CN108631594A - Isolated converter and its control circuit and control method - Google Patents
Isolated converter and its control circuit and control method Download PDFInfo
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- CN108631594A CN108631594A CN201710980596.XA CN201710980596A CN108631594A CN 108631594 A CN108631594 A CN 108631594A CN 201710980596 A CN201710980596 A CN 201710980596A CN 108631594 A CN108631594 A CN 108631594A
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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
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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)
- Dc-Dc Converters (AREA)
- Rectifiers (AREA)
Abstract
Disclose a kind of isolated converter and its control circuit and control method.Then the embodiment of the present invention carries out raising frequency operation again by when needing lifting switch frequency, first controlling master power switch with lower switching frequency operation one or more periods.Simultaneously, in secondary avris according to the switching frequency of the secondary side Parametric Detection master power switch of power stage circuit, when detecting that the switching frequency decline meets predetermined condition, control synchronous rectification switch is held off within multiple periods, is completed with waiting for the raising frequency of primary side side to operate.Synchronous rectification switch is controlled again according to the switching frequency turn-on and turn-off detected after the switching frequency of master power switch is stablized.As a result, under the premise of the signal communication between not depending on former secondary side, the turn-on instant of the master power switch of primary side side, safe shutdown synchronous rectification switch still can be sampled.The circuit structure of the embodiment of the present invention is simple, can be with steady operation.
Description
Technical field
The present invention relates to power electronic technique, and in particular to a kind of isolated converter and its control circuit and controlling party
Method.
Background technology
Synchronous rectification is to use the lower controllable switch device of on state resistance, for example, metal-oxide semiconductor (MOS) is brilliant
Body pipe (MOSFET), to replace diode to carry out rectification, to reduce the technology of rectifier loss.MOSFET belongs to voltage-controlled type device
Part, it conducting when C-V characteristic it is in a linear relationship.When with MOSFET rectifications, it is desirable that grid voltage must be rectified voltage
Phase keep synchronize.
Meanwhile isolated converter is in the case where working in continuous current mode (Continuous Current Mode, CCM)
When, the master power switch of primary side side can be connected before the synchronous rectification electric current of secondary avris drops to zero, and therefore, synchronous rectification is opened
It closes the switch for having to be turned off before master power switch conducting to avoid former secondary side while leading directly to.Become in the isolated form of fixed-frequency control
In parallel operation, the master power switch of primary side side can be according to fixed switch periods turn-on and turn-off.Control circuit can pass through detection
The switching frequency of master power switch makes synchronous rectifier be pacified before the master power switch conducting of primary side side according to the switching frequency
It is fully closed disconnected.But because light-load efficiency require and size requirement, control circuit need at light load control master power switch with compared with
Low frequency works to improve efficiency, is carrying out improving switching frequency when overloaded to reduce size.As a result, when load changes from underloading
To when overloaded, switching frequency is there are raising frequency action, and control circuit is difficult sampling or predicts the main power of primary side side and open at this time
The turn-on instant of pass cannot accomplish safe shutdown.
Invention content
In view of this, a kind of isolated converter of offer of the embodiment of the present invention and its control circuit and control method, so that
The conducting of control circuit master power switch that sampling primary side side is remained able to independent of the signal communication between former secondary side when
It carves, safe shutdown synchronous rectification switch.
According to a first aspect of the embodiments of the present invention, a kind of control method is provided, the work(for controlling isolated converter
Rate grade circuit, the power stage circuit include the synchronous rectification switch of the master power switch and secondary avris of primary side side, the method
Including：
When needing to reduce the switch periods of master power switch, the master power switch is controlled with first switch cycling
It is worked again with the switch periods after reduction after N number of period, the first switch period is more than the current of the master power switch and opens
Close the period；And
The switch periods of master power switch described in secondary side Parametric Detection according to the power stage circuit, it is described detecting
When the switch periods of master power switch increase to the first switch period, synchronous rectification switch shutdown is kept within M period, in M
After a period the synchronous rectification switch is controlled according to the switch periods of the master power switch detected；
Wherein, N is the natural number more than or equal to 1, and M is the natural number more than N.
According to a second aspect of the embodiments of the present invention, a kind of control circuit is provided, the work(for controlling isolated converter
Rate grade circuit, the power stage circuit include the synchronous rectification switch of the master power switch and secondary avris of primary side side, the control
Circuit includes：
Primary controller, for need reduce master power switch switch periods when, control the master power switch with
It is worked again with the switch periods after reduction after first switch cycling N number of period, the first switch period is more than the master
The current switch period of power switch；And
Secondary controller, the switch week for master power switch described in the secondary side Parametric Detection according to the power stage circuit
Phase keeps synchronizing whole when detecting that the switch periods of the master power switch increase to the first switch period within M period
Switch OFF is flowed, controlling the synchronous rectification according to the switch periods of the master power switch detected after M period opens
It closes；
Wherein, N is the natural number more than or equal to 1, and M is the natural number more than N.
