CN113922673B - Control circuit and equipment for realizing self-driving of active clamping flyback topology switching power supply - Google Patents

Control circuit and equipment for realizing self-driving of active clamping flyback topology switching power supply Download PDF

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Publication number
CN113922673B
CN113922673B CN202111029367.2A CN202111029367A CN113922673B CN 113922673 B CN113922673 B CN 113922673B CN 202111029367 A CN202111029367 A CN 202111029367A CN 113922673 B CN113922673 B CN 113922673B
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flyback
tube
driving
primary
circuit
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CN113922673A (en
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李保平
厉干年
李华铭
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Shanghai Juntao Technology Co ltd
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Shanghai Juntao Technology Co 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
    • H02M3/3353—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having at least two simultaneously operating switches on the input side, e.g. "double forward" or "double (switched) flyback" converter
    • 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
    • H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
    • H02M1/088—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters for the simultaneous control of series or parallel connected semiconductor devices
    • 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

Abstract

The invention discloses a control circuit and a device for realizing self-driving of an active clamping flyback topology switching power supply. The invention enables the flyback primary side circuit to transmit the primary side power switch tube driving signal to the first protection circuit by designing the control circuit, the first protection circuit transmits the first secondary side synchronous rectifier tube driving signal generated according to the primary side power switch tube driving signal to the flyback secondary side circuit, meanwhile, the second protection circuit transmits a driving control signal generated according to the comparison result of the sampling signal and the reference signal to the self-driving control circuit, the self-driving control circuit transmits a driving signal of a second secondary synchronous rectifier tube generated by the phase change of the flyback transformer to a flyback secondary circuit when the driving control signal is a high-level signal, the flyback secondary circuit respectively turns off and turns on the secondary synchronous rectifier tubes according to the driving signals of the first and second secondary synchronous rectifier tubes, therefore, the switching-on or switching-off of the secondary synchronous rectifier tube can be controlled in a self-adaptive manner, and the switching loss of the secondary synchronous rectifier tube is reduced.

Description

Control circuit and equipment for realizing self-driving of active clamping flyback topology switching power supply
Technical Field
The invention relates to the technical field of power supplies, in particular to a control circuit and equipment for realizing self-driving of an active clamp flyback topology switching power supply.
Background
The active clamp flyback topology switching power supply solves the disadvantage that the stress of a primary side tube of a flyback topology is large by adopting the active clamp, but the difficulty in realizing synchronous rectification is when a secondary side synchronous rectifying tube is switched on or off. In the prior art, a current-mode driving method is usually adopted, that is, the current of the secondary synchronous rectifier is detected to control the on or off of the secondary synchronous rectifier, so that the secondary synchronous rectifier is turned off when the secondary synchronous rectifier crosses zero. However, the disadvantage of this method is that the active clamp flyback topology switching power supply has to operate in the current discontinuous mode (DCM) in the whole range, which is detrimental to the conversion efficiency and the stress of the primary side power switch tube.
Disclosure of Invention
The invention provides a control circuit and a device for realizing self-driving of an active clamp flyback topology switching power supply, which can adaptively control the switching on or off of a secondary synchronous rectifier tube, reduce the switching loss of the secondary synchronous rectifier tube, and are beneficial to improving the conversion efficiency and protecting the active clamp flyback topology switching power supply.
In order to solve the above technical problem, in a first aspect, an embodiment of the present invention provides a control circuit for realizing self-driving of an active-clamp flyback topology switching power supply, including a flyback primary side line, a flyback secondary side line, a self-driving control line, a first protection line, and a second protection line; the flyback transformer comprises a flyback transformer, a flyback primary side line, a flyback secondary side line, a self-driven control line, a first protection line, a second protection line and a self-driven control line, wherein the flyback primary side line is connected with a primary side of the flyback transformer, the flyback secondary side line is connected with a secondary side of the flyback transformer, the self-driven control line is coupled with the flyback transformer, the flyback primary side line is connected with the flyback secondary side line through the first protection line, the first protection line is connected with the self-driven control line through the second protection line, and the self-driven control line is connected with the flyback secondary side line;
the flyback primary circuit is used for transmitting a primary power switching tube driving signal to the first protection circuit;
the first protection circuit is used for generating a first secondary synchronous rectifier tube driving signal according to the primary power switching tube driving signal and transmitting the first secondary synchronous rectifier tube driving signal to the flyback secondary circuit;
the flyback secondary line is used for switching off a secondary synchronous rectifier tube according to the driving signal of the first secondary synchronous rectifier tube;
the second protection circuit is used for generating a driving control signal according to a comparison result of a sampling signal and a reference signal obtained when the switching power supply stops working, and transmitting the driving control signal to the self-driving control circuit;
the self-driving control circuit is used for generating a second secondary synchronous rectifier tube driving signal when the flyback transformer changes the phase and transmitting the second secondary synchronous rectifier tube driving signal to the flyback secondary circuit when the driving control signal is a high-level signal;
and the flyback secondary circuit is also used for switching on the secondary synchronous rectifying tube according to the driving signal of the second secondary synchronous rectifying tube.
