CN106655792B - Asymmetric half-bridge flyback circuit - Google Patents

Asymmetric half-bridge flyback circuit Download PDF

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CN106655792B
CN106655792B CN201611117023.6A CN201611117023A CN106655792B CN 106655792 B CN106655792 B CN 106655792B CN 201611117023 A CN201611117023 A CN 201611117023A CN 106655792 B CN106655792 B CN 106655792B
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capacitor
switching tube
primary winding
tube
switching
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CN106655792A (en
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郑凌霄
宋建峰
冯刚
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Mornsun Guangzhou Science and Technology Ltd
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Mornsun Guangzhou Science and Technology Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/338—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 in a self-oscillating arrangement
    • H02M3/3381—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 in a self-oscillating arrangement using a single commutation path
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0048—Circuits or arrangements for reducing losses
    • H02M1/0054—Transistor switching losses
    • H02M1/0058—Transistor switching losses by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

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

Abstract

The invention discloses an asymmetric half-bridge flyback circuit which comprises two or more independent resonant circuits. When the main switching tube is switched on and the clamping switching tube is switched off, inductors and capacitors in all the resonant circuits are connected in series and resonate together to store energy for exciting the inductors and provide conditions for realizing ZVS for the clamping switching tube; when the main switching tube is cut off and the clamping switching tube is switched on, each resonant circuit independently resonates to release energy for the secondary side and provide conditions for the main switching tube to realize ZVS. Compared with the prior art, the soft switching power supply has a soft switching function and improves the efficiency of products in the application of the switching power supply with wide range and high input voltage; and the voltage stress of the primary side switching tube is low when the primary side switching tube is cut off, and a special high-voltage-resistant switching tube is not required to be selected, so that the cost is reduced.

Description

Asymmetric half-bridge flyback circuit
Technical Field
The invention relates to the field of switch converters, in particular to an asymmetric half-bridge flyback switch converter.
Background
The field of power electronics is rapidly developed, so that the application of a high-frequency switching power supply is more and more extensive. The input end of the traditional industrial and civil switching power supply needs to be powered from a power grid, and the power is converted into high direct current after passing through a rectifying and filtering circuit in the power supply, and then is input into a power conversion circuit to be converted into low-voltage direct current so as to provide electric energy for a load. In order to adapt to the power grid standards of different countries, a general two-phase alternating current input switching power supply has an input voltage range of 85VAC to 264VAC, and a rectified and filtered direct current voltage of about 120VDC to 373VDC. The switching power supply used in the occasion has more circuit topologies selected according to different powers, such as a flyback circuit and a forward circuit which have the characteristics of simple structure, low cost and the like; the structure is complex, but LLC with soft switch function, asymmetric half bridge, phase shift full bridge circuit, etc.
With the rapid development of new energy industries, the electric automobile, wind power generation, photovoltaic and other industries have more and more demands on the switching power supply with ultra-high and ultra-wide input voltage ranges, and the requirements are more and more stringent. The power supply used by a charging pile in the electric automobile industry requires an input voltage range of 200 VDC-800 VDC, and some requirements reach an upper limit of 1000 VDC; the power supply products used by photovoltaic combiner boxes, inverters and the like in the wind power generation and photovoltaic industries require an input voltage range of 150 VDC-1500 VDC. The application of such wide range and high input voltage improves the design difficulty of the switching power supply, including the voltage stress treatment of the switching tube; the increase of the input voltage leads to the increase of the on-off loss of the switching tube, and the heat treatment is caused; transformer process design, etc.
At present, a switching power supply with a wide range and high input voltage in the industry is realized by adopting a common flyback or forward circuit, and a practical application circuit thereof is that a primary side power winding of a transformer is divided into two or more than two windings, the two windings are respectively connected with a switching tube and then are connected in series to achieve the purpose of high voltage resistance (the circuit is shown in figures 1 and 2, the scheme is the prior known technology, and the detailed description is not provided here). However, both topologies are hard switching and cannot recover leakage inductance energy, thus limiting the efficiency and volume of low power products. Furthermore, it is difficult to apply it to a wide-range, high-input-voltage switching power supply of medium and high power. The switching tube is subjected to high voltage stress due to voltage spike stress caused by leakage inductance and high input voltage; in addition, hard switching has large switching loss and serious heating of the tube, so that a switching tube with higher voltage resistance and larger volume must be selected, and the cost is increased sharply. And the conduction impedance and the junction capacitance of the high-voltage-resistant switching tube are relatively large, so that the efficiency of the product is further deteriorated. Particularly, in recent years, the demand for a higher-power high-input-voltage switching power supply is gradually increased, and the disadvantages of the circuit topology in the application are particularly obvious. The problems of temperature rise and large volume caused by low power efficiency and high cost caused by using a high-voltage-resistant switching tube seriously restrict the development of a high-voltage power supply.
The demand in the power electronics industry for high power density, high reliability and small size switching power supplies has led to the development of soft switching technology. Soft switching technology is still one of the technological hotspots in the field of power electronics. The principle of inductance and capacitance resonance is utilized to enable a switching tube of a switching power supply to realize zero-voltage switching-on or zero-current switching-off, so that the switching loss of the switching tube is reduced, and the product efficiency is remarkably improved. However, since the duty ratio of circuits with soft switching functions, such as LLC and asymmetric half-bridge, is required to be less than 0.5, and the stress of the switching tube is equal to the input voltage, it is difficult to apply the circuits to switching power supplies with wide range and high input voltage, and a primary pre-regulation link is generally connected at the front stage. Although the duty ratio of the conventional asymmetric half-bridge flyback circuit can be more than 0.5, the stress of a switching tube of the conventional asymmetric half-bridge flyback circuit is equal to the input voltage, so the conventional asymmetric half-bridge flyback circuit is not suitable for occasions with high input voltage. The above is well known technology and will not be described in detail here.
Disclosure of Invention
In view of the above, the present invention provides an asymmetric half-bridge flyback circuit for solving the above problems, which is applied to a switching power supply with a wide range and a high input voltage, and has a soft switching function, so as to improve the efficiency of the product; and the voltage stress of the primary side switching tube is low when the primary side switching tube is turned off, and a special high-voltage-resistant switching tube is not required to be selected, so that the cost is reduced.
The invention aims to realize the purpose, and the asymmetric half-bridge flyback circuit comprises an input positive end, an input negative end, a transformer, a primary circuit connected with a primary winding of the transformer and a secondary circuit connected with a secondary winding of the transformer, wherein the primary circuit comprises a first capacitor and a second capacitor, one end of the first capacitor is connected with the input positive end, the other end of the first capacitor is connected with one end of the second capacitor, and the other end of the second capacitor is connected with the input negative end;
the transformer is provided with a first primary winding, a second primary winding and a first secondary winding, wherein the first primary winding and the second primary winding are connected in series;
the primary side circuit further includes:
the four switching tubes are a first switching tube, a second switching tube, a third switching tube and a fourth switching tube, drain-source electrodes of the four switching tubes are sequentially connected in series between an input positive end and an input negative end, the first switching tube and the third switching tube are main switching tubes, and driving signals are synchronous; the second switching tube and the fourth switching tube are clamping switching tubes, and driving signals are synchronous; the main switching tube and the clamping switching tube are complementary in driving signal, and a dead time is formed between the two driving signals;
the two inductors, namely the first inductor and the second inductor, are leakage inductances of a primary winding of the transformer;
two capacitors, namely a third capacitor and a fourth capacitor;
the homonymous end of a first primary winding of the transformer is connected with the drain electrode of the second switching tube through a first inductor, and the synonym end of the first primary winding is respectively connected with the source electrode of the second switching tube and the other end of the first capacitor through a third capacitor; the homonymous end of the second primary winding is connected with the drain electrode of the fourth switching tube through a second inductor, and the heteronymous end of the second primary winding is respectively connected with the source electrode of the fourth switching tube and the other end of the second capacitor through a fourth capacitor;
when the main switching tube is switched on and the clamping switching tube is switched off, an input voltage is applied to a series loop formed by a first inductor, a first primary winding, a third capacitor, a second inductor, a second primary winding and a fourth capacitor in sequence to generate resonance; in the first dead time when the main switching tube and the clamping switching tube are both cut off, the junction capacitors of the four switching tubes generate resonance through a series loop, and the energy of the junction capacitors of the clamping switching tubes is extracted to realize zero-voltage switching-on of the clamping switching tubes;
when the main switching tube is turned off and the clamping switching tube is turned on, the first inductor, the first primary winding, the third capacitor and the second switching tube form a first resonant circuit; the second inductor, the second primary winding, the fourth capacitor and the fourth switching tube form a second resonant circuit; in the second dead time when the main switching tube and the clamping switching tube are both cut off, the junction capacitors of the four switching tubes generate resonance through the series loop, and the energy of the junction capacitors of the main switching tubes is extracted to realize the zero-voltage switching-on of the main switching tubes. Preferably, the primary side circuit further comprises a first resistor, and the first resistor is connected in series between the other end of the first capacitor and the third capacitor.