According to a third aspect of the embodiments of the present invention, a kind of isolated converter is provided, including：
Power stage circuit includes the synchronous rectification switch of the master power switch of primary side side and secondary avris；And
Control circuit as described in second aspect, for controlling the power stage circuit.
The embodiment of the present invention is by when needing lifting switch frequency, first controlling master power switch with lower switching frequency
In work one or more periods, raising frequency operation is then carried out again.Meanwhile it being examined according to the secondary side parameter of power stage circuit in secondary avris
The switching frequency for surveying master power switch, when detecting that the switching frequency decline meets predetermined condition, control synchronous rectification is opened
Pass is held off within multiple periods, is completed with waiting for the raising frequency of primary side side to operate.Stablize in the switching frequency of master power switch
Synchronous rectification switch is controlled again afterwards according to the switching frequency turn-on and turn-off detected.As a result, between not depending on former secondary side
Under the premise of signal communication, the turn-on instant of the master power switch of primary side side still can be sampled, safe shutdown synchronous rectification is opened
It closes.The circuit structure of the embodiment of the present invention is simple, can be with steady operation.
Description of the drawings
By referring to the drawings to the description of the embodiment of the present invention, the above and other purposes of the present invention, feature and
Advantage will be apparent from, in the accompanying drawings：
Fig. 1 is the circuit diagram of the isolated converter of a comparative example；
Fig. 2 is the working waveform figure of the isolated converter of above-mentioned comparative example；
Fig. 3 is the circuit diagram of the isolated converter of the embodiment of the present invention；
Fig. 4 is the working waveform figure of the isolated converter of the embodiment of the present invention；
Fig. 5 is the schematic diagram of the secondary controller of the embodiment of the present invention；
Fig. 6 is the schematic diagram of the switch periods detection circuit of the embodiment of the present invention；
Fig. 7 is the working waveform figure of the switch periods detection circuit of the embodiment of the present invention；
Fig. 8 is the circuit diagram of the protection circuit of the embodiment of the present invention；
Fig. 9 is the flow chart of the control method of the embodiment of the present invention.
Specific implementation mode
Below based on embodiment, present invention is described, but the present invention is not restricted to these embodiments.Under
Text to the present invention datail description in, it is detailed to describe some specific detail sections.Do not have for a person skilled in the art
The description of these detail sections can also understand the present invention completely.In order to avoid obscuring the essence of the present invention, well known method, mistake
There is no narrations in detail for journey, flow, element and circuit.
In addition, it should be understood by one skilled in the art that provided herein attached drawing be provided to explanation purpose, and
What attached drawing was not necessarily drawn to scale.
It will also be appreciated that in the following description, " circuit " refer to passed through by least one element or sub-circuit it is electrical
The galvanic circle that connection or electromagnetism connect and compose.It " is connected when claiming element or another element of circuit " being connected to " or element/circuit
" between two nodes when, it can be directly coupled or connected another element or may exist intermediary element, element it
Between connection can be physically, in logic or its combination.On the contrary, when claiming element " being directly coupled to " or " directly connecting
Be connected to " another element when, it is meant that the two be not present intermediary element.
Unless the context clearly requires otherwise, "include", "comprise" otherwise throughout the specification and claims etc. are similar
Word should be construed as the meaning for including rather than exclusive or exhaustive meaning；That is, being containing for " including but not limited to "
Justice.
In the description of the present invention, it is to be understood that, term " first ", " second " etc. are used for description purposes only, without
It can be interpreted as indicating or implying relative importance.In addition, in the description of the present invention, unless otherwise indicated, the meaning of " multiple "
It is two or more.
In following explanation, illustrated by taking inverse-excitation type (Flyback) converter as an example.It should be understood that the present invention is implemented
The scheme of example is readily applicable to other types of isolated converter.
Fig. 1 is the circuit diagram of the isolated converter of a comparative example.As shown in Figure 1, the isolated converter includes
Using the power stage circuit 1 and control circuit 2 of reverse exciting topological.Wherein, power stage circuit 1 includes primary side winding L1, secondary side
It winding L2 and is set to and the master power switch S1 of primary side side and is set to the synchronous rectification switch S2 of secondary avris.Control circuit 2
Including primary controller 21, secondary controller 22, on-delay circuit 23 and signal circuit 24.Wherein, primary controller
21 for controlling master power switch S1 turn-on and turn-off to realize power conversion.Secondary controller 22 is opened for controlling synchronous rectification
It closes S2 and synchronizes rectification.The Continuity signal of the master power switch of primary side side can be transferred to secondary side control by signal circuit 24
Device 22 processed.Secondary controller 22 controls year-on-year rectifier switch S2 according to the primary side switch Continuity signal detected and turns off.Meanwhile it leading
Messenger drives master power switch S1 again after the delay of on-delay circuit 23, ensures that master power switch S1 exists in this way
The synchronous rectification switch of secondary avris turns off open-minded, realization safe shutdown after a dead time.Fig. 2 is the work of above-mentioned comparative example
Oscillogram.As shown in Fig. 2, when working under continuous current mode, the switch control signal VG_ of the generation of primary controller 21
The rising edge of PRI is switched on delay circuit 23 and postpones a scheduled dead time td, while its failing edge is not delayed by.Via
Treated the practical driving master power switches of drive signal VGS of on-delay circuit 23.Meanwhile switch control signal VG_PRI warps
Secondary controller 22 is transferred to by signal circuit 24.Secondary controller 22 is stood after detecting switch control signal VG_PRI
Synchronous rectification control signal VG_SEC is resetted, to control synchronous rectification switch S2 shutdowns.Thus, it is possible to ensure safe pass
It is disconnected.