Furthermore, the flyback primary side circuit comprises a flyback transformer primary side winding, a primary side switching tube, a primary side power switching tube driving circuit, a first capacitor and a second capacitor;
one end of the primary winding of the flyback transformer is connected with the voltage input end of the switching power supply, one end of the primary winding of the flyback transformer is further connected with the other end of the primary winding of the flyback transformer through the first capacitor, the other end of the primary winding of the flyback transformer is connected with the drain electrode of the primary power switching tube through the second capacitor, the grid electrode of the primary power switching tube is connected with the driving signal end of the primary power switching tube through the driving circuit of the primary power switching tube, the other end of the primary winding of the flyback transformer is further connected with the drain electrode of the primary switching tube, the grid electrode of the primary switching tube is connected with the driving signal end of the primary switching tube, and the other end of the primary winding of the flyback transformer, the source electrode of the primary power switching tube and the source electrode of the primary switching tube are all grounded.
Furthermore, the driving line of the primary side power switch tube consists of a third capacitor, a first resistor and a first diode;
the grid electrode of the primary side power switch tube is respectively connected with one end of the third capacitor, one end of the first resistor and the anode of the first diode, the other end of the third capacitor is connected with the driving end of the primary side power switch tube, and the other end of the first resistor and the cathode of the first diode are both grounded.
Further, the first protection circuit comprises a fourth capacitor, a second resistor, a second diode, a third diode, a transformer, a first switching tube, a fourth diode and an RC discharge circuit;
one end of the fourth capacitor is connected with a driving signal end of a primary power switch tube, the other end of the fourth capacitor is respectively connected with one end of the second resistor and the anode of the second diode, the other end of the second resistor, the cathode of the second diode and the cathode of the third diode are respectively connected with one end of a primary winding of the transformer, the other end of the primary winding of the transformer and the anode of the third diode are both grounded through the flyback primary circuit, one end of a secondary winding of the transformer is respectively connected with the grid electrode of the first switch tube and the anode of the fourth diode, the drain electrode of the first switch tube is connected with the grid electrode of the secondary synchronous rectifier tube, the other end of the secondary winding of the transformer and the source electrode of the first switch tube are both grounded, and the cathode of the fourth diode is grounded through the RC discharge circuit, the RC discharge line is connected with the second protection line.
Furthermore, the RC discharge circuit consists of a first voltage-regulator tube, a fifth capacitor and a third resistor;
the cathode of the first voltage-stabilizing tube, one end of the fifth capacitor and one end of the third resistor are respectively connected with the cathode of the fourth diode, and the anode of the first voltage-stabilizing tube, the other end of the fifth capacitor and the other end of the third resistor are all grounded.
Furthermore, the flyback secondary line comprises a flyback transformer secondary winding, the secondary synchronous rectifier tube and a sixth capacitor;
one end of the secondary winding of the flyback transformer is connected with the voltage output end of the switching power supply, one end of the secondary winding of the flyback transformer is connected with the other end of the secondary winding of the flyback transformer through the sixth capacitor, the other end of the secondary winding of the flyback transformer is connected with the drain electrode of the secondary synchronous rectifier tube, the grid electrode of the secondary synchronous rectifier tube is respectively connected into the first protection circuit and the self-driving control circuit, and the source electrode of the secondary synchronous rectifier tube is grounded.
