CN111865088B - Control circuit for synchronous rectification - Google Patents

Control circuit for synchronous rectification Download PDF

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CN111865088B
CN111865088B CN202010655302.8A CN202010655302A CN111865088B CN 111865088 B CN111865088 B CN 111865088B CN 202010655302 A CN202010655302 A CN 202010655302A CN 111865088 B CN111865088 B CN 111865088B
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circuit
signal
power supply
comparator
adjusting
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CN111865088A (en
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尹健
罗阳
李海松
易扬波
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Wuxi Chipown Micro Electronics Ltd
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Wuxi Chipown Micro Electronics 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
    • H02M3/33569—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
    • H02M3/33576—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements having at least one active switching element at the secondary side of an isolation transformer
    • H02M3/33592—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements having at least one active switching element at the secondary side of an isolation transformer having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer
    • 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
    • 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
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
    • H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
    • H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/21—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/217—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • 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)
  • Dc-Dc Converters (AREA)

Abstract

The invention discloses a control circuit for synchronous rectification, which is applied to a flyback switching power supply system and comprises a power sub-circuit and a control sub-circuit which are packaged in the same frame and are mutually connected, wherein the power sub-circuit comprises a sampling MOS (metal oxide semiconductor) tube and a power supply MOS tube which are integrated on the same silicon chip and are mutually connected, and the control sub-circuit comprises a self-adaptive adjusting and turning-off circuit, a starting comparator, an anti-misoperation starting circuit, a driving circuit and a power supply comparator. In the circuit structure of the invention, the control sub-circuit and the power sub-circuit are separated on different silicon chips and are sealed in a package, and the whole control circuit does not contain a high voltage resistant device, so that the whole working reliability of the circuit is improved, and the function expansibility of the controller is further improved.

Description

Control circuit for synchronous rectification
Technical Field
The invention relates to a control circuit, in particular to a control circuit which can be applied to a flyback switching power supply system and is used for synchronous rectification, and belongs to the technical field of switching power supplies.
Background
The switching power supply system is used as a core component of the modern electric energy conversion technology and a structural foundation of various electrical mechanisms and devices, and is used in various fields such as electric power, communication, traffic, industrial control and the like. The flyback switching power supply system has the advantages of simple circuit structure, isolated input and output voltages, low cost, small size and the like, and is widely applied.
However, when the flyback switching power supply system is applied to a scene with a large output current, the defects of large on-state loss, large reverse recovery loss and the like of the secondary rectifier diode in the conventional structure are further highlighted, so that the efficiency of the whole flyback switching power supply system is affected. In order to solve the problem, a switching MOS transistor with extremely low on-resistance is usually adopted in the prior art to replace a rectifying diode as a rectifier, and this synchronous rectification technology can significantly improve the conversion efficiency of the entire flyback switching power supply system.
The circuit structure of the existing control circuit for synchronous rectification is shown in fig. 1, a high-voltage-withstanding MOS transistor is generally used as a sampling MOS transistor N2 in the circuit, and the sampling MOS transistor N2 detects a part of a switch MOS transistor N1 where the drain-source voltage difference is lower than the VCC voltage, so as to obtain a sampling signal Vsense. In order to realize the normal operation of the control circuit in the continuous conduction mode, a turn-on comparator 101, a regulation comparator 102 and a turn-off comparator 103 are generally arranged in the circuit. The turn-on comparator 101 compares the sampling signal Vsense with a first threshold V1 to generate a turn-on signal Vsr _ on; the adjusting comparator 102 compares the sampled signal Vsense with a second threshold value V2 to generate an adjusting signal Vsr _ reg; the turn-off comparator 103 compares the sampled signal Vsense with a third threshold value V3 to generate a turn-off signal Vsr _ off. The driving circuit 105 in the circuit receives the turn-on signal Vsr _ on, the regulation signal Vsr _ reg and the turn-off signal Vsr _ off, and generates a driving signal Vsrg to control the switch of the switching MOS transistor N1. In addition to the above structure, the conventional control circuit is generally provided with an anti-false-start circuit 104, which directly obtains the drain-source voltage difference of the switching MOS transistor N1 through the SW pin to generate a start-up enable signal MOS _ ON _ EN and output the signal to the driving circuit 105.