But above-mentioned comparative example needs additional setting signal transmission circuit and on-delay circuit, circuit scale is big, cost
It is high.Meanwhile if carrying out the signal transmission of isolated form using winding method shown in FIG. 1, circuit volume also can be larger.
Fig. 3 is the circuit diagram of the isolated converter of the embodiment of the present invention.As shown in figure 3, the isolated converter packet
Include the power stage circuit 1 and control circuit 3 using reverse exciting topological.Wherein, power stage circuit 1 includes primary side winding L1, pair
It side winding L2 and is set to and the master power switch S1 of primary side side and is set to the synchronous rectification switch S2 of secondary avris.Control circuit
3 include primary controller 31 and secondary controller 32.Primary controller 31 is used in the switch for needing reduction master power switch S1
When the period (that is, when needing to carry out raising frequency), controls the master power switch S1 and worked a week with first switch cycle T s1
Then phase is worked with the switch periods after reduction again with notifying secondary controller 32 to carry out raising frequency operation.Wherein, described
One switch periods Ts1 is arranged to the current switch period of significantly more than master power switch S1, so that secondary controller can
To carry out the prompt of raising frequency operation by detecting the switch periods acquisition that primary side side is over.Secondary controller 32 is in basis
When the switch periods of the master power switch detected know that primary side side will carry out raising frequency operation, the S2 shutdowns of control synchronous rectification switch
Multiple periods, switching frequency was stablized, then further according to the switch of the master power switch S1 detected to wait for raising frequency operation to complete
Period controls synchronous rectification switch S2.Specifically, secondary controller 32 is used for the secondary side parameter according to the power stage circuit
The switch periods for detecting the master power switch S1 are detecting that it is all that the switch periods of master power switch S1 increase to first switch
When phase Ts1, (such as 3 periods) holding synchronous rectification switch shutdown within multiple periods, basis detects after multiple periods
The switch periods of the master power switch control the synchronous rectification switch.
Fig. 4 is the working waveform figure of the isolated converter of the embodiment of the present invention.In Fig. 4, pass through synchronous rectification switch
The voltage drop VDSEN of S2 detects the switch periods of master power switch S1.As shown in figure 4, after first end cycle, according to
External circuit Parameters variation, primary controller 31 need to carry out raising frequency operation.Primary controller 31 first extends in one cycle
The switch periods of switch control signal VG_PRI are worked with controlling master power switch with longer first switch cycle T s1.Due to
The first switch period is longer than current switch period, therefore, can be according to according to the synchronous rectification switch of original switch periods control
Switch periods shutdown originally, to ensure safe shutdown within the period.Meanwhile in first switch period corresponding period knot
Shu Hou, secondary controller 32 can detect that the switch periods of master power switch increase to the first switch period, to know original
Avris will carry out raising frequency operation.In response to this testing result, the synchronous rectification that secondary controller 32 generates controls signal VG_
SEC remains low level within the multiple switch period, and multiple periods are turned off to control synchronous rectification switch.Primary controller 31
After the long switch periods that worked, raising frequency operation is proceeded by, the switch periods of master power switch S1 are shortened.Secondary side control
Device 32 processed after having waited for multiple periods, complete by the operation of primary side side raising frequency, and the switch periods of master power switch S1 are stablized, secondary side control
Device 32 processed controls synchronous rectification switch S2 and restarts work.The signal communication between former secondary side is needed not rely upon as a result, so that it may
To sample the turn-on instant of the master power switch of primary side side, safe shutdown synchronous rectification switch ensures the steady of isolated converter
Fixed work.
It should be understood that in order to realize that the notice for secondary controller, primary controller 31 can also control master power switch
S1 works multiple periods under the first switch period, it is only necessary to ensure that secondary controller 32 turns off what synchronous rectification switch S2 was waited for
Amount of cycles is more than the periodicity of master power switch S1 frequency reducings work.
