CN114583923A - Control circuit and method thereof, chip, switching power supply and electronic device - Google Patents

Control circuit and method thereof, chip, switching power supply and electronic device Download PDF

Info

Publication number
CN114583923A
CN114583923A CN202210114362.8A CN202210114362A CN114583923A CN 114583923 A CN114583923 A CN 114583923A CN 202210114362 A CN202210114362 A CN 202210114362A CN 114583923 A CN114583923 A CN 114583923A
Authority
CN
China
Prior art keywords
voltage
threshold
synchronous rectifier
threshold comparator
module
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
CN202210114362.8A
Other languages
Chinese (zh)
Inventor
白文利
宋利军
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
SHENZHEN WINSEMI MICROELECTRONICS CO Ltd
Original Assignee
SHENZHEN WINSEMI MICROELECTRONICS CO Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by SHENZHEN WINSEMI MICROELECTRONICS CO Ltd filed Critical SHENZHEN WINSEMI MICROELECTRONICS CO Ltd
Priority to CN202210114362.8A priority Critical patent/CN114583923A/en
Publication of CN114583923A publication Critical patent/CN114583923A/en
Pending legal-status Critical Current

Links

Images

Classifications

    • 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
    • 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
    • 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
    • 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
    • H02M7/2176—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 comprising a passive stage to generate a rectified sinusoidal voltage and a controlled switching element in series between such stage and the output
    • 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, a method, a chip, a switching power supply and an electronic device of a synchronous rectifier tube, wherein the control circuit comprises: the device comprises a threshold comparator module and a driving voltage control module; the threshold comparator module is used for detecting drain-source voltage between a drain electrode and a source electrode of the synchronous rectifier tube, and the output end of the threshold comparator module is electrically connected with the driving voltage control module; when the threshold comparator module detects that the drain-source voltage is greater than or equal to a set third threshold voltage, the threshold comparator module outputs a third signal to the driving voltage control module, the driving voltage control module regulates the gate-source voltage, the gate-source voltage is clamped and pulled down to the clamping voltage, when the drain-source voltage rises to the cut-off threshold voltage, the threshold comparator module outputs a fourth signal to the driving voltage control module, and the driving voltage control module pulls down the gate-source voltage to turn off the synchronous rectifier tube. The invention can realize the quick turn-off of the synchronous rectifier tube.