Preferably, the transformer is also provided with a third primary winding which is connected with the second primary winding in series; the primary side circuit further comprises a sixth capacitor, a fifth switching tube, a sixth switching tube, a third inductor and a seventh capacitor, one end of the sixth capacitor is connected with the other end of the second capacitor, and the other end of the sixth capacitor is connected with the input negative end; a fifth switching tube and a sixth switching tube are sequentially connected in series with the four switching tubes between the input positive end and the input negative end, wherein the fifth switching tube is a main switching tube, and the sixth switching tube is a clamping switching tube; the dotted end of the third primary winding of the transformer is connected with the drain electrode of the sixth switching tube through a third inductor, and the different-dotted end of the third primary winding is respectively connected with the source electrode of the sixth switching tube and the other end of the sixth capacitor through a seventh capacitor; when the main switching tube is switched on and the clamping switching tube is switched off, an input voltage is applied to a series circuit formed by a first inductor, a first primary winding, a third capacitor, a second primary winding, a fourth capacitor, a third primary winding and a seventh capacitor in sequence to generate resonance; in the first dead time when the main switching tube and the clamping switching tube are both cut off, the junction capacitors of the six switching tubes generate resonance through the series loop, and the energy of the junction capacitors of the clamping switching tubes is extracted to realize zero-voltage switching-on of the clamping switching tubes; when the main switching tube is turned off and the clamping switching tube is turned on, the first primary winding, the third capacitor and the second switching tube form a first resonant circuit; the second primary winding, the fourth capacitor and the fourth switching tube form a second resonant circuit; a third primary winding, a seventh capacitor and a sixth switching tube form a third resonant circuit; in the second dead time when the main switching tube and the clamping switching tube are both cut off, the junction capacitors of the six switching tubes generate resonance through the series loop, and the energy of the junction capacitors of the main switching tubes is extracted to realize zero-voltage switching-on of the main switching tubes. Preferably, the primary circuit further includes a first resistor and a second resistor, the first resistor is connected in series between the other end of the first capacitor and the third capacitor; the second resistor is connected between the other end of the second capacitor and the fourth capacitor in series.
Preferably, the secondary side circuit of the asymmetric half-bridge flyback circuit comprises a first diode and a fifth capacitor, wherein the anode of the first diode is connected with the different name end of a first secondary winding of the transformer, and the cathode of the first diode is connected with one end of the fifth capacitor and is led out to serve as the output anode; the other end of the fifth capacitor is connected with the dotted end of the first secondary winding, and is led out to serve as an output cathode.
The invention also provides an asymmetric half-bridge flyback circuit which comprises a flyback transformer, a first diode, a first inductor, a second inductor, a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a first switching tube, a second switching tube, a third switching tube and a fourth switching tube, wherein the transformer comprises a first primary winding, a second primary winding and a first secondary winding. The connection relationship is as follows: the first capacitor and the second capacitor are connected in series, one end of each of two serially connected terminals is connected with the positive electrode of the input voltage and is simultaneously connected with the drain electrode of the first switch tube, and the other end of each of the two serially connected terminals is connected with the negative electrode of the input voltage and is simultaneously connected with the source electrode of the fourth switch tube; the source electrode of the first switch tube is connected with the drain electrode of the second switch tube; the source electrode of the first switch tube is also connected to one end of the first inductor; the other end of the first inductor is connected with the dotted end of the first primary winding of the transformer; the synonym of the first primary winding of the transformer is connected with one end of the third capacitor; the other end of the third capacitor is connected with the source electrode of the second switch tube, and is also connected with a middle node after the first capacitor and the second capacitor are connected in series, and is also connected with the drain electrode of the third switch tube; the source electrode of the third switching tube is connected with the drain electrode of the fourth switching tube; the source electrode of the third switching tube is also connected to one end of the second inductor; the other end of the second inductor is connected with the dotted terminal of a second primary winding of the transformer; the synonym of the second primary winding of the transformer is connected with one end of the fourth capacitor; the other end of the fourth capacitor is connected with the source electrode of the fourth switching tube; the other end of the fourth capacitor is also connected with the input negative end; the synonym end of the first secondary winding of the transformer is connected with the anode of the first diode; the cathode of the first diode is connected with one end of the fifth capacitor and is used as an output anode; the other end of the fifth capacitor is connected with the end with the same name of the first secondary winding of the transformer and is used as an output cathode.
The first switching tube and the third switching tube are main switching tubes, and driving signals are synchronous; the second switch tube and the fourth switch tube are clamping switch tubes, and driving signals are synchronous; the main switch tube and the clamping switch tube are complementary in driving signal, and a dead time exists between the two driving signals.
As the equivalent technical scheme of the original technical scheme, an asymmetric half-bridge flyback circuit is characterized in that: the flyback transformer comprises a flyback transformer, a first diode, a first inductor, a second inductor, a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a first switching tube, a second switching tube, a third switching tube and a fourth switching tube, and the flyback transformer comprises a first primary winding, a second primary winding and a first secondary winding. The connection relationship is as follows: the first capacitor and the second capacitor are connected in series, one end of two terminals after being connected in series is connected with the anode of the input voltage and is simultaneously connected with the drain electrode of the second switching tube, the other end of the two terminals after being connected in series is connected with the cathode of the input voltage and is simultaneously connected with the source electrode of the third switching tube; the drain electrode of the second switch is also connected with one end of the first inductor; the other end of the first inductor is connected with the dotted terminal of the first primary winding of the transformer; the synonym of the first primary winding of the transformer is connected with one end of the third capacitor; the other end of the third capacitor is connected with the source electrode of the second switch tube and is also connected with the drain electrode of the first switch tube; the source electrode of the first switch tube is connected with the drain electrode of the fourth switch tube and is also connected with a middle node after the first capacitor and the second capacitor are connected in series; the drain electrode of the fourth switching tube is also connected to one end of the second inductor; the other end of the second inductor is connected with the dotted terminal of a second primary winding of the transformer; the synonym of the second primary winding of the transformer is connected with one end of the fourth capacitor; the other end of the fourth capacitor is connected with the source electrode of the fourth switching tube and is also connected with the drain electrode of the third switching tube; the synonym end of the first secondary winding of the transformer is connected with the anode of the first diode; the cathode of the first diode is connected with one end of the fifth capacitor and is used as an output anode; the other end of the fifth capacitor is connected with the end with the same name of the first secondary winding of the transformer and is used as an output cathode.
The first switching tube and the third switching tube are main switching tubes, and driving signals are synchronous; the second switch tube and the fourth switch tube are clamping switch tubes, and driving signals are synchronous; the main switch tube and the clamping switch tube are complementary in driving signal, and a dead time exists between the two driving signals.
Preferably, the switch tube is an N-MOS tube.
