CN106452086A - Synchronous rectification control circuit - Google Patents
Synchronous rectification control circuit Download PDFInfo
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- CN106452086A CN106452086A CN201610932816.7A CN201610932816A CN106452086A CN 106452086 A CN106452086 A CN 106452086A CN 201610932816 A CN201610932816 A CN 201610932816A CN 106452086 A CN106452086 A CN 106452086A
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- Prior art keywords
- side switch
- switch pipe
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- time
- voltage
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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
-
- 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 synchronous rectification control circuit, and the circuit comprises a primary side circuit and an auxiliary side circuit. The primary side circuit comprises a primary side inductor, a primary side switching tube, and a primary side sampling resistor. The auxiliary side circuit comprises an auxiliary side inductor, an auxiliary switching tube, an auxiliary side first sampling resistor, an auxiliary side second sampling resistor, an auxiliary side capacitor, an auxiliary side load resistor, and a synchronous rectification control chip. The circuit detects the voltage Vd of a leakage end, connected with an auxiliary switching tube SR_MOSFET, of the auxiliary side inductor in a mode of cycle-by-cycle analogy, can enable an IC in a DCM/CCM mode to precisely control the time point of discharging finishing, effectively judges the switching-off point, achieves an advanced switching-off function, and solves a difficult problem that the precise switching-off cannot be achieved at the DCM/CCM modes at the same time in the prior art. The circuit can simplify the peripheral application circuits, and reduces application devices.
Description
Technical field
The present invention relates to synchronous rectification field, more particularly to a kind of synchronous commutating control circuit.
Background technology
Synchronous rectification is to adopt the extremely low special power MOSFFT of on state resistance to replace commutation diode to reduce rectification
One technology of loss.From primary side switch pipe cut-off time, secondary-side switch pipe is turned on, and secondary inductance starts electric discharge, in pair
At the end of side inductive discharge closes on, secondary-side switch pipe will be turned off, and particularly after the completion of secondary inductance electric discharge, secondary-side switch pipe must
Must turn off, can otherwise cause secondary output capacitance inversely to be discharged, have aircraft bombing risk.
The method that solution secondary-side switch pipe is turned off at present has following several：
1. voltagesecond product conservation is utilized：First sampling primary side switch pipe turn-on instant secondary inductance two 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 electric capacity), then
Re-sampling output voltage be converted into electric current electric capacity C2 charged when primary side switch pipe ends flyback, compare two voltages come real
The time point that existing secondary-side switch pipe is turned off.Even if the advantage of the method is that under discontinuous mode, the change of former limit ON time greatly can also
Accurately determine when to turn off secondary-side switch pipe；Which has the disadvantage easily to be disturbed by input voltage fluctuation, and needs to detect primary side electricity
Sense both end voltage.
2nd, direct sampling anti-phase terminal voltage Vd of secondary inductance：Secondary-side switch pipe is turned off when Vd is more than 0V, lead during less than 0V
Logical secondary-side switch pipe, the advantage of the method is that detection mode is simple, unrelated with the change of former limit sampled voltage under discontinuous mode；Shortcoming
It is continuous mode can not to be supported, is easily caused secondary inductance and inversely discharges, and requires to drive the speed for turning off secondary-side switch pipe
Fast.
3rd, other：For the synchronous rectification that former limit structure is done, control in linear zone after the conducting of secondary-side switch pipe, make secondary electricity
Stream reduce when secondary-side switch pipe Vgs increase and Vds is constant, such former limit sampled voltage is relatively stable, is conducive to system stability
Property, the advantage of the method is that former secondary structural system is stable；Have the disadvantage the work of secondary-side switch pipe in linear zone, loss is relative can be big
A bit.
It is therefore proposed that a kind of loss is little, while compatible continuous mode with the synchronous commutating control circuit of discontinuous mode is urgently
Problem to be solved.
Content of the invention
Based on the problem that prior art is present, the present invention proposes a kind of synchronous commutating control circuit, including：Primary circuit,
Secondary circuit；The primary circuit includes former limit inductance, primary side switch pipe, former limit sampling resistor, the homophase of the former limit inductance
One end of the end connection primary side switch pipe, the other end of the primary side switch pipe connects one end of the former limit sampling resistor,
The other end of the former limit sampling resistor connects the ground terminal of the primary circuit, the control end connection former limit of the primary side switch pipe
Control signal；The secondary circuit includes that secondary inductance, secondary-side switch pipe, the first sampling resistor of secondary, secondary second are sampled electricity
Resistance, secondary electric capacity, secondary load resistance, synchronous rectification control chip；It is whole that the in-phase end of the secondary inductance connects the synchronization
The power end of flow control chip, the positive pole of the secondary electric capacity, one end of the secondary load resistance；The secondary inductance anti-
Mutually end connects one end of the secondary-side switch pipe, one end of the first sampling resistor of the secondary；The first sampling resistor of the secondary
The other end connect the input of the synchronous rectification control chip, one end of the second sampling resistor of the secondary, the secondary
The negative pole of electric capacity, the other end of secondary 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 end of the secondary-side switch pipe connects the synchronous rectification control chip
, between one end of the secondary-side switch pipe and the other end, there is parasitic diode in outfan.
Preferably, the synchronous rectification control chip detects the voltage of the end of oppisite phase of the secondary inductance, when described anti-phase
The voltage at end is more than first threshold and/or is continued above the time of Second Threshold, and this voltage is active voltage, then to judge now institute
The conducting of primary side switch pipe is stated, the secondary inductance produces electromagnetic induction with the former limit inductance, and the secondary-side switch pipe is in pass
Disconnected state；When the primary side switch pipe is turned off, when the voltage of the end of oppisite phase drops to less than zero by the active voltage, described
Secondary-side switch pipe is turned on, the secondary inductance electric discharge, and the secondary electric capacity charges；Close in secondary inductance electric discharge and complete
When, the secondary-side switch pipe is turned off.
Preferably, the synchronous rectification control chip detects the voltage of end of oppisite phase described in this cycle by the active voltage
When dropping to less than zero, i.e., after the trailing edge or trailing edge of active voltage, for a period of time, output drive signal drives institute for time delay
State the conducting of secondary-side switch pipe.
Preferably, under the synchronous rectification control chip detects the voltage of the end of oppisite phase by the active voltage
When first trailing edge of drop is to first subsequent rising edge, output cut-off signals turn off the secondary-side switch pipe.
Preferably, the synchronous rectification control chip detects the mode of operation of the secondary inductance, with adjacent institute twice
The rising edge quantity that the voltage of the secondary inductance end of oppisite phase in the secondary-side switch pipe turn-off time is begun to ramp up is stated by zero volt or so
As basis for estimation, when the quantity of the rising edge is more than or equal to 2, judge that the secondary inductance is operated in discontinuous mode；No
Then, judge that the secondary inductance is operated in continuous mode.
