CN106941321A - A kind of control circuit of synchronous rectifier - Google Patents
A kind of control circuit of synchronous rectifier Download PDFInfo
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- CN106941321A CN106941321A CN201710173147.4A CN201710173147A CN106941321A CN 106941321 A CN106941321 A CN 106941321A CN 201710173147 A CN201710173147 A CN 201710173147A CN 106941321 A CN106941321 A CN 106941321A
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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
- H02M1/36—Means for starting or stopping converters
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- 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)
- Rectifiers (AREA)
Abstract
The invention discloses a kind of control circuit of synchronous rectifier, including voltage slope detection circuit, transformer and synchronous rectifier output-stage circuit, logic circuit and drive circuit, the voltage slope detection circuit, logic circuit, drive circuit and transformer and synchronous rectifier output-stage circuit are sequentially connected.The present invention detects circuit by setting voltage slope, detect the slope of the voltage change of synchronous rectifier drain electrode, it is due to that primary side main power tube is turned off after the shut-off of caused or synchronous rectifier caused by resonance to accurately distinguish its drain terminal voltage change, opened so as to avoid synchronous rectifier from being opened by mistake due to resonance, further realize the correct unlatching of synchronous rectifier.
Description
Technical field
Field, the control circuit of more particularly to a kind of synchronous rectifier are driven the present invention relates to power tube.
Background technology
Requirement of the switch power technology to efficiency is increasingly harsh, in order to improve the efficiency of on-off circuit, many using same at present
Rectification metal-oxide-semiconductor is walked to substitute fly-wheel diode.
But in the case where devices and primary side main switch signal do not communicate, how correctly to open synchronization
Rectification metal-oxide-semiconductor turns into key technology.
Moment after primary side main power tube is turned off, secondary side transformer starts afterflow by the body diode of synchronous rectifier,
At the same time synchronous rectifier needs the quick time of afterflow raising efficiency opened and reduce body diode.Existing synchronizing power pipe
Opening technology exactly, is changed into opening synchronous work(after negative voltage by detecting synchronous rectifier drain-source both end voltage drop from positive voltage
Rate pipe.
, can fault open synchronizing power pipe but this opening technology has the drawback that.Terminate it in secondary side current stream
Synchronous rectifier is turned off afterwards, and the resonance that the parasitic capacitance and primary side inductance of the drain electrode of primary side main power tube are produced make it that secondary side is synchronously whole
Flow tube drain-source two ends produce same resonant voltage waveforms, and this voltage can be similarly pressed onto between negative voltage from higher positive electricity to shake
Swing, middle Vds waveforms are from t4 time points to the change at t5 time points as shown in Figure 3.In this case, synchronous rectifier can be
After current stream terminates, again due to resonance and can be by fault open.
In order to solve fault open phenomenon caused by above-mentioned resonance, there is a kind of method to be, after synchronous rectifier shut-off
Intervals inner shield synchronous rectifier is again turned on.If but this shielding time is too short, it is impossible to played
The effect of full-shield, still can be by the unlatching of mistake after terminating in the shielding time；If the time of shielding is oversize, there can be mistake
Shield by mistake, normal open signal is shielded, causes body diode afterflow of the secondary side electric current by synchronous rectifier, further
System output voltage is caused to reduce.
Thus prior art could be improved and improve.
The content of the invention
In view of in place of above-mentioned the deficiencies in the prior art, it is an object of the invention to provide a kind of control of synchronous rectifier electricity
Road, it is due to cause after primary side main power tube is turned off or synchronous whole that can accurately distinguish the change of synchronous rectifier drain-source voltage
Resonance causes after flow tube shut-off, so as to realize the correct unlatching to synchronous rectifier.
In order to achieve the above object, this invention takes following technical scheme：
A kind of control circuit of synchronous rectifier, including：
Voltage slope detect circuit, for detect synchronous rectifier drain-source two ends voltage change slope and output control letter
Number；
Transformer and synchronous rectifier output-stage circuit；
Logic circuit, the control signal for detecting circuit output to voltage slope carries out logical calculated and output drive signal control
The break-make of synchronous rectifier processed；
Drive circuit, the drive signal for being exported according to logic circuit drives the break-make of synchronous rectifier；
The voltage slope detection circuit, logic circuit, drive circuit transformer and synchronous rectifier output-stage circuit are successively
Connection.