Furthermore, the self-driven control circuit comprises a driving winding, a fifth diode, a sixth diode, a second switching tube, a seventh capacitor, an eighth capacitor, a fourth resistor, a fifth resistor, a second voltage regulator tube and a sixth resistor, wherein the driving winding, the fifth diode, the sixth diode, the second switching tube, the seventh capacitor, the eighth capacitor, the fourth resistor, the fifth resistor, the second voltage regulator tube and the sixth resistor are coupled with the flyback transformer;
one end of the driving winding is respectively connected with the anodes of the fifth diode and the sixth diode, the cathode of the fifth diode is connected with the drain of the second switching tube, the cathode of the sixth diode is respectively connected with one end of the seventh capacitor, one end of the fourth resistor and one end of the fifth resistor, the other end of the fourth resistor is respectively connected with the grid electrode of the second switch tube, one end of the eighth capacitor and the cathode of the second voltage-regulator tube, the grid electrode of the second switch tube is connected with the second protection circuit, the source electrode of the second switch tube is connected with the grid electrode of the secondary side synchronous rectifying tube through the sixth resistor, the other end of the driving winding is connected with the other end of the seventh capacitor, the other end of the fifth resistor, the other end of the eighth capacitor and the anode of the second voltage regulator tube respectively.
Further, the second protection circuit comprises an operational amplifier and a seventh diode;
the positive input end of the operational amplifier is connected to the first protection circuit, the negative input end of the operational amplifier is connected to the reference signal end, the output end of the operational amplifier is connected to the cathode of the seventh diode, and the anode of the seventh diode is connected to the self-driving control circuit.
In a second aspect, an embodiment of the present invention provides a device for implementing self-driving by an active clamp flyback topology switching power supply, where the device includes the control circuit for implementing self-driving by an active clamp flyback topology switching power supply as described above.
Compared with the prior art, the embodiment of the invention has the following beneficial effects:
the flyback primary side circuit on the primary side of the flyback transformer is connected with a flyback secondary side circuit on the secondary side of the flyback transformer through a first protection circuit, the first protection circuit is connected with a self-driving control circuit coupled with the flyback transformer through a second protection circuit, the self-driving control circuit is connected with the flyback secondary side circuit, the flyback primary side circuit transmits a primary side power switch tube driving signal to the first protection circuit, the first protection circuit generates a first secondary synchronous rectifier tube driving signal according to the primary side power switch tube driving signal, the first secondary synchronous rectifier tube driving signal is transmitted to the flyback secondary side circuit, the flyback secondary side circuit turns off a secondary synchronous rectifier tube according to the first secondary synchronous rectifier tube driving signal, and meanwhile, the second protection circuit generates a driving control signal according to a comparison result of a sampling signal obtained when the switching power supply stops working and a reference signal, the driving control signal is transmitted to the self-driving control circuit, the self-driving control circuit generates a second secondary synchronous rectifier tube driving signal when the flyback transformer changes the phase, and transmits the second secondary synchronous rectifier tube driving signal to the flyback secondary circuit when the driving control signal is a high-level signal, and the flyback secondary circuit turns on the secondary synchronous rectifier tube according to the second secondary synchronous rectifier tube driving signal, so that the secondary synchronous rectifier tube can be turned on or off in a self-adaptive control mode, the switching loss of the secondary synchronous rectifier tube is reduced, the conversion efficiency is improved, and the active flyback clamp topology switching power supply is protected.
Drawings
Fig. 1 is a schematic structural diagram of a control circuit for implementing self-driving of an active clamp flyback topology switching power supply according to a first embodiment of the present invention;
wherein, the reference numbers in the attached figure 1 of the specification are as follows:
10: a flyback primary side line; 20: flyback secondary side lines; 30: a first protection circuit; 40: a self-driven control line; 50: and a second protection circuit.
Detailed Description
The technical solutions in the present invention will be described clearly and completely with reference to the accompanying drawings, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
As shown in fig. 1, a first embodiment provides a control circuit for realizing self-driving of an active clamp flyback topology switching power supply, which includes a flyback primary side line 10, a flyback secondary side line 20, a self-driving control line 40, a first protection line 30, and a second protection line 50; the flyback transformer T1 is connected with the primary side of the flyback transformer T1, the flyback secondary side line 20 is connected with the secondary side of the flyback transformer T1, the self-driving control line 40 is coupled with the flyback transformer T1, the flyback primary side line 10 is connected with the flyback secondary side line 20 through the first protection line 30, the first protection line 30 is connected with the self-driving control line 40 through the second protection line 50, and the self-driving control line 40 is connected with the flyback secondary side line 20; the flyback primary side circuit 10 is used for transmitting a primary side power switching tube driving signal (PWM1) to the first protection circuit 30; the first protection circuit 30 is configured to generate a first secondary synchronous rectifier driving signal according to a primary power switching tube driving signal (PWM1), and transmit the first secondary synchronous rectifier driving signal to the flyback secondary circuit 20; a flyback secondary line 20 for turning off the secondary synchronous rectifier Q4 according to the first secondary synchronous rectifier driving signal; a second protection line 50 for generating a drive control signal (Vsec control) based on a comparison result between a sampling signal obtained when the switching power supply stops operating and the reference signal, and transmitting the drive control signal (Vsec control) to the self-drive control line 40; a self-driving control line 40 for generating a second secondary synchronous rectifier driving signal when the flyback transformer T1 is phase-shifted, and transmitting the second secondary synchronous rectifier driving signal to the flyback secondary line 20 when the driving control signal (Vsec control) is a high level signal; the flyback secondary line 20 is further configured to turn on the secondary synchronous rectifier Q4 according to the second secondary synchronous rectifier driving signal.