Description

Control circuit and method thereof, chip, switching power supply and electronic device
Technical Field
The invention relates to the field of synchronous rectification, in particular to a control circuit and a method thereof, a chip, a switching power supply and an electronic device.
Background
In order to improve the efficiency of the switching circuit, it has been a trend to replace the freewheeling diode with a synchronous rectification MOS transistor, especially in the application of the switching power supply with an output current larger than 2A.
Even if the synchronous rectification circuit is provided, in order to achieve the highest efficiency, the conduction time of the synchronous rectification MOS tube is required to be as long as possible, and the conduction time of the body diode of the synchronous rectification MOS tube is required to be as short as possible, so that the loss generated by the body diode can be reduced.
Taking a flyback converter as an example, the operating waveforms shown in fig. 1 are shown. When the primary side main power tube Is turned off, the current Is of the secondary side winding starts to follow current through a body diode of the synchronous rectification tube, and after the turn-on delay time Td, the synchronous rectification MOS tube Is completely turned on;
when the output current is reduced to a certain value, the source-drain voltage V of the synchronous rectification MOS tubeDSWhen the voltage Is greater than the threshold voltage Vthoff, the synchronous rectification MOS tube Is turned off in advance, the current Is of the secondary winding starts to flow through the body diode of the synchronous rectification MOS tube again, and the time Is Tdiode. The body diode has high conduction voltage drop, so the conduction loss is large and the efficiency is low.
In the method, if the cut-off threshold voltage Vthoff is set to be very small, the conduction time of a body diode of the synchronous rectification MOS tube can be reduced theoretically, but actually, because the synchronous rectification MOS tube driving circuit has turn-off delay and the tolerance of the cut-off threshold voltage Vthoff parameter is considered, the synchronous rectification MOS tube and the primary side main power MOS tube are simultaneously turned on.
Disclosure of Invention
The technical problem to be solved by the present invention is to provide a synchronous rectifier control circuit, a method thereof, a chip, a switching power supply, and an electronic device, so that the synchronous rectifier has as long as possible on-time and as fast as possible off-speed, and high efficiency and fast off-speed are achieved. The technical scheme is as follows:
in one aspect, the present invention provides a synchronous rectifier control circuit, including: the device comprises a threshold comparator module and a driving voltage control module;
the threshold comparator module is used for detecting drain-source voltage between a drain electrode and a source electrode of the synchronous rectifier tube, the output end of the threshold comparator module is electrically connected with the driving voltage control module, and the output end of the driving voltage control module is electrically connected with a grid electrode of the synchronous rectifier tube;
when the threshold comparator module detects that the drain-source voltage is greater than or equal to a set third threshold voltage, the threshold comparator module outputs a third signal to the driving voltage control module, the driving voltage control module regulates the gate-source voltage, the gate-source voltage is clamped and pulled down to the clamping voltage, when the drain-source voltage rises to a cut-off threshold voltage, the threshold comparator module outputs a fourth signal to the driving voltage control module, the driving voltage control module pulls down the gate-source voltage to turn off the synchronous rectifier tube, wherein the third threshold voltage is less than the cut-off threshold voltage, and the cut-off threshold voltage is less than 0.
Preferably, the driving voltage control module comprises a clamping circuit, the clamping circuit is electrically connected with the threshold comparator module, and the clamping circuit is further used for being electrically connected with a grid electrode of the synchronous rectifier tube; when the threshold comparator module detects that the drain-source voltage is greater than or equal to a set third threshold voltage, the threshold comparator module outputs a third signal to the clamping circuit, and the clamping circuit regulates and controls the gate-source voltage to be clamped and pulled down to the clamping voltage.
Preferably, the clamping circuit comprises a voltage stabilizing circuit and a switching tube which are connected in series, and when the threshold comparator module controls the switching tube to be conducted, the voltage stabilizing circuit pulls the gate-source voltage of the synchronous rectifying tube to the clamping voltage.
Preferably, the clamping circuit comprises a voltage follower, the non-inverting input end of the voltage follower is connected with a clamping voltage, the enable end of the voltage follower is electrically connected with the threshold comparator module, and when the threshold comparator module controls the voltage follower to work, the voltage follower pulls the gate-source voltage of the synchronous rectifier tube to the clamping voltage.
Preferably, the driving voltage control module further includes a first micro-voltage drop circuit, when the threshold comparator module detects that the drain-source voltage is greater than or equal to a second threshold voltage, the threshold comparator module controls the circuits electrically connected to the gates of the synchronous rectifiers to be both turned off and the first micro-voltage drop circuit to be turned on, and the first micro-voltage drop circuit is configured to release the voltage across the gate-source parasitic capacitance of the synchronous rectifiers, where the second threshold voltage is less than the third threshold voltage.
Preferably, the first micro voltage drop circuit comprises a first resistor, one end of the first resistor is used for being electrically connected with the gate of the synchronous rectifier tube, and the other end of the first resistor is grounded.
Preferably, the driving voltage control module further comprises an on/off control logic module, an upper driving switch and a lower driving switch; the input end of the on-off control logic module is electrically connected with the output end of the threshold comparator module, the control end of the upper driving switch is electrically connected with the output end of the on-off control logic module, one end of the upper driving switch is connected with a normal driving voltage, the other end of the upper driving switch is used for being electrically connected with a grid electrode of the synchronous rectifier tube, and the upper driving switch is switched on or off according to an output signal of the on-off control logic module; one end of the lower driving switch is used for being connected with a grid electrode of the synchronous rectifier tube, the other end of the lower driving switch is grounded, a control end of the lower driving switch is electrically connected with an output end of the threshold comparator module, the lower driving switch is switched on or switched off according to an output signal of the threshold comparator module, and the normal driving voltage is larger than the clamping voltage.
Preferably, when the threshold comparator module detects that the drain-source voltage is less than or equal to a set first threshold voltage, the threshold comparator module outputs a first signal to the turn-on/off control logic module, the turn-on/off control logic module controls the upper driving switch to be turned on so as to turn on/off the synchronous rectifier tube, when the threshold comparator module detects that the drain-source voltage is greater than or equal to a set second threshold voltage, the threshold comparator module outputs a second signal to the turn-on/off control logic module, and the turn-on/off control logic module controls the upper driving switch to be turned off/off; when the threshold comparator module detects that the drain-source voltage is greater than or equal to the set cut-off threshold voltage, the threshold comparator module outputs a fourth signal to the lower driving switch, the lower driving switch is turned on to pull the gate-source voltage of the synchronous rectifier tube to 0, wherein the clamping voltage is between 0 and the normal driving voltage, the first threshold voltage is less than the second threshold voltage, and the second threshold voltage is less than the third threshold voltage.