Although the above control circuit in the prior art can bring some improvement to the conversion efficiency of the whole switching power supply system, it still has the following problems:
1. in the existing structure, a sampling MOS tube N2 is integrated on a silicon chip of a control circuit, and the MOS tube and a protection structure thereof occupy a large part of available area on the silicon chip; in the subsequent use process, negative pressure needs to be introduced into the sampling MOS tube N2, so that a high isolation requirement is provided for a structure separating the sampling MOS tube N2 from an internal circuit, and if the isolation effect of the sampling MOS tube N2 from the internal circuit is poor, the reliability of the whole switching power supply system can be directly influenced.
2. When the control circuit works in a continuous conduction mode, serious direct connection between primary and secondary circuits in the circuit occurs, and at the moment, excessive secondary negative current can cause damage to the system. Therefore, in order to pull the driving signal Vsrg down quickly, in the conventional structure, the GATE is generally pulled down in advance by using the regulating comparator 102, which helps the turn-off comparator 103 to pull the driving signal Vsrg down quickly to turn off the switching MOS transistor N1. However, such an operation mode greatly increases the on-resistance of the switching MOS transistor N1 and increases the conduction loss.
3. In order to prevent the switching MOS transistor N1 from being turned on by mistake due to the zero crossing of the secondary oscillating waveform in the ringing phase, in the conventional structure, the signal of the SW pin is generally introduced and distinguished by the area difference between the high-plateau waveform and the ringing waveform after the secondary is turned off, so as to generate the turn-on enable signal. However, the signal of the SW pin is a high voltage signal, which not only increases the difficulty for subsequent processing, but also makes the area difference between the SW pin and the SW pin no longer obvious in a specific situation for a switching power supply system with variable output, thereby increasing the resolution difficulty and causing the risk of false turn-on to still exist.
4. In the existing structure, a power supply port VCC of the control circuit is directly connected with the output of the system to take power, and for some switching power supply systems with low output voltage, the output power supply can not be supported by the internal power supply of the control circuit in such a setting mode.
Because of the above-mentioned shortcomings in the prior art, how to provide a control circuit for synchronous rectification with high reliability, low conduction loss and high circuit applicability based on the prior art becomes a problem to be solved by those skilled in the art.
Disclosure of Invention
In view of the above-mentioned drawbacks of the prior art, an object of the present invention is to provide a control circuit for synchronous rectification, which can be applied in a flyback switching power supply system, and is described as follows.
A control circuit for synchronous rectification is applied to a flyback switching power supply system and comprises a power sub-circuit and a control sub-circuit which are packaged in the same frame and connected with each other, wherein the frame is respectively provided with a high-voltage port, a power supply port, a driving port and a grounding port;
the control sub-circuit comprises a self-adaptive adjusting and turning-off circuit, a starting comparator, an anti-misoperation circuit, a driving circuit and a power supply comparator;
the self-adaptive adjusting and switching-off circuit respectively receives the sampling signal from the power sub-circuit and the driving signal from the driving circuit, generates an adjusting signal and a switching-off signal and outputs the adjusting signal and the switching-off signal to the driving circuit;
the terminal B of the starting comparator receives the sampling signal from the power sub-circuit, generates a starting signal and outputs the starting signal to the driving circuit;
the anti-misoperation circuit receives the sampling signal from the power sub-circuit, generates a starting enabling signal and outputs the starting enabling signal to the driving circuit;
the driving circuit respectively receives the adjusting signal and the turn-off signal from the adaptive adjusting and turn-off circuit, the turn-on signal from the turn-on comparator and the turn-on enabling signal from the anti-misoperation circuit, generates driving signals and respectively outputs the driving signals to the adaptive adjusting and turn-off circuit, the driving port and the power sub-circuit.
Preferably, the power sub-circuit is composed of a sampling MOS transistor and a power supply MOS transistor which are integrated on the same silicon chip and are connected to each other.
