CN115912923A - Asymmetric half-bridge forward and reverse flyback converter topological structure - Google Patents
Asymmetric half-bridge forward and reverse flyback converter topological structure Download PDFInfo
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- CN115912923A CN115912923A CN202211282076.9A CN202211282076A CN115912923A CN 115912923 A CN115912923 A CN 115912923A CN 202211282076 A CN202211282076 A CN 202211282076A CN 115912923 A CN115912923 A CN 115912923A
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Abstract
The invention provides an asymmetric half-bridge forward and reverse flyback converter topological structure which reduces the voltage stress when a primary side field tube is turned off so as to enable the voltage stress to be equal to the input voltage; the voltage stress of the secondary side rectifying diode is reduced and is equal to the output voltage; ZVS switching-on of two field tubes on the primary side and ZCS switching-off of two diodes on the secondary side can be realized in the full load range, and the soft switching range and conditions are more loose; the forward and backward excitation rectification mode of the secondary side allows the transformer to carry out bidirectional excitation, improves the utilization rate of a magnetic core and expands the power capacity of the converter; and the number of turns of the secondary of the transformer is reduced, and the volume of the required transformer is reduced.
Description
Technical Field
The invention belongs to the technical field of power electronic application, and particularly relates to a topological structure of an asymmetric half-bridge forward-flyback converter.
Background
In the field of new energy and some portable devices such as photovoltaic systems and vehicle-mounted inverters, storage batteries are commonly used as power supply devices. Most of the devices belong to medium and small power output, the power supply voltage is low, and the high-gain boost converter is required to be boosted to a high enough voltage to meet the requirement of the later stage. Although the cascaded converter can realize high boost ratio, the overall efficiency is the product of the efficiencies of the two stages of converters, so that the high-efficiency output is difficult to realize in practice. Therefore, on the occasion of medium and small power, a Boost converter is used as a basic structure, and a batch of non-isolated Boost converters are derived; a batch of isolated boost converters are derived by taking a flyback converter as a basic structure.
Active clamping, a soft switching technique, has been popularized in various forward and flyback converters to improve efficiency, but the voltage stress during the turn-off period of the switching tube is equal to the sum of the input voltage and the clamping voltage, and the disadvantage of high voltage stress exists. The asymmetric half-bridge converter can reduce the voltage stress of the switching tube, but when the asymmetric half-bridge converter is used in a boosting occasion, the number of turns of the secondary winding of the transformer is more than that of the flyback converter.
Therefore, it is desirable to provide a high-gain asymmetric half-bridge forward and flyback isolated dc converter
Disclosure of Invention
In order to solve the above problems, an object of the present invention is to provide a high-gain asymmetric half-bridge forward/reverse flyback converter, which expands the application field of the asymmetric half-bridge structure, makes the application of the asymmetric half-bridge structure wider, further improves the power efficiency, and reduces the circuit volume and weight.
In order to achieve the above object, the present invention provides the following technical solution, an asymmetric half-bridge forward-reverse converter topology, including:
the power supply comprises a first semiconductor power device Q1 and a second semiconductor power device Q2, wherein the source electrode of the first semiconductor power device Q1 is connected with the drain electrode of the second semiconductor power device Q2 to form a half-bridge type bridge arm which is bridged between an input bus and an input ground;
a primary side coil N1 unlike end of the power transformer T is connected with an input ground, and a primary side coil N1 like end is connected with a half-bridge type bridge arm through an LC series resonance circuit; a resonant capacitor Cr and a rectifier diode D2 which are connected in series are connected between the homonymous end and the synonym end of a secondary side coil N2 of the power transformer T;
the anode of the rectifier diode D2 is connected with the dotted terminal of a secondary side coil N2 of the power transformer T;
the cathode of the rectifier diode D1 is connected with the resonant capacitor C2 in series and then connected with the rectifier diode D2 in parallel, and the anode of the rectifier diode D1 is connected with the cathode of the rectifier diode D2;
the filter capacitor Co is connected in parallel with the resonant capacitor C2.
The topology structure of the asymmetric half-bridge forward-reverse converter provided by the invention is also characterized in that the first semiconductor power device Q1 and the second semiconductor power device Q2 adopt a complementary PWM driving mode.
The topological structure of the asymmetric half-bridge forward-reverse converter provided by the invention is also characterized in that the first semiconductor power device Q1 comprises a body parasitic capacitor CS1 and a body parasitic diode DS1; the second semiconductor power device Q2 includes a body parasitic capacitance CS2 and a body parasitic diode DS2 thereof.