In the control circuit of described synchronous rectifier, transformer and the synchronous rectifier output-stage circuit includes primary side
Transformer, primary side main power tube, primary side sampling resistor, secondary side transformer, output capacitance and synchronous rectifier, the primary side transformation
One end connection power input of device, the other end of the primary side transformer connects the drain electrode of the primary side main power tube, described
The source electrode of primary side main power tube is grounded by the primary side sampling resistor, and the grid of the primary side main power tube receives main driving letter
Number, one end connection power output end of the secondary transformer and one end of output capacitance, the other end of the secondary transformer
The drain electrode of the synchronous rectifier is connected, the source ground of the synchronous rectifier also connects the other end of the output capacitance,
The grid of the synchronous rectifier connects the drive circuit.
In the control circuit of described synchronous rectifier, the voltage slope detection circuit includes：
First voltage threshold detection unit, the high threshold part for detecting synchronous rectifier drain-source both end voltage, and export the
One comparison signal；
Second voltage threshold detection unit, the Low threshold part for detecting synchronous rectifier drain-source both end voltage, and export the
Two comparison signals；
Time detecting unit, for generation time reference quantity, and exports the 3rd comparison signal；
Signal processing unit, for carrying out logical calculated processing, and output control to the second comparison signal and the 3rd comparison signal
Signal is to the logic circuit；
The first voltage threshold detection unit, time detecting unit and signal processing unit are sequentially connected, the signal transacting
Unit is also connected with the second voltage threshold detection unit.
In the control circuit of described synchronous rectifier, the first voltage threshold detection unit includes first resistor, the
Two resistance and first comparator, one end of the first resistor is signal receiving end, receives the drain-source electricity of the synchronous rectifier
Pressure, also connects the second voltage threshold detection unit, one end of the other end connection second resistance of the first resistor and institute
The inverting input of first comparator is stated, the positive input terminal of the first comparator A1 inputs the first predetermined reference voltage, described
The output end of first comparator connects the time detecting unit, the other end ground connection of the second resistance.
In the control circuit of described synchronous rectifier, the second voltage threshold detection unit include the first metal-oxide-semiconductor and
Second comparator, one end of the drain electrode connection first resistor of first metal-oxide-semiconductor, also receives the leakage of the synchronous rectifier
Source voltage, the source electrode of first metal-oxide-semiconductor connects the inverting input of second comparator, the grid of first metal-oxide-semiconductor
VDD power supplys are connected, the positive input terminal of second comparator inputs the second predetermined reference voltage, the output of second comparator
The end connection signal processing unit.
In the control circuit of described synchronous rectifier, the time detecting unit includes current source, the first phase inverter, height
The first switch for the first comparison signal control exported by the first comparator that level conducting, low level disconnect, low level
The second switch, the first electric capacity and the 3rd comparator that are controlled by first inverter output signal that conducting, high level disconnect,
One end connection VDD power supplys of the current source, the other end of the current source connects one end of the first switch, described first
The output end of comparator exports the first comparison signal and controls being turned on or off for the first switch, the first switch it is another
End is grounded by the second switch, also connects the inverting input of the 3rd comparator and one end of the first electric capacity, described
The other end ground connection of first electric capacity, the positive input terminal of the 3rd comparator inputs the 3rd predetermined reference voltage, the 3rd ratio
Output end compared with device connects the signal processing unit, and the input of first phase inverter connects the defeated of the first comparator
Go out end, the output end output signal control second switch of first phase inverter is turned on or off.
In the control circuit of described synchronous rectifier, the signal processing unit includes the second phase inverter, the 3rd anti-phase
Device, the 4th phase inverter, first and door and the first trigger, the input of second phase inverter connect second comparator
The input of output end and the 4th phase inverter, the output end of second phase inverter connects the input of the 3rd phase inverter
End, the output end of the 3rd phase inverter connects the second input of described first and door, and described first inputs with the first of door
The output end of end connection the 3rd comparator, described first is connected the S ends of first trigger with the output end of door, described
The R ends of first trigger connect the output end of the 4th phase inverter, and the Q ends of first trigger connect the logic electricity
Road.