Preferably, the threshold comparator module includes a first threshold comparator, a non-inverting input terminal of the first threshold comparator is used for being electrically connected to a drain of the synchronous rectifier tube, an inverting input terminal of the first threshold comparator is connected to a first threshold voltage, and an output terminal of the first threshold comparator is electrically connected to the on-off control logic module; and/or the presence of a gas in the gas,
the threshold comparator module comprises a second threshold comparator, the non-inverting input end of the second threshold comparator is used for being electrically connected with the drain electrode of the synchronous rectifier tube, the inverting input end of the second threshold comparator is connected with a second threshold voltage, and the output end of the second threshold comparator is electrically connected with the on-off control logic module; and/or the presence of a gas in the gas,
the threshold comparator module comprises a third threshold comparator, the non-inverting input end of the third threshold comparator is used for being electrically connected with the drain electrode of the synchronous rectifier tube, the inverting input end of the third threshold comparator is connected with a third threshold voltage, and the output end of the third threshold comparator is electrically connected with the driving voltage control module; the output end of the third threshold comparator is also electrically connected with the on-off control logic module, when the third threshold comparator detects that the drain-source voltage is greater than or equal to a set third threshold voltage, the third threshold comparator outputs a third signal to the on-off control logic module, and the on-off control logic module keeps the upper drive switch in a disconnected state; and/or the presence of a gas in the gas,
the threshold comparator module comprises a fourth threshold comparator, wherein the non-inverting input end of the fourth threshold comparator is used for being electrically connected with the drain electrode of the synchronous rectifier tube, the inverting input end of the fourth threshold comparator is connected with a cut-off threshold voltage, and the output end of the fourth threshold comparator is electrically connected with the lower driving switch.
In another aspect, the present invention provides a method for controlling a synchronous rectifier, comprising the steps of:
s1: detecting the drain-source voltage between the drain and the source of the synchronous rectifier tube;
s2: when the drain-source voltage is greater than or equal to a set third threshold voltage, the regulation gate-source voltage is clamped and pulled down to a clamping voltage;
s3: when the drain-source voltage rises to a cut-off threshold voltage, the grid-source voltage is pulled down to turn off the synchronous rectifier tube, wherein the third threshold voltage is smaller than the cut-off threshold voltage, and the cut-off threshold voltage is smaller than 0.
Further, between step S1 and step S2, there is further included the step of:
when the drain-source voltage is greater than or equal to a set second threshold voltage, the circuits electrically connected with the grid electrode of the synchronous rectifier tube are controlled to be all turned off, and the first micro-voltage reduction circuit is controlled to be turned on so as to release the voltage on the grid-source parasitic capacitor of the synchronous rectifier tube, wherein the second threshold voltage is less than the third threshold voltage.
In another aspect, the present invention provides a control chip for a synchronous rectifier, which includes the control circuit for the synchronous rectifier.
In another aspect, the present invention provides a switching power supply, which includes a synchronous rectifier, and further includes a control circuit of the synchronous rectifier or a chip of the synchronous rectifier, wherein a source of the synchronous rectifier is grounded, a gate of the synchronous rectifier is electrically connected to the driving voltage control module, and a drain of the synchronous rectifier is electrically connected to the threshold comparator module.
In another aspect, the present invention provides an electronic device, which includes the above synchronous rectifier control circuit, or includes the above chip, or includes the above switching power supply.
The invention has the beneficial effects that: by utilizing the scheme of the invention, a threshold comparator module detects the drain-source voltage change of a synchronous rectifier tube, when the threshold comparator module detects that the drain-source voltage is greater than or equal to a set third threshold voltage, the threshold comparator module outputs a third signal to a driving voltage control module, the driving voltage control module regulates and controls the gate-source voltage, the gate-source voltage is clamped and pulled down to the clamping voltage, when the drain-source voltage rises to a cut-off threshold voltage, the threshold comparator module outputs a fourth signal to the driving voltage control module, and the driving voltage control module pulls down the gate-source voltage to turn off the synchronous rectifier tube, wherein the third threshold voltage is less than the cut-off threshold voltage, and the cut-off threshold voltage is less than 0; thereby drive voltage control module adjusts the grid source voltage of synchronous rectifier tube according to threshold value comparator signal of telecommunication, realizes turn-off the synchronous rectifier tube fast, and this scheme easily realizes, has the effect of turn-off the synchronous rectifier tube fast simultaneously.
Drawings
FIG. 1 is a waveform of a synchronous rectifier control circuit without driving voltage regulation in the prior art;
FIG. 2 is a functional block diagram of a synchronous rectifier control circuit according to an embodiment of the present invention;
FIG. 3 illustrates the operating waveforms for driving voltage regulation according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a clamp circuit according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of a clamp circuit according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of a control method according to an embodiment of the present invention;
FIG. 7 is a schematic diagram of an application circuit of a control chip of a synchronous rectifier control circuit according to an embodiment of the present invention;
fig. 8 is a schematic diagram of an application circuit of a control chip of a synchronous rectifier control circuit according to an embodiment of the invention.
Detailed Description
In order to facilitate an understanding of the invention, the invention is described in more detail below with reference to the accompanying drawings and specific examples. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
It is to be noted that, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
Example one
In one aspect, as shown in fig. 2 and 3, the present invention provides a synchronous rectifier control circuit, where the synchronous rectifier control circuit is used to control a synchronous rectifier Q1, and the synchronous rectifier control circuit of this embodiment is applied to a flyback converter. The synchronous rectifier control circuit includes: a threshold comparator module 1 and a driving voltage control module 2;
in this embodiment, the input terminal of the threshold comparator module 1 is used to electrically connect to the Drain of the synchronous rectifier Q1, the output terminal of the driving voltage control module 2 is used to electrically connect to the GATE of the synchronous rectifier Q1, the ground terminal Vs of the driving voltage control module 2 is also electrically connected to the Source of the synchronous rectifier Q1, the Source of the synchronous rectifier Q1 is grounded, and thus the voltage VD at the Drain of the synchronous rectifier Q1 is the Drain-Source voltage V of the synchronous rectifier Q1DS。