Preferably, the synchronous rectification control chip is detected and records the first conducting of primary side switch pipe described in a cycle
Time, and with some numerical value of first ON time less than or equal to the upper cycle as the first benchmark；With described
The first ON time of primary side switch pipe is cycle time, and to be less than or equal to the second ON time of secondary-side switch pipe sum
Some numerical value of the cycle time in a upper cycle be the second benchmark, by first ON time in this cycle with
First benchmark is compared, and according to comparative result, controls the shutoff moment of the secondary-side switch pipe.
Preferably, the synchronous rectification control chip detects the first ON time of the primary side switch pipe in this cycle
More than first benchmark, then have no progeny in the primary side switch pipe pass in this cycle, control the secondary-side switch pipe conducting, at this
When the cycle time in cycle is equal to second benchmark, the secondary-side switch pipe is controlled to turn off.
Preferably, the synchronous rectification control chip detects the first ON time of the primary side switch pipe in this cycle
Less than first benchmark, and both differences are less than the second setting value, meanwhile, detect synchronous commutating control circuit and be operated in
During discontinuous mode, then the primary side switch pipe in this cycle is closed and is had no progeny, and controls the secondary-side switch pipe conducting, in this cycle
When the cycle time is equal to second benchmark, the secondary-side switch pipe is controlled to turn off.
Preferably, the synchronous rectification control chip detects the first ON time of the primary side switch pipe in this cycle
Less than first benchmark, and both differences are more than or equal to the second setting value, meanwhile, detect circuit and be operated in discontinuous mode
When, then it is not turned in secondary-side switch pipe described in this cycle, is off state.
Preferably, the synchronous rectification control chip detects the first ON time of the primary side switch pipe in this cycle
Less than first benchmark, meanwhile, when detecting synchronous commutating control circuit and being operated in continuous mode, then described in this cycle
Primary side switch pipe is closed has no progeny, and controls the secondary-side switch pipe conducting, is equal to second base in the cycle time in this cycle
On time, the secondary-side switch pipe is controlled to turn off.
Preferably, the primary side switch pipe in this cycle is closed to have no progeny or close and has no progeny time delay for a period of time, and the synchronization is whole
Secondary-side switch pipe conducting described in flow control chip controls.
Preferably, the synchronous rectification control chip detects secondary-side switch pipe ON time described in this cycle more than the 3rd
During setting value, then turn off the secondary-side switch pipe.
The beneficial effect that the present invention is compared with the prior art is：
The present invention detects secondary inductance leakage connected with secondary-side switch pipe SR_MOSFET by way of Cycle by Cycle analogy
Terminal voltage Vd, can make synchronous rectification control chip in DCM/CCM pattern can the accurate time point that completes of control electric discharge, have
Breakpoint is closed in the judgement of effect, is realized shifting to an earlier date turn-off function, had both been realized high efficiency, can prevent SR_MOSFET from leading because of reverse electric discharge again
Cause the possibility of aircraft bombing；Solving cannot be while can realize the difficulty of accurate shutoff under DCM/CCM both of which in prior art
Topic；While peripheral applications circuit can be simplified, reduce application device.
Description of the drawings
Fig. 1 is a kind of structural representation of synchronous rectification chip of the present invention；
Fig. 2 is a kind of structural representation of the synchronous rectification chip of embodiment of the present invention；
Fig. 3 is the synchronous rectification chip discontinuous mode working waveform figure of the present invention；
Fig. 4 is the synchronous rectification chip continuous mode working waveform figure of the present invention；
Fig. 5 is the oscillogram for being turned off during the discontinuous mode of the present invention in advance；
Fig. 6 is the oscillogram of the discontinuous mode error protection of the present invention；
Fig. 7 is the advanced shutoff oscillogram during both of which of the present invention；
Fig. 8 is the structural representation of the synchronous commutating control circuit figure of the present invention；
Fig. 9 is the method for rectifying schematic flow sheet of the circuit of synchronous rectification of the present invention；
Figure 10 is the synchronous commutating control circuit oscillogram under the discontinuous mode of the present invention；
Figure 11 is the synchronous commutating control circuit oscillogram under the continuous mode of the present invention.
Specific embodiment
Fig. 1 show the synchronous rectification chip structure schematic diagram of the present invention, and the synchronous rectification chip includes：Conducting is initial
Change module 10, voltage detection module 20, mode decision module 30, failure protection module 40, advanced shutoff module 50, selecting module
60th, time setting module 70, control module 80, trigger module 90, drive module 100.The conducting initialization module 10, voltage
Detection module 20, mode decision module 30 are respectively connecting to voltage input end；The conducting initialization module 10 connects the electricity
Pressure detection module 20, the voltage detection module 20 connects the failure protection module 40, advanced shutoff module 50, control respectively
Module 80, trigger module 90；The mode decision 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 shutoff module 50, the ON time setting module
The input of the 70 connections control module 80；The selecting module 60 respectively with mode decision module 30, failure protection module
40th, control module 80 connects；The control module 80 respectively with time setting module 70, voltage detection module 20, advanced turn off
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 decision module 30, failure protection module 40 connect the input of the selecting module 60, the selection
Module 60, the advanced shutoff module 50, the time setting module 70 connect the input of the control module 80, the control
The outfan of molding block 80 connects the trigger module 90, and the outfan of the trigger module 90 connects the drive module 100.
1st, when the conducting initialization module 10 is used for judging input voltage for effective input voltage, output allows conducting letter
Number A1.Input voltage VS is compared by the conducting initialization module 10 with first threshold, when input voltage is more than the first threshold
When value and/or persistent period exceed Second Threshold, then this input voltage is effective input voltage, and conducting initialization module 10 is exported
Continuity signal A1 is allowed to voltage detection module 20.
The first threshold is for voltage, Second Threshold is default for the time, all.
High voltage input with low-voltage input when, first threshold be different, thus arrange two comparators 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 be input into two kinds of different conditions with low-voltage.First high voltage threshold is input into corresponding to high voltage, described
First low voltage threshold is input into corresponding to low-voltage.
2nd, the voltage detection module 20 is used for detecting numerical value, cycle time and effective input voltage of input voltage
The first persistent period；When the permission Continuity signal A1 is effective, output control Continuity signal A2 gives the trigger module 90；
The voltage detection module 20 exports first persistent period to the failure protection module 40；Will be defeated for the cycle time
Go out to the advanced shutoff module 50；According to effective input voltage and the ratio of the first setting value (the first setting value is less than or equal to zero)
Relatively result, output voltage comparing signals A 3 gives the control module 80.
When the permission Continuity signal A1 is effective, in effective input voltage trailing edge or time delay after trailing edge
For a period of time, output control Continuity signal A2 gives the trigger module 90；The trigger module 90 is according to the control conducting letter
Number A2 output 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, for voltage, is default
's.