In the control circuit of described synchronous rectifier, the logic circuit includes the second trigger, second triggering
The S ends of device connect the Q ends of first trigger, the R ends input cut-off signals of second trigger, second trigger
Q ends connect the drive circuit.
In the control circuit of described synchronous rectifier, the input of the drive circuit connects the Q ends of the second trigger,
The output end of the drive circuit connects the grid of the synchronous rectifier.
A kind of control circuit of the synchronous rectifier provided compared to prior art, the present invention, including voltage slope detection
Circuit, transformer and synchronous rectifier output-stage circuit, logic circuit and drive circuit, the voltage slope detect circuit, patrolled
Collect circuit, drive circuit and transformer and synchronous rectifier output-stage circuit is sequentially connected.The present invention is by setting voltage slope
Circuit is detected, the slope of the voltage change of synchronous rectifier drain electrode is detected, it is due to primary side to accurately distinguish its drain terminal voltage change
After still synchronous rectifier is turned off caused by main power tube shut-off caused by resonance, so as to avoid synchronous rectifier due to humorous
Shake and opened by mistake and opened, further realize the correct unlatching of synchronous rectifier.
Brief description of the drawings
The structured flowchart of the control circuit for the synchronous rectifier that Fig. 1 provides for the present invention.
The schematic diagram of the control circuit for the synchronous rectifier that Fig. 2 provides for the present invention.
Electric current and voltage waveform view during the synchronous rectifier work that Fig. 3 controls for the present invention.
In the control circuit for the synchronous rectifier that Fig. 4 provides for the present invention, the voltage slope detects the schematic diagram of circuit.
Embodiment
The present invention provides a kind of control circuit of synchronous rectifier, detects circuit by setting voltage slope, detection is synchronous
The slope of the voltage change of rectifying tube drain electrode, it is due to caused by the shut-off of primary side main power tube to accurately distinguish its drain terminal voltage change
Or after synchronous rectifier shut-off caused by resonance, it is to avoid synchronous rectifier is opened by mistake due to resonance to be opened.
To make the purpose of the present invention, technical scheme and effect clearer, clear and definite, develop simultaneously embodiment pair referring to the drawings
The present invention is further described.It should be appreciated that specific embodiment described herein is not used to only to explain the present invention
Limit the present invention.
Referring to Fig. 1, a kind of control circuit for synchronous rectifier that the present invention is provided, including voltage slope detection circuit
10, transformer and synchronous rectifier output-stage circuit 20, logic circuit 30 and drive circuit 40.
Wherein, the voltage slope detection circuit 10 is used for the slope for detecting the voltage change at synchronous rectifier drain-source two ends
And output control signal, specifically, the voltage slope detection circuit 10 can detect two different voltage thresholds respectively,
The time quantum between two voltage thresholds can also be detected simultaneously, according to the change deltaV's of voltage and time quantum deltaT
Ratio is that can obtain the change slope of voltage, while voltage slope detection circuit 10 also output control signal gives logic electricity
Road 30, by logic circuit 30 further control the break-make of synchronous rectifier after logical calculated.
The transformer and the synchronous pipe output-stage circuit 20 that arranges are the on-off circuits with synchronous rectifier, including primary side
Transformer L1, primary side main power tube M3, primary side sampling resistor Rcs, secondary side transformer L2, output capacitance Cout and synchronous rectifier
M2, the primary side transformer L1 one end receive input voltage vin, and the other end of the primary side transformer L1 connects the primary side
Main power tube M3 drain electrode, the source electrode of the primary side main power tube M3 is grounded by the primary side sampling resistor Rcs, the primary side
Main power tube M3 grid receives main drive signal, one end output output voltage Vout of the secondary transformer L2, and connects
Output capacitance Cout one end, the other end of the secondary transformer L2 connects the drain electrode of the synchronous rectifier M2, described same
Rectifying tube M2 source ground is walked, the other end of the output capacitance Cout is also connected, the grid of the synchronous rectifier M2 connects
Connect the drive circuit 40.