Preferably, the first inductor may be a leakage inductance of the first primary winding of the transformer.
Preferably, the second inductor may be a leakage inductance of the second primary winding of the transformer.
Preferably, the first inductor and the second inductor may be independent inductor elements.
Preferably, a resistor is connected between the intermediate node of the first capacitor and the second capacitor after being connected in series and the source electrode of the first switch tube.
As an improvement of the original technical scheme, on the basis of the improvement, a third primary winding is added to the transformer, and meanwhile, a sixth capacitor, a seventh capacitor, a fifth switch tube, a sixth switch tube and a third inductor are also added to the circuit; the improved circuit connection relationship is as follows: the sixth capacitor is connected in series with the first capacitor and the second capacitor, one end of the two serially connected terminals is connected with the positive electrode of the input voltage and is simultaneously connected with the drain electrode of the first switching tube, and the other end of the two serially connected terminals is connected with the negative electrode of the input voltage and is simultaneously connected with the source electrode of the sixth switching tube; the source electrode of the first switch tube is connected with the drain electrode of the second switch tube; the source electrode of the first switch tube is also connected to one end of the first inductor; the other end of the first inductor is connected with the dotted end of the first primary winding of the transformer; the synonym of the first primary winding of the transformer is connected with one end of the third capacitor; the other end of the third capacitor is connected with the source electrode of the second switch tube, and is also connected with a middle node after the first capacitor and the second capacitor are connected in series, and is also connected with the drain electrode of the third switch tube; the source electrode of the third switching tube is connected with the drain electrode of the fourth switching tube; the source electrode of the third switching tube is also connected to one end of the second inductor; the other end of the second inductor is connected with the dotted terminal of a second primary winding of the transformer; the synonym of the second primary winding of the transformer is connected with one end of the fourth capacitor; the other end of the fourth capacitor is connected with the source electrode of the fourth switching tube, is also connected with a middle node formed by connecting the second capacitor and the sixth capacitor in series, and is also connected with the drain electrode of the fifth switching tube; the source electrode of the fifth switching tube is connected with the drain electrode of the sixth switching tube; the source electrode of the fifth switch tube is also connected to one end of the third inductor; the other end of the third inductor is connected with the dotted terminal of a third primary winding of the transformer; the synonym end of the third primary winding of the transformer is connected with one end of the seventh capacitor; the other end of the seventh capacitor is connected with the source electrode of the sixth switching tube; the synonym end of the first secondary winding of the transformer is connected with the anode of the first diode; the cathode of the first diode is connected with one end of the fifth capacitor and is used as an output anode; the other end of the fifth capacitor is connected with the end with the same name of the first secondary winding of the transformer and is used as an output cathode;
the first switch tube, the third switch tube and the fifth switch tube are main switch tubes, and driving signals are synchronous; the second switch tube, the fourth switch tube and the sixth switch tube are clamping switch tubes, and driving signals are synchronous; the main switching tube and the clamping switching tube are complementary in driving signal, and a dead time exists between the two driving signals.
As an improvement of the equivalent technical scheme, on the basis of the improvement, a third primary winding is added to the transformer, and meanwhile, a sixth capacitor, a seventh capacitor, a fifth switching tube, a sixth switching tube and a third inductor are also added to the circuit; the improved circuit connection relationship is as follows: the sixth capacitor is connected in series with the first capacitor and the second capacitor, one end of the two serially connected terminals is connected with the positive electrode of the input voltage and is simultaneously connected with the drain electrode of the second switching tube, and the other end of the two serially connected terminals is connected with the negative electrode of the input voltage and is simultaneously connected with the source electrode of the fifth switching tube; the drain electrode of the second switch is also connected with one end of the first inductor; the other end of the first inductor is connected with the dotted end of the first primary winding of the transformer; the synonym of the first primary winding of the transformer is connected with one end of the third capacitor; the other end of the third capacitor is connected with the source electrode of the second switch tube and is also connected with the drain electrode of the first switch tube; the source electrode of the first switch tube is connected with the drain electrode of the fourth switch tube and is also connected with a middle node after the first capacitor and the second capacitor are connected in series; the drain electrode of the fourth switch tube is also connected to one end of the second inductor; the other end of the second inductor is connected with the dotted terminal of a second primary winding of the transformer; the synonym of a second primary winding of the transformer is connected with one end of the fourth capacitor; the other end of the fourth capacitor is connected with the source electrode of the fourth switching tube and is also connected with the drain electrode of the third switching tube; the source electrode of the third switching tube is connected with the drain electrode of the sixth switching tube and is also connected with the middle node after the second capacitor and the sixth capacitor are connected in series; the drain electrode of the sixth switching tube is also connected to one end of the third inductor; the other end of the third inductor is connected with the dotted terminal of a third primary winding of the transformer; the synonym end of a third primary winding of the transformer is connected with one end of the seventh capacitor; the other end of the seventh capacitor is connected with the source electrode of the sixth switching tube and is also connected with the drain electrode of the fifth switching tube; the synonym end of the first secondary winding of the transformer is connected with the anode of the first diode; the cathode of the first diode is connected with one end of the fifth capacitor and is used as an output anode; the other end of the fifth capacitor is connected with the end with the same name of the first secondary winding of the transformer and is used as an output cathode;
the first switch tube, the third switch tube and the fifth switch tube are main switch tubes, and driving signals are synchronous; the second switch tube, the fourth switch tube and the sixth switch tube are clamping switch tubes, and driving signals are synchronous; the main switching tube and the clamping switching tube are complementary in driving signal, and a dead time exists between the two driving signals.
Preferably, the switch tube is an N-MOS tube.
Preferably, the first inductor may be a leakage inductance of the first primary winding of the transformer.
Preferably, the second inductor may be a leakage inductance of the second primary winding of the transformer.
Preferably, the third inductor may be a leakage inductance of a third primary winding of the transformer.
Preferably, the first inductor, the second inductor and the third inductor may be independent inductor elements.
Preferably, a resistor is connected between a source electrode of the first switching tube and a middle node of the first capacitor and the second capacitor after the first capacitor and the second capacitor are connected in series.
Preferably, a resistor is connected between the intermediate node of the second capacitor and the sixth capacitor after being connected in series and the source of the third switching tube.
The working principle of the original technical solution of the present invention will be explained in detail in the embodiments, and here briefly described,
and in a steady state, the first switching tube and the third switching tube are simultaneously switched on. An input voltage is applied to a series loop of the first inductor, the first primary winding, the third capacitor, the second inductor, the second primary winding and the fourth capacitor, and resonance occurs. Because the first primary winding and the second primary winding have larger inductance and the resonant frequency is lower than the switching frequency, the exciting current is increased approximately linearly, and the first primary winding and the second primary winding store energy. At the moment, the voltage at the two ends of the second switching tube and the fourth switching tube is half of the input voltage.
When the first switching tube and the third switching tube are cut off, the second switching tube and the fourth switching tube are not opened, and the dead time is the time of the dead time. In the dead time, the first inductor, the second inductor, the first primary winding and the second primary winding need to follow current, the junction capacitors of the first switching tube, the third switching tube, the second switching tube and the fourth switching tube, the first inductor, the first primary winding, the third capacitor, the second inductor, the second primary winding and the fourth capacitor resonate to extract energy of the junction capacitor of the second switching tube and the fourth switching tube, and voltage at two ends of the second switching tube and the fourth switching tube drops. And simultaneously charging the junction capacitors of the first switching tube and the third switching tube, and increasing the voltage at two ends of the first switching tube and the third switching tube. When the junction capacitance voltage of the first switching tube and the third switching tube reaches the highest voltage and the junction capacitance voltage of the second switching tube and the fourth switching tube is pumped to zero, driving signals are applied to the grid electrodes of the second switching tube and the fourth switching tube, so that zero-voltage switching-on of the clamping switching tube is realized, and the zero-voltage switching-on is abbreviated as ZVS. At the moment, the first diode is positively conducted, the first primary winding and the second primary winding of the transformer are clamped by the reflected voltage, energy is released to the first secondary winding, the exciting current is linearly reduced, and the negative direction is linearly increased after the exciting current reaches zero. Meanwhile, the first inductor and the third capacitor resonate, and the current in the first primary winding changes according to the track of a sine wave; the second inductor and the fourth capacitor are in resonance; the current in the second primary winding changes according to the track of a sine wave. At this time, the voltage across the first switching tube and the third switching tube is one half of the input voltage.