Accordingly, when primary side side needs to carry out frequency redution operation (that is, increasing the switch periods of master power switch S1), by
Synchronous rectification switch S2 shutdowns can be controlled in secondary controller 32 according to the switch periods being over before.Therefore, it is opening
After closing period increase, it is not necessarily to additional control, synchronous rectification switch S2 is it is ensured that the shutdown before master power switch S1 conductings.Tool
Body, primary controller 31 is additionally configured to when needing to increase the switch periods of master power switch, is controlled the main power and is opened
It closes with the switching frequency operation after increasing.Secondary controller 32 is additionally configured to the secondary side parameter according to the isolated converter
The switch periods for detecting the master power switch control the synchronization according to the switch periods of the master power switch detected
Rectifier switch.
As a result, under the above-mentioned setting of the embodiment of the present invention, isolated converter can steadily carry out raising frequency operation and drop
Frequency operates.
Optionally, above-mentioned first switch cycle T s1 can be obtained according to the current switch period in real time, or
Predetermined period.
When being obtained in real time by current switch period, first switch can be obtained by the way that current switch period is multiplied by K
Cycle T s1.In the present embodiment, K is more than or equal to 1.5, preferably 2.For example, needing the switching frequency of master power switch S1
When being promoted to 65kHz by 25kHz, switching frequency is first reduced into half (that is, dropping to 12.5kHz), accordingly, switch periods increase
It is twice (that is, K=2).As a result, to notify secondary controller 32 to carry out raising frequency operation.
Alternatively it is also possible to obtain first switch week by the way that the current switch period is increased scheduled hop period
Phase.
Fig. 5 is the schematic diagram of the secondary controller of the embodiment of the present invention.As shown in figure 5, the secondary controller 32 includes
Switch periods detection circuit 32a and protection circuit 32b.Switch periods detection circuit 32a is used for according to the isolated converter
Secondary side Parametric Detection described in master power switch switch periods.Protection circuit 32b is for detecting the master power switch
Switch periods when increasing to the first switch period, synchronous rectification switch shutdown, the root after M period are kept within M period
According to the switch periods control synchronous rectification switch S2 of the master power switch detected.
Specifically, switch periods detection circuit 32a is configured as the voltage drop VDSEN of detection synchronous rectification switch S1, and
The parameter for characterizing the time span between two adjacent turn-on instants is obtained, to characterize the switch periods of master power switch S1.
Wherein, in turn-on instant, voltage drop VDSEN rises above second voltage threshold value VTH2, and after turn-on instant, voltage drop
VDSEN is remained above second voltage threshold value VTH2 until there is primary steep drop.It is described to be reduced to voltage drop VDSEN suddenly to be more than slope
The descending slope of threshold value Slop drops to less than first voltage threshold value VTH1.That is, it drops in voltage drop suddenly when turn-on instant
Before, and adjacent appearance is dropped suddenly with voltage drop, at the time of voltage drop VDSEN rises to second voltage threshold value VTH2.Pass through record
At the time of voltage drop VDSEN rises to second voltage threshold value VTH2 each time, and continue to judge follow-up whether primary close to occurring
Suddenly drop can detect turn-on instant to voltage.In order to obtain the parameter of characterization switch periods, switch periods detection circuit 32a can
During voltage drop VDSEN steep drops adjacent twice, the capacitor charging for being to label persistently, and detecting voltage drop
When VDSEN rises above second voltage threshold value VTH2, start to marking the capacitor charging for capacitance；Detecting voltage drop
It is right when VDSEN drops to less than first voltage threshold value VTH1 and descending slope and is less than slope threshold value Slop (that is, not steep drop)
It discharges labeled as from the capacitance of capacitance, and, when detecting that voltage drop VDSEN drops suddenly, obtain the capacitance labeled as main capacitance
Voltage and labeled as the capacitance from capacitance voltage difference as characterizing between adjacent twice steep of the voltage drop drop
The parameter of time span, and exchange main capacitance and the label from capacitance.
Fig. 6 is the schematic diagram of the switch periods detection circuit of the embodiment of the present invention.Fig. 7 is the switch week of the embodiment of the present invention
The working waveform figure of phase detection circuit.The operation principle of switch periods detection circuit is described in detail below in conjunction with Fig. 6 and Fig. 7.It opens
Close cycle detection circuit 32a include slope detecting circuit U1, comparator U2, U3, with door U4, rest-set flip-flop U5, d type flip flop U6,
With door U7 and U8, current source I1 and I2, switch Q1 and Q2, capacitance C1 and C2 and sample circuit U9.Wherein, slope detecting circuit
U1 is used to detect the descending slope of voltage drop VDSEN.Comparator U2 is for comparison voltage drop VDSEN and first voltage threshold value
VTH1.It is connect respectively with the output end of slope detecting circuit U1 and comparator U2 with the input terminal of door U4.
It should be understood that according to for useful signal setting and comparator U2 and slope detecting circuit U1 connection types not
Together, other logic gates are may be set to be with door U4 to realize identical function.
