Source of (D) and diode D L2 Anode of diode D 2 Cathode and diode D of (D) 1 Is connected with the switch tube S at the same time with the anode of 1 Drain electrode of (d) and switching tube S 2 A source of (a); coupling inductance L 2 And diode D L2 In series, the coupling inductance L of the series branch 2 One end is connected with the clamping capacitor C 2 Is a negative electrode of (a); coupling inductance L 1 And diode D L1 In series, the coupling inductance L of the series branch 1 One end is connected with the clamping capacitor C 1 Is a positive electrode of (a);
clamping capacitor C 4 Diode D 4 Diode D 3 Clamping capacitor C 3 The clamping capacitors C of the serial branches are serially connected in sequence 4 The positive electrode end is simultaneously connected with a switch tube S 4 Drain of (D) and diode D L3 A cathode of the series branch, a clamping capacitor C 3 Switch tube S with simultaneous connection of negative electrode end 3 Source of (D) and diode D L4 Anode of diode D 4 Cathode and diode D of (D) 3 Is connected with the switch tube S at the same time with the anode of 3 Drain electrode of (d) and switching tube S 4 A source of (a); coupling inductance L 4 And diode D L4 In series, the coupling inductance L of the series branch 4 One end is connected with the clamping capacitor C 4 Is a negative electrode of (a); coupling inductance L 3 And diode D L3 In series, the coupling inductance L of the series branch 3 One end is connected with the clamping capacitor C 3 Is a positive electrode of (a);
diode D L Is connected with the anode of the coupling inductance L 3 And diode D L3 Is a common node of diode D L The cathode of the transformer is connected with the primary side of the transformer in the converter; switch tube S 1 And S is 2 When turned off, the coupling inductance L 1 、L 2 、L 3 、L 4 The energy absorbed in each switching cycle passes through diode D L Feedback to the input side of the converter.
In FIG. 10 (Structure 2), the flyback winding L is added to the coupling inductance f And is connected with a diode D f For feeding back the energy absorbed by the passive clamp to the output side of the converter.
The 4 series switching tubes in the converter are divided into 2 pairs, two adjacent switching tubes are 1 pair, each pair of series switching tubes is provided with 1 clamping unit, and the switching tubes S 1 、S 2 The clamping unit of (1) comprises a clamping capacitor C 1 、C 2 The method comprises the steps of carrying out a first treatment on the surface of the Diode D 1 、D 2 、D L1 And D L2 The method comprises the steps of carrying out a first treatment on the surface of the Coupling inductance L 1 、L 2 The method comprises the steps of carrying out a first treatment on the surface of the Switch tube S 3 、S 4 The clamping unit of (1) comprises a clamping capacitor C 3 、C 4 The method comprises the steps of carrying out a first treatment on the surface of the Diode D 3 、D 4 、D L3 And D L4 The method comprises the steps of carrying out a first treatment on the surface of the Coupling inductance L 3 、L 4 The method comprises the steps of carrying out a first treatment on the surface of the Coupling inductance L 1 、L 2 、L 3 、L 4 The number of turns of the windings is the same and the windings are wound on the same magnetic core together;
Clamping capacitor C 2 Diode D 2 Diode D 1 Clamping capacitor C 1 The clamping capacitors C of the serial branches are serially connected in sequence 2 The positive electrode end is simultaneously connected with a switch tube S 2 Drain of (D) and diode D L1 A cathode of the series branch, a clamping capacitor C 1 Switch tube S with simultaneous connection of negative electrode end 1 Source of (D) and diode D L2 Anode of diode D 2 Cathode and diode D of (D) 1 Is connected with the switch tube S at the same time with the anode of 1 Drain electrode of (d) and switching tube S 2 A source of (a); coupling inductance L 2 And diode D L2 In series, the coupling inductance L of the series branch 2 One end is connected with the clamping capacitor C 2 Is a negative electrode of (a); coupling inductance L 1 And diode D L1 In series, the coupling inductance L of the series branch 1 One end is connected with the clamping capacitor C 1 Is a positive electrode of (a);
clamping capacitor C 4 Diode D 4 Diode D 3 Clamping capacitor C 3 The clamping capacitors C of the serial branches are serially connected in sequence 4 The positive electrode end is simultaneously connected with a switch tube S 4 Drain of (D) and diode D L3 A cathode of the series branch, a clamping capacitor C 3 Switch tube S with simultaneous connection of negative electrode end 3 Source of (D) and diode D L4 Anode of diode D 4 Cathode and diode D of (D) 3 Is connected with the switch tube S at the same time with the anode of 3 Drain electrode of (d) and switching tube S 4 A source of (a); coupling inductance L 4 And diode D L4 In series, the coupling inductance L of the series branch 4 One end is connected with the clamping capacitor C 4 Is a negative electrode of (a); coupling inductance L 3 And diode D L3 In series, the coupling inductance L of the series branch 3 One end is connected with the clamping capacitor C 3 Is a positive electrode of (a);
flyback winding L f And diode D f The series branch is connected in parallel with the output side of the converter, and the flyback winding L f And coupling inductance L 1 、L 2 、L 3 、L 4 Jointly wound on the same magnetic core, and coupled with the inductor L 1 、L 2 、L 3 、L 4 The energy absorbed in each switching cycle passes through the flyback winding L f And diode D f The series branch is fed back to the output side of the converter.