The asymmetric half-bridge forward-flyback converter topological structure provided by the invention is also characterized in that the LC series resonance circuit comprises a resonance capacitor Cc and a resonance inductor Lr.
Advantageous effects
The asymmetric half-bridge forward-reverse flyback converter topological structure provided by the invention reduces the voltage stress when the primary side field tube is turned off, so that the voltage stress is equal to the input voltage; the voltage stress of the secondary side rectifying diode is reduced and is equal to the output voltage; ZVS switching-on of two field tubes on the primary side and ZCS switching-off of two diodes on the secondary side can be realized in the full load range, and the soft switching range and conditions are more loose; the forward and backward excitation rectification mode of the secondary side allows the transformer to carry out bidirectional excitation, the utilization rate of a magnetic core is improved, and the power capacity of the converter is expanded; and the number of turns of the secondary of the transformer is reduced, and the volume of the required transformer is reduced.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings needed to be used in the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present disclosure, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a schematic diagram of a primary active clamp structure and an asymmetric half-bridge structure in the prior art;
FIG. 2 is a schematic diagram of a conventional full-wave rectification and forward-flyback rectification structure of a secondary side of a converter in the prior art
FIG. 3 is an active clamp buck-boost converter;
fig. 4 is a schematic structural diagram of an asymmetric half-bridge forward-reverse converter according to an embodiment of the present invention;
FIG. 5 is an asymmetric half-bridge forward-reverse converter with drive control;
FIG. 6 is an asymmetric complementary drive signal;
FIG. 7 is a diagram of the main operating waveforms of the converter during a switching cycle;
FIG. 8 is a schematic diagram of the energy transfer stage;
FIG. 9 is an asymmetric half-bridge interleaved forward flyback converter;
fig. 10 is an asymmetric half-bridge interleaved series forward flyback converter.
Detailed Description
The present invention is further described in detail with reference to the drawings and examples, but it should be understood that these embodiments are not limited to the invention, and that functional, methodological, or structural equivalents thereof, which are equivalent or substituted by those of ordinary skill in the art, are within the scope of the present invention.
In the description of the embodiments of the present invention, it should be understood that the terms "central", "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. indicate orientations or positional relationships based on those shown in the drawings, and are only used for convenience in describing and simplifying the description of the present invention, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention.
Furthermore, the terms "first," "second," "third," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicit to a number of indicated technical features. Thus, a feature defined as "first," "second," etc. may explicitly or implicitly include one or more of that feature. In the description of the invention, "a plurality" means two or more unless otherwise specified.
The terms "mounted," "connected," and "coupled" are to be construed broadly and may, for example, be fixedly coupled, detachably coupled, or integrally coupled; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the creation of the present invention can be understood by those of ordinary skill in the art through specific situations.
As shown in fig. 1-10, fig. 1 illustrates a conventional form of a primary side active clamp structure and an asymmetric half bridge structure. The devices are connected by the same number according to different combinations, so that different structures are formed. Q 1 And Q 2 Is a switching tube D S1 And D S2 Respectively their body parasitic diodes, C S1 And C S2 Respectively, are resonant capacitors (including body parasitic capacitors) connected in parallel at their drain terminals. C c The active clamping structure is a clamping capacitor, and the asymmetric half-bridge structure is a blocking capacitor; l is m For exciting inductance, L r Is a resonant inductor (including transformer leakage inductance). In active clamp structures, the voltage stress at which Q1 and Q2 are turned off is the sum V of the input voltage and the clamping voltage in +V Cc . In an asymmetric half-bridge configuration, the voltage stress at which Q1 and Q2 are turned off is the input voltage V in 。
Fig. 2 shows the common full-wave rectification and forward-flyback rectification structures for the secondary side of the converter. The two diodes of the full-wave rectification structure in fig. 2 (a) are replaced by capacitors, so that the full-wave rectification structure shown in fig. 2 (b) can be obtained, and then deformation is carried out, so that the forward and backward rectification structure shown in fig. 2 (c) is formed. When N is present 2 The end with the same name of the winding is positiveDiode D 1 Working; when the different name end is positive, the diode D 2 And (6) working. Therefore, the forward and flyback rectification mode is also a full-wave rectification mode in essence. Compared with a single forward or flyback rectification mode, the mode expands the power output capacity of the converter.