Comparator U3 drops VDSEN and second voltage threshold value VTH2 for comparison voltage.In the present embodiment, pass through setting one
The 85% corresponding value that a circuit sampling obtained the peak value of the voltage drop VDSEN in a upper period is used as second voltage threshold value,
That is, VTH2=85%*VDSEN_PEAK.The set end of rest-set flip-flop U5 is connect with the output end of comparator U2, reset terminal with than
Output end connection compared with device U3, positive output end are connected to and door U7 and U8.The input end of clock of d type flip flop U6 with it is defeated with door U4
Outlet connects, and positive output end Q is connected to be connected to and door U8 with door U7, reverse pumping outlet Qb.It is connected to out with the output end of door U7
Close the control terminal of Q2.The control terminal of switch Q1 is connected to the output end of door U8.Switch Q1, capacitance C1 and current source I1 compositions one
A charge-discharge circuit.Switch Q2, capacitance C2 and current source I2 form another charge-discharge circuit.Wherein, capacitance C1 and switch Q1
Parallel connection, current source I1 and above-mentioned parallel circuit in series.Capacitance C2 and switch Q2 are in parallel, current source I2 and above-mentioned parallel circuit string
Connection.As a result, when switch Q1 or Q2 are connected, corresponding capacitance C1 or C2 is discharged.When switch Q1 or Q2 are turned off, corresponding electricity
Hold C1 or C2 to be charged by current source I1 or I2.When the output current intensity of current source I1 and I2 is identical, the voltage Va of capacitance C1
Risen with identical slope when being electrically charged with the voltage Vb of capacitance C2.Sample circuit U9 is used to sample electricity when detecting steep drop
Hold the difference of the voltage Vb of the voltage Va and capacitance C2 of C1 the absolute value suddenly drop adjacent twice as the characterization voltage drop it
Between time span parameter.
It should be understood that according to for useful signal setting and comparator U2 and slope detecting circuit U1 connection types not
Together, other logic gates be may be set to be to realize identical function with door U7 and U8.
As shown in fig. 7, at the t0 moment, master power switch conducting.Voltage drop VDSEN is more than second voltage threshold value VTH2, than
Rest-set flip-flop U5 is resetted compared with device U3 output high level.The low level of rest-set flip-flop U5 output to export low level with door U7,
Switch Q2 is turned off, and current source I2 charges to capacitance C2 at this time.Meanwhile being continuously low level with door U8 outputs so that capacitance C1
Also it is continuously charged.
At the t1 moment, voltage drop VDSEN descending slopes are more than slope threshold value Slope, while rapidly dropping to first voltage
Threshold value VTH1 is hereinafter, that is, can detect steep drop.At this point it is possible to judge the t0 moment for the voltage drop VDSEN adjacent with dropping suddenly
It is turn-on instant at the time of rising above second voltage threshold value VTH2.Slope detecting circuit U1 exports high level, comparator U2
Export high level.High level is exported with door U4.The output switching activity of d type flip flop U6, positive output end Q export low level, reverse pumping outlet
Qb exports high level.Continue to charge to capacitance C2 with door U7 output low level controls.With door U8 output high level control switches Q1
Conducting control discharges to capacitance C1.The voltage Va of capacitance C1 drops to zero.Hereafter, capacitance C2 is persistently electrically charged as main capacitance,
Capacitance C1 is used as from capacitance.
At the t2 moment, voltage drop VDSEN rises above second voltage threshold value VTH2 due to oscillation.Comparator U3 outputs are high
Level resets rest-set flip-flop U5.Low level is exported with door U7 and U8.Due to being also low level before with door U7, electricity
Hold C2 to continue to be continuously charged, voltage Vb persistently rises.Meanwhile capacitance C1 also begins to be electrically charged, voltage Va starts from scratch rising.
At the t3 moment, voltage drop VDSEN drops to less than first voltage threshold value VTH1 due to oscillation.Comparator U2 outputs are high
Level set rest-set flip-flop U5.Since the slope of decline is less than slope threshold value Slope, slope detecting circuit U1 outputs are low
Level.Output low level is kept with door U4.D type flip flop hold mode is constant.Therefore, continue to keep output low level with door U7,
Capacitance C2 continues to be continuously charged, and voltage Vb persistently rises.And with door U8 since two inputs are high level, export high electricity
Flat, switch Q1 conducting controls discharge to capacitance C1.The voltage Va of capacitance C1 drops to zero.
At t4 the and t5 moment, voltage drop VDSEN vibrates similar with t2, t3 moment again, and during this, capacitance C2 is held
Continuous to be electrically charged, voltage Vb continues to rise.And capacitance C1 is discharged after being electrically charged a period of time.Voltage Va is reset at the t5 moment
Zero.
At the t6 moment, at this point, master power switch is connected, voltage drop VDSEN is more than second voltage threshold value VTH2, comparator U3
Output high level resets rest-set flip-flop U5.The low level of rest-set flip-flop U5 outputs to keep output low level, electricity with door U7
Hold C2 to be persistently electrically charged, voltage Vb continues to rise.Meanwhile export low level with door U8, capacitance C1 starts to be electrically charged, voltage Va from
Zero begins to ramp up.