Illustratively, the flyback primary side line 10 on the primary side of the flyback transformer T1 is connected with the flyback secondary side line 20 on the secondary side of the flyback transformer T1 through the first protection line 30, the first protection line 30 is connected with the self-driving control line 40 coupled with the flyback transformer T1 through the second protection line 50, and the self-driving control line 40 is connected with the flyback secondary side line 20.
In the control circuit, a flyback primary line 10 transmits a primary power switching tube driving signal (PWM1) to a first protection line 30 and provides primary power transmission, the first protection line 30 generates a first secondary synchronous rectifier tube driving signal according to the primary power switching tube driving signal (PWM1), the first secondary synchronous rectifier tube driving signal is transmitted to a flyback secondary line 20, the flyback secondary line 20 turns off a secondary synchronous rectifier tube Q4 according to the first secondary synchronous rectifier tube driving signal and provides secondary power transmission, advance control of turning off the secondary synchronous rectifier tube Q4 is achieved, and the primary switching tube Q1 and the secondary synchronous rectifier tube Q4 are prevented from being directly connected.
In the control circuit, a second protection circuit 50 generates a drive control signal (Vsec control) based on a comparison result of a sampling signal obtained when the switching power supply stops operating and a reference signal, transmits the drive control signal (Vsec control) to a self-drive control circuit 40, the self-drive control circuit 40 generates a second secondary synchronous rectifier driving signal when a flyback transformer T1 changes phase, and transmits the second secondary synchronous rectifier driving signal to a flyback secondary circuit 20 when the drive control signal (Vsec control) is a high level signal, the flyback secondary circuit 20 turns on a secondary synchronous rectifier Q4 based on the second secondary synchronous rectifier driving signal, realizes Zero Voltage (ZVS) turn-on of the secondary synchronous rectifier Q4, reduces switching loss of the secondary synchronous rectifier Q4, and turns off transmission of the drive control signal (Vscontrol) when the switching power supply is turned off or the drive signal is output due to protection stop, reducing the current back-flow.
The embodiment of the invention can adaptively control the turn-on or turn-off of the secondary synchronous rectifier tube Q4, reduce the switching loss of the secondary synchronous rectifier tube Q4, and is favorable for improving the conversion efficiency and protecting the active clamping flyback topology switching power supply.
In this embodiment, the flyback primary line 10 includes a flyback transformer T1 primary winding, a primary switching tube Q1, a primary power switching tube Q2, a primary power switching tube driving line, a first capacitor C1, and a second capacitor C2; one end of a primary winding of a flyback transformer T1 is connected with a voltage input end (Vin) of a switching power supply, one end of the primary winding of the flyback transformer T1 is further connected with the other end of the primary winding of the flyback transformer T1 through a first capacitor C1, the other end of the primary winding of the flyback transformer T1 is connected with a drain electrode of a primary power switch tube Q2 through a second capacitor C2, a grid electrode of the primary power switch tube Q2 is connected with a driving signal end of the primary power switch tube through a driving circuit of the primary power switch tube, the other end of the primary winding of the flyback transformer T1 is further connected with a drain electrode of a primary switch tube Q1, a grid electrode of the primary switch tube Q1 is connected with the driving signal end of the primary power switch tube, and the other end of the primary winding of the flyback transformer T1, the source electrode of the primary power switch tube Q2 and the source electrode of the primary switch tube Q1 are all grounded.
In this embodiment, the driving line of the primary side power switch tube is composed of a third capacitor C3, a first resistor R1, and a first diode D1; the grid electrode of the primary power switch tube Q2 is respectively connected with one end of a third capacitor C3, one end of a first resistor R1 and the anode of a first diode D1, the other end of the third capacitor C3 is connected with the driving end of the primary power switch tube, and the other end of the first resistor R1 and the cathode of the first diode D1 are both grounded.