The voltage detection module 20 records input voltage more than persistent period during first threshold, and during by described continuing
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 waveform cycle time AT is exported to advanced shutoff module 50.
3rd, the mode decision module 30 is used for judging that external circuit mode of operation is continuous mode or discontinuous mode.
Specifically, the mode decision module 30 is used for the vibration according to input voltage between two adjacent effective input voltages
Number of times judges that external circuit mode of operation is continuous mode or discontinuous mode.The record two of mode decision module 30 is adjacent effectively defeated
Enter the number of times of input voltage rising edge between voltage, when the number of times is more than or equal to 2, judge that mode of operation is discontinuous mode,
It is otherwise continuous mode；And output mode signal ccmH is to selecting module 60.Continuous mode or discontinuous mode refer to that chip is located
External circuit mode of operation.
4th, the failure protection module 40 is according to described the first of first persistent period in a upper cycle and this cycle
Persistent period, export error protection signal ftpL.
The failure protection module 40 is with a certain numerical value of first persistent period less than or equal to a upper cycle as the
One benchmark, according to first persistent period and the comparative result of first benchmark in this cycle, exports error protection signal
ftpL.
Failure protection module 40, the first duration waveform at of the effective input voltage for being exported with voltage detection module 20
It is foundation, the first persistent period of effective input voltage when recording a upper cycle, and to have during less than or equal to the upper cycle
The a certain numerical value of first persistent period of effect input voltage is the first benchmark.When this cycle effective input voltage first is held
The continuous time is less than the first benchmark, and when both differences are more than or equal to the second setting value, output error protection signal ftpL is to choosing
Select module 60.First persistent period is the persistent period of effective input voltage.
5th, the advanced module 50 that turns off is with a certain numerical value of the cycle time less than or equal to a upper cycle as second
Benchmark, according to the cycle time and the cycle time in a upper cycle in this cycle, exported advanced cut-off signals.
Described advanced turn off module with less than or equal to a upper cycle the cycle time a certain numerical value as the second benchmark,
According to the cycle time and the cycle time in a upper cycle in this cycle, advanced cut-off signals were exported.
Advanced shutoff module 50, with the periodic waveform AT of the output of voltage detection module 20 as foundation, a cycle on record
Cycle time, and with less than or equal to the upper a cycle cycle time a certain numerical value as the second benchmark, when this cycle
Cycle time more than the second benchmark when, export advanced cut-off signals A5.The cycle time in a upper cycle is from effectively input
Voltage starts, until effective input voltage drops to less than zero and terminates when being more than zero again.
6th, the selecting module 60 is used for judging whether the error protection signal is effective according to the mode of operation.
Error protection signal output in discontinuous mode is given described by the selecting module 60 according to the mode of operation
Control module, by the error protection signal shielding in continuous mode.
The selecting module 60 judges the error protection signal according to the output signal of the mode decision module 30
Effectively whether, when mode of operation is for continuous mode, the error protection signal is shielded ftpL, when mode of operation is interrupted mould
During formula, the error protection signal is effective.The selecting module exports selection signal A4.
7th, the ON time setting module 70 is used for controlling the maximum retention time of the Continuity signal, in ON time
When reaching maximum, output overtime signal A6 gives the control module 80.
The initial time of the sampling of ON time setting module 70 Continuity signal simultaneously starts timing, when Continuity signal continues
When time exceedes setting time, output overtime signal A6 gives the control module 80.
The ON time setting module 70, in the rising edge of trigger, the start recording triggered time, when closed between
During more than three setting values, 80 output overtime signal A6 of ON time setting module is to control module 80.3rd setting value
It is default.
The rising edge of trigger can also be in the chips relevant position sampling, not exclusively in the output of trigger module
End.
8th, the control module 80 is according to the selecting module 60, the voltage detection module 20, the advanced shutoff mould
Block 50, the output of the ON time setting module 70, output control cut-off signals give the trigger module 90.
The voltage detection module 20, the advanced shutoff module 50, the selecting module 60, the ON time set
When in module 70, the output signal of at least one module is effective, 80 output control cut-off signals of the control module give the triggering
Module 90；The trigger module 90 exports cut-off signals according to the control cut-off signals.
9th, the trigger module 90 is exported according to the voltage detection module 20 and the output signal of the control module 80
Continuity signal or cut-off signals.
Trigger module 90 is when the control Continuity signal A2 that voltage detection module 20 is exported is effective, and trigger module 90 is effective
After the trailing edge of input voltage or trailing edge, time delay exports Continuity signal for a period of time；The control for exporting in control module 80 is turned off
When signal is effective, trigger module 90 exports cut-off signals.
10th, the drive module 100 is used for according to the Continuity signal or the cut-off signals, output drive signal.
Below the method for work of above-mentioned synchronous rectification chip is elaborated.
Detection input voltage, allows to lead when exceeding Second Threshold more than first threshold and/or persistent period in input voltage
Logical, when the input voltage is that input voltage is less than zero effective input voltage, after effective input voltage that is, described
The trailing edge of effective input voltage, or after the trailing edge time delay for a period of time, the trigger module output Continuity signal of chip；
When input voltage by rising above zero less than zero, that is, input voltage more than or equal to the first setting value when, the triggering of chip
Module 90 exports cut-off signals.
The cycle time in a record upper cycle, with a certain numerical value of the cycle time less than or equal to a upper cycle as the second base
Accurate；The cycle time is from the beginning of effective input voltage, until effective input voltage drops to less than zero and again more than zero
When terminate.
A record upper cycle exceedes effective input of Second Threshold in input voltage more than first threshold and/or persistent period
First persistent period of voltage, with a certain numerical value less than or equal to first persistent period as the first benchmark.
The number of times of input voltage rising edge between a record upper cycle effective input voltage and this cycle effective input voltage,
The mode of operation of external circuit is judged with the value of the number of times, is discontinuous mode DCM when the value of the number of times is more than or equal to 2, no
It is then continuous mode CCM.
When the first persistent period of effective input voltage in this cycle the first benchmark is more than or equal to, according to voltagesecond product conservation
Rule, the cycle time in this cycle can be more than the second benchmark, then in trailing edge or the trailing edge of effective input voltage in this cycle
Time delay for a period of time, exports Continuity signal afterwards, when the cycle time in this cycle is more than or equal to the second benchmark, the trigger mode of chip
Block 90 exports cut-off signals, realizes advanced shutoff.
When this cycle effective input voltage the first persistent period less than the first benchmark when, and both differences are less than the
Two setting values, while when external circuit is operated in discontinuous mode, then, after the trailing edge of effective input voltage in this cycle, output is led
Messenger, when the cycle time in this cycle is more than or equal to the second benchmark, the trigger module 90 of chip exports cut-off signals, realizes
Advanced shutoff.
The first benchmark is less than when the persistent period of effective input voltage in this cycle, and both differences are more than or equal to second
Setting value, while when external circuit is operated in discontinuous mode, then after the trailing edge of effective input voltage in this cycle, the touching of chip
Send out module 90 and cut-off signals are exported, realize advanced shutoff.
The first benchmark is less than when the persistent period of effective input voltage in this cycle, while external circuit is operated in continuous mode
When, then after the trailing edge of effective input voltage in this cycle, trigger module 90 exports Continuity signal；At the cycle in this cycle
Between more than or equal to the second benchmark when, the trigger module 90 of chip exports cut-off signals, realizes advanced shutoff.
When chip trigger module 90 export the Continuity signal persistent period more than or equal to three setting values when, chip touch
Send out module 90 and export cut-off signals.
In the foundation that next cycle, chip are judged using first benchmark in this cycle, the second benchmark as shutoff, according to similar
Method of work, trigger module 90 exports Continuity signal and cut-off signals, while recording first benchmark in next cycle, the second base
Prepare to use.
Fig. 2 for the present invention a kind of embodiment synchronous rectification chip structural representation, wherein selecting module 60 be by
Realize with door, control module 80 is realized by nor gate, and trigger module 90 is realized by d type flip flop.
Fig. 3 is the synchronous rectification chip discontinuous mode working waveform figure of the present invention.As shown in figure 3, voltage detection module 20
Detection input voltage is more than zero with minus change.High level is exported when input voltage is more than zero, when input voltage is less than
Low level is exported when zero, and voltage comparison signal waveform between two neighboring effective input voltage, works as voltage as shown in figure A3
When the pulse number of comparison signal is more than or equal to 2,30 output mode of mode decision module judges signal ccmH for high level, represents
External circuit mode of operation is discontinuous mode DCM, and this high level lasts till that effectively input voltage terminates rear and one section of time delay next time
Time, when the pulse number of voltage comparison signal is less than 2,30 output mode of mode decision module judges signal ccmH for low electricity
Flat, represent that external circuit mode of operation is continuous mode CCM, mode of operation signal waveform is as shown in figure ccmH waveform；Or, electricity
Pressure detection module 20 detect input voltage be with less than zero or some numerical value more than zero be compared, show that voltage ratio is relatively believed
Number.
Input voltage Vs is compared by conducting initialization module 10 with first threshold, when input voltage Vs is more than the first threshold
When value and/or persistent period are more than Second Threshold, the input voltage is effective input voltage, and the conducting output of initialization module 10 is permitted
Perhaps Continuity signal is to voltage detection module 20, it is allowed to which Continuity signal waveform is as shown in figure A1.
Voltage detection module 20 allow Continuity signal effective when, in the trailing edge output control Continuity signal of input voltage
To trigger module 90, control Continuity signal waveform as shown in figure waveform A2；The output control when input voltage is again more than zero
Cut-off signals, trigger module 90 exports on or off signal according to control Continuity signal with control cut-off signals, and its waveform is such as
Shown in figure Gate.
Or, voltage detection module 20 is when allowing Continuity signal effective, and trigger module 90 is in the trailing edge of input voltage
Time delay output control Continuity signal again for a period of time afterwards, but input voltage more than zero when must output 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 the synchronous rectification chip continuous mode working waveform figure of the present invention；As shown in figure 4, voltage detection module 20
Detection input voltage more than zero with minus change, when input voltage more than zero when export high level, when input voltage is less than
Low level is exported when zero, voltage comparison signal is as shown in figure waveform A3.
Between two adjacent effective input voltages, when the pulse number of voltage comparison signal is less than 2, mode decision module
30 output low levels, represent that external circuit mode of operation is continuous mode, and mode decision waveform is as shown in figure ccmH waveform.
Input voltage Vs is compared by conducting initialization module 10 with first threshold, when input voltage Vs is more than the first threshold
When value and/or persistent period are more than Second Threshold, the input voltage is effective input voltage, and the conducting output of initialization module 10 is permitted
Perhaps Continuity signal is to voltage detection module 20, it is allowed to which Continuity signal waveform is as shown in figure A1.
Voltage detection module 20 is in the trailing edge of effective input voltage, that is, when allowing Continuity signal effective, output control is led
Messenger controls the oscillogram of Continuity signal as shown in figure waveform A2 to trigger module 90.
Trigger module 90 in the trailing edge output drive signal of effective input voltage, when input voltage is more than zero, also
It is that 80 output control cut-off signals of control module are to trigger module 90, and trigger module 90 is exported when voltage comparison signal is effective
Cut-off signals, 90 output waveform of trigger module is as shown in figure waveform Gate.Or, trigger module 90 is in effective input voltage
Time delay output drive signal again for a period of time after trailing edge, but input voltage more than zero when must export cut-off signals.
Fig. 5 is the oscillogram for being turned off during the discontinuous mode of the present invention in advance；As shown in figure 5, T1 was the cycle in a upper cycle
Time, t11 was the first persistent period of effective input voltage of the upper cycle, and t12 is upper periodical input voltage minus the
Two persistent period.
T2 is the cycle time in this cycle, and t21 is the first persistent period of this cycle effective input voltage, and t22 is this week
Phase input voltage minus second persistent period.
The waveform of the first persistent period is as shown in figure at waveform, and the waveform of cycle time is as shown in figure AT waveform；Mould
The output of formula judge module is as shown in figure ccmH waveform.
Take less than upper cycle duration t11 numerical value t3 be the first benchmark, take less than upper cycle time T1
Numerical value t1 be the second benchmark, when the first persistent period t21 in this cycle is more than or equal to numerical value t3, fixed according to voltagesecond product conservation
Rule, T2 is more than T1, is limited with the second benchmark t1, when the second benchmark t1 is equal to the cycle time in this cycle, turns off module in advance
The advanced cut-off signals of 50 outputs, control module 80 is according to the advanced cut-off signals output control cut-off signals to trigger module
90, advanced cut-off signals waveform is as shown in figure A5, and trigger module 90 exports cut-off signals, its waveform such as in figure Gate waveform institute
Show, in this example, the time delay after the trailing edge of effective input voltage of Gate waveform is just effective for a period of time.
In the present embodiment, t21 is more than t11, and error protection is no exported, as shown in ftpL waveform in Fig. 5.
Fig. 6 is the oscillogram of the discontinuous mode error protection of the present invention.In Fig. 6, mode decision module judges external circuit
Mode of operation is discontinuous mode, and exports the mode of operation signal as shown in figure ccmH waveform；
From unlike Fig. 5, the first persistent period t21 of effective input voltage in this cycle was less than the effective of a upper cycle
First persistent period t11, t3 of input voltage is less than the number of the first persistent period t11 of effective input voltage in a cycle
Value, is taken as first benchmark in this cycle, and t21 is more than or equal to the second setting value, error protection with the difference for being less than the first benchmark t3
Module 40 exports error protection signal, and error protection signal waveform is as shown in figure ftpL waveform；
In mode of operation signal and error protection signal while when effective, i.e., external circuit is operated in discontinuous mode state and sheet
First persistent period of effective input voltage in cycle is much smaller than the first persistent period of effective input voltage in a upper cycle, choosing
Selecting module 60 and selection signal A4 being exported to control module 80, control module 80 is given according to the control signal output control cut-off signals
Trigger module 90, trigger module 90 exports cut-off signals, then chip does not export Continuity signal in this cycle, is held off.
Fig. 7 is the advanced shutoff oscillogram during both of which of the present invention.As shown in fig. 7, cycle of the T1 for the period 1
Time, T2 is 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 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 for second round effective input voltage the first persistent period the first benchmark；In the period 1 and
Between the adjacent effective input voltage of two cycles two, there is vibration, the voltage comparison signal arteries and veins having more than 2 times in input voltage
Punching, mode decision module is judged that external circuit is operated in discontinuous mode, exports high level signal according to this umber of pulse；In second week
Between two adjacent effective input voltages of phase and period 3, input voltage be less than zero, voltage comparison signal no pulse, pattern
Judge module judges that external circuit is operated in continuous mode, exports low level signal；Mode decision signal waveform such as in figure ccmH institute
Show.
First persistent period t21 of second round effective input voltage is more than first benchmark of period 1, in second week
After the trailing edge of phase effective input voltage, for a period of time, trigger module 90 exports Continuity signal, in the cycle of second round for time delay
When time T2 is equal to the second benchmark t1 of period 1, advanced judge module 50 exports advanced cut-off signals to control module 80,
80 output control cut-off signals of control module export cut-off signals to trigger module 90, trigger module 90, realize advanced shutoff.
First persistent period t31 of effective input voltage of period 3 is much smaller than the first benchmark t4 of second round,
That is the first persistent period t31 of effective input voltage of period 3 is more than with the difference of the first benchmark t4 of second round
Equal to the second setting value, failure protection module 40 exports error protection signal, error protection signal waveform such as in figure ftpL waveform
Shown；
Because the mode of operation of period 3 external circuit is continuous mode, and during connection mode, the operating frequency of external circuit is solid
Fixed, i.e., cycle time, T3 was equal with T2, and therefore selecting module 60 masks this error protection signal, triggered pattern 90 the 3rd
After the trailing edge of effective input voltage in cycle, time delay exports Continuity signal for a period of time, Continuity signal waveform such as in figure Gate ripple
Shown in shape, when the cycle time of period 3, T3 was equal to the second benchmark t2 of second round, the output of advanced judge module 50 is super
Front cut-off signals are to control module 80, and 80 output control cut-off signals of control module are to trigger module 90, and trigger module 90 is exported
Cut-off signals, realize advanced shutoff.
Fig. 8 show a kind of structural representation of synchronous commutating control circuit of the present 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, former limit sampling resistor Rcs；The former limit inductance
One end of the in-phase end connection primary side switch pipe PR of Lp, the one of the other end connection former limit sampling resistor Rcs of primary side switch pipe PR
End, the ground terminal of another termination of former limit sampling resistor Rcs primary circuit, the control termination primary-side-control of primary side switch pipe PR
Signal.
The secondary circuit includes that secondary inductance L1, secondary-side switch pipe SR, secondary the first sampling resistor R1, secondary second are adopted
Sample resistance R2, secondary electric capacity C2, secondary load resistance R3, synchronous rectification control chip IC1；The synchronous rectification control chip
IC1 is aforesaid synchronous rectification control chip.
The power end of the in-phase end connection synchronous rectification control chip IC1 of secondary inductance L1, the positive pole of secondary electric capacity C2, institute
State one end of secondary load resistance R3；One end of the end of oppisite phase connection secondary switching tube SR of secondary inductance L1, secondary first are sampled
One end of resistance R1；The other end connection input of synchronous rectification control chip IC1 of secondary the first sampling resistor R1, secondary the
One end of two sampling resistor R2, the negative pole of secondary electric capacity C2, the other end of secondary load resistance R3, secondary-side switch pipe SR another
End, the ground terminal of synchronous rectification control chip IC1 are connected to the ground terminal of secondary circuit, and the control end connection of secondary-side switch pipe SR is synchronous
, between one end of secondary-side switch pipe SR and the other end, there is parasitic diode D1 in the outfan of rectification control chip.
Primary inductor L p, secondary inductance L1 are primary inductor L p of same transformator, secondary inductance L1 respectively.
The voltage Vd of synchronous rectification control chip IC1 detection secondary inductance L1 end of oppisite phase, as the voltage Vd of the end of oppisite phase
Partial pressure Vs more than first threshold and/or be continued above time of Second Threshold, this voltage be active voltage, then judge now former
Side switching tube PR conducting, the secondary inductance L1 produces electromagnetic induction with primary inductor L p, and secondary-side switch pipe is off state.
When the primary side switch pipe is turned off, when the voltage of the end of oppisite phase drops to less than zero by the active voltage, institute
The conducting of secondary-side switch pipe is stated, the secondary inductance discharges, and the secondary electric capacity charges, close in secondary inductance electric discharge and complete
When, the secondary-side switch pipe is turned off, and prevents the secondary electric capacity by the secondary-side switch tube discharge.
The synchronous rectification control chip detects the voltage of end of oppisite phase described in this cycle and is dropped to by the active voltage
During less than zero, i.e., after the trailing edge or trailing edge of active voltage, for a period of time, output drive signal drives the secondary for time delay
Switching tube is turned on.
The synchronous rectification control chip detects that the voltage of the end of oppisite phase is begun to decline by the active voltage
When one trailing 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 mode of operation of the secondary inductance, to open in adjacent described twice secondary
The rising edge quantity that in the pipe turn-off time of pass, the voltage of the secondary inductance end of oppisite phase is begun to ramp up by zero volt or so is used as judgement
Foundation, when the quantity of the rising edge is more than or equal to 2, judges that the secondary inductance is operated in discontinuous mode；Otherwise, judge institute
State secondary inductance and be operated in continuous mode.
The synchronous rectification control chip detects and records the first ON time of primary side switch pipe described in a cycle, and
With some numerical value of first ON time less than or equal to the upper cycle as the first benchmark；With the primary side switch
The first ON time of pipe is cycle time with the second ON time of secondary-side switch pipe sum, and to be less than or equal to a upper cycle
The cycle time some numerical value be the second benchmark, by first ON time in this cycle and first benchmark
It is compared, according to comparative result, controls the shutoff moment of the secondary-side switch pipe.
The synchronous rectification control chip detects the first ON time of the primary side switch pipe in this cycle more than institute
The first benchmark is stated, then the primary side switch pipe in this cycle is closed and had no progeny, control the secondary-side switch pipe conducting, in this cycle
When the cycle time is equal to second benchmark, the secondary-side switch pipe is controlled to turn off.
The synchronous rectification control chip detects the first ON time of the primary side switch pipe in this cycle less than institute
The first benchmark is stated, and both differences are less than the second setting value, meanwhile, detect synchronous commutating control circuit and be operated in interrupted mould
During formula, then the primary side switch pipe in this cycle is closed and is had no progeny, and controls the secondary-side switch pipe conducting, in the week in this cycle
When time phase is equal to second benchmark, the secondary-side switch pipe is controlled to turn off.
The synchronous rectification control chip detects the first ON time of the primary side switch pipe in this cycle less than institute
State the first benchmark, and both differences are more than or equal to the second setting value, meanwhile, when detecting circuit and being operated in discontinuous mode, then
It is not turned in secondary-side switch pipe described in this cycle, is off state.
The synchronous rectification control chip detects the first ON time of the primary side switch pipe in this cycle less than institute
The first benchmark is stated, meanwhile, when detecting synchronous commutating control circuit and being operated in continuous mode, then open in the former limit in this cycle
Guan Guanguan has no progeny, and controls the secondary-side switch pipe conducting, when second benchmark is equal to the cycle time in this cycle, control
Make secondary-side switch pipe shutoff.
Close to have no progeny or close in the primary side switch pipe in this cycle and have no progeny time delay for a period of time, the synchronous rectification controls core
Piece controls the secondary-side switch pipe conducting.
The synchronous rectification control chip detects secondary-side switch pipe ON time described in this cycle more than the 3rd setting value,
The secondary-side switch pipe is then turned off.
Below according to Fig. 9, the method for rectifying of synchronous commutating control circuit is described further.
The synchronous commutating control circuit includes primary circuit, secondary circuit, and the primary circuit is in electromagnetic coupled mode
Connection secondary circuit, the secondary circuit includes synchronous rectification control chip, secondary-side switch pipe, secondary inductance.Above one week
The cycle time of the first persistent period of the active voltage of phase secondary circuit and the synchronous commutating control circuit is foundation, incite somebody to action this
First persistent period of cycle active voltage was compared with the persistent period of the upper cycle active voltage, was compared
Relatively result；According to the anti-phase terminal voltage of secondary inductance, between upper cycle active voltage and this cycle active voltage, oscillatory regime is sentenced
The mode of operation of disconnected synchronous commutating control circuit；According to the comparative result and the mode of operation, secondary-side switch pipe is controlled to lead
Logical or cut-off, realizes controlling secondary circuit with Cycle by Cycle analogical pattern.
With the first persistent period less than or equal to the upper cycle active voltage as the first benchmark, with less than or equal to described
The cycle time in a upper cycle is the second benchmark.
When the anti-phase terminal voltage of the secondary inductance vibrates time between upper cycle active voltage and this cycle active voltage
When number is more than or equal to 2, decision circuitry is operated in discontinuous mode, and otherwise circuit is operated in continuous mode.
When synchronous commutating control circuit is operated in continuous mode, first persistent period of this cycle active voltage is less than
During first benchmark, then close in the primary side switch pipe and have no progeny, the secondary-side switch pipe conducting, in the cycle time in this cycle
During equal to second benchmark, the secondary-side switch pipe is turned off.
When synchronous commutating control circuit is operated in discontinuous mode, first persistent period of this cycle active voltage is less than
First benchmark, and both differences are less than the second setting value, then close in the primary side switch pipe and have no progeny, the secondary-side switch
Pipe is turned on, and when second benchmark is equal to the cycle time in this cycle, turns off the secondary-side switch pipe.
When synchronous commutating control circuit is operated in discontinuous mode, first persistent period of this cycle active voltage is less than
First benchmark, and both differences are more than or equal to the second setting value, then close in the primary side switch pipe and have no progeny, the secondary
Switching tube is not turned on, and is off state.
It is more than first benchmark when first persistent period of this cycle active voltage, then in the primary side switch pipe
Pass is had no progeny, the secondary-side switch pipe conducting, when second benchmark is equal to the cycle time in this cycle, turns off the secondary and opens
Guan Guan.
The secondary-side switch pipe conducting, is to close to have no progeny in the primary side switch pipe, or prolongs in primary side switch pipe shutoff
When for a period of time, control secondary-side switch pipe conducting.
When the secondary-side switch pipe ON time is more than three setting values, the secondary-side switch pipe is turned off.
When secondary circuit detects the primary side switch pipe and turns off, the pipe conducting of control secondary-side switch, when secondary circuit is examined
When measuring primary side switch pipe conducting, control secondary-side switch pipe is turned off.
The work process of circuit is described with reference to oscillogram：The ripple being operated in for circuit during discontinuous mode as shown in Figure 10
Shape figure, for convenience of description, is described in detail with time second round T2, by that analogy.
Between time period 1 T1, time second round T2, synchronous rectification control chip IC1 detects secondary inductance
Partial pressure Vs of anti-phase terminal voltage Vd of L1 has two from being less than zero to the rising edge more than zero, and decision circuit is operated in interrupted mould
Formula.
The ON time t11 of primary side switch pipe PR is recorded in time period 1 T1, synchronous rectification control chip IC1, and
With some numerical value less than or equal to t11 as the first benchmark, record is conducting to secondary inductance L1 from primary side switch pipe PR and has discharged
Become T1 cycle time before terminating, and with some numerical value less than or equal to T1 as the second benchmark.
When time second round T2, primary side switch pipe PR are turned on, i.e., in the t21 period, electric current in primary inductor L p, is had to lead to
Cross, primary inductor L p charges, primary inductor L p homophase terminal voltage is equal to Vcs, and because in inductance, electric current can not be mutated, Vcs gradually rises
Height, meanwhile, secondary inductance L1 senses electromagnetic energy, and anti-phase terminal voltage Vd of secondary inductance L1 is equal to V2, and synchronous rectification controls
Chip IC 1 detects partial pressure Vs of the voltage Vd of secondary inductance L1 end of oppisite phase more than first threshold and/or persistent period more than the
During two threshold values, it is to allow secondary-side switch pipe SR conducting to get ready, records the time value of t21 period；
Partial pressure Vs for arranging voltage Vd exceedes the judgement of Second Threshold more than first threshold and/or persistent period, be in order to
Erroneous judgement is prevented, because when circuit is operated in discontinuous mode, between two cycles, secondary inductance voltage can produce vibration, but shake
When swinging, the maximum voltage value V1 and persistent period t23 of the anti-phase terminal voltage of secondary inductance at least is turned on than primary side switch pipe
When the voltage V2 of secondary inductance L1 end of oppisite phase and the persistent period little, and the setting of first threshold and Second Threshold, it is to avoid in pair
During the circuit oscillation of side, secondary-side switch pipe SR misleads.
In the t22 period, primary side switch pipe PR is turned off, no current in primary inductor L p, and its anti-phase terminal voltage is F1, now,
The voltage Vd of secondary inductance L1 end of oppisite phase is sported less than zero (having but small oscillations), and secondary inductance L1 is put by parasitic diode D1
Electricity, secondary electric capacity C2 charges, and secondary current waveform is as shown in figure Is, and synchronous rectification control chip IC1 is by time second round
First benchmark of the primary side switch pipe PR ON time t21 and time period 1 T1 of T2 is compared, and is divided into several situations as follows：
When primary side switch pipe PR ON time t21 is more than first benchmark of period 1, T2 time time second round
Value more than time period 1 T1 time value, synchronous rectification control chip IC1 detect voltage Vd drop to from active voltage little
In zero, while or time delay (be in Fig. 10 time delay for a period of time) output drive signal leads secondary-side switch pipe SR for a period of time
Logical, synchronous rectification control chip IC1 exports cut-off signals when T2 time time second round the second benchmark is equal to, and drives secondary
Switching tube SR is turned off, and realizes advanced shutoff；
When primary side switch pipe PR ON time t21 is less than first benchmark of period 1, and both differences are less than second
During setting value, synchronous rectification control chip IC1 detects voltage Vd and drops to less than zero from active voltage, while or one section of time delay
Time (in Figure 10 be time delay for a period of time) output drive signal turns on secondary-side switch pipe SR, in T2 time time second round
Cut-off signals are exported equal to during the second benchmark, drive secondary-side switch pipe SR to turn off, realize advanced shutoff；
When primary side switch pipe PR ON time t21 is less than first benchmark of period 1, and both differences are more than or equal to
During the second setting value, synchronous rectification control chip IC1 makes secondary-side switch pipe SR in pass in this cycle output error protection signal
Disconnected state.
The oscillogram being operated in for circuit during continuous mode as shown in figure 11, continuous mode has similarity with discontinuous mode
Also there is difference.Equally for convenience of description, it is described in detail with time second round T2, by that analogy.
Similarity is：
The ON time t11 of primary side switch pipe PR is recorded in time period 1 T1, synchronous rectification control chip IC1, and
With some numerical value less than or equal to t11 as the first benchmark, record is conducting to secondary inductance L1 from primary side switch pipe PR and has discharged
Become T1 cycle time before terminating, and with some numerical value less than or equal to T1 as the second benchmark.
In time second round T2, when primary side switch pipe PR opens conducting, i.e., in the t21 period, in primary inductor L p, there is electricity
Stream passes through, primary inductor L p charge, primary inductor L p homophase terminal voltage be equal to Vcs, because in inductance, electric current can not be mutated, Vcs by
Edge up height, meanwhile, secondary inductance L1 senses electromagnetic energy, and anti-phase terminal voltage Vd of secondary inductance L1 is equal to V2, synchronous rectification
Control chip IC1 detects partial pressure Vs of the voltage Vd of secondary inductance L1 end of oppisite phase more than first threshold or persistent period more than the
During two threshold values, it is to allow secondary-side switch pipe SR conducting to get ready, records the time value of t21 period.
In the t22 period, primary side switch pipe PR is turned off, no current in primary inductor L p, and its anti-phase terminal voltage is F1, now,
The voltage Vd of secondary inductance L1 end of oppisite phase is sported less than zero (having but small oscillations), and secondary inductance L1 is put by parasitic diode D1
Electricity, secondary electric capacity C2 charges, and synchronous rectification control chip IC1 is by the primary side switch pipe PR ON time of time second round T2
First benchmark of t21 and time period 1 T1 is compared, and is divided into several situations as follows：
When primary side switch pipe PR ON time t21 is more than first benchmark of period 1, T2 time time second round
Value more than time period 1 T1 time value, synchronous rectification control chip IC1 detect voltage Vd drop to from active voltage little
In zero, while or time delay (be in Fig. 10 time delay for a period of time) output drive signal leads secondary-side switch pipe SR for a period of time
Logical, synchronous rectification control chip IC1 exports cut-off signals when T2 time time second round the second benchmark is equal to, and drives secondary
Switching tube SR is turned off, and realizes advanced shutoff；
It is a difference in that：
Between time period 1 T1, time second round T2, synchronous rectification control chip IC1 detects secondary inductance
Anti-phase terminal voltage Vd of L1 has two from being less than zero to the rising edge more than zero, and decision circuit is operated in discontinuous mode.
But when circuit is operated in continuous mode, between two cycles, secondary inductance voltage will not produce vibration or produce
The little vibration of number of times, and vibrate when the anti-phase terminal voltage of secondary inductance maximum voltage value V1 and persistent period t23 at least
When item is turned on than primary side switch pipe, the voltage V2 of secondary inductance L1 end of oppisite phase and persistent period are little, and first threshold and the second threshold
The setting of value, equally avoids the secondary-side switch pipe SR when secondary circuit vibrates and misleads.
When primary side switch pipe PR ON time t21 is less than first benchmark of period 1, but during continuous mode work, frequency
It is fixed frequency, that is to say, that T1 cycle time of period 1 is equal to T2 cycle time of second round, therefore, even if former
Side switching tube PR ON time t21 is less than first benchmark of period 1, and both differences are more than or equal to the second setting value, with
Step rectification control chip IC1 can mask the error protection signal under this mode of operation, detect voltage Vd from active voltage
When dropping to less than zero, while or time delay (in Figure 10 be time delay for a period of time) output drive signal makes secondary-side switch for a period of time
Pipe SR is turned on, and exports cut-off signals when T2 time time second round the second benchmark is equal to, and drives secondary-side switch pipe SR to turn off,
Realize advanced shutoff.
Although give detailed description above to the specific embodiment of the present invention and illustrate, but it should be noted that
We can carry out various equivalent changes according to the conception of the present invention and change to aforesaid way, and the function produced by which is still
Without departing from description and accompanying drawing covered spiritual when, all should be within protection scope of the present invention.