After the primary side main power tube is turned off, the threshold comparator module 1 is used for comparing the drain-source voltage V of the synchronous rectifier tube Q1DSVariation being detected, drain-source voltage VDSUndergoes the change of descending first and ascending second, and is at the drain-source voltage VDSIn the latter phase of the rise phase, the threshold comparator module 1 detects the drain-source voltage VDSWhen the threshold voltage is higher than the set third threshold voltage Vthcp, the threshold comparator module 1 outputs a third signal to the driving voltage control module 2, and the driving voltage control module 2 regulates and controls the gate-source voltage VGSWill gate source voltage VGSClamp pull down to clamp voltage Vclamp and hold it constant for clamp time Tcp, drain-source voltage VDSContinues to rise when the drain-source voltage VDSWhen the threshold voltage rises to a cut-off threshold voltage Vthoff close to zero voltage, the threshold comparator module 1 outputs a fourth signal to the driving voltage control module 2, and the driving voltage control module 2 pulls down a gate-source voltage VGSSo that the synchronous rectifier Q1 is turned off, wherein the third threshold voltage Vthcp is smaller than the cut-off threshold voltage Vthoff, which is smaller than 0.
It should be noted that fig. 1 and 3 both show the drain-source voltage V after the primary side main power tube is turned offDSDecreases from a positive value to a negative value and the drain-source voltage VDSThe subsequent rise is also from negative to positive, so that the drain-source voltage V is shown in conjunction with FIGS. 1 and 3DSRising mainly refers to a process in which its negative value gradually increases, but its absolute value gradually decreases. In addition, as shown in FIG. 3, four threshold voltages (first threshold voltage Vthon, second threshold voltage Vthreg, and third threshold voltage) are setVoltage Vthcp, cutoff threshold voltage Vthoff) are all negative values. By using the scheme of the invention, the threshold comparator module 1 can monitor the drain-source voltage V of the synchronous rectifier tube Q1 in real timeDSAnd at drain-source voltage VDSWhen reaching the third threshold voltage Vthcp, the gate-source voltage V is regulatedGSThe clamp is pulled down to a clamp voltage Vclamp and is kept unchanged, and after the clamp time Tcp is continued, the drain-source voltage VDSContinuously rising to a cut-off threshold voltage Vthoff close to zero voltage, and then changing the gate-source voltage VGSReducing to zero voltage to realize the fast turn-off of the synchronous rectifier tube Q1; the scheme is simple to realize and has the effect of quickly switching off the synchronous rectifier tube Q1.
Preferably, the driving voltage control module 2 includes a clamp circuit 21, a CIN terminal (control terminal) of the clamp circuit 21 is electrically connected to the threshold comparator module 1, and a CG terminal of the clamp circuit 21 is also electrically connected to a gate of the synchronous rectifier Q1; when the threshold comparator module 1 detects the drain-source voltage VDSWhen the threshold voltage is greater than or equal to the set third threshold voltage Vthcp, the threshold comparator module 1 outputs a third signal to the clamp circuit 21, and the clamp circuit 21 clamps the gate-source voltage VGSRegulated and maintained at a clamping voltage Vclamp, which is determined by circuitry internal to clamping circuit 21.
Fig. 4 shows an embodiment of the clamping circuit 21, and the clamping circuit 21 internally includes a regulator circuit including a zener diode and a switching transistor N2. When the input CIN terminal is at a high level, the switching transistor N2 is turned on, and the clamp voltage Vclamp at the output terminal GATE of the driving voltage control module 2 approaches the voltage of the zener diode, for example, 3.3V. Fig. 5 is another embodiment of an internal clamp circuit 21, the clamp circuit 21 including a voltage follower. When the threshold comparator module 1 controls the voltage follower to work, the voltage follower adjusts the voltage of the output terminal GATE of the driving voltage control module 2 to the clamping voltage Vclamp, namely, the GATE-source voltage V of the synchronous rectifier tube Q1GSPull down to the clamp voltage Vclamp.
The clamping circuit 21 of the present invention is not limited to the implementations of fig. 4 and 5, and other similar schemes for implementing the corresponding clamping voltage function are possible.
Preferably, the driving voltage control module further comprises a first micro-voltage reduction loop, when the threshold comparator module detects the drain-source voltage VDSWhen the threshold voltage Vthreg is greater than or equal to the set second threshold voltage Vthreg, the threshold comparator module 1 is configured to control all the loops electrically connected to the gates of the synchronous rectifiers to be turned off, and the first fine-step-down loop is turned on, and the first fine-step-down loop is configured to release the voltage across the gate-source parasitic capacitor C1 of the synchronous rectifier Q1, where the second threshold voltage Vthreg is less than the third threshold voltage Vthcp.
Preferably, with reference to fig. 2, the first micro-buck circuit includes a first resistor R1, one end of the first resistor R1 is used to be electrically connected to the gate of the synchronous rectifier Q1, and the other end of the first resistor R1 is grounded.
It can be seen that the gate-source voltage V of the synchronous rectifier Q1 is controlled by the clamping circuit 21GSBesides, the invention also uses the grid source parasitic capacitance C1 and the resistance R1 of the synchronous rectifier tube to form a loop for connecting the grid source voltage VGSSlowly, thereby further reducing losses. Furthermore, with this arrangement, the later-mentioned upper drive switch P1 can be turned off in advance, and the upper drive switch P1 is prevented from being turned on when the clamp circuit is turned on, and thus, the power consumption is low and the safety is not high.
Preferably, in conjunction with fig. 2, the driving voltage control module 2 further includes an on/off control logic module 22, an upper driving switch P1, and a lower driving switch N1; the input end of the on/off control logic module 22 is electrically connected to the output end of the threshold comparator module 1, the control end of the upper driving switch P1 is electrically connected to the output end of the on/off control logic module 22, one end of the upper driving switch P1 is connected to the normal driving voltage VCC, and the other end of the upper driving switch P1 is electrically connected to the gate of the synchronous rectifier tube, and is configured to turn on or off the upper driving switch P1 according to the output signal of the on/off control logic module 22, so as to control the gate of the synchronous rectifier tube Q1 to supply power or cancel power; two ends of the lower driving switch N1 are respectively connected with the grid and the grounding end of the synchronous rectifier tube Q1, and the control end of the lower driving switch N1 is electrically connected with the output end of the threshold comparator module 1For turning on the down-driving switch N1 according to the output signal of the threshold comparator module 1, thereby controlling the gate-source voltage V of the synchronous rectifier Q1GSAnd down to zero voltage, where the absolute value of the normal drive voltage is greater than the absolute value of the clamp voltage. In general, the absolute value of the normal driving voltage VCC ranges from 6V to 10V, for example, 6V, 7V, 8V, 9V, 10V, etc., the absolute value of the clamp voltage Vclamp is larger than the absolute value of the threshold voltage of the synchronous rectifier Q1, the absolute value of the clamp voltage Vclamp needs to be larger than the absolute value of the threshold voltage by about 1V or more depending on the requirement of the turn-off speed of the synchronous rectifier Q1, and for example, the absolute value of the clamp voltage Vclamp ranges from 1.5V to 4.5V, for example, 1.5V, 1.7V, 2V, 2.5V, 3V, 4V, 4.5V, etc.
Specifically, the on and off of the upper driving switch P1 directly controls the supply and the removal of power to the gate of the synchronous rectifier Q1, and the power supply can be an internal power supply or an external power supply.