When the second switching tube and the fourth switching tube are cut off, the first switching tube and the third switching tube are not opened, and the dead time is the time of the dead time. In the dead time, as the first inductor and the second inductor need to flow current, the junction capacitors of the first switch tube, the third switch tube, the second switch tube and the fourth switch tube, the first inductor, the third capacitor, the second inductor and the fourth capacitor resonate to extract the energy of the junction capacitors of the first switch tube and the third switch tube, and the voltage at two ends of the first switch tube and the third switch tube is reduced. And meanwhile, the junction capacitor of the second switching tube and the fourth switching tube is charged, and the voltage at the two ends of the second switching tube and the voltage at the two ends of the fourth switching tube are increased. When the junction capacitance voltage of the second switching tube and the fourth switching tube reaches the highest voltage and the junction capacitance voltage of the first switching tube and the third switching tube is pumped to zero, driving signals are applied to the grids of the first switching tube and the third switching tube, and therefore ZVS of the main switching tube is achieved. This completes a cycle and then continues to repeat following the same process.
According to the working principle, in the stages of opening of the main switching tube and closing of the clamping switching tube, the first inductor, the first primary winding, the third capacitor, the second inductor, the second primary winding and the fourth capacitor form a series resonant circuit to generate resonance, so that the ZVS of the clamping switching tube is provided for realizing the energy storage of the primary winding of the transformer at the same time. And in the stage that the main switching tube is cut off and the clamping switching tube is switched on, the first inductor and the third capacitor form an independent resonant circuit, and the second inductor and the fourth capacitor form another independent resonant circuit, namely the two independent resonant circuits are connected in parallel to release energy for a load, and conditions are provided for realizing the ZVS of the main switching tube in each resonant circuit.
Compared with the prior art, the invention has the following beneficial effects:
1. ZVS can be realized to all switch tubes, improves complete machine efficiency.
2. In the working process, the voltage of the switch tube when the switch tube is cut off is half of the input voltage, the leakage inductance of the transformer participates in resonance, the switch tube has no peak voltage stress, the common switch tube is convenient to use, and the cost is reduced.
Drawings
Fig. 1 is a diagram of a flyback circuit employed in a conventional wide-range, high-input-voltage switching power supply;
FIG. 2 is a diagram of a forward circuit employed by a prior art wide range, high input voltage switching power supply;
fig. 3-1 is a schematic diagram of an asymmetric half-bridge flyback circuit according to a first embodiment of the present invention;
fig. 3-2 is a schematic diagram of an asymmetric half-bridge flyback circuit according to the first embodiment of the present invention, in which a resonant tank is marked, and a dotted line indicates the resonant tank when the main switching transistors Q1 and Q3 are turned on and the clamping switching transistors Q2 and Q4 are turned off; the solid line shows that when the clamping switch tubes Q2 and Q4 are switched on and the main switch tubes Q1 and Q3 are switched off, two independent resonant circuits are formed;
fig. 4 is a waveform diagram illustrating the operation of the asymmetric half-bridge flyback circuit according to the first embodiment of the present invention;
fig. 5 is a schematic diagram of an asymmetric half-bridge flyback circuit according to a second embodiment of the present invention;
fig. 6 is a schematic diagram of an asymmetric half-bridge flyback circuit according to a third embodiment of the present invention;
fig. 7 is a schematic diagram of an asymmetric half-bridge flyback circuit according to a fourth embodiment of the present invention;
fig. 8 is a schematic diagram of an asymmetric half-bridge flyback circuit according to a fifth embodiment of the present invention.
Detailed Description
First embodiment
Fig. 3-1 shows a circuit diagram of an asymmetric half-bridge flyback circuit according to a first embodiment of the present invention, which includes a capacitor C1, a capacitor C2, a capacitor C3, a capacitor C4, a capacitor C5, an N-MOS transistor Q1, an N-MOS transistor Q2, an N-MOS transistor Q3, an N-MOS transistor Q4, and an output rectifier diode D1. The flyback transformer T1 includes: the inductor comprises a first primary winding Lp1, a second primary winding Lp2 and a first secondary winding Ls1, wherein a first inductor is a leakage inductor Lk1 of the Lp1, and a second inductor is a leakage inductor Lk2 of the Lp 2. In practical applications, the inductors Lp1 and Lp2 may also be external independent inductor elements. The specific connection relationship is as follows: the capacitor C1 and the capacitor C2 are connected in series, and one end of each of two serially connected terminals is connected with the positive electrode of the input voltage and is also connected with the drain electrode of the N-MOS tube Q1; after the capacitor C1 and the capacitor C2 are connected in series, the other end of the two terminals is connected with the negative electrode of the input voltage and is connected with the source electrode of the N-MOS transistor Q4; the source electrode of the N-MOS tube Q1 is connected with the drain electrode of the N-MOS tube Q2 and is also connected with one end of an inductor Lk 1; the other end of the inductor Lk1 is connected with the dotted end of the primary winding Lp 1; the synonym of the primary winding Lp1 is connected with one end of a capacitor C3; the other end of the capacitor C3 is connected with the source electrode of the N-MOS transistor Q2, and is also connected with the middle node after the capacitor C1 and the capacitor C2 are connected in series, and is also connected with the drain electrode of the N-MOS transistor Q3; the source electrode of the N-MOS tube Q3 is connected with the drain electrode of the N-MOS tube Q4; the source electrode of the N-MOS tube Q3 is also connected to one end of the inductor Lk 2; the other end of the inductor Lk2 is connected with the dotted end of the primary winding Lp 2; the synonym of the primary winding Lp2 is connected with one end of a capacitor C4; the other end of the capacitor C4 is connected with the source electrode of the N-MOS tube Q4; the synonym end of the secondary winding Ls1 is connected with the anode of a diode D1; the cathode of the diode D1 is connected with one end of the capacitor C5 and is used as the output anode; the other end of the capacitor C5 is connected with the end with the same name of the secondary winding Ls1 and is used as the negative output electrode.
The working principle of the embodiment is as follows:
the waveform in steady-state operation is shown in fig. 4, where N-MOS transistor Q1 and N-MOS transistor Q3 are main switching transistors, and N-MOS transistor Q2 and N-MOS transistor Q4 are clamp switching transistors. Vgs1, vgs2, vgs3 and Vgs4 are driving signal waveforms of an N-MOS transistor Q1, an N-MOS transistor Q2, an N-MOS transistor Q3 and an N-MOS transistor Q4 respectively; vds1, vds2, vds3 and Vds4 are drain and source voltage waveforms of an N-MOS tube Q1, an N-MOS tube Q2, an N-MOS tube Q3 and an N-MOS tube Q4 respectively; ir1 is a resonant current waveform flowing through the inductor Lk 1; ir2 is a resonant current waveform flowing through the inductor Lk 2; im1 is an excitation current waveform flowing through the primary winding Lp 1; im2 is the waveform of the excitation current flowing through the primary winding Lp 2; id1 is a waveform of a current flowing through the secondary winding Ls 1. And if the duty ratio of a driving signal of the main switching tube is D, the duty ratio of the clamping switching tube is (1-D), a certain dead time needs to be reserved for avoiding the common use of the main tube and the clamping tube, and the working period is T.