The asymmetric half-bridge forward-flyback converter topological structure provided by the embodiment of the invention adopts the active clamping structure in the figure 1 as the primary side and adopts the forward-flyback rectifying structure in the figure 2 (c) as the secondary side, so that the active clamping forward-flyback converter shown in the figure 3 is formed. The primary side is changed into an asymmetric half-bridge structure, so that the asymmetric half-bridge forward-reverse-flyback converter shown in the figure 4 is changed. Due to the blocking capacitor C c The primary side of the transformer T can form a bidirectional excitation path which is Q 1 And Q 2 Creates conditions for ZVS priming; due to resonant capacitance C r In the presence of, at Q 1 During the on-period, the resonant inductor L r And C r Resonance occurs as D 2 Creating ZCS turn-off conditions; at Q 2 During the on period, is D 1 Creating ZCS off conditions.
Fig. 5 is an asymmetric half-bridge forward-reverse converter with drive control according to the present invention, wherein the drive control circuit is characterized in that: generating two complementary drive signals V gs1 And V gs2 (shown in FIG. 6) respectively for driving Q 1 And Q 2 The device comprises a main control chip, a feedback voltage module and an isolation driving circuit. The main control chip can use an asymmetric half-bridge special control chip, such as LM5025, UCC2897 and the like. And the feedback voltage module is used for sampling the output voltage and sending the output voltage to the main control chip for closed-loop control. The isolation driving circuit is used for converting the output signal of the control chip into a driving signal meeting the requirement, and simultaneously has a corresponding protection function and an isolation function. The isolation driving circuit can adopt a special driving chip, and can also adopt a pulse transformer in view of cost.
In some embodiments, the primary side adopts the asymmetric half-bridge structure shown in fig. 1, and the secondary side adopts the forward-flyback rectifying structure shown in fig. 2 (c), so as to form the asymmetric half-bridge forward-flyback converter shown in fig. 4. Q 1 And Q 2 Using complementary controlMode (Q) 1 Duty ratio of D, Q 2 The duty ratio is 1-D, and dead time is reserved in the middle for preventing the bridge arms from being directly connected. Number of primary turns N of transformer 1 Number of secondary turns N 2 Transformation ratio N = N 2 ：N 1 The provided structure includes:
the source electrode of the first semiconductor power device Q1 is connected with the drain electrode of the second semiconductor power device Q2 to form a half-bridge type bridge arm which is bridged between an input bus and an input ground;
the power transformer T is characterized in that a primary side coil N1 synonym end of the power transformer T is connected with an input ground, and a primary side coil N1 synonym end is connected with a half-bridge type bridge arm through an LC series resonance circuit; a resonant capacitor Cr and a rectifier diode D2 which are connected in series are connected between the homonymous end and the synonym end of a secondary side coil N2 of the power transformer T;
the anode of the rectifier diode D2 is connected with the dotted terminal of a secondary side coil N2 of the power transformer T;
the cathode of the rectifier diode D1 is connected with the resonant capacitor C2 in series and then is connected with the rectifier diode D2 in parallel, and the anode of the rectifier diode D1 is connected with the cathode of the rectifier diode D2;
the filter capacitor Co is connected in parallel with the resonant capacitor C2.
In some embodiments, the first semiconductor power device Q1 and the second semiconductor power device Q2 adopt a complementary PWM driving method.
In some embodiments, the first semiconductor power device Q1 includes a body parasitic capacitor CS1 and a body parasitic diode DS1; the second semiconductor power device Q2 includes a body parasitic capacitance CS2 and a body parasitic diode DS2 thereof.
In some embodiments, the LC series resonant tank includes a resonant capacitance Cc and a resonant inductance Lr.
With respect to the structure provided by the foregoing embodiment:
8.1 Steady State analysis
For ease of steady state analysis, three assumptions were made: (1) Resonant inductor L r Much smaller than the excitation inductance L m (ii) a (2) Input voltage V in Output voltage V out And a partitionDirect voltage V Cc Are all direct current; neglecting the resonant capacitance C r Taking the average voltage of the alternating current ripples; (3) Neglecting Q 1 And Q 2 The dead time of (d).
(1) DC blocking capacitor C c Upper average voltage V Cc
When the converter works stably, the volt-second product of the primary winding is balanced.
(2) Resonant capacitor C r Upper average voltage V Cr
Q 1 On, Q 2 When turned off, the diode D 2 To C r And (6) charging.
V Cr ＝V Cc *n＝V in * D x n (formula 2)
(3) DC transfer ratio M of converter
Q 2 On, Q 1 When turned off, the output voltage V o Equal to the secondary voltage V of the transformer N2 And V Cr And (4) summing.
From equation 3, M is independent of the duty cycle D, is dependent only on the transformer transformation ratio n, and is equal to the conventional full-bridge converter at the same transformation ratio. Compared with the traditional half-bridge converter, half of the secondary winding of the transformer is saved.