Furthermore, it is understood that referring to Fig. 3, after Fig. 3 is primary side power tube M3 shut-offs, secondary side starts after afterflow correspondence
Electric current and voltage waveform.Wherein Isec represents secondary side transformer current waveform, that is, by synchronous rectifier M2 electric current
Waveform；Vds represents that the synchronous rectifier M2 drain-sources two ends correspond to electric current Isec voltage waveform.Can by Vds voltage waveforms
To obtain, voltage descending slope of the voltage from t1 to t2 in the time is substantially greater than descending slope of the voltage from t4 to t5, and Vds
Waveform it is from time t1 to time t2 decline be by the primary side main power tube M3 shut-off caused by, and Vds waveforms from time t4 to
Time t5, which declines, to be drawn by the resonance of the drain terminal parasitic capacitance of the primary side main power tube M3 and primary side transformer L1 generations
Rise, so can judge that drain-source voltage change is due to primary side by detecting the voltage slope at synchronous rectifier M2 drain-sources two ends
Caused by main power tube shut-off, or after synchronous rectifier shut-off caused by resonance, so as to avoid synchronous rectifier due to
Resonance and opened by opening by mistake.
The logic circuit 30 is used to detect voltage slope the control signal that circuit 10 is exported carries out logical calculated and defeated
Go out the break-make that drive signal controls synchronous rectifier, when it is high level that the voltage slope, which detects the signal that circuit 10 is exported,
The output drive signal of logic circuit 30 opens synchronous rectifier M2, when the voltage slope detects the letter that circuit 10 is exported
Number be low level when, the output drive signal of logic circuit 30 make synchronous rectifier M2 turn off.
The drive circuit 40 is used for the drive signal driving synchronous rectifier M2 exported according to logic circuit 30 break-make.
During specific implementation, the voltage slope detection circuit 10, logic circuit 30, drive circuit 40 and transformer and synchronization
Rectifying tube output-stage circuit 20 is sequentially connected.
Refer to Fig. 1, Fig. 2 and Fig. 4, the voltage slope detection circuit 10 include first voltage threshold detection unit 101,
Second voltage threshold detection unit 103, time detecting unit 102 and signal processing unit 104.
Wherein, the first voltage threshold detection unit 101 is used for the height for detecting synchronous rectifier M2 drain-source both end voltages
Threshold portion, and export the first comparison signal comp1.
The second voltage threshold detection unit 102 is used for the Low threshold portion for detecting synchronous rectifier M2 drain-source both end voltages
Point, i.e. negative pressure part, and export the second comparison signal comp2.
The time detecting unit 103 is used for generation time reference quantity Tref, and exports the 3rd comparison signal comp3.
The signal processing unit 104 is used to carry out logic to the second comparison signal comp2 and the 3rd comparison signal comp3
Calculating is handled, and outputs control signals to the logic circuit 30.
During specific implementation, the first voltage threshold detection unit 101, time detecting unit 103 and signal processing unit
104 are sequentially connected, and the signal processing unit 104 is also connected with the second voltage threshold detection unit 102.
Please continue to refer to Fig. 2 and Fig. 4, the first voltage threshold detection unit 101 includes first resistor R1, second resistance
R2 and first comparator A1, the first resistor R1 one end are signal receiving end, receive the drain-source of the synchronous rectifier M2
Voltage, also connects the second voltage threshold detection unit 102, the other end connection second resistance R2's of the first resistor R1
One end and the inverting input of the first comparator A1, the positive input terminal of the first comparator A1 input the first preset reference
Voltage Vref1, the first comparator A1 output end connect the time detecting unit 103, and the second resistance R2's is another
One end is grounded.