In the period from t0 to t1, the driving signal Vgs1 and the driving signal Vgs3 are at a high level, the driving signal Vgs2 and the driving signal Vgs4 are at a low level, the main switching tube is switched on, and the clamping switching tube is switched off. The input voltage is applied to a series loop consisting of an inductor Lk1, a primary winding Lp1, a capacitor C3, an inductor Lk2, a primary winding Lp2 and a capacitor C4, and resonance occurs. As shown by the dotted line in fig. 3-2, the resonant circuit is the resonant circuit when the main switching tubes Q1 and Q3 are turned on and the clamping switching tubes Q2 and Q4 are turned off. Because the inductance of the primary winding Lp1 and the inductance of the primary winding Lp2 are large, and the resonant frequency is lower than the switching frequency, the exciting current Im is increased approximately linearly, and the primary winding Lp1 and the primary winding Lp2 store energy. The exciting current Im1 is equal to the resonance current Ir1, the exciting current Im2 is equal to the resonance current Ir2, and the output rectifier diode D1 is turned off. At the moment, the voltages at the two ends of the N-MOS transistor Q2 and the N-MOS transistor Q4 are respectively half of the input voltage.
At time t1, the drive signal Vgs1 and the drive signal Vgs3 become low level, while the drive signal Vgs2 and the drive signal Vgs4 remain low level, and the main switching tube and the clamp switching tube are both turned off. In the dead time of the stage t 1-t 2, because the inductive current can not change suddenly, the inductor Lk1, the primary winding Lp1, the inductor Lk2 and the primary winding Lp2 need follow current, so the junction capacitors of the leakage and source electrodes of the main switching tube and the clamping switching tube, the inductor Lk1, the primary winding Lp1, the capacitor C3, the inductor Lk2, the primary winding Lp2 and the capacitor C4 resonate, the energy of the leakage and source electrode junction capacitors of the N-MOS tube Q2 and the N-MOS tube Q4 is extracted, and the voltage at two ends of the N-MOS tube Q2 and the N-MOS tube Q4 is reduced. And meanwhile, the junction capacitors of the drain and source electrodes of the N-MOS transistor Q1 and the N-MOS transistor Q3 are charged, and the voltages at the two ends of the N-MOS transistor Q1 and the N-MOS transistor Q3 rise. When the drain and source junction capacitance voltages of the N-MOS transistor Q1 and the N-MOS transistor Q3 reach the highest value and the drain and source junction capacitance voltages of the N-MOS transistor Q2 and the N-MOS transistor Q4 are pumped to zero, the driving signal Vgs2 and the driving signal Vgs4 become high level at the time t 2. Therefore, the drain and source voltages of the N-MOS transistor Q2 and the N-MOS transistor Q4 are reduced to zero before the driving signal becomes high level, so the ZVS of the clamping switch tubes such as the N-MOS transistor Q2 and the N-MOS transistor Q4 can be realized only by the design of the parameters of the resonant circuit without adding other circuits. In this stage, the exciting current Im1 is equal to the resonance current Ir1, the exciting current Im2 is equal to the resonance current Ir2, and the output rectifier diode D1 is turned off. The excitation currents Im1 and Im2 have very small amplitudes although increasing because the voltages across the primary winding Lp1 and the primary winding Lp2 decrease.
At the time t2, the clamping switch tube is conducted, the inductor Lk1, the primary winding Lp1, the capacitor C3 and the N-MOS tube Q2 form an independent resonant circuit, and the voltage Vc at two ends of the capacitor C3 is directly applied to the inductor Lk1 and the primary winding Lp 1; the inductor Lk2, the primary winding Lp2, the capacitor C4 and the N-MOS transistor Q4 form another independent resonant circuit, and the voltage Vc across the capacitor C4 is directly applied to the inductor Lk2 and the primary winding Lp 2. As shown by the solid line in fig. 3-2, namely, when the clamp switching tubes Q2 and Q4 are turned on and the main switching tubes Q1 and Q3 are turned off, two independent resonant circuits are formed. The secondary side diode is forward conducting. At the stage from t2 to t3, the primary winding Lp1 and the primary winding Lp2 are clamped and demagnetized by the output reflected voltage, energy is released to the secondary side, the exciting current Im1 and the exciting current Im2 linearly decrease, and the negative direction linearly increases after the exciting current Im1 and the exciting current Im2 reach zero. Meanwhile, the inductor Lk1 resonates with the capacitor C3, and the resonant current Ir1 changes according to a sine wave trajectory; the inductor Lk2 resonates with the capacitor C4, and the resonant current Ir2 changes along a sine wave trajectory. The difference between the excitation current Im1 and the resonance current Ir1 multiplied by the turn ratio N1 of the primary winding Lp1 to the secondary winding Ls1, and the difference between the excitation current Im2 and the resonance current Ir2 multiplied by the turn ratio N2 of the primary winding Lp2 to the secondary winding Ls1 are equal to the current flowing through the secondary winding Ls1, that is, the current flowing through the secondary winding Ls1 is
N 1 (I m1 -I r1 )+N 2 (I m2 -I r2 )＝I d1
In the period from t2 to t3, the voltage at the two ends of the N-MOS tube Q1 and the N-MOS tube Q3 is half of the input voltage.
At time t3, the drive signal Vgs2 and the drive signal Vgs4 become low level, while the drive signal Vgs1 and the drive signal Vgs3 remain low level, and the main switching tube and the clamp switching tube are both turned off. In the dead time of the stage t 3-t 4, because the inductive current can not change suddenly, the inductor Lk1 and the inductor Lk2 need follow current, so the junction capacitors of the main switch tube and the clamping switch tube, the inductor Lk1, the capacitor C3, the inductor Lk2 and the capacitor C4 resonate, the energy of the junction capacitors of the N-MOS tube Q1 and the N-MOS tube Q3 is extracted, and the voltage at two ends of the N-MOS tube Q1 and the N-MOS tube Q3 is reduced. And meanwhile, the junction capacitors of the drain and source electrodes of the N-MOS transistor Q2 and the N-MOS transistor Q4 are charged, and the voltages at the two ends of the N-MOS transistor Q2 and the N-MOS transistor Q4 rise. When the junction capacitance voltage of the N-MOS transistor Q2 and the N-MOS transistor Q4 reaches the highest value and the junction capacitance voltage of the N-MOS transistor Q1 and the N-MOS transistor Q3 is pumped to zero, the driving signal Vgs1 and the driving signal Vgs3 become high level at the time t 4. Therefore, the drain and source voltages of the N-MOS transistor Q1 and the N-MOS transistor Q3 are reduced to zero before the driving signal is changed into high level, so the ZVS of the main switching tubes such as the N-MOS transistor Q1 and the N-MOS transistor Q3 can be realized only by the design of the parameters of the resonant circuit without adding other circuits. At this time, the excitation current Im1 is equal to the resonance current Ir1, the excitation current Im2 is equal to the resonance current Ir2, and the output rectifier diode D1 is turned off. This completes a cycle and then continues to repeat following the same process.
The advantages of the invention are obvious:
1. from the view of the circuit, the circuit can realize soft switching and has high efficiency.
2. From the switch tube selection, in the working process, the voltage of the switch tube when the switch tube is cut off is half of the input voltage, the leakage inductance of the transformer participates in resonance, the switch tube has no peak voltage stress, and the common switch tube is convenient to use.
3. In the winding process of the transformer, the leakage inductance is utilized to participate in resonance, and a special winding mode is not needed to reduce the leakage inductance, so that the automatic machine winding process of the transformer is favorably realized.
A200W switching power supply is designed by using the scheme shown in FIG. 1 and the technical scheme of the invention, the input voltage range is 250 VDC-900 VDC, 24V/8.3A is output, and the efficiency, the voltage stress of a switching tube and other indexes of the two schemes are compared for further explanation.