The working principle is the same as in the second embodiment.
Fifth embodiment: next, referring to fig. 11 and fig. 12, this embodiment is an extension of the two-switching-tube serial forward converter in the third embodiment, in which the switching-tube serial auxiliary power supply adopts 2K switching-tube serial converters, and when k=2 is a four-switching-tube serial forward converter, the passive clamp circuit of fig. 11 feeds back the absorbed energy to the input side of the converter in each switching period, and the clamp circuit structure is the same as that of fig. 9; the passive clamp of fig. 12 feeds back the absorbed energy to the output side of the converter during each switching cycle, the clamp being identical to that of fig. 10; the clamp circuit is mainly composed of a clamp capacitor (C 1 ＝C 2 ＝C 3 ＝C 4 ) Coupling inductance (L) 1 ＝L 2 ＝L 3 ＝L 4 ) Diode (D) 1 、D 2 、D 3 、D 4 、D L1 、D L2 、D L3 、D L4 ) Composition is prepared. On the basis of this, a diode D is added in FIG. 11 (Structure 1) L The power supply circuit is used for feeding back the energy absorbed by the passive clamping circuit to the input side of the converter; in FIG. 12 (structure 2), the flyback winding L is added to the coupling inductance f And is connected with a diode D f For feeding back the energy absorbed by the passive clamp to the output side of the converter. The working principle is the same as in the third embodiment.

Claims (9)

1. Passive clamping circuit suitable for switching tube serial auxiliary power supply, wherein the switching tube serial auxiliary power supply adopts two switching tubes S 1 、S 2 The converters are connected in series, and are forward converters or flyback converters;
the passive clamp circuit is characterized by comprising a clamp capacitor C 1 、C 2 The method comprises the steps of carrying out a first treatment on the surface of the Diode D 1 、D 2 、D L1 And D L2 The method comprises the steps of carrying out a first treatment on the surface of the Coupling inductance L 1 、L 2 The method comprises the steps of carrying out a first treatment on the surface of the Coupling inductance L 1 、L 2 The number of turns of the windings is the same;
clamping capacitor C 2 Diode D 2 Diode D 1 Clamping capacitor C 1 The clamping capacitors C of the serial branches are serially connected in sequence 2 The positive electrode end is simultaneously connected with a switch tube S 2 Drain of (D) and diode D L1 A cathode of the series branch, a clamping capacitor C 1 Switch tube S with simultaneous connection of negative electrode end 1 Source of (D) and diode D L2 Anode of diode D 2 Cathode and diode D of (D) 1 Is connected with the switch tube S at the same time with the anode of 1 Drain electrode of (d) and switching tube S 2 A source of (a);
coupling inductance L 2 And diode D L2 In series, the coupling inductance L of the series branch 2 One end is connected with the clamping capacitor C 2 Is a negative electrode of (a);
coupling inductance L 1 And diode D L1 In series, the coupling inductance L of the series branch 1 One end is connected with the clamping capacitor C 1 Is a positive electrode of (a);
switch tube S 1 And S is 2 The maximum voltages during the switching operation of (2) are respectively C 1 And C 2 Clamped; the method comprises the following steps:
when clamping capacitor C 1 And C 2 When a voltage difference occurs, the inductor L is coupled 1 、L 2 Realize the mutual energy transmission, when C 1 Is higher than C 2 At a voltage of (2), energy is represented by C 1 By coupling inductance L 1 、L 2 To C 2 Transferring; when C 2 Is higher than C 1 At a voltage of (2), energy is represented by C 2 By coupling inductance L 1 、L 2 To C 1 Transfer to clamp capacitor C 1 And C 2 Is equal to the voltage of the switch tube S 1 And S is 2 Is a voltage equalization of (a).