Specifically, the drain-source voltage Vds of the synchronous rectifier M2 passes through first resistor R1 and second resistance R2 partial pressures
Drain-source voltage Vds high threshold part Vds_h=Vref1* (R1+R2)/R2 is obtained, so as to detect synchronous rectifier M2 leakage
Source voltage Vds high threshold part, while when synchronous rectifier M2 drain-source voltage Vds is less than its high threshold voltage Vds_h,
The output voltage rise of the first comparator A1, i.e. the first comparison signal comp1 of its output is high level.
Please continue to refer to Fig. 2 and Fig. 4, the second voltage threshold detection unit 102 includes the ratios of the first metal-oxide-semiconductor M1 and second
Compared with device A2, one end of the drain electrode connection first resistor of first metal-oxide-semiconductor also receives the drain-source of the synchronous rectifier M2
Voltage, the source electrode of the first metal-oxide-semiconductor M1 connects the inverting input of the second comparator A2, the first metal-oxide-semiconductor M1's
Grid connects VDD power supplys, positive input terminal input the second predetermined reference voltage Vref2 of the second comparator A2, described second
Comparator A2 output end connects the signal processing unit 104.
Specifically, the first metal-oxide-semiconductor M1 plays a part of protecting internal low-voltage device, when synchronous rectifier M2 leakage
During the control source of source, drain-source voltage Vds Low threshold part Vds_l=Vref2 are obtained by the first metal-oxide-semiconductor M1, so as to detect
Go out synchronous rectifier M2 drain-source voltage Vds Low threshold part, while when synchronous rectifier M2 drain-source voltage Vds is reduced to
Less than its low threshold voltage Vds_l, the second comparison signal of the second comparator A2 outputs switchs to high level by low level.
Please continue to refer to Fig. 2 and Fig. 4, the time detecting unit 103 includes current source I1, the first phase inverter A4, high electricity
The first switch K1 for the first comparison signal comp1 controls exported by the first comparator A1 that flat conducting, low level disconnect,
The second switch K2, the first electric capacity C1 that are controlled by the first phase inverter A4 output signals that low level conducting, high level disconnect
With the 3rd comparator A3, one end connection VDD power supplys of the current source I1, the other end connection described first of the current source I1
K1 one end is switched, the output end of the first comparator A1 exports the first comparison signal comp1 and controls the first switch K1
Be turned on or off, the other end of the first switch K1 is grounded by the second switch K2, is also connected the described 3rd and is compared
One end of device A3 inverting input and the first electric capacity C1, the other end ground connection of the first electric capacity C1, the 3rd comparator
A3 positive input terminal inputs the 3rd predetermined reference voltage Vref3, and the output end of the 3rd comparator A3 is connected at the signal
Unit 103 is managed, the input of the first phase inverter A4 connects the output end of the first comparator A1, first phase inverter
A4 output end output signal control second switch K2 is turned on or off.
Specifically, when synchronous rectifier M2 drain-source voltage Vds falls below Vds_h, the first comparator A1
Output voltage rise so that in the time detection circuit 102 first switch K1 closure, otherwise the first phase inverter A4 export
Signal cause second switch K2 disconnect, the current source I1 start give electric capacity C1 charging, now the 3rd comparator A3 output
3rd comparison signal comp3 remains high level, when the 3rd comparator A3 anti-phase terminal voltage reaches internal reference voltage ref3
When, the 3rd comparison signal comp3 of the 3rd comparator A3 outputs is changed into low level from high level, therefore can be charged according to electric capacity C1
Time and time period in synchronous rectifier M2 drain-source voltages change detect synchronous rectifier drain-source voltage change it is oblique
Rate, so that it is due to caused by the shut-off of primary side main power tube or synchronous rectifier further to accurately distinguish its drain terminal voltage change
After shut-off caused by resonance.
Please continue to refer to Fig. 2 and Fig. 4, the signal processing unit 104 include the second phase inverter A6, the 3rd phase inverter A7,
4th phase inverter A8, first and door A5 and the first trigger A9, input connection second ratio of the second phase inverter A6
The input of output end and the 4th phase inverter A8 compared with device A2, the output end connection the described 3rd of the second phase inverter A6
Phase inverter A7 input, the output end of the 3rd phase inverter A7 connects the second input of described first and door A5, described
First is connected the output end of the 3rd comparator A3 with door A5 first input end, and described first is connected with door A5 output end
The S ends of the first trigger A9, the R ends of the first trigger A9 connect the output end of the 4th phase inverter A8, described
First trigger A9 Q ends connect the logic circuit 103.