Table 1 comparison test results of full load efficiency between the scheme shown in fig. 1 and the technical scheme of the present invention
Input voltage Scheme shown in figure 1 Technical scheme of the invention
250VDC 87％ 91％
600VDC 90％ 92％
900VDC 89％ 91％
From the test data in table 1, the efficiency of the technical scheme of the invention is superior to that of the conventional scheme shown in fig. 1, especially when low voltage is input, the input current is large, and due to the soft switching function and the selection of the low-voltage-resistant N-MOS transistor, the loss of the switching transistor is greatly reduced, and the efficiency of the power supply is remarkably improved.
Table 2 comparative test results of voltage stress of switching tube between the scheme shown in fig. 1 and the technical scheme of the present invention
N-MOS Scheme shown in figure 1 Technical scheme of the invention
Q1 692V 450V
Q2 692V 450V
Q3 ---- 450V
Q4 ---- 450V
From the test data in table 2, the voltage stress of the four N-MOS transistors in the technical solution of the present invention is half of the input voltage, and a commonly used 600V withstand voltage transistor can be selected. The voltage stress of the N-MOS transistor in the conventional scheme shown in fig. 1 is equal to half of the input voltage, plus the output reflected voltage, plus the voltage peak generated by the leakage inductance, which is much larger than the voltage stress of the N-MOS transistor in the technical scheme of the present invention, and a hard switch is considered to leave a certain voltage margin, so that the N-MOS transistor with withstand voltage of over 800V, small junction capacitance and small on-resistance needs to be selected. The price of the N-MOS tube with the specification is 1 to 2 times higher than that of the commonly used 600V withstand voltage.
Second embodiment
Fig. 5 is a circuit diagram of an asymmetric half-bridge flyback circuit according to a second embodiment of the present invention, which is different from the first embodiment in that the positions of the main switch tube and the clamp switch tube are changed. The specific connection relationship is as follows: the capacitor C1 and the capacitor C2 are connected in series, one end of two terminals after being connected in series is connected with the anode of an input voltage and is simultaneously connected with the drain electrode of the N-MOS tube Q2, the other end of the two terminals is connected with the cathode of the input voltage and is simultaneously connected with the source electrode of the N-MOS tube Q3; the drain electrode of the N-MOS tube Q2 is also connected with one end of the inductor Lk 1; the other end of the inductor Lk1 is connected with the dotted end of the primary winding Lp1 of the transformer; the synonym of the primary winding Lp1 is connected with one end of the capacitor C3; the other end of the capacitor C3 is connected with the source electrode of the N-MOS tube Q2 and is also connected with the drain electrode of the N-MOS tube Q1; the source electrode of the N-MOS tube Q1 is connected with the drain electrode of the N-MOS tube Q4 and is also connected with the middle node after the capacitor C1 and the capacitor C2 are connected in series; the drain electrode of the N-MOS tube Q4 is also connected to one end of the inductor Lk 2; the other end of the inductor Lk2 is connected with the dotted end of the primary winding Lp2 of the transformer; the synonym of the primary winding Lp2 is connected with one end of the capacitor C4; the other end of the capacitor C4 is connected with the source electrode of the N-MOS transistor Q4 and is also connected with the drain electrode of the N-MOS transistor Q3; the synonym end of the secondary winding Ls1 is connected with the anode of a diode D1; the cathode of the diode D1 is connected with one end of the capacitor C5 and is used as the output anode; the other end of the capacitor C5 is connected with the end with the same name of the secondary winding Ls1 and is used as an output negative electrode;
the N-MOS tube Q1 and the N-MOS tube Q3 are main switching tubes, and driving signals are synchronous; the N-MOS tube Q2 and the N-MOS tube Q4 are clamping switch tubes, and driving signals are synchronous; the main switching tube and the clamping switching tube are complementary in driving signal, and a dead time exists between the two driving signals. The embodiment can also realize ZVS of the N-MOS tube, and the voltage of the drain and the source of each N-MOS tube is one half of the input voltage when the N-MOS tube is cut off.
Third embodiment
Fig. 6 is a circuit diagram of a third example, which is different from the first embodiment in that a third primary winding Lp3, a capacitor C6, a capacitor C7, an N-MOS transistor Q5, an N-MOS transistor Q6, and a leakage inductance Lk3 of the primary winding Lp3 are added to the transformer. In practical applications, the inductor Lp3 may also be an external independent inductor element. On the basis of the first embodiment, the connection relationship of the newly added components is as follows: the capacitor C6 is connected with the capacitor C1 and the capacitor C2 in series, one end of the two serially connected terminals is connected with the anode of the input voltage, the other end of the two serially connected terminals is connected with the cathode of the input voltage, and the other end of the two serially connected terminals is connected with the source electrode of the N-MOS transistor Q6; an intermediate node formed by serially connecting the capacitor C2 and the capacitor C6 is connected with the source electrode of the N-MOS tube Q4 and the drain electrode of the N-MOS tube Q5; the source electrode of the N-MOS tube Q5 is connected with the drain electrode of the N-MOS tube Q6 and is also connected with one end of the inductor Lk 3; the other end of the inductor Lk3 is connected with the dotted end of the primary winding Lp3 of the transformer; the synonym of the primary winding Lp3 of the transformer is connected with one end of the capacitor C7; the other end of the capacitor C7 is connected with the source electrode of the N-MOS transistor Q6;
the N-MOS tube Q1, the N-MOS tube Q3 and the N-MOS tube Q5 are main switching tubes, and driving signals are synchronous; the N-MOS tube Q2, the N-MOS tube Q4 and the N-MOS tube Q6 are clamping switch tubes, and driving signals are synchronous; the main switch tube and the clamping switch tube are complementary in driving signal, and a dead time exists between the two driving signals. The embodiment can also realize ZVS of the N-MOS tube, and the voltage of the drain and the source of each N-MOS tube is one third of the input voltage when the N-MOS tube is cut off, so that the N-MOS tube is suitable for being used on a switching power supply with higher input voltage.
Fourth embodiment
Fig. 7 is a circuit diagram of a fourth example, which is different from the second embodiment in that a third primary winding Lp3, a capacitor C6, a capacitor C7, an N-MOS transistor Q5, an N-MOS transistor Q6, and a leakage inductance Lk3 of the primary winding Lp3 are added to the transformer. In practical applications, the inductor Lp3 may also be an external independent inductor element. On the basis of the second embodiment, the connection relationship of the newly added components is: the capacitor C6 is connected with the capacitor C1 and the capacitor C2 in series, one end of the two serially connected terminals is connected with the anode of the input voltage, the other end of the two serially connected terminals is connected with the cathode of the input voltage, and the other end of the two serially connected terminals is connected with the source electrode of the N-MOS transistor Q5; the middle node of the capacitor C2 and the capacitor C6 which are connected in series is connected with the source electrode of the N-MOS tube Q3 and the drain electrode of the N-MOS tube Q6; the drain electrode of the N-MOS tube Q6 is also connected to one end of the inductor Lk 3; the other end of the inductor Lk3 is connected with the dotted end of the primary winding Lp3 of the transformer; the synonym of the primary winding Lp3 is connected with one end of the capacitor C7; the other end of the capacitor C7 is connected with the source electrode of the N-MOS tube Q6 and is also connected with the drain electrode of the N-MOS tube Q5.
The N-MOS tube Q1, the N-MOS tube Q3 and the N-MOS tube Q5 are main switching tubes, and driving signals are synchronous; the N-MOS tube Q2, the N-MOS tube Q4 and the N-MOS tube Q6 are clamping switch tubes, and driving signals are synchronous; the main switch tube and the clamping switch tube are complementary in driving signal, and a dead time exists between the two driving signals. The embodiment can also realize ZVS of the N-MOS tube, and the voltage of the drain and the source of each N-MOS tube is one third of the input voltage when the N-MOS tube is cut off, so that the N-MOS tube is suitable for being used on a switching power supply with higher input voltage.