2. The passive clamp circuit for a switching-tube series auxiliary power supply of claim 1, further comprising a diode D L Diode D L Is connected with the anode of the coupling inductance L 1 And diode D L1 Is a common node of diode D L The cathode of the converter is connected with the primary side of the converter; switch tube S 1 And S is 2 When turned off, the coupling inductance L 1 、L 2 The energy absorbed in each switching cycle passes through diode D L Feedback to the input side of the converter.
3. The passive clamp circuit for a switching tube serial auxiliary power supply of claim 2, wherein the coupling inductance L of the clamp circuit in the flyback converter 1 、L 2 The equivalent inductance value is:
simultaneously satisfies the conditions:
wherein: l (L) p Primary winding inductance L of transformer which is flyback converter lk Transformer equivalent leakage inductance of flyback converter, V C1 For clamping capacitor C 1 Voltage at two ends, and V C1 ＝V C2 ，V C2 For clamping capacitor C 2 Voltage at two ends, V i For the converter input side voltage, D is the switching tube S in each switching cycle 1 And S is 2 Is a duty cycle of (c).
4. The passive clamp circuit for a switching tube serial auxiliary power supply of claim 2, wherein the coupling inductance L of the clamp circuit in the forward converter 1 、L 2 The equivalent inductance value is:
simultaneously satisfies the conditions:
L m is a forward transformer T F Equivalent excitation inductance of V C1 For clamping capacitor C 1 Voltage at two ends, and V C1 ＝V C2 ，V C2 For clamping capacitor C 2 Voltage at two ends, V i For the converter input side voltage, D is the switching tube S in each switching cycle 1 And S is 2 Is a duty cycle of (c).
5. The passive clamp circuit for a switching tube series auxiliary power supply of claim 1, further comprising a flyback winding L f And diode D f Flyback winding L f And diode D f The series branch is connected in parallel with the output side of the converter, and the flyback winding L f And coupling inductance L 1 、L 2 Jointly wound on the same magnetic core, and coupled with the inductor L 1 、L 2 At each openingThe energy absorbed in the off period passes through the flyback winding L f And diode D f The series branch is fed back to the output side of the converter.
6. The passive clamp circuit for a switching tube series auxiliary power supply as defined in claim 5, wherein the coupling inductance L of the clamp circuit in the flyback converter 1 、L 2 The equivalent inductance value is:
simultaneously satisfies the conditions:
wherein: l (L) p Primary winding inductance L of transformer which is flyback converter lk Transformer equivalent leakage inductance of flyback converter, V C1 For clamping capacitor C 1 Voltage at two ends, and V C1 ＝V C2 ，V C2 For clamping capacitor C 2 Voltage at two ends, V i For the voltage at the input side of the converter, V o For the output side voltage of the converter, n f For coupling inductance L 1 Winding turns of (2) and flyback winding L thereof f Is provided for the ratio of the number of winding turns,d is a switching tube S in each switching period 1 And S is 2 Is a duty cycle of (c).
7. The passive clamp circuit for a switching tube series auxiliary power supply as defined in claim 5, wherein the coupling inductance L of the clamp circuit in the forward converter 1 、L 2 The equivalent inductance value is:
simultaneously satisfies the conditions:
L m is a forward transformer T F Equivalent excitation inductance of V C1 For clamping capacitor C 1 Voltage at two ends, and V C1 ＝V C2 ，V C2 For clamping capacitor C 2 Voltage at two ends, V i For the voltage at the input side of the converter, V o For the output side voltage of the converter, n f For coupling inductance L 1 Winding turns of (2) and flyback winding L thereof f Is provided for the ratio of the number of winding turns,d is a switching tube S in each switching period 1 And S is 2 Is a duty cycle of (c).
8. The passive clamping circuit is suitable for a switching tube serial auxiliary power supply, the switching tube serial auxiliary power supply adopts 2K converters with switching tubes connected in series, and the converters are forward converters or flyback converters; the passive clamping circuit is characterized by comprising K clamping units and a diode D L ；
2K series switching tubes in the converter are divided into K pairs, two adjacent switching tubes are 1 pair, each pair of series switching tubes is provided with 1 clamping unit, and the clamping unit comprises a clamping capacitor C 1 、C 2 The method comprises the steps of carrying out a first treatment on the surface of the Diode D 1 、D 2 、D L1 And D L2 The method comprises the steps of carrying out a first treatment on the surface of the Coupling inductance L 1 、L 2 The method comprises the steps of carrying out a first treatment on the surface of the Coupling inductance L 1 、L 2 The number of turns of the windings is the same;
clamping capacitor C 2 Diode D 2 Diode D 1 Clamping capacitor C 1 The clamping capacitors C of the serial branches are serially connected in sequence 2 The positive electrode end is simultaneously connected with a switch tube S 2 Drain of (D) and diode D L1 A cathode of the series branch, a clamping capacitor C 1 Switch tube S with simultaneous connection of negative electrode end 1 Source of (D) and diode D L2 Anode of diode D 2 Cathode and diode D of (D) 1 Is connected with the switch tube S at the same time with the anode of 1 Drain electrode of (d) and switching tube S 2 A source of (a);
coupling inductance L 2 And diode D L2 In series, the coupling inductance L of the series branch 2 One end is connected with the clamping capacitor C 2 Is a negative electrode of (a);
coupling inductance L 1 And diode D L1 In series, the coupling inductance L of the series branch 1 One end is connected with the clamping capacitor C 1 Is a positive electrode of (a);
the coupling inductors of the K clamping units are wound on the same magnetic core together;
diode D L Coupled inductance L in the anode-connected topmost clamping unit 1 And diode D L1 Is a common node of diode D L The cathode of the converter is connected with the primary side of the converter; switch tube S 1 And S is 2 When turned off, the coupling inductance L 1 、L 2 The energy absorbed in each switching cycle passes through diode D L Feedback to the input side of the converter.