Illustratively, the flyback primary line 10 enables normal primary operation of the flyback active clamp and transmits a primary power switching tube drive signal (PWM1) to the first protection line 30.
In the present embodiment, the first protection circuit includes a fourth capacitor C4, a second resistor R2, a second diode D2, a third diode D3, a transformer T2, a first switch tube Q3, a fourth diode D4, and an RC discharge line; one end of a fourth capacitor C4 is connected with the driving signal end of the primary side power switch tube, the other end of the fourth capacitor C4 is respectively connected with one end of a second resistor R2 and the anode of a second diode D2, the other end of the second resistor R2, the cathode of the second diode D2 and the cathode of the third diode D3 are respectively connected with one end of a primary winding of a transformer T2, the other end of the primary winding of the transformer T2 and the anode of the third diode D3 are both grounded through a flyback primary line 10, one end of a secondary winding of the transformer T2 is respectively connected with the grid of a first switch tube Q3 and the anode of a fourth diode D4, the drain of the first switch tube Q3 is connected with the grid of a secondary synchronous rectifier tube Q4, the other end of the secondary winding of the transformer T2 and the source of a first switch tube Q3 are both grounded, the cathode of the fourth diode D4 is grounded through an RC discharge line, and the RC discharge line is connected with the second protection line 50.
In the embodiment, the RC discharging circuit is composed of a first voltage regulator tube D5, a fifth capacitor C5, and a third resistor R3; the cathode of the first voltage-regulator tube D5, one end of the fifth capacitor C5 and one end of the third resistor R3 are respectively connected with the cathode of the fourth diode D4, and the anode of the first voltage-regulator tube D5, the other end of the fifth capacitor C5 and the other end of the third resistor R3 are all grounded.
It should be noted that the transformer T2 is a small-signal transformer, and the fourth capacitor C4 is a differential capacitor.
Illustratively, the primary power switch driving signal (PWM1) forms a first secondary synchronous rectifier driving signal (pulse signal) through the fourth capacitor C4, the first secondary synchronous rectifier driving signal (pulse signal) is transmitted to the flyback secondary line 20 through the transformer T2, and the flyback secondary line 20 turns off the secondary synchronous rectifier Q4 according to the first secondary synchronous rectifier driving signal. When the switching power supply normally works, a primary side power switching tube Q2 is turned off by a primary side power switching tube driving signal (PWM1), a certain dead time exists between the turning-on of the primary side switching tube Q1 by a primary side switching tube driving signal (PWM2), the first protection circuit 30 transmits the dead time to the flyback secondary side circuit 20, the secondary side synchronous rectifier tube Q4 is controlled to be turned off in advance, and the primary side switching tube Q1 and the secondary side synchronous rectifier tube Q4 are prevented from being directly connected.
In the present embodiment, the flyback secondary line 20 includes a flyback transformer T1 secondary winding, a secondary synchronous rectifier Q4, and a sixth capacitor C6; one end of a secondary winding of the flyback transformer T1 is connected with a voltage input end (Vo) of the switching power supply, one end of a secondary winding of the flyback transformer T1 is connected with the other end of the secondary winding of the flyback transformer T1 through a sixth capacitor C6, the other end of the secondary winding of the flyback transformer T1 is connected with a drain electrode of a secondary synchronous rectifier Q4, a grid electrode of the secondary synchronous rectifier Q4 is respectively connected to the first protection circuit 30 and the self-driving control circuit 40, and a source electrode of the secondary synchronous rectifier Q4 is grounded.
Illustratively, the flyback secondary line 20 turns off the secondary synchronous rectifier Q4 according to the first secondary synchronous rectifier driving signal transmitted from the first protection line 30, and turns on the secondary synchronous rectifier Q4 according to the second secondary synchronous rectifier driving signal transmitted from the driving control line 40.