Specifically, the on and off of the under-drive switch N1 is directly controlled to ground and remove the ground to the gate of the synchronous rectifier Q1, and the purpose of the ground is to synchronously connect the gate-source voltage V of the rectifier to the groundGSRapidly drops to zero, causing the synchronous rectifier Q1 to turn off rapidly.
Preferably, when the threshold comparator module 1 detects the drain-source voltage VGSWhen the voltage is less than or equal to the first threshold voltage Vthon, the threshold comparator module 1 outputs a first signal to the on/off control logic module 22, the on/off control logic module 22 controls the upper driving switch P1 to turn on the synchronous rectifier Q1, and when the threshold comparator module 1 detects the drain-source voltage VDSWhen the threshold voltage is greater than or equal to the set second threshold voltage Vthreg, the threshold comparator module 1 outputs a second signal to the on-off control logic module 22, the on-off control logic module 22 controls the upper driving switch P1 to be turned off and then to be kept turned off, and at this time, the lower driving switch N1 is kept turned off; when the threshold comparator module 1 detects the drain-source voltage VDSWhen the threshold voltage is greater than or equal to the set cut-off threshold voltage Vthoff, the threshold comparator module 1 outputs a fourth signal to the down-driving switch N1, downThe drive switch N1 is turned on to switch on the gate-source voltage V of the synchronous rectifier Q1GSPull down to 0, where the clamp voltage is between 0 and the normal driving voltage, the first threshold voltage Vthon is less than the second threshold voltage Vthreg, which is less than the third threshold voltage Vthcp.
Preferably, the threshold comparator module 1 includes a first threshold comparator CMP1, a non-inverting input terminal of the first threshold comparator CMP1 is electrically connected to the drain of the synchronous rectifier Q1, an inverting input terminal of the first threshold comparator CMP1 is connected to the first threshold voltage Vthon, and an output terminal of the first threshold comparator CMP1 is electrically connected to the on-off control logic module 22; for detecting drain-source voltage V of synchronous rectifier Q1DS<At Vthon, the output electrical signal controls the upper driving switch P1 to turn on, and supplies power to the gate of the synchronous rectifier Q1, so that the synchronous rectifier Q1 starts to turn on.
Preferably, the threshold comparator module 1 includes a second threshold comparator CMP2, a non-inverting input terminal of the second threshold comparator CMP2 is electrically connected to the drain of the synchronous rectifier Q1, an inverting input terminal of the second threshold comparator CMP2 is connected to the second threshold voltage Vthreg, and an output terminal of the second threshold comparator CMP2 is electrically connected to the on-off control logic module 22; for detecting drain-source voltage V of synchronous rectifier Q1DS>When Vthreg is in use, the output electric signal controls the upper driving switch P1 to be switched off, and power is removed from the grid of the synchronous rectifier tube Q1; at this time, the driving voltage control module 2 controls the gate-source voltage V of the synchronous rectifier Q1DSThe synchronous rectifier Q1 is kept in the on state with a slight decrease.
Preferably, the threshold comparator module 1 includes a third threshold comparator CMP3, a non-inverting input terminal of the third threshold comparator CMP3 is electrically connected to the drain of the synchronous rectifier Q1, an inverting input terminal of the third threshold comparator CMP3 is connected to a third threshold voltage Vthcp, and an output terminal of the third threshold comparator CMP3 is electrically connected to the driving voltage control module 2; for detecting drain-source voltage V of synchronous rectifier Q1DS>Vthcp, an electrical signal is output to the driving voltage control module 2, and the driving voltage control module 2 controls the gate-source voltage V of the synchronous rectifier Q1GSPulled to a clamped voltage Vclamp。
The output terminal of the third threshold comparator CMP3 is further electrically connected to the on/off control logic module 22 for detecting the drain-source voltage V of the synchronous rectifier Q1DS>At Vthcp, an electrical signal is output to the on/off control logic module 22, and the on/off control logic module 22 keeps the upper driving switch P1 turned off, i.e., keeps the synchronous rectifier Q1 in a power-off state.
Preferably, the threshold comparator module 1 includes a fourth threshold comparator CMP4, a non-inverting input terminal of the fourth threshold comparator CMP4 is electrically connected to the drain of the synchronous rectifier Q1, an inverting input terminal of the fourth threshold comparator CMP4 is connected to the cutoff threshold voltage Vthoff, and an output terminal of the fourth threshold comparator CMP4 is electrically connected to the lower driving switch N1; for detecting drain-source voltage V of synchronous rectifier Q1DS>Vthoff, the down-drive switch N1 is turned on, so that the gate of the synchronous rectifier Q1 is grounded, and the synchronous rectifier Q1 is turned off.
Specifically, the magnitude relationship of the reference voltage is:
Vthoff>Vthcp>Vthreg>Vthon。
therefore, the invention provides four comparison threshold values in total, and one to more specific circuits can be freely combined, so that the drain-source voltage V of the synchronous rectifier tube Q1 can be monitored in real time under different conditionsDSAnd comparing with different threshold values, and comparing the gate-source voltage V of the synchronous rectifier Q1 at four threshold pointsGSDifferent controls are carried out, thereby more finely controlling the drain-source voltage V of the synchronous rectifier Q1DSEnsuring the drain-source voltage V of the synchronous rectifier Q1 before turning offDSAs low as possible for faster shut-down and reduced losses.
Example two
On the other hand, referring to fig. 3 and 6, the present invention provides a method for controlling a synchronous rectifier Q1, and a part not described in this embodiment refers to the embodiment, and the method for controlling the synchronous rectifier Q1 includes:
s1: detecting the drain-source voltage V between the drain and the source of the synchronous rectifier Q1DS；
S2: when the drain-source voltage VDSWhen the voltage is greater than or equal to a set third threshold voltage Vthcp, the grid-source voltage V is regulated and controlledGSClamped down to a clamp voltage Vclamp;
s3: when the drain-source voltage VDSWhen rising to cut-off threshold voltage Vthoff, pull down grid source voltage VGSSo that the synchronous rectifier Q1 is turned off, wherein the third threshold voltage Vthcp is smaller than the cut-off threshold voltage Vthoff, which is smaller than 0.
Further, between the step S1 and the step S2, the method further comprises the steps of:
when the drain-source voltage VDSWhen the second threshold voltage Vthreg is greater than or equal to the set second threshold voltage Vthreg, the circuits electrically connected to the gate of the synchronous rectifier Q1 are all controlled to be turned off, and the first micro-buck circuit is controlled to be turned on to release the voltage on the gate-source parasitic capacitor C1 of the synchronous rectifier Q1, wherein the second threshold voltage Vthreg is less than the third threshold voltage Vthcp.
The clamp voltage Vclamp is between 0 and the normal driving voltage VCC, and the first threshold voltage Vthon is smaller than the second threshold voltage Vthreg, that is, the first threshold voltage Vthon, the second threshold voltage Vthreg, the third threshold voltage Vthcp, and the cut-off threshold voltage Vthoff have the following magnitude relations:
Vthoff>Vthcp>Vthreg>Vthon。
drain-source voltage VDSAfter the primary side main power MOS tube is turned off, the primary side main power MOS tube becomes a negative value and is reduced along with time; after the synchronous rectifier Q1 is turned on, the drain-source voltage VDSThe voltage increases gradually and eventually approaches the cut-off threshold voltage Vthoff at turn-off.