Preferably, the gate of the sampling MOS transistor is electrically connected to the power supply port, the capacitor in the flyback switching power supply system, the terminal B of the power supply comparator, and the cathode of the diode in the control sub-circuit, respectively;
the drain electrode of the sampling MOS tube is electrically connected with the drain electrode of the power supply MOS tube and the high-voltage port respectively;
and the source electrode of the sampling MOS tube is electrically connected with the self-adaptive adjusting and turn-off circuit, the end B of the start comparator and the anti-misoperation circuit respectively.
Preferably, the grid of the power supply MOS transistor is electrically connected to the signal output end of the power supply comparator;
the drain electrode of the power supply MOS tube is electrically connected with the drain electrode of the sampling MOS tube and the high-voltage port respectively;
and the source electrode of the power supply MOS tube is electrically connected with the anode of the diode in the control sub-circuit.
Preferably, a signal input end of the adaptive adjusting and turning-off circuit is electrically connected with a source electrode of the sampling MOS transistor, a signal output end of the driving circuit, the driving port, and a gate electrode of a switching MOS transistor in the flyback switching power supply system, respectively, and a signal output end of the adaptive adjusting and turning-off circuit is electrically connected with a signal input end of the driving circuit;
the end B of the starting comparator is electrically connected with the source electrode of the sampling MOS tube and the signal input end of the self-adaptive adjusting and turning-off circuit respectively, and the signal output end of the starting comparator is electrically connected with the signal input end of the driving circuit;
the signal input end of the anti-misoperation circuit is electrically connected with the source electrode of the sampling MOS tube, and the signal output end of the anti-misoperation circuit is electrically connected with the signal input end of the driving circuit;
the signal input end of the driving circuit is respectively and electrically connected with the signal output end of the self-adaptive adjusting and turning-off circuit, the signal output end of the turn-on comparator and the signal output end of the false turn-on preventing circuit, and the signal output end of the driving circuit is respectively and electrically connected with the signal input end of the self-adaptive adjusting and turning-off circuit, the driving port and the grid electrode of the switch MOS tube in the flyback switch power supply system;
and the end B of the power supply comparator is electrically connected with the grid electrode of the sampling MOS tube and the cathode of the diode in the control sub-circuit respectively, and the signal output end of the power supply comparator is electrically connected with the grid electrode of the power supply MOS tube.
Preferably, the adaptive adjusting and turning-off circuit comprises a driving adjusting timing module, a threshold adaptive adjusting module and an adjusting and turning-off signal generating module;
the driving adjustment timing module receives a driving signal from the driving circuit, generates a time signal and outputs the time signal to the threshold value adaptive adjustment module;
the threshold self-adaptive adjusting module receives a time signal from the driving adjusting timing module, a sampling signal from the power sub-circuit and set time respectively, generates an adjusting threshold and a turn-off threshold and outputs the adjusting threshold and the turn-off threshold to the adjusting and turn-off signal generating module;
the adjusting and turning-off signal generating module receives the sampling signal from the power sub-circuit and the adjusting threshold and the turning-off threshold from the threshold self-adaptive adjusting module respectively, generates an adjusting signal and a turning-off signal and outputs the adjusting signal and the turning-off signal to the driving circuit.
Preferably, the anti-false-start circuit comprises a first comparator, a second comparator, a pulse generation module and an and gate;
the terminal B of the first comparator receives the sampling signal from the power sub-circuit, generates a first comparison signal and outputs the first comparison signal to the pulse generation module;
the terminal B of the second comparator receives the sampling signal from the power sub-circuit, generates a second comparison signal and outputs the second comparison signal to the AND gate;
the pulse generation module receives a first comparison signal from the first comparator, generates a pulse signal and outputs the pulse signal to the AND gate;
and the AND gate respectively receives the pulse signal from the pulse generation module and the second comparison signal from the second comparator, generates an enable signal and outputs the enable signal to the drive circuit.
The advantages of the invention are mainly embodied in the following aspects:
the control circuit for synchronous rectification provided by the invention does not contain a high-voltage-resistant device inside, avoids the isolation defect existing in the existing structure that the high-voltage-resistant device and an internal circuit are combined together, and obviously improves the reliability of the control circuit.