9. The passive clamping circuit is suitable for a switching tube serial auxiliary power supply, the switching tube serial auxiliary power supply adopts 2K converters with switching tubes connected in series, and the converters are forward converters or flyback converters; the passive clamping circuit is characterized by comprising K clamping units and a flyback winding L f And diode D f ；
2K series switching tubes in the converter are divided into K pairs, two adjacent switching tubes are 1 pair, each pair of series switching tubes is provided with 1 clamping unit, and the clamping unit comprises a clamping capacitor C 1 、C 2 The method comprises the steps of carrying out a first treatment on the surface of the Diode D 1 、D 2 、D L1 And D L2 The method comprises the steps of carrying out a first treatment on the surface of the Coupling inductance L 1 、L 2 The method comprises the steps of carrying out a first treatment on the surface of the Coupling inductance L 1 、L 2 The number of turns of the windings is the same;
clamping capacitor C 2 Diode D 2 Diode D 1 Clamping capacitor C 1 The clamping capacitors C of the serial branches are serially connected in sequence 2 The positive electrode end is simultaneously connected with a switch tube S 2 Drain of (D) and diode D L1 A cathode of the series branch, a clamping capacitor C 1 Switch tube S with simultaneous connection of negative electrode end 1 Source of (D) and diode D L2 Anode of diode D 2 Cathode and diode D of (D) 1 Is connected with the switch tube S at the same time with the anode of 1 Drain electrode of (d) and switching tube S 2 A source of (a);
coupling inductance L 2 And diode D L2 In series, the coupling inductance L of the series branch 2 One end is connected with the clamping capacitor C 2 Is a negative electrode of (a);
coupling inductance L 1 And diode D L1 In series, the coupling inductance L of the series branch 1 One end is connected with the clamping capacitor C 1 Is a positive electrode of (a);
the coupling inductors of the K clamping units are wound on the same magnetic core together;
flyback winding L f And diode D f The series branch is connected in parallel with the output side of the converter, and the flyback winding L f Coupling inductance L with K clamping units 1 、L 2 Jointly wound on the same magnetic core, and coupled with the inductor L 1 、L 2 The energy absorbed in each switching cycle passes through the flyback winding L f And diode D f The series branch is fed back to the output side of the converter.
CN202111407121.4A 2021-11-24 2021-11-24 Passive clamping circuit suitable for switching tube serial auxiliary power supply Active CN113949255B (en)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104702105A (en) * 2015-04-01 2015-06-10 哈尔滨工业大学 Boost converter for similar active switch inductance network
CN108599560A (en) * 2018-05-11 2018-09-28 东南大学 More bootstrapping cascade connection type DC-DC converters of two capacitor-clampeds of photovoltaic system
CN108683332A (en) * 2018-07-25 2018-10-19 安徽工业大学 A kind of high-gain, wide Duty ratio control Boost
CN112865540A (en) * 2021-01-20 2021-05-28 西安石油大学 Lossless clamping network of primary-side feedback type flyback converter and design method

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104702105A (en) * 2015-04-01 2015-06-10 哈尔滨工业大学 Boost converter for similar active switch inductance network
CN108599560A (en) * 2018-05-11 2018-09-28 东南大学 More bootstrapping cascade connection type DC-DC converters of two capacitor-clampeds of photovoltaic system
CN108683332A (en) * 2018-07-25 2018-10-19 安徽工业大学 A kind of high-gain, wide Duty ratio control Boost
CN112865540A (en) * 2021-01-20 2021-05-28 西安石油大学 Lossless clamping network of primary-side feedback type flyback converter and design method

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