In the present embodiment, the self-driving control circuit 40 includes a driving winding coupled to the flyback transformer T1, a fifth diode D6, a sixth diode D7, a second switch tube Q5, a seventh capacitor C7, an eighth capacitor C8, a fourth resistor R4, a fifth resistor R5, a second voltage regulator tube D8, and a sixth resistor R6; one end of a driving winding is connected with anodes of a fifth diode D6 and a sixth diode D7 respectively, a cathode of a fifth diode D6 is connected with a drain of a second switch tube Q5, a cathode of a sixth diode D7 is connected with one ends of a seventh capacitor C7, a fourth resistor R4 and a fifth resistor R5 respectively, the other end of the fourth resistor R4 is connected with a gate of a second switch tube Q5, one end of an eighth capacitor C8 and a cathode of a second voltage regulator tube D8 respectively, a gate of the second switch tube Q5 is connected to a second protection circuit 50, a source of the second switch tube Q5 is connected with a gate of a secondary synchronous rectifier tube Q4 through a sixth resistor R6, and the other end of the driving winding is connected with the other end of a seventh capacitor C7, the other end of the fifth resistor R5, the other end of the eighth capacitor C8 and an anode of a second voltage regulator tube D8 respectively.
Illustratively, the driving winding is derived from a flyback transformer T1, and a secondary side synchronous rectifier Q4 is directly driven by a low dropout linear regulator (LDO) composed of a second voltage regulator D8 and a second switching tube Q5. When the flyback transformer T1 is phase-changed due to the fact that the primary side switch tube Q1 is turned off, the driving winding has forward driving voltage, the second switch tube Q5 transmits the forward driving voltage to the secondary side synchronous rectifier tube Q4, Zero Voltage (ZVS) turning-on of the secondary side synchronous rectifier tube Q4 is achieved, and switching loss of the secondary side synchronous rectifier tube Q4 is reduced.
In the present embodiment, the second protection circuit 50 includes an operational amplifier IC1, a seventh diode D9; the positive input terminal of the operational amplifier IC1 is connected to the first protection circuit 30, the negative input terminal of the operational amplifier IC1 is connected to the reference signal terminal, the output terminal of the operational amplifier IC1 is connected to the cathode of the seventh diode D9, and the anode of the seventh diode D9 is connected to the self-driving control circuit 40.
Illustratively, after the sampling signal is obtained through the RC discharge line, the sampling signal is compared with the reference signal (REF) by the operational amplifier IC1, and the driving control signal (Vsec control) is output according to the comparison result and transmitted to the self-driving control line 40. When the switching power supply is turned off or the output of the driving signal (PWM) is stopped due to protection, the voltage of the fifth capacitor C5 in the RC discharge line gradually decreases, and if the power supply of the fifth capacitor C5 is lower than the reference voltage, the operational amplifier IC1 outputs a low level. When the driving control signal (Vsec control) is at a high level, the self-driving control line 40 can transmit the second secondary synchronous rectifier driving signal to the flyback secondary line 20, and when the driving control signal (Vsec control) is at a low level, the self-driving control line 40 cannot transmit the second secondary synchronous rectifier driving signal to the flyback secondary line 20, so that the transmission of the driving control signal (Vsec control) is cut off when the switching power supply is turned off or the driving signal is stopped to be output due to protection, the current backward flow is reduced, the switching power supply is protected, and the service life of the switching power supply is prolonged.
In the embodiment, the operational amplifier IC1 which is not easily interfered by the external environment is used as the core device, which is beneficial to improving the adaptability to the environment.
The second embodiment provides a device for realizing self-driving of an active clamp flyback topology switching power supply, which includes a control circuit for realizing self-driving of the active clamp flyback topology switching power supply according to the first embodiment, and can achieve the same beneficial effects.
In summary, the embodiments of the present invention have the following beneficial effects:
the flyback primary side line 10 on the primary side of a flyback transformer T1 is connected with a flyback secondary side line 20 on the secondary side of a flyback transformer T1 through a first protection line 30, the first protection line 30 is connected with a self-driving control line 40 coupled with the flyback transformer T1 through a second protection line 50, the self-driving control line 40 is connected with the flyback secondary side line 20, the flyback primary side line 10 transmits a primary side power switch tube driving signal (PWM1) to the first protection line 30, the first protection line 30 generates a first secondary side synchronous rectifier tube driving signal according to the primary side power switch tube driving signal (PWM1), the first secondary side synchronous rectifier tube driving signal is transmitted to the flyback secondary side line 20, the flyback secondary side line 20 turns off a secondary side synchronous rectifier tube Q4 according to the first secondary side synchronous rectifier tube driving signal, and meanwhile the second protection line 50 generates a driving control signal (Vscontrol) according to the comparison result of a sampling signal and a reference signal obtained when a switching power supply stops working ) The driving control signal (Vsec control) is transmitted to the self-driving control line 40, the self-driving control line 40 generates a second secondary synchronous rectifier driving signal when the flyback transformer T1 changes phase, and transmits the second secondary synchronous rectifier driving signal to the flyback secondary line 20 when the driving control signal (Vsec control) is a high level signal, and the flyback secondary line 20 turns on the secondary synchronous rectifier Q4 according to the second secondary synchronous rectifier driving signal, so that the secondary synchronous rectifier Q4 can be adaptively controlled to be turned on or off, the switching loss of the secondary synchronous rectifier Q4 is reduced, and the conversion efficiency is improved and the active clamp flyback topology switching power supply is protected.