At the t7 moment, voltage drop VDSEN descending slopes are more than slope threshold value Slope and rapidly drop to first voltage threshold simultaneously
Value VTH1 or less., that is, steep drop can be detected.At this point it is possible to judge the t6 moment for the voltage drop VDSEN adjacent with dropping suddenly
It is turn-on instant at the time of rising above second voltage threshold value VTH2.Slope detecting circuit U1 exports high level, comparator U2
Export high level.High level is exported with door U4.The output switching activity of d type flip flop U6, positive output end Q export high level, reverse pumping outlet
Qb exports low level.High level is exported with door U7, the Q2 conductings of control switch discharge to C2.Low level, electricity are exported with door U8 simultaneously
Hold C1 to be electrically charged with continuing for.In the new period, in next cycle, capacitance C1 is switched to main capacitance, and capacitance C2 is cut
It is changed to from capacitance.
After judging to obtain turn-on instant, since the voltage of the capacitance C2 as main capacitance is begun to ramp up from the t0 moment, because
This, voltages of the capacitance C2 at the t6 moment can characterize switch periods.But switch periods detection circuit 32a actually exists
T7 just can confirm that the t6 moment is turn-on instant.This needs subtracts the time at characterization t6 moment at moment-t7 from the voltage of capacitance C2
The voltage of length.
At the t7 moment, for also experienced the upper of t6-t7 periods as the capacitance C1 from capacitance, voltage Va before
It rises.Also, it is rising of starting from scratch at the t6 moment as the capacitance C1 from capacitance..When charging current is identical, the electricity at t7 moment
Pressure Va can characterize the time span of t6-t7 this periods at moment.Therefore, the difference of voltage Vb and voltage Va can characterize t0-
The time span at t6 moment, that is, switch periods.
Fig. 8 is the circuit diagram of the protection circuit of the embodiment of the present invention.As shown in figure 8, the protection circuit 32b includes comparing
Device U10, NOT gate U11 and with door U12.Wherein, comparator U10 is used to compare the signal in characterization first switch period and currently terminates
Switch periods signal.NOT gate U11 is connect with the output end of comparator U10.With mono- input terminal of door U12 and NOT gate U11
Output end connects, another input terminal connection conducting enable signal exports synchronous rectification drive signal.It is detecting as a result,
When switch periods are more than the first switch period, comparator U10 exports high level, is triggered after being converted to low level via NOT gate U11
Protection so that synchronous rectification drive signal remains low.After protection is triggered, secondary controller 32 can pass through other parts
Circuit control synchronous rectification Continuity signal keep low level within several periods.
The present embodiment is by when needing lifting switch frequency, first controlling master power switch with lower switching frequency operation
Then one or more periods carry out raising frequency operation again.Meanwhile in secondary avris by being examined according to the secondary side parameter of power stage circuit
The switching frequency for surveying master power switch, when detecting that the switching frequency decline meets predetermined condition, control synchronous rectification is opened
Pass is held off within multiple periods, is completed with waiting for the raising frequency of primary side side to operate.Stablize in the switching frequency of master power switch
Synchronous rectification switch is controlled again afterwards according to the switching frequency turn-on and turn-off detected.Thus, it is possible to independent of former secondary side it
Between signal communication remain able to sampling primary side side master power switch turn-on instant, safe shutdown synchronous rectification switch.This
The circuit structure of inventive embodiments is simple, can be with steady operation.
Fig. 9 is the flow chart of the control method of the isolated converter of the embodiment of the present invention.The method includes：
Step S100, it when needing to reduce the switch periods of master power switch, controls the master power switch and is opened with first
It is worked again with the switch periods after reduction after closing cycling N number of period, the first switch period opens more than the main power
The current switch period of pass.
Step S200, the switch periods of master power switch described in the secondary side Parametric Detection according to the power stage circuit,
When detecting that the switch periods of the master power switch increase to the first switch period, synchronous rectification is kept to open within M period
Shutdown controls the synchronous rectification switch after M period according to the switch periods of the master power switch detected.
Wherein, N is the natural number more than or equal to 1, and M is the natural number more than N.
Further, the method further includes：
When needing to increase the switch periods of master power switch, the master power switch is controlled with the switch periods after increasing
Work；And
The switch periods of master power switch described in secondary side Parametric Detection according to the isolated converter, according to detecting
The switch periods of the master power switch control the synchronous rectification switch.
Further, the first switch period obtains according to the current switch period；Alternatively, the first switch week
Phase is predetermined period.
Further, the first switch period is obtained by the way that the current switch period is multiplied by K, and K is more than or equal to
1.5；Alternatively, the first switch period is obtained by the way that the current switch period is increased scheduled hop period.