Specifically, the first trigger A9 is rest-set flip-flop, when the second comparison signal comp2 and the 3rd comparison signal
Comp3 simultaneously for high level when, first to export the set end S of high level, i.e. rest-set flip-flop with door A5 be height, clear terminal R to be low,
The output end Q of rest-set flip-flop is high level, i.e. the control signal of voltage slope detection circuit output is high level；Compare when second
When having one in signal comp2 and the 3rd comparison signal comp3 for low level, first exports low level, i.e. RS triggerings with door A5
The set end S of device is low, and the output end Q of rest-set flip-flop is low level, i.e. the control signal of voltage slope detection circuit output is
Low level, therefore only the second comparison signal comp2 and the 3rd comparison signal comp3 is while when being high level, voltage slope is detected
The control signal of circuit output is just high level, and the synchronous rectifier M2 can just be unlocked, otherwise can not open.
Please continue to refer to Fig. 2, the logic circuit 30 includes the second trigger A10, the S ends of the second trigger A10
Connect the Q ends of the first trigger A9, the R ends input cut-off signals OFF of the second trigger A10, second triggering
Device A10 Q ends connect the drive circuit 40.
Please continue to refer to Fig. 2, the input of the drive circuit 40 connects the Q ends of the second trigger A10, the drive
The output end of dynamic circuit 40 connects the grid of the synchronous rectifier M2, so that the drive signal exported according to logic circuit 30 drives
Dynamic synchronous rectifier M2 break-make, when the drive signal that logic circuit 30 is exported is high level, drive circuit 40 drives synchronization
Rectifying tube M2 is opened, when the drive signal that logic circuit 30 is exported is low level, the driving synchronous rectifier of drive circuit 40 M2
Disconnect, so as to realize synchronous rectifier M2 correct unlatching.
In order to be better understood from the present invention, technical scheme is elaborated below in conjunction with accompanying drawing：
When Vd2 waveforms change from t1 to t2 in analysis chart 3 first, Vds voltages fall below its high threshold Vd2_ during t1 moment
H, the first comparator A1 output voltages be high level, now the current source I1 in the time detection circuit 102 start for
Electric capacity C1 charges, and when time t2, because the electric capacity C1 is not charged to the reference voltage Vref 3 yet, the 3rd compares letter
Number comp3 signals remain high level, but now Vds voltages are had been reduced to less than its low threshold voltage Vd2_l, now described
Second comparison signal comp2 of the second comparator A2 outputs switchs to high level by low level, so, when the second comparison signal
When comp2 and the 3rd comparison signal comp3 is simultaneously high, the control signal of the output of the signal processing circuit 104 is high electricity
Flat, the synchronous rectifier M2 can be unlocked.
Secondly when Vds waveforms change from t4 to t5 in analysis chart 3, Vds voltages fall below its high threshold during t4 moment
Vd2_h, the first comparison signal comp1 of the first comparator A1 outputs is high level, now the time detection circuit 102
In current source I1 start for electric capacity C1 charge, when time t5, due to the electric capacity C1 be charged to it is described with reference to electricity
Vref3 is pressed, the 3rd, which compares comp3 signals, switchs to low level, but now Vds voltages do not fall below its low threshold voltage still
Vd2_l, now the second comparison signal comp2 of the output of the second comparator A2 remain low level, compare letter when second
Number comp2 and the 3rd comparison signal comp3 non-concurrent for it is high when, the output signal ON of the signal processing circuit 104 is remained
Low level, phenomenon is opened so as to efficiently avoid because the synchronous rectifier M2 caused by resonance signal is opened by mistake.
In summary, the present invention detects circuit, the voltage change of detection synchronous rectifier drain electrode by setting voltage slope
Slope, accurately distinguish its drain terminal voltage change be due to primary side main power tube shut-off caused by or synchronous rectifier shut-off after
Caused by resonance, opened so as to avoid synchronous rectifier from being opened by mistake due to resonance, further realize synchronous rectifier just
Really open.