In the control circuit for synchronous rectification, the adjusting threshold value for controlling the sub-circuit to realize quick turn-off can be flexibly and automatically adjusted according to the use requirement, and the problem of increased conduction loss caused by adjusting the driving voltage in the existing structure is solved.
The control circuit for synchronous rectification is provided with the anti-false-start circuit with higher applicability, so that the recognition degree of high-platform waveforms and ringing waveforms is greatly improved, and the applicability of the whole circuit to a changeable system during working is enhanced.
In the synchronous rectification control circuit, the power supply source of the whole circuit does not only depend on system output, so that the normal support of the internal power supply of the control circuit is ensured, the circuit can be applied to some switching power supply systems with lower output voltage, and the application scene is expanded.
The following detailed description of the embodiments of the present invention is provided in connection with the accompanying drawings for the purpose of facilitating understanding and understanding of the technical solutions of the present invention.
Drawings
Fig. 1 is a schematic circuit diagram of a conventional control circuit with synchronous rectification function;
FIG. 2 is a schematic circuit diagram of a synchronous rectification control circuit according to the present invention;
FIG. 3 is a schematic diagram of a circuit structure of the adaptive tuning and shutdown circuit of the present invention;
FIG. 4 is a waveform diagram illustrating the operation of the adaptive tuning and shutdown circuit of the present invention;
FIG. 5 is a schematic circuit diagram of the false turn-on prevention circuit of the present invention;
fig. 6 is a waveform diagram illustrating the operation of the anti-false-start circuit according to the present invention.
Detailed Description
The invention discloses a control circuit which can be applied to a flyback switching power supply system and is used for synchronous rectification, and the control circuit is specifically as follows.
As shown in fig. 2, a control circuit for synchronous rectification is applied to a flyback switching power supply system, and includes a power sub-circuit 200A and a control sub-circuit 200B packaged in a same frame and connected to each other, where the frame is provided with a high-voltage port SW, a power supply port VCC, a driving port GATE, and a ground port GND, respectively.
The control sub-circuit 200B includes an adaptive adjusting and turning-off circuit 201, a turn-on comparator 202, an anti-false turn-on circuit 203, a driving circuit 204, and a power supply comparator 205.
The adaptive adjusting and turning-off circuit 201 receives the sampling signal VDET from the power sub-circuit 200A and the driving signal Vsrg from the driving circuit 204, respectively, generates an adjusting signal Vsr _ reg and a turning-off signal Vsr _ off, and outputs them to the driving circuit 204.
The terminal B of the turn-on comparator 202 receives the sampling signal VDET from the power sub-circuit 200A, generates a turn-on signal Vsr _ on, and outputs it to the driving circuit 204.
The anti-false-start circuit 203 receives the sampling signal VDET from the power sub-circuit 200A, generates a start-up enable signal MOS _ ON _ EN, and outputs the start-up enable signal MOS _ ON _ EN to the driving circuit 204.
The driving circuit 204 receives the adjusting signal Vsr _ reg and the turn-off signal Vsr _ off from the adaptive adjusting and turning-off circuit 201, the turn-ON signal Vsr _ ON from the turn-ON comparator 202, and the turn-ON enable signal MOS _ ON _ EN from the anti-false-turn-ON circuit 203, respectively, generates and outputs a driving signal Vsrg to the adaptive adjusting and turning-off circuit 201, the driving port GATE, and the power sub-circuit 200A, respectively.
The power sub-circuit 200A may be implemented by various high-voltage devices that need to be removed from the control sub-circuit 200B or added to implement further function expansion of the control circuit for synchronous rectification, and in an embodiment of the present invention, the power sub-circuit 200A is composed of a sampling MOS transistor N4 and a power supply MOS transistor N3 that are integrated on the same silicon chip and connected to each other.