(4) Stress of switch
Q 1 、Q 2 The voltage stress at turn-off is equal to the input voltage V in ，D 1 、D 2 The voltage stress when the diode is turned off is equal to the output voltage V out . Output current is controlled by D 1 、D 2 Are alternately provided so that the average current stress at turn-on is I o 。
(5) Primary current i p And an excitation current i m
Average value of primary current I in a switching period p And =0. Under the influence of the load current and the transformer transformation ratio, the average value I of the exciting current can be obtained according to the charge-discharge balance of the blocking capacitor m 。
8.2 timing analysis
Fig. 7 shows the main operation waveform of the converter in one switching cycle, and the operation process of the circuit can be divided into 8 time segments. For ease of description and understanding, the primary current i is defined as p
The zero-crossing time is set as the starting time t of one working cycle 0 。
8.3 Soft switching Condition
(1)Q 1 And Q 2 Zero voltage switching condition of
To satisfy Q 1 Zero voltage on condition of (2), at Q 2 Turn off, i.e. t 5 Time of day, L m Should have an energy storage greater than C S1 、C S2 Sum of stored energy and flow in the opposite direction, i.e.
From equation (5), it can be concluded that the excitation inductance L m
Q 1 When turned off, i m Is at the positive peak, therefore Q 2 The process of realizing soft switching, the process of approximate linear charging and discharging, only needs to be carried out at the primary current i p And the zero voltage switching-on can be realized by changing from positive to negative and completing the conduction before the zero crossing.
(2)D 1 、D 2 Zero current switching condition of
D 1 ZCS stripThe part must be present [ t ] 5 -t 6 ]A time period; d 2 The ZCS condition of (A) is that [ t ] must be present 1 -t 2 ]A time period. This requires L r And C r Period of resonance T r Is less than half of Q 1 Or Q 2 The small value of the on-time of both is a necessary condition for realizing the secondary diode ZCS, as shown in equations 7 and 8.
From the above process analysis, it can be known that the asymmetric half-bridge forward-reverse converter needs to realize Q 1 And Q 2 The zero voltage switching-on needs to meet certain conditions except reasonable selection of main circuit parameters L m 、C r 、L r Also, it is determined when Q is given 1 And Q 2 The drive signal of (1). This is critical, otherwise ZVS on and ZCS off conditions will be lost.
In some embodiments, two other embodiments are provided as provided in fig. 9 and 10.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention. The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.
Claims (4)
1. An asymmetric half-bridge forward-flyback converter topology, said topology comprising:
the power supply comprises a first semiconductor power device Q1 and a second semiconductor power device Q2, wherein the source electrode of the first semiconductor power device Q1 is connected with the drain electrode of the second semiconductor power device Q2 to form a half-bridge type bridge arm which is bridged between an input bus and an input ground;
the power transformer T is characterized in that a primary side coil N1 synonym end of the power transformer T is connected with an input ground, and a primary side coil N1 synonym end is connected with a half-bridge type bridge arm through an LC series resonance circuit; a resonant capacitor Cr and a rectifier diode D2 which are connected in series are connected between the homonymous end and the synonym end of a secondary side coil N2 of the power transformer T;
the anode of the rectifier diode D2 is connected with the dotted terminal of a secondary side coil N2 of the power transformer T;
the cathode of the rectifier diode D1 is connected with the resonant capacitor C2 in series and then connected with the rectifier diode D2 in parallel, and the anode of the rectifier diode D1 is connected with the cathode of the rectifier diode D2;
the filter capacitor Co is connected in parallel with the resonant capacitor C2.
2. The topology of claim 1, wherein the first and second semiconductor power devices Q1 and Q2 are driven by complementary PWM.
3. The asymmetric half-bridge forward-flyback converter topology of claim 1, wherein the first semiconductor power device Q1 comprises its body parasitic capacitance CS1 and body parasitic diode DS1; the second semiconductor power device Q2 includes a body parasitic capacitance CS2 and a body parasitic diode DS2 thereof.
4. The asymmetric half-bridge forward-flyback converter topology of claim 1, wherein the LC series resonant tank comprises a resonant capacitor Cc and a resonant inductor Lr.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116455236A (en) * | 2023-06-16 | 2023-07-18 | 广东优力普物联科技有限公司 | High-efficiency isolation circuit |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116455236A (en) * | 2023-06-16 | 2023-07-18 | 广东优力普物联科技有限公司 | High-efficiency isolation circuit |
| CN116455236B (en) * | 2023-06-16 | 2023-08-22 | 广东优力普物联科技有限公司 | High-efficiency isolation circuit |
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