While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention.

Claims (8)

1. A control circuit for realizing self-driving of an active clamp flyback topological switch power supply is characterized by comprising a flyback primary side circuit, a flyback secondary side circuit, a self-driving control circuit, a first protection circuit and a second protection circuit; the flyback transformer comprises a flyback transformer, a flyback primary side line, a flyback secondary side line, a self-driven control line, a first protection line, a second protection line and a self-driven control line, wherein the flyback primary side line is connected with a primary side of the flyback transformer, the flyback secondary side line is connected with a secondary side of the flyback transformer, the self-driven control line is coupled with the flyback transformer, the flyback primary side line is connected with the flyback secondary side line through the first protection line, the first protection line is connected with the self-driven control line through the second protection line, and the self-driven control line is connected with the flyback secondary side line;
the flyback primary side circuit comprises a flyback transformer primary side winding, a primary side switching tube, a primary side power switching tube driving circuit, a first capacitor and a second capacitor; one end of a primary winding of the flyback transformer is connected with a voltage input end of the switching power supply, one end of the primary winding of the flyback transformer is further connected with the other end of the primary winding of the flyback transformer through the first capacitor, the other end of the primary winding of the flyback transformer is connected with a drain electrode of the primary power switching tube through the second capacitor, a grid electrode of the primary power switching tube is connected with a driving signal end of the primary power switching tube through a driving circuit of the primary power switching tube, the other end of the primary winding of the flyback transformer is further connected with a drain electrode of the primary switching tube, the grid electrode of the primary switching tube is connected with the driving signal end of the primary switching tube, and the other end of the primary winding of the flyback transformer, a source electrode of the primary power switching tube and a source electrode of the primary switching tube are all grounded;
the flyback primary circuit is used for transmitting a primary power switching tube driving signal to the first protection circuit;
the first protection circuit is used for generating a first secondary synchronous rectifier tube driving signal according to the primary power switching tube driving signal and transmitting the first secondary synchronous rectifier tube driving signal to the flyback secondary circuit;
the flyback secondary line is used for switching off a secondary synchronous rectifier tube according to the driving signal of the first secondary synchronous rectifier tube;
the second protection circuit is used for generating a driving control signal according to a comparison result of the sampling signal and the reference signal and transmitting the driving control signal to the self-driving control circuit; when the switching power supply stops working, the driving control signal is at a low level;
the self-driving control circuit is used for generating a second secondary synchronous rectifier tube driving signal when the flyback transformer changes the phase and transmitting the second secondary synchronous rectifier tube driving signal to the flyback secondary circuit when the driving control signal is a high-level signal;
and the flyback secondary circuit is also used for switching on the secondary synchronous rectifying tube according to the driving signal of the second secondary synchronous rectifying tube.
2. The self-driven control circuit of the active-clamp flyback topology switching power supply of claim 1, wherein the driving line of the primary side power switch tube is composed of a third capacitor, a first resistor and a first diode;
the grid electrode of the primary side power switch tube is respectively connected with one end of the third capacitor, one end of the first resistor and the anode of the first diode, the other end of the third capacitor is connected with the driving signal end of the primary side power switch tube, and the other end of the first resistor and the cathode of the first diode are both grounded.
3. The control circuit for realizing self-driving of the active-clamp flyback topology switching power supply according to claim 1, wherein the first protection circuit comprises a fourth capacitor, a second resistor, a second diode, a third diode, a transformer, a first switch tube, a fourth diode and an RC discharge circuit;
one end of the fourth capacitor is connected with a driving signal end of the primary power switch tube, the other end of the fourth capacitor is respectively connected with one end of the second resistor and an anode of the second diode, the other end of the second resistor, a cathode of the second diode and a cathode of the third diode are respectively connected with one end of a primary winding of the transformer, the other end of the primary winding of the transformer and an anode of the third diode are both connected with the ground of the flyback primary circuit, one end of a secondary winding of the transformer is respectively connected with a grid electrode of the first switch tube and an anode of the fourth diode, a drain electrode of the first switch tube is connected with a grid electrode of the secondary synchronous rectifier tube, the other end of the secondary winding of the transformer and a source electrode of the first switch tube are both grounded, and a cathode of the fourth diode is grounded through the RC discharge circuit, the RC discharge line is connected with the second protection line.