Specifically, as shown in FIG. 3, the drain-source voltage VDSThe principle of curve transformation is as follows: the primary side of the transformer is high and low at the beginning, when the primary side main power MOS tube is closed, the primary side continues current, and at the same time, in order to prevent the breakdown caused by the increase of the voltage of the MOS tube body diode, the current is discharged back to the upper end of the primary side of the transformer through the diode and the resistor, so that the voltage of the lower end is higher than the voltage of the upper end, and the voltage of the secondary side is changed into the voltage of the upper end, the lower end and the upper end which are high and low (changed from the previous voltage of the lower end, the upper end and the lower end), so that the drain-source voltage VDSChange from positive to negative whenMeasuring drain-source voltage VDSWhen the voltage is changed to the first threshold voltage Vthon, the transistor Q1 is controlled to be conducted, but there is a small delay due to the circuit itself, the body diode is conducted, when the transistor Q1 is controlled to be conducted, the transistor Q1 works in the linear region, and the drain-source voltage V isDSThe absolute value of the voltage decreases with decreasing current, while the drain-source voltage V decreasesDSAt this time, it is negative, so the drain-source voltage VDSThe voltage increases with decreasing current.
Specifically, please refer to fig. 2 and fig. 3 in combination, when the drain-source voltage V is appliedDSWhen the voltage is lower than the first threshold voltage Vthon, the first threshold comparator CMP1 outputs a high level to control the totem-pole drive switch P1 to be turned on, the normal drive voltage VCC is applied to the gate of the synchronous rectifier Q1, and the synchronous rectifier Q1 is in a conducting state and is equivalent to a resistor.
In particular, considering the time delay of turn-on, as shown in fig. 3, the gate-source voltage V of the synchronous rectifier Q1GSAt a drain-source voltage VDSAfter reaching the first threshold voltage Vthon, a slope rising is performed after a period of time, and after a total turn-on delay Td, the on-voltage of the synchronous rectifier Q1 is reached, and then the voltage rises all the way to the normal driving voltage VCC and remains unchanged. Therefore, the turn-on delay Td time is taken into account in the subsequent time determination for more precise control of the turn-on and turn-off timings.
Specifically, a minimum on-time Tonmin is set for controlling the on-time of the synchronous rectifier Q1 below which the off-command is negligible. This further improves stability and avoids frequent on/off operations that could damage the synchronous rectifier Q1.
Further, when the circuit of the secondary winding continues the decrease of the current Is, the drain-source voltage VDSThe voltage increases (the absolute value becomes smaller). When the drain-source voltage VDSWhen the voltage is greater than the second threshold voltage Vthreg, the second threshold comparator CMP2 outputs a high level to control the turn-off of the upper driving switch P1, and the voltage at the output GATE of the driving voltage control module 2 is determined by the presence of the first micro-buck loopThe synchronous rectifier Q1 continues to remain open with a slight decrease.
Further, when the drain-source voltage V is appliedDSContinuing to increase to the third threshold voltage Vthcp, the third threshold comparator CMP3 outputs a high level, and controls the clamp circuit 21 to pull the voltage at the output terminal GATE of the driving voltage control block 2 to a clamp voltage Vclamp.
Specifically, the time from the second threshold voltage Vthreg to the clamping voltage Vclamp is defined as a free adjustment time Tr1, and may be adjusted according to different requirements, mainly by setting the magnitude of the third threshold voltage Vthcp. When the third threshold voltage Vthcp is detected, the gate-source voltage V of the synchronous rectifier Q1 is decreasedGSAt this time, the resistance of the synchronous rectifier Q1 increases, and the current of the continuous current Is almost constant, so that the drain-source voltage VDSThere will be a drop in voltage and thus a steep drop in the figure. The time point setting of the third threshold voltage Vthcp cannot be too early or too late, which is specifically caused by the following reasons: the third threshold voltage Vthcp cannot be too close in time to the second threshold voltage Vthreg because this would cause the resistance of the synchronous rectifier Q1 to increase (because the clamp circuit 21 pulls the gate-source voltage V sharplyGSCausing the impedance to become larger and to be earlier), thereby causing the loss of the synchronous rectifier Q1 to increase; the third threshold voltage Vthcp is not too close in time to the cut-off threshold voltage Vthoff (may overlap with the cut-off threshold voltage Vthoff and pull-down too late to directly follow the gate-source voltage VGSThe maximum voltage is pulled to zero, which results in too late turn-off), since the turn-off of the synchronous rectifier Q1 has a delay, the purpose of rapidly turning off the synchronous rectifier Q1 may not be achieved, the primary side and the secondary side may be simultaneously turned on, and thus a spike may occur, which may break down the synchronous rectifier Q1.
If the free adjustment time Tr1 is not available, the current is large, the loss of the synchronous rectifier Q1 is increased, and the free adjustment time Tr1 is set, so that the loss is favorably reduced.
Further, when the drain-source voltage V is appliedDSUpon continuing to increase to the cutoff threshold voltage Vthoff, the fourth threshold comparatorThe CMP4 outputs high level to control the on-off of the drive switch N1, and the gate-source voltage V of the synchronous rectifier Q1GSThe synchronous rectifier Q1 is quickly turned off by pulling down from the clamp voltage Vclamp to zero.
Therefore, the scheme provides four comparison thresholds (CMP1, CMP2, CMP3 and CMP4) in total, one or more specific circuits can be freely combined, the voltage difference value between the drain and the source of the synchronous rectifier Q1 is monitored in real time and compared with the four thresholds, and the gate-source voltage V of the synchronous rectifier Q1 is compared at the four threshold pointsGSDifferent control is performed, so that the voltage difference value between the drain and the source of the synchronous rectifier Q1 is more finely controlled, and the voltage difference value between the drain and the source of the synchronous rectifier Q1 is ensured to be reduced as much as possible before the synchronous rectifier Q1 is turned off, so that the turn-off is more rapid and the loss is reduced.
In still another aspect, referring to fig. 7, the invention provides a control chip for a synchronous rectifier, which includes the control circuit for a synchronous rectifier as above. The synchronous rectifier Q1 corresponds to the synchronous rectifier Q1, the 6 terminal corresponds to the input terminal VD of the threshold comparator module 1, and is used to connect the drain of the synchronous rectifier Q1, the 5 terminal corresponds to the output terminal GATE of the driving voltage control module 2, and is used to connect the GATE of the synchronous rectifier Q1, the 2 terminal corresponds to the ground terminal of the driving voltage control module 2, and the 4 terminal corresponds to the normal driving voltage provided by the internal power supply.
In another aspect, the present invention provides a switching power supply, which includes a synchronous rectifier, and further includes a control circuit of the synchronous rectifier or a chip thereof, wherein a source of the synchronous rectifier is grounded, a gate of the synchronous rectifier is electrically connected to the driving voltage control module, and a drain of the synchronous rectifier is electrically connected to the threshold comparator module. The switching power supply of the present invention is the aforementioned flyback converter (see fig. 7) or the half-bridge LLC resonant converter (see fig. 8), and when the switching power supply is the half-bridge LLC resonant converter, the primary side is always in operation.
In another aspect, the present invention provides an electronic device, which includes the above synchronous rectifier control circuit, or includes the above chip, or includes the above switching power supply. The electronic device is, for example, an LED lighting device, a television, a mobile phone, a notebook computer, a tablet computer, or the like.