The sampling MOS transistor N4 detects a voltage signal between the source and the drain of the switching MOS transistor N1 through the high-voltage port SW, and outputs a sampling signal VDET to the control sub-circuit 200B, and a series of control methods of the control circuit for synchronous rectification are executed based on the sampling signal VDET. The power supply MOS tube N3 supplies power to the power supply port VCC through the high-voltage port SW, and saves charges in a capacitor C1 in the flyback switching power supply system so as to maintain the normal work of the control circuit for synchronous rectification. The specific arrangement is as follows.
The gate of the sampling MOS transistor N4 is electrically connected to the power supply port VCC, the capacitor C1 in the flyback switching power supply system, the terminal B of the power supply comparator 205, and the cathode of the diode D1 in the control sub-circuit 200B, respectively.
The drain of the sampling MOS transistor N4 is electrically connected to the drain of the power supply MOS transistor N3 and the high voltage port SW, respectively.
The source of the sampling MOS transistor N4 is electrically connected to the adaptive adjustment and turn-off circuit 201, the B terminal of the start comparator 202, and the anti-false start circuit 203, and outputs a sampling signal VDET to the adaptive adjustment and turn-off circuit 201, the B terminal of the start comparator 202, and the anti-false start circuit 203.
The gate of the power supply MOS transistor N3 is electrically connected to the signal output terminal of the power supply comparator 205 and receives the power supply signal Vhv _ st from the power supply comparator 205.
The drain of the power supply MOS transistor N3 is electrically connected to the drain of the sampling MOS transistor N4 and the high voltage port SW, respectively.
The source of the power supply MOS transistor N3 is electrically connected to the anode of the diode D1 in the control sub-circuit 200B.
The signal input end of the adaptive adjusting and turning-off circuit 201 is electrically connected to the source of the sampling MOS transistor N4, the signal output end of the driving circuit 204, the driving port GATE, and the GATE of the switching MOS transistor N1 in the flyback switching power supply system, respectively, and the signal output end of the adaptive adjusting and turning-off circuit 201 is electrically connected to the signal input end of the driving circuit 204.
The end a of the on comparator 202 receives the fourth threshold V4, the end B of the on comparator 202 is electrically connected to the source of the sampling MOS transistor N4 and the signal input end of the adaptive adjusting and turning-off circuit 201, respectively, and the signal output end of the on comparator 202 is electrically connected to the signal input end of the driving circuit 204.
The signal input end of the anti-false-start circuit 203 is electrically connected with the source electrode of the sampling MOS tube N4, and the signal output end of the anti-false-start circuit 203 is electrically connected with the signal input end of the driving circuit 204.
The signal input end of the driving circuit 204 is electrically connected to the signal output end of the adaptive adjusting and turning-off circuit 201, the signal output end of the on comparator 202, and the signal output end of the false-start preventing circuit 203, respectively, and the signal output end of the driving circuit 204 is electrically connected to the signal input end of the adaptive adjusting and turning-off circuit 201, the driving port GATE, and the GATE of the switching MOS transistor N1 in the flyback switching power supply system, respectively.
The terminal a of the power supply comparator 205 receives the fifth threshold V5, the terminal B of the power supply comparator 205 is electrically connected to the gate of the sampling MOS transistor N4 and the cathode of the diode D1 in the control sub-circuit 200B, respectively, and the signal output terminal of the power supply comparator 205 is electrically connected to the gate of the power supply MOS transistor N3.
As shown in fig. 3, the adaptive tuning and shutdown circuit 201 includes a driving tuning timing module 201a, a threshold adaptive tuning module 201b, and a tuning and shutdown signal generating module 201 c.
The driving adjustment timing module 201a receives the driving signal Vsrg from the driving circuit 204, generates a time signal Treg, and outputs the time signal Treg to the threshold adaptive adjustment module 201 b.
The threshold adaptive adjusting module 201b receives the time signal Treg from the driving adjustment timing module 201a, the sampling signal VDET from the power sub-circuit 200A, and the set time Tset, respectively, generates an adjusting threshold Vth _ reg and a turn-off threshold Vth _ off, and outputs them to the adjusting and turn-off signal generating module 201 c.