4. The control circuit for realizing self-driving of the active-clamp flyback topology switching power supply according to claim 3, wherein the RC discharge line is composed of a first voltage regulator tube, a fifth capacitor and a third resistor;
the cathode of the first voltage-stabilizing tube, one end of the fifth capacitor and one end of the third resistor are respectively connected with the cathode of the fourth diode, and the anode of the first voltage-stabilizing tube, the other end of the fifth capacitor and the other end of the third resistor are all grounded.
5. The control circuit for realizing self-driving of the active-clamp flyback topology switching power supply according to claim 1, wherein the flyback secondary line comprises a flyback transformer secondary winding, the secondary synchronous rectifier tube and a sixth capacitor;
the one end of the flyback transformer secondary winding with switching power supply's voltage output end is connected, the one end of the flyback transformer secondary winding is passed through sixth electric capacity with the secondary synchronous rectifier tube with the other end of the flyback transformer secondary winding is connected, the other end of the flyback transformer secondary winding with the drain electrode of the secondary synchronous rectifier tube is connected, the grid of the secondary synchronous rectifier tube inserts respectively first protection circuit with from the drive control circuit, the source electrode ground of the secondary synchronous rectifier tube.
6. The control circuit for realizing self-driving of the active clamp flyback topology switching power supply of claim 1, wherein the self-driving control circuit comprises a driving winding coupled with the flyback transformer, a fifth diode, a sixth diode, a second switching tube, a seventh capacitor, an eighth capacitor, a fourth resistor, a fifth resistor, a second voltage regulator tube and a sixth resistor;
one end of the driving winding is respectively connected with the anodes of the fifth diode and the sixth diode, the cathode of the fifth diode is connected with the drain of the second switching tube, the cathode of the sixth diode is respectively connected with one end of the seventh capacitor, one end of the fourth resistor and one end of the fifth resistor, the other end of the fourth resistor is respectively connected with the grid electrode of the second switch tube, one end of the eighth capacitor and the cathode of the second voltage-regulator tube, the grid electrode of the second switch tube is connected with the second protection circuit, the source electrode of the second switch tube is connected with the grid electrode of the secondary side synchronous rectifying tube through the sixth resistor, the other end of the driving winding is connected with the other end of the seventh capacitor, the other end of the fifth resistor, the other end of the eighth capacitor and the anode of the second voltage regulator tube respectively.
7. The active-clamp flyback topology switching power supply self-driven control circuit of claim 1, wherein the second protection circuit comprises an operational amplifier, a seventh diode;
the positive input end of the operational amplifier is connected to the first protection circuit, the negative input end of the operational amplifier is connected to the reference signal end, the output end of the operational amplifier is connected to the cathode of the seventh diode, and the anode of the seventh diode is connected to the self-driven control circuit.
8. An apparatus for realizing self-driving of an active clamp flyback topology switching power supply, which is characterized by comprising a control circuit for realizing self-driving of the active clamp flyback topology switching power supply according to any one of claims 1 to 7.
CN202111029367.2A 2021-09-02 2021-09-02 Control circuit and equipment for realizing self-driving of active clamping flyback topology switching power supply Active CN113922673B (en)

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Citations (1)

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CN104506044A (en) * 2015-01-16 2015-04-08 深圳威迈斯电源有限公司 Synchronization rectifier driving circuit of convertor

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DE29901322U1 (en) * 1999-01-28 1999-07-08 Melcher Ag Voltage converter
CN100525044C (en) * 2005-11-28 2009-08-05 伊博电源（杭州）有限公司 Self driving circuit for three winding reverse exciting converter synchronous rectifier
JP2009268325A (en) * 2008-04-30 2009-11-12 Noritz Corp Fly back converter
US8067973B2 (en) * 2010-02-01 2011-11-29 Monolithic Power Systems, Inc. Driver for a flyback converter using a transconductance amplifier and a comparator

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Publication number Priority date Publication date Assignee Title
CN104506044A (en) * 2015-01-16 2015-04-08 深圳威迈斯电源有限公司 Synchronization rectifier driving circuit of convertor

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