Claims (14)

1. A control circuit for a synchronous rectifier, comprising: the device comprises a threshold comparator module and a driving voltage control module;
the threshold comparator module is used for detecting drain-source voltage between a drain electrode and a source electrode of the synchronous rectifier tube, the output end of the threshold comparator module is electrically connected with the driving voltage control module, and the output end of the driving voltage control module is used for being electrically connected with a grid electrode of the synchronous rectifier tube;
when the threshold comparator module detects that the drain-source voltage is greater than or equal to a set third threshold voltage, the threshold comparator module outputs a third signal to the driving voltage control module, the driving voltage control module regulates and controls the gate-source voltage, the gate-source voltage is clamped and pulled down to a clamping voltage, when the drain-source voltage rises to a cut-off threshold voltage, the threshold comparator module outputs a fourth signal to the driving voltage control module, and the driving voltage control module pulls down the gate-source voltage to turn off the synchronous rectifier, wherein the third threshold voltage is less than the cut-off threshold voltage, and the cut-off threshold voltage is less than 0.
2. The control circuit of claim 1,
the driving voltage control module comprises a clamping circuit, the clamping circuit is electrically connected with the threshold comparator module, and the clamping circuit is also used for being electrically connected with a grid electrode of the synchronous rectifier tube; when the threshold comparator module detects that the drain-source voltage is greater than or equal to a set third threshold voltage, the threshold comparator module outputs a third signal to the clamping circuit, and the clamping circuit regulates and controls the gate-source voltage to be clamped and pulled down to a clamping voltage.
3. The control circuit of claim 2,
the clamping circuit comprises a voltage stabilizing circuit and a switching tube which are connected in series, and when the threshold comparator module controls the switching tube to be conducted, the voltage stabilizing circuit pulls the gate-source voltage of the synchronous rectifying tube to the clamping voltage.
4. The control circuit of claim 2,
the clamping circuit comprises a voltage follower, the non-inverting input end of the voltage follower is connected with the clamping voltage, the enabling end of the voltage follower is electrically connected with the threshold comparator module, and when the threshold comparator module controls the voltage follower to work, the voltage follower pulls the gate-source voltage of the synchronous rectifying tube to the clamping voltage.
5. The control circuit of claim 1,
the driving voltage control module further comprises a first micro-voltage reduction loop, when the threshold comparator module detects that the drain-source voltage is greater than or equal to a set second threshold voltage, the threshold comparator module is used for controlling the loop electrically connected with the grid electrode of the synchronous rectifier tube to be turned off and the first micro-voltage reduction loop is turned on, the first micro-voltage reduction loop is used for releasing the voltage on the grid-source parasitic capacitor of the synchronous rectifier tube, and the second threshold voltage is less than the third threshold voltage.
6. The control circuit of claim 5, wherein the first micro-buck circuit comprises a first resistor, one end of the first resistor is electrically connected to the gate of the synchronous rectifier, and the other end of the first resistor is grounded.
7. The control circuit according to any one of claims 1-6, wherein the driving voltage control module further comprises an on/off control logic module, an upper driving switch, and a lower driving switch; the input end of the on-off control logic module is electrically connected with the output end of the threshold comparator module, the control end of the upper drive switch is electrically connected with the output end of the on-off control logic module, one end of the upper drive switch is connected with a normal drive voltage, the other end of the upper drive switch is used for being electrically connected with the grid electrode of the synchronous rectifier tube, and the upper drive switch is switched on or off according to an output signal of the on-off control logic module; one end of the lower driving switch is used for being connected with a grid electrode of the synchronous rectifier tube, the other end of the lower driving switch is grounded, a control end of the lower driving switch is electrically connected with an output end of the threshold comparator module, the lower driving switch is switched on or switched off according to an output signal of the threshold comparator module, and the normal driving voltage is larger than the clamping voltage.
8. The control circuit of claim 7, wherein when the threshold comparator module detects that the drain-source voltage is less than or equal to a first threshold voltage, the threshold comparator module outputs a first signal to the on-off control logic module, the on-off control logic module controls the upper driving switch to be turned on to turn on the synchronous rectifier, and when the threshold comparator module detects that the drain-source voltage is greater than or equal to a second threshold voltage, the threshold comparator module outputs a second signal to the on-off control logic module, the on-off control logic module controls the upper driving switch to be turned off; when the threshold comparator module detects that the drain-source voltage is greater than or equal to a set cut-off threshold voltage, the threshold comparator module outputs a fourth signal to the lower driving switch, the lower driving switch is turned on to pull the gate-source voltage of the synchronous rectifier tube to 0, wherein the clamping voltage is between 0 and a normal driving voltage, the first threshold voltage is less than the second threshold voltage, and the second threshold voltage is less than the third threshold voltage.
9. The control circuit of claim 7,
the threshold comparator module comprises a first threshold comparator, wherein the non-inverting input end of the first threshold comparator is used for being electrically connected with the drain electrode of the synchronous rectifier tube, the inverting input end of the first threshold comparator is connected with a first threshold voltage, and the output end of the first threshold comparator is electrically connected with the on-off control logic module; and/or the presence of a gas in the gas,
the threshold comparator module comprises a second threshold comparator, the non-inverting input end of the second threshold comparator is used for being electrically connected with the drain electrode of the synchronous rectifier tube, the inverting input end of the second threshold comparator is connected with a second threshold voltage, and the output end of the second threshold comparator is electrically connected with the on-off control logic module; and/or the presence of a gas in the gas,
the threshold comparator module comprises a third threshold comparator, wherein the non-inverting input end of the third threshold comparator is used for being electrically connected with the drain electrode of the synchronous rectifier tube, the inverting input end of the third threshold comparator is connected with a third threshold voltage, and the output end of the third threshold comparator is electrically connected with the driving voltage control module; the output end of the third threshold comparator is also electrically connected with the on-off control logic module, when the third threshold comparator detects that the drain-source voltage is greater than or equal to a set third threshold voltage, the third threshold comparator outputs a third signal to the on-off control logic module, and the on-off control logic module keeps the upper drive switch in a disconnected state; and/or the presence of a gas in the gas,
the threshold comparator module comprises a fourth threshold comparator, wherein the non-inverting input end of the fourth threshold comparator is used for being electrically connected with the drain electrode of the synchronous rectifier tube, the inverting input end of the fourth threshold comparator is connected with a cut-off threshold voltage, and the output end of the fourth threshold comparator is electrically connected with the lower driving switch.
10. A control method of a synchronous rectifier tube is characterized by comprising the following steps:
s1: detecting the drain-source voltage between the drain and the source of the synchronous rectifier tube;
s2: when the drain-source voltage is greater than or equal to a set third threshold voltage, regulating and controlling the grid-source voltage to be clamped and pulled down to a clamping voltage;
s3: and when the drain-source voltage rises to a cut-off threshold voltage, pulling down the gate-source voltage to turn off the synchronous rectifier tube, wherein the third threshold voltage is less than the cut-off threshold voltage, and the cut-off threshold voltage is less than 0.
11. The control method according to claim 10, further comprising, between step S1 and step S2, the step of:
when the drain-source voltage is larger than or equal to a set second threshold voltage, controlling the loops electrically connected with the grid electrode of the synchronous rectifier tube to be both turned off and controlling the first micro-voltage reduction loop to be turned on so as to release the voltage on the grid-source parasitic capacitor of the synchronous rectifier tube, wherein the second threshold voltage is smaller than the third threshold voltage.
12. A control chip for a synchronous rectifier comprising a control circuit for a synchronous rectifier as claimed in any one of claims 1 to 9.
13. A switching power supply comprising a synchronous rectifier, further comprising a control circuit of the synchronous rectifier according to any one of claims 1 to 9 or comprising the chip according to claim 12, wherein the source of the synchronous rectifier is grounded, the gate of the synchronous rectifier is electrically connected to the driving voltage control module, and the drain of the synchronous rectifier is electrically connected to the threshold comparator module.
14. An electronic device, characterized in that a control circuit comprising a synchronous rectifier as claimed in any of claims 1 to 9 or comprising a chip as claimed in claim 12 or comprising a switching power supply as claimed in claim 13.
CN202210114362.8A 2022-01-30 2022-01-30 Control circuit and method thereof, chip, switching power supply and electronic device Pending CN114583923A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202210114362.8A CN114583923A (en) 2022-01-30 2022-01-30 Control circuit and method thereof, chip, switching power supply and electronic device