It is understood that for those of ordinary skills, can be with technique according to the invention scheme and its hair
Bright design is subject to equivalent or change, and all these changes or replacement should all belong to the guarantor of appended claims of the invention
Protect scope.
Claims (9)
1. a kind of control circuit of synchronous rectifier, it is characterised in that including:
Voltage slope detect circuit, for detect synchronous rectifier drain-source two ends voltage change slope and output control letter
Number；
Transformer and synchronous rectifier output-stage circuit；
Logic circuit, the control signal for detecting circuit output to voltage slope carries out logical calculated and output drive signal control
The break-make of synchronous rectifier processed；
Drive circuit, the drive signal for being exported according to logic circuit drives the break-make of synchronous rectifier；
The voltage slope detection circuit, logic circuit, drive circuit and transformer and synchronous rectifier output-stage circuit are successively
Connection.
2. the control circuit of synchronous rectifier according to claim 1, it is characterised in that the transformer and synchronous rectification
Pipe output-stage circuit includes primary side transformer, primary side main power tube, primary side sampling resistor, secondary side transformer, output capacitance and same
Rectifying tube is walked, one end connection of the primary side transformer receives input voltage, and the other end connection of the primary side transformer is described
The drain electrode of primary side main power tube, the source electrode of the primary side main power tube is grounded by the primary side sampling resistor, the primary side master
The grid of power tube receives main drive signal, one end output output voltage of the secondary transformer, and connects output capacitance
One end, the drain electrode of the other end connection synchronous rectifier of the secondary transformer, the source ground of the synchronous rectifier,
Also the other end of the output capacitance is connected, the grid of the synchronous rectifier connects the drive circuit.
3. the control circuit of synchronous rectifier according to claim 2, it is characterised in that the voltage slope detects circuit
Including：
First voltage threshold detection unit, the high threshold part for detecting synchronous rectifier drain-source both end voltage, and export the
One comparison signal；
Second voltage threshold detection unit, the Low threshold part for detecting synchronous rectifier drain-source both end voltage, and export the
Two comparison signals；
Time detecting unit, for generation time reference quantity, and exports the 3rd comparison signal；
Signal processing unit, for carrying out logical calculated processing, and output control to the second comparison signal and the 3rd comparison signal
Signal is to the logic circuit；
The first voltage threshold detection unit, time detecting unit and signal processing unit are sequentially connected, the signal transacting
Unit is also connected with the second voltage threshold detection unit.
4. the control circuit of synchronous rectifier according to claim 3, it is characterised in that the first voltage threshold test
Unit includes first resistor, second resistance and first comparator, and one end of the first resistor is signal receiving end, receives described
The drain-source voltage of synchronous rectifier, also connects the second voltage threshold detection unit, the other end connection of the first resistor
One end of second resistance and the inverting input of the first comparator, the positive input terminal input first of the first comparator are pre-
If reference voltage, the output end of the first comparator connects the time detecting unit, another termination of the second resistance
Ground.
5. the control circuit of synchronous rectifier according to claim 4, it is characterised in that the second voltage threshold test
Unit includes the first metal-oxide-semiconductor and the second comparator, and one end of the drain electrode connection first resistor of first metal-oxide-semiconductor also connects
The drain-source voltage of the synchronous rectifier is received, the source electrode of first metal-oxide-semiconductor connects the inverting input of second comparator,
The grid connection VDD power supplys of first metal-oxide-semiconductor, the positive input terminal of second comparator inputs the second predetermined reference voltage,
The output end of second comparator connects the signal processing unit.