The adjusting and turning-off signal generating module 201c receives the sampling signal VDET from the power sub-circuit 200A and the adjusting threshold Vth _ reg and the turning-off threshold Vth _ off from the threshold adaptive adjusting module 201b, respectively, generates an adjusting signal Vsr _ reg and a turning-off signal Vsr _ off, and outputs them to the driving circuit 204.
Fig. 4 is a waveform diagram of the operation of the adaptive tuning and shutdown circuit 201, and with reference to the drawing, the specific operation mechanism of the adaptive tuning and shutdown circuit 201 is as follows.
In the stage t 0-t 1, the driving adjustment timing module 201a times out a time signal Treg of the adjustment stage where the driving signal Vsrg is located in the period, compares the time signal Treg with the set time Tset, and increases an adjustment threshold Vth _ reg and a turn-off threshold Vth _ off of the next period when the time signal Treg is longer than the set time Tset;
in the stage t 2-t 3, the time signal Treg in the period is still longer than the set time Tset, and the adjustment threshold value Vth _ reg and the turn-off threshold value Vth _ off in the next period are continuously increased;
in the stage t 4-t 5, the time signal Treg of the period is shorter than the set time Tset, and the adjusting threshold Vth _ reg and the turn-off threshold Vth _ off of the next period are reduced;
in the period t 6-t 7, the time signal Treg of the period is equal to the set time Tset, and after adjustment of several periods, the adjustment threshold Vth _ reg and the turn-off threshold Vth _ off are in a proper size.
As shown in fig. 5, the anti-false-turn-on circuit 203 includes a first comparator 203a, a second comparator 203b, a pulse generating module 203c, and an and gate I1.
The terminal a of the first comparator 203a receives the sixth threshold V6, and the terminal B of the first comparator 203a receives the sampling signal VDET from the power sub-circuit 200A, generates the first comparison signal comp1, and outputs it to the pulse generation module 203 c.
The terminal a of the second comparator 203B receives the seventh threshold V7, and the terminal B of the second comparator 203B receives the sampling signal VDET from the power sub-circuit 200A, generates a second comparison signal comp2, and outputs the second comparison signal comp2 to the and gate I1.
The pulse generating module 203c receives the first comparison signal comp1 from the first comparator 203a, generates a pulse signal pulse and outputs the pulse signal pulse to the and gate I1.
The and gate I1 receives the pulse signal pulse from the pulse generating module 203c and the second comparison signal comp2 from the second comparator 203b, respectively, generates an ON enable signal MOS _ ON _ EN, and outputs the ON enable signal MOS _ ON _ EN to the driving circuit 204.
Fig. 6 is a waveform diagram of the operation of the anti-false-start circuit 203, and the specific operation mechanism of the anti-false-start circuit 203 is as follows with reference to the drawings.
At the stage t 0-t 1, when the first comparator 203a detects that the input sampling signal VDET is lower than the sixth threshold V6 and the first comparison signal comp1 is high, the pulse generation module 203c generates a pulse signal pulse from the first comparison signal comp1, and when the second comparator 203b detects that the input sampling signal VDET is lower than the seventh threshold V7 and the second comparison signal comp2 is high, the falling time of the sampling signal VDET is longer and the pulse signal pulse disappears until the second comparison signal comp2 is high and the enable signal MOS _ ON _ EN is not generated during the ringing phase;
at the stage t 2-t 3, corresponding to the stage when the high platform finishes descending, the descending time of the sampling signal VDET is short, and at this time, the pulse signal pulse is high, and the signal can wait until the second comparison signal comp2 appears high, so as to generate the turn-ON enable signal MOS _ ON _ EN, and the switch MOS transistor N1 has a turn-ON condition.
In summary, the control circuit for synchronous rectification according to the present invention has the following advantages and significant effects:
1. in the circuit structure of the invention, the control sub-circuit and the power sub-circuit are separated on different silicon chips and are sealed in a package, and the whole control sub-circuit does not contain a high voltage resistant device, so that the whole working reliability of the circuit is improved, and the function expansibility of the controller is further improved.