Further, in step S200, master power switch described in the secondary side Parametric Detection according to the isolated converter
Switch periods include：
Step S210, the voltage drop of the synchronous rectification switch is detected.
Step S220, the parameter for characterizing the time span between two adjacent turn-on instants is obtained, to be opened described in characterization
Close the period.
Wherein, described to be reduced to the voltage drop suddenly first voltage threshold is dropped to less than with the descending slope more than slope threshold value
Value.
Further, step S220 includes：
Step S221, during the voltage drop steep drop adjacent twice, the capacitor charging for being to label persistently,
And when detecting that the voltage drop rises above second voltage threshold value, start the capacitor charging for capacitance to label,
It is capacitance to label when detecting that the voltage drop drops to less than first voltage threshold value and descending slope is less than slope threshold value
Capacitance electric discharge.
Step S222, when detecting that the voltage drop is dropped suddenly, the difference of the voltage of main capacitance and the voltage from capacitance is obtained
Value as characterize the voltage drop it is adjacent twice drop suddenly between time span parameter, and exchange main capacitance and from capacitance
Label.
The foregoing is merely the preferred embodiment of the present invention, are not intended to restrict the invention, for those skilled in the art
For, the present invention can have various modifications and changes.It is all within spirit and principles of the present invention made by any modification, equivalent
Replace, improve etc., it should all be included in the protection scope of the present invention.
Claims (15)
1. a kind of control method, the power stage circuit for controlling isolated converter, the power stage circuit include primary side side
Master power switch and secondary avris synchronous rectification switch, the method includes：
When needing to reduce the switch periods of master power switch, it is N number of with first switch cycling to control the master power switch
It is worked again with the switch periods after reduction after period, the first switch period is more than the current switch week of the master power switch
Phase；And
The switch periods of master power switch described in secondary side Parametric Detection according to the power stage circuit are detecting the main work(
When the switch periods of rate switch increase to the first switch period, synchronous rectification switch shutdown is kept within M period, M week
After phase the synchronous rectification switch is controlled according to the switch periods of the master power switch detected；
Wherein, N is the natural number more than or equal to 1, and M is the natural number more than N.
2. control method according to claim 1, which is characterized in that the method further includes：
When needing to increase the switch periods of the master power switch, the master power switch is controlled with the switch periods after increasing
Work；And
The switch periods of master power switch, are opened according to what is detected described in secondary side Parametric Detection according to the isolated converter
Close the period control synchronous rectification switch.
3. control method according to claim 1, which is characterized in that the first switch period is according to the current switch
Period obtains；
Alternatively, the first switch period is predetermined period.
4. control method according to claim 3, which is characterized in that the first switch period by described by currently opening
The pass period is multiplied by K acquisitions, and K is more than or equal to 1.5；Or
The first switch period is obtained by the way that the current switch period is increased scheduled hop period.
5. control method according to claim 1, which is characterized in that examined according to the secondary side parameter of the isolated converter
The switch periods for surveying the master power switch include：
Detect the voltage drop of the synchronous rectification switch；
The parameter that the time span between characterizing two adjacent turn-on instants is obtained according to the voltage drop, to be opened described in characterization
Close the period；
Wherein, in the turn-on instant, the voltage drop rises above second voltage threshold value, also, after turn-on instant, institute
It states voltage drop and is remained above shown second threshold voltage until the primary steep drop of appearance, described to be reduced to the voltage drop suddenly to be more than tiltedly
The descending slope of rate threshold value drops to less than first voltage threshold value.
6. control method according to claim 5, which is characterized in that obtain and characterize the voltage drop steep drop adjacent twice
Between the parameter of time span include：
During the voltage drop steep drop adjacent twice, the capacitor charging for being to label persistently, and detecting
When stating voltage drop and rising above second voltage threshold value, start to mark be capacitance capacitor charging, detecting the electricity
It is that the capacitance of capacitance discharges to marking when pressure drop drops to less than first voltage threshold value and descending slope and is less than slope threshold value；
When detecting that the voltage drop is dropped suddenly, obtain labeled as the voltage of the capacitance of main capacitance and labeled as the capacitance from capacitance
Voltage the difference steep drop adjacent twice as the voltage drop is characterized between time span parameter, and exchange main capacitance
With the label from capacitance.
7. a kind of control circuit, the power stage circuit for controlling isolated converter, the power stage circuit include primary side side
Master power switch and secondary avris synchronous rectification switch, the control circuit includes：
Primary controller, for when needing to reduce the switch periods of master power switch, controlling the master power switch with first
Switch periods are worked and are worked again with the switch periods after reduction after N number of period, and the first switch period is more than the main power
The current switch period of switch；And
Secondary controller is used for the switch periods of master power switch described in the secondary side Parametric Detection according to the power stage circuit,
When detecting that the switch periods of the master power switch increase to the first switch period, synchronous rectification is kept within M period
Switch OFF controls the synchronous rectification switch after M period according to the switch periods of the master power switch detected；
Wherein, N is the natural number more than or equal to 1, and M is the natural number more than N.