6. the control circuit of synchronous rectifier according to claim 5, it is characterised in that the time detecting unit includes
The the first comparison signal control exported by the first comparator that current source, the first phase inverter, high level conducting, low level disconnect
The second switch controlled by first inverter output signal that the first switch of system, low level conducting, high level disconnect, the
One electric capacity and the 3rd comparator, one end connection VDD power supplys of the current source, the other end connection described first of the current source
One end of switch, what the output end of the first comparator exported that the first comparison signal controls the first switch leads on-off
Open, the other end of the first switch is grounded by the second switch, also connect the inverting input of the 3rd comparator
With one end of the first electric capacity, the other end of first electric capacity is grounded, and the positive input terminal input the 3rd of the 3rd comparator is pre-
If reference voltage, the output end of the 3rd comparator connects the signal processing unit, the input of first phase inverter
The output end of the first comparator is connected, the output end output signal control second switch of first phase inverter leads on-off
Open.
7. the control circuit of synchronous rectifier according to claim 6, it is characterised in that the signal processing unit includes
Second phase inverter, the 3rd phase inverter, the 4th phase inverter, first and door and the first trigger, the input of second phase inverter
Connect the output end of second comparator and the input of the 4th phase inverter, the output end connection of second phase inverter
The input of 3rd phase inverter, the output end of the 3rd phase inverter connects the second input of described first and door, institute
The first output end that the 3rd comparator is connected with the first input end of door is stated, described first is connected described with the output end of door
The S ends of first trigger, the R ends of first trigger connect the output end of the 4th phase inverter, first trigger
Q ends connect the logic circuit.
8. the control circuit of synchronous rectifier according to claim 7, it is characterised in that the logic circuit includes second
Trigger, the S ends of second trigger connect the Q ends of first trigger, the R ends input shut-off of second trigger
Signal, the Q ends of second trigger connect the drive circuit.
9. the control circuit of synchronous rectifier according to claim 8, it is characterised in that the input of the drive circuit
The Q ends of the second trigger are connected, the output end of the drive circuit connects the grid of the synchronous rectifier.
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| CN109980946A (en) * | 2019-04-18 | 2019-07-05 | 深圳南云微电子有限公司 | A kind of synchronous commutating control circuit and its control method |
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| CN110855131B (en) * | 2019-12-09 | 2021-10-15 | 成都芯源系统有限公司 | Drive circuit of synchronous rectifier |
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| CN110752755A (en) * | 2019-12-10 | 2020-02-04 | 成都芯源系统有限公司 | Synchronous rectification switching power supply circuit, secondary side control circuit and method thereof |
| CN112134465A (en) * | 2020-09-09 | 2020-12-25 | 深圳市必易微电子股份有限公司 | Synchronous rectification control circuit and voltage converter |
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| CN112865541B (en) * | 2021-01-22 | 2022-03-29 | 成都启臣微电子股份有限公司 | Synchronous rectification controller, synchronous rectification system and synchronous rectification control method |
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| CN113141101A (en) * | 2021-04-08 | 2021-07-20 | 深圳市必易微电子股份有限公司 | Synchronous rectification control circuit, control method and isolated switching power supply |
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| CN113507215B (en) * | 2021-06-21 | 2022-09-20 | 艾科微电子(深圳)有限公司 | Synchronous rectification control device, power supply and synchronous rectification control method |
| WO2023004592A1 (en) * | 2021-07-27 | 2023-02-02 | 华为数字能源技术有限公司 | Method and apparatus for controlling power conversion circuit, storage medium, and program product |
| CN113746358A (en) * | 2021-08-16 | 2021-12-03 | 西安鼎芯微电子有限公司 | Synchronous rectification switch control circuit |
| CN113970375A (en) * | 2021-09-10 | 2022-01-25 | 北方广微科技有限公司 | Time sequence protection circuit applied to uncooled infrared focal plane reading circuit |
| CN113970375B (en) * | 2021-09-10 | 2023-12-19 | 北方广微科技有限公司 | Timing sequence protection circuit applied to uncooled infrared focal plane readout circuit |
| CN117155136A (en) * | 2023-10-27 | 2023-12-01 | 茂睿芯（深圳）科技有限公司 | Synchronous rectification control circuit and method for inhibiting ringing false turn-on of rectifier tube |
| CN117155136B (en) * | 2023-10-27 | 2024-01-26 | 茂睿芯（深圳）科技有限公司 | Synchronous rectification control circuit and method for inhibiting ringing false turn-on of rectifier tube |
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