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202210114362.8A CN114583923A (en) 2022-01-30 2022-01-30 Control circuit and method thereof, chip, switching power supply and electronic device

Publications (1)

Publication Number Publication Date
CN114583923A true CN114583923A (en) 2022-06-03

Family

ID=81769298

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202210114362.8A Pending CN114583923A (en) 2022-01-30 2022-01-30 Control circuit and method thereof, chip, switching power supply and electronic device

Country Status (1)

Country Link
CN (1) CN114583923A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115065245A (en) * 2022-08-04 2022-09-16 成都利普芯微电子有限公司 Synchronous rectification control circuit, chip and switching power supply

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115065245A (en) * 2022-08-04 2022-09-16 成都利普芯微电子有限公司 Synchronous rectification control circuit, chip and switching power supply
CN115065245B (en) * 2022-08-04 2022-12-16 深圳利普芯微电子有限公司 Synchronous rectification control circuit, chip and switching power supply

Similar Documents

Publication Publication Date Title
CN109802559B (en) Synchronous rectification control circuit and method and flyback switching circuit
US11736030B2 (en) Switching circuit, synchronous rectification control circuit and control method thereof
CN107342695B (en) Synchronous rectifier
US8885362B2 (en) Fast startup switching converter and method thereof
US20160233779A1 (en) Soft switching flyback converter
TWI548187B (en) Dynamic drive capability adjustment of the power control device
US20130107584A1 (en) Dynamic Mosfet Gate Drivers
US11245324B2 (en) Switching converter and a method thereof
CN107809171B (en) Switching power supply and driving method and driving circuit of power switching tube thereof
US20200382016A1 (en) Rectifying control module, active bridge rectifying control apparatus, and method of operating the same
JP2017070164A (en) Gate voltage controller
CN111786563A (en) Synchronous rectification control circuit and switching power supply
CN114583923A (en) Control circuit and method thereof, chip, switching power supply and electronic device
US10418910B2 (en) Isolated switch-mode power supply and control circuit and control method for isolated switch-mode power supply
TW201618446A (en) Power controller with dynamic driving capability adjustment
WO2024036800A1 (en) Anti-backflow circuit started by using full-bridge synchronous rectification, and electronic device
US9698666B2 (en) Power supply and gate driver therein
US11489451B1 (en) Power conversion apparatus and synchronous rectification controller thereof
CN108923625A (en) A kind of synchronous rectifier control method and circuit
US11424691B2 (en) Switch driving device and switching power supply using the same
CN219576854U (en) D-type gallium nitride switch driving circuit and switching power supply circuit
CN113746360B (en) Synchronous rectification driving voltage regulating circuit, system and regulating method
WO2024004469A1 (en) Converter circuit
CN210405092U (en) Control circuit of switching power supply circuit and switching power supply circuit
CN116094292A (en) D-type gallium nitride switch driving circuit and switching power supply circuit

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination