CN106452086B - A kind of synchronous commutating control circuit - Google Patents
A kind of synchronous commutating control circuit Download PDFInfo
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- CN106452086B CN106452086B CN201610932816.7A CN201610932816A CN106452086B CN 106452086 B CN106452086 B CN 106452086B CN 201610932816 A CN201610932816 A CN 201610932816A CN 106452086 B CN106452086 B CN 106452086B
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- switch pipe
- side switch
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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
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/10—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers
- H02H7/12—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers
- H02H7/1213—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers for DC-DC 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 synchronous commutating control circuit, the circuit includes: primary circuit, secondary circuit；The primary circuit includes primary side inductance, primary side switch pipe, primary side sampling resistor, and the secondary circuit includes secondary inductance, secondary-side switch pipe, secondary the second sampling resistor in the first sampling resistor, pair, the secondary load resistance in capacitor, pair, synchronous rectification control chip.The present invention is by way of Cycle by Cycle analogy, the drain terminal voltage Vd that detection secondary inductance is connected with secondary-side switch pipe SR_MOSFET, it can make IC work that can accurately control discharge the time point completed in DCM/CCM mode, effective judgement shutdown point, realize and shift to an earlier date turn-off function solve the problems, such as not realizing under DCM/CCM both of which and accurately turn off simultaneously in the prior art；It can simplify peripheral applications circuit simultaneously, reduce application device.
Description
Technical field
The present invention relates to synchronous rectification field more particularly to a kind of synchronous commutating control circuits.
Background technique
Synchronous rectification is the special power MOSFFT that uses on state resistance extremely low to replace rectifier diode to reduce rectification
One technology of loss.Since primary side switch pipe cut-off time, the conducting of secondary-side switch pipe, secondary inductance starts to discharge, in pair
At the end of side inductive discharge closes on, secondary-side switch pipe will be turned off, and especially after the completion of secondary inductance discharges, secondary-side switch pipe must
It must turn off, otherwise will lead to secondary output capacitance and inversely discharge, there is aircraft bombing risk.
The method for solving the shutdown of secondary-side switch pipe at present has following several:
1. utilize voltagesecond product conservation: first sample primary side switch pipe turn-on instant secondary inductance both ends voltage with hold time
Product (secondary inductance both end voltage be converted into current signal and and time integral, become the voltage on secondary side capacitor), then
Re-sampling output voltage and be converted into electric current when primary side switch pipe ends flyback and charge to capacitor C2, compare two voltages come it is real
The time point of existing secondary-side switch pipe shutdown.The advantages of the method is greatly can also be with even if the variation of primary side turn-on time under discontinuous mode
Accurately determine when shutdown secondary-side switch pipe；The disadvantage is that interfering vulnerable to input voltage fluctuation, and need to detect primary side electricity
Feel both end voltage.
2, it directly samples secondary inductance reverse side voltage Vd: turning off secondary-side switch pipe when Vd is greater than 0V, led when less than 0V
The advantages of logical secondary-side switch pipe, the method is that detection mode is simple, unrelated with the variation of primary side sampled voltage under discontinuous mode；Disadvantage
It is that cannot support continuous mode, secondary inductance is easy to cause inversely to discharge, and requires the speed of driving shutdown secondary-side switch pipe
It is fast.
3, other: the synchronous rectification done for primary side structure, control makes secondary side electricity in linear zone after the conducting of secondary-side switch pipe
The Vgs of secondary-side switch pipe increases when stream reduces and Vds is constant, and such primary side sampled voltage is relatively stable, is conducive to system and stablizes
Property, the advantages of the method is that former secondary side structural system is stablized；The disadvantage is that it is big that opposite meeting is lost in linear zone in the work of secondary-side switch pipe
A bit.
It is therefore proposed that a kind of loss is small, while compatible continuous mode and the synchronous commutating control circuit of discontinuous mode are urgently
Problem to be solved.
Summary of the invention
Based on problem of the existing technology, the present invention proposes a kind of synchronous commutating control circuit, comprising: primary circuit,
Secondary circuit；The primary circuit includes primary side inductance, primary side switch pipe, primary side sampling resistor, the same phase of the primary side inductance
End connects one end of the primary side switch pipe, and the other end of the primary side switch pipe connects one end of the primary side sampling resistor,
The other end of the primary side sampling resistor connects the ground terminal of the primary circuit, and the control terminal of the primary side switch pipe connects primary side
Control signal；The secondary circuit include secondary inductance, secondary-side switch pipe, it is secondary in the first sampling resistor, it is secondary while second sample electricity
Resistance, secondary load resistance, synchronous rectification in capacitor, pair control chip；The secondary inductance in-phase end connection it is described synchronize it is whole
One end of the power end of flow control chip, the secondary load resistance in positive, the described pair of capacitor；The secondary inductance it is anti-
Phase end connects one end of one end of the secondary-side switch pipe, the first sampling resistor of the secondary side；The first sampling resistor of the pair side
The other end connect one end of the input terminal of synchronous rectification control chip, the second sampling resistor of the secondary side, the pair side
The cathode of capacitor, the other end of secondary side load resistance, the other end of the secondary-side switch pipe, the synchronous rectification control chip
Ground terminal is connected to the ground terminal of the secondary circuit, and the control terminal of the secondary-side switch pipe connects the synchronous rectification control chip
Output end, there are parasitic diodes between one end and the other end of the secondary-side switch pipe.
Preferably, the synchronous rectification control chip detects the voltage of the reverse side of the secondary inductance, when the reverse phase
The voltage at end is greater than first threshold and/or is continued above the time of second threshold, this voltage is effective voltage, then judges institute at this time
The conducting of primary side switch pipe is stated, the secondary inductance and the primary side inductance generate electromagnetic induction, and the secondary-side switch pipe, which is in, to close
Disconnected state；It is described when the voltage of the reverse side drops to less than zero by the effective voltage when primary side switch pipe shutdown
The conducting of secondary-side switch pipe, the secondary inductance electric discharge, pair side capacitor charging；Completion is closed in secondary inductance electric discharge
When, the secondary-side switch pipe shutdown.
Preferably, the synchronous rectification control chip detects the voltage of reverse side described in this period by the effective voltage
It when dropping to less than zero, i.e., is delayed after the failing edge of effective voltage or failing edge a period of time, output drive signal drives institute
State the conducting of secondary-side switch pipe.
Preferably, under synchronous rectification control chip detects the voltage of the reverse side by the effective voltage
When first failing edge of drop is to first subsequent rising edge, output cut-off signals make the secondary-side switch pipe shutdown.
Preferably, the synchronous rectification control chip detects the operating mode of the secondary inductance, in adjacent institute twice
State the rising edge quantity that the voltage of the secondary inductance reverse side in the secondary-side switch pipe turn-off time is begun to ramp up by zero volt or so
As judgment basis, when the quantity of the rising edge is more than or equal to 2, judge the secondary inductance work in discontinuous mode；It is no
Then, judge the secondary inductance work in continuous mode.
Preferably, the synchronous rectification control chip detects and records the first conducting of primary side switch pipe described in a period
Time, and to be less than or equal to some numerical value of first turn-on time in a upper period for the first benchmark；With described
The sum of the first turn-on time of primary side switch pipe and second turn-on time of secondary-side switch pipe are cycle time, and to be less than or equal to
Some numerical value of the cycle time in a upper period be the second benchmark, by first turn-on time in this period with
First benchmark is compared, and according to comparison result, controls the shutdown moment of the secondary-side switch pipe.
Preferably, the synchronous rectification control chip detects the first turn-on time of the primary side switch pipe in this period
Greater than first benchmark, then after the primary side switch pipe shutdown in this period, the secondary-side switch pipe conducting is controlled, at this
When the cycle time in period is equal to second benchmark, the secondary-side switch pipe shutdown is controlled.
Preferably, the synchronous rectification control chip detects the first turn-on time of the primary side switch pipe in this period
Less than first benchmark, and the difference of the two is less than the second setting value, meanwhile, detect that synchronous commutating control circuit work exists
When discontinuous mode, then after the primary side switch pipe shutdown in this period, the secondary-side switch pipe conducting is controlled, in this period
When the cycle time is equal to second benchmark, the secondary-side switch pipe shutdown is controlled.
Preferably, the synchronous rectification control chip detects the first turn-on time of the primary side switch pipe in this period
Less than first benchmark, and the difference of the two is more than or equal to the second setting value, meanwhile, detect circuit work in discontinuous mode
When, then the secondary-side switch pipe described in this period is not turned on, in an off state.
Preferably, the synchronous rectification control chip detects the first turn-on time of the primary side switch pipe in this period
Less than first benchmark, meanwhile, synchronous commutating control circuit work is detected in continuous mode, then described in this period
After the shutdown of primary side switch pipe, the secondary-side switch pipe conducting is controlled, is equal to second base in the cycle time in this period
On time, the secondary-side switch pipe shutdown is controlled.
Preferably, this period the primary side switch pipe shutdown after or shutdown after be delayed a period of time, it is described synchronize it is whole
The conducting of secondary-side switch pipe described in flow control chip controls.
Preferably, the synchronous rectification control chip detects that secondary-side switch pipe turn-on time described in this period is more than third
When setting value, then the secondary-side switch pipe is turned off.
The beneficial effect of the present invention compared with the prior art is:
The present invention detects the leakage that secondary inductance is connected with secondary-side switch pipe SR_MOSFET by way of Cycle by Cycle analogy
Voltage Vd is held, can make synchronous rectification control chip that can accurately control discharge the time point completed in DCM/CCM mode, have
The judgement of effect turns off point, realizes and shifts to an earlier date turn-off function, not only realizes high efficiency, but also can prevent SR_MOSFET from leading because of reverse electric discharge
Cause the possibility of aircraft bombing；The difficulty accurately turned off can not while can be realized under DCM/CCM both of which in the prior art by solving
Topic；It can simplify peripheral applications circuit simultaneously, reduce application device.
Detailed description of the invention
Fig. 1 is a kind of structural schematic diagram of synchronous rectification chip of the invention；
Fig. 2 is a kind of structural schematic diagram of the synchronous rectification chip of embodiment of the invention；
Fig. 3 is synchronous rectification chip discontinuous mode working waveform figure of the invention；
Fig. 4 is synchronous rectification chip continuous mode working waveform figure of the invention；
The waveform diagram that Fig. 5 is turned off in advance when being discontinuous mode of the invention；
Fig. 6 is the waveform diagram of discontinuous mode error protection of the invention；
Advanced shutdown waveform diagram when Fig. 7 is both of which of the invention；
Fig. 8 is the structural schematic diagram of synchronous commutating control circuit figure of the invention；
Fig. 9 is the method for rectifying flow diagram of circuit of synchronous rectification of the invention；
Figure 10 is the synchronous commutating control circuit waveform diagram under discontinuous mode of the invention；
Figure 11 is the synchronous commutating control circuit waveform diagram under continuous mode of the invention.
Specific embodiment
Fig. 1 show synchronous rectification chip structure schematic diagram of the invention, and the synchronous rectification chip includes: that conducting is initial
Change module 10, voltage detection module 20, mode deciding module 30, failure protection module 40, advanced shutdown module 50, selecting module
60, time setting module 70, control module 80, trigger module 90, drive module 100.The conducting initialization module 10, voltage
Detection module 20, mode deciding module 30 are respectively connected to voltage input end；The conducting initialization module 10 connects the electricity
Detection module 20 is pressed, the voltage detection module 20 is separately connected the failure protection module 40, advanced shutdown module 50, control
Module 80, trigger module 90；The mode deciding module 30, failure protection module 40 connect the input of the selecting module 60
End；The selecting module 60, the voltage detection module 20, the advanced shutdown module 50, the turn-on time setting module
The input terminal of the 70 connection control modules 80；The selecting module 60 respectively with mode deciding module 30, failure protection module
40, control module 80 connects；The control module 80 respectively with time setting module 70, voltage detection module 20, advanced shutdown
Module 50, selecting module 60, trigger module 90 connect；The time setting module 70 respectively with trigger module 90, drive module
100 connections.The mode deciding module 30, failure protection module 40 connect the input terminal of the selecting module 60, the selection
Module 60, the advanced shutdown module 50, the time setting module 70 connect the input terminal of the control module 80, the control
The output end of molding block 80 connects the trigger module 90, and the output end of the trigger module 90 connects the drive module 100.
1, the conducting initialization module 10 is for when judging input voltage for effective input voltage, output to allow that letter is connected
Number A1.Input voltage VS is compared by the conducting initialization module 10 with first threshold, when input voltage is greater than the first threshold
When value and/or duration are more than second threshold, then this input voltage is effective input voltage, and conducting initialization module 10 exports
Allow Continuity signal A1 to voltage detection module 20.
The first threshold for voltage, second threshold for the time, be preset.
When high voltage input is inputted with low-voltage, first threshold is different, thus two comparators are arranged to input
Voltage is compared.Specifically, the first threshold includes the first high voltage threshold and/or the first low voltage threshold, right respectively
High voltage input is answered to input two kinds of different conditions with low-voltage.First high voltage threshold is inputted corresponding to high voltage, described
First low voltage threshold is inputted corresponding to low-voltage.
2, the voltage detection module 20 is used to detect numerical value, cycle time and the effective input voltage of input voltage
The first duration；When the permission Continuity signal A1 is effective, control Continuity signal A2 is exported to the trigger module 90；
The voltage detection module 20 exports first duration to the failure protection module 40；The cycle time is defeated
Out to the advanced shutdown module 50；According to the ratio of effective input voltage and the first setting value (the first setting value is less than or equal to zero)
Compared with as a result, output voltage comparing signals A 3 gives the control module 80.
When the permission Continuity signal A1 is effective, it is delayed in effective input voltage failing edge or after failing edge
For a period of time, control Continuity signal A2 is exported to the trigger module 90；The trigger module 90 is connected according to the control to be believed
Number A2 exports Continuity signal；The drive module is according to the Continuity signal output driving Continuity signal.
Input voltage VS is compared by the voltage detection module 20 with the first setting value, output voltage comparing signals A 3
To control module 80；First setting value is less than or equal to no-voltage.First setting value is default for voltage
's.
The voltage detection module 20 records duration when input voltage is greater than first threshold, and will it is described persistently when
Between waveform at export to failure protection module 40.
The voltage detection module 20 records input voltage from effective input voltage rising edge to another subsequent rising
The time on edge using time period as a cycle, and the cycle time waveform AT is exported to advanced shutdown module 50.
3, the mode deciding module 30 is for judging that external circuit operating mode is continuous mode or discontinuous mode.
Specifically, the mode deciding module 30 is used for the oscillation according to input voltage between two adjacent effective input voltages
Number judges that external circuit operating mode is continuous mode or discontinuous mode.The record of mode deciding module 30 two is adjacent effectively defeated
The number for entering input voltage rising edge between voltage determines that operating mode is discontinuous mode when the number is more than or equal to 2,
It otherwise is continuous mode；And output mode signal ccmH is to selecting module 60.Continuous mode or discontinuous mode refer to where chip
External circuit operating mode.
4, the failure protection module 40 is according to described the first of first duration in a upper period and this period
Duration exports error protection signal ftpL.
The failure protection module 40 be less than or equal to a upper period first duration a certain numerical value for the
One benchmark exports error protection signal according to the comparison result of first duration in this period and first benchmark
ftpL。
Failure protection module 40, with the first duration waveform at of effective input voltage that voltage detection module 20 exports
For foundation, the first duration of effective input voltage when a upper period was recorded, and to have when being less than or equal to the upper period
The a certain numerical value for imitating first duration of input voltage is the first benchmark.First when this period effective input voltage holds
The continuous time, and when the difference of the two is more than or equal to the second setting value, output error protection signal ftpL was to selecting less than the first benchmark
Select module 60.First duration is the duration of effective input voltage.
5, the advanced shutdown module 50 is with a certain numerical value of the cycle time less than or equal to a upper period for second
Benchmark exported advanced cut-off signals according to the cycle time of the cycle time in this period and a upper period.
It is described it is advanced shutdown module be less than or equal to a upper period the cycle time a certain numerical value be the second benchmark,
According to the cycle time of the cycle time in this period and a upper period, advanced cut-off signals were exported.
Advanced shutdown module 50, the periodic waveform AT exported using voltage detection module 20 is foundation, a cycle on record
Cycle time, and be less than or equal to the upper a cycle cycle time a certain numerical value be the second benchmark, when this period
Cycle time be greater than the second benchmark when, export advanced cut-off signals A5.The cycle time in a upper period inputs from effective
Voltage starts, until termination when effective input voltage drops to less than zero and is greater than zero again.
6, the selecting module 60 for determining whether the error protection signal is effective according to the operation mode.
According to the operation mode, the error protection signal in discontinuous mode is exported to described for the selecting module 60
Control module, by the error protection signal shielding in continuous mode.
The selecting module 60 determines the error protection signal according to the output signal of the mode deciding module 30
Whether ftpL is effective, and when operating mode is continuous mode, the error protection signal is shielded, when operating mode is interrupted mould
The error protection signal is effective when formula.The selecting module exports selection signal A4.
7, the turn-on time setting module 70 is used to control the maximum retention time of the Continuity signal, in turn-on time
Output overtime signal A6 gives the control module 80 when reaching maximum value.
The turn-on time setting module 70 samples the initial time of Continuity signal and starts timing, when Continuity signal continues
When time is more than setting time, output overtime signal A6 gives the control module 80.
The turn-on time setting module 70, in the rising edge of trigger signal, the start recording triggered time, when closed between
When more than third setting value, 80 output overtime signal A6 of turn-on time setting module is to control module 80.The third setting value
It is preset.
The rising edge of trigger signal can also in the chips relevant position sampling, not only in the output of trigger module
End.
8, the control module 80 is according to the selecting module 60, the voltage detection module 20, the advanced shutdown mould
The output of block 50, the turn-on time setting module 70 exports control cut-off signals to the trigger module 90.
The voltage detection module 20, the advanced shutdown module 50, the selecting module 60, turn-on time setting
When the output signal of at least one module is effective in module 70, the control module 80 exports control cut-off signals to the triggering
Module 90；The trigger module 90 exports cut-off signals according to the control cut-off signals.
9, output signal of the trigger module 90 according to the voltage detection module 20 and the control module 80, output
Continuity signal or cut-off signals.
For trigger module 90 when the control Continuity signal A2 that voltage detection module 20 exports is effective, trigger module 90 is effective
Delay a period of time output Continuity signal after the failing edge or failing edge of input voltage；In the control shutdown that control module 80 exports
When signal is effective, trigger module 90 exports cut-off signals.
10, the drive module 100 is used for according to the Continuity signal or the cut-off signals, output drive signal.
It elaborates below to the working method of above-mentioned synchronous rectification chip.
Input voltage is detected, allows to lead when input voltage is greater than first threshold and/or the duration is more than second threshold
Logical, the input voltage is effective input voltage, when input voltage is less than zero after effective input voltage, that is, it is described
The failing edge of effective input voltage, or be delayed after the failing edge a period of time, the trigger module of chip exports Continuity signal；
When input voltage is by rising above zero less than zero, that is, input voltage is more than or equal to the first setting value, the triggering of chip
Module 90 exports cut-off signals.
The cycle time in a upper period was recorded, with a certain numerical value of the cycle time less than or equal to a upper period for the second base
It is quasi-；The cycle time is since effective input voltage, until effective input voltage drops to less than zero and is greater than zero again
When terminate.
A record upper period is greater than first threshold in input voltage and/or the duration is more than effective input of second threshold
First duration of voltage, to be less than or equal to a certain numerical value of first duration for the first benchmark.
The number of input voltage rising edge between effective input voltage of the upper period and this period effective input voltage was recorded,
The operating mode that external circuit is judged with the value of the number is discontinuous mode DCM when the value of the number is more than or equal to 2, no
It is then continuous mode CCM.
When the first duration of effective input voltage in this period being more than or equal to the first benchmark, according to voltagesecond product conservation
The cycle time of rule, this period can be greater than the second benchmark, then in the failing edge or failing edge of effective input voltage in this period
Delay a period of time afterwards exports Continuity signal, when the cycle time in this period being more than or equal to the second benchmark, the trigger mode of chip
Block 90 exports cut-off signals, realizes advanced shutdown.
When the first duration of effective input voltage in this period is less than the first benchmark, and the difference of the two is less than
Two setting values, while external circuit work in discontinuous mode, then after the failing edge of effective input voltage in this period, output is led
Messenger, when the cycle time in this period being more than or equal to the second benchmark, the trigger module 90 of chip exports cut-off signals, realizes
Advanced shutdown.
When this period effective input voltage duration less than the first benchmark, and the difference of the two is more than or equal to second
Setting value, while external circuit works in discontinuous mode, then after the failing edge of effective input voltage in this period, the touching of chip
It sends out module 90 and exports cut-off signals, realize advanced shutdown.
When this period effective input voltage duration less than the first benchmark, while external circuit work is in continuous mode
When, then after the failing edge of effective input voltage in this period, trigger module 90 exports Continuity signal；At the period in this period
Between when being more than or equal to the second benchmark, the trigger module 90 of chip exports cut-off signals, realizes advanced shutdown.
When the Continuity signal duration that the trigger module 90 of chip exports being more than or equal to third setting value, the touching of chip
It sends out module 90 and exports cut-off signals.
In next period, the foundation that chip is judged using first benchmark in this period, the second benchmark as shutdown, according to similar
Working method, trigger module 90 exports Continuity signal and cut-off signals, while recording first benchmark in a period, the second base
Prepare to use.
Fig. 2 be a kind of embodiment of the invention synchronous rectification chip structural schematic diagram, wherein selecting module 60 be by
It is realized with door, control module 80 is realized that trigger module 90 is realized by d type flip flop by nor gate.
Fig. 3 is synchronous rectification chip discontinuous mode working waveform figure of the invention.As shown in figure 3, voltage detection module 20
It detects input voltage and is greater than zero and minus variation.High level is exported when input voltage is greater than zero, when input voltage is less than
Low level is exported when zero, voltage comparison signal waveform between two neighboring effective input voltage, works as voltage as shown in A3 in figure
When the pulse number of comparison signal is more than or equal to 2,30 output mode of mode deciding module judges that signal ccmH for high level, is indicated
External circuit operating mode is discontinuous mode DCM, after this high level continues to effective input voltage next time and is delayed one section
Time, when the pulse number of voltage comparison signal is less than 2,30 output mode of mode deciding module judges signal ccmH for low electricity
Flat, expression external circuit operating mode is continuous mode CCM, and operating mode signal waveform is as shown in ccmH waveform in figure；Alternatively, electric
Pressing detection module 20 to detect input voltage is compared with some numerical value less than zero or greater than zero, show that voltage compares letter
Number.
Input voltage Vs is compared by conducting initialization module 10 with first threshold, when input voltage Vs is greater than the first threshold
When value and/or duration are greater than second threshold, which is effective input voltage, and the conducting output of initialization module 10 is permitted
Perhaps Continuity signal allows Continuity signal waveform as shown in A1 in figure to voltage detection module 20.
Voltage detection module 20 is when allowing Continuity signal effective, in the failing edge output control Continuity signal of input voltage
To trigger module 90, Continuity signal waveform is controlled as shown in waveform A2 in figure；Control is exported when input voltage is greater than zero again
Cut-off signals, trigger module 90 export on or off signal according to control Continuity signal and control cut-off signals, and waveform is such as
In figure shown in Gate.
Alternatively, voltage detection module 20 allow Continuity signal it is effective when, failing edge of the trigger module 90 in input voltage
Delay a period of time exports control Continuity signal again afterwards, but when input voltage is greater than zero must export control cut-off signals.
In the present embodiment, the first setting value is zero；In this application, the first setting value is some less than or equal to zero
Numerical value.
Fig. 4 is synchronous rectification chip continuous mode working waveform figure of the invention；As shown in figure 4, voltage detection module 20
It detects input voltage and is greater than zero and minus variation, high level is exported when input voltage is greater than zero, when input voltage is less than
Low level is exported when zero, voltage comparison signal is as shown in waveform A3 in figure.
Between two adjacent effective input voltages, when the pulse number of voltage comparison signal is less than 2, mode deciding module
30 output low levels, expression external circuit operating mode is continuous mode, and mode decision waveform is as shown in ccmH waveform in figure.
Input voltage Vs is compared by conducting initialization module 10 with first threshold, when input voltage Vs is greater than the first threshold
When value and/or duration are greater than second threshold, which is effective input voltage, and the conducting output of initialization module 10 is permitted
Perhaps Continuity signal allows Continuity signal waveform as shown in A1 in figure to voltage detection module 20.
Voltage detection module 20 is in the failing edge of effective input voltage, i.e., when permission Continuity signal is effective, output control is led
Messenger controls the waveform diagram of Continuity signal as shown in waveform A2 in figure to trigger module 90.
Trigger module 90 effective input voltage failing edge output drive signal, input voltage be greater than zero when, also
It is when voltage comparison signal is effective, control module 80 exports control cut-off signals to trigger module 90, and trigger module 90 exports
Cut-off signals, 90 output waveform of trigger module is as shown in waveform Gate in figure.Alternatively, trigger module 90 is in effective input voltage
Delay a period of time output drive signal again after failing edge, but when input voltage is greater than zero, must export cut-off signals.
The waveform diagram that Fig. 5 is turned off in advance when being discontinuous mode of the invention；As shown in figure 5, T1 was the period in a upper period
Time, t11 are the first duration of a upper period effective input voltage, and t12 is upper periodical input voltage minus the
Two duration.
T2 is the cycle time in this period, and t21 is the first duration of this period effective input voltage, and t22 is this week
Phase input voltage minus second duration.
The waveform of first duration is as shown at waveform in figure, and the waveform of cycle time is as shown in AT waveform in figure；Mould
The output of formula judgment module is as shown in ccmH waveform in figure.
Taking the numerical value t3 less than upper cycle duration t11 is the first benchmark, is taken less than upper cycle time T1
Numerical value t1 be the second benchmark, it is fixed according to voltagesecond product conservation when the first duration t21 in this period is more than or equal to numerical value t3
Rule, T2 are greater than T1, are limited with the second benchmark t1, when the cycle time in this period being equal to the second benchmark t1, turn off module in advance
The 50 advanced cut-off signals of output, control module 80 export control cut-off signals to trigger module according to the advanced cut-off signals
90, for advanced cut-off signals waveform as shown in A5 in figure, trigger module 90 exports cut-off signals, waveform such as Gate waveform institute in figure
Show, Gate waveform is delayed just effective for a period of time after the failing edge of effective input voltage in this example.
T21 is greater than t11 in the present embodiment, and error protection is without output, as shown in ftpL waveform in Fig. 5.
Fig. 6 is the waveform diagram of discontinuous mode error protection of the invention.In Fig. 6, mode deciding module judges external circuit
Operating mode is discontinuous mode, and exports the operating mode signal as shown in ccmH waveform in figure；
Different from Fig. 5 to be, the first duration t21 of effective input voltage in this period was less than the effective of a upper period
First duration t11 of input voltage, t3 are less than the number of the first duration t11 of effective input voltage in a period
Value, is taken as first benchmark in this period, and t21 is more than or equal to the second setting value, error protection with the difference less than the first benchmark t3
Module 40 exports error protection signal, and error protection signal waveform is as shown in ftpL waveform in figure；
In operating mode signal and error protection signal effective simultaneously, i.e., external circuit work is in discontinuous mode state and sheet
First duration of first duration of effective input voltage in period much smaller than effective input voltage in a upper period, choosing
Select module 60 and export selection signal A4 to control module 80, control module 80 according to the control signal export control cut-off signals to
Trigger module 90, trigger module 90 export cut-off signals, then chip does not export Continuity signal in this period, is held off.
Advanced shutdown waveform diagram when Fig. 7 is both of which of the invention.As shown in fig. 7, T1 is the period of period 1
Time, T2 are the cycle time of second round, and T3 is the cycle time of period 3；T1 is the of the cycle time of period 1
Two benchmark, t2 is the second benchmark of the cycle time of second round, when t3 continues for the first of period 1 effective input voltage
Between the first benchmark, t4 be second round effective input voltage the first duration the first benchmark；In the period 1 and the
Between the two adjacent effective input voltages of two cycles, there is oscillation in input voltage, there is the voltage comparison signal arteries and veins more than 2 times
Punching, mode deciding module judge that external circuit work in discontinuous mode, exports high level signal according to this umber of pulse；In second week
Between phase and period 3 two adjacent effective input voltages, input voltage is less than zero, voltage comparison signal no pulse, mode
Judgment module judges that external circuit work in continuous mode, exports low level signal；Mode decision signal waveform such as ccmH institute in figure
Show.
First duration t21 of second round effective input voltage is greater than the first benchmark of period 1, in second week
It is delayed after the failing edge of phase effective input voltage a period of time, trigger module 90 exports Continuity signal, in the period of second round
When time T2 is equal to the second benchmark t1 of period 1, advanced judgment module 50 exports advanced cut-off signals to control module 80,
Control module 80 exports control cut-off signals to trigger module 90, and trigger module 90 exports cut-off signals, realizes advanced shutdown.
First duration t31 of effective input voltage of period 3 is much smaller than the first benchmark t4 of second round,
That is the difference of the first benchmark t4 of the first duration t31 and second round of effective input voltage of period 3 is greater than
Equal to the second setting value, failure protection module 40 exports error protection signal, ftpL waveform in error protection signal waveform such as figure
It is shown；
Because the operating mode of period 3 external circuit is continuous mode, and the working frequency of external circuit is solid when connection mode
Fixed, i.e. cycle time T3 is equal with T2, therefore selecting module 60 masks this error protection signal, triggers mode 90 in third
Delay a period of time exports Continuity signal, Gate wave in Continuity signal waveform such as figure after the failing edge of effective input voltage in period
Shown in shape, when the cycle time T3 of period 3 is equal to the second benchmark t2 of second round, the advanced output of judgment module 50 is super
Preceding cut-off signals are to control module 80, and control module 80 exports control cut-off signals to trigger module 90, and trigger module 90 exports
Cut-off signals realize advanced shutdown.
Fig. 8 show a kind of structural schematic diagram of synchronous commutating control circuit of the invention.The synchronous rectification control electricity
Road includes primary circuit, secondary circuit.
The primary circuit includes primary inductor L p, primary side switch pipe PR, primary side sampling resistor Rcs；The primary side inductance
One end of the in-phase end connection primary side switch pipe PR of Lp, the one of the other end connection primary side sampling resistor Rcs of primary side switch pipe PR
The control at end, the ground terminal of another termination primary circuit of primary side sampling resistor Rcs, primary side switch pipe PR terminates primary-side-control
Signal.
The secondary circuit include secondary inductance L1, secondary-side switch pipe SR, it is secondary in the first sampling resistor R1, it is secondary while second adopt
Sample resistance R2, secondary load resistance R3, synchronous rectification in capacitor C2, pair control chip IC 1；The synchronous rectification controls chip
IC1 is that synchronous rectification above-mentioned controls chip.
The in-phase end connection synchronous rectification of secondary inductance L1 controls the power end of chip IC 1, the anode of pair side capacitor C2, institute
State one end of secondary side load resistance R3；First sampling in one end, the pair of switching tube SR of the reverse side auxiliary connection of secondary inductance L1
One end of resistance R1；The input terminal of the secondary other end connection synchronous rectification control chip IC 1 in the first sampling resistor R1, it is secondary while the
One end of two sampling resistor R2, the secondary cathode in capacitor C2, it is secondary while the other end of load resistance R3, secondary-side switch pipe SR it is another
The ground terminal that end, synchronous rectification control chip IC 1 is connected to the ground terminal of secondary circuit, and the control terminal of secondary-side switch pipe SR, which connects, to be synchronized
The output end of rectification control chip, there are parasitic diode D1 between one end and the other end of secondary-side switch pipe SR.
The primary inductor L p, secondary inductance L1 are the primary inductor L p of the same transformer, secondary inductance L1 respectively.
Synchronous rectification controls the voltage Vd that chip IC 1 detects secondary inductance L1 reverse side, as the voltage Vd of the reverse side
Partial pressure Vs be greater than first threshold and/or be continued above time of second threshold, this voltage is effective voltage, then judges former at this time
Side switching tube PR conducting, the secondary inductance L1 and primary inductor L p generate electromagnetic induction, and secondary-side switch pipe is in an off state.
When the primary side switch pipe turns off, when the voltage of the reverse side drops to less than zero by the effective voltage, institute
The conducting of secondary-side switch pipe, the secondary inductance electric discharge are stated, pair side capacitor charging closes on completion in secondary inductance electric discharge
When, the secondary-side switch pipe shutdown prevents the secondary side capacitor from passing through the secondary-side switch tube discharge.
The synchronous rectification control chip detects that the voltage of reverse side described in this period is dropped to by the effective voltage
When less than zero, i.e., it is delayed after the failing edge of effective voltage or failing edge a period of time, the output drive signal driving secondary side
Switching tube conducting.
Synchronous rectification control chip detects that the voltage of the reverse side is begun to decline by the effective voltage
When one failing edge is to first subsequent rising edge, output cut-off signals turn off the secondary-side switch pipe.
The synchronous rectification control chip detects the operating mode of the secondary inductance, to open on the adjacent secondary side described twice
The voltage for closing the secondary inductance reverse side in the pipe turn-off time is used as judgement by the rising edge quantity that zero volt or so is begun to ramp up
Foundation judges the secondary inductance work in discontinuous mode when the quantity of the rising edge is more than or equal to 2；Otherwise, judge institute
Secondary inductance work is stated in continuous mode.
The synchronous rectification control chip detects and records the first turn-on time of primary side switch pipe described in a period, and
With some numerical value of first turn-on time less than or equal to the upper period for the first benchmark；With the primary side switch
The sum of the first turn-on time of pipe and second turn-on time of secondary-side switch pipe are cycle time, and to be less than or equal to a upper period
The cycle time some numerical value be the second benchmark, by first turn-on time in this period and first benchmark
It is compared, according to comparison result, controls the shutdown moment of the secondary-side switch pipe.
The synchronous rectification control chip detects that the first turn-on time of the primary side switch pipe in this period is greater than institute
The first benchmark is stated, then after the primary side switch pipe shutdown in this period, the secondary-side switch pipe conducting is controlled, in this period
When the cycle time is equal to second benchmark, the secondary-side switch pipe shutdown is controlled.
The synchronous rectification control chip detects that the first turn-on time of the primary side switch pipe in this period is less than institute
State the first benchmark, and the difference of the two is less than the second setting value, meanwhile, detect synchronous commutating control circuit work in interrupted mould
When formula, then after the primary side switch pipe shutdown in this period, the secondary-side switch pipe conducting is controlled, in the week in this period
When time phase is equal to second benchmark, the secondary-side switch pipe shutdown is controlled.
The synchronous rectification control chip detects that the first turn-on time of the primary side switch pipe in this period is less than institute
The first benchmark is stated, and the difference of the two is more than or equal to the second setting value, meanwhile, detect that circuit works in discontinuous mode, then
The secondary-side switch pipe described in this period is not turned on, in an off state.
The synchronous rectification control chip detects that the first turn-on time of the primary side switch pipe in this period is less than institute
The first benchmark is stated, meanwhile, detect that synchronous commutating control circuit work in continuous mode, is then opened in the primary side in this period
After closing pipe shutdown, the secondary-side switch pipe conducting, when the cycle time in this period being equal to second benchmark, control are controlled
Make the secondary-side switch pipe shutdown.
It is delayed a period of time after the primary side switch pipe shutdown in this period or after shutdown, the synchronous rectification controls core
Piece controls the secondary-side switch pipe conducting.
The synchronous rectification control chip detects that secondary-side switch pipe turn-on time described in this period is more than third setting value,
Then turn off the secondary-side switch pipe.
It is described further below according to method for rectifying of the Fig. 9 to synchronous commutating control circuit.
The synchronous commutating control circuit includes primary circuit, secondary circuit, and the primary circuit is in a manner of electromagnetic coupling
Secondary circuit is connected, includes that synchronous rectification controls chip, secondary-side switch pipe, secondary inductance in the secondary circuit.Above one week
First duration of the effective voltage of phase secondary circuit and the cycle time of the synchronous commutating control circuit are foundation, incite somebody to action this
First duration of period effective voltage is compared with the duration of the upper period effective voltage, is compared
Relatively result；According to secondary inductance reverse side voltage, oscillatory regime is sentenced between upper period effective voltage and this period effective voltage
The operating mode of disconnected synchronous commutating control circuit；According to the comparison result and the operating mode, controls secondary-side switch pipe and lead
Logical or cut-off, realizes and controls secondary circuit with Cycle by Cycle analogical pattern.
To be less than or equal to the first duration of the upper period effective voltage for the first benchmark, described in being less than or equal to
The cycle time in a upper period is the second benchmark.
When the secondary inductance reverse side voltage vibrates time between upper period effective voltage and this period effective voltage
When number is more than or equal to 2, decision circuitry work is in discontinuous mode, and otherwise circuit work is in continuous mode.
When synchronous commutating control circuit works in continuous mode, first duration of this period effective voltage is less than
When first benchmark, then after primary side switch pipe shutdown, the secondary-side switch pipe conducting, in the cycle time in this period
When equal to second benchmark, the secondary-side switch pipe is turned off.
When synchronous commutating control circuit works in discontinuous mode, first duration of this period effective voltage is less than
First benchmark, and the difference of the two is less than the second setting value, then after primary side switch pipe shutdown, the secondary-side switch
Pipe conducting turns off the secondary-side switch pipe when the cycle time in this period being equal to second benchmark.
When synchronous commutating control circuit works in discontinuous mode, first duration of this period effective voltage is less than
First benchmark, and the difference of the two is more than or equal to the second setting value, then after primary side switch pipe shutdown, the pair side
Switching tube is not turned on, in an off state.
It is greater than first benchmark when first duration of this period effective voltage, then in the primary side switch pipe
After shutdown, the secondary-side switch pipe conducting turns off the secondary side and opens when the cycle time in this period being equal to second benchmark
Guan Guan.
The secondary-side switch pipe conducting is prolonged after primary side switch pipe shutdown, or in primary side switch pipe shutdown
When for a period of time, control secondary-side switch pipe conducting.
When the secondary-side switch pipe turn-on time is more than third setting value, the secondary-side switch pipe shutdown.
When secondary circuit detects primary side switch pipe shutdown, control secondary-side switch pipe conducting, when secondary circuit is examined
When measuring primary side switch pipe conducting, control secondary-side switch pipe shutdown.
Illustrate the course of work of circuit below with reference to waveform diagram: the wave to work as shown in Figure 10 for circuit in discontinuous mode
Shape figure is described in detail for convenience of description with time second round T2, and so on.
Between time period 1 T1, time second round T2, synchronous rectification control chip IC 1 detects secondary inductance
There are two from less than zero, to the rising edge for being greater than zero, decision circuit work is in interrupted mould by the partial pressure Vs of the reverse side voltage Vd of L1
Formula.
In time period 1 T1, synchronous rectification controls the turn-on time t11 that chip IC 1 records primary side switch pipe PR, and
With some numerical value less than or equal to t11 for the first benchmark, record is conducting to secondary inductance L1 from primary side switch pipe PR and has discharged
At the cycle time T1 before termination, and with some numerical value less than or equal to T1 for the second benchmark.
In time second round T2, when primary side switch pipe PR is connected, i.e., there is electric current logical on the t21 period, primary inductor L p
It crosses, primary inductor L p charging, primary inductor L p in-phase end voltage is equal to Vcs, and because electric current cannot be mutated in inductance, Vcs is gradually risen
Height, meanwhile, secondary inductance L1 senses that electromagnetic energy, the reverse side voltage Vd of secondary inductance L1 are equal to V2, synchronous rectification control
It is more than that chip IC 1, which detects that the partial pressure Vs of the voltage Vd of secondary inductance L1 reverse side is greater than first threshold and/or duration,
When two threshold values, gets ready to allow secondary-side switch pipe SR to be connected, record the time value of t21 period；
The partial pressure Vs that voltage Vd is arranged is greater than the judgement that first threshold and/or duration are more than second threshold, be in order to
It prevents from judging by accident, because circuit work, in discontinuous mode, between two periods, secondary inductance voltage can generate oscillation, but shake
The maximum voltage value V1 and duration t23 of secondary inductance reverse side voltage at least one is connected than primary side switch pipe when swinging
When secondary inductance L1 reverse side voltage V2 and the duration it is small, and the setting of first threshold and second threshold is avoided in pair
Secondary-side switch pipe SR misleads when the circuit oscillation of side.
In the t22 period, primary side switch pipe PR is turned off, no current on primary inductor L p, and reverse side voltage is F1, at this point,
The voltage Vd of secondary inductance L1 reverse side is sported less than zero (having but small oscillations), and secondary inductance L1 is put by parasitic diode D1
Electricity, secondary side capacitor C2 charging, for secondary current waveform as shown in Is in figure, synchronous rectification controls chip IC 1 for time second round
The first benchmark of the primary side switch pipe PR turn-on time t21 and time period 1 T1 of T2 compares, and is divided into following several situations:
When primary side switch pipe PR turn-on time t21 is greater than the first benchmark of period 1, T2 time time second round
Value is greater than time period 1 T1 time value, and it is small that synchronous rectification control chip IC 1 detects that voltage Vd drops to from effective voltage
In zero, while or delay a period of time (in Figure 10 be delay a period of time) output drive signal lead secondary-side switch pipe SR
Logical, synchronous rectification controls chip IC 1 and exports cut-off signals when T2 time time second round being equal to the second benchmark, drives secondary side
Advanced shutdown is realized in switching tube SR shutdown；
When primary side switch pipe PR turn-on time t21 is less than the first benchmark of period 1, and the difference of the two is less than second
When setting value, synchronous rectification control chip IC 1 detects that voltage Vd drops to less than zero, while or one section of delay from effective voltage
Secondary-side switch pipe SR is connected in time (being delay a period of time in Figure 10) output drive signal, in T2 time time second round
Cut-off signals are exported when equal to the second benchmark, advanced shutdown is realized in driving secondary-side switch pipe SR shutdown；
When primary side switch pipe PR turn-on time t21 is less than the first benchmark of period 1, and the difference of the two is more than or equal to
When the second setting value, synchronous rectification controls chip IC 1 makes secondary-side switch pipe SR be in pass in this period output error protection signal
Disconnected state.
The waveform diagram to work as shown in figure 11 for circuit in continuous mode, continuous mode and discontinuous mode have similarity
Also there is difference.Equally for convenience of description, it is described in detail with time second round T2, and so on.
Similarity is:
In time period 1 T1, synchronous rectification controls the turn-on time t11 that chip IC 1 records primary side switch pipe PR, and
With some numerical value less than or equal to t11 for the first benchmark, record is conducting to secondary inductance L1 from primary side switch pipe PR and has discharged
At the cycle time T1 before termination, and with some numerical value less than or equal to T1 for the second benchmark.
There is electricity on the t21 period, primary inductor L p when primary side switch pipe PR opens conducting in time second round T2
Stream passes through, primary inductor L p charging, primary inductor L p in-phase end voltage be equal to Vcs, because electric current cannot be mutated in inductance, Vcs by
Edge up height, meanwhile, secondary inductance L1 senses that electromagnetic energy, the reverse side voltage Vd of secondary inductance L1 are equal to V2, synchronous rectification
It is more than that control chip IC 1, which detects that the partial pressure Vs of the voltage Vd of secondary inductance L1 reverse side is greater than first threshold or duration,
When two threshold values, gets ready to allow secondary-side switch pipe SR to be connected, record the time value of t21 period.
In the t22 period, primary side switch pipe PR is turned off, no current on primary inductor L p, and reverse side voltage is F1, at this point,
The voltage Vd of secondary inductance L1 reverse side is sported less than zero (having but small oscillations), and secondary inductance L1 is put by parasitic diode D1
Electricity, secondary side capacitor C2 charging, synchronous rectification control chip IC 1 for the primary side switch pipe PR turn-on time of time second round T2
The first benchmark of t21 and time period 1 T1 compares, and is divided into following several situations:
When primary side switch pipe PR turn-on time t21 is greater than the first benchmark of period 1, T2 time time second round
Value is greater than time period 1 T1 time value, and it is small that synchronous rectification control chip IC 1 detects that voltage Vd drops to from effective voltage
In zero, while or delay a period of time (in Figure 10 be delay a period of time) output drive signal lead secondary-side switch pipe SR
Logical, synchronous rectification controls chip IC 1 and exports cut-off signals when T2 time time second round being equal to the second benchmark, drives secondary side
Advanced shutdown is realized in switching tube SR shutdown；
It is a difference in that:
Between time period 1 T1, time second round T2, synchronous rectification control chip IC 1 detects secondary inductance
There are two from less than zero, to the rising edge for being greater than zero, decision circuit work is in discontinuous mode by the reverse side voltage Vd of L1.
But circuit works in continuous mode, and between two periods, secondary inductance voltage will not generate oscillation or generation
The seldom oscillation of number, and vibrate when secondary inductance reverse side voltage maximum voltage value V1 and duration t23 at least one
The voltage V2 of secondary inductance L1 reverse side and duration are small when item is than the conducting of primary side switch pipe, and first threshold and the second threshold
The setting of value equally avoids the secondary-side switch pipe SR in secondary circuit oscillation and misleads.
When primary side switch pipe PR turn-on time t21 is less than the first benchmark of period 1, but continuous mode works, frequency
It is fixed frequency, that is to say, that the cycle time T1 of period 1 is equal to the cycle time T2 of second round, therefore, even if former
Side switching tube PR turn-on time t21 is less than the first benchmark of period 1, and the difference of the two is more than or equal to the second setting value, together
Step rectification control chip IC 1 can mask the error protection signal under this operating mode, detect voltage Vd from effective voltage
When dropping to less than zero, while or delay a period of time (be in Figure 10 delay a period of time) output drive signal make secondary-side switch
Pipe SR conducting exports cut-off signals when T2 time time second round being equal to the second benchmark, and driving secondary-side switch pipe SR is turned off,
Realize advanced shutdown.
Although the detailed description and description of the specific embodiments of the present invention are given above, it should be noted that
We can carry out various equivalent changes and modification to aforesaid way according to the concept of the present invention, and generated function is still
It, should all be within protection scope of the present invention when the spirit covered without departing from specification and attached drawing.
Claims (13)
1. a kind of synchronous commutating control circuit, which is characterized in that the circuit includes: primary circuit, secondary circuit；
The primary circuit includes primary side inductance, primary side switch pipe, primary side sampling resistor, the in-phase end connection of the primary side inductance
One end of the primary side switch pipe, the other end of the primary side switch pipe connect one end of the primary side sampling resistor, the original
The other end of side sampling resistor connects the ground terminal of the primary circuit, the control terminal connection primary-side-control letter of the primary side switch pipe
Number；
The secondary circuit includes secondary inductance, secondary-side switch pipe, secondary the second sampling resistor, pair in the first sampling resistor, pair
Load resistance, synchronous rectification control chip while capacitor, secondary；The in-phase end of the secondary inductance connects the synchronous rectification control
One end of the power end of chip, the secondary load resistance in positive, the described pair of capacitor；The reverse side of the secondary inductance connects
Connect one end of the secondary-side switch pipe, one end of the first sampling resistor of the secondary side；Pair side first sampling resistor it is another
End connects one end of the input terminal of the synchronous rectification control chip, the second sampling resistor of the secondary side, pair side capacitor
The ground terminal company of cathode, the other end of secondary side load resistance, the other end of the secondary-side switch pipe, synchronous rectification control chip
It is connected to the ground terminal of the secondary circuit, the control terminal of the secondary-side switch pipe connects the output of the synchronous rectification control chip
End, there are parasitic diodes between one end and the other end of the secondary-side switch pipe；
More than synchronous rectification control chip the first duration of the effective voltage of one period secondary circuit with it is described synchronous
The cycle time of rectifier control circuit is foundation, by first duration of this period effective voltage and a upper period
The duration of effective voltage is compared, and obtains comparison result, realizes and controls secondary circuit with Cycle by Cycle analogical pattern.
2. synchronous commutating control circuit according to claim 1, it is characterised in that:
The synchronous rectification control chip detects the voltage of the reverse side of the secondary inductance, when the voltage of the reverse side is greater than
First threshold and/or the time for being continued above second threshold, this voltage are effective voltage, then judge the primary side switch pipe at this time
Conducting, the secondary inductance and the primary side inductance generate electromagnetic induction, and the secondary-side switch pipe is in an off state；
When the primary side switch pipe turns off, when the voltage of the reverse side drops to less than zero by the effective voltage, the pair
The conducting of side switching tube, the secondary inductance electric discharge, pair side capacitor charging；When secondary inductance electric discharge closes on completion,
The secondary-side switch pipe shutdown.
3. synchronous commutating control circuit according to claim 2, it is characterised in that:
The synchronous rectification control chip detects that the voltage of reverse side described in this period is dropped to less than by the effective voltage
It when zero, i.e., is delayed after the failing edge of effective voltage or failing edge a period of time, output drive signal drives the secondary-side switch
Pipe conducting.
4. synchronous commutating control circuit according to claim 3, it is characterised in that:
The synchronous rectification control chip detects first that the voltage of the reverse side is begun to decline by the effective voltage
When failing edge is to first subsequent rising edge, the secondary-side switch pipe is connected in output Continuity signal.
5. synchronous commutating control circuit according to claim 1, it is characterised in that:
The synchronous rectification control chip is effective in upper period effective voltage and this period according to secondary inductance reverse side voltage
Oscillatory regime judges the operating mode of synchronous commutating control circuit between voltage；According to the comparison result and the Working mould
Formula controls secondary-side switch pipe on or off.
6. synchronous commutating control circuit according to claim 5, it is characterised in that:
The synchronous rectification control chip detects the operating mode of the secondary inductance, in the adjacent secondary-side switch pipe described twice
The rising edge quantity that the voltage of the secondary inductance reverse side is begun to ramp up by zero volt or so in turn-off time as judgment basis,
When the quantity of the rising edge is more than or equal to 2, judge the secondary inductance work in discontinuous mode；Otherwise, judge the pair
Side inductance works in continuous mode.
7. synchronous commutating control circuit according to claim 6, it is characterised in that:
The synchronous rectification control chip detects and records the first turn-on time of primary side switch pipe described in a period, and with small
In be equal to the upper period first turn-on time some numerical value be the first benchmark；With the primary side switch pipe
The sum of one turn-on time and second turn-on time of secondary-side switch pipe are cycle time, and to be less than or equal to the upper period
The cycle time some numerical value be the second benchmark, by first turn-on time in this period and first benchmark
It is compared, according to comparison result, controls the shutdown moment of the secondary-side switch pipe.
8. synchronous commutating control circuit according to claim 7, it is characterised in that:
Synchronous rectification control chip detects that the first turn-on time of the primary side switch pipe in this period is greater than described the
One benchmark controls the secondary-side switch pipe conducting, described in this period then after the primary side switch pipe shutdown in this period
When cycle time is equal to second benchmark, the secondary-side switch pipe shutdown is controlled.
9. synchronous commutating control circuit according to claim 7, it is characterised in that:
Synchronous rectification control chip detects that the first turn-on time of the primary side switch pipe in this period is less than described the
One benchmark, and the difference of the two is less than the second setting value, meanwhile, detect synchronous commutating control circuit work in discontinuous mode
When, then after the primary side switch pipe shutdown in this period, the secondary-side switch pipe conducting is controlled, in the period in this period
When time is equal to second benchmark, the secondary-side switch pipe shutdown is controlled.
10. synchronous commutating control circuit according to claim 7, it is characterised in that:
Synchronous rectification control chip detects that the first turn-on time of the primary side switch pipe in this period is less than described the
One benchmark, and the difference of the two is more than or equal to the second setting value, meanwhile, circuit work is detected in discontinuous mode, then at this
Secondary-side switch pipe described in period is not turned on, in an off state.
11. synchronous commutating control circuit according to claim 7, it is characterised in that:
Synchronous rectification control chip detects that the first turn-on time of the primary side switch pipe in this period is less than described the
One benchmark, meanwhile, synchronous commutating control circuit work is detected in continuous mode, then in the primary side switch pipe in this period
After shutdown, controls the secondary-side switch pipe conducting and control institute when the cycle time in this period being equal to second benchmark
State the shutdown of secondary-side switch pipe.
12. according to synchronous commutating control circuit described in claim 8,9 or 11, it is characterised in that:
It is delayed a period of time after the primary side switch pipe shutdown in this period or after shutdown, the synchronous rectification controls chip control
Make the secondary-side switch pipe conducting.
13. synchronous commutating control circuit according to claim 7, it is characterised in that: the synchronous rectification control chip inspection
When measuring secondary-side switch pipe turn-on time described in this period more than third setting value, then the secondary-side switch pipe is turned off.
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| CN108631594B (en) * | 2017-10-19 | 2020-03-06 | 西安矽力杰半导体技术有限公司 | Isolated converter and control circuit and control method thereof |
| CN109274272B (en) * | 2018-10-19 | 2020-11-17 | 成都芯源系统有限公司 | Switching power supply circuit, synchronous rectification control circuit and control method thereof |
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