Claims (12)
1. a kind of synchronous commutating control circuit, it is characterised in that the circuit includes：Primary circuit, secondary circuit；
The primary circuit includes former limit inductance, primary side switch pipe, former limit sampling resistor, the in-phase end connection of the former limit inductance
One end of the primary side switch pipe, the other end of the primary side switch pipe connects one end of the former limit sampling resistor, the original
The other end of side sampling resistor connects the ground terminal of the primary circuit, the control end connection primary-side-control letter of the primary side switch pipe
Number；
The secondary circuit includes secondary inductance, secondary-side switch pipe, the first sampling resistor of secondary, the second sampling resistor of secondary, pair
Side electric capacity, secondary load resistance, synchronous rectification control chip；The in-phase end of the secondary inductance connects the synchronous rectification control
The power end of chip, the positive pole of the secondary electric capacity, one end of the secondary load resistance；The end of oppisite phase of the secondary inductance is even
Connect one end, one end of the first sampling resistor of the secondary of the secondary-side switch pipe；The first sampling resistor of the secondary another
The input of the end connection synchronous rectification control chip, one end of the second sampling resistor of the secondary, the secondary electric capacity
Negative pole, the other end of secondary load resistance, the other end of the secondary-side switch pipe, the ground terminal of the synchronous rectification control chip connect
The ground terminal of the secondary circuit is connected to, the control end of the secondary-side switch pipe connects the output of the synchronous rectification control chip
, between one end of the secondary-side switch pipe and the other end, there is parasitic diode in end.
2. synchronous commutating control circuit according to claim 1, it is characterised in that preferred：
The synchronous rectification control chip detects the voltage of the end of oppisite phase of the secondary inductance, when the voltage of the end of oppisite phase is more than
First threshold and/or time of Second Threshold is continued above, this voltage is active voltage, then to judge the now primary side switch pipe
Conducting, the secondary inductance produces electromagnetic induction with the former limit inductance, and the secondary-side switch pipe is off state；
When the primary side switch pipe is turned off, when the voltage of the end of oppisite phase drops to less than zero by the active voltage, the pair
Side switching tube conducting, the secondary inductance electric discharge, the secondary electric capacity charges；The secondary inductance electric discharge close on complete when,
The secondary-side switch pipe is turned off.
3. synchronous commutating control circuit according to claim 2, it is characterised in that：
The synchronous rectification control chip detects the voltage of end of oppisite phase described in this cycle and is dropped to less than by the active voltage
When zero, i.e., after the trailing edge or trailing edge of active voltage, for a period of time, output drive signal drives the secondary-side switch for time delay
Pipe is turned on.
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 end of oppisite phase is begun to decline by the active voltage
When trailing edge is to first subsequent rising edge, output cut-off signals turn off the secondary-side switch pipe.
5. synchronous commutating control circuit according to claim 2, it is characterised in that：
The synchronous rectification control chip detects the mode of operation of the secondary inductance, with adjacent described twice secondary-side switch pipe
The rising edge quantity that in turn-off time, the voltage of the secondary inductance end of oppisite phase is begun to ramp up by zero volt or so as basis for estimation,
When the quantity of the rising edge is more than or equal to 2, judge that the secondary inductance is operated in discontinuous mode；Otherwise, judge the pair
Side inductance is operated in continuous mode.
6. synchronous commutating control circuit according to claim 5, it is characterised in that：
The synchronous rectification control chip is detected and records the first ON time of primary side switch pipe described in a cycle, and with little
It is the first benchmark in some numerical value for first ON time for being equal to the upper cycle；With the primary side switch pipe
One ON time is cycle time with the second ON time of secondary-side switch pipe sum, and to be less than or equal to the upper cycle
The cycle time some numerical value be the second benchmark, by first ON time in this cycle and first benchmark
It is compared, according to comparative result, controls the shutoff moment of the secondary-side switch pipe.
7. synchronous commutating control circuit according to claim 6, it is characterised in that：
The synchronous rectification control chip detects the first ON time of the primary side switch pipe in this cycle more than described the
One benchmark, then have no progeny in the primary side switch pipe pass in this cycle, controls the secondary-side switch pipe conducting, described in this cycle
When cycle time is equal to second benchmark, the secondary-side switch pipe is controlled to turn off.
8. synchronous commutating control circuit according to claim 6, it is characterised in that：
The synchronous rectification control chip detects the first ON time of the primary side switch pipe in this cycle less than described the
One benchmark, and both differences are less than the second setting value, meanwhile, detect synchronous commutating control circuit and be operated in discontinuous mode
When, then the primary side switch pipe in this cycle is closed and is had no progeny, and controls the secondary-side switch pipe conducting, in the cycle in this cycle
When time is equal to second benchmark, the secondary-side switch pipe is controlled to turn off.
9. synchronous commutating control circuit according to claim 6, it is characterised in that：
The synchronous rectification control chip detects the first ON time of the primary side switch pipe in this cycle less than described the
One benchmark, and both differences are more than or equal to the second setting value, meanwhile, when detecting circuit and being operated in discontinuous mode, then at this
Described in cycle, secondary-side switch pipe is not turned on, and is off state.
10. synchronous commutating control circuit according to claim 6, it is characterised in that：
The synchronous rectification control chip detects the first ON time of the primary side switch pipe in this cycle less than described the
One benchmark, meanwhile, when detecting synchronous commutating control circuit and being operated in continuous mode, then in the primary side switch pipe in this cycle
Pass is had no progeny, and controls the secondary-side switch pipe conducting, when second benchmark is equal to the cycle time in this cycle, controls institute
State the shutoff of secondary-side switch pipe.
11. synchronous commutating control circuits according to claim 7,8 or 10, it is characterised in that：
Close to have no progeny or close in the primary side switch pipe in this cycle and have no progeny time delay for a period of time, the synchronous rectification control chip control
Make secondary-side switch pipe conducting.
12. synchronous commutating control circuits according to claim 6, it is characterised in that：The synchronous rectification control chip inspection
When measuring that described in this cycle, secondary-side switch pipe ON time is more than three setting values, then turn off the secondary-side switch pipe.
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
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| CN110098750A (en) * | 2019-01-23 | 2019-08-06 | 上海权策微电子技术有限公司 | A kind of electric current compensation of delay structure for primary-side-control |
| CN112087148A (en) * | 2020-09-29 | 2020-12-15 | 上海新进芯微电子有限公司 | Synchronous rectification control circuit and flyback switching power supply |
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| CN108631594A (en) * | 2017-10-19 | 2018-10-09 | 西安矽力杰半导体技术有限公司 | Isolated converter and its control circuit and control method |
| 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 |
| CN109274272A (en) * | 2018-10-19 | 2019-01-25 | 成都芯源系统有限公司 | Switching power supply circuit, synchronous rectification 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 |
| CN110098750A (en) * | 2019-01-23 | 2019-08-06 | 上海权策微电子技术有限公司 | A kind of electric current compensation of delay structure for primary-side-control |
| CN112087148A (en) * | 2020-09-29 | 2020-12-15 | 上海新进芯微电子有限公司 | Synchronous rectification control circuit and flyback switching power supply |
| TWI787914B (en) * | 2021-07-19 | 2022-12-21 | 通嘉科技股份有限公司 | Synchronous rectifiers and charging methods used therein |
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