8. control circuit according to claim 7, which is characterized in that the primary controller is additionally configured to needing to increase
When the switch periods of big master power switch, controls the master power switch and worked with the switch periods after increasing；And
The secondary controller is additionally configured to master power switch described in the secondary side Parametric Detection according to the isolated converter
Switch periods, control the synchronous rectification switch according to the switch periods that detect.
9. control circuit according to claim 7, which is characterized in that the first switch period is according to the current switch
Period obtains；
Alternatively, the first switch period is predetermined period.
10. control circuit according to claim 9, which is characterized in that the first switch period will be by will be described current
Switch periods are multiplied by K acquisitions, and K is more than or equal to 1.5；Or
The first switch period is obtained by the way that the current switch period is increased scheduled hop period.
11. control circuit according to claim 7, which is characterized in that the secondary controller includes：
Switch periods detection circuit, for opening for master power switch described in the secondary side Parametric Detection according to the isolated converter
Close the period；And
Circuit is protected, it is all at M for when detecting that the switch periods of the master power switch increase to the first switch period
Synchronous rectification switch shutdown is kept in phase, according to the control of the switch periods of the master power switch detected after M period
The synchronous rectification switch.
12. control circuit according to claim 11, which is characterized in that the switch periods detection circuit is configured as examining
Survey the voltage drop of the synchronous rectification switch, and according to the voltage drop obtain between characterizing two adjacent turn-on instants when
Between length parameter, to characterize the switch periods；Wherein, in the turn-on instant, the voltage drop rises above second
Voltage threshold, and after turn-on instant, the voltage drop is remained above shown second threshold voltage and is once dropped suddenly up to occurring,
It is described to be reduced to the voltage drop suddenly first voltage threshold value is dropped to less than with the descending slope more than slope threshold value.
13. control circuit according to claim 12, which is characterized in that the switch periods detection circuit is configured as
During the voltage drop steep drop adjacent twice, the capacitor charging for being to label persistently, and detecting the voltage
When drop rises above second voltage threshold value, start to marking the capacitor charging for capacitance, in the case where detecting the voltage drop
It drops to when being less than slope threshold value less than first voltage threshold value and descending slope, is that the capacitance of capacitance discharges to marking, and,
When detecting that the voltage drop is dropped suddenly, the voltage labeled as the voltage of the capacitance of main capacitance and labeled as the capacitance from capacitance is obtained
The difference steep drop adjacent twice as the voltage drop is characterized between time span parameter, and exchange main capacitance and from electricity
The label of appearance.
14. control circuit according to claim 13, which is characterized in that the switch periods detection circuit includes：
Slope detecting circuit, the descending slope for detecting the voltage drop；
First comparator is used for the voltage drop and the first voltage threshold value；
First logic gate, input terminal are connect with the output end of the slope detecting circuit and the first comparator respectively；
Second comparator is used for the voltage drop and the second voltage threshold value；
Rest-set flip-flop, set end are connect with the output end of the first comparator, the output of reset terminal and second comparator
End connection；
D type flip flop, input end of clock are connect with the output end of first logic gate；
Second logic gate, input terminal are connect with the positive output end of the output end of the rest-set flip-flop and d type flip flop respectively；
Third logic gate, input terminal are connect with the reverse pumping outlet of the output end of the rest-set flip-flop and the d type flip flop respectively；
First charge-discharge circuit, including the first capacitance, the first charge-discharge circuit are controlled by the output signal of second logic gate
To first capacitor charging or electric discharge；
Second charge-discharge circuit, including the second capacitance, second charging circuit are controlled by the output letter of the third logic gate
Number to second capacitor charging or electric discharge；And
Sample circuit, the difference of the voltage of voltage and second capacitance for sampling first capacitance when detecting steep drop
The parameter of time span between the absolute value of the value steep drop adjacent twice as the voltage drop is characterized.
15. a kind of isolated converter, including：
Power stage circuit includes the synchronous rectification switch of the master power switch of primary side side and secondary avris；And
Control circuit as described in any one of claim 7-14, for controlling the power stage circuit.
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| CN113179006A (en) * | 2019-11-08 | 2021-07-27 | 矽力杰半导体技术(杭州)有限公司 | Zero-voltage switching-on control circuit and method and switching power supply applying same |
| CN113224933A (en) * | 2021-05-14 | 2021-08-06 | 杭州欧佩捷科技有限公司 | Secondary side-to-primary side isolation control method of isolation converter |
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Application publication date: 20181009 Assignee: Silergy Corp. Assignor: Silergy Semiconductor Technology (Hangzhou) Ltd. Contract record no.: X2021990000823 Denomination of invention: Isolated converter and its control circuit and control method Granted publication date: 20200306 License type: Common License Record date: 20211227 |
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