Fifth embodiment
Fig. 8 is a circuit diagram of a fifth example, which is different from the first embodiment in that a resistor R1 is further connected between a midpoint of the capacitor C1 and the capacitor C2 after being connected in series and the source of the N-MOS transistor Q2, and other connection relationships are not changed. The resistor R1 has the functions of: because the impedance of a series loop formed by the capacitor C1, the N-MOS tube Q1, the inductor Lk1, the primary winding Lp1 and the capacitor C3 and the impedance of a series loop formed by the capacitor C2, the N-MOS tube Q3, the inductor Lk2, the primary winding Lp2 and the capacitor C4 cannot be completely equal (caused by component parameter precision deviation), the peak current of the two loops is different. The resistance value is properly larger than the difference value of the two loop impedances so as to weaken the influence of the impedance being not equal and reduce the difference of the peak currents of the two loops to the maximum extent.
Similarly, the series-in resistor scheme of the fifth embodiment is also applicable to the third embodiment, that is, a resistor R2 is further connected between the midpoint of the capacitor C2 and the capacitor C6 after being connected in series and the source of the N-MOS transistor Q6, and other connection relations are not changed. The function of the resistor R2 is substantially the same as that of the resistor R1.
The above is only a preferred embodiment of the present invention, and it should be noted that the above preferred embodiment should not be considered as a limitation to the present invention, and it will be apparent to those skilled in the art that several modifications and decorations can be made, such as the output rectifying diode D1 is replaced by a MOS transistor for synchronous rectification, without departing from the spirit and scope of the present invention; one or more primary windings, N-MOS tubes, inductors and capacitors are added to the transformer; one or more secondary windings are added to the transformer to form multi-path output and the like; such modifications and decorations shall be considered as the protection scope of the present invention, which shall not be described herein by way of example, and shall be subject to the limitations defined by the claims.

Claims (15)

1. The utility model provides an asymmetric half-bridge flyback circuit, includes the positive end of input, input negative terminal, transformer, the primary circuit of being connected with the primary winding of transformer and the secondary circuit of being connected with the secondary winding of transformer, and the primary circuit includes first electric capacity and second electric capacity, and the one end and the input positive end of first electric capacity are connected, and the other end and the one end of second electric capacity of first electric capacity are connected, and the other end and the input negative terminal of second electric capacity are connected, its characterized in that:
the transformer is provided with a first primary winding, a second primary winding and a first secondary winding, wherein the first primary winding and the second primary winding are connected in series;
the primary side circuit further includes:
the four switching tubes are a first switching tube, a second switching tube, a third switching tube and a fourth switching tube, drain-source electrodes of the four switching tubes are sequentially connected in series between an input positive end and an input negative end, the first switching tube and the third switching tube are main switching tubes, and driving signals are synchronous; the second switching tube and the fourth switching tube are clamping switching tubes, and driving signals are synchronous; the main switching tube and the clamping switching tube are complementary in driving signal, and a dead time is formed between the two driving signals;
two inductors, namely a first inductor and a second inductor;
two capacitors, namely a third capacitor and a fourth capacitor;
the dotted terminal of a first primary winding of the transformer is connected with the drain electrode of the second switching tube through a first inductor, and the dotted terminal of the first primary winding is respectively connected with the source electrode of the second switching tube and the other end of the first capacitor through a third capacitor; the homonymous end of the second primary winding is connected with the drain electrode of the fourth switching tube through a second inductor, and the heteronymous end of the second primary winding is respectively connected with the source electrode of the fourth switching tube and the other end of the second capacitor through a fourth capacitor;
when the main switching tube is switched on and the clamping switching tube is switched off, an input voltage is applied to a series loop formed by a first inductor, a first primary winding, a third capacitor, a second inductor, a second primary winding and a fourth capacitor in sequence to generate resonance; in the first dead time when the main switching tube and the clamping switching tube are both cut off, the junction capacitors of the four switching tubes generate resonance through a series loop, and the energy of the junction capacitors of the clamping switching tubes is extracted to realize zero-voltage switching-on of the clamping switching tubes;
when the main switching tube is turned off and the clamping switching tube is turned on, the first inductor, the first primary winding, the third capacitor and the second switching tube form a first resonant circuit; a second resonant circuit is formed by the second inductor, the second primary winding, the fourth capacitor and the fourth switching tube; in the second dead time when the main switching tube and the clamping switching tube are both cut off, the junction capacitors of the four switching tubes generate resonance through the series loop, and the energy of the junction capacitors of the main switching tubes is extracted to realize the zero-voltage switching-on of the main switching tubes.
2. The asymmetric half-bridge flyback circuit of claim 1, wherein: the transformer is also provided with a third primary winding which is connected with the second primary winding in series; the primary side circuit further comprises a sixth capacitor, a fifth switching tube, a sixth switching tube, a third inductor and a seventh capacitor, one end of the sixth capacitor is connected with the other end of the second capacitor, and the other end of the sixth capacitor is connected with the input negative end; a fifth switching tube and a sixth switching tube are sequentially connected in series with the four switching tubes between the input positive end and the input negative end, wherein the fifth switching tube is a main switching tube, and the sixth switching tube is a clamping switching tube;
the dotted end of the third primary winding of the transformer is connected with the drain electrode of the sixth switching tube through a third inductor, and the different-dotted end of the third primary winding is respectively connected with the source electrode of the sixth switching tube and the other end of the sixth capacitor through a seventh capacitor;
when the main switching tube is switched on and the clamping switching tube is switched off, an input voltage is applied to a series circuit formed by a first inductor, a first primary winding, a third capacitor, a second primary winding, a fourth capacitor, a third primary winding and a seventh capacitor in sequence to generate resonance; in the first dead time when the main switching tube and the clamping switching tube are both cut off, the junction capacitors of the six switching tubes generate resonance through the series loop, and the energy of the junction capacitors of the clamping switching tubes is extracted to realize zero-voltage switching-on of the clamping switching tubes;
when the main switching tube is turned off and the clamping switching tube is turned on, the first primary winding, the third capacitor and the second switching tube form a first resonant circuit; the second primary winding, the fourth capacitor and the fourth switching tube form a second resonant circuit; a third primary winding, a seventh capacitor and a sixth switching tube form a third resonant circuit; in the second dead time when the main switching tube and the clamping switching tube are both cut off, the junction capacitors of the six switching tubes generate resonance through the series loop, and the energy of the junction capacitors of the main switching tubes is extracted to realize zero-voltage switching-on of the main switching tubes.
3. The asymmetric half-bridge flyback circuit of claim 1, wherein: the primary side circuit further comprises a first resistor, and the first resistor is connected between the other end of the first capacitor and the third capacitor in series.
4. The asymmetric half-bridge flyback circuit of claim 2, wherein: the primary side circuit further comprises a first resistor and a second resistor, and the first resistor is connected between the other end of the first capacitor and the third capacitor in series; the second resistor is connected between the other end of the second capacitor and the fourth capacitor in series.
5. An asymmetric half-bridge flyback circuit according to any of claims 1-4, characterized in that: the secondary side circuit comprises a first diode and a fifth capacitor,
the anode of the first diode is connected with the different name end of the first secondary winding of the transformer, and the cathode of the first diode is connected with one end of the fifth capacitor and is led out to be used as an output anode; the other end of the fifth capacitor is connected with the dotted end of the first secondary winding, and is led out to be used as an output cathode.