2. In the circuit structure of the invention, a self-adaptive adjusting circuit used for dealing with the change of the output load of the system under different working modes is arranged in the control sub-circuit, the self-adaptive adjusting circuit can automatically select an optimal adjusting threshold value, the output signal of a sampling tube integrated on the power sub-circuit is utilized to realize the rapid turn-off under the continuous conduction mode, and the increase of the conduction loss caused by adjusting the driving voltage is avoided.
3. In the circuit structure of the invention, the control sub-circuit is internally provided with an anti-false-start circuit which realizes the anti-false-start function by utilizing the output signal of the sampling tube integrated on the power sub-circuit without accessing the high-voltage signal of the sampling SW pin, thereby simplifying the circuit structure design, and simultaneously, the judgment accuracy of the anti-false-start circuit is obviously improved by taking the speed difference of the descending stages of the high-platform waveform and the ringing waveform as the differentiation basis.
4. In the circuit structure of the invention, the power supply tube integrated on the power sub-circuit is used for realizing the function of high-voltage power supply, and the power supply is not dependent on the output power supply of the system, so that the internal power supply of the power supply system is not influenced when the power supply system is applied to some switching power supply systems with lower output voltage.
In addition, the invention also provides reference for other related schemes in the same field, can be expanded and extended on the basis of the reference, is applied to design schemes of other control circuits in the same field, and has wide application prospect.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein, and any reference signs in the claims are not intended to be construed as limiting the claim concerned.
Finally, it should be understood that although the present description refers to embodiments, not every embodiment contains only a single technical solution, and such description is for clarity only, and those skilled in the art should integrate the description, and the technical solutions in the embodiments can be appropriately combined to form other embodiments understood by those skilled in the art.

Claims (3)

1. The utility model provides a control circuit for synchronous rectification, is applied to among the flyback switching power supply system which characterized in that: the power supply circuit comprises a power sub-circuit (200A) and a control sub-circuit (200B) which are packaged in the same frame and are mutually connected, wherein the frame is respectively provided with a high-voltage port (SW), a power supply port (VCC), a drive port (GATE) and a ground port (GND);
the control sub-circuit (200B) comprises a self-adaptive adjusting and turning-off circuit (201), a starting comparator (202), an anti-misoperation circuit (203), a driving circuit (204) and a power supply comparator (205);
the adaptive adjusting and turning-off circuit (201) receives a sampling signal from the power sub-circuit (200A) and a driving signal from the driving circuit (204) respectively, generates an adjusting signal and a turning-off signal and outputs the adjusting signal and the turning-off signal to the driving circuit (204);
the terminal B of the starting comparator (202) receives a sampling signal from the power sub-circuit (200A), generates a starting signal and outputs the starting signal to the driving circuit (204);
the anti-misoperation circuit (203) receives a sampling signal from the power sub-circuit (200A), generates a start-up enabling signal and outputs the start-up enabling signal to the drive circuit (204);
the driving circuit (204) receives the adjusting signal and the turn-off signal from the adaptive adjusting and turning-off circuit (201), the turn-on signal from the turn-on comparator (202) and the turn-on enable signal from the anti-false turn-on circuit (203), generates driving signals and outputs the driving signals to the adaptive adjusting and turning-off circuit (201), the driving port (GATE) and the power sub-circuit (200A) respectively;
the power sub-circuit (200A) is composed of a sampling MOS tube (N4) and a power supply MOS tube (N3) which are integrated on the same silicon chip and are mutually connected;
the grid electrode of the sampling MOS tube (N4) is respectively and electrically connected with the power supply port (VCC), the capacitor (C1) in the flyback switching power supply system, the terminal B of the power supply comparator (205) and the cathode of the diode (D1) in the control sub-circuit (200B);
the drain electrode of the sampling MOS tube (N4) is respectively and electrically connected with the drain electrode of the power supply MOS tube (N3) and the high-voltage port (SW);
the source electrode of the sampling MOS tube (N4) is respectively and electrically connected with the self-adaptive adjusting and turning-off circuit (201), the end B of the turn-on comparator (202) and the anti-misoperation circuit (203);
the grid electrode of the power supply MOS tube (N3) is electrically connected with the signal output end of the power supply comparator (205);
the drain electrode of the power supply MOS tube (N3) is respectively and electrically connected with the drain electrode of the sampling MOS tube (N4) and the high-voltage port (SW);
the source electrode of the power supply MOS tube (N3) is electrically connected with the anode electrode of a diode (D1) in the control sub-circuit (200B);
the signal input end of the adaptive adjusting and turning-off circuit (201) is respectively electrically connected with the source electrode of the sampling MOS tube (N4), the signal output end of the driving circuit (204), the driving port (GATE) and the grid electrode of the switching MOS tube (N1) in the flyback switching power supply system, and the signal output end of the adaptive adjusting and turning-off circuit (201) is electrically connected with the signal input end of the driving circuit (204);
the terminal B of the turn-on comparator (202) is electrically connected with the source of the sampling MOS tube (N4) and the signal input terminal of the adaptive adjusting and turning-off circuit (201), and the signal output terminal of the turn-on comparator (202) is electrically connected with the signal input terminal of the driving circuit (204);
the signal input end of the anti-misoperation circuit (203) is electrically connected with the source electrode of the sampling MOS tube (N4), and the signal output end of the anti-misoperation circuit (203) is electrically connected with the signal input end of the drive circuit (204);
the signal input end of the driving circuit (204) is respectively and electrically connected with the signal output end of the adaptive adjusting and turning-off circuit (201), the signal output end of the turn-on comparator (202) and the signal output end of the anti-misoperation opening circuit (203), and the signal output end of the driving circuit (204) is respectively and electrically connected with the signal input end of the adaptive adjusting and turning-off circuit (201), the driving port (GATE) and the grid electrode of the switching MOS (N1) in the flyback switching power supply system;
the terminal B of the power supply comparator (205) is electrically connected with the grid of the sampling MOS tube (N4) and the cathode of the diode (D1) in the control sub-circuit (200B), and the signal output end of the power supply comparator (205) is electrically connected with the grid of the power supply MOS tube (N3).
2. A control circuit for synchronous rectification as claimed in claim 1, wherein: the adaptive adjusting and turning-off circuit (201) comprises a driving adjusting timing module (201 a), a threshold adaptive adjusting module (201 b) and an adjusting and turning-off signal generating module (201 c);
the driving adjustment timing module (201 a) receives a driving signal from the driving circuit (204), generates a time signal and outputs the time signal to the threshold value adaptive adjustment module (201 b);
the threshold value self-adaptive adjusting module (201 b) receives a time signal from the driving adjusting timing module (201 a), a sampling signal from the power sub-circuit (200A) and set time respectively, generates an adjusting threshold value and a turn-off threshold value and outputs the adjusting threshold value and the turn-off threshold value to the adjusting and turn-off signal generating module (201 c);
the adjusting and turning-off signal generating module (201 c) receives the sampling signal from the power sub-circuit (200A) and the adjusting threshold and the turning-off threshold from the threshold adaptive adjusting module (201 b), respectively, generates an adjusting signal and a turning-off signal, and outputs the adjusting signal and the turning-off signal to the driving circuit (204).
3. A control circuit for synchronous rectification as claimed in claim 1, wherein: the anti-misoperation circuit (203) comprises a first comparator (203 a), a second comparator (203 b), a pulse generation module (203 c) and an AND gate (I1);
the terminal B of the first comparator (203 a) receives the sampling signal from the power sub-circuit (200A), generates a first comparison signal and outputs the first comparison signal to the pulse generating module (203 c);
the terminal B of the second comparator (203B) receives the sampling signal from the power sub-circuit (200A), generates a second comparison signal and outputs the second comparison signal to the AND gate (I1);
the pulse generating module (203 c) receives the first comparison signal from the first comparator (203 a), generates a pulse signal and outputs the pulse signal to the and gate (I1);
the and gate (I1) receives the pulse signal from the pulse generation module (203 c) and the second comparison signal from the second comparator (203 b), generates an enable signal, and outputs the enable signal to the driving circuit (204).
CN202010655302.8A 2020-07-09 2020-07-09 Control circuit for synchronous rectification Active CN111865088B (en)

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