6. An asymmetric half-bridge flyback circuit, comprising a transformer, characterized in that:
the transformer comprises a first primary winding, a second primary winding and a first secondary winding;
the asymmetric half-bridge flyback circuit further comprises a first diode, a first inductor, a second inductor, a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a first switching tube, a second switching tube, a third switching tube and a fourth switching tube, wherein the first switching tube and the third switching tube are main switching tubes, and driving signals are synchronous; the second switching tube and the fourth switching tube are clamping switching tubes, and driving signals are synchronous; the main switch tube and the clamping switch tube are complementary in driving signal, a dead time is formed between the two driving signals, and the connection relationship is as follows: the first capacitor and the second capacitor are connected in series, one end of two terminals after being connected in series is connected with the positive input end and the drain electrode of the first switch tube, the other end of the two terminals after being connected in series is connected with the negative input end and the source electrode of the fourth switch tube; the source electrode of the first switch tube is connected with the drain electrode of the second switch tube; the source electrode of the first switching tube is also connected to one end of a first inductor, and the other end of the first inductor is connected with the dotted end of the first primary winding; the synonym end of the first primary winding is connected with one end of a third capacitor; the other end of the third capacitor is connected with the source electrode of the second switching tube, is also connected with a middle node after the first capacitor and the second capacitor are connected in series, and is also connected with the drain electrode of the third switching tube; the source electrode of the third switching tube is connected with the drain electrode of the fourth switching tube; the source electrode of the third switching tube is also connected to one end of the second inductor; the other end of the second inductor is connected with the dotted end of a second primary winding of the transformer; the synonym of a second primary winding of the transformer is connected with one end of the fourth capacitor; the other end of the fourth capacitor is connected with the source electrode of the fourth switching tube; the other end of the fourth capacitor is also connected with the input negative terminal.
7. The asymmetric half-bridge flyback circuit of claim 6, wherein: the transformer is also provided with a third primary winding which is connected with the second primary winding in series; the asymmetric half-bridge flyback circuit further comprises a sixth capacitor, a fifth switch tube, a sixth switch tube, a third inductor and a seventh capacitor, wherein the fifth switch tube is a main switch tube, the sixth switch tube is a clamping switch tube, and the connection relationship is as follows: the sixth capacitor is connected in series with the first capacitor and the second capacitor, one end of two terminals after being connected in series is connected with the anode of the input voltage and is simultaneously connected with the drain electrode of the first switching tube, the other end of the two terminals is connected with the cathode of the input voltage and is simultaneously connected with the source electrode of the sixth switching tube; the other end of the fourth capacitor is connected with the source electrode of the fourth switching tube, is also connected with a middle node formed by connecting the second capacitor and the sixth capacitor in series and is also connected with the drain electrode of the fifth switching tube; the source electrode of the fifth switching tube is connected with the drain electrode of the sixth switching tube; the source electrode of the fifth switching tube is also connected to one end of the third inductor; the other end of the third inductor is connected with the dotted end of a third primary winding of the transformer; the synonym end of a third primary winding of the transformer is connected with one end of a seventh capacitor; the other end of the seventh capacitor is connected with the source electrode of the sixth switching tube.
8. The asymmetric half-bridge flyback circuit of claim 6, wherein: the asymmetric half-bridge flyback circuit further comprises a first resistor, and the first resistor is connected in series between the other end of the third capacitor and an intermediate node formed by connecting the first capacitor and the second capacitor in series.
9. The asymmetric half-bridge flyback circuit of claim 7, wherein: the asymmetric half-bridge flyback circuit also comprises a first resistor and a second resistor, wherein the first resistor is connected in series between the other end of the third capacitor and an intermediate node formed by the first capacitor and the second capacitor after being connected in series; the second resistor is connected in series between the other end of the fourth capacitor and an intermediate node formed by connecting the second capacitor and the sixth capacitor in series.
10. An asymmetric half-bridge flyback circuit according to any of claims 6-9, wherein: the asymmetric half-bridge flyback circuit also comprises a secondary side circuit, wherein the secondary side circuit comprises a first diode and a fifth capacitor, the anode of the first diode is connected with the synonym end of a first secondary winding of the transformer, the cathode of the first diode is connected with one end of the fifth capacitor, and the first diode is led out to serve as an output anode; the other end of the fifth capacitor is connected with the dotted end of the first secondary winding, and is led out to serve as an output cathode.
11. An asymmetric half-bridge flyback circuit, comprising a transformer, characterized in that:
the transformer comprises a first primary winding, a second primary winding and a first secondary winding;
the asymmetric half-bridge flyback circuit further comprises a first diode, a first inductor, a second inductor, a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a first switching tube, a second switching tube, a third switching tube and a fourth switching tube, wherein the first switching tube and the third switching tube are main switching tubes, and driving signals are synchronous; the second switching tube and the fourth switching tube are clamping switching tubes, and driving signals are synchronous; the main switch tube and the clamping switch tube are complementary in driving signal, a dead time is formed between the two driving signals, and the connection relationship is as follows: the first capacitor and the second capacitor are connected in series, one end of two terminals after being connected in series is connected with the anode of the input voltage and is simultaneously connected with the drain electrode of the second switching tube, the other end of the two terminals after being connected in series is connected with the cathode of the input voltage and is simultaneously connected with the source electrode of the third switching tube; the drain electrode of the second switch is also connected with one end of the first inductor; the other end of the first inductor is connected with the dotted end of a first primary winding of the transformer; the synonym of the first primary winding of the transformer is connected with one end of the third capacitor; the other end of the third capacitor is connected with the source electrode of the second switch tube and is also connected with the drain electrode of the first switch tube; the source electrode of the first switch tube is connected with the drain electrode of the fourth switch tube and is also connected with the middle node after the first capacitor and the second capacitor are connected in series; the drain electrode of the fourth switching tube is also connected to one end of the second inductor; the other end of the second inductor is connected with the dotted end of a second primary winding of the transformer; the synonym of a second primary winding of the transformer is connected with one end of a fourth capacitor; the other end of the fourth capacitor is connected with the source electrode of the fourth switching tube and is also connected with the drain electrode of the third switching tube.
12. The asymmetric half-bridge flyback circuit of claim 11, wherein: the transformer is also provided with a third primary winding which is connected with the second primary winding in series; the asymmetric half-bridge flyback circuit further comprises a sixth capacitor, a fifth switch tube, a sixth switch tube, a third inductor and a seventh capacitor, wherein the fifth switch tube is a main switch tube, the sixth switch tube is a clamping switch tube, and the connection relationship is as follows: the sixth capacitor is connected in series with the first capacitor and the second capacitor, one end of two terminals after series connection is connected with the anode of the input voltage and is simultaneously connected with the drain electrode of the second switching tube, the other end of the two terminals is connected with the cathode of the input voltage and is simultaneously connected with the source electrode of the fifth switching tube; the source electrode of the third switching tube is connected with the drain electrode of the sixth switching tube and is also connected with the middle node after the second capacitor and the sixth capacitor are connected in series; the drain electrode of the sixth switching tube is also connected to one end of the third inductor; the other end of the third inductor is connected with the dotted end of a third primary winding of the transformer; the synonym end of a third primary winding of the transformer is connected with one end of a seventh capacitor; the other end of the seventh capacitor is connected with the source electrode of the sixth switching tube and is also connected with the drain electrode of the fifth switching tube.
13. The asymmetric half-bridge flyback circuit of claim 11, wherein: the asymmetric half-bridge flyback circuit further comprises a first resistor, and the first resistor is connected in series between the other end of the third capacitor and a middle node formed by the first capacitor and the second capacitor after the third capacitor is connected in series.
14. The asymmetric half-bridge flyback circuit of claim 12, wherein: the asymmetric half-bridge flyback circuit further comprises a first resistor and a second resistor, wherein the first resistor is connected in series between the other end of the third capacitor and an intermediate node formed by connecting the first capacitor and the second capacitor in series; the second resistor is connected in series between the other end of the fourth capacitor and an intermediate node formed by connecting the second capacitor and the sixth capacitor in series.
15. An asymmetric half-bridge flyback circuit as in any of claims 11-14, wherein: the asymmetric half-bridge flyback circuit also comprises a secondary side circuit, wherein the secondary side circuit comprises a first diode and a fifth capacitor, the anode of the first diode is connected with the synonym end of a first secondary winding of the transformer, the cathode of the first diode is connected with one end of the fifth capacitor, and the first diode is led out to serve as an output anode; the other end of the fifth capacitor is connected with the dotted end of the first secondary winding, and is led out to serve as an output cathode.
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